Publications

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purification and crystallization of kokobera virus helicase.kokobera virus is a mosquito-borne flavivirus belonging, like west nile virus, to the japanese encephalitis virus serocomplex. the flavivirus genus is characterized by a positive-sense single-stranded rna genome. the unique open reading frame of the viral rna is transcribed and translated as a single polyprotein which is post-translationally cleaved to yield three structural and seven nonstructural proteins, one of which is the ns3 gene that encodes a c-terminal helicase domain consisting of 431 ...200717329812
interference in dengue virus adsorption and uncoating by carrageenans.this study demonstrated that the lambda- and iota-carrageenans, sulfated polysaccharides containing linear chains of galactopyranosyl residues, are potent inhibitors of dengue virus type 2 (denv-2) and 3 (denv-3) multiplication in vero and hepg2 cells, with values of effective concentration 50% from 0.14 to 4.1 microg/ml. this activity was assayed by plaque reduction, virus yield inhibition and antigen expression tests, and was independent of the input multiplicity of infection in the range 0.00 ...200717337028
ilheus virus isolate from a human, ecuador. 200717582910
functional characterization of cis and trans activity of the flavivirus ns2b-ns3 protease.flaviviruses are serious human pathogens for which treatments are generally lacking. the proteolytic maturation of the 375-kda viral polyprotein is one target for antiviral development. the flavivirus serine protease consists of the n-terminal domain of the multifunctional nonstructural protein 3 (ns3) and an essential 40-residue cofactor (ns2b(40)) within viral protein ns2b. the ns2b-ns3 protease is responsible for all cytoplasmic cleavage events in viral polyprotein maturation. this study desc ...200717337448
structural and functional comparison of the non-structural protein 4b in flaviviridae.flaviviridae are evolutionarily related viruses, comprising the hepatitis c virus (hcv), with the non-structural protein 4b (ns4b) as one of the least characterized proteins. ns4b is located in the endoplasmic reticulum membrane and is assumed to be a multifunctional protein. however, detailed structure information is missing. the hydrophobic nature of ns4b is a major difficulty for many experimental techniques. we applied bioinformatics methods to analyse structural and functional properties of ...200717507273
assessing flavivirus, lentivirus, and herpesvirus exposure in free-ranging ring-tailed lemurs in southwestern madagascar.the ring-tailed lemur (lemur catta) is an endangered species found in southwestern madagascar, and understanding infectious disease susceptibility is an essential step towards the preservation of wild and captive lemur populations. lemurs are primates that are widely dispersed throughout the island of madagascar and may serve as hosts or reservoirs for zoonotic infections. the aim of this study was to determine the prevalence of antibodies to west nile virus (wnv), simian immunodeficiency virus ...200717347392
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
computational analysis and identification of amino acid sites in dengue e proteins relevant to development of diagnostics and vaccines.we have identified 72 completely conserved amino acid residues in the e protein of major groups of the flavivirus genus by computational analyses. in the dengue species we have identified 12 highly conserved sequence regions, 186 negatively selected sites, and many dengue serotype-specific negatively selected sites. the flavivirus-conserved sites included residues involved in forming six disulfide bonds crucial for the structural integrity of the protein, the fusion motif involved in viral infec ...200717508277
nuclear localization of dengue virus nonstructural protein 5 through its importin alpha/beta-recognized nuclear localization sequences is integral to viral infection.dengue virus nonstructural protein 5 (ns5) is a large multifunctional protein with a central role in viral replication. we previously identified two nuclear localization sequences (nlss) within the central region of dengue virus type-2 (denv-2) ns5 ('anls' and 'bnls') that are recognized by the importin alpha/beta and importin beta1 nuclear transporters, respectively. here, we demonstrate the importance of the kinetics of ns5 nuclear localization to virus production for the first time and show t ...200717537211
development and evaluation of sybr green i-based one-step real-time rt-pcr assay for detection and quantitation of japanese encephalitis virus.one-step sybr green i-based real-time rt-pcr assay for rapid detection as well as quantitation of japanese encephalitis virus (jev) in acute-phase patient csf samples by targeting the ns3 gene was developed. the assay developed in this study was found to be more sensitive as compared to conventional rt-pcr. the specificity of the reported assay system was established through melting curve analysis as well as by cross-reactivity studies with related members of flavivirus. the applicability of rea ...200717403544
efficacy of a live attenuated tetravalent candidate dengue vaccine in naïve and previously infected cynomolgus macaques.the development of a safe and effective vaccine against dengue is a public health priority. attempts to evaluate candidate vaccine formulations in human volunteers were largely unsuccessful, at least in part due to too high reactogenicity of some of the candidate vaccines tested. we evaluated a live attenuated tetravalent dengue vaccine candidate in flavivirus naïve and dengue virus type 3 immune non-human primates. immune responses were measured both at the humoral and the cellular level and th ...200717560694
early evening questing and oviposition activity by the culex (diptera: culicidae) vectors of west nile virus in northeastern north america.to determine whether the culex (diptera: culicidae) mosquitoes that transmit west nile virus (family flaviviridae, genus flavivirus, wnv) in the northeastern united states seek hosts and oviposit contemporaneously, we recorded when these mosquitoes attacked caged birds and when they deposited eggs. they traversed oviposition sites most frequently approximately 2 h after astronomical sunset, and eggs generally were deposited at that time. although they most frequently approached avian hosts appro ...200717427688
interaction of tia-1/tiar with west nile and dengue virus products in infected cells interferes with stress granule formation and processing body assembly.the west nile virus minus-strand 3' terminal stem loop (sl) rna was previously shown to bind specifically to cellular stress granule (sg) components, t cell intracellular antigen-1 (tia-1) and the related protein tiar. in vitro tiar binding was 10 times more efficient than tia-1. the 3'(-)sl functions as the promoter for genomic rna synthesis. colocalization of tiar and tia-1 with the viral replication complex components dsrna and ns3 was observed in the perinuclear regions of west nile virus- a ...200717502609
