Researchers say antiretroviral (ART) drugs may prevent HIV infection

By David Brown
Washington Post Staff Writer
Saturday, February 20, 2010

SAN FRANCISCO -- The antiretroviral drugs that revolutionized the care of people with AIDS are on the threshold of a new life as tools to prevent infection in individuals and brake the epidemic in populations as a whole.

Studies are underway testing whether periodic use of the drugs, either as pills or as vaginal or rectal gels, can prevent transmission of HIV in high-risk sexual encounters. At the same time, it's becoming clear that the incidence of HIV infection declines over time in places where most infected people know their status and are on treatment -- and thus are less likely to pass the virus to others.

Description of these effects at a big AIDS conference here is likely to spur a further swing of the treatment pendulum toward early and widespread treatment of HIV infection.

"Arguably the greatest progress in the AIDS epidemic has been in the development of highly effective drugs," said John W. Mellors, an AIDS researcher at the University of Pittsburgh and chairman of the 17th Retrovirus Conference. "This is now being applied not only to help infected individuals but as a public health approach to the whole epidemic."

Since the advent of "combination antiretroviral therapy" (ART) in 1996, patients and physicians have debated how aggressively the drugs should be used.

Recognition of ART's dramatic life-extending effect was followed by the appearance of unexpected side effects, including increased risk of diabetes and heart disease and changes in many patients' appearance. As a consequence, researchers over the last 15 years have conducted dozens of studies seeking to learn how long an infected person could safely put off starting the drugs, or whether an infected person could stop taking them periodically without harm.

It's now clear that interrupting treatment is not a good idea and that starting it early in the course of infection may have real benefits, even though it means a lifetime of daily pill-taking. The new studies discussed here are likely to only increase the use of the drugs, which now number more than 30.

Antiretroviral drugs are already being given to babies born to infected mothers immediately after birth and during breast-feeding to greatly reduce the chance of infection.

"We know prevention works in babies. It shouldn't be any different in adults," Mellors said.

Several studies are underway testing "pre-exposure prophylaxis" with the drugs in people at high risk for acquiring HIV, including commercial sex workers. Some results may be available late this year.

There are already indirect hints that AIDS medicines can be prevention tools just like condoms and abstinence. Specifically, when an infected person is on a successful ART regimen, the amount of the virus in the bloodstream falls to such a low level that the chance of infecting someone else is almost nil.

In a study presented Friday, Deborah Donnell of the Fred Hutchinson Cancer Research Center in Seattle described this effect in "discordant couples" -- a couple in which only one partner is infected -- in seven African countries. When a person's HIV infection got to the stage at which ART was started, the chance that the partner would become infected fell by 92 percent.

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