Heterogeneity and temporal dynamics of evolution of G1 human rotaviruses in a settled population

Genetic characterization of rotavirus A strains circulating in children under 5 years of age with acute gastroenteritis in Tehran, Iran, in 2023-2024: dissemination of the emerging equine-like G3P[8]-I2-E2 DS-1-like strains

The present study was conducted to monitor the genotype diversity of circulating species A rotavirus (RVA) in Iran. A total of 300 faecal specimens were collected from children under 5 years of age hospitalized for acute gastroenteritis between October 2023 and October 2024. G3P[8] represented 72.91% (70/96) of all RVA-positive samples, further subdivided into equine-like G3P[8]-I2-E2 DS-1-like and human G3P[8]-I1-E1 Wa-like. A retrospective genetic analysis of G3P[8] strains isolated from 2015 to 2017 was also performed and showed that G3P[8] strains belong to the G3P[8]-E1-I1 Wa-like genetic pattern, which is typically similar to human G3P[8] Wa-like strains in this study. The emergence of equine-like G3P[8] DS-1-like strains in Iran may not be related to selection pressure from rotavirus vaccination, but rather to cross-border migration of rotavirus strains due to population movements.

Epidemiological, molecular, and evolutionary characteristics of G1P[8] rotavirus in China on the eve of RotaTeq application

Introduction

This study, conducted in China prior to RotaTeq's launch, examined the epidemiological, molecular, and evolutionary features of the G1P[8] genotype RVA in children admitted with diarrhea, to aid in evaluating its efficacy and impact on G1P[8] RVA in China.

Methods

Data from the Chinese viral diarrhea surveillance network were collected from January 2016 to December 2018. RVA strains identified as the G1P[8] genotype were subjected to whole-genome sequencing. Neutralizing epitope, amino acid selection pressure, and evolution dynamics analyses on VP7 and VP4 were performed using BioEdit v.7.0.9.0 and PyMOL v.2.5.2, four algorithms (MEME, SLAC, FEL, and FUBAR) in the Datamonkey online software, and the MCMC model in BEAST v. 1.10.4, respectively. Phylogenetic and identity features of 11 genes were assessed by DNAStar and MEGA v.7.

Results

Results showed that the detection rate of G1P[8] in China from 2016 to 2018 was generally low with significant seasonality. The whole genome of G1P[8] of four 2016 childhood diarrhea specimens was successfully sequenced. Phylogenetic and neutralizing epitope analysis showed that Rotavin-M1 might have better protection on G1P[8] prevalent in China than Rotarix and RotaTeq. Two conserved N-glycosylation sites on VP7 of Chinese G1P[8] might affect the protective effect of the vaccine. Evolution rate and selection pressure analysis identified the possibility of rapidly evolving and adapting to the new environment introduced by vaccines of G1P[8], whereas positive selection specific to VP4 indicated the potential tendency to select for dominant traits. Identity and phylogeny analysis showed that Chinese G1P[8] from before 2018 was generally stable with possible genetic recombination among local strains.

Discussion

These findings not only are of great significance for predicting the prevalence of G1P [8] in China, but also provide data reference for evaluating rotavirus vaccine efficacy.

Circulating rotavirus strains in children with acute gastroenteritis in Iran, 1986 to 2023 and their genetic/antigenic divergence compared to approved vaccines strains (Rotarix, RotaTeq, ROTAVAC, ROTASIIL) before mass vaccination: Clues for vaccination policy makers

In the present study, first, rotaviruses that caused acute gastroenteritis in children under five years of age during the time before the vaccine was introduced in Iran (1986 to 2023) are reviewed. Subsequently, the antigenic epitopes of the VP7 and VP4/VP8 proteins in circulating rotavirus strains in Iran and that of the vaccine strains were compared and their genetic differences in histo-blood group antigens (HBGAs) and the potential impact on rotavirus infection susceptibility and vaccine efficacy were discussed. Overall data indicate that rotavirus was estimated in about 38.1 % of samples tested. The most common genotypes or combinations were G1 and P[8], or G1P[8]. From 2015 to 2023, there was a decline in the prevalence of G1P[8], with intermittent peaks of genotypes G3P[8] and G9P[8]. The analyses suggested that the monovalent Rotarix vaccine or monovalent vaccines containing the G1P[8] component might be proper in areas with a similar rotavirus genotype pattern and genetic background as the Iranian population where the G1P[8] strain is the most predominant and has the ability to bind to HBGA secretors. While the same concept can be applied to RotaTeq and RotasIIL vaccines, their complex vaccine technology, which involves reassortment, makes them less of a priority. The ROTASIIL vaccine, despite not having the VP4 arm (P[5]) as a suitable protection option, has previously shown the ability to neutralize not only G9-lineage I strains but also other G9-lineages at high titers. Thus, vaccination with the ROTASIIL vaccine may be more effective in Iran compared to RotaTeq. However, considering the rotavirus genotypic pattern, ROTAVAC might not be a good choice for Iran. Overall, the findings of this study provide valuable insights into the prevalence of rotavirus strains and the potential effectiveness of different vaccines in the Iranian and similar populations.

Immunogenicity of a Rotavirus VP8* Multivalent Subunit Vaccine in Mice

Rotavirus remains a significant public health threat, especially in low-income countries, where it is the leading cause of severe acute childhood gastroenteritis, contributing to over 128,500 deaths annually. Although the introduction of the Rotarix and RotaTeq vaccines in 2006 marked a milestone in reducing mortality rates, approximately 83,158 preventable deaths persisted, showing ongoing challenges in vaccine accessibility and effectiveness. To address these issues, a novel subcutaneous vaccine formulation targeting multiple rotavirus genotypes has been developed. This vaccine consists of nine VP8* proteins from nine distinct rotavirus genotypes and sub-genotypes (P[4], P[6], P[8]LI, P[8]LIII, P[8]LIV, P[9], P[11], P[14], and P[25]) expressed in E. coli. Two groups of mice were immunized either with a single immunogen, the VP8* from the rotavirus Wa strain (P[8]LI), or with the nonavalent formulation. Preliminary results from mouse immunization studies showed promising outcomes, eliciting antibody responses against six of the nine immunogens. Notably, significantly higher antibody titers against VP8* P[8]LI were observed in the group immunized with the nonavalent vaccine compared to mice specifically immunized against this genotype alone. Overall, the development of parenteral vaccines targeting multiple rotavirus genotypes represents a promising strategy in mitigating the global burden of rotavirus-related morbidity and mortality, offering new avenues for disease prevention and control.

Whole-genome analysis of human group A rotaviruses in 1980s Japan and evolutionary assessment of global Wa-like strains across half a century

Historically, the Wa-like strains of human group A rotavirus (RVA) have been major causes of gastroenteritis. However, since the 2010s, the circulation of non-Wa-like strains has been increasingly reported, indicating a shift in the molecular epidemiology of RVA. Although understanding RVA evolution requires the analysis of both current and historical strains, comprehensive pre-1980's sequencing data are scarce globally. We determined the whole-genome sequences of representative strains from six RVA gastroenteritis outbreaks observed at an infant home in Sapporo, Japan, between 1981 and 1989. These outbreaks were mainly caused by G1 or G3 Wa-like strains, resembling strains from the United States in the 1970s-1980s and from Malawi in the 1990s. Phylogenetic analysis of these infant home strains, together with Wa-like strains collected worldwide from the 1970s to 2020, revealed a notable trend: pre-2010 strains diverged into multiple lineages in many genomic segments, whereas post-2010 strains tended to converge into a single lineage. However, Bayesian skyline plot indicated near-constant effective population sizes from the 1970s to 2020, and selection pressure analysis identified positive selection only at amino acid 75 of NSP2. These results suggest that evidence supporting the influence of rotavirus vaccines, introduced globally since 2006, on Wa-like RVA molecular evolution is lacking at present, and phylogenetic analysis may simply reflect natural fluctuations in RVA molecular evolution. Evaluating the long-term impact of RV vaccines on the molecular evolution of RVA requires sustained surveillance.

