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Fulltext Serologic assays for the detection and strain identification of Pteropine orthoreovirus

Singh H, Shimojima M, Fukushi S, Fukuma A, Tani H, Yoshikawa T, et al.

Emerg Microbes Infect, 2016;5:e44.
PMID: 27165561 DOI: 10.1038/emi.2016.35

Pteropine orthoreovirus (PRV), potentially of bat origin, is reported to be a causative agent of emerging respiratory tract infections among humans in Southeast Asia. We evaluated the efficacy of serologic assays using the major outer capsid and cell attachment proteins (CAP) of PRV strains in the screening, confirmation and identification of three groups of human PRV infections; Indonesian/Japanese, Indonesian/Hong Kong and Malaysian strains. The different serologic assays were tested using rabbit polyclonal antisera raised against these proteins of selected PRV strains, and validation was carried out using sera from a Miyazaki-Bali/2007 PRV-infected patient and the patient's contacts. The results of this study showed that rabbit polyclonal antisera raised against the CAP of the Miyazaki-Bali/2007 PRV strain showed the highest reactivity to the Miyazaki-Bali/2007 PRV and to a lesser extent, cross-reactivity with the HK23629/07 and Melaka PRVs, respectively. Neutralization activity against the Miyazaki-Bali/2007 PRV was observed using rabbit anti-Miyazaki-Bali/2007 PRV CAP (320) but not with rabbit anti-HK23629/07 (<20) and Melaka (<20) PRV CAP. This lack of cross-neutralization, suggests the potential for human reinfection with different strains. The use of sera collected from contacts of the Miyazaki-Bali/2007 PRV-infected patient suggested that human-to-human infections with PRV are unlikely. Previously reported cases of PRV infections among human have been mild. However, the expanding geographic distribution of these viruses, of which its virulence remains unknown, warrants close monitoring to enable the development of prevention and control strategies in the event that a change in virulence occurs.
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.
Fulltext Imported case of acute respiratory tract infection associated with a member of species nelson bay orthoreovirus

Yamanaka A, Iwakiri A, Yoshikawa T, Sakai K, Singh H, Himeji D, et al.

PLoS One, 2014;9(3):e92777.
PMID: 24667794 DOI: 10.1371/journal.pone.0092777

A Japanese man suffered from acute respiratory tract infection after returning to Japan from Bali, Indonesia in 2007. Miyazaki-Bali/2007, a strain of the species of Nelson Bay orthoreovirus, was isolated from the patient's throat swab using Vero cells, in which syncytium formation was observed. This is the sixth report describing a patient with respiratory tract infection caused by an orthoreovirus classified to the species of Nelson Bay orthoreovirus. Given the possibility that all of the patients were infected in Malaysia and Indonesia, prospective surveillance on orthoreovirus infections should be carried out in Southeast Asia. Furthermore, contact surveillance study suggests that the risk of human-to-human infection of the species of Nelson Bay orthoreovirus would seem to be low.