진드기매개뇌염바이러스 (Tick-Borne Encephalitis Virus)에 대한 실험실 진단 및 국가 감시체계 구축에 대한 연구

초록

Purpose : The isolation of tick-borne encephalitis virus(TBEV) has not been reported in Korea. However, its vectors, Ixodes species, have been recorded since 1940's and TBEVs have been isolated near the countries including Japan, China, Russia. To determine the prevalence of TBEV in Ixodes species and humans showing unknown encephalitis we need to establish serological assays and RT-nested PCR which have high sensitivity and specificity to diagnose the disease. The research is provided information for surveillance system in national public health as construction the accurate and quick laboratory diagnosis of the TBE disease. Methods : We examined samples of vectors(Ixodes sp. Heamaphysalis sp.), animal host(lungs, livers, spleens) and sera from humans who showed encephalitis unidentified by serological assays, IFA, ELISA and plaque reduction neutralization test(PRNT). RT-nested PCR was used to detect TBEVs from vectors and sera of humans. For controls of serological assays and RT-nested PCR, we used reference TBEVs and polyclonal antibodies and designed subtype specific primers. The samples positive for the envelope(E) gene of TBEV by RT-nested PCR were inoculated in suckling mice and BHK-21 cells for virus isolation. Also we determined complete E protein gene nucleotide and deduced amino acid sequences to investigated molecular characteristics in E protein gene of five Korean TBEV strains isolated from wild rodents in 2006. Results : We tested 505 samples of wild animals, 264 pooled specimens of ticks which were 2,027 individuals belonging six species and 422 sera of patients. By serological assays, among 422 of patient's sera 16, 13 and zero were positive for TBEV antibodies by IFA, ELISA, PRNT, respectively. TBEVs were detected by RT-nested PCR from three in 264 pools, three in 505 hosts and four in 244 human sera. But we were not able to isolate the virus from positive samples. As a results, comparative sequence alignment and phylogenetic analysis based on the complete E protein gene sequences showed that all of the five isolates have characteristics of the Western subtypes. Conclusions : In this study, TBEVs were detected from animal hosts, ticks and patients and 5 strains of TBEVs were isolated from wild rodents. The isolates were characterized to be western subtypes. This study suggests the occurrence of TBE should be possible in Korea. Serological and genetic methods established in this study would provide useful tools to diagnose unidentified encephalitis.

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