Mutant and recombinant avian retroviruses with extended host range.

Avian retroviruses of subgroups B and D efficiently infect chicken (C/E) but not turkey (T/BD) cells. We describe here three variants of subgroup B and D viruses that infect both cell types equally well. One of these viruses, NTRE-4, was a recombinant between transformation-defective Prague (Pr) strain Rous sarcoma virus (RSV) subgroup B and the endogenous virus RAV-0; the second, SR-DE-1, was a recombinant between Schmidt-Ruppin RSV subgroup D and defective endogenous virus information. T1 oligonucleotide fingerprint analysis of the genomes of these two viruses showed only a small alteration in the portion of the env gene responsible for subgroup specificity, as indicated by the presence of a single subgroup E oligonucleotide in an otherwise purely subgroup B or D gene. The third virus, hrBO1Pr-B, was a variant of Pr-RSV-B that did not appear to be a recombinant and whose altered host range we attribute to mutation. Analysis of the host range of all three viruses by infection of selectively resistant cells and by interference testing indicates that all use the subgroup B receptor on chicken cells and the subgroup E receptor on turkey cells. These viruses may be analogous to the polytropic recombinant viruses recently found to be associated with leukemia in some strains of mice.