New HIV Drugs Protect Uninfected Partners

(CN) - HIV-controlling antiretroviral therapy greatly reduces heterosexual transmission of the virus to uninfected partners, National Institutes of Health investigators reported on Monday.

A decade-long study was designed to evaluate whether antiretroviral therapy reduces sexual transmission of HIV, funded primarily by the National Institute of Allergy and Infectious Diseases, or NIAID, part of the NIH.

The HIV Prevention Trials Network began work in April 2005, led by Myron Cohen, director of the University of North Carolina - Chapel Hill's Institute for Global Health and Infectious Diseases, according to the NIH.

The trial reportedly enrolled 1,763 adult, heterosexual couples - each with just one HIV-infected partner - in Botswana, Brazil, India, Kenya, Malawi, South Africa, Thailand, the United States and Zimbabwe, who were randomly split into two groups.

Investigators say that in the first group, HIV-infected partners began taking a combination of three antiretroviral drugs right away, but in the second, they waited until their CD4+ T-cell levels - a key measure of immune system health - fell below 250 cells per cubic millimeter or an AIDS-related event occurred, weakening their immune system.

NIAID says it gave all participants condoms and counseling on how to protect their partners from sexual transmission of HIV. All infected study participants then began antiretroviral therapy immediately and the trial continued for another four years, through this spring.

The journal Science chose the study as the 2011 Breakthrough of the Year after investigators reported that starting HIV treatment early lowered the risk of sexually transmitting the virus to an uninfected partner by 96 percent over 18 months.

On Monday, investigators reported that starting antiretroviral treatment early reduced HIV transmission by 93 percent over the course of a decade. Study results were presented at the 8th International AIDS Society Conference on HIV Pathogenesis, Treatment & Prevention in Vancouver, Canada.

Researchers say only eight participants transmitted HIV to their uninfected partners, four of whom most likely got HIV just before treatment started and were diagnosed soon after.

Treatment was no longer working for the other infected participants and the virus was replicating, possibly because their partners had not taken their antiretroviral drugs as prescribed or had an HIV strain that was resistant to them, NIAID reported.

"The study now makes crystal clear that when an HIV-infected person takes antiretroviral therapy that keeps the virus suppressed, the treatment is highly effective at preventing sexual transmission of HIV to an uninfected heterosexual partner," NIAID Director Anthony Fauci said. "For heterosexuals who can achieve and maintain viral suppression, the risk to their partners is exceedingly low."

Investigators reported that having a relatively high level of HIV in the blood at the start of therapy could increase the risk for virus transmission. Support for the study was also provided by the NIH-funded AIDS Clinical Trials Group.

The agency also reported Monday that another study showed that starting antiretroviral therapy early prevents not only serious AIDS-related diseases, but also the onset of cancer, cardiovascular disease and other non-AIDS-related diseases in HIV-infected people.

The NIH is comprised of 27 institutes and centers, according to its website.

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