Design and Immunogenicity of a Nanoparticle Combination Vaccine for Salmonella in Poultry

Salmonella enterica serovars (Salmonella) are common causes of bacterial gastroenteritis (salmonellosis) often associated with the consumption of poultry products. The control of Salmonella in broiler chickens is difficult because colonized birds may carry this pathogen undetected into the slaughterhouse and cause meat contamination. Poultry vaccines can mitigate colonization, and one promising production method is via plants. Iron is an essential nutrient for Salmonella; therefore, our goal was to exploit iron uptake systems as vaccine targets that could starve this pathogen of iron and thus prevent it from colonizing chickens. One challenge with this approach is that Salmonella possesses several iron acquisition proteins that are redundant in function. Therefore, we created nanoparticle-based plant-produced vaccine candidates against four different Salmonella iron acquisition proteins to create a multivalent vaccine that may be more effective than targeting a single protein. Extracellular antigenic peptides from each of these proteins were fused in tandem to the N-terminus of the self-assembling Brucella spp. lumazine synthase. These fusion constructs were then expressed in Nicotiana benthamiana plants. The resulting recombinant proteins were extracted, purified and characterized. The vaccine candidates administered individually or in combination elicited specific antibodies in mice and bound to the surface of Salmonella, indicating their potential in preventing Salmonella colonization in poultry.