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PubMed2006

Pneumococcal neuraminidases A and B both have essential roles during infection of the respiratory tract and sepsis.

We examined the role of the neuraminidases NanA and NanB in colonization and infection in the upper and lower respiratory tract by Streptococcus pneumoniae, as well as the role of these neuraminidases in the onset and development of septicemia following both intranasal and intravenous infection. We demonstrated for the first time using outbred MF1 mouse models of infection that both NanA and NanB were essential for the successful colonization and infection of the upper and lower respiratory tract, respectively, as well as pneumococcal survival in nonmucosal sites, such as the blood. Our studies have shown that in vivo a neuraminidase A mutant is cleared from the nasopharynx, trachea, and lungs within 12 h postinfection, while a neuraminidase B mutant persists but does not increase in either the nasopharynx, trachea, or lungs. We also demonstrated both neuraminidase mutants were unable to cause sepsis following intranasal infections. When administered intravenously, however, both mutants survived initially but were unable to persist in the blood beyond 48 h postinfection and were progressively cleared. The work presented here demonstrates the importance of pneumococcal neuraminidase A and for the first time neuraminidase B in the development of upper and lower respiratory tract infection and sepsis.

Animals↗

PubMed2001

Cloning, expression, and characterization of a neuraminidase gene from Arcanobacterium pyogenes.

Arcanobacterium pyogenes is an opportunistic pathogen, associated with suppurative infections in domestic animals. In addition to pyolysin, a pore-forming, cholesterol-binding toxin, A. pyogenes expresses a number of putative virulence factors, including several proteases and neuraminidase activity. A 3,009-bp gene, nanH, was cloned and sequenced and conferred neuraminidase activity on an Escherichia coli host strain. The predicted 107-kDa NanH protein displayed similarity to a number of bacterial neuraminidases and contained the RIP/RLP motif and five copies of the Asp box motif found in all bacterial neuraminidases. Recombinant His-tagged NanH was found to have pH and temperature optima of 5.5 to 6.0 and 55 degrees C, respectively. Insertional deletion of the nanH gene resulted in the reduction, but not absence, of neuraminidase activity, indicating the presence of a second neuraminidase gene in A. pyogenes. NanH was localized to the A. pyogenes cell wall. A. pyogenes adhered to HeLa, CHO, and MDBK cells in a washing-resistant manner. However, the nanH mutant was not defective for adherence to epithelial cells. The role of NanH in host epithelial cell adherence may be masked by the presence of a second neuraminidase in A. pyogenes.

Actinomycetaceae↗

PubMed2004

Immunization with native or recombinant Streptococcus pneumoniae neuraminidase affords protection in the chinchilla otitis media model.

Streptococcus pneumoniae neuraminidase has been implicated as a virulence factor in the pathogenesis of pneumococcal otitis media. In this study, native neuraminidase was partially purified from cultures of S. pneumoniae by serial chromatography with DEAE-Sepharose and Sephacryl S-200. Recombinant neuraminidase, a 3,038-bp fragment of the neuraminidase A (nanA) gene, was cloned into the pET-28b vector and then expressed at high levels in Escherichia coli. Chinchillas were immunized subcutaneously with either the gel-purified native or recombinant neuraminidase, and all responded with elevated titers of antineuraminidase antibody in serum. Immunization with neuraminidase resulted in a significant reduction in nasopharyngeal colonization as well as in the incidence of otitis media with effusion. These data demonstrate for the first time that neuraminidase affords protection against S. pneumoniae nasopharyngeal colonization and experimental otitis media.

Animals↗

PubMed1976

Antigenic relationships among influenza virua A neuraminidase (N2) antigens by immunodiffusion and postinfection neutralization tests.

The antigenic relationships among the neuraminidases of influenza A strains from 1957 to 1973 were examined by postinfection application of neuraminidase antisera. This procedure causes inhibition of virus spread and apparent neutralization. Neuraminidase (apparent) neutralization and neuraminidase inhibition tests with chicken antisera gave similar results. Neuraminidase inhibition tests were more discriminating than neuraminidase neutralization tests when rabbit and goat antisera were used. Antibody absorption studies revealed that the neuraminidase, like the hemagglutinin, may possess two kinds of antigenic determinants, which can give rise to "common," or "cross-reacting," and "specific" antibodies. "Specific" antibody appears to be more effective in the inhibition of enzyme activity than in the inhibition of virus spread.

Animals↗

PubMed1977

Virulence factors of influenza A viruses: WSN virus neuraminidase required for plaque production in MDBK cells.

