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This glossary was compiled to define words which are used to describe HIV, its pathogenesis, associated treatments, and the medical management of related conditions.
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A
ACROMEGALY:
A chronic disease caused by hypersecretion of the pituitary
growth hormones. It is characterized by enlargement of many
parts of the skeleton, especially the nose, ears, jaws,
fingers and toes. See also Pituitary Gland.
ACTG:
See AIDS Clinical Trials Group.
ACUTE INFECTION:
An infection causing disease with a sudden onset, severity and
(often) short course. As related to HIV infection: Once the
virus enters the body, HIV infects a large number of CD4+ T
cells and replicates rapidly. During this acute or primary
phase of infection, the blood contains many viral particles
that spread throughout the body, seeding themselves in various
organs, particularly the lymphoid tissues. See also Acute
Retroviral Syndrome; CD4 (T4) or CD4+ Cells; Infection;
Lymphoid Organs.
ACUTE RETROVIRAL SYNDROME:
The acute or primary HIV infection often passes unrecognized,
but may be present as a mononucleosis-like syndrome within
three months of the infection. The diagnosis is made by
demonstrating HIV antibody seroconversion. See also
Seroconversion.
ACYCLOVIR:
(Acycloguanosine). A nucleoside analog antiviral drug used to
treat the symptoms of the genital form of herpes simplex virus
infection. See also Herpes Simplex Virus; Nucleoside Analog.
ADENOPATHY:
Any disease involving or causing enlargement of glandular
tissues, especially one involving the lymph nodes.
ADJUVANT:
An ingredient-as in a prescription or solution-that
facilitates or modifies the action of the principal
ingredient. May be used in HIV therapies or for HIV vaccines.
ADMINISTRATION:
(Route of Administration). A term used to refer to how a drug
or therapy is introduced into the body. Systemic
administration means that the drug goes throughout the body
(usually carried in the bloodstream), and includes oral
administration (by mouth) and intravenous administration
(injection into the vein). Local administration means that the
drug is applied or introduced into the specific area affected
by the disease, such as application directly onto the affected
skin surface (topical administration). The effects of most
therapies depend upon the ability of the drug to reach the
affected area, thus the route of administration and consequent
distribution of a drug in the body is an important determinant
of its effectiveness.
ADVERSE EVENT:
In a clinical trial, an unwanted effect detected in
participants. The term is used whether or not the effect can
be attributed to the intervention under study.
ADVERSE REACTION:
See Side Effects.
AEROSOLIZED:
A form of administration in which a drug, such as pentamidine,
is turned into a fine spray or mist by a nebulizer and
inhaled. See also Pentamidine.
AETC:
See AIDS Education and Training Centers.
AFFECTED COMMUNITY:
This includes HIV-positive people, persons living with AIDS
and other individuals, including their families, friends and
advocates, directly impacted by HIV infection and its
physical, psychological and sociological ramifications.
AGAMMAGLOBULINEMIA:
A nearly total absence of immunoglobulins. See also
Antibodies.
AGENCY FOR HEALTH CARE POLICY AND RESEARCH (AHCPR):
An agency of the Public Health Service that supports
activities to enhance health care services and improve access
to them.
AHCPR:
See Agency for Health Care Policy and Research.
AIDS:
See Acquired Immunodeficiency Syndrome.
AIDS BIBLIOGRAPHY:
The National Library of Medicine publishes the monthly AIDS
Bibliography, which includes all citations from the
AIDSLINE database. The AIDS Bibliography is available from the
Superintendent of Documents (Phone: 202-783-3238). See also
AIDSLINE.
AIDS CLINICAL TRIALS GROUP (ACTG):
The ACTG is composed of a number of US medical centers that
valuate treatment for HIV and HIV-associated infections. ACTG
studies are sponsored by the National Institute of Allergy and
Infectious Diseases.
AIDS DEMENTIA COMPLEX:
About half the people infected with HIV, the virus that causes
AIDS, develop infections or other problems involving the brain
or spinal cord. These neurological complications may include
inflammation of the brain (encephalitis), or of the membrane
surrounding the brain (meningitis), infections of the brain,
brain or spinal cord tumors, nerve damage, difficulties in
thinking and behavioral changes (i.e., AIDS dementia complex)
and stroke.
AIDSDRUGS:
An online database service administered by the National
Library of Medicine, with references to drugs undergoing
testing against AIDS, AIDS-related complex and related
opportunistic infections.
AIDS EDUCATION AND TRAINING CENTERS (AETC):
The Health Resources and Services Administration supports a
network of 17 regional centers that serve as resources for
educating health professionals in prevention, diagnosis and
care of HIV-infected patients. The centers train primary
caregivers to incorporate HIV prevention strategies into their
clinical priorities, along with diagnosis, counseling and care
of HIV-infected persons and their families.
AIDS KNOWLEDGE BASE:
Full-text electronic database on AIDS, available in print as
well as electronic form, produced and maintained by physicians
and other health care professionals. The database is edited by
P.T. Cohen (San Francisco General Hospital), Merle Sande, and
Paul Volberding.
AIDSLINE:
An online database service administered by the National
Library of Medicine, with citations and abstracts covering the
published scientific and medical literature on AIDS and
related topics.
AIDS-RELATED CANCERS:
Several cancers are more common or more aggressive in people
infected with HIV, the virus that causes AIDS. These
malignancies include certain types of immune system cancers
known as lymphomas, Kaposi's sarcoma and anogenital cancers
primarily affecting the cervix and the anus. HIV, or the
immune suppression it induces, appears to play a role in the
development of these cancers. See also Cervical Cancer;
Kaposi's Sarcoma; Lymphoma.
AIDS-RELATED COMPLEX (ARC):
1. A term, not officially defined or recognized by the Centers
for Disease Control and Prevention, that has been used to
describe a variety of symptoms and signs found in some persons
infected with HIV. These may include recurrent fevers,
unexplained weight loss, swollen lymph nodes, and/or fungus
infection of the mouth and throat. Also commonly described as
symptomatic HIV infection.
2. Symptoms that appear to be
related to infection by the HIV virus. They include an
unexplained, chronic deficiency of white blood cells
(leukopenia) or a poorly functioning lymphatic system with
swelling of the lymph nodes (lymphadenopathy) lasting for more
than three months without the opportunistic infections
required for a diagnosis of AIDS.
See also Wasting Syndrome.
AIDS RESEARCH ADVISORY COMMITTEE:
Board that advises and makes recommendations to the Director,
National Institute of Allergy and Infectious Diseases, on all
aspects of HIV-related research, vaccine development,
pathogenesis and epidemiology.
AIDS SERVICE ORGANIZATION (ASO):
A health association, support agency or other service active
in the prevention and treatment of AIDS.
AIDSTRIALS:
An online database service administered by the National
Library of Medicine, with information about clinical trials of
agents under evaluation against HIV infection, AIDS and
related opportunistic infections.
AIDS WASTING SYNDROME:
See Wasting Syndrome.
ALKALINE PHOSPHATASE:
An enzyme that is normally present in certain cells within the
liver, bone, kidney, intestine and placenta. When the cells
are destroyed in those tissues, more of the enzyme leaks into
the blood, and levels rise in proportion to the severity of
the condition. Measurement of this enzyme is used as an
indication of the health of the liver.
ALOPECIA:
The loss of hair that frequently occurs in patients undergoing
chemotherapy for cancer or suffering from other diseases,
such as AIDS, where cell-killing, or cytotoxic, drugs are
used.
ALTERNATIVE THERAPY:
In Western countries, alternative therapy refers to any type
of medicine that supplements or is used in lieu of biomedicine
(i.e., conventional medicine) or allopathic medicine. In other
parts of the world, where traditional medicine predominates,
the term may refer to biomedicine itself.
ALUM:
Potassium aluminum sulfate or ammonium aluminum sulfate,
used
especially as an emetic (i.e., an agent that induces
vomiting), an astringent (i.e., a substance that contracts
tissues) and styptic (i.e., a substance that tends to check
bleeding by contracting the tissues or blood vessels).
ALVEOLAR:
Pertaining to the alveoli sac, the site of gas exchange in the
lungs.
AMEBIASIS:
An inflammation of the intestines caused by infestation with
Entameba histolytica (a type of ameba) and characterized by
frequent, loose stools flecked with blood and mucus.
AMINO ACIDS:
Any of a class of organic compounds having a carboxyl group
(COOH) and an amino group (NH2). Some 22 amino acids are
commonly found in animals, and more than 100 less common
forms
are found in nature, chiefly in plants. When the carboxyl
carbon atom of one amino acid binds to the nitrogen of another
with the release of a water molecule, a linkage called a
peptide bond is formed. Chains of amino acids, joined
head-to-tail in this manner, are synthesized by living systems
and are called polypeptides (up to about 50 amino acids) and
proteins (over 50 amino acids). See also Peptide; Proteins.
AMNIOCENTESIS:
The surgical insertion of a hollow needle through the
abdominal wall and into the uterus of a pregnant female to
obtain amniotic fluid (i.e., the serous fluid in which the
embryo is suspended) especially to examine the fetal
chromosomes for an abnormality or for the determination of the
sex of the embryo. See also Uterus.
ANALOG:
In chemistry, a compound with a structure similar to that of
another compound, but differing from it in respect to certain
components or structural makeup; it may have a similar or
opposite action metabolically.
ANAMNESTIC RESPONSE:
The heightened immunologic reaction elicited by a second or
subsequent exposure to a particular pathogenic microorganism
or antigen. See also Antigen.
ANAPHYLACTIC SHOCK:
A life-threatening allergic reaction characterized by a
swelling of body tissues (including the throat) and a sudden
decline in blood pressure.
ANEMIA:
A lower than normal number of red blood cells.
ANERGY:
1. The loss or weakening of the body's immunity to an
irritating agent, or antigen. The strength of the body's
immune response is often quantitatively measured by means of
a skin test where a solution containing an antigen known to
cause a response, such as mumps or candida, is injected
immediately under the skin. The lack of a reaction to these
common antigens indicates anergy. See also Antigen.
2.
Researchers in cell culture have shown that CD4+T cells can be
turned off by a signal from HIV that leaves them unable to
respond to further immune system stimulation. This inactivated
state is known as anergy.
See also CD4 (T4) or CD4+ Cells.
ANTIBIOTIC:
An antimicrobial agent, derived from cultures of a
microorganism or produced semisynthetically, used to treat
infections.
ANTIBODIES:
Molecules in the blood or secretory fluids that tag, destroy
or neutralize bacteria, viruses or other harmful toxins. They
are members of a class of proteins known as immunoglobulins,
which are produced and secreted by B lymphocytes in response
to stimulation by antigens. An antibody is specific to an
antigen. See also Antigen; Lymphocyte.
ANTIBODY-DEPENDENT CELL-MEDIATED CYTOTOXICITY (ADCC):
An immune response in which antibodies bind to target cells,
identifying them for attack by the immune system. See also
Antibodies.
ANTIFOLATE:
An agent that inhibits intracellular (i.e., inside cells)
production of folinic acid. See also Folinic Acid.
ANTIGEN:
A substance that, when introduced into the body, is capable of
inducing the production of a specific antibody. See also
Antibodies.
ANTIIDIOTYPE:
An antibody that recognizes and binds to another antibody
(idiotype).
ANTINEOPLASTIC:
Inhibiting or preventing the proliferation of tumor cells.
ANTIRETROVIRAL AGENTS:
Substances used against retroviruses such as HIV. See also
Retrovirus.
ANTITOXINS:
Antibodies that recognize and inactivate toxins produced by
certain bacteria, plants or animals. See also Antibodies.
ANTIVIRAL:
A substance or process that destroys a virus or suppresses its
replication.
APOPTOSIS:
Cellular suicide, also known as programmed cell death. HIV may
induce apoptosis in both infected and uninfected immune system
cells. Uninfected cells may also undergo apoptosis. Normally
when CD4+ T cells mature in the thymus gland, a small
proportion of these cells are unable to distinguish self from
nonself. Because these cells would otherwise attack the body's
own tissues, they receive a biochemical signal from other
cells that results in apoptosis. See also CD4 (T4) or CD4+
Cells; Thymus.
ARC:
See AIDS-Related Complex.
ARM:
A group of participants in a clinical trial, all of whom
receive the same treatment or placebo. See also Placebo.
ARTHRALGIA:
A pain in a joint.
ASO:
See AIDS Service Organization.
ASPERGILLOSIS:
A fungal infection (resulting from the fungus Aspergillus) of
the lungs that can spread through the blood to other organs.
Symptoms include fever, chills, difficulty in breathing and
coughing up blood. If the infection reaches the brain, it may
cause dementia. See also Dementia.
ASSEMBLY AND BUDDING:
Names for a portion of the processes by which new HIV virus
is formed in infected host cells. Viral core proteins,
enzymes and RNA (ribonucleic acid) gather just inside the
cell's membrane, while the viral envelope proteins aggregate
within the membrane. An immature viral particle is formed and
then pinches off from the cell, acquiring an envelope and the
cellular and HIV proteins from the cell membrane. The immature
viral particle then undergoes processing by an HIV enzyme
called protease to become an infectious virus. See also
Enzyme; Ribonucleic Acid.
ASYMPTOMATIC:
Without symptoms. Usually used in AIDS literature to describe
a person who has a positive reaction to one of several tests
for HIV antibodies, but who shows no clinical symptoms of the
disease.
ATTENUATED:
Weakened or decreased. For example, an attenuated virus can no
longer produce disease, but might be used to produce a
vaccine.
AUTOANTIBODY:
1. An antibody that is active against some of the tissues of
the organism that produced it.
2. An antibody directed
against
the body's own tissue. See also Antibodies.
AUTOIMMUNIZATION:
The induction in an individual of an immune response to its
own cells (tissue). See also Immune Response.
AUTOINOCULABLE:
Susceptible of being inoculated with microorganisms from one's
own body.
AUTOLOGOUS:
Pertaining to the same organism or one of its parts;
originating within an organism itself.
AZT:
Azidothymidine (also called zidovudine or ZDV; the
Burroughs-Wellcome trade name is Retrovir). One of the first
drugs used against HIV infection, AZT is a nucleoside analog
that suppresses replication of HIV. See also Nucleoside
Analog.
B
BACTERICIDAL:
Capable of killing bacteria.
BACTERIOSTATIC:
Capable of inhibiting reproduction of bacteria.
BACTERIUM:
A microscopic organism composed of a single cell. Many
bacteria can cause disease in humans.
BACULOVIRUS:
A virus of insects used in the production of some HIV
vaccines. See also Vaccine.
BASELINE:
1. Information gathered at the beginning of a study from which
variations found in the study are measured.
2. A known value
or quantity with which an unknown is compared when measured
or
assessed.
BASOPHIL:
A type of white blood cell, also called a granular leukocyte,
filled with granules of toxic chemicals that can digest
microorganisms. Basophils, as well as other types of white
blood cells, are responsible for the symptoms of allergy. The
granules stain blue when exposed to a basic dye for
microscopic examination.
B CELL LYMPHOMA:
See Lymphoma.
B CELLS:
See B Lymphocytes.
BILIRUBIN:
1. A bile pigment whose measurement can be used as an
indication of the health of the liver.
2. A substance released
from old or damaged red blood cells. Small amounts of
bilirubin normally enter the bloodstream and circulate until
they reach the liver and then into the bowel, where bilirubin
is further broken down and excreted. The normal value is 0.1
to 1.5 milligrams per liter of blood.
BINDING ANTIBODY:
As related to HIV infection: An antibody that attaches to some
part of the HIV virus. Binding antibodies may or may not
adversely affect the virus.
BIOLOGICAL RESPONSE MODIFIERS (BRMs):
Substances, either natural or synthesized, that boost, direct
or restore normal immune defenses. BRMs include interferons,
interleukins, thymus hormones and monoclonal antibodies. See
also Interferon; Interleukin-2; Monoclonal Antibody; Thymus.
BIOPSY:
The surgical removal of a piece of tissue from a living
subject for microscopic examination to make a diagnosis (for
example, to determine whether abnormal cells such as cancer
cells are present).
BIOTECHNOLOGY:
1. The use of living organisms or their products to make or
modify a substance. These include recombinant DNA techniques
(also referred to as genetic engineering) and hybridoma
technology.
