Submitted to: Veterinary Immunology and Immunopathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/3/2003
Publication Date: 9/3/2003
Citation: Babu, U., Scott, M., Myers, M.J., Okamura, M., Gaines, D., Yancy, H.F., Lillehoj, H.S., Heckert, R., Raybourne, R. 2003. Effects of live attenuated and killed salmonella vaccine on t-lymphocyte mediated immunity in laying hens. Veterinary Immunology and Immunopathology. 91:39-44. Interpretive Summary: Understanding basic immunology of host-pathogen interactions is important in the development of new control strategy against poultry pathogens. In this paper, scientists at the US Food and Drug administration, University of Maryland and ARS conducted a collaborative study to evaluate Salmonella vaccine. The results indicated that differential impact of live and killed Salmonella enteritidis (SE) vaccines on cell-mediated immunity (CMI) and that live vaccine may be more effective eliciting cell-mediated immunity. The information will be useful for poultry industry to improve the current Salmonella vaccine strategy.
Technical Abstract: Differential impact of live and killed Salmonella enteritidis (SE) vaccines on cell-mediated immunity (CMI) was investigated in 16- and 32-week-old White Leghorn hens. The hens were vaccinated with the 2 vaccines, and two weeks later, CMI was assessed using splenic lymphocyte proliferation, expression of IL-2 mRNA in concanavalin A (Con A) stimulated cells and flow cytometric analysis of cell subpopulation changes. Mitogen and SE flagella antigen-mediated proliferation of spleen cells from SE-vaccinated and unvaccinated chickens was determined by 3H-thymidine uptake. Con A-mediated and the SE flagella mediated proliferation were enhanced in the 16 week old and 32 week old chickens vaccinated with live vaccine, compared to the corresponding control chickens. Con A-mediated response was higher in the killed vaccine group of only the 16-week old birds compared to the corresponding control, whereas SE-flagella antigen-mediated proliferation was significantly higher in the killed vaccine group compared to the control group in 32-week old chickens. These functional changes were accompanied by significant changes in the splenic lymphocyte subpopulations, which included increased CD4+ lymphocytes in the live vaccine group compared to the control and the killed vaccine groups. Correspondingly, there was a reduction in the CD8+ lymphocyte in the live vaccine group, compared to the killed vaccine group. Changes in splenic gamma delta T cells were similar to those with the CD8 lymphocytes. A significant reduction in gamma delta T cells was observed in the 16-week old live vaccine treated chickens. No significant changes were observed in the alpha beta T lymphocytes. Relative expression of IL-2 mRNA in splenocytes from 16 week old birds were similar among the three treatment. Overall, live vaccine induced greater functional changes in T-lymphocyte mediated immune responses including mitogen- and antigen-induced proliferation of splenic lymphocytes and splenic CD4+ cell subpopulation compared to the killed vaccine. This enhanced CMI may prove beneficial in protecting hens against SE infection.