Changes in the distribution of lineage constellations of G2P[4] Rotavirus A strains detected in Japan over 32years (1980–2011)

Evolution of DS-1-like G8P[8] rotavirus A strains from Vietnamese children with acute gastroenteritis (2014-21): Adaptation and loss of animal rotavirus-derived genes during human-to-human spread

Animal rotaviruses A (RVAs) are considered the source of emerging, novel RVA strains that have the potential to cause global spread in humans. A case in point was the emergence of G8 bovine RVA consisting of the P[8] VP4 gene and the DS-1-like backbone genes that appeared to have jumped into humans recently. However, it was not well documented what evolutionary changes occurred on the animal RVA-derived genes during circulation in humans. Rotavirus surveillance in Vietnam found that DS-1-like G8P[8] strains emerged in 2014, circulated in two prevalent waves, and disappeared in 2021. This surveillance provided us with a unique opportunity to investigate the whole process of evolutionary changes, which occurred in an animal RVA that had jumped the host species barrier. Of the 843 G8P[8] samples collected from children with acute diarrhoea in Vietnam between 2014 and 2021, fifty-eight strains were selected based on their distinctive electropherotypes of the genomic RNA identified using polyacrylamide gel electrophoresis. Whole-genome sequence analysis of those fifty-eight strains showed that the strains dominant during the first wave of prevalence (2014-17) carried animal RVA-derived VP1, NSP2, and NSP4 genes. However, the strains from the second wave of prevalence (2018-21) lost these genes, which were replaced with cognate human RVA-derived genes, thus creating strain with G8P[8] on a fully DS-1-like human RVA gene backbone. The G8 VP7 and P[8] VP4 genes underwent some point mutations but the phylogenetic lineages to which they belonged remained unchanged. We, therefore, propose a hypothesis regarding the tendency for the animal RVA-derived genes to be expelled from the backbone genes of the progeny strains after crossing the host species barrier. This study underlines the importance of long-term surveillance of circulating wild-type strains in order to better understand the adaptation process and the fate of newly emerging, animal-derived RVA among the human population. Further studies are warranted to disclose the molecular mechanisms by which spillover animal RVAs become readily transmissible among humans, and the roles played by the expulsion of animal-derived genes and herd immunity formed in the local population.

Phylodynamic characteristics of reassortant DS-1-like G3P[8]-strains of rotavirus type A isolated in Nizhny Novgorod (Russia)

Since 2013, there has been an increase in reports of the spread of a double intergroup reassortant strain of rotavirus type A (RVA) with the genotype G3P[8] and other genes belonging to the second genogroup I2-R2-C2-M2-A2-N2-T2-E2-H2. In our study, we provide a molecular genetic characterization of rotaviruses with genotype G3P[8]-I2 isolated in Nizhny Novgorod. In our study, we used RT-PCR, Sanger sequencing, RNA-PAGE methods. Phylogenetic and phylodynamic analysis were performed using the Bayesian approach. According to our study, there was a significant increase in the proportion of G3P[8] from 15% during the period of 2020-2021 to 53% during the period of 2021-2022 in Nizhny Novgorod, Russia. Phylogenetic analysis based on the VP4 gene revealed that DS-1-like RVAs isolated in Nizhny Novgorod belong to different clusters of the P[8]-3.1 lineage, with a level of variation ranging from 1.1% to 1.3%. Based on the VP6 gene, the equine-like RVAs identified by us carry genetic variants belonging to three distinct clusters of the lineage I2-V, with a variation level ranging from 2.0% to 4.5%. These data indicate the genotypic diversity of circulating DS-1-like G3 RVAs. Phylogenetic analysis of the VP7 gene allowed us to assign the isolates identified in our study to the G3-1 lineage. We estimated that the circulation of the most recent common ancestor of the spreading strains dates back to 2002. Additionally, we determined the typical level of mutations in the VP7 gene, which amounted to 2.14*10-3 substitutions/per site/per year.

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.

Genomic epidemiology of the rotavirus G2P[4] strains in coastal Kenya pre- and post-rotavirus vaccine introduction, 2012-8

The introduction of rotavirus vaccines into the national immunization programme in many countries has led to a decline in childhood diarrhoea disease burden. Coincidentally, the incidence of some rotavirus group A (RVA) genotypes has increased, which may result from non-vaccine-type replacement. Here, we investigate the evolutionary genomics of rotavirus G2P[4] which has shown an increase in countries that introduced the monovalent Rotarix® vaccine. We examined sixty-three RVA G2P[4] strains sampled from children (aged below 13 years) admitted to Kilifi County Hospital, coastal Kenya, pre- (2012 to June 2014) and post-(July 2014 to 2018) rotavirus vaccine introduction. All the sixty-three genome sequences showed a typical DS-1-like genome constellation (G2-P[4]-I2-R2-C2-M2-A2-N2-T2-E2-H2). Pre-vaccine G2 sequences predominantly classified as sub-lineage IVa-3 and co-circulated with low numbers of sub-lineage IVa-1 strains, whereas post-vaccine G2 sequences mainly classified into sub-lineage IVa-3. In addition, in the pre-vaccine period, P[4] sub-lineage IVa strains co-circulated with low numbers of P[4] lineage II strains, but P[4] sub-lineage IVa strains predominated in the post-vaccine period. On the global phylogeny, the Kenyan pre- and post-vaccine G2P[4] strains clustered separately, suggesting that different virus populations circulated in the two periods. However, the strains from both periods exhibited conserved amino acid changes in the known antigenic epitopes, suggesting that replacement of the predominant G2P[4] cluster was unlikely a result of immune escape. Our findings demonstrate that the pre- and post-vaccine G2P[4] strains circulating in Kilifi, coastal Kenya, differed genetically but likely were antigenically similar. This information informs the discussion on the consequences of rotavirus vaccination on rotavirus diversity.

