[factors that cause a change in the antigenic structure of of the influenza virus hemagglutinin].crossing of norakin-resistant mutant nr1 of a/waybridge (h7n7) strain of fowl plague virus (fpv) with human influenza virus strains produced recombinants inheriting the hemagglutinin (ha) gene of the nr1 mutant and neuraminidase (na) genes of human influenza virus strains. the r120 recombinant produced by crossing of nr1 with a/taiwan/1/86 (h1n1) strain, unlike other recombinants and nr1 mutant, lost the capacity of reacting in h1 test with two monoclonal antibodies (mca) to ha7: 71/4 and 46/6. ...19921281944
relation between drug resistance and antigenicity among norakin-resistant mutants of influenza a (fowl plague) virus.norakin-resistant (nr) mutants of fowl plague virus (a/fpv/weybridge, h7n7) have 1 to 2 (in one instance 3) amino acid substitutions in different positions of the heavy (ha 1) and/or light (ha 2) subunits of the haemagglutinin (ha) molecule. investigation of nr mutants using the haemagglutination inhibition test with monoclonal antibodies (mab) to the ha of a/seal/massachusetts/80 (h7n7) virus revealed that one of the mutants (nr 1) differs antigenically from the wild-type fowl plague virus: its ...19921373939
diversity of the antibody responses produced in ponies and mice against the equine influenza a virus h7 haemagglutinin.a large panel of mouse monoclonal antibodies was produced and tested against field isolates of the equine h7n7 influenza a virus subtype. only a limited degree of h7 haemagglutinin variation was detected. at least four antigenic sites were identified by selecting variant viruses in eggs. the limited variation in the field did not correlate with the frequency of variant viruses detected in eggs; this frequency was similar to those reported for other influenza viruses. we sought to determine wheth ...19921376770
carbohydrate masking of an antigenic epitope of influenza virus haemagglutinin independent of oligosaccharide size.comparison of the haemagglutinins (ha) of the pathogenic avian influenza viruses a/fpv/dutch/27 (h7n7) and a/fpv/rostock/34 (h7n1) revealed 94.7% nucleotide and 93.8% amino acid sequence homologies. six of the seven n-glycosidic oligosaccharides of the rostock ha are at the same positions as the six carbohydrates of the dutch strain. the additional oligosaccharide side chain of the rostock strain, which is of the complex type, is attached to asparagine149 in antigenic epitope b. the accessibilit ...19921379858
subtype h7 influenza viruses: comparative antigenic and molecular analysis of the ha-, m-, and ns-genes.antigenic analysis of the haemagglutinin and matrix protein with corresponding sets of monoclonal antibodies as well as sequence analysis of ha-, m-, and ns-genes were carried out to establish antigenic and genetic relationships between four fowl plague virus (fpv) strains of h7 subtype. the data obtained revealed close genetic relatedness between the oldest known influenza a virus, a/chicken/brescia/1902 (h7n7), and two fpv strains, a/fpv/dobson (h7n7) and a/fpv/weybridge (h7n7). these three st ...19921530908
hemagglutinin activation of pathogenic avian influenza viruses of serotype h7 requires the protease recognition motif r-x-k/r-r.the hemagglutinin of influenza virus a/fpv/rostock/34 (h7) was altered at its multibasic cleavage site by site-directed mutagenesis and assayed for proteolytic activation after expression in cv-1 cells. the results indicated that the cellular protease responsible for activation recognizes the tetrapeptide motif r-x-k/r-r that must be presented in the correct sequence position. studies on plaque variants of influenza virus a/fowl/victoria/75 (h7n7) showed that alteration of the consensus sequence ...19921566583
sequence analysis of the equine h7 influenza virus haemagglutinin gene.the nucleotide sequences of ten haemagglutinin genes of representative h7n7 equine influenza viruses isolated between 1956 and 1977 have been determined by primer extension sequencing. their nucleotide and deduced amino acid sequences demonstrate a high degree of homology. these equine viruses can be divided into two distinct subgroups, the prototype-like, and a group comprising the early american isolates and the remaining equine viruses. the equine h7 haemagglutinins form a quite distinct grou ...19921566601
interference of maternal antibodies with the immune response of foals after vaccination against equine influenza.the purpose of the study was twofold. first, using two groups of 22 foals each, we investigated the extent to which maternal antibodies interfere with the humoral response against equine influenza. the foals were born to mares that had been vaccinated twice yearly against influenza since 1982. foals of group i were vaccinated three times at early ages (12, 16, and 32 weeks of age), and foals of group ii were likewise vaccinated but a later ages (24, 28, and 44 weeks of age). after the first and ...19921574831
maternal antibodies against equine influenza virus in foals and their interference with vaccination.foals that were born to mares vaccinated twice a year against influenza had moderate to high haemagglutination-inhibition antibody titers at 24 hours after birth. the foals were vaccinated at six and ten weeks of age, and again at three to five months after birth. four months after the third vaccination no antibodies against a/h7n7 and a/h3n8 influenza viruses were detected in these foals. thus, maternal antibodies probably prevented the development of antibodies against equine influenza virus a ...19911656657
reassortants with equine 1 (h7n7) influenza virus hemagglutinin in an avian influenza virus genetic background are pathogenic in chickens.reassortants possessing the hemagglutinin (ha) gene from a/equine/london/1416/73 (h7n7) [eq/lond] and five or more genes from a/chicken/pennsylvania/1370/83 (h5n2) [ck/penn] were lethal in chickens. this result demonstrates that horses can maintain influenza viruses whose has are capable of promoting virulence. thus, reassortment of equine and avian influenza virus genes could generate viruses that might be lethal in domestic poultry.19911871981
protection of chickens from lethal influenza virus infection by influenza a/chicken/pennsylvania/1/83 virus: characterization of the protective effect.the influenza a/chicken/pennsylvania/1/83 (h5n2) virus is the first known example of an influenza virus isolated from a natural infection which contained primarily defective interfering particles (t. m. chambers and r. g. webster, j. virol. 61, 1517-1523, 1987). in chickens, coinoculation of this virus together with the closely related but highly virulent influenza a/chicken/pennsylvania/1370/83 virus results in reduced mortality compared to virulent virus infection alone (bean et al., j. virol. ...19912053293
the critical cut-off temperature of avian influenza viruses.we have measured the pathogenicity for 6-week-old chicks of infection by h7 avian influenza viruses. one virus, strain s3 from a/fpv/rostock/34(h7n1) showed a temperature sensitive phenotype at 41.5 degrees c and reduced pathogenicity. by analysis of reassortants made between virus s3 and a/fpv/dobson/27(h7n7), a fully pathogenic virus, two conclusions arise. (1) the critical cut-off temperature for avian influenza virus in 6-week-old chicks is 41.5 degrees. (2) rna segment 1 of virus s3 is resp ...19902077784
