Genotypic linkages of gene segments of rotaviruses circulating in pediatric patients with acute gastroenteritis in Thailand

Identification of a cooperative effect between amino acids 169 and 174 in the rotavirus NSP4 double-layered particle-binding domain

Segmented RNA viruses are capable of exchanging genome segments via reassortment as a means of immune evasion and to maintain viral fitness. Reassortments of single-genome segments are common among group A rotaviruses. Multiple instances of co-reassortment of two genome segments, GS6(VP6) and GS10(NSP4), have been documented in surveillance. Specifically, a division between NSP4 genotypes has been observed in the NSP4 double-layered particle (DLP)-binding domain. A previously hypothesized mechanism for this co-reassortment has been suggested to be the interaction between VP6 and NSP4 during DLP transport from viroplasms for particle maturation. In this study, we used sequence analysis, RNA secondary structure prediction, molecular dynamics and reverse genetics to form a hypothesis regarding the role of the NSP4 DLP-binding domain. Sequence analysis showed that the polarity of NSP4 DLP-binding domain amino acids 169 and 174 is clearly divided between E1 and E2 NSP4 genotypes. Viruses with E1 NSP4s had 169A/I or 169S/T with 174S. E2 NSP4s had 169R/K and 174A. RNA secondary structure prediction showed that mutation in both 545 (aa169) and 561 (aa174) causes global structure remodelling. Molecular dynamics showed that the NSP4/VP6 interaction stability is increased by mutating both aa positions 169 and 174. Using reverse genetics, we showed that an R169I mutation alone does not prevent rescue. Conversely, 174A to 174S prevented rescue, and rescue could be returned by combining 174S with 169I. When compared to rSA11 NSP4-wt, both rSA11 NSP4-R169I and rSA11 NSP4-R169I/A174S had a negligible but significant reduction in titre at specific time points. This study suggests that amino acid 174 of NSP4 may be essential in maintaining the VP6/NSP4 interaction required for DLP transport. Our results suggest that maintenance of specific polarities of amino acids at positions 169 and 174 may be required for the fitness of rotavirus field strains.

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.

Prevalence and diversity of human rotavirus among Thai adults

Rotavirus infections have become one of the most common causes of infectious gastroenteritis in children. Although rotavirus infections have been intensively studied in infants and young children, the study in adults has been limited. As such, this study assessed the prevalence of rotaviruses and performed the molecular characterization of rotaviruses circulating in Thai adults experiencing acute gastroenteritis between January 2018 and December 2018. Group A human rotaviruses were detected in 100 feces samples by rapid immunochromatography. The peak incidence of infection occurred in February and began to decline in the summer months. From January 2018 to December 2018, there were 1344 acute gastroenteritis adult cases in the Hospital for Tropical Diseases, Bangkok, Thailand. Among these, 310 cases were rotavirus-suspected cases. Only 100 samples tested positive for rotavirus via an immunochromatography test. Twentynine out of the 100 rotavirus-positive samples were further characterized by real-time polymerase chain reaction. The G3[P8] strain was identified as the most prevalent (31.0%) followed by G1P[8], G8P[8] and G9P[8], and G2P[8], which accounted for 20.8%, 17.2%, and 13.8%, respectively. Because of the detection of rare rotavirus genotypes, such as G8, the surveillance of rotavirus epidemiology is crucial in monitoring new emergences of rotavirus strains, leading to a better understanding of the effects of strain variation for further vaccine development.

Prevalence and Genotypic Distribution of Rotavirus in Thailand: A Multicenter Study

Rotavirus has been one of the major etiological agents causing severe diarrhea in infants and young children worldwide. In Thailand, rotavirus contributes to one-third of reported pediatric diarrheal cases. We studied stool samples from 1,709 children with acute gastroenteritis and 1,761 children with no reported gastroenteritis whose age ranged from 3 months to 5 years from four different regions in Thailand between March 2008 and August 2010. The samples were tested for the presence of rotavirus by real-time reverse transcription-polymerase chain reaction (RT-PCR) amplification of vp6 gene and enzyme-linked immunosorbent assay. The positive samples were further characterized for their G and P genotypes (vp7 and vp4 genes) by conventional RT-PCR. From all four regions, 26.8% of cases and 1.6% of controls were positive for rotavirus, and G1P[8] was the most predominant genotype, followed by G2P[4], G3P[8], and G9P[8]. In addition, the uncommon genotypes including G1P[4], G1P[6], G2P[6], G2P[8], G4P[6], G9P[4], G9P[6], G12P[6], and G12P[8] were also detected at approximately 14% of all samples tested. Interestingly, G5P[19], a recombinant genotype between human and animal strains, and G1P7[5], a reassortant vaccine strain which is closely related to four human-bovine reassortant strains of RotaTeq^™ vaccine, were detected in control samples. Data reported in this study will provide additional information on molecular epidemiology of rotavirus infection in Thailand before the impending national implementation of rotavirus vaccination program.

