New tack to block HIV raises prospect of vaccine for AIDS

A new compound has blocked HIV infection so well in monkeys that it may be able to function as a vaccine against AIDS, scientists reported Wednesday.

HIV has defied more than 30 years of conventional efforts to fashion a vaccine. The new method stimulates muscle cells to produce proteins that somewhat resemble normal antibodies, which have Y-shaped heads. These proteins have a head and a tail, and they use them to simultaneously block two sites on each “spike” that the virus uses to attach itself to a cell.

If both sites can be blocked on every spike, the virus becomes helpless and drifts off unattached into eventual oblivion by the immune system.

“It’s a twofer,” said Dr. Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases, which supported the work. “It’s very impressive, and the method is quite promising. But it’s still just in an animal model, so we’ll need to see evidence of whether it works in humans.”

The technique, the paper’s lead author said, has now completely protected four monkeys for nearly a year against repeated attempts to infect them with large doses of several strains of SHIV, a version of HIV adapted for use in lab monkeys.

The author, Dr. Michael Farzan, an infectious disease specialist at the Scripps Research Institute in Florida, described the new compound as “the broadest and most potent entry inhibitor described so far.”

It is simpler and works better, he said, than the current method that scientists are experimenting with: giving monkeys cocktails of several different antibodies that each neutralize only one or two strains of HIV, sometimes imperfectly.

The study was published online by the journal Nature.

The work also involved researchers from Harvard, Princeton, and Rockefeller universities, the University of Southern California, the Pasteur Institute in France, and elsewhere.

The next step, Farzan said, will be to test the compound in infected monkeys and see if it can stop the virus from replicating further, which is what antiretroviral medicines do. If that proves safe and effective, he said, he hopes to start human trials in three stages.

In the first, humans would be injected every few weeks with jthe antibody-like protein, not the vector that stimulates muscle cells to produce it. If that were successful, the vector would be injected into humans who have HIV but are not taking antiretroviral pills. Finally, it would be given to healthy people at high risk to see if it protects them.

The new approach uses cutting-edge techniques that are not entirely understood by scientists.

Historically, vaccines have been made by killing or weakening whole viruses and injecting them into people at risk. This process stimulates the immune system to produce antibodies that recognize and attack the real virus.

Newer vaccines splice genes for particular antibodies into weakened viruses. Generally, the genes are carried into a cell by the virus, incorporated into the cell genome, and begin producing necessary antibodies.

But this new method splices the desired gene into a stretch of DNA so short that it cannot function like a virus at all.