“Our compound is the broadest and most potent entry inhibitor described so far,” said Michael Farzan, a professor on TSRI’s Florida campus who led the effort. “Unlike antibodies, which fail to neutralize a large fraction of HIV-1 strains, our protein has been effective against all strains tested, raising the possibility it could offer an effective HIV vaccine alternative.”
TSRI says that the drug blocks every strain of HIV-1, HIV-2 and SIV (simian immunodeficiency virus) that has been isolated from humans or rhesus macaques.
It also protects against much-higher doses of virus than occur in most human transmission and does so for at least eight months after injection – which would mean it could be used as an unconventional vaccine.
Here’s how it works
When HIV infects a cell, it targets the CD4 lymphocyte, an integral part of the body’s immune system. HIV fuses with the cell and inserts its own genetic material—in this case, single-stranded RNA—and transforms the host cell into a HIV manufacturing site.
The new study builds on previous discoveries by the Farzan laboratory, which show that a co-receptor called CCR5 contains unusual modifications in its critical HIV-binding region, and that proteins based on this region can be used to prevent infection.
Farzan and his team developed the new drug candidate so that it binds to two sites on the surface of the virus simultaneously, preventing entry of HIV into the host cell.
“When antibodies try to mimic the receptor, they touch a lot of other parts of the viral envelope that HIV can change with ease,” said TSRI Research Associate Matthew Gardner, the first author of the study with Lisa M. Kattenhorn of Harvard Medical School.
“We’ve developed a direct mimic of the receptors without providing many avenues that the virus can use to escape, so we catch every virus thus far.”
Bill Condie is a science journalist based in Adelaide, Australia.
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