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powassan virus infection presenting as acute disseminated encephalomyelitis in tennessee.powassan virus is a rarely diagnosed cause of encephalitis, and is associated with significant neurologic sequelae. although symptomatic infections with powassan virus occur primarily in adults, we report a case of confirmed powassan neuroinvasive disease in a child presenting to a tennessee hospital, with symptoms and imaging studies suggestive of acute disseminated encephalomyelitis.201120736878
distribution and phylogenetic comparisons of a novel mosquito flavivirus sequence present in culex tarsalis mosquitoes from western canada with viruses isolated in california and colorado.in a previous study, a new flavivirus genome sequence was identified in culex tarsalis mosquitoes obtained in alberta, canada and was shown to be genetically related to but distinct from members of the insect-specific flaviviruses. nonstructural protein 5-encoding sequences amplified from cx. tarsalis pools from western canada have shown a high similarity to genome sequences of novel flaviviruses isolated from mosquitoes in california and colorado. despite wide distribution of this virus, design ...201121734143
evaluation of the human host range of bovine and porcine viruses that may contaminate bovine serum and porcine trypsin used in the manufacture of biological products.current u.s. requirements for testing cell substrates used in production of human biological products for contamination with bovine and porcine viruses are u.s. department of agriculture (usda) 9cfr tests for bovine serum or porcine trypsin. 9cfr requires testing of bovine serum for seven specific viruses in six families (immunofluorescence) and at least 2 additional families non-specifically (cytopathicity and hemadsorption). 9cfr testing of porcine trypsin is for porcine parvovirus. recent con ...201122000165
tick cell lines for study of crimean-congo hemorrhagic fever virus and other arboviruses.abstract continuous cell lines derived from many of the vectors of tick-borne arboviruses of medical and veterinary importance are now available. their role as tools in arbovirus research to date is reviewed and their potential application in studies of tick cell responses to virus infection is explored, by comparison with recent progress in understanding mosquito immunity to arbovirus infection. a preliminary study of propagation of the human pathogen crimean-congo hemorrhagic fever virus (cc ...201121955214
Tembusu virus in ducks, china.In China in 2010, a disease outbreak in egg-laying ducks was associated with a flavivirus. The virus was isolated and partially sequenced. The isolate exhibited 87%-91% identity with strains of Tembusu virus, a mosquito-borne flavivirus of the Ntaya virus group. These findings demonstrate emergence of Tembusu virus in ducks.201122000358
tick-borne encephalitis virus in dogs - is this an issue?abstract: the last review on tick-borne encephalitis (tbe) in dogs was published almost ten years ago. since then, this zoonotic tick-borne arbovirus has been geographically spreading and emerging in many regions in eurasia and continues to do so. dogs become readily infected with tbe virus but they are accidental hosts not capable to further spread the virus. they seroconvert upon infection but they seem to be much more resistant to the clinical disease than humans. apart from their use as sent ...201121489255
a snapshot of the ixodes scapularis degradome.parasitic encoded proteases are essential to regulating interactions between parasites and their hosts and thus they represent attractive anti-parasitic druggable and/or vaccine target. we have utilized annotations of ixodes scapularis proteases in gene bank and version 9.3 merops database to compile an index of at least 233 putatively active and 150 putatively inactive protease enzymes that are encoded by the i. scapularis genome. the 233 putatively active protease homologs hereafter referred t ...201121596113
requirement of glycosylation of west nile virus envelope protein for infection of, but not spread within, culex quinquefasciatus mosquito vectors.abstract. most of sequenced west nile virus (wnv) genomes encode a single n-linked glycosylation site on their envelope (e) proteins. we previously found that wnv lacking the e protein glycan was severely inhibited in its ability to replicate and spread within two important mosquito vector species, culex pipiens and cx. tarsalis. however, recent work with a closely related species, cx. pipiens pallens, found no association between e protein glycosylation and either replication or dissemination. ...201121813861
