CD4^＋ T-cell dependence of primary CD8^＋ T-cell response against vaccinia virus depends upon route of infection and viral dose

CD4^＋ T-cell help （CD4 help） plays a pivotal role in CD8^＋ T-cell responses against viral infections. However, the role in primary CD8^＋ T-cell responses remains controversial. We evaluated the effects of infection route and viral dose on primary CD8^＋ T-cell responses to vaccinia virus （VACV） in MHC class II^-/- mice. CD4 help deficiency diminished the generation of VACV-specific CD8^＋ T cells after intraperitoneal （i.p.） but not after intranasal （i.n.） infection. A large viral dose could not restore normal expansion of VACV-specific CD8^＋ T cells in i.p. infected MHC II-/- mice. In contrast, dependence on CD4 help was observed in i.n. infected MHC II-/- mice when a small viral dose was used. These data suggested that primary CD8~ T-cell responses are less dependent on CD4 help in i.n. infection compared to i.p. infection. Activated CD8~ T cells produced more I FN-y, TNF-a and granzyme B in i.n. infected mice than those in i.p. infected mice, regardless of CD4 help. IL-2 signaling via CD25 was not necessary to drive expansion of VACV-specific CD8~ T cells in i.n. infection, but it was crucial in i.p. infection. VACV-specific CD8^＋ T cells underwent increased apoptosis in the absence of CD4 help, but proliferated normally and had cytotoxic potential, regardless of infection route. Our results indicate that route of infection and viral dose are two determinants for CD4 help dependence, and intranasal infection induces more potent effector CD8^＋ T cells than i.D. infection.

Mettl3依赖的m^(6)A甲基化调控CD8^(+)T细胞效应分化和记忆形成

Efficient immune responses rely on the proper differentiation of CD8^(+)T cells into effector and memory cells.Here,we show a critical requirement of N^6-Methyladenosine(m^(6)A)methyltransferase Mettl3 during CD8^(+)T cell responses upon acute viral infection.Conditional deletion of Mettl3 in CD8^(+)T cells impairs effector expansion and terminal differentiation in an m^(6)A-dependent manner,subsequently affecting memory formation and the secondary response of CD8^(+)T cells.Our combined RNA-seq and m^(6)AmiCLIP-seq analyses reveal that Mettl3 deficiency broadly impacts the expression of cell cycle and transcriptional regulators.Remarkably,Mettl3 binds to the Tbx21 transcript and stabilizes it,promoting effector differentiation of CD8^(+)T cells.Moreover,ectopic expression of T-bet partially restores the defects in CD8^(+)T cell differentiation in the absence of Mettl3.Thus,our study highlights the role of Mettl3 in regulating multiple target genes in an m^(6)A-dependent manner and underscores the importance of m^(6)A modification during CD8^(+)T cell response.

The IL-1R/TLR signaling pathway is essential for efficient CD8+ T-cell responses against hepatitis B virus in the hydrodynamic injection mouse model

The outcome of hepatitis B viral(HBV)infection is determined by the complex interactions between replicating HBV and the immune system.While the role of the adaptive immune system in the resolution of HBV infection has been studied extensively,the contribution of innate immune mechanisms remains to be defined.Here we examined the role of the interleukin-1 receptor/Toll-like receptor(IL-1R/TLR)signaling pathway in adaptive immune responses and viral clearance by exploring the HBV mouse model.Hydrodynamic injection with a replication-competent HBV genome was performed in wild-type mice(WT)and a panel of mouse strains lacking specific innate immunity component expression.We found higher levels of HBV protein production and replication in Tlr2^(−/−),Tlr23479^(−/−),3d/Tlr24^(−/−),Myd88/Trif^(−/−)and Irak4^(−/−)mice,which was associated with reduced HBV-specific CD8+T-cell responses in these mice.Importantly,HBV clearance was delayed for more than 2 weeks in 3d/Tlr24^(−/−),Myd88/Trif^(−/−)and Irak4^(−/−)mice compared to WT mice.HBV-specific CD8+T-cell responses were functionally impaired for producing the cytokines IFN-γ,TNF-αand IL-2 in TLR signaling-deficient mice compared to WT mice.In conclusion,the IL-1R/TLR signaling pathway might contribute to controlling HBV infection by augmenting HBV-specific CD8+T-cell responses.

