As antiretroviral treatment (ART) is scaled up in Africa and other settings where resources remain limited, its potential benefits for preventing new HIV infections need to be evaluated. An Article published Online First and in an upcoming Lancet shows that in patients on antiretroviral therapy (ART), there was a 92% lower risk of transmitting HIV to their sexual partners. The greatest benefit of ART in reducing HIV transmission was among HIV-infected persons with CD4 counts less than 200 per µl. Additionally, the investigators found that among HIV-infected people with CD4 counts above 200 per µl, HIV transmission rates were highest among those with a viral load above 50 000 copies per ml, suggesting that targeting this group could be an effective way to achieve further population-level reductions in HIV. The Article is by Dr Deborah Donnell, International Clinical Research Center, University of Washington, and Vaccine and Infectious Disease Institute, Fred Hutchinson Cancer Research Center, Seattle, WA, USA, and colleagues.
In this study, which was funded mostly by the Bill & Melinda Gates Foundation, HIV-infected individuals and their HIV negative partners were enrolled. The HIV-1 infected participants had CD4 counts of 250 cells per μL or greater and did not meet national guidelines for ART (typically at CD4 counts less than 200 per μL). During 24 months of follow-up, CD4 counts were measured every 6 months and ART was initiated if the person's CD4 cell count fell below 200. Uninfected partners were tested for HIV-1 every 3 months. The primary outcome of the study was HIV-1 transmission between the partners which was identified through genetic analysis. Rates of HIV-1 transmission were compared by ART status of infected participants.
A total of 3381 couples were eligible for analysis. 349 (10%) participants with HIV-1 initiated ART during the study, at a median CD4 cell count of 198 (IQR 161�) cells per μL. Only one of 103 genetically-linked* HIV-1 transmissions was from an infected participant who had started ART, corresponding to transmission rates of 0•37 per 100 person-years in those who had initiated treatment and 2•24 per 100 person-years in those who had not, which after data adjustment showed a 92% reduction in transmission in patients who had started ART. In participants not on ART, the highest HIV-1 transmission rate (8•79 per 100 person-years) was from those with CD4 cell counts lower than 200 cells per μL. In couples in which the HIV-1 infected partner had a CD4 cell count greater than 200 cells per μL, 66 (70%) of 94 transmissions occurred when plasma HIV-1 concentrations exceeded 50 000 copies per mL.
The authors say: "ART use by the infected person was accompanied by a 92% reduction in risk of HIV-1 transmission to their partner...The greatest effect of ART on HIV-1 transmission risk was in participants with CD4 cell counts lower than 200 cells per μL, emphasising the potential synergy of clinical and prevention benefits of ART in those with CD4 cell counts lower than this threshold."
They add: "Targeting of HIV-1 infected individuals with high plasma HIV-1 concentrations could achieve maximum HIV-1 prevention benefits of ART. Development of inexpensive point-of-care tests for plasma HIV-1 concentration could allow ART provision to be targeted to patients with high CD4 cell counts and high plasma HIV-1 concentrations.
Furthermore, they say: "This cohort received frequent counselling during 3-monthly follow-up, and our data reinforce previous findings that ART initiation does not lead to increased sexual activity or decreased condom use in heterosexual couples. On an individual basis, counselling is needed to reinforce that potential for HIV-1 transmission remains after ART initiation."
The authors highlight that the results of another study by the US National Institutes of Health are eagerly awaited—namely a 5-year study in which analyses ART initiation at CD4 cell counts of 350� cells per μL vs at <250 cells per μL. The authors say this "will be invaluable for understanding of the balance of long-term risks and benefits of ART for treatment and prevention".
They conclude: "The greatest priority for ART provision for both treatment and prevention of HIV-1 coincides in patients with CD4 cell counts lower than 200 cells per μL. As countries strategise for optimum use of resources to expand ART provision beyond individuals with low CD4 cell counts, targeting of treatment to those with high plasma HIV-1 concentrations could be a cost-effective strategy to achieve maximum population-level reductions in HIV-1 transmission, as a step toward universal ART provision to all patients with HIV-1."
In an accompanying Comment, Dr François Dabis, INSERM U897, Institute of Public Health, Epidemiology and Development, Université Victor Segalen, Bordeaux, France, and colleagues say: "During the one hour it takes to read this [complete] comment and linked article, 300 new HIV infections will have occurred in Africa. We should not wait for the results of further models, observational studies, or the ongoing couple-based prevention trial before engaging in population-based trials of 'test-and-treat'. Prevention of new infections would be the main goal but individual-level benefits can also be expected; to be evaluated against initially increased costs to the health-care system. Indeed today's results argue powerfully for a new generation of research on HIV prevention at population level, using the best possible scientific methodology, including cluster-randomised trials."
For Dr Deborah Donnell, Vaccine and Infectious Disease Institute, Fred Hutchinson Cancer Research Center, Seattle, WA, USA, please contact Media Contact: Toni Maddox T) + 1206-520-3825 / +1 206-399-2415 E) Deborah@fhcrc.org / tmaddox@u.washington.edu
Dr François Dabis, INSERM U897, Institute of Public Health, Epidemiology and Development, Université Victor Segalen, Bordeaux, France. T) + 33 5 57 57 14 36 E) francois.dabis@isped.u-bordeaux2.fr
For full Article and Comment, see: http://press.thelancet.com/hivtransmission.pdf
Note to editors: *genetically linked: genetic analysis was undertaken to establish that the HIV infection was caused by the person's partner
Journal
The Lancet