generation of seal influenza virus variants pathogenic for chickens, because of hemagglutinin cleavage site changes.influenza virus a/seal/mass/1/80 (h7n7) was adapted to grow in mdck cells and chicken embryo cells (cec) in the absence of exogenous protease. the biological properties of the virus variants obtained coincided with intracellular activation of the hemagglutinin (ha) by posttranslational proteolytic cleavage and depended on the cell type used for adaptation. mdck cell-adapted variants contained point mutations in regions of the ha more distant from the cleavage site. it is proposed that these muta ...19902191148
deproteinization of influenza virus in the presence of rimantadine.virion deproteinization and viral rna transport to the isolated cell nuclei have been studied in the presence of rimantadine with rimantadine-sensitive influenza viruses fowl plague (h7n7), a/krasnodar/101/59 (h2n2) and rimantadine-resistant influenza strains (wsn/h1n1 and a/krasnodar/101/59-r). rimantadine failed to affect deproteinization during incubation with the isolated cellular plasma membranes as well as the transport to isolated cell nuclei of the viral rna of either sensitive or resist ...19852408452
is bivalent binding of monoclonal antibodies to different antigenic areas on the hemagglutinin of influenza virus required for neutralization of viral infectivity?biological activities of fab fragments of monoclonal igg antibodies to each of four nonoverlapping antigenic areas on the hemagglutinin molecule of a/seal/massachusetts/1/80 (h7n7) influenza virus were examined. fab fragments of the antibodies belonging to groups i and ii neutralized viral infectivity. these fab fragments inhibited hemagglutination of the virus and virus-induced hemolysis at ph 5.9. on the other hand, fab fragments of groups iii and iv antibodies showed neither neutralization no ...19852411245
protection against lethal influenza with neuraminidase.the role of the neuraminidase in eliciting protection against a lethal influenza a virus [a/ck/penn/1370/83 (h5n2)] infection was investigated in chickens. isolated n2 neuraminidase administered in adjuvant did not prevent infection but did prevent systemic spread of virus and death of chickens. n2 expressed in a recombinant vaccinia virus protected chickens when administered in adjuvant but was less effective when allowed to replicate and produce pox on the chicken's comb. chickens vaccinated w ...19882452514
molecular and biological properties of a variant of avian influenza a/seal/massachusetts/1/80 (h7n7) virus that is pathogenic for mice.a/seal/mass/80 influenza virus has been shown to be closely related antigenically and genetically to avian influenza h7n7 viruses, however, the virus does not replicate efficiently in avian species but does replicate in most mammals, except mice (hinshaw et al., infect. immun., 34, 351-361, 1981). in order to develop a model defining the molecular changes that occur during acquisition of virulence, the a/seal/mass/80 virus was adapted to growth in mouse lungs. the adaptation was accompanied by c ...19892565673
lesions in chickens experimentally infected with 1985 h7n7 avian influenza virus. 19892735898
production of monoclonal antibodies against equine influenza: application to a comparative study of various strains of the virus.monoclonal antibodies (mo abs) were prepared against influenza/a/equine/prague/1/56 (h7n7) and influenza/a/equine/miami/1/63 (h3n8) reference strains of equine influenza virus. these monoclonals were tested against the 2 reference strains, 8 field strains of equine influenza virus, 3 human influenza viruses possessing the h3 hemagglutinin, and one virus of human origin possessing the h1 hemagglutinin. two antibodies were obtained in one fusion against the prague/1/56 strain and reacted only with ...19892817730
retrovirus-expressed hemagglutinin protects against lethal influenza virus influenza virus hemagglutinin gene, h7, has been expressed in a replication-competent schmidt-ruppin rous sarcoma virus-derived vector. this virus, p1/h7, expressed a glycosylated precursor of the h7 protein which was processed to a mature form and transported to the cell surface. the expressed h7 glycoprotein could not be detected in p1/h7 virus particles. a p1/h7 stock which expressed 5 to 10% of the level of h7 observed in influenza virus-infected chicken embryo fibroblasts was used to imm ...19882839718
studies of some biological and molecular characteristics of avian influenza a/h7 (hav1) subtypes.current isolates of the subtypes h7n3 and h7n7 from 1979 to 1981 were examined and compared with the reference strains with regard to their antigenic variability and to their pathogenicity for birds and mammals in order to establish the potentiality of influenza a/h7 virus (hav1) transmission from birds to mammals. the analysis of the electrophoretic mobility of virus-induced polypeptides and of the double-stranded rna segments after hybridization revealed equal, similar and deviating patterns. ...19862871730
isolation of influenza a viruses from migratory waterfowls in san-in district, western japan, in the winter of 1982-1983.from november 1982 to march 1983, winter migratory waterfowls of some species staying in san-in district, western japan, were surveyed for influenza virus at five stations. a total of eight influenza a viruses were isolated from 354 faeces samples of whistling swans; in contrast, no virus was isolated from any sample of 261 black-tailed gulls, of 113 pintails and of 10 mallards. five of eight isolates belonged to human pandemic subtype h2n2, two isolates belonged to fowl plague subtype h7n7, and ...19872891283
spin-labeling of influenza virus hemagglutinin permits analysis of the conformational change at low ph and its inhibition by study the conformational changes in the hemagglutinin (ha) molecule of a/seal/mass/1/80 (h7n7) (seal) influenza virus at low ph, a spin-labeling method was used. this method also permits study of antibody interaction with the ha. a synthetic nitroxide compound was used for spin-labeling of tyrosine residues of the isolated ha molecule. electron spin resonance (esr) spectra of the spin-labeled ha at various ph values indicated that a conformational transition occurred under acidic conditions, ...19863017016
molecular epidemiology of influenza viruses: memorandum from a who meeting.this memorandum summarizes recent information on influenza viruses of non-human hosts, discussed at the who consultation on molecular epidemiology of influenza viruses, athens, georgia, usa, in september 1986. it was noted that a wide variety of antigenic variants of influenza viruses have been isolated from non-human hosts, especially birds. of particular epidemiological interest in recent years has been the isolation of h7n7 influenza viruses from epidemics of disease in seals, the isolation o ...19873038357
influenza virus iscoms: antibody response in animals.a monovalent experimental iscom vaccine has been prepared with the envelope glycoproteins haemagglutinin and neuraminidase of the equine virus strain a/solvalla/79 (h3n8). in vaccination trials on balb/c mice the iscom vaccine induced more than ten times higher serum antibody titres measured in elisa than a corresponding experimental micelle vaccine. similarly, in guinea-pigs the iscoms induced about tenfold higher haemagglutination inhibition (hi) and neuraminidase inhibition (ni) titres than a ...19883354258
