Tumor necrosis factor-alpha (TNFα) gene polymorphism and expression of membrane-bound TNFα protein on CD11b+ and IgM+ cells in cows naturally infected with bovine leukemia virus

Effect of heat stress on TNF-α, TNFRI and TNFRII expression in BLV infected dairy cattle

High temperatures for extended periods, which do not allow animals to recover from heat stress, affect in particular those BLV-infected animals that carry a high proviral load. For this study, animals were discriminated between BLV (+) and BLV (-), and those belonging to the first group, were classified based on their proviral load. The expression of the inflammatory cytokine TNF-α and its receptors, which play an important role in disease progression, were quantified by qPCR in two different seasons. During the summer, average temperature was 19.8 °C, maximums higher than 30 °C were frequent. Instead, during the autumn, the average temperature was 12.63 °C, and temperatures never exceeded 27 °C. During this season, almost no periods of temperatures exceeded the comfort limit. Our results revealed that the expression levels of TNF-α and its receptors were downregulated in animals with high proviral load. This fact could affect their antiviral response and predispose to viral dissemination; over time, animals with a poorer immune system are prone to acquiring opportunistic diseases. Conversely, animals with LPL maintained their expression profile, with behavior comparable to non-infected animals. These findings should be considered by producers and researchers, given the problems that global warming is causing lately to the planet.

Polymorphisms in the Bovine Tumour Necrosis Factor Receptor Type Two Gene (TNF-RII) and Cell Subpopulations Naturally Infected with Bovine Leukaemia Virus

Introduction

Numerous mutations in the bovine tumour necrosis factor receptor type two (TNF-RII) gene have been identified, but their biological consequences remain poorly understood. The aim of this study was to determine whether polymorphism in the analysed loci of the bovine TNF-RII gene is linked with the size of cell subpopulations naturally infected with bovine leukaemia virus (BLV) which serve important immune functions in the host.

Material and Methods

Samples originated from 78 cows. Polymorphisms in the studied gene were determined by PCR-RFLP and DNA sequencing by capillary electrophoresis. BLV infection was diagnosed by the immunofluorescence (IMF) technique and nested PCR. Cell subpopulations were immunophenotyped with IMF.

Results

Similar and non-significant differences in the average percentages of TNFα±, IgM+TNFα±, and CD11b+TNFα±cells infected with BLV were noted in individuals with various genotypes in the polymorphic sites g.-1646T > G and g. 16534T > C of the TNF-RII gene, and significant differences in the percentages of these subpopulations were observed between selected microsatellite genotypes (g.16512CA_(n)).

Conclusion

STR polymorphism and the number of CA dinucleotide repeats in intron 1 of the TNF-RII gene influence the frequency of TNF+, CD11b+TNF+, and IgM+TNF+ subpopulations naturally infected with BLV. Polymorphism in the gene's other two sites do not affect the size of these cell subpopulations.