Genomic Constellation of Human Rotavirus G8 Strains in Brazil over a 13-Year Period: Detection of the Novel Bovine-like G8P[8] Strains with the DS-1-like Backbone

Rotavirus (RVA) G8 is frequently detected in animals, but only occasionally in humans. G8 strains, however, are frequently documented in nations in Africa. Recently, an increase in G8 detection was observed outside Africa. The aims of the study were to monitor G8 infections in the Brazilian human population between 2007 and 2020, undertake the full-genotype characterization of the four G8P[4], six G8P[6] and two G8P[8] RVA strains and conduct phylogenetic analysis in order to understand their genetic diversity and evolution. A total of 12,978 specimens were screened for RVA using ELISA, PAGE, RT-PCR and Sanger sequencing. G8 genotype represented 0.6% (15/2434) of the entirely RVA-positive samples. G8P[4] comprised 33.3% (5/15), G8P[6] 46.7% (7/15) and G8P[8] 20% (3/15). All G8 strains showed a short RNA pattern. All twelve selected G8 strains displayed a DS-1-like genetic backbone. The whole-genotype analysis on a DS-1-like backbone identified four different genotype-linage constellations. According to VP7 analysis, the Brazilian G8P[8] strains with the DS-1-like backbone strains were derived from cattle and clustered with newly DS-1-like G1/G3/G9/G8P[8] strains and G2P[4] strains. Brazilian IAL-R193/2017/G8P[8] belonged to a VP1/R2.XI lineage and were grouped with bovine-like G8P[8] strains with the DS-1-like backbone strains detected in Asia. Otherwise, the Brazilian IAL-R558/2017/G8P[8] possess a “Distinct” VP1/R2 lineage never previously described and grouped apart from any of the DS-1-like reference strains. Collectively, our findings suggest that the Brazilian bovine-like G8P[8] strains with the DS-1-like backbone strains are continuously evolving and likely reassorting with local RVA strains rather than directly relating to imports from Asia. The Brazilian G8P[6]-DS-1-like strains have been reassorted with nearby co-circulating American strains of the same DS-1 genotype constellation. However, phylogenetic analyses revealed that these strains have some genetic origin from Africa. Finally, rather than being African-born, Brazilian G8P[4]-DS-1-like strains were likely imported from Europe. None of the Brazilian G8 strains examined here exhibited signs of recent zoonotic reassortment. G8 strains continued to be found in Brazil according to their intermittent and localized pattern, thus, does not suggest that a potential emergence is taking place in the country. Our research demonstrates the diversity of G8 RVA strains in Brazil and adds to the understanding of G8P[4]/P[6]/P[8] RVA genetic diversity and evolution on a global scale.

Genomic Analysis of G2P[4] Group A Rotaviruses in Zambia Reveals Positive Selection in Amino Acid Site 7 of Viral Protein 3

The G2P[4] genotype is among the rotavirus strains that circulate commonly in humans. Several countries have reported its immediate upsurge after the introduction of rotavirus vaccination, raising concern about sub-optimal vaccine effectiveness against this genotype in the long term. This study aimed to gain insight into the evolution of post-vaccine Zambian G2P[4] group A rotavirus (RVA) strains and their overall genetic make-up by analysis of sequence alignments at the amino acid (AA) level. Twenty-nine Zambian G2P[4] rotavirus strains were subjected to whole-genome sequencing using the Illumina MiSeq^® platform. All the strains exhibited the typical DS-1-like genotype constellation, and the nucleotide sequences of the 11 genome segments showed high nucleotide similarities (>97%). Phylogenetic analyses together with representative global G2P[4] RVA showed that Zambian strains clustered into human lineages IV (for VP2, VP4, VP7, NSP1, and NSP5), V (for VP1, VP3, VP6, NSP2, and NSP3), and XXIII (for NSP4). The AA differences between the lineages where the study strains clustered and lineages of global reference strains were identified and analyzed. Selection pressure analysis revealed that AA site seven in the Viral Protein 3 (VP3) genome segment was under positive selection. This site occurs in the region of intrinsic disorder in the VP3 protein, and Zambian G2P[4] strains could potentially be utilizing this intrinsically disordered region to survive immune pressure. The Zambian G2P[4] strains from 2012 to 2016 comprised the G2P[4] strains that have been circulating globally since the early 2000s, highlighting the epidemiological fitness of these contemporary G2P[4] strains. Continuous whole-genome surveillance of G2P[4] strains remains imperative to understand their evolution during the post-vaccination period.

Complete genome analyses of G12P[8] rotavirus strains from hospitalized children in Surabaya, Indonesia, 2017-2018

Rotavirus A (RVA) is a major viral cause of acute gastroenteritis (AGE) worldwide. G12 RVA strains have emerged globally since 2007. There has been no report of the whole genome sequences of G12 RVAs in Indonesia. We performed the complete genome analysis by the next-generation sequencing of five G12 strains from hospitalized children with AGE in Surabaya from 2017 to 2018. All five G12 strains were Wa-like strains (G12-P[8]-I1-R1-C1-M1-A1-N1-T1-E1-H1) and were clustered into lineage-III of VP7 gene phylogenetic tree. STM430 sample was observed as a mixed-infection between G12 and G1 strains: G12/G1-P[8]-I1-R1-C1-M1-A1-N1-T1-E1-H1. A phylogenetic tree analysis revealed that all five Indonesian G12 strains (SOEP379, STM371, STM413, STM430, and STM433) were genetically close to each other in all 11 genome segments with 98.0%-100% nucleotide identities, except VP3 and NSP4 of STM430, suggesting that these strains have originated from a similar ancestral G12 RVA. The VP3 and NSP4 genome segments of STM430-G12P[8] were separated phylogenetically from those of the other four G12 strains, probably due to intra-genotype reassortment between the G12 and G1 Wa-like strains. The change from G12P[6] lineage-II in 2007 to G12P[8] lineage-III 2017-2018 suggests the evolution and diversity of G12 RVAs in Indonesia over the past approximately 10 years.

A reverse genetics system for human rotavirus G2P[4]

Rotaviruses (RVs) are an important cause of acute gastroenteritis in young children. Recently, versatile plasmid-based reverse genetics systems were developed for several human RV genotypes; however, these systems have not been developed for all commonly circulating human RV genotypes. In this study, we established a reverse genetics system for G2P[4] human RV strain HN126. Nucleotide sequence analysis, including that of the terminal ends of the viral double-stranded RNA genome, revealed that HN126 possessed a DS-1-like genotype constellation. Eleven plasmids, each encoding 11 gene segments of the RV genome, and expression plasmids encoding vaccinia virus RNA capping enzyme (D1R and D12L), Nelson Bay orthoreovirus FAST, and NSP2 and NSP5 of HN126, were transfected into BHK-T7 cells, and recombinant strain HN126 was generated. Using HN126 or simian RV strain SA11 as backbone viruses, reassortant RVs carrying the outer and intermediate capsid proteins (VP4, VP7 and VP6) of HN126 and/or SA11 (in various combinations) were generated. Viral replication analysis of the single, double and triple reassortant viruses suggested that homologous combination of the VP4 and VP7 proteins contributed to efficient virus infectivity and interaction between other viral or cellular proteins. Further studies of reassortant viruses between simian and other human RV strains will contribute to developing an appropriate model for human RV research, as well as suitable backbone viruses for generation of recombinant vaccine candidates.