genotype v japanese encephalitis virus is emerging.japanese encephalitis (je) is a global public health issue that has spread widely to more than 20 countries in asia and has extended its geographic range to the south pacific region including australia. je has become the most important cause of viral encephalitis in the world. japanese encephalitis viruses (jev) are divided into five genotypes, based on the nucleotide sequence of the envelope (e) gene. the muar strain, isolated from patient in malaya in 1952, is the sole example of genotype v je ...201121750744
evaluation of widely used diagnostic tests to detect west nile virus infections in horses previously infected with st. louis encephalitis virus or dengue virus type 2.primary west nile virus (wnv) infections can be diagnosed using a number of tests that detect infectious particles, nucleic acid, and specific igm and/or igg antibodies. however, serological identification of the infecting agent in secondary or subsequent flavivirus infections is problematic due to the extensive cross-reactivity of flavivirus antibodies. this is particularly difficult in the tropical americas where multiple flaviviruses cocirculate. a study of sequential flavivirus infection in ...201121346058
mutational analysis of three predicted 5'-proximal stem-loop structures in the genome of tick-borne encephalitis virus indicates different roles in rna replication and translation.flavivirus gene expression is modulated by rna secondary structure elements at the terminal ends of the viral rna molecule. for tick-borne encephalitis virus (tbev), four stem-loop (sl) elements have been predicted in the first 180 nucleotides of the viral genome: 5'-sl1, 5'-sl2, 5'-sl3 and 5'-sl4. the last three of these appear to be unique to tick-borne flaviviruses. here, we report their characterization by mutagenesis in a tbev luciferase reporter system. by manipulating their thermodynamic ...201121645915
mutational analysis of the zippering reaction during flavivirus membrane fusion.the current model of flavivirus membrane fusion is based on atomic structures of truncated forms of the viral fusion protein e in its dimeric prefusion and trimeric postfusion conformations. these structures lack the two transmembrane domains (tmds) of e as well as the so-called stem, believed to be involved in an intra- and intermolecular zippering reaction within the e trimer during the fusion process. in order to gain experimental evidence for the functional role of the stem in flavivirus mem ...201121697495
the unique transmembrane hairpin of flavivirus fusion protein e is essential for membrane fusion.the fusion of enveloped viruses with cellular membranes is mediated by proteins that are anchored in the lipid bilayer of the virus and capable of triggered conformational changes necessary for driving fusion. the flavivirus envelope protein e is the only known viral fusion protein with a double membrane anchor, consisting of two antiparallel transmembrane helices (tm1 and tm2). tm1 functions as a stop-transfer sequence and tm2 as an internal signal sequence for the first nonstructural protein d ...201121325407
west nile virus disease and other arboviral diseases --- united states, 2010.arthropod-borne viruses (arboviruses) are transmitted to humans primarily through the bites of infected mosquitoes and ticks. since west nile virus (wnv) was first detected in the western hemisphere in 1999, it has become the leading cause of neuroinvasive arboviral disease in the united states. however, several other arboviruses continue to cause sporadic cases and seasonal outbreaks of neuroinvasive disease (i.e., meningitis, encephalitis, or acute flaccid paralysis). this report summarizes su ...201121814163
misdiagnosis of early lyme disease as the summer flu.lyme disease is often identified by the hallmark erythema migrans rash, but not all early cases present with a rash. in other cases the rash may be unseen or unrecognized by a physician. in these situations, lyme disease is difficult to diagnose because it masquerades as a non-specific viral-like illness. the seasonal peak of lyme disease ranging from may through september overlaps with that of viral illnesses such as enteroviral infections, west nile virus, and in rare years such as 2009, early ...201122053255
trim79α, an interferon-stimulated gene product, restricts tick-borne encephalitis virus replication by degrading the viral rna polymerase.in response to virus infection, type i interferons (ifns) induce several genes, most of whose functions are largely unknown. here, we show that the tripartite motif (trim) protein, trim79α, is an ifn-stimulated gene (isg) product that specifically targets tick-borne encephalitis virus (tbev), a flavivirus that causes encephalitides in humans. trim79α restricts tbev replication by mediating lysosome-dependent degradation of the flavivirus ns5 protein, an rna-dependent rna polymerase essential for ...201121925107
