Analysis of Molluscum-induced Interference in Mouse Embryo Cells: Growth of Encephalomyocarditis Virus and Dose-response Relationships in Molluscum-inhibited Cultures

Molluscum contagiosum virus failed to inactivate encephalomyocarditis virus when incubated with it in the absence of cells. Adsorption and eclipse of encephalomyocarditis virus occurred normally in mouse embryo cell monolayers treated with molluscum virus but its growth was reduced according to the dose and duration of molluscum pretreatment. Encephalomyocarditis virus dose-response curves plotted by direct plaque count, by infective centre assay and by single cycle yields all showed a directly proportionate relationship, at low multiplicities of challenge, in both control and inhibited cultures. With high multiplicities of challenge, yield experiments suggested that interference might have been partially overcome at the cellular level but this was not confirmed in infective centre studies. Interference appeared to result in a uniform reduction of challenge virus growth in all the cells of a culture rather than in the complete protection of some of them. Certain features suggested the production and operation in inhibited cultures of a propagated interfering principle.