Defining mechanisms for induction of antibacterial lung-resident CD4 T cells - Project Abstract Pneumonia is a leading cause of infectious deaths worldwide; over 2 million people die of pneumonia each year. The leading bacterial cause of pneumonia is Streptococcus pneumoniae (Spn), an opportunistic pathogen that colonizes the human respiratory tract. While there are >100 known serotypes of Spn worldwide, current immunization strategies protect only against a limited few. Recent advances in our understanding of mucosal immunology have identified lung-resident CD4+ memory T (TRM) cells as critical determinants of broad protection against multiple serotypes of Spn. However, despite their clinical value from the public health perspective, little is known about mechanisms that drive the establishment of these CD4+ TRM cells in the lungs. Furthermore, it is unclear whether Spn may alter CD4+ TRM cell formation in the lungs using its own virulence factors. Understanding these mechanisms is instrumental for development of next generation cross-protective immunization strategies against this pathogen. Relevant to this, our preliminary data suggest that the Spn toxin pneumolysin (Ply) and bacterial sensing by NLRP3 are both key to recruitment and establishment of CD4+ TRM cell in the lungs. However, it remains unclear whether pore-forming activity or complement-activating biology of Ply is required for CD4+ TRM cell formation nor is it known how NLRP3 sensing of Spn may coax CD4+ TRM cell formation. In this proposal we will test the hypothesis that Spn drives CD4+ TRM cell formation via Ply’s pore forming activity and induction of macrophage-epithelial crosstalk via NLRP3. This hypothesis will be tested through two specific aims: Aim 1 will determine whether pore formation activity of Ply drives CD4+ TRM cell formation by boosting T cell recruitment, and Aim 2 will determine whether NLRP3 sensing of Spn is required for macrophage-epithelial crosstalk to drive CD4+ TRM cell formation. These studies will be accomplished by using isogenic Spn mutant strains, genetically engineered mice, intratracheal murine infection models, adoptive transfers, spectral flow cytometry, and single cell- and bulk-RNA sequencing. Findings from these innovative studies will guide development of more effective, broadly protective Spn immunization strategies that will prevent life-threatening Spn-pneumonia and subsequent diseases. This proposal will support the applicant with her scientific, technical, personal, professional, and career development which includes courses and workshops, guidance from a strong mentoring team and dissertation advisory committee, opportunities to develop science communication skills, and opportunities to mentor junior students in the lab and classroom. The University of Michigan offers top academic training, connections with esteemed faculty in pulmonology, microbiology, and immunology, and state-of-the-art resources to achieve the proposed aims. Completion of this proposal will also support the applicant’s rigorous training in experimental design, microbiology and immunology techniques, and data interpretation that will usher her towards becoming a successful, independent scientist.