characterization of the dengue virus envelope glycoprotein expressed in pichia pastoris.the full-length and truncated forms of recombinant envelope (e) glycoprotein from dengue virus type 1, singapore strain s275/90 were expressed in the yeast, pichia pastoris, using a secretory vector. a truncated form of the e protein in which the transmembrane domain was deleted was secreted successfully into the culture medium. the e protein was also co-expressed with c and prm proteins using a non-secretory yeast vector. the co-expression of c, prm and e proteins resulted in the spontaneous fo ...200717502678
early production of type i interferon during west nile virus infection: role for lymphoid tissues in irf3-independent interferon production.infection of cells with flaviviruses in vitro is reduced by pretreatment with small amounts of type i interferon (ifn-alpha/beta). similarly, pretreatment of animals with ifn and experiments using mice defective in ifn signaling have indicated a role for ifn in controlling flavivirus disease in vivo. these data, along with findings that flavivirus-infected cells block ifn signaling, suggest that flavivirus infection can trigger an ifn response. to investigate ifn gene induction by the very first ...200717567689
the opioid receptor antagonist, naloxone, protects spinal motor neurons in a murine model of alphavirus encephalomyelitis.spread of neuroadapted sindbis virus (nsv) to motor neurons (mn) of the spinal cord (sc) causes severe hind limb weakness in c57bl/6 mice and models the paralysis that can accompany alphavirus and flavivirus encephalomyelitis in humans. the fate of spinal mn dictates the severity of nsv-induced paralysis, and recent data suggest that mn damage can occur indirectly via the actions of activated microglial cells. because the opioid receptor antagonist, naloxone (nal), blocks microglial-mediated neu ...200717459376
essential role of dengue virus envelope protein n glycosylation at asparagine-67 during viral propagation.dengue virus envelope protein (e) contains two n-linked glycosylation sites, at asn-67 and asn-153. the glycosylation site at position 153 is conserved in most flaviviruses, while the site at position 67 is thought to be unique for dengue viruses. n-linked oligosaccharide side chains on flavivirus e proteins have been associated with viral morphogenesis, infectivity, and tropism. here, we examined the relevance of each n-linked glycan on dengue virus e protein by removing each site in the contex ...200717459925
identification of residues critical for the interferon antagonist function of langat virus ns5 reveals a role for the rna-dependent rna polymerase domain.all pathogenic flaviviruses examined thus far inhibit host interferon (ifn) responses by suppressing the janus kinase-signal transducer and activator of transcription (jak-stat) pathway. both langat virus (lgtv; a member of the tick-borne encephalitis virus serogroup) and japanese encephalitis virus use the nonstructural protein ns5 to suppress jak-stat signaling. however, ns5 is also critical to virus replication, contributing methyltransferase and rna-dependent rna polymerase (rdrp) activities ...200717459929
[synthetic fragments of the ns1 protein of the tick-borne encephalitis virus exhibiting a protective effect].potentially immunoactive regions of the ns1 nonstructural protein of the tick-borne encephalitis virus that can stimulate the antibody formation in vivo and protect animals from this disease were chosen on the basis of theoretical calculations. eleven 16- to 27-aa peptides containing the chosen regions were synthesized. the ability of the free peptides (without any high-molecular-mass carrier) to stimulate the production of antipeptide antibodies in mice of three lines and ensure the formation o ...200717476983
prevalence of west nile virus neutralizing antibodies in colonial aquatic birds in southern spain.the rapid expansion of west nile virus (wnv) throughout the new world has raised interest in understanding the population dynamics and patterns of dispersal of emerging infectious diseases by wildlife. wnv affects humans, although its main reservoirs are various species of birds. here we analyse the prevalence of wnv-neutralizing antibodies in nearly full-grown chicks belonging to seven different species of colonial waterbirds at three localities in southern spain. chicks with neutralizing antib ...200717497333
biochemical characterization of a recombinant japanese encephalitis virus rna-dependent rna polymerase.japanese encephalitis virus (jev) ns5 is a viral nonstructural protein that carries both methyltransferase and rna-dependent rna polymerase (rdrp) domains. it is a key component of the viral rna replicase complex that presumably includes other viral nonstructural and cellular proteins. the biochemical properties of jev ns5 have not been characterized due to the lack of a robust in vitro rdrp assay system, and the molecular mechanisms for the initiation of rna synthesis by jev ns5 remain to be el ...200717623110
interaction between the cellular protein eef1a and the 3'-terminal stem-loop of west nile virus genomic rna facilitates viral minus-strand rna synthesis.rnase footprinting and nitrocellulose filter binding assays were previously used to map one major and two minor binding sites for the cell protein eef1a on the 3'(+) stem-loop (sl) rna of west nile virus (wnv) (3). base substitutions in the major eef1a binding site or adjacent areas of the 3'(+) sl were engineered into a wnv infectious clone. mutations that decreased, as well as ones that increased, eef1a binding in in vitro assays had a negative effect on viral growth. none of these mutations a ...200717626087
antibody recognition of cell surface-associated ns1 triggers fc-gamma receptor-mediated phagocytosis and clearance of west nile virus-infected cells.previous studies have suggested that monoclonal antibodies (mabs) to flavivirus nonstructural protein-1 (ns-1) protect against infection in mice through an fc-gamma receptor-dependent pathway. to identify a specific mechanism, we evaluated the protective activity of anti-ns1 mabs to wnv using mice and cells with deficiencies of specific fc-gamma receptors. our results suggest that only mabs that recognize cell surface-associated ns1 trigger fc-gamma receptor i- and/or iv-mediated phagocytosis an ...200717582005
[strokes caused by infection in the tropics].almost three out of every four people in the world who suffer a fatal stroke live in developing countries. a number of different tropical diseases may appear in europe in the coming years as a consequence of the demographic change that is being brought about by migratory flows. we review the main infectious causes of strokes in the tropics.200717583870
reduced infection in mosquitoes exposed to blood meals containing previously frozen flaviviruses.the increased difficulty and expense of using live animals for delivering infectious blood meals in arthropod-borne virus vector competence experiments has resulted in an increase in the use of artificial feeding systems. compared to live hosts, artificial systems require higher viral titers to attain mosquito infection, thereby limiting the utility of such systems with low or moderate titer virus stocks. based on the report that freshly propagated virus is more infectious than previously frozen ...200717686541
epitope-blocking enzyme-linked immunosorbent assay to differentiate west nile virus from japanese encephalitis virus infections in equine sera.west nile virus (wnv) is now widely distributed worldwide, except in most areas of asia where japanese encephalitis virus (jev) is distributed. considering the movement and migration of reservoir birds, there is concern that wnv may be introduced in asian countries. although manuals and guidelines for serological tests have been created in japan in preparedness for the introduction of wnv, differential diagnosis between wnv and jev may be complicated by antigenic cross-reactivities between these ...200717596430
