Identification and characterization of recombinant subgroup J avian leukosis viruses (ALV) expressing subgroup A ALV envelope

Three recombinant avian leukosis subgroup J viruses, ADOL 5701A, ADOL 5701A Delta, and ADOL 6803A, carrying a subgroup A envelope have been isolated a nd characterized. These viruses were identified by their ability to replica te in DF-1/J, a recombinant chicken embryo fibroblast (CEF) cell line expre ssing the subgroup J envelope that is resistant to subgroup J replication. Flow cytometric analysis of DF-1/J cells infected with ADOL 5701 and ADOL 6 803, two subgroup J isolates, indicated cross-reactivity with subgroup A ch icken polyclonal serum. Based on published sequences of subgroups A and J i solates, we designed a series of primers to PCR amplify the envelope and LT R of these viruses. PCR products were obtained when the forward primer was specific for subgroup A gp85 envelope protein gene and the reverse primer w as specific for subgroup J LTR. Sequence analysis of the PCR products indic ated that these viruses had a subgroup A gp85, a subgroup E gp37, and a sub group J LTR. Interestingly, these Viruses had previously been propagated in CEF from the alv6 chicken line, a line that carries a replication defectiv e recombinant endogenous virus expressing a subgroup A envelope (RAV 0-A(1) ). Sequence analysis of RAV 0-A(1) gp85 and gp37 envelope proteins indicate d that they were almost identical to those of the recombinants ADOL 5701A a nd ADOL 6803A. These results indicate that these three recombinant viruses arose by recombination between exogenous subgroup J isolates and a recombin ant defective endogenous Virus with subgroup A envelope. (C) 2000 Academic Press.