The success of antiretroviral-based HIV prevention, including topical and oral pre-exposure prophylaxis and treatment for prevention, along with the modest success of a HIV vaccine, are some of the recent developments that have transformed the HIV prevention landscape after a history of disappointing clinical trial results. A Review in this week's HIV Special Issue of The Lancet says these and other developments, along with a difficult financial climate, mean that limited financial resources must be focused on known effective HIV prevention with an emphasis on measuring population-level impact. The Review is by Professor Nancy S Padian, University of California, Berkeley, CA, USA, and the Office of the US Global AIDS Coordinator within the US Government, Dr Sandra I McCoy, University of California, Berkeley, CA, USA, and colleagues.
The Review is clear that prevention priorities have expanded beyond biomedical discovery alone to include implementation science and determining the impact of combination HIV prevention at the population level. Several effective prevention strategies remain dominated by implementation challenges, specifically HIV testing, prevention of mother-to-child transmission, voluntary medical male circumcision, and behavioural and structural approaches. The key needs for these approaches focus on implementation science questions to facilitate scale-up and reduce both supply- and demand-side barriers.
However, some prevention approaches remain squarely in the discovery stage: the search for a vaccines and cure. Research priorities in this area focus on product development and proof-of concept studies. In particular, researchers continue to analyse data from the Thailand vaccine trial (2010) that showed a 31% reduction in new HIV cases in those vaccinated, in order to determine the immune responses that gave protection. Meanwhile, a new class of cancer drugs has entered clinical trials that could force the so-called latent pool of HIV-infected cells that hide in the body to replicate, exposing them to the effects of traditional ART therapy that usually cannot reach these cells.
Antiretroviral-based prevention (both oral and topical pre-exposure products and "treatment for prevention") has emerged as a potential cornerstone of combination prevention. A trial earlier this year demonstrated that a vaginal gel containing an ART drug reduced new infections in women by 39%, and a second trial reported that when ART was given to an HIV-infected heterosexual person, it reduced by 96% the chances of HIV transmission to that person's partner. The value of ARV-based prevention for both HIV positive and HIV negative individuals has emphasised the overlap of treatment and prevention, and reinforces the need for unified prevention and care and treatment strategies, as opposed to separate strategies.
The research priorities in this area focus on determining eligibility and distribution given ethical considerations, ensuring adherence, and the promotion of HIV testing—the essential gateway to prevention services. The essential message is that: "The extent to which pre-exposure prophylaxis and ART reach individuals with the greatest potential for acquisition or onward transmission is central to the success of prevention approaches based on antiretroviral drugs. The main challenge is whether the right people have the right drug concentrations of the right drugs at the right time."
A significant change in new prevention findings is the promise of prevention strategies whose initiation and implementation is under the control for women, who are disproportionately affected in many regions. For example, the success of topical vaginal antiretroviral gel has the potential to change the epidemic enormously, because of the promise that women could use such products without the knowledge or consent of their male partners. This is critical in settings where women face social and economic inequities.
The authors conclude: "The past year marked the end of the steady stream of disappointing results [in HIV prevention], and a concomitant change is evident in public perception and the opinions of policy makers. The discourse on HIV prevention now includes the possibility that the epidemic can be stopped… Our challenge is to carefully select a group of effective interventions that together have an increased chance of success by complementing each other to achieve the elusive goal of changing the course of the HIV epidemic."
Professor Nancy S Padian, University of California, Berkeley, CA, and Office of the US Global AIDS Coordinator within the US Government, Washington, DC, USA. Please e-mail to arrange interview E) nancy.padian@gmail.com
Dr Sandra I McCoy, University of California, Berkeley, CA, USA. Please e-mail to arrange interview E) smccoy@berkeley.edu
Journal
The Lancet