Stem cell-like memory T cells:Role in viral infections and autoimmunity

Stem cell-like memory T(TSCM)cells possess stem cell properties including multipotency and self-renewal and are being recognized as emerging players in various human diseases.Advanced technologies such as multiparametric flowcytometry and single cell sequencing have enabled their identification and molecular characterization.In case of chronic viral diseases such as human immunodeficiency virus-1,CD4+T_(SCM) cells,serve as major reservoirs of the latent virus.However,during immune activation and functional exhaustion of effector T cells,these cells also possess the potential to replenish the pool of functional effector cells to curtail the infection.More recently,these cells are speculated to play important role in protective immunity following acute viral infections such as coronavirus disease 2019 and might be amenable for therapeutics by ex vivo expansion.Similarly,studies are also investigating their pathological role in driving autoimmune responses.However,there are several gaps in the understanding of the role of T_(SCM) cells in viral and autoimmune diseases to make them potential therapeutic targets.In this minireview,we have attempted an updated compilation of the dyadic role of these complex T_(SCM) cells during such human diseases along with their biology and transcriptional programs.

Specific CD8^+ T cell response immunotherapy for hepatocellular carcinoma and viral hepatitis

Hepatocellular carcinoma (HCC), chronic hepatitis B (CHB) and chronic hepatitis C (CHC) are characterized by exhaustion of the specific CD8+ T cell response. This process involves enhancement of negative co-stimulatory molecules, such as programmed cell death protein-1 (PD-1), cytotoxic T-lymphocyte antigen-4 (CTLA-4), 2B4, Tim-3, CD160 and LAG-3, which is linked to intrahepatic overexpression of some of the cognate ligands, such as PD-L1, on antigen presenting cells and thereby favouring a tolerogenic environment. Therapies that disrupt these negative signalling mechanisms represent promising therapeutic tools with the potential to restore reactivity of the specific CD8+ T cell response. In this review we discuss the impressive in vitro and in vivo results that have been recently achieved in HCC, CHB and CHC by blocking these negative receptors with monoclonal antibodies against these immune checkpoint modulators. The article mainly focuses on the role of CTLA-4 and PD-1 blocking monoclonal antibodies, the first ones to have reached clinical practice. The humanized monoclonal antibodies against CTLA-4 (tremelimumab and ipilimumab) and PD-1 (nivolumab and pembrolizumab) have yielded good results in testing of HCC and chronic viral hepatitis patients. Trelimumab, in particular, has shown a significant increase in the time to progression in HCC, while nivolumab has shown a remarkable effect on hepatitis C viral load reduction. The research on the role of ipilimumab, nivolumab and pembrolizumab on HCC is currently underway.

Linker phosphorylation of Smad3 promotes fibro-carcinogenesis in chronic viral hepatitis of hepatocellular carcinoma

Epidemiological and clinical data point to a close association between chronic hepatitis B virus infection or chronic hepatitis C virus infection and development of hepatocellular carcinoma (HCC). HCC develops over several decades and is associated with fibrosis. This sequence suggests that persistent viral infection and chronic inflammation can synergistically induce liver fibrosis and hepatocarcinogenesis. The transforming growth factor-β (TGF-β) signaling pathway plays a pivotal role in diverse cellular processes and contributes to hepatic fibro-carcinogenesis under inflammatory microenvironments during chronic liver diseases. The biological activities of TGF-β are initiated by the binding of the ligand to TGF-β receptors, which phosphorylate Smad proteins. TGF-β type I receptor activates Smad3 to create COOH-terminally phosphorylated Smad3 (pSmad3C), while pro-inflammatory cytokine-activated kinases phosphorylates Smad3 to create the linker phosphorylated Smad3 (pSmad3L). During chronic liver disease progression, virus components, together with pro-inflammatory cytokines and somatic mutations, convert the Smad3 signal from tumor-suppressive pSmad3C to fibro-carcinogenic pSmad3L pathways, accelerating liver fibrosis and increasing the risk of HCC. The understanding of Smad3 phosphorylation profiles may provide new opportunities for effective chemoprevention and personalized therapy for patients with hepatitis virus-related HCC in the future.

Regulatory T cells in viral hepatitis

The pathogenesis and outcome of viral infections are significantly influenced by the host immune response. The immune system is able to eliminate many viruses in the acute phase of infection. However, some viruses, like hepatitis C virus (HCV) and hepatitis B virus (HBV), can evade the host immune responses and establish a persistent infection. HCV and HBV persistence is caused by various mechanisms, like subversion of innate immune responses by viral factors, the emergence of T cell escape mutations, or T cell dysfunction and suppression. Recently, it has become evident that regulatory T cells may contribute to the pathogenesis and outcome of viral infections by suppressing antiviral immune responses. Indeed, the control of HCV and HBV specific immune responses mediated by regulatory T cells may be one mechanism that favors viral persistence, but it may also prevent the host from overwhelming T cell activity and liver damage. This review will focus on the role of regulatory T cells in viral hepatitis.

