1. Persistence of Wild-Type Japanese Encephalitis Virus Strains Cross-Neutralization 5 Years After JE-CV Immunization
- Author
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Feroldi, Emmanuel, Boaz, Mark, Yoksan, Sutee, Chokephaibulkit, Kulkanya, Thisyakorn, Usa, Pancharoen, Chitsanu, Monfredo, Céline, and Bouckenooghe, Alain
- Subjects
Encephalitis Virus, Japanese ,Male ,Time Factors ,Japanese encephalitis vaccines ,long-term protection ,cross-neutralization ,India ,Cross Reactions ,Antibodies, Viral ,Antibodies, Neutralizing ,Major Articles and Brief Reports ,wild-type strains ,genotypes ,Child, Preschool ,Viruses ,Animals ,Humans ,Female ,Asia, Southeastern - Abstract
Background The live-attenuated Japanese encephalitis (JE) vaccine (JE-CV; IMOJEV) induces a protective response in children. A shift in circulating JE virus strains suggests that a genotype shift phenomenon may occur throughout Southeast Asia. We assessed the neutralization of wild-type (WT) JE virus isolates at distal time points after vaccination. Methods We analyzed serum samples from a subset of 47 children who had received a JE-CV booster after an inactivated JE vaccine primary immunization. We measured antibody titers (50% plaque reduction neutralization test) using a panel of WT JE strains at baseline, then after the booster at 28 days and 6 months in all subjects present at the time points and in a subset at year 5. Three additional recent isolates were tested at year 5. Results Of 47 subjects, 43 (91.5%) subjects had JE neutralizing antibody titers ≥10 (reciprocal serum dilution) against the homologous strain before JE-CV boost; all were seroprotected up to year 5 after the JE-CV boost. Baseline WT seroprotection ranged between 78.7% and 87.2%; all subjects were seroprotected against the 4 WT strains at 28 days and 6 months; year 5 seroprotection ranged between 95.7% and 97.9%. Similar rates of protection against 3 additional WT isolates were observed at year 5. Conclusions The long-term immune responses induced after a JE-CV booster dose in toddlers were able to neutralize WT viruses from various genotypes circulating in Southeast Asia and India. Clinical Trials Registration NCT00621764.
- Published
- 2016