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experimental milk-borne transmission of powassan virus in the goat.a lactating goat with a 74-day-old kid was inoculated with 10(3) mouse 50% lethal dose (ld50) of powassan virus. no ensuing viremia could be detected, but virus was secreted in the milk on postinoculation days 7 through 15, with a titer of 10(5) ld50/ml on day 12. neutralizing antibody was found in the serum on days 22 through 36 and in the milk on day 36. the offspring was not inoculated but was allowed to continue feeding on its mother's milk. it developed neutralizing antibody by day 22. sinc ...1977190910
powassan virus in ixodes cookei and mustelidae in new england.powassan virus was recovered from a pool of 3 nymphal and 1 adult female ixodes cookei removed from a striped skunk (mephitis mephitis) trapped in massachusetts during 1967 and from a pool of 9 nymphal i. cookei from a long-tailed weasel (mustela frenata) captured in connecticut during 1978. virus was detected in the blood of both mammals. hemagglutination-inhibiting (hi) antibody to powassan virus was demonstrated in 16.0% of the skunks sampled in connecticut, and neutralizing antibody was dete ...1979230364
[the specific reactivity of cdna and deoxyoligonucleotide probes, complementary to the tick-borne encephalitis virus genome, with the rna of strains of different geographical origins].hybridization experiments with rna of 143 tick-borne encephalitis (tbe) virus strains isolated in different parts of the distribution area were used to study the reactivity of kdna- and a set of 10 synthetic deoxyoligonucleotide probes. the kdna probe under certain conditions was shown to hybridize with rna of all the strains under study, and under other (strict) hybridization conditions did so selectively with a small number of strains. the capacity of oligonucleotide probes for hybridization w ...19921290224
differentiation of strains of tick-borne encephalitis virus by means of rna-dna hybridization.cloned cdna and synthetic deoxyoligonucleotides, complementary to various parts of the genomic rna of tick-borne encephalitis virus (tbev), strain sofjin, were used to distinguish between strains of tbev and other flaviviruses. the cdna probe hybridized with strains of tbev and related flaviviruses of the tbe complex except for powassan virus, and it did not react with flaviviruses of the japanese encephalitis and dengue subgroups. viruses of the tbe complex and some strains of tbev were differe ...19902374007
[a survey of antibodies to arboviruses in residents in south-western part of yunnan province].in order to provide serological evidence for arbovirus infection in yunnan province, 760 samples of human sera collected from nine counties in south-western part of yunnan province were examined for hi antibodies to 11 arboviral antigens. the viruses used in this experiment included 3 alphaviruses (may, vee and chik) and 8 flaviviruses (je, mve, kun, den3, den4, kfd, lgt and pow). 275 samples were found positive for hi antibodies to alphaviruses (36.2%) and 189 of them (68.7%) reacted with may v ...19892544277
california serogroup and powassan virus infection of cats.one hundred and seventy five sera from cats in ontario, canada, were tested for hemagglutination inhibition (hi) antibodies to three arboviruses; namely, powassan (pow) of the flavivirus serogroup, and snowshoe hare (ssh) and jamestown canyon (jc) viruses of the california (cal) serogroup. all sera were negative for antibodies to pow virus. twelve cats possessed cal serogroup antibodies including 3 with antibodies to ssh alone, 6 with antibodies to jc alone, and 3 with antibodies to both ssh and ...19872825952
evidence that the mature form of the flavivirus nonstructural protein ns1 is a dimer.evidence is presented which indicates that the dengue-2 virus nonstructural protein ns1 (soluble complement fixing antigen) exists in infected bhk and mosquito cell cultures as part of a stable oligomer. identification of the dissociation products of the isolated oligomer and comparison of the number of n-linked glycans in native and denatured ns1 is consistent with the idea that the high-molecular-weight form of ns1 is a homodimer. by analyzing lysates of bhk cells infected with st. louis encep ...19882827377
agents of equine viral encephalomyelitis: correlation of serum and cerebrospinal fluid antibodies.a survey was conducted by testing 115 paired equine serum and cerebrospinal fluid samples by hemagglutination-inhibition for antibodies to powassan and snowshoe hare viruses, and by virus neutralization for antibodies to equine herpesvirus type 1. twenty-five samples were from horses with spontaneous neurological disease and the remainder from horses euthanized because of various nonneurological disorders. all sera and cerebrospinal fluids were negative for antibodies to powassan virus. fifty-on ...19882836046
experimental encephalitis in monkeys caused by the powassan virus.we have carried out a comparative study of the experimental infection of monkeys with the p-40 strain of the powassen virus, isolated in the primor'e territory of the ussr, and with the canadian prototype lb strain. the powassan virus was found to be pathogenic for macaca rhesus. the clinical and pathomorphological picture of the experimental encephalitis was studied, and the full identity of the infection produced in the monkeys by the p-40 strain and the canadian lb strain of the powassan viru ...19852987750
powassan viral encephalitis: a review and experimental studies in the horse and rabbit.powassan virus strain m794, a member of the flavivirus genus known to infect man and animals in canada, was inoculated intracerebrally into rabbits and horses. no clinical signs were observed in rabbits, but widespread encephalitis resulted, characterized by lymphoid perivascular cuffing, lymphocytic meningitis, and lymphocytic choroiditis. in horses, eight days after inoculation, prominent neurological signs occurred and lesions were those of non-suppurative encephalomyelitis, neuronal necrosis ...19852996203
[isolation of the powassan virus from haemaphysalis neumanni dönitz, 1905 ticks in the maritime territory]. 19744439875
immunization of mice against russian spring-summer virus complex and monkeys against powassan virus with attenuated langat e5 virus. duration of protection. 19734630881
a non-fatal human case of powassan virus encephalitis. 19734684890
powassan virus infection. a report of three human cases of encephalitis. 19744856896
localization of powassan virus in dermacentor andersoni ticks by immunofluorescence. 19694905045
westward extension of powassan virus prevalence. 19685657172