viruses infecting reptiles.a large number of viruses have been described in many different reptiles. these viruses include arboviruses that primarily infect mammals or birds as well as viruses that are specific for reptiles. interest in arboviruses infecting reptiles has mainly focused on the role reptiles may play in the epidemiology of these viruses, especially over winter. interest in reptile specific viruses has concentrated on both their importance for reptile medicine as well as virus taxonomy and evolution. the imp ...201122163336
Crystal structure of the Japanese encephalitis virus envelope protein.Japanese Encephalitis Virus (JEV) is the leading global cause of viral encephalitis. The JEV envelope protein (E) facilitates cellular attachment and membrane fusion and is the primary target of neutralizing antibodies. Herein, we have determined the 2.1Å resolution crystal structure of the JEV E ectodomain refolded from bacterial inclusion bodies. The E protein possesses the three domains characteristic of flavivirus envelopes and epitope mapping of neutralizing antibodies onto the structure re ...201122156523
pathogen-pathogen interaction: a syndemic model of complex biosocial processes in disease.there is growing awareness of the health implications of fact that infectious agents often do not act independently; rather their disease potential is mediated in diverse and significant ways by their relationships with other pathogens. pathogen-pathogen interaction (ppi), for example, impacts various virulence factors in human infection. although still in its infancy, the study of ppi, a form of epidemiological synergism, is emerging as an important arena of new research and new understanding i ...201021178409
variability of powassan virus cultured in tissue explants and organism of hyalomma anatolicum ticks.the variability of powassan virus was studied during successive passages in hyalomma anatolicum ticks or prolonged reproduction in their tissue explants. it had been shown that in the course of tick passages and during reproduction in the explants, pathogenicity of the virus in respect to causing acute disease in mice after peripheral inoculation was decreased, while virus ability to cause death after intracerebral (i.c.) inoculation remained unchanged. in mice infected with the original strain ...20102864833
high-throughput procedure for tick surveys of tick-borne encephalitis virus and its application in a national surveillance study in switzerland.tick-borne encephalitis (tbe), a viral infection of the central nervous system, is endemic in many eurasian countries. in switzerland, tbe risk areas have been characterized by geographic mapping of clinical cases. since mass vaccination should significantly decrease the number of tbe cases, alternative methods for exposure risk assessment are required. we established a new pcr-based test for the detection of tbe virus (tbev) in ticks. the protocol involves an automated, high-throughput nucleic ...201020453126
bioinformatics in new generation flavivirus vaccines.flavivirus infections are the most prevalent arthropod-borne infections world wide, often causing severe disease especially among children, the elderly, and the immunocompromised. in the absence of effective antiviral treatment, prevention through vaccination would greatly reduce morbidity and mortality associated with flavivirus infections. despite the success of the empirically developed vaccines against yellow fever virus, japanese encephalitis virus and tick-borne encephalitis virus, there i ...201020467477
molecular epidemiology of powassan virus in north america.powassan virus (pow) is a tick-borne flavivirus distributed in canada, the northern usa and the primorsky region of russia. pow is the only tick-borne flavivirus endemic to the western hemisphere, where it is transmitted mainly between ixodes cookei and groundhogs (marmota monax). deer tick virus (dtv), a genotype of pow that has been frequently isolated from deer ticks (ixodes scapularis), appears to be maintained in an enzootic cycle between these ticks and white-footed mice (peromyscus leucop ...201020631087
pcp consensus sequences of flaviviruses: correlating variance with vector competence and disease phenotype.computational methods are needed to design multivalent vaccines against flaviviruses (fvs) such as the west nile virus or the dengue virus (denv).201019969003
update on powassan virus: emergence of a north american tick-borne flavivirus.powassan virus (pow) (flaviviridae: flavivirus) is the cause of rare but severe neuroinvasive disease in north america and russia. the virus is transmitted among small- and medium-sized mammals by ixodid ticks. human infections occur via spillover from the main transmission cycle(s). since the late 1990s, the incidence of human disease seems to be increasing. in addition, pow constitutes a genetically diverse group of virus genotypes, including deer tick virus, that are maintained in distinct en ...201019961325