Emergence of human G2P[4] rotaviruses containing animal derived gene segments in the post-vaccine era

The introduction of Rotarix into the Belgian immunization program in June 2006 coincided with an increase of the relative prevalence of G2P[4] strains. However, the genetic composition of these persistent G2P[4] strains has not been investigated. Therefore, we have investigated the NSP4 gene of 89 Belgian G2P[4] strains detected between 1999 and 2013, covering both pre- and post-vaccination periods. The NSP4 genes were divided over seven separate clusters of which six were more closely related to animal than to human strains. The NSP4 genes that clustered more closely to animal DS-1-like strains were isolated after 2004–2005 and were found throughout multiple seasons. Complete genome sequencing of 28 strains identified several other gene segments that clustered more closely to animal than to human DS-1-like strains. These findings suggest that frequent interspecies reassortments may have played a role in the spread of G2P[4] rotaviruses in the post-vaccination period in Belgium.

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.

Complete genome analysis of a rare G12P[6] rotavirus isolated in Thailand in 2012 reveals a prototype strain of DS-1-like constellation

Species A rotaviruses (RVAs) are a major cause of severe diarrhea in children worldwide. G12 RVA detection is currently increasing and has been reported from many countries around the world. However, few studies have reported whole genome sequences of G12 RVAs. In the present study, the complete genome sequence of a G12P[6] RVA strain (RVA/Human-wt/THA/CMHN49-12/2012/G12P[6]) detected in a stool sample from a child with acute gastroenteritis in 2012 in Thailand was analyzed. In the CMHN49-12 strain, all genome segments had a DS-1-like backbone: G12-P[6]-I2-R2-C2-M2-A2-N2-T2-E2-H2 indicates that it is most likely the prototype strain of G12P[6] with a DS-1-like genotype constellation. Based on a Bayesian evolutionary analysis of VP7 nucleotide sequence, G12 RVA strains reported previously from Thailand during the period of 2007-2012 could be divided into 3 clusters, indicating that they originated from at least 3 different ancestral G12 strains. The evolutionary rate of G12 calculated by Bayesian Markov Chain Monte Carlo analysis indicated that the nucleotide substitution rate of G12 was 1.11×10(-3) mutations/site/year. The finding of a G12P[6] RVA possessing a DS-1-like backbone provides insights into the evolution of global G12 RVAs.

Review of global rotavirus strain prevalence data from six years post vaccine licensure surveillance: is there evidence of strain selection from vaccine pressure?

Comprehensive reviews of pre licensure rotavirus strain prevalence data indicated the global importance of six rotavirus genotypes, G1P[8], G2P[4], G3P[8], G4P[8], G9P[8] and G12P[8]. Since 2006, two vaccines, the monovalent Rotarix (RV1) and the pentavalent RotaTeq (RV5) have been available in over 100 countries worldwide. Of these, 60 countries have already introduced either RV1 or RV5 in their national immunization programs. Post licensure vaccine effectiveness is closely monitored worldwide. This review aimed at describing the global changes in rotavirus strain prevalence over time. The genotype distribution of the nearly 47,000 strains that were characterized during 2007-2012 showed similar picture to that seen in the preceding period. An intriguing finding was the transient predominance of heterotypic strains, mainly in countries using RV1. Unusual and novel antigen combinations continue to emerge, including some causing local outbreaks, even in vaccinated populations. In addition, vaccine strains have been found in both vaccinated infants and their contacts and there is evidence for genetic interaction between vaccine and wild-type strains. In conclusion, the post-vaccine introduction strain prevalence data do not show any consistent pattern indicative of selection pressure resulting from vaccine use, although the increased detection rate of heterotypic G2P[4] strains in some countries following RV1 vaccination is unusual and this issue requires further monitoring.

