Interferon Antagonists Induced by Newcastle Disease Virus (NDV)

Abstract

Discussion and Summary

NDV induces in human, mouse and chick cells the synthesis of a substance termed stimulon which decreases the antiviral state induced by interferon. Similar substances were previously described in cells infected with a number of oncogenic and nononcogenic viruses (13), and also in L cells infected with NDV. These substances have to be distinguished from tissue antagonists of interferon (TAI) present in normal tissues. Stimulon has no direct effect on interferon or on viruses. Both stimulon and TAI affect, however, the antiviral state after its establishment. Experiments using antimetabolites (14-16) and somatic monkey-mouse hybrid cells (17) have established that IF is not directly responsible for the antiviral state, but acts through a second protein. Both stimulon and TAI act on the antiviral activity of this second protein. Many of the basic physi-cochemical properties of the substance described here resemble a glycoprotein rather than a protein. The antiinterferon activity induced by NDV in this system could be related to breakdown cellular products, to virus induced proteins, or to a mixture of the two. Since the viral envelope could contain cellular and viral antigens, it seems possible that at least some of the TAI and stimulon, or both, are integrated in the envelope of the virion. This problem is under current investigation.