cryo-electron microscopy and three-dimensional reconstructions of hepatitis c virus particles.the structural details of hepatitis c virus (hcv) have been elusive because of the lack of a robust tissue culture system for producing an adequate amount of virions from infectious sources for in-depth three-dimensional (3d) structural analysis. using both negative-stain and cryo-electron microscopy (cryoem), we show that hcv virions isolated from cell culture have a rather uniform size of 500 a in diameter and that recombinantly expressed hcv-like particles (hcv-lps) have similar morphologic, ...200717618667
monoclonal antibody-mediated enhancement of dengue virus infection in vitro and in vivo and strategies for prevention.infection with dengue virus (denv) or any other flavivirus induces cross-reactive, but weakly neutralizing or nonneutralizing, antibodies that recognize epitopes involving the fusion peptide in the envelope glycoprotein. humanized mab igg 1a5, derived from a chimpanzee, shares properties of cross-reactive antibodies. mab igg 1a5 up-regulated denv infection by a mechanism of antibody-dependent enhancement (ade) in a variety of fc receptor-bearing cells in vitro. a 10- to 1,000-fold increase of vi ...200717517625
yellow fever virus ns3 protease: peptide-inhibition studies.a recombinant form of yellow fever virus (yfv) ns3 protease, linked via a nonapeptide to the minimal ns2b co-factor sequence (cf40-gly-ns3pro190), was expressed in escherichia coli and shown to be catalytically active. it efficiently cleaved the fluorogenic tetrapeptide substrate bz-norleucine-lysine-arginine-arginine-amc, which was previously optimized for dengue virus ns2b/3 protease. a series of small peptidic inhibitors based on this substrate sequence readily inhibited its enzymic activity. ...200717622626
a single positively selected west nile viral mutation confers increased virogenesis in american crows.west nile virus (wnv), first recognized in north america in 1999, has been responsible for the largest arboviral epiornitic and epidemic of human encephalitis in recorded history. despite the well-described epidemiological patterns of wnv in north america, the basis for the emergence of wnv-associated avian pathology, particularly in the american crow (amcr) sentinel species, and the large scale of the north american epidemic and epiornitic is uncertain. we report here that the introduction of a ...200717694056
crystal structure of the murray valley encephalitis virus ns5 methyltransferase domain in complex with cap analogues.we have determined the high resolution crystal structure of the methyltransferase domain of the ns5 polypeptide from the murray valley encephalitis virus. this domain is unusual in having both the n7 and 2'-o methyltransferase activity required for cap 1 synthesis. we have also determined structures for complexes of this domain with nucleotides and cap analogues providing information on cap binding, based on which we suggest a model of how the sequential methylation of the n7 and 2'-o groups of ...200717622627
complete genome characterization of rocio virus (flavivirus: flaviviridae), a brazilian flavivirus isolated from a fatal case of encephalitis during an epidemic in sao paulo state.the flaviviruses of major medical importance in south american countries are yellow fever, dengue, saint louis encephalitis, west nile and rocio viruses. rocio virus (rocv) has been responsible for epidemics of severe encephalitis in brazil with a case-fatality rate of 10 % and development of sequelae in 20 % of the survivors. we have sequenced and characterized the entire genome of rocv for the first time, by determining the general traits of the open reading frame and the characteristics of vi ...200717622628
controlled peptide solvation in portion-mixing libraries of fret peptides: improved specificity determination for dengue 2 virus ns2b-ns3 protease and human cathepsin s.the solubility of peptides in aqueous buffers used for the enzyme assays is a common limitation for all peptide libraries. in principle, the more water-soluble peptides are, the more susceptible they will be to peptidase hydrolysis. we have demonstrated that this bias can be circumvented in a portion-mixing fluorescence resonance energy transfer (fret) peptide library by introducing k (lysine in the d-form) in both termini of the peptides. this more solvated library and another one without the k ...200717563123
complex adenovirus-mediated expression of west nile virus c, prem, e, and ns1 proteins induces both humoral and cellular immune responses.west nile virus (wnv), a member of the family flaviviridae, was first identified in africa in 1937. in recent years, it has spread into europe and north america. the clinical manifestations of wnv infection range from mild febrile symptoms to fatal encephalitis. two genetic lineages (lineages i and ii) are recognized; lineage ii is associated with mild disease, while lineage i has been associated with severe disease, including encephalitis. wnv has now spread across north america, significantly ...200717634508
[west nile fever/encephalitis].west nile virus (wnv), a member of the family flaviviridae (genus flavivirus), is a mosquito-borne virus first isolated in 1937 in the west nile district of uganda. the disease in humans is characterized by a dengue-like illness with fever, and a more severe form is characterized by central nervous system involvement, including encephalitis, meningitis, and myelitis. wn encephalitis was first reported in the western hemisphere in the summer of 1999, there was an outbreak in new york city. epidem ...200718357758
proliferative index in astrocytic tumours.the accurate grading of astrocytic tumours is of prime importance because it is critical to the patient management and survival/outcome. although internationally accepted who grading system of cns tumours is based on histological features of h&e stained sections, yet there are cases where differentiation between grade ii and grade iii is difficult particularly when the biopsy is small. proliferative index derived from mib-1 immunostaining has been found to be useful in the distinction between va ...200718306542
elisa as an alternative tool for epidemiological surveillance for dengue in mosquitoes: a report from thailand.dengue fever (df), dengue hemorrhagic fever (dhf) and dengue shock syndrome (dss) are the re-emerging infectious diseases caused by the four serotypes of dengue (den) virus, type 1 to 4, belonging to the family flaviviridae and genus flavivirus. in the absence of a safe and effective mass immunisation, the prevention and control of dengue outbreaks depend upon the surveillance of cases and mosquito vector. the aim of this work is to test enzyme-linked immunosorbent assay (elisa) tool for the vir ...200718092535
