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PubMed1980

[Neuraminidase-producing pneumococci in the pathogenesis of hemolytic-uremic syndrome].

Hemolytic-uremic syndrome (HUS) accompanied by pneumococcal infections forms a characteristic subgroup of HUS. Pneumococcal neuraminidase splits off neuraminic acid from the glycoproteins present on the surface of red cells, thrombocytes and endothelial cells, and thus exposes the hidden Thomsen cryptantigen (T-Ag). The T-Ag can then react with a complement-fixing antibody of the IgM class which is present in all human plasmas after the age of 6 months. Early diagnosis of T-transformation should be attempted. Highly suggestive hints are: pneumonia, hemolytic anemia, reticulocytopenia, difficulties in ABO typing, a positive direct Coombs test and a positive minor cross-match. The definite diagnosis of T-transformation is established with the aid of anti-T agglutinins from Arachis hypogaea, the common peanut. Two children aged 19 and 22 months with pneumonia, Coombs-positive hemolytic anemia, HUS and exposure of the T-Ag on the red cell membrane are described. In one of them, circulating neuraminidase and circulating pneumococcal antigen of serotype 3 were found. In both children exchange transfusions resulted in elimination of circulating neuraminidase and of T-transformed red cells prone to hemolysis.

Female↗

PubMedDate not supplied

[Maturation of the hemagglutinin and neuraminidase polypeptides of the influenza virus in infected cells].

Maturation of virus-specific hemagglutinin and neuraminidase polypeptides was studied in chick embryo fibroblasts infected with influenza A virus, the WSN strain. Hemagglutinin maturation is accompanied by a decrease in the electrophoretic mobility of the protein. The processes occurring in maturation are localized on the part of the molecule corresponding to the major hemagglutinin subunit. The previously reported virus-induced proteins III and IV have been identified as immature precursor and mature polypeptide of virus neuraminidase, respectively. This is concluded on the basis of the membrane localization of both proteins, the presence of sugars in at least one of them, the antigenic specificity of the proteins, their behavior in electrophoresis under nonreducing conditions, as well as the results of "pulse'chase" label experiments. The nature of the modifications accompanying viral neuraminidase maturation remains obscure; some possibilities are considered.

Animals↗

PubMedDate not supplied

[Purification and study of influenza virus neuraminidases].

Purified preparations of polypeptides of neuraminidases of 10 influenza A virus strains were obtained by two-dimensional electrophoresis of proteins in polyacrylamide gel in which proteins with intact disulphid bonds were used for phoresis in the first direction and those with destroyed disulphid bonds for phoresis in the second direction. Fractionation of tryptic tyrosinil-peptides of neuraminidases labeled in vitro with radioactive iodine was carried out by two-dimensional dispersal by means of electrophoresis and chromatography. Comparison of oligopeptide maps of neuraminidases gave both expected results (for some specimens, correlation of similarities in peptide maps with similar antigenic structure) and some unexpected findings.

Electrophoresis, Polyacrylamide Gel↗

PubMedDate not supplied

[Enzymatic properties of neuraminidase from corynebacterium diptherial].

Enzymatic properties of neuraminidase isolated from non-toxigenic strain C7 of diphteritic bacteria are studied. The enzyme has the pH optimum 5.5--6.0 in acetate buffer and the temperature optimum 38 degrees C. Neuraminidase has the highest substrate affinity to glycoproteins of equine blood serum, the lowest affinity--to 3-N-acetylneuraminosyllactose and ovomucin. The Km values was 4.3-10(-4) at optimal conditions under the hydrolysis of 3-N-acetylneuraminosyllactose, Vm was 0.05+/-0.02 muM NANA/hour/mg of protein. The following esters of N-glyconoyl-glycine were shown to be competitive inhibitors of neuraminidase: 1) methyl ester of 3-aza-4-oxo-2,3,4-trideoxy-D-arabinooctonic acid; 2) methyl ester of 3-aza-4-oxo-2,3,4-trideoxy-D-glucoheptodecanic acid; 3) methyl ester of 3-aza-4-oxo-2,3,4-trideoxy-D-galactonic acid; 4) methyl ester of 3-aza-4-oxo-2,3,4-trideoxy-D-gluconic acid, Ki values being 6.5-10(-4), 4.5-10(-4); 9.5-10(-4) and 7.1-(10-3) M, respectively.

Animals↗

PubMedDate not supplied

[The participation of the neuraminidase of Yersinia pestis in the transmission of the transmembrane signal].

Neuraminidase isolated from Yersinia pestis [correction of the plaque microbe] and purified has been studied for its effect on the peritoneal leukocytes of the white mice with results presented. Neuraminidase exerted the insulin-like effect on the peritoneal leukocytes of the white mice and this effect depended on the used dose. The priming of leukocytes by neuraminidase preparation was accompanied by the sharp increase of hydrogen peroxide production under effect of the capsule antigen of the plaque microbe and, apparently, by the appearance of additional binding sites for the adhesion piles of the plaque agent.