A comparison of virus concentration methods for molecular detection and characterization of rotavirus in bivalve shellfish species

The objectives of this study were to develop a method for concentrating rotavirus, to assess the detection rate, and to characterize the genotype of naturally occurring rotavirus in bivalve shellfish species; including oysters (Saccostrea forskali), cockles (Anadara nodifera), and mussels (Perna viridis). The results demonstrated that an adsorption-twice elution-extraction method was less-time consuming method of concentrating the spiked rotavirus, yielding high sensitivity of 1.14 genome copies/g of digestive tissues from all three shellfish species, as detected using an RT-nested PCR. In seeding experiments, rotavirus as low as 1.39 genome copies was able to be detected in 4 g of digestive tissues or per sample. In the period of August 2011 to July 2012, of the 300 bivalve shellfish samples collected and tested, 24 (8.0%) were found to be contaminated with rotavirus, the figures being: oysters, 13/100 samples; mussels, 10/100 samples; and cockles, 1/100 samples. By DNA sequencing of the RT-nested PCR products and phylogenetic analysis, the rotaviruses detected were classified into G1, lineage II (4 samples); G3 (10 samples): lineage I (3 samples), lineage IIIc (3 samples), lineage IIId (3 samples), lineage IV (1 sample); G9 (6 samples); and G12, lineage III (1 sample). These findings suggest that this virus concentration method provides high sensitivity for the detection of rotavirus from the three bivalve shellfish species. The prevalence of rotavirus and the identified genotypes contribute to the molecular epidemiology of rotavirus in different shellfish species.

Molecular epidemiology and genetic evolution of the whole genome of G3P[8] human rotavirus in Wuhan, China, from 2000 through 2013

BACKGROUND

Rotaviruses are a major etiologic agent of gastroenteritis in infants and young children worldwide. Since the latter of the 1990s, G3 human rotaviruses referred to as "new variant G3" have emerged and spread in China, being a dominant genotype until 2010, although their genomic evolution has not yet been well investigated.

METHODS

The complete genomes of 33 G3P[8] human rotavirus strains detected in Wuhan, China, from 2000 through 2013 were analyzed. Phylogenetic trees of concatenated sequences of all the RNA segments and individual genes were constructed together with published rotavirus sequences.

RESULTS

Genotypes of 11 gene segments of all the 33 strains were assigned to G3-P[8]-I1-R1-C1-M1-A1-N1-T1-E1-H1, belonging to Wa genogroup. Phylogenetic analysis of the concatenated full genome sequences indicated that all the modern G3P[8] strains were assigned to Cluster 2 containing only one clade of G3P[8] strains in the US detected in the 1970s, which was distinct from Cluster 1 comprising most of old G3P[8] strains. While main lineages of all the 11 gene segments persisted during the study period, different lineages appeared occasionally in RNA segments encoding VP1, VP4, VP6, and NSP1-NSP5, exhibiting various allele constellations. In contrast, only a single lineage was detected for VP7, VP2, and VP3 genes. Remarkable lineage shift was observed for NSP1 gene; lineage A1-2 emerged in 2007 and became dominant in 2008-2009 epidemic season, while lineage A1-1 persisted throughout the study period.

CONCLUSION

Chinese G3P[8] rotavirus strains have evolved since 2000 by intra-genogroup reassortment with co-circulating strains, accumulating more reassorted genes over the years. This is the first large-scale whole genome-based study to assess the long-term evolution of common human rotaviruses (G3P[8]) in an Asian country.

Rotavirus associated gastroenteritis in Thailand

Group A rotavirus is the leading cause of severe diarrhea in infants and young children, and in young animals of many species worldwide. Rotavirus is also the major cause of deaths of children younger than 5 years of age, particularly, in developing countries in Asia and Africa. In Thailand, the burden of rotavirus infection rate in children admitted to the hospitals with acute gastroenteritis ranged from 28.4 to 44.5 %. The seasonality of rotavirus gastroenteritis in Thailand was detected all-year-round with the peak from November to April of the following year. The distributions of G genotypes in pediatric patients during twelve-year surveillances of 2000-2011 were G1, G2, G3, G4, G9, and G12. The G9 was detected as the most predominant genotype in 2000-2004 while G1 and G3 were predominated in 2005-2009 and 2009-2011, respectively. The G4 was detected only in 2001-2003 and G12 only in 2007-2009 but was not detectable in any other years of surveillances. For P genotype, P[8] was the only P genotype that always existed as the most predominant with high prevalence. The G-P combination of human rotavirus strains circulated in Thailand were G1P[8], G2P[4], G2P[8], G3P[3], G3P[8], G3P[9], G3P[10], G3P[19], G9P[8], G12P[6], and G12P[8]. The G1P[8] was the most predominant strain followed by G9P[8], G2P[4], G3P[8], G12P[8], G3P[9], G3P[10], G3P[3], G2P[8], G3P[19], and G12P[6]. The studies of animal rotaviruses were performed mainly on porcine rotaviruses and a wide variety of porcine rotavirus strains have been reported, including G2P[27], G3P[6], G3P[13], G3P[19], G3P[23], G4P[6], G4P[13], G4P[19], G4P[23], G5P[6], G5P[13], G9P[7], G9P[13], and G9P[19]. Several unusual strains of human rotaviruses that carried the genes with nucleotide sequences closely related to those of animal rotaviruses have been described in Chiang Mai, Thailand which provided evidences for interspecies transmission of rotaviruses between humans and animals, and also animals to animals are occurring in nature.

