title: An intranasal challenge model for testing Japanese encephalitis vaccines in rhesus monkeys.
abstract: Placebo-controlled field efficacy trials of new Japanese encephalitis (JE) vaccines may be impractical. Therefore, an animal model to evaluate efficacy of candidate JE vaccines is sought. Previous work has shown that exposure of monkeys to JE virus (JEV) via the intranasal route results in encephalitis. Here we report the further development of this model and the availability of titered virus stocks to assess the protective efficacy of JE vaccines. To determine the effective dose of our JE challenge virus, dilutions of a stock JEV (KE-93 isolate) were inoculated into four groups of three rhesus monkeys. A dose-dependent response was observed and the 50% effective dose (ED50) was determined to be 6.0 x 10(7) plaque forming units (pfu). Among animals that developed encephalitis, clinical signs occurred 9-14 days postinoculation. Infection with JEV was confirmed by detection of JEV in nervous tissues and IgM to JEV in the cerebrospinal fluid. Viremia with JEV was also detected intermittently throughout infection. Validation of the model was performed using a known effective JE vaccine and saline control. One ED90 of virus (2.0 x 10(9) pfu) was used as a challenge dose. Four of four animals that received saline control developed encephalitis while one of four monkeys administered the JE vaccine did so. This study demonstrates that the virus strain, route of inoculation, dose, and the outcome measure (encephalitis) are suitable for assessment of protective efficacy of candidate JE vaccines.
authors.affiliation: Department of Virology, Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand.
authors.forename: B
authors.initials: B
authors.lastname: Raengsakulrach
authors.forename: A
authors.initials: A
authors.lastname: Nisalak
authors.forename: M
authors.initials: M
authors.lastname: Gettayacamin
authors.forename: V
authors.initials: V
authors.lastname: Thirawuth
authors.forename: G D
authors.initials: GD
authors.lastname: Young
authors.forename: K S
authors.initials: KS
authors.lastname: Myint
authors.forename: L M
authors.initials: LM
authors.lastname: Ferguson
authors.forename: C H
authors.initials: CH
authors.lastname: Hoke
authors.forename: B L
authors.initials: BL
authors.lastname: Innis
authors.forename: D W
authors.initials: DW
authors.lastname: Vaughn
mesh_terms: D000281:Administration, Intranasal; D000818:Animals; D000833:Animals, Suckling; D000914:Antibodies, Viral / Q000097:blood / Q000134:cerebrospinal fluid; D017931:DNA Primers / Q000737:chemistry; D004279:DNA, Viral / Q000737:chemistry; D004195:Disease Models, Animal; D004587:Electrophoresis, Agar Gel; D004664:Encephalitis Virus, Japanese / Q000276:immunology* / Q000472:pathogenicity; D004672:Encephalitis, Japanese / Q000276:immunology / Q000517:prevention & control*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006385:Hemagglutination Inhibition Tests; D007114:Immunization; D008253:Macaca mulatta; D008297:Male; D051379:Mice; D009500:Neutralization Tests; D012367:RNA, Viral / Q000032:analysis / Q000097:blood / Q000134:cerebrospinal fluid; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014765:Viral Vaccines / Q000008:administration & dosage / Q000276:immunology / Q000592:standards*; D014766:Viremia / Q000134:cerebrospinal fluid
chemical_list: D000914:Antibodies, Viral; D017931:DNA Primers; D004279:DNA, Viral; D012367:RNA, Viral; D014765:Viral Vaccines