New Hopes for Preventing AIDS The success of anti-retroviral （抑止肿瘤病毒) drugs in treat

New Hopes for Preventing AIDS

The success of anti-retroviral (抑止肿瘤病毒) drugs in treating HIV is getting researchers at the 16th International AIDS conference excited at the prospect that the potent medicines might be exploited to perform. double duty. Why not use the power of these ARVs to prevent an HIV transmission or infection from taking hold in the first place？ Bill and Melinda Gates asked that provocative question on the opening day of the conference, and are committing their considerable financial resources toward finding an answer. In their remarks, they highlighted the need to develop microbicides and oral-prevention drugs while we wait for a vaccine. And they will get their first hint at how smart their decision was this Thursday, when scientists from West Africa report the initial results from the first trial studying an oral prevention drug.

So how realistic are the Gates in expecting even more from the ARVs？ "I do think the range of prevention options we have within the next decade will greatly expand," says Dr. Helene Gayle, President of Care USA and co-chair of the conference. "The biologic plausibility for both microbicides and oral-prevention drags is so great." Dr. Mark Dybul, U.S. Global AIDS Coordinator, said that if a microbicide or prevention drug becomes available to protect people from infections, they would be funded under the President's Emergency Plan for AIDS Relief if countries chose to use them. "We would support all of that; it would be perfectly within our mandate to do all that," he told TIME.

Preventing HIV is the only way to keep the number of new infections that occur each year -- 4 million -- from growing. And yet prevention strategies, always the ugly stepsister to treatment programs, have not really taken hold in the developing nations where the rate of infection is highest. An effective vaccine, of course, is the ultimate prevention weapon, but as the Gates' pointed out, an HIV shot is still a long way off. In the meantime, microbicides could be one way to co-opt ARVs into the prevention war; these are chemical compounds, usually in the form. of a gel or cream, that women can use vaginally prior to intercourse to stop the transmission of HIV -- it's the same idea behind spermicides (杀精子剂), which are chemical barriers to sperm entering the vagina and causing pregnancy. It's an elegantly simple approach, made even simpler by the fact that researchers didn't really have to start from scratch to come up with new anti-HIV compounds; they already have them in the ARVs, which now interrupt the virus from infecting cells at various points in its life cycle.

The key difference is that in a microbicide, the drugs are being used in healthy people rather than in those infected with HIV. When ARVs are used for treatment, both doctors and patients are willing to tolerate a higher level of side effects -- after all, if the choice is between dying from HIV-AIDS and side effects, most patients opt for the latter. If the drugs are to be used to prevent infection, however, everything changes; understandably, healthy people aren't as likely to accept the same level of side effects and toxicities as those already infected.

That's why clinical trials are so significant. So far, there are 30 to 40 different microbicide candidates being tested in animals, and five trials in Ghana, Nigeria and other developing nations at the most advanced stages of testing in women. Dr. Gita Ramjee, of the HIV Prevention Research Unit in Durban, South Africa, has worked with all five, and is hopeful that they will prove effective and make an impact on the disease. Because these latest microbicides are reformulated ARVs, however, the problem of the virus becoming resistant to them is a potential drawback. Dr. Peter Plot, of UNAIDS, suggests basing microbicides only on the drugs do not make it through the pharmaceutical pipeline many are rejected becaus

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