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Human placental neuraminidase. Activation, stabilization and association with beta-galactosidase and its protective protein.

Supernatant of homogenized human placenta hardly contains lysosomal neuraminidase activity. It is, however, possible to generate remarkably high activity by concentration of a partially purified glycoprotein fraction. This activity is labile to dilution, but can be stabilized by incubation at 37 degrees C and acid pH. Using beta-galactosidase specific affinity chromatography and immunotitration, we show that the activated and stabilized human lysosomal neuraminidase exists in a complex with beta-galactosidase. Sucrose density gradient centrifugation experiments demonstrate that the neuraminidase activity is exclusively present in a high density multimeric form of beta-galactosidase. The formation of multimeric forms of beta-galactosidase is known to require a 32000-Mr 'protective' protein. Monospecific antibodies against this 'protective' protein were purified from a conventional antiserum containing a mixture of antibodies against the 64000-Mr beta-galactosidase protein and against the 32000-Mr 'protective' protein, using a nitrocellulose blot immunoaffinity purification procedure. Immunotitration experiments with these antibodies show that the 32000-Mr 'protective' protein is present both in association with the beta-galactosidase multimer and with the high-density multimeric form together with neuraminidase. Our data further suggest that association of the 32000-Mr 'protective' protein and another yet unidentified subunit is essential for the catalytic activity of lysosomal neuraminidase. These results explain the absence of neuraminidase activity in the autosomal recessive human lysosomal storage disorder galactosialidosis, where the 32000-Mr 'protective' protein is known to be absent.

Carboxypeptidases↗

The production of neuraminidase and fucosidase by Helicobacter pylori: their possible relationship to pathogenicity.

The pathogenicity of enterobacteria often correlates with their production of neuraminidase (sialidase). Forty-nine Helicobacter pylori isolates have therefore been examined for their production of neuraminidase and other glycosidases. All 49 isolates produced considerable neuraminidase (median 228 IU/microg protein, interquartile range 121-370), pH optimum 7.5. Nine of the 49 also produced fucosidase (median 23 IU/microg protein, interquartile range 12-39), pH optimum 7.0. Production of these enzymes did not correlate with bacterial Cag A expression or duodenal ulceration. Neutrophils exposed to neuraminidase show increased adherence to endothelium so the neuraminidase production by H. pylori could partly explain the predominant neutrophil inflammatory infiltrate seen in H. pylori-associated gastritis. Inhibition of this enzyme by use of neuraminidase-inhibitors could be a useful therapeutic approach.

Adult↗

Parainfluenza 3 virus: plaque-type variants lacking neuraminidase activity.

Virus clones lacking detectable neuraminidase activity (SC-YN and M-YN) as well as those possessing it (LT-910N and LT-YN) were isolated from bovine strains of parainfluenza 3 virus. LT-910N and LT-YN viruses produced large turbid plaques in MDBK cells, and SC-YN virus produced small clear plaques. Incorporation of a bacterial neuraminidase in agar overlay medium made SC-YN virus form large turbid plaques, whereas it made M-YN virus form large clear plaques. However, M-YN virus formed only pinhole plaques or no plaques in the absence of neuraminidase. The exogenous neuraminidase had little effect on the plaque formation of LT-910N and LT-YN viruses. M-YN virus induced extensive syncytial formation, and SC-YN virus produced less extensive syncytial formation. The exogenous neuraminidase enhanced replication of SC-YN and M-YN viruses and reduced syncytial formation by these viruses. The enzyme had little effect on replication and cytopathic effect of LT-910N and LT-YN viruses. The reason for these effects of the exogenous neuraminidase is discussed.

Animals↗

Extracellular neuraminidase production by a Pasteurella multocida A:3 strain associated with bovine pneumonia.

