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PubMed1987

Effect of neuraminidase on Fc and C3b receptors on rabbit corneal cells infected with herpes simplex virus.

The effect of neuraminidase on Fc receptors (FcR) and C3b receptors (C3bR) was studied in epithelial, stromal and endothelial cells of the rabbit cornea infected with type 1 (HSV-1) and type 2 herpes simplex virus (HSV-2) in vitro. FcR were induced on epithelial, stromal and endothelial cells of the rabbit cornea by both HSV-1 and HSV-2, but their activities were not enhanced by neuraminidase. On the other hand, the treatment of HSV-infected corneal cells with neuraminidase resulted in the enhancement of C3bR activities on epithelial, stromal and endothelial cells infected with HSV-1, and the enhancing effect of neuraminidase was more pronounced on corneal endothelial cells. A similar neuraminidase treatment had no significant effect on C3bR activities on the corneal cells infected with HSV-2.

Animals↗
PubMed1975

[The virulence of erysipelothrix rhusiopathiae strains and their neuraminidase production (author's transl)].

We studied the virulence of 20 Erysipelothrix rhusiopathiae strains in albino mice and investigated the interdependence between virulence, growth rate, and neuraminidase production. The minimal number of germs, lethal to mice (LD100) varied among the strains between 10(1) and mor ethan 10(7) per animal. The course of the disease was also very different. Some strains killed the mice rapidly within 3 days. In other strains, however, even a very high number of bacteria caused death only 7 days after infection or later, in which cases the disease became manifest long in advance by ruffled fur and glutinous eyes. A significant correlation was found between the average neuraminidase production in different media and the virulence (p equal to 99%; Fig. 2). We found a less marked dependence between growth rate and virulence (Fig. 3). Neuraminidase activity and growth rate seem to influence virulence rather independently. This is concluded from the fact, that some virulent strains are characterized by quick growth and by producing either no neuraminidase or in small quantities only. On the other hand, neuraminidase production cannot be separated completely from growth rate. An induction of neuraminidas activity in vivo was not observed, even when the bacteria persisted in the mice over a long period of time. We therefore conclude that a short term enzyme induction is not probable.

Enzyme Induction↗
PubMed1975

[Occurrence of neuraminidase in Sporothrix schenckii and Ceratocystis stenoceras and its role in ecology and pathomechanism of these fungi (author's transl)].

Some strains of Sporothrix schenckii and one strain of Ceratocystis stenoceras were investigated and the occurrence of the enzyme neuraminidase (= sialidase, N-acetylneuraminate glycohydrolase, EC 3.2.1.18) was proved not only by Warren's thiobarbituric acid assay but also by immunoelectrophoresis technique using monospecific antisera against 25 human glycoproteins, lipoproteins, immunoglobulins, fibrinogen and some other proteins (Table 1). There are also fibrinolytic and lipolytic enzyme activities in strains of Sporothrix chenckii corresponding with similar findings of other authors and also in the Ceratocystis stenoceras strain. The temperature optimum of production of neuraminidase seems to be lower than 37 degrees C (Table 2) and all strains failed to produce the enzyme after cultivation at 37 degrees C during some months. The findings of the existence of neuraminidase in the both species confirm also their close relationship. Because the occurrence of N-acylneuraminate was shown only in animals and in some microorganisms but not in plants it can be suggested that also Sporothrix schenckii and Ceratocystis stenoceras grow on animal or neuraminate containing microbial material but not on plants as it is assumed hitherto. Corresponding to this hypothesis the pathogenicity of Sporothrix schenckii and also the facultative pathogenicity of Ceratocystis stenoceras are to see in connexion with the action of neuraminidase and other enzymes metabolizing animal substrates. It can be concluded that neuraminidase is a possible additional pathogenic factor in sporotrichosis below 37 degrees C.

Ascomycota↗
PubMed1976

Effect of neuraminidase and papain treatment on lectin-induced agglutination of Novikoff tumor cells and assay of lectin receptor activity of the glycopeptides released from the cell surface by papain.

