AIDS Vaccine Found? Drug eCD4-lg Proves Successful in Monkeys

Scientists have successfully conducted trials on monkeys a drug that can block AIDS virus strain Hiv1 and HIV2.

The promising results obtained by scientists at the Scripps Research Institute in Florida, Harvard Medical School and about dozen more institutes, shows that the new drug candidate tested on rhesus macaques, or monkeys which can carry simian HIV virus that is similar to the one that infects humans too.

The drug compound known as eCD4-lg was injected in these monkeys and they did not catch the virus despite repeatedly exposed to high levels of the virus for eight months. They also found that the drug was able to block both the known strains of HIV1 and HIV2 virus that infect humans.

Michael Farzan

“Our compound is the broadest and most potent entry inhibitor described so far,” lead researcher Michael Farzan from the Scripps Research Institute said. “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.”

The researchers said they were able to make the drug after a decade’s research into a receptor called CCR5, which makes HIV to latch onto the surface of a cell and begin multiplying. They developed the new drug that can bind on two sides of the virus at the same time, thus preventing it from infecting a 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.”

A model of eCD4-Ig bound to the HIV-1 Env trimer.

“When we did our original work on CCR5, people thought it was interesting, but no one saw the therapeutic potential. That potential is starting to be realized,” said lead researcher Farzan. They made the drug to work like a vaccine by attaching eCD4-lg to an adeno-associated virus (AAV), a virus harmless to humans that can be used as a vehicle.

Nobel laureate David Baltimore, who is working on a separate gene therapy to tackle HIV, told Science that these findings are “impressive” but too early to conclusively say pending the trials on humans. “It’s perhaps a better construct than the antibodies we’ve been using, but it’s a matter of how it plays out in human trials,” Baltimore said.

The findings of Farzan team’s study have veen published in the journal Nature.

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