July 20, 2015

Antiretroviral therapy (ART) for HIV infection provides lasting protection against the sexual transmission of the virus from infected men and women to their HIV-uninfected sexual partners. The discovery, made by investigators from the University of North Carolina at Chapel Hill and the HIV Prevention Trials Network (HPTN), was reported July 20 at the 8th International AIDS Society (IAS) Conference on HIV Pathogenesis, Treatment and Prevention in Vancouver, Canada.

Dr. Myron Cohen (Photo courtesy newsobserver.com)

Dr. Myron Cohen (Photo courtesy of newsobserver.com)

Myron Cohen, MD, professor of epidemiology at UNC’s Gillings School of Global Public Health and director of UNC’s Institute for Global Health and Infectious Diseases, was principal investigator for the study, known as HPTN 052. Cohen is also Yeargan-Bate Eminent Distinguished Professor of Medicine, Microbiology and Immunology.

HPTN 052 began in 2005 and enrolled 1,763 HIV sero-discordant couples – i.e., one member of the couple is HIV-infected, and the other is not – at 13 sites in nine countries. Ninety-seven percent of the couples were heterosexual. HIV-infected partners were assigned either to initiate ART at the beginning of the study, called the “early” arm, or later in the study, called the “delayed” arm. Those on the delayed arm started ART when their bodies’ immune systems were declining.

“These findings demonstrate that antiretroviral therapy, when taken until viral suppression is achieved and sustained, is a highly effective, durable intervention for HIV prevention,” Cohen said. “The HPTN 052 trial was designed to address two questions — whether providing antiretroviral therapy to an HIV-infected person would prevent HIV transmission to a sexual partner, and whether earlier antiretroviral therapy offered long-lasting health benefits. The answer to both is a resounding ‘yes.’”

In 2011, an interim review of the study data showed a 96 percent reduction of HIV transmission within the couples assigned to early ART, which was considered a major breakthrough finding. After the release of the results, all participants in the delayed ART arm were offered the opportunity to begin ART, and the study continued for four more years.

By the end of the study, 1,171 couples remained in follow-up.

As reported July 20 at the IAS conference, the final results show a sustained 93 percent reduction of HIV transmission within couples when the HIV-infected partner was taking ART as prescribed and viral load was suppressed. Notably, there were only eight cases of HIV transmission within couples after the HIV-infected partner was given ART. However, four of these eight cases were diagnosed soon after ART initiation, and transmission likely occurred before the HIV-infected partner was virally suppressed.

The other four were diagnosed when the HIV-infected partner had detectable levels of virus in the blood, despite being on ART (indicating treatment failure). Treatment failure may have occurred because participants either did not take their antiretroviral drugs as prescribed or had an HIV strain that resisted or acquired resistance to one or more of the drugs in their treatment regimen.

HPTN 052 investigators also are reporting findings at the IAS conference concerning the relationship between viral load, viral suppression, treatment failure and drug resistance. Investigators found that having a relatively high level of HIV in the blood at the start of treatment was associated with a longer time to viral suppression which, in turn, was associated with both treatment failure and a shorter time to treatment failure.

In addition, among the HPTN 052 participants who failed treatment, investigators found that those who had a higher viral load when they joined the study were more likely to develop resistance to their antiretroviral drugs. More research is needed to understand this association, according to the investigators.

“These results have important implications for programs seeking to combine other HIV prevention measures with treatment as prevention,” Cohen said. “In the setting of such programs, special efforts should be made to minimize HIV transmission risk before viral suppression has been achieved, to maintain suppression on ART, and to identify and address ART failure.”

HPTN 052 was funded primarily by the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health (NIH).

A video interview with Cohen is available online.


Gillings School of Global Public Health contact: David Pesci, director of communications, (919) 962-2600 or dpesci@unc.edu

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