| The exponential growth of the global human population in the last five hundred years has paved the way for the emergence of a multitude of new infectious diseases. As humans, livestock, and wild animals live in increasingly closer proximity to each other the potential threat for the emergence of new pathogens is heightened by interspecies interactions and contact. In addition to the emergence of new pathogens, existing pathogens are developing resistance to once powerful antibiotics and antiviral drugs at a faster rate than we can discover new compounds. The clear alternative has been in vaccination programs designed to generate herd immunity in endemic areas. While many of the antigens and pathogen associated molecular patterns (PAMPs) that are implicated in the adaptive and innate immune responses to pathogens have been identified, we are still struggling to find a way to deliver them in a way that is safe, efficacious, stably reproducible, and cost-effective.; This dissertation is focused on the development of bacterial minicells derived from a non-invasive commensal E. coli strain to deliver DNA and protein antigens with the intent of generating protective immune responses. In preliminary studies it is demonstrated that minicells can be engineered to target and deliver DNA to normally non-phagocytic eukaryotic cells in culture by stimulating receptor-mediated endocytosis. The next series of experiments demonstrates that minicells delivering both protein antigen and the corresponding eukaryotic expression plasmid could elicit robust antibody responses to a general antigen even in a single intramuscular administration. Also demonstrated in those studies was that minicells could be delivered orally or nasally to generate both systemic IgG and mucosal IgA responses.; Building on these preliminary experiments, minicells were then demonstrated to elicit cellular responses capable of protecting mice from a lethal intracranial challenge with LCMV after mucosal immunization. While many questions remain unanswered, this dissertation is the first reported evidence to suggest that minicells could be further developed as a broad spectrum mucosal vaccine delivery vehicle. |