powassan virus transmission by ixodid ticks infected after feeding on viremic rabbits injected intravenously. 19695798511
interferon production in powassan virus infections of chickens. 19655836041
powassan virus: vernal spread during 1965.powassan virus was isolated from seven pools of ixodes cookei ticks removed from groundhogs (marmota monax) collected near north bay, ontario, between may and august 1965, including five pools obtained during spring. tick pools, each comprising one to nine ticks, contained 2.0 to 5.5 log(10) tcd(50) of virus upon titration in monolayer cultures of primary swine kidney cells. powassan virus neutralizing antibody prevalence in sera of the current season's groundhogs increased steadily from zero du ...19665904925
a chick embryo attenuated strain (tp21 e5) of langat virus. 3. the ability to protect against homologous virus and powassan virus in cross-challenge experiments. 19665920389
powassan virus: persistence of virus activity during 1966.powassan virus isolations were achieved from three of 60 pools of ixodes cookei ticks removed from 286 groundhogs (marmota monax) which were collected some 200 miles north of toronto between may 5 and september 5, 1966. virus yields per pool of one to 11 ticks ranged from 10(2.5) to 10(6.0) tcd(50) for primary swine kidney tissue cultures, and positive pools were collected on june 24, july 15 and august 10. powassan neutralizing antibodies were detected by mouse inoculation tests in 143 of 362 a ...19676019677
[comparative analysis of the electrophoretic mobility of the high-molecular virus-specific proteins of flaviviruses].a comparative study of high molecular virus-specific proteins in cells infected with flaviviruses from 5 serological subgroups was carried out. proteins nv5, nv4, and v3 were found to have similar electrophoretic mobility in viruses of the tick-borne encephalitis (tbe) complex with the exception of powassan virus protein. proteins nv5 and nv4 of mosquito-borne flaviviruses differ in electrophoretic mobility both from the corresponding proteins of the tbe complex viruses and from each other. prot ...19846152087
antigenic relationships among viruses of the tick-borne encephalitis complex as studied by monoclonal antibodies.tick-borne encephalitis (tbe) monoclonal antibodies showed haemagglutination-inhibiting (hi) activity against viruses belonging to the tbe complex except of powassan virus. the hi titre with kyasanur forest disease virus was lower than with tick-borne encephalitis virus, when monoclonal antibodies were incubated with the antigen at +4 degrees c for 30 min. langat virus could be distinguished from other viruses of the tbe complex when the antigen was incubated with monoclonal antibodies at +4 deg ...19846201061
[role of powassan virus in the etiological structure of tick-borne encephalitis in the primorsky kray].composite studies conducted annually in the primorsky kray showed the tick-borne encephalitis virus to play the main etiological role in the group of encephalites with the spring-summer incidence. in 1976--1978, virological studies of 69 cases of the disease yielded 11 strains of tick-borne encephalitis virus. in 1978, from the blood of clinically normal woman after a tick bite strain 555 was first isolated which was identified as powassan virus, and antigenemia was observed for 53 days using th ...19806247844
[experimental monkey encephalitis caused by powassan virus].a comparative study of the experimental infection of monkeys caused by brain p-40 of powassan virus isolated in the primorye territory of the ussr and by the prototype canadian strain lb was carried out. powassan virus was found to be pathogenic for macaca rhesus. clinical and pathomorphological picture of the experimental encephalitis was studied. full identity of the infection caused in the monkeys by the strain p-40 and the canadian strain lb of powassan virus has been proved. on electronmicr ...19816263023
powassan virus infection in snowshoe hares (lepus americanus).sera from snowshoe hares (lepus americanus) trapped near rochester, alberta, canada were tested for powassan virus antibody by the constant virus/serum dilution neutralization test. of 1264 serum samples tested, 137 had an antibody titer of at least 1:4 for powassan virus. ten hares were inoculated with powassan virus in the laboratory. viremia lasted 4-5 days and ceased with the appearance of powassan antibody in the serum. neutralizing antibody reached a peak titer of 1:119 on day 15 post-inoc ...19816264168
[biological properties and antigenic interconnection between tiuleniy and karshi flaviviruses].biological properties of flaviviruses tyuleny and karshi, new for the science, were studied. the viruses are highly pathogenic for laboratory animals; they replicate fairly well in primary chick embryo cells and ps cells. bhk-21 cells were found susceptible to replication of karshi virus. tyuleny and karshi viruses were found capable of initiating and maintaining a persistent infection in primary brain cell cultures from suckling syrian hamsters for at least 3 months. both the viruses showed cyt ...19947716902
[genome sequence and antigen structure of the powassan virus: analysis of genetic elements of tick-transmitted flaviviruses]. 19957886964
complete genomic sequence of powassan virus: evaluation of genetic elements in tick-borne versus mosquito-borne flaviviruses.the complete nucleotide sequence of the positive-stranded rna genome of the tick-borne flavivirus powassan (10,839 nucleotides) was elucidated and the amino acid sequence of all viral proteins was derived. based on this sequence as well as serological data, powassan virus represents the most divergent member of the tick-borne serocomplex within the genus flaviviruses, family flaviviridae. the primary nucleotide sequence and potential rna secondary structures of the powassan virus genome as well ...19938097605
medically important arboviruses of the united states and canada.of more than 500 arboviruses recognized worldwide, 5 were first isolated in canada and 58 were first isolated in the united states. six of these viruses are human pathogens: western equine encephalitis (wee) and eastern equine encephalitis (eee) viruses (family togaviridae, genus alphavirus), st. louis encephalitis (sle) and powassan (pow) viruses (flaviviridae, flavivirus), lacrosse (lac) virus (bunyaviridae, bunyavirus), and colorado tick fever (ctf) virus (reoviridae, coltivirus). their scien ...19948118792
