SEARCH · PubMed Health

Results for “NEURAMINIDASE”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 775 records · Page 43Linked to original sources

PubMed2004

Surveillance of influenza isolates for susceptibility to neuraminidase inhibitors during the 2000-2002 influenza seasons.

Neuraminidase (NA) inhibitors (NI) have recently been licensed for the prophylaxis and treatment of influenza virus infection in humans. This study has utilized a new chemiluminescent (CL) neuraminidase assay to routinely monitor more than a thousand influenza field isolates collected worldwide during the 2000-2002 seasons for susceptibility to both licensed NIs, zanamivir, and oseltamivir by determining the 50% inhibitory concentration (IC50). Our data demonstrated that influenza A viruses of the N2 subtype were less susceptible to zanamivir, but not oseltamivir, than those of the N1 subtype such that 41 of 45 confirmed H1N2 isolates could be reliably differentiated from H1N1 viruses based on their zanamivir susceptibility. Pre-titration of influenza A viruses appeared to have no effect on IC50 determined for either NI, while pre-titration of influenza B viruses significantly reduced oseltamivir IC50 and increased zanamivir IC50. Influenza B viruses were less susceptible to either compound than type A isolates. The CL assay is a rapid and reliable method for screening large numbers of influenza isolates for NI susceptibility. Reassortant viruses of the H1N2 subtype that started to circulate worldwide during the 2001-2002 season can be reliably separated from H1N1 viruses based on their zanamivir susceptibility, enabling large scale screening of H1 isolates for determining the prevalence of such reassortants.

Acetamides↗

PubMed2004

Molecular mechanisms of influenza virus resistance to neuraminidase inhibitors.

A wide use of inhibitors of influenza virus neuraminidase (NAIs) to control influenza in humans demands a better understanding of the mechanisms involved in the resistance emergence. In vitro studies demonstrate that both neuraminidase (NA) and hemagglutinin (HA) influence virus susceptibility to NAIs. Drug resistance conferred due to changes in the NA could be monitored in the NA inhibition assays. Zanamivir-selected viruses acquired the NA substitutions at residues 119 and 292; oseltamivir-selected--at 274 and 292; peramivir-selected--at 292; and A-315675-selected--at 119. The HA binding efficiency and therefore susceptibility to NAIs are affected by the amino acids forming the HA receptor-binding site, the location and number of oligosaccharide chains, and structure of the neuraminic acid-containing cellular receptors. The lack of suitable cell culture-based assays hampers the assessment of virus susceptibility in humans. Emergence of the viruses with the NAI-induced substitutions in the NA is uncommon in drug-treated humans, however a compromised state of the immune system promotes emergence of drug resistance. In vivo, the zanamivir-selected mutant contained a substitution at 152 (B/NA); the oseltamivir-selected mutants-at residues 119 (A/N2), 198 (B/NA), 274 (A/N1), and 292 (A/N2). Substitutions in the NA were often accompanied by impairment of virus infectivity and virulence in animal models. Because of complexity of mechanisms of virus resistance, further analysis of the viruses recovered from the drug-treated humans is warranted.

Antiviral Agents↗

PubMed2004

Identification of a human influenza type B strain with reduced sensitivity to neuraminidase inhibitor drugs.

A total of 126 influenza B isolates isolated between 1998 and 2002 from Australasia and the Asia-Pacific region were tested for their sensitivity to the neuraminidase (NA) inhibitor drugs zanamivir and oseltamivir carboxylate using a fluorescence-based enzyme assay. The mean (+/-1 S.D.) 50% inhibitory concentration (IC50) of the influenza B viruses tested was 1.41+/-0.53 nM against zanamivir and 14.91+/-14.31 nM with oseltamivir carboxylate. However, a single type B isolate (B/Perth/211/2001) from an infant who had not been treated with either of the NA inhibitor drugs, showed a nine-fold lower sensitivity to zanamivir and a 14-fold lower sensitivity to oseltamivir carboxylate compared with the mean IC50 of influenza B strains. A decrease in sensitivity to oseltamivir carboxylate and RWJ-270201 was also seen in both: a chemiluminescent assay and a second different fluorescent assay. Sequence analysis of the haemagglutinin HA1 region and the neuraminidase gene of B/Perth/211/2001 revealed no amino acid changes in sites that have previously been reported to confer resistance to either of the NAI drugs. Further investigations are in progress to identify the basis for this reduced sensitivity.

