Inhibition of Sindbis Virus Plaque Formation by Extracts of Escherichia coli

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Abstract
Extracts prepared from washed cells of Escherichia coli B by sonic treatment and subsequent filtration through a 0.45 - [mu] membrane filter significantly inhibited plaque formation with Sindbis virus in cultures or primary chick embryo cells up to a dilution of 1:20,000. The inhibitor acted on the cells rather than directly on the virus. The inhibiting substance was nondialyzable. Treatment of crude extracts with nucleases, trypsin, chymotrypsin, pepsin, or ether had no effect on the activity. Treatment with pronase destroyed the virus-inhibiting effect. Extracts prepared from two strains of E. coli B and one strain of E. coli K-12 all showed inhibitory activity against Sindbis virus. The inhibitor was present in the cytoplasmic fraction of bacteria. It was also active against Sindbin virus in human cells and showed some activity against vesicular stomatitis and vaccinia viruses in different types of cells. Interferon was not shown to be involved in the inhibition, although actinomycin D partially reversed the inhibitory activity of the extracts.