Influenza A virus (IAV) is a major cause of serious respiratory illness worldwide, leading to approximately 5 million severe cases and 500,000 deaths per year. Given the disease severity, associated economic costs, and recent appearance of novel IAV strains, there is a renewed interest in developing novel and efficacious “universal” IAV vaccination strategies as well as therapeutic remedies. Previous studies from our laboratory have concentrated on IAV-specific CD8 T cell-mediated protection against IAV infection as IAV-specific CD8 T cells are needed for efficient clearance of virus. Recent studies highlight that immunizations capable of generating local (i.e., nasal mucosa and lung) tissue-resident memory T and B cells in addition to systemic immunity offer the greatest protection against future IAV encounters. Current IAV vaccines are designed to largely stimulate IAV-specific antibodies, but do not generate the lung-resident memory T and B cells induced during IAV infections. In order to effectively generate lung-resident memory populations, it is believed a local antigen depot is needed as tissue-resident memory formation is enhanced by the presence of local antigen. Recently, polyanhydride nanoparticles have been demonstrated to slowly release their contents at the site of inoculation serving as an antigen depot. However, the ability of an intranasal vaccination with polyanhydride nanoparticles to induce IAV-specific lung-resident immune responses and provide protection against subsequent IAV infection has not been determined.
Here, I report on the intranasal administration of a biocompatible polyanhydride nanoparticle-based IAV vaccine (IAV-nanovax). IAV-nanovax is capable of providing protection against subsequent homologous and heterologous IAV infections in both inbred and outbred populations. My findings demonstrate that vaccination with IAV-nanovax promotes the induction of germinal center B cells within the lungs that are associated with both systemic IAV-specific IgG as well as local lung IAV-specific IgG and IgA antibodies. Furthermore, intranasal IAV-nanovax vaccination leads to a significant increase in IAV-specific CD4 and CD8 T cells within the lung vasculature as well as in the lung tissue. Most importantly, my studies demonstrate that IAV-nanovax induced lung-resident IAV-specific CD4 and CD8 T cells express canonical tissue-resident memory markers.
This dissertation further explores a novel regulation pathway previously identified by our laboratory where plasmacytoid dendritic cells (pDCs) eliminate IAV-specific CD8 T cells early during high-dose and high-pathogenic IAV infections in a FasL:Fas (pDCs:CD8 T cell) dependent manner. However, recent studies suggest that B cells are the predominate lymphocyte to express FasL in mice. Here, I demonstrate that FasLpos B cells greatly outnumber FasLpos pDC within the lung draining lymph nodes (dLNs) during IAV infections. Interestingly, my results demonstrate the presence of two subsets, CD11cpos and CD11cneg, of FasL-expressing B cells that differentially influence the IAV-specific CD8 T cell response during high-dose IAV infections. While CD11cneg B cells kill IAV-specific CD8 T cells, contributing to lethality during high-dose IAV infections, CD11cpos B cells may instead be protective.
In addition to the negative impacts of high-dose IAV infections, I also demonstrate that chronic ethanol (EtOH) consumption detrimentally impacts existing IAV-specific CD8 T cell memory responses. Here, my results reveal that chronic EtOH consumption causes a numerical loss in existing IAV-specific CD8 T cell memory responses. This numerical loss in existing IAV-specific CD8 T cell memory is associated with a reduction in cytotoxic activity within the lungs as well as an increase in morbidity and mortality during a secondary IAV challenge.
Together, the results presented herein demonstrate the ability of a novel polyanhydride nanovaccine to induce robust pulmonary IAV-specific T and B cell responses and further our understanding of factors that can negatively impact IAV-specific CD8 T cells as well as protection against IAV infection. Overall these findings highlight the importance of IAV-specific CD8 T cells, as well as CD4 T cells and B cells, in providing protection against IAV infections.