Multivalent Oral Vaccine against Enterotoxigenic Escherichia coli and Enteric Fevers

Enteric diseases caused by enterotoxigenic E coli ETEC strains Shigella spp and Salmonella Typhi all of which are NIAID Category B priority agents collectively affect andgt million people annually worldwide Currently there is no vaccine against ETEC or shigellosis A typhoid vaccine exists An affordable effective oral multivalent vaccine against all organisms would have enormous public health importance and a substantial commercial market among travelers and military personnel Our long term goal is to create a stable orally administered vaccine against ETEC shigellosis and typhoid To begin the process of achieving this goal we have used the licensed Ty a typhoid vaccine to express the O antigen of Shigella sonnei to produce a vaccine candidate called TyOraSs which is under development The major virulence determinants of ETEC are the colonization factor antigens CFAs or adhesins and two enterotoxins the heat labile LT and heat stable toxin STa An effective ETEC vaccine should induce antibodies that block bacterial attachment and or to neutralize the toxins In animal models antibodies to CFA and toxin are synergistically protective It has been shown by members of our team that a multi epitope fusion antigen MEFA representing separate CFA ETEC adhesins and two toxins can be fused as a single protein designated here as MEFA T to induce cross protective antibodies that blocks adherence of heterogeneous ETEC strains to human colon cancer cells in vitro and neutralizes two toxins in all ETEC strains In this project we will stably express these multiple adhesins and the toxoid form of both toxins stably as a holotoxin structured CFA toxoid fusion cassette antigen in Ty a and assess immunogenicity and protective efficacy of our Ty a ETEC vaccine using the suckling piglet and rabbit challenge models Specifically we will Generate and characterize vaccine strain s of genetically optimized Ty a expressing chromosomally integrated ETEC multi epitope fusion antigen MEFA toxoid LT STa designated Ty a ETEC MEFA T either intra cellularly or in secreted form Demonstrate immunogenicity against ETEC and S Typhi by mucosal immunization of mice and Establish protective efficacy against ETEC in the rabbit colonization model and suckling piglet lethal infection model Our proposal is unique because of our expertise at construction of multivalent ETEC fusion antigens experience with using Ty a as a platform for expressing heterologous antigens and capabilities with animal models to unambiguously assess vaccine protective efficacy A stand alone ETEC typhoid vaccine would have substantial impact however our aim to use success in this project as a foundation for the development of a multivalent vaccine against ETEC typhoid and shigellosis In Phase II we will generate a single triple pathogen vaccine TyOraSs ETEC vaccine or two bivalent vaccines generate a master cell bank of the vaccine candidate strain s for manufacturing in compliance with cGMPs and as a foam dried vaccine product s conduct required pre clinical studies design a clinical protocol and prepare an IND Our goal is to develop a multivalent oral vaccine that will simultaneously protect against multiple disease agents is easy to administer needle free is a safe oral vaccine vector platform for stable expression and delivery of multiple foreign antigens that generates long term efficacy following a rapid immunization regimen and which can be distributed without the need for refrigeration To address these challenges we exploit the extensive safety record of the existing live oral attenuated Salmonella Typhi Ty a typhoid vaccine by utilizing it as our lead candidate vector to develop a combination oral vaccine that will simultaneously protect against both typhoid fever with cross protection against some paratyphoid fevers and enteric fevers We hypothesize that this vaccine can be formulated to be safe stable highly immunogenic and can be easily administered orally