Evolutionary changes between pre- and post-vaccine South African group A G2P[4] rotavirus strains, 2003-2017

The transient upsurge of G2P[4] group A rotavirus (RVA) after Rotarix vaccine introduction in several countries has been a matter of concern. To gain insight into the diversity and evolution of G2P[4] strains in South Africa pre- and post-RVA vaccination introduction, whole-genome sequencing was performed for RVA positive faecal specimens collected between 2003 and 2017 and samples previously sequenced were obtained from GenBank (n=103; 56 pre- and 47 post-vaccine). Pre-vaccine G2 sequences predominantly clustered within sub-lineage IVa-1. In contrast, post-vaccine G2 sequences clustered mainly within sub-lineage IVa-3, whereby a radical amino acid (AA) substitution, S15F, was observed between the two sub-lineages. Pre-vaccine P[4] sequences predominantly segregated within sub-lineage IVa while post-vaccine sequences clustered mostly within sub-lineage IVb, with a radical AA substitution R162G. Both S15F and R162G occurred outside recognised antigenic sites. The AA residue at position 15 is found within the signal sequence domain of Viral Protein 7 (VP7) involved in translocation of VP7 into endoplasmic reticulum during infection process. The 162 AA residue lies within the hemagglutination domain of Viral Protein 4 (VP4) engaged in interaction with sialic acid-containing structure during attachment to the target cell. Free energy change analysis on VP7 indicated accumulation of stable point mutations in both antigenic and non-antigenic regions. The segregation of South African G2P[4] strains into pre- and post-vaccination sub-lineages is likely due to erstwhile hypothesized stepwise lineage/sub-lineage evolution of G2P[4] strains rather than RVA vaccine introduction. Our findings reinforce the need for continuous whole-genome RVA surveillance and investigation of contribution of AA substitutions in understanding the dynamic G2P[4] epidemiology.

Whole Genome Analysis of Human Rotaviruses Reveals Single Gene Reassortant Rotavirus Strains in Zambia

Rotarix^® vaccine was implemented nationwide in Zambia in 2013. In this study, four unusual strains collected in the post-vaccine period were subjected to whole genome sequencing and analysis. The four strains possessed atypical genotype constellations, with at least one reassortant genome segment within the constellation. One of the strains (UFS-NGS-MRC-DPRU4749) was genetically and phylogenetically distinct in the VP4 and VP1 gene segments. Pairwise analyses demonstrated several amino acid disparities in the VP4 antigenic sites of this strain compared to that of Rotarix^®. Although the impact of these amino acid disparities remains to be determined, this study adds to our understanding of the whole genomes of reassortant strains circulating in Zambia following Rotarix^® vaccine introduction.

Genotype constellations of the rotavirus A strains circulating in Nizhny Novgorod, Russia, 2017-2018

Currently, the full-genome-based classification is widely used to investigate rotavirus A (RVA) strains found in different countries around the world. However, the information on the full genotypes of rotaviruses circulating in Russia is limited. Using partial sequencing, this study determined the full genotype constellations of 15 RVA strains in total commonly detected in Nizhny Novgorod (European part of Russia) in 2017-2018, three from each of the following genotypes G1P[8], G4P[8], and G9P[8] and six from G2P[4]. There were two intergenogroup mono-reassortants possessing an identical genotype constellation of G4-P[8]-I1-R1-C1-M1-A1-N1-T1-E2-H1 with the DS-1-like NSP4 gene of probably local origin. A variety of subgenotype lineages and their combinations of Wa-like rotaviruses and genetic heterogeneity among G9P[8] and G1P[8] strains were shown on the basis of phylogenetic analysis of each gene. Moreover, two distinct co-circulating variants that differed in all 11 genome segments were found among DS-1-like rotaviruses.

Phylodynamics of G4P[8] and G2P[4] strains of rotavirus A isolated in Russia in 2017 based on full-genome analyses

Rotavirus A is a dynamically evolving pathogen causing acute gastroenteritis in children during the first years of life. In the present study, we conducted a phylodynamic analysis based on the complete sequences of 11 segments of rotaviruses with the G4P[8] and G2P[4] genotypes isolated in Russia in 2017. Since rotavirus has a segmented genome, our analysis was performed using the Bayesian approach based on separate samples of nucleotide sequences for each gene of the strains studied. For the strain with the genotype G4P[8], the most likely geographical locations of the nearest common ancestor were Russia (VP7, VP4, VP6), China (VP1), Thailand (VP3), Belgium (NSP1), Hungary (VP2, NSP2, NSP3), Italy (NSP4) and Japan (NSP5). For the strain with the G2P[4] genotype, India (VP7, VP4, VP6, NSP1, NSP4), Malawi (VP2, NSP2, NSP3), Australia (VP1), Italy (NSP5) and Bangladesh (VP3). The closest common ancestor of the strain with the genotype G4P[8] circulated in 2001-2012, depending on the gene being analyzed. For the strain with the G2P[4] genotype, the closest common ancestor dates from 2006 to 2013.

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.

Genetic analysis of Ghanaian G1P[8] and G9P[8] rotavirus A strains reveals the impact of P[8] VP4 gene polymorphism on P-genotyping

The World Health Organisation rotavirus surveillance networks have documented and shown eclectic geographic and temporal diversity in circulating G- and P- genotypes identified in children <5 years of age. To effectively monitor vaccine performance and effectiveness, robust molecular and phylogenetic techniques are essential to detect novel strain variants that might emerge due to vaccine pressure. This study inferred the phylogenetic history of the VP7 and VP4 genes of previously non-typeable strains and provided insight into the diversity of P[8] VP4 sequences which impacted the outcome of our routine VP4 genotyping method. Near-full-length VP7 gene and the VP8* fragment of the VP4 gene were obtained by Sanger sequencing and genotypes were determined using RotaC v2.0 web-based genotyping tool. The genotypes of the 57 rotavirus-positive samples with sufficient stool was determined. Forty-eight of the 57 (84.2%) had the P[8] specificity, of which 43 (89.6%) were characterized as P[8]a subtype and 5 (10.4%) as the rare OP354-like subtype. The VP7 gene of 27 samples were successfully sequenced and their G-genotypes confirmed as G1 (18/27) and G9 (9/27). Phylogenetic analysis of the P[8]a sequences placed them in subcluster IIIc within lineage III together with contemporary G1P[8], G3P[8], G8P[8], and G9P[8] strains detected globally from 2006-2016. The G1 VP7 sequences of the study strains formed a monophyletic cluster with African G1P[8] strains, previously detected in Ghana and Mali during the RotaTeq vaccine trial as well as Togo. The G9 VP7 sequences of the study strains formed a monophyletic cluster with contemporary African G9 sequences from neighbouring Burkina Faso within the major sub-cluster of lineage III. Mutations identified in the primer binding region of the VP8* sequence of the Ghanaian P[8]a strains may have resulted in the genotyping failure since the newly designed primer successfully genotyped the previously non-typeable P[8] strains. In summary, the G1, G9, and P[8]a sequences were highly similar to contemporary African strains at the lineage level. The study also resolved the methodological challenges of the standard genotyping techniques and highlighted the need for regular evaluation of the multiplex PCR-typing method especially in the post-vaccination era. The study further highlights the need for regions to start using sequencing data from local rotavirus strains to design and update genotyping primers.

