在丙型肝炎病毒急性感染期间短暂的免疫抑制：对辅助性T细胞应答体内试验分析

丙型肝炎病毒（HCV）在急性感染后可以很快地获得长期存活下来的能力。细胞免疫应答被认为在控制病毒感染方面起着重要作用。在急性感染时，CD4＋T细胞功能丧失与病毒持续感染有关．但具体机制还不清楚。作用新型Ⅱ类四聚体来研究急性感染时体内辅助性T细胞的功能。研究人员测定了一个HCV急性感染病人HCV特异性CD4＋T细胞的应答。     

FoxP3＋T 细胞在 HBV 感染中的作用

FoxP3,又名叉头状转录因子,是 CD4＋ CD25＋调节性 T 细胞（CD4＋ CD25＋ Treg）的特异性细胞内标志物,目前作为鉴别CD4＋ CD25＋ Treg 的首选分子,以 FoxP3＋ T 细胞或 FoxP3＋Treg 表示。Treg 在抑制抗病毒 T 细胞免疫应答过程中发挥重要的作用。一方面,FoxP3＋ Treg 抑制过强的 T 细胞免疫应答避免对机体造成过度损伤;另一方面,由于限制了 T 细胞的抗病毒反应,病毒不能被及时清除而可能引起感染的持续存在。慢性乙型肝炎（CHB）是一种具有严重危害性传染病,细胞免疫应答是慢性乙型肝炎发病的主要病因。免疫耐受是造成HBV 感染慢性化的主要发病机制。本文就近年来关于FoxP3＋ T 细胞在 HBV 感染中的作用的研究进展作一综述。     

聚乙二醇干扰素对慢性丙型肝炎患者淋巴细胞亚群的影响

目的：研究聚乙二醇干扰素α-2b治疗慢性丙型肝炎（CHC）的疗效与机体免疫状态的关系。方法：采用流式细胞仪检测聚乙二醇干扰素α-2b治疗前后CHC患者T淋巴细胞亚群CD3＋、CD4＋、CD8＋T淋巴细胞及NK（自然杀伤细胞）、CTL（细胞毒性T淋巴细胞）的变化。结果：应答组患者血清CD3＋、CD4＋T淋巴细胞、NK细胞、CD4＋/CD8＋比值的上升程度及CD8＋、CTL细胞的下降程度明显高于无应答组,而持续应答组又相应优于复发组。结论：聚乙二醇干扰素α-2b治疗后患者的细胞免疫状态明显增强,检测患者T淋巴细胞亚群、NK、CTL细胞的变化,可以预测患者干扰素治疗的疗效。     

滤泡性辅助性T细胞与HCV感染的相关性

目的检测慢性HCV感染者外周血CD4＋T细胞中滤泡性辅助性T细胞（Tfh）所占比例,ICOS及负性调控因子PD-1、Tim-3在Tfh细胞上的表达。方法以31例HCV感染者、9例HCV感染自愈者（SR-HCV患者）及12例健康志愿者作为研究对象,应用流式细胞术分析外周血中CD4＋CXCR5＋Tfh细胞在CD4＋T细胞中所占比率,同时检测其ICOS、PD-1及Tim-3分子表达,通过酶联免疫吸附法测定血浆中白细胞介素（IL）21及HCV抗体水平,实时定量PCR检测HCV RNA滴度;多组数据比较采用单因素方差分析,双变量之间相关性采用Spearman秩相关分析。结果与健康对照组相比,HCV感染者及自愈者外周血CD4＋T细胞比率升高（P〈0.05）;HCV感染者CD4＋CXCR5＋Tfh细胞比率高于自愈及健康对照（P〈0.05）;HCV感染及自愈者CD4＋CX-CR5＋Tfh细胞ICOS、PD-1、Tim-3显著高于健康对照（P〈0.05）;血清IL-21水平HCV感染者与健康对照无统计学差异（P〉0.05）;HCV感染者HCV RNA载量与Tfh细胞比例呈负相关。结论 CD4＋CXCR5＋Tfh可能参与了抗HCV感染免疫应答。     

