ABSTRACT The requirement for multiple mutations for protease inhibitor (PI) resistance necessitates a better understanding of the molecular basis of resistance development. The novel bioinformatics resistance determination approach presented here elaborates on genetic profiles observed in clinical human immunodeficiency virus type 1 (HIV-1) isolates. Synthetic protease sequences were cloned in a wild-type HIV-1 background to generate a large number of close variants, covering 69 mutation clusters between multi-PI-resistant viruses and their corresponding genetically closely related, but PI-susceptible, counterparts. The vast number of mutants generated facilitates a profound and broad analysis of the influence of the background on the effect of individual PI resistance-associated mutations (PI-RAMs) on PI susceptibility. Within a set of viruses, all PI-RAMs that differed between susceptible and resistant viruses were varied while maintaining the background sequence from the resistant virus. The PI darunavir was used to evaluate PI susceptibility. Single sets allowed delineation of the impact of individual mutations on PI susceptibility, as well as the influence of PI-RAMs on one another. Comparing across sets, it could be inferred how the background influenced the interaction between two mutations, in some cases even changing antagonistic relationships into synergistic ones or vice versa. The approach elaborates on patient data and demonstrates how the specific mutational background greatly influences the impact of individual mutations on PI susceptibility in clinical patterns.

Heterosexual transmission of human immunodeficiency virus (HIV) remains the major route of infection worldwide; thus, there is an urgent need for additional prevention strategies, particularly strategies that could be controlled by women, such as topical microbicides. Potential microbicide candidates must be both safe and effective. Using cellular and tissue explant models, we have evaluated the activity of the nonnucleoside reverse transcriptase inhibitor (NNRTI) dapivirine as a vaginal microbicide. In tissue compatibility studies, dapivirine was well tolerated by epithelial cells, T cells, macrophages, and cervical tissue explants. Dapivirine demonstrated potent dose-dependent inhibitory effects against a broad panel of HIV type 1 isolates from different clades. Furthermore, dapivirine demonstrated potent activity against a wide range of NNRTI-resistant isolates. In human cervical explant cultures, dapivirine was able not only to inhibit direct infection of mucosal tissue but also to prevent the dissemination of the virus by migratory cells. Activity was retained in the presence of semen or a cervical mucus simulant. Furthermore, dapivirine demonstrated prolonged inhibitory effects: it was able to prevent both localized and disseminated infection for as long as 6 days posttreatment. The prolonged protection observed following pretreatment of genital tissue and the lack of observable toxicity suggest that dapivirine has considerable promise as a potential microbicide candidate.

Methods DUET patients were randomized 1:1 to ETR (200 mg BID) or placebo, both with a background regimen of NRTIs, darunavir/ritonavir and optional enfuvirtide. Subgroup analyses of the effect of HIV-1 subtype on the proportion of patients with viral load (VL) <50 HIV-1 RNA copies/mL (TLOVR imputation algorithm) were conducted on pooled week 48 data. Genotype/subtype and phenotype determinations were performed using the Virco® TYPE HIV-1 and AntivirogramTM assays, respectively. The effect of HIV-1 subtype on ETR fold change in EC50 value (FC) was analyzed in HIV-1 recombinant clinical isolates from treatment-naive patients enrolled in other Tibotec trials (n = 872) that included 49% of HIV-1 subtype non-B (18% CRF01_AE; 16% C; 5% A1; 3% CRF12_BF; 2% CRF02_AG; 1% F1; 3% other).

Non-nucleoside reverse transcriptase inhibitors (NNRT1s) represent a chemically diverse class of HIV-1 specific antiretroviral drugs. NNRTIs are non competitive inhibitors of the HIV reverse transcriptase (RT) that bind to a hydrophobic pocket in the vicinity of the active site of RT and as such inhibit polymerization via an allosteric mechanism. Three representatives are currently approved at the EU level : nevirapine and efavirenz (first generation NNRTls) and the recently approved etravirine, a next generation NNRTI. A deep understanding of first generation NNRTI resistance mechanisms as well as a particular attention to chemical structure and binding modes has driven class optimization.

Purpose of the studyIn the randomised, controlled, Phase III TITAN trial, at week 96, significantly more patients on darunavir coadministered with low-dose ritonavir (DRV/r) than on lopinavir/r (LPV/r) achieved HIV-1 RNA <400 copies/mL (67.5% vs. 59.5%;difference 8%, 95% CI 0.1-15.8),confirming non-inferiority (p < 0.001) and superiority of DRV/r over LPV/r (p = 0.034).A detailed resistance characterisation of virological failures (VFs) was performed.