The properties of an extracellular neuraminidase produced by a Pasteurella multocida A:3 strain that was isolated in a case of bovine pneumonia were examined during growth in a defined medium. This enzyme (isolated from concentrated culture supernatants of P. multocida A:3) was active against N-acetylneuramin lactose, human alpha-1-acid glycoprotein, fetuin, colominic acid, and bovine submaxillary mucin. Enzyme elaboration was correlated with the growth of the organism in a defined medium, with maximum quantities produced in the stationary phase. The enzyme was purified by a combination of ammonium sulfate fractionation, ion exchange on DEAE-Sephacel, and gel filtration on Sephadex G-200. The purified neuraminidase possessed a specific activity of 9.36 mumol of sialic acid released per min per mg of protein against fetuin. The enzyme possessed a pH optimum of 6.0 and a Km of 0.03 mg/ml. The P. multocida A:3 neuraminidase had a molecular weight of approximately 500,000 as estimated by gel filtration. The enzyme was stable at 4 and 37 degrees C for 3 h. Approximately 75% of the neuraminidase activity was lost within 30 min at 50 degrees C. Greater than 90% of the enzyme activity was destroyed within 10 min at temperatures of > or = 65 degrees C. The P. multocida neuraminidase does not appear to be serologically related to the Pasteurella haemolytica A1 neuraminidase since antiserum prepared against the purified P. haemolytica enzyme did not neutralize the P. multocida enzyme.

Animals↗

Pneumococcal neuraminidase.

Lee, L. T. (Columbia University, New York, N.Y.), and C. Howe. Pneumoccal neuraminidase. J. Bacteriol. 91:1418-1426. 1966.-The elaboration of neuraminidase by pneumococci grown under optimal conditions in liquid medium was studied in relation to the bacterial growth cycle. The enzyme was found free in the culture medium in increasing concentration throughout most of the logarithmic phase of growth, at the end of which enzyme concentration had reached a maximum. Only a small fraction of the total neuraminidase was cell-associated at any time. It appears, therefore, that pneumococcal neuraminidase is actively secreted by dividing cells and does not accumulate solely as a result of cellular autolysis. Neuraminidase in cell-free extracts (types I, III, VII, and XIV) was neutralized both by homotypic and by heterotypic antibody, thus demonstrating it to be a group antigen. The enzyme was separable in agar gel electrophoresis from other protein and polysaccharide pneumococcal antigens. Limited immunochemical data suggest that pneumococcal neuraminidase may be of relatively low molecular weight.

Antibodies↗

Evaluation of the single radial hemolysis test for measuring hemagglutinin- and neuraminidase-specific antibodies to H3N2 influenza strains and antibodies to influenza B.

Antibodies to the H3 hemagglutinin of influenza A virus could be specifically measured by single radial hemolysis (SRH) when test antigens were recombinant viruses containing the relevant H3 hemagglutinin antigen and irrelevant Neq1 neuraminidase of A/equine/Prague/1/56 virus. Antibodies to influenza B virus could also be measured by the SRH technique. Antibody rises to influenza A or B virus measured by SRH agreed with results of hemagglutination inhibition (HI) tests for about 80% of the sera tested, including sera from volunteers receiving killed influenza vaccine and sera from patients naturally infected with influenza. Correlation between antibody titers measured by SRH and HI was also good. Antibodies to the N2 neuraminidase of influenza A virus could be specifically measured by SRH when test antigens were recombinant viruses containing the relevant N2 neuraminidase antigen and irrelevant Heq1 hemagglutinin of A/equine/Prague/1/56 virus. The SRH test for neuraminidase antibodies was more strain specific than was the SRH test for hemagglutinin antibodies. Probably for this reason, agreement between neuraminidase antibody determinations in human sera by the SRH test and by the neuraminidase inhibition test was poorer than agreement between the SRH test for hemagglutinin antibodies and the HI test.

Antibodies, Viral↗

Antiviral activity of antiserum specific for an influenza virus neuraminidase.

Antiserum specific for influenza A(2) neuraminidase was produced by immunization of rabbits with the purified enzyme which had been isolated by electrophoresis from the proteins of a detergent-disrupted A(0)A(2) influenza virus recombinant [X-7 (F1)]. This recombinant contained hemagglutinin of the A(0) subtype and A(2) neuraminidase. Antiserum to the isolated A(2) neuraminidase did not react in any of four serological tests with A(0) or A(2) subtype viruses that lacked the A(2) enzyme. In contrast, the antiserum inhibited the neuraminidase activity only of wild-type and recombinant viruses containing the A(2) enzyme, regardless of the nature of their hemagglutinin proteins. The antiserum caused hemagglutination-inhibition of some, but not all, viruses bearing the A(2) enzyme, and it reduced the plaque size or plaque number of all viruses tested that contained A(2) neuraminidase. In the chick embryo and in cell culture, low dilutions of antiserum reduced the yield of virus. True neutralization of virus in the chick embryo did not occur. We conclude that an antiserum specific for A(2) neuraminidase influenced the yield and release of virus from influenza virus-infected cells.

