HIV Induces RSAD2/Viperin To Promote Sustained Infection of Monocyte-Derived Macrophages
HIV establishes long-term latent infection in memory CD4+ T cells, but also establishes sustained long-term productive infection in macrophages, especially in the CNS.  To better understand how HIV sustains infection in macrophages, we performed RNAseq analysis after infection of human-monocyte derived macrophages (MDMs) with the brain-derived HIV-1 strain YU2 and compared this with acute infection of CD4+ T cells. HIV infection in MDM and CD4+ T-cells altered many gene transcripts, but with few overlaps between these different cell types. We found interferon pathways upregulated in both MDM and CD4+ T-cells, but with different gene signatures.  The interferon-stimulated gene RSAD2/Viperin was among the most upregulated genes following HIV infection in MDMs, but not in CD4+ T-cells.  RSAD2/Viperin was induced early after infection with various HIV strains, was sustained over time, and remained elevated in established MDM infection even if new rounds of infection were blocked by antiretroviral treatment.  Immunofluorescence microscopy revealed that RSAD2/Viperin was induced strongly in HIV infected cells, as well as in some uninfected neighboring cells, and was frequently localized at junctions between cells.  Knockdown of RSAD2/Viperin following establishment of infection in MDMs reduced production of HIV transcripts and viral p24 antigen.  This correlated with reduction in the number of multinucleated giant cells, and changes in the histone modifications at the HIV LTR, including loss of histone H3K7ac and H3K9me3, epigenetic marks that we have found associated with HIV in MDMs.  RNA-seq transcriptomic analysis of RSAD2/Viperin knockdown during HIV infection of MDMs revealed activation of interferon alpha and gamma pathways and inactivation of Rho GTPase pathways. Taken together, these results suggest that RSAD2/Viperin supports HIV infection in macrophages through multiple mechanisms, potentially including the attenuation of the interferon response. Overall design: We knocked down RSAD2 in HIV infected MDMs using siRNA (siRSAD2 or siControl) and then studied the effect of knockdown on MDM transcriptomic response by RNA-seq.