Association between Nef-specific CD8 T-cell responses and disease progression in HIV-1 subtype B infection

Background The correlation between HIV-1 Nef-specific CD8 T-cell responses and markers of HIV-1 disease progression still remains unclear. This study analysed and compared the role of HIV-1 Nef-specific CD8 T-cell responses in patients with different disease status. Methods Two groups of patients with HIV-1 subtype B infection were selected according to CD4 count and clinical manifestations： long-term nonprogresssors （LTNPs, n = 20） and advanced progressors （APs, CD4 count 〈500 cells/pl, n = 34）. Nef-specific CD8 T-cell responses were studied by interferon- T ELISpot assay against 3 pools of HIV-Nef peptides. Results Nef-specific CD8 T-cell responses did not correlate with viral load or CD4 count in all patients and no significant differences were found in the magnitude of Nef-specific CD8 T-cell responses between groups LTNPs and APs （670 SFC/106 peripheral blood mononuclear cells vs 1107 SFC/106 peripheral blood mononuclear cells, P = 0.255）. Further comparisons showed that there were also no significant correlations observed in group LTNPs, but Nef-specific CD8 T cells correlated negatively with viral load （r = -0.397, P = 0.020） and positively with CD4 count （r = 0.364, P = 0.034） in group APs. Conclusion These data suggest that different correlation patterns between Nef-specific CD8 T-cell responses and disease progression exist in LTNPs and APs. Although a negative association was observed with concurrent plasma HIV RNA in APs, Nef-specific CD8 T-cell responses might fail to play a protective role in different stages of HIV- 1 infection.

Regulation of CD8^(+)T memory and exhaustion by the mTOR signals

CD8^(+)T cells are the key executioners of the adaptive immune arm,which mediates antitumor and antiviral immunity.Naïve CD8^(+)T cells develop in the thymus and are quickly activated in the periphery after encountering a cognate antigen,which induces these cells to proliferate and differentiate into effector cells that fight the initial infection.Simultaneously,a fraction of these cells become long-lived memory CD8^(+)T cells that combat future infections.Notably,the generation and maintenance of memory cells is profoundly affected by various in vivo conditions,such as the mode of primary activation(e.g.,acute vs.chronic immunization)or fluctuations in host metabolic,inflammatory,or aging factors.Therefore,many T cells may be lost or become exhausted and no longer functional.Complicated intracellular signaling pathways,transcription factors,epigenetic modifications,and metabolic processes are involved in this process.Therefore,understanding the cellular and molecular basis for the generation and fate of memory and exhausted CD8^(+)cells is central for harnessing cellular immunity.In this review,we focus on mammalian target of rapamycin(mTOR),particularly signaling mediated by mTOR complex(mTORC)2 in memory and exhausted CD8^(+)T cells at the molecular level.

Activation or exhaustion of CD8^(+) T cells in patients with COVID-19

In addition to CD4^(+)T cells and neutralizing antibodies,CD8^(+)T cells contribute to protective immune responses against SARS-CoV-2 in patients with coronavirus disease 2019(COVID-19),an ongoing pandemic disease.In patients with COVID-19,CD8^(+)T cells exhibiting activated phenotypes are commonly observed,although the absolute number of CD8^(+)T cells is decreased.In addition,several studies have reported an upregulation of inhibitory immune checkpoint receptors,such as PD-1,and the expression of exhaustion-associated gene signatures in CD8^(+)T cells from patients with COVID-19.However,whether CD8^(+)T cells are truly exhausted during COVID-19 has been a controversial issue.In the present review,we summarize the current understanding of CD8^(+)T-cell exhaustion and describe the available knowledge on the phenotypes and functions of CD8^(+)T cells in the context of activation and exhaustion.We also summarize recent reports regarding phenotypical and functional analyses of SARS-CoV-2-specific CD8^(+)T cells and discuss long-term SARS-CoV-2-specific CD8^(+)T-cell memory.

