title: Partially neutralizing potency against emerging genotype I virus among children received formalin-inactivated Japanese encephalitis virus vaccine.
abstract: BACKGROUND
  Genotype I (GI) Japanese encephalitis virus (JEV) that replaced GIII virus has become the dominant circulating virus in Asia. Currently, all registered live and inactivated JEV vaccines are derived from genotype III viruses. In Taiwan, the compulsory JEV vaccination policy recommends that children receives four doses of formalin-inactivated Nakayama (GIII) JEV vaccine.
  
  
  RESULTS
  To evaluate the influence of genotype replacement on the post-vaccination viral neutralizing ability by GIII and GI viruses, the small panel of vaccinated-children serum specimens was assembled, and the reciprocal 50% plaque-reduction neutralizing antibody titers (PRNT(50)) were measured against Nakayama vaccine strain, CJN GIII human brain isolate and TC2009-1 GI mosquito isolate. The seropositivity rate (PRNT(50) ≥ 1:10) and geometric mean titers (GMT) against the TC2009-1 virus were the lowest among the three viruses. The protective threshold against the CJN and TC2009-1 viruses could only be achieved when the GMT against Nakayama virus was ≥ 1:20 or ≥ 1:80, respectively. Using undiluted vaccinees' sera, the enhancement of JEV infection in K562 cells was observed in some low or non-neutralizing serum specimens.
  
  
  CONCLUSIONS
  Our preliminary study has shown that neutralizing antibodies, elicited by the mouse brain-derived and formalin-inactivated JEV Nakayama vaccine among a limited number of vaccinees, have reduced neutralizing capacity against circulating GI virus, but more detailed studies are needed to address the potential impact on the future vaccine policy.
authors.affiliation: Graduate Institute of Microbiology and Public Health, College of Veterinary Medicine, National Chung Hsing University, Taichung, Taiwan.
authors.forename: Yi-Chin
authors.initials: YC
authors.lastname: Fan
authors.forename: Jo-Mei
authors.initials: JM
authors.lastname: Chen
authors.forename: Hsien-Chung
authors.initials: HC
authors.lastname: Chiu
authors.forename: Yi-Ying
authors.initials: YY
authors.lastname: Chen
authors.forename: Jen-Wei
authors.initials: JW
authors.lastname: Lin
authors.forename: Chen-Chang
authors.initials: CC
authors.lastname: Shih
authors.forename: Chih-Ming
authors.initials: CM
authors.lastname: Chen
authors.forename: Chao-Chin
authors.initials: CC
authors.lastname: Chang
authors.forename: Gwong-Jen J
authors.initials: GJ
authors.lastname: Chang
authors.forename: Shyan-Song
authors.initials: SS
authors.lastname: Chiou
mesh_terms: D000293:Adolescent; D000818:Animals; D057134:Antibodies, Neutralizing / Q000097:blood*; D000914:Antibodies, Viral / Q000097:blood*; D001208:Asia; D002648:Child; D002675:Child, Preschool; D004664:Encephalitis Virus, Japanese / Q000145:classification / Q000235:genetics / Q000276:immunology*; D004672:Encephalitis, Japanese / Q000276:immunology / Q000517:prevention & control* / Q000821:virology*; D005838:Genotype; D006801:Humans; D007223:Infant; D022321:Japanese Encephalitis Vaccines / Q000008:administration & dosage / Q000276:immunology*; D051379:Mice; D009500:Neutralization Tests; D013624:Taiwan; D015164:Vaccines, Inactivated / Q000008:administration & dosage / Q000276:immunology; D010948:Viral Plaque Assay
chemical_list: D057134:Antibodies, Neutralizing; D000914:Antibodies, Viral; D022321:Japanese Encephalitis Vaccines; D015164:Vaccines, Inactivated