Immune Responses in Acute Hepatitis C

描述(申请人提供)：在美国，丙型肝炎病毒(丙型肝炎病毒)是导致进行性肝炎、肝硬变和肝细胞癌的主要原因。了解允许大约15%的人清除急性丙型肝炎的免疫类型是开发疫苗的关键。对黑猩猩和人类的探索性研究表明，靶向多种丙型肝炎病毒蛋白的T细胞似乎是清除丙型肝炎病毒所必需的。为了更好地了解与保护相关的免疫类型，需要对成功的反应进行仔细研究。注射吸毒者的新丙型肝炎病毒感染率最高，但通常情况下，许多人会因为随访而迷失方向。在当地200多名注射者的流行病学队列中，发现并跟踪了高比率(28%/人/年)的新丙型肝炎病毒感染。这使得对急性丙型肝炎患者进行前瞻性研究成为可能。在这个项目中，Aim 1建议从诊断的角度前瞻性地检查丙型肝炎病毒特异性抗体和T细胞反应(基于转换为丙型肝炎病毒核糖核酸或抗体阳性)。通过结合淋巴增殖、细胞内细胞因子染色和ELISpot分析，将确定CD4+T细胞和CD8+T细胞反应的丙型肝炎病毒蛋白靶点和活力。将进行定性和定量抗体分析，扩大针对丙型肝炎病毒的特异性CTL，检查其谱系，精确绘制其表位和人类白细胞抗原限制图。将合成一些人类白细胞抗原/多肽表位的MHC-I类四聚体，以便更高分辨率地比较解析者和进展者的CTL谱系。多肽表位内的进化被认为是导致病毒逃避CTL的结果。这种免疫逃逸模式将在AIM 2中进行测试，因为CTL表位变体被测序、合成并在CTL检测中进行测试。CTL仍能识别其变异体的表位将构成合乎逻辑的疫苗成分。最近的实验证明，丙型肝炎病毒特异性CTL可以表达一系列抑制和激活受体(NKR)。NKR的配基库取决于人的人类白细胞抗原类型，这表明NKR+CTL可能根据肝脏中的配基相互作用而受到不同的调节。这一点将在目标3中进行测试。总体而言，这项研究将为抗丙型肝炎病毒免疫的保护机制提供独特的见解。这也将为疫苗设计奠定基础。

DESCRIPTION (provided by applicant): In the US, hepatitis C virus (HCV) is the leading cause of progressive hepatitis, cirrhosis and liver cell cancer. Understanding the type of immunity that allows approximately 15% people to clear acute hepatitis C holds the key to developing a vaccine. Exploratory studies in chimpanzee and humans show that T cells targeting multiple HCV proteins seem necessary for HCV clearance. To better understand the type of immunity that correlates with protection, careful study of successful responses will be required. Injection drug users have the highest rates of new HCV infection but typically many get lost to follow-up. In a local epidemiological cohort of over 200 injectors a high rate (28%/person/year) of new HCV infections has been identified and followed up. This now permits prospective study of people with acute hepatitis C. In this project, Aim 1 proposes to prospectively examine HCV-specific antibody and T cell responses from the point of diagnosis (based on conversion to HCV RNA or antibody positivity). The HCV protein targets and vigor of CD4+ T cell and CD8+ T cell responses will be determined by combining lymphoproliferation, intracellular cytokine staining, and ELISpot assays. Qualitative and quantitative antibody analysis will be conducted and CTL specific for HCV will be expanded, their repertoires examined and their epitopes and HLA restriction precisely mapped. MHC class I tetramers of some HLA/peptide epitopes will be synthesized for higher resolution comparison of CTL repertoires in resolvers and progressors. Evolution within peptide epitopes is hypothesized to result in viral escape from CTL. This model of immune escape will be tested in Aim 2, as CTL epitope variants are sequenced, synthesized and tested in CTL assays. An epitope whose ange of variants can still be recognized by CTL would constitute a logical vaccine component. Recent experiments have demonstrated expression of arrays of inhibitory and activating receptors (NKR) by HCV-specific CTL. The NKR ligand repertoire depends on the person's HLA type suggesting that NKR+ CTL may be variably regulated depending on ligand interaction in the liver. This will be tested in Aim 3. Overall this investigation will provide unique insights into protective mechanisms of immunity against HCV. It will also lay a foundation for vaccine design.