2. The industrial application of the results of
biological research, particularly in fields such as
recombinant DNA or gene splicing, which permits the production
of synthetic hormones or enzymes by combining genetic material
from different species.
BLINDED STUDY:
A clinical trial in which participants are unaware as to
whether or not they are in the experimental or control arm of
the study.
BLOOD BRAIN BARRIER:
The barrier between brain blood vessels and brain tissues
whose effect is to restrict what may pass from the blood into
the brain.
B LYMPHOCYTES (B CELLS):
One of the two major classes of lymphocytes. During
infections, these cells are transformed into plasma cells that
produce large quantities of antibody directed at specific
pathogens. This transformation occurs through interactions
with various types of T cells and other components of the
immune system. In persons with AIDS, the functional ability of
both the B and the T lymphocytes is damaged, with the T
lymphocytes being the principal site of infection by the HIV
virus. See also Lymphocyte; T Cells.
BODY FLUIDS:
Any fluid in the human body, such as blood, urine, saliva,
sputum (spit), tears, semen, mother's milk or vaginal
secretions. Only blood, semen, mother's milk and vaginal
secretions have been linked directly to the transmission of
the HIV virus.
BONE MARROW:
Soft tissue located in the cavities of the bones where blood
cells such as erythrocytes, leukocytes and platelets are
formed. See also Erythrocytes; Leukocytes; Platelets.
BOOSTER:
A second or later dose of a vaccine given to increase the
immune response to the original dose. See also Vaccine.
BRANCHED DNA ASSAY:
A sensitive, rapid test that can be used to monitor the amount
of HIV in a patient's bloodstream (i.e., the viral burden).
See also Viral Burden.
BREAKTHROUGH INFECTION:
An infection, caused by the infectious agent the vaccine is
designed to protect against, that occurs during the course of
a vaccine trial. These infections may be caused by exposure to
the infectious agent before the vaccine has taken effect, or
before all doses of the vaccine have been given. Breakthrough
infections also occur in trial participants receiving
placebos.
BRONCHOSCOPY:
Visual examination of the bronchial passages of the lungs
through a tube of an endoscope inserted into the upper lungs
or extraction of material from the lungs by means of a
bronchoscope. See also Endoscopy.
BUDDING:
See Assembly and Budding.
BURKITT'S LYMPHOMA:
A lymphatic cancer that involves not only the lymphatic and
the associated reticuloendothelial system, but also other body
tissues. This disease, which is most common in Central Africa,
is thought to be possibly caused by the Epstein-Barr virus.
Also called African lymphoma, Burkitt's tumor. See also
Epstein-Barr Virus; Lymph; Reticuloendothelial Cells.
C
CACHEXIA:
General ill health and malnutrition, marked by weakness and
emaciation, usually associated with serious disease. See also
Wasting Syndrome.
CANDIDA:
Yeast-like fungi commonly found in the normal flora of the
mouth, skin, intestinal tract and vagina, but can become
clinically infectious in immune compromised people. See also
Fungus.
CANDIDIASIS:
An infection with a fungus of the Candida family, generally
Candida albicans; it most commonly involves the skin
(dermatocandidiasis), oral mucosa (thrush), respiratory tract
(bronchocandidiasis) and vagina (vaginitis). Candidiasis of
the esophagus, trachea, bronchi or lungs is an indicator
disease for AIDS. See also Fungus; Thrush.
CARCINOGEN:
Any cancer-producing substance.
CATHETER:
A tubular medical device for insertion into canals, vessels,
passageways or body cavities, usually to permit injection
(e.g., through an intravenous catheter into a vein) or
withdrawal of fluids, or to keep a passage open.
CBCT:
See Community-Based Clinical Trial.
CBO:
See Community-Based Organization.
CDC:
See Centers for Disease Control and Prevention.
CD8 (T8) CELLS:
A protein embedded in the cell surface of suppressor T
lymphocytes. Also called cytotoxic T cells. See also CD
Nomenclature; CD4 (T4) or CD4+ Cells; T Cells.
CD4 (T4) or CD4+ CELLS:
1. White blood cells killed or disabled during HIV infection.
These cells normally orchestrate the immune response,
signaling other cells in the immune system to perform their
special functions. Also known as T helper cells.
2. HIV's
preferred targets are cells that have a docking molecule
called cluster designation 4 (CD4) on their surfaces. Cells
with this molecule are known as CD4-positive (or CD4+) cells.
Destruction of CD4+ lymphocytes is the major cause of the
immunodeficiency observed in AIDS, and decreasing CD4+
lymphocyte levels appear to be the best indicator of morbidity
in these patients. Although CD4 counts fall, the total T-cell
level remains fairly constant through the course of HIV
disease, due to a concomitant increase in the CD8+ cells. The
ratio of CD4+ to CD8+ cells is therefore an important measure
of disease progression. See also CD Nomenclature; CD8 (T8)
Cells; Immunodeficiency.
CDC NATIONAL AIDS CLEARINGHOUSE:
The CDC's comprehensive reference, referral and publication
distribution service for HIV and AIDS information. The
Clearinghouse works in partnership with national, regional,
state and local organizations that develop and deliver
HIV prevention programs and services.
CD NOMENCLATURE:
This nomenclature was developed to standardize and compare
monoclonal antibodies from different sources. Antibodies with
similar reactivity patterns are assigned to CD groups
representing "clusters of differentiation." T lymphocytes are
CD3+ and can be separated into the CD4+ T helper cells and the
CD8+ cytotoxic/suppressor cells. Although CD4+ cells are
predominantly T lymphocytes, some monocytes are also CD4+.
CELL LINES:
Specific cell types artificially maintained in the laboratory
(i.e., in vitro) for scientific purposes.
CELL-MEDIATED IMMUNITY (CMI):
The branch of the immune system in which the reaction to
foreign material is performed by specific defense cells (i.e.,
killer cells, macrophage and other white blood cells) rather
than antibodies.
CELLULAR IMMUNITY:
See Cell-Mediated Immunity.
CENTERS FOR DISEASE CONTROL AND PREVENTION (CDC):
A Public Health Service agency responsible (among others) for
assessing the status and characteristics of the AIDS epidemic
and the prevalence of HIV infections. CDC supports the design,
implementation and evaluation of prevention activities, and
maintains various HIV/AIDS information services, such as the
CDC National AIDS Clearinghouse.
CENTRAL NERVOUS SYSTEM (CNS):
Composed of the brain, spinal cord and its coverings
(meninges).
CENTRAL NERVOUS SYSTEM (CNS) DAMAGE:
(By HIV infection). Although monocytes and macrophages can be
infected by HIV, they appear to be relatively resistant to
killing. However, these cells travel throughout the body and
carry HIV to various organs, especially the lungs and the
brain. People infected with HIV often experience abnormalities
in the central nervous system. Investigators have hypothesized
that an accumulation of HIV in brain and nerve cells or the
inappropriate release of cytokines or toxic byproducts by
these cells may be to blame for the neurological
manifestations of HIV disease. See also Cytokines; Macrophage;
Monocyte.
CEREBRAL:
Pertaining to the cerebrum, the main portion of the brain.
CERVICAL CANCER:
A neoplasm of the uterine cervix that can be detected in the
early curable stage by the Papanicolaou (Pap) test. See also
Cervical Dysplasia; Cervix; Pap Smear.
CERVICAL DYSPLASIA:
A precursor lesion for cervical cancer. Studies indicate an
increase in prevalence of cervical dysplasia among
HIV-infected women. Additional studies have documented that a
higher prevalence is associated with greater immuno
suppression. HIV infection also may adversely affect the
clinical course and treatment of cervical dysplasia and
cancer. See also Dysplasia.
CERVICAL INTRAEPITHELIAL NEOPLASIA (CIN1, CIN2, CIN3):
Dysplasia of the cervix epithelium, often pre-malignant (i.e.,
cancerous), characterized by various degrees of hyperplasia,
abnormal keratinization (forming horny epidermal tissue) and
condylomata. Considerable evidence implicates human papilloma
virus (HPV) in the development of CIN. Immunosuppression may
also play an important role in facilitating infection or
persistence of HPV in the genital tract and progression of
HPV-induced neoplasia. See also Cervix; Condyloma; Dysplasia;
Epithelium; Hyperplasia; Neoplasm.
CERVIX:
The part of the uterus that protrudes into the cavity of the
vagina. See also Uterus.
CHALLENGE:
In vaccine experiments, the exposure of an immunized animal to
the infectious agent.
CHEMOTHERAPY:
The treatment, mostly of cancer, by the use of a series of
cytotoxic drugs that attack cancerous cells. This treatment
commonly has adverse side effects that may include the
temporary loss of the body's natural immunity to infections,
loss of hair, digestive upset and a general feeling of
illness. Although unpleasant, the adverse effects of treatment
are tolerated considering the life-threatening nature of the
cancers usually treated by chemotherapy. See also Cytotoxic.
CHRONIC IDIOPATHIC DEMYELINATING POLYNEUROPATHY (CIPD):
Chronic, spontaneous loss or destruction of myelin. Myelin is
a soft, white, somewhat fatty material that forms a thick
sheath around the protoplasmic core of myelinated nerve fiber.
CIPD:
See Chronic Idiopathic Demyelinating Polyneuropathy.
CIRCULATING IMMUNE COMPLEXES:
See Immune Complex.
CLADE:
A group of related HIV variants, classified according to
degree of genetic similarity. HIV variants are currently
grouped into clades A, B, C, D, E, F and O.
CLINICAL:
Pertaining to or founded on observation and treatment of
patients, as distinguished from theoretical or basic science.
CLINICAL ALERT:
A mechanism, adopted by the National Institutes of Health in
onjunction with the editors of several biomedical journals,
for urgent cases in which timely and broad dissemination of
results of clinical trials could prevent morbidity (sickness)
and mortality (death). The Clinical Alert does not become a
barrier to subsequent publication of the full research paper.
Clinical Alerts are widely distributed electronically through
the National Library of Medicine and through standard
mailings.
CLINICAL LATENCY:
The state or period of an infectious agent, such as a virus or
bacterium, living or developing in a host without producing
clinical symptoms. As related to HIV infection: Although
infected individuals usually exhibit a period of clinical
latency with little evidence of disease, the virus is never
truly latent. Even early in the disease, HIV is active within
lymphoid organs where large amounts of virus become trapped in
the FDC network. Surrounding germinal centers are areas rich
in CD4+ T cells. These cells increasingly become infected and
viral particles accumulate both in infected cells and as free
virus. See also CD4 (T4) or CD4+ Cells; Lymphoid Organs.
CLINICAL PRACTICE GUIDELINES:
Standards for physicians to adhere to in prescribing care for
a given condition or illness.
CLINICAL TRIAL:
A carefully designed and executed investigation of the effects
of a drug (or vaccine) administered to human subjects. The
goal is to define the clinical efficacy and pharmacological
effects (toxicity, side effects, incompatibilities or
interactions) of the drug. The US government, through the Food
and Drug Administration, requires strict testing of all new
drugs and vaccines prior to their approval for use as
therapeutic agents.
CLONE:
1. A group of genetically identical cells or organisms
descended from a common ancestor. To produce such genetically
identical copies.
2. A genetically identical replication of a
living cell that is valuable for the investigation and
reproduction of test cultures.
CMV:
See Cytomegalovirus.
CNS:
See Central Nervous System.
COCCIDIOIDOMYCOSIS:
An infectious fungal disease caused by the inhalation of
spores of Coccidioides immitis, which is carried on windblown
dust particles. The disease is endemic in hot dry regions of
the Southwestern US and Central and South America, and is an
opportunistic disease associated with AIDS. Also called desert
fever, San Joaquin fever, valleyfever. See also Fungus;
Opportunistic Infection.
COFACTORS:
1. Substances, microorganisms or characteristics of
individuals that may influence the progression of a disease or
the likelihood of becoming ill.
2. A substance, such as a
metallic ion or coenzyme, that must be associated with an
enzyme for the enzyme to function.
3. A situation or activity
that may increase a person's susceptibility to AIDS. Examples
of such cofactors are other infections, drugs and alcohol use,
poor nutrition, genetic factors and stress.
COHORT:
In epidemiology, a group of individuals with some
characteristics in common.
COLITIS:
Inflammation of the colon.
COMMUNITY-BASED CLINICAL TRIAL (CBCT):
A clinical trial conducted primarily through primary-care
physicians rather than academic research facilities.
COMMUNITY-BASED ORGANIZATION (CBO):
A locally based service organization that provides social
services at the community level.
COMMUNITY PROGRAMS FOR CLINICAL RESEARCH ON AIDS (CPCRA):
An initiative of the National Institute of Allergy and
Infectious Diseases (NIAID) to broaden the base of clinical
investigations by involving community physicians in AIDS
research and trials. NIAID started the CPCRA in 1989. It is
one of four HIV clinical trials programs supported by NIAID.
In 1992 the name of the program was officially changed to the
Terry Beirn Community Programs for Clinical Research on AIDS.
(See also Terry Beirn Community Programs for Clinical Research
on AIDS).
COMPASSIONATE USE:
A method of providing experimental drugs to very sick patients
who have no other treatment options. Often, case-by-case
approval must be obtained from the Food and Drug
Administration for "compassionate use" of a drug.
COMPLEMENT:
A group of proteins in normal blood serum and plasma which, in
combination with antibodies, causes the destruction of
antigens, particularly bacteria and foreign blood corpuscles.
See also Antibodies; Antigen.
COMPLEMENT CASCADE:
A precise sequence of events, usually triggered by an
antigen-antibody complex, in which each component of the
complement system is activated in turn. See also Antibodies;
Antigen.
CONCOMITANT DRUGS:
Drugs that are taken together. Certain concomitant medications
may have adverse interactions.
CONCORDE STUDY:
Joint French/British clinical trial of AZT in asymptomatic
HIV-positive individuals. See also AZT.
CONDYLOMA:
(Condyloma acuminatum). A papilloma with a central core of
connective tissue in a treelike structure covered with
epithelium, usually occurring on the mucous membrane or skin
of the external genitals or in the perianal (tissue
surrounding the anus) region. Although the lesions are usually
few in number, they may aggregate to form large
cauliflower-like masses. Caused by the human papilloma virus
(HPV), it is infectious and autoinoculable (i.e., capable of
being transmitted by inoculation from one part of the body to
another). Also called acuminate or venereal warts. See also
Epithelium; Papilloma.
CONTAGIOUS:
Any infectious disease capable of being transmitted by casual
contact from one person to another. Casual contact can be
defined as normal day-to-day contact between people at home,
school, work or in the community. A contagious infection
(e.g., a common cold) can be communicable by casual contact;
an infectious infection, on the other hand, is communicable by
intimate contact such as sex. AIDS is infectious, not
contagious.
CONTRAINDICATION:
A specific circumstance when the use of certain treatments
could be harmful.
CONTROL:
A standard against which experimental observations may be
evaluated. In clinical trials, one group of patients is given
an experimental drug, while another group (i.e., the control
group) is given either a standard treatment for the disease or
a placebo. See also Placebo.
CORE PROTEIN:
As related to HIV: An integral protein of the HIV virus
composed of three units, p24, p15 and p18.
CORRELATES OF IMMUNITY/CORRELATES OF PORTECTION:
The immune responses that protect an individual from a certain
disease. The precise identities of the correlates of immunity
in HIV are unknown.
CPCRA:
See Community Programs for Clinical Research on AIDS.
CREATININE:
A protein found in muscles and blood, and excreted by the
kidneys in the urine. The level of creatinine in the blood and
urine provides a measure of kidney function.
CRYPTOCOCCAL MENINGITIS:
A life-threatening infection of the membranes (meninges) that
line the brain and the spinal cord. Cryptococcal disease is
caused by a fungus (Cryptococcus neoformans). Most people have
been exposed to this organism, which is found in soil
contaminated by bird droppings, but it usually does not cause
disease in healthy people. The majority of people with
cryptococcal meningitis have immune systems that are damaged
by disease, such as AIDS, or suppressed by drugs. The organism
can infect almost all organs of the body, although it most
commonly causes disease of the meninges, skin or lungs.
CRYPTOCOCCOSIS:
An infectious disease seen in HIV-infected patients due to the
fungus Cryptococcus neoformans, which is acquired via
the respiratory tract. It can spread from the lungs to the
brain, the central nervous system, the skin, skeletal system
and urinary tract. See also Cryptococcal Meningitis.
