Bovine cytokine expression during different phases of bovine leukemia virus infection

The potential role of aberrant cytokine production in the pathogenesis of bovine leukemia virus (BLV) was studied by analyzing cytokine mRNA expression in pokeweed-stimulated PBMLs of cows in different phases of disease progression. To analyze the mRNA, a semi-quantitative RT-PCR assay was developed. The RT-PCR assay was developed for detection of IL-2, -4, -6, -10, -12, IFN-γ and actin using cDNA derived from phorbol-stimulated peripheral blood mononuclear leukocytes. Using a PCR specific for BLV tax, agar gel immunodiffusion and white blood cell counts, BLV-negative, BLV-positive aleukemic (AL), and BLV-positive persistently lymphocytotic (PL) cattle were identified. Peripheral blood lymphocytes cultured in vitro for 24 h in pokeweed mitogen were analyzed for cytokine production using the RT-PCR assay. Consistently elevated levels of IL-2 and IL-12 in AL and PL cattle in pokeweed mitogen-stimulated cells was detected, while IFN-γ was elevated in the AL but not the PL cattle.