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

Clement Loh Chee Hoou, Faculty of Medicine, University of New South Wales, Sydney, Australia

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].

References: 

1. Baeten JM, Donnell D, Ndase P, Mugo NR, Campbell JD, Wangisi J, et al. Antiretroviral Prophylaxis for HIV Prevention in Heterosexual Men and Women. New England Journal of Medicine. 2012;367(5):399-410. doi:10.1056/NEJMoa1108524

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