Persistence of Wild-Type Japanese Encephalitis Virus Strains Cross-Neutralization 5 Years After JE-CV Immunization.
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.


BACKGROUND
NCT00621764.
Clinical Development, Sanofi Pasteur, Marcy l'Etoile, France.
Emmanuel
E
Feroldi
Global Clinical Immunology, Sanofi Pasteur, Swiftwater, Pennsylvania.
Mark
M
Boaz
Center for Vaccine Development, Institute of Molecular Biosciences, Mahidol University, Thailand and Translational Research Unit, Chulabhorn Research Institute.
Sutee
S
Yoksan
Division of Infectious Diseases, Siriraj Hospital, Bangkok.
Kulkanya
K
Chokephaibulkit
Department of Pediatrics, Chulalongkorn Hospital, Bangkok, Thailand.
Usa
U
Thisyakorn
Department of Pediatrics, Chulalongkorn Hospital, Bangkok, Thailand.
Chitsanu
C
Pancharoen
Clinical Development, Sanofi Pasteur, Marcy l'Etoile, France.
Céline
C
Monfredo
Medical Affairs and Clinical R&D, Sanofi Pasteur, Singapore.
Alain
A
Bouckenooghe
D000818:Animals; D057134:Antibodies, Neutralizing / Q000097:blood*; D000914:Antibodies, Viral / Q000097:blood*; D001210:Asia, Southeastern; D002675:Child, Preschool; D003429:Cross Reactions; D004664:Encephalitis Virus, Japanese / Q000276:immunology*; D005260:Female; D006801:Humans; D007194:India; D022321:Japanese Encephalitis Vaccines / Q000008:administration & dosage* / Q000276:immunology*; D008297:Male; D013997:Time Factors
D057134:Antibodies, Neutralizing; D000914:Antibodies, Viral; D022321:Japanese Encephalitis Vaccines
Japanese encephalitis vaccines; cross-neutralization; genotypes; long-term protection; wild-type strains