classification of a new member of the tbe flavivirus subgroup by its immunological, pathogenetic and molecular characteristics: identification of subgroup-specific pentapeptides.the antigenic, pathogenic and molecular characteristics of turkish sheep encephalitis (tse) virus, strain tte80, were compared with other members of the tick-borne encephalitis (tbe) virus complex. monoclonal antibodies with defined specificity for the flavivirus envelope glycoprotein distinguished tse virus from louping ill (li), western or far eastern tbe, langat and powassan virus in indirect immunofluorescence, haemagglutination-inhibition and neutralization tests. on the other hand, tse vir ...19938249442
a new tick-borne encephalitis-like virus infecting new england deer ticks, ixodes dammini.to determine if eastern north american ixodes dammini, like related ticks in eurasia, maintain tick-borne encephalitis group viruses, we analyzed ticks collected from sites where the agent of lyme disease is zoonotic. two viral isolates were obtained by inoculating mice with homogenates from tick salivary glands. the virus, which was described by reverse transcriptase polymerase chain reaction and direct sequencing of the amplification products, was similar to, but distinct from, powassan virus ...19979204297
african swine fever virus infection in the argasid host, ornithodoros porcinus porcinus.the pathogenesis of african swine fever virus (asfv) infection in ornithodoros porcinus porcinus was examined in nymphal ticks infected with the asfv isolate chiredzi/83/1. at times postinfection (p.i.) ranging from 6 h to 290 days, ticks or dissected tick tissues were titrated for virus and examined ultrastructurally for evidence of virus replication. the asfv infection rate in ticks was 100% in these experiments, and virus infection was not associated with a significant increase in tick mortal ...19989499019
spontaneous and engineered deletions in the 3' noncoding region of tick-borne encephalitis virus: construction of highly attenuated mutants of a flavivirus.the flavivirus genome is a positive-strand rna molecule containing a single long open reading frame flanked by noncoding regions (ncr) that mediate crucial processes of the viral life cycle. the 3' ncr of tick-borne encephalitis (tbe) virus can be divided into a variable region that is highly heterogeneous in length among strains of tbe virus and in certain cases includes an internal poly(a) tract and a 3'-terminal conserved core element that is believed to fold as a whole into a well-defined se ...19989499069
etiology of acute childhood encephalitis at the hospital for sick children, toronto, 1994-1995.of 145 patients admitted to our hospital because of encephalitis-like illness, 50 patients hospitalized for > or =72 hours underwent standardized microbiological investigations. a confirmed or probable etiologic agent was identified in 20 cases (40%), including mycoplasma pneumoniae (9 cases). m. pneumoniae and enterovirus (2), herpes simplex virus (4), epstein-barr virus (1), human herpes-virus 6 (hhv-6) (1), hhv-6 and influenza virus type a (1), influenza virus type a (1), and powassan virus ( ...19989502462
charged residues in the transmembrane domains of hepatitis c virus glycoproteins play a major role in the processing, subcellular localization, and assembly of these envelope proteins.for most membrane proteins, the transmembrane domain (tmd) is more than just an anchor to the membrane. the tmds of hepatitis c virus (hcv) envelope proteins e1 and e2 are extreme examples of the multifunctionality of such membrane-spanning sequences. indeed, they possess a signal sequence function in their c-terminal half, play a major role in endoplasmic reticulum localization of e1 and e2, and are potentially involved in the assembly of these envelope proteins. these multiple functions are su ...200010729138
standardization of immunoglobulin m capture enzyme-linked immunosorbent assays for routine diagnosis of arboviral infections.immunoglobulin m antibody-capture enzyme-linked immunosorbent assay (mac-elisa) is a rapid and versatile diagnostic method that readily permits the combination of multiple assays. test consolidation is especially important for arthropod-borne viruses (arboviruses) which belong to at least three virus families: the togaviridae, flaviviridae, and bunyaviridae. using prototype viruses from each of these families and a panel of well-characterized human sera, we have evaluated and standardized a comb ...200010790107
rapid detection of west nile virus from human clinical specimens, field-collected mosquitoes, and avian samples by a taqman reverse transcriptase-pcr assay.the authors report on the development and application of a rapid taqman assay for the detection of west nile (wn) virus in a variety of human clinical specimens and field-collected specimens. oligonucleotide primers and fam- and tamra-labeled wn virus-specific probes were designed by using the nucleotide sequence of the new york 1999 wn virus isolate. the taqman assay was compared to a traditional reverse transcriptase (rt)-pcr assay and to virus isolation in vero cells with a large number ( app ...200011060069
biophysical characterization and vector-specific antagonist activity of domain iii of the tick-borne flavivirus envelope protein.the molecular determinants responsible for flavivirus host cell binding and tissue tropism are largely unknown, although domain iii of the envelope protein has been implicated in these functions. we examined the solution properties and antagonist activity of langat virus domain iii. our results suggest that domain iii adopts a stably folded structure that can mediate binding of tick-borne flaviviruses but not mosquito-borne flaviviruses to their target cells. three clusters of phylogenetically c ...200111264392
mutational evidence for an internal fusion peptide in flavivirus envelope protein e.the envelope protein e of the flavivirus tick-borne encephalitis (tbe) virus promotes cell entry by inducing fusion of the viral membrane with an intracellular membrane after uptake by endocytosis. this protein differs from other well-studied viral and cellular fusion proteins because of its distinct molecular architecture and apparent lack of involvement of coiled coils in the low-ph-induced structural transitions that lead to fusion. a highly conserved loop (the cd loop), which resides at the ...200111287576
essential role of cyclization sequences in flavivirus rna replication.a possible role in rna replication for interactions between conserved complementary (cyclization) sequences in the 5'- and 3'-terminal regions of flavivirus rna was previously suggested but never tested in vivo. using the m-fold program for rna secondary-structure predictions, we examined for the first time the base-pairing interactions between the covalently linked 5' genomic region (first ~160 nucleotides) and the 3' untranslated region (last ~115 nucleotides) for a range of mosquito-borne fla ...200111413342
