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N V Kaverin

Publications and source records attributed to N V Kaverin.

At least 37 records · Page 2Linked to original sources
PubMed1991

[The role of polymerase protein genes of influenza A virus in the transition from the early to late stage of replication].

Regulation of influenza virus RNA replication was studied with the use of A/FPV/Rostock/34 strain ts-mutants. Mutants C44, C15, C45 possessing the ts-defects in the PB2, PB1 and PA genes respectively were used for the infection of chick embryo cultured cells and H-uridine-labelled nucleocapsid-associated RNA was analysed in polyacrylamide gel electrophoresis to assess the kinetics of vRNA synthesis. A typical early-late transition of the pattern of vRNA synthesis was observed in the cells infected with C44, whereas the other two mutants exhibited a slightly changed (C15) or strongly distorted (C45) pattern. In shift up experiments after the transfer to non-permissive temperature all the mutants exhibited partial reversion to an early pattern of vRNA synthesis. The results are discussed in connection with the mechanism of the early-late transition of influenza virus-specific RNA synthesis.

Autoradiography↗
PubMed1991

[Analysis of the reassorted influenza virus clone genome: data for use of ordered selection of RNA segments].

Chicken embryonated eggs were coinfected with influenza A/FPV/Rostock and A/FPV/Weybridge strains. 25 plaque isolates were obtained from the mixed yield and their genetic content was analysed by polyacrylamide gel electrophoresis of H3-uridine-labelled vRNA in a modified gel system. At least 18 clones out of 25 plaque isolates proved to be reassortants; however, only one among them contained the homologous RNA-segments belonging to both parents. The results are in agreement with the concept of an ordered recruitment of vRNA-segments into virions.

Animals↗
PubMed1989

Studies on the genetic basis of human influenza A virus adaptation to mice: degrees of virulence of reassortants with defined genetic content.

A highly virulent mouse-adapted variant of influenza virus A/Aichi/2/68 (H3N2) was crossed either with the original A/USSR/90/77 (H1N1) influenza virus strain or with its mouse-adapted, moderately mouse virulent variant. The reassortants were characterized with respect to their genetic content and pneumovirulence for mice. The reassortants fell into three categories: avirulent, highly virulent (resembling in this respect the parent A/Aichi/2/68 virus) and moderately virulent (resembling the mouse-adapted A/USSR/90/77 parent virus). The analysis of the parental origin of the genes of 6 reassortants allowed to suggest that changes in the HA gene and in a polymerase gene (most likely, PB1) were necessary for the acquisition of virulence by the A/USSR/90/77 virus in the course of adaptation to mice, whereas the changes in two other polymerase genes as well as in the genes NA and NS were not involved. The low degree of pathogenicity characteristic of the mouse-adapted A/USSR/90/77 virus was determined by gene(s) other than HA.

Adaptation, Physiological↗
PubMed1989

[Synthesis of virus-specific RNA in cells infected with influenza B virus].

Synthesis of virus-specific RNA in cells infected with influenza B virus was studied by means of PAGE analysis of RNA hybrid duplexes or nucleocapsid-associated RNA. A switch from an "early" to "late" pattern was registered in the relative rates of synthesis of the corresponding mRNA as well as in the synthesis of vRNA segments 7 and 8. Contrary to the pattern described earlier for influenza A virus, the relative rate of synthesis of mRNA 5 was increased at the late stage of the replication cycle; besides, the efficiency of transcription of the polymerase genes was higher. Partial suppression of protein synthesis with moderate concentration of cycloheximide at a late stage of infection resulted in a differential inhibition of vRNA segments synthesis and stimulation of mRNA synthesis, leading to restoration of an "early" pattern in both cases. The results confirm the general outline of regulation as presented for influenza A virus in an earlier publication and reveal several peculiarities in regulation of influenza B viral RNA synthesis.

Animals↗
PubMed1988

Human-avian influenza virus reassortants: effect of reassortment pattern on multi-cycle reproduction in MDCK cells.

Human-avian influenza reassortants possessing the HA gene of the avian parent virus were tested for their ability to replicate in MDCK cells at 37 degrees C and 31 degrees C. Both avian parent viruses, A/Duck/Ukraine/1/63 (H3N8) and A/Duck/Hoshimin/014/78 (H5N3) induced an efficient multi-cycle infection at 37 degrees C, but replicated poorly at 31 degrees C, whereas the human parent virus, MDCK-adapted variant of A/USSR/90/77 (H1N1) strain, replicated efficiently at both temperatures. The reassortant clone possessing the HA gene of A/Duck/Ukraine/1/63 virus and the other 7 genes of A/USSR/90/77 virus replicated at both temperatures almost as efficiently as the human parent virus. Among the reassortants between A/Duck/Hoshimin/014/78 and A/USSR/90/77, the clones possessing the HA and NA genes of the avian strain, or the HA, NA, NP, and NS genes of the avian strain, and the other genes of the human parent virus, replicated poorly at both temperatures, especially at 31 degrees C, whereas the reassortant possessing the HA, NA, and M genes of the avian virus replicated at both temperatures fairly efficiently. The results are discussed in connection with the limitations imposed by different genes upon avian influenza viruses' ability to replicate in mammalian cells.