tick-borne encephalitis among u.s. travelers to europe and asia - 2000-2009.tick-borne encephalitis virus (tbev) is the most common arbovirus transmitted by ticks in europe. approximately 10,000 cases of tick-borne encephalitis (tbe) are reported annually in europe and russia. although tbe is endemic in parts of china, information regarding its incidence is limited. tbev is closely related to powassan virus (powv), another tick-borne flavivirus that is a rare cause of encephalitis in north america and russia; tbev and powv can cross-react in serologic tests. before 2000 ...201020339345
deciphering the molecular basis for nucleotide selection by the west nile virus rna helicase.the west nile virus rna helicase uses the energy derived from the hydrolysis of nucleotides to separate complementary strands of rna. although this enzyme has a preference for atp, the bias towards this purine nucleotide cannot be explained on the basis of specific protein-atp interactions. moreover, the enzyme does not harbor the characteristic q-motif found in other helicases that regulates binding to atp. in the present study, we used structural homology modeling to generate a model of the we ...201020421212
tickborne powassan virus infections among wisconsin residents.powassan virus (powv) is a tickborne flavivirus that causes a rare but potentially life-threatening illness. the first reported case of powv infection in a wisconsin resident occurred in 2003. enhanced surveillance and testing detected 2 additional cases.201020443328
evidence of simultaneous circulation of west nile and usutu viruses in mosquitoes sampled in emilia-romagna region (italy) in 2009.in recent years human diseases due to mosquito-borne viruses were increasingly reported in emilia-romagna region (italy), from the chikungunya virus in 2007 to the west nile virus (wnv) in 2008. an extensive entomological survey was performed in 2009 to establish the presence and distribution of mosquito arboviruses in this region, with particular reference to flaviviruses.201021179462
structural and functional analyses of a conserved hydrophobic pocket of flavivirus methyltransferase.the flavivirus methyltransferase (mtase) sequentially methylates the n7 and 2'-o positions of the viral rna cap (gpppa-rna → m(7)gpppa-rna → m(7)gpppam-rna), using s-adenosyl-l-methionine (adomet) as a methyl donor. we report here that sinefungin (sin), an adomet analog, inhibits several flaviviruses through suppression of viral mtase. the crystal structure of west nile virus mtase in complex with sin inhibitor at 2.0-å resolution revealed a flavivirus-conserved hydrophobic pocket located next t ...201020685660
development of human-murine chimeric immunoglobulin g for use in the serological detection of human flavivirus and alphavirus antibodies.diagnosis of human arboviral infections relies heavily on serological techniques such as the immunoglobulin m (igm) antibody capture enzyme-linked immunosorbent assay (mac-elisa) and the indirect igg elisa. broad application of these assays is hindered by the lack of standardized positive human control sera that react with a wide variety of flaviviruses (e.g., dengue, west nile, yellow fever, japanese encephalitis, saint louis encephalitis, and powassan viruses), or alphaviruses (e.g., eastern e ...201020739503
loop analysis for pathogens: niche partitioning in the transmission graph for pathogens of the north american tick ixodes scapularis.in population biology, loop analysis is a method of decomposing a life cycle graph into life history pathways so as to compare the relative contributions of pathways to the population growth rate across species and populations. we apply loop analysis to the transmission graph of five pathogens known to infect the black-legged tick, ixodes scapularis. in this context loops represent repeating chains of transmission that could maintain the pathogen. they hence represent completions of the life cyc ...201020950628
tick histamine release factor is critical for ixodes scapularis engorgement and transmission of the lyme disease agent.ticks are distributed worldwide and affect human and animal health by transmitting diverse infectious agents. effective vaccines against most tick-borne pathogens are not currently available. in this study, we characterized a tick histamine release factor (thrf) from ixodes scapularis and addressed the vaccine potential of this antigen in the context of tick engorgement and b. burgdorferi transmission. results from western blotting and quantitative reverse transcription-pcr showed that thrf is s ...201021124826
persistence of pathogens with short infectious periods in seasonal tick populations: the relative importance of three transmission routes.the flaviviruses causing tick-borne encephalitis (tbe) persist at low but consistent levels in tick populations, despite short infectious periods in their mammalian hosts and transmission periods constrained by distinctly seasonal tick life cycles. in addition to systemic and vertical transmission, cofeeding transmission has been proposed as an important route for the persistence of tbe-causing viruses. because cofeeding transmission requires ticks to feed simultaneously, the timing of tick acti ...201020668521
