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Frederick, Maryland, July 11, 1997
A newly discovered protein called
cyanovirin-N inactivates the human immunodeficiency virus in vitro and has
characteristics that make it a particularly attractive candidate for microbicide
development.
The virucidal protein was isolated and sequenced by a multicenter team led by Dr. Michael R. Boyd of the National Cancer Institute in Frederick, Maryland. The investigators report that in low nanomolar concentrations, cyanovirin-N irreversibly inactivates diverse laboratory strains and primary isolates of HIV-1 as well as strains of HIV type 2 and simian immunodeficiency virus. The protein also inhibits cell-to-cell fusion and cell-to-cell, as well as virus-to-cell, transmission of infection, according to the researchers. Uninfected cells were not killed by exposure to high concentrations of cyanovirin-N, they note.
Cyanovirin-N was isolated from cultures of the blue-green alga Nostoc ellipsosporum. The extract from which the discovery evolved was among a collection of cyanobacterial (blue-green algal) extracts from the U.S. National Cancer Institute's Natural Products Repository. The team had selected the extract for detailed investigation both based on its strong inhibition of HIV cytopathicity in an empirical screen and because there were indications that the active constituent was a protein. This is the first time an antiviral protein has been isolated from a cyanobacterium.
The investigators speculate that the effects of the protein are most likely related to its unique interactions with the viral surface envelope glycoprotein gp120. Its activity is highly resistant to physiochemical degradation and it has been produced recombinantly in E. coli.
The researchers conclude that the discovery of cyanovirin-N provides a novel lead for further investigation of new potential therapeutic and preventive strategies against HIV infection.
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