Animals↗

PubMedDate not supplied

Safety and efficacy of the neuraminidase inhibitor GG167 in experimental human influenza.

OBJECTIVE: The current study evaluated whether intranasal administration of the sialic acid analog 4-guanidino-Neu5Ac2en (GG167), an inhibitor of influenza virus neuraminidase, was effective and safe in either preventing or treating experimental human influenza. METHODS: Four randomized, double-blind, placebo-controlled trials involving three prophylaxis limbs, two early treatment limbs, and one delayed treatment limb were conducted. SETTING: Isolation in individual rooms. PARTICIPANTS: Susceptible (serum hemagglutination-inhibition antibody titer < or = 1:8) adult volunteers (n = 166) were inoculated intranasally with 10(5) TCID50 influenza A/Texas/91 (H1N1) virus. INTERVENTION: GG167, 3.6 to 16 mg, was administered intranasally two or six times daily beginning 4 hours before inoculation (prophylaxis) or 1 or 2 days afterward (early or delayed treatment). MAIN OUTCOMES: Virological measures were frequency of infection based on viral shedding and/or seroconversion (prophylaxis) or quantitative viral shedding based on titers and duration of virus recovery (treatment). Clinical measures were the frequency of febrile illness and symptom severity scores. RESULTS: Intranasal GG167 was well tolerated for both prophylaxis and therapy. For all dose groups combined, GG167 prophylaxis was 82% effective in preventing laboratory evidence of infection and 95% effective in preventing febrile illness (P < .01 vs placebo). Early treatment with GG167 reduced peak viral titers by 2.0 log10, the median duration of viral shedding by 3 days, and the frequency of febrile illness by 85% (P < .05 for each comparison). Other measures of illness were reduced by approximately 50% to 70% in the GG167 dosing groups. Twice daily dosing was as effective as six times daily. CONCLUSIONS: Direct respiratory administration of the selective neuraminidase inhibitor GG167 appears safe and effective for both prevention and early treatment of experimental influenza. Influenza virus neuraminidase is important for viral replication in humans.

Administration, Intranasal↗

PubMed1977

[Lysosomal neuraminidase, beta-galactosidase and beta-N-acetylglucosaminidase of regenerating liver tissue].

Neuraminidase (EC 3.2.1.18) beta-galactosidase (EC 3.2.1.23) and beta-N-acetylglucosaminidase (EC 3.2.1.30) were studied in normal and regenerating rat liver. All these glycosidases were shown to be predominantly localized in lysosome rich fraction. The activity of lysosomal neuraminidase in regenerating rat liver increased 24 hours after partial hepatectomy, whereas those of beta-galactosidase and beta-N-acetylglucosaminidase decreased. The presence of inhibitor of neurominidase in regenerating liver homogenate was shown. Actinomycin D and cycloheximide were shown to have no significant effect on lysosomal neuraminidase in regenerating rat liver.

Acetylglucosaminidase↗

PubMed1977

Increase in titer of the naturally occurring human antibody to neuraminidase-treated lymphocytes after influenza.

Nine of 25 (36%) humans suffering from naturally acquired influenza A infection developed significant increases in the titer of a "naturally" occurring antibody to neuraminidase-treated human lymphocytes. Only two of 43 normal and noninfluenza respiratory infection controls showed titer changes of this antibody, p less than 0.001. The antibody was not directed at influenza virus C fixation, hemagglutination inhibition, or neuraminidase antigens. Three of 10 normals given a highly immunogenic, formalin-killed influenza A vaccine developed significant titer rises. These results suggest that influenza virus, live or dead, can provoke an increase in antibody to a cross-reacting antigen present on neuraminidase-treated human lymphocytes.

Adolescent↗

PubMed1997

[Structure and function of influenza virus neuraminidase].

Crystallographic studies of neuraminidase and neuraminidase-sialic acid complexes enabled to design new potent antiviral drugs against influenza. In addition, recent advance in reverse genetics of influenza virus provides us a better understanding of interrelationship between structure and function of the neuraminidase. Progress in elucidating the relationship between structure and function will further contribute to the control of influenza.

Neuraminidase↗

PubMed1998

[Comparison of the synonymous and non-synonymous substitution rates in various regions of the neuraminidase and hemagglutinin genes of the influenza A virus].

A new, statistically justified approach was used to estimate the synonymous and non-synonymous substitution rates in several antigenic variants of influenza-virus surface proteins. The rates were compared for antigenic and nonantigenic regions of neuraminidase and hemagglutinin, as well as for neuraminidase surface and internal amino acids identified by X-ray analysis. For neuraminidase, the estimation was performed for the first time. The non-synonymous substitution rate was shown to be significantly higher in antigenic than in nonantigenic sites. However, neither subsample of antigenic sites displayed a fixation rate of non-synonymous substitutions higher than that of synonymous substitutions, which would confirm the effect of positive selection on these sites and argue against a neutral evolution character. Specific features of methods used to estimate the substitution fixation rates and problems in their interpretation are discussed.

