Macrophages Harbor Transcriptionally Active Defective HIV Provirus Which Contribute to Immune Activation

Abstract

Abstract People living with HIV suffer from a variety of co-morbidities including neurological deficits and cardiovascular disease even while on antiretroviral therapy (ART). Chronic inflammation has been implicated in these co-morbidities and has long been described in HIV patients. Characterization of the HIV DNA (provirus) reservoir in CD4 T cells from HIV patients on ART has revealed that more than 90% are defective and unable to complete the viral life cycle. Macrophages are susceptible to HIV infection and are positioned at the nexus of pathogen detection, inflammation, and priming of adaptive immune responses. We hypothesized that HIV-infected macrophages harbor defective HIV proviruses which remain transcriptionally competent and affect adaptive immune responses. To test this, we examined the status of HIV proviruses in primary human monocyte-derive macrophages (MDMs) and their expression of HIV transcripts. MDMs were infected with HIV in vitro and using an intact provirus detection assay we observed that roughly half of HIV proviruses were defective. Reverse transcription droplet-digital PCR (RT-ddPCR) detected a distribution of HIV transcripts, many of which lack the full 5′ LTR sequence consistent with transcription starting from an intragenic site. When CD8 T cells were co-cultured with autologous HIV-infected MDMs, they increased their expression of CD107a, a degranulation marker, indicating that infected macrophages could trigger CD8+ activation. Together, these results support that alternative transcriptional mechanisms, which persist in the absence of a fully functional LTR, are active during HIV infection in macrophages, contributing to macrophage dysfunction and persistent HIV-associated diseases.