Correlation of the stage of cytopathic change with the release of poliomyelitis virus

Abstract

Cytological examination of infected cover slip cultures of monkey kidney, HeLa, and human fetal cells showed that each type underwent similar cytopathic changes and that these changes were identical for each of the strains of poliomyelitis used (Types I, Mahoney; II, MEF-1; III, Saukett). The cytological observations were given a quantitative evaluation in terms of the total cell count per cover slip and in terms of the numbers of cells per cytological type in each control and infected culture. The cytological cell types included mitosis, nonspecific degeneration, interphase, and four arbitrarily designated stages of the cytopathic change: stage I, early nuclear pyknosis, no obvious cytoplasmic changes; stage II, advanced nuclear pyknosis with its displacement to one side of the cell, contraction of the cytoplasm; stage III, formation of a light-staining lesion in the center of the cell, nuclear staining material condensed into a small mass, cell rounded; stage IV, cell disintegration. Samples of the media in which the cells were maintained after infection were assayed by the plaque technique on monolayer cultures of monkey kidney cells. A correlation of the stage of cytopathic change with the time of virus release indicates that the release occurs several hours after stage III, and before stage IV.