Relationship between polymorphism in the tumour necrosis factor-alpha gene and selected indices and cell subpopulations in naturally bovine leukaemia virus-infected and healthy cows

Abstract

The bovine leukaemia virus (BLV) is the aetiological agent of enzootic bovine leukosis. The aim of this study was to determine whether polymorphism in the TNFα gene at positions –824 A"G and –793 C"T in the 5' flanking region, and g.1787 in exon 4 influences leukocyte counts, the percentages of monocytes and apoptotic cells and the sizes of CD14⁺, CD14⁺TNF⁺, TNF⁺p24⁺ and CD11b⁺TNF⁺p24⁺ cell subsets in BLV-infected and healthy cows. A total of 127 Polish black and white Holstein-Friesian cows at 3–8 years of age were analysed. SNPs in the TNFα gene were determined using PCR-RFLP. BLV infection was diagnosed with the use of indirect immunofluorescence (IMF) and nested PCR tests. Peripheral blood mononuclear cells (PBMCs) were identified using IMF. Apoptotic cells were detected with the Annexin-V-FLUOS Staining Kit. The data were analysed using the Kruskal-Wallis test and a multiple comparison test in Statistica 12.0 software. TNFα gene polymorphism was associated with significant differences in the sizes of CD14⁺, CD14⁺TNF⁺, TNF⁺p24⁺ and CD11b⁺TNF⁺p24⁺ subsets in BLV⁺ cows, but not in healthy animals. CD11b⁺TNF⁺ cells homozygous for G/G (–824) and T/T (–793) in the 5' flanking region appear to be more prone to BLV infection than opposite homozygotes. TNFα gene polymorphism was correlated with leukocyte counts and the percentage of apoptotic cells, but only in healthy cows. In conclusion, different relationships were observed between the analysed SNPs and selected indices in BLV⁺ and healthy animals. These findings could suggest that the interaction between TNFα gene polymorphism and BLV affects the size of CD14⁺, CD14⁺TNF⁺, TNF⁺p24⁺ and CD11b⁺TNF⁺p24⁺ subsets. Such an interaction was not observed for the other analysed parameters.