Submitted to: Veterinary Immunology and Immunopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/27/2000
Publication Date: N/A
Interpretive Summary: Bovine tuberculosis due to Mycobacterium bovis is nearly eradicated from the United States. Recently, M. bovis was isolated from wild white-tailed deer in northeastern Michigan. Mycobacterium bovis was subsequently detected in cattle in this same area. Wildlife reservoirs have hindered eradication efforts in other developed countries. White-tailed deer, therefore, represent a serious threat to tuberculosis eradication efforts within the United States. In the present study, we evaluated the immune response of white-tailed deer to M. bovis infection. It was determined that a distinct subset of immune cells from M. bovis-infected white-tailed deer respond during a progressive M. bovis infection. These findings will aide in the development of improved methods to diagnose M. bovis infection of white-tailed deer; thereby, enhancing bovine tuberculosis eradication efforts within the United States.
Technical Abstract: White-tailed deer are significant wildlife reservoirs of Mycobacterium bovis for cattle, predators, and, potentially, humans. Infection of cattle with M. bovis stimulates an antigen-specific T cell response, with both CD4+ and CD8+ cells implicated in protective immunity. Few studies, however, have examined lymphocyte subset responses to experimental M. bovis infection of white-tailed deer. In this study, a flow cytometric proliferation assay was used to determine the relative contribution of individual peripheral blood mononuclear cell subsets of M. bovis-infected white-tailed deer in the recall response to M. bovis antigen. Naive deer were challenged with M. bovis by cohabitation with infected deer. These M. bovis-challenged deer developed significant in vivo (delayed type hypersensitivity) and in vitro (proliferative) responses to M. bovis purified protein derivative (PPD). At necropsy, typical tuberculous lesions containing M. bovis were detected within lungs and lung-associated lymph nodes of infected deer. The predominant subset of lymphocytes that proliferated in response to in vitro stimulation with PPD was the CD4+ subset. Minimal proliferative responses were detected from CD8+, gamma/delta TCR+, and B cells. Addition of monoclonal antibodies specific for MHC II antigens, but not MHC I or CD1 antigens, abrogated the proliferative response. Together, these findings indicate that while CD4+ cells from infected deer proliferate in the recall response to M. bovis antigens, this response is not sufficient to clear M. bovis and immunologic intervention may require stimulation of alternate subsets of lymphocytes.