Prevention of HIV transmission through interference with HIV entry, reverse transcriptase, protease and integrase with regard to the development of new candidate microbicides

Vaginal microbicides, which are antimicrobial agents formulated in a vaginal gel, film, or ring, are urgently needed to empower women to protect themselves from sexual HIV transmission. Regrettably the development of an effective and safe microbicide appears to be a challenging task. First generation microbicides failed in clinical trials due to toxicity or lack of efficacy. Second generation microbicides, however, are based on more potent, specific anti-HIV agents that interfere with viral entry, reverse transcription, integration or proteolysis steps of the HIV life cycle. In the present thesis, we evaluated these antiretroviral drug classes for their preventive potential as microbicide using in vitro research to address their main disadvantages.;We showed that the non-nucleoside reverse transcriptase inhibitors (NNRTIs) which are currently under development as microbicides, display major cross-resistance against first-line therapeutic NNRTIs. Moreover, most NNRTI-resistance mutations did not impact viral replicative fitness suggesting that they might be transmitted at similar frequency as wild-type viruses. Hence, if these microbicides select for drug resistance in the female genital tract, the large-scale introduction of single-NNRTI-based microbicides may increase therapy failure in sub-Saharan Africa. Therefore, only NNRTIs with a high genetic barrier to resistance that can overcome common therapeutic resistance mutations should be further developed into a microbicide. To rapidly screen these NNRTI candidates, we described an alternative method that eliminates the need for cell-cultures using SPR-based biosensor technology.;Specific entry inhibitors (Els) on the other hand, will not cause similar resistance problems as they are not part of first-line therapy. However, it is currently unclear whether these Els are able to inhibit cell-associated HIV originating from infected seminal T cells and macrophages. We therefore showed that all antiretrovirals, including Els, are able to block cell-to-cell spread from different types of cell-associated virus. Moreover only protease inhibitors (Pis) could block virus production from infected effector cells. Furthermore we demonstrated that budding virus from migrating seminal leucocytes may be rendered defective by prior vaginal exposure to certain Els. As such, a window of opportunity may be provided to the immune system to eliminate these invading cells before systemic infection can be established. Els and Pls are thus eligible drug classes for inclusion in future combination microbicides.