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N6-methyladenosine (m6A) is present in diverse viral RNA and plays important regulatory roles in virus replication and host antiviral innate immunity. However, the role of m6A in regulating JEV replication has not been investigated. Here, we show that the JEV genome contains m6A modification upon infection of mouse neuroblast cells (neuro2a). JEV infection results in a decrease in the expression of m6A writer METTL3 in mouse brain tissue. METTL3 knockdown by siRNA leads to a substantial decrease in JEV replication and the production of progeny viruses at 48 hpi. Mechanically, JEV triggered a considerable increase in the innate immune response of METTL3 knockdown neuro2a cells compared to the control cells. Our study has revealed the distinctive m6A signatures of both the virus and host in neuro2a cells infected with JEV, illustrating the positive role of m6A modification in JEV infection. Our study further enhances understanding of the role of m6A modification in Flaviviridae viruses. [ABSTRACT FROM AUTHOR]

Objective We examined the expression of IL-33 as an indicator of an innate immune response in relapsing remitting MS (RRMS) and controls. We proposed a link between the expression of IL-33 and IL-33 regulated genes to histone deacetylase (HDAC) activity and in particular HDAC3, an enzyme that plays a role in the epigenetic regulation of a number genes including those which regulate inflammation. Methods Using TaqMan low density arrays, flow cytometry and ELIZA, expression of IL-33, and family of innate immune response genes which regulate cytokine gene expression was examined in RRMS patients and controls. Results Intracellular expression of IL-33 and IL-33 regulated genes are increased in patients with RRMS. In addition, following in vitro culture with TLR agonist lipopolysaccharide (LPS), there is increased induction of both IL-33 and HDAC3 in RRMS patients over that seen in controls. Also, culture of PBMC with IL-33 led to the expression of genes which overlapped with that seen in RRMS patients suggesting that the gene expression signature seen in RRMS is likely to be driven by IL-33 mediated innate immune pathways. Expression of levels of IL-33 but not IL-1 (another gene regulated by TLR agonists) is completely inhibited by Trichostatin A (TSA) establishing a closer regulation of IL-33 but not IL-1 with HDAC. Interpretation These results demonstrate the over expression of innate immune genes in RRMS and offer a causal link between the epigenetic regulation by HDAC and the induction of IL-33. [ABSTRACT FROM AUTHOR]

Abstract: We examined the activation of innate immune pathway mediated by nucleotide-binding oligomerization domain-containing protein 2 (NOD2) in oligodendrocyte precursor cells (OPCs). We show that activation of NOD2 by ligand peptidoglycan (PGN) leads to the recruitment and phosphorylation of receptor-interacting serine/threonine kinase 2 (RIPK2). Phosphorylation of RIPK2 is followed by phosphorylation of neuronal nitric oxide synthase (nNOS), increase in NOS activity and subsequent accumulation of nitric oxide (NO) mediated N-tyrosinylated compounds in OPCs. The reversal of NOS activity by the nNOS inhibitor 7-nitroindazole (7-NI), but not by the iNOS inhibitor l-canavanine, supported the conclusion that the increased NOS activity was due to the selective activation of nNOS in OPCs. In addition, NO mediated injury to OPC was reflected in reduction in activity of respiratory enzymes such as complex I and IV, decrease in mitochondrial membrane potential and release of cytochrome-C from mitochondria. Furthermore, intracerebral injection of PGN into corpus callosum (CC) of rats led to the development of demyelination, which appeared as early as by day 3 post-injection, and involved the trunk of the CC by day 14. Accumulation of N-tyrosinylated proteins was seen in oligodendrocytes in regions of the CC which were in close proximity to the injection site. Taken together, these results suggest that PGN induced formation of NO, mitochondrial dysfunction and accumulation of N-tyrosinylated proteins in oligodendrocytes are likely mediators of central nervous system demyelination. [Copyright &y& Elsevier]

• Axl-deficient (Axl−/−) mice exhibited increased susceptibility and decreased survival rate compared with WT mice under JEV infection. • JEV replication in Axl−/− primary neurons is significantly enhanced and the up-regulation of antiviral ISGs in Axl−/− neurons was significantly lower than that in WT neurons. • Axl might play a positive antiviral role in neurons through upregulating ISGs to inhibit JEV replication. Japanese encephalitis virus (JEV) causes the most commonly diagnosed viral encephalitis in Asia. JEV is a highly neurotropic flavivirus that can replicate efficiently in the brain. Axl belongs to the TAM (Tyro3, Axl, Mer) family, a group of tyrosine kinase receptors involved in the viral entry, micked as apoptotic bodies and regulation of innate immunity. However, the underlying mechanisms on its regulation in the neurons for JEV are unclear. Here, we found that Axl was upregulated in neurons after JEV infection. Unexpectedly, Axl deficient (Axl−/−) mice were more susceptible to JEV infection with increased viral loads in neurons. The RNA-sequencing analysis between the wild type neurons and Axl−/− neurons infected with JEV showed that many interferon-stimulated genes were downregulated in the Axl−/− neurons which innate immunity was attenuated largely. The rescue experiment in Axl−/− neurons indicated that Axl may be positively involved in the regulation of antiviral immunity. Taken together, our data demonstrated that Axl may play an antiviral role in JEV replication within neurons by modulating neuronal innate immunity. [ABSTRACT FROM AUTHOR]