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.     

CD4＋CD25＋调节性T细胞与衰老关系的研究进展

衰老伴随着免疫系统多种功能和表型的改变,使机体免疫力下降。CD4＋CD25＋调节性T细胞址体内具有免疫抑制活性的一群细胞,它在维持自身内环境稳定、抑制移植排斥反应以及防止自身免疫忤疾病的发生等方面发挥重要的保护作用,同时也是免疫力衰退的重要因素之一。调节性T细胞在机体衰老过程中发生变化,并发挥重要的作用。现将衰老过程中调节性T细胞的数量、功能、表型等的变化,以及调节性T细胞与老年相关性疾病的关系进行综述。     

CD4^＋T细胞功能性分化的研究进展

近年来关于ＣＤ４＾＋Ｔ细胞功能性分化的研究包括ＣＤ４＾＋Ｔ细胞亚群的分化,ＣＤ４＾＋Ｔ细胞亚群的多样性、稳定性和ＴＨ１、ＴＨ２效应细胞的功能。这些研究有助于进一步探讨免疫性疾病的发病机理及治疗途径。     

CD4＋ T cell responses in hepatitis C virus infection

Hepatitis C virus (HCV) infection is a major cause of liver damage, with virus-induced end-stage disease such as liver cirrhosis and hepatocellular carcinoma resulting in a high rate of morbidity and mortality worldwide. Evidence that CD4+ T cell responses to HCV play an important role in the outcome of acute infection has been shown in several studies. However, the mechanisms behind viral persistence and the failure of CD4+ T cell responses to contain virus are poorly understood. During chronic HCV infection, HCV-specific CD4+ T cell responses are rela- tively weak or absent whereas in resolved infection these responses are vigorous and multispecific. Persons with a T-helper type I profile, which promotes cellular effec- tor mechanisms are thought to be more likely to experi- ence viral clearance, but the overall role of these cells in the immunopathogenesis of chronic liver disease is not known. To define this, much more data is required on the function and specificity of virus-specific CD4+ T cells, especially in the early phases of acute disease and in the liver during chronic infection. The role and possible mechanisms of action of CD4+ T cell responses in deter- mining the outcome of acute and chronic HCV infection will be discussed in this review.     

Depletion of CD25^＋CD4^＋T cells （Tregs） enhances the H BV-specific CD8^＋ T cell response primed by DNA immunization

AIM: Persistent hepatitis B virus (HBV) infection is characterized by a weak CD8+ T cell response to HBV. Immunotherapeutic strategies that overcome tolerance and boost these suboptimal responses may facilitate viral clearance in chronically infected individuals. Therefore, we examined whether CD25+CD4+ regulatory T (Treg) cells might be involved in a inhibition of CD8+T cell priming or in the modulation of the magnitude of the 'peak' antiviral CD8+ T cell response primed by DNA immunization. METHODS: B10.D2 mice were immunized once with plasmid pCMV-S. Mice received 500 μg of anti-CD25 mAb injected intraperitoneally 3 d before DNA immunization to deplete CD25+ cells. Induction of HBV-specific CD8+ T cells in peripheral blood mononuclear cells (PBMCs) was measured by S28-39 peptide loaded DimerX staining and their function was analyzed by intracellular IFN-γ staining. RESULTS: DNA immunization induced HBV-specific CD8+ T cells. At the peak T cell response (d 10), 7.1±2.0% of CD8+ T cells were HBV-specific after DNA immunization, whereas 12.7±3.2% of CD8+ T cells were HBV-specific in Treg-depleted mice, suggesting that DNA immunization induced more antigen-specific CD8+ T cells in the absence of CD25+ Treg cells (n = 6, P<0.05). Similarly, fewer HBV specific memory T cells were detected in the presence of these cells (1.3±0.4%) in comparison to Treg-depleted mice (2.6±0.9%) on d 30 after DNA immunization (n - 6, P<0.01). Both IFN-γ production and the avidity of the HBV-specific CD8+ T cell response to antigen were higher in HBV-specific CD8+ T cells induced in the absence of Treg cells. CONCLUSION: CD25+ Treg cells suppress priming and/or expansion of antigen-specific CD8+ T cells during DNA immunization and the peak CD8+ T cell response is enhanced by depleting this cell population. Furthermore, Treg cells appear to be involved in the contraction phase of the CD8+ T cell response and may affect the quality of memory T cell pools. The elimination of Treg cells or their inhibition may be important in immunotherapeutic strategies to control HBV infection by inducing virus-specific cytotoxic T lymphocyte responses in chronically infected subjects.     