最新信息四则：一、丙型肝炎发病机制与Th1／Th2平衡（医学のめぬみ214：270-272，2005．广石和正）

近年研究提示，CTL应在HCV感染中可能有抑制病毒生长作用，病毒特异性CTL在初感染时的病毒消除上发挥有重要功能。于HCV已告清除的病例，在其后35年的漫长期间里均可验证有对HCV之CD4＋与CD8＋T细胞之应答。遗憾的是HCV感染的机体免疫应答不够强，病毒惹发的急性肝炎肝损害不重。故而容易造成转为持续感染。如果诱发Th1免疫应答则可酿成急性或亚急性重型肝炎而导致重度肝损害。     

HCV感染患者免疫细胞部分细胞因子分泌情况的初步研究

目的研究与正常人比较丙型肝炎病毒（HCV）感染患者免疫细胞分泌γ干扰素（IFN-γ）、白细胞介素10（IL-10）、肿瘤坏死因子α（TNF-α）及白细胞介素4（IL-4）的细胞频数情况,了解HCV感染对其影响。方法分离外周血单核细胞（PBMCs）,应用IL-10、IFN-γ、TNF-α及IL-4流式抗体进行细胞内因子染色,应用FACSCalibur流式细胞仪及FACSCalibur软件进行检测分析。结果HCV感染患者分泌IL-10、IFN-γ、IL-4的细胞频数在CD4＋CD8-T细胞、CD4-CD8＋T细胞、NK细胞和NKT细胞均发生明显下降;分泌TNF-α的细胞频数在CD4-CD8＋T淋巴细胞及NK细胞出现下降;HCV感染患者NK细胞、NKT细胞分泌IL-10和IFN-γ的细胞频数较CD4＋CD8-T淋巴细胞、CD4-CD8＋T淋巴细胞下降得更加明显。结论HCV感染患者的细胞免疫功能受到明显的损害,细胞因子分泌能力明显减低;固有免疫细胞功能受损可能是HCV感染慢性化的重要原因;细胞因子分泌的调节是抗HCV感染免疫治疗过程中需要调节的方向。     

丙型肝炎疫苗的研究现状

丙型肝炎在全世界广泛流行,全球有2～3亿的慢性HCV感染者,亟待研制有效的丙肝疫苗。然而,丙肝疫苗的研制尚面临诸多困难。本文就丙型肝炎疫苗的研究现状及相关的免疫学进展作一综述。 1 HCV与机体免疫应答体液免疫应答在保护机体免受病毒的攻击中发挥着重要作用,包括与HCV同属的黄热病毒、登革热病毒、tickbone脑炎病毒等的疫苗设计均着力于诱生机体的中和抗体,接种后机体均能产生具有中和作用的包膜抗体,并能抵抗随后相应病毒的攻击,然对HCV而言,目前尚不能确定其中和抗体表位。有研究表明,HCV-E_2区的高变区(HVR1)含有具有中和作用的B细胞表位,并发现HCV-E_2蛋白能与细胞上的CD81分子结合(CD81被认为是感染肝细胞的HCV受体)。     

轮状病毒细胞免疫机制的研究进展

轮状病毒（RV）是婴幼儿腹泻的主要病原，随着对RV感染免疫研究的不断深入，细胞免疫在其发病和疫苗研究中的作用越来越受到重视。T淋巴细胞参与了RV感染的免疫及保护，CD4^＋T细胞与CD8^＋T细胞对于RV感染清除均起到非常关键的作用，而且对于不同的RV表位随着时间的变化及组织的不同T细胞的应答也不同。细胞毒性T细胞则通过杀伤RV感染的细胞以清除病毒感染。此外IL-6、IL-2、IL-12、TNF—α和IFN-γ等细胞因子在轮状病毒感染时均有升高，在轮状病毒免疫调节中发挥作用。     

