HIV infection impairs host immunity, leading to progressive disease. An anti-retroviral treatment efficiently controls viremia but cannot completely restore the immune dysfunction in HIV-infected individuals. Both host and viral factors determine the rate of disease progression. Among the host factors, innate immunity plays a critical role; however, the mechanism(s) associated with dysfunctional innate responses are poorly understood among HIV disease progressors, which was investigated here. The gene expression profiles of TLRs and innate cytokines in HIV-infected (LTNPs and progressors) and HIV-uninfected individuals were examined. Since the progressors showed a dysregulated TLR-mediated innate response, we investigated the role of TLR agonists in restoring the innate functions of the progressors. The stimulation of PBMCs with TLR3 agonist-poly:(I:C), TLR7 agonist-GS-9620 and TLR9 agonist-ODN 2216 resulted in an increased expression of IFN-α, IFN-β and IL-6. Interestingly, the expression of IFITM3, BST-2, IFITM-3, IFI-16 was also increased upon stimulation with TLR3 and TLR7 agonists, respectively. To further understand the molecular mechanism involved, the role of miR-155 was explored. Increased miR-155 expression was noted among the progressors. MiR-155 inhibition upregulated the expression of TLR3, NF-κB, IRF-3, TNF-α and the APOBEC-3G, IFITM-3, IFI-16 and BST-2 genes in the PBMCs of the progressors. To conclude, miR-155 negatively regulates TLR-mediated cytokines as wel l as the expression of host restriction factors, which play an important role in mounting anti-HIV responses; hence, targeting miR-155 might be helpful in devising strategic approaches towards alleviating HIV disease progression.

Although persistent neurological sequelae in long COVID are reportedly well associated with neuroinflammation, the underlying regulatory mechanisms remain poorly characterized. Previously, we identified dysregulated microRNA expression, including let-7a-5p, in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike S1-stimulated human microglial cells by RNA sequencing; however, how let-7a-5p regulates the S1-mediated neuroinflammatory processes remains undetermined. In the present study, we examined the functional role of let-7a-5p in alleviating S1-induced microglial inflammation in the CHME3 cell line as well as in human monocyte-derived microglia (MDMi) using a loss- and gain-of-function approach. Functional inhibition of let-7a-5p resulted in mitigating S1-induced inflammatory cytokine release and markers of pyroptosis. Mechanistically, we established SHIP-1 as a direct target of let-7a-5p using luciferase reporter assay validation. Interestingly, we noted upregulated expression of the TLR3 gene alongside TLR2/4 in S1-stimulated microglia. Although we could not establish exactly how TLR3 is stimulated in S1-induced neuroinflammatory processes, using siRNA-mediated inhibition and a pharmacological inhibitor in both CHME3 cells and MDMi, our study certainly provides evidence of TLR3 involvement during S1-induced microglial inflammation, which needs further investigation. Together, these in vitro findings demonstrate that the let-7a-5p/SHIP-1 axis regulates S1-induced inflammatory cascades in CHME3 and MDMi cells, providing mechanistic insight into its role in SARS-CoV-2-associated neuroinflammation and warranting further validation in appropriate in vivo/organoid models.