Memory CD8+ T cell differentiation in viral infection: A cell for all seasons

Chronic viral infections such as hepatitis B virus (HBV), hepatitis C virus (HCV) and human immunodeficiency virus (HIV) are major global health problems affecting more than 500 million people worldwide. Virus-specific CD8+ T cells play an important role in the course and outcome of these viral infections and it is hypothesized that altered or impaired differentiation of virus- specific CD8+ T cells contributes to the development of persistence and/or disease progression. A deeper understanding of the mechanisms responsible for functional differentiation of CD8+ T cells is essential for the generation of successful therapies aiming to strengthen the adaptive component of the immune system.

Role of T cell death in maintaining immune tolerance during persistent viral hepatitis

Virus-specific T cells play an important role in the resolution of hepatic infection. However, during chronic hepatitis infection these cells lack their effector functions and fail to control the virus. Hepatitis B virus and hepatitis C virus have developed several mechanisms to generate immune tolerance. One of these strategies is the depletion of virus-specific T cells by apoptosis. The immunotolerogenic liver has unique property to retain and activate na ve T cell to avoid the over reactivation of immune response against antigens which is exploited by hepatotropic viruses to persist. The deletion of the virus-specific T cells occurs by intrinsic (passive) apoptotic mechanism. The pro-apoptotic molecule Bcl-2 interacting mediator (Bim) has attracted increasing attention as a pivotal involvement in apoptosis, as a regulator of tissue homeostasis and an enhancer for the viral persistence. Here, we reviewed our current knowledge on the evidence showing critical role of Bim in viral-specific T cell death by apoptotic pathways and helps in the immune tolerance.

γδ T Cells Contribute to the Outcome of Murine Fulminant Viral Hepatitis via Effector Cytokines TNF-α and IFN-γ

The mechanisms involved in virus-induced severe hepatitis have not been fully elucidated. In this study, we investigated the role of gamma delta T cell receptors （γδ） T cells in the pathogenesis of fulminant viral hepatitis （FVH） induced by murine hepatitis virus strain 3 （MHV-3）. The model of FVH was established by intraperitoneal injection of MHV-3 into Balb/cJ mice. The survival days of mice, and the serum levels of alanine aminotransferase （ALT） and aspartate aminotransferase （AST） were examined. The proportions of γδ T cells in blood, spleen and liver, and cytokines secreted by hepatic γδ T cells were analyzed by flow cytometry. The function of hepatic γδ T cells was examined by cytotoxicity assay. Balb/cJ mice died in 3 to 6 days post MHV-3 infection, with severe hepatic necrosis and significant augmentation of serum ALT and AST levels. The proportions of γδ T cells in blood, spleen and liver were significantly increased post MHV-3 infection, while those of the early activating molecule CD69-expressing γδ T cells and productions of cytokines tumor necrosis factor-alpha （TNF-α） and interferon-y （IFN-3,） increased remarkably in the liver. These highly activated liver γδ T cells were cytotoxic to MHV-3-infected hepatocytes in vitro and this effect of liver γδ T cells against hepatocytes might involve the TNF-α and IFN-γ pathway. These results demonstrated that γδ T cells might contribute to the pathogenesis of MHV-3-induced FVH through the effector cytokines TNF-α and IFN-γ. Key words： fulminant viral hepatitis; murine hepatitis virus strain 3; gamma delta T cell receptors T cells; tumor necrosis factor-a; interferon-α

Immunohistochemical study of hepatic oval cells in human chronic viral hepatitis

AIM: To detect immunohistochemically the presence of oval cells in chronic viral hepatitis with antibody against c-kit. METHODS: We detected oval cells in paraffin embedded liver sections of 3 normal controls and 26 liver samples from patients with chronic viral hepatitis, using immunohistochemistry with antibodies against c-kit, piclass glutathione S-transferase (pi-GST) and cytokeratins 19 (CK19). RESULTS: Oval cells were not observed in normal livers. In chronic viral hepatitis, hepatic oval cells were located predominantly in the periportal region and fibrosis septa,characterized by an ovoid nucleus, small size,and scant cytoplasm. Antibody against stem cell factor receptor, c-kit, had higher sensitivity and specificity than pi-GST and CK19. About 50%-70% of c-kit positive oval cells were stained positively for either pi-GST or CK19. CONCLUSION: Oval cells are frequently detected in human livers with chronic viral hepatitis, suggesting that oval cell proliferation is associated with the liver regeneration in this condition.

