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Vaccine For The Prevention of Necrotic Enteritis in Poultry


Our major goal is to develop a vaccine that can be applied in water or by coarse spray, to protect broiler birds against necrotic enteritis. The approach involves the use of novel, attenuated Salmonella Typhimurium strains for antigen delivery, thereby providing immunity against Salmonella as well.WWe will be using a novel S. Typhimurium antigen delivery strain, c11802 ((del)PmurA25::TT araC PBAD murA (del)asdA27::TT araC PBAD c2 (del)(wza-wcaM)-8 (del)pmi-2426 (del)relA198::araC PBAD lacI TT (del)recF126). Relevant phenotypes include lysis in the absence of arabinose and diaminopimelic acid (DAP) and mannose-dependent O-antigen synthesis. In the vaccine (c11802 + C. perfringens antigens), the DAP requirement is complemented by addition of an AsdA+ antigen-encoding plasmid, but the arabinose requirement is not complemented, leading to lysis of the vaccine in vivo.ObjectivesIdentify and clone new C. perfringens antigens, in addition to the ones we have already cloned. Leading
candidates include fructose 1,6-biphosphate aldolase (FBA), a hypothetical protein, HP, with proven efficacy, fimbriae and/or adhesins, and peptides derived from the large clostridial toxin, TpeL.Peptide mapping of TpeL to identify immunogenic regions suitable for cloning and expression in the vaccine strain.Construct live attenuated S. Typhimurium strains that produce at least three protective proteins from Clostridium perfringens. If this is not possible, we will construct multiple vaccine strains producing one or two antigens that can be co-administered.Characterize vaccine strains in vitro. This will include demonstrating arabinose-regulated antigen production, mannose-regulated O-antigen synthesis and plasmid stability over 50 generations of bacterial growth. Vaccine lysis in the absence of arabinose will also be tested.Evaluate the immunogenicity of vaccine constructs in broiler birds. This will include evaluations of serum, mucosal and cellular immunity elicited by the vaccines
against relevant Clostridial and Salmonella antigens.Evaluation of protection against virulent C. perfringens challenge after vaccination. Primary outputs measured will be survival (though most birds survive challenge) and intestinal lesions.Evaluation of protection against colonization by wild-type S. Typhimurium. This assay will be done with the vaccine strains providing the best protection against C. perfringens challenge.

Roland, K.
Arizona State University
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