Animals↗

Effect of neuraminidase treatment of cells and effect of soluble glycoproteins on type 3 reovirus attachment to murine L cells.

The effect of pretreatment of murine L cells with bacterial neuraminidases on type 3 reovirus attachment was examined. We observed that such treatments resulted in a 60 to 80% decrease of subsequent attachment of 35S-labeled type 3 reovirus in a time- and dose-dependent manner. This result was specific for removal of cell surface sialic acid residues since the specific neuraminidase inhibitor 2-deoxy-2,3-dehydro-n-acetyl neuraminic acid completely prevented the observed effect. Although the total amount of radiolabeled virus bound to neuraminidase-treated cells was greatly reduced, unlabeled reovirus competed only slightly less efficiently for the attachment of 35S-labeled reovirus to neuraminidase-treated versus mock-treated L cells, suggesting that the specificity of the virus interaction with cellular receptor sites was only slightly diminished. Saturation experiments with mock-treated cells or with cells treated with Vibrio cholerae or with V. cholerae plus Arthrobacter ureafaciens neuraminidases indicated that the number of specific cellular receptor sites for type 3 reovirus were reduced by about 47%. We determined that under the neuraminidase digestion conditions used in this experiment we were able to remove a maximum 75% of the total N-acetylneuraminic acid of L cells. Our results also demonstrated that glycoproteins bearing a large amount of sialic acid containing oligosaccharides as well as purified N-acetylneuraminic acid, N-glycolylneuraminic acid, and N-acetylneuraminyl lactose were inhibitors of attachment, while proteins containing no sialic acid or negligible amounts of sialic acid did not inhibit attachment. High concentrations of various monosaccharides and lactose had no effect on reovirus attachment, in agreement with the recent results of Armstrong and his collaborators (Armstrong et al., Virology, 138:37-48, 1984). These data are also supported by the observation that gangliosides are inhibitors of viral attachment (Armstrong et al., Virology, 138:37-48, 1984). Taken together, our results suggest that cell surface sialic acid-containing glycoconjugates are involved in type 3 reovirus binding to murine L cells.

Animals↗

Effect of neuraminidase on the expression of the 3-fucosyl-N-acetyllactosamine antigen in human tissues.

The monoclonal antibody AGF4.48 detects the 3-fucosyl-N-acetyllactosamine carbohydrate structure and reacts with a variety of human tissues, as shown by an immunoperoxidase method on paraffin sections of formalin fixed material. The intensity and distribution of the immunoperoxidase reactivity were affected by treatment of sections with neuraminidase. In some sites, such as bone marrow, brain, breast, and pituitary, the reaction was more intense after neuraminidase treatment. In several organs, including kidney, oesophagus, pancreas, submandibular gland, and uterus, the reaction was more widespread after neuraminidase treatment. Other organs, such as liver, lung, lymph node, skin, and uterine tube, showed an altered distribution of reactivity with AGF4.48 after sections were treated with neuraminidase. These results show that the 3-fucosyl-N-acetyllactosamine antigen is cryptic in many tissues. The antigen is masked to a variable extent in different tissues by neuraminic acid residues and can be revealed by the simple procedure of pretreating sections with neuraminidase. The value of using AGF4.48 antibody in combination with the enzyme neuraminidase to show accessible and cryptic antigen is that this reveals distinctive patterns of sialylation within various normal tissues. Whether similar patterns occur in disease will be of particular interest.

Antibodies, Monoclonal↗

Production of the Pseudomonas aeruginosa neuraminidase is increased under hyperosmolar conditions and is regulated by genes involved in alginate expression.