Sub-genotype phylogeny of the non-G, non-P genes of genotype 2 Rotavirus A strains

Recent increase in the detection of unusual G1P[8], G3P[8], G8P[8], and G9P[4] Rotavirus A (RVA) strains bearing the DS-1-like constellation of the non-G, non-P genes (hereafter referred to as the genotype 2 backbone) requires better understanding of their evolutionary relationship. However, within a genotype, there is lack of a consensus lineage designation framework and a set of common sequences that can serve as references. Phylogenetic analyses were carried out on over 8,500 RVA genotype 2 genes systematically retrieved from the rotavirus database within the NCBI Virus Variation Resource. In line with previous designations, using pairwise comparison of cogent nucleotide sequences and stringent bootstrap support, reference lineages were defined. This study proposes a lineage framework and provides a dataset ranging from 34 to 145 sequences for each genotype 2 gene for orderly lineage designation of global genotype 2 genes of RVAs detected in human and animals. The framework identified five to 31 lineages depending on the gene. The least number of lineages (five to seven) were observed in genotypes A2 (NSP1), T2 (NSP3) and H2 (NSP5) which are limited to human RVA whereas the most number of lineages (31) was observed in genotype E2 (NSP4). Sharing of the same lineage constellations of the genotype 2 backbone genes between recently-emerging, unusual G1P[8], G3P[8], G8P[8] and G9P[4] reassortants and many contemporary G2P[4] strains provided strong support to the hypothesis that unusual genotype 2 strains originated primarily from reassortment events in the recent past involving contemporary G2P[4] strains as one parent and ordinary genotype 1 strains or animal RVA strains as the other. The lineage framework with selected reference sequences will help researchers to identify the lineage to which a given genotype 2 strain belongs, and trace the evolutionary history of common and unusual genotype 2 strains in circulation.

Whole-genome characterization of G12 rotavirus strains detected in Mozambique reveals a co-infection with a GXP[14] strain of possible animal origin

A high prevalence of G12 rotavirus strains has previously been reported in southern Mozambique. In this study, the full genomes of five Mozambican G12 strains were determined directly from stool using an Illumina Miseq platform. One sample (0060) contained an intergenogroup co-infection of a G12P[8] Wa-like strain and a GXP[14] DS-1-like strain. The sequences of seven genome segments, detected for the GXP[14] strain, clustered with a diverse group of mostly animal strains, suggesting co-infection with a strain of possible animal origin. The stool samples contained G12P[6] rotavirus strains with Wa-like backbones. Phylogenetic analyses of the VP4 and VP7 encoding segments of the G12P[6] strains suggested that they were reassortants containing backbones that are similar to that of the G12P[8] strain. The study confirms previous observations of interspecies transmission and emphasizes the importance of whole-genome sequencing in order to evaluate rotavirus co-infections and reassortants.

First Detection of DS-1-like G1P[8] Double-gene Reassortant Rotavirus Strains on The American Continent, Brazil, 2013

Emergence of DS-1-like-G1P[8] rotavirus in Asia have been recently reported. We report for the first time the detection and the whole genome phylogenetic analysis of DS-1-like-G1P[8] strains in America. From 2013 to 2017, a total of 4226 fecal samples were screened for rotavirus by ELISA, PAGE, RT-PCR and sequencing. G1P[8] represented 3.7% (30/800) of all rotavirus-positive samples. DS-1-like-G1P[8] comprised 1.6% (13/800) detected exclusively in 2013, and Wa-like-G1P[8] comprised 2.1% (17/800) detected from 2013 to 2015. Whole genome sequencing confirmed the DS-1-like backbone I2-R2-C2-M2-A2-N2-T2-E2-H2. All genome segments of the Brazilian DS-1-like-G1P[8] strains clustered with those of Asian strains, and apart from African DS-1-like-G1P[8] strains. In addition, Brazilian DS-1-like-G1P[8] reassortants distantly clustered with DS-1-like backbone strains simultaneously circulating in the country, suggesting that the Brazilian DS-1-like-G1P[8] strains are likely imported from Asia. Two distinct NSP4 E2 genotype lineages were also identified, indicating the existence of a co-circulating pool of different DS-1-like G1P[8] strains. Surveillance systems must be developed to examine if RVA vaccines are still effective for the prevention against unusual DS-1-like-G1P[8] strains.

Study of Complete Genome Sequences of Rotavirus A Epidemics and Evolution in Japan in 2012-2014

A comprehensive molecular epidemiological study using next-generation sequencing technology was conducted on 333 rotavirus A (RVA)-positive specimens collected from six sentinel hospitals across Japan over three consecutive seasons (2012–2014). The majority of the RVA isolates were grouped into five genotype constellations: Wa-like G1P[8], DS-1-like G1P[8], G2P[4], G3P[8] and G9P[8]. Phylogenetic analysis showed that the distribution of strains varied by geographical locations and epidemic seasons. The VP7 genes of different G types were estimated to evolve at 7.26 × 10^-4–1.04 × 10^-3 nucleotide substitutions per site per year. The Bayesian time-scaled tree of VP7 showed that the time to the most recent common ancestor of epidemic strains within a region was 1–3 years, whereas that of the epidemic strains across the country was 2–6 years. This study provided, for the first time, the timeframe during which an epidemic strain spread locally and within the country and baseline information needed to predict how rapidly RVAs spread.