CRYPTOSPORIDIOSIS:
An opportunistic infection caused by the protozoan parasite
Cryptosporidium parvum.
CT:
(Computed Tomography). Radiography (using X-rays) in which a
three-dimensional image of a body structure is constructed by
computer from a series of plane cross-sectional images made
along an axis. Also referred to as CAT scan.
CTL:
See Cytotoxic T Lymphocyte.
CUTANEOUS:
Of, pertaining to or affecting the skin.
CYTOKINES:
1. Immune system proteins involved in the normal regulation of
the immune response. They may also help to activate HIV.
2.
Proteins used for communication by cells of the immune system.
Central to the normal regulation of the immune response.
CYTOMEGALOVIRUS (CMV):
A herpes virus that is a common cause of opportunistic
diseases in people with AIDS and other people with immune
suppression. While CMV can infect most organs of the body,
people with AIDS are most susceptible to CMV retinitis
(disease of the eye) and colitis (disease of the colon). See
also Cytomegalovirus (CMV) Retinitis.
CYTOMEGALOVIRUS (CMV) RETINITIS:
Most adults in the US have been infected by cytomegalovirus,
although the virus usually does not cause disease in healthy
people. Because the virus remains in the body for life, it can
cause disease if the immune system becomes severely damaged
by
disease or suppressed by drugs. CMV retinitis is an eye
disease common among people who are infected with HIV.
Without
treatment, people with CMV retinitis can lose their vision.
CMV infection can affect both eyes and is the most common
cause of blindness among people with AIDS.
CYTOPENIA:
Deficiency in the cellular elements of the blood.
CYTOPLASM:
All of the substance of a cell other than the nucleus.
CYTOTOXIC:
An agent or process that is toxic to cells (i.e., it causes
suppression of function or cell death).
CYTOTOXIC T LYMPHOCYTE (CTL):
A lymphocyte that is able to kill foreign cells that have been
marked for destruction by the cellular immune system. See also
CD8 (T8) Cells; Lymphocyte.
D
DATABASE:
An organized compilation of information, usually maintained in
a computer system.
DATA SAFETY AND MONITORING BOARD (DSMB):
An independent committee, composed of community
representatives and clinical research experts, that reviews
data while a clinical trial is in progress to ensure that
participants are not exposed to undue risk. A DSMB may
recommend that a trial be stopped if there are safety concerns
or if the trial objectives have been achieved.
DATRI:
See Division of AIDS Treatment Research Initiative.
DDC:
Dideoxycytidine (zalcitabine, HIVID), a nucleoside analog drug
that inhibits the replication of HIV. See also Nucleoside
Analog.
DDI:
Dideoxyinosine (didanosine, Videx), a nucleoside analog drug
that inhibits the replication of HIV. See also Nucleoside
Analog.
DELETION:
Elimination of a gene (i.e., from a chromosome) either in
nature or in the laboratory. See also Gene.
DEMENTIA:
Chronic intellectual impairment (i.e., loss of mental
capacity) with organic origins that affects a person's ability
to function in a social or occupational setting. See also AIDS
Dementia Complex.
DEMYELINATION:
Destruction, removal or loss of the myelin sheath of a nerve
or nerves. See also Myelin.
DENDRITE:
Any of the usual branching protoplasmic processes that conduct
impulses toward the body of a nerve cell. See also Protoplasm.
DENDRITIC CELLS:
Patrolling immune system cells that may begin the HIV disease
process by carrying the virus from the site of the infection
to the lymph nodes, where other immune cells become infected.
Dendritic cells travel through the body and bind to foreign
invaders-such as HIV-especially in external tissues, such as
the skin and the membranes of the gut, lungs and reproductive
tract. They then ferry the foreign substance to the lymph
nodes to stimulate T cells and initiate an immune response. In
laboratory experiments, the dendritic cells that carry HIV
also bind to CD4+ T cells, thereby allowing HIV to infect the
CD4+ T cells. CD4+ T cells are the critical immune system
cells targeted by HIV and depleted during HIV infection. See
also CD4 (T4) or CD4+ Cells; Lymph Nodes; T Cells.
D4T:
(Also known as Stavudine and Zerit). d4T is a
dideoxynucleoside pyrimidine analog
(2'3'-didehydro-3'-deoxythymidine). Like other nucleoside
analogs, d4T inhibits HIV replication by inducing premature
viral DNA chain termination. d4T has been approved for
patients with advanced HIV infection intolerant to or failing
other antiretroviral drugs. See also Nucleoside Analog.
DIAGNOSIS:
The determination of the presence of a specific disease or
infection, usually accomplished by evaluating clinical
symptoms and laboratory tests.
DIARRHEA:
Uncontrolled, loose and frequent bowel movements. In the
United States, almost all people with AIDS develop diarrhea at
some time in the course of their disease. Severe or prolonged
diarrhea can lead to weight loss and malnutrition. The
excessive loss of fluid that may occur with AIDS-related
diarrhea can be life-threatening. There are many possible
causes of diarrhea in people who have AIDS. The most common
infectious organism causing AIDS-related diarrhea include
cytomegalovirus (CMV); the parasites Cryptosporidium,
Microsporidia and Giardia lamblia; and the bacterium
Mycobacterium avium-inracellulare (MAC). Other bacteria and
parasites that cause diarrheal symptoms in otherwise healthy
people may cause more severe, prolonged or recurrent diarrhea
in people with HIV or AIDS. See also Cytomegalovirus;
Giardiasis; Microsporidiosis; Mycobacterium Avium Complex.
DIPLOPIA:
Double vision.
DISSEMINATED:
Spread (of a disease) throughout the body.
DIVISION OF AIDS TREATMENT RESEARCH INITIATIVE (DATRI):
An organization established by the National Institute of
Allergy and Infectious Diseases as a national network to test
new therapies for HIV-infected persons. Its hallmark is the
ability to rapidly conduct clinical trials and related
research that evaluates new therapies and novel treatment
approaches for those with HIV disease.
DNA:
(Deoxyribonucleic Acid). 1. The molecular chain found in genes
within the nucleus of each cell, which carries the genetic
information that enables cells to reproduce. 2. DNA is the
principal constituent of chromosomes, the structures that
transmit hereditary characteristics. The amount of DNA is
constant for all typical cells of any given species of plant
or animal (including humans), regardless of the size or
function of that cell. Each DNA molecule is a long,
two-stranded chain made up of subunits, called nucleotides,
containing a sugar (deoxyribose), a phosphate group and one of
four nitrogenous bases: adenine (A), guanine (G), thymine (T)
and cytosine (C). In 1953 J.D. Watson and F.H. Crick proposed
that the strands, connected by hydrogen bonds between the
bases, were coiled in a double helix. Adenine bonds only with
thymine (A-T or T-A) and guanine only with cytosine (G-C or
C-G). The complementarity of this bonding ensures that DNA
can be replicated (i.e., that identical copies can be made in
order to transmit genetic information to the next generation).
DOMAIN:
A region of a gene or gene product. See also Gene.
DORMANCY:
See Latency.
DOSE-RANGING STUDY:
A clinical trial in which two or more doses of an agent (such
as a drug) are tested against each other to determine which
dose works best and is least harmful. See also Clinical Trial.
DOSE-RESPONSE RELATIONSHIP:
The relationship between the dose of some agent (such as a
drug), or the extent of exposure, and a physiological
response. A dose-response effect means that as the dose
increases so does the effect.
DOUBLE-BLIND STUDY:
A clinical trial design in which neither the participating
individuals nor the study staff know which patients are
receiving the experimental drug and which are receiving
placebo or another therapy. Double-blind trials are thought
to produce objective results, since the doctor's and patient's
expectations about the experimental drug do not affect the
outcome. See also Clinical Trial; Placebo.
DRUG-DRUG INTERACTION:
A modification of the effect of a drug when administered with
another drug. The effect may be an increase or a decrease in
the action of either substance, or it may be an adverse effect
that is not normally associated with either drug.
DSMB:
See Data Safety and Monitoring Board.
DYSPLASIA:
Any abnormal development of tissues or organs. In pathology,
alteration in size, shape and organization of adult cells.
DYSPNEA:
Difficult or labored breathing.
E
EFFICACY:
(Of a drug or treatment). The maximum ability of a drug or
treatment to produce a result regardless of dosage. A drug
passes efficacy trials if it is effective at the dose tested
and against the illness for which it is prescribed. In the
procedure mandated by the Food and Drug Administration, phase
II clinical trials gauge efficacy, phase III trials confirm
it.
ELISA:
(Enzyme-Linked Immunosorbent Assay). A laboratory test to
determine the presence of antibodies to HIV in the blood. A
positive ELISA test generally is confirmed by the Western Blot
test. See also Antibodies; Western Blot.
EMPIRICAL:
Based on experimental data, not on a theory.
ENCEPHALITIS:
A general term denoting inflammation of the brain.
ENDEMIC:
Pertaining to diseases associated with particular locales or
population groups.
ENDOGENOUS:
Relating to or produced by the body.
ENDOSCOPY:
Viewing the inside of a body cavity (e.g., colon) with an
endoscope, a device using flexible fiber optics.
ENDOTOXIN:
A toxin present inside a bacterial cell.
END-STAGE DISEASE:
Final period or phase in the course of a disease leading to a
person's death.
ENTERIC:
Pertaining to the intestines.
ENTERITIS:
Inflammation of the intestine.
ENV:
A gene of HIV that codes for the protein gp160, the precursor
of the envelope proteins gp120 and gp41. See also Gene.
ENVELOPE:
In virology, a protein covering that packages the virus's
genetic information. The outer coat, or envelope, of HIV is
composed of two layers of fat-like molecules called lipids
taken from the membranes of human cells. Embedded in the
envelope are numerous cellular protein, as well as
mushroom-shaped HIV proteins that protrude from the surface.
Each mushroom is thought to consist of a cap made of four
glycoprotein molecules called gp120 and a stem consisting of
four gp41 molecules embedded in the envelope. The virus uses
these proteins to attach to and infect cells. See also
Glycoprotein; gp41; gp120; Lipid.
ENZYME:
A protein that accelerates a specific chemical reaction
without altering itself (i.e., a catalyst).
EOSINOPHIL:
A type of white blood cell, called granulocyte, that can
digest microorganisms. The granules can be stained by the acid
dye, eosin, for microscopic examination.
EPIDEMIC:
A disease that spreads rapidly through a demographic segment
of the human population, such as everyone in a given
geographic area, a military base, or similar population unit,
or everyone of a certain age or sex, such as the children or
women of a region. Epidemic diseases can be spread from person
to person or from a contaminated source such as food or water.
EPIDEMIOLOGIC SURVEILLANCE:
The ongoing and systematic collection, analysis and
interpretation of data about a disease or health condition. As
part of a surveillance system to monitor the HIV epidemic in
the US, the CDC, in collaboration with state and local health
departments, other federal agencies, blood collection agencies
and medical research institutions, conducts standardized HIV
seroprevalence surveys in designated subgroups in the US
population. Collecting blood samples for the purpose of
surveillance is called serosurveillance. See also Centers for
Disease Control and Prevention; Seroprevalence; Surveillance.
EPIDEMIOLOGY:
The branch of medical science that deals with the incidence,
distribution and control of a disease in a population.
EPITHELIUM:
The covering of the internal and external organs of the body.
Also the lining of vessels, body cavities, glands and organs.
It consists of cells bound together by connective material and
varies in the number of layers and the kinds of cells.
EPITOPE:
A unique shape or marker carried on an antigen's surface that
triggers a corresponding antibody response. See also
Antibodies; Antigen.
EPSTEON-BARR VIRUS (EBV):
A herpes-like virus that causes one of the two kinds of
mononucleosis (the other is caused by CMV). It infects the
nose and throat and is contagious. EBV lies dormant in the
lymph glands and has been associated with Burkitt's lymphoma
and hairy leukoplakia. See also Burkitt's Lymphoma;
Cytomegalovirus; Hairy Leukoplakia.
ERYTHEMA:
Redness or inflammation of the skin or mucous membranes.
ERYTHEMA MULTIFORME:
A skin disease characterized by papular (small, solid, usually
conic elevation of the skin) or vesicular lesions (blisters),
and reddening or discoloration of the skin often in concentric
zones about the lesion. Erythema multiforme has been
associated with many infections, collagen disease, drug
sensitivities, allergies and pregnancy. A severe form of this
condition is Stevens-Johnson Syndrome. See also Lesion;
Stevens-Johnson Syndrome.
ERYTHEMATOUS:
Red or reddened.
ERYTHROCYTES:
Red blood cells whose major function is to carry oxygen to
cells.
ETIOLOGY:
The study or theory of the factors that cause disease.
EXCLUSION/INCLUSION CRITERIA:
The medical or social standards determining whether a person
may or may not be allowed to enter a clinical trial. For
example, some trials may not include people with chronic liver
disease, or may exclude people with certain drug allergies;
others may exclude men or women or only include people with a
lowered T-cell count.
EXOGENOUS:
Developed or originating outside the body.
EXOTOXIN:
A toxic substance, made by bacteria, that is released outside
the bacterial cell.
EXPANDED ACCESS:
A general term for methods of distributing experimental drugs
to patients who are unable to participate in ongoing clinical
trials and have no other treatment options. Specific types of
expanded access mechanisms include parallel track, Treatment
IND, and compassionate use. See also Investigational New Drug.
EXPRESSION SYSTEM:
In HIV vaccine production, cells into which an HIV gene has
been inserted to produce desired HIV proteins.
F
FALLOPIAN TUBES:
Part of the female reproductive system. A pair of ducts
opening at one end into the uterus and at the other end into
the peritoneal cavity, over the ovary. Each tube serves as a
passage through which the ovum (egg) is carried to the uterus
and through which spermatozoa (sperm) move toward the ovary.
See also Ovary; Uterus.
FDA:
See Food and Drug Administration.
FDCs:
See Follicular Dendritic Cells.
FOLIC ACID:
A crystalline vitamin of the B complex that is used especially
in the treatment of nutritional anemias. It occurs in green
plants, fresh fruit, liver and yeast. Also called folacin,
folate, vitamin B9.
FOLINIC ACID:
Also called citrovorum factor. A metabolically active form of
folic acid that has been used in cancer therapy to protect
normal cells against methotrexate (a cancer chemotherapy
agent). Also used to treat megaloblastic anemias. See also
Folic Acid.
FOLLICLE:
A small anatomical cavity or deep narrow-mouthed depression;
a small lymph node.
FOLLICULAR DENDRITIC CELLS (FDCs):
Cells found in the germinal centers of lymphoid organs. FDCs
have thread-like tentacles that form a weblike network to trap
invaders and present them to other cells of the immune system
(for destruction). See also Lymphoid Organs.
FOMITE:
An inanimate object that can harbor pathogenic microorganisms
and thus serve as an agent of transmission of an infection.
FOOD AND DRUG ADMINISTRATION (FDA):
The Public Health Service agency responsible for (among
others) ensuring the safety and effectiveness of drugs,
biologics, vaccines and medical devices used in the diagnosis,
treatment and prevention of HIV infection, AIDS and
AIDS-related opportunistic infections. The FDA also works with
the blood banking industry to safeguard the nation's blood
supply. See also Public Health Service.
FUNCTIONAL ANTIBODY:
An antibody that binds to an antigen and has an effect. For
example, neutralizing antibodies inactivate HIV or prevent it
from infecting other cells. See also Antibodies; Antigen.
FUNGUS:
1. A general term used to denote a class of microbes
including mushrooms, yeasts and molds.
2. Fungi, which
were once classified as plants, have since been reclassified
as unmoving organisms that lack chlorophyll.
Mycologists (scientists working with fungi) estimate that
there are 100,000 species of fungi, ranging from baker's yeast
to dermatophytes (fungi that cause ringworm and athlete's
foot) to potentially invasive species such as Candida albicans
and Aspergillus. As many as 150 of these organisms have now
been linked to animal or human diseases.
G
GAMMA INTERFERON:
A T cell-derived stimulating substance that suppresses virus
reproduction, stimulates other T cells and activates
macrophage cells. See also Macrophage; T Cells.
GANGLION:
A mass of nervous tissue, composed principally of nerve-cell
bodies, usually lying outside the central nervous system.
