August 19, 2008 - By Ruthann Richter
David Katzenstein, MD, professor of infectious diseases, is a longtime HIV/AIDS specialist who attended the International AIDS Conference Aug. 3 to 8 in Mexico City. The conference drew some 23,000 scientists, public health experts, caregivers and activists. Katzenstein has done studies in Zimbabwe on preventing HIV transmission from mother to child. At the end of the conference, he answered questions from Ruthann Richter about the most pressing aspects of the AIDS epidemic.
1. What do you see as the most exciting and important things to emerge from this conference?
Katzenstein: The conviction that it is possible to put so many people on antiretroviral therapy. It's a rare example of international collaboration to achieve a solid, albeit quixotic goal, but a worthwhile one - universal access.
2. There are 3 million people on antiretroviral therapy, but there are still some 70 percent of infected individuals who need these drugs to survive. The theme of the conference was Universal Action Now. Given our limited resources, what do you think should be the priorities?
Katzenstein: I think the 'action now' theme is a very good one because it will spur the continued action, hard work and commitment to reach those goals. It's kind of like global warming - something that we know is a big problem, and it's only going to get worse, and we ought to do something about it right now. The fight against HIV and AIDS is the first global health effort that actually includes provision of treatment on a universal access basis. That it has fallen short of its goal is to be expected. We just have to work harder to get there.
3. What about the science? Some disappointing results emerged from the conference. Vaccine trials have failed. Microbicide trials haven't born fruit. Given the limits of our scientific knowledge, where should the research focus be?
Katzenstein: I think Dr. (Anthony) Fauci (director of the National Institute of Allergy and Infectious Diseases) suggested we need to go back to the drawing board in terms of biomedical prevention. For vaccines and microbicides, we have to think much harder about them. Although simply creating new drugs is no one's first choice for prevention, we should heed the call from Mike Cohen, MD (of the University of North Carolina), and others who have recognized that treatment is prevention. Because the behavioral interventions, microbicides and vaccines are still a long way from having any effect on incidence, we have to focus on what works. Brazil, which made universal access to treatment a high priority in the early '90s, has achieved an absolute fall in incidence. The U.S. incidence remains constant at about 40,000 to 50,000 new infections a year, largely due to effective prevention through treatment.
4. Are there new drugs on the horizon that you think will really make a difference for people?
Katzenstein: Yes, there are new classes of drugs which are still in a very boutique phase of development. There's great excitement about integrase inhibitors, with one that is out, Raltegravir, and a second one that is coming along. Maraviroc is the Pfizer drug for CCR5 (chemokine coreceptor 5) inhibition. It is a very radical concept, and a very different kind of drug because it actually blocks virus entry into cells. The potential to use entry inhibitors as microbicides or as oral prophylaxis for prevention is very exciting.
5. As for prevention, the speakers at the conference noted the number of new infections continues to rise. What do you think we should be doing to strengthen prevention efforts?
Katzenstein: We're betting that treatment is, in fact, going to prevent transmission. The HIV Prevention Trials Network is working in Africa, Latin America and Asia, enrolling discordant couples. If the infected partner has very high CD 4 counts (a measure of certain T-cells targeted by HIV) and would not qualify for treatment otherwise, half are put on treatment and half are not. Most of us think there is going to be prevention of transmission in the high-CD4, healthy people receiving treatment. With the current drugs having become much less toxic, it is hoped that the benefits of early treatment will outweigh any of the possible risks. And showing that drug treatment of people with HIV prevents them from transmitting the virus will encourage policy changes to increase access. By this logic, it may be possible to limit transmission (and hopefully to stop it entirely) by providing access to early treatment to everyone who is infected.
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