Novel HIV-1 MiRNAs Stimulate TNFα Release in Human Macrophages via TLR8 Signaling Pathway

Abstract

PurposeTo determine whether HIV-1 produces microRNAs and elucidate whether these miRNAs can induce inflammatory response in macrophages (independent of the conventional miRNA function in RNA interference) leading to chronic immune activation.MethodsUsing sensitive quantitative Real Time RT-PCR and sequencing, we detected novel HIV-derived miRNAs in the sera of HIV+ persons, and associated with exosomes. Release of TNFα by macrophages challenged with HIV miRNAs was measured by ELISA.ResultsHIV infection of primary alveolar macrophages produced elevated levels of viral microRNAs vmiR88, vmiR99 and vmiR-TAR in cell extracts and in exosome preparations from conditioned medium. Furthermore, these miRNAs were also detected in exosome fraction of sera from HIV-infected persons. Importantly, vmiR88 and vmiR99 (but not vmiR-TAR) stimulated human macrophage TNFα release, which is dependent on macrophage TLR8 expression. These data support a potential role for HIV-derived vmiRNAs released from infected macrophages as contributing to chronic immune activation in HIV-infected persons, and may represent a novel therapeutic target to limit AIDS pathogenesis.ConclusionNovel HIV vmiR88 and vmiR99 are present in the systemic circulation of HIV+ persons and could exhibit biological function (independent of gene silencing) as ligands for TLR8 signaling that promote macrophage TNFα release, and may contribute to chronic immune activation. Targeting novel HIV-derived miRNAs may represent a therapeutic strategy to limit chronic immune activation and AIDS progression.

Exosomes from HIV-1-infected Cells Stimulate Production of Pro-inflammatory Cytokines through Trans-activating Response (TAR) RNA

“…Our data strongly suggest that exosome-packaged full-size TAR RNA (ϳ90%), as well as TAR miRNA (ϳ10%), may bind to TLRs in recipient cells and activate the NF-B pathway. A similar analogous finding has been shown for TNF-␣ release and TLR8 signaling (75). The final net effect would be to keep the uninfected recipient cells in an active state to potentially allow the incoming virus to enter and replicate efficiently in these cells or simply contribute to a cytokine "storm" phenotype.…”

Extracellular vesicles and viruses: Are they close relatives?

“…The PRRs in EVtargeted cells may recognize such RNAs as pathogen-associated molecular patterns (PAMPs) and respond by triggering the innate antiviral response (38,61). HIV-infected macrophages also release EV containing viral RNAs (viral miRNAs vmiR88 and -99) that trigger endosomal TLR8 and NF-κB signaling in EV-targeted bystander macrophages (61).…”

Transcellular delivery of vesicular SOCS proteins from macrophages to epithelial cells blunts inflammatory signaling

“…cellular membranes, they often harbor overlapping cargo (Choi et al, 2013). Little is known about vesicular secretion in macrophages, and we are aware of only one report of Exos secretion (Bernard et al, 2014) and no reports of MP secretion in AMs. SOCS1 and SOCS3 proteins were trafficked in AMs largely through different types of vesicles; however, because both types of vesicle undergo uptake by target cells with intracellular delivery of cargo molecules, as reflected by the ability of both AM-derived MPs and Exos to inhibit STAT activation, the functional significance of these divergent vesicular trafficking pathways is not clear at this time.…”