Lectins, plant proteins that bind specific saccharide determinants, have been utilized to examine the effect of neuraminidase digestion on the structure and/or expression of oligosaccharide moieties present at the periphery of Novikoff ascites hepatoma cells. Five lectins were utilized: concanavalin A (Con A), specific for alpha-D-manno- or alpha-D-glucopyranosyl residues; wheat germ agglutinin, specific for 2-acetamido-2-deoxy-D-glucopyranosyl residues; Ricinus communis agglutinin I (RCAI), specific for D-glucopyranosyl residues; R. communis agglutinin II (RCAII), specific for D-galacto- or 2-acetamido-2-deoxy-D-galactopyranosyl residues; and soybean agglutinin, specific for 2-acetamido-2-deoxy-D-galactopyranosyl residues. Neuraminidase treatment of Novikoff cells did not alter their agglutination by Con A or wheat germ agglutinin. Similar treatment produced only a 2-fold increase in their agglutination by RCAI but a 12-fold increase in their agglutination by RCAII, indicating that 2-acetamido-2-deoxy-D-galactopyranosyl residues become expressed upon neuraminidase treatment. This conclusion was confirmed by the observation that neuraminidase-treated Novikoff cells acquired agglutinability by soybean agglutinin. Binding studies using ferritin-conjugated RCAII indicated that neuraminidase treatment exposed cryptic cell surface receptors for RCAII. To ascertain the role of cell surface glycoproteins in lectin-induced agglutination of Novikoff cells, glycopeptides cleaved from the cell surface by papain were assayed for lectin receptor activity. The cell surface glycopeptides exhibited receptor activity for Con A, wheat germ agglutinin and RCAI but not for RCAII and soybean agglutinin. A cell surface macrosialoglycopeptide fraction, resolved by gel filtration and ion-exchange chromatography, possessed a major portion of the Con A and RCAI receptor activity.

Agglutination↗
PubMed1976

Neuraminidase reversal of resistance to lysis of herpes simplex virus-infected cells by antibody and complement.

The susceptibility to lysis by antibody and complement was examined in four human cell lines. The cells were infected with herpes simplex virus type 1 and lysis was assessed by the 51Cr release test by using antibodies to herpes simplex virus and guinea pig serum as a source of complement. The four cell lines were found to differ in their susceptibility to lysis, although virus replication was readily demonstrated in the different cell lines. By indirect immunofluorescence, no differences in the expression of virus antigens at the surface of the cells could be found between the different cell lines. Treatment of cells with neuraminidase markedly enhanced the sensitivity of the cells which were relatively insensitive to lysis. The enhancement of susceptibiltiy to lysis by neuraminidase occurred if cells were treated before reaction of the cells with antibody and if the cells were reacted with antibody before treatment with the enzyme. No enhancement was observed when cells were reacted with antibody and complement before neuraminidase treatment. Neuraminidase treatment did not seem to enhance appreciably the quantity of antibody which reacted at the cell surface. The observations suggest that surface properties of certain cells render the cells resistant to lysis by antibody and complement and that the resistance to lysis can be abrogated by treating the cells with neuraminidase.

Antibodies, Viral↗
PubMed1978

Parainfluenza-3 virus: difference in capacity of neuraminidase-weak and strong strains to infect young calves and to elicit cellular immune response.

Calves less than four weeks old could not be infected with a neuraminidase-weak strain of parainfluenza-3 virus (Pi3) but were successfully infected with either of two neuraminidase-strong strains. The criteria for infection were virus excretion, cell-mediated and antibody-mediated immune responses. In the lymphocyte stimulation test, calves infected with the neuraminidase-strong Pi3 strain Tüb-E6 responded more strongly to antigen prepared from this strain than to antigen from the heterologous Pi3 strain Um-23. The non-immunoglobulin haemagglutination inhibition activity of the liquid phase of nasal secretions of newborn calves decreased after treatment with Vibrio cholerae neuraminidase. For virus-bound neuraminidase the liquid phase from newborn calves was a richer substrate than the liquid phase from older animals.