Amino Acid Substitution↗

PubMed1983

Interferon-induced increase in neuraminidase-releasable sialic acid and glycosphingolipid metabolism in mouse lymphoma and L1210 leukemic cell lines: correlation with susceptibility to natural killer cell-mediated lysis.

Changes in sialoglycoconjugates and glycosphingolipid (GSL)5 metabolism were demonstrated in mouse EL4, P52 and YAC-1 lymphoma and L1210 leukemia cell lines treated with beta-interferon (IFN). Expression of cell surface (neuraminidase-releasable) sialic acid on IFN-treated cells was markedly elevated (three- to six-fold). The increase in neuraminidase-releasable sialic acid is contributed by sialoglycoproteins and particularly by cell-surface gangliosides in IFN-treated cells. Incorporation of [3H]-galactose into all GSL was elevated in IFN-treated cells. Thin-layer chromatographic analysis of GSL of IFN-treated cells showed an increase in several GSL homologues with striking changes in ganglioside with chromatographic migration of GM2, GM1, and GD1a relative to control cells. IFN-treated tumor-cell lines became resistant to lysis by virus-induced IFN-activated natural killer (NK) cells, as shown previously, but addition of neuraminidase to IFN-treated and untreated cells caused only a moderate increase in NK-sensitivity. This suggests that IFN-mediated protection of target cells from NK lysis was not due to a preferential masking of target structure by elevated levels of sialic acid. These membrane-associated changes in GSL and sialic acid in IFN-treated cells may be potentially significant, because a correlation between certain GSL expression, sialic acid phenotype and susceptibility of target cells to NK-cell-mediated lysis have been found in several other systems.

Animals↗

PubMed1984

Total gangliosides, ganglioside species and the activity of neuraminidase in different brain regions and spinal cord of normal and undernourished rats.

Total gangliosides, their concentrations and the distribution of individual ganglioside species were determined in the spinal cord, pons-medulla, midbrain, cerebellum, hypothalamus, cerebral cortex, olfactory lobes and the rest of the forebrain, of 18- and 33-day-old normal and food-restricted and rehabilitated rats. The activity of neuraminidase in the different regions of the brain and spinal cord was determined. Differences in total gangliosides as well as individual species in different regions of the brain were observed. Among brain regions, while total ganglioside content was significantly reduced in the case of the cerebellum, the hypothalamus was the most affected in the distribution of ganglioside species and the activity of neuraminidase was decreased. The significance of the distribution of ganglioside species in different brain regions in relation to the activity of neuraminidase is discussed.

Animals↗

PubMed1993

Crystals of hemagglutinin-neuraminidase of parainfluenza virus contain triple-stranded helices.

When purified dimers of hemagglutinin-neuraminidase molecules released by protease digestion from three strains of human parainfluenza virus 1 were used in crystallization trials, long thin needle crystals formed. Electron microscopic analysis of these needle crystals revealed that they are composed of stacks of triple-stranded helices with each strand of the helix made up of subunits of hemagglutinin-neuraminidase. To our knowledge, this is the first direct demonstration of the assembly of protein subunits into large triple-stranded helices. An understanding of the organization of these triple helices may shed light on the structural properties of the hemagglutinin-neuraminidase molecules that cause them to form these helices.

Crystallization↗

PubMed1991

Location of amino acid residues important for the structure and biological function of the haemagglutinin-neuraminidase glycoprotein of Sendai virus by analysis of escape mutants.

To locate sites important for the structure and function of the haemagglutinin-neuraminidase glycoprotein (HN) of Sendai virus, the biological characteristics of antibody-selected escape mutants were correlated with mutations in the primary HN amino acid sequence. An escape mutant virus deficient only in neuraminidase function but with an HN content equal to that of the wild-type virus had an amino acid change at residue 184, implying that this position may be important for maintaining a functionally active enzymic site. In contrast, other escape mutant viruses with reductions in haemagglutination (eightfold) and neuraminidase activities (70 to 80%) had a sharply diminished HN content and substitutions either at residue 375, or double mutations at residues 279 and 461. The loss of biological activity with the concomitant loss of HN content suggests that these sites may be important for the processing and transport of HN, or in maintaining a structure resistant to proteolytic degradation; residue 451 was shown to have an undefined role in fusion activity. The monoclonal antibodies (MAbs) used to isolate the mutant viruses included those of the IgA and IgG classes and were divided into four operational groups based on their haemagglutination-inhibition pattern against the selected mutants. MAbs of the IgA class recognized epitopes overlapping with (group A) as well as epitopes distinct from (groups C and D) those recognized by the IgG class; group B included only IgG antibodies. The epitopes recognized by IgA antibodies may identify residues important for the secretory immune response to the HN molecule.