Animals↗
PubMed1988

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. The lysates were immunoprecipitated with antihemagglutinin antibodies specific for one of the co-infecting viruses. The immunoprecipitates were analysed by PAGE. Cells infected separately with each virus and mixed before lysis were used as a control sample in every experiment. In the lysates of cells doubly infected with H2 and H5 influenza viruses the analysis revealed the presence of structures containing HA monomers of both viruses, whereas no such structures were revealed in the lysate of a mixture of separately infected cells. Mixed structures (most likely HA trimers containing monomers of the two co-infecting viruses) were also found in the lysates of cells doubly infected with strains belonging to H1 and H2 subtypes. No such structures were revealed when the cells were co-infected with viruses belonging to H1 and H3 subtypes or H3 and H7 subtypes. The results suggest an extensive formation of mixed HA trimers in the course of double infection with viruses belonging to closely related subtypes, whereas the formation of mixed trimers by more distantly related HA monomers does not occur or is very scarce. The identity of the mixed structures as HA trimers was confirmed by immunoprecipitation experiments with 9S structures.

Amino Acid Sequence↗
PubMed1988

[Role of the NS gene in regulating the synthesis of RNA-segments of the influenza A virus].

To find the role of any influenza virus gene in regulation of the RNA-segments replication the transfer of ts-mutants to nonpermissive temperature on the late step of infection has been used (shift-up). The mutants having impaired the NS or NP-genes have been obtained and studied. The transfer of mutants to partially nonpermissive conditions (when the amount of replication is decreased, but it still continues) results in the distinct return to the early mode of replication in ts-mutant with the mutation in NS-gene. This suggests the NS-gene role in replication of viral RNA-segments, in particular, in the switch from the "early" stage of replication to the "late" one. In NP-gene mutant only the decrease in general replication takes place without the shift to "early" replication mode.

Electrophoresis, Polyacrylamide Gel↗
PubMed1988

[Genetic basis of influenza virus virulence: gene composition and virulence of reassortants between mouse-adapted and nonadapted strains from different subtypes].

Reassortment analysis of the pneumovirulence for mice marker of influenza virus has been performed. The original A/USSR/90/77 (H1H1) influenza virus strain or its mouse-adapted variant were crossed with a variant of A/Aichi/2/68 (H3N2) influenza virus highly virulent for mice. The reassortant having HA gene of the original A/USSR/90/77 virus and the other genes of the highly virulent A/Aichi/2/68 strain was avirulent for mice, whereas a similar reassortant possessing HA gene of the mouse-adapted A/USSR/90/77 strain was as virulent as A/Aichi/2/68 parent virus. The reasortant having HA and M genes of A/Aichi/2/68 and other genes of the mouse-adapted A/USSR/90/77 was moderately virulent, resembling in this respect the latter parent. The data indicates that changes in the different genes in course of viral adaptation to mice result in a differential acquisition of virulence for mice.

Adaptation, Biological↗
PubMed1988

[Regulation of synthesis of virus-specific RNA in cells infected with influenza virus].

Interrelationships between the level of protein synthesis and the pattern of virus-specific transcription in influenza virus-infected cells have been studied with the use of a wide range of concentrations of a protein synthesis inhibitor (cycloheximide). The obtained data reveal a predominant stimulation of the transcription for some viral genes by partial suppression of protein synthesis. The data also suggest the existence of cRNA (full transcripts) synthesis regulation, in addition to the regulation of vRNA and mRNA synthesis described earlier.

Animals↗
PubMed1988

[Properties of reassortants of human and avian influenza viruses. Reproduction in MDCK cells at suboptimum temperatures].

A series of reassortants has been constructed by crossing of UV-inactivated avian influenza virus of H3N8 subtype and live human influenza virus of H1N1 subtype, adapted to growth in continuous canine kidney cell line (MDCK). The analysis of RNA duplexes has shown that the reassortants contain HA gene of avian influenza virus whereas the other genes belong to human parent virus. The reassortants were efficiently reproduced in MDCK cells at low temperature (limiting for the avian parent virus). The data suggest that the avian virus HA gene does not hamper the reproduction of reassortant viruses in mammalian cells under the conditions unfavorable for the multiplication of avian influenza subtype H3N8 viruses.

Animals↗
PubMed1987

Regulation of the replication of influenza virus RNA segments: partial suppression of protein synthesis restores the 'early' replication pattern.