phylogeny of north american powassan virus.to determine whether powassan virus (pow) and deer tick virus (dtv) constitute distinct flaviviral populations transmitted by ixodid ticks in north america, we analysed diverse nucleotide sequences from 16 strains of these viruses. two distinct genetic lineages are evident, which may be defined by geographical and host associations. the nucleotide and amino acid sequences of lineage one (comprising new york and canadian pow isolates) are highly conserved across time and space, but those of linea ...200111413377
tick-borne langat/mosquito-borne dengue flavivirus chimera, a candidate live attenuated vaccine for protection against disease caused by members of the tick-borne encephalitis virus complex: evaluation in rhesus monkeys and in mosquitoes.langat virus (lgt), strain tp21, a naturally avirulent tick-borne flavivirus, was used to construct a chimeric candidate virus vaccine which contained lgt genes for premembrane (prem) and envelope (e) glycoprotein and all other sequences derived from dengue type 4 virus (den4). the live virus vaccine was developed to provide resistance to the highly virulent, closely related tick-borne flaviviruses that share protective e epitopes among themselves and with lgt. toward that end the chimera, initi ...200111483771
nucleotide sequencing and serological evidence that the recently recognized deer tick virus is a genotype of powassan virus.deer tick virus (dtv) is a recently recognized north american virus isolated from ixodes dammini ticks. nucleotide sequencing of fragments of structural and non-structural protein genes suggested that this virus was most closely related to the tick-borne flavivirus powassan (pow), which causes potentially fatal encephalitis in humans. to determine whether dtv represents a new and distinct member of the flavivirus genus of the family flaviviridae, we sequenced the structural protein genes and 5' ...200111551648
genomic sequencing of deer tick virus and phylogeny of powassan-related viruses of north america.powassan (pow) virus is responsible for central nervous system infection in humans in north america and the eastern parts of russia. recently, a new flavivirus, deer tick (dt) virus, related to pow virus was isolated in the united states, but neither its pathogenic potential in human nor the taxonomic relationship with pow virus has been elucidated. in this study, we obtained the near-full-length genomic sequence of the dt virus and complete sequences of 3 genomic regions of 15 strains of pow-re ...200111716135
nucleic acid sequence-based amplification assays for rapid detection of west nile and st. louis encephalitis viruses.the development and application of nucleic acid sequence-based amplification (nasba) assays for the detection of west nile (wn) and st. louis encephalitis (sle) viruses are reported. two unique detection formats were developed for the nasba assays: a postamplification detection step with a virus-specific internal capture probe and electrochemiluminescence (nasba-ecl assay) and a real-time assay with 6-carboxyfluorescein-labeled virus-specific molecular beacon probes (nasba-beacon assay). the sen ...200111724870
outbreak of powassan encephalitis--maine and vermont, 1999-2001.powassan (pow) virus, a north american tickborne flavivirus related to the eastern hemisphere's tickborne encephalitis viruses, was first isolated from a patient with encephalitis in 1958. during 1958-1998, 27 human pow encephalitis cases were reported from canada and the northeastern united states. during september 1999-july 2001, four maine and vermont residents with encephalitis were found to be infected with pow virus. these persons were tested for other arbovirus infections found in the nor ...200111787585
use of immunoglobulin m cross-reactions in differential diagnosis of human flaviviral encephalitis infections in the united states.to define the virus specificity of the immunoglobulin m (igm) antibody-capture enzyme-linked immunosorbent assay (mac-elisa) among the medically important members of the japanese encephalitis (je) virus serocomplex of flaviviruses, 103 igm-positive human serum samples from patients with confirmed west nile (wn) virus, st. louis encephalitis (sle) virus, or je virus infections were assembled and simultaneously tested against all three viral antigens in a standardized mac-elisa. of the serum sampl ...200211986257
characterization of a siberian virus isolated from a patient with progressive chronic tick-borne encephalitis.a strain of tick-borne encephalitis virus designated zausaev (za) was isolated in siberia from a patient who died of a progressive (2-year) form of tick-borne encephalitis 10 years after being bitten by a tick. the complete genomic sequence of this virus was determined, and an attempt was made to correlate the sequence with the biological characteristics of the virus. phylogenetic analysis demonstrated that this virus belongs to the siberian subtype of tick-borne encephalitis virus. comparison o ...200312477807
first isolation of west nile virus from a patient with encephalitis in the united states.west nile virus (wnv) was isolated from a patient who developed encephalitis while undergoing treatment with chop (cyclophosphamide, hydroxydoxorubicin, vincristine [oncovin], predisone) and rituximab for a non-hodgkin b-cell lymphoma. both standard reverse transcription-polymerase chain reaction (rt-pcr) and taqman rt-pcr established the diagnosis of wnv infection from cerebrospinal fluid (csf). several whole blood samples and one serum sample underwent further testing. csf and serum samples we ...200212498649
tick-borne encephalitis.tick-borne encephalitis (tbe) is one of the most dangerous human infections occurring in europe and many parts of asia. the etiological agent tick-borne encephalitis virus (tbev), is a member of the virus genus flavivirus, of the family flaviviridae. tbev is believed to cause at least 11,000 human cases of encephalitis in russia and about 3000 cases in the rest of europe annually. related viruses within the same group, louping ill virus (liv), langat virus (lgtv) and powassan virus (powv), also ...200312615309
flavivirus capsid is a dimeric alpha-helical protein.the capsid proteins of two flaviviruses, yellow fever virus and dengue virus, were expressed in escherichia coli and purified to near homogeneity suitable for biochemical characterization and structure determination by nuclear magnetic resonance. the oligomeric properties of the capsid protein in solution were investigated. in the absence of nucleic acid, both proteins were predominantly dimeric in solution. further analysis of both proteins with far-uv circular dichroism spectroscopy indicated ...200312768036
