Non-Heritable Interferon Resistance in a Fraction of Virus Populations

Abstract

Summary Attempts to select interferon resistant mutants of EMC virus were unsuccessful. Virus was found unchanged in its sensitivity to interferon despite 10 passages in ME cultures which had been treated with high concentrations of the inhibitor. During the course of these experiments, it was observed that a fraction of the virus population varying from 10 to 15% of the input virus was capable of multiplying in interferon-treated cultures. The resistance of this “persistent fraction” to interferon was not due to a genetic property of the virus and superficially resembled similar phenomena observed with other virus inactivating agents. Stocks of VSV and vaccinia virus were also shown to contain interferon “persistent fractions.” The magnitude of the “persistent fraction” may vary, depending on the virus, type of cell, as well as the cellular environment.