GASTROINTESTINAL:
Relating to the stomach and intestines.
GENE:
1. A unit of DNA that carries information for the biosynthesis
of a specific product (in the cell).
2. Ultimate unit by which
inheritable characteristics are transmitted to succeeding
generations in all living organisms. Genes are contained by,
and arranged along the length of, the chromosome. The gene is
composed of deoxyribonucleic acid (DNA). Each chromosome of
each species has a definite number and arrangement of genes,
which govern both the structure and metabolic functions of the
cells and thus of the entire organism. They provide
information for the synthesis of enzymes and other proteins
and specify when these substances are to be made. Alteration
of either gene number or arrangement can result in mutation (a
change in the inheritable traits).
See also DNA.
GENETIC ENGINEERING:
Group of new research techniques that manipulate the DNA
(genetic material) of cells. The gene-splicing technique,
which produces recombinant DNA, is a method of transporting
selected genes from one species to another. For example, in
this technique, the genes, which are actually portions of
molecules of DNA, are removed from the donor (insect, plant,
mammal or other organism) and spliced into the genetic
material of a virus; then the virus is allowed to
infect recipient bacteria. In this way the bacteria
become recipients of both viral and foreign genetic
material. When the virus replicates within the bacteria,
large quantities of the foreign as well as viral material are
made.
GENITOURINARY TRACT:
The system of organs comprising the organs concerned with the
production and excretion of urine and those concerned with
reproduction. Also called genitourinary system, urogenital
system, urogenital tract.
GENOME:
The complete set of genes in the chromosomes of each cell of
a particular organism. See also Gene.
GERMINAL CENTERS:
Structures within lymphoid tissues that contain FDCs in which
immune responses are initiated. See also Follicular Dendritic
Cells.
GIARDIASIS:
A common protozoal infection of the small intestine spread via
contaminated food and water and direct person-to-person
contact.
GLYCOPROTEIN:
A conjugated protein in which the nonprotein group is a
carbohydrate (i.e., a sugar molecule); also called
glucoprotein.
GP41:
Glycoprotein 41, a protein embedded in the outer envelope of
HIV. Plays a key role in HIV's infection of CD4+ T cells by
facilitating the fusion of the viral and the cell membranes.
See also CD4 (T4) or CD4+ Cells; Envelope.
GP120:
Glycoprotein 120, a protein that protrudes from the surface of
HIV and binds to CD4+ T cells. See also CD4 (T4) or CD4+
Cells.
GP160:
Glycoprotein 160, a precursor of HIV envelope proteins gp41
and gp120.
GRANULOCYTE:
A cell type of the immune system filled with granules of toxic
chemicals that enable them to digest microorganisms.
Basophils, neutrophils, and eosinophils are examples of
granulocytes. See also Basophil; Eosinophil; Neutrophil.
GUILLIAN-BARRE SYNDROME:
1. An acute febrile (i.e., with fever) polyneuritis.
2. An
acute disease that produces bilateral (i.e., affecting the
right and left sides of the body) weakness or paralysis, most
commonly in the legs and feet. See also Polyneuritis.
H
HAIRY LEUKOPLAKIA:
A whitish, slightly raised lesion that appears on the side of
the tongue. Thought to be related to Epstein-Barr virus
infection, it was not observed before the HIV epidemic. See
also Epstein-Barr Virus.
HALF-LIFE:
The time required for half the amount of a drug to be
eliminated from the body.
HEALTH RESOURCES AND SERVICES ADMINISTRATION (HRSA):
A Public Health Service agency that administers (among others)
education and training programs for health care providers and
community service workers who care for AIDS patients. HRSA
also administers programs to demonstrate how communities can
organize their health care resources to develop an integrated,
comprehensive system of care for those with AIDS and HIV
infection. See also Public Health Service.
HELPER/SUPPRESSOR RATIO:
(Of T cells). T cells are lymphocytes (white blood cells) that
are formed in the thymus and are part of the immune
system; they have been found to be abnormal in people
with AIDS. The normal ratio of helper T cells (CD4+ cells)
to suppressor T cells (CD8+ cells) is approximately 2:1. This
becomes inverted in people with AIDS, but may be abnormal for
a host of other temporary reasons. See also CD4 (T4) or CD4+
Cells; CD8 (T8) Cells; Lymphocyte; Thymus.
HELPER T CELLS:
See CD4 (T4) or CD4+ Cells.
HEMATOCRIT:
A laboratory measurement that determines the percentage of
packed red blood cells in a given volume of blood.
HEMATOTOXIC:
Poisonous to the blood or bone marrow.
HEMOGLOBIN:
The component of red blood cells that carries oxygen.
HEMOLYSIS:
The rupture of red blood cells.
HEMOPHILIA:
An inherited disease that prevents the normal clotting of
blood.
HEPATIC:
Pertaining to the liver.
HEPATITIS:
An inflammation of the liver caused by certain viruses and
other factors such as alcohol abuse, some medications
and trauma. Although many cases of hepatitis are not a
serious threat to health, the disease can become chronic and
can sometimes lead to liver failure and death. There are four
major types of viral hepatitis: (a) hepatitis A, caused by
infection with the hepatitis A virus; (b) hepatitis B, caused
by infection with the hepatitis B virus (HBV), which is most
commonly passed on to a partner during intercourse, especially
during anal sex, as well as through sharing drug needles; (c)
non-A, non-B hepatitis, caused by the hepatitis C virus, which
appears to be spread through sexual contact as well as through
sharing drug needles (another type of non-A, non-B hepatitis
is caused by the hepatitis E virus, principally spread through
contaminated water) (d) delta hepatitis occurs only in people
who are already infected with HBV and is caused by the HDV
virus; most cases of delta hepatitis occur among people who
are frequently exposed to blood and blood products such as
people with hemophilia. See also Hemophilia.
HERPES SIMPLEX VIRUS I (HSV-I):
A virus that causes cold sores or fever blisters on the mouth
or around the eyes, and can be transmitted to the
genital region. The latent virus can be reactivated by stress,
trauma, other infections or suppression of the immune system.
HERPES SIMPLEX VIRUS II (HSV-II):
A virus causing painful sores of the anus or genitals that may
lie dormant in nerve tissue. It can be reactivated to produce
the symptoms. HSV-II may be transmitted to a neonate (newborn
child) during birth from an infected mother, causing
retardation and/or other serious complications. HSV-II is a
precursor of cervical cancer. See also Cervical Cancer.
HERPES VARICELLA ZOSTER VIRUS:
The varicella virus causes chicken pox in children and may
reappear in adults as herpes zoster. Also called shingles,
herpes zoster consists of very painful blisters on the skin
that follow nerve pathways.
HISTOCOMPATIBILITY TESTING:
A method of matching the self antigens on the tissues of a
transplant donor with those of a recipient. The closer
the match, the better the chance that the transplant will not
be rejected. See also Human Leukocyte Antigens.
HISTOPLASMOSIS:
A fungal infection, commonly of the lungs, caused by the
fungus Histoplasma capsulatum. This fungus is commonly found
in bird and/or bat droppings in the Ohio and Mississippi
Valley region, the Caribbean Islands and in parts of
the Northeast US. It is spread by breathing in the spores
of the fungus. The most definitive test for the fungus has
been from fungal stains and bone marrow cultures. Blood
testing has proved to be less reliable. In areas where H.
capsulatum is prevalent, 80 percent or more of the population
has been exposed to infection through breathing in airborne
spores produced by the fungus. People with severely damaged
immune systems, such as those with AIDS, are vulnerable to a
very serious disease known as progressive disseminated
histoplasmosis. Nationwide, about 5 percent of people with
AIDS have histoplasmosis, but in geographic areas where the
fungus is common, people with AIDS are at high risk for
disseminated histoplasmosis.
HIV-1:
See Human Immunodeficiency Virus Type 1.
HIV-2:
See Human Immunodeficiency Virus Type 2.
HIV DISEASE:
Characterized by a gradual deterioration of immune function.
During the course of infection, crucial immune cells called
CD4+ T cells are disabled and killed, and their numbers
progressively decline. CD4+ T cells play a crucial role in the
immune response, signaling other cells in the immune system to
perform their special functions. See also Acquired
Immunodeficiency Syndrome; CD4 (T4) or CD4+ Cells; Human
Immunodeficiency Virus Type 1.
HIV-RELATED TUBERCULOSIS:
See Tuberculosis.
HLA:
See Human Leukocyte Antigens.
HODGKIN'S DISEASE:
See Lymphoma.
HOMOLOGOUS:
Similar in appearance or structure, but not necessarily
function.
HOST:
A plant or animal harboring another organism.
HOST FACTORS:
The body's potent mechanisms for containing HIV, including
immune system cells called CD8+ T cells, which may prove more
effective than any antiretro-viral drug in controlling HIV
infection. See also Antiretroviral Agents; CD8 (T8) Cells.
HRSA:
See Health Resources and Services Administration.
HUMAN IMMUNODEFICIENCY VIRUS TYPE 1 (HIV-1):
1. The retrovirus isolated and recognized as the etiologic
(i.e., causing or contributing to the cause of a disease)
agent of AIDS. HIV-1 is classified as a lentivirus in a
subgroup of retroviruses. See also Lentivirus; Retrovirus.
2.
Most viruses and all bacteria, plants and animals have genetic
codes made up of DNA, which uses RNA to build specific
proteins. The genetic material of a retrovirus such as HIV is
the RNA itself. HIV inserts its own RNA into the host cell's
DNA, preventing the host cell from carrying out its natural
functions and turning it into an HIV virus factory.
See also
DNA; Ribonucleic Acid.
HUMAN IMMUNODEFICIENCY VIRUS TYPE 2 (HIV-2):
A virus closely related to HIV-1 that has been found to cause
immune suppression. Most commonin Africa.
HUMAN LEUKOCYTE ANITGENS (HLA):
Markers that identify cells as "self" and prevent the immune
system from attacking them.
HUMAN PAPILLOMA VIRUS (HPV):
A virus that is the cause of warts of the hands and feet, as
well as lesions of the mucous membranes of the oral, anal and
genital cavities. More than 50 types of HPV have been
identified, some of which are associated with cancerous and
precancerous conditions. The virus can be transmitted through
sexual contact and is a precursor to cancer of the cervix.
There is no specific cure for an HPV infection, but the virus
often can be controlled by podophyllin (medicine derived from
the roots of the plant Podophyllum peltatum) or interferon,
and the warts can be removed by cryosurgery, laser treatment
or conventional surgery. See also Cervical Cancer; Condyloma.
HUMORAL IMMUNITY:
The branch of the immune system that relies primarily on
antibodies.See also Antibodies; Cell-Mediated Immunity.
HYBRID:
An offspring produced from mating plants or animals from
different species, varieties or genotypes.
HYBRIDOMA:
A hybrid cell produced by the fusion of an antibody-producing
lymphocyte with a tumor cell. Hybridomas are used in the
production of monoclonal antibodies. See also Hybrid;
Lymphocyte; Monoclonal Antibodies.
HYPERPLASIA:
Abnormal increase in the elements composing a part (as tissue
cells).
HYPOGAMMAGLOBULINEMIA:
Abnormally low levels of immunoglobulins. See also Antibodies.
HYPOTHESIS:
A tentative statement or supposition that may then be tested
through research.
HYPOXIA:
Reduction of oxygen supply to tissue.
I
IDIOPATHIC:
Without a known cause.
IDIOTYPES:
The unique and characteristic parts of an antibody's variable
region, which can themselves serve as antigens. See also
Antibodies; Antigen.
IHS:
See Indian Health Service.
IMMUNE COMPLEX:
Clusters formed when antigens and antibodies bind together.
IMMUNE DEFICIENCY:
A breakdown or inability of certain parts of the immune system
to function, thus making a person susceptible to certain
diseases that they would not ordinarily develop.
IMMUNE RESPONSE:
The activity of the immune system against foreign substances.
IMMUNE SYSTEM:
The complex functions of the body that recognize foreign
agents or substances, neutralize them and recall the response
later when confronted with the same challenge.
IMMUNE THROMBOCYTOPENIC PURPURA (ITP):
Also Idiopathic Immune Thrombocyto-penic Purpura. A condition
in which the body produces antibodies against the platelets in
the blood, which are cells responsible for blood clotting. ITP
is very common in HIV-infected people. See also Antibodies;
Platelets.
IMMUNITY:
A natural or acquired resistance to a specific disease.
Im-munity may be partial or complete, long-lasting or
temporary.
IMMUNOCOMPETENT:
1. Capable of developing an immune response.
2. Possessing a
normal immune system.
IMMUNODEFICIENCY:
A deficiency of immune response or a disorder characterized by
deficient immune response; classified as antibody (B cell),
cellular (T cell), combined deficiency or phagocytic
dysfunction disorders.
IMMUNOGEN:
A substance, also called an antigen, capable of provoking an
immune response. See also Antigen.
IMMUNOGENICITY:
The ability of an antigen or vaccine to stimulate an immune
response. See also Antigen.
IMMUNOGLOBULIN:
See Antibodies.
IMMUNOLOGICAL SURVEILLANCE or IMMUNOSURVEILLANCE:
See Surveillance.
IMMUNOMODULATOR:
Any substance that influences the immune system.
IMMUNOSTIMULANT:
Any agent or substance that triggers or enhances the body's
defense; also called immunopotentiators.
IMMUNOSUPPRESSION:
A state of the body in which the immune system is damaged and
does not perform its normal functions. Immunosuppression may
be induced by drugs or result from certain disease processes,
such as HIV infection. See also Immune System.
IMMUNOTHERAPY:
Treatment aimed at reconstituting an impaired immune system.
See also Immune System.
IMMUNOTOXIN:
A plant or animal toxin (i.e., poison) that is attached to a
monoclonal antibody and used to destroy a specific target
cell. See also Antibiotic; Monoclonal Antibody.
INCIDENCE:
The number of new cases occurring in a given population over
a certain period of time.
INCLUSION/EXCLUSION CRITERIA:
The medical or social standards determining whether a person
may or may not be allowed to enter a clinical trial.
For example, some trials may not allow people with chronic
liver disease or with certain drug allergies; others may
exclude men or women, or only include people with a lowered
T-cell count.
INCUBATION PERIOD:
The time interval between the initial exposure to infection
and appearance of the first symptom or sign of disease.
IND:
See Investigational New Drug.
INDIAN HEALTH SERVICE (IHS):
A Public Health Service agency providing a comprehensive
health service delivery system for American Indians and Alaska
Natives. See also Public Health Service.
INFECTION:
The state or condition in which the body (or part of the body)
is invaded by an infectious agent (e.g., a bacterium, fungus
or virus), which multiplies and produces an injurious effect
(active infection). As related to HIV: Infection typically
begins when HIV encounters a CD4+ cell. The HIV surface
protein gp120 binds tightly to the CD4 molecule on the cell's
surface. The membranes of the virus and the cell fuse, a
process governed by gp41, another surface protein. The viral
core, containing HIV's RNA, proteins and enzymes, is released
into the cell. See CD4 (T4) or CD4+ Cells; gp41; gp120.
INFECTIOUS:
Capable of being transmitted by infection, with or without
actual contact. See also Infection.
INFORMED CONSENT:
Type of protection available to people considering entering a
drug trial. Before entering the trial, participants must sign
a consent form that contains an explanation of:
(a) why the
research is being done,
(b) what researchers want to
accomplish,
(c) what will be done during the trial and for
how long,
(d) what risks are in the trial,
(e) what benefits
can be expected from the trial,
(f) what other treatments are
available, and
(g) the participant's right to leave the trial
at any time.
See also Clinical Trial.
INOCULATION:
The introduction of a substance (inoculum; e.g., a vaccine,
serum or virus) into the body to produce or to increase
immunity to the disease or condition associated with
the substance. See also Vaccine.
INSTITUTIONAL REVIEW BOARD (IRB):
1. A committee of physicians, statisticians, community
advocates and others that ensures that a clinical trial is
ethical and that the rights of study participants are
protected. All clinical trials in the United States must
be approved by an IRB before they begin. See also Clinical
Trial.
2. Every institution that conducts or supports
biomedical or behavioral research involving human subjects
must, by federal regulation, have an IRB that initially
approves and periodically reviews the research so as to
protect the rights of human subjects.
