Characterization of viral inhibitory substance released from fused splenocyte

The D variant of the encephalomyocarditis (EMC-D) virus is diabetogenic in mice by infecting and destroying pancreatic beta cells, but the EMC-B and EMC-DV viruses are not diabetogenic. We have presumed that the nondiabetogenicity of EMC-B and EMC-DV is mainly caused by release of some viral inhibitory factors from lymphocytes or phagocytic cells. Mice were infected with EMC-B and their splenocytes were fused with myeloma cells. The splenocyte hybridoma 12D8 releases the viral inhibitory substance (VIS) which is neither immunoglobulin nor interferon. VIS has inhibitory effects against EMC-D in several kinds of cell lines, and against EMC-D, EMC-B, coxsackie B4, reovirus and the vesicular stomatitis virus in the L cell. VIS has a strong preventive effect (100%) against EMC-D induced diabetes in SJL/J mice and DBN/2N mice. In both pre- and post-treatment studies, VIS remarkably decreased the incidence of both illness and death in SJL/J mice infected with the EMC-D virus. VIS, culture supernate itself of hybridoma, had viral inhibitory activities equivalent to 10(6)-10(7) IU/ml of interferon. VIS was very labile to heat (75% loss of activities at 37 degrees C for 18 h), stable only at pH 5-9, and precipitated at 50% (NH4)2SO4 solution. VIS activities existed in supernatant and pellet prepared from ultracentrifugation, but the properties of their activities could be differentiated quantitatively and qualitatively. It is speculated that VIS may be composed of at least two factors even though interferon may partially participate in one component of supernatant. The prevention and treatment effect of VIS on EMC-D infection in SJL/J mice might be due to the inhibition of the virus replication by VIS.