Animals↗
PubMedDate not supplied

[Analysis of the antigenic specificity of the neuraminidases of influenza B viruses isolated in different years].

The antigenic structure of neuraminidases of influenza B viruses isolated in 1940-1984 was studied. Lectin test has first been employed for analysis of influenza B virus neuraminidase. The antigenic composition of neuraminidases of these viruses was shown to be different. The strains isolated in the epidemic of 1983-1984 underwent further drift of the neuraminidase component and represent a heterogeneous group in this respect. The use of monospecific antiserum to purified neuraminidase helped specify antigenic relationships of this protein.

Antigens, Viral↗
PubMedDate not supplied

[Neuraminidase forms in human chorion].

Detection of various forms of neuraminidase from human chorion was carried out by means of evaluation of the enzyme stability of freezing-thawing and of its ability to bind lectin. Freezing of chorion in liquid nitrogen enabled to find in the tissue labile neuraminidase, which occurred in soluble fraction as well as the more stable enzyme form, precipitated with cell particles. At the same time, properties of soluble and membrane-bound neuraminidases, involving pH optima and specificity towards synthetic substrates, were similar. The precipitated neuraminidase from human chorion consisted of two forms, bound- and unbound with Con A-Sepharose. Both these forms exhibited similar pH optima and Km values but were dissimilar in their stability. The neuraminidases from human chorion, dissimilar in their property of lectin-binding, resembled the enzymes from human leukocytes. Besides, beta-galactosidases from both human chorion and leukocytes were bound with Con A-Sepharose practically completely.

Chorion↗
PubMed1987

[Effect of neuraminidase and x-rays (2 Gy and 8 Gy) on microvilli and membrane invaginations of Ehrlich ascites tumor cells in monolayer culture].

A monolayer culture (Eagle basal medium plus 10% of fetal calf serum) of Ehrlich ascites tumor cells was exposed to X-radiation with 2 Gy and 8 Gy and treated with Vibrio cholerae neuraminidase alone or combined with sublethal X-ray irradiation (2 Gy). Pictures of the Ehrlich ascites tumor cells taken with the electron microscope were investigated in order to find out any cell surface modifications due to membrane invaginations and microvilli. The results showed that the rate of microvilli as well as that of membrane invaginations became higher with the increasing X-ray dose (2 Gy; 8 Gy). Following to neuraminidase treatment there was a considerable augmentation of membrane invaginations as compared to control cells, whereas the number of microvilli was slightly reduced. As it has been already described before, the influence of neuraminidase produced an increased endocytosis activity and a strengthening of the cytoskeleton. Combined treatment with neuraminidase and sublethal X-radiation (2 Gy) caused a higher rate of membrane invaginations than each method alone; the number of microvilli was slightly increased by combined treatment. The conclusion is drawn that these structure modifications are due to reparation processes induced by radiation on the one hand and to an enzymic action of neuraminidase on the cell surface on the other hand.

Animals↗
PubMed1975

Studies on parainfluenza-3 virus neuraminidase.

Various parainfluenza-3 virus (PIV-3) strains differ in neuraminidase (NA) activity, some being neuraminidase strong (NAS) and some neuraminidase weak (NAW). No difference in the ability of these strains to elicit antibody activity to hemagglutinin (HA) or NA of PIV-3 was observed. Samples of formalin-treated PIV-3 released more N-acteylneuraminic acid (NANA) than samples of Piv-3 not treated with formalin when these samples were incubated with the substrate sialolactose for 16 h at 37 degrees C. The initial activity of PIV-3 NA, and the Km-value, were similar for a NAS strain whether it was treated with formalin or not. The results suggest that formalin stabilized the NA structure of PIV-3. A NAS strain of PIV-3 dialyzed against distilled water showed an increased initial neuraminidase activity as compared to virus dialyzed against isotonic NaCL or to non-dialyzed virus. The increased enzyme activity indicates an increased affinity of NA tothe substrate sialolactose as an increased Km-value was also obtained. It is suggested that PIV-3 neuraminidase facilitates the penetration of the virion through the mucociliary barrier of the respiratory tract by releasing the virus from inhibitors in the gel phase. It has been found that antibody in the gel phase of nasal secretion inhibits the NA activity of PIV-3 Following exposure of a gel phase of bovine tracheal secretion to a NAS strain of PIV-3 an increased initial viscosityof this phase was observed. The gel phase of bovine nasal secretion showed a structural change in scanning electronmicroscopy following exposure to a NAS strain. Stimultaneously an increased amount of free N-acetylneuraminic acid was found in the gel.