Whole genome analyses of DS-1-like Rotavirus A strains detected in children with acute diarrhoea in southern Mozambique suggest several reassortment events

We report the first whole genome constellations of Mozambican rotavirus A strains detected between 2012 and 2013 in the Mavalane General Hospital in Maputo city and Manhiça District Hospital in the Manhiça district. Consensus sequences for ten DS-1-like strains (G2P[4] and G8P[4]) were identified with an Illumina Miseq platform using cDNA prepared from dsRNA extracted from stool samples, without genome amplification or prior adaptation to cell culture. Comparison of previously reported genotyping results and the consensus sequences described in this study, indicated that the genotype primers specific for G12 and P[4] might require revision. Phylogenetic analyses indicated diversity among the G2P[4] Mozambican strains and suggested reassortment between G2P[4] and G8P[4] Mozambican strains, as well as the intragenogroup reassortment of all the genome segments encoding VP1, 2, 3 and 6 for strain RVA/Human-wt/MOZ/0045/2012G8P[4]. These results highlight the necessity to determine whole genome constellations to confirm surveillance data in Africa and to monitor the growing diversity in DS-1-like strains.

Rotavirus analyses by SYBR Green real-time PCR and microbiological contamination in bivalves cultivated in coastal water of Amazonian Brazil

The contamination of mussels and oysters by viruses and bacteria is often associated with water contamination and gastroenteritis in humans. The present study evaluated viral and bacterial contamination in 380 samples, from nine mollusk-producing regions in coastal water north of the Brazilian Amazon. Rotavirus contamination was studied for groups A to H, using a two-step SYBR Green RT-qPCR (quantitative reverse transcription polymerase chain reaction), and bacterial families Enterobacteriaceae, Vibrionaceae, and Aeromonadaceae by classical and molecular methods. From the 19 pools analyzed, 26.3% (5/19) were positive for group A Rotavirus, I2 genotype for VP6 region, without amplifications for groups B-H. Bacteriological analysis identified Escherichia coli isolates in 89.5% (17/19) with identification of atypical enteropathogenic E. coli aEPEC in 10.5% (2/19), Salmonella (Groups C1 and G) (10.5%, 2/19), Vibrio alginolyticus (57.9%, 11/19) V. parahaemolyticus (63.2%, 12/19), V. fluvialis (42.1%, 8/19), V. vulnificus (10.5%, 2/19), V. cholerae non-O1, non O139(10.5%, 2/19) and Aeromonas salmonicida (52.6%, 10/19). All the samples investigated presented some level of contamination by enterobacteria, rotavirus, or both, and these results may reflect the level of contamination in the Northern Amazon Region, due to the natural maintenance of some of these agents or by the proximity with human populations and their sewer.

Spread of the emerging equine-like G3P[8] DS-1-like genetic backbone rotavirus strain in Brazil and identification of potential genetic variants

In 2013, the equine-like G3P[8] DS-1-like rotavirus (RVA) strain emerged worldwide. In 2016, this strain was reported in northern Brazil. The aims of the study were to conduct a retrospective genetic investigation to identify the possible entry of these atypical strains in Brazil and to describe their distribution across a representative area of the country. From 2013 to 2017, a total of 4226 faecal samples were screened for RVA by ELISA, PAGE, RT-PCR and sequencing. G3P[8] represented 20.9 % (167/800) of all RVA-positive samples, further subdivided as equine-like G3P[8], DS-1-like (11.0 %; 88/800) and Wa-like G3P[8] (9.9 %; 79/800). Six equine-like G3P[8] DS-1-like samples were selected for whole-genome investigation, confirming the backbone I2-R2-C2-M2-A2-N2-T2-E2-H2. During 2013-2014, Wa-like G3P[8] was predominant and no equine-like G3P[8] DS-1-like was detected. Equine-like G3P[8] DS-1-like was first identified in Paraná in March/2015, suggesting that the strain entered Brazil through the Southern region. Equine-like G3P[8] rapidly spread across the area under surveillance and displayed a marked potential to replace Wa-like G3P[8] strains. Brazilian equine-like G3P[8] DS-1-like strains clustered with contemporary equine-like G3P[8] DS-1-like detected worldwide, but exhibited a distinct NSP2 genotype (N2) compared to the previously reported Amazon equine-like G3P[8] DS-1-like strain (N1). Two distinct NSP4 E2 genotype lineages were also identified. Taken together, these data suggest that different variants of equine-like G3P[8] DS-1-like strains might have been introduced into the country at distinct time points, and co-circulated in the period 2015-2017. The global emergence of equine-like G3P[8] DS-1-like strains, predominantly in countries using the Rotarix vaccine, raises the question of whether vaccines may be inducing selective pressures on zoonotic strains.

Phylogenetic analysis of human G9P[8] rotavirus strains circulating in Jiangsu, China between 2010 and 2016

Rotavirus A (RVA) is the leading cause of acute viral gastroenteritis in children under 5 years of age worldwide. G9P[8] is a common RVA genotype that has been persistently prevalent in Jiangsu, China. To determine the genetic diversity of G9P[8] RVAs, 7 representative G9P[8] strains collected from Suzhou Children's Hospital between 2010 and 2016 (named JS2010-JS2016) were analyzed through whole-genome sequencing. All evaluated strains showed the Wa-like constellation G9-P[8]-I1-R1-C1-M1-A1-N1-T1-E1-H1. Furthermore, phylogenetic analysis revealed that the VP7 genes of all strains clustered into lineage G9-III and G9-VI. With the exception of strain JS2012 (P[8]-4), the VP4 sequences of all strains belonged to the P[8]-3 lineage. Sequencing further revealed that amino acid substitutions were present in the antigenic regions of the VP7 and VP4 genes of all strains. Moreover, there were multiple substitutions in antigenic sites I and II of the nonstructural protein 4 (NSP4) genes, whereas the other NSP genes were relatively conserved. In conclusion, our phylogenetic analysis of these 7 G9P[8] strains suggests that RVA varied across regions and time. Therefore, our findings suggest that continued surveillance is necessary to explore the molecular evolutionary characteristics of RVA for better prevention and treatment of acute viral gastroenteritis.

Emergence of Human G2P[4] Rotaviruses in the Post-vaccination Era in South Korea: Footprints of Multiple Interspecies Re-assortment Events

After the introduction of two global rotavirus vaccines, RotaTeq in 2007 and Rotarix in 2008 in South Korea, G1[P8] rotavirus was the major rotavirus genotype in the country until 2012. However, in this study, an emergence of G2P[4] as the dominant genotype during the 2013 to 2015 season has been reported. Genetic analysis revealed that these viruses had typical DS-1-like genotype constellation and showed evidence of re-assortment in one or more genome segments, including the incorporation of NSP4 genes from strains B-47/2008 from a cow and R4/Haryana/2007 from a buffalo in India, and the VP1 and VP3 genes from strain GO34/1999 from a goat in Bangladesh. Compared to the G2 RotaTeq vaccine strain, 17–24 amino acid changes, specifically A87T, D96N, S213D, and S242N substitutions in G2 epitopes, were observed. These results suggest that multiple interspecies re-assortment events might have contributed to the emergence of G2P[4] rotaviruses in the post-vaccination era in South Korea.