Wa-VP4* as a candidate rotavirus vaccine induced homologous and heterologous virus neutralizing antibody responses in mice, pigs, and cynomolgus monkeys

Group A rotavirus (RVA) is the primary etiological agent of acute gastroenteritis (AGE) in children under 5 years of age. Despite the global implementation of vaccines, rotavirus infections continue to cause over 120,000 deaths annually, with a majority occurring in developing nations. Among infants, the P[8] rotavirus strain is the most prevalent and can be categorized into four distinct lineages. In this investigation, we expressed five VP4(aa26-476) proteins from different P[8] lineages of human rotavirus in E. coli and assessed their immunogenicity in rabbits. Among the different P[8] strains, the Wa-VP4 protein, derived from the MT025868.1 strain of the P[8]-1 lineage, exhibited successful purification in a highly homogeneous form and significantly elicited higher levels of neutralizing antibodies (nAbs) against both homologous and heterologous rotaviruses compared to other VP4 proteins derived from different P[8] lineages in rabbits. Furthermore, we assessed the immunogenicity of the Wa-VP4 protein in mice, pigs, and cynomolgus monkeys, observing that it induced robust production of nAbs in all animals. Interestingly, there was no significant difference between in nAb titers against homologous and heterologous rotaviruses in pigs and mankeys. Collectively, these findings suggest that the Wa-VP4* protein may serve as a potential candidate for a rotavirus vaccine.

Identification of a novel intra-genotype reassortant G1P[8] rotavirus in Italy, 2021

OBJECTIVES

Rotaviruses G1P[8] are epidemiologically relevant and are targeted by vaccines. The introduction of vaccines has altered rotavirus epidemiology. Hospital-based surveillance conducted in Sicily, Italy, showed a progressive decline in rotavirus prevalence since 2014, along with an increasing vaccine coverage (63.8% in 2020), and a marked decrease in circulation of G1P[8] strains. Surprisingly in 2021, G1P[8] viruses accounted for 90.5% (19/21) of rotavirus infections. This study aimed to understand if the increased activity of G1P[8]'s was related to virus-related peculiarities.

DESIGN

In 2021, 266 patients <15 years of age were hospitalized with acute gastroenteritis (AGE) and included in rotavirus surveillance. Viral proteins (VP7 and VP4) genotyping and sequence data were generated from all rotavirus-positive samples. The genetic makeup of G1P[8] rotaviruses was investigated by full-genome sequencing.

RESULTS

Peculiar G1P[8] rotaviruses, with VP7 and VP4 belonging to novel sub-lineages, circulated in 2021, accounting for 76.2% (16/21) of all rotavirus infections. On full-genome analysis, the novel G1P[8] variant displayed an intra-genotype (Wa-like) reassortant constellation, involving G12 and G1 strains, into a unique arrangement never observed before. The novel G1P[8] variant showed peculiar amino acid substitutions in 8-1 and 8-3 epitopes of the VP4 with respect to the Rotarix strain.

CONCLUSIONS

Prompt identification of virus variants circulating in the human population is pivotal to understanding epidemiological trends and assessing vaccine efficacy.

Genetic diversity and Genomic analysis of G3P[6] and equine-like G3P[8] in Children Under-five from Southern Highlands and Eastern Tanzania

Rotavirus group A genomic characterization is critical for understanding the mechanisms of rotavirus diversity, such as reassortment events and possible interspecies transmission. However, little is known about the genetic diversity and genomic relationship of the rotavirus group A strains circulating in Tanzania. The genetic and genomic relationship of RVA genotypes was investigated in children under the age of five. A total of 169 faecal samples were collected from under-five with diarrhea in Mbeya, Iringa and Morogoro regions of Tanzania. The RVA were screened in children under five with diarrhea using reverse transcription PCR for VP7 and VP4, and the G and P genotypes were determined using Sanger dideoxynucleotide cycle sequencing. Whole-genome sequencing was performed on selected genotypes. The overall RVA rate was 4.7% (8/169). The G genotypes were G3 (7/8) and G6 (1/8) among the 8 RVA positives, while the P genotypes were P[6] (4/8) and P[8] (2), and the other two were untypeable. G3P[6] and G3P[8] were the identified genotype combinations. The genomic analysis reveals that the circulating G3P[8] and G3P[6] isolates from children under the age of five with diarrhea had a DS-1-like genome configuration (I2-R2-C2-M2-Ax-N2-T2-E2-H2). The phylogenic analysis revealed that all 11 segments of G3P[6] were closely related to human G3P[6] identified in neighboring countries such as Uganda, Kenya, and other African countries, implying that G3P[6] strains descended from a common ancestor. Whereas, G3P[8] were closely related to previously identified equine-like G3P[P8] from Kenya, Japan, Thailand, Brazil, and Taiwan, implying that this strain was introduced rather than reassortment events. We discovered amino acid differences at antigenic epitopes and N-linked glycosylation sites between the wild type G3 and P[8] compared to vaccine strains, implying that further research into the impact of these differences on vaccine effectiveness is warranted. The phylogenic analysis of VP7 also identified a bovine-like G6. For the first time in Tanzania, we report the emergence of novel equine-like G3 and bovine-like G6 RVA strains, highlighting the importance of rotavirus genotype monitoring and genomic analysis of representative genotypes.

Co-Surveillance of Rotaviruses in Humans and Domestic Animals in Central Uganda Reveals Circulation of Wide Genotype Diversity in the Animals

Rotavirus genotypes are species specific. However, interspecies transmission is reported to result in the emergence of new genotypes. A cross-sectional study of 242 households with 281 cattle, 418 goats, 438 pigs, and 258 humans in Uganda was undertaken between 2013 and 2014. The study aimed to determine the prevalence and genotypes of rotaviruses across co-habiting host species, as well as potential cross-species transmission. Rotavirus infection in humans and animals was determined using NSP3 targeted RT-PCR and ProSpecT Rotavirus ELISA tests, respectively. Genotyping of rotavirus-positive samples was by G- and P-genotype specific primers in nested RT-PCR assays while genotyping of VP4 and VP7 proteins for the non-typeable human positive sample was done by Sanger sequencing. Mixed effect logistic regression was used to determine the factors associated with rotavirus infection in animals. The prevalence of rotavirus was 4.1% (95% CI: 3.0–5.5%) among the domestic animals and 0.8% (95% CI: 0.4–1.5%) in humans. The genotypes in human samples were G9P[8] and P[4]. In animals, six G-genotypes, G3(2.5%), G8(10%), G9(10%), G11(26.8%), G10(35%), and G12(42.5%), and nine P-genotypes, P[1](2.4%), P[4](4.9%), P[5](7.3%), P[6](14.6%), P[7](7.3%), P[8](9.8%), P[9](9.8%), P[10](12.2%), and P[11](17.1%), were identified. Animals aged 2 to 18 months were less likely to have rotavirus infection in comparison with animals below 2 months of age. No inter-host species transmission was identified.

Rotavirus Strain Trends in United States, 2009-2016: Results from the National Rotavirus Strain Surveillance System (NRSSS)

Before the introduction of vaccines, group A rotaviruses (RVA) were the leading cause of acute gastroenteritis in children worldwide. The National Rotavirus Strain Surveillance System (NRSSS) was established in 1996 by the Centers for Disease Control and Prevention (CDC) to perform passive RVA surveillance in the USA. We report the distribution of RVA genotypes collected through NRSSS during the 2009-2016 RVA seasons and retrospectively examine the genotypes detected through the NRSSS since 1996. During the 2009-2016 RVA seasons, 2134 RVA-positive fecal specimens were sent to the CDC for analysis of the VP7 and VP4 genes by RT-PCR genotyping assays and sequencing. During 2009-2011, RVA genotype G3P[8] dominated, while G12P[8] was the dominant genotype during 2012-2016. Vaccine strains were detected in 1.7% of specimens and uncommon/unusual strains, including equine-like G3P[8] strains, were found in 1.9%. Phylogenetic analyses showed limited VP7 and VP4 sequence variation within the common genotypes with 1-3 alleles/lineages identified per genotype. A review of 20 years of NRSSS surveillance showed two changes in genotype dominance, from G1P[8] to G3P[8] and then G3P[8] to G12P[8]. A better understanding of the long-term effects of vaccine use on epidemiological and evolutionary dynamics of circulating RVA strains requires continued surveillance.