hts identifies novel and specific uncompetitive inhibitors of the two-component ns2b-ns3 proteinase of west nile virus.west nile virus (wnv), a member of the flavividae family, is a mosquito-borne, emerging pathogen. in addition to wnv, the family includes dengue, yellow fever, and japanese encephalitis viruses, which affect millions of individuals worldwide. because countermeasures are currently unavailable, flaviviral therapy is urgently required. the flaviviral two-component nonstructural ns2b-ns3 proteinase (protease [pro]) is essential for viral life cycle and, consequently, is a promising drug target. we r ...200718181690
yellow fever: a disease that has yet to be conquered.yellow fever virus (yfv) is the prototype member of the genus flavivirus, a group of viruses that are transmitted between vertebrates by arthropod vectors. the virus is found in tropical regions of africa and south america and is transmitted to primates by mosquitoes: aedes spp. in africa and haemagogus and sabethes spp. in south america. despite the availability of an effective vaccine, yellow fever (yf) is considered a reemerging disease owing to its increased incidence in the past 25 years. m ...200716913829
analysis of the domain interactions between the protease and helicase of ns3 in dengue and hepatitis c virus.flaviviridae non-structural 3 protein (ns3) is a multifunctional enzyme, composed by a protease domain (ns3pro) and an rna helicase domain (ns3hel). the activities present in ns3 have proved to be critical for viral replication. the replicative cycle of flaviviridae requires coordinated regulation of all the activities present in the full-length ns3 protein, however, the exact nature of these interactions remains unclear. the present work aimed to determine common structural features between ns3 ...200716762573
preparation and immunogenic properties of a recombinant west nile subunit vaccine.while several west nile vaccines are being developed, none are yet available for humans. in this study aimed at developing a vaccine for humans, west nile virus (wnv) envelope protein (e) and non-structural protein 1 (ns1) were produced in the drosophila s2 cell expression system. the c-terminal 20% of the e protein, which contains the membrane anchor portion, was deleted, thus allowing for efficient secretion of the truncated protein (80e) into the cell culture medium. the proteins were purifie ...200716996661
development of multiplex real-time reverse transcriptase pcr assays for detecting eight medically important flaviviruses in mosquitoes.a multiplex real-time reverse transcriptase pcr has been developed for the rapid detection and identification of eight medically important flaviviruses from laboratory-reared, virus-infected mosquito pools. the method used involves the gene-specific amplification of yellow fever virus (yfv), japanese encephalitis virus (jev), west nile virus (wnv), st. louis encephalitis virus (slev), and dengue virus (denv) serotypes 1 to 4 (denv-1 to denv-4, respectively) by use of the flavivirus consensus amp ...200717108075
cell-specific adaptation of two flaviviruses following serial passage in mosquito cell culture.west nile virus (wnv) is a mosquito-borne flavivirus that was introduced into the u.s. in the new york city area in 1999. despite its successful establishment and rapid spread in a naive environment, wnv has undergone limited evolution since its introduction. this evolutionary stability has been attributed to compromises made to permit alternating cycles of viral replication in vertebrate hosts and arthropod vectors. outbreaks of a close relative of wnv, st. louis encephalitis virus (slev), occu ...200716963095
antiviral peptides targeting the west nile virus envelope protein.west nile virus (wnv) can cause fatal murine and human encephalitis. the viral envelope protein interacts with host cells. a murine brain cdna phage display library was therefore probed with wnv envelope protein, resulting in the identification of several adherent peptides. of these, peptide 1 prevented wnv infection in vitro with a 50% inhibition concentration of 67 mum and also inhibited infection of a related flavivirus, dengue virus. peptide 9, a derivative of peptide 1, was a particularly p ...200717151121
defective interfering rnas of japanese encephalitis virus found in mosquito cells and correlation with persistent infection.defective interfering (di) rnas are deletion mutants of viral genomes that are known in many cases to contribute to persistent infection and modification of viral pathogenesis. cell type also plays a critical role in the establishment of viral persistence. in this study we have identified for the first time the generation of di rnas of japanese encephalitis virus in c6/36 mosquito cells. a persistent infection was established by replacing growth medium on surviving cells and continued cell passa ...200717134784
a mouse cell-adapted ns4b mutation attenuates west nile virus rna synthesis.an adaptive mutation (e249g) within west nile virus (wnv) ns4b gene was consistently recovered from replicon rnas in c3h/he mouse cells. the e249g is located at the c-terminal tail of ns4b predicted to be on the cytoplasmic side of the endoplasmic reticulum membrane. the e249g substitution reduced replicon rna synthesis. compared with the wild-type ns4b, the e249g mutant protein exhibited a similar efficiency in evasion of interferon-beta response. recombinant e249g virus exhibited smaller plaqu ...200717178141
structural analysis of viral nucleocapsids by subtraction of partial projections.the nucleocapsid of flavivirus particles does not have a recognizable capsid structure when using icosahedral averaging for cryo-electron microscopy structure determinations. the apparent absence of a definitive capsid structure could be due to a lack of synchronization of the symmetry elements of the external glycoprotein layer with those of the core or because the nucleocapsid does not have the same structure within each particle. a technique has been developed to determine the structure of th ...200717064936
cleavage preference distinguishes the two-component ns2b-ns3 serine proteinases of dengue and west nile viruses.regulated proteolysis of the polyprotein precursor by the ns2b-ns3 protease is required for the propagation of infectious virions. unless the structural and functional parameters of ns2b-ns3 are precisely determined, an understanding of its functional role and the design of flaviviral inhibitors will be exceedingly difficult. our objectives were to define the substrate recognition pattern of the ns2b-ns3 protease of west nile and dengue virises (wnv and dv respectively). to accomplish our goals, ...200717067286
direct repeats in the flavivirus 3' untranslated region; a strategy for survival in the environment?previously, direct repeats (drs) of 20-70 nucleotides were identified in the 3' untranslated regions (3'utr) of flavivirus sequences. to address their functional significance, we have manually generated a pan-flavivirus 3'utr alignment and correlated it with the corresponding predicted rna secondary structures. this approach revealed that intra-group-conserved drs evolved from six long repeated sequences (lrss) which, as approximately 200-nucleotide domains were preserved only in the genomes of ...200717067651
immunopathology of flavivirus infections.with the recent emergence of the flavivirus, west nile virus (wnv), in particular, the new york strain of lineage i wnv in north america in 1999, there has been a significant increase in activity in neurotropic flavivirus research. these viruses cause encephalitis that can result in permanent neurological sequelae or death. attempts to develop vaccines have made progress, but have been variably successful, despite considerable commercial underwriting. thus, the discovery of ways and means to com ...200717146465