Detection and molecular characterization of two rare G8P[14] and G3P[3] rotavirus strains collected from children with acute gastroenteritis in Japan

This study describes the detection and molecular characterization of two rare G8P[14] and G3P[3] rotavirus strains, which were collected from children with acute gastroenteritis in 2014 in Japan. Among 247 rotaviruses, one G8P[14] (strain 12,597) and one G3P[3] (strain 12,638) rotaviruses were detected. The genotypes of 11 gene segments of these two rotavirus strains (RVA/Human-wt/JPN/12597/2014/G8P[14] and RVA/Human-wt/JPN/12638/2014/G3P[3]) were characterized. The genotype constellation of strain 12,597 was assigned to G8-P[14]-I2-R2-C2-M2-A3-N2-T9-E2-H3, and this strain possessed a rare T9 genotype of NSP3 gene which has never been reported previously in combination with G8 genotype of VP7 gene. Molecular characterization and phylogenetic analysis suggested that the strain 12,597 had the consensus G8P[14] backbone that originated from the rotaviruses of animal origins such as cows, deer, dogs, and cats. The genotype constellation of strain 12,638 was identified as G3-P[3]-I3-R3-C3-M3-A9-N2-T3-E3-H6. The VP7 and VP4 genotypes of strain 12,638 was similar to those of the Cat97-like strains, but the VP1, VP2, and VP3 were closely related to those of the AU-1-like strain. Interestingly, the NSP1 to NSP3 genes shared highest identities with those of a bat rotavirus (RVA/Bat-wt/ZMB/LUS12-14/2012/G3P[3] strain). These findings indicated that the strain 12,638 was an intra-genotype reassortant strain among the AU-1-like strains, the Cat97-like strains and the bat strain. Interestingly, the strains 12,597 and 12,638 possessed the same N2 genotype of NSP2 gene. The results of this study support the possible roles of interspecies transmission and multiple reassortment events for generating the genetic diversity of rotavirus in human.

Molecular epidemiology of rotavirus gastroenteritis in Japan during 2014-2015: Characterization of re-emerging G2P[4] after rotavirus vaccine introduction

Rotavirus vaccines have been available in Japan since 2011. This study conducted to monitor the trend of group A rotavirus (RVA) genotypes 3 years after vaccine introduction. A total of, 539 fecal samples were collected from children with acute gastroenteritis in six regions during July 2014-June 2015. Among them, 178 samples (33.0%) were positive for RVA. The most predominant genotype was G1P[8] (35.9%) followed by G2P[4] (26.4%), G9P[8] (21.3%), G3P[8] (4.5%), and G3P[9] (4.5%). The detection rate of G2P[4] was increased soon after vaccine introduction. Sequence analyses of VP7 and VP4 genes of the representative G2P[4] strains were found to be clustered in sub-lineage IVa of lineage IV. It is noteworthy that one amino acid substitution in the antigenic epitope (Q114P) of VP4 gene was found in representative G2P[4] strains of the current study. However, it is unclear whether the change in antigenic epitope is due to the effect of vaccination or due to natural variation, warranting further continuous monitoring of rotavirus evolution after vaccine introduction.

Genetic analysis of rotavirus G2P[4] strains in Pune, Western India: circulation of a novel reassortant bearing E6 NSP4 genotype

In India, G2P[4] strains are known to be the second most predominant group A rotaviruses causing acute gastroenteritis among children. This study was performed to determine the diversity within VP7(G), VP4(P), VP6(I) and NSP4(E) genes of 16 G2P[4] rotavirus strains detected in children hospitalized for acute gastroenteritis in Pune, Western India during 2009-2013. Fourteen strains showed G2-P[4]-I2-E2 and two strains showed G2-P[4]-I2-E6 genotype constellation. Phylogenetic analysis showed their clustering into G2-IV-a3, P[4]-5bi/ii, I2-3ii and E2-4i/ii or E6 genotypes/lineages. These data reveal inter- and/or intra-genotypic variations in a genogroup-2 constellation of G2P[4] rotavirus strains circulating in Pune, Western India, providing evidence of a novel G2P[4] reassortant bearing a rare NSP4 genotype, E6 during 2009-2013.

Characterisation of a rare, reassortant human G10P[14] rotavirus strain detected in Honduras

BACKGROUND

Although first detected in animals, the rare rotavirus strain G10P[14] has been sporadically detected in humans in Slovenia, Thailand, United Kingdom and Australia among other countries. Earlier studies suggest that the strains found in humans resulted from interspecies transmission and reassortment between human and bovine rotavirus strains.

OBJECTIVES

In this study, a G10P[14] rotavirus genotype detected in a human stool sample in Honduras during the 2010-2011 rotavirus season, from an unvaccinated 30-month old boy who reported at the hospital with severe diarrhea and vomiting, was characterised to determine the possible evolutionary origin of the rare strain.

METHODS

For the sample detected as G10P[14], 10% suspension was prepared and used for RNA extraction and sequence independent amplification. The amplicons were sequenced by next-generation sequencing using the Illumina MiSeq 150 paired end method. The sequence reads were analysed using CLC Genomics Workbench 6.0 and phylogenetic trees were constructed using PhyML version 3.0.

FINDINGS

The next generation sequencing and phylogenetic analyses of the 11-segmented genome of the G10P[14] strain allowed classification as G10-P[14]-I2-R2-C2-M2-A3-N2-T6-E2-H3. Six of the genes (VP1, VP2, VP3, VP6, NSP2 and NSP4) were DS-1-like. NSP1 and NSP5 were AU-1-like and NSP3 was T6, which suggests that multiple reassortment events occurred in the evolution of the strain. The phylogenetic analyses and genetic distance calculations showed that the VP7, VP4, VP6, VP1, VP3, NSP1, NSP3 and NSP4 genes clustered predominantly with bovine strains. NSP2 and VP2 genes were most closely related to simian and human strains, respectively, and NSP5 was most closely related to a rhesus strain.

MAIN CONCLUSIONS

The genetic characterisation of the G10P[14] strain from Honduras suggests that its genome resulted from multiple reassortment events which were possibly mediated through interspecies transmissions.