Animals↗
PubMed1984

Monoclonal antibodies as functional probes of the HN glycoprotein of Newcastle disease virus: antigenic separation of the hemagglutinating and neuraminidase sites.

A panel of nine monoclonal antibodies has been used to construct a functional inhibition profile of four antibody-binding sites previously delineated on the HN glycoprotein of Newcastle disease virus. Antibodies to all four sites are capable of neutralizing infectivity and inhibiting hemolysis and neuraminidase activity with fetuin. There is a good correlation between the fractions of infectivity and neuraminidase activity which survive antibody treatment. However, the inhibition of hemolysis is in the inverse relative order of the neutralization of infectivity. Antibodies to sites 1 and 2 are capable of inhibiting hemagglutination, whereas only antibodies to site 2 can inhibit neuraminidase activity on the smaller substrate N-acetyl neuraminlactose. This antigenically separates the hemagglutinin and neuraminidase sites on the HN glycoprotein. We used these functional inhibition studies to speculate about the location of the four antigenic sites relative to the hemagglutinin and neuraminidase sites.

Animals↗
PubMed1982

Effects of neuraminidase treatment on CFUs properties and CFUs numbers.

Incubation of bone marrow cells with Vibrio cholerae neuraminidase decreases the number of CFUs to a minimum of 25% of control numbers. It is shown that this decrease in CFUs numbers is not due to cytotoxic effects of neuraminidase but to a decrease in the spleen seeding efficiency of colony forming cells. Neuraminidase acts in two ways. It removes negatively charged neuraminic acids from membrane glycoproteins and glycolipids and it can adsorb to the cell surface. It is investigated which of the two enzyme effects is responsible for the decrease in CFUs numbers. Inhibition of the enzyme reaction by EDTA prevents to a great extent the decrease in CFUs numbers, while tests with mouse spleen cells and human erythrocytes show that EDTA has no or a positive effect on the adsorption of neuraminidase to the cell surface. This indicates that the neuraminidase induced decrease in CFUs numbers is caused by the enzymatic removal of neuraminic acids rather than by the adsorption of the enzyme to the cell surface.

Adsorption↗
PubMed1981

[Action of x-rays and neuraminidase on pinocytotic activity and microtubule-microfilament system of Ehrlich ascites tumor cells in monolayer culture (author's transl)].

Monolayer cultures of Ehrlich ascites tumor cells in exponential growth phase were treated with X-rays and neuraminidase alone or in combination. A radiation dose of 2 Gy (200 rd) and higher effected a significant inhibition of DNA synthesis and cell proliferation. Neuraminidase treatment in addition to irradiation did not modify the growth-inhibitory irradiation effect. Cells pretreated for 0.5 to 1.0 hours with neuraminidase (in Earle's salt solution) and cultured thereafter (4h) in serum-containing growth medium exhibited an enhanced development of the microtubule-microfilament-system. Morphometric analysis of microtubules on electronmicroscopic sections revealed a nearly 4-fold increased number in neuraminidase treated cells while the average length of microtubules was similar to controls. Pinocytosis as measured by the ultrastructural uptake of ferritin appeared to be increased following neuraminidase treatment. A connection between neuraminic acid containing components (glycoproteins or glycolipids?) of the cell membrane or cell surface, on the one hand, and the cytoskeleton and the endocytotic process of these tumor cells, on the other hand, is suggested.

