PROJECT SUMMARY/ABSTRACT Over 1.8 million people are newly infected with HIV each year, and despite decades of research since the onset of the AIDS pandemic, we still do not have an efficacious vaccine. A major goal of vaccine design is the elicitation of broadly neutralizing antibodies (bNAbs), which target highly conserved epitopes on the HIV Envelope glycoprotein (Env) and block viral entry into host cells, thereby conferring protection against infection with a wide variety of strains. One such conserved bNAb epitope is the V3-glycan patch, which is the focus of this application. BNAbs arise naturally in some chronically infected patients as a result of prolonged antibody-virus coevolution but have never been induced by vaccination in humans. A roadblock in previous vaccination studies was that the heavy glycosylation of Env leads to concealment of bNAb epitopes, and as such, wildtype Env is not a viable immunogen. To overcome this challenge, modified Envs have been engineered by removing several glycans in an attempt to expose the underlying bNAb epitopes, and these have shown moderate success at stimulating bNAb precursor B cells. However, these bNAb precursors generally have poor neutralization activity and thus do not endow protective immunity. Attempts have been made to shepherd bNAb precursors into bona fide bNAbs via immunization with a series of decreasingly engineered Env proteins, a concept termed sequential immunization, though this has yielded inconsistent results. As such, the outstanding problem which this proposal seeks to address is: how to boost V3-glycan-targeting bNAb precursors to guide their maturation into bNAbs with high neutralization breadth and potency. An innovative two-pronged approach will be used to tackle this problem. In Aim 1, the evolution of a bNAb precursor-like lineage will be rigorously dissected using an immunoglobulin knockin mouse model. In Aim 2, antibody-virus coevolution will be studied in rhesus macaques immunized with engineered Env immunogens and subsequently infected with a related chimeric Simian-Human Immunodeficiency Virus. Together, the results will inform the design of novel immunogens and vaccination regimens to elicit V3-glycan-targeted bNAbs in animals and potentially humans. This work will be performed by MD-PhD student Ashwin Skelly under the mentorship and guidance of Sponsor Dr. Beatrice Hahn and Co-sponsor Dr. Amelia Escolano. The individualized training plan emphasizes gaining a solid foundation in immunology and microbiology, developing written and oral scientific communication skills, and engaging in clinical and professional development activities. The research will be conducted in the excellent training environment of the University of Pennsylvania and the Wistar Institute, which are equipped with all the cutting-edge resources and facilities needed for these projects including cores for flow cytometry, next- generation sequencing, and bioinformatics. In sum, the vibrant resear...