[The role of hemagglutinin cleavage in influenza virus adsorption and penetration into the cell].

Adsorption and penetration into chick fibroblast cells of WSN virus with completely cleaved hemagglutinin precursor (virus grown in chick embryos), partially cleaved hemagglutinin precursor (virus grown in chick fibroblasts), and virus treated with trypsin added to infected cells or virions were studied. Treatment with trypsin in both instances resulted in complete cleavage of hemagglutinin precursor and in more than 100-fold increase of the infectious activity. Chick embryo-grown virus adsorbed in the same manner as the culture-grown virus not treated with trypsin, but penetrated into the cells 2--3 times more effectively.

[Infectivity of fowl plague virus RNA in the process of infection].

The conditions for isolation and detection of the infectious properties of nucleic acid preparations extracted from cells infected with fowl plague virus were studied. It is suggested that double-stranded virus-specific RNAs possess the infectious properties.