Acetamides↗

PubMed1997

Dynamic properties of Newcastle Disease Virus envelope and their relations with viral hemagglutinin-neuraminidase membrane glycoprotein.

The lipid composition of Newcastle Disease Virus (NDV) Clone-30 strain shows a low lipid/protein ratio, a high cholesterol/phospholipid molar ratio, and major phospholipids being qualitatively different to other NDV strains. The major fatty acyl constituents are palmitic, stearic, oleic, and linoleic acids; cerebrosides, sulfatides and two kinds of gangliosides are also found in the NDV membrane. It is reported for the first time in NDV that phospholipid classes are asymmetrically distributed over the two leaflets of the membrane: 60 +/- 4.5% of the phosphatidylcholine and 70 +/- 5.0% of the sphingomyelin are in the outer monolayer. Intact viral membranes and reconstituted NDV envelopes showed similar dynamic properties. Hemagglutinin-neuraminidase (HN) and fusion (F) proteins of NDV membrane affect the lipid thermotropic behaviour in reconstituted proteoliposomes made up of a single class of phospholipids. It is shown that the lipid composition is more important than the bulk membrane fluidity/order for both sialidase (neuraminidase) and hemagglutinating HN activities. Sialidase and hemagglutinating activities requires the presence of definite phospholipids (phosphatidylethanolamine) in its environment.

Fatty Acids↗

PubMed1987

A photoreactive competitive inhibitor of the human lysosomal neuraminidase in cultured skin fibroblasts.

A photoreactive, potent, competitive inhibitor of the human lysosomal neuraminidase in cultured skin fibroblasts has been prepared. The starting material, 2,3 dehydro-N-acetyl neuraminic acid methyl ester, was selectively tosylated at the C-9 position with tosyl chloride and subsequently peracetylated with acetic anhydride. The tosyl group was displaced with potassium thio acetate in dimethylformamide at 60 degrees C for 80 min. 4-fluoro-3-nitrophenylazide was incorporated by reaction with the thio acetate product and equimolar sodium methoxide in methanol followed by reacetylation. Base hydrolysis gave the final product, 9-S-(4-azido-2-nitrophenyl)-5-acetamido-2,6 anhydro-2,3,5,9-tetradeoxy-9-thio-D-glycero-D-galacto-non-2-enonic acid (W5). The yields at each step were 50-70%. Competitive inhibition kinetics were observed when W5 was tested with the fibroblast neuraminidase using 4-methylumbelliferyl-N-acetyl-neuraminic acid as substrate giving an apparent Ki of about 10 microM. These results suggest that the terminal hydroxyl group at C-9 may not be important in the recognition and binding of the substrate by the enzyme. Also, the compounds prepared here may be useful as photoaffinity probes or ligands for affinity chromatography for purification.

Affinity Labels↗

PubMed1988

Expression of cDNA encoding the human "protective protein" associated with lysosomal beta-galactosidase and neuraminidase: homology to yeast proteases.

The "protective protein" is a glycoprotein that associates with lysosomal beta-galactosidase and neuraminidase and is deficient in the autosomal recessive disorder galactosialidosis. We have isolated the cDNA encoding human "protective protein". The clone recognizes a 2 kb mRNA in normal cells that is not evident in fibroblasts of an early infantile galactosialidosis patient. The cDNA directs the synthesis of a 452 amino acid precursor molecule that is processed in vivo to yield mature "protective protein," a heterodimer of 32 kd and 20 kd polypeptides held together by disulfide bridges. This mature form is also biologically functional since it restores beta-galactosidase and neuraminidase activities in galactosialidosis cells. The predicted amino acid sequence of the "protective protein" bears homology to yeast carboxypeptidase Y and the KEX1 gene product. This suggests a protease activity for the "protective protein."

Amino Acid Sequence↗

PubMed2000

Influenza virus neuraminidase inhibitors.