Animals↗
PubMed1981

[Neuraminidase-Inhibiting Antibodies to Avian Influenza Virus Subtypes in Human Sera (author's transl)].

400 human sera were tested both in hemagglutination inhibition (HI) and neuraminidase inhibition (NI) tests for antibodies to avian and animal influenza virus subtypes. In the H1 test we only found antibodies to the avian subtype Hav 7 and the animal subtypes Hsw 1 and Heq 2 whereby the latter was mainly demonstrated in elderly persons 60 to 100 years old. The findings of Hav 7 are due to H 3 antibodies and reflect the relationship between both antigens. In the NI test we obtained positive results in 21.8% of the human sera with the neuraminidase subtype N 3 (Nav 2/3) with a peak in persons who were 60 to 70 years old. 11.0% of the sera contained antibodies to the neuraminidase subtype N 8 (Neq 2) and were found exclusively in people 60 to 100 years old, and 9.3% of sera showed positive reactions with the subtype N5 (Nav 5). Until now an immunological relationship between the neuraminidase subtypes N 1, N 2, and N 3 is not known, and could'nt be found in our own studies. Contaminations of antigens can also be excluded. The possible origin of these antibodies to avian neuraminidase subtypes is discussed.

Adolescent↗
PubMed1977

Effectiveness of neuraminidase in experimental immunotherapy of two murine pulmonary carcinomas.

The effects of direct intratumoral inoculation with Vibrio cholerae neuraminidase and inoculation of tumor-bearing mice with tumor cells incubated with neuraminidase in vitro were studied in C57BL/6 X DBA/2 F1 mice bearing s.c.-transplanted, methylcholanthrene-induced pulmonary squamous cell or Lewis lung carcinomas. The growth of the squamous cell tumor was more greatly inhibited by both treatments than was the Lewis lung tumor. In the squamous cell tumor-bearing mice, both modes of neuraminidase treatment depressed tumor growth by approximately 80%. However, 20% of the mice in the group treated with the neuraminidase-incubated squamous cell vaccine and 10% of those treated intratumorally underwent total tumor regression and developed specific immunity to the squamous cell tumor. although the growth rate of the Lewis lung tumor was suppressed by both types of treatment, the direct intratumoral neuraminidase treatment group underwent a greater depression in tumor growth (73 versus 42%). A possible explanation of the different results of the two treatments in squamous cell and Lewis lung tumor systems may be based on tumor etiology and cellular composition.

Animals↗
PubMed1995

The role of antigenically different virus neuraminidases as structures implicated in receptor-binding processes.

Influenza A viruses exhibit segmented nucleic acid coding for eight different proteins, two of them as glycoproteins exposed on their lipoprotein envelopes, hemagglutinin (HA) and neuraminidase (NA). Hemagglutinin exhibits receptor-binding activity while neuraminidase develops sialidase cleavage activity which acts on cell receptors. Influenza A strains responsible for human, avian, equine and porcine respiratory infections all over the world present antigenically different hemagglutinin (H1 to H14) and neuraminidase (N1 to N9) structures on their surface. The objective of the present investigation was to study the role of N2, N8, and N9, antigenically diverse neuraminidase structures of human (N2) and animal (N8 and N9) influenza viruses, in the receptor-binding process. Receptor-binding activity of N2 and N8 was analyzed by crossed tests using H3N2 and H3N8 antisera and the hemagglutination inhibition test as a model. Hemagglutinating activity of antigenically different N2 and N8 structures was demonstrable and was inhibited by homologous antisera (N2-H3N2, N8-H3N8) but not by heterologous antisera (N2-H3N8,N8-H3N2). This previously demonstrated N9 hemagglutinating activity was analyzed for receptor-binding specificity using hemagglutination tests and NeuAc alpha2,3Gal and NeuAc alpha2,6Gal derivatized erythrocytes. This highly purified N9 strain was obtained from a virus strain isolated from terns by Dr. Peter Colman (CSIRO Division of Biomolecular Engineering, Parkville, Victoria, Australia). It exhibited receptor-binding specificity for NeuAc alpha2,3Gal sequences, a property similar to that observed in hemagglutinins from avian strains. These results indicate the importance of antigenically different neuraminidase structures as alternative agents for developing receptor-binding activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Hemagglutination, Viral↗
PubMed1997

Modeling the paramyxovirus hemagglutinin-neuraminidase protein.