INTEGRASE:
An HIV enzyme used by the virus to integrate its genetic
material into the host cell's DNA. See also DNA; Enzyme.
INTEGRATION:
The process by which the different parts of an organism are
made a functional and structural whole, especially through the
activity of the nervous system and of hormones. As related to
HIV: The process by which the viral DNA migrates to the cell's
nucleus, where it is spliced into the host's DNA with the help
of viral integrase. Once incorporated, HIV DNA is called the
provirus and is duplicated together with the cell's genes
every time the cell divides. Recent reports suggest that HIV's
DNA also can integrate into the DNA of nondividing cells such
as macro-phages and brain and nerve cells. See also Integrase;
Macrophage.
INTENT TO TREAT:
Analysis of clinical trial results that includes all data from
patients in the groups to which they were randomized (i.e.,
assigned through random distribution) even if they never
received the treatment. See also Clinical Trial.
INTERFERON:
A general term used to describe a family of 20-25 proteins
that cause a cell to become resistant to a wide variety of
viruses. They are produced by cells infected by almost any
virus.
INTERLEUKIN-2 (IL-2):
One of a family of molecules that control the growth and
function of many types of lymphocytes. Interleukin-2 is an
immune system protein produced in the body by T cells. It has
potent effects on the proliferation, differentiation and
activity of a number of immune system cells, including T
cells, B cells and natural killer cells. Commercially, IL-2 is
produced by recombinant DNA technology and is approved by the
Food and Drug Administration for the treatment of metastatic
renal (i.e., kidney) cell cancer. Studies have shown that in
the test tube, addition of IL-2 can improve some of the
immunologic functions that are abnormal in HIV-infected
patients. In addition, IL-2 is a growth factor for T cells,
causing them to increase in number. In a clinical study with
IL-2, it was found that in a small number of HIV-infected
patients, IL-2 boosted levels of CD4+ T cells (i.e., the
infection-fighting white blood cells normally destroyed during
HIV infection) for more than two years, a far longer time than
typically seen with currently available anti-HIV drugs. See
also Biotechnology; B Lymphocytes; Genetic Engineering; Killer
T Cells; Lymphocyte; T Cells.
INTERSTITIAL:
Relating to or situated in the small, narrow spaces between
tissues or parts of an organ.
INTRAMUSCULAR:
Injected directly into a muscle.
INTRATHECAL:
Injected into the fluid surrounding the spinal cord.
INTRAVENOUS (IV):
Of or pertaining to the inside of a vein, as of a thrombus, or
an injection, infusion or catheter.
INTRAVITREAL:
Within the eye.
INVESTIGATIONAL NEW DRUG (IND):
The status of an experimental drug after the Food and Drug
Administration agrees that it can be tested in people.
IN VITRO:
("In glass"). An artificial environment created outside a
living organism (e.g., a test tube or culture plate) used in
experimental research to study a disease or process.
IN VIVO:
("In life"). Studies conducted within a living organism (e.g.,
animal or human studies).
IRB:
See Institutional Review Board.
ISOLATE:
An individual (as a spore or a single organism), viable part
of an organism (as a cell) or a strain that has been isolated
(as from diseased tissue, contaminated water or the air).
Also, a pure culture produced from such an isolate. A
particular strain of HIV taken from a patient.
ITP:
See Immune Thrombocytopenic Purpura.
K
KAPOSI'S SARCOMA:
1. A previously uncommon form of cancer that attacks the
connective tissue, bones, cartilage and muscles of the body.
The cancer may spread and also attack the eyes. If the
cancerous area is near the surface of the skin, lesions inches
in length may develop. This disease was initially seen only in
elderly men and natives of Central Africa. Experimental work
has shown that the AIDS-related Kaposi's sarcoma and the
Central African variety respond differently to some types of
medications. Radiotherapy and chemotherapy are usually
recommended.
2. A type of cancer characterized by abnormal
growths of blood vessels that develop into purplish or brown
lesions. It is suspected that the cause of Kaposi's sarcoma is
a newly found herpes virus.
KARNOFSKY SCORE:
A subjective score between 0-100, assigned by a physician to
describe a patient's ability to perform common tasks.
KILLER T CELLS:
Killer cells infected with HIV or other viruses or transformed
by cancer. Also known as cytotoxic T cells (or cytotoxic T
lymphocytes). See also Null Cell; T Cells.
KUPFFER CELLS:
Specialized macrophages in the liver. See also Macrophage.
L
LAI:
A group of closely related HIV isolates that includes the LAV,
IIIB and BRU strains of HIV. Used in HIV vaccine development.
See also Isolate.
LAK CELLS:
Lymphocytes transformed in the laboratory into lymphokine
activated killer cells, which attack tumor cells. See also
Lymphocyte; Lymphokines.
LANGERHANS CELLS:
Dendritic cells in the skin that pick up an antigen and
transport it to the lymph nodes. See also Antigen; Dendritic
Cells; Lymph Nodes.
LAS:
See Lymphadenopathy Syndrome.
LATENCY:
The period when an organism (i.e., a virus or a bacterium) is
in the body and not producing any ill effects. See also
Clinical Latency.
LAV:
Lymphadenopathy Associated Virus (see Human
Immunodeficiency
Virus Type I).
LENTIVIRUS:
"Slow" virus characterized by a long interval between
infection and the onset of symptoms. HIV is a lentivirus as is
the simian immunodeficiency virus (SIV), which infects
nonhuman primates. See also Simian Immunodeficiency Virus.
LESION:
A general term to describe an area of altered tissue (e.g.,
the infected patch or sore in a skin disease).
LEUKOCYTES:
All white blood cells.
LEUKOPENIA:
A decrease in the number of white blood cells. The threshold
value for leukopenia is usually taken as less than 5000 white
blood cells per cubic millimeter of blood.
LIP:
See Lymphoid Interstitial Pneumonitis.
LIPID:
Any of a group of fats and fat-like compounds, including
sterols, fatty acids and many other substances.
LIPOSOMES:
A spherical particle in an aqueous (watery) medium (e.g.,
inside a cell) formed by a lipid bilayer enclosing an aqueous
compartment. See also Lipid.
LONG TERMINAL REPEAT SEQUENCE (LTR):
A component of the AIDS genome. See also Genome.
LONG-TERM NON-PROGRESSORS:
Individuals who are HIV-infected for seven or more years, have
stable CD4+ T cell counts of 600 or more cells per cubic
millimeter of blood, no HIV-related diseases and no previous
antiretroviral therapy. Data suggest that this phenomenon is
associated with the maintenance of the integrity of the
lymphoid tissues and with less virus-trapping in the lymph
nodes than seen in other HIV-infected individuals.
LTR:
See Long Terminal Repeat Sequence.
LUMBAR:
Of, relating to or constituting the loins or the vertebrae
between the thoracic vertebrae and the sacrum region. The
sacrum is the triangular bone made up of five fused vertebrae
and forming the posterior section of the pelvis. The thorax is
the part of the human body between the neck and the diaphragm,
partially encased by the ribs and containing the heart and
lungs; the chest.
LUMBAR PUNCTURE:
A procedure in which fluid from the subarachnoid space in the
lumbar region is tapped for examination. Also known as spinal
tap. See also Lumbar; Subarachnoid Space.
LYMPH:
A transparent, slightly yellow fluid that carries lymphocytes.
Lymph is derived from tissue fluids collected from all parts
of the body and is returned to the blood via lymphatic
vessels. See also Lymphatic Vessels; Lymphocyte.
LYMPHADENOPATHY SYNDROME (LAS):
Swollen, firm and possibly tender lymph nodes. The cause may
range from an infection such as HIV, the flu, mononucleosis or
lymphoma (cancer of the lymph nodes). See also Lymph Nodes.
LYMPHATIC VESSELS:
A bodywide network of channels, similar to the blood vessels,
that transport lymph to the immune organs and into the
bloodstream. See also Lymph.
LYMPH NODES:
Small, bean-sized organs of the immune system, distributed
widely throughout the body. Lymph fluid is filtered through
the lymph nodes in which all types of lymphocytes take up
temporary residence. Antigens that enter the body find their
way into lymph or blood and are filtered out by the lymph
nodes or spleen respectively, for attack by the immune system.
See also Antigen; Lymphocyte.
LYMPHOCYTE:
A white blood cell. Present in the blood, lymph and lymphoid
tissue. See also B Lymphocytes; Lymph; T Cells.
LYMPHOID INTERSTITIAL PNEUMONITIS (LIP):
A form of pneumonia that involves the lower lobes (of the
lungs) with extensive alveolar infiltration by mature
lymphocytes, plasma cells and histiocytes. LIP is associated
with AIDS, dysproteinemia and other conditions. See also
Alveolar; Lymphocyte; Macrophage.
LYMPHOID ORGANS:
Include tonsils, adenoids, lymph nodes, spleen and other
tissues. Act as the body's filtering system, trapping
invaders(i.e., foreign particles from bacteria, viruses, etc.)
and presenting them to squadrons of immune cells that
congregate there. Within these lymphoid tissues, immune
activity is concentrated in regions called germinal centers,
where the thread-like tentacles of follicular dendritic cells
(FDCs) form networks that trap invaders. See also Follicular
Dendritic Cells; Lymph Nodes.
LYMPHOKINES:
1. Products of the lymphatic cells that stimulate the
production of disease-fighting agents and the activities of
other lymphatic cells. Among the lymphokines are gamma
interferon and interleukin-2. See also Gamma Interferon;
Interleukin-2.
2. Nonanti-body mediators of immune
responses,
released by activated lymphocytes. See also Immune Response;
Lymphocyte.
LYMPHOMA:
Cancer of the lymphoid tissues. Lymphomas are often described
as being large or small cell types, cleaved or noncleaved,
diffuse or nodular. The different types often have different
prognoses (i.e., prospect of survival or recovery). Some of
these lymphomas are named after the physicians who first
described them (e.g., Burkitt's lymphoma, Hodgkin's disease).
Lymphomas can also be referred to by the organ where they are
active such as CNS lymphomas, which are in the central nervous
system, and GI lymphomas, which are in the gastrointestinal
tract. The types of lymphomas most commonly associated with
HIV infection are called non-Hodgkin's lymphomas or B cell
lymphomas. In these types of cancers, certain cells of the
lymphatic system grow abnormally. They divide rapidly, growing
into tumors.
LYSIS:
Rupture and destruction of a cell.
M
MACROPHAGE:
A large immune cell that devours invading pathogens and other
intruders. Stimulates other immune cells by presenting them
with small pieces of the invader. Macrophages can harbor large
quantities of HIV without being killed, acting as reservoirs
of the virus.
MAGNETIC RESONANCE IMAGING (MRI):
Medical imaging that uses radiofrequency radiation as its
source. MRI is a noninvasive diagnostic technique that can
provide information on the form and function of internal
tissues and organs of the body.
MAJOR HISTOCOMPATIBILITY COMPLEX (MHC):
A group of genes that control aspects of the immune response.
The products of these genes, the histocompatibility antigens,
are present on every cell of the body and serve as markers to
distinguish self from nonself cells. See also Antigen;
Histocompatibility Testing.
MALABSORPTION SYNDROME:
Decreased intestinal absorption resulting in loss of appetite,
muscle pain and weight loss.
MALAISE:
A generalized, nonspecific feeling of discomfort.
MAST CELL:
A granulocyte found in tissue. The contents of the mast cells,
along with those of basophils, are responsible for the
symptoms of allergy. See also Basophil; Granulocyte.
MEAN:
The arithmetic average, or the sum of all the values divided
by the number of values.
MEDIAN:
The middle number in a sequence of numbers, taken as the
average of the two middle numbers when the sequence has an
even number of numbers (e.g., 4 is the median of 1, 3, 4, 8,
9).
MEMORY CELLS:
A subset of T lymphocytes that have been exposed to specific
antigens and can then proliferate (i.e., reproduce) on
subsequent immune system encounters with the same antigen.
See
also Antigen; T Cells.
MESSENGER RNA:
Also referred to as mRNA. An RNA (ribonucleic acid) that
carries the genetic code for a particular protein from the
nuclear DNA (i.e., the DNA in the cell's nucleus) to a
ribosome in the cytoplasm and acts as a template, or pattern,
for the formation of that protein. See also Cytoplasm;
Ribosome.
METABOLISM:
The sum of the processes by which a particular substance is
handled (as by assimilation and incorporation, or by
detoxification and excretion) in the living body.
METABOLITE:
Any substance produced by metabolism or by a metabolic
process. See also Metabolism.
METASTASIS:
Transfer of a disease-producing agent (e.g., cancer cells or
bacteria) from an original site of disease to another part of
the body with development of a similar lesion in the new
location (e.g., spread of cancer from an original site to
other sites in the body).
MHC:
See Major Histocompatibility Complex.
MICROBES:
Microscopic living organisms, including bacteria, protozoa and
fungi.
MICROBICIDE:
An agent (e.g., a chemical or antibiotic) that destroys
microbes. See also Microbes.
MICROENCAPSULATED:
Surrounded by a thin layer of protection. A means of
protecting a drug or vaccine from rapid breakdown.
MICROSPORIDIOSIS:
Disease resulting from infection with a protozoal pathogen
from the Microsporida order. See also Pathogen; Protozoa.
MN:
A strain of HIV used in vaccine development.
MOLECULE:
The smallest particle of a compound that has all the chemical
properties of that compound. Molecules are made up of two or
more atoms, either of the same element or of two or more
different elements. Ionic compounds, such as common salt, are
made up not of molecules, but of ions arranged in a
crystalline structure. Unlike ions, molecules carry no
electrical charge. Molecules differ in size and molecular
weight as well as in structure.
MOLLUSCUM CONTAGIOSUM:
A disease of the skin and mucous membranes caused by a
poxvirus. It is characterized by scattered flesh-toned white
papules. The disease most frequently occurs in children and
adults with impaired immune response. It is transmitted from
person to person by direct or indirect contact and lasts up to
three years.
MONOCLONAL ANTIBODIES:
Antibodies produced by a hybridoma or antibody-producing cell
source for a specific antigen. Monoclonal antibodies are
useful as a tool for identifying specific protein molecules.
See also Antibodies; Antigen; Hybridoma.
MONOCYTE:
A large white blood cell that ingests microbes or other cells
and foreign particles. When a monocyte enters tissues, it
develops into a macrophage. See also Macrophage.
MONOVALENT VACCINE:
A vaccine that is specific for only one antigen. See also
Antigen.
MRI:
See Magnetic Resonance Imaging.
MUCOCUTANEOUS:
Anything that concerns or pertains to mucous membranes and the
skin (e.g., mouth, vagina, lips, anal area). See also Mucous
Membrane.
MUCOSA:
See Mucous Membrane.
MUCOSAL IMMUNITY:
Resistance to infection across the mucous membranes. Dependent
on immune cells and antibodies present in the lining of the
urogenital tract, gastrointestinal tract and other parts of
the body exposed to the outside world. See also Antibodies;
Genitourinary Tract; Mucous Membrane.
MUCOUS MEMBRANE:
A moist layer of tissue that lines body cavities or passages
that have an opening to the external world (e.g., the lining
of the mouth, nostrils or vagina).
MUTATION:
In biology, a sudden change in a gene or unit of hereditary
material that results in a new inheritable characteristic. In
higher animals and many higher plants, a mutation may be
transmitted to future generations only if it occurs in germ-or
sex cell-tissue; body cell mutations cannot be inherited.
Changes within the chemical structure of single genes may be
induced by exposure to radiation, temperature extremes and
certain chemicals. The term mutation may also be used to
include losses or rearrangements of segments of chromosomes,
the long strands of genes. Drugs such as colchicine double the
normal number of chromosomes in a cell by interfering with
cell division. Mutation, which can establish new traits in a
population, is important in evolution. As related to HIV: HIV
mutates rapidly. During the course of HIV disease, viral
strains may emerge in an infected individual that differ
widely in their ability to infect and kill different cell
types, as well as in their rate of replication. Strains of HIV
from patients with advanced disease appear to be more virulent
and infect more cell types than strains obtained earlier from
the same individual. See also Gene.
MYCOBACTERIUM:
Any bacterium of the genus Mycobacterium or a closely related
genus.
MYCOBACTERIUM AVIUM COMPLEX (MAC):
1. A common opportunistic infection caused by two very similar
mycobacterial organisms, Mycobacterium avium and
Mycobacterium
intracellulare.
