A novel serotype independent protein nanoemulsion, SAVE, to prevent shigellosis

Project Summary Shigella flexneri is the primary cause of dysentery in children and the elderly in low- and middle-income countries (LMIC) and it poses a serious health threat to individuals traveling to LMICs. While significant resources have been dedicated to developing effective enteric vaccines, a viable vaccine against shigellosis remains to be realized. With the rapid emergence of antibiotic-resistant Shigella spp, developing new vaccines against multi- drug resistant (MDR) strains is essential. Unfortunately, many Shigella spp vaccines in the pipeline target non- conserved surface components such as lipopolysaccharide. These targets are protective against a specific bacterial species or subset of serotypes, but they have limited use in a diverse Shigella world with many unique serotypes. Moreover, since these vaccines target polysaccharides, they have a short-lived duration. Development of broadly a protective vaccine targeting highly conserved antigens is urgently needed. The goal of the proposed research is to address this major public health gap by testing our novel vaccine platform (Self- Adjuvanting Vaccine Enabled formulation, SAVE) against all Shigella serotypes, thereby potentially revolutionizing the prevention and management of life-threatening dysentery. SAVE targets all Shigella spp by combining multiple components packaged within an innovative formulation, including 1) two genetically fused surface exposed proteins that are >98% conserved across all Shigella spp; 2) the potent mucosal adjuvant LTA1; and 3) a nano-emulsion formulation designed to stimulate IL-17 secretion and enhance protective serum bactericidal activity. With the development of the NLRC4-/- (N-/-) model systems, we can now ask questions about the mechanisms conferring protection in a model more representative of human shigellosis and we can prepare for FDA approvals using an FDA-approved animal model. In this investigation, we hypothesize that SAVE elicits a coordinated activation of innate and adaptive immunity characterized by a balanced Th1/Th17-driven response at mucosal sites to protect adult and infant mice. Moreover, the SAVE formulation can be delivered safely by the intranasal route to promote protective responses at multiple mucosal sites (e.g. lung, GI tract, etc.) which allows use of the FDA-accepted guinea pig keratoconjunctivitis model to prepare for future FDA approvals. Toward this end, we propose to pursue the following specific aims: 1) Determine how SAVE modulates innate and adaptive responses leading to activation of Th1/17 and other effector cells using N-/- mice. 2) Determine protective immunity in infant mice following SAVE immunization mediated by maternally transferred antibodies and direct vaccination. 3) Determine the safety profile of SAVE and its protective efficacy in the gold-standard FDA- approved guinea pig keratoconjunctivitis model.