mutation analysis of the fusion domain region of st. louis encephalitis virus envelope protein.the immune response to flavivirus infections produces both species-specific and flavivirus cross-reactive antibodies. the presence of cross-reactive antibodies complicates serodiagnosis of flavivirus infections, especially secondary infections caused by a heterologous virus. a successful public health response to the growing global threat posed by flaviviruses necessitates the development of virus-specific diagnostic antigens. the flavivirus envelope (e) glycoprotein is the principle antigen sti ...200717157348
genetic characterization of a new insect flavivirus isolated from culex pipiens mosquito in japan.we found a new flavivirus that is widespread in culex pipiens and other culex mosquitoes in japan. the virus isolate, named culex flavivirus (cxfv), multiplied only in mosquito cell lines producing a moderate cytopathic effect, but did not grow in mammalian cells. the cxfv genome is single-stranded rna, 10,834 nt in length and containing a single open reading frame encoding a polyprotein of 3362 aa with 5' and 3' untranslated regions (utrs) of 91 and 657 nt, respectively. phylogenetic analyses r ...200717070886
genetic characterization of tick-borne flaviviruses: new insights into evolution, pathogenetic determinants and taxonomy.here, we analyze the complete coding sequences of all recognized tick-borne flavivirus species, including gadgets gully, royal farm and karshi virus, seabird-associated flaviviruses, kadam virus and previously uncharacterized isolates of kyasanur forest disease virus and omsk hemorrhagic fever virus. significant taxonomic improvements are proposed, e.g. the identification of three major groups (mammalian, seabird and kadam tick-borne flavivirus groups), the creation of a new species (karshi viru ...200717169393
a gis tool to estimate west nile virus risk based on a degree-day model.west nile virus (flaviviridae: flavivirus) is a serious infectious disease that recently spread across the north america continent. a spatial analysis tool was developed on the arcmap 9.x platform to estimate potential west nile virus activity using a spatially explicit degree-day model. the model identifies when the virus extrinsic incubation period (eip) is completed within the vector longevity during mid-summer months. the eip is treated as a threshold indicator of the potential for virus eme ...200717106782
detection of west nile virus in formalin-fixed, paraffin-embedded human tissues by rt-pcr: a useful adjunct to conventional tissue-based diagnostic methods.west nile virus (wnv), a member of genus flavivirus, causes febrile illness, encephalitis, meningitis, myelitis, and occasional deaths in humans. although several reverse transcription-polymerase chain reaction (rt-pcr) assays have been developed for detection of wnv in serum, cerebrospinal fluid, and fresh tissues, the usefulness of wnv rt-pcr assays for rna extracted from formalin-fixed human tissues has not previously been demonstrated.200717161650
enzymatic characterization of a trypsin-like serine protease encoded by the genome of cell fusing agent virus.cell fusing agent virus (cfav) is a positive strand rna insect virus first isolated from a mosquito cell line. based on viral morphology, phenotypic and phylogenetic studies, cfav had been tentatively assigned to the genus flavivirus (family flaviviridae). the determination of the cfav polyprotein complete sequence showed a putative serine protease domain analogue to the flaviviral ns2b/ns3 complex. this complex had been extensively studied, because it represented one of the main targets for ant ...200717143721
substrate specificity of recombinant dengue 2 virus ns2b-ns3 protease: influence of natural and unnatural basic amino acids on hydrolysis of synthetic fluorescent substrates.a recombinant dengue 2 virus ns2b-ns3 protease (ns means non-structural virus protein) was compared with human furin for the capacity to process short peptide substrates corresponding to seven native substrate cleavage sites in the dengue viral polyprotein. using fluorescence resonance energy transfer peptides to measure kinetics, the processing of these substrates was found to be selective for the dengue protease. substrates containing two or three basic amino acids (arg or lys) in tandem were ...200717184724
west nile virus infection in mosquitoes in the mid-south usa, 2002-2005.west nile virus (family flaviviridae, genus flavivirus, wnv) was first detected in the tennessee valley and in alabama in august 2001. in summer 2002, intensive viral activity was seen, but in subsequent years, viral activity settled into an enzootic pattern. here, we report an analysis of viral activity in the mosquito fauna in the mid-south from 2002 (the first year viral activity was detected in mosquitoes) through 2005. eight mosquito species were infected with wnv during 2002. however, vira ...200717294929
construction and biological properties of yellow fever 17d/dengue type 1 recombinant virus.dengue virus, a mosquito-borne flavivirus, is one of the most formidable public health threats in tropical and subtropical regions. as yet, there is no licensed vaccine to protect against the disease. a chimeric yellow fever (yf) 17d/dengue (den) type 1 virus was constructed by replacing the pre-membrane and envelope genes of yf 17d virus with those from den 1 vemir95 virus, a venezuelan isolate. the chimeric yf 17d/den 1 vemir95 virus was regenerated from full-length infectious clones stably pr ...200717169387
chronic st. louis encephalitis virus infection in the golden hamster (mesocricetus auratus).to further study the phenomenon of flavivirus persistent infection, golden hamsters (mesocricetus auratus) were inoculated intraperitoneally with a low pathogenicity strain of st. louis encephalitis virus (slev). after inoculation, the animals remained asymptomatic and developed high levels of specific neutralizing antibodies in their sera. however, about one half of the hamsters continued to shed infectious slev in their urine for prolonged periods of time. by co-cultivation, slev was recovered ...200717297039
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
characterization of the west nile virus protease substrate specificity and inhibitors.west nile virus (wnv), a mosquito-borne member of flaviviridae, is a human pathogen causing widespread disease for which there is no vaccine or chemotherapy. the two-component viral serine protease consists of a heterodimeric complex between the hydrophilic domain of the cofactor, ns2b (ns2bh) and the protease domain (ns3-pro). the protease is essential for polyprotein processing followed by assembly of viral replicase and genome replication. therefore, the protease is an excellent target for de ...200717188926
expression and purification of a two-component flaviviral proteinase resistant to autocleavage at the ns2b-ns3 junction region.regulated proteolysis of the polyprotein precursor of west nile virus (wnv) by the essential ns2b-ns3(pro)tease, a promising drug target for wnv inhibitors, is required for the propagation of infectious virions. structural and drug design studies, however, require pilot-scale quantities of a pure and catalytically active wnv protease that is resistant to self-proteolysis. autolytic cleavage at the ns2b-ns3 boundary leads to individual, non-covalently associated, ns2b and ns3 domains, together wi ...200717189703
