A Correlative Evaluation of the Diagnostic Importance of Adaptive Cell-Mediated Tests in Bovine Tuberculosis

  • Marina SPINU 1University of Agricultural Sciences and Veterinary Medicine, Cluj-Napoca, Romania
Keywords: tuberculosis, bovine, diagnosis, cellular immunity

Abstract

Knowledge of the immune responses which develop in cattle following infection with Mycobacterium bovis is essential both to the understanding of disease pathogenesis and to the logical development of immune-dependent tools, such as diagnostic tests and vaccines, which can be used to combat the disease (Pollock et al., 2001). The early, preclinical stages of bovine TB can be detected in live animals by the use of tests of cellular immunity (the skin, cinterferon and lymphocyte transformation tests)(de la Rua-Domenech et al., 2006). In tuberculosis, both macrophages and lymphocytes are sensitized to tuberculin, which in low concentrations is capable of inducing their activation both in vivo and in vitro. This study aimed to evaluate the diagnostic relevance of monitoring adaptive cell-mediated responses such as skin test (IDR), gamma interferon (IFN) synthesis (Bovigam TM, ELISA test), in vitro blast transformation test (RPMI 1640 medium, 72 h incubation) and leukocyte migration inhibition tests (RPMI 1640 medium, 18 h incubation) to avian and bovine tuberculins. The skin test was performed on 79 Romanian spotted adult bovine, aged 5 to 10 years. Blood samples on heparin (50 IU/ml) were taken from the 34 IDR positive animals (1.14±0.83 mm and 7.28±1.58 mm responses to avian and bovine tuberculin, respectively, accompanied by local edema) and subjected to the other cell mediated immunity tests. Correlation coefficients between the tests were calculated. No significant correlation between the IDR and IFN for the bovine tuberculin, yet a strong positive correlation (p<0.001) for the avian tuberculin were obtained, suggesting the independent variation of the two indicators. Both IDR - leukocyte migration (r = 0.513, p< 0.01) and IDR-blast transformation (r = 0.592, p< 0.001) correlations were positive and statistically significant, when bovine tuberculin was used. We concluded that the latter two tests could be used when specific sensitization to M. tuberculosis bovine subtype is to be detected in IDR positive animals.