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Molecular phylogenetic and evolutionary analyses of Muar strain of Japanese encephalitis virus reveal it is the missing fifth genotype

Mohammed MA, Galbraith SE, Radford AD, Dove W, Takasaki T, Kurane I, et al.

Infect Genet Evol, 2011 Jul;11(5):855-62.
PMID: 21352956 DOI: 10.1016/j.meegid.2011.01.020

Japanese encephalitis virus (JEV) is the most important cause of epidemic encephalitis worldwide but its origin is unknown. Epidemics of encephalitis suggestive of Japanese encephalitis (JE) were described in Japan from the 1870s onwards. Four genotypes of JEV have been characterised and representatives of each genotype have been fully sequenced. Based on limited information, a single isolate from Malaysia is thought to represent a putative fifth genotype. We have determined the complete nucleotide and amino acid sequence of Muar strain and compared it with other fully sequenced JEV genomes. Muar was the least similar, with nucleotide divergence ranging from 20.2 to 21.2% and amino acid divergence ranging from 8.5 to 9.9%. Phylogenetic analysis of Muar strain revealed that it does represent a distinct fifth genotype of JEV. We elucidated Muar signature amino acids in the envelope (E) protein, including E327 Glu on the exposed lateral surface of the putative receptor binding domain which distinguishes Muar strain from the other four genotypes. Evolutionary analysis of full-length JEV genomes revealed that the mean evolutionary rate is 4.35 × 10(-4) (3.4906 × 10(-4) to 5.303 × 10(-4)) nucleotides substitutions per site per year and suggests JEV originated from its ancestral virus in the mid 1500s in the Indonesia-Malaysia region and evolved there into different genotypes, which then spread across Asia. No strong evidence for positive selection was found between JEV strains of the five genotypes and the E gene has generally been subjected to strong purifying selection.
Chikungunya fever from Malaysia

Yamamoto K, Matumoto K, Lim CK, Moi ML, Kotaki A, Takasaki T

Intern. Med., 2010;49(5):501-5.
PMID: 20190493

An adult Malaysian woman returned to Japan from Kuala Lumpur and had onset of dengue fever-like symptoms including high fever, malaise and arthritis in early January 2009. Serum obtained on the following day was tested at the National Institute of Infectious Diseases in Tokyo, where it was determined to be positive for chikungunya virus (CHIKV) RNA. IgM antibody against CHIKV was negative on January 6 and sero-converted to be positive on January 14, confirming a recent CHIKV infection. Except for arthralgia, all her symptoms resolved uneventfully within 10 days.
Clinical and radiological features of imported chikungunya fever in Japan: a study of six cases at the National Center for Global Health and Medicine

Mizuno Y, Kato Y, Takeshita N, Ujiie M, Kobayashi T, Kanagawa S, et al.

J Infect Chemother, 2011 Jun;17(3):419-23.
PMID: 20862507 DOI: 10.1007/s10156-010-0124-y

Chikungunya fever (CHIKF) is currently distributed in Africa and in South and Southeast Asia; outbreaks have occurred periodically in the region over the past 50 years. After a large outbreak had occurred in countries in the western Indian Ocean region in 2005, several countries reported cases of CHIKF from travelers who had visited affected areas. In Japan, there have been only 15 cases of CHIKF patients so far, according to the National Institute of Infectious Diseases. Therefore, to evaluate the clinical and radiological features associated with the disease, we describe 6 imported cases of CHIKF. All of the patients had had prolonged arthralgia on admission to our hospital, and diagnosis was confirmed with specific antibodies by using an IgM-capture enzyme-linked immunoassay and a plaque reduction neutralizing antibody assay. Magnetic resonance imaging (MRI) of one patient revealed erosive arthritis and tenosynovitis during the convalescence stage. Clinicians should be aware of the late consequences of infection by the chikungunya virus (CHIKV) and recognize the possible association of subacute and chronic arthritis features. In addition, competent vectors of CHIKV, Aedes aegypti, can now be found in many temperate areas of the eastern and western hemispheres, including Japan. This fact raises concern that the virus could be introduced and become established in these areas. This necessitates an increased awareness of the disease, because imported cases are likely to contribute to the spread of CHIKV infection wherever the competent mosquito vectors are distributed.
Fulltext Dengue virus infection-enhancing activity in serum samples with neutralizing activity as determined by using FcγR-expressing cells

Moi ML, Lim CK, Chua KB, Takasaki T, Kurane I

PLoS Negl Trop Dis, 2012;6(2):e1536.
PMID: 22389741 DOI: 10.1371/journal.pntd.0001536

