Even Attenuated Bovine Leukemia Virus Proviruses Can Be Pathogenic in Sheep

Even attenuated bovine leukemia virus proviruses can be pathogenic in sheep.

Based on a reverse genetics approach, we previously reported that bovine leukemia virus (BLV) mutants harboring deletions in the accessory R3 and G4 genes persist at very low proviral loads and are unable to induce leukemia or lymphoma in sheep, indicating that these R3 and G4 gene sequences are required for pathogenesis. We now show that lymphoma can occur, albeit infrequently (1 case of 20) a...

Even transcriptionally competent proviruses are silent in bovine leukemia virus induced tumor cells.

To investigate the role of proviral integration and expression in cellular transformation induced by bovine leukemia virus (BLV), three BLV-induced tumors harboring a single proviral copy were selected upon restriction and hybridization analysis. Tumors 344 and 395 were shown to contain a full-size proviral copy, whereas in tumor 1345 the provirus appeared to be heavily deleted. RNA gel blot hy...

Pathology of lymphosarcoma in sheep induced with bovine leukemia virus.

Sixty-nine sheep were infected with bovine leukemia virus from bovine lymphosarcoma materials. Twenty-four developed lymphosarcoma and died from 13 to 66 (average, 29) months later. Circulating lymphocytes were increased to leukemia levels (70,000 to 403,000/cu mm blood) in only eight sheep within 2 to 3 months of death. Various lymph nodes and visceral organs including heart, abomasum, uterus,...

Fetal infection with bovine leukemia virus in sheep.

Several sheep fetuses were thymectomized, and their tails were removed at 58 to 65 days of gestation for tissue culture. Bovine leukemia virus (BLV) antigens were detected in serial culture of tissues from fetuses whose dams and sires were both BLV positive. However, no BLV antigens were detected in serial cultures of tissues from fetuses whose dams were negative but whose sire was positive. Pr...

Development of an Attenuated Live Virus Vaccine against Sheep Pox