Genotype Distribution and Evolutionary Analysis of Rotavirus Associated with Acute Diarrhea Outpatients in Hubei, China, 2013–2016

Group A human rotaviruses (RVAs) annually cause the deaths of 215,000 infants and young children. To understand the epidemiological characteristics and genetic evolution of RVAs, we performed sentinel surveillance on RVA prevalence in a rotavirus-surveillance network in Hubei, China. From 2013 to 2016, a total of 2007 fecal samples from hospital outpatients with acute gastroenteritis were collected from four cities of Hubei Province. Of the 2007 samples, 153 (7.62%) were identified positive for RVA by real-time RT-PCR. RVA infection in Hubei mainly occurred in autumn and winter. The highest detection rate of RVA infection was in 1–2 years old of outpatients (16.97%). No significant difference of RVA positive rate was observed between females and males. We performed a phylogenetic analysis of the G/P genotypes based on the partial VP7/VP4 gene sequences of RVAs. G9P[8] was the most predominant strain in all four years but the prevalence of G2P[4] genotype increased rapidly since 2014. We reconstructed the evolutionary time scale of RVAs in Hubei, and found that the evolutionary rates of the G9, G2, P[8], and P[4] genotypes of RVA were 1.069 ​× ​10⁻³, 1.029 ​× ​10⁻³, 1.283 ​× ​10⁻³ and 1.172 ​× ​10⁻³ nucleotide substitutions/site/year, respectively. Importantly, using a molecular clock model, we showed that most G9, G2, P[8], and P[4] genotype strains dated from the recent ancestor in 2005, 2005, 1993, and 2013, respectively. The finding of the distribution of RVAs in infants and young children in Hubei Province will contribute to the understanding of the epidemiological characteristics and genetic evolution of RVAs in China.

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A four-year study of sentinel surveillance program of RVAs was performed in Hubei, China.

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The key population of rotavirus infection is 1–2 years old of outpatients with acute gastroenteritis.

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G9P[8] was the most predominant strain between 2013 and 2016.

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The estimating time to the most recent common ancestor for the G9 genotype based on partial VP7 gene was 46 years.

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RVA distribution in Hubei Province contributes to the understanding of the epidemiological characteristics of RVAs in China.

Genetic characterization of P[8] rotavirus strains circulated in Iran between 2009 and 2017

Group A rotavirus (RVA) is the most common cause of acute gastroenteritis (AGE) worldwide, which is responsible for causing an estimated 120,000 deaths in children under 5 years of age, which mostly occur in the lower income countries of Asia and Africa. The G1P[8] is a common genotype of RVA that has spread throughout the world, including Iran and this genotype is present in two commonly used RVA vaccines, Rotarix^TM and RotaTeq^TM . In this study, we investigated the genetic diversity, viral evolutionary, and differences between antigenic epitopes of Iran's P[8] strains and two licensed vaccines. The phylogenetic and evolutionary analysis was carried out, using MEGA vs 6.0 and BEAST respectively. Antigenic epitopes of VP8* were compared to determine the differences between strains from Iran and Rotarix^TM and RotaTeq^TM . The P[8]-lineages III and IV was found as the predominant P genotype that circulating in Iran. The TMRCA of P[8]-lineages III and IV was estimated at 1987 and 2009 respectively. The P[8]-lineage III strains showed 12 amino acid changes compared to Rotarix^TM and 10 amino acid changes compared to RotaTeq^TM . The P[8]-lineage IV strains showed 10 amino acid variations for both Rotarix^TM and RotaTeq^TM strains. The results revealed that the P[8] strains circulating in Iran differs from Rotarix^TM and RotaTeq^TM strains. To monitor the long-term effects of vaccines on the emergence of P[8] strains with different lineages, routine and successful monitoring of these strains will be crucial. This article is protected by copyright. All rights reserved.

Impact of Vaccination on Rotavirus Genotype Diversity: A Nearly Two-Decade-Long Epidemiological Study before and after Rotavirus Vaccine Introduction in Sicily, Italy

Sicily was the first Italian region to introduce rotavirus (RV) vaccination with the monovalent G1P[8] vaccine Rotarix® in May 2012. In this study, the seasonal distribution and molecular characterization of RV strains detected over 19 years were compared to understand the effect of Rotarix® on the evolutionary dynamics of human RVs. A total of 7846 stool samples collected from children < 5 years of age, hospitalized with acute gastroenteritis, were tested for RV detection and genotyping. Since 2013, vaccine coverage has progressively increased, while the RV prevalence decreased from 36.1% to 13.3% with a loss of seasonality. The local distribution of RV genotypes changed over the time possibly due to vaccine introduction, with a drastic reduction in G1P[8] strains replaced by common and novel emerging RV strains, such as equine-like G3P[8] in the 2018−2019 season. Comparison of VP7 and VP4 amino acid (aa) sequences with the cognate genes of Rotarix® and RotaTeq® vaccine strains showed specific aa changes in the antigenic epitopes of VP7 and of the VP8* portion of VP4 of the Italian RV strains. Molecular epidemiological surveillance data are required to monitor the emergence of novel RV strains and ascertain if these strains may affect the efficacy of RV vaccines.

Evolutionary analysis of rotavirus G1P[8] strains from Chennai, South India

Rotaviruses by virtue of its segmented genome generate numerous genotypes. G1P[8] is the most common genotype reported globally. We intend to identify the evolutionary differences among G1P[8] strains from the study with vaccine strains. Stool samples collected from children <5 years were screened for rotavirus antigen by enzyme linked immunosorbent assay. The samples that tested positive for rotavirus were subjected to VP7 and VP4 semi-nested RT-PCR. Sanger sequencing was performed in randomly chosen VP7 and VP4 rotavirus strains. Phylogenetic analysis showed less homology between study strains and vaccine strains and they were placed in different lineages. The VP7 and VP4 proteins of rotavirus were analyzed by two different platforms to identify the amino acid substitutions in the epitope regions. Nine amino acid substitutions with respect to Rotarix®, RotaTeq® and Rotasiil®-V66A, A/T68S, Q72R, N94S, D100E, T113I, S123N, M217T, and I281T were observed in VP7. There were five amino acid substitutions-S145G, N/D195G, N113D, N/I78T, E150D in VP4 (VP8 portion) with respect to Rotarix® and RotaTeq® vaccine strains. M217T substitution in VP7 (epitope 7-2) and N113D, D195G substitution in VP4 (epitope 8-3, 8-1) confer changes in polarity/electrical charge with respect to vaccine strains, thus indicating the need for continued surveillance.

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.