2. A bacterial infection that can be localized
(limited to a specific organ or area of the body) or
disseminated throughout the body. It is a life-threatening
disease, although new therapies offer promise for both
prevention and treatment. MAC disease is extremely rare in
people who are not infected with HIV.
See also Opportunistic
Infection.
MYCOPLASMA:
1. Smallest free-living organisms known to infect humans.
Mycoplasma cause a variety of illnesses, especially of the
lungs and sexual organs.
2. Any microorganism of the genus
Mycoplasma, also called pleuropneumonia-like organism.
MYCOSIS:
Any disease caused by a fungus. See also Fungus.
MYELIN:
A substance that sheathes nerve cells, acting as an electric
insulator that facilitates the conduction of nerve impulses.
MYELOSUPPRESSION:
Impairment of the blood cell-producing function of the bone
marrow.
MYELOTOXIC:
Destructive to bone marrow.
N
NATIONAL AIDS CLEARINGHOUSE:
See CDC National AIDS Clearinghouse.
NATIONAL CANCER INSTITUTE (NCI):
An NIH institute with the overall mission of conducting and
supporting research, training and disseminating health
information with respect to the causes, diagnosis and
treatment of cancer. NCI also performs these functions for HIV
infections and associated diseases. See also National
Institutes of Health.
NATIONAL INSTITUTE OF ALLERGY AND INFECTIOUS DISEASES
(NIAID):
An NIH institute that conducts and supports research to study
the causes of allergic, immunologic and infectious diseases,
and to develop better means of preventing, diagnosing and
treating illnesses. NIAID is responsible for the federally
funded, national basic research program in AIDS. See also
National Institutes of Health.
NATIONAL INSTITUTE OF CHILD HEALTH AND HUMAN
DEVELOPMENT (NICHD):
An NIH institute that conducts and supports research on the
reproductive, developmental and behavioral processes that
determine the health of children, adults, families and
populations. Thus, NICHD supports clinical research related to
the transmission of HIV from infected mothers to their
offspring, the progression of disease in HIV-infected infants
and children, and the testing of potential therapies and
preventatives for this population. See also National
Institutes of Health.
NATIONAL INSTITUTES OF HEALTH (NIH):
A multi-institute agency of the Public Health Service, NIH is
the federal focal point for health research. It conducts
research in its own laboratories and supports research in
universities, medical schools, hospitals and research
institutions throughout this country and abroad. See also
Public Health Service.
NATIONAL LIBRARY OF MEDICINE (NLM):
An NIH institute, NLM is one of three US national libraries.
It is the world's largest research library in a single
scientific and professional field (i.e., medicine). NLM
provides (among others) electronic and print information
services relating to HIV/AIDS, including AIDSLINE, AIDSTRIALS,
AIDSDRUGS and the AIDS Bibliography. See also AIDS
Bibliography; AIDSDRUGS; AIDSLINE; AIDSTRIALS; National
Institutes of Health.
NATURAL HISTORY STUDY:
Study of the natural development of something (such as an
organism or a disease) over a period of time.
NATURAL KILLER CELLS:
(NK cells). A type of lymphocyte that does not carry the
markers to be B cells or T cells. Like cytotoxic T cells, they
attack and kill tumor cells and protect against a wide variety
of infectious microbes. They are "natural" killers because
they do not need additional stimulation or need to recognize
a specific antigen in order to attack and kill. Persons with
immunodeficiences such as those caused by HIV infection have
a decrease in "natural" killer cell activity. See also
Antigen; B Lymphocytes; Cytotoxic; Lymphocyte; Null Cell; T
Cells.
NCI:
See National Cancer Institute.
NEBULIZED:
See Aerosolized.
NECROLYSIS:
Shedding of surface components of tissue, such as cells from
internal body surfaces, due to death of a portion of tissue.
NEF:
One of the regulatory genes of the HIV virus. Three HIV
regulatory genes-tat, rev and nef-and three so-called
auxiliary genes-vif, vpr and vpu-contain information necessary
for the production of proteins that control the virus's
ability to infect a cell, produce new copies of the virus or
cause disease. See also rev; tat.
NEONATAL:
Concerning the first four weeks of life after birth.
NEOPLASM:
An abnormal and uncontrolled growth of tissue; a tumor.
NEPHROTOXIC:
Poisonous to the kidneys.
NEURALGIA:
A sharp, shooting pain along a nerve pathway.
NEUROLOGICAL COMPLICATIONS OF AIDS:
See Central Nervous System (CNS) Damage.
NEUROPATHY:
The name given to a group of disorders involving nerves.
Symptoms range from a tingling sensation or numbness in the
toes and fingers to paralysis. It is estimated that 35 percent
of people with HIV disease have some form of neuropathy. A
"peripheral neuropathy" refers to the peripheral nerves
outside the spinal cord.
NEUTRALIZATION:
The process by which an antibody binds to specific antigens,
thereby "neutralizing" the microorganism. See also Antibodies;
Antigen.
NEUTRALIZING ANTIBODY:
An antibody that keeps a virus from infecting a cell, usually
by blocking receptors on the cell or the virus. See also
Antibodies; Receptor.
NEUTRALIZING DOMAIN:
The section of the HIV envelope protein gp120 that elicits
antibodies with neutralizing activities. See also Antibodies;
gp120.
NEUTROPENIA:
An abnormal decrease in the number of neutrophils (the most
common type of white blood cells) in the blood. The decrease
may be relative or absolute. Neutropenia is associated with
acute leukemia, infection, rheumatoid arthritis and other
conditions.
NEUTROPHIL:
Also called polymorphonuclear neutrophil (PMN). A white blood
cell that plays a central role in defense of a host against
infection. Neutrophils engulf and kill foreign microorganisms.
NIAID:
See National Institute of Allergy and Infectious Diseases.
NICHD:
See National Institute of Child Health and Human Development.
NIH:
See National Institutes of Health.
NLM:
See National Library of Medicine.
NON-HODGKIN'S LYMPHOMA:
See Lymphoma.
NSAID:
Nonsteroidal anti-inflammatory (i.e., counteracting
inflammation) drug.
NUCLEIC ACID:
Organic substance, found in all living cells, in which the
hereditary information is stored and from which it can be
transferred. Nucleic acid molecules are long chains that
generally occur in combination with proteins. The two chief
types are DNA (deoxyribonucleic acid), found mainly in cell
nuclei, and RNA (ribonucleic acid), found mostly in cytoplasm.
Each nucleic acid chain is composed of subunits called
nucleotides, each containing a sugar, a phosphate group, and
one of four bases: adenine (symbolized A), guanine (G),
cytosine (C) and thymine (T). RNA contains the sugar ribose
instead of deoxyribose and the base uracil (U) instead of
thymine. The specific sequences of nucleotides constitute the
cell's genetic information: Each three-nucleotide DNA sequence
specifies one particular amino acid. The long sequences of DNA
nucleotides thus correspond to the sequences of amino acids in
the cell's proteins. In order to be expressed as protein, the
genetic information is carried to the protein-synthesizing
machinery of the cell, usually in the cell cytoplasm. Forms of
RNA mediate this process. DNA not only provides information,
but also specifies its own exact replication. The cell
replicates its DNA by making a complementary copy of its exact
nucleotide sequence: T for every A, C for every G, G for every
C, A for every T. Although the triplet nucleotide code seems
to be universal, the actual sequences of the nucleotides vary
according to the species and individual. See also Gene;
Genetic Engineering; Mutation.
NUCLEOLI:
Bodies in the nucleus that become enlarged during protein
synthesis and contain the DNA template for ribosomal RNA. See
also Ribonucleic Acid; Ribosome.
NUCLEOSIDE ANALOG:
Nucleosides are related to nucleotides, the subunits of
nucleic acids; however, they do not carry the phosphate groups
of the nucleotides. Nucleoside analogs generally are synthetic
compounds similar to one of the components of DNA or RNA; a
general type of antiviral drug (e.g., acyclovir and AZT). See
also Acyclovir; AZT; Nucleic Acid.
NUCLEUS:
1. The central controlling body within a living cell, usually
a spherical unit enclosed in a membrane and containing genetic
codes for maintaining the life systems of the organism and for
issuing commands for growth and reproduction.
2. The
nucleus
of a cell is an organelle (i.e., a cellular organ) that is
essential to such cell functions as reproduction and protein
synthesis. It is composed of nuclear sap and a
nucleoprotein-rich network from which chromosomes and
nucleoli
arise and is enclosed in a definite membrane. See also
Nucleoli.
NULL CELL:
A lymphocyte that develops in the bone marrow and lacks the
characteristic surface markers of the B and T lymphocytes.
Null cells represent a small proportion of the lymphocyte
population. Stimulated by the presence of antibody, null cells
can attack certain cellular targets directly and are known as
"natural killer" or NK cells. See also Lymphocyte.
O
OCULAR:
Pertaining to the eye.
OPEN-LABEL TRIAL:
A clinical trial in which doctors and participants know which
drug or vaccine is being administered. See also Clinical
Trial.
OPPORTUNISTIC INFECTION:
1. An illness caused by an organism that usually does not
cause disease in a person with a normal immune system. People
with advanced HIV infection suffer opportunistic infections of
the lungs, brain, eyes and other organs.
2. Opportunistic
infections common in AIDS patients include Pneumocystis
carinii pneumonia, Kaposi's sarcoma, shigellosis,
histoplasmosis and other parasitic, viral, and fungal
infections, and some types of cancers.
See also
Histoplasmosis; Kaposi's Sarcoma; Pneumocystis carinii
Pneumonia.
OROPHARYNGEAL:
Relating to that division of the pharynx between the soft
palate and the epiglottis. Pharynx is a tube that connects the
mouth and nasal passages with the esophagus, the connection to
the stomach. Epiglottis is a thin, valvelike structure that
covers the glottis, the opening of the upper part of the
larynx (the part of the throat containing the vocal cords),
during swallowing.
OVARY:
Part of the female reproductive system. One of a pair of
female gonads (a gamete-producing gland) found on each side of
the lower abdomen, beside the uterus, in a fold of the broad
ligament. At ovulation, an egg is extruded from a follicle on
the surface of the ovary under the stimulation of certain
hormones.
P
p24:
1. Within the envelope of the HIV virus is a bullet-shaped
core made of another protein, p24, that surrounds the viral
RNA.
2. The p24 antigen test looks for the presence of this
protein in a patient's blood.
3. A positive result for the p24
antigen suggests active HIV replication. p24 found in the
peripheral blood is thought to also correlate with the amount
of virus in the peripheral blood. It is believed that there
are measurable levels of p24 when first infected with the
virus after which there is a strong antibody response to p24
in early disease. Low or unmeasurable levels of p24 may
indicate that the virus is in a dormant stage. Spikes in p24
levels may indicate that HIV has begun active replication.
PALLIATIVE:
A treatment that provides symptomatic relief, but not a cure.
PANCREAS:
A gland situated near the stomach that secretes a digestive
fluid into the intestine through one or more ducts and also
secretes the hormone insulin.
PANCREATITIS:
Inflammation of the pancreas that can produce severe pain and
debilitating illness. See also Pancreas.
PANCYTOPENIA:
Deficiency of all cell elements of the blood.
PANDEMIC:
A disease prevalent throughout an entire country, continent or
the whole world. See also Epidemic.
PAP SMEAR:
A method for the early detection of cancer and other
abnormalities of the female genital tract, especially of the
cervix and uterus, employing exfoliated cells (cells that have
been shed into vaginal fluid) and a special staining technique
for microscopic examination that differentiates diseased
tissue. Also known as Papanicolaou Smear after George
Papanicolaou, the American cytologist who developed this
method and published it in 1943. See also Cervix; Uterus.
PAPILLOMA:
1. A benign tumor (as a wart or condyloma) resulting from an
overgrowth of epithelial tissue on papillae of vascularized
connective tissue (as of the skin).
2. An epithelial tumor
caused by a virus. See also Condyloma; Epithelium.
PARALLEL TRACK:
A system of distributing experimental drugs to patients who
are unable to participate in ongoing clinical efficacy trials
and have no other treatment options. See also Clinical Trial.
PARASITE:
A plant or animal that lives and feeds on or within another
living organism; does not necessarily cause disease.
PARENCHYMA:
The tissue of an organ (as distinguished from supporting or
connective tissue).
PARENTERAL:
Not in or through the digestive system. For example,
parenteral can pertain to blood being drawn from a vein in the
arm or introduced into that vein via a transfusion
(intravenous), or to injection of medications or vaccines
through the skin (subcutaneous) or into the muscle
(intramuscular).
PARESTHESIA:
Any subjective sensation, experienced as numbness, tingling or
a "pins-and-needles" feeling.
PATHOGEN:
Any disease-producing microorganism or material.
PATHOGENESIS:
The origin and development of a disease.
PBMC:
See Peripheral Blood Mononuclear Cell.
PCP:
See Pneumocystis carinii Pneumonia.
PCR:
See Polymerase Chain Reaction.
PEER REVIEW:
The process by which new scientific or medical findings,
announced by one researcher, are reviewed by other scientists
or physicians before these findings are published.
PELVIC INFLAMMATORY DISEASE (PID):
A term used to describe infections of the uterus, the
fallopian tubes and the ovaries. PID is usually the result of
untreated sexually transmitted disease, primarily chlamydia or
gonorrhea. See also Fallopian Tubes; Ovary; Uterus.
PENTAMIDINE:
An approved antiprotozoal drug used for the treatment and
prevention of Pneumocystis carinii pneumonia (PCP) infection.
It can be delivered intravenously or intramuscularly or
inhaled as an aerosol. Aerosolized pentamidine is approved for
the prophylaxis of PCP in HIV-positive individuals with CD4+
counts below 200 per cubic millimeter or for those with prior
episodes of PCP. The drug is also known under the names Pentam
and NebuPent. See also Pneumocystis carinii Pneumonia.
PEPTIDE:
(Also polypeptide). Biochemical formed by the linkage of up to
about 50 amino acids to form a chain. Longer chains are called
proteins. The amino acids are coupled by a peptide bond, a
special linkage in which the nitrogen atom of one amino acid
binds to the carboxyl carbon atom of another. Many peptides,
such as the hormones vasopressin and ACTH, have physiological
or antibacterial activity. See also Amino Acids.
PERIANAL:
Around the anus.
PERINATAL:
Events that occur at or around the time of birth.
PERIPHERAL BLOOD MONONUCLEAR CELL (PBMC):
Cells in the bloodstream with one nucleus. See also Nucleus.
PERSISTENT GENERALIZED LYMPHADENOPATHY (PGL):
Chronic, diffuse, noncancerous lymph node enlargement.
Typically it has been found in those with immune system
disturbances who develop frequent and persistent bacterial,
viral and fungal infections.
PGL:
See Persistent Generalized Lymphadenopathy.
PHA:
See Phytohemagglutinin.
PHAGOCYTE:
A cell that is able to ingest and destroy foreign matter,
including bacteria.
PHAGOCYTOSIS:
The process of ingesting and destroying a virus or other
foreign matter by phagocyte. See also Macrophage; Monocyte.
PHARMACOKINETICS:
The processes (in a living organism) of absorption,
distribution, metabolism and excretion of a drug or vaccine.
PHS:
See Public Health Service.
PHYTOHEMAGGLUTININ (PHA):
A plant chemical used to stimulate the multiplication of white
blood cells.
PITUITARY GLAND:
Small, oval endocrine gland that lies at the base of the
brain. It is called the master gland because the other
endocrine glands depend on its secretions for stimulation. The
pituitary has two distinct lobes, anterior and posterior. The
anterior lobe secretes at least six hormones: human growth
hormone, which stimulates overall body growth;
ACTH(adrenocorticotropic hormone), which controls steroid
hormone secretion by the adrenal cortex; thyrotropic hormone,
which stimulates the activity of the thyroid gland; and three
gonadotropic hormones, which control growth and reproductive
activity of the gonads (ovaries and testes). The posterior
lobe secretes antidiuretic hormone, which causes water
retention by the kidneys, and oxytocin, which stimulates the
mammary glands to release milk and also causes uterine
contractions. An overactive pituitary during childhood can
cause gigantism; during adulthood, it can cause acromegaly.
