Decreases in Both the Seroprevalence of Serum Antibodies and Seroprotection against Japanese Encephalitis Virus among Vaccinated Children
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The incidence of Japanese encephalitis (JE) has significantly decreased in China due to JE vaccines. In this study, we investigated the post-JE vaccination seroprevalence and protection provided by vaccinated sera against Japanese encephalitis virus (JEV) to elucidate the persistence and waning of antibodies to JEV among JE-SA14-14-2-vaccinated children. A total of 300 serum samples were collected from vaccinated children aged 3–10 years in Zhaotong, Yunnan, China. The seroprevalence of anti-JEV antibodies was determined by enzyme-linked immune sorbent assay and plaque reduction neutralization test. The highest seropositivity of 82% was observed in vaccinated children during the first 0.5–1.5 years after booster vaccination. Then, the seropositivity began to decline and remained lower than the original level observed in the 0.5–1.5-year group. An association was found between the waning of seroprevalence and elapsed time of the post-booster vaccination. Similarly, the neutralizing antibody (nAb) titres gradually decreased over time, and the levels showed a positive correlation with the protective efficacy in mice. This finding suggests that nAbs play an important role in the antiviral process and that the nAb titre is an adequately credible parameter for evaluating the protective efficacy induced by the JE vaccine. Our results provide data that clarify the persistence and waning of antibodies to JEV, which may help elucidate the pathogenesis of JE.
KeywordsJapanese encephalitis virus (JEV) SA14-14-2 Seroprevalence Neutralizing antibodies Waning of antibody
This work was supported by grants from the National Natural Science Foundation of China (81471957, 81772172, 81671971, U1602223 and 81871641) and a grant from the Open Research Projects of Key Laboratory of Beijing Ditan Hospital, Capital Medical University (DTKF201705). These funding sources played no part in the decision to publish, data analysis, or writing of the manuscript.
RW designed and performed the experiments, analysed the data and wrote the manuscript; LX collected serum samples, demographic information from the vaccinated children and informed consent; NG analysed the data. DF contributed reagents and materials; HC and PW helped with the experiments; HZ designed the research and organized the collaboration; JA principally designed the experiments, revised the manuscript, organized the collaboration and directed the project. All authors read and approved the final manuscript.
Compliance with Ethical Standards
Conflict of interest
The authors declare that there are no competing interests.
Animal and Human Rights Statement
All animal experiments were performed under approval of the Institutional Animal Care and Use Committee of Chinese Capital Medical University. All animal experiments were performed under diethyl ether anaesthesia, and all efforts were made to minimize suffering. This study was performed in strict accordance with institutional review board approval from the Ethics Committee of Yunnan Institute of Parasitic Diseases, China. Written informed consent for serum sample collection was obtained from the parents or legal guardians on behalf of the vaccinated children. Their guardians completed questionnaires including demographic information and their integrated JE vaccination history. According to records from the local Centre for Disease Control and Prevention, these children had received two doses of the SA14-14-2 JE vaccine (Chengdu Institute of Biological Products, China).
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