Development of antibody-based vaccines against the trimeric viral envelope spike protein is critical for prevention of HIV-1 infection. Viral sequence diversity, conformational variability and extensive envelope glycosylation have made this a challenging task. With that said, three of the most broadly neutralizing antibodies (BNABs) isolated from human B cells (4E10, 2F5, Z13e1) are directed at the uniquely accessible yet highly conserved segment of gp41 known as the membrane proximal ectodomain region (MPER). While viral-like particles (VLP)-gp41 constructs containing the MPER stimulated strong antibody responses, we observed that their anti-gp41 specificity was preferentially directed at the C-helix and away from the MPER. Consequently, to reduce immunogen complexity, we have recently used NMR and EPR methods to characterize lipid-embedded MPER segments on liposomes, bicelles and micelles prior to and after, BNAB binding. These findings suggest a novel HIV immunization strategy by identifying BNAB triggered conformational alterations in the viral MPER region induced by 4E10 and 2F5 and suggest how these two BNABs perturb function of tryptophan residues therein, critical for fusion pore activity. By contrast, Z13e1 freezes the hinge motion of the helix-hinge-helix MPER segment. Four groups of investigators plan to utilize their collective talents in structural immunology, vaccinology, inflammation research, biomaterials and B cell biology to deliver lipid-embedded MPER nanoparticles for vaccination of animals in order to generate BNABs. The ReinherzA/Vagner groups will analyze structures of HIV MPERs in lipid environments in free- and antibody-bound states, correlating neutralization with antibody-triggered conformational changes around the metastable hinge-linked MPER segment. The Irvine group will create multi-functional MPER nanoparticles consisting of PLGA core particles embedding CD4 T cell epitopes and encapsulated by an outer lipid vesicle or skin for MPER presentation to the immune system via directed targeting to TLRs. The Sitkovskv group will amplify immune responses during vaccination through prevention of downregulation of vaccine-induced inflammation via antagonism of A2AR/A2BR extracellular adenosine receptor-mediated immunosuppression. The Kelsoe group will analyze induction of germinal centers, Ig class switch recombination and hypermutation, affinity maturation of serum antibodies and germinal center B cells in response to MPER immunogens. In conjunction with Projects 1- 3, kinetics of memory B cell and long-lived plasma cell populations will be ascertained and optimized. An Administrative Core with a Partnership Plan is included.
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