title: Archival Isolates Confirm a Single Topotype of West Nile Virus in Australia.
abstract: West Nile virus is globally wide-spread and causes significant disease in humans and animals. The evolution of West Nile virus Kunjin subtype in Australia (WNVKUN) was investigated using archival samples collected over a period of 50 years. Based on the pattern of fixed amino acid substitutions and time-stamped molecular clock analyses, a single long-term lineage (or topotype) was inferred. This implies that a bottleneck exists such that regional strains eventually die out and are replaced with strains from a single source. This was consistent with current hypotheses regarding the distribution of WNVKUN, whereby the virus is enzootic in northern Australia and is disseminated to southern states by water-birds or mosquitoes after flooding associated with above average rainfall. In addition, two previous amino acid changes associated with pathogenicity, an N-Y-S glycosylation motif in the envelope protein and a phenylalanine at amino acid 653 in the RNA polymerase, were both detected in all isolates collected since the 1980s. Changes primarily occurred due to stochastic drift. One fixed substitution each in NS3 and NS5, subtly changed the chemical environment of important functional groups, and may be involved in fine-tuning RNA synthesis. Understanding these evolutionary changes will help us to better understand events such as the emergence of the virulent strain in 2011.
authors.affiliation: Public Health Virology Laboratory, Queensland Health Forensic and Scientific Services, Archerfield, Australia.
authors.forename: Bixing
authors.initials: B
authors.lastname: Huang
authors.affiliation: School of Chemistry and Molecular Biosciences, The University of Queensland, St Lucia, Queensland, Australia.|QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia.
authors.forename: Natalie A
authors.initials: NA
authors.lastname: Prow
authors.affiliation: Public Health Virology Laboratory, Queensland Health Forensic and Scientific Services, Archerfield, Australia.
authors.forename: Andrew F
authors.initials: AF
authors.lastname: van den Hurk
authors.affiliation: School of Pathology and Laboratory Medicine, University of Western Australia, Nedlands, Australia.|Translational Cancer Pathology Laboratory, Pathwest Laboratory Medicine WA, QEII Medical Centre, Nedlands, Australia.
authors.forename: Richard J N
authors.initials: RJ
authors.lastname: Allcock
authors.affiliation: Public Health Virology Laboratory, Queensland Health Forensic and Scientific Services, Archerfield, Australia.
authors.forename: Peter R
authors.initials: PR
authors.lastname: Moore
authors.affiliation: Department of Medical Entomology, Pathology West-ICPMR, Westmead Hospital, Westmead, Australia.
authors.forename: Stephen L
authors.initials: SL
authors.lastname: Doggett
authors.affiliation: Public Health Virology Laboratory, Queensland Health Forensic and Scientific Services, Archerfield, Australia.
authors.forename: David
authors.initials: D
authors.lastname: Warrilow
mesh_terms: D001315:Australia; D005838:Genotype; D006801:Humans; D010802:Phylogeny; D014764:Viral Proteins / Q000235:genetics; D014901:West Nile Fever / Q000821:virology*; D014902:West Nile virus / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*
chemical_list: D014764:Viral Proteins