Even with the best of available treatments, it may take as long as 60 years to eliminate HIV once an infected person has established a reservoir of infected immune cells, according to data presented at an HIV/AIDS symposium sponsored by the Institute of Human Virology. Although the event, which attracted some 1,000 participants from the U.S. and abroad, wrapped up without the announcement of a spectacular breakthrough, a few research areas showed promise.
"I think it's a return to realism. I think the public needs to get that as well," Martin Delaney, founding director of the AIDS advocacy group Project Inform, tells WebMD.
But many researchers were upbeat about the prospects of developing a treatment or preventive vaccine that would immobilize a tiny but crucial HIV component called "Tat," or transactivating protein. "It's not going to be a panacea. It's not going to be the cure of AIDS. But we believe we can help people with it," says Robert Gallo, MD.
Gallo, director of the institute and the co-discoverer of the AIDS virus, HIV, says that Tat is a unique molecular product of HIV infection and is essential to maintaining and spreading the disease. He calls it "a missile to uninfected cells." Studies on animals and early trials in people by one of Gallo's collaborators have shown that a Tat-inhibiting vaccine can inhibit the virus and boost the immune system. According to Gallo, the vaccine would be "dirt cheap" and without side effects, but three injections a year would be required.
Another vaccine approach generating interest at the meeting involves using another immune modulator, called a chemokine, that seems to play a key role in HIV. The chemokine, says Gallo, normally attaches itself to the same site on infection-targeted cells as the virus does. The idea would be to somehow activate the chemokine to block the attacking virus. "This has got a way to go, but it opens up an avenue," says Gallo.
However, Anthony Fauci, MD, director of the National Institute of Allergy and Infectious Diseases, takes a more cautious approach: "I'm not so sure we're getting closer to a vaccine. There's certainly a lot more interest in vaccines, which is good ... but we don't have any trials yet showing efficacy of any candidate," Fauci tells WebMD.
Whatever the prospects for vaccines may be, Fauci says that no new blockbuster drug treatments like protease inhibitors are on the immediate horizon. While he acknowledges that highly active antiretroviral therapy (HAART) has been a "spectacular success," Fauci says that some patients will fail on the regimen. This phenomenon already appears under way with the recent release of government data showing that the steep decline in AIDS deaths has begun to level off.
Optimism has also dimmed about the possibility of eliminating HIV from the body within two or three years using HAART -- a theory espoused by David Ho, MD, of the Aaron Diamond AIDS Research Center in New York. Ho suggests that the "intrinsic decay rate" of the virus would amount to a half-life of 6 months, or perhaps 10 years to total elimination.
However, Robert Silicano, MD, of Johns Hopkins University in Baltimore, says that his studies with 50 AIDS patients indicate that a reservoir of about one million infected cells remains stable. He calculates that it would take about 60 years to clear this type of virus reservoir in an HIV-infected person even with the best available drugs and strict adherence to taking the medications. In other words, he says, they would be on the treatment for life.
Fauci says that his efforts to clear out the HIV reservoirs in infected patients using interleukin-2, a protein that affects the immune response, have had limited success. "Though their reservoir was [reduced] substantially," he says, "when we took them off therapy, they still rapidly bounced back with their viral load."
