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A A Shilov

Publications and source records attributed to A A Shilov.

At least 19 recordsLinked to original sources
PubMed2005

Postreassortment changes in a model system: HA-NA adjustment in an H3N2 avian-human reassortant influenza virus.

In our previous studies we described the postreassortment changes in the hemagglutinin (HA) of H2N1, H3N1, H4N1 and H13N1 influenza A virus reassortants with HAs derived from avian viruses and low-functional neuraminidase (NA) of a human parent virus A/USSR/90/77 (H1N1). The changes involved amino acid substitutions that increased the negative local charge in the vicinity of the receptor-binding pocket and decreased the affinity of HA to sialic acid receptors. In the present report we describe the studies performed with H3N2 reassortant viruses having HA of A/Duck/Ukraine/1/63 (H3N8) virus and NA of A/Aichi/2/68 (H3N2) virus. Amino acid changes in the HA gene registered in virus variants selected in the course of serial passages resulted in a decrease in the affinity to sialic acid-containing substrates and cell receptors. However, the decrease was less expressed than in the reassortants containing the low-functional NA of N1 subtype described in our earlier studies, and the amino acid changes were not necessarily associated with an increase of negative charge. In one passage variant an amino acid substitution in NA was detected. The relevance of these results for the evolution of the H3N2 virus of the 1968 pandemic is discussed.

Amino Acid Substitution↗
PubMed2004

[Size of viable myocardium and collateral blood flow in patients with coronary artery occlusion].

The aim of the study was to investigate correlation between collateral blood flow to occluded coronary vessel and the size of viable myocardium in the area fed by that artery. Total 295 patients with coronary artery occlusion were divided into 2 groups. The 1st group included 193 patients with the history of Q-wave myocardial infarction (MI), the 2nd group - 102 patients with non-Q-wave MI or without MI. Left ventriculography evidenced lesser volume of viable myocardium in the 1st group compared with the 2nd. All patients were assessed for collateral blood flow (CBF) to occluded vessel. There was significantly higher incidence of minor (grade I) or absent (grade 0) CBF in the 1st group - 71 (36.9%) and 10 (5.1%) cases, respectively - compared with the 2nd group - 15 (14.7%) and 0 (0%) cases, respectively (p<0.05). Unlike this, satisfactory (grade II) and good (grade III) CBF to distal segments of occluded artery was more frequent in the 2nd group - 71 (69.6%) and 16 (15.7%) cases, respectively, compared with the 1st group - 102 (52.9%) and 10 (5.1%) cases, respectively (p<0.05). The authors conclude that evaluation of CBF level can complement the assessment of viable myocardium in the occluded coronary artery area, and the presence of the II-III grade CBF can support the necessity of occluded vessel angioplasty.

Adult↗
PubMed2003

[Acute diffuse thrombosis of left coronary artery complicating coronary angioplasty].

The paper presents a case report for successful treatment of acute diffuse thrombosis developed in left coronary artery after coronary angioplasty fulfilled for 39-year-old patient with acute coronary syndrome. Heparin resistance accompanied by intracoronary intervention triggered severe ascending thrombosis of the whole anterior descending artery with involvement of circumflex artery ostium. Therapeutic measures included: repeated Heparin bolus injection (total 27,000 U), bolus intracoronary Streptokinase injection (500,000 U) with subsequent Streptokinase infusion (1,000,000 U in 1 hour), stenting of circumflex artery ostium for thrombus mechanical destruction. This enabled us to restore adequate coronary flow and to resolve critical condition with minimal loss (periprocedural complication - repeated non-Q wave myocardial interfaction).

Acute Disease↗
PubMed2000

Intergenic HA-NA interactions in influenza A virus: postreassortment substitutions of charged amino acid in the hemagglutinin of different subtypes.

