Pre-exposure prophylaxis: a new approach towards HIV prevention?

As the spread of HIV infection is fast reaching epidemic proportions in many parts of the world. Pre-exposure prophylaxis has emerged as a new approach towards HIV prevention for people at risk of HIV infection.

The recent paper published by Baeten et al. in the New England Journal of Medicine (NEJM) reported on a randomised controlled trial regarding the efficacy of using antiretroviral pre-exposure prophylaxis in preventing HIV infection in HIV-1 disconcordant couples. The study was conducted in Kenya and Uganda; 4758 couples were recruited and the seronegative partner was randomised to one of three study regimens: tenofovir once daily, combination tenofovir-emtricitabine once daily or matching placebo. Patients were then followed up monthly for 36 months [1].

Upon completion of the trial, 82 seronegative partners acquired HIV infection during the study, of which, 17 were in the tenofovir only group, 13 in the combination tenofovir-emtricitabine group and 52 in the placebo group. This indicates a relative reduction of the incidence of HIV-1 infection by 67% in the tenofovir only group and by 75% in the combination tenofovir-emtricitabine group. There is no statistically significant difference in the protective effects between tenofovir only and combination tenofovir-emtricitabine therapy [1].

However, HIV infection acquired prior to pre-exposure prophylaxis can result in development of resistance to the antiretroviral agents used. In the study, of the 8 participants who acquired HIV infection prior to commencement of pre-exposure prophylaxis, 25 % (2 participants) developed resistance to the antiretroviral agents used [1]. Use of tenofovir has been reported to cause reductions in GFR. Further studies are required to determine its long-term safety profile.
This is a proof-of-concept study where the results have demonstrated that antiretroviral prophylaxis therapy is effective in reducing HIV-1 infection in high risk individuals. This may serve as an effective strategy for infection prevention in individuals whose partners are HIV-1 positive but not on antiretroviral treatment. Antiretroviral based prevention strategies may offer an alternative option for HIV disconcordant couples planning to have children. Overall, successful prevention of HIV-1 infection will still require multiple biomedical and behavioural strategies including HIV1 testing, risk-reduction counselling and other primary prevention strategies in combination with pre-exposure prophylaxis [1].