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H Meier-Ewert

Publications and source records attributed to H Meier-Ewert.

At least 37 records · Page 2Linked to original sources
PubMed1994

Persistent influenza C virus possesses distinct functional properties due to a modified HEF glycoprotein.

A model of long term viral persistence has been established by selecting a spontaneous mutant strain of influenza C/Ann Arbor/1/50 virus in a permanent carrier culture of MDCK cells. Infectivity and cell tropism are mainly determined by the multifunctional viral membrane glycoprotein (HEF). HEF analysis was aimed at identifying a putative correlation between sequence and function, i.e. receptor binding, enzymatic activity, antigenicity and rate of infection. The current experimental picture is summarized by the following findings: (i) C/Ann Arbor/1/50 persistent virus carries a modified receptor-binding sequence, (ii) receptor-binding activity is altered, as indicated by a higher efficiency in recognizing low amounts of the receptor determinant N-acetyl-9-O-acetylneuraminic acid, (iii) direct attachment to cell surfaces differs from that of wild-type virus, as measured by slower kinetics of viral elution, (iv) receptor-destroying enzymatic activity is diminished, (v) characteristic features of virion surface morphology are altered or unstable, (vi) persistent-type HEF epitopes are distinguishable by monoclonal antibodies from wild-type and (vii) viral infectivity is intensified for cells bearing a low number of receptors. The sum of these changes highlights a structurally and functionally modified HEF glycoprotein that allows long term viral persistence. In order to clarify which of the described points are required for the persistent viral phenotype, a working concept is presented.

Animals↗
PubMed1993

Productive and non-productive phases during long-term persistence of influenza C virus.

Persistent infection with a variant of influenza C/Ann Arbor/1/50 virus in MDCK cells has been previously reported. However, the precise molecular mechanism of persistence is still unknown. We show that the release of active progeny virus, as tested for by haemagglutination and acetylesterase profiles, does not take place in freshly seeded MDCK cells. Productive virus replication occurs simultaneously with massive production of structural proteins as shown by immunoprecipitation and immunofluorescence. PCR for the HEF structural protein-encoding segment 4 revealed that positive-sense RNA is present only during virus multiplication whereas negative-sense RNA appears to be constantly detectable. In this study we give initial evidence that influenza C virus can persist in the form of its genomic minus strand RNA, and plus strand transcription, protein synthesis and virus replication remain restricted to productive phases.

Animals↗
PubMed1992

Nucleotide sequence analysis of the HA1 coding portion of the haemagglutinin gene of swine H1N1 influenza viruses.

The nucleotide and deduced amino acid sequences coding for the HA1 portion of the haemagglutinin (HA) genes of three swine influenza viruses were determined and compared with published HA sequence data for human H1N1 influenza viruses. Sequence differences between the classic swine influenza HAs sw37 (A/swine/29/37) and NJ76 (A/New Jersey/11/76) were randomly distributed in the molecule without being confined to antigenic sites. In contrast, sequence differences between the HAs of sw37 and the antigenically atypical strains sw38 (A/swine/Northern Ireland/38) and sw39 (A/swine/Cambridge/39) were clustered in hypervariable regions, similar to the pattern of changes that was present between sw37 and the human strains PR834 (A/PR/8/34) and WSN33 (A/WSN/33). Sequence homologies of the European swine influenza strains (sw38, sw39) were higher with the HAs of the human strains (PR834, WSN33) than with the classic swine influenza HAs (sw37, NJ76). Phylogenetic analysis showed that the HA genes of these two European swine influenza strains emerged from a different evolutionary lineage of H1 HAs than the HAs of classic swine influenza strains.

Amino Acid Sequence↗
PubMed1990

Flow cytometric analysis of virus-infected cells and its potential use for screening antiviral agents.

