Role of Tim-3 in hepatitis B virus infection:An overview

Hepatitis B virus(HBV) infection has received increasing public attention. h BV is the prototypical member of hepadnaviruses, which naturally infect only humans and great apes and induce the acute and persistent chronic infection of hepatocytes. A large body of evidence has demonstrated that dysfunction of the host anti-viral immune response is responsible for persistent HBV replication, unresolved inflammation and disease progression. Many regulatory factors are involved in immune dysfunction. Among these, T cell immunoglobulin domain and mucin domain-3(Tim-3), one of the immune checkpoint proteins, has attracted increasing attention due to its critical role in regulating both adaptive and innate immune cells. In chronic HBV infection, Tim-3 expression is elevated in many types of immune cells, such as T helper cells, cytotoxic T lymphocytes, dendritic cells, macrophages and natural killer cells. Tim-3 over-expression is often accompanied by impaired function of the abovementioned immunocytes, and Tim-3 inhibition can at least partially rescue impaired immune function and thus promote viral clearance. A better understanding of the regulatory role of Tim-3 in host immunity during HBV infection will shed new light on the mechanisms of h BV-related liver disease and suggest new therapeutic methods for intervention.

Peptide targeting the interaction of S protein cysteine-rich domain with Ezrin restricts pan-coronavirus infection

Dear Editor,To date,seven human coronaviruses(HCoVs)have been identified,among which the highly pathogenic severe acute respiratory syndrome-associated coronavirus(SARS-CoV),Middle East respiratory syndrome coronavirus(MERS-CoV),and severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)have caused public health disasters worldwide.

Palmitoylation of SARS-CoV-2 S protein is essential for viral infectivity

Dear Editor,Severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)is the causative agent of the unprecedented coronavirus disease 2019(COVID-19).SARS-CoV-2 entry into host cells is mediated by the viral transmembrane spike(S)glycoprotein that forms homotrimers protruding from the viral surface.

SARS-CoV-2 NSP5 and N protein counteract the RIG-I signaling pathway by suppressing the formation of stress granules

As a highly pathogenic human coronavirus,SARS-CoV-2 has to counteract an intricate network of antiviral host responses to establish infection and spread.The nucleic acid-induced stress response is an essential component of antiviral defense and is closely related to antiviral innate immunity.However,whether SARS-CoV-2 regulates the stress response pathway to achieve immune evasion remains elusive.In this study,SARS-CoV-2 NSP5 and N protein were found to attenuate antiviral stress granule(avSG)formation.Moreover,NSP5 and N suppressed IFN expression induced by infection of Sendai virus or transfection of a synthetic mimic of dsRNA,poly(I:C),inhibiting TBK1 and IRF3 phosphorylation,and restraining the nuclear translocalization of IRF3.Furthermore,HEK293T cells with ectopic expression of NSP5 or N protein were less resistant to vesicular stomatitis virus infection.Mechanistically,NSP5 suppressed avSG formation and disrupted RIG-I–MAVS complex to attenuate the RIG-I–mediated antiviral immunity.In contrast to the multiple targets of NSP5,the N protein specifically targeted cofactors upstream of RIG-I.The N protein interacted with G3BP1 to prevent avSG formation and to keep the cofactors G3BP1 and PACT from activating RIG-I.Additionally,the N protein also affected the recognition of dsRNA by RIG-I.This study revealed the intimate correlation between SARS-CoV-2,the stress response,and innate antiviral immunity,shedding light on the pathogenic mechanism of COVID-19.

Intrinsic PD-L1 promotes antitumor activity of CD8^(+)cytotoxic T lymphocytes via in cis interaction with CD80

Dear Editor,Programmed cell death-ligand 1(PD-L1)on tumor cells can inhibit CD8+cytotoxic T lymphocyte(CTL)-mediated antitumor response by trans-engagement with programmed death protein 1(PD-1).Besides tumor cells,PD-L1 is expressed on T cells.However,the intrinsic role of PD-L1 in T cells has not been widely studied.PD-L1 expression is essential for the survival of activated CD8+T cells,and PD-L1 blockade at the contraction stage reduced the number of effector T cells[1].CD8+T cell responses to influenza virus infection were also impaired in PD-L1-deficient mice[2].

