This thesis focuses on the design of novel strategies for the prevention and treatment of bacterial infections using polyanhydride nanoparticles as a vaccine delivery platform. The overall goal of this research is to design efficacious vaccines against the respiratory bacterial pathogens Streptococcus pneumoniae and Yersinia pestis using polyanhydride nanoparticles to elicit a protective immune response to the pneumococcal surface protein, PspA, and the Yersinia fusion protein, F1-V, respectively.

Polymers and copolymers based on the various anhydride chemistries (i.e., CPTEG, CPH, and SA) were investigated as nanovaccine formulations for antigen delivery. The mechanism of action of polyanhydride nanoparticles as vaccine adjuvants was investigated to better understand how these nanovaccines interact with immune cells at early time points (48 hours) and through the evaluation of the immune response at extended time points (~several months). Fluorescently-labeled antigen was delivered in 50:50 CPTEG:CPH nanoparticles and compared to soluble protein and protein adjuvanted with MPLA initially. Polyanhydride nanoparticle-encapsulated protein demonstrated enhanced persistence, cellular uptake and immune cell interactions at early time points compared to soluble protein, or MPLA-adjuvated protein. To investigate how prolonged antigen presence affected vaccine efficacy, several polyanhydride chemistries were tested and compared to MPLA at 14, 36, and 63 days after administration. The 50:50 CPTEG:CPH nanovaccine formulation elicited a robust humoral immune response, which significantly increased in titer and avidity at each of the time points investigated, suggesting the presence of long-lived plasma cells as a result of immunization with this polyanhydride nanovaccine.

Once a better understanding of the mechanism of action of polyanhydride nanoparticles was obtained, these findings were used to design efficacious nanovaccines against two respiratory pathogens, S. pneumoniae and Y. pestis. The encapsulation and release of PspA from polyanhydride nanoparticles was examined and it was demonstrated that PspA retaining its stability, antigenicity, and biological functionality upon release from both 50:50 CPTEG:CPH and 20:80 CPH:SA nanoparticles. Based on these results, the in vivo immune response to vaccination with PspA nanovaccine formulations was evaluated and a protective vaccine against lethal challenge with S. pneumoniae based on polyanhydride nanoparticles was designed. Additionally, the in vivo immune response to vaccination with F1-V nanovaccine formulations was examined to design a protective vaccine against lethal challenge with Y. pestis including novel small molecule adjuvants in nanovaccine formulations with the goal of inducing protective immunity against Y. pestis challenge at both early time points (~several weeks) as well as after extended periods of time (~several months). Overall, the work described in this thesis lays a platform for the use of polyanhydride nanoparticles for a combination vaccine against both influenza and pneumonia as well as for the delivery of antimicrobial drugs.