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Cellular responses and Mycobacterium bovis BCG growth inhibition by bovine lymphocytes
E Carpenter1, L Fray, E Gormley
1Department of Veterinary Pathology and Public Health, Massey University, Palmerston North, New Zealand.
Insights
Cattle vaccinated with Mycobacterium bovis bacille Calmette-Guerin (BCG) showed enhanced immune cell responses. However, lymphocyte presence, not just IFN-gamma, was key for inhibiting BCG growth, suggesting innate resistance.
Area of Science:
- Veterinary Immunology
- Mycobacterial Infections
- Bovine Health
Background:
- Mycobacterium bovis bacille Calmette-Guerin (BCG) vaccination is used to stimulate immune responses.
- Understanding cellular responses in cattle post-BCG vaccination is crucial for disease control.
- Investigating innate and adaptive immunity against M. bovis BCG in cattle.
Purpose of the Study:
- To measure and compare in vitro cellular responses in BCG-immunized cattle versus controls.
- To investigate the role of lymphocytes and IFN-gamma in controlling M. bovis BCG growth.
- To assess the contribution of innate resistance to M. bovis BCG in cattle.
Main Methods:
- Subcutaneous immunization of cattle with a low dose of M. bovis BCG vaccine.
- In vitro measurement of peripheral blood mononuclear cell (PBMC) proliferation and IFN-gamma production.
- Co-culture experiments with M. bovis BCG-infected autologous macrophages and lymphocytes.
- Assessment of M. bovis BCG growth inhibition and effect of recombinant IFN-gamma.
Main Results:
- BCG-immunized cattle PBMCs proliferated and produced IFN-gamma upon M. bovis BCG stimulation.
- PBMCs from immunized cattle induced IFN-gamma secretion when added to infected macrophages.
- M. bovis BCG growth was inhibited by lymphocytes from both immunized and control cattle, independent of IFN-gamma levels.
- Recombinant IFN-gamma did not affect intracellular M. bovis BCG growth.
Conclusions:
- BCG vaccination in cattle stimulates a T cell-mediated immune response.
- Cattle may possess significant innate resistance to M. bovis BCG, requiring lymphocyte presence for effective control.
- Further research is needed to elucidate the mechanisms of innate resistance and lymphocyte-mediated inhibition of M. bovis BCG.
Abstract:
Cellular responses of a group of cattle immunized subcutaneously with a low dose of Mycobacterium bovis bacille Calmette-Guerin vaccine (BCG) were measured in vitro and compared with nonimmunized control animals. PBMC taken from immunized animals proliferated and produced IFN-gamma in the presence of M. bovis BCG culture filtrate proteins. The addition of PBMC from immunized animals to M. bovis BCG-infected autologous macrophages also resulted in secretion of IFN-gamma. In contrast, the responses of PBMC from control animals were comparatively low over the period of study. In experiments to study the interaction of non-adherent lymphocytes with infected macrophages, M. bovis BCG growth was inhibited in cultures containing autologous PBMC from immunized and non-immunized control animals. The degree of inhibition was related to lymphocyte concentration but did not correlate with IFN-gamma production. Treatment of macrophages with recombinant IFN-gamma prior to, or postinfection did not alter the intracellular growth kinetics of mycobacteria. It appears, therefore, that although M. bovis BCG immunization of cattle stimulates the generation of a T cell-mediated immune response to M. bovis BCG, the cattle may already possess a high level of innate resistance to M. bovis BCG that requires the presence of lymphocytes.
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