Mechanisms and immunotherapies of HBV- and NAFLD-related hepatocellular carcinoma

Hepatitis B virus(HBV)infection remains the most important risk factor for hepatocellular carcinoma(HCC)worldwide and nonalcoholic fatty liver disease(NAFLD)has developed as major etiology of chronic liver diseases,cirrhosis and eventually HCC in the last decades.Although nucleos(t)ide analogs are recommended as the first-line drug for patients with chronic hepatitis B,incomplete eradication of HBV serves as an obstacle for effective cure of chronic hepatitis B and even HCC.NAFLD refers to a spectrum of hepatic metabolic disorders,compromised with multi-system diseases.Considering the specificity of hepatocytes and enrichment of immune cells in liver,this review aims to summarize the mechanisms of direct pro-tumorigenesis to hepatocytes induced by HBV infection and abnormal lipid metabolism,and indirect oncogenic processes mediated by immune cells.We also discuss similarities and differences of immune cells between HBV-and NAFLD-HCC and finally focus on the novel immunotherapies concerning preclinical and clinical studies for liver cancer.

The SARS-CoV-2 main protease induces neurotoxic TDP-43 cleavage and aggregates

Dear Editor,Neurologic manifestations associated with many COVID-19 patients,including acute infection with severe acute respiratory syndrome coronavirus-2(SARS-CoV-2)and long COVID,have been proven by increasing evidence.1 To date,most studies have focused on how SARS-CoV-2 invades the nervous system and the consequent neuropathological changes.2,3 In contrast,the specific mechanism by which SARS-CoV-2 infection leads to neurological disease remains unclear.

Increased Tim-3 expression alleviates liver injury by regulating macrophage activation in MCD-induced NASH mice

As an immune checkpoint,Tim-3 plays roles in the regulation of both adaptive and innate immune cells including macrophages and is greatly involved in chronic liver diseases.However,the precise roles of Tim-3 in nonalcoholic steatohepatitis(NASH)remain unstated.In the current study,we analyzed Tim-3 expression on different subpopulations of liver macrophages and further investigated the potential roles of Tim-3 on hepatic macrophages in methionine and choline-deficient diet(MCD)-induced NASH mice.The results of flow cytometry demonstrated the significantly increased expression of Tim-3 on all detected liver macrophage subsets in MCD mice,including F4/80^(+)CD11b^(+),F4/80^(+)CD68^(+),and F4/80^(+)CD169^(+)macrophages.Remarkably,Tim-3 knockout(KO)significantly accelerated MCD-induced liver steatosis,displaying higher serum ALT,larger hepatic vacuolation,more liver lipid deposition,and more severe liver fibrosis.Moreover,compared with wild-type C57BL/6 mice,Tim-3 KO MCD mice demonstrated an enhanced expression of NOX2,NLRP3,and caspase-1 p20 together with increased generation of IL-1βand IL-18 in livers.In vitro studies demonstrated that Tim-3 negatively regulated the production of reactive oxygen species(ROS)and related downstream pro-inflammatory cytokine secretion of IL-1βand IL-18 in macrophages.Exogenous administration of N-Acetyl-L-cysteine(NAC),a small molecular inhibitor of ROS,remarkably suppressed caspase-1 p20 expression and IL-1βand IL-18 production in livers of Tim-3 KO mice,thus significantly reducing the severity of steatohepatitis induced by MCD.In conclusion,Tim-3 is a promising protector in MCD-induced steatohepatitis by controlling ROS and the associated pro-inflammatory cytokine production in macrophages.

