Infection of chick cells by subgroup E viruses

Abstract

Studies were carried out to determine whether there is a restriction of replication of the endogenous chicken leukosis virus Rous associated virus type O (RAV-0) in chick embryo fibroblasts (CEF) beyond that imposed by the known cell surface barrier. Following either Sendai virus mediated fusion of RAV-O with surface resistant CEF ( C E cells), or infection of CEF lacking the surface barrier ( C O cells), a quantitative 10 3- to 10 4-fold restriction in replication was noted in comparison with RAV-60, a recombinant leukosis virus bearing the same subgroup E envelope as RAV-0 The failure of this internal restriction to operate against subgroup E leukosis viruses was investigated in detail in a series of cloned subgroup E sarcoma virus recombinants isolated following mixed infection with RAV-0 and Prague strain of Rous sarcoma virus subgroup C (PR-C) (i.e., two factor crosses) or following PR-C infection of chf + CEF. RNA from one of these PR-E clones was shown to contain a nearly full complement of RAV-0 specific and RSV specific nucleotide sequences, but that isolate and six others were all free of the restriction observed with RAV-0 replication. One clone may be subject to some restriction. Thus some genetic function(s) of RAV-0 lost or inoperative in recombinant viruses appears important for this restriction. Since RAV-0 can replicate to a “normal” titer in some CEF from particular lines of chickens (line 7, line 100 × 7, and line 15), but apparently not in embryo culture from chicken flocks used in these studies, some cell function(s) also appears important for this restriction.