tick-borne encephalitis with hemorrhagic syndrome, novosibirsk region, russia, 1999.eight fatal cases of tick-borne encephalitis with an unusual hemorrhagic syndrome were identified in 1999 in the novosibirsk region, russia. to study these strains, we sequenced cdna fragments of protein e gene from six archival formalin-fixed brain samples. phylogenetic analysis showed tick-borne encephalitis variants clustered with a far eastern subtype (homology 94.7%) but not with the siberian subtype (82%).200312781020
epitope-blocking enzyme-linked immunosorbent assays for detection of west nile virus antibodies in domestic mammals.we evaluated the ability of epitope-blocking enzyme-linked immunosorbent assays (elisas) to detect west nile virus (wnv) antibodies in domestic mammals. sera were collected from experimentally infected horses, cats, and pigs at regular intervals and screened in elisas and plaque reduction neutralization tests. the diagnostic efficacies of these techniques were similar.200312791902
viral meningitis and encephalitis: traditional and emerging viral agents.in the united states, the annual number of central nervous system (cns) infections that occur as a result of viral agents far exceeds that of infections caused by bacteria, yeast, molds, and protozoa combined. the recent incursion of west nile virus (wnv) into north america has led to a dramatic change in the incidence and epidemiology of summer-associated viral cns disease. as a result of increased testing for wnv, lesser known viral causes of cns infection have been identified. even the epidem ...200312881794
isolation of a virus closely related to powassan virus from dermacentor andersoni collected along north cache la poudre river, colo. 196013838002
powassan and silverwater viruses: ecology of two ontario arboviruses.powassan virus was isolated from a pool of ixodes marxi ticks collected during late august 1962, from a red squirrel, tamiasciurus hudsonicus, and from blood obtained from a red squirrel during early october 1962 near powassan, ontario, where a child contracted fatal encephalitis due to this virus in september 1958. the frequent detection of powassan virus neutralizing antibody in sera of squirrels captured during autumn, but rarely at other seasons, and the frequent i. marxi infestation of squi ...196313932161
powassan virus: morphology and cytopathology.powassan virus, a north american tickborne group b arbovirus, multiplied after simultaneous inoculation into bottles or tubes of virus and trypsinized suspension of continuous-line cultures of rhesus monkey kidney cells, strain llc-mk2. cytopathic effects comprising cell rounding and cytoplasmic vacuolation were first observed five days after inoculation. mixture of powassan antiserum with virus before inoculation into tissue cultures inhibited the appearance of cytopathic effects. hemagglutinin ...196414146854
powassan virus: field investigations during the summer of 1963. 196414205898
powassan virus: summer infection cycle, 1964.between may 1, and september 15, 1964, neutralizing antibody to powassan virus was detected in sera from 163 of 464 forest mammals captured in the powassan-north bay area of northern ontario. these included 159 of 358 groundhogs and four of 43 red squirrels. acquisition of antibody by juvenile groundhogs occurred principally during july and august. powassan virus strains were isolated from tick pools containing two to 15 ixodes cookei per pool which were removed from eight of 91 groundhogs in th ...196414230913
the importance of the q motif in the atpase activity of a viral helicase.ns3 proteins of flaviviruses contain motifs which indicate that they possess protease and helicase activities. the helicases are members of the dexd/h box helicase superfamily and ns3 proteins from some flaviviruses have been shown to possess atpase and helicase activities in vitro. the q motif is a recently recognised cluster of nine amino acids common to most dexd/h box helicases which is proposed to regulate atp binding and hydrolysis. in addition a conserved residue occurs 17 amino acids ups ...200314623116
tick-borne flaviviruses.tick-borne encephalitis (tbe), one of the most dangerous neuroinfections in europe and asia, is caused by tick-borne encephalitis virus (tbev) and currently involves approximately 11,000 human cases annually, mostly in russia. this chapter describes the main problems associated with the epidemiology, ecology, pathogenesis, and control of this disease. we have attempted to review the factors that influence the incidence and distribution of tbe, and to discuss possible reasons for the different cl ...200314714436
solution structure of dengue virus capsid protein reveals another fold.dengue virus is responsible for approximately 50-100 million infections, resulting in nearly 24,000 deaths annually. the capsid (c) protein of dengue virus is essential for specific encapsidation of the rna genome, but little structural information on the c protein is available. we report the solution structure of the 200-residue homodimer of dengue 2 c protein. the structure provides, to our knowledge, the first 3d picture of a flavivirus c protein and identifies a fold that includes a large di ...200414993605
evolution and dispersal of encephalitic flaviviruses.there are two major groups of encephalitic flaviviruses, those that infect and are transmitted by ticks, particularly ixodes spp. and those that infect and are transmitted by mosquitoes, particularly culex spp. the tick-borne encephalitic flaviviruses exhibit evolutionary characteristics that are largely determined by the protracted life cycle of the tick, its habitat and the prevailing climatic conditions. these viruses appear to have evolved gradually from non-encephalitic viruses that radiate ...200415119763
enzyme-linked immunosorbent assays using recombinant envelope protein expressed in cos-1 and drosophila s2 cells for detection of west nile virus immunoglobulin m in serum or cerebrospinal fluid.humans infected with west nile virus (wnv) develop immunoglobulin m (igm) antibodies soon after infection. the microtiter-based assays for wnv igm antibody detection used by most state public health and reference laboratories utilize wnv antigen isolated from infected vero cells or recombinant envelope protein produced in cos-1 cells. recombinant antigen produced in cos-1 cells was used to develop a wnv igm capture enzyme immunoassay (eia). a supplementary eia using wnv envelope protein expresse ...200415242936
