Characterization of an Unusual DS-1-Like G8P[8] Rotavirus Strain from Japan in 2017: Evolution of Emerging DS-1-Like G8P[8] Strains through Reassortment

Complete genome constellations of two bovine rotavirus A strains isolated in Japan reveal a unique T9 NSP3 genotype

Full genome sequencing of two bovine rotavirus A (RVA) strains isolated in Japan in 2019 revealed two genotype constellations; one had a constellation of G8-P[1]-I2-R2-C2-M2-A3-N2-T9-E2-H3. Thereupon, genotype T9 carried by RVA/Bovine-tc/JPN/AH1041/2022/G8P[1], constitutes a rare NSP3 genotype, and only two unusual Japanese bovine RVA strains have thus far been reported to carry this genotype. The other RVA/Bovine-tc/JPN/AH1207/2022/G6P[5] strain possessed a constellation of G6-P[5]-I2-R2-C2-M2-A3-N2-T6-E2-H3. Phylogenetic analyses indicate that the majority of gene segments were most closely related to Japanese bovine RVAs, suggesting that both strains might have derived through multiple reassortment events from RVA strains circulating within Japanese cattle. The emergence of RVA strains in Japan and their reassortment with locally circulating atypical RVAs could have implications for current vaccination strategies.

Detection and full-genotype determination of rare and reassortant rotavirus A strains in Nizhny Novgorod in the European part of Russia

Reassortant DS-1-like rotavirus A strains have been shown to circulate widely in many countries around the world. In Russia, the prevalence of such strains remains unclear due to the preferred use of the traditional binary classification system. In this work, we obtained partial sequence data from all 11 genome segments and determined the full-genotype constellations of rare and reassortant rotaviruses circulating in Nizhny Novgorod in 2016-2019. DS-1-like G3P[8] and G8P[8] strains were found, reflecting the global trend. Most likely, these strains were introduced into the territory of Russia from other countries but subsequently underwent further evolutionary changes locally. G3P[8], G9P[8], and G12P[8] Wa-like strains of subgenotypic lineages that are unusual for the territory of Russia were also identified. Reassortant G2P[8], G4P[4], and G9P[4] strains with one Wa-like gene (VP4 or VP7) on a DS-1-like backbone were found, and these apparently had a local origin. Feline-like G3P[9] and G6P[9] strains were found to be phylogenetically close to BA222 isolated from a cat in Italy but carried some traces of reassortment with human strains from Russia and other countries. Thus, full-genotype determination of rotavirus A strains in Nizhny Novgorod has clarified some questions related to their origin and evolution.

Surveillance of Human Rotaviruses in Wuhan, China (2019-2022): Whole-Genome Analysis of Emerging DS-1-like G8P[8] Rotavirus

Group A rotaviruses (RVAs) are major etiologic agents of gastroenteritis in infants and young children worldwide. To study the prevalence and genetic characteristics of RVAs, a hospital-based surveillance study was conducted in Wuhan, China from June 2019 through May 2022. The detection rates of RVAs were 19.40% (142/732) and 3.51% (8/228) in children and adults, respectively. G9P[8] was the predominant genotype, followed by G8P[8] and G3P[8]. G8P[8] emerged and was dominant in the 2021-2022 epidemic season. The genome constellation of six G8P[8] strains was assigned to G8-P[8]-I2-R2-C2-M2-A2-N2-T2-E2-H2. Phylogenetic analysis revealed that the VP7, VP4, VP2, VP3, NSP1, NSP2, NSP3, and NSP5 genes of these G8P[8] strains clustered closely with those of the G8P[8] strains in Asia and were distant from those of the P[8] and G2P[4] strains simultaneously detected in Wuhan. In contrast, the VP1, VP6, and NSP4 genes were closely related to the typical G2P[4] rotavirus, including those of G2P[4] strains simultaneously detected in Wuhan. The detection rate of RVAs decreased in the COVID-19 pandemic era. It was deduced that the G8P[8] rotaviruses that emerged in China may be reassortants, carrying the VP6, VP1, and NSP4 genes derived from the G2P[4] rotavirus in the backbone of the neighboring DS-1-like G8P[8] strains represented by CAU17L-103.