flavivirus rna cap methyltransferase: structure, function, and inhibition.many flaviviruses are significant human pathogens. the plus-strand rna genome of a flavivirus contains a 5' terminal cap 1 structure (m(7)gpppamg). the flavivirus encodes one methyltransferase (mtase), located at the n-terminal portion of the ns5 rna-dependent rna polymerase (rdrp). here we review recent advances in our understanding of flaviviral capping machinery and the implications for drug development. the ns5 mtase catalyzes both guanine n7 and ribose 2'-oh methylations during viral cap fo ...201021927615
prevalence of tick-borne encephalitis virus in ticks from southern korea.the prevalence of tick-borne encephalitis virus (tbev) in southern korea was determined by collecting ticks using tick drags. a total of 4,077 of 6,788 ticks collected were pooled (649 pools) according to collection site, species, and developmental stage and assayed for tbev. the tbev protein e and ns5 gene fragments were detected using rt-nested pcr in six pools of nymphs collected from jeju island (2,491 ticks). the minimum field detection rates for tbev were 0.17% and 0.14% for haemaphysalis ...201020706026
assessment of polymicrobial infections in ticks in new york state.ixodes scapularis ticks are clinically important hematophagous vectors. a single tick bite can lead to a polymicrobial infection. we determined the prevalence of polymicrobial infection with borrelia burgdorferi, anaplasma phagocytophilum, babesia microti, borrelia miyamotoi, and powassan virus in 286 adult ticks from the two counties in new york state where lyme disease is endemic, utilizing a masstag multiplex polymerase chain reaction assay. seventy-one percent of the ticks harbored at least ...201019725770
structure and functionality in flavivirus ns-proteins: perspectives for drug design.flaviviridae are small enveloped viruses hosting a positive-sense single-stranded rna genome. besides yellow fever virus, a landmark case in the history of virology, members of the flavivirus genus, such as west nile virus and dengue virus, are increasingly gaining attention due to their re-emergence and incidence in different areas of the world. additional environmental and demographic considerations suggest that novel or known flaviviruses will continue to emerge in the future. nevertheless, u ...201019945487
extraction of total nucleic acids from ticks for the detection of bacterial and viral pathogens.ticks harbor numerous bacterial, protozoal, and viral pathogens that can cause serious infections in humans and domestic animals. active surveillance of the tick vector can provide insight into the frequency and distribution of important pathogens in the environment. nucleic-acid based detection of tick-borne bacterial, protozoan, and viral pathogens requires the extraction of both dna and rna (total nucleic acids) from ticks. traditional methods for nucleic acid extraction are limited to extrac ...201020180313
emergence of zoonotic arboviruses by animal trade and migration.abstract: arboviruses are transmitted in nature exclusively or to a major extend by arthropods. they belong to the most important viruses invading new areas in the world and their occurrence is strongly influenced by climatic changes due to the life cycle of the transmitting vectors. several arboviruses have emerged in new regions of the world during the last years, like west nile virus (wnv) in the americas, usutu virus (usuv) in central europe, or rift valley fever virus (rvfv) in the arabian ...201020377873
rapid identification of vector-borne flaviviruses by mass spectrometry.flaviviruses are a highly diverse group of rna viruses classified within the genus flavivirus, family flaviviridae. most flaviviruses are arthropod-borne, requiring a mosquito or tick vector. several flaviviruses are highly pathogenic to humans; however, their high genetic diversity and immunological relatedness makes them extremely challenging to diagnose. in this study, we developed and evaluated a broad-range flavivirus assay designed to detect both tick- and mosquito-borne flaviviruses by us ...201020412852
homogeneity of powassan virus populations in naturally infected ixodes scapularis.powassan virus (powv, flaviviridae: flavivirus) is the sole north american member of the tick-borne encephalitis complex and consists of two distinct lineages that are maintained in ecologically discrete enzootic transmission cycles. the underlying genetic mechanisms that lead to niche partitioning in arboviruses are poorly understood. therefore, intra- and interhost genetic diversity was analyzed to determine if powv exists as a quasispecies in nature and quantify selective pressures within and ...201020434750
