The envelope glycoprotein (Env) of BLV, which constitutes the causative agent of enzootic bovine leukosis, the most common neoplastic disease of cattle, and is closely related to human T-cell leukemia viruses (HTLVs), contains two overlapping copies of the (YXXL/I)2 sequence serving as the ITAM at the C-terminal domain of the transmembrane (TM) protein [1,5]. This evidence concerns the gene ERVW-1 and neoplasm.