丙型肝炎病毒核心蛋白——免疫逃逸的“核心”？

丙型肝炎病毒（HCV）的特性是可以引起大多数病人的慢性感染。这主要是由于宿主免疫系统无法清除最初的HCV感染。强大的HCV特异性CD4＋和CDg＋T细胞活化与急性感染的清除有关，同时在慢性感染中，针对许多病毒决定基的HCV特异性T细胞的克隆是存在的，但其发生率低且没有发挥有效的功能。慢性HCV感染的异常免疫应答包括固有免疫系统的不完全活化，如单核细胞产生过度的炎性级联反应以及树突状细胞（DC）功能的改变。     

丙型肝炎

丙型肝炎病毒致病性研究新进展（综述），丙型肝炎病毒NS3蛋白促进人源肝细胞的增殖及其相关机制研究，血清HCVRNA荧光定量与丙型肝炎诊断意义，丙型肝炎病毒内源性靶向基因疫苗对荷瘤小鼠抑瘤效果的初步研究，丙型肝炎病毒体外可感染树晌肝细胞，慢性丙型肝炎患CD4^＋CD25^＋调节性T细胞表达增加,蛋白芯片、抗体检测及RT-PCR技术研究不同HCV感染人群的病原学差异.[编按]     

Current status of a hepatitis C vaccine: Encouraging results but significant challenges ahead

Persistent hepatitis C virus (HCV) infection affects 170 million people worldwide. Acute HCV infection is often asymptomatic, but many infected individuals develop persistent infections that may lead to development of end-stage liver diseases, including liver cirrhosis and hepatocellular carcinoma. Thus, an HCV vaccine that could significantly lower the chronicity rate would have a major impact on the disease burden. Unfortunately, HCV is a highly mutable virus, and escape mutations can undermine vaccine-induced virus-specific immunity. Also, HCV exists as multiple genotypes, and so genotype-specific vaccines might be required to achieve broad protection. Finally, vaccine development has been hampered by the lack of a small animal model and cell culture systems, but these are currently being established. Despite these obstacles, several vaccine candidates tested in the chimpanzee HCV model have shown some encouraging results.     

Immune responses in hepatitis C: is virus or host the problem?

PURPOSE OF REVIEW: Hepatitis C virus is an RNA virus that usually establishes persistent infection in its host. As an important cause of cirrhosis and hepatocellular carcinoma worldwide, hepatitis C is a growing public health concern. Despite recent advances in therapy, most people infected with the virus can expect lifelong infection. In the minority of those exposed and who spontaneously clear virus, a robust hepatitis C virus-specific T cell response of T helper 1 type correlates with resolution. The longevity of this response in the recovered state and the potential for hepatitis C virus-specific T cells to protect against future infection are critical parameters for vaccine design. RECENT FINDINGS: The literature of the past year dissected components of protective immunity to hepatitis C and emphasized the importance of the CD4 helper response in both the expansion and maintenance of hepatitis C virus-specific CD8(+) T cells. Other important studies examined how the virus interacts with immune cells to subvert both innate and adaptive immune responses in acute and chronic infection. SUMMARY: Defining the essential components of protective immunity against a highly mutable virus like hepatitis C underpins successful vaccine design. By understanding viral and host factors which influence hepatitis C virus-specific T cell maintenance and function, we are better equipped to devise immunomodulatory therapies and vaccines which induce robust and lasting immunity.     

Perspectives for a vaccine against hepatitis C virus

There is no vaccine for HCV and the only available treatment, IFNalpha alone or in combination with ribavirin, has proven efficacious in less than 50% of patients. Given that approximately 200 million chronic HCV infections have been estimated worldwide, there is a pressing need to develop vaccination strategies aimed at preventing and possibly eradicating HCV infection. However, several major practical and scientific problems arise in designing an HCV vaccine. First, HCV is only readily detected as RNA by PCR. Second, the only species that can be infected by HCV are humans and chimpanzees. Third, the virus does not replicate efficiently in vitro. Fourth, some viral proteins have very high mutability. Last, there is little information on correlates of immunity. Although an ideal vaccine should protect from infection, in that it should elicit sterilizing immunity, this is quite an ambitious goal in the PCR era. In the case of HCV, where acute HCV infection is a very limited health problem and infection can only be assessed by PCR, a more realistic goal might be to look for vaccines capable of protecting from chronic infection. We have preliminary evidence in chimpanzees that an HCV vaccine consisting of recombinant envelope proteins can elicit antibodies and inflammatory CD4+ T cell responses which can prevent chronic infection in the majority of vaccinees. Although the scientific and clinical challenges that need to be addressed are still substantial, advances in recombinant protein technology, novel adjuvants, and DNA vaccines, will be key in developing strategies to generate protective immunity against chronic HCV infection.     