Role of Deoxyribonucleoside Triphosphates(dNTPs)in Cell Transformation

Deoxyribenucleoside triphosphate (dNTP) pools were measured in normal BALB/c3T3 cells, transformation-treated cells and transformed cells with reverse-phase HPLC. The fluctuation of dNTP pools was similar after transformation treatment with alkylating mutagen glycidyl methacrylate(GMA) or Nmethyl- N'- nitro N- nitrosoguanidine (MNNG ). However,the gap between deoxyguanosine triphosphate + deoxyadenosine triphosphate (dGTP + dATP) pools and deoxythymidine triphosphate + deoxycytidine triphosphate (dTTP + dCTP) pools was greatly intensified. The measurements also indicated that the dNTP pools in transformed cells were quite different from those in normal cells. The results suggested that dNTP pools may play an important role in cell transformation

Viral infections and cell cycle G2/M regulation

Progression of cells from G2 phase of the cell cycle to mitosis is a tightly regulated cellular process that requires activation of the Cdc2 kinase, which determines onset of mitosis in all eukaryotic cells. In both human and fission yeast (Schizosaccharomyces pombe) cells, the activity of Cdc2 is regulated in part by the phosphorylation status of tyrosine 15 (Tyr15) on Cdc2, which is phosphorylated by Wee1 kinase during late G2 and is rapidly dephosphorylated by the Cdc25 tyrosine phosphatase to trigger entry into mitosis. These Cdc2 regulators are the downstream targets of two well- characterized G2/M checkpoint pathways which prevent cells from entering mitosis when cellular DNA is damaged or when DNA replication is inhibited. Increasing evidence suggests that Cdc2 is also commonly targeted by viral proteins, which modulate host cell cycle machinery to benefit viral survival or replication. In this review, we describe the effect of viral protein R (Vpr) encoded by human immunodeficiency virus type 1 (HIV-1) on cell cycle G2/M regulation. Based on our current knowledge about this viral effect, we hypothesize that Vpr induces cell cycle G2 arrest through a mechanism that is to some extent different from the classic G2/M checkpoints. One the unique features distinguishing Vpr-induced G2 arrest from the classic checkpoints is the role of phosphatase 2A (PP2A) in Vpr-induced G2 arrest. Interestingly, PP2A is targeted by a number of other viral proteins including SV40 small T antigen, polyomavirus T antigen, HTLV Tax and adenovirus E4orf4. Thus an in-depth understanding of the molecular mechanisms underlying Vpr-induced G2 arrest will provide additional insights into the basic biology of cell cycle G2/M regulation and into the biological significance of this effect during host-pathogen interactions.

TRAITEMENT DE L'HEPATITE VIRALE FULMINANTE PAR TRANSPLANTATION DES CELLULES HEPATIQUES FOETALES HUMAINES——ETUDE PRELIMINAIRE SUR 8 CAS

The authors achieved a clinical study on the treatment of fulminant viral hepatitis by the transplantation of human fetal liver cells. 47fetal livers were used for 8 patients with a survival of 6 cases. The side-effects of this new therapy were analysed and the mechanism of action of fetal liver cells discussed.

Intracellular Transport of HIV-1 Matrix Protein Associated with Viral RNA

HIV-1 matrix protein (MA) is a multifunctional structural protein localized on N terminus of Gag precursor p55. MA participates in HIV-1 assembly as membranotropic part of Gag precursor as well as an individual protein spliced from Gag early in infection. MA is found in the nuclei of infected cells and in plasma membrane, the site of virus assembly, in association with viral genome RNA. MA mutated variant M4 which contains two changed amino acids in N-terminal regions is also associated with viral RNA, but it is localized in the nuclear and cytoskeleton fractions but not in the plasma membrane suggesting that the mutant is deprived of membranotropic signal and “sticks” in the nuclei an d cytoskeleton, its previous location sites. These data allow suggesting that MA involved into transmission of viral RNA is transported to plasma membrane by cytoskeleton.