switching the substrate specificity of the two-component ns2b-ns3 flavivirus proteinase by structure-based mutagenesis.the flavivirus ns2b-ns3(pro)teinase is an essential element in the proteolytic processing of the viral precursor polyprotein and therefore a potential drug target. recently, crystal structures and substrate preferences of ns2b-ns3pro from dengue and west nile viruses (dv and wnv) were determined. we established that the presence of gly-gly at the p1'-p2' positions is optimal for cleavage by wnv ns3pro, whereas dv ns3pro tolerates well the presence of bulky residues at either p1' or p2'. structur ...200717301157
full-length sequencing and genomic characterization of bagaza, kedougou, and zika viruses.many members of the genus flavivirus are the agents of important diseases of humans, livestock, and wildlife. currently, no complete genome sequence is available for the three african viruses, bagaza, zika, and kedougou viruses, each representing a distinct virus subgroup according to the latest virus classification. in this study, we obtained a complete genome sequence of each of those three viruses and characterized the open reading frames (orfs) with respect to gene sizes, cleavage sites, pot ...200717195954
role of the mutant spectrum in adaptation and replication of west nile virus.west nile virus (wnv) has successfully spread throughout the usa, canada, mexico, the caribbean and parts of central and south america since its 1999 introduction into north america. despite infecting a broad range of both mosquito and avian species, the virus remains highly genetically conserved. this lack of evolutionary change over space and time is common with many arboviruses and is frequently attributed to the adaptive constraints resulting from the virus cycling between vertebrate hosts a ...200717325359
the envelope glycoprotein domain iii of dengue virus serotypes 1 and 2 inhibit virus entry.dengue virus (dv) is a flavivirus and its urban transmission is maintained largely by its mosquito vectors and vertebrate host, often human. in this study, investigation was carried out on the involvement of domain iii of the envelope (e) glycosylated protein of dengue virus serotypes 1 and 2 (dv-1 and dv-2 diii) in binding to host cell surfaces, thus mediating virus entry. domain iii protein of flavivirus can also serve as an attractive target in inhibiting virus entry. the respective dv diii p ...200717196419
prophylactic treatment with recombinant eimeria protein, alone or in combination with an agonist cocktail, protects mice from banzi virus infection.a recombinant eimeria protozoan protein antigen (rea) has been shown to have antitumor and antiviral activity. the purpose of this study was to determine the effect of rea treatment alone or in combination with an agonist cocktail consisting of granulocyte macrophage colony stimulating factor (gm-csf), interferon gamma (ifn-gamma), interleukin 4 (il-4), and anti cd-40 antibody, in the treatment of banzi virus (bv) disease in balb/c mice. treatment with rea resulted in a significant increase in s ...200717210189
attenuating characteristics of den-2 pdk53 in flavivirus-naïve peripheral blood mononuclear cells.a live-attenuated den-2 virus, den-2 strain 16681-pdk53, has been found to be attenuated for both humans and mice with an unknown mechanism. to partially answer this question, responses of flavivirus-naïve primary human pbmc to infection with attenuated den-2 pdk53 (d2/ic-vv45r) virus and its parental, virulent den-2 16681 virus (d2/ic-30p-a) were investigated at the cellular and genetic levels using cdna array analysis. both den-2 viruses produced similar replication kinetics in flavivirus-naïv ...200717316931
t7 phage display of ep15 peptide for the detection of wnv igg.west nile virus (wnv) is one of the major emerging infectious diseases in north america. wnv belongs to the genus flavivirus, and its rapid and extensive global spread has highlighted the necessity for accurate and specific assays for diagnosis of wnv infection. this study presents the first phage displayed peptide based elisa for detection of wnv immunoglobulin g (igg). the ep15 epitope, derived from the wnv e protein diii, was cloned into a t7 phage display system that was then used as recombi ...200717215048
origin and evolution of 3'utr of flaviviruses: long direct repeats as a basis for the formation of secondary structures and their significance for virus transmission.the 3' untranslated regions (3'utrs) of flaviviruses are reviewed and analyzed in relation to short sequences conserved as direct repeats (drs). previously, alignments of the 3'utrs have been constructed for three of the four recognized flavivirus groups, namely mosquito-borne, tick-borne, and nonclassified flaviviruses (mbfv, tbfv, and ncfv, respectively). this revealed (1) six long repeat sequences (lrss) in the 3'utr and open-reading frame (orf) of the tbfv, (2) duplication of the 3'utr of th ...200717222695
c-src protein kinase inhibitors block assembly and maturation of dengue virus.dengue virus is a mosquito-borne flavivirus that represents an important emerging infectious disease and is an international health concern. currently, there is no vaccine or effective antiviral therapy to prevent or to treat dengue virus infection. the slow progress in developing antiviral agents might be alleviated by the availability of efficient high-throughput anti-dengue virus screening assays. in this study, we report an immunofluorescence image-based assay suitable for identification of ...200717360676
correlation between breakdown of the blood-brain barrier and disease outcome of viral encephalitis in mice.changes in the permeability of the blood-brain barrier (bbb) were evaluated in two mouse models of viral encephalitis. the ability of sodium fluorescein (nafl) to cross the bbb from the serum into the central nervous system was assayed in animals inoculated with virulent strains of either banzi or semliki forest viruses. to test the hypothesis that increases in bbb permeability were associated with poor disease outcome subsequent experiments measured bbb permeability in conjunction with treatmen ...200717223204
west nile virus strain kunjin ns5 polymerase is a phosphoprotein localized at the cytoplasmic site of viral rna synthesis.using west nile virus strain kunjin virus (wnv(kun)) as a model system for flavivirus replication, we showed that the virus replication complex (rc) is associated with the dsrna template located in induced membranes only in the cytoplasm. in this report we established for the first time that the rna-dependent rna polymerase ns5 is located in flavivirus-induced membranes, including the site of viral rna replication. we found no evidence for nuclear localization of the essential rc components ns5 ...200717374759
a detailed mutagenesis study of flavivirus cross-reactive epitopes using west nile virus-like particles.human flavivirus infections elicit virus species-specific and cross-reactive immune responses. the flavivirus envelope (e) glycoprotein is the primary antigen inducing protective immunity; however, the presence of cross-reactive antibodies in human sera creates problems for serodiagnosis. using a west nile virus-like particle system, we performed mutagenesis across all three e protein functional domains to identify epitope determinants for a panel of monoclonal antibodies (mabs) raised against d ...200717374760
