Synthesis of virus-specific RNA in cells infected with two different variants of measles virus.

Abstract

Vero cells were infected with the DP (diluted passage) and UP (undiluted passage) measles virus variants at input multiplicities of 0.01 and 0.002, respectively. The amount and sedimentation characteristics of virus-specific RNA synthesized was determined by pulse-labelling with H3-uridine for periods of 4 hours in the presence of actinomycin D. During the first two days after infection the quantity and quality of RNA synthesized by the two variants was comparable. Hereafter the rate of RNA synthesis in DP virus-infected cells increased and reached maximum after another three days, at which time there were signs of a general cytopathic degeneration. In contrast hereto the rate of RNA synthesis in UP virus-infected cells decreased markedly during the period between two and five days after infection and remained at a low level during an additional observation period of ten days. Cytopathic degeneration of UP virus infected cultures did not become pronounced until between 10 and 14 days after infection.