Neuraminidase promotes influenza virus release from infected cells and facilitates virus spread within the respiratory tract. Several potent and specific inhibitors of this enzyme have been developed, and two (zanamivir and oseltamivir) have been approved for human use. Unlike amantadine and rimantadine that target the M2 protein of influenza A viruses, these drugs inhibit replication of both influenza A and B viruses. Zanamivir is delivered by inhalation because of its low oral bioavailability whereas oseltamivir is administered by mouth. Early treatment with either drug reduces the severity and duration of influenza symptoms and associated complications. Both agents are effective for chemoprophylaxis. Because of a broader antiviral spectrum, better tolerance, and less potential for emergence of resistance than is seen with the M2 inhibitors, the neuraminidase inhibitors represent an important advance in the treatment of influenza.

Acetamides↗

PubMed1997

Small neuraminidase gene of Clostridium perfringens ATCC 10543: cloning, nucleotide sequence, and production.

The small nanH gene encoding a neuraminidase from Clostridium perfringens ATCC 10543 was cloned in JM109 using pUC19 as a vector. Sequence analysis revealed an ORF, nt 310-1455, encoding 382 amino acids that was proceeded by a typical Shine-Dalgarno sequence, GGACGAGA. The nt sequence in the 15-402 region had in vivo promoter activity in an Escherichia coli promoter probe plasmid pKK232-8, which suggested that the small nanH promoter is functional in E. coli. Four regions of amino acids demonstrated great similarity to the "Asp boxes" (-Ser-X-Asp-X-Gly-X-Thr-Trp-) of other bacterial nanH proteins. The small nanH expressing clone, pCPN-1, which was cultured under aerobic conditions resulted in NanH activity which was 203-fold in culture and 211-fold in intracellular fraction compared to that of C. perfringens which has to be cultured under anaerobic conditions. Production of small NanH was also induced by adding sialyllactose to the culture medium of JM109 [pCPN-1]. The enzyme activity could be detected in the periplasmic fraction and the culture medium of JM109 [pCPN-1] after culturing to the stationary phase. The molecular weight, K(m), and optimum pH and pI of the cloned enzyme are identical to those of the parent strain. The cloned, small nanH could be used to study the structure-functional relationship of nanH, while the pCPN-1 clone could be used in the aerobic production of neuraminidase.

Amino Acid Sequence↗

PubMed2001

Expression and characterization of soluble human parainfluenza virus type 1 hemagglutinin-neuraminidase glycoprotein.

Human parainfluenza virus types 1 (hPIV-1), 2, and 3 represent significant respiratory pathogens for which no antiviral treatment is currently available. To characterize the biochemical functions of the hPIV-1 hemagglutinin-neuraminidase (HN) glycoprotein, a potential target for antiviral therapy, we cloned and expressed a soluble portion of hPIV-1 HN (amino acid residues 137-575), lacking the N-terminal hydrophobic membrane anchorage region, in insect cells using the baculovirus secretion expression system. The expressed HN protein was purified through cation-exchange chromatography followed by metal affinity chromatography, using the 6xHis epitope introduced at the carboxyl terminus of the recombinant protein. N-terminal amino acid sequence analysis of purified HN indicated that the honeybee melittin secretion signal peptide was correctly removed during post-translational processing. Further characterization revealed that the purified HN protein was N-glycosylated and exhibited neuraminidase activity whose characteristics resembled those of the native HN protein of hPIV-1 virions. The establishment of this expression and purification system has allowed us to further explore the biochemical characteristics of paramyxovirus HN and to obtain material that could be suitable for X-ray crystallography studies.

Amino Acid Sequence↗

PubMed2000

The neuraminidase inhibitor GS4104 (oseltamivir phosphate) is efficacious against A/Hong Kong/156/97 (H5N1) and A/Hong Kong/1074/99 (H9N2) influenza viruses.

