DNA Po lymerase o f Bov ine Leukaemia V i rus

A virus designated bovine leukaemia virus (BLV), associated with leukaemia n cattle and previously demonstrated to induce the disease in sheep, was purified from chronically infected sheep cell cultures. Electrophoretic analysis showed a major protein of mol. wt. about 24ooo (p24) which reacted in gel diffusion and complement-fixation ests with sera from naturally infected cattle, experimentally infected sheep, and guinea pigs immunized with p24. BLV p24 has an isoelectric point of 8-6. Interspecies antigenic reactivities characteristic of mammalian Type C virus p3os were not detected in disrupted BLV or on p24. Sheep and guinea pig antisera to BLV, reactive with p24, also did not precipitate several Type C virus p3os in radioimmunoassays. BLV is also distinguished from Type C viruses and resembles mouse mammary turnout virus and Mason-Pfizer virus in having an RNA-dependent DNA polymerase which is preferentially active in the presence of Mg ++ when synthetic templates areused. Along with previously published morphological data, the above indicates hat BLV is not a Type C virus as classically defined. Four hundred and forty one human sera from cancer patients and matched controls were non-reactive with disrupted BLV, BLV infected cells, and BLV p24 in complement-fixation tests