Submitted to: Comparative Immunology Microbiology and Infectious Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 15, 2003
Publication Date: N/A
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 collaborated in a study designed to investigate the underlying immune mechanisms of host innate immunity against Salmonella infection in poultry. The results showed that younger chickens mounted a more robust antigen-specific immune response to the Salmonella vaccination compared with older birds and vaccination induced not only T-cell-mediated responses but also host innate and pro-inflammatory responses. This information will provide important new knowledge to poultry industry scientists and enhance our ability to better control salmonellosis.
Two experimental approaches were used to investigate the immunological responses of chickens to a commercial killed Salmonella enteritidis (SE) vaccine. In the first, the effects of host age on antigen-specific proliferative responses and cytokine production were examined. Compared with non-vaccinated controls, 4-wk-old vaccinated chickens showed higher proliferation to SE LPS and flagella. In contrast, the proliferative responses to these antigens in 8-mo-old vaccinates was either not different compared to non-vaccinated controls. Increased production of interferon-gamma (IFN-gamma) and interleukin-2 (IL-2) by antigen-stimulated splenocytes following vaccination were, in general, more often observed in 4-wk-old compared with 8-mo-old chickens, whereas serum levels of these cytokines were consistently higher in the vaccinated birds compared with controls regardless of age. The second set of experiment were designed to determine the effects of SE vaccination on mitogen- or antigen-induced splenocyte proliferation and serum nitric oxide (NO) and cytokine levels. Splenocytes from vaccinated chickens stimulated with SE flagella showed significantly increased numbers of TCR + cells at 7 days post-vaccination compared with non-vaccinated birds. In contrast, no differences were noted with CD4+, CD8+, or TCR + cells at any time points examined. Higher levels of NO production were observed following stimulation with SE flagella at 4, 7, 11, and 14 days after SE vaccination while serum levels of IFN-gamma, IL-1, IL-6, and IL-8 were elevated only at day 7 post-vaccination. In conclusion, younger chickens mounted a more robust antigen-specific immune response to the SE vaccine compared with older birds and vaccination induced not only T-cell-mediated responses but also host innate and pro-inflammatory responses.