PCR amplification using primer pairs Fe-8S/Fe-4S and Fe-3R encompassed the entire FeLV env gene, and resulted in a fragment of predicted size (approximately 1.9 kb) when applied to AH927 cells infected with FeLV-A Glasgow-1 (GA5), FeLV-B Gardner-Arnstein (GB) or FeLV-C Sarma (SC) (Fig. 2B), and when applied to FT-1 cell lines [5] derived from the thymic lymphoma of a FeLV-positive cat, and samples of FeLV antigen-positive blood (SN5, MZ29). Here, ERVW-1 is linked to thymus lymphoma.