Unexpected Role of Rotavirus G3P[8] Infection in Causing Severe Diarrhea in a Major Tertiary Referral Hospital in the Prevaccine Era

Background: Rotavirus A species is associated with severe gastroenteritis in children. Rotavirus G1P[8] was the most prevalent genotype found in Kuwait in a study conducted between 2005 and 2006. The RotaTeq vaccine was included in the Kuwait national immunization program at the end of 2017. Objectives: Since there is no available data on the rotavirus genotypes circulating before the introduction of the vaccine, we conducted a study to investigate the role of rotaviruses in causing severe diarrhea in children hospitalized in a major tertiary referral hospital in Kuwait during the year 2016. Methods: Viral RNA was isolated from the stool samples of 101 children under five years of age, hospitalized for acute gastroenteritis. Rotavirus VP4 and VP7 dsRNA were detected by RT-PCR, and their partial sequences were analyzed by phylogenic analysis. Results: Rotavirus dsRNA was detected in 24.7% of children with median age of 1 year. The genotype G3P[8] accounted for 47% of cases, followed by G1P[8] (26%), G9P[8] (10.5%), G4P[8] (10.5%), and G9P[4] (5%). Only VP7 nucleotide sequences of rotavirus G3 or G4 type clustered in the same lineage as RotaTeq vaccine, while most VP4 nucleotide sequences of rotavirus P[8] type clustered in a different lineage compared to Rotarix and RotaTeq vaccines. Conclusions: Our findings highlight the role of rotavirus G3P[8] in causing severe diarrhea and invites future investigations to know whether the recent introduction of RotaTeq vaccine in Kuwait selects certain genotypes and subgenomic lineages.

Emergence in 2017-2019 of novel reassortant equine-like G3 rotavirus strains in Palermo, Sicily

Rotavirus A (RVA) is a major etiologic agent of gastroenteritis in children worldwide. Hospital-based surveillance of viral gastroenteritis in paediatric population in Palermo (Italy) from 2017 onwards revealed a sharp increase in G3P[8] RVAs, accounting for 71% of all the RVAs detected in 2019. This pattern had not been observed before in Italy, with G3 RVA usually being detected at rates lower than 3%. In order to investigate this unique epidemiological pattern, the genetic diversity of G3 RVAs identified during a 16-year long surveillance (2004-2019) was explored by systematic sequencing of the VP7 and VP4 genes and by whole genome sequencing of selected G3 strains, representative of the various RVA seasons. Sequence and phylogenetic analyses of the VP7 and VP4 genes revealed the emergence, in 2017 of reassortant equine-like G3P[8], which gradually replaced former G3P[8] strains. The G3P[8] circulating before 2017 showed a Wa-like constellation of genome segments while the G3P[8] that emerged in 2017 had a DS-1-like backbone. On direct inspection of the VP7 and VP4 antigenic epitopes, the equine-like G3P[8] strains possessed several amino acid variations in neutralizing regions compared with vaccine strains. The equine-like G3P[8] RVAs are a further example of the zoonotic impact of animal viruses on human health.

The Rotavirus Vaccine Landscape, an Update

Rotavirus is the leading cause of severe acute childhood gastroenteritis, responsible for more than 128,500 deaths per year, mainly in low-income countries. Although the mortality rate has dropped significantly since the introduction of the first vaccines around 2006, an estimated 83,158 deaths are still preventable. The two main vaccines currently deployed, Rotarix and RotaTeq, both live oral vaccines, have been shown to be less effective in developing countries. In addition, they have been associated with a slight risk of intussusception, and the need for cold chain maintenance limits the accessibility of these vaccines to certain areas, leaving 65% of children worldwide unvaccinated and therefore unprotected. Against this backdrop, here we review the main vaccines under development and the state of the art on potential alternatives.

Comparative genomic analysis of genogroup 1 and genogroup 2 rotaviruses circulating in seven US cities, 2014-2016

For over a decade, the New Vaccine Surveillance Network (NVSN) has conducted active rotavirus (RVA) strain surveillance in the USA. The evolution of RVA in the post-vaccine introduction era and the possible effects of vaccine pressure on contemporary circulating strains in the USA are still under investigation. Here, we report the whole-gene characterization (eleven ORFs) for 157 RVA strains collected at seven NVSN sites during the 2014 through 2016 seasons. The sequenced strains included 52 G1P[8], 47 G12P[8], 18 G9P[8], 24 G2P[4], 5 G3P[6], as well as 7 vaccine strains, a single mixed strain (G9G12P[8]), and 3 less common strains. The majority of the single and mixed strains possessed a Wa-like backbone with consensus genotype constellation of G1/G3/G9/G12-P[8]-I1-R1-C1-M1-A1-N1-T1-E1-H1, while the G2P[4], G3P[6], and G2P[8] strains displayed a DS-1-like genetic backbone with consensus constellation of G2/G3-P[4]/P[6]/P[8]-I2-R2-C2-M2-A2-N2-T2-E2-H2. Two intergenogroup reassortant G1P[8] strains were detected that appear to be progenies of reassortment events between Wa-like G1P[8] and DS-1-like G2P[4] strains. Two Rotarix^® vaccine (RV1) and two RV5 derived (vd) reassortant strains were detected. Phylogenetic and similarity matrices analysis revealed 2-11 sub-genotypic allelic clusters among the genes of Wa- and DS-1-like strains. Most study strains clustered into previously defined alleles. Amino acid (AA) substitutions occurring in the neutralization epitopes of the VP7 and VP4 proteins characterized in this study were mostly neutral in nature, suggesting that these RVA proteins were possibly under strong negative or purifying selection in order to maintain competent and actual functionality, but fourteen radical (AA changes that occur between groups) AA substitutions were noted that may allow RVA strains to gain a selective advantage through immune escape. The tracking of RVA strains at the sub-genotypic allele constellation level will enhance our understanding of RVA evolution under vaccine pressure, help identify possible mechanisms of immune escape, and provide valuable information for formulation of future RVA vaccines.

Whole Genome Characterization and Evolutionary Analysis of G1P[8] Rotavirus A Strains during the Pre- and Post-Vaccine Periods in Mozambique (2012-2017)

Mozambique introduced the Rotarix^® vaccine (GSK Biologicals, Rixensart, Belgium) into the National Immunization Program in September 2015. Although G1P[8] was one of the most prevalent genotypes between 2012 and 2017 in Mozambique, no complete genomes had been sequenced to date. Here we report whole genome sequence analysis for 36 G1P[8] strains using an Illumina MiSeq platform. All strains exhibited a Wa-like genetic backbone (G1-P[8]-I1-R1-C1-M1-A1-N1-T1-E1-H1). Phylogenetic analysis showed that most of the Mozambican strains clustered closely together in a conserved clade for the entire genome. No distinct clustering for pre- and post-vaccine strains were observed. These findings may suggest no selective pressure by the introduction of the Rotarix^® vaccine in 2015. Two strains (HJM1646 and HGM0544) showed varied clustering for the entire genome, suggesting reassortment, whereas a further strain obtained from a rural area (MAN0033) clustered separately for all gene segments. Bayesian analysis for the VP7 and VP4 encoding gene segments supported the phylogenetic analysis and indicated a possible introduction from India around 2011.7 and 2013.0 for the main Mozambican clade. Continued monitoring of rotavirus strains in the post-vaccine period is required to fully understand the impact of vaccine introduction on the diversity and evolution of rotavirus strains.

Molecular epidemiology and surveillance of circulating rotavirus among children with gastroenteritis in Bangladesh during 2014-2019

Acute gastroenteritis is one of the major health problems in children aged <5 years around the world. Rotavirus A (RVA) is an important pathogen of acute gastroenteritis. The burden of rotavirus disease in the pediatric population is still high in Bangladesh. This study investigated the prevalence of group A, B, and C rotavirus (RAV, RBV, RCV), norovirus, adenovirus (AdV) and human bocavirus (HBoV) infections in children with acute gastroenteritis in Bangladesh from February 2014 to January 2019. A total of 574 fecal specimens collected from children with diarrhea in Bangladesh during the period of February 2014-January 2019 were examined for RAV, RBV and RCV by reverse transcriptase- multiplex polymerase chain reaction (RT- multiplex PCR). RAV was further characterized to G-typing and P-typing by RT-multiplex PCR and sequencing method. It was found that 24.4% (140 of 574) fecal specimens were positive for RVA followed by AdV of 4.5%. RBV and RCV could not be detected in this study. Genotype G1P[8] was the most prevalent (43%), followed by G2P[4] (18%), and G9P[8] (3%). Among other genotypes, G9P[4] was most frequent (12%), followed by G1P[6] (11%), G9P[6] (3%), and G11P[25] (3%). We found that 7% RVA were nontypeable. Mutations at antigenic regions of the VP7 gene were detected in G1P[8] and G2P[4] strains. Incidence of rotavirus infection had the highest peak (58.6%) during November to February with diarrhea (90.7%) as the most common symptom. Children aged 4-11 months had the highest rotavirus infection percentage (37.9%). By providing baseline data, this study helps to assess efficacy of currently available RVA vaccine. This study revealed a high RVA detection rate, supporting health authorities in planning strategies such as introduction of RVA vaccine in national immunization program to reduce the disease burden.

