Chemical inhibition of DPP9 sensitizes the CARD8 inflammasome in HIV-1-infected cells

Non-nucleoside reverse transcriptase inhibitors (NNRTIs) induce pyroptosis of HIV-1-infected CD4+ T cells through induction of intracellular HIV-1 protease activity, which activates the CARD8 inflammasome. Because high concentrations of NNRTIs are required for efficient elimination of HIV-1-infected cells, it is important to elucidate ways to sensitize the CARD8 inflammasome to NNRTI-induced activation. We show that this sensitization can be achieved through chemical inhibition of the CARD8 negative regulator DPP9. The DPP9 inhibitor Val-boroPro (VbP) can kill HIV-1-infected cells without the presence of NNRTIs and act synergistically with NNRTIs to promote clearance of HIV-1-infected cells in vitro and in humanized mice. More importantly, VbP is able to enhance clearance of residual HIV-1 in CD4+ T cells isolated from people living with HIV (PLWH). We also show that VbP can partially overcome NNRTI resistance. This offers a promising strategy for enhancing NNRTI efficacy in the elimination of HIV-1 reservoirs in PLWH.

Characterization of Nucleoside Reverse Transcriptase Inhibitor-Associated Mutations in the RNase H Region of HIV-1 Subtype C Infected Individuals

The South African national treatment programme includes nucleoside reverse transcriptase inhibitors (NRTIs) in both first and second line highly active antiretroviral therapy regimens. Mutations in the RNase H domain have been associated with resistance to NRTIs but primarily in HIV-1 subtype B studies. Here, we investigated the prevalence and association of RNase H mutations with NRTI resistance in sequences from HIV-1 subtype C infected individuals. RNase H sequences from 112 NRTI treated but virologically failing individuals and 28 antiretroviral therapy (ART)-naive individuals were generated and analysed. In addition, sequences from 359 subtype C ART-naive sequences were downloaded from Los Alamos database to give a total of 387 sequences from ART-naive individuals for the analysis. Fisher's exact test was used to identify mutations and Bayesian network learning was applied to identify novel NRTI resistance mutation pathways in RNase H domain. The mutations A435L, S468A, T470S, L484I, A508S, Q509L, L517I, Q524E and E529D were more prevalent in sequences from treatment-experienced compared to antiretroviral treatment naive individuals, however, only the E529D mutation remained significant after correction for multiple comparison. Our findings suggest a potential interaction between E529D and NRTI-treatment; however, site-directed mutagenesis is needed to understand the impact of this RNase H mutation.

Identification of Novel Resistance-Related Polymorphisms in HIV-1 Subtype C RT Connection and RNase H Domains from Patients Under Virological Failure in Brazil

Mutations in the connection and RNase H C-terminal reverse transcriptase (RT) domains of HIV-1 have been shown to impact drug resistance to RT inhibitors. However, their impact in the context of non-B subtypes has been poorly assessed. This study aimed to characterize resistance-related mutations in the C-terminal portions of RT in treatment-failing patients from southern Brazil, a region with endemic HIV-1 subtype C (HIV-1C). Viral RNA was isolated and reverse transcribed from 280 infected subjects, and genomic regions were analyzed by polymerase chain reaction, DNA sequencing, and phylogenetic analysis. Two novel mutations, M357R and E529D, were evidenced in Brazilian HIV-1C strains from treatment-failing patients. In global viral isolates of subjects on treatment, M357R was selected in HIV-1C and CRF01_AE and E529D was selected in HIV-1 subtype B (HIV-1B). While most C-terminal RT mutations described for HIV-1B also occur in HIV-1C, this work pinpointed novel mutations that display subtype-specific predominance or occurrence.