Crosstalk between IL-15Rα^(+)tumor-associated macrophages and breast cancer cells reduces CD8+T cell recruitment

Background:Interleukin-15(IL-15)is a promising immunotherapeutic agent owing to its powerful immune-activating effects.However,the clinical benefits of these treatments are limited.Crosstalk between tumor cells and immune cells plays an important role in immune escape and immunotherapy drug resistance.Herein,this study aimed to obtain in-depth understanding of crosstalk in the tumor microenvironment for providing potential therapeutic strategies to prevent tumor progression.Methods:T-cell killing assays and co-culture models were developed to determine the role of crosstalk between macrophages and tumor cells in breast cancer resistant to IL-15.Western blotting,histological analysis,CRISPR-Cas9 knockout,multi-parameter flow cytometry,and tumor cell-macrophage co-injection mouse models were developed to examine the mechanism by which IL-15Rα^(+)tumor-associated macrophages(TAMs)regulate breast cancer cell resistance to IL-15.Results:We found thatmacrophages contributed to the resistance of tumor cells to IL-15,and tumor cells induced macrophages to express high levels of theαsubunit of the IL-15 receptor(IL-15Rα).Further investigation showed that IL-15Rα^(+)TAMs reduced the protein levels of chemokine CX3C chemokine ligand 1(CX3CL1)in tumor cells to inhibit the recruitment of CD8^(+)T cells by releasing the IL-15/IL-15Rαcomplex(IL-15Rc).Administration of an IL-15Rc blocking peptide markedly suppressed breast tumor growth and overcame the resistance of cancer cells to anti-programmed cell death protein 1(PD-1)antibody immunotherapy.Interestingly,Granulocyte-macrophage colony-stimulating factor(GMCSF)inducedγchain(γc)expression to promote tumor cell-macrophage crosstalk,which facilitated tumor resistance to IL-15.Additionally,we observed that the non-transcriptional regulatory function of hypoxia inducible factor-1alpha(HIF-1α)was essential for IL-15Rc to regulateCX3CL1 expression in tumor cells.Conclusions:The IL-15Rc-HIF-1α-CX3CL1 signaling pathway serves as a crosstalk between macrophages and tumor cells in the tumormicroenvironment of breast cancer.Targeting this pathway may provide a potential therapeutic strategy for enhancing the efficacy of cancer immunotherapy.

Defect of CD8^+ Memory T Cells Developed in Absence of IL-12 Priming for Secondary Expansion

IL-12 priming plays an important role in stimulation of CD8^＋ effector T cells and development of CD8^＋ memory T （Tm） cells. However, the functional alteration of CD8^＋ Tm cells developed in the absence of IL-12 priming is elusive. In this study, we investigated the capacity of secondary expansion of CD8~ Tm cells developed from transgenic OT I CD8^＋ T cells. The latter cells were in vitro and in vivo stimulated by ovalbumin （OVA）-pulsed dendritic cells [DCovA and （IL-12^-/-）DCovA] derived from wild-type C57BL/6 and IL-12 gene knockout mice, respectively. We demonstrated that IL-12 priming is important not only in CD8^＋ T cell clonal expansion, but also in generation of CD8^＋ Tm cells with the capacity of secondary expansion upon antigen re-encounter. However, IL-12 signaling is not involved in CD8^＋ Tm cell survival and recall responses. Therefore, this study provides useful information for vaccine design and development. Cellular ＆ Molecular Immunology.

Unravelling the Functions of Regulatory T Cells during Infection

Accumulating evidences have suggested that Treg have an active role in the regulation of immunity to infection. Treg suppress not only autoimmune responses but also other immune responses for instance, during acute infections, against commensal microbes in inflammatory diseases or during chronic illness. Treg have been shown to limit exacerbated inflammation to avoid collateral tissue damage. Treg are also suggested to provide early protective responses in some viral infections as the permitting timely entry of effector cells in infected tissue. Furthermore, Treg have been shown to contribute to form memory pool after resolution of infection. In this review, we survey and analysis our current knowledge and relative dynamics of Treg in a wide range of infection settings and elaborate the examples in which these cells are of critical importance in conferring tolerance, suppressing pathogenesis, inducing protection and optimizing immunity to eliminate infection.