Whole Genome In-Silico Analysis of South African G1P[8] Rotavirus Strains Before and After Vaccine Introduction Over A Period of 14 Years

Rotavirus G1P[8] strains account for more than half of the group A rotavirus (RVA) infections in children under five years of age, globally. A total of 103 stool samples previously characterized as G1P[8] and collected seven years before and seven years after introducing the Rotarix® vaccine in South Africa were processed for whole-genome sequencing. All the strains analyzed had a Wa-like constellation (G1-P[8]-I1-R1-C1-M1-A1-N1-T1-E1-H1). South African pre- and post-vaccine G1 strains were clustered in G1 lineage-I and II while the majority (84.2%) of the P[8] strains were grouped in P[8] lineage-III. Several amino acid sites across ten gene segments with the exception of VP7 were under positive selective pressure. Except for the N147D substitution in the antigenic site of eight post-vaccine G1 strains when compared to both Rotarix® and pre-vaccine strains, most of the amino acid substitutions in the antigenic regions of post-vaccine G1P[8] strains were already present during the pre-vaccine period. Therefore, Rotarix® did not appear to have an impact on the amino acid differences in the antigenic regions of South African post-vaccine G1P[8] strains. However, continued whole-genome surveillance of RVA strains to decipher genetic changes in the post-vaccine period remains imperative.

Comparative Analysis of G1P[8] Rotaviruses Identified Prior to Vaccine Implementation in Pakistan With Rotarix™ and RotaTeq™ Vaccine Strains

Group A rotavirus (RVA) is the leading cause of severe childhood diarrhea globally, even with all effective interventions, particularly in developing countries. Among the diverse genotypes of RVA, G1P[8] is a common genotype that has continued to pervade around the world, including Pakistan. Two universally accepted rotavirus vaccines-Rotarix™ and RotaTeq™ contain the genotype G1P[8]. The current work was aimed at identifying differences between antigenic epitopes of Pakistan’s G1P[8] strains and those of the two licensed vaccines. We sequenced 6 G1P[8] rotavirus strains previously reported in Rawalpindi, Islamabad, Pakistan in 2015 and 2016 for their outer capsid genes (VP7 and VP4). Phylogenetic analysis was then conducted in order to classify their specific lineages and to detect their association with strains isolated throughout world. Compared with the Rotarix™ and RotaTeq™ vaccine strains (G1-lineage II, P[8]-lineage III), our study G1-lineage I, P[8]-lineage IV strains showed 3 and 5 variations in the VP7 epitopes, respectively, and 13 and 11 variations in the VP4 epitopes, respectively. The G1 lineage II strains showed no single amino acid change compared to Rotarix™ (lineage II), but exhibited changes at 2 positions compared to RotaTeq™ (lineage III). So, this has been proposed that these G1 strains exist in our natural setting, or that they may have been introduced in Pakistan from other countries of the world. The distinct P[8]-lineage IV (OP354-like) strains showed twelve and thirteen amino acid variations, with Rotarix™ and RotaTeq™ (lineages II and III) strains, respectively. Such findings have shown that the VP4-P[8] component of the G1P[8] strains circulating in Pakistan differs considerably from that of the vaccine viruses compared to that of the VP7-G1. To monitor the long-term effects of vaccines on the emergence of G1P[8] strains with different lineages, routine and successful monitoring of these strains will be crucial.

Whole genome and in-silico analyses of G1P[8] rotavirus strains from pre- and post-vaccination periods in Rwanda

Rwanda was the first low-income African country to introduce RotaTeq vaccine into its Expanded Programme on Immunization in May 2012. To gain insights into the overall genetic make-up and evolution of Rwandan G1P[8] strains pre- and post-vaccine introduction, rotavirus positive fecal samples collected between 2011 and 2016 from children under the age of 5 years as part of ongoing surveillance were genotyped with conventional RT-PCR based methods and whole genome sequenced using the Illumina MiSeq platform. From a pool of samples sequenced (n = 158), 36 were identified as G1P[8] strains (10 pre-vaccine and 26 post-vaccine), of which 35 exhibited a typical Wa-like genome constellation. However, one post vaccine strain, RVA/Human-wt/RWA/UFS-NGS:MRC-DPRU442/2012/G1P[8], exhibited a RotaTeq vaccine strain constellation of G1-P[8]-I2-R2-C2-M2-A3-N2-T6-E2-H3, with most of the gene segments having a close relationship with a vaccine derived reassortant strain, previously reported in USA in 2010 and Australia in 2012. The study strains segregated into two lineages, each containing a paraphyletic pre- and post-vaccine introduction sub-lineages. In addition, the study strains demonstrated close relationship amongst each other when compared with globally selected group A rotavirus (RVA) G1P[8] reference strains. For VP7 neutralization epitopes, amino acid substitutions observed at positions T91A/V, S195D and M217T in relation to the RotaTeq vaccine were radical in nature and resulted in a change in polarity from a polar to non-polar molecule, while for the VP4, amino acid differences at position D195G was radical in nature and resulted in a change in polarity from a polar to non-polar molecule. The polarity change at position T91A/V of the neutralizing antigens might play a role in generating vaccine-escape mutants, while substitutions at positions S195D and M217T may be due to natural fluctuation of the RVA. Surveillance of RVA at whole genome level will enhance further assessment of vaccine impact on circulating strains, the frequency of reassortment events under natural conditions and epidemiological fitness generated by such events.

Uncovering the First Atypical DS-1-like G1P[8] Rotavirus Strains That Circulated during Pre-Rotavirus Vaccine Introduction Era in South Africa

Emergence of DS-1-like G1P[8] group A rotavirus (RVA) strains during post-rotavirus vaccination period has recently been reported in several countries. This study demonstrates, for the first time, rare atypical DS-1-like G1P[8] RVA strains that circulated in 2008 during pre-vaccine era in South Africa. Rotavirus positive samples were subjected to whole-genome sequencing. Two G1P[8] strains (RVA/Human-wt/ZAF/UFS-NGS-MRC-DPRU1971/2008/G1P[8] and RVA/Human-wt/ZAF/UFS-NGS-MRC-DPRU1973/2008/G1P[8]) possessed a DS-1-like genome constellation background (I2-R2-C2-M2-A2-N2-T2-E2-H2). The outer VP4 and VP7 capsid genes of the two South African G1P[8] strains had the highest nucleotide (amino acid) nt (aa) identities of 99.6–99.9% (99.1–100%) with the VP4 and the VP7 genes of a locally circulating South African strain, RVA/Human-wt/ZAF/MRC-DPRU1039/2008/G1P[8]. All the internal backbone genes (VP1–VP3, VP6, and NSP1-NSP5) had the highest nt (aa) identities with cognate internal genes of another locally circulating South African strain, RVA/Human-wt/ZAF/MRC-DPRU2344/2008/G2P[6]. The two study strains emerged through reassortment mechanism involving locally circulating South African strains, as they were distinctly unrelated to other reported atypical G1P[8] strains. The identification of these G1P[8] double-gene reassortants during the pre-vaccination period strongly supports natural RVA evolutionary mechanisms of the RVA genome. There is a need to maintain long-term whole-genome surveillance to monitor such atypical strains.