Severe acute respiratory syndrome coronavirus 2(SARSCoV-2)membrane(M)protein inhibits type I and III interferon production by targeting RIG-I/MDA-5 signaling

Coronavirus disease 2019(COVID-19),caused by severe acute respiratory syndrome coronavirus 2(SARS-CoV-2),has quickly spread worldwide and has affected more than 10 million individuals.A typical feature of COVID-19 is the suppression of type I and III interferon(IFN)-mediated antiviral immunity.However,the molecular mechanism by which SARS-CoV-2 evades antiviral immunity remains elusive.Here,we reported that the SARS-CoV-2 membrane(M)protein inhibits the production of type I and III IFNs induced by the cytosolic dsRNA-sensing pathway mediated by RIG-I/MDA-5–MAVS signaling.In addition,the SARS-CoV-2 M protein suppresses type I and III IFN induction stimulated by SeV infection or poly(I:C)transfection.Mechanistically,the SARS-CoV-2 M protein interacts with RIG-I,MAVS,and TBK1,thus preventing the formation of the multiprotein complex containing RIG-I,MAVS,TRAF3,and TBK1 and subsequently impeding the phosphorylation,nuclear translocation,and activation of IRF3.Consequently,ectopic expression of the SARS-CoV-2 M protein facilitates the replication of vesicular stomatitis virus.Taken together,these results indicate that the SARS-CoV-2 M protein antagonizes type I and III IFN production by targeting RIG-I/MDA-5 signaling,which subsequently attenuates antiviral immunity and enhances viral replication.This study provides insight into the interpretation of SARS-CoV-2-induced antiviral immune suppression and illuminates the pathogenic mechanism of COVID-19.

Anti-PD-L1/TGF-BR fusion protein (SHR-1701) overcomes disrupted lymphocyte recovery-induced resistance to PD-1/PD-L1 inhibitors in lung cancer

Background:Second-generation programmed cell death-protein 1/pro-grammed death-ligand 1(PD-1/PD-L1)inhibitors,such as bintrafusp alfa(M7824),SHR-1701,and YM101,have been developed to simultaneously block PD-1/PD-L1 and transforming growth factor-beta/transforming growth factor-beta receptor(TGF-P/TGF-βR).Consequently,it is necessary to identify predictive factors of lung cancer patients who are not only resistant to PD-1/PD-LI inhibitors but also sensitive to bifunctional drugs.The purpose of this study was to search for such predictors.Methods:Multivariable Cox regression was used to study the association between the clinical outcome of treatment with PD-1/PD-L1 inhibitors and lym-phocyte recovery after lymphopenia in lung cancer patients.Murine CMT167 lung cancer cells were engineered to express the firefly luciferase gene and implanted orthotopically in the lung of syngeneic mice.Bioluminescence imag-ing,flow cytometry,and immunohistochemistry were employed to detrmine response to immunotherapy and function of tumor-infiltrating immune cells.Results:For lung cancer patients treated with anti-PD-1/PD-LI antibodies,poor lymphocyte recovery was associated with a shorter progression-free survival(PFS;P<0.001),an accumulation of regulatory T cells(Tregs),and an elimi-nation of CD8+T cells in the peripheral blood.Levels of CD8+T cells and Treg cells were also imbalanced in the tumors and peripheral immune organs of mice with poor lymphocyte recovery after chemotherapy.Moreover,these mice failed to respond to anti-PD-1 antibodies but remained sensitive to the anti-PD-LI/TGF-βR fusion protein(SHR-1701).Consistently,SHR-1701 but not anti-PD-1 antibod-ies,markedly enhanced IFN-γproduction and Ki-67 expression in peripheral CD8+T cells from patients with impaired lymphocyte recovery.Conclusions:Lung cancer patients with poor lymphocyte recovery and suffer-ing from persistent lymphopenia after previous chemotherapy are resistant to anti-PD-1/PD-L1 antibodies but might be sensitive to second-generation agents such as SHR-1701.

