丙型肝炎疫苗研究的新理念、挑战与策略

丙型肝炎病毒（HCV）感染是引起慢性肝病的主要原因之一,严重危害人类健康,目前抗病毒治疗的标准方案为聚乙二醇干扰素α（PEG-IFN-α）联合利巴韦林,其有效率仅为50%70%,且疫苗研究进展缓慢,已成为严峻的公共卫生问题。近10多年来,对HCV感染发病机制、保护性免疫应答和病毒持续感染机制的认识取得了很大进展,中和抗体以及CD4＋和CD8＋T细胞在内的强烈的T细胞免疫应答已被证明与HCV的清除相关,这将是研制丙型肝炎疫苗的希望所在。当前HCV疫苗的研究主要集中在多肽疫苗、核酸疫苗、病毒载体疫苗、重组多表位疫苗、以抗原递呈细胞为载体的树突状细胞（DC）疫苗等,已有多种疫苗正在研制并进行进入临床试验前的测试。我们结合多年来对HCV的研究基础,通过与国内外同行交流,提出变＂单纯预防＂为＂防治结合,以诱导持续免疫应答和维持病毒抑制状态为基本目标＂的HCV疫苗研究新理念,发展以诱导细胞免疫为主的预防和治疗性疫苗,尤其是既能在体内有效激发HCV特异性细胞毒性T淋巴细胞（CTL）反应,又能维持CD4＋记忆T细胞功能的治疗性细胞疫苗。本文综述关于HCV保护性免疫应答及持续感染的机制,HCV疫苗研究新理念,目前面临的挑战以及研究策略。     

丙型肝炎实验室诊断技术研究进展

丙型肝炎是一种由HCV感染引起的主要经血液传播的疾病,部分患者可发展为肝硬化甚至肝细胞肝癌（HCC）,目前尚无有效疫苗,亦无有效治愈方法,故早期、准确诊断HCV感染状况有重要意义.现将丙型肝炎实验室诊断技术的研究进展综述如下.     

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)。     

树突状细胞与丙型病毒性肝炎

树突状细胞（DC）是目前已知体内功能最强的抗原递呈细胞,在丙型肝炎病毒（HCV）感染的患者,DC功能减弱可促进病毒的持续感染,造成疾病的慢性化。目前DC成为HCV疫苗的研究重点,可能成为治疗慢性丙型肝炎（CHC）的有效免疫学方法,本文就DC与丙型肝炎的关系及其在治疗中的应用前景作一综述。     

丙型肝炎疫苗研究现状与方向

丙型肝炎(丙肝)病毒(hepatitis C virus,HCV)主要经血液传播,是急性和慢性肝炎、肝硬化、肝癌的重要致病因子。目前全球HCV感染者约有1.7亿,每年新增感染者达300万～400万,我国HCV感染者近4 000万。HCV感染的慢性率高达70%以上,至今尚无有确切保护作用的疫苗问世,迫切需要发展有效的疫苗预防、控制HCV的感染和传播。     

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丙型肝炎病毒(HCV)感染不仅可导致肝脏炎症坏死,而且大部分患者会形成慢性感染,发展为肝纤维化和肝硬化,甚至肝细胞肝癌(HCC).据世界卫生组织统计,全球HCV的感染率约为3%,约1.7亿人感染了HCV,每年新发丙型肝炎约3.5万例.     

重叠乙型和丙型肝炎病毒感染的临床与病理分析

目的 观察HBV和HCV重叠感染的临床与病理,探讨HBV和HCV相互作用的特点.方法 收集226例慢性肝病患者的血清学指标,实时荧光定量PCR法测定HBV DNA和HCVRNA,ELISA检测HBV血清标志物、抗-HCV抗体.行肝穿刺活组织病理检查、免疫组织化学HBsAg、HBcAg和原位杂交HBV DNA、HCV RNA检测.计数资料比较采用X2检验或Fisher确切率检验.结果 HBV和HCV重叠感染的重度慢性肝炎患者比例为62.50%,高于HBV或HCV单独感染者的27.05%和30.56%(X2=14.70,P＜0.01).HBV感染组的血ALT、AST、TBil、DBil和Alb高于HBV和HCV重叠感染组和HCV感染组,差异均有统计学意义(X2=8.52,P＜0.05).重叠感染组和HBV感染组的血HBsAg与肝内HBsAg一致率比较,差异均有统计学意义(X2=15.60,P＜0.01).HBV和HCV重叠感染组血清HBV DNA阳性率为12.5%,低于HBV单独感染组的87.7%(X2=17.66,P＜0.01);而HBV和HCV重叠感染组HCV RNA阳性率为75.0%,低于HCV单独感染组的80.6%,差异无统计学意义(P＞0.05).结论 HBV和HCV重叠感染导致的肝损伤更明显.     