Dwarfism results from pituitary deficiency in childhood. See
also Acromegaly.
PLACEBO:
An inactive substance against which investigational treatments
are compared for efficacy. See also Placebo Controlled Study.
PLACEBO CONTROLLED STUDY:
A method of investigation of drugs in which an inactive
substance (the placebo) is given to one group of patients,
while the drug being tested is given to another group. The
results obtained in the two groups are then compared.
PLACEBO EFFECT:
A physical or emotional change occurring after a substance is
taken or administered that is not the result of any special
property of the substance. The change may be beneficial,
reflecting the expectations of the patient and, often, the
expectations of the person giving the substance.
PLASMA:
That 10 percent of the blood that contains nutrients,
electrolytes (dissolved salts), gases, albumin, clotting
factors, wastes and hormones.
PLASMA CELLS:
Large antibody-producing cells that develop from B cells. See
also Antibodies; B Lymphocytes.
PLASMAPHERESIS:
The selective removal of certain proteins or antibodies from
the blood (followed by reinjection of the blood). This process
is sometimes used in the treatment of some peripheral
neuropathies and is an integral part of passive
immunotherapies for HIV. See also Neuropathy.
PLATELETS:
Active agents of inflammation when damage occurs to a blood
vessel. They are not actually cells, but fragments released by
megakaryocyte cells. Megakaryocyte is a large cell in the bone
marrow whose function is to produce platelets. When vascular
damage (i.e., damage to blood vessels) occurs, the platelets
stick to the vascular walls, forming clots to prevent the loss
of blood. Thus, it is important to have adequate numbers of
normally functioning platelets to maintain effective
coagulation of the blood. There are drugs that can potentially
alter the platelet count, making it necessary to monitor the
count. Also, some people with HIV infection develop
thrombocytopenia (a condition characterized by a platelet
count of less than 100,000 platelets per cubic millimeter of
blood). The normal value for men is 154,000-354,000 platelets
per cubic millimeter of blood. For women, it is
162,000-380,000 platelets per cubic millimeter of blood.
PML:
See Progressive Multifocal Leukoencephalopathy.
PNEUMOCYSTIS CARINII PNEUMONIA (PCP):
1. A protozoal infection of the lungs.
2. A life-threatening
lung infection that can affect people with weakened immune
systems, such as those infected with HIV. More than
three-quarters of all people with HIV disease will develop PCP
if they do not receive treatment to prevent it. The standard
treatment for people with PCP is either a combination of
trimethoprim and sulfamethoxazole (TMP/SMX, also called
Bactrim or Septra) or pentamidine.
See also Pentamidine;
Protozoa.
POLYMERASE:
Any of several enzymes that catalyze the formation of DNA or
RNA from precursor substances in the presence of preexisting
DNA or RNA acting as templates (i.e., patterns). See also DNA;
Enzyme; Ribonucleic Acid.
POLYMERASE CHAIN REACTION (PCR):
1. A laboratory process that selects a DNA segment from a
mixture of DNA chains and rapidly replicates it; used to
create a large, readily analyzed sample of a piece of DNA. It
is used in DNA fingerprinting and in medical tests to identify
diseases from the infectious agent's DNA. See also DNA.
2. As
related to HIV: A sensitive laboratory technique that can
detect and quantify HIV in a person's blood or lymph node.
POLYNEURITIS:
Inflammation of many nerves at once.
POLYVALENT VACCINE:
A vaccine that is active against multiple viral strains.
PRECURSOR CELLS:
Cells from which other cells are formed by natural processes.
PREVALENCE:
A measure of the proportion of people in a population affected
with a particular disease at a given time.
PROCTITIS:
Inflammation of the rectum.
PRODROME:
A symptom that indicates the onset of a disease.
PROGENITOR:
Parent or ancestor.
PROGRESSIVE MULTICOCAL LEUKOENCEPHALOPATHY (PML):
An opportunistic infection resulting from reactivation or new
infection with the JC virus. See also Opportunistic Infection.
PROPHYLAXIS:
Treatment that helps to prevent a disease or condition before
it occurs or recurs.
PROTEASE:
An enzyme that hydrolyzes (i.e., breaks down) proteins to
their component peptides. See also Enzyme; Peptide; Proteins.
PROTEASE INHIBITORS:
HIV protease is an aspartyl enzyme essential to the
replicative life cycle of HIV. The three-dimensional molecular
structure of the HIV protease has been fully determined.
Pharmaceutical developers are therefore able to rationally
design compounds to inhibit it and thus interfere with
replication of the virus. In the US, five peptide-based
protease inhibitors (saquinavir, Roche; A-80987, ABT-538,
Abbott Laboratories; L735,524, Merck; KNI-272, NCI) are in
clinical development. All compounds inhibit HIV-1 in vitro in
nanomolar concentrations. In Europe, two peptide-based
compounds (ABT-987, Abbott Laboratories; AG-1343, Agouron
Pharmaceuticals, Inc.) are currently in development. See also
In Vitro.
PROTEINS:
Any of the group of highly complex organic compounds found in
all living cells. Protein is the most abundant class of all
biological molecules, comprising about 50 percent of cellular
dry weight. Classified by biological function, proteins
include the enzymes, which catalyze cellular reactions;
collagen, keratin and elastin, which are structural, or
support, proteins; hemoglobin and other transport proteins;
casein, ovalbumin and other nutrient proteins; antibodies,
which are necessary for immunity; protein hormones, which
regulate metabolism; and proteins such as actin and myosin,
the contractile muscle proteins that perform mechanical work.
Structurally, proteins are large molecules composed of one or
more chains of varying amounts of the same 22 amino acids,
which are linked by peptide bonds. Each protein is
characterized by a unique and invariant amino acid sequence.
Protein chains may contain hundreds of amino acids; some
proteins also incorporate phosphorus or such metals as iron,
zinc and copper. The amino acid sequence also determines the
molecule's three-dimensional structure; this so-called native
state is required for proper biological function. The
information for the syntheses of the specific amino acid
sequences from free amino acids is carried by the cell's
nucleic acid. See also Peptide; Ribonucleic Acid.
PROTOCOL:
The detailed plan for a clinical trial that states the trial's
rationale, purpose, drug or vaccine dosages, length of study,
routes of administration, who may participate and other
aspects of trial design. See also Clinical Trial;
Inclusion/Exclusion Criteria.
PROTOPLASM:
Fundamental material composing all living things. Protoplasm,
which exists in all plants and animals in the small units
called cells, is mainly (85-90 percent) water and also
contains proteins, fatty substances and inorganic salts. It is
always enclosed by a thin surface membrane that controls the
passage of materials into and out of the cell. It displays the
general properties associated with life-the capacity to
respond to stimuli and the ability to perform the essential
physiological functions.
PROTOZOA:
A group of one-celled animals. Some protozoa can cause human
disease.
PSEUDOVIRION:
A virus-like particle.
PUBLIC HEALTH SERVICE (PHS):
A multi-agency organizational component of the US Department
of Health and Human Services. See also Centers for Disease
Control and Prevention; Health Resources and Services
Administration; National Institutes of Health.
PULMONARY:
Pertaining to the lungs.
R
RANDOMIZED TRIAL:
A study in which participants are randomly assigned to either
a treatment arm or placebo arm of a clinical trial. See also
Clinical Trial; Placebo.
REACTOGENICITY:
The capacity to produce adverse reactions.
RECEPTOR:
A molecule on the surface of a cell that serves as a
recognition or binding site for antigens, antibodies or other
cellular or immunological components. See also Antibodies;
Antigen.
RECOMBINANT:
An organism whose genome contains integrated genetic material
from a different organism. See also Genome.
RECOMBINANT DNA:
See Biotechnology; Genetic Engineering.
REGULATORY GENES:
As related to HIV: Three regulatory HIV genes-tat, rev and
nef-and three so-called auxiliary genes-vif, vpr and
vpu-contain information for the production of proteins that
control (i.e., regulate) the virus's ability to infect a cell,
produce new copies of the virus or cause disease. See also
nef; rev; tat.
REGULATORY T CELLS:
T cells that direct other immune cells to perform special
functions. The chief regulatory cell, the CD4+ T cell or T
helper cell, is HIV's chief target. See also CD4 (T4) or CD4+
Cells; T Cells.
REMISSIONS:
The lessening of the severity or duration of outbreaks of a
disease, or the abatement (diminution in degree or intensity)
of symptoms altogether over a period of time.
RENAL:
Pertaining to the kidneys.
RETICULOENDOTHELIAL CELLS:
A system of interstitial cells that includes all the
phagocytic cells, which trap and consume foreign agents,
except the leukocytes circulating in the bloodstream. This
system forms a network throughout the body and is another of
the body's defense systems against invading organisms in the
connective tissues of the body. See also Leukocytes;
Phagocyte.
RETINA:
Light-sensitive tissue at the back of the eye that transmits
visual impulses via the optic nerve to the brain.
RETINITIS:
Inflammation of the retina, linked in AIDS to CMV infection.
Untreated, it can lead to blindness. See also Cytomegalovirus;
Retina.
RETROVIRUS:
HIV and other viruses that carry their genetic material in the
form of RNA and that have the enzyme reverse transcriptase.
Like all viruses, HIV can replicate only inside cells,
commandeering the cell's machinery to reproduce. Like other
retroviruses, HIV uses the enzyme called reverse transcriptase
to convert its RNA into DNA, which is then integrated into the
host cell DNA. See also DNA; Reverse Transcriptase;
Ribonucleic Acid.
REV:
One of the regulatory genes of the HIV virus. Three HIV
regulatory genes-tat, rev and nef-and three so-called
auxiliary genes-vif, vpr and vpu-contain information necessary
for the production of proteins that control the virus's
ability to infect a cell, produce new copies of the virus or
cause disease. See also nef; tat.
REVERSE TRANSCRIPTASE:
This enzyme of the HIV virus (and other retroviruses) converts
the single-stranded viral RNA into DNA, the form in which the
cell carries its genes. The antiviral drugs approved in the US
for the treatment of HIV infection-AZT, ddC and ddI-all work
by interfering with this stage of the viral life cycle. See
also AZT; ddC; ddI; DNA; Ribonucleic Acid.
RIBONUCLEIC ACID (RNA):
1. A nucleic acid, found mostly in the cytoplasm of cells,
that is important in the synthesis of proteins. The amount of
RNA varies from cell to cell. RNA, like the structurally
similar DNA, is a chain made up of subunits called
nucleotides. In protein synthesis, messenger RNA (mRNA)
replicates the DNA code for a protein and moves to sites in
the cell called ribosomes. There, transfer RNA (tRNA)
assembles amino acids to form the protein specified by the
messenger RNA. Most forms of RNA (including messenger and
transfer RNA) consist of a single nucleotide strand, but a few
forms of viral RNA that function as carriers of genetic
information (instead of DNA) are double-stranded.
2. A
nucleic
acid associated with the control of chemical activities inside
a cell. One type of RNA transfers information from the cell's
DNA to the protein-forming system of a cell outside the
nucleus. Some viruses (e.g., HIV) carry RNA instead of the
more usual genetic material DNA.
See also Cytoplasm; DNA;
Retrovirus.
RIBOSOME:
A cytoplasmic organelle composed of ribonucleic acid and
protein that functions in the synthesis of protein. Ribosomes
interact with messenger RNA and transfer RNA to join together
amino acid units into a polypeptide chain according to the
sequence determined by the genetic code. See also Cytoplasm;
Ribonucleic Acid.
RNA:
See Ribonucleic Acid.
ROUTE OF ADMINISTRATION:
See Administration.
RYAN WHITE CARE ACT:
The Ryan White Comprehensive AIDS Resources Emergency
(CARE)
Act of 1990 represents the largest dollar investment made by
Congress to date specifically for the provision of services
for people with HIV infection. The purpose of the Act is "to
improve the quality and availability of care for individuals
and families with HIV disease."
S
SEBORRHEIC DERMATITIS:
A chronic inflammatory disease of the skin of unknown etiology
(i.e., cause or origin), characterized by moderate erythema;
dry, moist or greasy scaling; and yellow crusted patches on
various areas, including the mid-parts of the face, ears,
supraorbital regions (above the orbit of the eye), umbilicus
(the navel), genitalia, and especially the scalp. See also
Erythematous.
SEROCONVERSION:
The development of antibodies to a particular antigen. When
people develop antibodies to HIV or an experimental HIV
vaccine, they "seroconvert" from antibody-negative to
antibody-positive. See also Antibodies; Antigen.
SEROLOGIC TEST:
Any of a number of tests that are performed on the clear
portion of blood (serum). Often refers to a test that
determines the presence of antibodies to antigens such as
viruses. See also Antibodies; Antigen; Serum.
SEROPREVALENCE:
As related to HIV infection: The proportion of persons who
have serologic (i.e., pertaining to serum) evidence of HIV
infection at any given time. See also Serum.
SEROSTATUS:
Results of a test for specific antibodies. See also
Antibodies.
SERUM:
The clear, thin and sticky fluid portion of the blood that
remains after coagulation. Serum contains no blood cells,
platelets or fibrinogen.
SEXUALLY TRANSMITTED DISEASE (STD):
Also called venereal disease. A contagious disease usually
acquired by sexual intercourse or genital contact.
Historically, the five venereal diseases were: gonorrhea,
syphilis, chancroid, granuloma inguinale and lymphogranuloma
venereum. To these have been added scabies, herpes genitalis
and anorectal herpes and warts, pediculosis, trichomoniasis,
genital candidiasis, molluscum contagiosum, nonspecific
urethritis, chlamydial infections, cytomegalovirus and AIDS.
See also Herpes Simplex Virus II; Molluscum Contagiosum.
SF-2:
A strain of HIV used in vaccine development.
SHINGLES:
See Herpes Varicella Zoster Virus.
SHIV:
Genetically engineered hybrid virus having an HIV envelope and
an SIV core. See also Genetic Engineering; Hybrid; Simian
Immunodeficiency Virus.
SIDE EFFECTS:
The action or effect of a drug (or vaccine) other than that
desired. The term usually refers to undesired or negative
effects, such as headache, skin irritation or liver damage.
Experimental drugs must be evaluated for both immediate and
long-term side effects.
SIMIAN IMMUNODEFICIENCY VIRUS (SIV):
An HIV-like virus that infects monkeys, chimpanzees and other
nonhuman primates.
SIV:
See Simian Immunodeficiency Virus.
SPINAL TAP:
See Lumbar Puncture.
SPLENOMEGALY:
An enlarged spleen.
STANDARDS OF CARE:
Treatment regimen or medical management based on
state-of-the-art patient care.
STATISTICAL SIGNIFICANCE:
A term based on statistical tests that is used to denote the
probability that the observed association could have occurred
by chance alone. Does not refer to medical or biological
significance of an association. For example, a statistical
significance at the 1-percent level indicates a 1-in-100
chance that a result can be ascribed to chance.
STD:
See Sexually Transmitted Disease.
STEM CELLS:
Cells from which all blood cells derive. Bone marrow is rich
in stem cells.
STERILIZING IMMUNITY:
An immune response that completely eliminates an infection.
STEVENS-JOHNSON SYNDROME:
A severe and sometimes fatal form of erythema multiforme that
is characterized by conjunctivitis (eye inflammation) and
often results in blindness, Vincent's angina (trench mouth)
and ulceration of the genitals and anus. See also Erythema
Multiforme.
STOMATITIS:
Any of numerous inflammatory diseases of the mouth having
various causes, such as mechanical trauma, irritants, allergy,
vitamin deficiency or infection.
STRATIFICATION:
A layered configuration.
SUBARACHNOID SPACE:
The space through which the spinal fluid circulates.
SUBCLINICAL INFECTION:
An infection, or phase of infection, without readily apparent
symptoms or signs of disease.
SUBCUTANEOUS:
Beneath or introduced beneath the skin (e.g., subcutaneous
injections).
SUBUNIT HIV VACCINE:
A genetically engineered vaccine that is based on only part of
the HIV molecule. See also Genetic Engineering.
SULFA DRUG:
Any of a class of synthetic chemical substances derived from
sulfanilamide and used to treat bacterial infections. These
drugs inhibit the action of para-aminobenzoic acid, a
substance bacteria needed in order to reproduce. Sulfa drugs
are used primarily in the treatment of urinary tract
infections and ulcerative colitis. Antibiotics have largely
replaced them in the treatment of other bacterial infections.