Intrahepatic CD8^＋ lymphocyte trapping during tolerance induction using mushroom derived formulations： A possible role for liver in tolerance induction

AIM： To determine the immunomodulatory effect of Shiitake （a mushroom extract）, we tested its effect on liver-mediated immune regulation in a model of immune-mediated colitis. METHODS： Four groups of mice were studied. Colitis was induced by intracolonic instillation of TNBS in groups A and B. Groups A and C were treated daily with Shiitake extract, while groups B and D received bovine serum albumin. Mice were evaluated for development of macroscopic and microscopic. The immune effects of Shiitake were determined by FACS analysis of intra-hepatic and intrasplenic lymphocytes and IFN-γ ELISPOT assay. RESULTS： Administration of Shiitake resulted in marked alleviation of colitis, manifested by significant improvement in the macroscopic and microscopic scores, and by reduction in IFN-γ-producing colonies in group A, compared to group B mice （1.5 pfu/mL vs 3.7 pfu/mL, respectively）. This beneficial effect was associated with a significant increase in the intrahepatic CD8^＋ lymphocyte trapping, demonstratedby an increased intrasplenic/intrahepatic CD4/CD8 lymphocyte ratio. These effects were accompanied by a 17% increase in the number of intrahepatic natural killer T （NKT） cells. A similar effect was observed when Shiitake was administered to animals without disease induction. CONCLUSION： Shiitake extract affected livermediated immune regulation by altering the NKT lymphocyte distribution and increasing intrahepatic CD8^＋ T lymphocyte trapping, thereby leading to alleviation of immune-mediated colitis.     

抗病毒治疗对慢性丙型肝炎CD4^＋CD25^＋调节性T细胞频率和功能的影响

目的研究抗病毒治疗前后慢性丙型肝炎患者CD4^＋CD25^＋调节性T细胞（Treg）频率和功能的变化。方法筛选HLA—A2阳性慢性丙型肝炎患者31例，给予聚乙二醇化干扰素α-2a（相对分子质量为40000）180μg每周1次皮下注射，联合口服利巴韦林。分别在治疗前和治疗结束随访24周时应用流式细胞仪检测患者CD4^＋CD25^＋ Treg细胞占外周血CD4^＋T细胞的频率，应用液闪计数仪检测其对HCV特异性CD8^＋T细胞增殖的抑制作用，ELISA法检测细胞培养上清γ干扰素（IFN-γ）水平的变化情况。结果治疗结束随访24周，患者外周血CD4^＋CD25^＋ Treg细胞频率为（9．6±3．0）％，明显低于治疗前的（11．0±2．3）％（t=2．028，P〈0．05）；持续病毒学应答（SVR）组CD4^＋CD25^＋ Treg细胞频率为（8．9±2．7）％，明显低于未获得SVR患者组的（10．4±2．3）％（t=3．324，P〈0．01）。抗病毒治疗后CD4^＋CD25^＋ Treg细胞抑制HCV特异性CD8^＋T细胞增殖的作用减弱。治疗后患者IFN-γ水平为（3959±577）pg／ml，明显高于治疗前的（1965±326）pg／ml（t=16．1，P〈0．01）；获得SVR患者组IFN-γ（6824±568）pg／ml，明显高于未获得SVR患者组的（2219±286）pg／ml（t=29．853，P〈0．001）。结论慢性丙型肝炎患者随着HCV RNA水平的下降，CD4^＋CD25^＋Treg细胞频率降低，抑制HCV特异性CD8^＋T细胞增殖的作用减弱。     

CD4+CD25+调节性T细胞对慢性丙型肝炎患者病毒特异性CD8+T细胞的抑制作用

HCV感染是严重危害人民健康的传染病，易发展成慢性丙型肝炎、肝硬化，且与原发性肝癌密切相关。HCV持续感染的一个重要原因是HCV特异性CD8^＋T细胞数量及功能缺陷，表现在体外增殖能力下降和IFN-γ分泌水平降低。CD4^＋CD25^＋调节性T细胞（T regulatory cells，Treg）主要在机体免疫系统中发挥负向调节作用，在移植物抗宿主病、自身免疫病、过敏性疾病等的发病机制和临床治疗中有潜在应用价值。已有研究表明，     

Evidence for a relation between the viral load and genotype and hepatitis C virus-specific T cell responses

BACKGROUND/AIMS: The reason why patients with hepatitis C virus (HCV) genotype non-1 infection respond better to antiviral therapy than patients with genotype 1 infection is not known. The aim of this study is to explore the relation between the viral genotype, viral load, and the endogenous T cell response. METHODS: The viral genotype, the viral load, and the endogenous proliferative T cell response to the non-structural 3 protein (NS3) was analysed using serum and peripheral blood mononuclear cells from 103 patients with chronic HCV infection. RESULTS: Among 71 nontreated patients a T cell response was more common among those infected by genotype 3, as compared to those infected with genotype 1 (P<0.05). Among 32 patients undergoing antiviral therapy, presence of a T cell response was more common in genotype non-1 infected patients than in those infected by genotype 1 (P<0.01). Presence of a T cell response was related to a more rapid viral clearance (P<0,05), a negative HCV RNA test at week 12 (P<0.05), and a shorter viral half-life (P<0.05). CONCLUSIONS: The presence of an NS3-specific T cell response is related to the viral genotype and to a more rapid clearance of HCV RNA during antiviral therapy.     