Genetic Diversity of Human Rotavirus A Among Hospitalized Children Under-5 Years in Lebanon

Human rotavirus remains a major cause of gastroenteritis worldwide despite the availability of effective vaccines. In this study, we investigated the genetic diversity of rotaviruses circulating in Lebanon. We genetically characterized the VP4 and VP7 genes encoding the outer capsid proteins of 132 rotavirus-associated gastroenteritis specimens, previously identified in hospitalized children (<5 years) from 2011 to 2013 in Lebanon. These included 43 vaccine-breakthrough specimens and the remainder were from non-vaccinated subjects. Phylogenetic analysis of VP4 and VP7 genes revealed distinct clustering compared to the vaccine strains, and several substitutions were identified in the antigenic epitopes of Lebanese specimens. No unique changes were identified in the breakthrough specimens compared to non-breakthroughs that could explain the occurrence of infection in vaccinated children. Further, we report the emergence of a rare P[8] OP354-like strain with a G9 VP7 in Lebanon, possessing high genetic variability in their VP4 compared to vaccine strains. Therefore, human rotavirus strains circulating in Lebanon and globally have accumulated numerous substitutions in their antigenic sites compared to those currently used in the licensed vaccines. The successful spread and continued genetic drift of these strains over time might undermine the effectiveness of the vaccines. The effect of such changes in the antigenic sites on vaccine efficacy remains to be assessed.

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.

Rotavirus Burden, Genetic Diversity and Impact of Vaccine in Children under Five in Tanzania

In Tanzania, rotavirus infections are responsible for 72% of diarrhea deaths in children under five. The Rotarix vaccine was introduced in early 2013 to mitigate rotavirus infections. Understanding the disease burden and virus genotype trends over time is important for assessing the impact of rotavirus vaccine in Tanzania. When assessing the data for this review, we found that deaths of children under five declined after vaccine introduction, from 8171/11,391 (72% of diarrhea deaths) in 2008 to 2552/7087 (36% of diarrhea deaths) in 2013. Prior to vaccination, the prevalence of rotavirus infections in children under five was 18.1–43.4%, 9.8–51%, and 29–41% in Dar es Salaam, Mwanza and Tanga, respectively, and after the introduction of vaccines, these percentages declined to 17.4–23.5%, 16–19%, and 10–29%, respectively. Rotaviruses in Tanzania are highly diverse, and include genotypes of animal origin in children under five. Of the genotypes, 10%, 28%, and 7% of the strains are untypable in Dar es Salaam, Tanga, and Zanzibar, respectively. Mixed rotavirus genotype infection accounts for 31%, 29%, and 12% of genotypes in Mwanza, Tanga and Zanzibar, respectively. The vaccine effectiveness ranges between 53% and 75% in Mwanza, Manyara and Zanzibar. Rotavirus vaccination has successfully reduced the rotavirus burden in Tanzania; however, further studies are needed to better understand the relationship between the wildtype strain and the vaccine strain as well as the zoonotic potential of rotavirus in the post-vaccine era.

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.

Unraveling the role of the secretor antigen in human rotavirus attachment to histo-blood group antigens

Rotavirus is the leading agent causing acute gastroenteritis in young children, with the P[8] genotype accounting for more than 80% of infections in humans. The molecular bases for binding of the VP8* domain from P[8] VP4 spike protein to its cellular receptor, the secretory H type-1 antigen (Fuc-α1,2-Gal-β1,3-GlcNAc; H1), and to its precursor lacto-N-biose (Gal-β1,3-GlcNAc; LNB) have been determined. The resolution of P[8] VP8* crystal structures in complex with H1 antigen and LNB and site-directed mutagenesis experiments revealed that both glycans bind to the P[8] VP8* protein through a binding pocket shared with other members of the P[II] genogroup (i.e.: P[4], P[6] and P[19]). Our results show that the L-fucose moiety from H1 only displays indirect contacts with P[8] VP8*. However, the induced conformational changes in the LNB moiety increase the ligand affinity by two-fold, as measured by surface plasmon resonance (SPR), providing a molecular explanation for the different susceptibility to rotavirus infection between secretor and non-secretor individuals. The unexpected interaction of P[8] VP8* with LNB, a building block of type-1 human milk oligosaccharides, resulted in inhibition of rotavirus infection, highlighting the role and possible application of this disaccharide as an antiviral. While key amino acids in the H1/LNB binding pocket were highly conserved in members of the P[II] genogroup, differences were found in ligand affinities among distinct P[8] genetic lineages. The variation in affinities were explained by subtle structural differences induced by amino acid changes in the vicinity of the binding pocket, providing a fine-tuning mechanism for glycan binding in P[8] rotavirus.

The interaction of viruses with host glycans has become an important topic in the study of enteric virus infectivity. This interaction modulates several aspects of the viral cycle, including viral attachment, which in most cases depends on the host glycobiology dictated by the secretor and Lewis genotypes. The capacity to synthesize secretory type-I antigen H (fucose-α1,2-galactose-β1,3-N-acetylglucosamine; H1) at the mucosae, dictated by the presence of one or two functional copies of the fucosyl-transferase FUT2 gene (secretor status), has been clearly linked to infectivity in important enteric viruses such as the noroviruses. However, a big controversy existed about the contribution of H1 antigen to infection in the leading cause of viral gastroenteritis in young children (rotavirus). It has not been until recently that epidemiological data evidenced a diminished incidence of rotavirus in non-secretor individuals unable to produce H1. In the present manuscript we offer the evidence that P[8] RV bind H1 via a binding site common for the P[II] RV genogroup and that the H1 precursor lacto-N-biose (galactose-β1,3-N-acetylglucosamine; LNB) is also bound to this pocket with diminished affinity. The P[8] VP8* structures show a marginal role for the L-fucose moiety from H1 in protein interaction. However, its presence provides conformational changes in the LNB moiety that increase the affinity of VP8* for the H1 ligand and would account for a stronger RV binding to mucosa in individuals expressing H1 (secretors). We thus offer a mechanistic explanation for the different incidence of P[8] RV infection in different secretor phenotypes.

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.

Distribution of rotavirus genotypes associated with acute diarrhoea in Zimbabwean children less than five years old before and after rotavirus vaccine introduction

BACKGROUND

Sentinel surveillance for diarrhoea is important to monitor changes in rotavirus epidemiological trends and circulating genotypes among children under 5 years before and after vaccine introduction. The Zimbabwe Ministry of Health and Child Care introduced rotavirus vaccine in national immunization program in May 2014.

METHODS

Active hospital-based surveillance for diarrhoea was conducted at 3 sentinel sites from 2008 to 2016. Children aged less than 5 years, who presented with acute gastroenteritis as a primary illness and who were admitted to a hospital ward or treated at the emergency unit, were enrolled and had a stool specimen collected and tested for rotavirus by enzyme immunoassay (EIA). Genotyping of positive stools was performed using reverse-transcription polymerase chain reaction and genotyping assays. Pre-vaccine introduction, 10% of all positive stool specimens were genotyped and all adequate positive stools were genotyped post-vaccine introduction.

RESULTS

During the pre-vaccine period, a total of 6491 acute gastroenteritis stools were collected, of which 3016 (46%) tested positive for rotavirus and 312 (10%) of the rotavirus positive stools were genotyped. During the post-vaccine period, a total of 3750 acute gastroenteritis stools were collected, of which 937 (25%) tested positive for rotavirus and 784 (84%) were genotyped. During the pre-vaccine introduction the most frequent genotype was G9P[8] (21%) followed by G2P[4] (12%), G1P[8] (6%), G2P[6] (5%), G12P[6] (4%), G9P[6] (3%) and G8P[4] (3%). G1P[8] (30%) was most dominant two years after vaccine introduction followed by G9P[6] (20%), G2P[4] (15%), G9P[8] (11%) and G1P[6] (4%).

