Molecular cloning of provirus DNA from bovine leukaemia lymphocytes and its application as a probe for diagnostic purpose.

The provirus DNA isolated from lymphocytes of a cow infected with the bovine leukaemia virus (BLV; positive immunodiffusion test), was subjected to molecular cloning and identified by comparing with the 32P-labelled provirus cDNA isolated in Belgium. Hybridization revealed a clone containing 8.5 kb DNA fragment of the BLV provirus. The probe based on the "Polish fragment" of leukaemia virus was tested on 10 cows with a positive serological response. The presence of provirus DNA in the cellular genome of lymphocytes was confirmed.