the neglected arboviral infections in mainland china.the major arboviral diseases in mainland china include japanese encephalitis, dengue fever, crimean-congo hemorrhagic fever (also known as xinjiang hemorrhagic fever), and tick-borne encephalitis. these and other newly found arbovirus infections due to banna virus and tahyna virus contribute to a large and relatively neglected disease burden in china. here we briefly review the literature regarding these arboviral infections in mainland china with emphasis on their epidemiology, primary vectors, ...201020436960
tick-borne flaviviruses.there has been a remarkable increase in tick-borne flaviviral disease incidence throughout the past 2 decades. transmission of tick-borne viruses, like other vector-borne agents, is impacted by a very broad set of factors, both natural (eg, climate and ecology) and man-made (eg, human mobility and agricultural patterns). as our encroachment into areas of virus endemicity intensifies, and as changes in global economic and environmental conditions continue to promote the expansion of tick populati ...201020513549
quantum of infection of francisella tularensis tularensis in host-seeking dermacentor variabilis.the american dog tick, dermacentor variabilis, is fundamental to the perpetuation of francisella tularensis tularensis on martha's vineyard, massachusetts, u.s.a. although infected ticks are relatively common on the island, human cases deriving from tick bite are rare. it may be that the quantum of bacteria within these naturally infected ticks is frequently too small to cause disease. accordingly, we quantified the amount of f.t. tularensis bacteria in host-seeking ticks from the island. contra ...201020563231
characterization of dengue virus resistance to brequinar in cell culture.brequinar is an inhibitor of dihydroorotate dehydrogenase, an enzyme that is required for de novo pyrimidine biosynthesis. here we report that brequinar has activity against a broad spectrum of viruses. the compound not only inhibits flaviviruses (dengue virus, west nile virus, yellow fever virus, and powassan virus) but also suppresses a plus-strand rna alphavirus (western equine encephalitis virus) and a negative-strand rna rhabdovirus (vesicular stomatitis virus). using dengue virus serotype ...201020606073
an adenosine nucleoside inhibitor of dengue virus.dengue virus (denv), a mosquito-borne flavivirus, is a major public health threat. the virus poses risk to 2.5 billion people worldwide and causes 50 to 100 million human infections each year. neither a vaccine nor an antiviral therapy is currently available for prevention and treatment of denv infection. here, we report a previously undescribed adenosine analog, nitd008, that potently inhibits denv both in vitro and in vivo. in addition to the 4 serotypes of denv, nitd008 inhibits other flavivi ...200919918064
environmental health indicators of climate change for the united states: findings from the state environmental health indicator collaborative.to develop public health adaptation strategies and to project the impacts of climate change on human health, indicators of vulnerability and preparedness along with accurate surveillance data on climate-sensitive health outcomes are needed. we researched and developed environmental health indicators for inputs into human health vulnerability assessments for climate change and to propose public health preventative actions.200920049116
[genetic diversity of ixodid tick-borne pathogens in tomsk city and suburbs].we studied two urban and two suburban biotypes of tomsk city for tick-transmitted diseases prevalence in naturally collected ticks. tick-borne encephalitis virus (tbev) was found in 6.5% of tick samples, west nile virus (wnv) in 2.2%, borrelia spp. in 8%, rickettsia spp. in 2.5%, and ehrlichia spp. in 1.7% of samples. genetic markers of powassan virus, bartonella spp., and balbesia spp. were not found. analysis of the genetic diversity of revealed pathogens resulted in the following conclusions: ...200919957906
virus-host coevolution: common patterns of nucleotide motif usage in flaviviridae and their hosts.virus-host biological interaction is a continuous coevolutionary process involving both host immune system and viral escape mechanisms. flaviviridae family is composed of fast evolving rna viruses that infects vertebrate (mammals and birds) and/or invertebrate (ticks and mosquitoes) organisms. these host groups are very distinct life forms separated by a long evolutionary time, so lineage-specific anti-viral mechanisms are likely to have evolved. flaviviridae viruses which infect a single host l ...200919617912
