Phenotypic expression of HA-NA combinations in human-avian influenza A virus reassortants.

Human-avian and human-mammalian influenza A virus reassortant clones with the neuraminidase (NA) gene of the A/USSR/90/77 (H1N1) strain and hemagglutinin (HA) genes of H3, H4 and H13 subtypes had been shown in an earlier publication to produce low HA yields in the embryonated chicken eggs. The low HA titers had been shown to be due, at least in part, to the formation of virion clusters at 4 degrees C; the clustering was removed by the treatment with bacterial neuraminidase [Rudneva et al., Arch.

Formation of mixed hemagglutinin trimers in the course of double infection with influenza viruses belonging to different subtypes.

Chick embryo primary cultured cells were infected with influenza viruses belonging to H1, H2, H3, H5 or H7 subtypes of hemagglutinin. The cells were subjected to a single or a double infection, labelled with 14C-amino acids from 2 to 6 hours postinfection, lysed with a mixture of ionic and non-ionic detergents, and the lysates were clarified by low-speed centrifugation. The clarified lysates contained 14C-labelled hemagglutinin mostly in the form of 9S trimers, as shown by velocity sedimentation in sucrose gradients with polyacrylamide gel electrophoresis (PAGE) analysis of the gradient fractions.

Studies on influenza-virus virulence in recombinants between epidemic and vaccine strains.

Influenza virus recombinants between epidemic strains A/Brazil/11/78 (H1N1), A/USSR/382/78 (H3N2) and vaccine strains A/Leningrad/9/46 (H1N1), A/Victoria/35/72/50 (H3N2) have been tested for virulence for humans and albino mice; their genome structure has also been determined. It has been shown that after the replacement of surface antigens of A/Leningrad/9/46 (H1N1) strain by surface antigens of A/Brazil/11/78 (H1N1) or A/USSR/382/78 (H3N2), strains, the virus becomes totally nonpathogenic for mice whereas its virulence for humans is enhanced. The combination in recombinant X/28 (H1N1) of haemagglutinin and neuraminidase of A/Brazil/11/78 (H1N1) virus and othercomponents of A/Leningrad/9/46 virus determines its high affinity to the epithelium of the upper respiratory tract of humans, as well as its marked virulence for seronegative volunteers.

Dissociation of the haemagglutination inhibition and the infectivity neutralization in the reactions of influenza A/USSR/90/77 (H1N1) virus variants with monoclonal antibodies.

Variants of influenza A/USSR/90/77 (H1N1) virus selected with monoclonal antibody HC 142 (Res 142-1 and Res 142-2) were resistant to this antibody in a virus-neutralization (VN) test, but were inhibited in a haemagglutination-inhibition (HI) test. A variant selected with HC 22 monoclonal antibody (Res 22) was resistant to HC 142 only in VN tests. A mouse-adapted variant of A/USSR/90/77, shown previously to be resistant to HC 22, reacted with HC 142 in a manner similar to that of Res 142-1, Res 142-2 and Res 22.

Virions and intracellular nucleocapsids produced during mixed heterotypic influenza infection of MDCK cells.

Phenotypically mixed virus yields, obtained by coinfection of MDCK cells with influenza A/WSN/33 and B/Lee/40 viruses, contained both A/WSN/33 and B/Lee/40 NP proteins, as revealed by polyacrylamide gel electrophoresis of the purified 14C-amino acids-labeled virus. Virions were lysed with 0.6 M KCl-Triton X-100 buffer, and nucleocapsids were immunoprecipitated with antibodies against NP protein of influenza A virus.

Studies on heterotypic interference between influenza A and B viruses: a differential inhibition of the synthesis of viral proteins and RNAs.

Mixed infection of MDCK cells with influenza A and influenza B viruses leads to a reduction in the rate of synthesis of haemagglutinin (HA) and nucleoprotein (NP) as compared to their rate of synthesis in cells separately infected with these viruses. The reduction is much stronger for influenza A virus proteins. The synthesis of the nonstructural NS1 protein of both viruses is relatively resistant to the heterotypic interference.

Processing of influenza HA protein in MDCK cells: components with different mobilities in polyacrylamide gel electrophoresis and their precursor-product relationships.

In influenza virus-infected MDCK cells labelled with 14C-chlorella hydrolysate or 35S-methionine a virus-specific protein component is revealed migrating slightly faster than HA protein in polyacrylamide gel electrophoresis. Under chase conditions the component disappears either completely or partially, with a concomitant intensification of the HA band. The rate and extent of this transition are strain-dependent.

Herpes simplex virus phosphoproteins. I. Phosphate cycles on and off some viral polypeptides and can alter their affinity for DNA.

We report on phosphorylation, the stability of the bound phosphate, and the properties of several phosphorylated infected-cell polypeptides (ICPs) synthesized in cells infected with herpes simplex virus 1 and 2. Our results and conclusions are as follows. (i) Phosphorylation of ICPs occurs by at least two different pathways.

Structural proteins of infectious bovine rhinotracheitis virus.

Infectious bovine rhinotracheitis (IBR) virus grown in bovine embryo kidney cell cultures was concentrated and purified in Ficoll density gradients. The polypeptide composition of the virus was studied by polyacrylamide gel electrophoresis. The mature virion was found to contain 18 structural proteins with molecular weights from 250,000 to 29,000 daltons; 8 of them were glycosylated.

Strain-specific degradation of a viral glycoprotein in Newcastle disease virus-infected cells.

In cells infected with mesogenic or lentogenic strain of Newcastle disease virus the level of neuraminidase and hemagglutinin activities sharply decreased after the addition of cycloheximide. With two velogenic strains such decreases did not occur. The infected cells were labelled with 14C-amino acids (leucine or valine) and further incubated with an excess of unlabelled precursor.