[Maturation of the hemagglutinin and neuraminidase polypeptides of the influenza virus in infected cells]. / Sozrevanie polipeptidov gemaggliutinina i neiraminidazy virusa grippa v zarazhennykh kletkakh.

Maturation of virus-specific hemagglutinin and neuraminidase polypeptides was studied in chick embryo fibroblasts infected with influenza A virus, the WSN strain. Hemagglutinin maturation is accompanied by a decrease in the electrophoretic mobility of the protein. The processes occurring in maturation are localized on the part of the molecule corresponding to the major hemagglutinin subunit. The previously reported virus-induced proteins III and IV have been identified as immature precursor and mature polypeptide of virus neuraminidase, respectively. This is concluded on the basis of the membrane localization of both proteins, the presence of sugars in at least one of them, the antigenic specificity of the proteins, their behavior in electrophoresis under nonreducing conditions, as well as the results of "pulse'chase" label experiments. The nature of the modifications accompanying viral neuraminidase maturation remains obscure; some possibilities are considered.

[The role of hemagglutinin cleavage in influenza virus adsorption and penetration into the cell]. / Rol' narezaniia gemaggliutinina v adsorbtsii i proniknovenii virusa grippa v kletku.

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. The culture-grown virus after treatment with trypsin adsorbed better but penetrated in the same way as the original culture-grown virus. Treatment of the infected cells with trypsin led to more effective penetration with unchanged adsorption. The experimental results suggest that cleavage of hemagglutinin precursor is essential both for adsorption and penetration. Depending on the method of treatment, the effectiveness of one or the other process is increased.

[Processing of influenza virus-induced proteins in infected cells]. / Protsessing belkov, indutsiruemykh virusom grippa v zarazhennykh kletkakh.

Several classes of previously unknown virus-induced proteins were found in cells of monolayer chick embryo and MDCK cultures infected with influenza A0/WSN virus. One of them, HAb, is a hemagglutinin precursor and appears to contain less sugar residues than the mature molecule. HAb leads to HA processing occurs during transportation of the precursor from the site of synthesis in rough membranes into smooth membranes. Protein II found in the study is a product of viral NP protein modification. Finally, protein III is very likely to be a precursor of protein IV. Some data suggest neuraminidase nature of proteins III and IV.