Outer Membrane Remodeling of Attenuated Salmonella to Create A Mucosal Vaccine Against Acinetobacter Baumannii

ABSTRACT While rapid identification of pathogens, novel therapeutic interventions, and passive immunizationhave critical roles in disease control, none can substitute for pre-existing protective immunity. Mucosallydelivered bacterial live vector vaccines represent a practical and effective strategy for immunization. In livevector vaccines, genes that encode protective antigens of unrelated pathogens are expressed in anattenuated vaccine strain and delivered mucosally to generate relevant local and systemic immuneresponses. The broad hypothesis of this research plan is that by appropriate manipulation of novelSalmonella enterica serovar Typhi live vector platform technologies, we can construct a mucosallyadministered bivalent vaccine against potentially lethal infections caused by Acinetobacter baumannii. Thisunique research plan is designed to remodel the outer membrane of an attenuated S. Typhi-based livevector vaccine into an antigen presentation platform in which protective outer membrane antigens from A.baumannii are mucosally delivered to immune inductive sites via a novel inducible outer membrane vesicledelivery system. Mucosal delivery of recombinant outer membrane vesicles (rOMVs) via live vectorvaccines offers significant advantages over conventional acellular OMV-based vaccination strategiesincluding: 1] sustained in vivo delivery to mucosal inductive sites, and 2] delivery of rOMVs enriched inproperly folded protective antigens. To implement this unique vaccination strategy, we will engineersynthetic genes encoding two protective outer membrane proteins, AbOmpA and AbOmpW, expressedfrom cassettes stably integrated into the chromosome of our live vector vaccine. To enhance delivery ofthese protective antigens to immune effector cells, thereby improving the protective efficacy of this mucosalvaccine, we will enhance delivery of rOMVs carrying AbOmpA and AbOmpW through inducible over-expression of the hypervesiculating proteins ClyA or PagL. The immunogenicity of these optimized livevector strains will be determined using a murine intranasal model of immunogenicity; efficacy will beevaluated after challenging immunized mice with a hypervirulent A. baumannii clinical isolate, proven to belethal to naïve mice within 48 hours post-challenge by either the systemic or intranasal routes of challenge.Success with this proposal will produce a bivalent mucosal live vector vaccine, effective against potentiallylethal systemic and pulmonary infections with A. baumannii, which could prove highly valuable in bothcivilian and military settings.