Prospects for prophylactic and therapeutic vaccines against hepatitis C virus

Natural cross-protective immunity is induced after spontaneous clearance of primary hepatitis C virus (HCV) infection. Although this suggests that effective prophylactic vaccines against HCV are possible, there are still several areas that require further study. Current data indicate that, at best, vaccine-induced immunity may not completely prevent HCV infection but rather prevent persistence of the virus. However, this may be an acceptable goal, because chronic persistence of the virus is the main cause of pathogenesis and the development of serious liver conditions. Therapeutic vaccine development is also highly challenging; however, strategies have been pursued in combination with current or new treatments in an effort to reduce the costs and adverse effects associated with antiviral therapy. This review summarizes the current state of HCV vaccines and the challenges faced for future development and clinical trial design.     

Vaccine development for hepatitis C

Given the global disease burden and public health impact of hepatitis C, the development of an effective vaccine is of paramount importance. However, many challenging obstacles loom ahead of this goal. The hepatitis C virus (HCV), being an RNA virus, can mutate rapidly in adaptation to the environment, thus contributing to the high sequence divergence of multiple viral isolates in the world. The highest heterogeneity has been found in the hypervariable region of the envelope glycoprotein 2, which contains a principal neutralization epitope. HCV also causes persistent infection in a high percentage of immunocompetent hosts despite active immune response. The lack of an efficient tissue culture system for propagating HCV and testing neutralizing antibodies adds further complexity to the task of vaccine development. The immunologic correlates associated with disease progression or protection are yet to be defined, but recent studies suggest that a vigorous multispecific cellular immune response is important in the resolution of infection. Induction of high-titer, long-lasting, and cross-reactive antienvelope antibodies and a vigorous multispecific cellular immune response that includes both helper and cytotoxic T lymphocytes may be necessary for an effective vaccine. Several promising approaches have been used to develop an HCV vaccine. Novel vaccine candidates based on molecular technology such as recombinant proteins, peptides, viruslike particles, naked DNA, and recombinant viruses are being explored. The final vaccine product may require multiple components that target various aspects of protective immunity. Finally, sterilizing immunity may not be necessary if a vaccine can be developed to prevent chronic infection, which is the major cause of morbidity and mortality from this disease.     

Structure-Based and Rational Design of a Hepatitis C Virus Vaccine

A hepatitis C virus (HCV) vaccine is a critical yet unfulfilled step in addressing the global disease burden of HCV. While decades of research have led to numerous clinical and pre-clinical vaccine candidates, these efforts have been hindered by factors including HCV antigenic variability and immune evasion. Structure-based and rational vaccine design approaches have capitalized on insights regarding the immune response to HCV and the structures of antibody-bound envelope glycoproteins. Despite successes with other viruses, designing an immunogen based on HCV glycoproteins that can elicit broadly protective immunity against HCV infection is an ongoing challenge. Here, we describe HCV vaccine design approaches where immunogens were selected and optimized through analysis of available structures, identification of conserved epitopes targeted by neutralizing antibodies, or both. Several designs have elicited immune responses against HCV in vivo, revealing correlates of HCV antigen immunogenicity and breadth of induced responses. Recent studies have elucidated the functional, dynamic and immunological features of key regions of the viral envelope glycoproteins, which can inform next-generation immunogen design efforts. These insights and design strategies represent promising pathways to HCV vaccine development, which can be further informed by successful immunogen designs generated for other viruses.     