In 1997, an H5N1 avian influenza A/Hong Kong/156/97 virus transmitted directly to humans and killed six of the 18 people infected. In 1999, another avian A/Hong/1074/99 (H9N2) virus caused influenza in two children. In such cases in which vaccines are unavailable, antiviral drugs are crucial for prophylaxis and therapy. Here we demonstrate the efficacy of the neuraminidase inhibitor GS4104 (oseltamivir phosphate) against these H5N1 and H9N2 viruses. GS4071 (the active metabolite of oseltamivir) inhibited viral replication in MDCK cells (EC(50) values, 7.5-12 microM) and neuraminidase activity (IC(50) values, 7.0-15 nM). When orally administered at doses of 1 and 10 mg/kg per day, GS4104 prevented death of mice infected with A/Hong Kong/156/97 (H5N1), mouse-adapted A/Quail/Hong Kong/G1/97 (H9N2), or human A/Hong Kong/1074/99 (H9N2) viruses and reduced virus titers in the lungs and prevented the spread of virus to the brain of mice infected with A/Hong Kong/156/97 (H5N1) and mouse-adapted A/Quail/Hong Kong/G1/97 (H9N2) viruses. When therapy was delayed until 36 h after exposure to the H5N1 virus, GS4104 was still effective and significantly increased the number of survivors as compared with control. Oral administration of GS4104 (0.1 mg/kg per day) in combination with rimantadine (1 mg/kg per day) reduced the number of deaths of mice infected with 100 MLD(50) of H9N2 virus and prevented the deaths of mice infected with 5 MLD(50) of virus. Thus, GS4104 is efficacious in treating infections caused by H5N1 and H9N2 influenza viruses in mice.

Acetamides↗

PubMed2002

Influenza virus carrying an R292K mutation in the neuraminidase gene is not transmitted in ferrets.

A model of influenza transmission has been established in ferrets in which wild-type influenza infection in a donor ferret can be transmitted sequentially to other ferrets. We have studied the transmission in ferrets of a clinical isolate of A/Sydney/5/97 (H3N2) carrying the neuraminidase 292K mutation compared with the corresponding wild-type virus from the same subject. Donor ferrets (n=four per group) were inoculated intranasally with mutant or wild-type virus and each housed with three naïve contact ferrets. All donor ferrets inoculated with wildtype virus were productively infected and transmitted virus to all 12 contacts, who in turn had high viral titres in their nasal washes. In contrast, only two of the donor ferrets inoculated with mutant virus were productively infected. There was little or no evidence that the two infected donor animals transmitted mutant virus to their contact animals. This ferret model has demonstrated that the mutant influenza virus with lysine at position 292 of the neuraminidase is of reduced infectivity and does not transmit under conditions in which the wild-type virus with arginine at position 292 readily transmits.

Animals↗

PubMed2002

Susceptibility of recent Canadian influenza A and B virus isolates to different neuraminidase inhibitors.

Forty-two influenza A and 23 influenza B isolates collected from untreated subjects during the 1999-2000 influenza season in Canada were tested for their susceptibility to three neuraminidase inhibitors (zanamivir, oseltamivir carboxylate and RWJ-270201 or BCX-1812) using a chemiluminescent neuraminidase assay. Influenza B isolates were less susceptible than A viruses to all tested drugs. RWJ-270201 was the most potent drug against both influenza A(H3N2) (mean IC(50): 0.60 nM) and B (mean IC(50): 0.87 nM) viruses. Oseltamivir carboxylate was more active than zanamivir for influenza A(H3N2) isolates (mean IC(50): 0.73 vs. 2.09 nM) whereas it was less potent against B viruses (mean IC(50): 11.53 vs. 4.15 nM).

Acetamides↗

PubMed1998

Inhibition of influenza virus infections in mice by GS4104, an orally effective influenza virus neuraminidase inhibitor.