Peripheral Tc17 and Tc17/Interferon-γ Cells are Increased and Associated with Lung Function in Patients with Chronic Obstructive Pulmonary Disease

Background：Chronic obstructive pulmonary disease （COPD） is characterized by progressive loss of lung function and local and systemic inflammation,in which CD8＋ T-cells are believed to play a key role.Activated CD8＋ T-cells differentiate into distinct subpopulations,including interferon-γ（IFN-γ）-producing Tc 1 and interleukin （IL）-17-producing Tc 1 7 cells.Recent evidence indicates that Tc 17 cells exhibit considerable plasticity and may convert into IL-17/IFN-γ-double producing （Tc1 7/IFN-γ） cells when driven by inflammatory conditions.The aim of this study was to investigate the Tc 17/IFN-γ subpopulation in peripheral blood of patients with COPD and to evaluate their potential roles in this disease.Methods：Peripheral blood samples were collected from 15 never-smokers,23 smokers with normal lung function,and 25 patients with COPD （Global Initiative for Chronic Obstructive Lung Disease 2-4）.Proportions of the IL-17/IFN-γ-double expressing subpopulation were assessed using flow cytometry.Plasma concentrations of cytokines favoring Tc 17/IFN-γ differentiation were measured by enzymelinked immunosorbent assay.Results：Patients with COPD had higher proportions of Tc17 cells and Tc17/IFN-γ cells in the peripheral blood than smokers and never-smokers.The plasticity of Tc 17 cells was higher than that of Th 17 cells.The percentages ofTc 17 cells and Tc 17/IFN-γcells showed negative correlations with forced expiratory volume in 1 s % predicted value （r =-0.418,P =0.03;r =-0.596,P =0.002,respectively）.The plasma concentrations of IL-6,transforming growth factor-β1,and IL-12 were significantly higher in patients with COPD compared with smokers and never-smokers.Conclusions：Peripheral Tc17 cells are increased and more likely to convert to Tc17/IFN-γ cells in COPD,suggesting that Tc17 cell plasticity may be involved in persistent inflammation of the disease.

Distinct roles but cooperative effect of TLR3/9 agonists and PD-1 blockade in converting the immunotolerant microenvironment of irreversible electroporation-ablated tumors

Irreversible electroporation(IRE)is a new cancer ablation technology,but methods to improve IRE-induced therapeutic immunity are only beginning to be investigated.We developed a mouse model bearing large primary(300 mm^(3))and medium distant(100 mm^(3))EG7 lymphomas engineered to express ovalbumin(OVA)as a nominal tumor antigen.We established experimental protocols including IRE alone and IRE combined with Toll-like receptor(TLR)3/9 agonists(poly I:C/CpG)(IRE+pIC/CpG),PD-1 blockade(IRE+PD-1 blockade),or both(IRE+Combo)to investigate therapeutic effects on primary and distant EG7 tumors and conversion-promoting effects on the immunotolerant tumor microenvironment(TME).We demonstrated that IRE alone simulated very weak OVA-specific CD8^(+)T cell responses and did not inhibit primary tumor growth.IRE+pIC/CpG synergistically stimulated more efficient OVA-specific CD8^(+)T cell responses and primary tumor growth inhibition than IRE+PD-1 blockade.IRE+pIC/CpG played a major role in the modulation of immune cell profiles but a minor role in the downregulation of PD-L1 expression in the TME and vice versa for IRE+PD-1 blockade.IRE+Combo cooperatively induced potent OVA-specific CD8^(+)T cell immunity and rescued exhausted intratumoral CD8^(+)T cells,leading to eradication of not only primary tumors but also untreated concomitant distant tumors and lung metastases.IRE+Combo efficiently modulated immune cell profiles,as evidenced by reductions in immunotolerant type-2(M2)macrophages,myeloid-derived suppressor-cells,plasmacytoid dendritic cells,and regulatory T cells and by increases in immunogenic M1 macrophages,CD169^(+)macrophages,type-1 conventional dendritic cells,and CD8^(+)T cells,leading to conversion of immunotolerance in not only primary TMEs but also untreated distant TMEs.IRE+Combo also showed effective therapeutic effects in two breast cancer models.Therefore,our results suggest that IRE+Combo is a promising strategy to improve IRE ablation therapy in cancer.