The genetic basis for the distinctive capacity of influenza A/WSN/33 (H0N1) virus (WSN virus) to produce plaques on bovine kidney (MDBK) cells was found to be related to virus neuraminidase. Recombinant viruses that derived only the neuraminidase of WSN virus were capable of producing plaques, whereas recombinant viruses identical to WSN except for neuraminidase did not produce plaques. With viruses that do not contain WSN neuraminidase, infectivity of virus yields from MDBK cells was increased approximately 1,000-fold after in vitro treatment with trypsin. In contrast, no significant increase in infectivity was observed after trypsin treatment of viruses containing WSN neuraminidase. In addition, polyacrylamide gel analysis of proteins of WSN virus obtained after infection of MDBK cells demonstrated that hemagglutinin was present in the cleaved form (HA1 + HA2), whereas only uncleaved hemagglutinin was obtained with a recombinant virus that derived all of its genes from WSN virus except its neuraminidase. These data are in accord with the hypothesis that neuraminidase may facilitate production of infectious particles by removing sialic acid residues and exposing appropriate cleavage sites on hemagglutinin.

Animals↗

PubMed1995

Influenza type A virus neuraminidase does not play a role in viral entry, replication, assembly, or budding.

We have used a neuraminidase-deficient influenza virus, NWS-Mvi, which was selected by supplying bacterial neuraminidase in the medium (C. Liu and G. M. Air, Virology 194:403-407, 1993), to define the role of neuraminidase in influenza virus replication. Electron microscopy showed that virions of the NWS-Mvi mutant assembled normally and formed large aggregates associated with cell surfaces. The NWS-Mvi virus grown in the absence of neuraminidase was able to carry out a second round of replication in MDCK cells without added neuraminidase, indicating that the virus particles contained in these aggregates were infectious. Aggregates of virus were also found in cytoplasmic vacuoles. When virus-infected cells were incubated in the presence of ferritin, such aggregates were found to be labeled with ferritin, indicating that they are derived from uptake at the cell surface. When the neuraminidase-deficient virus was administered intranasally to C57BL/6 mice, low titers of virus were recovered from the lungs and major histocompatibility complex class I-restricted cytotoxic T cells were generated: evidence that cells were infected in vivo. In C57BL/6 nu/nu mice, the low level of virus persisted for at least 28 days but never increased. These results suggest that neuraminidase is not required for influenza virus entry, replication, or assembly in cell culture or in mice.

Animals↗

PubMed1988

Studies on sequestration of neuraminidase-treated red blood cells.

The effects of reduction in the surface charge of red blood cells (RBCs) on regional blood flow and RBC distribution were studied in rats anesthetized with pentobarbital sodium. RBCs were treated with neuraminidase to reduce their electrophoretic mobility by 56%. Normal and neuraminidase-treated RBCs labeled with 51Cr or 111In were injected into a femoral vein while an equal volume of blood was simultaneously withdrawn from a femoral artery. More than 70% of the neuraminidase-treated RBCs injected disappeared from the circulating blood in 30 min compared with less than 2% of normal RBCs. The relative distributions of neuraminidase-treated RBCs to normal RBCs, as determined from radioactivity counting, were significantly greater than 1 in the spleen (5.65 +/- 0.97, mean +/- SD), the liver (2.84 +/- 0.21), the lung (1.48 +/- 0.31), and the kidney (1.49 +/- 0.27), indicating a preferential trapping of neuraminidase-treated RBCs in these regions. This ratio was approximately 1 in all other organs. Regional blood flows in tissues were determined with 15-micron microspheres in the control period and after the infusion of neuraminidase-treated RBCs (experimental). Experimental-to-control blood flow ratios were 0.40 +/- 0.05 in the spleen, 0.66 +/- 0.06 in the liver, 0.78 +/- 0.03 in the lung, and 0.78 +/- 0.09 in the kidneys; this ratio was approximately 1 in all other organs. An experimental-to-control blood flow ratio less than 1 indicates a reduction in blood flow; this occurred in the same organs as those with trapping of neuraminidase-treated RBCs.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Effects of neuraminidase on airway reactivity in the guinea pig.

