PROJECT SUMMARY The purpose of this NIH F30 application is to obtain support for the PI, Jacob Files, for his mentored research and career development for the next three years. These activities are part of his training requirements that are necessary for him to obtain his MD/PhD degree, and they will strengthen his potential to become a successful physician scientist. The major goal of this project is to develop his skills in order to study CD4+ T-cell responses (CD4 responses) in HIV-1 vaccine recipients using both immunological laboratory assays and computational techniques. The primary objective of the research proposal is to investigate the impact of HLA-II associated viral adaptation on CD4 responses in the setting of HIV-1 vaccination. CD4 responses have been found to play an important role in generating HIV-specific antibodies; therefore, an optimal CD4 response is likely to be an important component of future preventative HIV-1 vaccines. Our preliminary studies show that current HIV-1 vaccine studies encode a high percentage of HLA-II associated adapted epitopes and that these adapted epitopes elicit weaker responses in HIV-1 vaccine recipients compared to HLA-II associated non-adapted epitopes. Therefore, it is possible that a fully HLA-II non-adapted HIV-1 vaccine could lead to a more optimal CD4 response. This project will investigate the functionality and heterogeneity of the non-adapted and adapted epitope-specific CD4 responses, with a focus on identifying epitope-specific Tfh cells in HIV-1 vaccine recipients (Aim 1). Then, the project will determine the contribution of these CD4 responses to the frequency of HIV-specific antibodies and to B-cell maturation (Aim 2). By characterizing the functionality of the CD4 responses to these HLA-II associated epitopes and determining their impact on antibody production, our long-term objective is to inform future HIV-1 vaccine studies of strategies that can improve HIV-specific antibody production, leading to durable protection from HIV-1 infection. The proposed training plan for the PI is sponsored by his PhD mentor, Dr. Paul Goepfert. Included in the training plan are experiences that will help him develop in three major areas: 1) rigorous immunological research in HIV- 1, which includes developing familiarity with the existing literature, critically evaluating published studies, and training in principles of scientific integrity and responsible conduct of research; 2) competence in bioinformatic techniques and biostatistical analysis; and 3) career and professional development, including grant writing, journal article review, clear communication through presentation and manuscript preparation, and translation of research findings to clinical applications. After completion, this training plan will provide the PI with the foundation necessary for a successful career as a physician scientist. His ultimate career goal is to one day lead a translational research team that performs laboratory-ba...