关于丙型肝炎病毒疫苗的前景

问：抗HCV疫苗的前景如何？ 答：在过去的20年中，关于抗病毒性肝炎疫苗的发展已有了很大的进步。尤其是安全和有效的抗HBV疫苗已使用大约20年了，并且在大多数国家中从婴儿开始接种已成为一种常规。同样安全和有效的抗甲肝疫苗也很有作用，尽管该疫苗不推荐全部婴儿接种但可广泛使用在具有甲肝病毒感染风险的旅行者和其他个体中。     

血液透析患者丙型和庚型肝炎病毒感染的研究

为了解血液透析患者中丙型肝炎病毒(HCV)和庚型肝炎病毒(HGV)的感染情况,并探讨相对危险因素,对48例在302医院和武警总医院进行维持性血液透析的患者用逆转录聚合酶链(PCR)反应和酶联免疫法检测了血清中HCV RNA、HGV RNA及其抗体水平。结果显示,抗-HCV和HCV RNA阳     

北美小儿胃肠病、肝脏病和营养学会婴儿、儿童和青少年丙型肝炎诊断及管理实践指南

HCV是一种RNA病毒,全球有超过1．8亿慢性HCV感染患者。北美地区人群中抗一HCV阳性率约为1％～1．5％,其中6～11岁抗-HCV阳性率为0．17％（31000人）,12～19岁抗一HCV阳性率为0．39％（101000人）。基于儿童人口学特征及危险因素分析,慢性HCV感染可影响0．1％～2％的儿童,而6岁以上慢性HCV感染患病率略有下降。因此,在儿科胃肠病及肝病学专家看来,未成年人的HCV感染是很重要的问题。     

HBV/HCV重叠感染的研究进展

HBV是一种嗜肝DNA病毒,HBV DNA和HBV特异P蛋白由核壳包裹成为核心颗粒,再由脂蛋白外膜包裹成完整的病毒颗粒。HCV是黄病毒科病毒,为单股正链RNA。HBV和HCV均由肠道外途径传播,2种病毒常可由相同途径发生感染。归纳了HBV/HCV重叠感染的发病机制、与隐匿性HBV感染和肝细胞癌以及器官移植、HBV疫苗之间的关系,同时介绍了重叠感染的治疗。指出存在于患者体内的HBV和HCV在病毒学方面相互干扰,在病变方面相互叠加。     

Mixing particles from various HCV genotypes increases the HBV‐HCV vaccine ability to elicit broadly cross‐neutralizing antibodies

The development of a safe, effective and affordable prophylactic vaccine against hepatitis C virus (HCV) remains a medical priority. Hepatitis B‐C subviral envelope particles, which could be produced by industrial procedures adapted from those established for the hepatitis B virus vaccine, appear promising for use for this purpose. The prototype HBV‐HCV bivalent vaccine‐bearing genotype 1a HCV envelopes can induce neutralizing antibodies against this genotype, but is less effective against other genotypes. We show here, in a small animal model, that the use of a set of vaccine particles harbouring envelopes from different HCV genotypes in various association strategies can induce broad neutralizing protection or an optimized protection against a particular genotype prevalent in a given region, such as genotype 4 in Egypt. This vaccine could help to control the hepatitis C epidemic worldwide.     

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 virus and the immunological response to hepatitis B virus vaccine in dialysis patients: meta-analysis of clinical studies

It is well known that the seroconversion rate of patients following hepatitis B virus (HBV) vaccination is lower in uraemic than healthy subjects. A variety of inherited or acquired factors have been implicated in this diminished response, and the high prevalence of hepatitis C virus (HCV) infection among patients on maintenance dialysis has been suggested to play a role. However, the impact of HCV on the immune response to HB vaccine in patients receiving long-term dialysis is not entirely understood. Here, we evaluate the influence of HCV infection on the immunological response to HBV vaccine in dialysis population by performing a systematic review of the literature with a meta-analysis of clinical studies.We used the random-effects model of DerSimonian and Laird with heterogeneity and sensitivity analyses. The end-point of interest was the rate of patients showing seroprotective anti-hepatitis B titres at completion of HBV vaccine schedule among HCV-positive versus HCV-negative patients on chronic dialysis. We identified eight studies involving 520 unique patients on long-term dialysis. Aggregation of study results did not show a significant decrease in response rates among HCV-infected versus noninfected patients [pooled odds ratio = 0.621 (95% CI, 0.285; 1.353)]. The P-value was 0.007 for our test of study heterogeneity. Stratified analysis in various subgroups of interest did not meaningfully change our results. Our meta-analysis showed no association between immunological response to hepatitis B vaccine and HCV infection in individuals on long-term dialysis. These results support the use of recombinant vaccine against hepatitis B in patients on regular dialysis with HCV infection.     

Does antiviral therapy for hepatitis B and C prevent hepatocellular carcinoma?