isolation of kyasanur forest disease virus from febrile patient, yunnan, china.we recently determined that nanjianyin virus, isolated from serum of a patient in yunnan province, china, in 1989, is a type of kyasanur forest disease virus. results of a 1987-1990 seroepidemiologic investigation in yunnan province had shown that residents of the hengduan mountain region had been infected with nanjianyin virus.200919193286
impact of climate change and other factors on emerging arbovirus diseases.while some skeptics remain unconvinced that global climate change is a reality, there is no doubt that during the past 50 years or so, patterns of emerging arbovirus diseases have changed significantly. can this be attributed to climate change? climate is a major factor in determining: (1) the geographic and temporal distribution of arthropods; (2) characteristics of arthropod life cycles; (3) dispersal patterns of associated arboviruses; (4) the evolution of arboviruses; and (5) the efficiency ...200918799177
human granulocytic anaplasmosis: first reported case in canada.human granulocytic anaplasmosis (hga) is a tick-borne rickettsial infection of peripheral blood neutrophils caused by anaplasma phagocytophilum. while this infection is increasingly recognized as endemic throughout much of the united states, no canadian cases have been previously described, despite the agent being identified in canadian ticks. herein we present a case of hga acquired in an urban alberta centre. canadian physicians must be aware of the possibility of tick-borne rickettsial diseas ...200920808448
characterization of powassan viruses from far eastern russia.we report the isolation and detailed characterization of the novel strain, partizansk/2006, of powassan virus (powv) from a human case of infection, which occurred in primorsky krai, russia, in 2006. comparative complete genome sequence analysis of the far eastern strains spassk-9 (1975), nadezdinsk-1991 and partizansk/2006 of powv revealed that these strains are 99.8% similar to the lb strain, which was isolated in canada in 1958. phylogenetic analysis of 5' utr sequences of five other strains ...200919363586
fatal case of deer tick virus encephalitis.deer tick virus is related to powassan virus, a tickborne encephalitis virus. a 62-year-old man presented with a meningoencephalitis syndrome and eventually died. analyses of tissue samples obtained during surgery and at autopsy revealed a widespread necrotizing meningoencephalitis. nucleic acid was extracted from formalin-fixed tissue, and the presence of deer tick virus was verified on a flavivirus-specific polymerase-chain-reaction (pcr) assay, followed by sequence confirmation. immunohistoch ...200919439744
development of a human-murine chimeric immunoglobulin m antibody for use in the serological detection of human flavivirus antibodies.current diagnosis of human flaviviral infections relies heavily on serological techniques such as the immunoglobulin m (igm) antibody capture enzyme-linked immunosorbent assay (mac-elisa). broad application of this assay is hindered by a lack of standardized human positive-control sera that react with the wide variety of flaviviruses that can cause human disease, e.g., dengue virus (denv), west nile virus (wnv), yellow fever virus (yfv), japanese encephalitis virus (jev), and st. louis encephali ...200919297614
blood feeding by the rocky mountain spotted fever vector, dermacentor andersoni, induces interleukin-4 expression by cognate antigen responding cd4+ t cells.abstract:200919814808
stable prevalence of powassan virus in ixodes scapularis in a northern wisconsin focus.deer tick virus (dtv), a variant of powassan virus (powv), appears to be maintained in nature in an enzootic cycle between ixodes scapularis ticks and small mammals. although powv infection of human beings is rare, a recent report suggests increasing incidence and the possibility that powv may be an emerging tick-borne zoonosis. therefore, we assessed the long-term stability of the powv transmission cycle in northwestern wisconsin. adult i. scapularis and dermacentor variabilis were collected fr ...200819052313
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
identification of genetic determinants of a tick-borne flavivirus associated with host-specific adaptation and pathogenicity.tick-borne flaviviruses are maintained in nature in an enzootic cycle involving a tick vector and a vertebrate host. thus, the virus replicates in two disparate hosts, each providing selective pressures that can influence virus replication and pathogenicity. to identify viral determinants associated with replication in the individual hosts, plaque purified langat virus (tp21pp) was adapted to growth in mouse or tick cell lines to generate two virus variants, mnbp20 and isep20, respectively. viru ...200818823640