We investigated the effects of neuraminidase, a viral enzyme that cleaves alpha ketosidic cell-bound sialic acids, to see if it accounts for parainfluenza and influenza virus-induced airway hyperreactivity. Accordingly, Vibrio cholerae neuraminidase was administered intratracheally in guinea pigs, and airway reactivity was assessed 3 h later. Removal of sialic acid residues was evaluated by histologic studies. Airway responsiveness was determined in anesthetized, tracheotomized, and mechanically ventilated guinea pigs by exposing them to increasing concentrations of aerosolized bronchoconstrictor agents. Respiratory system conductance was measured by the occlusion method. Neuraminidase injected intratracheally did not change airway reactivity to 10(-4) to 10(-2) M acetylcholine or 10(-4) to 2.5 x 10(-3) M histamine; nor did it prevent aerosolized albuterol from inhibiting histamine-induced bronchoconstriction. Substance P (10(-6) to 5 x 10(-5) M) had no significant bronchoconstrictor effect on guinea pigs pretreated with saline or neuraminidase. In guinea pigs pretreated with aerosols of the neutral endopeptidase inhibitor phosphoramidon (10(-4) M) before the concentration curve to aerosolized substance P was recorded, neuraminidase significantly reduced substance P-induced bronchoconstriction. When bronchoconstriction was induced by the 4-11 fragment of substance P (10(-5) to 10(-2) M), which is devoid of positive charges, it did not differ significantly in guinea pigs pretreated with saline and those pretreated with neuraminidase. These results indicate that in the guinea pig, neuraminidase injected intratracheally does not induce non-specific airway hyperreactivity and may alter the binding of substance P to its receptors.

Albuterol↗

PubMed1976

Effect of neuraminidase treatment on the biological activity of highly purified ovine FSH and LH in hypophysectomized immature male and female rats.

Highly purified ovine FSH and LH were treated with neuraminidase to remove sialic acid and the desialylated derivatives were examined for biological activity in hypophysectomized immature male and female rats. The male rats were hypophysectomized at 22 days of age and beginning on day 25 were injected sc twice daily for 4 days with native or neuraminidase-treated FSH (total dose, 15 or 60 mug) or LH (12 mug). The ventral prostates, seminal vesicles, and testes were then removed and weighed, and serum testosterone levels were measured by radioimmunoassay. The female rats were hypophysectomized on day 28 and beginning on day 35 were injected sc twice daily for 4 days with native or neuraminidase-treated FSH (8 mug) or saline. On the morning of day 39, the rats were given an ovulating dose of gonadotropin (8 mug native or neuraminidase-treated FSH, or 1.28 mug native or neuraminidase-treated LH) or 1.0 ml saline iv via tail vein. Twenty-four hours later ova were counted in the oviducts the ovaries were weighed, and serum levels of progesterone and 20alpha-dihydroprogesterone were determined by radioimmunoassay. Treatment of ovine LH with neuraminidase did not diminish the ability of this hormone to increase prostate and testes weights and serum testosterone levels. Desialylation also did not decrease the ability of LH to induce ovulation. Although native ovine FSH significantly increased the weights of the ventral prostate, seminal vesicles, and testes, and elevated plasma testosterone levels, the desialylated derivative was essentially inactive. Neuraminidase treatment also eliminated the ability of ovine FSH to increase ovarian weight, to induce ovulation, and to elevate serum progesterone and 20alpha-dihydroprogesterone. These results indicate that the LH-like activity of ovine FSH is an intrinsic property of the FSH molecule.

Animals↗

PubMedDate not supplied

Enhancement of carcinoembryonic antigen (CEA) expression in colorectal tumors by neuraminidase.

Twelve colorectal carcinomas with transitional mucosa and 10 colorectal adenomas which previously displayed weak or no carcinoembryonic antigen (CEA) expression were selected to verify whether neuraminidase unmasks CEA carbohydrate epitopes and, consequently, enhances the CEA expression. Peroxidase-antiperoxidase (PAP) method was performed on routinely processed tissues, without and with neuraminidase pretreatment of the sections. Lysine, without and with neuraminidase pretreatment of the sections. Lysine, as a modifier of electrostatic charge at cell surface, instead of neuraminidase was used to clarify whether the enzyme yields a specific or non-specific influence on CEA expression. All colorectal tumors exhibited more CEA after neuraminidase pretreatment, while previous negative specimens developed CEA expression. The same effect was observed in some transitional mucosa sections. This has not occurred in normal mucosa, probably owing to a resistant sialylation. The enhancement effect of lysine, although more weakly and not entirely superimposed to that or neuraminidase, suggests non-specific mechanisms of enzyme action. The removal of the negative charge at cell surface, especially due to sialic acid, allows more anti-CEA antibodies to react. The neuraminidase pretreatment of the sections is a useful method to demonstrate the real incidence of CEA in the colorectal tumors.

