Characterization of two Japanese encephalitis virus strains isolated in Thailand

Abstract

Two strains of Japanese encephalitis (JE) virus were isolated from a pool of Culex tritaeniorhynchus captured in 1992 and another pool of Cx. vishnui captured in 1993, in Chiang Mai Area, Northern Thailand. These two strains, ThCMAr44/92 and ThCMAr67/93, could not be identified either as Nakayama or JaGAr01 subtype by the hemagglutination-inhibition (HI) and the neutralization (N) tests using immune sera raised against these standard JE virus strains. Reverse transcription-polymerase chain reaction showed the presence of JE-specific conserved sequences in these strains. Sequencing of 240 nucleotides in their PrM gene region identified that these two strains belong to the genotype 1 of JE virus. Nucleotide and encoded amino acid sequences of their envelope glycoprotein gene revealed 98.8 and 99.8% identity, respectively. These two strains shared 77.8 to 87.7% homology in the nucleotide sequence and 90.0 to 98.8% homology in the amino acid sequence with other reported JE strains. Five strain-specific amino acid changes were noted in ThCMAr44/92 strain, while one in ThCMAr67/93. In addition, four common amino acid changes were found in both strains. Thus, the findings indicated that these two strains were structurally different from each other as well as different from all the reported strains which was in agreement with the serological tests by hemagglutination-inhibition and neutralization.

Encephalitis and retarded growth of chicks caused by Sitiawan virus, a new isolate belonging to the genus Flavivirus.

“…[17][18][19][20] Tembusu virus is one of such viruses that was isolated from mosquitoes in Kuala Lumpur in 1955. 17,21 Since then, Tembusu virus has been isolated from mosquitoes of Culex species in Peninsular Malaysia, East Malaysia (Sarawak), and Thailand.…”

Antigenic and Genetic Variations among Japanese Encephalitis Virus Strains Belonging to Genotype 1

“…cDNA synthesis for cloning was performed by direct reverse transcription-polymerase chain reaction (RT-PCR) using extracted RNA as described previously (1). The PCR-amplified products were separated in 3% NuSieve GTG agarose gels.…”

“…The prM nucleotide sequence information of 56 JE strains was obtained from previous publications (9,10). The nucleotide sequence data of the E protein genes of Nakayama, Beijing-1, Kamiyama, 691004 and Muar were obtained from Hasegawa et al (18) and ThCMAr4492 and ThCMAr6793 from our previous report (1). The secondary structure and hydrophobicity of the protein were predicted by Chou and Fasman (11) and Hoop and Woods (25) methods, respectively.…”

“…In our previous report, we showed the peculiar antigenic characteristics of two new JE virus strains isolated in Thailand (1). In this study, we prepared mouse polyclonal antibodies against these two strains as well as two standard strains, Nakayama and JaGAr01, and examined the antigenic variations among 12 JE virus strains isolated in Thailand using the neutralization test.…”

Prevention and Control of Japanese Encephalitis Viruses: A Challenged Issue

“…According to the continue public health impact of JE in Thailand, it has led to effort in childhood immunization and vaccine production in 1985. It was demonstrated by hemagglutination inhibition and neutralization assay that there are definitive antigenic differences among JEV Thai strain and between Thai strains and the standard subtypes, Nakayama and Beijing strains (Ali et al, 1995;Ali & Igarashi, 1997). Most of JEV isolated in Thailand are belonging to genotype I, while some belonging to genotype II, which strains Nakayama and Beijing are belonging to genotype III (Ali & Igarashi, 1997).…”