In our previous studies influenza A virus reassortants having neuraminidase (NA) gene of A/USSR/90/77 (H1N1) strain and hemagglutinin (HA) genes of H3, H4 and H13 subtypes were shown to produce a low virus yield and to exhibit a strong tendency to virion aggregation. More detailed studies with the use of a H3N1 reassortant and its high-yield non-aggregating variants revealed that NA of A/USSR/90/77 strain is inefficient in the removal of the terminal sialic acid residues from the virion components, and that the inefficiency of NA may be compensated by mutations in HA gene leading to a decrease of the receptor-binding affinity (Kaverin, N.V. , Gambaryan, A.S., Bovin, N.V., Rudneva, I.A., Shilov, A.A., Khodova, O.M., Varich, N.L., Sinitsin, B.V., Makarova, N.L., Kaverin, N.V., 1998. Postreassortment changes in influenza virus hemagglutinin restoring HA-NA functional match, Virology 244, 315-321). The present report describes studies performed with the use of H2N1 and H4N1 reassortants having HA genes of A/Pintail/Primorie/695/76 (H2N3) and A/Duck/Czechoslovakia/56 (H4N6) strains respectively and NA gene of A/USSR/90/77 strain. The low-yield reassortants and their high-yield non-aggregating variants were studied in both direct and competitive binding assays with sialic acid-containing substrates. The non-aggregating variants were shown to have a decreased affinity as compared to the initial reassortants toward high-molecular-weight sialic acid-containing substrates. The sequencing of HA genes revealed that all non-aggregating variants of H2N1 and H4N1 reassortants had amino acid substitutions increasing the negative charge of the HA molecule in the vicinity of the receptor-binding pocket. The results suggest that the influenza virus reassortants containing low-functional NA undergo similar postreassortment changes irrespective of the HA subtype: their receptor-binding activity decreased due to negatively charged amino acid substitutions in the vicinity of the receptor-binding pocket.

Amino Acid Substitution↗
PubMed1998

Effects of host-dependent glycosylation of hemagglutinin on receptor-binding properties on H1N1 human influenza A virus grown in MDCK cells and in embryonated eggs.

There is growing evidence that the receptor-binding characteristics of influenza viruses are affected by the host-dependent glycosylation of viral hemagglutinin (HA). To better understand these effects, we propagated two variants of the human influenza virus USSR/90/77 (which differed by the mutation Asn131 reversible Asp131 in the glycosylation sequon of their HA) in either embryonated chicken eggs or MDCK cell. Those variants were then compared for their ability to bind soluble receptor analogs and to attach to receptors represented on a solid phase. The carbohydrate chain at position 131 of the HA (CHO 131) interfered with virus binding to soluble Sia2-6Gal-containing macromolecular receptors, but had little or no effect on its binding to Sia2-3Gal-containing macromolecules. This specificity could be explained by the different orientation of the asialic parts of the 2-3-linked sialosides versus 2-6-linked sialosides with respect to the receptor-binding site (Eisen et al., 1997, Virology 232, 19-31). In the case of virus attachment to solid-phase immobilized receptors, MDCK-grown viruses bound substantially more weakly than their egg-grown counterparts to receptors of avian origin, whereas binding to mammalian cell membranes was only marginally affected by differences in host-specific glycosylation of the virus. Our data indicated that the effects of the carbohydrate side chain of HA on virus receptor-binding activity are dependent on both the cells in which the virus was grown and the nature of the cellular receptors or intercellular inhibitors to which the virus binds.

Animals↗
PubMed1998

Postreassortment changes in influenza A virus hemagglutinin restoring HA-NA functional match.