Host and viral factors contributing to CD8+ T cell failure in hepatitis C virus infection

Virus-specific CD8+ T cells are thought to be the major anti-viral effector cells in hepatitis C virus (HCV) infection. Indeed, viral clearance is associated with vigorous CD8+ T cell responses targeting multiple epitopes. In the chronic phase of infection, HCV-specific CD8+ T cell responses are usually weak, narrowly focused and display often functional defects regarding cytotoxicity, cytokine production, and proliferative capacity. In the last few years, different mechanisms which might contribute to the failure of HCV-specific CD8+ T cells in chronic infection have been identified, including insufficient CD4+ help, deficient CD8+ T cell differentiation, viral escape mutations, suppression by viral factors, inhibitory cytokines, inhibitory ligands, and regulatory T cells. In addition, host genetic factors such as the host’s human leukocyte antigen (HLA) background may play an important role in the efficiency of the HCV- specific CD8+ T cell response and thus outcome of infection. The growing understanding of the mechanisms contributing to T cell failure and persistence of HCV infection will contribute to the development of successful immunotherapeutical and -prophylactical strategies.

Cell transformation as aberrant differentiation: Environmentally dependent sportaneous transformation of NIH 3T3 cells

NIH 3T3 cells, a mouse fibroblast cell line used as routine target cells for transfection experiments, undergo spontaneous transformation in our experiments after they form a confluent sheet in medium containing fetal bovina serum (FBS) or lower coneentrafcion of calf serum (CS). The transformation takes the form of foci of multiplying cells among the surrounding cells which have stopped cell division. However, no focus of transformed cells could be seen in medium containing high concentration (10%) of OS. Further experiments indicated that the frequency of transformation is highly dependent on the concentration of serum and the transformation in OS is changeable when the cells are passaged in FBS. 8H-thymidine autoradiography has been proved to be a sensitive measurement indicator for foous formation. Our results suggest that the high frequency of transformation and its dependence on confmenoy as well as on medium composition are characteristics of cell differentiation rather than mutation. The role of the NIH 3T3 cell line as a cancer-initiated cell population and its accelerated transformation by rat oncogene might be considered as a form of tumor promotion is discussed.

Use of a tissue clearing technique combined with retrograde trans-synaptic viral tracing to evaluate changes in mouse retinorecipient brain regions following optic nerve crush

Successful establishment of reconnection between retinal ganglion cells and retinorecipient regions in the brain is critical to optic nerve regeneration.However,morphological assessments of retinorecipient regions are limited by the opacity of brain tissue.In this study,we used an innovative tissue cleaning technique combined with retrograde trans-synaptic viral tracing to observe changes in retinorecipient regions connected to retinal ganglion cells in mice after optic nerve injury.Specifically,we performed light-sheet imaging of whole brain tissue after a clearing process.We found that pseudorabies virus 724(PRV724)mostly infected retinal ganglion cells,and that we could use it to retrogradely trace the retinorecipient regions in whole tissue-cleared brains.Unexpectedly,PRV724-traced neurons were more widely distributed compared with data from previous studies.We found that optic nerve injury could selectively modify projections from retinal ganglion cells in the hypothalamic paraventricular nucleus,intergeniculate leaflet,ventral lateral geniculate nucleus,central amygdala,basolateral amygdala,Edinger-Westphal nucleus,and oculomotor nucleus,but not the superior vestibular nucleus,red nucleus,locus coeruleus,gigantocellular reticular nucleus,or facial nerve nucleus.Our findings demonstrate that the tissue clearing technique,combined with retrograde trans-synaptic viral tracing,can be used to objectively and comprehensively evaluate changes in mouse retinorecipient regions that receive projections from retinal ganglion cells after optic nerve injury.Thus,our approach may be useful for future estimations of optic nerve injury and regeneration.

Higher Viral Load and Prolonged Viral Shedding Period is Associated with Impaired Th17 Cell Response in Patients with H1N1 Influenza A

Objective To explore whether age,disease severity,cytokines and lymphocytes in H1N1 influenza A patients correlate with viral load and clearance.Methods Total of 70 mild and 16 severe patients infected with H1N1 influenza A virus were enrolled in this study.Results It was found that the patients under 14 years old and severe patients displayed significantly higher viral loads and prolonged viral shedding periods compared with the patients over 14 years old and mild patients,respectively(P < 0.05).Moreover,the patients under 14 years old and severe patients displayed significantly lower Th17 cell frequency than the patients over 14 years old and mild patients(P < 0.01).The viral shedding period inversely correlated with the frequency of IL-17+IFN-γ-CD4+ T cells.Additionally,the decreased concentration of serum TGF-β correlated with the decreased frequency of IL-17+IFN-γ-CD4+ T cells.Conclusions Both younger and severe patients are associated with higher viral loads and longer viral shedding periods,which may partially be attributed to the impaired Th17 cell response.

Renal cell carcinoma and viral infections:A dangerous relationship?