Progress in dengue vaccine development has been hampered by limited understanding of protective immunity against dengue virus infection. Conventional neutralizing antibody titration assays that use FcγR-negative cells do not consider possible infection-enhancement activity. We reasoned that as FcγR-expressing cells are the major target cells of dengue virus, neutralizing antibody titration assays using FcγR-expressing cells that determine the sum of neutralizing and infection-enhancing activity, may better reflect the biological properties of antibodies in vivo.
Fulltext Whole Genome Sequencing-Based Molecular Epidemiologic Analysis of Autochthonous Dengue Virus Type 1 Strains Circulating in Japan in 2014

Tajima S, Nakayama E, Kotaki A, Moi ML, Ikeda M, Yagasaki K, et al.

Jpn J Infect Dis, 2017 Jan 24;70(1):45-49.
PMID: 27169954 DOI: 10.7883/yoken.JJID.2016.086

Cases of autochthonous infections of dengue virus type 1 (DENV-1) were detected in Japan after a 70-year period devoid of dengue outbreaks. We previously showed that E gene sequences are identical in 11 of the 12 DENV-1 strains autochthonous to Japan. However, the E sequence represents only 14% of the DENV-1 genome. In the present study, we have sequenced the entire genome of 6 autochthonous DENV-1 strains that were isolated from patients during the 2014 outbreak. Sequencing of 5 Yoyogi group strains with identical E sequences and 1 Shizuoka strain with a different E sequence revealed that the first Yoyogi group strain differed from the Shizuoka strain by 18 amino acid residues. Furthermore, 2 Yoyogi group strains had different genomic sequences while the other 3 had identical genomes. Phylogenetic analyses indicated that the Hyogo strain, a Yoyogi group strain, was the first to diverge from the other 4 Yoyogi group strains. The E gene sequence of the Yoyogi group strains exhibits the highest homology to those of the strains isolated in Malaysia and Singapore between 2013 and 2014. The patient infected with the Hyogo strain visited Malaysia before the onset of dengue fever, suggesting that this was a case of dengue infection imported from Malaysia.
Fulltext Genotype-Dependent Immunogenicity of Dengue Virus Type 2 Asian I and Asian/American Genotypes in Common Marmoset (Callithrix jacchus): Discrepancy in Neutralizing and Infection-Enhancing Antibody Levels between Genotypes

Azami NAM, Moi ML, Ami Y, Suzaki Y, Taniguchi S, Tajima S, et al.

Microorganisms, 2021 Oct 21;9(11).
PMID: 34835327 DOI: 10.3390/microorganisms9112196

Owing to genotype-specific neutralizing antibodies, analyzing differences in the immunogenic variation among dengue virus (DENV) genotypes is central to effective vaccine development. Herein, we characterized the viral kinetics and antibody response induced by DENV type 2 Asian I (AI) and Asian/American (AA) genotypes using marmosets (Callithrix jacchus) as models. Two groups of marmosets were inoculated with AI and AA genotypes, and serial plasma samples were collected. Viremia levels were determined using quantitative reverse transcription-PCR, plaque assays, and antigen enzyme-linked immunosorbent assay (ELISA). Anti-DENV immunoglobulin M and G antibodies, neutralizing antibody titer, and antibody-dependent enhancement (ADE) activity were determined using ELISA, plaque reduction neutralization test, and ADE assay, respectively. The AI genotype induced viremia for a longer duration, but the AA genotype induced higher levels of viremia. After four months, the neutralizing antibody titer induced by the AA genotype remained high, but that induced by the AI genotype waned. ADE activity toward Cosmopolitan genotypes was detected in marmosets inoculated with the AI genotype. These findings indicate discrepancies between heterologous genotypes that influence neutralizing antibodies and viremia in marmosets, a critical issue in vaccine development.
A summary of the imported cases of Chikungunya fever in Japan from 2006 to June 2016

Nakayama E, Tajima S, Kotaki A, Shibasaki KI, Itokawa K, Kato K, et al.

