Molecular and biological characterization of a non-glycosylated isolate of St Louis encephalitis virus

Vorndam, Vance; Mathews, James H.; Barrett, Alan D.T.; Roehrig, John T.; Trent, Dennis W.

doi:10.1099/0022-1317-74-12-2653

Cited by 41 publications

(33 citation statements)

References 52 publications

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“…Analysis of the E Phe 156 →Ser locus indicated that this amino acid change would result in a putative N-linked glycosylation site at amino acids 154-156 (Asn-Tyr-Phe→Asn-Tyr-Ser) that is present in other SLE virus strains [40]. In the present study, we have not investigated the glycosylation state of the E protein of the chimeric viruses with this change, but such studies will be performed on the recombinant virus that is being engineered to contain only the E Phe 156 →Ser mutation.…”

Section: Discussionmentioning

confidence: 99%

“…In the present study, we have not investigated the glycosylation state of the E protein of the chimeric viruses with this change, but such studies will be performed on the recombinant virus that is being engineered to contain only the E Phe 156 →Ser mutation. SLE strains have been identified with varying patterns of E glycosylation, but the contribution of the carbohydrate chain at the glycosylation site to virulence is not well-defined [40,41] and needs further study.…”

Section: Discussionmentioning

confidence: 99%

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Evaluation of St. Louis encephalitis virus/dengue virus type 4 antigenic chimeric viruses in mice and rhesus monkeys

Blaney

Speicher

Hanson

et al. 2008

Vaccine

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SummaryTo develop a live attenuated virus vaccine against St. Louis encephalitis virus (SLE), two antigenic chimeric viruses were generated by replacing the membrane precursor and envelope protein genes of dengue virus type 4 (DEN4) with those from SLE with or without a 30 nucleotide deletion in the DEN4 3′ untranslated region of the chimeric genome. Chimeric viruses were compared with parental wild-type SLE for level of neurovirulence and neuroinvasiveness in mice and for safety, immunogenicity, and protective efficacy in rhesus monkeys. The resulting viruses, SLE/DEN4 and SLE/DEN4Δ30, had greatly reduced neuroinvasiveness in immunodeficient mice but retained neurovirulence in suckling mice. Chimerization of SLE with DEN4 resulted in only moderate restriction in replication in rhesus monkeys, whereas the presence of the Δ30 mutation led to overattenuation. Introduction of previously described attenuating paired charge-to-alanine mutations in the DEN4 NS5 protein of SLE/DEN4 reduced neurovirulence in mice and replication in rhesus monkeys. Two modified SLE/DEN4 viruses, SLE/DEN4-436,437 clone 41 and SLE/DEN4-654,655 clone 46, have significantly reduced neurovirulence in mice and conferred protective immunity in monkeys against SLE challenge. These viruses may be considered for use as SLE vaccine candidates and for use as diagnostic reagents with reduced virulence.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Evaluation of St. Louis encephalitis virus/dengue virus type 4 antigenic chimeric viruses in mice and rhesus monkeys

Blaney

Speicher

Hanson

et al. 2008

Vaccine

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“…Furthermore, as mentioned earlier, strain variation exists at least for SLEV (Spence, 1980;Vorndam et al, 1993;Diaz et al, 2006). Thus, basically the function of the potential sites in ROCV remains unknown in the absence of experimental data; and, clearly, further experimental studies are necessary to clarify the functional significance.…”

Section: Discussionmentioning

confidence: 99%

“…However, it should be noted that strain variation in the number of sites has been reported. Thus, in the E gene of SLEV, while the Argentine 66 has one, strain MSI-7 has two, but strain Tr 9464 has no glycosylation sites (Kuno & Chang, 2005;Vorndam et al, 1993). Regarding cysteine residues, as strictly required for stabilizing disulfide bridges in all mosquito-borne viruses, 12 residues were found in the ectodomain of E and in NS1 genes of ROCV.…”

Section: Cleavage Sites Glycosylation Sites and Cysteine Residuesmentioning

confidence: 99%

Complete genome characterization of Rocio virus (Flavivirus: Flaviviridae), a Brazilian flavivirus isolated from a fatal case of encephalitis during an epidemic in São Paulo state

