Interferon induction by viruses. XIX. Vesicular stomatitis virus—New Jersey: High multiplicity passages generate interferon-inducing, defective-interfering particles

Abstract

The infectious particles of plaque-derived, low multiplicity passaged wild-type VSV of New Jersey origin consistently induce about 1800 units of interferon ( IFN) 10 7 aged chick embryo cells. This inducing capacity is sensitive to both uv radiation and heat (50°). Virus obtained after two successive high multiplicity passages in GMK-Vero cells consistently induced over 25,000 units of IFN 10 7 cells. The IFN induction dose-response curve showed that one IFN-inducing particle (IFP) per cell sufficed to produce a quantum yield of IFN, but infection with two or more IFPs led initially to a marked suppression in the yield of IFN. IFN induction was attributed to two distinct defective particles that differed in size, both containing snap-back RNA, i.e., covalently linked, self-complementary[±]RNA. The IFN-inducing capacity of these defective-interfering particles was not inactivated by uv or heat. However, heat did eliminate the IFN suppressing activity observed at higher multiplicities, implicating a heat-sensitive component in the virion as a regulator of IFN yield, and involving possibly the virion transcriptase and 3′-leader RNA product.