[primary structure of the full-length dna copy of the neuraminidase gene in the avian influenza virus of the n7 antigenic subtype].complete nucleotide sequence of the cloned full-length dna copy of the influenza virus a/fpv weybridge (h7n7) neuraminidase gene has been determined.19883382443
nucleotide sequence of rna segment 7 and the predicted amino sequence of m1 and m2 proteins of fpv/weybridge (h7n7) and wsn (h1n1) influenza viruses.since the gene products (m1 and m2) of influenza virus rna segment 7 have been implicated in host range restriction, sensitivity to the drug amantadine, virus yield in chicken embryos as well as in virus assembly and morphology, we have determined the nucleotide sequence of this rna segment for an avian [a/fpv/weybridge (h7n7)] and a human [a/wsn/33 (h1n1)] virus and compared it to that of the other influenza a virus strains. the results show that all ten strains of influenza a virus contain an ...19883414185
[intracellular proteolytic cleavage of the influenza virus protein np as a sign of the epidemicity of virus strains?].the main nucleocapsid protein (np) of human epidemic viruses was found to be cleaved via np56----hp53 mol. wt. reduction in infected cells, while the np of animal influenza viruses was refractory to analogous intracellular modification. like animal influenza viruses, the strain a/baku/799/82(h1n3) isolated from a sick child has been observed to exhibit the intracellular resistance of np to intracellular proteolysis. the similar np resistance has been revealed for a/new jersey/8/76(h1n1) and a/se ...19873553909
molecular analysis of the hemagglutinin genes of australian h7n7 influenza viruses: role of passerine birds in maintenance or transmission?in 1985 a fowl plague-like disease occurred in chickens in lockwood, victoria, australia and caused high mortality. an h7n7 influenza virus was isolated from the chickens (a/chicken/victoria/1/85); additionally, an antigenically similar virus was isolated from starlings (a/starling/victoria/5156/85) and serological evidence of h7n7 virus infection was found in sparrows. antigenic analysis with monoclonal antibodies to h7, oligonucleotide mapping of total vrna, and sequence analysis of the ha gen ...19873660587
the pathogenicity of an avian influenza virus isolated in influenza virus (h7n7) isolated from an outbreak of disease in chickens in victoria, was examined for its ability to cause disease in inoculated chickens, turkeys and ducks. the virus was highly pathogenic in chickens and turkeys but produced no clinical disease in ducks. transmission of infection occurred from inoculated chickens to those in direct contact but other chickens separated by a distance of 3m directly downwind developed neither clinical disease nor antibody to the virus.19863800804
molecular changes in a/chicken/pennsylvania/83 (h5n2) influenza virus associated with acquisition of of the unresolved questions concerning the acquisition of virulence by the a/chicken/pennsylvania/83 (h5n2) influenza virus is which gene segments other than the hemagglutinin (ha) showed changes that were relevant. to answer this question, reassortants were made possessing the hemagglutinin gene of the virulent virus and the seven other genes from the avirulent parent. since both the virulent and avirulent h5n2 strains are antigenically almost indistinguishable, it was necessary to transfer ...19863946082
biological activity of monoclonal antibodies to operationally defined antigenic regions on the hemagglutinin molecule of a/seal/massachusetts/1/80 (h7n7) influenza virus. 19826182687
comparative study and grouping of nonstructural (ns1) proteins of influenza a viruses by the method of oligopeptide mapping.oligopeptide mapping of 35s-methionine labeled non-structural (ns1) proteins of 23 influenza. a virus strains showed the presence of both common and variable oligopeptides. analysis of the oligopeptide maps revealed at least four groups of ns1 proteins. the first group includes ns1 proteins of several human h1n1 influenza viruses (that were designated as h0n1 according to the old classification). the second group is composed of ns1 proteins of h1n1 and h2n2 viruses. the third group includes ns1 ...19836229233
[comparative analysis of primary structure of m-genes in remantadine-resistant and remantadine-sensitive strains of influenza virus a/fpv/weybridge (h7n7) strains].full-length dna copies of m-gene of remantadine-sensitive and remantadine-resistant variants of the influenza virus strain a/fpv/weybridge (h7n7) have been synthesised and cloned. complete nucleotide sequences of both cdnas were determined by the maxam-gilbert method. there are three nucleotide substitutions, two of which lead to amino acid changes in m1 and m2 proteins. the existence of m3 protein, a polypeptide 68 amino acids long, encoded by the negative strand of rna, is suggested. amino aci ...19873450279
the standardization of inactivated equine influenza vaccines by single-radial immunodiffusion.single-radial-immunodiffusion (srd) assays were used for measuring the haemagglutinin (ha) antigen content of equine influenza vaccines containing the virus strains a/equine/prague/56 (h7n7) and a/equine/miami/63 (h3n8). three bivalent aqueous vaccines and one bivalent adjuvanted vaccine were standardized by srd to contain graded amounts of ha antigen activity. the srd reaction was influenza subtype specific and was not influenced by the presence of adjuvant in vaccine.19836408096
[antigenic properties of variants of the influenza virus h7n7 and its recombinants].passages of the a/seal/massachusetts/1/80 strain in different biological systems (chick embryos, mice, chickens, organ cultures of human embryo trachea) yielded variants differing from the original virus both in their biological and antigenic properties. the m20 variant selected in passages of the seal virus in mouse lungs differed from the latter only in biological but not antigenic properties. the oc20 and c20 variants produced by passages of the seal virus in organ cultures and chicken lungs ...19854002687
evaluation of the a/seal/mass/1/80 virus in squirrel influenza a virus isolated from seals [a/seal/mass/1/80 (h7n7)] and an isolate of this virus obtained from a human conjunctiva were evaluated for replication and virulence in squirrel monkeys. when the seal virus was administered intratracheally, it replicated in lungs and nasopharynges and induced illness almost to the same extent that a human influenza a virus [a/udorn/72 (h3n2)] did. in one monkey that died of pneumonia, the seal virus was recovered from spleen, liver, and muscle as well a ...19836618672
development of an enzyme-linked immunosorbent assay (elisa) for the detection of specific antibodies against an h7n7 and an h3n8 equine influenza virus.this paper describes a solid-phase microtitre plate enzyme-linked immunosorbent assay (elisa) for the detection of antibodies to equine influenza viruses. using egg-grown influenza viruses as the antigens attached to the solid phase, cross-reactions were observed between an h7n7 equine virus (designated a1) and an h3n8 equine influenza virus (designated a2) when untreated antisera were tested. absorption of antisera with egg-grown a/porcine/shope/1/33 influenza virus eliminated cross-reactive an ...19846512260
