Oil-in-Water Nanoemulsions as Mucosal Vaccine Adjuvants: Characterization, Mechanism, Formulation, and Development of a Nanoemulsion-Based Burkholderia Cenocepacia Vaccine.

Abstract

Surface active oil-in-water nanoscale emulsions have been developed as mucosal vaccine adjuvants capable of producing robust systemic, mucosal, and cellular immune responses against diverse microbial and recombinant antigenic proteins. This dissertation examines the development of nanoemulsion (NE) as a new generation nasopharyngeal adjuvant. Part of the thesis is organized to address the characterization of NE-induced immune response and includes the pre-clinical studies of a novel NE-based recombinant hepatitis B vaccine (HBsAg-NE). Our results suggest that nasal immunization with HBsAg-NE may be a safe and effective hepatitis B vaccine. The adjuvant induces specific IgG, mucosal IgA, and a Th1-biased cellular immunity. Immunogenicity is comparable to the standard alum-based vaccine. HBsAg-NE is stable for months at elevated temperatures because of the physical association of NE with the antigen and its stability was enhanced with buffered salt diluents. We also report that NE-based vaccines do not require specially engineered delivery devices. The prolonged stability and ease of delivery are direct advantages for use of NE-based vaccines in developing populations. We also evaluate the mechanism of NE adjuvant activity. NE promotes antigen internalization in nasal epithelium and loading into mucosal dendrtici cells (DC). Trafficking of the antigen to the submandibular lymph nodes and thymus occurs within 24 hours of intranasal vaccination. Administration of NE was not associated with the typical induction of local inflammation or histopathological changes. Microarray analysis shows the upregulation of only 1.6% of genes responsible for the production of acute phase inflammatory cytokines including IL6. Hallmark inflammatory cytokines such as IL4, and INF-γ were not measured in nasal secretions. The role of IL6 in NE adjuvant activity was examined by evaluating immunogenicity in IL6 mutant mice. The final component of the dissertation addresses the development of a NE-based Burkholderia cenocepacia outer membrane protein (OMP) vaccine. We demonstrate that NE is as a strong mucosal adjuvant for OMP and OMP-NE protects against experimental lung infections in mice. Overall, these findings confirm that NE is an excellent mucosal stimulant and support the further development of nanoemulsions as nasopharyngeal adjuvants. We conclude that nanoemulsion exhibits all the major desired characteristics of an adjuvant.