Investigation of the rules dictating plasma cell longevity - Project Summary Gut-associated lymphoid structures, such as Peyer's patches, are some of the major inducers of plasma cells at steady state conditions. While most of these cells are short-lived, some may become long-lived plasma cells (LLPCs) in sites such as the bone marrow and lamina propria, where they produce antibodies and confer protection against reinfection by many different pathogens. Viral infections at mucosal interfaces induce germinal center (GC) reactions and boost PC numbers, but their establishment and persistence in the bone marrow remains an obstacle against seasonal respiratory infections, such as flu. While HA-based vaccines are known to engage significant protection, its immune memory is not sufficient for long-periods of time, requiring the population to take booster shots every year. It is known that LLPCs cells originate from GC direct export or GC-derived memory B cells following infection or vaccination, although it is still unknown how to efficiently engage and promote longevity in these populations at mucosal surfaces, which could generate both IgG and IgA isotypes. Despite substantial advances in vaccine design and adjuvant development, the mechanisms that determine whether plasma cells generated at mucosal sites joins the LLPC pool or undergoes cell death remain poorly understood. Defining the molecular basis about how influenza and gastroenteritis-induced PCs evolve over time and achieve longevity is the central objective of this proposal. To address this question, we developed an innovative mouse model that enables tracking of GC-derived plasma cells, revealing how distinct cohorts compete for survival, where they reside, and which cells successfully establish long-term persistence. This mouse will be combined with different models of infection (influenza, rotavirus, norovirus) and high-throughput technologies, including single-cell RNA sequencing, B-cell receptor sequencing, ATAC-seq, and other 10X Genomics-based approaches, allowing comprehensive analysis of the molecular, cellular, and clonal changes associated with plasma cell maturation and longevity induced upon mucosal infections. Importantly, the model enables fate-mapping of LLPCs across multiple tissues, such as bone marrow and the small intestine's lamina propria. To complement these studies, we will employ a second model developed in our laboratory, which enables temporally controlled gene deletion specifically in plasma cells. This system provides a powerful platform to directly assess the contribution of candidate genes to plasma cell maintenance and differentiation into LLPCs under both steady-state and inflammatory conditions. By integrating longitudinal fate-mapping with targeted genetic perturbation, we aim to identify the key factors that regulate plasma cell longevity across tissues harboring PCs induced at mucosal sites, and how they differ from non-mucosal perturbation settings. These studies will provide fundamental insight into the biology of durable humoral immunity while informing strategies to improve vaccine-induced LLPC generation against pathogens for which broadly neutralizing antibody responses remain difficult to achieve, including gastrointestinal viruses and influenza.
