Immunological responses to BCG vaccination in Mycobacterium bovis-challenged cattle
Abstract number: P1324
Witchell J., Vordermeier M., Wangoo A., Goyal M.
Objectives: BCG vaccination studies in cattle have shown extreme variability in protection against Mycobacterium bovis infection. A critical first step in the development of an improved vaccination is the understanding of the host immune response to infection and vaccination.
Methods: This study focused on four experimental cattle groups BCG Pasteur vaccinated M. bovis challenged, BCG vaccinated non challenged, non vaccinated M. bovis challenged and non vaccinated non challenged. mRNA expression levels of IFN gamma, TNF alpha, IL10 and IL4 were measured within thoracic lymph nodes of each animal using quantitative real time PCR. Protein levels of IFN gamma and TNF alpha were measured within each lymph node using immunohistochemistry.
Results: Challenge with M. bovis significantly increased IFN gamma mRNA levels (94%), reduced IL10 mRNA levels (56%) and suppressed IL4 mRNA expression completely. There was a significant increase in IFN gamma protein levels (on a score scale of 14, challenged animals averaged at 2.75 compared to non-challenged at 1.3) however TNF alpha mRNA and protein levels were not significantly affected by M. bovis challenge. BCG vaccination prior to challenge reduced the level of IFN gamma mRNA (81%) and IFN gamma protein (averaged score of 1.5) as compared to the non vaccinated challenged cattle. BCG vaccination without challenge appeared to have no effect on the cytokine and protein levels however IL4 mRNA was detectable. There was a strong positive correlation between IFN gamma mRNA and IFN gamma protein levels but no correlation was observed between TNF alpha mRNA and TNF alpha protein.
Conclusion:M. bovis infection activates a strong cell mediated immune response signified by the dramatic increase in IFN gamma mRNA expression. Subsequently IFN gamma protein levels increased leading to a strong T helper (TH) class 1 profile with the related reduction of IL10 and IL4 mRNA expression.
Cattle vaccinated with BCG before challenge showed an increase in IFN gamma mRNA expression but to a lesser degree as compared to non vaccinated animals due to the primed immune response. The IL10 mRNA levels were not significantly reduced in vaccinated animals and so dampened the pro-inflammatory response producing a lower level of pathology within the vaccinated animals. Finally, it appears that IL10 mRNA may experience post transcriptional regulation due to the absence of a correlation between mRNA and protein levels.
|Session name:||18th European Congress of Clinical Microbiology and Infectious Diseases|
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