Suppression of HIV-1 infection with antiretroviral therapy reduced by 93% the risk of transmission of the virus between serodiscordant partners, according to data from the HIV Prevention Trials Network presented at the 21st International AIDS Conference.
“We hope that the newly emphasized importance of early initiation of ART will encourage patients with HIV-1 infection to start such therapy without delay,” the investigators reported in their paper, which was published simultaneously online July 18 in the New England Journal of Medicine.
The international 5-year study in serodiscordant couples randomized 886 HIV-1 infected individuals to antiretroviral therapy as soon as they were enrolled in the study, while the other 877 participants initiated antiretroviral therapy only if their CD4+ cell count showed a sustained decline or they developed an illness suggestive of AIDS.
Overall, 46 genetically-linked new HIV infections were observed during the trial – 3 in the early ART group and 43 in the delayed therapy group – with early antiretroviral therapy therefore showing a 93% lower risk of linked partner infection. Eight of the linked-partner transmissions were diagnosed after the infected partner had begun ART; four of these were diagnosed less than 90 days after they had started treatment (N Engl J Med 2016 July 18. doi: 10.1056/NEJMoa1600693).
“In these cases, further analysis suggested that all four of these infections probably occurred before the virus was virally suppressed in the index participant,” wrote Dr. Myron S. Cohen of the University of North Carolina at Chapel Hill and his coauthors. “In the other four cases, partner infection occurred after ART failed in the index participant.”
While the study was obviously not able to measure viral load at the time of the transmission event, the authors said the observed relationship between viremia and HIV transmission signaled the importance of counseling serodiscordant couples about the risks of transmission before viral suppression is achieved, as well as the need to closely monitor viral load during treatment.
They also noted that they did not observe a single case of transmission occurring when the index case had stable viral suppression on antiretroviral therapy.
Even after the interim results of the HPTN trial were released and study participants were informed of the benefits of early antiretroviral therapy, 17% of individuals in the delayed initiation group still chose not to begin therapy. The authors suggested this may be the result of the previous recommendations that therapy is not required unless there is a drop in CD4+ cell count or decline in health.
The study was supported by grants from the National Institutes of Health, and study drugs were donated by Abbott Laboratories, Boehringer Ingelheim, Bristol-Myers Squibb, Gilead Sciences, GlaxoSmithKline/Viiv Healthcare, and Merck. Several authors declared grants from the NIH, and several declared support, grants, and fees from private companies, including those who donated study drugs.