Immune-mediated diseases of the CNS, such as multiple sclerosis and its animal model, experimental autoimmune encephalitis (EAE), are characterized by the activation of antigen-presenting cells and the infiltration of autoreactive lymphocytes within the CNS, leading to demyelination, axonal damage, and neurological deficits. Hepatocyte growth factor (HGF) is a pleiotropic factor known for both neuronal and oligodendrocytic protective properties. Here, we assess the effect of a selective overexpression of HGF by neurons in the CNS of C57BL/6 mice carrying an HGF transgene (HGF-Tg mice). EAE induced either by immunization with myelin oligodendrocyte glycoprotein peptide or by adoptive transfer of T cells was inhibited in HGF-Tg mice. Notably, the level of inflammatory cells infiltrating the CNS decreased, except for CD25 ⁺ Foxp3 ⁺ regulatory T (T _reg ) cells, which increased. A strong T-helper cell type 2 cytokine bias was observed: IFN-γ and IL-12p70 decreased in the spinal cord of HGF-Tg mice, whereas IL-4 and IL-10 increased. Antigen-specific response assays showed that HGF is a potent immunomodulatory factor that inhibits dendritic cell (DC) function along with differentiation of IL-10–producing T _reg cells, a decrease in IL-17–producing T cells, and down-regulation of surface markers of T-cell activation. These effects were reversed fully when DC were pretreated with anti-cMet (HGF receptor) antibodies. Our results suggest that, by combining both potentially neuroprotective and immunomodulatory effects, HGF is a promising candidate for the development of new treatments for immune-mediated demyelinating diseases associated with neurodegeneration such as multiple sclerosis.

Studies in experimental autoimmune encephalomyelitis (EAE), a murine model of multiple sclerosis (MS), have shown that regulatory B cells modulate the course of the disease via the production of suppressive cytokines. While data indicate a role for transforming growth factor (TGF)-β1 expression in regulatory B cell functions, this mechanism has not yet been tested in autoimmune neuroinflammation. Transgenic mice deficient for TGF-β1 expression in B cells (B–TGF-β1^−/−) were tested in EAE induced by recombinant mouse myelin oligodendrocyte glycoprotein (rmMOG). In this model, B–TGF-β1^−/− mice showed an earlier onset of neurologic impairment compared to their littermate controls. Exacerbated EAE susceptibility in B–TGF-β1^−/− mice was associated with augmented CNS T helper (Th)1/17 responses. Moreover, selective B cell TGF-β1–deficiency increased the frequencies and activation of myeloid dendritic cells, potent professional antigen-presenting cells (APCs), suggesting that B cell-derived TGF-β1 can constrain Th1/17 responses through inhibition of APC activity. Collectively our data suggest that B cells can down-regulate the function of APCs, and in turn encephalitogenic Th1/17 responses, via TGF-β1, findings that may be relevant to B cell-targeted therapies.

There is growing awareness that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, even in its mild or moderate respiratory forms, can include long-term neuropsychological deficits. Standardized neuropsychological, psychiatric, neurological, and olfactory tests were administered to 45 patients 236.51 ± 22.54 days after hospital discharge following severe, moderate, or mild respiratory severity from SARS-CoV-2 infection (severe = intensive care unit hospitalization, moderate = conventional hospitalization, mild = no hospitalization). Deficits were found in all domains of cognition, and the prevalence of psychiatric symptoms was relatively high in the three groups. The severe infection group performed more poorly on long-term episodic memory tests and exhibited greater anosognosia than did the other two groups. Those with moderate infection had poorer emotion recognition, which was positively correlated with persistent olfactory dysfunction. Individuals with mild infection were more stressed, anxious, and depressed. The data support the hypothesis that the virus targets the central nervous system (notably the limbic system) and the notion that there are different neuropsychological phenotypes.