Pullorum disease, caused by the Salmonella enterica serovar Gallinarum biovar Pullorum, is a highly contagious disease in the poultry industry, leading to significant economic losses in many developing countries. Due to the emergence of multidrug-resistant (MDR) strains, immediate attention is required to prevent their endemics and global spreading. To mitigate the prevalence of MDR Salmonella Pullorum
infections in poultry farms, it is urgent to develop effective
vaccines. Reverse vaccinology (RV) is a promising approach using expressed genomic sequences to find new
vaccine targets. The present study used the RV approach to identify new
antigen candidates against Pullorum disease. Initial epidemiological investigation and virulent assays were conducted to select strain R51 for presentative and general importance. An additional complete genome sequence (4.7 Mb) for R51 was resolved using the Pacbio RS II platform. The
proteome of Salmonella Pullorum was analyzed to predict outer membrane and extracellular
proteins, and was further selected for evaluating transmembrane domains, protein prevalence, antigenicity, and solubility. Twenty-two high-scored
proteins were identified among 4713
proteins, with 18
recombinant proteins successfully expressed and purified. The chick embryo model was used to assess protection efficacy, in which
vaccine candidates were injected into 18-day-old chick embryos for in vivo immunogenicity and protective effects. The results showed that the PstS, SinH, LpfB, and SthB
vaccine candidates were able to elicit a significant immune response. Particularly, PstS confers a significant protective effect, with a 75% survival rate compared to 31.25% for the PBS control group, confirming that identified
antigens can be promising targets against Salmonella Pullorum
infection. Thus, we offer RV to discover novel effective
antigens in an important veterinary infectious agent with high priority.