in situ reactions of monoclonal antibodies with a viable mutant of murray valley encephalitis virus reveal an absence of dimeric ns1 protein.studies on the ns1 protein of flaviviruses have concluded that formation of a stable homodimer is required for virus replication. however, previous work has reported that substitution of a conserved proline by leucine at residue 250 in ns1 of kunjin virus (kunv) eliminated dimerization, but allowed virus replication to continue. to assess whether this substitution has similar effects on other flaviviruses, it was introduced into an infectious clone of murray valley encephalitis virus (mvev). con ...200717374761
west nile virus.west nile virus is a mosquito-borne flavivirus originally isolated in 1937 from the blood of a febrile woman in the west nile province of uganda. the virus is widely distributed in africa, europe, australia, and asia, and, since 1999, it has spread rapidly throughout the western hemisphere, including the usa, canada, mexico, and the caribbean and into parts of central and south america. before 1994, outbreaks of west nile virus were sporadic and occurred primarily in the mediterranean region, af ...200717239804
serologic evidence of west nile virus exposure in north american mesopredators.sera from 936 mammalian mesopredators (virginia opossums, gray foxes, striped skunks, hooded skunks, raccoons, a bobcat, and a red fox) were collected during 2003 and 2004 in california, arizona, texas, louisiana, ohio, and wyoming and screened for flavivirus-specific antibodies by an epitope-blocking enzyme-linked immunosorbent assay (blocking elisa). serum samples positive for antibodies against flaviviruses were screened for west nile virus (wnv)-specific antibodies by blocking elisa and sele ...200717255248
caspase 3-dependent cell death of neurons contributes to the pathogenesis of west nile virus encephalitis.west nile virus (wnv) is a neurotropic, arthropod-borne flavivirus that has become a significant global cause of viral encephalitis. to examine the mechanisms of wnv-induced neuronal death and the importance of apoptosis in pathogenesis, we evaluated the role of a key apoptotic regulator, caspase 3. wnv infection induced caspase 3 activation and apoptosis in the brains of wild-type mice. notably, congenic caspase 3(-/-) mice were more resistant to lethal wnv infection, although there were no sig ...200717192305
crystal structure of the dengue virus rna-dependent rna polymerase catalytic domain at 1.85-angstrom resolution.dengue fever, a neglected emerging disease for which no vaccine or antiviral agents exist at present, is caused by dengue virus, a member of the flavivirus genus, which includes several important human pathogens, such as yellow fever and west nile viruses. the ns5 protein from dengue virus is bifunctional and contains 900 amino acids. the s-adenosyl methionine transferase activity resides within its n-terminal domain, and residues 270 to 900 form the rna-dependent rna polymerase (rdrp) catalytic ...200717301146
american society of tropical medicine and hygiene--55th annual meeting. vaccine development against flaviviruses. 12-16 november 2006, atlanta, ga, usa. 200717285458
crystal structure of the rna polymerase domain of the west nile virus non-structural protein 5.viruses of the family flaviviridae are important human and animal pathogens. among them, the flaviviruses dengue (denv) and west nile (wnv) cause regular outbreaks with fatal outcomes. the rna-dependent rna polymerase (rdrp) activity of the non-structural protein 5 (ns5) is a key activity for viral rna replication. in this study, crystal structures of enzymatically active and inactive wnv rdrp domains were determined at 3.0- and 2.35-a resolution, respectively. the determined structures were sho ...200717287213
murray valley encephalitis in an adult traveller complicated by long-term flaccid paralysis: case report and review of the literature.murray valley encephalitis (mve) virus, a mosquito-borne flavivirus, is the most common cause of viral encephalitis in the tropical 'top end' of northern australia. clinical encephalitis due to mve virus has a mortality rate of approximately 30%, with a similar proportion of patients being left with significant neurological deficits. we report the case of a 25-year-old man from the uk who acquired mve while travelling through northern australia. he required prolonged admission to the intensive c ...200717161855
viral infections of the central nervous system in brazil.epidemiological studies have shown that most central nervous system (cns) infections are viral. the objective of this study is to contribute to the knowledge base concerning viral cns infections in ribeirão preto, brazil.200717198733
west nile virus: recent trends in diagnosis and vaccine development.west nile virus (wnv) is a mosquito-borne flavivirus, native to africa, europe, and western asia. in many respects, wnv is an outstanding example of a zoonotic pathogen that has leaped geographical barriers and can cause severe disease in human and horse. before the emergence of wnv in the usa, only few methods of diagnosis were available. recently, many changes in the fields of wn diagnosis and prevention have happened. this paper will review all these new tools. after a description of the main ...200717292514
immunization of flavivirus west nile recombinant envelope domain iii protein induced specific immune response and protection against west nile virus infection.the domain iii of the west nile virus (wnv) envelope glycoprotein (e) was shown to serve as virus attachment domain to the cellular receptor, and neutralizing abs have been mapped to this specific domain. in this study, domain iii of the wnv e protein (wnv e diii) was expressed as a recombinant protein and its potential as a subunit vaccine candidate was evaluated in balb/c mice. immunization of wnv e diii protein with oligodeoxynucleotides (cpg-dna) adjuvant by i.p. injection was conducted over ...200717312111
structure and function of flavivirus ns5 methyltransferase.the plus-strand rna genome of flavivirus contains a 5' terminal cap 1 structure (m7gpppamg). the flaviviruses encode one methyltransferase, located at the n-terminal portion of the ns5 protein, to catalyze both guanine n-7 and ribose 2'-oh methylations during viral cap formation. representative flavivirus methyltransferases from dengue, yellow fever, and west nile virus (wnv) sequentially generate gpppa-->m7gpppa-->m7gpppam. the 2'-o methylation can be uncoupled from the n-7 methylation, since m ...200717267492
structural evidence for regulation and specificity of flaviviral proteases and evolution of the flaviviridae fold.pathogenic members of the flavivirus family, including west nile virus (wnv) and dengue virus (dv), are growing global threats for which there are no specific treatments. the two-component flaviviral enzyme ns2b-ns3 cleaves the viral polyprotein precursor within the host cell, a process that is required for viral replication. here, we report the crystal structure of wnv ns2b-ns3pro both in a substrate-free form and in complex with the trypsin inhibitor aprotinin/bpti. we show that aprotinin bind ...200717400917
