Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.4 (trypsin)
 42,187 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The infectivity of influenza A viruses like fowl plague virus (FPV) with a cleaved hemagglutinin (HA) is highly sensitive to treatment at pH 5, while strains like PR 8 or virus N with a noncleaved HA survive under this condition. After double infection of chick embryo cells with FPV and PR 8 or virus N, the yield of virus with the HA gene of FPV is greatly reduced. However, it can now survive treatment at pH 5, and the surviving FPV particles form plaques only in the presence of trypsin, indicating that they were coated by the HA of PR 8 or virus N, depending on the coinfecting virus. The results are discussed with respect to the build-up and maintenance of a large reservoir of nonpathogenic influenza A viruses with noncleavable HA in water fowl.
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PMID:Interference between influenza A viruses with a cleavable and a noncleavable hemagglutinin; pH-stability after mixed infection. 341 77

Normal guinea-pig serum (GPS) lacking detectable antiviral antibody efficiently neutralized the infectivity of influenza B virus grown in chick embryos or MDCK cells. The inhibitor was heat-labile and sensitive to trypsin digestion. This beta-like inhibitor required Ca2+ and the complement components C1 and C4 for its activity. In contrast, GPS did not inactivate influenza A virus. Influenza B virus from which the neuraminidase activity of the spikes on the viral envelope had been eliminated by trypsin digestion was also inactivated to a level comparable to untreated virus. Complement component C1 alone bound directly to influenza B virus and inhibited its haemagglutinin activity. We suggest that the beta-like inhibitor in GPS is a component of the classical complement pathway which is triggered by the protein moiety of influenza B virus haemagglutinin, leading to virus neutralization.
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PMID:Inactivation of influenza B virus by normal guinea-pig serum. 357 57

Comparative sequence analysis of the hemagglutinin (HA) genes of a highly virulent H5N8 virus isolated from turkeys in Ireland in 1983 and a virus of the same subtype detected simultaneously in healthy ducks showed only four amino acid differences between these strains. Partial sequencing of six of the other genes and antigenic similarity of the neuraminidases established the overall genetic similarity of these two viruses. Comparison of the complete sequence of two H5 gene sequences and partial sequences of other virulent and avirulent H5 viruses provides evidence for at least two different lineages of H5 influenza virus in the world, one in Europe and the other in North America, with virulent and avirulent members in each group. In vivo studies in domestic ducks showed that all of the H5 viruses that are virulent in chickens and turkeys replicate in the internal organs of ducks but did not produce any disease signs. Additionally, both viruses isolated from turkeys and ducks in Ireland were detected in the blood. These studies provide the first conclusive evidence for the possibility that fully virulent influenza viruses in domestic poultry can arise directly from viruses in wild aquatic birds. Studies on the cleavability of the HA of virulent and avirulent H5 viruses showed that the principles established for H7 viruses (F. X. Bosch, M. Orlich, H. D. Klenk, and R. Rott, 1979, Virology 95, 197-207; F. X. Bosch, W. Garten, H. D. Klenk, and R. Rott, 1981, Virology 113, 725-735) also apply to the H5 subtype. These are (1) only the HAs of virulent influenza viruses were cleaved in tissue culture in the absence of trypsin and (2) virulent H5 influenza viruses contain a series of basic amino acids at the cleavage site of the HA, whereas avirulent strains contain only a single arginine with the exception of the avirulent Chicken/Pennsylvania virus. Thus, a series of basic amino acids at the cleavage site probably forms a recognition site for the enzyme(s) responsible for cleavage.
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PMID:Molecular analyses of the hemagglutinin genes of H5 influenza viruses: origin of a virulent turkey strain. 357 72

The anticholinergic anti-parkinsonism drug Norakin is an inhibitor of influenza virus multiplication. By crossing a Norakin-resistant variant of fowl plague virus (FPV) strain Weybridge with the sensitive FPV/Rostock/34 wild-type virus, Norakin-resistant recombinants were obtained. Analyses of the gene composition showed that all Norakin-resistant recombinants had inherited their haemagglutinin gene from the Norakin-resistant parent strain. The majority of the recombinants had received all the other gene segments from the sensitive parent strain. Norakin was shown to inhibit red blood cell lysis induced either by purified virions or by the haemagglutinin of a sensitive FPV strain at low pH, but failed to affect the Norakin-resistant FPV variant. No aggregation of autoliposomes containing the haemagglutinin of a sensitive FPV strain or digestion of the HA1 subunit of haemagglutinin by trypsin occurred in the presence of Norakin at acid pH. The data suggest that the haemagglutinin of FPV is the target for the antiviral activity of Norakin, which acts by inhibiting the conformational change in the haemagglutinin at acid pH important for lysis.
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PMID:Haemagglutinin of influenza A virus is a target for the antiviral effect of Norakin. 371 65