An important function of influenza virus neuraminidase (NA) is the removal of sialic acid residues from virion components in order to prevent the aggregation of virus particles. In previous communications we have reported that reassortant viruses containing the NA gene of A/USSR/90/77 (H1N1) virus and HA genes of H3, H4, H10, or H13 subtypes had a tendency to virion aggregation at 4 degrees C and that the virion clusters irreversibly dissociated after the treatment with bacterial neuraminidase. It was concluded that in such reassortants the removal of sialic acid residues is inefficient. Nonaggregating variants of the reassortants were selected in the course of serial passages in embryonated chicken eggs. In the present paper a reassortant virus, R2, having the HA gene of A/Duck/Ukraine/1/63 (H3N8) virus and the other genes of A/USSR/90/77 (H1N1) virus, as well as its non-aggregating passage variants and both parent viruses, have been studied in order to reveal the presence of unremoved sialic acid residues in the virions. An assay of sialic acid content by high-performance liquid chromatography with fluorescent detection has revealed the presence of sialic acid in the purified virus preparations of A/USSR/90/77 (H1N1) virus and the R2 reassortant and its nonaggregating variants, whereas only trace amounts of sialic acid have been detected in the A/Duck/Ukraine/1/63 (H3N8) parent virus. The data obtained with the use of the labeled "indicator" virus suggest that the unremoved sialic acid residues are present at the virion surface. The nonaggregating variants have been shown to possess a lower affinity toward high-molecular-weight sialic acid-containing substrates compared to the initial reassortant R2. Sequencing of HA genes has revealed amino acid changes in the nonaggregating variants compared to the initial reassortant. One substitution, N248D in HA1, is the same in two independently selected nonaggregating variants. The presented data suggest that the complete removal of sialic acid residues by viral NA from the virion components is not obligatory for the absence of virus particle aggregation: the latter may be achieved (in the reassortants and, presumably, in the wild-type virus) through a balance between the degree of HA affinity toward the sialic acid-containing receptors and the extent of the removal of sialic acid residues by NA.

Amino Acid Substitution↗
PubMed1990

Mapping mutations in influenza A virus resistant to norakin.

To elucidate the mode of action of norakin against influenza A virus we sequenced the hemagglutinin gene of 11 norakin-resistant mutants. Resistance was coupled with 1-3 amino acid exchanges. The majority of mutations was localized in the HA2 polypeptide and was mostly associated with changes in charge or polarity of the amino acids. The amino acid substitutions are discussed in the context of the 3D structure of X31 hemagglutinin considered to be representative of the influenza hemagglutinins. Most of the mutations appear to destabilize the pH 7.0 structure by distorting or destroying hydrogen bonds as well as salt-bridges which are responsible for intra- and intersubunit contacts, while others destabilize the location of the fusion peptide, facilitating conformational changes in the presence of the inhibitor.

Amino Acids↗
PubMed1988

Multicopy expression vector based on temperature-regulated lac repressor: expression of human immunodeficiency virus env gene in Escherichia coli.

A new expression vector (pBB1) has been constructed for the regulated expression of genes in Escherichia coli. Based on the pUC plasmids, the pBB1 carries lacIts allele of the lac repressor gene. This makes it possible to control expression of cloned genes by shifting the temperature from 30 degrees C to 42 degrees C. Thus the vector combines advantages of the pUC plasmids with convenient regulation by temperature. Expression of a fragment of HIV-1 env gene was achieved with the help of this vector and shown by enzyme-linked immunosorbent assay and Western-blot analysis.

Blotting, Western↗
PubMed1985

Comparative studies of A/Leningrad/134/57 wild-type and 47-times passaged cold-adapted mutant influenza viruses: oligonucleotide mapping and RNA-RNA hybridization studies.

Direct biochemical evidence for the existence of mutations in five of the RNA segments of the A/Leningrad/134/57 cold-adapted 47th passage mutant as compared with its wild-type progenitor has been obtained using two techniques. T1 oligonucleotide mapping of total viral RNA as well as of individual RNA segments revealed changes in RNAs 4, 5 and 6. Analysis of S1 nuclease-treated RNA-RNA hybrids on polyacrylamide gels revealed changes in at least one of the polymerase genes as well as in RNAs 4, 5, 6 and 7. These findings provide a direct demonstration for the existence of multiple mutations in the cold-adapted mutant vaccine strain.

Cold Temperature↗
PubMed1981

On the origin of the H1N1 (A/USSR/90/77) influenza virus.

The influenza virus H1N1 (the A/USSR/90/77 strain) that reappeared in 1977 after the H1N1 influenza viruses had disappeared from the human population, is compared with the A/FM/1/47 and the A/FW/1/50 influenza viruses by the method of oligonucleotide mapping of individual segments of the viral RNAs. Seven genes of the A/USSR/90/77 virus appear to be very similar to the corresponding genes of the A/FW/1/50 virus, whereas the gene coding for the M protein displays considerable homology to the corresponding gene of the A/FM/1/47 virus. The data demonstrate that the A/USSR/90/77 strain is a recombinant virus.

Genes, Viral↗