The function of atypical B cells in the immune response against malaria - PROJECT SUMMARY Every year, Plasmodium parasites cause an estimated 240 million cases of malaria and kill more than half a million people, the large majority among young children. Malaria is associated with an accumulation of atypical B cells that have a poorly understood role in the immune response. On the one hand, atypical B cells are part of a normal immune response elicited by vaccination and infection, and serve as a distinct population of memory B cells that can produce antibodies upon re-exposure to antigen. On the other hand, studies suggest that these cells are a by-product of the highly inflammatory environment during a malaria episode and are functionally impaired. Importantly, malaria-experienced individuals with pre-existing atypical B cells may have suboptimal immune responses to malaria vaccines. Given the critical need to improve the efficacy of malaria vaccines, it is essential to better understand the function of atypical B cells in anti-parasite immunity. Preliminary data generated in our lab show that malaria-associated atypical B cells can be divided into a functional and a dysfunctional subset. Based on these results, we hypothesize that functional atypical B cells are associated with protection against malaria and encode potent parasite-inhibitory antibodies. If this hypothesis is correct, we speculate that understanding the developmental pathways and the molecular mechanisms that drive functional atypical B cell development will open avenues for optimizing immune responses to infection and vaccination. In Specific Aim 1, we will determine the phenotype of atypical B cell subsets associated with protection against malaria using multi-parameter spectral flow cytometry to analyze atypical B cell subsets in two groups of malaria- experienced children who have been matched for age and parasite exposure, but who differ in their level of immunological protection against malaria. In Specific Aim 2, we will analyze the antigen-specificity of antibodies produced by each subset of atypical B cells using protein microarrays of parasite antigens. In addition, we will isolate monoclonal antibodies from the two subsets to test their ability to inhibit parasite replication. In Specific Aim 3, we will perform multi-modal single-cell sequencing analysis of gene expression and chromatin accessibility to determine the molecular mechanisms that drive atypical B cell development. Collectively, these studies will provide in-depth understanding into the development of these cells and their role in protection against malaria. This insight will be critical for enhancing vaccine-elicited immunity in individuals with pre-existing immune responses to P. falciparum.
