Bovine leukemia virus high tax molecular clone experimentally induces leukemia/lymphoma in sheep

Sheep were inoculated with high tax coded pBLV-IF (H group, Nos.1-5) of bovine leukemia virus (BLV), wild tax coded pBLV-IF (W group, Nos. 6-11), or control plasmid (C group, Nos. 12-14). During the observation period (4 to 46 months), 5 of 5 cases in H group and 3 of 6 cases (Nos. 6, 7, 9) in W group became positive tor gp51. Only 1 case in H group became leukemic, and one case each of H and W groups developed lymphoma. In No. 3, lesions Were found in multiple organs including the lymph nodes, gastrointestinal tract following abomasum, and heart. In No. 6, lesions of lymphoma were found only in the jejunum, and heart. Morphologically, small to middle-sized lymphocytic neoplastic (NP) cells were found in both cases, but lymphoblastic NP cells were found only in No. 3. By immunohistochemical examination, the phenotypes of NP dwells were determined as CD1(-), CD4(-), CD5(-)-, CD8 alpha(-), sIgM(+), lambda light chain(+), B-B4(+), MHC class II+ in both case. The results of this study indicate that inoculation of pBLV-IF can induce lymphocytic and lymphoblastic leukemia/lymphoma in sheep. Additionally, it is suggested that the expression rate of tax gene is not associated with the development of leukemia/lymphoma in sheep experimentally inoculated with pBLV-IF.