Approximately 75% to 80% of hepatocellular carcinomas (HCC) worldwide are attributed to chronic hepatitis B virus (HBV) and chronic hepatitis C virus (HCV) infection. Thus, effective prevention of HBV and HCV infection and progression from acute HBV and HCV infection to chronic hepatitis, cirrhosis and HCC might prevent as many as 450,000 deaths from HCC each year. The most effective approach to preventing HCC is to prevent HBV and HCV infection through vaccination. Indeed HBV vaccine is the first vaccine demonstrated to prevent cancers. However, a vaccine for HCV is not available and for persons who are chronically infected with HBV or HCV, antiviral therapy is the only option for preventing HCC. Direct evidence supporting a benefit of antiviral therapy on the prevention of HCC has been shown in a few randomized controlled trials. There is abundant evidence that antiviral therapy, in patients with long-term virological response, can improve liver histology, providing indirect support that antiviral therapy may prevent HCC by slowing progression of liver disease and possibly even reversing liver damage. Nevertheless, the risk of HCC remains in patients with chronic HBV or chronic HCV infection if treatment is initiated after cirrhosis is established. These data indicate that treatment might be of greater benefit if instituted earlier in the course of chronic hepatitis B or C. Safer, more effective, and more affordable antiviral therapies are needed for both hepatitis B and hepatitis C so more patients can benefit from treatment and more HCCs can be prevented.     

Hepatitis C virus evasion mechanisms from neutralizing antibodies

Hepatitis C virus (HCV) represents a major public health problem, affecting 3% of the world's population. The majority of infected individuals develop chronic hepatitis, which can progress to cirrhosis and hepatocellular carcinoma. To date, a vaccine is not available and current therapy is limited by resistance, adverse effects and high costs. Although it is very well established that cell-mediated immunity is necessary for viral clearance, the importance of host antibodies in clearing HCV infection is being increasingly recognized. Indeed, recent studies indicate that neutralizing antibodies are induced in the early phase of infection by patients who subsequently clear viral infection. Conversely, patients who do not clear the virus develop high titers of neutralizing antibodies during the chronic stage. Surprisingly, these antibodies are not able to control HCV infection. HCV has therefore developed mechanisms to evade immune elimination, allowing it to persist in the majority of infected individuals. A detailed understanding of the mechanisms by which the virus escapes immune surveillance is therefore necessary if novel preventive and therapeutic treatments have to be designed. This review summarizes the current knowledge of the mechanisms used by HCV to evade host neutralizing antibodies.     

趋化因子在丙型肝炎免疫发病机制中的作用

丙型肝炎（丙肝）感染后易于慢性化,与肝硬化及肝细胞癌的发生密切相关,目前尚无特效药物和疫苗。趋化因子是一类与炎症反应密切相关的小分子蛋白质,在机体抗病毒免疫中起重要作用。越来越多的研究表明,趋化因子及其受体与丙肝的持续感染、致病以及抗病毒效果等密切相关。因此,本文就趋化因子及其受体在丙肝免疫发病机制中的作用进行了简要的综述。     

Development of a recombinant murine tumour model using hepatoma cells expressing hepatitis C virus nonstructural antigens

Hepatitis C virus (HCV) chronically infects 2%‐3% of the world's population, causing liver disease and cancer with prolonged infection. The narrow host range of the virus, being restricted largely to human hepatocytes, has made the development of relevant models to evaluate the efficacy of vaccines a challenge. We have developed a novel approach to accomplish this by generating a murine hepatoma cell line stably expressing nonstructural HCV antigens which can be used in vitro or in vivo to test HCV vaccine efficacies. These HCV‐recombinant hepatoma cells formed large solid‐mass tumours when implanted into syngeneic mice, allowing us to test candidate HCV vaccines to demonstrate the development of an HCV‐specific immune response that limited tumour growth. Using this model, we tested the therapeutic potential of recombinant anti‐HCV‐specific vaccines based on two fundamentally different attenuated pathogen vaccine systems—attenuated Salmonella and recombinant adenoviral vector based vaccine. While attenuated Salmonella that secreted HCV antigens limited growth of the HCV‐recombinant tumours when used in a therapeutic vaccination trial, replication‐competent but noninfectious adenovirus expressing nonstructural HCV antigens showed overall greater survival and reduced weight loss compared to non‐replicating nondisseminating adenovirus. Our results demonstrate a model with anti‐tumour responses to HCV nonstructural (NS) protein antigens and suggest that recombinant vaccine vectors should be explored as a therapeutic strategy for controlling HCV and HCV‐associated cancers.     

The Neutralizing Antibody Responses of Individuals That Spontaneously Resolve Hepatitis C Virus Infection

Hepatitis C virus (HCV) infection is a major global health problem. In the majority of cases the virus is not cleared by the host immune response and progresses to chronic infection. Studies of the neutralizing antibody responses in individuals that naturally clear infection are limited. Understanding what constitutes a successful antibody response versus one that has ‘failed’ and resulted in chronic infection is important to understand what type of antibody response would need to be elicited by a protective vaccine. Samples from spontaneous clearers are difficult to obtain therefore studies are often limited. In our study through HCV Research UK, we had access to a cohort of over 200 samples. We identified the samples that contained HCV neutralizing antibodies using ELISA and HCV pseudoparticle (HCVpp) assays. We then utilised mutagenesis and cross-competition analysis to determine the profile of the neutralizing antibody responses. In addition, we analysed a cohort of samples from chronic infection using the same techniques to enable direct comparison of the antibody profiles observed in both cohorts. We conclude that similar profiles are present in both cohorts indicating that it is not the neutralizing antibody response per se that determines the outcome of infection. These data will provide useful information for future HCV vaccine design.