Medeiros

Nunes

Vasconcelos

et al. 2007

Journal of General Virology

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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 viral genes including the potential cleavage sites, conserved or unique motifs, cysteine residues and potential glycosylation sites. The conserved sequences in the 39-non-coding region were identified, and the predicted secondary structures during cyclization between 59-and 39-non-coding regions were studied. Multiple protein and phylogenetic analyses based on antigenically important and phylogenetically informative genes confirmed a close relationship between ROCV and Ilheus virus (ILHV), together constituting a unique and distinct phylogenetic subgroup as well as the genetic relationship of ROCV with several members of the Japanese encephalitis group. Although ROCV is phylogenetically related to ILHV, our study shows that it is still a virus distinct from the latter virus. This is the first flavivirus uniquely indigenous to Brazil that has been sequenced completely and the genome characterized. The data should be useful for further studies at the molecular level, including construction of infectious clone, identification of gene function, improved disease surveillance based on molecular diagnostic tools and vaccine development. INTRODUCTIONIn South America, until the mid-1970s, the two neurotropic flaviviruses had been Saint Louis encephalitis virus (SLEV) and Ilheus virus (ILHV). However, in contrast to North America, an epidemic of encephalitis in humans by SLEV in South America was not recorded for many years until the first outbreak in Argentina in 2005(Diaz et al., 2006, despite accumulated records of virus isolation from mosquitoes and vertebrate hosts throughout the continent (Spence, 1980). As for the other virus, ILHV, human infection was sporadic and development of neurotropic manifestations has been even more infrequent. Thus, the sudden emergence of an outbreak of encephalitis caused by a flavivirus in 1974-75 in Brazil was unexpected.Rocio virus (ROCV) belongs to the genus Flavivirus in the family Flaviviridae. Its prototype (strain SPH 34675) was isolated in Ribeira Valley in the south-eastern São Paulo state of Brazil in 1975 from the cerebellum of a fatal human case during an epidemic of encephalitis that could not be readily diagnosed with the reagents then available for known encephalitic viruses. The epidemic, which began in 1974, spread to more than 20 municipalities over the following 2 years causing approximately 1000 diagnosed cases.Members of the genus Flavivirus (hereafter called flaviviruses) are positive-sense, single-stranded RNA viruses that infect humans and other vertebrates. They are mainly...

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“…Glycosylation of the E protein is more variable, usually occurring at residues 153/154 and at residue 67 in the four serotypes of DENV (Bryant et al, 2007;Lee et al, 2010). However, some strains of WNV (Beasley et al, 2005;Botha et al, 2008; Shirato et al, 2004b;Wengler et al, 1985), including KUNV (Adams et al, 1995), as well as strains of St Louis encephalitis virus (SLEV) (Vorndam et al, 1993), Alfuy virus (May et al, 2006 and YFV-17D (Post et al, 1992) lack any active carbohydrate modification in E. Therefore, such glycosylation is not absolutely required for flavivirus replication.The significance of prM glycosylation in flaviviruses appears to be twofold, impacting on both particle assembly and release. Glycosylation of the prM protein (at residue N15 in WNV) appears to be absolutely required for authentic virion assembly.…”

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confidence: 99%

Post-translational regulation and modifications of flavivirus structural proteins

Roby

Setoh

Hall

et al. 2015

Journal of General Virology

102

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Flaviviruses are a group of single-stranded, positive-sense RNA viruses that generally circulate between arthropod vectors and susceptible vertebrate hosts, producing significant human and veterinary disease burdens. Intensive research efforts have broadened our scientific understanding of the replication cycles of these viruses and have revealed several elegant and tightly co-ordinated post-translational modifications that regulate the activity of viral proteins. The three structural proteins in particular -capsid (C), pre-membrane (prM) and envelope (E) -are subjected to strict regulatory modifications as they progress from translation through virus particle assembly and egress. The timing of proteolytic cleavage events at the C-prM junction directly influences the degree of genomic RNA packaging into nascent virions. Proteolytic maturation of prM by host furin during Golgi transit facilitates rearrangement of the E proteins at the virion surface, exposing the fusion loop and thus increasing particle infectivity. Specific interactions between the prM and E proteins are also important for particle assembly, as prM acts as a chaperone, facilitating correct conformational folding of E. It is only once prM/E heterodimers form that these proteins can be secreted efficiently. The addition of branched glycans to the prM and E proteins during virion transit also plays a key role in modulating the rate of secretion, pH sensitivity and infectivity of flavivirus particles. The insights gained from research into post-translational regulation of structural proteins are beginning to be applied in the rational design of improved flavivirus vaccine candidates and make attractive targets for the development of novel therapeutics. FlavivirusesThe genus Flavivirus in the family Flaviviridae comprises small, enveloped viruses with non-segmented genomes consisting of single-stranded, positive-sense RNA. These RNA genomes are flanked by 59 and 39 untranslated regions (UTRs) and encode a single polyprotein that is cleaved coand post-translationally to generate between 10 and 11 viral proteins. The 59 UTR contains a type 1 m 7 GpppNm cap structure and the 39 UTR lacks a polyadenylated tail. Structural elements within the UTRs regulate genome replication, translation and host immune responses. Viral proteins are divided between structural proteins, which form the virion, and non-structural proteins, which are involved in genomic replication and modulating host immunity (Fig. 1a) (Lindenbach et al., 2007;Roby et al., 2012).Flaviviruses are maintained predominantly in natural transmission cycles between vertebrate reservoir species (normally mammalian or avian) and haematophagous arthropod vectors (mosquitoes or ticks). Notable exceptions are the viruses that are maintained solely in mosquito hosts (insectspecific flaviviruses) and viruses with no known invertebrate vector (Cook et al., 2012;Mackenzie et al., 2004). As of 2013, the International Committee on Taxonomy of Viruses has classified 53 different viral species as belonging to ...

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Molecular and biological characterization of a non-glycosylated isolate of St Louis encephalitis virus

Cited by 41 publications

References 52 publications

Evaluation of St. Louis encephalitis virus/dengue virus type 4 antigenic chimeric viruses in mice and rhesus monkeys

Evaluation of St. Louis encephalitis virus/dengue virus type 4 antigenic chimeric viruses in mice and rhesus monkeys

Complete genome characterization of Rocio virus (Flavivirus: Flaviviridae), a Brazilian flavivirus isolated from a fatal case of encephalitis during an epidemic in São Paulo state

Post-translational regulation and modifications of flavivirus structural proteins

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