sentence: Molecular clones KV1772 ( 46 ) , pBIV127 ( 47 ) , pSPeiav19 ( 48 ) , pEECC-FeLV ( 49 ) , pcHSRV2 ( 50 ) were sources of maedi-visna virus ( MVV ) , bovine immunodeficiency virus ( BIV ) , EIAV , feline leukemia virus ( FeLV ) and PFV DNA , respectively .