Progress in the development of preventive and therapeutic vaccines for hepatitis C virus

Hepatitis C virus (HCV) is a blood borne disease estimated to chronically infect 3% of the worlds' population causing significant morbidity and mortality. Current medical therapy is curative in approximately 50% of patients. While recent treatment advances of genotype 1 infection using directly acting antiviral agents (DAAs) are encouraging, there is still a need to develop vaccine strategies capable of preventing infection. Moreover, vaccines may also be used in future in combination with DAAs enabling interferon-free treatment regimens. Viral and host specific factors contribute to viral evasion and present important impediments to vaccine development. Both, innate and adaptive immune responses are of major importance for the control of HCV infection. However, HCV has evolved ways of evading the host's immune response in order to establish persistent infection. For example, HCV inhibits intracellular interferon signalling pathways, impairs the activation of dendritic cells, CD8(+) and CD4(+) T cell responses, induces a state of T-cell exhaustion and selects escape variants with mutations CD8(+) T cell epitopes. An effective vaccine will need to produce strong and broadly cross-reactive CD4(+), CD8(+) T cell and neutralising antibody (NAb) responses to be successful in preventing or clearing HCV. Vaccines in clinical trials now include recombinant proteins, synthetic peptides, virosome based vaccines, tarmogens, modified vaccinia Ankara based vaccines, and DNA based vaccines. Several preclinical vaccine strategies are also under development and include recombinant adenoviral vaccines, virus like particles, and synthetic peptide vaccines. This paper will review the vaccines strategies employed, their success to date and future directions of vaccine design.     

Sequence analysis of the hepatitis C virus (HCV) core gene suggests the core protein as an appropriate target for HCV vaccine strategies

Summary. Hepatitis C virus (HCV) is a major health problem with a prevalence of 1% in the United States population, and a significant percentage of infected patients progress to chronic liver disease and cirrhosis. Interferon therapy has demonstrated that the immune system can be modulated to alter the acute course of the disease, but long-term treatments remain elusive. Prevention of hepatitis C infection is therefore an important strategy to mitigate the impact of this disease. Initial attempts at vaccination have focused on recombinant envelope vaccines, which have shown an ability to protect against very low titre challenges of HCV in chimps. The need for vaccines capable of protecting against higher titre challenges has led to the search for alternative vaccine strategies. The most highly conserved structural protein in the HCV genome is the core protein, and vaccine strategies targeting the core protein have been proposed to increase vaccine efficacy. The variability of HCV core sequences and genotypes in the Ann Arbor patient population are not known, and the present study was undertaken to assess the theoretical feasibility of developing a HCV core vaccine by excluding promiscuous core (C) gene variability as a mechanism of vaccine failure. Results of nucleotide and deduced amino acid sequence analysis from 13 of 14 patients studied reveal a 93% nucleotide and 96.4% amino acid core sequence homology in the C gene regions studied. Genotype analysis revealed four of 14 to be type 1a and nine of 14 to be type 1b with one infection not being sufficiently characterized to determine genotype. These results demonstrate a sufficiently high degree of conservation of HCV core sequences in our patient population to permit design of a vaccine directed against core protein.     

Hepatitis C vaccine: supply and demand

Despite difficulties associated with extreme variability and mutability of hepatitis C virus (HCV), several vaccines that prevent initial infection or viral persistence, or that clear viraemia in individuals with chronic HCV infections, are currently in development. At least one vaccine that may prevent chronic persistent infections will soon be available for testing. We review the widespread importance of HCV infection and disease, the immune response to HCV and correlates of protection, prevention strategies and vaccine candidates, and groups that will need the vaccine and provide suitable populations for assessing vaccine safety and efficacy. The evaluation of prophylactic vaccines is particularly problematic since distribution must focus upon individuals at high risk of exposure-for example, intravenous drug users and health-care providers in areas with high HCV prevalence. Although there is a huge need for therapeutic vaccines, further immunological hurdles must be cleared before one becomes available.