SULFONAMIDES:
See Sulfa Drug.
SUPERANTIGEN:
Investigators have proposed that a molecule known as a
superantigen, either made by HIV or an unrelated agent, may
stimulate massive quantities of CD4+ T cells at once,
rendering them highly susceptible to HIV infection and
subsequent cell death. See also Antigen; CD4 (T4) or CD4+
Cells.
SUPPRESSOR T CELLS:
(T8, CD8). Subset of T cells that halt antibody production and
other immune responses. See also Antibodies; T Cells.
SURROGATE MARKER:
A substitute; a person or thing that replaces another. In HIV
disease, the number of CD4+ T cells and CD8+ cells is a
surrogate immunological marker of disease progression. See
also CD4 (T4) or CD4+ Cells; CD8 (T8) Cells.
SURVEILLANCE:
Close or continuous observation or testing (e.g.,
serosurveillance), used, among others, in epidemiology.
Immunological surveillance, or immunosurveillance, is a
monitoring process of the immune system that detects and
destroys neoplastic (e.g., cancerous) cells and that tends to
break down in immunosuppressed individuals. See also
Epidemiologic Surveillance.
SUSCEPTIBLE:
Vulnerable or predisposed to a disease.
SYMPTOMS:
Any perceptible, subjective change in the body or its
functions that indicates disease or phases of disease, as
reported by the patient.
SYNCYTIA:
("Giant Cells"). Dysfunctional multicellular clumps formed by
cell-to-cell fusion. Cells infected with HIV may also fuse
with nearby uninfected cells, forming balloonlike giant cells
called syncytia. In test tube experiments, these giant cells
have been associated with the death of uninfected cells. The
presence of so-called syncytia-inducing variants of HIV has
been correlated with rapid disease progression in HIV-infected
individuals.
SYNDROME:
A group of symptoms and diseases that together are
characteristic of a specific condition.
SYNERGISM/SYNERGISTIC:
An interaction between two or more agents (drugs) that
produces or enhances an effect that is greater than the sum of
the effects produced by the individual agents.
SYNTHESIS:
1. In chemistry, the formation of a compound from simpler
compounds or elements.
2. The production of a substance
(e.g.,
as in protein synthesis) by the union of chemical elements,
groups or simpler compounds, or by the degradation (i.e.,
breaking down) of a complex compound.
SYPHILIS:
A disease (usually sexually transmitted) resulting from
infection with the spirochete (a bacterium) Treponema
pallidum.
T
TAT:
One of the regulatory genes of the HIV virus. Three HIV
regulatory genes-tat, rev and nef-and three so-called
auxiliary genes-vif, vpr and vpu-contain information necessary
for the production of proteins that control the virus's
ability to infect a cell, produce new copies of the virus or
cause disease. The tat gene is thought to enhance virus
replication. See also nef; rev.
TB:
See Tuberculosis.
T CELLS:
(T Lymphocytes). A thymus-derived white blood cell that
participates in a variety of cell-mediated immune reactions.
Three fundamentally different types of T cells are recognized:
helper, killer and suppressor (each has many subdivisions). T
lymphocytes are CD3+ and can be separated into the CD4+ T
helper cells and the CD8+ cytotoxic/suppresssor cells. See
also Thymus.
TEMPLATE:
A gauge, pattern or mold used as a guide to the form of the
piece being made. In biology, a molecule (such as DNA) that
serves as a pattern for the generation of another
macromolecule (e.g., messenger RNA).
TERATOGENICITY:
The production of physical defects in offspring in utero
(i.e., causing birth defects).
TERRY BEIRN COMMUNITY PROGRAMS FOR CLINICAL RESEARCH ON
AIDS
(CPCRA):
The National Institute of Allergy and Infectious Diseases
(NIAID) started the CPCRA in 1989, adding Terry Beirn's name
in 1991 in honor of the late, former manager of the American
Foundation for AIDS Research and health policy consultant for
Senator Edward Kennedy. CPCRA is one of four HIV clinical
trials programs supported by NIAID. See also National
Institute of Allergy and Infectious Diseases; Community
Programs for Clinical Research on AIDS.
THERAPEUTIC HIV VACCINE:
A vaccine designed to boost the immune response to HIV in
persons already infected with the virus.
3TC:
Also known as Lamivudine, 3TC is composed of the (-)
enantiomer of the racemic mixture 2'-deoxy-3'-thiacytidine.
Like other nucleoside analogs, 3TC inhibits HIV replication
through viral DNA chain termination. It has been used in
clinical trials in combination with AZT. See also AZT;
Nucleoside Analog.
THROMBOCYTOPENIA:
A decreased number of blood platelets (cells important for
blood clotting). See also Platelets.
THRUSH:
Sore patches in the mouth caused by the fungus Candida
albicans. Thrush is one of the most frequent early symptoms of
an immune disorder. The fungus commonly lives in the mouth,
but only causes problems when the body's resistance is reduced
either by antibiotics that have reduced the number of
competitive organisms in the mouth, or by an immune deficiency
such as HIV disease. See also Candida.
THYMOSIN:
A polypeptide hormone of the thymus that influences the
maturation of T cells destined for an active role in
cell-mediated immunity. See also T Cells; Thymus.
THYMUS:
A mass of glandular tissue located in the neck or chest of
most vertebrates. Found in the upper chest under the
breastbone in humans, the thymus is essential to the
development of the body's system of immunity beginning in
fetal life (i.e., before birth). The thymus processes white
blood cells, known as lymphocytes, which kill foreign cells
and stimulate other immune cells to produce antibodies. The
gland grows throughout childhood until puberty and then
gradually decreases in size. See also Antibodies; Lymphocyte.
TISSUE:
A collection of similar cells acting together to perform a
particular function. There are four basic tissues in the body:
epithelial, connective, muscle and nerve.
TITER:
(Also "titre"). A laboratory measurement of the amount (or
concentration) of a given compound in solution.
T LYMPHOCYTE PROLIFERATION ASSAY:
Measures the strength of response of T memory cells (a
subgroup of T lymphocytes) to HIV. See also T Cells.
T LYMPHOCYTES:
See T Cells.
TOXICITY:
The extent, quality or degree of being poisonous or harmful to
the body.
TOXOPLASMOSIS:
Toxoplasmosis is an infection that is caused by the protozoan
parasite Toxoplasma gondii. The parasite is carried by cats,
birds and other animals and is found in soil contaminated by
cat feces and in meat, particularly pork. The parasite can
infect the lungs, retina of the eye, heart, pancreas, liver,
colon and testes. Once T. gondii invades the body, it remains
there, but the immune system in a healthy person usually
prevents the parasite from causing disease. If the immune
system becomes severely damaged, as in people with AIDS, or is
suppressed by drugs, T. gondii can begin to multiply and cause
severe disease. The most common site of toxoplasmosis is the
brain. When T. gondii invades the brain, causing inflammation,
the condition is called toxoplasmic encephalitis. While the
disease can occur in persons with healthy immune systems, it
can normally be cured successfully. See also Protozoa.
TRANSAMINASE:
A liver enzyme. A laboratory test that measures transaminase
levels is used to assess the health of the liver.
TRANSCRIPTION:
The process of constructing a messenger RNA molecule using a
DNA molecule as a template with the resulting transfer of
genetic information to the messenger RNA. As related to HIV:
The process by which the provirus produces new viruses. RNA
copies called messenger RNA must be made that can be read by
the host cell's protein-making machinery. Transcription is
facilitated by cellular enzymes, including RNA polymerase II.
The viral genes may partly control this process: tat, for
example, encodes a protein that accelerates the transcription
process by binding to a section of the newly made viral RNA.
See also Integration; Messenger RNA; tat; Template.
TRANSFER FACTOR:
A fraction of white blood cells that apparently "transfers"
capability to mount an immune response to a specific antigen.
See also Antigen.
TRANSFUSION:
1. The process of transfusing fluid (such as blood) into a
vein.
2. The transfer of whole blood or blood products from
one individual to another.
TRANSLATION:
As related to HIV: The process by which HIV messenger RNA is
processed in a cell's nucleus and transported to the
cytoplasm, the cellular material outside the nucleus. In the
cytoplasm, the cell's protein-making machinery translates the
messenger RNA into viral protein and enzymes. See also
Cytoplasm; Enzyme; Messenger RNA; Nucleus.
TRANSMISSION:
In the context of HIV disease: HIV is spread most commonly by
sexual contact with an infected partner. The virus can enter
the body through the mucosal lining of the vagina, vulva,
penis, rectum or, very rarely, the mouth during sex. The
likelihood of transmission is increased by factors that may
damage these linings, especially other sexually transmitted
diseases that cause ulcers or inflammation. Studies of SIV
infection of the genital membranes of nonhuman primates
suggest that the sentinel cells known as mucosal dendritic
cells may be the first cells infected. Infected dendritic
cells may migrate to lymph nodes and infect other cells. HIV
also is spread through contact with infected blood, most often
by the sharing of drug needles or syringes contaminated with
minute quantities of blood containing the virus. Children can
contract HIV from their infected mothers either during
pregnancy or birth, or postnatally, via breastfeeding. Current
research indicates that the AIDS virus may be 100 to 1000
times more contagious during the first two months of
infection, when routine AIDS tests are unable to tell whether
people are infected. See also Lymph Nodes; Simian
Immunodeficiency Virus.
TREATMENT IND:
A program to provide experimental treatments to a class of
patients who lack satisfactory alternative treatment. IND
stands for Investigational New Drug application, which is part
of the process to get approval from the Food and Drug
Administration for marketing a new prescription drug in the
US. See also Investigational New Drug.
TUBERCULOSIS (TB):
A bacterial infection caused by Mycobacterium tuberculosis. TB
bacteria are spread by airborne droplets expelled from the
lungs when a person with active TB coughs, sneezes or speaks.
Repeated exposure to these droplets can lead to infection in
the air sacs of the lungs. The immune defenses of healthy
people usually prevent TB infection from spreading beyond a
very small area of the lungs. If the body's immune system is
impaired because of infection with HIV, aging, malnutrition or
other factors, the TB bacterium may begin to spread more
widely in the lungs or to other tissues.
U
UTERUS:
A hollow muscular organ located in the pelvic cavity of female
mammals in which the fertilized egg implants and develops.
Also called womb.
V
V3 LOOP:
Section of the gp120 protein on the surface of HIV. Appears to
be important in stimulating neutralizing antibodies. See also
Antibodies; gp120.
VACCINATION:
Inoculation of a substance (vaccine) into the body for the
purpose of producing active immunity against a disease. The
vaccine is usually a weakened culture of the agent causing the
disease; the use of vaccines is a cornerstone of preventive
medicine. Vaccination was used in ancient times in China,
India and Persia, and was introduced to the West in the late
18th century by E. Jenner. Vaccinations have eradicated
smallpox and are used today to prevent diphtheria,
poliomyelitis, rabies and typhoid. Experimental vaccines for
certain cancers have been developed for laboratory mice. See
also Inoculation.
VACCINE:
A substance that contains antigenic components from an
infectious organism. By stimulating an immune response (but
not disease), it protects against subsequent infection by that
organism. See also Antigen; Vaccination.
VACCINIA:
A cowpox virus, formerly used in human smallpox vaccines.
Employed as a vector in HIV vaccine research to transport HIV
genes into the body. See also Vaccination; Vector.
VARIABLE REGION:
The part of an antibody's structure that differs from one
antibody to another. See also Antibodies.
VECTOR:
A nonpathogenic bacterium or virus used to transport an
antigen into the body to stimulate protective immunity (e.g.,
in a vaccine). See also Antigen.
VIRAL BURDEN:
(Viral Load). The amount of HIV virus in the circulating
blood. Monitoring a person's viral burden is important because
of the apparent correlation between the amount of virus in the
blood and the severity of the disease: sicker patients
generally have more virus than those with less advanced
disease. A new, sensitive, rapid test-called the branched DNA
assay for HIV-1 infection-can be used to monitor the HIV viral
burden. In the future, this procedure may help clinicians to
decide when to give anti-HIV therapy. It may also help
investigators determine more quickly if experimental HIV
therapies are effective.
VIRAL CORE:
1. Typically a virus contains an RNA (ribonucleic acid) or DNA
(deoxyribonucleic acid) core of genetic material surrounded by
a protein coat. See also DNA; Ribonucleic Acid.
2. As related
to HIV: Within HIV's envelope is a bullet-shaped core made of
another protein, p24, that surrounds the viral RNA. Each
strand of HIV RNA contains the virus' nine genes. Three of
these-gag, pol and env-are structural genes that contain
information needed to make structural proteins. The env gene,
for example, codes for gp160, a protein that is later broken
down to gp120 and gp41.
See also env; gp41; gp120; gp160;
p24.
VIRAL CULTURE:
A laboratory method for growing viruses.
VIRAL ENVELOPE:
As related to HIV: HIV is spherical in shape with a diameter
of 1/10,000 of a millimeter. The outer coat, or envelope, is
composed of two layers of fat-like molecules called lipids,
taken from the membranes of human cells. Embedded in the
envelope are numerous cellular proteins, as well as
mushroom-shaped HIV proteins that protrude from the surface.
Each mushroom is thought toconsist of a cap made of four
glycoprotein molecules called gp120, and a stem consisting of
four gp41 molecules embedded in the envelope. The virus uses
these proteins to attach to and infect cells.
VIRAL LOAD:
See Viral Burden.
VIREMIA:
The presence of virus in the bloodstream.
VIRION:
A virus particle existing freely outside a host cell. A mature
virus.
VIROLOGY:
The study of viruses and viral disease.
VIRUCIDE:
Any agent that destroys or inactivates a virus.
VIRUS:
Organism composed mainly of nucleic acid within a protein
coat, ranging in size from 100 to 2000 angstroms (unit of
length; 1 angstrom is equal to 10-10 meters); they can be seen
only with an electron microscope. During the stage of their
life cycle when they are free and infectious, viruses do not
carry out the usual functions of living cells, such as
respiration and growth; however, when they enter a living
plant, animal or bacterial cell, they make use of the host
cell's chemical energy and protein- and nucleic
acid-synthesizing ability to replicate themselves. Viral
nucleic acids are single- or double-stranded and may be DNA
(deoxyribonucleic acid) or RNA (ribonucleic acid). After viral
components are made by the infected host cell, virus particles
are released; the host cell is often dissolved. Some viruses
do not kill cells but transform them into a cancerous state;
some cause illness and then seem to disappear, while remaining
latent and later causing another, sometimes much more severe,
form of disease. Viruses, known to cause cancer in animals,
are suspected of causing cancer in humans. Viruses also cause
measles, mumps, yellow fever, poliomyelitis, influenza and the
common cold. Some viral infections can be treated with drugs.
See also DNA; Nucleic Acid; Ribonucleic Acid.
VISCERAL:
Pertaining to the major internal organs.
W
WASTING SYNDROME:
The HIV wasting syndrome involves involuntary weight loss of
10 percent of baseline body weight plus either chronic
diarrhea (two loose stools per day for more than 30 days) or
chronic weakness and documented fever (for 30 days or more,
intermittent or constant) in the absence of a concurrent
illness or condition other than HIV infection that would
explain the findings.
WESTERN BLOT:
A laboratory test for the presence of specific antibodies,
more accurate than the ELISA test. See also Antibodies; ELISA.
S O U R C E S
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American Heritage Dictionary of the English Language, Third Edition. New York: Houghton Mifflin, 1992.
CDC National Serosurveillance Summary, Vol. 3. Atlanta: Centers for Disease Control and Prevention, 1992.
Clinical Manual for Care of the Adult Patient With HIV Infection. Edited by H. Libmen, M.D., and R.A. Witzburg, M.D. Boston: Boston City Hospital, Department of Medicine, 1990.
Concise Columbia Encyclopedia. New York: Columbia University Press, 1991.
Dendritic Cells: A Key to Early HIV Infection. NIAID News. Rockville, Maryland: National Institute of Allergy and Infectious Diseases, January 30, 1995.
Dorland's Illustrated Medical Dictionary, 28th Edition. Philadelphia: W.B. Saunders Company, 1988.
Emerging Fungal Threat, by S. Sterber. Science, Vol. 266, No. 5191 (December 9, 1994), pp. 1632-1634.
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