Class II Processing and Presentation During Secondary Responses to Influenza

描述(由申请人提供)：初始的CD4+T细胞(TCD4+)的激活是由MHC II类(MHCII)结合肽(表位)驱动的，这些表位显示在树突状细胞(DC)的表面，这些树突状细胞(DC)已经从感染部位运输到区域淋巴结。虽然大多数研究都集中在最初的反应上，但自然界中的大多数病原体暴露都是在完全不同的背景下反复发生的。事实上，我们假设，记忆TCD4+的激活从根本上是不同的，它越来越被认为是回忆反应的一个关键方面。这在很大程度上是由于抗原特异性B细胞的存在，这种细胞具有独特的抗原处理能力。因此，这推动了从召回与初级反应中出现的TCD4+特异性的显著变化。通过充分利用两个共同PIs的经验的成熟的流感模型，这一假说将通过两个紧密联系的具体目标来追求。在第一个目标中，将通过以下方式评估B细胞在二次反应中的影响：a)在二次挑战之前选择性地消除或打开记忆B细胞上的MHCII，以及b)通过设计包含选择性miRNA靶向序列的病毒，将流感蛋白的表达限制在特定的细胞类型。在第二个目标中，将通过体外TCD4+激活试验来评估体外流感特异性B细胞与DC的抗原处理和提呈能力。预测这些抗原提呈细胞(APC)类型之间的差异将为在二次与一次反应中放大的TCD4+特异性提供基础。该项目有望为探索促进B细胞介导的呈现的处理机制、记忆B细胞在对其他病原体的反应中的作用以及更多利用由此产生的原理来增强合理疫苗设计的应用研究奠定基础。

DESCRIPTION (provided by applicant): Activation of naive CD4+ T cells (TCD4+) is driven by MHC class II (MHCII)-bound peptides (epitopes) displayed at the surfaces of dendritic cells (DCs) that have trafficked from sites of infection to regional lymph nodes. While most studies concentrate on the primary response, the majority of pathogen exposures in nature are repeat encounters that play out in decidedly different contexts. Indeed, we hypothesize that activation of memory TCD4+, increasingly appreciated as a key aspect of the recall response, is fundamentally distinct. This is attributable in large part to the presence of antigen-specific B cells, which possess unique antigen processing capabilities. Consequently, this drives a significant shift in the TCD4+ specificities that emerge from recall vs. primary responses. Through well-established influenza models that play to the experience of both co-PIs, this hypothesis will be pursued via two tightly linked specific aims. In the first aim the impact of B cells in the secondary response will be assessed by: a) selectively eliminating or turning on MHCII on memory B cells prior to a secondary challenge, and b) restricting flu protein expression to specific cell types by engineering viruses that contain selective miRNA targeting sequences. In the second aim the antigen processing and presenting capabilities of ex vivo flu-specific B cells vs. DCs will be assessed by in vitro TCD4+ activation assays. The prediction is that the observed differences between these antigen presenting cell (APC) types will provide a basis for the TCD4+ specificities that are amplified during the secondary vs. primary responses. This project is expected to set the stage for studies that explore the processing machinery that facilitates B cell-mediated presentation, the role of memory B cells in responses to other pathogens, as well as more applied studies that leverage resulting principles to enhance rational vaccine design.