Investigation on the biological activity of fowl plague virus ribonucleoprotein.

: Fowl plague virus (FPV) ribonucleoprotein (RNP) bands in sucrose density gradient in a heterogeneous peak with sedimentation coefficients from 45 to 70 S, whereas in cesium chloride gradient it has a homogeneous density of 1.33-1.34 g/cm3. FPV RNP contains 7.4-8% RNA. Upon inoculation of chick embryo cell cultures. FPV RNP shows no infectivity, does not induce virus-specific protein synthesis and does not participate in complementation or recombination interactions with ts mutants of FPV. The biological activity of FPV RNP demonstrable under certain experimental conditions is due to admixture of undestroyed virions and is completely eliminated by treatment of the preparation with gamma-globulin fraction of antiserum to FPV haemagglutinin, but not with antiserum to RNP proteins.