A cell-free assay has been developed for the delivery of influenza virus neuraminidase to the plasma membrane. Two types of postnuclear supernatant, which acted as donor and acceptor of the enzyme, were prepared from baby hamster kidney cells. Donor preparations were obtained from cells infected with influenza virus and containing neuraminidase en route to the plasma membrane. Acceptor preparations were obtained from cells containing, bound to their plasma membranes, Semliki Forest virus with envelope glycoproteins bearing [3H]N-acetylneuraminic acid. Fusion between vesicles from these two preparations permits access of the enzyme to its substrate, which results in the release of free [3H]N-acetylneuraminic acid. This release was detected through the transfer of radioactivity from a trichloroacetic acid-insoluble to a trichloroacetic acid-soluble fraction. An ATP-dependent component of release was found, which appears to be a consequence of vesicle fusion. This component was enhanced when the donor was prepared from cells in which the enzyme had been concentrated in a compartment between the Golgi complex and the plasma membrane, which indicates that a specific exocytic fusion event has been reconstituted. The extent of fusion is greatly reduced by pre-treatment of donor and acceptor preparations with trypsin, which points to the involvement of proteins in the fusion reaction.
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PMID:A cell-free assay for the insertion of a viral glycoprotein into the plasma membrane. 378 85

We have developed a convenient method for assaying the receptor-destroying enzyme (RDE) activity of influenza C virus. This method measures the ability of the RDE to destroy the hemagglutination-inhibition activity of a potent inhibitor present in rat serum. Some physico-chemical properties of the RDE of influenza C virus were investigated by using this method. The temperature optimum for maximal activity of this enzyme was found to be 45 C to 53 C. There was little difference in thermostability between the RDE and hemagglutinating activities of influenza C virus. When influenza C virions were treated with various concentrations of trypsin, the RDE activity decreased in parallel with the decrease in the amount of residual gp88 glycoprotein, suggesting association of RDE with this glycoprotein.
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PMID:An assay for the receptor-destroying activity of influenza C virus. 383 20

In developing countries it is often impractical to use conventional methods to isolate and identify influenza viruses. The use of trypsin-treated LLC-MK2 cells for the isolation of myxoviruses, in conjunction with the indirect fluorescent antibody technique for identification of isolates and for direct detection of viral antigens in specimens, was an effective combination of techniques which enabled our laboratory in Papua New Guinea to participate in an influenza surveillance programme. The application of these techniques in routine respiratory virus surveillance and in the investigation of an outbreak of influenza-like illness is described.
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PMID:Influenza surveillance: alternative laboratory techniques for a developing country. 387 37

MDCK, HeLa, L or primary chick embryo cells were infected with different influenza A virus strains and labelled with [32P]orthophosphate. The nucleoprotein was immunoprecipitated and digested by trypsin. The resulting tryptic fingerprints were strain-specific and dependent on the host cell in which the virus strains had been propagated. Virus mutants had different fingerprints. It is suggested that specific cellular protein phosphokinases are involved in virus replication and that these may determine host range and cell tropism by site-specific phosphorylation of viral phosphoproteins.
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PMID:Phosphopeptide fingerprints of nucleoproteins of various influenza A virus strains grown in different host cells. 388 83

The protein composition of two influenza A virus strains from different serological groups was studied. For preliminary separation of envelope and core proteins the virus was treated with nonionic detergent Triton X-100 solution followed by chromatography in ultragel AcA 34. After their separation by disk electrophoresis and treatment with trypsin they were labeled with tritium and peptide analysis was carried out. Differences in peptide maps between the appropriate light and heavy chains of hemagglutinins of the strains under study were demonstrated. Differences in the composition of nucleoprotein and matrix protein were insignificant.
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PMID:[Peptide mapping of the major proteins in 2 strains of influenza virus]. 392 20

During major epidemics with influenza, there is an increased number of pneumonias due to Staphylococcus aureus with a subsequent high mortality rate. We have postulated that influenza A virus infection of host cells promotes the adherence of S. aureus ultimately resulting in bacterial superinfection. In the present study we compared the adherence of seven strains of 3H-labeled S. aureus to Madin-Darby canine kidney (MDCK) cell monolayers, uninfected and infected with influenza A/FM/1/47 virus. Test strains included: Cowan I; a Cowan I protein A-deficient mutant (PA-); EMS, a protein A and clumping factor-deficient mutant; HSmR; 52A5, a teichoic acid-deficient mutant of HSmR; M, an encapsulated strain; and, No. 1071, a clinical isolate. By radioassay, six of the seven strains demonstrated significantly enhanced adherence to virus-infected cell monolayers compared to uninfected controls; only the M strain was adherence negative. Surface hydrophobicity of the staphylococci did not correlate with their ability to adhere. Four strains of labeled staphylococci (Cowan I, PA-, EMS, and No. 1071), untreated or treated with 2.5% trypsin, 1.25% protease, or by autoclaving, were tested in the radioassay. Protease treatment, which was more effective than trypsin treatment, reduced adherence of all four test strains by 74-96%. Results of heat treatment suggested the presence of both thermolabile and thermostable adhesins. Staphylococcal thermal extracts, profiled by anion-exchange HPLC, were used to pretreat monolayers in a blocking radioassay. Adherence was decreased to control cells (9-78%) and to virus-infected cells (56-90%). The data suggest that multiple distinct surface proteins mediate the binding of S. aureus to uninfected and influenza A virus-infected cells.
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PMID:Staphylococcus aureus adherence to influenza A virus-infected and control cell cultures: evidence for multiple adhesins. 394 12


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