The Origin of Hybrid Variants Derived from Subtype Strains of Foot-and-Mouth Disease Virus

Summary Two strains of foot-and-mouth disease virus, distinguishable by four marker characteristics in addition to their antigenic subtype, could be separated by countercurrent distribution in an aqueous polymer phase system. This technique of separation was applied to the analysis of the progeny virus obtained from pig kidney cells simultaneously infected with these two strains. Selection for recombinant virus yielded a number of isolates with the appropriate recombinant phenotype. These isolates subsequently segregated into a number of clones of various phenotypes including parental and recombinant types. Possible interpretations of this phenomenon are discussed. It is suggested that the segregating isolates may have originated from foci of infection inititated by viral aggregates. The serological data suggest that the frequency of recombinants in the progeny may be greater than indicated by multiple marker exchanges.