HIV infection risk for uninfected sex partners reduced by early ART

Early commencement of oral antiretroviral therapy (ART) by men and women infected with HIV substantially reduced the risk that they would transmit the virus to their uninfected sexual partners, according to findings from a large multinational clinical study conducted by the HIV Prevention Trials Network (HPTN), a global partnership dedicated to reducing the transmission of HIV through cutting-edge biomedical, behavioral, and structural interventions.

The randomized controlled study was designed to evaluate whether immediate versus delayed use of ART by HIV-infected individuals would reduce transmission of the virus to their uninfected partners, as well as whether the HIV-infected individual would benefit. Beginning in April 2005, the study enrolled 1,763 couples in which 1 member was HIV-infected and the other was HIV-uninfected; 97% were heterosexual. The HIV-infected individuals were required to have a CD4 cell count between 350-550 per cubic millimeter (cells/mm3) at enrollment, which would not require HIV treatment for their own health. Couples were randomized to the immediate ART group, which began ART instantly, or to the delayed ART group, which did not begin ART until participants’ CD4 cell counts fell below 250 cells/mm3 or they developed an AIDS-related illness.

An independent Data and Safety Monitoring Board (DSMB) reviewed the data and concluded that initiation of ART by HIV-infected individuals reduced the risk of HIV transmission to the uninfected partner by 96%. Among the 877 couples in the delayed ART group, 27 HIV transmissions occurred. Only 1 transmission occurred in the immediate ART group - a highly statistically significant difference.

In those who were originally infected with HIV and in the delayed ART group, 17 developed extrapulmonary tuberculosis, whereas 3 originally infected individuals in the immediate ART group developed the disease. This also was a statistically significant finding. During the study 23 deaths occurred: 13 in the delayed ART group and 10 in the immediate ART group. Investigators are continuing to follow all study participants for at least 1 more year.

“Previous data about the potential value of antiretrovirals in making HIV-infected individuals less infectious to their sexual partners came largely from observational and epidemiological studies,” Anthony S. Fauci, MD, director of the National Institute of Allergy and Infectious Diseases, said in a press release. “This new finding convincingly demonstrates that treating the infected individual - and doing so sooner rather than later - can have a major impact on reducing HIV transmission.”