increased recognition of powassan encephalitis in the united states, 1999-2005.powassan virus (powv) disease is a rare human disease caused by a tick-borne encephalitis group flavivirus maintained in a transmission cycle between ixodes cookei and other ixodid ticks and small and medium-sized mammals. during 1958-1998, only 27 powv disease cases (mostly powassan encephalitis) were reported from eastern canada and the northeastern united states (average, 0.7 cases per year). during 1999-2005, nine cases (described herein) of serologically confirmed powv disease were reported ...200818959500
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
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
detection and serotyping of dengue virus in serum samples by multiplex reverse transcriptase pcr-ligase detection reaction assay.the detection and successful typing of dengue virus (denv) from patients with suspected dengue fever is important both for the diagnosis of the disease and for the implementation of epidemiologic control measures. a technique for the multiplex detection and typing of denv serotypes 1 to 4 (denv-1 to denv-4) from clinical samples by pcr-ligase detection reaction (ldr) has been developed. a serotype-specific pcr amplifies the regions of genes c and e simultaneously. the two amplicons are targeted ...200818685000
serum antibodies to west nile virus in naturally exposed and vaccinated horses.a polyvalent elisa and plaque reduction neutralization tests (prnts) were used to measure serum antibodies to west nile virus (wnv) in horses naturally exposed to or vaccinated against this flavivirus in connecticut and new york state, usa. relying on a prnt as a 'gold standard', the main objective was to validate a modified elisa containing a recombinant wnv envelope protein antigen. it was also important to assess specificity by testing sera from horses that had other, undiagnosed illnesses. s ...200818719177
powassan encephalitis and colorado tick fever.this article discusses two tick-borne illnesses: powassan encephalitis, a rare cause of central nervous system infection caused by the powassan virus, and colorado tick fever, an acute febrile illness caused by the colorado tick fever virus common to the rocky mountain region of north america.200818755390
experimental infection of eastern gray squirrels (sciurus carolinensis) with west nile virus.eastern gray squirrels (sciurus carolinensis) have shown high west nile virus (wnv) seroprevalence, and wnv infection has been suggested as a cause of morbidity and mortality in this species. we experimentally infected nine eastern gray squirrels with wnv to determine the clinical effects of infection and to assess their potential role as amplifying hosts. we observed no morbidity or mortality attributable to wnv infection, but lesions were apparent in several organs. we detected mean viremias o ...200818784241
the west nile virus mutant spectrum is host-dependant and a determinant of mortality in mice.to define the impact of mosquitoes and birds on intrahost wnv population dynamics, the mutant spectra that arose as a result of 20 serial in vivo passages in culex pipiens and young chickens were examined. genetically homogeneous wnv was serially passaged 20 times in each host. genetic diversity was greater in mosquito-passaged wnv compared to chicken-passaged wnv. changes in the viral consensus sequence occurred in wnv passaged in mosquitoes earlier and more frequently than in chicken-passaged ...200717134731
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
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
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
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
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
phidias: a pathogen-host interaction data integration and analysis system.the pathogen-host interaction data integration and analysis system (phidias) is a web-based database system that serves as a centralized source to search, compare, and analyze integrated genome sequences, conserved domains, and gene expression data related to pathogen-host interactions (phis) for pathogen species designated as high priority agents for public health and biological security. in addition, phidias allows submission, search and analysis of phi genes and molecular networks curated fro ...200717663773
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
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
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
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
the rash of west nile virus infection. 200515911857
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
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
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
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
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
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
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
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
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