Phenotypic Mixing between Group A Arboviruses

Abstract

WHEN two different viruses infect the same cell some of the progeny may exhibit phenotypic mixing: that is, the genome of one parent may be enclosed in a coat determined, at least in part, by the genome of the other parent. Thus the phenotype may not correspond to the genotype. This anomaly disappears after one cycle of growth if further mixed infections are avoided. Phenotypic mixing was first detected in bacteriophage¹ and has subsequently been observed in polio viruses² and myxoviruses³. We shall describe a double mutant of Sindbis virus (a group A arbovirus) that can be used in a simple test for phenotypic mixing with other wild-type arboviruses. Such a test for phenotypic mixing may be useful in confirming or suggesting relationships among these viruses. The methods used for the growth and titration of arboviruses in primary chick embryo cultures have been described⁴.