Changing distribution of rotavirus A genotypes circulating in Japanese children with acute gastroenteritis in outpatient clinic, 2014-2020

BACKGROUND

Rotavirus A (RVA) is a major cause of severe acute gastroenteritis (AGE) in infants and children worldwide. In Japan, two kinds of rotavirus vaccines have been introduced as voluntary vaccines in 2011 and 2012, respectively, and launched into the national vaccine program in October 2020.

METHODS

In this study, we investigated prevalence of RVA and their molecular characterization in the stool samples collected from infants and children with AGE who visited one outpatient clinic in Japan, from July 2014 to June 2020, during voluntary vaccination with two kinds of rotavirus vaccines.

RESULTS

The RVA detection rates decreased from 44.7 % in 2014-2015 to 35.4 % in 2018-2019, whereas in 2019-2020 the numbers of samples collected were dramatically decreased and none of RVA was detected. During this study period, rotavirus vaccination rates in this area increased from 32.4 % to 62.2 %. Distribution of RVA VP7 (G), VP4 (P), and VP6 (I) genotypes in this area had changed year by year; the major genotype combinations were G1P[8]I1 and G1P[8]I2 in 2014-2015, G2P[4]I2 and G9P[8]I1 in 2015-2016, G1P[8]I1 and G8P[8]I2 in 2017-2018, and G8P[8]I2 in 2018-2019. Phylogenetic analysis demonstrated that VP7 nucleotide sequences of G1 were genetically diverse compared with those of other G genotypes in this study. Meanwhile, predominance of unusual G2P[8]I1, G2P[8]I2 and mixed P genotypes were observed only in 2016-2017, but did not carry on in 2017-2019. The equine-like G3 was detected only in 2016-2017.

CONCLUSIONS

The results revealed diversity of RVA genotypes and the genotype combinations have changed year by year in Japan, during the study period of 2016-2020.

Whole genome sequence of an uncommon G9P[4] species A rotavirus containing DS-1-like (genotype 2) genes in Japan

Species A rotaviruses (RVAs) have been recognized as one of the leading causes of acute gastroenteritis in humans worldwide. Here, the complete coding sequences of 11 RNA segments of an uncommon G9P[4] RVA strain, which was detected in feces of a diarrheal child in Japan, were determined by next-generation sequencing technology. Its genomic constellation, VP7-VP4-VP6-VP1-VP2-VP3-NSP1-NSP2-NSP3-NSP4-NSP5, was determined as G9-P[4]-I2-R2-C2-M2-A2-N2-T2-E2-H2. This work reports the complete coding sequences of a G9P[4] RVA strain containing DS-1-like (genotype 2) genes that was isolated in Japan in 2013.

Molecular and clinical characterization of the equine-like G3 rotavirus that caused the first outbreak in Japan, 2016

Since 2013, equine-like G3 rotavirus (eG3) strains have been detected throughout the world, including in Japan, and the strains were found to be dominant in some countries. In 2016, the first eG3 outbreak in Japan occurred in Tomakomai, Hokkaido prefecture, and the strains became dominant in other Hokkaido areas the following year. There were no significant differences in the clinical characteristics of eG3 and non-eG3 rotavirus infections. The eG3 strains detected in Hokkaido across 2 years from 2016 to 2017 had DS-1-like constellations (i.e. G3-P[8]-I2-R2-C2-M2-A2-N2-T2-E2-H2), and the genes were highly conserved (97.5-100 %). One strain, designated as To16-12 was selected as the representative strain for these strains, and all 11 genes of this strain (To16-12) exhibited the closest identity to one foreign eG3 strain (STM050) seen in Indonesia in 2015 and two eG3 strains (IS1090 and MI1125) in another Japanese prefecture in 2016, suggesting that this strain might be introduced into Japan from Indonesia. Sequence analyses of VP7 genes from animal and human G3 strains found worldwide did not identify any with close identity (>92 %) to eG3 strains, including equine RV Erv105. Analysis of another ten genes indicated that the eG3 strain had low similarity to G2P[4] strains, which are considered traditional DS-1-like strains, but high similarity to DS-1-like G1P[8] strains, which first appeared in Asia in 2012. These data suggest that eG3 strains were recently generated in Asia as mono-reassortant strain between DS-1-like G1P[8] strains and unspecified animal G3 strains. Our results indicate that rotavirus surveillance in the postvaccine era requires whole-genome analyses.

