Development and Production of Salmonella Multi-Serotypic and Multi-Subunit Vaccines for Hens

Salmonella is the leading pathogen for bacterial food-borne illness. It is estimated one million cases annually, leading to more than 20,000 hospitalizations and 350 deaths. Outbreaks are often associated with consumption and handling of poultry products. Despite the efforts to control this pathogen by poultry producers, processors and government, the number of human salmonellosis has not drastically declined. Many strategies for reduction of Salmonella contamination in poultry have been investigated. Vaccination with Salmonella serovar Enteritidis (SE) has been proved to effectively control SE in commercial chickens. However, these current vaccines for Salmonella target at SE, but not for non-SE. Because live attenuated vaccines increase selection of pathogen virulence, the next generation of poultry vaccines will be multi-serotypic and multi-subunit vaccines that can target various Salmonella serovars, and subsequently reduce Salmonella contamination in poultry products. The advantage of the subunit vaccines is that the components are well-defined and are specific to virulence factors. It is well known that both flagella and lipopolysaccharide (LPS) are important virulence factors in Salmonella pathogenesis and are protective antigens. Our hypothesis is that expression of various Salmonella flagellar proteins has the potential for discovery of antigens that can have cross-protection to reduce the Salmonella contamination in commercial eggs. The specific objectives of this proposal are to: (1) Clone, express and purify five flagellar proteins (FliC, FliD, FlgE, FlgK and FlgL) from non-SE serovars commonly found in poultry. The reasons for targeting these five genes are that the gene products of these five genes are located outside the microorganism so they are potential targets for host immune response. (2) To isolate O-antigens from non-SE serovars. Bacterial LPS, extended from the outer membrane, is also regarded as an important virulence factor and is a B cell antigen. The O-antigen from LPS contributes serotypic diversity of Salmonella, but is not toxic as the lipid A component. (3) To conjugate the O-antigens to purified flagellar proteins. The purpose of this objective is to increase the antigenic diversity and enhance success rate in vaccination against various serovars. (4) To assay the immune response in hens for these Salmonella antigens. The purpose of this assay is to identify which flagellar proteins and/or conjugates is immunogenic for vaccination trials. (5) To examine populations of the bacterium in the hen gastrointestinal and oviduct systems following vaccination. This study is to determine whether the vaccines will affect the microbiota in gastrointestinal and oviduct systems of vaccinated hens.