Innate Immune Training Enhances the Reactivation of Latently Infected HIV-1 from Monocytic Cell lines

Abstract HIV virus can persist in a latent but activatable chronic state in resting CD4 +T-cells and macrophages that are more persistent, leading to the requirement of lifelong combination antiretroviral therapy (cART). The latency of HIV-1 in macrophage cells is associated with increased chromatin condensation induced by histone methylation at HIV-1 integration sites. Innate immune training of macrophages has been shown to relieve chromosome condensation through epigenetic rewiring. We hypothesized that training of macrophages could enhance the reactivation of HIV-1 by opening the chromatin to facilitate transcription in response to Latency Reversing Agents (LRAs). We used beta-glucan, Syk inhibitor and Rutaecarpine to train the THP89GFP cell line, which is an experimental model for latently infected HIV-1 monocytes. We found that these trained THP89GFP cells have higher transcription of HIV-1 specific genes in response to PMA stimulation. To check the epigenetic changes associated with training in the proviral HIV-1 DNA of THP89GFP, we performed a chromatin immunoprecipitation for the histone mark, H3K27Ac. Consistent with the higher induction of transcription of HIV-1 genes, we observed that multiple regions of the HIV-1 LTR had higher deposition of H3K27Ac in the trained macrophages. Our studies thus show that induction of trained innate immunity may be a viable approach to the reactivation of latently infected HIV-1. This finding supports the hypothesis that innate immune training stimuli could be developed as novel candidates for enhancing reactivation of latently infected HIV-1, which may facilitate elimination of macrophage reservoirs. This work was supported by the Intramural Research Program of NIAID, NIH This work was supported by the Intramural Research Program of NIAID, NIH and Office of AIDS research.