Bay Area Reporter - August 24, 2006
Liz Highleyman, liz@black-rose.com

Even as the Bush administration came under criticism for its "ABC" prevention policy that promotes abstinence and being faithful over the use of condoms, advocates acknowledged that traditional prevention methods such as condoms and clean needles are not enough to stem the epidemic.

"I just don't believe we can reverse this if we keep having more people infected every year than we are increasing the number of people on medication," said former President Bill Clinton at a special session last Tuesday, August 15.

Pre-exposure prophylaxis

One of the new technologies in the spotlight is pre-exposure prophylaxis, or PREP û the use of antiretroviral drugs by HIV-negative people to prevent infection. Studies in monkeys have shown that tenofovir (Viread), manufactured by South San Francisco-based Gilead Sciences, can help prevent HIV infection through rectal exposure, particularly when used in combination with another Gilead drug, emtricitabine (FTC).

Trials are under way to evaluate the safety and effectiveness of PREP among men who have sex with men in San Francisco and Atlanta, injection drug users in Thailand, and heterosexuals in Botswana. However, similar studies, including one of sex workers in Cambodia, have been canceled due to ethical issues raised by activists. The prospect of PREP has provoked concerns about side effects, drug resistance, and the possibility that a preventive drug that is not 100 percent effective could cause users to abandon safer sex, thereby actually contributing to the spread of HIV.

At a late-breaker session last Thursday, Dr. Albert Liu, from the San Francisco Department of Public Health, presented data from a survey of awareness of and attitudes toward PREP among men who have sex with men. The researchers surveyed 851 self-identified gay and bisexual men recruited at various venues in San Francisco; at the San Francisco sexually transmitted disease clinic; and at the White Party, an annual circuit event in Palm Springs.

About one-fifth of the men had heard of PREP, with the most common sources of information being the media and friends. Men who reported recent unprotected anal sex were more likely to say they knew about PREP. Just one respondent said he had used PREP, and 2 percent said they knew someone who had done so. But a substantial majority (68 percent) said they would be likely to use PREP if it were shown to work.

Liu's findings conflict with those of a 2004 survey conducted at Pride events in four cities, including San Francisco and Oakland. In that study, about 25 percent of respondents said they had heard of PREP, and 7 percent said they had used it.

Definitive data about whether PREP works are not likely to be available for several years, and researchers are worried that misinformation could lead to increased levels of risky sex.

"It is critical that we wait for safety and efficacy data," said Liu. "It is important to stress that we don't know if it works."

Speaking at the same session, Dr. Robert Grant, from UCSF's Gladstone Institute of Virology and Immunology, presented estimates from a mathematical model showing that even a 50 percent increase in high-risk behavior could completely offset the benefits of partially effective PREP.

PREP in Africa

Another study also presented at the same session offered some of the first preliminary evidence that tenofovir may reduce the risk of HIV infection in humans.

Leigh Peterson of Family Health International reported on a PREP study in 936 HIV-negative women in Cameroon, Ghana, and Nigeria. A total of eight women became infected with HIV, two in the tenofovir group and six taking placebo û a difference that was not statistically significant. The study also found that while the number of sex acts increased while using PREP, the number of sexual partners decreased and the rate of condom use rose from 52 percent to 94 percent, highlighting the value of the intensive risk-reduction counseling offered to study participants.

Session moderator Dr. Ronald Valdiserri, from the Centers for Disease Control and Prevention, called the findings "very hopeful," but all speakers emphasized that the results are preliminary and the study was too small to say with any certainty that PREP can help reduce HIV transmission.

Other prevention advances

Dozens of other sessions at the conference covered various aspects of prevention, including HIV vaccines and microbicides. While several candidates in both categories are undergoing clinical trials, progress has been slow. Advocates emphasized the need for more funding to move potential products through the development pipeline, but acknowledged that daunting technical challenges remain. In contrast, treatment of sexually transmitted diseases such as genital herpes has proven to be a cheap and readily available way to reduce HIV transmission.

Another intervention receiving considerable attention is adult male circumcision in high-prevalence countries. In June, the National Institutes of Health decided to continue two circumcision trials in Kenya and Uganda, which together include several thousand men. A recent South African study found that circumcision reduced the rate of HIV acquisition by about 60 percent, but the World Health Organization and UNAIDS have declined to endorse the procedure until data from the ongoing studies are reported next year.

"Our position is that the evidence to date is compelling and persuasive, but it's generally unwise to base major policy decisions on the basis of one trial," said WHO Department of HIV/AIDS director Dr. Kevin De Cock.

However, if men are still reluctant to use condoms to reduce the risk of contracting or transmitting HIV, it remains to be seen how eager they will be to undergo a painful procedure that may permanently diminish sexual sensitivity. And, as with PREP, there is concern that an increase in high-risk sex could wipe out any benefits.

Finally, Dr. Julio Montaner of the British Columbia Centre for Excellence in HIV/AIDS in Vancouver proposed another possible prevention approach: treating every HIV-positive person with antiretroviral therapy, whether they need it or not. The current federal treatment guidelines suggest that people should start HAART when their CD4 T-cell count falls below 350 cells. Effective treatment that decreases HIV viral load to a very low or undetectable level dramatically reduces the odds of transmitting the virus. Based on a mathematical model, Montaner's group estimated that if all people with HIV received treatment at once, the rate of new infections could drop by as much as 70 percent over 45 years.

The enthusiasm expressed at last week's conference suggests that prevention will join treatment as a major focus in the HIV/AIDS field in the years to come. And, just as activism made the difference in ensuring the development of novel AIDS treatments and their accessibility in the developing world, a similar effort is needed with regards to prevention.

"You proved [that activism works] when you pushed for new treatment," keynote speaker Melinda Gates said at the opening session. "The world now needs you to push even harder for prevention."

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