Multivalent Oral Vaccine against Enterotoxigenic Escherichia coli and Enteric Fevers

Period of Performance: 08/18/2016 - 07/31/2017


Phase 1 SBIR

Recipient Firm

Protein Potential LLC
Rockville, MD 20850
Principal Investigator


Enteric diseases caused by enterotoxigenic E. coli (ETEC) strains, Shigella spp, and Salmonella Typhi, all ofwhich are NIAID Category B priority agents, collectively affect > 400 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 3 organisms would have enormous public health importance, and asubstantial commercial market among travelers and military personnel. Our long-term goal is to create astable, orally administered vaccine against ETEC, shigellosis and typhoid. To begin the process of achievingthis goal we have used the licensed Ty21a typhoid vaccine to express the O-antigen of Shigella sonnei toproduce a vaccine candidate called TyOraSs, which is under development. The major virulence determinantsof ETEC are the colonization factor antigens (CFAs or adhesins) and two enterotoxins, the heat-labile (LT) andheat-stable toxin (STa). An effective ETEC vaccine should induce antibodies that block bacterial attachmentand/or to neutralize the toxins. In animal models antibodies to CFA and toxin are synergistically protective. Ithas been shown by members of our team that a multi-epitope fusion antigen (MEFA) representing 7 separateCFA ETEC adhesins and two toxins can be fused as a single protein (designated here as MEFA+T) to inducecross-protective antibodies that blocks adherence of heterogeneous ETEC strains to human colon cancer cellsin vitro, and neutralizes two toxins in all ETEC strains. In this project we will stably express these multipleadhesins and the toxoid form of both toxins stably as a holotoxin structured CFA-toxoid fusion cassette antigenin Ty21a, and assess immunogenicity and protective efficacy of our Ty21a-ETEC vaccine using the sucklingpiglet and rabbit challenge models. Specifically we will, 1) Generate and characterize vaccine strain(s) ofgenetically optimized Ty21a expressing chromosomally integrated, ETEC multi-epitope fusion antigen (MEFA)+ toxoid LT-STa (designated Ty21a-ETEC MEFA-T) either intra-cellularly or in secreted form, 2) Demonstrateimmunogenicity against ETEC and S. Typhi, by mucosal immunization of mice, and 3) Establish protectiveefficacy against ETEC in the rabbit colonization model and suckling piglet lethal infection model. Our proposalis unique because of our expertise at construction of multivalent ETEC fusion antigens, experience with usingTy21a as a platform for expressing heterologous antigens, and capabilities with animal models tounambiguously assess vaccine protective efficacy. A stand-alone ETEC-typhoid vaccine would havesubstantial impact, however our aim to use success in this project as a foundation for the development of amultivalent vaccine against ETEC, typhoid, and shigellosis. In Phase II we will generate a single triplepathogen vaccine, TyOraSs-ETEC vaccine, or two bivalent vaccines; generate a master cell bank of thevaccine candidate strain(s) for manufacturing in compliance with cGMPs and as a foam-dried vaccineproduct(s); conduct required pre-clinical studies; design a clinical protocol; and prepare an IND.