title: Tick-borne flaviviruses alter membrane structure and replicate in dendrites of primary mouse neuronal cultures.
abstract: Neurological diseases caused by encephalitic flaviviruses are severe and associated with high levels of mortality. However, detailed mechanisms of viral replication in the brain and features of viral pathogenesis remain poorly understood. We carried out a comparative analysis of replication of neurotropic flaviviruses: West Nile virus, Japanese encephalitis virus and tick-borne encephalitis virus (TBEV), in primary cultures of mouse brain neurons. All the flaviviruses multiplied well in primary neuronal cultures from the hippocampus, cerebral cortex and cerebellum. The distribution of viral-specific antigen in the neurons varied: TBEV infection induced accumulation of viral antigen in the neuronal dendrites to a greater extent than infection with other viruses. Viral structural proteins, non-structural proteins and dsRNA were detected in regions in which viral antigens accumulated in dendrites after TBEV replication. Replication of a TBEV replicon after infection with virus-like particles of TBEV also induced antigen accumulation, indicating that accumulated viral antigen was the result of viral RNA replication. Furthermore, electron microscopy confirmed that TBEV replication induced characteristic ultrastructural membrane alterations in the neurites: newly formed laminal membrane structures containing virion-like structures. This is the first report describing viral replication in and ultrastructural alterations of neuronal dendrites, which may cause neuronal dysfunction. These findings encourage further work aimed at understanding the molecular mechanisms of viral replication in the brain and the pathogenicity of neurotropic flaviviruses.
authors.affiliation: Laboratory of Public Health, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan.
authors.forename: Minato
authors.initials: M
authors.lastname: Hirano
authors.affiliation: Laboratory of Public Health, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Yoshii
authors.affiliation: Laboratory of Public Health, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan.
authors.forename: Mizuki
authors.initials: M
authors.lastname: Sakai
authors.affiliation: Laboratory of Veterinary Hygiene, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan.
authors.forename: Rie
authors.initials: R
authors.lastname: Hasebe
authors.affiliation: Laboratory of Anatomy, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Ichii
authors.affiliation: Laboratory of Public Health, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Kariwa
mesh_terms: D000818:Animals; D000956:Antigens, Viral / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism* / Q000648:ultrastructure; D002478:Cells, Cultured; D003712:Dendrites / Q000821:virology*; D004664:Encephalitis Virus, Japanese / Q000502:physiology*; D004669:Encephalitis Viruses, Tick-Borne / Q000502:physiology*; D005260:Female; D051379:Mice; D046529:Microscopy, Electron, Transmission; D009474:Neurons / Q000821:virology*; D014779:Virus Replication; D014902:West Nile virus / Q000502:physiology*
chemical_list: D000956:Antigens, Viral