Genomic analysis of group A rotavirus G12P[8] including a new Japanese strain revealed evidence for intergenotypic recombination in VP7 and VP4 genes

Group A rotavirus is a leading cause of severe acute gastroenteritis worldwide. In this study, the first complete coding sequences of 11 RNA segments of human group A rotavirus G12P[8] in Japan were determined by an unbiased viral metagenomics. Its genomic constellation (VP7-VP4-VP6-VP1-VP2-VP3-NSP1-NSP2-NSP3-NSP4-NSP5 genes) was identified as G12-P[8]-I1-R1-C1-M1-A1-N1-T1-E1-H1. When performing the genetic analysis, we discovered an intergenotypic recombination event in the pig group A rotavirus G12P[8] strain BUW-14-A008. The novel recombination was found between two different genotypes G12 and G3 in the VP7 gene, and P[8] and P[13] in the VP4 gene.

Unusual mono-reassortant of a Wa-like G1P[8] species A rotavirus containing a DS-1-like (genotype 2) NSP4 gene

Species A rotaviruses are a major cause of acute gastroenteritis in infants and young children worldwide. Reassortment is a common phenomenon due to the segmented nature of the rotavirus genome. The complete coding sequences of a species A rotavirus strain isolated from the feces of a child with acute gastroenteritis in Japan in 2018 were determined using an unbiased viral metagenomics approach. The genetic analysis revealed that the rotavirus strain had an unusual genomic constellation (G1-P[8]-I1-R1-C1-M1-A1-N1-T1-E2-H1), suggesting reassortment of a genotype 1 with a genotype 2 rotavirus, from which the NSP4-encoding gene was acquired.

Full genome characterization of novel DS-1-like G9P[8] rotavirus strains that have emerged in Thailand

The emergence and rapid spread of unusual DS-1-like intergenogroup reassortant rotaviruses having G1/3/8 genotypes have been recently reported from major parts of the world (Africa, Asia, Australia, Europe, and the Americas). During rotavirus surveillance in Thailand, three novel intergenogroup reassortant strains possessing the G9P[8] genotype (DBM2017-016, DBM2017-203, and DBM2018-291) were identified in three stool specimens from diarrheic children. In the present study, we determined and analyzed the full genomes of these three strains. On full-genomic analysis, all three strains were found to share a unique genotype constellation comprising both genogroup 1 and 2 genes: G9-P[8]-I2-R2-C2-M2-A2-N2-T2-E2-H2. Phylogenetic analysis demonstrated that each of the 11 genes of the three strains was closely related to that of emerging DS-1-like intergenogroup reassortant, human, and/or locally circulating human strains. Thus, the three strains were suggested to be multiple reassortants that had acquired the G9-VP7 genes from co-circulating Wa-like G9P[8] rotaviruses in the genetic background of DS-1-like intergenogroup reassortant (likely equine-like G3P[8]) strains. To our knowledge, this is the first description of emerging DS-1-like intergenogroup reassortant strains having the G9P[8] genotype. Our observations will add to the growing insights into the dynamic evolution of emerging DS-1-like intergenogroup reassortant rotaviruses through reassortment.

