Overall Component Vaccines are one of the most cost effective and extraordinarily successful medical interventions. Most of those vaccines depend on CD4 T+ cells and their help to B cells. Our understanding of in vivo, specific human CD4+ T cell responses to pathogens remains hazy, due to the complexity of the biology, the rarity of the cells, relatively inaccessible tissue localization, and technical challenges of identifying specific CD4+ T cells. Therefore, our approach to this serious problem has been to develop multiple new techniques to study human CD4+ T cells over the past several years. While CD4+ T cell-dependent antibody responses have been the source of protection for most licensed vaccines (Project 1), there is a very good argument to be made that many of the diseases for which we do not have successful vaccines require adaptive immune responses beyond antibodies for protection (Projects 2 and 3). The three Projects proposed here vigorously pursue an understanding of the mechanisms regulating human anti-pathogen CD4+ T cells, linked by new experimental approaches.
Overall Component Our understanding of in vivo, antigen-specific human CD4+ T cell responses to pathogens remains hazy, due to the complexity of the biology, the rarity of the cells, and technical challenges of identifying antigen-specific CD4+ T cells, since they can be so heterogeneous in phenotype and cytokine potential. The overall, innovative, technological themes of all three Projects in this CCHI proposal are (1) Studying human antigen-specific CD4+ T cells using novel, highly sensitive live cell techniques in a cytokine-agnostic manner; (2) Utilization of single- cell RNA-seq for in-depth characterization of antigen-specific CD4+ T cell and B cell biology, heterogeneity and TCR/BCR repertoire; and (3) Direct analysis of CD4+ T cells and germinal centers in lymphoid tissues via fine needle aspirates and whole lymph node and tonsil biopsies. Each of these are used heavily in Project 1 (Crotty), Project 2 (Sette), and Project 3 (Vijayanand), such that the three Projects proposed here vigorously pursue an understanding of human anti-pathogen CD4+ T cells, linked by new experimental approaches and novel preliminary findings regarding CD4 T cell biology.