Recombination between two strains of vaccinia virus

Abstract

Two strains of vaccinia virus were selected which differed by five separate markers: pock morphology on the chorioallantoic membrane of the chick embryo, the production of haemagglutinin, heat resistance, mouse virulence when inoculated intracerebrally and type of skin lesion produced in the rabbit. homogeneous for the five markers, and that the markers were stable on pure culture passage. cultures were infected with mixtures of the two strains and an analysis was made of the progeny of such infections. One hundred and forty-nine progeny clones were isolated, and of these seventeen differed from both parental strains in their marker characteristics. It is believed that these arose by genetic recombination. Intermediates were found for the markers: pock morphology, mouse virulence and type of rabbit skin lesion, whereas haemagglutinin production and heat resistance appeared to be all-or-none characters. A preliminary analysis was made of single HeLa cell yields and of the proportion of heat resistant recombinants to the total progeny.