Molecular Analysis of HCV-specific T Cell Responses

越来越多的证据表明，强有力的HCV特异性CD 4+辅助反应和CD 8 + T细胞反应是解决感染所必需的。上一个资助期的研究表明，CD 4 + T细胞耗竭的动物在病毒再激发后发生慢性感染。我们在前一个资助期的研究表明，针对显性病毒表位的T细胞受体（TCR）库的多样性与感染的解决之间存在联系。消退的感染与针对显性CD 4+和CD 8 + T细胞表位的不同TCR库相关。相反，慢性感染与缺乏CD 4 + T细胞应答和针对CD 8 + T细胞表位的狭窄TCR库相关。这些狭窄的定向反应先于免疫逃逸和慢性病毒感染的建立。我们假设，针对显性表位的不同TCR库产生于 在急性感染后早期，至少有两个原因是有益的。首先，不同的TCR库更可能包括能够识别潜在表位变体的TCR克隆型，从而限制免疫逃逸。第二，早期产生的多样性库可能包括扩展TCR克隆型与高亲合力的肽/MCH复合物。本项目中的研究将直接补充项目1中进行的功能和表型研究，并将使我们能够在高度相关的动物模型中直接测试这些假设。我们建议用以下具体目标来检验这一假设：具体目标1：确定是否产生不同的表位特异性CD 4 + TCR库预测丙型肝炎病毒感染的解决。具体目标2：确定不同表位特异性CD 8 + TCR库的产生是否预测HCV感染的消退，以及CD 8 + T细胞应答的维持是否依赖于不同TCR库的CD 4 + T细胞应答的维持。具体目标3：确定在已消退HCV的动物中，在主要MHC I类或II类表位中含有逃逸突变的HCV变异体的传播是否逃脱了现有TCR库的免疫识别。

Accumulating evidence suggests that robust HCV-specific CD4+ helper responses and CD8+ T cell responses are necessary for resolution of infection. Studies from the previous funding period demonstrated that CD4+ T cell-depleted animals developed chronic infection after virus rechallenge. Our studies over the prior funding period demonstrate a link between the diversity of T cell receptor (TCR) repertoires directed against dominant viral epitopes, and resolution of infection. Resolved infection was associated with diverse TCR repertoires directed against dominant CD4+ and CD8+ T cell epitopes. In contrast, chronic infection was associated with lack of CD4+ T cell responses, and narrow TCR repertoires directed against CD8+ T cell epitopes. These narrowly directed responses preceded immune escape and establishment of chronic viral infection. We hypothesize that diverse TCR repertoires directed against dominant epitopes arise early after acute infection, and are beneficial for at least 2 reasons. First, diverse TCR repertoires are far more likely to include TCR clonotypes able to recognize potential epitope variants, thus limiting immune escape. Second, the early generation of a diverse repertoire may include the expansion of TCR clonotypes with high avidity for the peptide/MCH complex. The studies in this project will directly complement the functional and phenotypic studies performed in project one, and will allow us to directly test these hypotheses in a highly relevant animal model. We propose to test this hypothesis with the following specific aims: Specific aim 1: Determine whether the generation of diverse epitope-specific CD4+ TCR repertoires predict resolution of HCV infection. Specific aim 2: Determine whether the generation of diverse epitope-specific CD8+ TCR repertoires predict resolution of HCV infection, and whether the maintenance of CD8+ T cell responses is dependent upon the maintenance of CD4+ T cell responses with diverse TCR repertoires. Specific aim 3: Determine whether transmission of HCV variants containing escape mutations in dominant MHC class I or II epitopes escape immune recognition from existing TCR repertoires in animals with resolved HCV.