Abstract A Japanese Black cow presented with anorexia. Exophthalmos, a subcutaneous mass, and astasia were noted on physical examination. Hematological examination revealed lymphocytosis (5544/μL). Serum biochemical findings included elevated activities of lactate dehydrogenase and thymidine kinase. Antibodies against bovine leukemia virus (BLV) were detected. The animal was euthanized and necroscopic evaluation was performed, and masses were found in both orbit and left pectoral region; white solid tissue growth in fatty tissue was observed throughout the body. Yellowish-white solid tissue was also observed around the right nerve roots from the 9th thoracic spinal nerves to the 4th lumbar spinal nerves. Immunohistochemical examination showed neoplastic B-cells (positive for BLA-36, CD79α, and PAX5, and negative for CD3) proliferation in the mass lesions and yellowish-white solid tissues. Two integration sites of BLV provirus in peripheral blood and tumor tissues were detected by inverse PCR. Based on these findings, the present case was diagnosed with enzootic bovine leukosis (EBL). The BLV provirus was found to have integrated into the introns of itchy E3 ubiquitin protein ligase ( ITCH ) and Selenoprotein I ( SELENOI ). ITCH is a key player of TNF-related apoptosis-inducing ligand (TRAIL)-mediated apoptosis, and SELENOI adjusts oxidative stress in tissues. Integration of BLV provirus into these genes might have contributed to the onset of EBL and influenced the distribution of neoplastic lesions.
MAEZAWA et al. (Fri,) studied this question.