The replication of influenza virus RNA was monitored by RNA-RNA hybridization with subsequent analysis of hybrid duplexes, as well as by immunosorption of viral nucleocapsids from extracts of [3H]uridine-labelled cells followed by the isolation and characterization of nucleocapsid-associated RNA. The nucleocapsid-associated RNA preparations contained mostly negative-strand genomic RNA. Electrophoresis of the hybrid RNA duplexes or single-stranded nucleocapsid-associated RNA in polyacrylamide gel revealed an 'early' replication pattern, with a predominance of the NP and NS gene segments, in cells labelled from 0 to 1 h post-infection. At later stages of infection the pattern changed to the 'late' one, with the M gene segment in excess of NS, and the NP gene no longer predominant. Cycloheximide added as late as 2 or 3 h post-infection suppressed RNA replication. Moderate concentrations of cycloheximide inhibited the replication of NS and NP gene segments to a lesser degree than the replication of the other RNA segments, thus restoring the 'early' replication pattern. Cycloheximide treatment resulted in a slight increase in the percentage of positive strands in nucleocapsid-associated RNA. The role of protein synthesis in the transition from the 'early' to the 'late' pattern of influenza virus RNA synthesis is discussed.

Animals↗
PubMed1987

[Formation of mixed hemagglutinin trimers during double infection with influenza virus strains of the same subtype].

Formation of hemagglutinin spikes in the course of the mixed infection of cell culture by two influenza virus strains belonging to the same antigenic subtype or to different subtypes was studied by means of immunoprecipitation of [14C]-labelled hemagglutinins from cell lysates. The immunoprecipitates were further analysed by polyacrylamide gel electrophoresis. Lysates of separately infected cells mixed before lysis were used as control samples. The analysis of immunoprecipitates revealed the formation of chimeric hemagglutinin spikes in the cells infected by the strains possessing hemagglutinins of the same subtype but not in the cells infected by the strains of different subtypes (H1 and H3). The results are discussed in connection with the homology of amino-acid sequences of influenza virus hemagglutinins.

Amino Acid Sequence↗
PubMed1986

Studies on the genetic determinants of influenza virus pathogenicity for mice with the use of reassortants between mouse-adapted and non-adapted variants of the same virus strain.

The original influenza virus strain A/USSR/90/77 (H 1 N 1) and its mouse-adapted variant, differing in their reactivity with anti-hemagglutinin monoclonal antibodies HC 22 and HC 124, were crossed in MDCK cells and in chicken embryos, and 21 clones were isolated by non-selective random cloning. In all the clones the virulence for mice was found to be linked to the antigenic specificity of hemagglutinin (HA). An independent marker, formation of filamentous forms, was reassorted with an expected frequency. In the crosses between UV-irradiated mouse-adapted variant and live non-adapted strain, with selection of clones by a mixture of monoclonal antibodies discriminating between HA of the two variants, virulence also was linked to HA gene. On the contrary, in the experiments with A/Aichi/2/68 (H 3 N 2) strain and its mouse-adapted highly virulent variant these two characteristics--virulence and HA antigenic specificity--could be dissociated. A pathogenic clone having HA of the non-adapted strain was readily obtained; its virulence, however, was weaker than that of the mouse-adapted parent. In the inter-subtypic crosses between A/USSR/90/77 and A/Aichi/2/68 the transfer of the HA gene of the mouse-adapted A/Aichi/2/68 did not confer virulence to the reassortant. The results are discussed in terms of the genetic basis of virulence acquired in the course of influenza virus adaptation to a new host.

Animals↗
PubMed1986

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. Another monoclonal antibody, HC 125, behaved similarly to HC 142. The addition of anti-immunoglobulin serum restored the ability of HC 142 and HC 125 (already bound to the virus) to neutralize the infectivity of the resistant variants. Polyacrylamide gel electrophoresis revealed differences in the mobility of haemagglutinin among the variants.

Antibodies, Monoclonal↗
PubMed1985

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. Polyacrylamide gel electrophoresis of the immunoprecipitate revealed NP protein of A/WSN/33 but not of B/Lee/40 virus. However, in similar experiments with the lysates of doubly infected cells, the band of B/Lee/40 NP protein was revealed in the polyacrylamide gel electrophoresis patterns of the immunoprecipitates. In an attempt to analyze the RNA content of the immune complexes, we absorbed the lysates of doubly infected [3H]uridine-labeled cells with protein A-containing Staphylococcus aureus covered with antibodies against the NP protein of influenza A virus. RNA extracted from the immune complexes contained genomic RNA segments of both A/WSN/33 and B/Lee/40 viruses. In control samples containing an artificial mixture of cell lysates separately infected with each virus, the analysis revealed homologous components (i.e., A/WSN/33 NP protein or RNA segments) in the immune complexes. The results suggest the presence of phenotypically mixed nucleocapsids in the cells doubly infected with influenza A and B viruses; in the course of the virion formation, the nucleocapsids lacking the heterologous NP protein are selected.

Animals↗