Molecular Mechanisms and Host Factors Involved in HIV-1 Latency

Abstract

The Human Immunodeficiency virus-1 can stay undetected and unaffected by host immune surveillance and antiretroviral therapy. This phenomenon is called proviral latency and the cells harbouring such viruses are part of the latently infected cell reservoir. In this situation, the viral genome integrates into the host's genome upon infection, whereby infected cells exhibit either very low levels or no viral transcription, and hence no viral proteins or egress viruses are produced that can be detected by the immune system. However, viral transcription can be re-activated to produce infectious viruses under certain circumstances. Host-encoded retroviral restriction factors like APOBEC3 (A3) proteins are part of our intrinsic immune defences against retroviral infection, introducing mutations in viral replication intermediates. We hypothesize that low levels of G-to-A transition mutations in the HIV-1 LTR region, introduced by APOBEC3G/F, could lead to a latency-like phenotype. These latent viruses pose major hurdles for HIV-1 cure therapies. Our lab previously created a library of clones possessing mutations in the LTR introduced by A3G/F. Later, mutated LTRs were cloned into 3 types of plasmid backbones: 1) a pEGFP expression vector to study the transcriptional activity of the mutated promoter, 2) into non-replicative pNL4 ∆env ∆vif viral expression vector, and 3) into a replicative pNL4-CXCR4 viral vector to study infection and induction by latency reversal agent (LRA) treatment to better understand the mechanism of latency and transcriptional induction. Viruses produced from these plasmids carrying mutated promoters are referred to as latency-prone viruses or LPVs in this thesis. Characterizing the transcription, infection, and induction to PMA/I of the LPVs would essentially help in evaluating the role of A3 mutations in viral latency and further help in the development of new therapeutics.