CONCLUSION

The decline in positivity rate is an indication of early vaccine impact. Diversity of circulating strains underscores the importance of continued monitoring and strain surveillance after vaccine introduction.

Molecular evolutionary analysis of type-1 human astroviruses identifies putative sites under selection pressure on the capsid protein

Human astroviruses (HAstV) are important enteric pathogens that can be classified into eight sero/genotypes (HAstV-1 to -8). Although the various HAstV types show global spread, type-1 strains tend to be predominant. Molecular analysis of the genomic region encoding the capsid protein (ORF2) has revealed discrete sequence variation, with different lineages within each HAstV type and at least three major lineages have been identified within HAstV-1. Longitudinal epidemiological surveillance has revealed temporal shift of the various HAstV-1 lineages. Metadata analysis of HAstV-1 sequences available in the databases also revealed temporal shifts of the circulation of HAstV-1 lineages, suggesting possible antigenic-related mechanisms of selection at the sub-genotype level. By comparison of HAstV-1 capsid sequences, lineage-defining residues under positive selection were identified. Structural analysis of HAstV-1 capsid allowed identifying at least six residues exposed on the virion surface. Two residues were located in the VP34 (shell region) whilst four residues were mapped in the VP25/27 (protruding region) of HAstV capsid protein, in proximity of the putative receptor binding S site. These findings suggest that mechanisms similar to those observed and/or hypothesized for other enteric viruses are also shaping the evolution of HAstVs, with intra-typic diversification being a possible mechanism to decrease the antigenic pressure to which these viruses are exposed.

Phylogenetic comparison of the VP7, VP4, VP6, and NSP4 genes of rotaviruses isolated from children in Nizhny Novgorod, Russia, 2015-2016, with cogent genes of the Rotarix and RotaTeq vaccine strains

Group A rotaviruses (RVA) are one of the leading causes of gastroenteritis in young children worldwide. The introduction of universal mass vaccination around the world has contributed to a reduction in hospitalizations and outpatient visits associated with rotavirus infection. Continued surveillance of RVA strains is needed to determine long-term effects of vaccine introduction. In the present work, we carried out the analysis of the genotypic diversity of RVA strains isolated in Nizhny Novgorod (Russia) during the 2015-2016 epidemic season. Also we conducted a comparative analysis of the amino acid sequences of T-cell epitopes of wild-type and vaccine (RotaTeq and Rotarix) strains. In total, 1461 samples were examined. RVAs were detected in 30.4% of cases. Rotaviruses with genotype G9P[8] (40.5%) dominated in the 2015-16 epidemic season. Additionally, RVAs with the following genotypes were detected: G4P[8] (25.4%), G1P[8] (13%), G2P[4] (3.2%). Rotaviruses with genotypes G3P[9], G6P[9], and G1P[9] totaled 3%. The number of partially typed and untyped RVA samples was 66 (14.9%). The findings of a RVA of G6P[9] genotype in Russia were an original observation. Our analysis of VP6 and NSP4 T-cell epitopes showed highly conserved amino acid sequences. The found differences seem not to be caused by the immune pressure but were rather related to the genotypic affiliations of the proteins. Vaccination against rotavirus infection is not included in the national vaccination schedule in Russia. Monitoring of the genotypic and antigenic diversity of contemporary RVA will allow providing a comparative analysis of wild-type strains in areas with and without vaccine campaign.

Clinical severity and molecular characteristics of circulating and emerging rotaviruses in young children attending hospital emergency departments in France

Group A rotavirus (RVA) is the leading cause of acute gastroenteritis in young children worldwide. A prospective surveillance network has been set up to investigate the virological and clinical features of RVA infections and to detect the emergence of potentially epidemic strains in France. From 2009 to 2014, RVA-positive stool samples were collected from 4800 children <5 years old attending the paediatric emergency units of 16 large hospitals. Rotaviruses were then genotyped by RT-PCR with regard to their outer capsid proteins VP4 and VP7. Genotyping of 4708 RVA showed that G1P[8] strains (62.2%) were predominant. The incidence of G9P[8] (11.5%), G3P[8] (10.4%) and G2P[4] (6.6%) strains varied considerably, whereas G4P[8] (2.7%) strains were circulating mostly locally. Of note, G12P[8] (1.6%) strains emerged during the seasons 2011-12 and 2012-13 with 4.1% and 3.0% prevalence, respectively. Overall, 40 possible zoonotic reassortants, such as G6 (33.3%) and G8 (15.4%) strains, were detected, and were mostly associated with P[6] (67.5%). Analysis of clinical records of 624 hospitalized children and severity scores from 282 of them showed no difference in clinical manifestations or severity in relation to the genotype. The relative stability of RVA genotypes currently co-circulating and the large predominance of P[8] type strains may ensure vaccine effectiveness in France. The surveillance will continue to monitor the emergence of new reassortants that might not respond to current vaccines, all the more so as all genotypes can cause severe infections in infants.

Phylogenetic inference of the porcine Rotavirus A origin of the human G1 VP7 gene

Rotavirus A (RVA) is an important cause of acute gastroenteritis in children worldwide. The most common VP7 genotype of human RVA is G1, but G1 is rarely detected in porcine strains. To understand the evolutionary relationships between human and porcine G1 VP7 genes, we sequenced the VP7 genes of three Japanese G1 porcine strains; the first two (PRV2, S80B) were isolated in 1980 and the third (Kyusyu-14) was isolated in 2001. Then, we performed phylogenetic and in-silico structural analyses. All three VP7 sequences clustered into lineage VI, and the mean nucleotide sequence identity between any pair of porcine G1 VP7 sequences belonging to lineage VI was 91.9%. In contrast, the mean nucleotide sequence identity between any pair of human G1 VP7 sequences belonging to lineages I-V was 95.5%. While the mean nucleotide sequence identity between any pair of porcine lineage VI strain and human lineage I-V strain was 85.4%, the VP7 genes of PRV2 and a rare porcine-like human G1P[6] strain (AU19) were 98% identical, strengthening the porcine RVA origin of AU19. The phylogenetic tree suggests that human G1 VP7 genes originated from porcine G1 VP7 genes. The time of their most recent common ancestor was estimated to be 1948, and human and porcine RVA strains evolved along independent pathways. In-silico structural analyses identified 7 amino acid residues within the known neutralisation epitopes that show differences in electric charges and shape between different porcine and human G1 strains. When compared with much divergent porcine G1 VP7 lineages, monophyletic, less divergent human G1 VP7 lineages support the hypothesis that all human G1 VP7 genes included in this study originated from a rare event of a porcine RVA transmitting to humans that was followed by successful adaptation to the human host. By contrast, AU19 represents interspecies transmission that terminated in dead-end infection.

Molecular characterisation of wild-type G1P[8] and G3P[8] rotaviruses isolated in Vietnam 2008 during a vaccine trial

Rotavirus vaccines work better in developed countries than in developing countries, leading to the question of whether the circulating strains are different in these two settings. In 2008, a clinical trial of the pentavalent rotavirus vaccine was performed in Nha Trang, Vietnam, in which the efficacy was reported to be 64 %. Although samples were collected independently from the clinical trial, we examined faecal specimens from children hospitalised for rotavirus diarrhoea and found that G3P[8] and G1P[8] were co-dominant at the time of the clinical trial. The aim of this study was to explore whether they were divergent from the strains circulating in the developed countries where the vaccine efficacy is high. Two G3P[8] and two G1P[8] strains that were regarded as representatives based on their electropherotypes were selected for full-genome sequencing. The genotype constellation was G1/G3-P[8]-I1-R1-C1-M1-A1-N1-T1-E1-H1. All but the VP4 genes, one of which belonged to the emerging P[8]b genotype (OP354-like VP4), clustered into one or more lineages/alleles with the strains circulating in developed countries, with ≥97.5 % nucleotide sequence identity. Additionally, 10 G1 and 12 G3 VP7 sequences as well as 31 VP4 sequences were determined. No amino acid differences were observed between the Vietnamese strains and strains in the developed countries that were likely to have affected the neutralisation specificity of their VP7 and VP4. In conclusion, apart from prevalent P[8]b VP4, virtually no differences were observed between the predominant strains circulating in Vietnam at the time of the clinical trial and the strains in the developed countries; hence, the lower vaccine efficacy was more likely to be due to factors other than strain divergence.