Novel T cells with improved in vivo anti-tumor activity generated by RNA electroporation

The generation of T cells with maximal anti-tumor activities will significantly impact the field of T-cell- based adoptive immunotherapy. In this report, we found that OKT3/IL-2-stimulated T cells were phenotypically more heterogeneous, with enhanced anti-tumor activity in vitro and when locally administered in a solid tumor mouse model. To further improve the OKT3/IL-2-based T cell manufacturing procedure, we developed a novel T cell stimulation and expansion method in which peripheral blood mononuclear cells were electroporated with mRNA encoding a chimeric membrane protein consisting of a single-chain variable fragment against CD3 and the intracellular domains of CD28 and 4-1BB （OKT3-28BB）. The expanded T cells were phenotypically and functionally similar to T cells expanded by OKT3/IL-2. Moreover, co-electroporation of CD86 and 4-1BBL could further change the phenotype and enhance the in vivo anti-tumor activity. Although T cells expanded by the co- electroporation of OKT3-28BB with CD86 and 4-1BBL showed an increased central memory phenotype, the T cells still maintained tumor lytic activities as potent as those of OKT3/IL-2 or OKT3-28BB-stimulated T cells. In different tumor mouse models, T cells expanded by OKT3-28BB RNA electroporation showed anti-tumor activities superior to those of OKT3/IL-2 T cells. Hence, T cells with both a less differentiated phenotype and potent tumor killing ability can be generated by RNA electroporation, and this T cell manufacturing procedure can be further optimized by simply co-delivering other splices of RNA, thus providing a simple and cost-effec- tive method for generating high-quality T cells for adop- tive immunotherapy.

Monocyte-derived KCs(MoKCs)contribute to the KC pool in NASH

Nonalcoholic fatty liver disease(NAFLD)is now recognized as the most common liver disease worldwide and has increasingly become a serious hazard to human health.NAFLD consists of a spectrum of disease states ranging from simple steatosis to more severe disease termed nonalcoholic steatohepatitis(NASH),fibrosis,cirrhosis,and even hepatocellular carcinoma.

The hepatic macrophage pool in NASH

Nonalcoholic fatty liver disease(NAFLD)and its inflammatory subtype nonalcoholic steatohepatitis(NASH)are currently the most common chronic liver diseases worldwide and emerging risk factors for hepatocellular carcinoma.1 Numerous studies have demonstrated the critical involvement of hepatic macrophages,including resident Kupffer cells(KCs)and recruited monocyte-derived macrophages(MoMFs).

Severe acute respiratory syndrome coronavirus 2 (SARSCoV-2) membrane (M) protein inhibits type I and IIIinterferon production by targeting RIG-I/MDA-5 signaling

Coronavirus disease 2019(COVID-19),caused by severe acute respiratory syndrome coronavirus 2(SARS-CoV-2),has quickly spread worldwide and has affected more than 10 million individuals.A typical feature of COVID-19 is the suppression of type I and III interferon(IFN)-mediated antiviral immunity.However,the molecular mechanism by which SARS-CoV-2 evades antiviral immunity remains elusive.Here,we reported that the SARS-CoV-2 membrane(M)protein inhibits the production of type I and III IFNs induced by the cytosolic dsRNA-sensing pathway mediated by RIG-I/MDA-5–MAVS signaling.In addition,the SARS-CoV-2 M protein suppresses type I and III IFN induction stimulated by SeV infection or poly(I:C)transfection.Mechanistically,the SARS-CoV-2 M protein interacts with RIG-I,MAVS,and TBK1,thus preventing the formation of the multiprotein complex containing RIG-I,MAVS,TRAF3,and TBK1 and subsequently impeding the phosphorylation,nuclear translocation,and activation of IRF3.Consequently,ectopic expression of the SARS-CoV-2 M protein facilitates the replication of vesicular stomatitis virus.Taken together,these results indicate that the SARS-CoV-2 M protein antagonizes type I and III IFN production by targeting RIG-I/MDA-5 signaling,which subsequently attenuates antiviral immunity and enhances viral replication.This study provides insight into the interpretation of SARS-CoV-2-induced antiviral immune suppression and illuminates the pathogenic mechanism of COVID-19.