Genetic diversity of rotavirus strains circulating in environmental water and bivalve shellfish in Thailand

Rotavirus is a common cause of acute diarrhea in young children worldwide. This study investigated the prevalence and molecular characterization of rotavirus in environmental water and oyster samples in Thailand. A total of 114 water samples and 110 oyster samples were collected and tested for group A rotavirus using RT-nested PCR. Rotavirus genotype was identified by phylogenetic analysis of the VP7 genetic sequences. Group A rotavirus was detected in 21 water samples (18.4%) and six oyster samples (5.4%). Twenty five rotavirus strains were successfully sequenced and classified into four genotypes; G1, G2, G3, and G9. Rotavirus G1 (three strains), G2 (three strains), and G9 (two strains) demonstrated the genetic sequences similar to human strains (90%-99% nucleotide identity), whereas G3 (17 strains) was closely related to animal strains (84%-98% nucleotide identity). G1 strains belonged to lineages I (sub-lineage c) and II. G2 strains belonged to lineage II. G9 strains belonged to lineages III (sub-lineage b) and IV. G3 strains belonged to lineages I, III (sub-lineage c), and IV with a predominance of lineage I. The present study provides important information on the rotavirus strains circulating in the environment.

Complete genotype constellation of human rotavirus group A circulating in Thailand, 2008-2011

This study has identified diverse and re-assorted group A rotavirus (RVA) strains by sequence and phylogenetic analysis of the 11 genomic segments. The 22 cases investigated in this study were collected from children with diarrhea between 2008 and 2011. The RVA genomic constellations identified in this study were identified as G1-P[8]-I1-R1-C1-M1-A1-N1-T1-E1-H1 22.7% (5/22); G2-P[4]-I2-R2-C2-M2-A2-N2-T2-E2-H2 27.3% (6/22); G3-P[8]-I1-R1-C1-M1-A1-N1-T1-E1-H1 18.2% (4/22); G3-P[9]-I3-R3-C3-M3-A3-N3-T3-E3-H6 4.6% (1/22); G9-P[8]-I1-R1-C1-M1-A1-N1-T1-E1-H1 9.1% (2/22); G12-P[6]-I1-R1-C1-M1-A1-N1-T1-E1-H1 4.6% (1/22) and G12-P[8]-I1-R1-C1-M1-A1-N1-T1-E1-H1 13.6% (3/22). Two RVA strains, possessing a complete AU-1-like genomic backbone, showed re-assortment for genes 3 and 11, revealing possible zoonotic re-assortment events between human and canine strains. In addition, one of the analyzed strains revealed a G12 specificity for VP7 in combination with a porcine-like P[6] VP4 and a complete Wa-like constellation. Continuous surveillance of rotavirus strains and their evolution may be useful for understanding the emergence of novel strains through interspecies genome re-assortment between human and animal viruses.

Diversity and relationships of cocirculating modern human rotaviruses revealed using large-scale comparative genomics

Group A rotaviruses (RVs) are 11-segmented, double-stranded RNA viruses and are primary causes of gastroenteritis in young children. Despite their medical relevance, the genetic diversity of modern human RVs is poorly understood, and the impact of vaccine use on circulating strains remains unknown. In this study, we report the complete genome sequence analysis of 58 RVs isolated from children with severe diarrhea and/or vomiting at Vanderbilt University Medical Center (VUMC) in Nashville, TN, during the years spanning community vaccine implementation (2005 to 2009). The RVs analyzed include 36 G1P[8], 18 G3P[8], and 4 G12P[8] Wa-like genogroup 1 strains with VP6-VP1-VP2-VP3-NSP1-NSP2-NSP3-NSP4-NSP5/6 genotype constellations of I1-R1-C1-M1-A1-N1-T1-E1-H1. By constructing phylogenetic trees, we identified 2 to 5 subgenotype alleles for each gene. The results show evidence of intragenogroup gene reassortment among the cocirculating strains. However, several isolates from different seasons maintained identical allele constellations, consistent with the notion that certain RV clades persisted in the community. By comparing the genes of VUMC RVs to those of other archival and contemporary RV strains for which sequences are available, we defined phylogenetic lineages and verified that the diversity of the strains analyzed in this study reflects that seen in other regions of the world. Importantly, the VP4 and VP7 proteins encoded by VUMC RVs and other contemporary strains show amino acid changes in or near neutralization domains, which might reflect antigenic drift of the virus. Thus, this large-scale, comparative genomic study of modern human RVs provides significant insight into how this pathogen evolves during its spread in the community.