Adenoma↗

PubMed1975

[Contribution to the antigenic study of influenza viruses in animals. I.--Neuraminidase of the equine influenza viruses (author's transl)].

From the Revised Nomenclature of WHO, the fowl influenza virus A/Duck/Ukraine/63 (Hav7 Neq2) has the same neuraminidase as the equine virus A/equi 2/Miami/63 (Heq2 Neq2); the A/Chicken Germany "N"/49 virus has the same neuraminidase as the equine virus A/equi 1/Prague/56. A comparative study of the antigenic specificities confirms that the Neq2 neuraminidases are closely connected, whatever their animal origin, and that the fowl strain Hav7 Neq2 can be used for the titration of anti Neq2 antibodies in the serums of animals immunized with the equine virus Heq2 Neq2. The Neqi neuraminidases of various animal origins are connected, but the neuraminidase of the fowl strain Hav2 Neqi is slightly inhibited by the anti Neq1 antibodies of animals immunized with the Heq1 Neq1 virus: to titrate the anti Neq1 antibodies of equine origin, the H72 Neq1 recombinant should therefore be used. The antigenic characterization of the different equine influenza strains isolated since 1967 by the study of their neuraminidase has been completed: The various neuraminidases, like the hemagglutinins of the various strains belonging to the sub-type A equi2 are closely connected; a minor antigenic variation, concerning the two surface antigens, seems to exist between the strain A equi 1/Prague/56 and the strain of the same subtype isolated in 1973.

Animals↗

PubMed1996

Correlation between low neuraminidase blood levels and a predisposition toward family-related breast cancer.

It has been shown that high sialic acid levels are often found in conjunction with breast cancer, and these high concentrations are thought to be due to deficiency of the enzyme neuraminidase. The study proposes to elicit a relationship between low levels of blood neuraminidase and a family history of breast cancer. Neuraminidase blood levels were measured in 30 healthy women between the ages of 35 and 65 years with no evidence of a family history of breast cancer (control group), and in 33 healthy women between the ages of 35 to 65 years, all of whom had immediate members of their families with breast cancer (study group). The mean level of the blood neuraminidase was found to be 1.375 units in the control group. On the other hand, the mean level for the study group was 1.256 units. The difference between the two groups is statistically significant, (P value < 0.01). It is important to note that in the study group 20 of the 33 participants, 60.6 per cent, had neuraminidase levels below the mean of the study group, whereas only 3 of the 30, 10 per cent, in the control group had neuraminidase levels below the mean of the study group. Deficiency of the enzyme neuraminidase may suggest an elevated risk for breast cancer.

Adult↗

PubMed1994

Inhibition of Sendai virus hemagglutinin neuraminidase by the fusion protein.

The Sendai virus envelope contains two glycoproteins: the fusion (F) protein and the hemagglutinin-neuraminidase (HN). Inactivation of F causes the loss of fusogenic activity and an increase of the neuraminidase activity of HN. After inactivation of F, HN can be inhibited by fetuin or asialofetuin, as already observed on the water-soluble, C-terminal fragment of HN (Dallocchio, F., Bellini, T., Martuscelli, G., Baiocchi, M., & Tomasi, M. (1991) Biochem. Int. 25, 663-668). Disruption of viral envelopes by detergents does not affect the neuraminidase activity of virions containing inactive F, while it causes an increase of the neuraminidase activity in native virions. Reconstitution of HN into liposomes is accompanied by a decrease of enzymatic activity, due to the random inside-outside distribution of the protein. However, the decrease of the neuraminidase activity is higher in liposomes containing both HN and F. These data suggest that F inhibits the neuraminidase activity of HN.

Animals↗

PubMed1976

Effect of Ca++ on the stability of influenza virus neuraminidase.

The neuraminidases of different strains of influenza virus varied in their stability at 37 degrees C. The enzymes of the strains with N1 neuraminidases were found to be unstable during incubation at 37 degrees C whereas the enzymes of the strains with the N2 neuraminidases were stable. Among the strains with N2 neuraminidases, the enzymes of some strains were inactivated during dialysis at 37 degrees C whereas the enzymes of others were stable. This observed loss of enzyme activity during dialysis at 37 degrees C was not restricted to a single substrate as the same loss of enzyme activity was observed irrespective of the size of the substrate used in the assay. The enzymically inactive neuraminidase was found to be non-antigenic and non-immunogenic. The inactivation of the enzyme could be prevented by the addition of Ca++ but not Mg++. Out results suggest that Ca++ is essential for the stability of the enzyme at 37 degrees C. The results would also suggest that the enzymic, antigenic and immunogenic sites are either the same or very closely situated on the surface of the neuraminidase molecule.

