Large yellow croaker(Larimichthys crocea)mitofusin 2 inhibits type I IFN responses by degrading MAVS via enhanced K48‑linked ubiquitination

In mammals,mitofusin 2(MFN2)is involved in mitochondrial fusion,and suppresses the virus-induced RIG-I-like receptor(RLR)signaling pathway.However,little is known about the function of MFN2 in non-mammalian species.In the present study,we cloned an MFN2 ortholog(LcMFN2)in large yellow croaker(Larimichthys crocea).Phylogenetic analysis showed that MFN2 emerged after the divergence of amphioxus and vertebrates.The protein sequences of MFN2 were well conserved from fsh to mammals.LcMFN2 was expressed in all the tissues/organs examined at diferent levels,and its expression was upregulated in response to poly(I:C)stimulation.Overexpression of LcMFN2 inhibited MAVS-induced type I interferon(IFN)promoter activation and antiviral gene expression.In contrast,knockdown of endogenous LcMFN2 enhanced poly(I:C)induced production of type I IFNs.Additionally,LcMFN2 enhanced K48-linked polyubiquitination of MAVS,promoting its degradation.Also,overexpression of LcMFN2 impaired the cellular antiviral response,as evidenced by the increased expression of viral genes and more severe cytopathic efects(CPE)in cells infected with spring viremia of carp virus(SVCV).These results indicated that LcMFN2 inhibited type I IFN response by degrading MAVS,suggesting its negative regulatory role in cellular antiviral response.Therefore,our study sheds a new light on the regulatory mechanisms of the cellular antiviral response in teleosts.

A finTRIM member 100 (FTR100) is unique to Otomorpha fish for constitutive regulation of IFN response

Vertebrate interferon(IFN)expression is fine-tuned in order to avoid excessive tissue injury under normal conditions and during virus infection.FinTRIM(fish novel TRIM,FTR)proteins are reported to regulate the fish IFN response.Here,we identify a novel finTRIM gene from yellow catfish(Pelteobagrus fulvidraco),which is sequentially named PfFTR100 according to the nomenclature rule in zebrafish.Genome-wide analyses reveal that FTR100 is unique to Otomorpha fish,with a single copy in spite of additional genome duplication in some fish species.Considering that few of the 99 finTRIM genes identified in zebrafish are conserved in main fish branches and most,such as FTR100,are unique to distinct branches due to lineage-specific expansion of finTRIM genes,we develop a nomenclature for newly cloned finTRIM genes from different fish species.PfFTR100 mRNA is not induced by virus infection,with a relatively high expression level comparable to that of cellular IFN and some IFN-stimulated genes(ISGs)in virally-infected tissues.However,ectopically-expressed PfFTR100 protein is attenuated in virally-infected cells through the proteasomal-dependent pathway.Overexpression of PfFTR100 promotes SVCV replication by downregulating the constitutive and inducible IFN response via a mechanism by which PfFTR100 targets IRF3 and IRF7 to attenuate their mRNA levels rather than their protein levels.Our results indicate that yellow catfish FTR100 is essential for homeostatic regulation of fish tonic IFN response.

Th1 cells inducing IFNγ response improves immunotherapy efficacy in gastric cancer

Objective: Cancer immunotherapy has made remarkable advances in recent years, but its effectiveness in treating gastric cancer is often limited by the complexity of the tumor microenvironment and the lack of effective biomarkers. This study aimed to identify effective biomarkers for immunotherapy treatment by characterizing the tumor microenvironment.Methods: We retrieved the RNA-seq data from gastric cancer patients treated with the programmed death 1(PD-1) blockade pembrolizumab. Differentially expressed genes associated with clinical outcomes were identified and further analyzed using gene ontology(GO) and Kyoto Encyclopedia of Genes and Genomes(KEGG) pathway analysis. Gene signature scores were calculated by single sample Gene Set Enrichment Analysis(ssGSEA). The infiltration levels of immune cells were quantified using the xCell website. Cell type enrichment analysis was performed to compare treatment response and non-response groups, and regression analysis was used to investigate the relationship between interferon gamma(IFNγ) immune response and immune cell infiltration. Biomarkers were identified using least absolute shrinkage and selection operator(LASSO) analysis.Results: Compared to normal tissues, cytokine activity and interleukin-6 production were highly activated in gastric tumors. Responders to pembrolizumab showed significantly up-regulated expression of IFNγ responserelated genes. Cell type enrichment analysis revealed that Th1 cells were significantly enriched in the tumor microenvironment of responders. Regression analysis indicated that Th1 cells induced IFNγ response more efficiently than other cell types. Using signatures of Th1 cells, stromal cells and IFNγ response, a set of eight genes were identified that effectively predicted the efficacy of immunotherapy treatment and patient prognosis.Conclusions: Th1 cells promote therapeutic efficacy of PD-1 blockade by promoting IFNγ immune response in gastric cancer. The identified biomarkers have the potential to improve the effectiveness of immunotherapy treatment for gastric cancer patients.

