Prevalence of Neutralizing Antibodies to Japanese Encephalitis Virus among High-Risk Age Groups in South Korea, 2010.

Eun Ju Lee,Won-Ja Lee,Go-Woon Cha,Young Ran Ju,Young Eui Jeong,Myung Guk Han,Nagendra R Hegde

doi:10.1371/journal.pone.0147841

Abstract

After an extensive vaccination policy, Japanese encephalitis (JE) was nearly eliminated since the mid-1980s in South Korea. Vaccination in children shifted the affected age of JE patients from children to adults. However, an abrupt increase in JE cases occurred in 2010, and this trend has continued. The present study aimed to investigate the prevalence of neutralizing antibodies to the JE virus (JEV) among high-risk age groups (≥40 years) in South Korea. A plaque reduction neutralization test was conducted to evaluate the prevalence of neutralizing antibodies to JEV in 945 subjects within four age groups (30–39, 40–49, 50–59, and 60–69 years) in 10 provinces. Of the 945 enrolled subjects, 927 (98.1%) exhibited antibodies against JEV. No significant differences were found in the prevalence of neutralizing antibodies according to sex, age, or occupation. However, there were significant differences in the plaque reduction rate according to age and occupation; oldest age group had a higher reduction rate, and subjects who were employed in agriculture or forestry also had a higher value than the other occupations. We also found that three provinces (Gangwon, Jeonnam, and Gyeongnam) had a relatively lower plaque reduction rate than the other locations. In addition, enzyme-linked immunosorbent assays were conducted to determine recent viral infections and 12 (2.2%) subjects were found to have been recently infected by the virus. In conclusion, the present study clearly indicated that the prevalence of neutralizing antibodies has been maintained at very high levels among adult age groups owing to vaccination or natural infections, or both. In the future, serosurveillance should be conducted periodically using more representative samples to better understand the population-level immunity to JE in South Korea.

Highlights

Japanese encephalitis (JE) is a highly prevalent human viral encephalitis in Asian countries.The causative pathogen, the JE virus (JEV), is a mosquito-borne flavivirus in the family Flaviviridae [1]
Multistage cluster sampling for the 2010 KNHANES resulted in 8,598 subjects representing each age group, sex, and residence location throughout the country
No one had a diabetic history among the 18 subjects who had a negative antibody response

Summary

Introduction

Japanese encephalitis (JE) is a highly prevalent human viral encephalitis in Asian countries.The causative pathogen, the JE virus (JEV), is a mosquito-borne flavivirus in the family Flaviviridae [1]. Japanese encephalitis (JE) is a highly prevalent human viral encephalitis in Asian countries. The polyprotein consists of three structural proteins and seven non-structural proteins, and is flanked by un-translated regions at the 5' and 3' ends of the genome [1]. The virus is transmitted by a zoonotic cycle between vector mosquitoes and pigs or water birds as amplifiers, humans and horses are infected incidentally and considered as dead-end hosts that cannot transmit the virus [4, 5]. Since the first recognized JEV infection in the 1870s in Japan, the affected areas expanded to most Asian countries in the 2010s [6, 7]. Despite the present availability of several vaccines, including inactivated or live-attenuated forms [8, 9], approximately 67,900 annual JE cases are estimated to occur in Asia and the western Pacific regions [6]

Methods

Results

Discussion

Conclusion