Biological and electron microscopic studies on the phenotypic mixing of the thermolabile mutant of vesicular stomatitis virus,tl-17, with avian RNA tumor viruses

Abstract

A thermolabile as well as thermosensitive mutant of vesicular stomatitis virus, VSV-tl-17, could be thermostabilized by phenotypic mixing with avian RNA tumor viruses (ATV). Biological, immunological and morphological studies revealed that this effect is due to a replacement of the thermolabile projections of the VSV by the avian tumor viral projections. The arrangement of projections of VSV and ATV on phenotypically mixed viria was studied by electron microscopy. A-type particles were detected in chick embryo cells which were doubly infected by ATV and VSV. Their intracytoplasmic appearance seemed to be the result of a disturbed maturation of ATV due to the relative deficiency of envelope proteins which were depleted by VSV maturation in the course of phenotypic mixing.

The Pseudotypic Paradox

“…Choppin & Compans, 1970;Z/tvada, 1972a;Z~ivada & Rosenbergov/t, t968), virus mutants with temperature-sensitive (ts) or thermolabile (tO defects in the surface gp (Breitman & Prevec, 1977;Weiss & Bennett, 1980;Z~vada, 1972a, b;Z~vada & Z~vodsk~i, 1973), polyacrylamide gel (PAGE) analysis of isotopically labelled virus (McSharry et al, 1971) or ferritin-labelled antibodies in conjunction with electron microscopy (Chan et al, 1978;Choppin & Compans, 1970). However, in the example of vesicular stomatitis virus (VSV) pseudotypes with avian tumour virus, the retrovirus spikes can be seen by electron microscopy even without the aid of tagged antibodies (Ogura & Bauer, 1976). In another instance, a haemagglutination-inhibition test was employed (Granoff & Hirst, 1954).…”

“…Calafat, personal communication;Chan et al, 1978), or mixedly grown with a paramyxovirus (Choppin & Compans, 1970), contain many gp molecules acquired from the donor virus. As mentioned above, VSV(oncovirus) pseudotype particles can be recognized in the electron microscope without antibodies (Ogura & Bauer, 1976).…”

“…These mutants are BH-RSV, produced in the absence of helper viruses in chicken chf-or in Japanese quail cells (De Giuli et al, 1975;Ogura & Friis, 1975;Scheele & Hanafusa, 1971) and ts mutants of VSV belonging to complementation group V (which at non-permissive temperature synthesize the polypeptide of the gp, but this is not transported to the cell surface membrane and is not assembled into VSV virions) (Ogura & Bauer, 1976;. Both BH-RSV and VSV ts(V) produce virions which appear naked (no surface projections) in electron micrographs, and PAGE analysis of polypeptides of purified virus preparations demonstrates the absence of virus-specific gp as well as of any other proteins of the host cell.…”

Effects of Dexamethasone on the Morphogenesis of Two Mutants of Rous Sarcoma Virus

“…Intracyto plasmic A-type particles can rarely be observed and are reported as aberrant avian tumor viruses [30][31][32][33][34][35][36]. The incidence of intracytoplasmic A-type par ticles was suggested to be caused by the disturbance of late assembly of avian C-type viruses [33][34][35],…”

“…FRG). BH RSV(-)Q, BH RSV(RAV-3)Q, CEC infected with B77, and CEC infected with LA 334 and kept at the permissive (35 ) or nonpermissive (41 ) temperature were treated with 10 n or 10 5 m dexamethasone, concentrations which have been reported to be optimal for the stimulation of murine endogenous C-type particles [6,17],…”