New animal models for hepatitis C viral infection and pathogenesis studies

Hepatitis C virus (HCV) is a major cause of chronic live disease, cirrhosis and hepatocellular carcinoma (HCC) In man, the pathobiological changes associated wit HCV infection have been attributed to both the immun system and direct viral cytopathic effects. Until now, th lack of simple culture systems to infect and propagat the virus has hampered progress in understandin the viral life cycle and pathogenesis of HCV infection including the molecular mechanisms implicated in HCV induced HCC. This clearly demonstrates the need t develop small animal models for the study of HCV associated pathogenesis. This review describes an discusses the development of new HCV animal models t study viral infection and investigate the direct effects o viral protein expression on liver disease.     

IL-10 directly suppresses CD4 but not CD8 T cell effector and memory responses following acute viral infection

Mounting effective T cell responses is critical for eliciting long-lasting immunity following viral infection and vaccination. A multitude of inhibitory and stimulatory factors are induced following infection, and it is the compilation of these signals that quantitatively and qualitatively program the ensuing effector and memory T cell response. In response to lymphocytic choriomeningitis virus (LCMV) infection, the immunosuppressive cytokine IL-10 is rapidly up-regulated; however, how IL-10 is regulating what is often considered an “optimal” immune response is unclear. We demonstrate that IL-10 directly inhibits effector and memory CD4 T cell responses following an acutely resolved viral infection. Blockade of IL-10 enhanced the magnitude and the functional capacity of effector CD4 T cells that translated into increased and more effective memory responses. On the other hand, lack of IL-10 signaling did not impact memory CD8 T cell development. We propose that blockade of IL-10 may be an effective adjuvant to specifically enhance CD4 T cell immunity and protection following vaccination.     

正常T细胞分泌激活因子基因多态性与HIV-1感染者病毒载量、CD+4细胞计数和CD+4/CD+8比值的关系

目的分析正常T细胞分泌激活因子(RANTES)启动子和内含子等位基因,对艾滋病病毒1型(HIV-1)感染者外周血CD+4细胞计数、CD+4/CD+8比值和病毒载量的关系,以期探讨RANTES单核苷酸多态性(SNP)和艾滋病(AIDS)发病的关系.方法用流式细胞仪和real time法对40例汉族HIV-1感染者测定外周血CD+4、CD+8细胞计数和病毒载量,应用PCR-RFLP法进行基因分型.结果对RANTES-403、-28和In1.1三个位点等位基因与外周血CD+4T淋巴细胞计数、CD+4/CD+8+比值和病毒载量的关系的分析表明,具有RANTESIn1.1 C/C和T/C基因型的感染者,与较高的病毒载量、较低的C+4T细胞计数和C+4/CD+8比值有关.In1.1 T/T与T/C、C/C基因型的log10病毒载量的差异有非常显著的统计学意义(P＜0.01),但是不同基因型之间CD+4T淋巴细胞计数和CD+4/CD+8细胞比值则无显著性差异.log10病毒载量和CD+4T淋巴细胞计数(r=-0.447,P＜0.01)、CD+4/CD+8比值(r=-0.369,P＜0.05)有显著的负相关关系.结论所研究人群中,具有RANTES In1.1C的基因型者,与较高的病毒载量、较低的CD+4T细胞计数和CD+4/CD8+比值有关,它们是反映AIDS进程的主要指标,可能加速AIDS发病进程;而RANTES-403和-28等位基因的影响则处于相对次要的作用.     

丙型肝炎病毒感染个体的准种源于感染过程中的病毒核酸突变

目的研究丙型肝炎病毒(HCV)准种特性与感染慢性化的关系,以及个体准种特性的来源形式。方法收集HCVRNA阳性的10例急性丙肝、20例慢性丙型肝炎(丙肝)和11例肝细胞癌(HCC)患者,采用单链构型多态性分析(SSCP)方法进行HCV准种检测。结果急性丙肝、慢性丙肝和HCC患者中,SSCP电泳条带数分别为2．7±1．16、4．8±1．68和5．2±2．85。慢性丙肝和HCC的条带数显著高于急性丙肝(P＜0．05)。进行DNA序列分析研究发现,准种高变区间的变异性显著低于本地株间和异地株间的变异性(P＜0．01)。结论SSCP是检测准种相对简便而有效的方法。HCV准种特性与其感染慢性化相关。HCV感染个体准种的来源主要为感染过程中的核酸突变。