Wednesday, September 06, 2006

Prevention the Focus at the Toronto AIDS Conference

Prevention the Focus at the Toronto AIDS Conference
By Bob Roehr
Copyright by THe Windy City Times

Treatment of HIV without prevention is not sustainable in the developing world. That reality brought a renewed focus on prevention to the 16th International AIDS Conference in Toronto, Aug. 13-18. The marathon event has swollen to over 20,000 participants from around the globe, while science has played a shrinking role on the program.

With the prospect of a successful preventive vaccine still a distant glimmer, seemingly no closer today than 10 years ago, AIDS advocates increasingly acknowledge that it will take a variety of interventions, each contributing a bit toward reducing the risk of transmission of HIV, in order to rein in the pandemic.

Circumcision received a boost last year from a study in South Africa. The trial randomized adult volunteers to be circumcised either immediately or after waiting a year, and it tracked them over that period. It was stopped early because it showed that those who were circumcised had a dramatic 60 percent reduction in risk of becoming infected. To allow the trial to continue would have been unethical.

The biology behind it is that the mucosal tissue on the head of an uncircumcised penis and the foreskin contain high concentrations of cells that are readily infected by HIV. Circumcision allows that tissue to harden into regular external skin, including a layer of tough dead skin, that offers a barrier against infection.

Other circumcision trials are underway in Kenya and Uganda. An interim review earlier this year by the safety committees allowed those trials to continue. Speculation is that if they had seen results as dramatic as those in the South Africa trial, the safety committee would have stopped the trials; but that did not happen.

The Bill and Melinda Gates Foundation has become a leading supporter of research into microbicides, those topical gels, foams, and other agents used during vaginal intercourse to prevent the sexual transmission of HIV.

The theme of empowering women to protect themselves from infection is a powerful one. But given that at least a quarter of African women have been raped or had coercive sex, prior application of such a product will not always be possible.

A handful of large efficacy trials of the first generation of microbicides are underway and it is possible that a product could be available as early as 2010. Those agents will offer some protection, and so will have an impact on restraining the pandemic within the overall population, but their efficacy is likely to fall far short of the 95 percent protection that is the minimum thought necessary to gain approval and public acceptance in the US.

And rectal use of microbicides is often at best an afterthought; as if women and gay men never engage in anal sex. Most of the microbicides in trails for efficacy in protecting against vaginal transmission of HIV have not even been tested for safety in the rectum, while efficacy trials of rectal use remain a dream.

It has long been known that infection with any of more than a dozen other sexually transmitted diseases increases the risk of both acquiring and transmitting HIV. So effort has gone into treating those other infections.

This year the focus was on genital herpes, herpes simplex virus-2 ( HSV-2 ) . Infection with HSV-2 can double the risk of acquisition of HIV, accelerate its progress, and facilitate its transmission to others by increasing the shedding of virus.

Treatment with acyclovir and other drugs in the same family can resolve genital lesions, and when used at suppressive doses can minimize recurrence of outbreaks. Large clinical trials are underway to determine the extent to which suppressive therapy for HSV-2 might reduce the spread of HIV, with the first results anticipated as early as next year.

Others are enamored with the concept of pre-exposure prophylaxis ( PrEP ) , taking anti-HIV drugs on a regular basis in order to kill off any virus one might become exposed to, before infection can become established.

Tenofovir has been the drug of choice for such study because it is strong, easy to use, and has few side effects. However, when used alone as monotherapy, it is relatively easy for HIV to develop resistance to it, so researchers have turned to the combination with emtricitabine, which is sold in the US as a single pill under the name Truvada.

A trial among gay men is underway in Atlanta and San Francisco. Trials at some sites in Africa and Asia have been stopped because of hysterical charges that participants were being used as guinea pigs, but they continue elsewhere.

But even if the trials prove effective, many question how applicable the intervention will be in the real world. The wholesale price of Truvada in the US is about $9,000 a year, though discounts are offered in the developing world. It will cost many, many times what condoms do, and is likely to be less effective.

Gilead Sciences, which makes the drug, is supporting the trial. But a company spokesman has said that it would not seek a preventive label indication because of liability concerns. And even with such an indication, what health plan would agree to cover the costs? Would the CDC, which has cut back on funding for condoms, pour money inot a much more expensive ( and pleasurable ) way to have sex?

This emphasis on biomedical approaches of HIV prevention drew criticism from Dr. Cristina Pimenta from the Brazilian Interdisciplinary AIDS Association. She believes they need to be seen as part of a balanced approach.

She warned, such “quick…magical solutions to HIV/AIDS prevention…deflect or redirect attention away from the fundamentally political barriers that have been erected in recent years by some government agencies impeding the implementation of proven effective educational approaches, such as condom use and harm reduction.”

The HIV epidemic, both in the US and internationally, is being driven by sex and drug use, said Julie Davids with the Community HIV/AIDS Mobilization Project ( CHAMP ) , a national advocacy group based in New York City.

She criticized the Bush administration for its focus on abstinence only HIV prevention programs, continued opposition to programs with demonstrated success such as needle exchange and condom distribution programs.


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