PROJECT SUMMARY / ABSTRACT Age-related defects of the immune response contribute to reduced efficacy of the influenza vaccine in older adults. Influenza A virus (IAV) infection results in greater risk of complications and higher hospitalization rates in older adults, with approximately 90% of deaths occurring in adults over age 65. Therefore, the development of a safe and effective vaccine that promotes protective immunity for the aged is an urgent public health need. The overall goal of this revised R01 application is to identify the effect of vaccine biomaterials and adjuvants on DC metabolism, and subsequent effects on antibody and T cell memory to develop a nanovaccine to overcome age-related immune impairments. Vaccines for older adults can be further optimized with biomaterials that enhance multiple arms of the immune system and provide a platform to expand antigen selection, broadening protection. Our studies will establish the contribution of specific biomaterials and adjuvants in improving B and T cell outcomes resulting in protection by enhancing vaccine efficacy. The goals are to: 1) develop an efficacious influenza nanovaccine for older populations; and 2) to understand the mechanisms by which rational selection of biomaterials and co-adjuvants in vaccines can enhance immune capabilities of aged individuals. Our two polymeric nanovaccine platforms, polyanhydride nanoparticles and pentablock copolymer micelles, have been shown to increase antibody titers, improve cell-mediated immunity, and prolong antigen delivery resulting in a protective immune response with reduced viral load upon delivery of recombinant hemagglutinin and nucleoprotein in an IAV challenge model. Compelling preliminary data demonstrates that these formulations differentially alter dendritic cell (DC) metabolic profile compared to traditional adjuvants. Aim 1 will identify how nanovaccine biomaterials and adjuvants that promote DC metabolic health augment the immune response in aged mice. Different vaccine formulations will compare adjuvants that produce high glycolytic responses with formulations that retain some oxidative phosphorylation and spare respiratory capacity to optimize DC function. In the second aim, we will optimize the nanovaccine formulation(s) that enhance B cell activation in aged mice and peripheral blood B cells from aged humans. Additionally, we will identify mechanisms by which our nanovaccine improves T follicular helper responses and the induction of protective immunity on an aging background. Traditional inactivated IAV vaccine will be used as a control so as to identify the formulation providing superior protection than the current vaccine. In Aim 3, we will determine how nanovaccine-induced metabolically-optimized DC-T cell priming contributes to T cell memory and heterologous protection against IAV in aged mice. Measures of viral load, serum antibody, and lung T cell responses will be evaluated in homologous and heterosubtypic IAV challeng...