Project Summary/Abstract. A small fraction of individuals infected with HIV-1 generate antibodies that can potently neutralize diverse circulating strains of HIV-1. Such broadly neutralizing antibodies (bnAbs) have provided sterilizing immunity in passive immunization studies in animal models. Therefore, the induction of such antibodies by vaccination is a global health priority as a means to prevent HIV infection. The membrane proximal external region (MPER) of the HIV-1 envelope protein (Env) is a site of particular interest. A promising strategy to initiate bnAb induction is germline targeting (GT) in which immunogens are engineered to specifically activate B cell precursors of bnAbs. Previous work generated germline-targeting priming MPER epitope scaffolds capable of activating and expanding 10E8-like precursor B cell receptors (BCRs) in mouse and non-human primate (NHP) models. This project seeks to develop soluble and membrane-bound boost immunogens that present the MPER epitope in a more native-like context with the aim of maturing primed BCRs to acquire bnAb features. Known bnAbs have high degrees of somatic hypermutation (SHM); therefore, I hypothesize that vaccine induction of bnAbs will require sequential immunization with multiple immunogens designed to shepherd affinity maturation of the BCR to acquire neutralization breadth and potency. I will test this hypothesis through three primary aims to: 1) determine effect of mRNA vs. protein immunogen delivery on immunogenicity and BCR maturation of 10E8-GT priming candidates; 2) develop and test epitope-scaffold boost candidates for the ability to engage and mature B cells activated by GT primes; 3) generate stabilized transmembrane envelope constructs that preferentially bind MPER targeting antibodies. I expect the results of these aims will generate candidate immunogens that bind with high affinity to 10E8-like antibodies with various levels of mutation and maturity in order to shepherd antibodies towards breadth. During this process, I will receive training in immunology, structural biology, and immunology from my interdisciplinary mentors. The resources available at Scripps Research and from other collaborators will ensure I develop the skills needed for my long-term goal of leading a vaccine development research group.