gb virus b disrupts rig-i signaling by ns3/4a-mediated cleavage of the adaptor protein mavs.understanding the mechanisms of hepatitis c virus (hcv) pathogenesis and persistence has been hampered by the lack of small, convenient animal models. gb virus b (gbv-b) is phylogenetically the closest related virus to hcv. it causes generally acute and occasionally chronic hepatitis in small primates and is used as a surrogate model for hcv. it is not known, however, whether gbv-b has evolved strategies to circumvent host innate defenses similar to those of hcv, a property that may contribute t ...200717093192
a single m protein mutation affects the acid inactivation threshold and growth kinetics of a chimeric flavivirus.numerous viruses of the flaviviridae family, including dengue, yellow fever, japanese encephalitis, and west nile, cause significant disease in humans and animals. the structure and function of the molecular components of the flavivirus envelope are therefore of significant interest. to our knowledge, a membrane (m) protein mutation which affects the ph at which flavivirus particles are inactivated in vitro has never been reported. here we show that substitution of proline for glutamine at resid ...200717303204
characterization of a structural intermediate of flavivirus membrane fusion.viral membrane fusion proceeds through a sequence of steps that are driven by triggered conformational changes of viral envelope glycoproteins, so-called fusion proteins. although high-resolution structural snapshots of viral fusion proteins in their prefusion and postfusion conformations are available, it has been difficult to define intermediate structures of the fusion pathway because of their transient nature. flaviviruses possess a class ii viral fusion protein (e) mediating fusion at acidi ...200717305426
does feeding on infected mosquitoes (diptera: culicidae) enhance the role of song sparrows in the transmission of arboviruses in california?song sparrows, melopiza melodia, inoculated subcutaneously with either western equine encephalomyelitis virus (family togaviridae, genus alphavirus, weev) or west nile virus (family flaviviridae, genus flavivirus, wnv) developed elevated viremias, and they were considered to be competent experimental hosts for both viruses. however, birds that ingested from three to 20 mosquitoes containing comparable amounts of either weev or wnv failed to become infected, indicating limited oral susceptibility ...200717427703
ability of transstadially infected ixodes pacificus (acari: ixodidae) to transmit west nile virus to song sparrows or western fence lizards.the hypothesis that ixodes pacificus cooley & kohls (acari: ixodidae) may serve as a reservoir and vector of west nile virus (family flaviviridae, genus flavivirus, wnv) in california was tested by determining the ability of this tick species to become infected with the ny99 strain of wnv while feeding on viremic song sparrows, to maintain the infection transstadially, and then to transmit wnv to recipient naive song sparrows and western fence lizards during the nymphal stage. the percentage of ...200717427704
infection and vertical transmission of kamiti river virus in laboratory bred aedes aegypti mosquitoes.kamiti river virus (krv) is an insect-only flavivirus that was isolated from field-collected ae. macintoshi mosquitoes in 1999, and is closely related to cell fusing agent virus. both of these viruses belong to the family flaviviridae, which also contains other viruses of medical importance, such as yellow fever virus, west nile virus and dengue. because ae. macintoshi is the only known natural host to krv, the main objective of this study was to establish the possibility that other mosquito hos ...200720337552
detection and isolation of japanese encephalitis virus from blood clots collected during the acute phase of infection.clinical specimens from an encephalitis outbreak in the lakhimpur area of uttar pradesh, india, were investigated for identification and characterization of the etiologic agent. igm capture elisa showed recent japanese encephalitis virus (jev) infection. jev isolation was attempted from white blood cells (wbcs) separated from blood clots of 12 patients (9 igm positive and 3 negative) by serial co-culturing with phytohemagglutinin p-stimulated peripheral blood mononuclear leukocytes (pbmcs) obtai ...200718165537
development of novel antivirals against flaviviruses.dengue virus is responsible for a significant amount of human disease in predominantly tropical areas of the world. much effort has focused on the development of vaccines against the four serotypes of dengue, and within the next few years a vaccine is anticipated. less progress has been made at developing antivirals that might reduce disease severity. recent advances in the structural biology of dengue virus and other flaviviruses have opened new possibilities for the rational design of small mo ...200617319153
entry functions and antigenic structure of flavivirus envelope proteins.the envelope proteins (e) of flaviviruses form an icosahedral cage-like structure of homodimers that cover completely the surface of mature virions and are responsible for receptor-binding and membrane fusion. fusion is triggered by the acidic ph in endosomes which induces dramatic conformational changes of e that drive the merger of the membranes. we have identified an alternative trigger that induces the first phase of the fusion process only, but then leads to an arrest at an intermediate sta ...200617319154
multiple enzyme activities of flavivirus proteins.dengue viruses (denv) have 5'-capped rna genomes of (+) polarity and encode a single polyprotein precursor that is processed into mature viral proteins. ns2b, ns3 and ns5 proteins catalyse/activate enzyme activities that are required for key processes in the virus life cycle. the heterodimeric ns2b/ns3 is a serine protease required for processing. using a high-throughput protease assay, we screened a small molecule chemical library and identified -200 compounds having > or = 50% inhibition. more ...200617319155
towards the design of flavivirus helicase/ntpase inhibitors: crystallographic and mutagenesis studies of the dengue virus ns3 helicase catalytic domain.infectious diseases caused by flaviviruses are important emerging public health concerns and new vaccines and therapeutics are urgently needed. the ns3 protein from flavivirus is a multifunctional protein with protease, helicase and nucleoside 5' triphosphatase activities (ntpase). thus, ns3 plays a crucial role in viral replication and represents an interesting target for the development of specific antiviral inhibitors. we have solved the structure of an enzymatically active fragment of the de ...200617319156
molecular biology of flaviviruses.flaviviruses are enveloped viruses with a single-stranded, 10.7kb positive-sense rna genome. the genomic rna, which has a 5' cap but no poly(a) tail, is translated as a single polyprotein that is then cleaved into three structural proteins and seven non-structural (ns) proteins by both viral and host proteases. the ns proteins include an rna-dependent rna polymerase (ns5), a helicase/protease (ns3), and other proteins that form part of the viral replication complex. sequences and structures in t ...200617319152
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