A putative interferon induced in hamsters by poly(I) . poly(C)

Encephalomyocarditis (EMC) virus causes lethal infection of hamsters against which poly(I) . poly(C) causes dose-dependent protection. In contrast, no antiviral effects occur with poly(I) . poly(C) against influenza virus infection of hamsters. Serum from poly(I) . poly(C) treated hamsters protects other hamsters against EMC virus infection with maximum protection with serum removed 3h after poly(I) . poly(C) treatment of the donor hamsters. In such assays the factor was found to be inactivated by trypsin and pH 2 and 56 degrees C for 1 hr. The serum factor did not confer protection against EMC virus infection of L-929, BHK, Hak or primary hamster embryo cells. The amount of poly(I) . poly(C) carried over into serum samples of poly(I) . poly(C) treated hamsters was insufficient to account for the antiviral effects. The antiviral serum factor is presumed to be a form of interferon despite the fact that it does not titrate in cell cultures and has a novel set of properties from those which describe known interferons.