The carbocyclic transition state sialic acid analog GS4071 ([3R,4R,5S]-4-acetamido-5-amino-3-[1-ethylpropoxy]-1-cyclohexane-1 -carboxylic acid), a potent influenza virus neuraminidase inhibitor, was highly inhibitory to influenza A/NWS/33 (H1N1), A/Victoria/3/75 (H3N2), A/Shangdong/09/93 (H3N2) and B/Hong Kong/5/72 viruses in Madin Darby canine kidney (MDCK) cells. The 50% effective concentrations in these experiments ranged from 1.8 to 59.5 microM, with no cytotoxicity evident at 1000 microM, using inhibition of viral cytopathic effect determined visually and by neutral red dye uptake. The ethyl ester prodrug of GS4071, GS4104, administered by oral gavage (p.o.), had significant inhibitory effects on infections in mice induced by these viruses. Antiviral effects were seen as prevention of death, increase in mean day to death, inhibition of decline of arterial oxygen saturation, lessened lung consolidation and inhibition of infectious virus recovered from the lungs. No toxicity was seen in dosages up to 100 mg/kg/day (highest evaluated). Comparison experiments run versus the influenza A (H1N1) virus-induced infection using GS4104, GS4071 and the neuraminidase inhibitor zanamivir (GG167, 4-guanidino-Neu5Ac2en), all administered p.o., indicated a 10-fold or greater potency for inhibiting the infection by GS4104. The minimum effective dosage for GS4104 was 0.1 mg/kg/day, with the compound administered twice daily for 5 days beginning 4 h pre-virus exposure. Oral therapy with GS4104 could be delayed from 48 to at least 60 h after exposure of mice to influenza A (H1N1) virus and still render a significant antiviral effect, the time of delay being dependent on the viral challenge dose. Intranasal instillation of GS4071 and GG167 to mice infected with influenza virus was highly inhibitory to the infection, the minimum effective dosages to significantly prevent death being 0.01 mg/kg/day for GS4071 and 0.1 mg/kg/day for GG167. Caging of infected mice treated with 10 mg/kg/day of GS4104 with infected saline-treated animals did not transfer any influenza-inhibitory effect to the latter animals. These data provide strong evidence of the potential of orally administered GS4104 for treatment of influenza A and B virus infections in humans.

Acetamides↗

PubMed2001

Glycosylation of haemagglutinin and stalk-length of neuraminidase combine to regulate the growth of avian influenza viruses in tissue culture.

The influence on virus replication in culture of the presence and location of glycosylation sites on the haemagglutinin (HA) glycoprotein of avian influenza viruses and differences in length of the stalk region of their neuraminidase (NA) glycoprotein was examined using reassortant viruses. Plaque size was measured in the presence or absence of bacterial neuraminidase (CPNA) and/or an influenza virus NA inhibitor, zanamivir, to assess the relative contribution of the NA to replication efficiency in tissue culture. The following conclusions were drawn, (1) HA lacking glycosylation at 158 gives inefficient growth when combined with short-stalked NAs, and efficient growth when combined with long-stalked NAs. (2) Glycosylation at 158 of HA makes the virus less dependent on NA for release from its receptors. (3) HA with glycosylation at 158 gives efficient growth when combined with short-stalked NAs but, when combined with long-stalked NAs, growth is very efficient and excess NA activity is disadvantageous. (4) HA having glycosylation at 158 combined with short-stalked NAs, or HA lacking glycosylation at 158 combined with long-stalked NAs may represent optimal combinations. The results reinforce the importance of a balance of HA and NA activity for efficient virus exit from, and entry into cells.

Animals↗

PubMed1987

Effect of inhibitors of proteases and glycosidases on functional lability of newly synthesized hemagglutinin-neuraminidase glycoprotein in avirulent NDV strain-infected cells.

Inhibition of either glycosylation or the protein synthesis leads to sharp drop of hemagglutinating (HA) and neuraminidase (Nase) activities in Newcastle disease virus (NDV)-infected cells. The drop can be prevented by tosyl-lysyl-chloromethyl-ketone, an inhibitor of trypsin-like proteases, or D-galactonolactone, an inhibitor of glycosidases, if added together with cycloheximide. Tosyl-lysyl-chloromethyl-ketone when added alone increases the level of both the HA and Nase activities as compared with non-treated virus-infected cells. It has been suggested that the actual level of the HA and Nase activities in the virus-infected cells is a result of dynamic equilibrium between the synthesis and post-translational functional maturation of the hemagglutinin-neuraminidase (HN) molecules, on the one hand, and the protease and glycosidase-mediated functional inactivation, on the other.

Animals↗

PubMedDate not supplied

Supplementation of conventional influenza A vaccine with purified viral neuraminidase results in a balanced and broadened immune response.