use of recombinant e protein domain iii-based enzyme-linked immunosorbent assays for differentiation of tick-borne encephalitis serocomplex flaviviruses from mosquito-borne flaviviruses.the serological diagnosis of infection by flaviviruses is complicated by the presence of flavivirus cross-reactive antibodies that produce false-positive results for flavivirus infections, especially in regions where more than one virus is endemic. current diagnostic reagents for tick-borne flavivirus infection have been found to cross-react with yellow fever- or dengue virus-positive sera. this study utilized recombinant flavivirus e protein domain 3 (re-d3) as a diagnostic reagent to different ...200415364996
short report: duration of tick attachment required for transmission of powassan virus by deer ticks.infected deer ticks (ixodes scapularis) were allowed to attach to naive mice for variable lengths of time to determine the duration of tick attachment required for powassan (pow) virus transmission to occur. viral load in engorged larvae detaching from viremic mice and in resulting nymphs was also monitored. ninety percent of larval ticks acquired pow virus from mice that had been intraperitoneally inoculated with 10(5) plaque-forming units (pfu). engorged larvae contained approximately 10 pfu. ...200415381804
noninfectious recombinant antigen for detection of st. louis encephalitis virus-specific antibodies in serum by enzyme-linked immunosorbent assay.proper surveillance of virus activity and a timely response to viral outbreaks depend upon the rapid diagnosis of viral infections. the immunoglobulin m (igm) antibody-capture enzyme-linked immunosorbent assay (mac-elisa) is a fast, sensitive test routinely used for the diagnosis of the medically important west nile and st. louis encephalitis flaviviruses. however, the suckling mouse brain-derived (smb) antigen used in this assay is tedious to prepare and has a risk of exposing personnel to live ...200415472331
an animal model for the tickborne flavivirus--omsk hemorrhagic fever virus.the tickborne encephalitis (tbe) serocomplex of flaviviruses consists primarily of viruses that cause neurologic disease; these viruses include omsk hemorrhagic fever virus (ohfv), a virus that is genetically related to other tbe serocomplex viruses but that circulates in an ecologically distinct niche and causes markedly different human disease. the objective of this study was to examine a potential small-animal model for ohfv and to compare the pathology of infection with that of the neurotrop ...200415593010
tick-borne virus diseases of human interest in europe.several human diseases in europe are caused by viruses transmitted by tick bite. these viruses belong to the genus flavivirus, and include tick-borne encephalitis virus, omsk haemorrhagic fever virus, louping ill virus, powassan virus, nairovirus (crimean-congo haemorrhagic fever virus) and coltivirus (eyach virus). all of these viruses cause more or less severe neurological diseases, and some are also responsible for haemorrhagic fever. the epidemiology, clinical picture and methods for diagnos ...200415606630
nucleic acid amplification assays for detection of la crosse virus rna.we report the development of nucleic acid sequence-based amplification (nasba) and quantitative real-time reverse transcription (rt)-pcr assays for the detection of la crosse (lac) virus in field-collected vector mosquito samples and human clinical samples. the sensitivities of these assays were compared to that of a standard plaque assay in vero cells. the nasba and quantitative real-time rt-pcr assays demonstrated sensitivities greater than that of the standard plaque assay. the specificities ...200515815013
low diversity of alkhurma hemorrhagic fever virus, saudi arabia, 1994-1999.alkhurma hemorrhagic fever virus (genus flavivirus, ahfv) was recently identified as the agent of a viral hemorrhagic fever in saudi arabia and characterized serologically and genetically as a variant genotype of kyasanur forest disease virus (kfdv). since viral diagnosis and vaccine development may be hindered by genetic diversity, this study was intended to address ahfv genetic heterogeneity. eleven strains isolated from hospitalized patients from 1994 to 1999 in saudi arabia were sequenced in ...200515890119
peptide inhibitors of dengue virus and west nile virus infectivity.viral fusion proteins mediate cell entry by undergoing a series of conformational changes that result in virion-target cell membrane fusion. class i viral fusion proteins, such as those encoded by influenza virus and human immunodeficiency virus (hiv), contain two prominent alpha helices. peptides that mimic portions of these alpha helices inhibit structural rearrangements of the fusion proteins and prevent viral infection. the envelope glycoprotein (e) of flaviviruses, such as west nile virus ( ...200515927084
comparative analysis of immunoglobulin m (igm) capture enzyme-linked immunosorbent assay using virus-like particles or virus-infected mouse brain antigens to detect igm antibody in sera from patients with evident flaviviral infections.the use of immunoglobulin m (igm) antibody-capture enzyme-linked immunosorbent assay (mac-elisa) serves as a valuable tool for the diagnosis of acute flaviviral infections, since igm antibody titers are detectable early, peak at about 2 weeks postinfection, and subsequently decline to lower levels over the next few months. traditionally, virus-infected tissue culture or suckling mouse brain (smb) has been the source of viral antigens used in the assay. in an effort to provide a reliable source o ...200516000440
genetic variation in west nile virus from naturally infected mosquitoes and birds suggests quasispecies structure and strong purifying selection.intrahost genetic diversity was analysed in naturally infected mosquitoes and birds to determine whether west nile virus (wnv) exists in nature as a quasispecies and to quantify selective pressures within and between hosts. wnv was sampled from ten infected birds and ten infected mosquito pools collected on long island, ny, usa, during the peak of the 2003 wnv transmission season. a 1938 nt fragment comprising the 3' 1159 nt of the wnv envelope (e) coding region and the 5' 779 nt of the non-stru ...200516033965
inhibition of interferon-stimulated jak-stat signaling by a tick-borne flavivirus and identification of ns5 as an interferon antagonist.the tick-borne encephalitis (tbe) complex of viruses, genus flavivirus, can cause severe encephalitis, meningitis, and/or hemorrhagic fevers. effective interferon (ifn) responses are critical to recovery from infection with flaviviruses, and the mosquito-borne flaviviruses can inhibit this response. however, little is known about interactions between ifn signaling and tbe viruses. langat virus (lgtv), a member of the tbe complex of viruses, was found to be highly sensitive to the antiviral effec ...200516188985
