Detection of monoclonal or oligoclonal integration of bovine leukemia virus proviral DNA by inverse polymerase chain reaction for diagnosis of enzootic bovine leucosis

Enzootic bovine leukosis (EBL) is characterized by systemic B-cell lymphoma associated with bovine leukemia virus (BLV) infection in cattle over 3 years old. This study evaluated the use of inverse polymerase chain reaction (PCR) as a diagnostic method for EBL. Inverse PCR revealed monoclonal or biclonal integration of BLV proviral DNA in the genomes of 71 of 82 cattle with EBL, and polyclonal integration of BLV proviral DNA in the genomes of 16 cattle with B-cell type sporadic bovine leukosis (SBL), 5 cattle with T-cell type SBL, 4 cattle with tumors other than lymphoma, 20 cattle with inflammatory diseases, 5 cattle with diseases other than tumors and inflammatory diseases, and 20 healthy cattle. The sensitivity, specificity, positive predictive value, and negative predictive value of inverse PCR for diagnosis of EBL were 86.6%, 100%, 100%, and 86.4%, respectively, suggesting that the risk of false positives is low. Inverse PCR can be a useful tool for definitive diagnosis of EBL in cattle with difficult diagnosis, such as young cattle.