Influenza virus neuraminidase was chromatographically extracted from A/Johannesburg/33/94 (H3N2) and used to supplement conventional monovalent H3JHN2JH inactivated influenza vaccine. Immunization of mice with this preparation resulted in high titers of antibodies to both hemagglutinin (HA) and neuraminidase (NA) equivalent for each antigen to titers in animals immunized with either antigen alone. Homotypic infection was suppressed and greater reduction in viral replication was observed following heterotypic infectious challenge than was observed following the non-supplemented vaccine. There was no evidence of suppression of the immune response to the HA despite the presence of high amounts of NA in the vaccine. Supplementation of conventional inactivated influenza vaccine with NA takes advantage of the equivalent immunogenicity of dissociated HA and NA, to produce a more balanced immune response to both surface antigens, without the antigenic competition tht occurs after immunization with conventional vaccine or infection. These studies in a mouse model system suggest that supplementation of current inactivated influenza vaccines offers the prospect of improved immunization of humans against influenza.

Animals↗

PubMed1999

Immunization with influenza A virus hemagglutinin and neuraminidase produced in recombinant baculovirus results in a balanced and broadened immune response superior to conventional vaccine.

Influenza A virus hemagglutinin (HA) and neuraminidase (NA) from A/Nanchang/933/95 were expressed by recombinant baculovirus-infected insect cell lines. HA and NA were chromatographically purified then combined in a single vaccine preparation. Immunization of mice with this preparation resulted in high titers of antibodies to both HA and NA equivalent for each antigen to titers in animals immunized with either antigen alone. Anti-NA antibody titers, measured by either enzyme linked immunoabsorbant assay or neuraminidase inhibition test were higher in the combined recombinant vaccine than in conventional monovalent inactivated vaccine. There was no difference in the anti-HA antibody titers between these two vaccine preparations. Homotypic and closely related heterotypic infections were suppressed and greater reduction in viral replication was observed following a distantly related heterotypic infectious challenge than was observed with conventional inactivated vaccine. The combined HA and NA vaccine takes advantage of the equivalent immunogenicity of dissociated HA and NA, to produce a broader and more balanced immune response to both antigens, without the HA-dominant antigenic competition that occurs with natural infection or immunization with conventional vaccine. Additionally, the recombinant baculovirus expression system offers a reliable rapid production system without the use of massive numbers of embryonated chicken eggs. These studies in a mouse model system suggest that production of a combined HA and NA vaccine from recombinant baculovirus offers an improved alternative to conventional inactivated influenza vaccine.

Animals↗

PubMed1986

Possible role of neuraminidase in the pathogenesis of arteritis and thrombocytopenia induced in rats by Erysipelothrix rhusiopathiae.

The role of the neuraminidase produced by Erysipelothrix rhusiopathiae (E. rhusiopathiae) in the pathogenesis of arteritis and induced thrombocytopenia was examined using young and adult rats. There was a close correlation between bacterial invasion, desialation and cell infiltration in the common iliac artery. E. rhusiopathiae induced arteritis from the second and third day after inoculation with 3 X 10(8) viable bacteria in the young and adult rats, respectively. This delay with age was closely related to the increase of free sialic acid in the plasma. The sites invaded by E. rhusiopathiae coincided with the desialated lesions, and the bacteria invaded the periarterial region which was always accompanied by desialation when examined with FITC-conjugated peanut lectin. The free sialic acid in the plasma was, at least partly, considered to originate from the desialation of the arterial wall caused by E. rhusiopathiae. The platelet number decreased significantly after inoculation. The sialic acid content of the platelets prepared from circulating blood at 12 and 18 hours after inoculation showed a slight decrease and decreased further when the platelets were incubated with the bacteria. Platelets obtained from circulating blood within 24 hours after inoculation or incubated with the bacteria had demonstrated desialated sites as detected by immunofluorescent staining with FITC-conjugated peanut lectin. In conclusion, free sialic acid in the plasma was considered to be a good marker of the desialation of the arteries caused by E. rhusiopathiae, and the neuraminidase produced by the bacteria would be a key to solve the pathogenesis of the arteritis and thrombocytopenia.

Age Factors↗