Canine distemper virus in chick embryo cell culture: Plaque assay, growth, and stability

Abstract

Three strains of canine distemper virus were cultivated serially in chick embryo cell cultures with the development of cytopathic effects. Following multiple passage in cell culture, the egg-adapted Onderstepoort strain demonstrated a reduced capability to form lesions on the chorioallantoic membrane. Plaques formed slowly under agar overlay, attaining 90% of final count by 10 days. A linear relationship between virus concentration and plaque number was demonstrated. Virus attached slowly to chick embryo cell monolayers at 36°. Approximately 50% of the virus was adsorbed at 30 minutes, although maximal attachment did not occur until 4 hours. Canine distemper virus was relatively thermolabile. The half-life at 21°, 37°, 45°, and 56° was 120 minutes, 60 minutes, 10 minutes, and 2–3 minutes, respectively. Growth studies revealed an eclipse period of 8–10 hours, followed by a logarithmic increase in cell-associated virus (0.3 log/hour). Virus appeared in the fluid phase 2–4 hours following the first increase in cell-associated virus. Cell-associated virus exceeded that found in the fluid phase throughout the growth cycle.