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The angiotensin-converting enzyme 2 (ACE2) is a primary cell surface viral binding receptor for SARS-CoV-2, so finding new regulatory molecules to modulate ACE2 expression levels is a promising strategy against COVID-19. In the current study, we utilized islet organoids derived from human embryonic stem cells (hESCs), animal models and COVID-19 patients to discover that fibroblast growth factor 7 (FGF7) enhances ACE2 expression within the islets, facilitating SARS-CoV-2 infection and resulting in impaired insulin secretion. Using hESC-derived islet organoids, we demonstrated that FGF7 interacts with FGF receptor 2 (FGFR2) and FGFR1 to upregulate ACE2 expression predominantly in ? cells. This upregulation increases both insulin secretion and susceptibility of ? cells to SARS-CoV-2 infection. Inhibiting FGFR counteracts the FGF7-induced ACE2 upregulation, subsequently reducing viral infection and replication in the islets. Furthermore, retrospective clinical data revealed that diabetic patients with severe COVID-19 symptoms exhibited elevated serum FGF7 levels compared to those with mild symptoms. Finally, animal experiments indicated that SARS-CoV-2 infection increased pancreatic FGF7 levels, resulting in a reduction of insulin concentrations in situ. Taken together, our research offers a potential regulatory strategy for ACE2 by controlling FGF7, thereby protecting islets from SARS-CoV-2 infection and preventing the progression of diabetes in the context of COVID-19.

Advancements in vaccination and sanitation have significantly reduced the prevalence and burden of infectious diseases; however, these benefits have coincided with a marked rise in autoimmune and allergic disorders. Recent studies have investigated these linked trends through the lens of host-microbiome alterations, proposing these shifts as a potential explanatory mechanism. Previously, we demonstrated that vancomycin-induced depletion of short-chain fatty acid (SCFA)-producing bacteria results in hyperactivation of ILC2s and exacerbated allergic responses. Here we investigate the effects of low-dose streptomycin on innate and adaptive immune cell populations and their activation states. Although streptomycin-treated mice exhibit normal allergic responses, they display heightened susceptibility to Th1/Th17-mediated disease, specifically hypersensitivity pneumonitis (HP). This is characterized by a two-fold increase in ILC3s and Th17 cells in the lungs, alongside activation of antigen-presenting cells (APCs) at steady state-an effect that is further amplified upon exposure to HP-inducing agents. Shotgun metagenomic analysis revealed that streptomycin-induced dysbiosis reduces microbial diversity, depletes bile acid-metabolizing bacteria, and enriches for metabolic pathways involved in branched-chain amino acid biosynthesis, including leucine-a known activator of mTORC1. Strikingly, administration of the secondary bile acid metabolite isolithocholic acid (an inverse agonist of RORγt), or an IL-23 neutralizing antibody, reverses the enhanced susceptibility to HP. Inhibition of mTORC1 significantly reduced Th17/ILC3 responses and histopathology. Our findings underscore microbial equilibrium as a key determinant of susceptibility to HP and uncover a positive feedback loop between IL and 23-producing APCs and ILC3/Th17 cells that mechanistically links dysbiosis to sustained type 3 inflammation, and we identify a simple, actionable means of intervention.

The COVID-19 pandemic reminded us of the urgent need for new antivirals to control emerging infectious diseases and potential future pandemics. Immunotherapy has revolutionized oncology and could complement the use of antivirals, but its application to infectious diseases remains largely unexplored. Nucleoside analogs are a class of agents widely used as antiviral and anti-neoplastic drugs. Their antiviral activity is generally based on interference with viral nucleic acid replication or transcription. Based on our previous work and computer modeling, we hypothesize that antiviral adenosine analogs, like remdesivir, have previously unrecognized immunomodulatory properties which contribute to their therapeutic activity. In the case of remdesivir, we here show that these properties are due to its metabolite, GS-441524, acting as an Adenosine A2A Receptor antagonist. Our findings support a new rationale for the design of next-generation antiviral agents with dual - immunomodulatory and intrinsic - antiviral properties. These compounds could represent game-changing therapies to control emerging viral diseases and future pandemics.

Alveolar macrophages (AM) perform a primary defense mechanism in the lung through phagocytosis of inhaled particles and microorganisms. AM are known to be relatively immunosuppressive consistent with the aim to limit alveolar inflammation and maintain effective gas exchange in the face of these constant challenges. How AM respond to T cell derived cytokine signals, which are critical to the defense against inhaled pathogens, is less well understood. For example, successful containment of Mycobacterium tuberculosis (Mtb) in lung macrophages is highly dependent on IFN-$\gamma$ secreted by Th-1 lymphocytes, however, the proteomic IFN-$\gamma$ response profile in AM remains mostly unknown. In this study, we measured IFN-$\gamma$ induced protein abundance changes in human AM and autologous blood monocytes (MN). AM cells were activated by IFN-$\gamma$ stimulation resulting in STAT1 phosphorylation and production of MIG/CXCL9 chemokine. However, the global proteomic response to IFN-$\gamma$ in AM was dramatically limited in comparison to that of MN (9 AM vs 89 MN differentially abundant proteins). AM hypo-responsiveness was not explained by reduced JAK-STAT1 signaling nor increased SOCS1 expression. These findings suggest that AM have a tightly regulated response to IFN-$\gamma$ which may prevent excessive pulmonary inflammation but may also provide a niche for the initial survival and growth of Mtb and other intracellular pathogens in the lung.