Swine cell systems as interferon producers. IV. Comparative studies on the correlation between virulence of different Newcastle disease virus strains and their potency as interferon inducers.

Comparative studies concerning a correlation between virulence of various Newcastle virus strains and their interferon-inducing potency confirmed that such a correlation existed. The nearly avirulent La Sota strain of NDV was the poorest interferon inducer, the virulent Hertfordshire strain manifested a very good inducing potency. However, the most virulent J.B. strain virus was a poorer interferon inducer than the Hertfordshire strain. This should not be viewed as contradictory to the conclusion of the correlation between virulence and interferon-inducing ability of NDV since the highly virulent strain might destroy faster the interferon-producing cells, before the latter produced the maximum interferon quantity which they potentially could produce.