Detection of Common, Emerging and Uncommon VP4, and VP7 Human Group A Rotavirus Genotypes from Urban Sewage Samples in Uruguay

Environmental approach has proven to be a useful tool for epidemiological studies demonstrating through environmental studies the diversity of viruses circulating in a given population. The aim of this study was to perform a phylogenetic characterization of the group A rotavirus (RVA) glycoprotein (G)- and protease-sensitive (P)-genotypes obtained from sewage samples (n = 116) collected in six cities of Uruguay during March 2011 to April 2013. A worldwide standardized semi-nested multiplex RT-PCR (SNM RT-PCR) protocol directed against VP4 and VP7 genes were conducted for RVA detection and consensual DNA fragments were submitted to nucleotide sequencing. P and/or G genotype was successfully determined by phylogenetic analysis in 61% (n = 37) of the positive samples obtained by SNM RT-PCR (n = 61). The RVA genotypes were as follow: G1 (n = 2), G2 (n = 14), G3 (n = 5), G12 (n = 2), P[4] (n = 4), P[8] (n = 16), and P[3] (n = 2). Interestingly, through phylogenetic analysis, emerging, and uncommon human genotypes could be detected. Results obtained from the comparison of RVA genotypes detected in the current study and Uruguayan RVA strains previously described for contemporary clinical pediatric cases showed that monitoring sewage may be a good screening option for a rapid and economical overview of the circulating genotypes in the surrounding human population and a useful approximation to study RVA epidemiology in a future vaccine monitoring program. The present study represents the first report in Uruguay that describes the phylogenetic diversity of RVA from urban sewage samples.

Rotavirus genotypes and the indigenous children of Brazilian midwest in the vaccine era, 2008-2012: Footprints of animal genome

World group A rotavirus (RVA) surveillance data provides useful estimates of the disease burden, however, indigenous population might require special consideration. The aim of this study was to describe the results of G- and P-types from Brazilian native children ≤ 3 years. Furthermore, selected strains have been analyzed for the VP7, VP6, VP4, and NSP4 encoding genes in order to gain insight into genetic variability of Brazilian strains. A total of 149 samples, collected during 2008-2012, were tested for RVA using ELISA and PAGE, following by RT-PCR and sequencing. RVA infection was detected in 8.7% of samples (13/149). Genotype G2P[4] was detected in 2008 and 2010, G8P[6] in 2009, and G3P[8] in 2011. The phylogenetic analysis of the VP7 and VP4 genes grouped the Brazilian G2P[4] and G3P[8] strains within the lineages currently circulating in humans worldwide. However, the phylogenetic analysis of the VP6 and NSP4 from the Brazilian G2P[4] strains, and the VP7 and NSP4 from the Brazilian G3P[8] strains suggest a distant common ancestor with different animal strains (bovine, caprine, and porcine). The epidemiological and genetic information obtained in the present study is expected to provide an updated understanding of RVA genotypes circulating in the native infant population, and to formulate policies for the use of RVA vaccines in indigenous Brazilian people. Moreover, these results highlight the great diversity of human RVA strains circulating in Brazil, and an in-depth surveillance of human and animal RVA will lead to a better understanding of the complex dynamics of RVA evolution.

Hospital based surveillance and genetic characterization of rotavirus strains in children (<5 years) with acute gastroenteritis in Kolkata, India, revealed resurgence of G9 and G2 genotypes during 2011-2013

INTRODUCTION

India accounts for an estimated 457,000-884,000 hospitalizations and 2 million outpatient visits for diarrhea. In spite of the huge burden of rotavirus (RV) disease, RV vaccines have not been introduced in national immunization programme of India. Therefore, continuous surveillance for prevalence and monitoring of the circulating genotypes is needed to assess the disease burden prior to introduction of vaccines in this region.

METHODS

During January 2011 through December 2013, 830 and 1000 stool samples were collected from hospitalized and out-patient department (OPD) patients, respectively, in two hospitals in Kolkata, Eastern India. After primary screening, the G-P typing was done by multiplex semi-nested PCR using type specific primers followed by sequencing. Phylogenetic analysis for the VP7 gene of 25 representative strains was done.

RESULTS

Among hospitalized and OPD patients, 53.4% and 47.5% cases were positive for rotaviruses, respectively. Unlike previous studies where G1 was predominant, in hospitalized cases G9 rotavirus strains were most prevalent (40%), followed by G2 (39.6%) whereas G1 and G12 occurred at 16.4% and 5.6% frequency. In OPD cases, the most prevalent strain was G2 (40.3%), followed by G1, G9 and G12 at 25.5%, 22.8%, 9.3%, respectively. Phylogenetically the G1, G2 and G9 strains from Kolkata did not cluster with corresponding genotypes of Rotarix, RotaTeq and Rotavac (116E) vaccine strains.

CONCLUSION

The study highlights the high prevalence of RV in children with gastroenteritis in Kolkata. The circulating genotypes have changed over the time with predominance of G9 and G2 strains during 2011-2013. The current G2, G9 and G1 Kolkata strains shared low amino acid homologies with current vaccine strains. Although there is substantial evidence for cross protection of vaccines against a variety of strains, still the strain variation should be monitored post vaccine introduction to determine if it has any impact on vaccine effectiveness.

Sequence analysis of VP7 and VP4 genes of G1P[8] rotaviruses circulating among diarrhoeic children in Pune, India: a comparison with Rotarix and RotaTeq vaccine strains

BACKGROUND

The G1P[8] rotaviruses are a common cause of rotavirus diarrhoea among children in India. Two rotavirus vaccines licensed in India, Rotarix and RotaTeq, contain strains with G1 and P[8] genotypes. A comparative analysis of these genotypes in the live rotavirus vaccines with circulating rotavirus strains is essential for assessment of rotavirus diversity.

METHODS

G1P[8] strains detected during rotavirus surveillance among diarrhoeic children hospitalized in Pune in 1992-1993 and 2006-2008, were included in the study. Amplification, sequencing and phylogenetic analysis of the VP7 and VP4 genes were carried out for identification of the G1 and P[8] lineages, respectively. Antigenic epitopes of VP7 and VP4 encoded proteins were compared to determine the differences between the G1P[8] strains from Pune and the vaccine strains.

RESULTS

G1-Lineage 1, P[8]-Lineage 3 strains were predominant in Pune during 1992-1993 and 2006-2008. Strains of G1-Lineage 2, P[8]-Lineage 3 and G1-Lineage 1, P[8]-Lineage 4 were detected at low levels during 2006-2008. The G1-Lineage 1, P[8]-Lineage 3 strains showed up to eight amino acid changes, each in the VP7 and VP4 epitopes, with respect to the Rotarix vaccine strain (G1-Lineage 2, P[8]-Lineage 1) and the G1 (Lineage-3) and P[8] (Lineage 2) components of the RotaTeq vaccine. The G1-Lineage 2 strains were closer to both vaccine strains with no or only two amino acid substitutions in the VP7 epitopes. The divergent P[8]-Lineage 4 (OP354-like) strains showed fourteen and fifteen amino acid differences, with Rotarix and RotaTeq vaccine strains, respectively, in the VP4 epitopes.

CONCLUSION

The differences between the G1P[8] strains in Pune and the G1 and P[8] components of the vaccine strains need to be described for appropriate evaluation of vaccine shedding. Continuous monitoring of the G1P[8] subgenotypic lineages would be necessary to study any long term impact of vaccine use on G1P[8] strain evolution.