Animals↗

PubMed1982

Human lymphocyte membrane proteins treated with neuraminidase.

Human peripheral blood lymphocytes were surface-iodinated, treated with neuraminidase from Vibrio cholerae and lysed with non-ionic detergent. In addition, surface membrane fractions were isolated from surface-iodinated cells in the absence of detergents and treated with neuraminidase after membrane isolation. The effect of neuraminidase treatment on the membrane proteins was studied by two-dimensional gel electrophoresis. One surface-labelled protein of 45 000 molecular weight which is characterized by its association with the detergent-resistant matrix of the cells and by its specific enrichment in an isolated membrane fraction, was found to be particularly sensitive to neuraminidase treatment both of intact cells and isolated membranes. A prominent labelled protein of apparent molecular weight of 60 000 is observed in the soluble fraction after neuraminidase treatment of intact cells. The analogous protein is detected when isolated membrane fractions are treated with neuraminidase.

Cell Membrane↗

PubMed1991

Synthesis of linkage-specific sialoside substrates for colorimetric assay of neuraminidases.

Neuraminidase substrates suitable for analysis of linkage specificity were enzymically synthesized in good yield by linking N-acetylneuraminic acid (Neup5Ac) to O-6 and O-3 of 4-nitrophenyl beta-D-galactopyranoside with beta-D-galactoside-alpha-(2----6)-sialyltransferase and beta-D-galactoside-alpha-(2----3)-sialyltransferase, respectively. By use of these substrates, a convenient colorimetric assay method was developed for the determination of linkage specificity of bacterial and viral neuraminidases. The substrates are incubated with viral or bacterial neuraminidase and subsequently treated with beta-D-galactosidase to convert the liberated 4-nitrophenyl beta-D-galactopyranoside to 4-nitrophenol. The amount of liberated 4-nitrophenol is equivalent to the amount of Neup5Ac released from the substrate, thus allowing measurement of neuraminidase activity. The results showed that bacterial and viral neuraminidases can discriminate between these two compounds, making them useful substrates for the rapid determination of neuraminidase linkage specificity.

Bacteria↗

PubMed1989

Influenza neuraminidase is delivered directly to the apical surface of MDCK cell monolayers.

The aim of this study was to investigate whether influenza neuraminidase travels directly from the Golgi complex to the apical domain of the plasma membrane in virally infected epithelial (MDCK) cell monolayers, or whether it passes transiently through the basolateral domain. Using a new assay for the delivery of neuraminidase to the plasma membrane, we found that the time course of transport of this protein from the Golgi complex to the apical surface of MDCK cell monolayers was very similar to that for influenza haemagglutinin, which is known to be delivered directly to its destination. In addition, a similar time course of neuraminidase transport was found in BHK cells, which are not asymmetric and in which delivery must therefore be direct. Finally, basolateral exposure of MDCK cell monolayers grown on nitrocellulose filters to an anti-neuraminidase antibody was shown to have no effect on the delivery of active neuraminidase to the apical surface. We conclude from these results that neuraminidase, like haemagglutinin, is delivered directly to the apical surface.

Biological Transport↗

PubMed1976

Enhanced E- and EAC-rosette formation by neuraminidase.

Pre-treatment by neuraminidase of lymphocytes obtained from peripheral blood of normal donors significantly enhanced E- and EAC-rosette formation. Of other lymphoid cells only spleen cells showed significant enhancement of E-rosettes. The EAC-rosettes slightly increased when the peripheral blood lymphocytes from patients with acute lymphoblastic leukemia or chronic lymphocytic leukemia and MOLT-4 lymphoid cells were pre-treated with this enzyme. The EAC-rosettes were not increased by neuraminidase treatment of phytohemagglutinin-induced blasts, thymus cells or spleen cells. Pre-treatment of peripheral blood lymphocytes with neuraminidase also increased the proportion of stable E-rosettes resistant to incubation at 37 degrees C and to vigorous shaking. Various concentrations of neuraminidase (1-100 U/ml) produced enhancement of E- and EAC-rosettes with the highest activity at 25 and 50 U/ml. Neuraminidase treatment of sheep red blood cells failed to increase the proportion of E-rosettes of peripheral blood lymphocytes. The increased rosette forming capacity induced by neuraminidase is probably related to changes in lymphocyte surface properties.

Complement System Proteins↗