InVivoMAb anti-LCMV nucleoprotein

Persistent viral infections are simultaneously associated with chronic inflammation and highly potent immunosuppressive programs mediated by IL-10 and PDL1 that attenuate antiviral T cell responses. Inhibiting these suppressive signals enhances T cell function to control persistent infection; yet, the underlying signals and mechanisms that program immunosuppressive cell fates and functions are not well understood. Herein, we use lymphocytic choriomeningitis virus infection (LCMV) to demonstrate that the induction and functional programming of immunosuppressive dendritic cells (DCs) during viral persistence are separable mechanisms programmed by factors primarily considered pro-inflammatory. IFNγ first induces the de novo development of naive monocytes into DCs with immunosuppressive potential. Type I interferon (IFN-I) then directly targets these newly generated DCs to program their potent T cell immunosuppressive functions while simultaneously inhibiting conventional DCs with T cell stimulating capacity. These mechanisms of monocyte conversion are constant throughout persistent infection, establishing a system to continuously interpret and shape the immunologic environment. MyD88 signaling was required for the differentiation of suppressive DCs, whereas inhibition of stimulatory DCs was dependent on MAVS signaling, demonstrating a bifurcation in the pathogen recognition pathways that promote distinct elements of IFN-I mediated immunosuppression. Further, a similar suppressive DC origin and differentiation was also observed in Mycobacterium tuberculosis infection, HIV infection and cancer. Ultimately, targeting the underlying mechanisms that induce immunosuppression could simultaneously prevent multiple suppressive signals to further restore T cell function and control persistent infections.

The central nervous system is surrounded by three interconnected membranes referred to as the meninges, which host a diverse immune network1-3. Within the skull-interfacing dura mater are venous sinuses, large veins that are traditionally viewed as passive blood drains for the brain and skull4,5. However, these structures also constitute an important neuroimmune interface6-8. Here we used intravital microscopy to gain mechanistic insight into this interface and reveal that dural sinuses and their endothelial cells form a highly dynamic surface that continually restructures to regulate blood flow, fluid movement and immune surveillance. We show that sinuses are not passive conduits, but instead undergo RAMP1-dependent constriction and dilation mediated by smooth muscle, resembling arterial behaviour. Moreover, the superior sagittal sinus in mice is bifurcated into upper and lower chambers that contribute to intracranial pressure regulation. Both chambers are lined by specialized, highly fenestrated sinus endothelial cells (SECs) that permit movement of fluids, macromolecules and microorganisms between the sinus lumen and leukocyte-rich perisinus space. To safeguard this permeable interface, SECs dynamically open and close intercellular boundaries in a RAMP2-dependent manner. Transcranial RAMP2 antagonism impaired SEC boundary dynamics and reduced immune cell trafficking along the sinus wall during homeostasis and systemic viral infection. Disruption of SEC dynamics during infection compromised local antiviral immunity and promoted pathogen entry into the meninges. Together, these findings establish dural sinuses as dynamic venous structures that regulate fluid exchange and support immune surveillance and antiviral defence.

Emerging and reemerging viruses pose a significant threat to global health. Although direct-acting antivirals have shown success, their efficacy is limited by the rapid emergence of drug-resistant viral variants. Hence, there is an urgent need for additional broad spectrum antiviral therapeutic strategies. Here, we identify by phenotypic screening a set of stereochemically defined photoreactive small molecules (photo-stereoprobes) that stereoselectively suppress SARS-CoV-2 replication in human lung epithelial cells. Structure-activity relationship-guided chemical proteomics identified the eukaryotic translation termination factor 1 (ETF1) as a target of the photo-stereoprobes, and this interaction was recapitulated with recombinant purified ETF1. We found that the photo-stereoprobes modulate programmed ribosomal frameshifting mechanisms essential for SARS-CoV-2 infection without causing ETF1 degradation, thus distinguishing the photo-stereoprobes from other known ETF1-directed small molecules. We finally show that the photo-stereoprobes also inhibit the replication of additional viruses with noncanonical ribosomal frameshifting mechanisms. Our findings identify a mechanistically distinct class of ETF1 ligands that implicate host translation termination processes as a potential drug target for antiviral development.

Mast cells are tissue-resident immune sentinels. However, their spatial localization and potential role in the antiviral response within the meninges-the protective barrier surrounding the central nervous system-remain unclear. Here, the distribution pattern along meningeal vasculature is maped and identified a post-weaning maturation process. Single-cell RNA sequencing reveals that mast cells mount a robust immune response against LCMV infection. Ablation of mast cells results in reduced CD8+ T cell infiltration and impairs viral clearance. Mechanistic dissection identifies a critical role for the IL-33 receptor on mast cells, which responds to IL-33 derived from stromal cells, in mediating antiviral immunity. Further analysis shows that mast cells synergistically upregulate cytokines and chemokines in response to IL-33 and ATP released by virus-infected stromal cells. Collectively, these findings reveal a critical role for mast cells in enhancing meningeal antiviral immunity and highlight potential strategies for brain protection during infection.