Virus-infected cells were analyzed using multiparameter flow cytometry. Two virus-cell systems were investigated: HSV-1-infected VF cells and influenza C virus JHB/1/66-infected MDCK cells. Analysis included the measurement of the appearance of virus specific antigens. On individual cells, with polyclonal antibodies, antigens were first detected at 12 h p.i., and the numbers of labeled cells were followed up to 96 h p.i. The efficacy of four antiviral agents was tested with this system. The results were in good agreement with those of plaque reduction tests and indicated that this new method may be extremely useful for the correlation of viral and cellular events with antiviral activity. Finally, it was demonstrated that infected cells in both systems have a considerably greater volume than non-infected cells.

Animals↗
PubMed1990

Fusion characteristics of influenza C viruses.

A number of different influenza C virus strains were tested for their fusion properties using a resonance energy assay which allows direct monitoring of fusion between virus membranes and artificial lipid vesicles. The fusion pH of various strains was found to range between 5.6 and 6.1. Haemolytic activity of the different strains with chicken erythrocytes was observed at slightly lower pH values and varied between 5.1 and 5.7. Studies of the kinetics of influenza C virus fusion showed distinct characteristics in fusion activity. A lag before onset of fusion was found with influenza C virus which was not observed for influenza A or B viruses. In addition, studies on the rate of conformational change of the influenza C virus glycoprotein, as determined by morphological changes and endogenous tryptophan fluorescence, suggest that the conformational change is rate-limiting in the fusion process, whereas for influenza A viruses the glycoprotein conformational change is fast and a later step in the fusion process is rate-limiting. Monitoring the conformational change of influenza C virus glycoprotein by the onset of trypsin susceptibility showed, however, that membrane fusion occurred in some cases without onset of trypsin susceptibility, indicating that the trypsin-susceptible conformation is a post-fusogenic conformation.

Animals↗
PubMed1988

Isolation of the influenza C virus glycoprotein in a soluble form by bromelain digestion.

The spike glycoprotein of influenza C/Johannesburg/1/66 was isolated in a soluble form by digestion of MDCK cell-grown virions with bromelain. The whole ectodomain of the glycoprotein could be recovered with an apparent molecular weight of 75,000 daltons determined in SDS-PAGE. Comparison to Triton X-100-isolated glycoprotein revealed that a C-terminal peptide of 3000-4500 daltons must have remained in the viral membrane. When purified by sucrose density gradient centrifugation the glycoprotein sedimented with a sedimentation coefficient of 10 S, indicating a molecular weight of 206,000 daltons, which is consistent with a trimeric structure of the spike molecule. The trimeric form was stabilized in sucrose gradients by Ca2+ ions. Bromelain digestion of virions with uncleaved glycoprotein, grown in MDCK cells without trypsin, produced two disulphide-linked subunits with similar electrophoretic mobilities in SDS-PAGE to the biologically active glycoprotein. The smaller subunit differed from the product cleaved in vivo (gp 30) by the presence of an additional arginine residue at the N-terminus. The soluble glycoprotein appears to possess both receptor-binding and receptor-destroying enzyme activities, as isolated glycoprotein inhibited hemagglutination of intact influenza C virions and showed RDE activity in an in vitro test. Glycoprotein exposed to low pH, which was sensitive to trypsin digestion, also demonstrated both these biological activities. Glycoprotein-mediated hemolysis could not be observed.

Amino Acid Sequence↗
PubMed1988

Clinical efficacy and tolerance of fleroxacin in patients with urethritis caused by Chlamydia trachomatis.

In an open study, 22 patients with genito-urinary infection by Chlamydia trachomatis were treated with oral fleroxacin in varying dosage. Symptoms were relieved and cultures became negative in 19 patients, with three patients not assessable. Adverse reactions, affecting the central nervous system, the gastrointestinal tract and the skin (photosensitivity), were reported in seven patients.

Anti-Infective Agents↗
PubMed1988

In-vitro activity of fleroxacin against Chlamydia trachomatis.

