Enzootic bovine leukosis caused by bovine leukemia virus classified as Group C based on viral whole genome sequencing in a 23-month-old Holstein-Friesian heifer

A clinical case of enzootic bovine leukosis in a Holstein cow with minor clonality of B-cell in the peripheral blood

A 4-year 9-month-old Holstein-Friesian dairy cow presented with anorexia. On physical examination, swelling of superficial lymph nodes, pelvic masses, and prolonged urination posture after urinating a small amount were noted. Hematological examination revealed no lymphocytosis. The bovine leukemia virus proviral load was relatively high. At necropsy, enlarged lymph nodes, a large mass in the pelvic cavity, and mass lesions in several organs were observed. Histopathological examination revealed the proliferation of neoplastic lymphocytes, which were immune-positive for CD79α and negative for CD3. B-cell clonality test indicated the presence of monoclonality in the urine, masses, and lymph nodes and minor clonality in the peripheral blood. These findings led to a diagnosis of EBL with minor clonality of B-cell in the peripheral blood.

A clinical case of B-cell lymphoma in a Japanese Black cow with monoclonal proliferation of B-cells as revealed by polymerase chain reaction based on the immunoglobulin light chain gene

A 35-month-old Japanese Black cow was presented to a local veterinarian with a main complaint of premature labor. There was no swelling of lymph nodes on the body surface and no palpable mass on rectal examination. Although atypical lymphocytes were observed in the peripheral blood, no lymphocytosis was recorded. On Day 12, the cow developed hindlimb paresis and was euthanized. Necropsy revealed swelling of some lymph nodes, and white nodules in uterus and right atrial appendage. Histopathological examination revealed B-cell lymphoma. In clonality analysis of peripheral blood and tumor tissue, monoclonal proliferation was detected by PCR for immunoglobulin light chain (IgL) λ, suggesting neoplastic proliferation of B-cell. IgL-PCR is thought to be a possible tool for diagnosis of B-cell lymphoma.

Infection with bovine leukemia virus belonging to group A or B-1 contributes more strongly to the development of enzootic bovine leukosis in young cattle than the presence of bovine lymphocyte antigen-DRB3 susceptibility alleles

In this study, we compared the effects of different bovine leukemia virus (BLV) strains and bovine lymphocyte antigen (BoLA)-DRB3 alleles in cattle with enzootic bovine leukosis (EBL) aged either <3 years or ≥3 years. The frequency of infection with BLV belonging to group A or B-1 in cattle aged <3 years with EBL was significantly higher than that in cattle aged ≥3 years, regardless of which BoLA-DRB3 allele was present. This suggests that infection with group A or B-1 BLV contributes more strongly to the development of EBL in young cattle than the presence of early-EBL-onset susceptibility BoLA-DRB3 alleles.

Diffuse large B-cell lymphoma with DNA copy number changes in a Japanese black calf

A 2-month-old Japanese Black calf exhibited mandibular and superficial cervical lymph node swelling. Fine needle aspiration cytology of the superficial cervical lymph node revealed large lymphoblast-like cells with mitoses. Hematological examination revealed remarkable lymphocytosis with atypical lymphocytes. Increased activities of serum total lactate dehydrogenase and thymidine kinase were detected. At necropsy, generalized swelling of lymph nodes was observed. Histopathological analysis revealed diffuse proliferation of medium-sized round centroblastic neoplastic cells that were positive for CD20, CD79α, PAX5, and BLA-36, and negative for CD3, CD5, CD10, and CD34. The calf was diagnosed with centroblastic diffuse large B-cell lymphoma (DLBCL) based on these findings. Analysis of DNA copy number variation revealed an increased copy number for the GIMAP family relative to that in healthy cattle. Moreover, decreases in copy numbers of GBP-1, MIR3141, OR5P1E, and PTPRG relative to those in healthy cattle were also observed. Because DNA copy number variation represent a major contribution to the somatic mutation landscapes in human tumors, these findings suggest that DNA copy number changes might have contributed to the onset of DLBCL in the present case.