are seals frequently infected with avian influenza viruses?influenza a virus isolates of the h4n5 subtype (which has previously been detected only in birds) were recovered from harbor seals dying of viral pneumonia on the new england coast from june 1982 through march 1983. when these isolates were compared with other mammalian and avian viruses in serological assays and rna-rna competitive hybridization, it was found that the seal viruses were most closely related antigenically and genetically to recent avian virus strains and were readily distinguisha ...19846471169
contact infection of mink with 5 subtypes of avian influenza virus. brief report.avian influenza viruses of h3n8, h11n4, h7n7, h8n4, and h5n3 infected mink by contact.19836314940
isolation of an influenza a virus from seals.influenza a virus of serotype hav1 neq1 (h7n7 by the 1980 revised influenza typing system proposed by who experts) was repeatedly isolated from lung and brain tissues taken from harbor seals (phoca vitulina) found suffering from pneumonia on cape cod peninsula (u.s.a.) in the winter of 1979-1980. the seal isolates, although of a serotype identical to some fowl plaque virus strains, were harmless to chickens and turkeys in transmission experiments. an earlier human infection by a hav1 neq1 influe ...19816168245
studies with inactivated equine influenza vaccine. 1. serological responses of ponies to graded doses of vaccine.serological responses to three bivalent aqueous equine influenza vaccines of different potency and an adjuvanted bivalent vaccine containing inactivated a/equine/prague/56 (h7n7) and a/equine/miami/63 (h3n8) viruses, were examined in seronegative ponies. potencies of the vaccines, measured by single-radial-diffusion tests, ranged from 4 to 56 micrograms of haemagglutinin (ha) antigen activity/virus strain per dose. serological responses to vaccination were examined by haemagglutination-inhibitio ...19836345659
further characterization of h7n7 avian influenza virus isolated from migrating starlings wintering in israel. 19826815937
influenza virus m2 protein ion channel activity is not required to maintain the equine-1 hemagglutinin in its native form in infected cells.the equine-1 influenza virus a/cornell/74 (h7n7) hemagglutinin (ha) is cleaved to ha1 and ha2 in the trans golgi network (tgn) of infected cells. the avian influenza virus a/chicken/germany/34 (fowl plague virus rostock) h7 ha is also cleaved to ha1 and ha2 intracellularly in the tgn. to maintain the fowl plague virus rostock ha in its native form during transport through the tgn, a functioning m2 ion channel activity is required, otherwise the ha undergoes its transition to the low-ph form (sug ...19947518161
isolation of influenza a viruses from birds in great britain during 1980 and 1981.during 1980 and 1981 influenza a viruses of subtypes h3n2, h3n8, h4n1, h4n6, h6n2, h6n8, h7n7, h11n8 and h11n9 were isolated from birds in great britain, usually as a result of investigations of disease or death. however, all viruses were shown to be of low virulence for chickens in pathogenicity index tests. there was one occurrence of influenza virus infection of turkeys (h6n8) but viruses were frequently obtained from domestic ducks. other viruses were isolated from exotic birds in zoos or bi ...19826815876
inhibition of replication of avian influenza viruses by the neuraminidase inhibitor 4-guanidino-2,4-dideoxy-2,3-dehydro-n-acetylneuraminic acid.the sialidase inhibitor 4-guanidino-2,4-dideoxy-2,3-dehydro-n-acetylneuraminic acid (4-guanidino-neu5ac2en), designed with computer assistance and knowledge of the crystal structure of influenza virus neuraminidase, has shown antiviral effects in animal models of human influenza (m. von itzstein et al., nature, 363, 418-423, 1993). here we demonstrate that the compound efficiently inhibits the enzyme activity of all nine subtypes of avian influenza a neuraminidase in vitro. when administered int ...19957571401
mass mortality of harbor seals: pneumonia associated with influenza a virus.more than 400 harbor seals, most of them immature, died along the new england coast between december 1979 and october 1980 of acute pneumonia associated with influenza virus, a/seal/mass/1/180 (h7n7). the virus has avian characteristics, replicates principally in mammals, and causes mild respiratory disease in experimentally infected seals. concurrent infection with a previously undescribed mycoplasma or adverse environmental conditions may have triggered the epizootic. the similarities between ...19827063847
pathogenicity of influenza a/seal/mass/1/80 virus mutants for mammalian species.increases in infectiousness, neurotropism and virulence were found in a laboratory variant of influenza a/seal/massachussets/1/80 (h7n7) virus having a highly cleavable hemagglutinin. sequential passage from host to host further increased pathogenicity of the h7n7 virus in mice, ferrets and rats.19957710359
inhibition of virus-induced hemolysis with monoclonal antibodies to different antigenic areas on the hemagglutinin molecule of a/seal/massachusetts/1/80 (h7n7) influenza virus.a/seal/massachusetts/1/80 (h7n7) influenza virus caused maximal hemolysis at ph 5.9 monoclonal antibodies to each of the four nonoverlapping antigenic areas on the hemagglutinin molecule of the virus inhibited the hemolysis whereas those belonging to two of the groups did not inhibit hemagglutination of the virus. hemolysis also occurred when the virus was incubated at ph 5.9 prior to addition of erythrocytes. such hemolysis caused by acid-treated virus was inhibited with the antibodies as well. ...19836191738
[ph-dependent hemolytic and neuraminidase activity of remantadine-sensitive and -resistant variants of influenza virus].a comparative study of ph-dependence of hemolytic and neuraminidase activities of four remantadin-sensitive influenza a virus strains capv (classical avian plague virus) (h7n7), ussr/090/77 (h1n1), ann arbor (h2n2), and texas (h3n2) and their remantadin-resistant variants was carried out. the original strains were shown to produce hemolysis in a narrow ph range (5.0 and 5.5) and to have maximal neuraminidase activity at the same ph values. in remantadin-resistant variants the optimal ph values f ...19836845715
diagnosis of equine influenza by the polymerase chain reaction.influenza a is a common respiratory infection of horses, and rapid diagnosis is important for its detection and control. sensitive detection of influenza currently requires viral culture and is not always feasible. the polymerase chain reaction (pcr) was used to detect dna produced by reverse transcription of equine influenza in stored nasal secretions, vaccines, and allantoic fluids. primers directed at a target of 212 bp on conserved segment 7 (matrix gene) of human influenza a/bangkok/1/79(h3 ...19948011780
