Immunogenicity and Protection against Mycobacterium caprae Challenge in Goats Vaccinated with BCG and Revaccinated after One Year

Abstract

Vaccination has been proposed as a supplementary tool for the control of tuberculosis in livestock. The long-term immunogenicity elicited by bacillus Calmette–Guerin (BCG) and the efficacy of revaccination were investigated in thirty goat kids distributed into three groups: unvaccinated controls, BCG (vaccinated at week 0) and BCG-BCG (vaccinated at weeks 0 and 56). Sixty-four weeks after the first vaccination, all animals were challenged with Mycobacterium caprae and examined post-mortem (pathology and bacterial load) at week 73. Antigen-specific interferon-gamma (IFN-γ) release was measured throughout the experiment. At week 59, peripheral blood mononuclear cells were stained for CD4, CD45RO and IFN-γ to determine the presence of antigen-specific cells secreting IFN-γ. The BCG-BCG group showed reductions in rectal temperatures, M. caprae DNA load in pulmonary lymph nodes (LN), the volume of lesions in pulmonary LN, mineralization in lungs, and higher weight gains compared to unvaccinated controls. IFN-γ responses were undetectable from 32 weeks after primary vaccination until revaccination, when the BCG-BCG group showed detectable IFN-γ production and a greater percentage of antigen-specific CD4+CD45RO+IFNγ+ and CD4−CD45RO+IFNγ+ cells compared to the BCG and control groups, which may be an indicator of the mechanisms of protection. Thus, re-vaccination of goats with BCG appears to prolong protection against infection with M. caprae.

A proof-of-concept study to investigate the efficacy of heat-inactivated autovaccines in Mycobacterium caprae experimentally challenged goats

“…In long-term trials, a wane of BCG-induced ex vivo IFN-γ response has been observed in goats from 24 weeks p.v. onwards 9 and, approximately one year after vaccination, the proportion of PPD-B-specific IFN-γ-producing T-memory cells (CD45RO+) was similar to that of unvaccinated goats, although it increased significantly when measured three weeks after revaccination 32 .…”

“…Comparisons of clinical parameters, particularly the body weight increase and rectal temperature kinetics, were very consistent with post-mortem results. The body weight change and the rectal temperature at 3 to 5 weeks post-challenge are useful indicators of vaccination outcome as previously demonstrated in experimental trials conducted in goats and sheep 18,31,32 , and should be considered as valuable parameters in experiments to assess the efficacy of vaccines and treatments against TB.…”

“…At week 0 (before challenge), peripheral blood mononuclear cells (PBMC) were isolated from blood samples and stimulated for 16 h (2 × 10 6 cells/well) with PPD-B (10 μg/ml) as previously described 32 . At week 0, 2 × 10 5 cells were stained with monoclonal antibodies (mAb) that recognise bovine IFN-γ (antibovine CC302 IgG1-Alexa Fluor® 647) from Bio-Rad Laboratories Inc. (Hercules, CA, USA), CD4 (anti-sheep 44.38 IgG2A-FITC), CD45RO (anti-bovine IL-A116 IgG3-RPE) and CD62L (anti-bovine CC32 IgG1-APC-Cy7) as previously described 32 . Stained cells were re-suspended in 200 µl PBS with 1% paraformaldehyde and Antibody detection assays.…”

Experimental Mycobacterium microti Infection in Bank Voles (Myodes glareolus)

“…Amplifi-cation was performed in a 7500 fast real-time PCR system (Applied Biosystems, Walham, MA, USA). M. microti CFU genomic equivalents were calculated by the extrapolation of Ct value obtained for each DNA sample according to previously described [24]. Once titrated, the remaining subcultured suspension was diluted in sterile PBS at a final suspension of 10 7 CFU/mL.…”