Comparison of immune peripheral blood cells in tuberculin reactor cattle that are seropositive or seronegative for Mycobacterium bovis antigens.

Bovine tuberculosis (bTB) is a major economic problem in animal husbandry and is a public health risk in nonindustrialized countries. It is generally accepted that protection against TB is generated through cell-mediated immunity. Previous investigations have shown that WC1(+) γδ, CD4(+) and CD8(+) T-cell subpopulations are important in the immune response to bTB. It is known that changes in the immune balance from a dominant T helper 1 (Th1)-type response toward a more prominent Th2 response may be observed during disease progression. In this study, we aimed to investigate immune peripheral blood cells in tuberculin reactor cattle that are seropositive or seronegative for Mycobacterium bovis antigens, using flow cytometry and hematological analysis. The evaluation of the T cell subpopulations revealed a decrease in CD8(+) T cells of the seropositive and seronegative animals compared with the control animals (p=0.0001). Moreover, the seropositive group exhibited a lower percentage of CD8(+) T cells than the seronegative group. The percentage of B cells was significantly increased in the seropositive group compared with the seronegative group and the control group (p=0.0009). No difference was observed in the percentage of WC1(+) γδ and CD4(+) T cells among the groups. Furthermore, following 24h of peripheral blood culture with bovine purified protein derivative (PPD), both apparently infected groups showed an increase in the levels of cellular activation compared with the control group (p<0.0001). The seropositive group displayed a higher level of cellular activation than the seronegative group. In both apparently infected groups, the hematological analysis showed an increase in total leukocyte (p=0.0012), lymphocyte (p=0.0057), monocyte (p=0.0010) and neutrophil (p=0.0320) counts in comparison with the healthy animals. Our results demonstrated differences in immune peripheral blood cells of tuberculin reactor cattle that are seropositive or seronegative for M. bovis antigens, probably due to different stages of bTB among the groups. The percentages of CD8(+) T cells, B cells and the T cell activation levels may represent biomarkers for the progression of the disease. However, general characteristics shared by both apparently infected groups as lymphocytosis and monocytosis may also be indicative of the disease. Further experiments are required to understand the variations between cellular and humoral immunities throughout the course of bTB infection. A detailed knowledge of the peripheral blood cells involved in all stages of the bTB immune response of naturally infected cattle is essential for the optimal exploitation of diagnosis and vaccination models.

Evaluation of BCG vaccine and Mycobacterium bovis culture filtrate proteins against bovine tuberculosis.

The objective of this study was to evaluate the degree of protection against TB of three immunogens in calves experimentally challenged with a pathogenic Mycobacterium bovis strain by identification of lesions during necropsy. Twenty-four calves free of TB were distributed into four groups: group 1 was inoculated with M. bovis CFPE, group 2 with CFPE/IFN-gamma, group 3 with M. bovis BCG, and group 4 remained as control. After 6 months all animals were challenged with an M. bovis field strain, and 6 months later the animals were euthanized and the presence of lesions was evaluated. Several degrees of protection were observed in the vaccinated groups, particularly in the group vaccinated with BCG, as shown by the absence or decrease in severity of lesions. Vaccination could be useful in high-prevalence zones where it is economically unfeasible to slaughter animals.

A microsatellite study of bovine solute carrier family 11 a1 (Slc11a1) gene diversity in Mexico in relation to bovine tuberculosis

Bovine tuberculosis, caused by Mycobacterium bovis, is a disease of socio-economic and public health importance and of significance to international trade regulation. Allelic variants of several genes have been implicated in the genetic susceptibility to tuberculosis in some human populations, but little is known in cattle. We surveyed 34 European, 18 Asian, 20 Creole and 23 hybrid bovines for polymorphisms of the bovine solute carrier family 11 a1(Slc11a1) gene, formerly known as natural resistance associated macrophage protein (Nramp1), gene by typing the cattle using two microsatellite loci closely linked to this gene. The microsatellites used were 311-22, located at the 3' untranslated region (3' UTR) of the Slc11a1 gene, and ARO28 situated about 0.6 cM upstream of the same gene Based on allele size in base pairs (bp) we determined five 311-223 locus variants (221, 223, 225, 227 and 229 bp) and 12 ARO28 loci. There was marked diversity and a very high level of heterozygosity in most of the cattle surveyed except the Europeans bovines and especially Holsteins in relation to the 3' UTR microsatellite locus.