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  • 1
    Electronic Resource
    Electronic Resource
    Cross-protection and reassortment studies with avian H2 influenza viruses (2000)
    Springer
    Archives of virology 145 (2000), S. 1059-1066 
    Details
    ISSN: 1432-8798
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary.  In order to assess the degree of immune cross-protection among avian H2 influenza virus strains, mice were immunised with β-propiolactone-inactivated virus preparations and infected intranasally with mouse-adapted variant of A/Black Duck/New Jersey/1580/78 (H2N3) strain. The experiments with 11 avian H2 strains revealed that both Eurasian and American H2 avian influenza viruses exhibit either high or moderate degree of cross-protection. The grouping of the strains in accordance with their cross-protection efficiency does not coincide with H2 phylogenetic branches. Several reassortant clones were obtained with the use of A/Pintail Duck/Primorie/695/76 (H2N3) strain and high-yield X-67 reassortant as parent viruses, among them a high-yield H2N3 reassortant. Taking into account the data on cross-protection among avian H2 strains, the high-yield H2N3 reassortant may be regarded as a prototype strain to be used for the preparation of killed vaccines in the case of a new appearance of avian H2 haemagglutinin in circulation in humans.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007050070109
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  • 2
    Electronic Resource
    Electronic Resource
    Influenza A virus reassortants with surface glycoprotein genes of the avian parent viruses: effects of HA and NA gene combinations on virus aggregation (1993)
    Springer
    Archives of virology 133 (1993), S. 437-450 
    Details
    ISSN: 1432-8798
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A series of 33 human-avian and human-mammalian influenza virus reassortant clones possessing either HA or both HA and NA genes of the avian or mammalian virus was obtained by crosses of A/USSR/90/77 (H1N1) human virus with 5 avian and 1 mammalian influenza virus strains. All of the reasortants possessing NA genes of the H1N1 human parent virus and HA gene of an avian or mammalian parent virus had high values of infectivity/HA activity ratio. Since this feature could result from a limited virion aggregation, several reassortants were analyzed by velocity sucrose gradient centrifugation. In all cases tested, the reassortants of H3N1, H4N1, H10N1 and H13N1 composition were shown to be aggregated, whereas the preparations of the parent H1N1 virus and the reassortants possessing both HA and NA genes from the avian parents were represented mostly by single virions. The aggregates were formed at 4°C and dissociated at 37°C. The dissociation was blocked by an inhibitor of neuraminidase activity (2-deoxy-2,3-dehydro-N-acetyl-neuraminic acid). The dissociation was reversible since the virions reaggregated at 4°C; however, treatment with bacterial neuraminidase led to an irreversible dissociation of the aggregates. The tendency of the reassortants to aggregate correlates with an increased infectivity/HA ratio. No regular decrease in the neuraminidase activity in the virions of reassortants as compared to the parent H1N1 virus was revealed. The most likely explanation of the observed phenomenon seems to be an inefficient removal of sialic acid residues from the avian virus hemagglutinin by the human virus N1 neuraminidase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01313781
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  • 3
    Electronic Resource
    Electronic Resource
    Studies on the regulation of influenza virus RNA replication: a differential inhibition of the synthesis of vRNA segments in shift-up experiments withts mutants (1991)
    Springer
    Archives of virology 121 (1991), S. 9-17 
    Details
    ISSN: 1432-8798
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The regulation of influenza virus vRNA synthesis in the course of the reproduction cycle was studied with the use of a series ofts mutants in shift-up experiments. The synthesis of vRNA segments was registered by means of polyacrylamide gel electrophoresis of nucleocapsid-associated RNA isolated from the infected cells labelled with [3H]uridine after the shift-up to a semipermissive temperature. Each mutant exhibited a specific differential pattern of vRNA synthesis inhibition after the shift-up. The most affected segments were either vRNA 4, vRNAs 4 and 7, or vRNAs 4, 6, and 7 in cells infected, respectively, withts mutants C15 (ts lesion in PB1 gene), C45 (ts lesion in PA gene) and CmN3 (ts lesion in NS gene). The synthesis of vRNAs 1, 2, and 3 was relatively resistant to the shift-up in the cells infected with C15 or C45 and more sensitive in the cells infected with C44 (ts lesion in PB2 gene) or CmN3. The replication of the “early” genes (vRNAs 5 and 8) was generally least affected by the shift-up. The results are discussed in connection with the “early-late” transition of vRNA synthesis pattern in the course of infection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01316740
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  • 4
    Electronic Resource
    Electronic Resource
    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 (1986)
    Springer
    Archives of virology 90 (1986), S. 237-248 
    Details
    ISSN: 1432-8798
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The original influenza virus strain A/USSR/90/77 (H1N1) 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01317373
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  • 5
    Electronic Resource
    Electronic Resource
    Sedimentation and hybridization analysis of virus-specific RNA in the course of Newcastle disease virus replication cycle (1972)
    Springer
    Archives of virology 38 (1972), S. 183-191 
    Details
    ISSN: 1432-8798
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Self-annealing of 50 S virion RNA of Newcastle disease virus (egg-grown Beaudette strain) reveals no complementary base sequences. Virus-induced 18 S RNA consists exclusively of „minus“ strands,i.e. base sequences complementary to virion RNA. In 22 S RNA a small amount of “plus” strands is revealed both by annealing with an excess of virion RNA and by self-annealing. The sedimentation pattern of virus-specific RNA varies in the course of infection: an increase in the overall rate of synthesis towards the end of the reproduction cycle is due predominantly to the synthesis of smaller (18–35 S) RNA species. The content of “plus” strands in virus-induced RNA as revealed by self-annealing seems to depend mostly on the duration of exposure of cells to actinomycin D and not on the stage of infection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01249669
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