Cytomegalovirus: development and progression of cytopathic effects in human cell culture

Cytopathic effects of cytomegalovirus infection were studied in human cell cultures at various time intervals. Cells derived from human embryonic thyroid, skin-muscle, and lung were infected with five different strains of cytomegalovirus at multiplicities of infection of approximately 5 plaque forming units per cell. Under these conditions, cell rounding and early cytoplasmic inclusions were first apparent at 5 hours postinfection, whereas nuclear inclusions were first observed as a homogenous eosinophilic bead at 24 hours postinfection. Cytoplasmic and nuclear inclusions underwent extensive morphogenesis through 96 to 120 hours postinfection. Development of nuclear inclusions included the formation of distinctive beadlike subunits, which increased in size from their first appearance at 48 to 72 hours postinfection and underwent apparent contraction and breakup after 96 hours postinfection. While the cytopathology induced by various cytomegalovirus strains studied was generally similar, the kinetics of their development was different and independent of both the multiplicities of infection and the source of the fibroblastic cells. Such cytomegalovirus strain-associated differences in cytopathology could result from variances in biologic characteristics of the strains studied.