The pathogenesis of Pseudomonas aeruginosa infection in cystic fibrosis (CF) is a complex process attributed to specific characteristics of both the host and the infecting organism. In this study, the properties of the PAO1 neuraminidase were examined to determine its potential role in facilitating Pseudomonas colonization of the respiratory epithelium. The PAO1 neuraminidase was 1000-fold more active than the Clostridium perfringens enzyme in releasing sialic acid from respiratory epithelial cells. This effect correlated with increased adherence of PAO1 to epithelial cells after exposure to PAO1 neuraminidase and was consistent with in vitro studies demonstrating Pseudomonas adherence to asialoganglioside receptors. The regulation of the neuraminidase gene nanA was examined in Pseudomonas and as cloned and expressed in Escherichia coli. In hyperosmolar conditions neuraminidase expression was increased by 50% (P less than 0.0004), an effect which was OmpR dependent in E. coli. In Pseudomonas the osmotic regulation of neuraminidase production was dependent upon algR1 and algR2, genes involved in the transcriptional activation of algD, which is responsible for the mucoid phenotype of Pseudomonas and pathognomonic for chronic infection in CF. Under the hyperosmolar conditions postulated to exist in the CF lung, nanA is likely to be expressed to facilitate the initial adherence of Pseudomonas to the respiratory tract.

Alginates↗

Neuraminidase activity in middle ear effusions.

Analyses of Streptococcus pneumoniae culture filtrates and middle ear effusions (MEE) containing S pneumoniae for various hydrolytic enzymes have demonstrated substantial levels of neuraminidase activity when measured employing a sensitive fluorometric assay. S pneumoniae neuraminidase exhibits optimum activity near neutral pH (6.0 to 6.5), and catalyzes the cleavage of sialic acid residues from glycoproteins, gangliosides and mucopolysaccharides. S pneumoniae begins secreting large amounts of neutral neuraminidase (mean [means] = 43.3 units/mL culture filtrate) when cells enter the stationary phase. Nearly all (96%) human chronic MEEs yielding positive cultures for S pneumoniae contain neuraminidase activity (means = 0.200 units/mg protein), while only 21.1% to 45.5% of all other effusions contain the enzyme. Middle ear effusions obtained from S pneumoniae infected-chinchillas contained large amounts of neuraminidase activity (approximately 200 units/mL), which decayed exponentially in vivo with an apparent half-life of 8 1/2 days. Three neuraminidase isoenzymes (designated I-III) were identified in S pneumoniae culture filtrates, as well as in MEEs from chinchillas infected with the organism, using a combination of ion-exchange and gel filtration chromatography. With 4-methylumbelliferyl-N-acetylneuraminic acid serving as substrate, preparation I from both culture filtrates and MEEs was characterized by a high Michaelis constant (Km), while forms II and III had low Km values. Preferred substrates were orosomucoid and neuramin-lactose; gangliosides, thyroglobulin, and bovine submaxillary mucin were poorer substrates.

Animals↗

Purification and characterization of neuraminidase from Clostridium perfringens.

Clostridium perfringens cells were cultivated on a large scale using an automatic system. Neuraminidase secreted by the cells into the culture medium was purified 380 000-fold by: precipitation with ammonium sulfate between 50 and 85% saturation, filtration on Sephadex G-75, electrophoresis on polyacrylamide gel, and by isoelectric focusing. Three enzyme fractions with different migration rates were obtained by preparative disc electrophoresis in polyacrylamide gel, and five fractions with isoelectric points between pH 4.7 and 5.4 were observed after isoelectric focusing. This microheterogeneity disappeared after denaturation of the enzyme in 0.1% sodium dodecylsulfate or 8M urea. The isoelectric point of the denatured enzyme corresponded to pH 4.3. All enzyme fractions were identical with regard to their immunological and kinetic properties; they had the same molecular weights. The origin of the different "conformers" of neuraminidase is discussed. The existence of genuine isoenzymes could largely be excluded. The yield of neuraminidase was 65%, which corresponded to about 10 mg of pure enzyme from 100 l of culture medium. The enzyme was free of protease and various other glycosidase activities. The neuraminidase preparation appeared not to be contaminated by other proteins as judged by electrophoretic analysis using either the native enzyme or the enzyme denatured by sodium dodecylsulfate or urea; ultracentrifugation; chromatography on Sephadex G-200; and immunological methods. The molecular weights of the native or denatured enzyme were found to be in the range between 60 000 and 69 000 (on an average 63 750) using four independent methods. The existence of subunits of neuraminidase was excluded. The neuraminidase exhibited a spec. act. of 580 or 615 U/mg protein with glycopeptides from edible birds' nests or sialyllactose, respectively, as substrates. Additional kinetic properties and the UV-absorption spectrum of the enzyme are described.