The in-vitro activities of fleroxacin, tetracycline, erythromycin and clindamycin against two clinical isolates of Chlamydia trachomatis were compared. The MIC of fleroxacin (4.0 mg/l) was comparable to that of clindamycin (2.0 mg/l), but was higher than the MICs of both tetracycline (0.4 mg/l) and erythromycin (0.2-0.4 mg/l). Repeated passaging of C. trachomatis in the presence of sub MIC concentrations of fleroxacin did not affect the MIC and resulted in a rapid and complete loss of inclusions. The effect of combining fleroxacin with the other antibiotics was investigated by chequerboard titrations of pairs of antibiotics. The mean fractional inhibitory concentration index was calculated for each combination. Results showed indifference for the combinations fleroxacin/tetracycline, fleroxacin/erythromycin and fleroxacin/clindamycin and synergism for the combination tetracycline/clindamycin.

Anti-Infective Agents↗
PubMed1984

Influenza-C-virion-associated RNA-dependent RNA-polymerase activity.

The addition of detergent-solubilized influenza C virus to a reaction mixture containing ATP, CTP, GTP, [3H]UTP, and Mg2+ leads to the synthesis of an acid-insoluble, radioactive product, which is ribonuclease-sensitive. The dinucleoside monophosphate ApG clearly enhances the reaction rate, a fact which indicates that influenza C viruses follow the same strategy of transcription as influenza A and B viruses, the other members of the orthomyxovirus family.

Adenosine Monophosphate↗
PubMed1984

3'-Terminal sequences of influenza C virion RNA. Brief report.

The 3'-terminal nucleotides of the genome segments of influenza C/Taylor/47. C/Bavaria/79 and C/Johannesburg/1/66 were identified by two RNA sequencing techniques. These comprised 11 nucleotides (3' UCGUCUUCGUC) which were found to be conserved among the genome segments of each virus.

Base Sequence↗
PubMed1981

Oligonucleotide fingerprint analyses of influenza C virion RNA recovered from five different isolates.

Five different isolates of influenza C virus which were isolated over a period of 32 years and from four different continents were compared by RNA genome oligonucleotide fingerprinting analyses. The earliest isolate of influenza C virus was reported in 1949 by Taylor (19) and served as a reference strain for this study. The results obtained using this technique of comparing relatedness between viruses clearly showed that all strains are distinct. However, the similarities in the pattern of the oligonucleotide fingerprints are marked for the more recent virus isolates (1966-1979), whereas the reference strain C/Taylor shows more pronounced differences. The results are consistent with the high degree of serological crossreaction amongst influenza C viruses isolated over a long period of time, a property which sets this group of viruses apart from type A and B members of the orthomyxoviridae.

Hemagglutination Inhibition Tests↗
PubMed1979

[Immunity against poliomyelitis in the German Federal Republic (author's transl)].

The immunity of the populations of several countries of the GFR against poliovirus 1, 2 and 3 was investigated in 11 laboratories. Sera of 4707 persons aged 0 to 30 years were assessed for neutralising antibodies (serum dilution 1:4) against the 3 types of poliovirus. 34.5% of the 4707 investigated sera had no neutralising antibodies at least against one type of the poliovirus, 4.7% showed no antibodies against all 3 types of the virus. Especially children aged 0 to 4 years were protected incompletely against the 3 types of poliovirus. In comparison with similar investigations of 1969 and 1972 no decisive change of immunity of the population of the GFR against poliomyelitis has occurred.

Adolescent↗
PubMed1979

RNA'S of influenza C virus strains.

Up to 9 RNA segments with molecular weights (MW) 2.3--9.4 X 10(5) were found in an influenza C virus by polyacrylamide gel electrophoresis at 50 degrees C and three different strains. All contained RNA of the same mobility. Possible coding assignments of the RNA segments is discussed.

Electrophoresis, Polyacrylamide Gel↗