Distribution of rotavirus genotypes in Japan from 2015 to 2018: Diversity in genotypes before and after introduction of rotavirus vaccines

BACKGROUND

Diversity in group A rotavirus (RVA) strains after introduction of RV-vaccines remains an emerging concern worldwide. In this study, we investigated the prevalence and distribution of RVA genotypes in Japanese children with acute gastroenteritis (AGE) from 2015 to 2018. In addition, a comparison of the genotypes in pre-vaccination (2006-2012) and post-vaccination (2012-2018) periods was conducted to understand the impact of these vaccines on genotype distribution.

METHODS

Fecal samples were collected regularly from outpatient clinics in six localities: Hokkaido, Tokyo, Shizuoka, Osaka, Kyoto, and Saga. RVA were screened and genotyped by RT-PCR and sequence-based genotyping.

RESULTS

During the period 2015-2018, RVA was detected in 307 (19.7%) samples out of 1557 specimens: 29.9% (95% CI: 25.8% to 34.3%), 17.9% (95% CI: 14.7% to 21.5%), and 13% (95% CI: 10.3% to 16.0%) were detected RVA-positive in 2015-2016, 2016-2017 and 2017-2018, respectively. The average detection of RVA in pre-vaccination (2006-2012) and post-vaccination (2012-2018) era remained almost similar (18%-20%). The G2P[4]I2 (52.1%, 95% CI: 43.5%-60.6%) remained the most common genotype in 2015-2016, whereas G8P[8]I2 (55.9%, 95% CI: 45.2%-66.2%) dominated in 2016-2017. In 2017-2018, G9P[8]I2 (42.0%, 95% CI: 30.5%-53.9%) prevailed, followed by G9P[8]I1 (23.0%, 95% CI: 14.0%-34.2%). The detection rate of some common genotypes of pre-vaccination era like G1P[8] and G3P[8] has been reduced after introduction of RV-vaccine, whereas genotypes that were sporadic before the introduction of vaccines like G2P[4], G2P[8], G9P[8] and G8P[8] were emerged/reemerged in post-vaccination period.

CONCLUSIONS

Our study presented the diversity in circulating RVA genotypes in Japan before and after introduction of RV-vaccines. Sudden emergence of DS-1-like (I2) unusual strains in post-vaccination era remains alarming. Continuous monitoring of RVA genotypes is therefore indispensable to refine future vaccine strategy.

Molecular Characteristics of Novel Mono-Reassortant G9P[8] Rotavirus A Strains Possessing the NSP4 Gene of the E2 Genotype Detected in Tokyo, Japan

Rotavirus A (RVA) has been detected in patients with gastroenteritis even after vaccine introduction in Japan. To investigate circulating RVA strains, RVA-positive stool specimens obtained in Tokyo in 2017 and 2018 were analyzed using next-generation sequencing. A total of 50 and 21 RVA samples were obtained in 2017 and 2018, respectively. In 2017, G2P[4] (40.0%) was the most prevalent strain, followed by G3P[8] (DS-1-like) (28.0%), G8P[8] (10.0%), G3P[8] (Wa-like) (8.0%), G9P[8]-E1 (8.0%), and mixed infection (6.0%). In 2018, G3P[8] (DS-1-like) (28.6%) and G9P[8]-E2 (28.6%) were the most prevalent strains, followed by G9P[8]-E1 (19.0%), G2P[4] (9.5%), G8P[8] (9.5%), and mixed infection (4.8%). Six G9P[8]-E2 strains detected in 2018 showed an atypical genotype constellation (G9P[8]-I1-R1-C1-M1-A1-N1-T1-E2-H1), which had not been reported previously. Phylogenetic analyses suggested that the RVA virus was generated by inter-genogroup reassortment between commonly circulating G9P[8] and G2P[4] strains in Japan. The G9P[8] strain seemed to be reassorted with only the NSP4 gene of the E2 genotype of the G2P[4] strain. Since this newly-emerged G9P[8]-E2 virus was detected in different locations in Tokyo, the virus appears to have already begun to spread to a wider area.