the modeled structure of the rna dependent rna polymerase of gbv-c virus suggests a role for motif e in flaviviridae rna polymerases.the flaviviridae virus family includes major human and animal pathogens. the rna dependent rna polymerase (rdrp) plays a central role in the replication process, and thus is a validated target for antiviral drugs. despite the increasing structural and enzymatic characterization of viral rdrps, detailed molecular replication mechanisms remain unclear. the hepatitis c virus (hcv) is a major human pathogen difficult to study in cultured cells. the bovine viral diarrhea virus (bvdv) is often used as ...200516225688
cleavage targets and the d-arginine-based inhibitors of the west nile virus ns3 processing proteinase.mosquito-borne wnv (west nile virus) is an emerging global threat. the ns3 proteinase, which is essential for the proteolytic processing of the viral polyprotein precursor, is a promising drug target. we have isolated and biochemically characterized the recombinant, highly active ns3 proteinase. we have determined that the ns3 proteinase functions in a manner that is distantly similar to furin in cleaving the peptide and protein substrates. we determined that aprotinin and d-arginine-based 9-12- ...200616229682
functional analysis of the tick-borne encephalitis virus cyclization elements indicates major differences between mosquito-borne and tick-borne flaviviruses.the linear, positive-stranded rna genome of flaviviruses is thought to adopt a circularized conformation via interactions of short complementary sequence elements located within its terminal regions. this process of rna cyclization is a crucial precondition for rna replication. in the case of mosquito-borne flaviviruses, highly conserved cyclization sequences (cs) have been identified, and their functionality has been experimentally confirmed. here, we provide an experimental identification of c ...200616571826
understanding helicases as a means of virus control.helicases are promising antiviral drug targets because their enzymatic activities are essential for viral genome replication, transcription, and translation. numerous potent inhibitors of helicases encoded by herpes simplex virus, severe acute respiratory syndrome coronavirus, hepatitis c virus, japanese encephalitis virus, west nile virus, and human papillomavirus have been recently reported in the scientific literature. some inhibitors have also been shown to decrease viral replication in cell ...200616611118
tickborne encephalitis virus, norway and denmark.serum from 2 norwegians with tickborne encephalitis (tbe) (1 of whom was infected in denmark) and 810 norwegian ticks were tested for tbe virus (tbev) rna by reverse transcription-polymerase chain reaction. sequencing and phylogenetic analysis were performed. this is the first genome detection of tbev in serum from norwegian patients.200616836835
recombination and selection in the evolution of picornaviruses and other mammalian positive-stranded rna viruses.picornaviridae are a large virus family causing widespread, often pathogenic infections in humans and other mammals. picornaviruses are genetically and antigenically highly diverse, with evidence for complex evolutionary histories in which recombination plays a major part. to investigate the nature of recombination and selection processes underlying the evolution of serotypes within different picornavirus genera, large-scale analysis of recombination frequencies and sites, segregation by serotyp ...200616956935
distinct rna elements confer specificity to flavivirus rna cap methylation events.the 5' end of the flavivirus plus-sense rna genome contains a type 1 cap (m(7)gpppamg), followed by a conserved stem-loop structure. we report that nonstructural protein 5 (ns5) from four serocomplexes of flaviviruses specifically methylates the cap through recognition of the 5' terminus of viral rna. distinct rna elements are required for the methylations at guanine n-7 on the cap and ribose 2'-oh on the first transcribed nucleotide. in a west nile virus (wnv) model, n-7 cap methylation require ...200717301144
alkhurma hemorrhagic fever virus in ornithodoros savignyi ticks.evidence for the tickborne nature of alkhurma hemorrhagic fever virus (ahfv) is indirect because ahfv has not been detected in arthropods. one ornithodoros savignyi tick from saudi arabia contained ahfv rna. this is the first direct evidence that ahfv is a tickborne flavivirus and confirms the association between human ahfv cases and tickbite history.200717370534
identification of dengue virus in respiratory specimens from a patient who had recently traveled from a region where dengue virus infection is endemic.dengue is the most important arthropod-borne viral disease, and it is a major public health problem in subtropical and tropical regions. the virus is transmitted to humans by the bite of infected female mosquitoes of the genus aedes. the global resurgence of dengue is thought to be due to failure to control the aedes populations, uncontrolled urbanization, population growth, climate change, and increased airplane travel. in this paper we describe the methods used to detect dengue virus infection ...200717376878
structural bases for substrate recognition and activity in meaban virus nucleoside-2'-o-methyltransferase.viral methyltransferases are involved in the mrna capping process, resulting in the transfer of a methyl group from s-adenosyl-l-methionine to capped rna. two groups of methyltransferases (mtases) are known: (guanine-n7)-methyltransferases (n7mtases), adding a methyl group onto the n7 atom of guanine, and (nucleoside-2'-o-)-methyltransferases (2'omtases), adding a methyl group to a ribose hydroxyl. we have expressed and purified two constructs of meaban virus (mv; genus flavivirus) ns5 protein m ...200717473012
west nile virus infection in tree squirrels (rodentia: sciuridae) in california, 2004-2005.west nile virus (wnv) transmission generally involves a mosquito vector and an avian reservoir host, with mammals as incidental hosts. although most mammalian wnv infections cause low or no morbidity or mortality, tree squirrels are susceptible to wnv-associated neurologic disease with infection prevalence comparable to that in dead birds. positive species included fox squirrel (sciurus niger), western gray squirrel (s. griseus), and eastern gray squirrel (s. carolinensis). kidney tissue (dissec ...200717488896