The paramyxovirus hemagglutinin-neuraminidase (HN) protein exhibits neuraminidase activity and has an active site functionally similar to that in influenza neuraminidases. Earlier work identified conserved amino acids among HN sequences and proposed similarity between HN and influenza neuraminidase sequences. In this work we identify the three-dimensional fold and develop a more detailed model for the HN protein, in the process we examine a variety of protein structure prediction methods. We use the known structures of viral and bacterial neuraminidases as controls in testing the success of protein structure prediction and modeling methods, including knowledge-based threading, discrete three-dimensional environmental profiles, hidden Markov models, neural network secondary structure prediction, pattern matching, and hydropathy plots. The results from threading show that the HN protein sequence has a 6 beta-sheet propellor fold and enable us to assign the locations of the individual beta-strands. The three-dimensional environmental profile and hidden Markov model methods were not successful in this work. The model developed in this work helps to understand better the biological function of the HN protein and design inhibitors of the enzyme and serves as an assessment of some protein structure prediction methods, especially after the x-ray crystallographic solution of its structure.

Amino Acid Sequence↗
PubMed1991

Glycosylation of the hemagglutinin-neuraminidase glycoprotein of human parainfluenza virus type 1 affects its functional but not its antigenic properties.

The hemagglutinin-neuraminidase (HN) glycoprotein of human parainfluenza virus type 1 (hPIV-1) has been shown to be similar in predicted protein sequence and structure to those of Sendai virus, but it is more highly glycosylated. Because glycosylation can modify protein structure and function, we investigated the effect of glycosylation on the antigenic structure and biological function of the HN of hPIV-1. Antigenic and functional analyses were carried out with purified hPIV-1 virions treated with Endoglycosidase F, which removes carbohydrate moieties, because treatment of hPIV-1-infected LLC-MK2 cells with an inhibitor of glycosylation resulted in virions which were deficient in both HN and F surface glycoproteins. No change in the antigenic structure of the HN of hPIV-1 was detected after carbohydrate removal; epitope recognition by a panel of 7 hPIV-1 HN monoclonal antibodies (MAbs) was unchanged compared to untreated virions. Moreover, there was no change in the cross-reactivity of 8 of 10 Sendai virus HN MAbs, and only a slight change in the remaining 2. Nor did carbohydrate removal appear to affect hemagglutinating or neuraminidase activities; hemagglutination titers with chicken erythrocytes (cRBC) were unchanged, and in vitro neuraminidase activity with a small substrate (N-acetylneuraminlactose) showed only a 20% reduction. However, elution of deglycosylated hPIV-1 from agglutinated cRBC as a result of neuraminidase activity was reduced by 80%. These results suggest that the enzymatic activity of hPIV-1 HN was not directly affected by carbohydrate removal but that the reduction in elution was due to a change in the interaction of the HN with the host receptor. This was further supported by a 2- to 16-fold reduction in the ability of all 7 hPIV-1 HN MAbs to inhibit hemagglutination of deglycosylated hPIV-1 virus. Such a change in HN-host receptor interaction was found to involve a change in receptor specificity because deglycosylated virus was able to fully agglutinate cRBC stripped of receptors required by the native, glycosylated virus. We propose the following model for our results: deglycosylation of the HN of hPIV-1 causes the hemagglutinating portion of the molecule to recognize a new receptor which is not susceptible to enzymatic cleavage by the neuraminidase.

Antibodies, Monoclonal↗