Abstract
Summary
Escherichia colt 0111:B4:2 in doses greater than 108 heat-killed cells protected 13-day chicken embryos against challenge with a lethal dose of Newcastle disease virus or neurotropic influenza virus. Intact cells were not required since antiviral resistance was also produced by most E. coli fractions, including a 100,000g soluble fraction obtained from differential centrifugation of disrupted bacterial cells. The resistance-inducing material appeared to be a protein. Various proteolytic enzymes reduced the antiviral activity of the 100,000g soluble fraction, while treatment with lipolytic enzymes or nucleases did not affect activity. The protective ability of this fraction was not extractable into lipid solvents nor was it removed by periodate treatment to destroy carbohydrate. The resistance-inducing moiety was recovered in the precipitates formed by ammonium sulfate or ethanol-ether. E. coli mutants deficient in cell-wall lipopolysaccharide provided antiviral resistance equivalent to that produced by the wild-type E. coli. It remains uncertain which bacterial structure(s) is the source of the resistance-inducing protein.
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