Isolation and characterization of host range mutants of avian sarcoma virus

Two host range mutants of avian sarcoma virus (ASV) were isolated from a clone of the Bratislava 77 strain, subgroup C (B77-C). An HR- mutant was obtained by adaptation to duck cells and showed almost the same efficiencies of transformation (e.o.t.) and growth in cultures of chick embryo fibroblasts (CEF) and duck embryo fibroblasts (DEF). An HR+ mutant showed lower e.o.t. and slower growth on DEF than on CEF. Characterization of these mutants and wild-type B77-C showed that (i) unlike the host range mutants reported previously, these mutants and wild-type B77-C have common antigenicity, (ii) the number of infective centres is almost the same for the two mutants and the wild-type, and so the adsorption and integration of these viruses are similar, and (iii) the content of viral RNA in DEF infected with HR- is increased and decreased in the case of HR+ compared with the wild-type.