J Travel Med, 2018 01 01;25(1).
PMID: 29394382 DOI: 10.1093/jtm/tax072

Background: Due to the huge 2-way human traffic between Japan and Chikungunya (CHIK) fever-endemic regions, 89 imported cases of CHIK fever were confirmed in Japan from January 2006 to June 2016. Fifty-four of 89 cases were confirmed virologically and serologically at the National Institute of Infectious Diseases, Japan and we present the demographic profiles of the patients and the phylogenetic features of 14 CHIK virus (CHIKV) isolates.
Methods: Patients were diagnosed with CHIK fever by a combination of virus isolation, viral RNA amplification, IgM antibody-, IgG antibody-, and/or neutralizing antibody detection. The whole-genome sequences of the CHIKV isolates were determined by next-generation sequencing.
Results: Prior to 2014, the source countries of the imported CHIK fever cases were limited to South and Southeast Asian countries. After 2014, when outbreaks occurred in the Pacific and Caribbean Islands and Latin American countries, there was an increase in the number of imported cases from these regions. A phylogenetic analysis of 14 isolates revealed that four isolates recovered from three patients who returned from Sri Lanka, Malaysia and Angola, belonged to the East/Central/South African genotype, while 10 isolates from 10 patients who returned from Indonesia, the Philippines, Tonga, the Commonwealth of Dominica, Colombia and Cuba, belonged to the Asian genotype.
Conclusion: Through the phylogenetic analysis of the isolates, we could predict the situations of the CHIK fever epidemics in Indonesia, Angola and Cuba. Although Japan has not yet experienced an autochthonous outbreak of CHIK fever, the possibility of the future introduction of CHIKV through an imported case and subsequent local transmission should be considered, especially during the mosquito-active season. The monitoring and reporting of imported cases will be useful to understand the situation of the global epidemic, to increase awareness of and facilitate the diagnosis of CHIK fever, and to identify a future CHIK fever outbreak in Japan.
Dengue epidemic in Malaysia: urban versus rural comparison of dengue immunoglobulin G seroprevalence among Malaysian adults aged 35-74 years

Azami NAM, Moi ML, Salleh SA, Neoh HM, Kamaruddin MA, Jalal NA, et al.

Trans R Soc Trop Med Hyg, 2020 11 06;114(11):798-811.
PMID: 32735681 DOI: 10.1093/trstmh/traa056

BACKGROUND: A periodic serosurvey of dengue seroprevalence is vital to determine the prevalence of dengue in countries where this disease is endemic. This study aimed to determine the prevalence of dengue immunoglobulin G (IgG) seropositivity among healthy Malaysian adults living in urban and rural areas.
METHODS: A total of 2598 serum samples (1417 urban samples, 1181 rural samples) were randomly collected from adults ages 35-74 y. The presence of the dengue IgG antibody and neutralising antibodies to dengue virus (DENV) 1-4 was determined using enzyme-linked immunosorbent assay and the plaque reduction neutralisation test assay, respectively.
RESULTS: The prevalence of dengue IgG seropositivity was 85.39% in urban areas and 83.48% in rural areas. The seropositivity increased with every 10-y increase in age. Ethnicity was associated with dengue seropositivity in urban areas but not in rural areas. The factors associated with dengue seropositivity were sex and working outdoors. In dengue IgG-positive serum samples, 98.39% of the samples had neutralising antibodies against DENV3, but only 70.97% of them had neutralising antibodies against DENV4.
CONCLUSION: The high seroprevalence of dengue found in urban and rural areas suggests that both urban and rural communities are vital for establishing and sustaining DENV transmission in Malaysia.
Fulltext First round of external quality assessment of dengue diagnostics in the WHO Western Pacific Region, 2013

Pok KY, Squires RC, Tan LK, Takasaki T, Abubakar S, Hasebe F, et al.

Western Pac Surveill Response J, 2015 Jun 30;6(2):73-81.
PMID: 26306220 DOI: 10.5365/WPSAR.2015.6.1.017

Accurate laboratory testing is a critical component of dengue surveillance and control. The objective of this programme was to assess dengue diagnostic proficiency among national-level public health laboratories in the World Health Organization (WHO) Western Pacific Region.
Enterovirus 71 encephalomyelitis and Japanese encephalitis can be distinguished by topographic distribution of inflammation and specific intraneuronal detection of viral antigen and RNA

Wong KT, Ng KY, Ong KC, Ng WF, Shankar SK, Mahadevan A, et al.

Neuropathol. Appl. Neurobiol., 2012 Aug;38(5):443-53.
PMID: 22236252 DOI: 10.1111/j.1365-2990.2011.01247.x

To investigate if two important epidemic viral encephalitis in children, Enterovirus 71 (EV71) encephalomyelitis and Japanese encephalitis (JE) whose clinical and pathological features may be nonspecific and overlapping, could be distinguished.