Evaluation of rBapB, rOmpC and rOmpA proteins of Salmonella Typhimurium as vaccine candidates for control of zoonotic salmonellosis in poultry

Abstract

Background: Non-typhoidal salmonellosis is an important zoonotic infection worldwide, and a leading cause of food poisoning in humans caused by mainly Salmonella Typhimurium and Salmonella Enteritidis from poultry sources is the leading cause of zoonotic infections. Vaccination of birds is considered to be effective tool in controlling zoonotic salmonellosis. There is a continuous search to find suitable vaccine candidates for development of reliable vaccine. The aim of the present study was to evaluate the use of cocktail of recombinant biofim associated protein B (BapB), Outer membrane protein A (OmpA) and outer membrane C (OmpC) for immunization of birds to elucidate its protection against virulent Salmonella Typhimurium. Methods and materials: The three recombinant proteins were prepared after cloning and expressing the respective genes and were characterized by SDS-PAGE and Western blot analyses. The protein preparations were tested as vaccine candidate in layer birds by comparing the immune response, protection and organ clearance against commercial vaccine and control. One hundred birds were divided into 5 groups (rBapB + adjuvant, rBapB + rOmpA + adjuvant rOmpC, rOmpA + rOmpC + adjuvant, commercial vaccine and PBS control) and immunized with 150 μg dose i/m. The kinetics of antibody production against the recombinant proteins were monitored by ELISA and the CMI response was measured by the flow cytometry analysis of the CD4+ or CD8+ of PBM cells. Results: The cocktail of recombinant proteins i.e., BapB, OmpC, OmpA proved to be good immunogens, which induced a significantly higher humoral immune response than control. The protective index (based on faecal shedding of organism) of cocktail of recombinant proteins ranged between 50 and 85.7% as observed for 3 weeks after challenge. The rBapB + rOmpA + rOmpC cocktail group yielded higher humoral and cell-mediated immune response against both S. Typhimurium and S. Enteritidis in comparision to rOmpA + rOmpC cocktail group. Therefore, the protein preparations conferred satisfactory protection against challenge infections with virulent strains of S. Typhimurium as evidenced by limited faecal shedding and minimal detection of Salmonella from edible tissues. Conclusion: The study indicate that the cocktail of expressed rBapB, rOmpA and rOmpC in prokaryotic expression system afforded a satisfactory protective response and organ clearance against virulent S. Typhimurium and S. Enteritidis challenge in birds.