Enhancement of mitochondrial function fosters B cell immune memory

Differentiation of T and B cells to effector and memory cell fates are associated with extensive metabolic changes which are accompanied by altered mitochondrial dynamics. However, whether alterations in mitochondrial structure and function plays an active role in regulating effector versus memory cell fate decisions during immune responses remains unclear. Our studies here characterize changes in mitochondrial dynamics in activated B cells and show that increased mitochondrial mass and activity is a distinct feature of memory B cell lineage commitment in vivo. Using a directed screen of mitochondrial modulators, we identify mitochondrial fission inhibitor, Mdivi-1 as an agent that could enhance mitochondrial mass and function leading to augmented memory B cell differentiation. The enhanced memory B cell responses mediated by Mdivi-1, translated to more robust recall responses upon secondary antigen exposures. Moreover, Mdivi-1 when used in combination with subunit (SARS-CoV2) and inactivated (H1N1 influenza) vaccines led to remarkably improved vaccine efficacies and protection from lethal viral (H1N1) challenge. Single-cell transcriptomics revealed enhanced commitment to memory lineage differentiation in B cells following Mdivi-1 treatment. We propose that mitochondrial modulators such as Mdivi-1 are a novel class of "immune enhancers" that specifically reinforces immunological memory and could be broadly applied to improve the fidelity of immune responses and vaccine efficacies.