Work Package 5
Characterization of TFH cells in germinal centers and antigen-specific T cell responses to infectious bursal disease virus in chickens
The adaptive immune response is essential for protecting chickens against pathogens. Traditionally, antibody titers have been the primary measure of immunity; however, they often provide an incomplete approximation of protection. Effective pathogenspecific cellular immunity, particularly mediated by αβ T cells, is increasingly recognized as a critical component of a robust immune defense. Effector CD8+ cytotoxic T cells and CD4+ T helper subsets are essential for targeting infected cells and pathogens, while specialized T follicular helper (Tfh) cells orchestrate effective B cell responses in germinal centers (GCs). While Tfh and antigen-specific effector T cells are well-characterized in mammals, their roles in chickens – particularly in the context of T cell clonal specificity – remain largely unexplored. Recent advancements in T cell receptor (TCR) repertoire analysis, including the comprehensive profiling of all chicken TCR chains established by our group during the first funding period, have become a powerful tool for studying T cell responses at the clonal level. However, establishing a direct link between specific TCR clonotypes and their corresponding antigens remains a significant challenge.
This project will address these critical knowledge gaps in two complementary Aims.
Aim 1: Perform a detailed analysis of T- and B-cell populations in chicken germinal centers to identify Tfh cells, their phenotypic diversity, and the signals essential for T cell- dependent humoral immunity. This will involve adapting bulk TCR and B cell receptor (BCR) sequencing to single-cell resolution, combined with transcriptomic analyses. Subsequent ex vivo and in vitro studies will characterize chicken Tfh cells to elucidate their functional roles. Aim 2: Investigate antigen-specific T cell immunity in response to Infectious Bursal Disease Virus (IBDV), a major pathogen affecting chickens. Cutting-edge methodologies will be utilized, including TCR repertoire sequencing with bioinformatic prediction of antigen-specific TCRs, IBDV-MHC tetramer staining, and T cell peptide stimulation assays integrated with TCR profiling. These approaches will, for the first time, identify IBDV-reactive T cells and establish the link between TCR clonotypes and viral antigens, enabling a detailed readout of protective T cell responses.
The proposed work builds on tools established in the first funding period by us and other members of the ImmunoChick consortium and requires continued collaboration. In summary, this project will significantly advance our understanding of antigen-specific effector T cell responses and the role of Tfh cells in optimizing humoral immunity. These insights are crucial for the rational design of improved vaccines to enhance chicken health.