a novel carbohydrate addition site on the hemagglutinin protein of a highly pathogenic h7 subtype avian influenza virus.the highly pathogenic (hp) avian influenza isolate, a/fowl/victoria/76 (h7n7), contains two naturally occurring hemagglutinin (ha) variants. the two hemagglutinin proteins differ only in the possession of a potential asparagine-linked glycosylation site at amino acid position 188-190, which is near the proposed receptor binding region of the ha. expanded virus plaques which possess the addition site exhibit more slowly migrating ha1 subunits and are significantly more lethal in chickens than tho ...19957483275
thermolysin activation mutants with changes in the fusogenic region of an influenza virus hemagglutinin.influenza virus a/seal/mass/1/80 (h7n7) mutants were obtained; the hemagglutinins (has) of the mutants were not activated by trypsin, as in the wild-type virus, but by thermolysin. the mutants grew efficiently under multiple replication cycle conditions and formed plaques in chicken embryo cells only when thermolysin was added to the culture medium. they exhibited hemolytic activity and induced protective immunity in chickens after an asymptomatic course of infection. nucleotide sequencing of th ...19947933138
antigenicity and immunogenicity of experimental equine influenza iscom vaccines.a comparison of the antigenicity and immunogenicity of iscom vaccines prepared from equine influenza viruses h3n8 and h7n7 was made with inactivated whole-virus vaccines containing equivalent amounts of virus haemagglutinin. iscoms stimulated superior antibody responses in terms of both amount and duration. as with conventional whole-virus vaccines, the levels of antibody to virus haemagglutinin induced by iscoms correlated with protection.19947975864
sequence of the hemagglutinin gene from influenza virus a/seal/mass/1/80.a double-strand dna copy of the influenza virus a/seal/mass/1/80 (h7n7) [seal] hemagglutinin (ha) gene was cloned into the plasmid pat153/pvuii/8 and sequenced to deduce the primary amino acid sequence. the gene is 1731 nucleotides long and codes for a protein of 560 amino acids with a nonglycosylated molecular weight of 62098 da. the deduced amino acid sequence displays similarities to all other sequenced hemagglutinins by retaining six of seven potential glycosylation sites, showing conversati ...19836688691
a rapid method for the analysis of influenza virus genes: application to the reassortment of equine influenza virus genes.we describe a rapid method for genetic characterisation of influenza virus genes using reverse transcription and amplification by polymerase chain reaction (rt/pcr) of all virus segments simultaneously (multiplex rt/pcr) using primers based on the conserved terminal sequences. the product has been shown to be suitable for determination of partial nucleotide sequences which can be used to search nucleotide sequence databases and rapidly map the genetic origin of each segment. we illustrate the us ...19947521550
nonhomologous recombination between the hemagglutinin gene and the nucleoprotein gene of an influenza virus.mutants of the influenza virus a/seal/mass/1/80 (h7n7) are described which contain an insertion of 60 nucleotides in the hemagglutinin (ha) gene, derived most probably by recombination between the ha gene and the nucleoprotein gene of the same virus. the nonhomologous rna recombination resulted in an enhanced hemagglutinin cleavability associated with broadening of the host cell spectrum, increased hemolytic activity, and increased pathogenicity for chickens.19948091680
single radial immunodiffusion potency test for standardization of indigenous equine influenza vaccine.single radial immunodiffusion (srd) assays were used for measuring the haemagglutinin antigen contents of equine influenza vaccine prepared from an indian virus isolate. a/equine-2/ludhiana/1/87 (h3n8). five different preparations of the vaccine were standardized by srd to prepare 913 doses, each containing 20 micrograms ha/ml-1 dose-1. this test also showed influenza virus subtype specificity as no cross reaction was observed between subtype 1 (h7n7) and subtype 2 (h3n8) viruses.19938112772
[pathogenicity of equine influenza viruses in chickens].in the present paper the pathogenicity of equine subtype a/equi 1 (h7n7) and a/equi 2 (h3n8) for chicks was studied. strains previously isolated in brazil, representatives of both subtypes, were used. eight experiments were performed for a/equi 2, using 89 chicks (4 to 18-day old). six hundred thirty three samples of cloacal material were collected from 01 to 15 days pos-infection (p.i.) and inoculated in 11-day old chick embryos for recuperation of virus. twelve samples showed positive results. ...19938303046
influenza virus subtypes in aquatic birds of eastern germany.we report the findings of a 12-year surveillance study (1977-89) of avian influenza a viruses in eastern germany. viruses were isolated directly from feral ducks (n = 236) and other wild birds (n = 89); from domestic ducks (n = 735) living on a single farm; and from white pekin ducks (n = 193) used as sentinels for populations of wild aquatic birds; mainly sea birds. the efficiency of virus isolation was 9.9% overall, with considerable variability noted among species: 8.7% in wild ducks, 0.9% in ...19948198436
isolation of an influenza a virus of unusual subtype (h1n7) from pigs in england, and the subsequent experimental transmission from pig to pig.a novel h1n7 influenza virus (a/swine/eng/191973/92) was isolated from nasal swabs collected from two pigs on a farm where there had been recent clinical disease due to infection with an h1n1 virus (a/swine/eng/195852/92). antigenically, the haemagglutinin (ha) of the h1n7 virus was related most closely to the ha of a/ussr/90/77, whilst the neuraminidase (na) appeared to be related most closely to the na of a/equine/prague/1/56 (h7n7). pigs infected experimentally with a/swine/eng/191973/92 deve ...19948203118
the relationship between single radial hemolysis, hemagglutination inhibition, and virus neutralization assays used to detect antibodies specific for equine influenza viruses.antibodies specific for equine influenza viruses are usually quantified using single radial hemolysis (srh), hemagglutination inhibition (hi) or virus neutralization (vn). neutralizing antibodies are thought to provide optimum protection to challenged animals. the purpose of this study was to determine the extent to which srh and hi assays detect antibodies which neutralize equine influenza viruses. acute and convalescent sera from 41 horses were analyzed using vn, srh, and hi assays. these hors ...19957653031
susceptibility of pigeons to avian influenza.susceptibility to infection with avian influenza virus (aiv) was studied in pigeons inoculated via oculonasal (experiment 1) or intravenous (experiment 2) route. chickens were included as susceptible hosts in both experiments. two subtypes each of the highly pathogenic aiv (hpaiv; hp ck/pa h5n2 and hp ck/australia h7n7) and non-pathogenic aiv (npaiv; np ck/pa h5n2 and np emu/tx h7n1) at a dose of 10(5) embryo infective dose per bird were used as inoculum. the pigeons inoculated with hp ck/pa h5n ...19968883790
characterization of a/eq-1 virus isolated during the equine influenza epidemic in india.the equine influenza virus, ludhiana/5/87, isolated from the clinical material during the epidemic of equine influenza in india in 1987 was inhibited in haemagglutination-inhibition test by the antiserum against the prototype a/eq/prague/1/56 (h7n7) virus and by post-epidemic horse sera. in haemagglutinin and neuraminidase analysis, the a/eq/ludhiana/5/87 isolate appeared similar to the prototype a/eq/prague/1/56 virus and was characterized as the h7n7 subtype.19948067310