Virus-related cancers in humans are widely recognized,but in the case of renal cancer,the link with the world of viruses is not clearly established in humans,despite being known in animal biology.In the present review,we aimed to explore the literature on renal cell carcinoma(RCC)for a possible role of viruses in human RCC tumorigenesis and immune homeostasis,hypothesizing the contribution of viruses to the immunogenicity of this tumor.A scientific literature search was conducted using the PubMed,Web of Science,and Google Scholar databases with the keywords“virus”or“viruses”or“viral infection”matched with(“AND”)“renal cell carcinoma”or“kidney cancer”or“renal cancer”or“renal carcinoma”or“renal tumor”or“RCC”.The retrieved findings evidenced two main aspects testifying to the relationship between RCC and viruses:The presence of viruses within the tumor,especially in non-clear cell RCC cases,and RCC occurrence in cases with pre-existing chronic viral infections.Some retrieved translational and clinical data suggest the possible contribution of viruses,particularly Epstein-Barr virus,to the marked immunogenicity of sarcomatoid RCC.In addition,it was revealed the possible role of endogenous retrovirus reactivation in RCC oncogenesis,introducing new fascinating hypotheses about this tumor’s immunogenicity and likeliness of response to immune checkpoint inhibitors.

CELL TRANSFORMATION IN VITRO BY -RAY COMBINED WITH EP

Malignant transformation of syrian hamsterembryo(SHE) cells in vitro was induced bylow-dose of Co-60 γ-ray combined withestradiol valerate and hydroxyprogesteronecaproate (EP).The transformation was notobserved in the groups that the γ-ray or EPwas given alone.SHE cells were seeded

The role of plasmacytoid dendritic cells(pDCs)in immunity during viral infections and beyond

Type I and III interferons(IFNs)are essential for antiviral immunity and act through two different but complimentary pathways.First,IFNs activate intracellular antimicrobial programs by triggering the upregulation of a broad repertoire of viral restriction factors.Second,IFNs activate innate and adaptive immunity.Dysregulation of IFN production can lead to severe immune system dysfunction.It is thus crucial to identify and characterize the cellular sources of IFNs,their effects,and their regulation to promote their beneficial effects and limit their detrimental effects,which can depend on the nature of the infected or diseased tissues,as we will discuss.Plasmacytoid dendritic cells(pDCs)can produce large amounts of all IFN subtypes during viral infection.pDCs are resistant to infection by many different viruses,thus inhibiting the immune evasion mechanisms of viruses that target IFN production or their downstream responses.Therefore,pDCs are considered essential for the control of viral infections and the establishment of protective immunity.A thorough bibliographical survey showed that,in most viral infections,despite being major IFN producers,pDCs are actually dispensable for host resistance,which is achieved by multiple IFN sources depending on the tissue.Moreover,primary innate and adaptive antiviral immune responses are only transiently affected in the absence of pDCs.More surprisingly,pDCs and their IFNs can be detrimental in some viral infections or autoimmune diseases.This makes the conservation of pDCs during vertebrate evolution an enigma and thus raises outstanding questions about their role not only in viral infections but also in other diseases and under physiological conditions.

Hemodialysis bilayer bionic blood vessels developed by the mechanical stimulation of hepatitis B viral X(HBX)genetransfected hepatic stellate cells

Artificial vascular graft(AVG)fistula is widely used for hemodialysis treatment in patients with renal failure.However,it has poor elasticity and compliance,leading to stenosis and thrombosis.The ideal artificial blood vessel for dialysis should replicate the structure and components of a real artery,which is primarily maintained by collagen in the extracellular matrix(ECM)of arterial cells.Studies have revealed that in hepatitis B virus(HBV)-induced liver fibrosis,hepatic stellate cells(HSCs)become hyperactive and produce excessive ECM fibers.Furthermore,mechanical stimulation can encourage ECM secretion and remodeling of a fiber structure.Based on the above factors,we transfected HSCs with the hepatitis B viral X(HBX)gene for simulating the process of HBV infection.Subsequently,these HBX-HSCs were implanted into a polycaprolactonepolyurethane(PCL-PU)bilayer scaffold in which the inner layer is dense and the outer layer consists of pores,which was mechanically stimulated to promote the secretion of collagen nanofiber from the HBX-HSCs and to facilitate crosslinking with the scaffold.We obtained an ECM-PCL-PU composite bionic blood vessel that could act as access for dialysis after decellularization.Then,the vessel scaffold was implanted into a rabbit’s neck arteriovenous fistula model.It exhibited strong tensile strength and smooth blood flow and formed autologous blood vessels in the rabbit’s body.Our study demonstrates the use of human cells to create biomimetic dialysis blood vessels,providing a novel approach for creating clinical vascular access for dialysis.