Correlation of Cytokine Gene Expression with Pathology in White-Tailed Deer ( Odocoileus virginianus ) Infected with Mycobacterium bovis

Mycobacterium bovis -infected white-tailed deer (WTD) in northeast Michigan are a reservoir of mycobacteria that pose a threat to both domestic animals and humans. Relatively little work has been done to characterize the immune response of WTD to M. bovis infection; however, an understanding of the immune response to infection and pathogenesis may be critical to the development of an effective vaccine. Immunological responses to infection were characterized by monitoring cytokine gene expression in M. bovis -infected and uninfected deer. Peripheral blood leukocytes (PBL) from infected WTD expressed more gamma interferon (IFN-γ), interleukin-12p40 (IL-12p40), granulocyte-monocyte colony-stimulating factor, and IL-4 mRNA than did PBL from uninfected deer; however, differences were not detected in expression of IL-10 and transforming growth factor-β mRNA. Infected animals could be divided into two groups based on pathology. Lesions were confined primarily to the lymph nodes of the head in animals with less severe pathology. Animals with more severe pathology had lesions in the lung and associated lymph nodes as well as the lymph nodes of the head. More robust IFN-γ mRNA expression correlated with pathology early in infection. These findings indicate that IFN-γ expression likely plays a role in both protection and pathogenesis.