Evaluation of Glycosylated FlpA and SodB as Subunit Vaccines Against Colonisation in Chickens.

is the leading bacterial cause of human gastroenteritis worldwide and the handling or consumption of contaminated poultry meat is the key source of infection. proteins FlpA and SodB and glycoconjugates containing the -glycan have been separately reported to be partially protective vaccines in chickens. In this study, two novel glycoproteins generated by protein glycan coupling technology-G-FlpA and G-SodB (with two and three -glycosylation sites, respectively)-were evaluated for efficacy against intestinal colonisation of chickens by strain M1 relative to their unglycosylated variants. Two independent trials of the same design were performed with either a high challenge dose of 10 colony-forming units (CFU) or a minimum challenge dose of 10 CFU of M1. While antigen-specific serum IgY was detected in both trials, no reduction in caecal colonisation by M1 was observed and glycosylation of vaccine antigens had no effect on the outcome. Our data highlight inconsistencies in the outcome of vaccination trials that may reflect antigen-, challenge strain-, vaccine administration-, adjuvant- and chicken line-specific differences from previously published studies. Refinement of glycoconjugate vaccines by increasing glycosylation levels or using highly immunogenic protein carriers could improve their efficacy.