Complex reassortment events of unusual G9P[4] rotavirus strains in India between 2011 and 2013

Rotavirus A (RVA) is the predominant etiological agent of acute gastroenteritis in young children worldwide. Recently, unusual G9P[4] rotavirus strains emerged with high prevalence in many countries. Such intergenogroup reassortant strains highlight the ongoing spread of unusual rotavirus strains throughout Asia. This study was undertaken to determine the whole genome of eleven unusual G9P[4] strains detected in India during 2011-2013, and to compare them with other human and animal global RVAs to understand the exact origin of unusual G9P[4] circulating in India and other countries worldwide. Of these 11 RVAs, four G9P[4] strains were double-reassortants with the G9-VP7 and E6-NSP4 genes on a DS-1-like genetic backbone (G9-P[4]-I2-R2-C2-M2-A2-N2-T2-E6-H2). The other strains showed a complex genetic constellation, likely derived from triple reassortment event with the G9-VP7, N1-NSP2 and E6-NSP4 on a DS-1-like genetic backbone (G9-P[4]-I2-R2-C2-M2-A2-N1-T2-E6-H2). Presumably, these unusual G9P[4] strains were generated after several reassortment events between the contemporary co-circulating human rotavirus strains. Moreover, the point mutation S291L at the interaction site between inner and outer capsid proteins of VP6 gene may be important in the rapid spread of this unusual strain. The complex reassortment events within the G9[4] strains may be related to the high prevalence of mixed infections in India as reported in this study and other previous studies.

Completely genomic and evolutionary characteristics of human-dominant G9P[8] group A rotavirus strains in Yunnan, China

G9P[8] rotavirus A (RVA) has been identified as the predominant genotype circulating in Yunnan, China. To elucidate the molecular characteristics of its genetic composition at the whole-genome level, the genomes of 12 strains isolated from paediatric patients with diarrhoea were fully sequenced and characterized. Eleven of the 12 strains were genotyped as G9-P[8]-I1-R1-C1-M1-A1-N1-T1-E1-H1, which is closely related to the Wa-like genotype 1 constellation. In contrast, one strain was genotyped as G9-P[8]-I1-R1-C1-M1-A1-N2-T1-E1-H1, with the NSP2 gene characterized as a DS-1 like genotype. Bayesian phylogenetic analysis indicated that G9 strains had emerged in 1932 with an estimated average evolutionary rate of 1.63×10-3 substitutions/site/year. Considering the high prevalence and fast evolutionary rate of G9P[8] rotaviruses, our results suggest that G9P[8] RVA should be strictly monitored in China.

Molecular characterization of emerging G9P[4] rotavirus strains possessing a rare E6 NSP4 or T1 NSP3 genotype on a genogroup-2 backbone using a refined classification framework

Rotavirus infections associated with unusual strains are an emerging concern in rotavirus vaccination programmes. Recently, an increase in circulation of unusual G9P[4] strains was reported from different regions of India, placing this genotype in third position, after G1P[8] and G2P[4], of the most common rotavirus strains. The aim of the present study was to analyse the complete genomic constellation of three G9P[4] strains (RV09, RV10 and RV11), determine their genetic relatedness to other genogroup-2 strains and understand the evolution of a rare E6 and other NSP4 genotypes. All strains revealed the presence of a genogroup-2 backbone, with RV09 constituting the NSP3 T1 genotype and RV10 and RV11 bearing the NSP4 E6 genotype. A refined criterion adopted to classify the nine internal gene segments of G2P[4] and non-G2P[4] strains with the genogroup-2 backbone into lineages and sub-lineages indicated divergence of >8 % (except NSP1: >5.5 %) for lineages and >3 % for sub-lineages. The VP1 and/or VP3 genes of study strains showed close relationships with animal-like human rotaviruses. The estimated evolutionary rate for the NSP4 E6 genotype was marginally higher (3.78×10-3 substitutions per site per year) than that of genotypes E1 (2.6×10-3 substitutions per site per year) and E2 (3.06×10-3 substitutions per site per year), suggesting a step towards adaptation of E6 on a genogroup-2 backbone. The time and origin of the most recent common ancestor of E6 genotype were estimated to be 1981 and South Asia, respectively. Full-genome and evolutionary analyses performed in this study for G9P[4] strains will help better understand the extent of gene reassortment and origin in unusual rotavirus strains that may remain viable and cause infections in humans.

Whole genomic analysis of G2P[4] human Rotaviruses in Mymensingh, north-central Bangladesh

Rotavirus A (RVA) is a dominant causative agent of acute gastroenteritis in children worldwide. G2P[4] is one of the most common genotypes among human rotavirus (HRV) strains, and has been persistently prevalent in South Asia including Bangladesh. In the present study, whole genome sequences of a total of 16 G2P[4] HRV strains (8 strains each in 2010 and 2013) detected in Mymensingh, north-central Bangladesh were determined. These strains had typical DS-1-like genotype constellation. Most of gene segments from DS-1 genogroup exhibited high level sequence identities to each other (>98%), while slight diversity was observed for VP1, VP3, and NSP4 genes. By phylogenetic analysis, individual RNA segments were classified into one (V) or two-three lineages (V–VI or V–VII). In terms of lineages (sublineages) of 11 gene segments, the 16 Bangladeshi strains could be further classified into four clades (A-D) containing 8 lineage constellations, revealing the presence of three clades (A-C) with three lineage constellations in 2010, and a single clade (D) with four constellations in 2013. Therefore, co-existence of multiple G2P[4] HRV strains with different lineage constellations, and change in clades for the study period were demonstrated. Although amino acids in the antigenic regions on VP7 and VP4 were mostly identical to those of global G2P[4] strains after 2000, VP4 of clade D RVAs in 2013 had alanine and proline at positions 88 and 114, respectively, which are novel substitutions compared with recent global G2P[4] strains. Replacement of lineage constellations associated with unique amino acid changes in the antigenic region in VP4 suggested continuous genetic evolutionary state for emerging new G2P[4] rotavirus strains in Bangladesh.