Animals↗

PubMed1970

Isolation of hemagglutinin and neuraminidase subunits of hemagglutinating virus of Japan.

When purified hemagglutinating virus of Japan (HVJ) was treated with trypsin, two major surface antigens were released from the virus. The "hemagglutinin" subunits obtained by this method were reactive with homologous hemagglutination-inhibition antibody and could be detected by an antibody-blocking test. They adsorbed to but did not agglutinate red cells and thus appeared to be "monovalent." The neuraminidase subunits were obtained in fully active form and did not adsorb to red cells. This finding suggests that these two activities of HVJ are associated with different subunits of the virus particle. The hemagglutinin and neuraminidase subunits could be partially separated by zonal rate centrifugation or gel filtration on Sephadex G-200. The molecular weights estimated for these subunits were approximately 124,000 and 114,000, respectively. After treatment with trypsin, virus-associated hemagglutinin and neuraminidase activities were both reduced significantly. The electron micrographs of such trypsinized virus particles showed complete or partial loss of surface projections. These results suggested that the subunits obtained by this method seemed to be those projections liberated from the virus by the action of trypsin.

Animals↗

PubMed1988

Isolation of a biologically active soluble form of the hemagglutinin-neuraminidase protein of Sendai virus.

As a first step in establishing the three-dimensional structure of the Sendai virus hemagglutinin-neuraminidase (HN), we have isolated and characterized a potentially crystallizable form of the molecule. The sequence of HN, a surface glycoprotein, predicts a protein with an uncharged hydrophobic region near the amino terminus which is responsible for anchorage in the viral envelope. To avoid rosette formation (aggregation), which would preclude crystallization, this hydrophobic tail was removed from a membrane-free form of HN by proteolytic digestion. This digestion resulted in a single product with a molecular weight of about 10,000 less than native HN. N-terminal amino acid sequence analysis of cleaved HN (C-HN) indicated a single cleavage site at amino acid residue 131, resulting in a product consisting of the carboxyl-terminal 444 amino acids of HN. Functional analyses revealed that C-HN retained full neuraminidase activity and was able to bind erythrocytes, indicating that the N-terminal 131 residues were not necessary for these biological activities. Furthermore, this cleavage product retained the antigenic structure of intact HN, since monoclonal antibodies still bound to C-HN in enzyme-linked immunosorbent assay and Western (immuno-) blot analysis. Viewed by electron microscopy, the dimeric and tetrameric forms of intact HN form rosettes while C-HN maintains the oligomeric structure but no longer aggregates. Furthermore, the electron micrographs revealed a C-HN tetramer strikingly similar to the influenza virus neuraminidase in both size and gross structural features.

Animals↗

PubMed2002

Probing the sialic acid binding site of the hemagglutinin-neuraminidase of Newcastle disease virus: identification of key amino acids involved in cell binding, catalysis, and fusion.

We recently reported the first crystal structure of a paramyxovirus hemagglutinin-neuraminidase (HN) from Newcastle disease virus. This multifunctional protein is responsible for binding to cellular sialyl-glycoconjugate receptors, promotion of fusion through interaction with the second viral surface fusion (F) glycoprotein, and processing progeny virions by removal of sialic acid from newly synthesized viral coat proteins. Our structural studies suggest that HN possesses a single sialic acid recognition site that can be switched between being a binding site and a catalytic site. Here we examine the effect of mutation of several conserved amino acids around the binding site on the hemagglutination, neuraminidase, and fusion functions of HN. Most mutations around the binding site result in loss of neuraminidase activity, whereas the effect on receptor binding is more variable. Residues E401, R416, and Y526 appear to be key for receptor binding. The increase in fusion promotion seen in some mutants that lack receptor binding activity presents a conundrum. We propose that in these cases HN may be switched into a fusion-promoting state through a series of conformational changes that propagate from the sialic acid binding site through to the HN dimer interface. These results further support the single-site model and suggest certain residues to be important for the triggering of fusion.

Amino Acids↗

PubMed1984

[Restoration of the biological activity of hemagglutinin--neuraminidase in NDV with phospholipids].

The phospholipids in the membrane of the Newcastle disease virus were hydrolysed by means of the phospholipase enzyme C, whereas the infectious titer of the virus did not change, however its neuraminidase activity dropped. It was found that sphingomyelin in conc. of 250 micrograms/cm3 or lipids of the Newcastle disease virus membrane added to phospholipase C-treated hemagglutinin-neuraminidase restored its activity. The phospholipid 'phosphatidiletanolamine' could not restore the activity of the virus neuraminidase.

HN Protein↗