Optimizing Human B and T Cell Vaccines Against HIV Using Humanized BLT Mice

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DESCRIPTION (provided by applicant): This P01 Program Project Grant is focused on optimizing the induction of vaccine-elicited human B cell and T cell responses against HIV utilizing the recently developed BLT (bone marrow, liver, thymus) humanized mouse model. While the SlV-infected macaque model has proven invaluable to HIV vaccine development, differences between macaque and human host genetics (e.g. MHC, TCR, BCR), as well as sequence differences between SIV and HIV, results in entirely distinct virus-specific responses in humans and macaques to these pathogens. Similarly, the cost and duration of HIV vaccine studies in humans limits the ability to rapidly conduct iterative studies to improve upon promising findings. As such, our ability to study, optimize and translate specific mechanisms by which human immune humoral and cellular immune responses control HIV in humans, especially with respect to immune specificity, remains restricted, as does our ability to identify approaches to best induce these precise types of responses in humans. This proposal builds on the investigators' strong track records in understanding neutralizing antibody and CD8+ T cell responses against HIV, and in developing novel nanoparticle delivery approaches to induce high levels of mucosal homing responses. Moreover, it translates these efforts into a newly developed BLT (bone marrow, liver, thymus) humanized mouse model of HIV infection that robustly supports HIV infection, and recapitulates human cellular and humoral immune responses, specificities, and characteristics critical to accurately defining the correlates of immune control and approaches to elicit protective vaccine-induced immunity. RELEVANCE: Understanding the precise mechanisms of immune control of HIV will be critical to the development of an effective HIV vaccine capable of recapitulating these responses. The recent development of the humanized BLT mouse model provides the unique opportunity to explore the correlates of immune protection against HIV and rapidly test iterative vaccine design approaches to optimize human responses to HIV. Project 1: Optimizing CD8+ T Cell Vaccine Responses Against HIV Project Leader (PL): Allen, Todd M. DESCRIPTION (as provided by applicant): Project 1 seeks to apply a rational approach to the optimization of an effective CD8+ T cell response to HIV, capitalizing on viral fitness constraint to exploit the natural limits of HIV sequence evolution and CD8 immunodominance hierarchies and the plasticity of the immune response to block viral escape pathways. It also brings to bear recent advances in high throughput genomic sequencing to tackle the enormous sequence diversity of HIV, while applying novel and potent nanoparticle-based vaccine adjuvant systems. Most importantly, it serves to translate identified correlates of immune control of HIV into a nove humanized mouse model capable of recapitulating HIV infection as well as human HIV-specific immune responses. Thus, this work will enable for the first time the direct study of human (not rhesus monkey) immune responses against HIV (not SIV) in order to define the mechanisms of this protection and iteratively improve vaccine approaches to optimize these effects. Project 1 responds to five specific objectives of the HIVRAD Program: 1) Identifying correlates of vaccine-induced immune protection to HIV/AIDS; 2) How vaccine design can better address the heterogeneity of HIV; 3) Improved animal model systems (and challenge viruses) to address vaccine efficacy; 4) Approaches to increase the immunogenicity of HIV antigens (e.g., novel adjuvants), and 5) Determining how immune cells can be mobilized to the portal of infection, and will address the following specific aims: Aim 1: Characterize the magnitude, kinetics, specificity and efficacy of HIV-specific CD8+ T cell responses in the humanized BLT mouse model to facilitate studies of HIV-specific vaccine immunity. Aim 2: Determine whether vaccination can overcome natural CD8+ T cell immunodominance hierarchies to avoid targeting of 'decoy' CD8 epitopes, and induce variant-specific CD8+ T cell responses. Aim 3: Determine whether the induction of strong, mucosal-homing CD8+ T cell responses by novel nanoparticle delivery systems can prevent the early systemic dissemination of HIV in BLT mice. RELEVANCE: The newly developed humanized mouse model provides the unique opportunity to explore the correlates of immune protection of HIV by cellular immune responses within a system capable of supporting HIV infection and mounting human HIV-specific type responses. This model will also enable us to rapidly test iterative vaccine design approaches to further optimize cellular immune responses to HIV.