observations on the relationship in chickens between the virulence of some avian influenza viruses and their pathogenicity for various organs.comparative histological and immunocytochemical studies were conducted on formalin-fixed tissues from chickens infected with avian influenza viruses of varying virulence. results showed a distinct pattern of disease that depended on the virulence of the virus and the susceptibility of the birds. at 3 days post-intranasal inoculation with a highly virulent h7n7 virus, all 6-to-8-week-old specific-pathogen-free (spf) birds were affected, and all developed pancreatic necrosis and encephalitis assoc ...19958561728
[the mechanisms of the antiviral action of the bora-adamantane derivative preparation bg-12].the effect of one of the derivatives of boraadamantane, preparation bg-12, on reproduction of influenza type a and b viruses was studied. this preparation was shown to inhibit multiplication of a wide range of influenza type a and b virus strains. it is important that bg-12 inhibits in cell culture the replication of a mutant of fowl plague virus a/fpv/weibridge resistant to remantadine. bg-12 was found to exert a marked viricidal effect, to inhibit the hemolytic activity of both influenza a and ...19938073750
infectious agents in acute respiratory disease in horses in ontario.a study of acute respiratory disease in horses in ontario was undertaken to determine the identity of current causative infectious agents. a nasopharyngeal swab was designed and utilized to maximize isolation of viruses, mycoplasma, and pathogenic bacteria. serum samples were collected for parallel determination of antibody titers to equine influenza virus type a subtype 1 (h7n7) and subtype 2 (h3n8), equine rhinovirus types 1 and 2, equine herpesvirus type 1, mycoplasma equirhinius, and mycopla ...19979087920
protection against a lethal influenza virus challenge by immunization with a haemagglutinin-expressing plasmid dna inoculations have been used to demonstrate that in vivo transfections can be used to elicit protective immune responses. the direct inoculation of an h7 haemagglutinin-expressing dna protected chickens against lethal challenge with an h7n7 influenza virus. three-week-old chickens were vaccinated by inoculating 100 micrograms of plasma dna by each of three routes (intravenous, intraperitoneal and subcutaneous). one month later, chickens were boosted with 100 micrograms of dna by each o ...19938212843
[role of certain factors in intracellular oligomerization of influenza virus nucleoproteins].oligomerization of influenza virus nucleoprotein (np) depends on the virus strain. np monomers of viruses a/duck/ukraine/63 (h3n8) and a/seal/massachusets/1/80/ (h7n7) are oligomerized completely. the a/ussr/90/77 virus (h1n1) np is characterized by just partial oligomerization, similarly as a reassortant containing surface protein genes of virus a/duck/ukraine and internal protein genes of a/ussr/90 virus. hence, it is probable that np gene controls the type of np oligomerization. np oligomeriz ...19989559532
fusion of influenza virus with the endosomal membrane is inhibited by monoclonal antibodies to defined epitopes on the hemagglutinin.epitopes on the hemagglutinin (ha) of a/seal/massachusetts/1/80 (h7n7) influenza virus were mapped by genetic analysis of variants selected with monoclonal antibodies (mabs). electron microscopic studies demonstrated that the sites and the directions to which hemagglutination-inhibiting (hi) mabs and non-hi mabs bound were different on the ha molecule. morphological analysis revealed that hi mabs blocked attachment of the virus to the cells, while non-hi mabs did not. virus particles bound with ...19989620205
characterisation of an avian influenza a virus isolated from a human--is an intermediate host necessary for the emergence of pandemic influenza viruses?the partial sequencing of the internal and the neuraminidase genes of isolate 268/96 obtained from a woman with conjunctivitis showed all seven to have closest homology with avian influenza viruses. the entire nucleotide sequence of the haemagglutinin gene of 268/96 had close, 98.2%, homology with an h7n7 virus isolated from turkeys in ireland in 1995. this appears to be the first reported case of isolation of an influenza a virus from a human being infected as a result of direct natural transmi ...19989638147
antibody responses of japanese horses to influenza viruses in the past few years.a total of 305 horse sera collected in the hidaka district of hokkaido in the years 1988-90 were tested for the presence of hemagglutination-inhibition (hi) antibodies to a/equine/newmarket/1/77 (h7n7), a/equine/tokyo/2/71 (h3n8) and a/equine/kentucky/1/81 (h3n8, kentucky) strains of equine influenza (ei) virus. antibodies to the 3 strains were detected in hardly of the 45 sera from 2-years-old horses which were collected before vaccination. many of the 51 horses, after vaccination with inactiva ...19938461424
different hemagglutinin cleavage site variants of h7n7 in an influenza outbreak in chickens in leipzig, germany.the hemagglutinin (ha) genes from four avian h7n7 influenza a isolates, from a single outbreak, were shown to possess different cleavage sites that contain varying numbers of basic amino acid residues (kkkkr, krkkr, kkrkkr, kkkkkkr). all four variants are highly pathogenic in chickens and share an immediate common ancestral ha with a/tern/potsdam/342-6/79 (h7n7) and a/swan/potsdam/63-6/81 (h7n7). these viruses are nonpathogenic and contain no extra basic amino acids at the cleavage site of their ...19968615031
comparative pathology of chickens experimentally inoculated with avian influenza viruses of low and high pathogenicity.pathologic changes and distribution of viral antigen as determined by immunohistochemistry were compared among 4-wk-old specific-pathogen-free chickens inoculated intratracheally with avian influenza virus (aiv) isolates of either low or high pathogenicity. viruses of low pathogenicity, previously characterized as mildly pathogenic (mp), included a/chicken/pennsylvania/21525/83 (h5n2) (mp-penn) and a/chicken/alabama/7395/75 (h4n8) (mp-alab). viruses of high pathogenicity included a/chicken/penns ...19979087329
influence of host species on the evolution of the nonstructural (ns) gene of influenza a viruses.the matrix (m) and nonstructural (ns) genes of influenza a viruses each encode two overlapping proteins. in the m gene, evolution of one protein affects that of the other. to determine whether or not this evolutionary influence operating between the two m proteins also occurs in the ns gene, we sequenced the ns genes of 36 influenza a viruses isolated from a broad spectrum of animal species (wild and domestic birds, horses, pigs, humans, and sea mammals) and analyzed them phylogenetically, toget ...19989725667
