• Vaginal bacteria modify HIV tenofovir microbicide efficacy in African women

    Research by a Mucosal Immunology research collaboration between CAPRISA’s mucosal immunology team in Durban and scientists from the USA and Canada was published in Science this week. The study provides new evidence linking vaginal bacteria to microbicide efficacy through tenofovir depletion via bacterial metabolism.

    Antiretroviral-based strategies for HIV prevention have shown inconsistent results in women. Although variability in the levels of adherence has been shown to be a major contributing factor for the diverse trial outcomes in women, little is known about what biological factors may also contribute to the variability in these results.

    This study, which included biological samples from 688 HIV-negative women from the CAPRISA 004 trial, used a metaproteomic approach to assess whether vaginal bacteria modulate the efficacy of the topical microbicide tenofovir in preventing
    HIV infection.

    Two major vaginal bacterial community types were identified; one dominated by Lactobacillus (59.2%), and the other where Gardnerella vaginalis predominated with other anaerobic bacteria (40.8%).

    Tenofovir reduced HIV incidence by 61% (P=0.013) in Lactobacillus-dominant women but only 18% (P=0.644) in women with non-Lactobacillus bacteria - a threefold difference in efficacy (Figure below).

    An in vitro culture system was used to assess potential biodegradation of tenofovir by the major bacterial species present in this cohort. The results show that detectible
    mucosal tenofovir was lower in non-Lactobacillus women, negatively correlating with G. vaginalis and other anaerobic bacteria, which depleted tenofovir by metabolism more rapidly than target cells convert to pharmacologically active drug.

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Centre for the AIDS Programme of Research in South Africa

CAPRISA was created in 2001 and formally established in 2002 under the NIH-funded Comprehensive International Program of Research on AIDS (CIPRA) by five partner institutions; University of KwaZulu-Natal, University of Cape Town, University of Western Cape, National Institute for Communicable Diseases, and Columbia University in New York. CAPRISA is a designated UNAIDS Collaborating Centre for HIV Prevention Research. The main goal of CAPRISA is to undertake globally relevant and locally responsive research that contributes to understanding HIV pathogenesis, prevention and epidemiology as well as the links between tuberculosis and AIDS care.