Hepatitis B virus evades immune recognition via RNA adenosine deaminase ADAR1-mediated viral RNA editing in hepatocytes

HBV is considered as a“stealth”virus that does not invoke interferon(IFN)responses;however,the mechanisms by which HBV bypasses innate immune recognition are poorly understood.In this study,we identified adenosine deaminases acting on RNA 1(ADAR1),which is a key factor in HBV evasion from IFN responses in hepatocytes.Mechanically,ADAR1 interacted with HBV RNAs and deaminated adenosine(A)to generate inosine(I),which disrupted host immune recognition and thus promoted HBV replication.Loss of ADAR1 or its deficient deaminase activity promoted IFN responses and inhibited HBV replication in hepatocytes,and blocking the IFN signaling pathways released the inhibition of HBV replication caused by ADAR1 deficiency.Notably,the HBV X protein(HBx)transcriptionally promoted ADAR1 expression to increase the threshold required to trigger intrinsic immune activation,which in turn enhanced HBV escape from immune recognition,leading to persistent infection.Supplementation with 8-azaadenosine,an ADAR1 inhibitor,efficiently enhanced liver immune activation to promote HBV clearance in vivo and in vitro.Taken together,our results delineate a molecular mechanism by which HBx promotes ADAR1-derived HBV immune escape and suggest a targeted therapeutic intervention for HBV infection.

α-Lipoic Acid Exerts Its Antiviral Effect against Viral Hemorrhagic Septicemia Virus(VHSV) by Promoting Upregulation of Antiviral Genes and Suppressing VHSV-Induced Oxidative Stress

Viral hemorrhagic septicemia virus(VHSV), belonging to the genus Novirhabdovirus, Rhabdoviridae family, is a causative agent of high mortality in fish and has caused significant losses to the aquaculture industry. Currently, no effective vaccines, Food and Drug Administration-approved inhibitors, or other therapeutic intervention options are available against VHSV. α-Lipoic Acid(LA), a potent antioxidant, has been proposed to have antiviral effects against different viruses. In this study, LA(CC_(50)= 472.6 lmol/L) was repurposed to exhibit antiviral activity against VHSV. In fathead minnow cells,LA significantly increased the cell viability post-VHSV infection(EC_(50)= 42.7 lmol/L), and exerted a dose-dependent inhibitory effect on VHSV induced-plaque, cytopathic effects, and VHSV glycoprotein expression. The time-of-addition assay suggested that the antiviral activity of LA occurred at viral replication stage. Survival assay revealed that LA could significantly upregulated the survival rate of VHSV-infected largemouth bass in both co-injection(38.095% vs. 1.887%,P < 0.01) and post-injection manner(38.813% vs. 8.696%, P < 0.01) compared with the control group. Additional comparative transcriptome and q RT-PCR analysis revealed LA treatment upregulated the expression of several antiviral genes, such as IRF7, Viperin, and ISG15. Moreover, LA treatment reduced VHSV-induced reactive oxygen species production in addition to Nrf2 and SOD1 expression. Taken together, these data demonstrated that LA suppressed VHSV replication by inducing antiviral genes expression and reducing VHSV-induced oxidative stress. These results suggest a new direction in the development of potential antiviral candidate drugs against VHSV infection.