tick-borne flavivirus infection in ixodes scapularis larvae: development of a novel method for synchronous viral infection of ticks.following a bite from an infected tick, tick-borne flaviviruses cause encephalitis, meningitis and hemorrhagic fever in humans. although these viruses spend most of their time in the tick, little is known regarding the virus-vector interactions. we developed a simple method for synchronously infecting ixodes scapularis larvae with langat virus (lgtv) by immersion in media containing the virus. this technique resulted in approximately 96% of ticks becoming infected. lgtv infection and replication ...200717490700
tickborne encephalitis in naturally exposed monkey (macaca sylvanus).we describe tickborne encephalitis (tbe) in a monkey (macaca sylvanus) after natural exposure in an area at risk for tbe. tbe virus was present in the brain and could be identified as closely related to the european subtype, strain neudoerfl.200717553233
differentiation of west nile and st. louis encephalitis virus infections by use of noninfectious virus-like particles with reduced cross-reactivity.differential diagnosis of st. louis encephalitis virus (slev) and west nile virus (wnv) infections can be complicated due to the high degree of cross-reactivity observed in most serodiagnostic assays. in an effort to provide a more specific diagnostic test, we developed virus-like particle (vlp) antigens with reduced cross-reactivity for both slev and wnv by identifying and mutating envelope protein amino acids within the cross-reactive epitopes of vlp expression plasmids. to determine the serod ...200717715375
powassan virus: surveys of human and animal sera. 196018017788
serological studies of west nile virus in a liver transplant population.background: solid organ transplant populations are at increased risk for serious clinical manifestations of west nile virus (wnv) infection. objective: to monitor liver transplant recipients during the 2003 wnv season in manitoba and to identify incidence, clinical presentation and serology. methods: serial blood specimens were obtained from adult patients followed at the liver transplant outpatient clinic between may 2003 and october 2003. studies for wnv infection included immunoglobulin (ig) ...200418159505
evaluation of the langat/dengue 4 chimeric virus as a live attenuated tick-borne encephalitis vaccine for safety and immunogenicity in healthy adult volunteers.with the steady rise in tick-borne encephalitis virus (tbev) infections in europe, development of a live attenuated vaccine that will generate long-lasting immunity would be of considerable benefit. a chimeric flavivirus, designated lgt/den4, was previously constructed to have a genome containing the prm and e protein genes of langat virus (lgt), a naturally attenuated member of the tbev complex, and the remaining genetic sequences derived from dengue 4 virus (den4). lgt/den4 was highly attenuat ...200818207289
novel variant of tickborne encephalitis virus, russia.we isolated a novel strain of tickborne encephalitis virus (tbev), glubinnoe/2004, from a patient with a fatal case in russia. we sequenced the strain, whose landmark features included 57 amino acid substitutions and 5 modified cleavage sites. phylogenetically, glubinnoe/2004 is a novel variant that belongs to the eastern type of tbev.200718258012
enzyme-linked immunosorbent assays using novel japanese encephalitis virus antigen improve the accuracy of clinical diagnosis of flavivirus infections.the cross-reactive antibodies induced by flavivirus infections confound serodiagnosis and pathogenesis, especially in secondary infections caused by antigenically closely related yet distinct flaviviruses. the envelope (e) glycoprotein fusion peptide contains immunodominant cross-reactive determinants. using a recombinant japanese encephalitis virus (jev) premembrane and e expression plasmid producing jev virus-like particles (vlps), dramatic reductions in cross-reactivity were produced by the g ...200818337381
land use and west nile virus seroprevalence in wild mammals.we examined west nile virus (wnv) seroprevalence in wild mammals along a forest-to-urban gradient in the us mid-atlantic region. wnv antibody prevalence increased with age, urbanization, and date of capture for juveniles and varied significantly between species. these findings suggest several requirements for using mammals as indicators of transmission.200818507915
flavivirus methyltransferase: a novel antiviral target.many flaviviruses are significant human pathogens. no effective antiviral therapy is currently available for treatment of flavivirus infections. development of antiviral treatment against these viruses is urgently needed. the flavivirus methyltransferase (mtase) responsible for n-7 and 2'-o methylation of the viral rna cap has recently been mapped to the n-terminal region of nonstructural protein 5. structural and functional studies suggest that the mtase represents a novel antiviral target. her ...200818571739
north american encephalitic arboviruses.arboviruses continue to be a major cause of encephalitis in north america, and west nile virus neuroinvasive disease is now the dominant cause of encephalitis. transmission to humans of north american arboviruses occurs by infected mosquitoes or ticks. most infections are asymptomatic or produce a flulike illness. rapid serum or cerebrospinal fluid igm antibody capture elisa assays are available to diagnosis the acute infection for all north american arboviruses. unfortunately, no antiviral drug ...200818657724
a complex rna motif defined by three discontinuous 5-nucleotide-long strands is essential for flavivirus rna replication.tertiary or higher-order rna motifs that regulate replication of positive-strand rna viruses are as yet poorly understood. using japanese encephalitis virus (jev), we now show that a key element in jev rna replication is a complex rna motif that includes a string of three discontinuous complementary sequences (tdcs). the tdcs consists of three 5-nt-long strands, the left (l) strand upstream of the translation initiator aug adjacent to the 5'-end of the genome, and the middle (m) and right (r) st ...200818669441
genetic and serologic properties of zika virus associated with an epidemic, yap state, micronesia, 2007.zika virus (zikv) is a mosquito-borne flavivirus first isolated in uganda from a sentinel monkey in 1947. mosquito and sentinel animal surveillance studies have demonstrated that zikv is endemic to africa and southeast asia, yet reported human cases are rare, with <10 cases reported in the literature. in june 2007, an epidemic of fever and rash associated with zikv was detected in yap state, federated states of micronesia. we report the genetic and serologic properties of the zikv associated wit ...200818680646
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