HIV-1 latent infection modulates RNA sensors and innate immunity signaling in human brain pericytes

BACKGROUND. Cerebrovascular and neurological diseases are frequent co-morbidities among people with HIV. Our laboratory has described that brain pericytes (BP) can harbor HIV infection and function as a reservoir of viral latent infection in the Central Nervous System. Given that the interaction between pericytes and endothelial cells in the blood-brain barrier (BBB) are necessary for proper formation, development, stabilization, and maintenance of the BBB, we investigated whether active and/or latent HIV-1 infection can differently modulate inflammatory response in BPs, with a focus on RNA sensor and type I interferon (IFN) pathways. METHODS. Primary cultures of human brain vascular pericytes were infected with 60 ng/ml of p24 HIV (NL4-3 strain). Three and 7 days post-infection (dpi), which were previously shown to correspond to active and latent infection, respectively, protein and total RNA were extracted from infected and uninfected control cultures. Expression or protein content of RNA sensors and downstream activators and members of type I IFN response and IFN response genes were determined by RT-qPCR and western blotting, respectively. RESULTS. At 3 dpi, HIV gag transcripts were detected at high levels in infected cultures, which dropped significantly at 7 dpi. RIG-1 protein levels were significantly increased at 7 dpi (2.3-fold), whereas MDA5 was decreased by 0.5-fold. Similarly, STING (Stimulator of IFN genes) mRNA and protein levels were increased at 7 dpi, accompanied by increased expression of MAVS and of TBK1 (TANK-binding kinase 1, 1.7-fold), and phosphorylation of IRF3 (interferon regulatory factor 3). The IFN-α/β receptor type I (IFNAR1) and STAT1 transcripts were selectively increased at 7 dpi. Expression of interferon-induced protein with tetratricopeptide repeats-1 (IFIT1) was transiently increased at 3 dpi and reduced at 7 dpi. No changes in the cGAS, TRAF3, IFN-stimulated gene 15 (ISG15) and Interferon-induced GTP-binding protein Mx1 were observed at the mRNA levels in infected cultures, as compared to controls. CONCLUSIONS. HIV-1 differentially modulates IFN responses in BPs, which can affect BBB integrity in chronic infections. Interestingly, latently infected BPs can contribute to long-term neuroinflammatory stimuli in the CNS.