mutation of neuraminidase cysteine residues yields temperature-sensitive influenza viruses.the influenza virus neuraminidase (na) is a tetrameric, virus surface glycoprotein possessing receptor-destroying activity. this enzyme facilitates viral release and is a target of anti-influenza virus drugs. the na structure has been extensively studied, and the locations of disulfide bonds within the na monomers have been identified. because mutation of cysteine residues in other systems has resulted in temperature-sensitive (ts) proteins, we asked whether mutation of cysteine residues in the ...199910482558
phylogenetic analyses of the matrix and non-structural genes of equine influenza viruses.matrix (m) and nonstructural (ns) genes of thirteen equine h3n8 and h7n7 influenza viruses were sequenced and analyzed from an evolutionary point of view. the m and ns genes of h3n8 viruses isolated between 1989 and 1993 evolved into two minor branch clusters, including isolates from europe and the american continent, respectively. it was noteworthy to reveal that the nucleotide sequences of the m and ns genes of an earlier american strain showed highest homology to those of recent european viru ...19989739336
neuropathological studies of chickens infected with highly pathogenic avian influenza viruses.central nervous system lesions of chickens inoculated with three highly pathogenic avian influenza virus strains, a/chicken/victoria/1/85 (h7n7), a/turkey/england/50-92/91 (h5n1), and a/tern/south africa/61 (h5n3), were examined histologically and immunohistochemically. the chickens either died within 7 days of inoculation or were killed 2 weeks after inoculation. no significant differences were observed in the lesions induced by these three viruses. the lesions were divided into two types, diss ...19968920214
a pcr based method for the identification of equine influenza virus from clinical this paper we describe the development of a nested rt-pcr assay for the rapid diagnosis and characterisation of influenza virus directly from clinical specimens. viral rna is extracted from nasal swabs by the guanidine thiocyanate extraction method, and subsequently reverse transcribed. the complementary dna is then used as template in a nested pcr reaction. primers designed for use in this assay are specific for three templates; (1) the nucleoprotein (np) gene, (2) the haemagglutinin gene of ...199910418871
replacement of internal protein genes, with the exception of the matrix, in equine 1 viruses by equine 2 influenza virus genes during evolution in establish the evolutionary association between the equine 1 h7 ha and m genes, phylogenetic analyses of the six internal gene segments of equine 1 influenza viruses (h7n7 subtype) were performed using partial nucleotide sequences. the results demonstrated that five internal genes (pbi, pb2, pa, np and ns) of equine 1 viruses isolated after 1964 were replaced by those of equine 2 h3n8 viruses. however, the m gene was maintained during the evolution of these equine 1 viruses. these findings sug ...199910487248
recent zoonoses caused by influenza a viruses.influenza is a highly contagious, acute illness which has afflicted humans and animals since ancient times. influenza viruses are part of the orthomyxoviridae family and are grouped into types a, b and c according to antigenic characteristics of the core proteins. influenza a viruses infect a large variety of animal species, including humans, pigs, horses, sea mammals and birds, occasionally producing devastating pandemics in humans, such as in 1918, when over twenty million deaths occurred worl ...200011189716
evaluation of antibody responses of emus (dromaius novaehollandiae) to avian influenza virus infection.emu antibody responses to avian influenza virus (aiv) infection were evaluated by the competitive enzyme-linked immunosorbent assay (c-elisa), agar gel immunodiffusion (agid) and hemagglutination inhibition (hi) tests. all birds infected with aiv h5n1, h5n3, or h7n7 developed antinucleoprotein (np) antibodies as early as 7 days postinfection as detected by the c-elisa. the responses lasted 49 days for the emus receiving h5n3 and at least 56 days for emus receiving the other two viruses. by evalu ...19989876845
defective segment 1 rnas that interfere with production of infectious influenza a virus require at least 150 nucleotides of 5' sequence: evidence from a plasmid-driven system.the presence of at least 80-90 and more typically around 200 nucleotides (nt) at the 5' end of the virion-sense rna in all naturally occurring defective influenza a virus rnas suggests that this is essential sequence, whereas the 3'-end sequence may be as short as 25 nt. the stability of defective rna on serial passage with infectious helper virus also depends on the length of 5'-end sequence. here, we have studied the influence of 5'-end sequences of a panel of six defective segment 1 rnas from ...200211807233
genetic characterisation of an influenza a virus of unusual subtype (h1n7) isolated from pigs in h1n7 influenza a virus, isolated from pigs in england in 1992, was examined genetically to determine the characteristics and probable origin of the eight gene segments. six of the rna segments encoding pb2, pb1, pa, ha, np and ns were related most closely to those of human viruses, whilst two of the rna segments (na and m) were related most closely to those of equine viruses. the ha gene was most similar to that of a/ussr/90/77 (h1n1) but amino acid differences suggested independent genetic d ...19979191869
detection of influenza a subtypes in community-based surveillance.a rapid microtitre cell enzyme immuno assay (cell-eia) was developed for the detection of influenza a subtypes in nasopharyngeal(nps) swabs taken for surveillance. during the 1997/1998 influenza season in the united kingdom, cell-eia was compared to cell culture for the detection and typing of influenza a viruses in nps obtained by sentinel general practitioners in community surveillance. the cell eia can also be used to detect different influenza a subtypes (h3n2, h1n1, h5n3, h5n1, h7n7, and h9 ...200111505459
occurrence of infectious upper respiratory tract disease and response to vaccination in horses on six sentinel premises in northern colorado.horses vaccinated against common agents of infectious upper respiratory disease (iurd) may not have detectable serum antibody and may not be protected from clinical disease.200312553466
strategies for inducing protection against avian influenza a virus subtypes with dna vaccines.the cross-species transfer of a h5n1 influenza virus from birds to humans, and the systemic spread of this virus in mice, has accelerated the efforts to devise protective strategies against lethal influenza viruses. dna vaccination with the highly conserved nucleoprotein gene appears to provide cross protection against influenza a viruses in murine models. whether such vaccines would protect human hosts against different influenza a viruses, including strains with pandemic potential, is unclear. ...200010775793
[complete oligomerization of the nucleoprotein and various strains of influenza virus].previously we demonstrated that in the course of intracellular reproduction of wsn influenza virus strain, part of monomeric nucleoprotein (np) undergo polymerization into dimers and trimers, which dissociate into monomers after boiling. further studies showed that different strains of influenza virus are characterized by different degree of np-oligomerization. specifically, duck/ ukraine/63 (h3n8) and seal massacuhsets 1/80 (h7n7) np monomers are completely transformed into oligomers. as a resu ...19968999311
