UNINTEGRATED BOVINE LEUKEMIA-VIRUS DNA - ASSOCIATION WITH VIRAL EXPRESSION AND DISEASE

The correlation between bovine leukemia virus (BLV) unintegrated DNA, viral expression, land stage of disease was determined in cattle natur ally infected with BLV, The concomitant presence of unintegrated BLV D NA with viral transcriptional activity was observed in 53% (18 of 34) of hematologically normal, BLV-seropositive cattle and in 100% (10 of 10) of BLV-seropositive cattle with the preneoplastic syndrome persist ent lymphocytosis. In vitro studies suggested that accumulation of uni ntegrated BLV DNA resulted from a process of reinfection rather than i ntracellular reverse transcription of newly synthesized BLV RNA, Inter estingly, unintegrated BLV DNA was not detected in tumor cells from ca ttle with BLV-associated lymphocytic leukemia/malignant lymphoma despi te viral transcriptional activity in 100% (eight of eight) of these ca ttle. Thus, the presence of unintegrated BLV DNA differentiated nonneo plastic from neoplastic conditions in BLV-infected cattle, These resul ts demonstrate that unintegrated viral DNA serves as a marker of disea se progression in BLV-infected cattle but is not necessarily associate d with induction or maintenance of the neoplastic state.