Intragenic Transcription from Defective HIV Proviruses Triggers Interferon Responses in Myeloid Cells

The persistent HIV-1 reservoir includes a subset of cells harboring transcriptionally repressed latent HIV-1 that contributes to rebound upon antiretroviral treatment (ART) interruption. However, the majority of the reservoir consists of defective proviral genomes with mutations that prevent production of HIV -1 virions. People with HIV (PWH), even with suppression of viremia, demonstrate comorbidities of the central nervous system, heart, gut, and general aging-associated inflammation. Previously, we identified a transcriptionally active element within the envelope gene (env) of HIV-1 which mediates the expression of aberrant HIV-1 RNAs. We hypothesize that spurious expression of defective proviruses contributes to the general inflammation that drives these comorbidities. We observed correlations between levels of pro-inflammatory cytokines in serum of PWH and levels of HIV-1 transcripts from this intragenic promoter. To investigate the impact of defective proviruses, we employed CRISPR-Cas9 to render the 5' Long Terminal Repeat (LTR), which acts as the enhancer and promoter for proviral transcription, non-functional. HIV-1 infected cells harboring this deletion produce significantly higher levels of IP-10 in vitro in both monocytic cell lines and primary monocyte-derived macrophages. Transcripts generated from the env promoter, include a 5' cap and polyA tail and the induction of IP-10 expression was dependent on the cytosolic innate immune sensing pathway components MDA5 and MAVS. We propose that defective HIV proviruses contribute to chronic inflammation in PWH via an MDA5-dependent induction of type I interferon pathways.