Alternative Pathways for CD4+ T Cell Epitope Generation from Influenza Antigens

描述（由申请人提供）：CD4 T 细胞 (TCD4) 的充分参与对于多种人类感染（包括流感）的积极结果至关重要。 TCD4 被病原体衍生肽（表位）和主要组织相容性 II 类分子 (MHCII) 的复合物激活，这些复合物在承载抗原的细胞内产生，然后转运到细胞表面，在那里它们可以被 T 细胞受体结合。根据惯例，肽-MHCII 复合物是在外源抗原内化、内吞区室中蛋白水解并加载到晚期内体区室中的新生 MHCII 上之后形成的。这一经典途径主要是通过对持久球状蛋白的研究而推导出来的。当使用感染剂时，肽生成的其他途径（“抗原加工”）变得明显，其中一些始于内源性抗原来源（在呈递细胞内合成）。我们开始解决的一个关键问题是这些替代途径在多大程度上驱动 TCD4 对真正病原体的总体反应。使用流感感染的 C57Bl/6 (B6) 模型，初步结果表明，在解释 TCD4 反应的 14 个表位中，惊人的 13 个表位可以非经典地产生。因此，这一研究方向可以极大地修改基础免疫学的基本原理。这里提出的工作分为四个独立但高度整合的具体目标，将巩固和扩展这些发现，研究不同“专业”APC（树突状细胞、巨噬细胞和 B 细胞）在初级和次级反应期间替代处理流感蛋白的相对能力，并确定用于生成表位的处理途径是否会影响 TCD4 功能水平，从而影响保护能力。这些研究的结果可能会极大地影响针对一系列病原体的疫苗的合理设计。此外，他们还可以指出癌症免疫治疗的新方法，并为自身免疫性疾病的发生和治疗提供重要的见解。

DESCRIPTION (provided by applicant): Sufficient engagement of CD4+ T cells (TCD4+) is critical for a positive outcome in several human infections, including influenza (flu). TCD4+ are activated by complexes of pathogen-derived peptides (epitopes) and major histocompatibility class II molecules (MHCII) that are generated within the antigen bearing cell and then transported to the cell surface where they can be engaged by T cell receptor. According to convention, peptide-MHCII complexes are formed following internalization of exogenous antigen, proteolysis within the endocytic compartment and loading onto nascent MHCII in a late endosomal compartment. This classical pathway has been deduced mainly through study of durable globular proteins. When infectious agents are used, additional pathways of peptide generation ("antigen processing") become apparent, some that begin with endogenous sources of antigen (synthesized within the presenting cell). A critical question that we have begun to address is the extent to which these alternative pathways drive the total TCD4+ response to a bona fide pathogen. Using a C57Bl/6 (B6) model of influenza infection, preliminary results indicate that an astonishing 13 of the 14 epitopes that account for the TCD4+ response can be generated non-classically. Thus, this line of investigation could dramatically revise a fundamental principle of basic immunology. Organized in four independent but highly integrated specific aims, the work proposed here will solidify and expand upon these findings, investigate the relative capacities of the different "professional" APCs (dendritic cells, macrophages and B cells) for alternative processing of flu proteins during primary and secondary responses, and determine whether the processing pathway utilized to generate an epitope can impact the level of TCD4+ functionality and, hence, protective capacity. The results of these studies could considerably impact the rational design of vaccines against an array of pathogens. In addition, they could point to new approaches to cancer immunotherapy, and provide important insight into the genesis and treatment of autoimmune diseases.