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

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.