Differentiation of closely related cells by a variant of poliovirus, type 2, MEF1 strain.

By application of a variant of poliovirus, Type 2, MEF(1) strain, as a selective agent it was possible to distinguish among stable parent strains of epithelial cells and their clonal derivatives by their differential morphologic response to infection. The variant of poliovirus grew in a number of cell strains without induction of observable cytopathogenic changes. Other strains of cells reacted to viral infection by manifesting partial or complete degeneration. Parent HeLa cells and virus underwent simultaneous serial propagation in the absence of homotypic antiserum to virus. The stability of the virus-cell relationship was established by results from replicate experiments conducted over a period of years. Some cell strains of common origin maintained in different laboratories did not react similarly to the cytopathogenic effect of virus. Representative experiments revealed that the morphologic response of HeLa cells to MEF virus infection was not influenced by the presence or absence of pleuropneumonia-like organisms. The differential morphologic response of cells to infection was confirmed by efficiency-of-plating experiments which revealed differences in the capacity of MEF virus to form plaques in the test cell strains. Serial passages of MEF virus in cell strains demonstrated differences in their selection for cytopathogenic "mutants" of virus.