Clostridium perfringens↗

Demonstration of neuraminidase activity in human blood serum and human milk using a modified, radioactively labelled alpha1-glycoprotein as substrate.

N-Acetylneuramini acid of alpha1-glycoprotein was oxidized with a small molar excess of periodate and reduced with tritium-labelled borohydride. By this method about 50% of the N-acetylneuraminic acid was converted to its radioactively labelled C8-analog and 25% to its C7-analog. Using this modified alpha1-glycoprotein as substrate, minimum neuraminidase concentrations of 10(-18) units/ml, related to the activity of neuraminidase from Vibrio cholerae, could be determined. Neuraminidase activity was demonstrated in 95% of the sera or blood plasma samples from a series of 417 healthy or ill human individuals and in milk samples from 5 different donors. The neuraminidase in both serum and milk had optimal activity at pH 5.5. On an average, 10(-10) neuraminidase units were found in 1 ml serum and 10(-8) units in 1 ml milk. Although the neuraminidase activities in the sera varied, a correlation with definite pathological states is not yet possible. N-Acetylneuraminate pyruvate-lyase activity could not be detected in human serum.

Female↗

Influence of neuraminidase on fertility and on sperm storage in the hen's oviduct.

Preinsemination incubation of semen with neuraminidase (4 IU/2 x 10(9) spermatozoa) significantly reduced fertility in one out of two trials. No differences were observed in fertility between semen treated with 4 versus 8 or 4 versus 16 IU of neuraminidase in Trials 1 or 2. All three levels of neuraminidase (4, 8, or 16 IU) removed the same amount (about 45%) of the bound sialic acids from spermatozoa during incubation. The removal of sialic acid from spermatozoa had a slight but nonsignificant affect on sperm storage within the uterovaginal (UV) sperm-host glands. Hens inseminated with neuraminidase-treated spermatozoa had decreased numbers of full and partially full UV sperm-host glands and increased numbers of empty glands, compared to hens inseminated with untreated but incubated spermatozoa. In the present study, reduced fertility resulting from the treatment of spermatozoa with neuraminidase from Clostridium perfringens indicates the desirability of exploring the use of other neuraminidases to see whether a correlation exists between the amount of sialic acid removed from spermatozoa and their subsequent fertility.

Animals↗

Neuraminidase assay of influenza vaccines.

At present influenza vaccines are standardized on their haemagglutinin content only. Recently it has been shown that both neuraminidase and haemagglutinin antibodies are important in providing protection against the influenza virus. We have, therefore, developed an automated neuraminidase assay, based on the enzymic method of Kendal, but modified to minimise the interference by sucrose. A neuraminidase standard has been established and samples assayed against the standard have a coefficient of variation of plus or minus 6.8 percent. The assay has been adapted to measure the neuraminidase antibody level in serum. The neuraminidase to haemagglutinin ratio has been determined for various influenza strains. Both neuraminidase and haemagglutinin titres are being compared with results obtained by the single radial diffusion method.

Antibodies↗

Effects on platelet function of removal of platelet sialic acid by neuraminidase.