Genomic constellation and evolution of Ghanaian G2P[4] rotavirus strains from a global perspective

Understanding of the genetic diversity and evolution of Rotavirus A (RVA) strains, a common cause of severe diarrhoea in children, needs to be based on the analysis at the whole genome level in the vaccine era. This study sequenced the whole genomes of six representative G2P[4] strains detected in Ghana from 2008 to 2013, and analysed them phylogenetically with a global collection of G2P[4] strains and African non-G2P[4] DS-1-like strains. The genotype constellation of the study strains was G2-P[4]-I2-R2-C2-M2-A2-N2-T2-E2-H2. Strains from the same season were highly identical across the whole genome while strains from different seasons were more divergent from each other. The VP7, VP4, VP2, NSP1, and NSP5 genes belonged to lineage IVa; the VP6, VP1, NSP2, and NSP3 genes belonged to lineage V, and all these genes evolved in the same fashion as the global strains. In the NSP4 gene, lineages V (2008) and X (2009) were replaced by VI (2012/2013) whereas in the VP3 gene, lineage V (2008/2009) was replaced by VII (2012/2013) and these replacements coincided with the vaccine introduction period (2012). The evolutionary rate of the NSP4 gene was 1.2×10^-3 substitutions/site/year and was rather comparable to that of the remaining 10 genes. The multiple NSP4 lineages were explained by intra-genotype reassortment with co-circulating African human DS-1-like strains bearing G2[6], G3P[6], G6[6] and G8. There was no explicit evidence of the contribution of animal RVA strains to the genome of the Ghanaian G2P[4] strains. In summary, this study revealed the dynamic evolution of the G2P[4] strains through intra-genotype reassortment events leading to African specific lineages such IX and X in the NSP4 gene. So far, there was no evidence of a recent direct involvement of animal RVA genes in the genome diversity of African G2P[4] strains.

Whole genome analysis of Vietnamese G2P[4] rotavirus strains possessing the NSP2 gene sharing an ancestral sequence with Chinese sheep and goat rotavirus strains

Because imminent introduction into Vietnam of a vaccine against Rotavirus A is anticipated, baseline information on the whole genome of representative strains is needed to understand changes in circulating strains that may occur after vaccine introduction. In this study, the whole genomes of two G2P[4] strains detected in Nha Trang, Vietnam in 2008 were sequenced, this being the last period during which virtually no rotavirus vaccine was used in this country. The two strains were found to be >99.9% identical in sequence and had a typical DS-1 like G2-P[4]-I2-R2-C2-M2-A2-N2-T2-E2-H2 genotype constellation. Analysis of the Vietnamese strains with >184 G2P[4] strains retrieved from GenBank/EMBL/DDBJ DNA databases placed the Vietnamese strains in one of the lineages commonly found among contemporary strains, with the exception of the NSP2 and NSP4 genes. The NSP2 genes were found to belong to a previously undescribed lineage that diverged from Chinese sheep and goat rotavirus strains, including a Chinese rotavirus vaccine strain LLR with 95% nucleotide identity; the time of their most recent common ancestor was 1975. The NSP4 genes were found to belong, together with Thai and USA strains, to an emergent lineage (VIII), adding further diversity to ever diversifying NSP4 lineages. Thus, there is a need to enhance surveillance of locally-circulating strains from both children and animals at the whole genome level to address the effect of rotavirus vaccines on changing strain distribution.

G2 rotavirus within an emergent VP7 evolutionary lineage circulating in children with acute diarrhea in Guangxi Province of China, 2014

Routine surveillance revealed that the prevalence of P[4] rotaviruses circulating in children with acute diarrhea in Guangxi Province, China, increased in 2014. However, VP7 genotyping for these P[4] rotaviruses was unsuccessful. Exhaustive database searching and sequence analysis indicated that the G genotype of these P[4] rotaviruses was G2, and the VP7 genes clustered with recently emerging G2 strains in several countries within an emergent evolutionary lineage that was distinct from the previously designated lineages I-IV as well as lineage V including porcine rotaviruses. Further studies are essential to monitor the potential global spread of this emerging G2 rotavirus.

Genetic analysis of human rotavirus C: The appearance of Indian-Bangladeshi strain in Far East Asian countries

Rotaviruses C (RVCs) circulate worldwide as an enteric pathogen in both humans and animals. Most studies of their genetic diversity focus on the VP7 and VP4 genes, but the complete genomes of 18 human RVCs have been described in independent studies. The genetic background of the Far East Asian RVCs is different than other human RVCs that were found in India and Bangladesh. Recently, a RVC detected in 2010 in South Korea had genetic background similar to the Indian-Bangladeshi RVCs. This study was undertaken to determine the whole genome of eight Japanese RVCs detected in 2005-2012, and to compare them with other human and animal global RVCs to better understand the genetic background of contemporary Far East Asian RVC. By phylogenetic analysis, the human RVCs appeared to be distinct from animal RVCs. Among human RVCs, three lineage constellations had prolonged circulation. The genetic background of the Far East Asian RVC was distinguished from Indian-Bangladeshi RVC as reported earlier. However, we found one Japanese RVC in 2012 that carried the genetic background of Indian-Bangladeshi RVC, whereas the remaining seven Japanese RVCs carried the typical genetic background of Far East Asian RVC. This is the first report of the Indian-Bangladeshi RVC in Japan. With that observation and the reassortment event of human RVCs in Hungary, our study indicates that the RVCs are spreading from one region to another.

Abrupt emergence and predominance in Vietnam of rotavirus A strains possessing a bovine-like G8 on a DS-1-like background

An apparently single rotavirus A strain possessing a genotype constellation of G8-P[8]-I2-R2-C2-M2-A2-N2-T2-E2-H2 abruptly emerged, caused diarrhoea in children requiring hospitalisation, and increased to reach 27 % of strains detected during the first half of 2015 in Vietnam.

Whole genomic constellation of the first human G8 rotavirus strain detected in Japan

Human G8 Rotavirus A (RVA) strains are commonly detected in Africa but are rarely detected in Japan and elsewhere in the world. In this study, the whole genome sequence of the first human G8 RVA strain designated AU109 isolated in a child with acute gastroenteritis in 1994 was determined in order to understand how the strain was generated including the host species origin of its genes. The genotype constellation of AU109 was G8-P[4]-I2-R2-C2-M2-A2-N2-T2-E2-H2. Phylogenetic analyses of the 11 genome segments revealed that its VP7 and VP1 genes were closely related to those of a Hungarian human G8P[14] RVA strain and these genes shared the most recent common ancestors in 1988 and 1982, respectively. AU109 possessed an NSP2 gene closely related to those of Chinese sheep and goat RVA strains. The remaining eight genome segments were closely related to Japanese human G2P[4] strains which circulated around 1985-1990. Bayesian evolutionary analyses revealed that the NSP2 gene of AU109 and those of the Chinese sheep and goat RVA strains diverged from a common ancestor around 1937. In conclusion, AU109 was generated through genetic reassortment event where Japanese DS-1-like G2P[4] strains circulating around 1985-1990 obtained the VP7, VP1 and NSP2 genes from unknown ruminant G8 RVA strains. These observations highlight the need for comprehensive examination of the whole genomes of RVA strains of less explored host species.