defective influenza a virus generated entirely from plasmids: its rna is expressed in infected mouse lung and modulates disease.naturally produced defective influenza virus has antiviral activity and, in sufficient amount, can protect mice from lethal influenza, irrespective of the virus subtype causing the disease. however, such defective virus preparations contain many undefined defective rna sequences, and it is thus not possible to establish dose-response relationships. to address this situation, we have transfected dna encoding a cloned defective rna into vero cells along with the 17 a/wsn (h1n1) plasmids required f ...200312565156
[avian influenza and oseltamivir; a retrospective view].the outbreak of avian influenza a due to an h7n7 virus in dutch poultry farms turned out to have public-health effects for those who were involved in the management of the epidemic and who were thus extensively exposed to contaminated excreta and dust. an outbreak-management team (omt) of experts in virology, infectious diseases and public health advised the dutch government with respect to the potential health effects on humans. strict hygiene measures were advised. moreover, vaccination agains ...200312822517
profound protection against respiratory challenge with a lethal h7n7 influenza a virus by increasing the magnitude of cd8(+) t-cell memory.the recall of cd8(+) t-cell memory established by infecting h-2(b) mice with an h1n1 influenza a virus provided a measure of protection against an extremely virulent h7n7 virus. the numbers of cd8(+) effector and memory t cells specific for the shared, immunodominant d(b)np(366) epitope were greatly increased subsequent to the h7n7 challenge, and though lung titers remained as high as those in naive controls for 5 days or more, the virus was cleared more rapidly. expanding the cd8(+) memory t-ce ...200011090168
isolation and characterization of a low-pathogenicity h7n7 influenza virus from a turkey in a small mixed free-range poultry flock in germany.a hemagglutinating virus was isolated from a dead turkey in a small mixed free-range flock in southern germany. it was identified as influenza virus type a of subtype h7n7. the pathogenicity was low. an intravenous pathogenicity index of 0.03 was recorded, and the nucleotide sequencing revealed the amino acid sequence nvpeipkgr*glfg at the cleavage site of the hemagglutinin. antibodies as well as virus were detected in the affected flock. further virus spreading to other flocks was prevented by ...200314575121
avian influenza and human health.natural infections with influenza a viruses have been reported in a variety of animal species including humans, pigs, horses, sea mammals, mustelids and birds. occasionally devastating pandemics occur in humans. although viruses of relatively few ha and na subtype combinations have been isolated from mammalian species, all 15 ha subtypes and all 9 na subtypes, in most combinations, have been isolated from birds. in the 20th century the sudden emergence of antigenically different strains transmis ...200212062786
influenza.although most influenza infections are self-limited, few other diseases exert such a huge toll of suffering and economic loss. despite the importance of influenza, there had been, until recently, little advance in its control since amantadine was licensed almost 40 years ago. during the past decade, evidence has accrued on the protection afforded by inactivated vaccines and the safety and efficacy in children of live influenza-virus vaccines. there have been many new developments in vaccine tech ...200314643124
update: influenza activity--united states and worldwide, 2002-03 season, and composition of the 2003-04 influenza collaboration with the world health organization (who), its collaborating laboratories, state and local health departments, health-care providers, and vital statistic registries, cdc conducts surveillance to monitor influenza activity and to detect antigenic changes in the circulating strains of influenza viruses. during the 2002-03 influenza season, influenza a (h1), a (h3n2), and b viruses co-circulated in the northern hemisphere. human infections with avian influenza a (h5n1) and a (h7n7) ...200312803198
transmission of h7n7 avian influenza a virus to human beings during a large outbreak in commercial poultry farms in the outbreak of highly pathogenic avian influenza a virus subtype h7n7 started at the end of february, 2003, in commercial poultry farms in the netherlands. although the risk of transmission of these viruses to humans was initially thought to be low, an outbreak investigation was launched to assess the extent of transmission of influenza a virus subtype h7n7 from chickens to humans.200414987882
combined antiinfluenza virus activity of flos verbasci infusion and amantadine derivatives.the infusion prepared from flowers of verbascum thapsiforme schrad. (scrophulariaceae) (fvi) reduced the infectious and haemagglutination yields of a range of influenza viruses in tissue cultures. amantadine hydrochloride is an accepted and well studied selective inhibitor of influenza virus reproduction. the combined application of the plant preparation fvi and three amantadine derivatives resulted in a marked enhancement of the inhibitory effect of fvi on the reproduction of influenza virus a/ ...200011054856
in vitro anti-influenza virus activity of the pavine alkaloid (-)-thalimonine isolated from thalictrum simplex l.the pavine alkaloid (-)-thalimonine (thl), isolated from the mongolian plant thalictrum simplex inhibited markedly the reproduction of influenza virus a/germany/27, str. weybridge (h7n7) and a/germany/34, str. rostock (h7n1) in cell cultures of chicken embryo fibroblasts. in a number of assays at a non-toxic concentration range of 0.1-6.4 microm the alkaloid inhibited viral reproduction in a selective and specific way (selectivity index = 640, 106.6, respectively). expression of viral glycoprote ...200312856918
avian influenza a virus (h7n7) associated with human conjunctivitis and a fatal case of acute respiratory distress syndrome.highly pathogenic avian influenza a viruses of subtypes h5 and h7 are the causative agents of fowl plague in poultry. influenza a viruses of subtype h5n1 also caused severe respiratory disease in humans in hong kong in 1997 and 2003, including at least seven fatal cases, posing a serious human pandemic threat. between the end of february and the end of may 2003, a fowl plague outbreak occurred in the netherlands. a highly pathogenic avian influenza a virus of subtype h7n7, closely related to low ...200414745020
avian influenza a virus (h7n7) epidemic in the netherlands in 2003: course of the epidemic and effectiveness of control epidemic of high-pathogenicity avian influenza (hpai) a virus subtype h7n7 occurred in the netherlands in 2003 that affected 255 flocks and led to the culling of 30 million birds. to evaluate the effectiveness of the control measures, we quantified between-flock transmission characteristics of the virus in 2 affected areas, using the reproduction ratio rh. the control measures markedly reduced the transmission of hpai virus: rh before detection of the outbreak in the first infected flock was ...200415551206
Displaying items 1 - 100 of 373