A number of investigators have implicated sialic acid on the surface of platelets in platelet function. In this study we have quantitated the amount of sialic acid removed by purified neuraminidase from the surface of washed platelets of man, rabbit, or pig and examined the effects of this removal. Purified neuraminidase did not induce the release of platelet granule contents. Platelets were pre-labeled with 14C-serotonin for measurement of the release reaction or with 51Cr for determination of adherence to a collagen-coated surface or damaged aortic surface, and for in vivo platelet survival studies. Washed, neuraminidase-treated platelets were resuspended in Tyrode's solution containing 0.35 per cent albumin or in citrated platelet-free plasma from the same species. Both resuspending fluids contained apyrase. Aggregating agents tested were ADP, acid-soluble collagen, thrombin, ristocetin (with human platelets), polylysine, and serotonin (with rabbit platelets). With all of these agents except polylysine, aggregation of neuraminidase-treated human or rabbit platelets was slightly enhanced compared with control platelets; aggregation of pig platelets was unchanged. When release-inducing agents were used, neuraminidase-treated platelets released more of their 14C-serotonin than control platelets. The extent to which rabbit platelets adhered to a collagen-coated surface or to the damaged surface of everted rabbit aorta was unchanged by pretreatment of platelets with neuraminidase. Therefore it seems unlikely that sialic acid is involved in platelet adherence to collagen. When more than 15 per cent of total sialic acid had been removed from rabbit platelets, they were completely cleared from the circulation within 1 hour of their injection into rabbits. When 8 to 10 per cent of total sialic acid had been removed, the platelets were not cleared immediately from the circulation but were cleared more quickly than control platelets. Thus, although removal of up to 65 per cent of platelet sialic acid has only a slightly enhancing effect on platelet aggregation and release in vitro, removal of as little as 8 to 10 per cent results in the recognition of platelets as "foreign" in vivo.

Adenosine Diphosphate↗

[Neuraminidase induced hemolytic anemia. Experimental and clinical observations (author's transl)].

Recently, increasing attention has been focussed on the in vivo action of neuraminidase as possible pathogenetical factor of hemolytic anemia and even hemolytic-uremic syndrome. Neuraminidase action in red cell membranes results in the release of neuraminic acid, and thereby the uncovering of previously hidden receptors, socalled cryptantigens. With special reference to the phythemagglutinin Anti-TAh from the peanut (Arachis hypogae) and the agglutinin Anti-AHP from the albumin gland of the small Helix pomatia we describe some new methods for the detection of these cryptantigens. In addition to the screebubg genagglutination test with Anti-TAh we developed an "Anti-T-consumption test" for quantitative detection of neuraminidase action on red cells. With the purified reagents we developed an indirect fluorescnet antibody method on blood smears for the detection of cryptantigens on single cells. By animal experiments we could show that not only the membranes of red cells but the intima of renal capillaries as well are damaged by neuraminidase. With these new methods we observed 14 patients suffering from hemolytic anemia due to bacterial or viral neuraminidase. Some of these patients developed a hemolytic-uremic syndrome. We believe that the positive reaction with Anti-T Ah should lead to prophylactic heparinization to prevent dissiminated intravascular coagulation. Neuraminidase is the first identified toxin which directly acts on the membranes of red cells and the intima of renal capillaries as well, and thereby in some patients may induce hemolytic-uremic syndrome. Possibly, these results may stimulate the development of further testsystems for the detection of still unknown toxins which are not tested with our reagents, but may equally be involved in the damage of cell membranes.

Anemia, Hemolytic↗

Antibodies to human influenzavirus neuraminidase (the A-Asian-57 H2N2 strain) in sera from Australian pelagic birds.

Sera collected from Australian pelagic birds specifically inhibited the neuraminidase of the Asian/57 (H2N2) strain of human influenzavirus. Neuraminidase inhibition titres of some sera were high and the avidity of the inhibitor was comparable to that of specific antibody. The neuraminidase of A/Hong Kong/1/68 (H3N2), which has undergone considerable antigenic drift in man since 1957, was inhibited to a lesser extent by the bird sera, while the neuraminidases of the A/BEL/42 (H0N1) and A/FM/1/47 (H1N1) strains were not inhibited at all. The inhibitor could be removed from the sera by adsorption with A/57 virus particles, but not by particles of A/BEL or A/FM1 viruses. These results suggested that the inhibitor in the bird sera was specific antibody. The antibodies to A/57 neuraminidase were found in sera from wedge-tailed shearwaters (Puffinus pacificus) and noddy terns (Anous minutus) nesting on islands off the north-east coast of Australia. They were not found in sera from bridled terns (Sterna anaetheta) or brown gannets (Sula leucogaster) nesting on the same islands. Antibodies to A/57 neuraminidase were also detected in sera from short-tailed shearwaters (Puffinus tenuirostris), which migrate around the Pacific Ocean, suggesting that these birds may be responsible for bringing avian influenzaviruses from areas in the Northern Hemisphere into Australian coastal waters.

Animals↗