Whole genome analyses of African G2, G8, G9, and G12 rotavirus strains using sequence-independent amplification and 454® pyrosequencing

Whole-Genome Characterization of Rotavirus G9P[6] and G9P[4] Strains That Emerged after Rotavirus Vaccine Introduction in Mozambique

Mozambique introduced the Rotarix® vaccine into the National Immunization Program in September 2015. Following vaccine introduction, rotavirus A (RVA) genotypes, G9P[4] and G9P[6], were detected for the first time since rotavirus surveillance programs were implemented in the country. To understand the emergence of these strains, the whole genomes of 47 ELISA RVA positive strains detected between 2015 and 2018 were characterized using an Illumina MiSeq-based sequencing pipeline. Of the 29 G9 strains characterized, 14 exhibited a typical Wa-like genome constellation and 15 a DS-1-like genome constellation. Mostly, the G9P[4] and G9P[6] strains clustered consistently for most of the genome segments, except the G- and P-genotypes. For the G9 genotype, the strains formed three different conserved clades, separated by the P type (P[4], P[6] and P[8]), suggesting different origins for this genotype. Analysis of the VP6-encoding gene revealed that seven G9P[6] strains clustered close to antelope and bovine strains. A rare E6 NSP4 genotype was detected for strain RVA/Human-wt/MOZ/HCN1595/2017/G9P[4] and a genetically distinct lineage IV or OP354-like P[8] was identified for RVA/Human-wt/MOZ/HGJM0644/2015/G9P[8] strain. These results highlight the need for genomic surveillance of RVA strains detected in Mozambique and the importance of following a One Health approach to identify and characterize potential zoonotic strains causing acute gastroenteritis in Mozambican children.

Genomic Analysis of Rwandan G9P[8] Rotavirus Strains Pre- and Post-RotaTeq® Vaccine Reveals Significant Distinct Sub-Clustering in a Post-Vaccination Cohort

Although the introduction of rotavirus vaccines has substantially contributed to the reduction in rotavirus morbidity and mortality, concerns persist about the re-emergence of variant strains that might alter vaccine effectiveness in the long term. The G9 strains re-emerged in Africa during the mid-1990s and have more recently become predominant in some countries, such as Ghana and Zambia. In Rwanda, during the 2011 to 2015 routine surveillance period, G9P[8] persisted during both the pre- and post-vaccine periods. The pre-vaccination cohort was based on the surveillance period of 2011 to 2012, and the post-vaccination cohort was based on the period of 2013 to 2015, excluding 2014. The RotaTeq® vaccine that was first introduced in Rwanda in 2012 is genotypically heterologous to Viral Protein 7 (VP7) G9. This study elucidated the whole genome of Rwandan G9P[8] rotavirus strains pre- and post-RotaTeq® vaccine introduction. Fecal samples from Rwandan children under the age of five years (pre-vaccine n = 23; post-vaccine n = 7), conventionally genotyped and identified as G9P[8], were included. Whole-genome sequencing was then performed using the Illumina® MiSeq platform. Phylogenetic analysis and pair-wise sequence analysis were performed using MEGA6 software. Distinct clustering of three post-vaccination study strains was observed in all 11 gene segments, compared to the other Rwandan G9P[8] study strains. Specific amino acid differences were identified across the gene segments of these three 2015 post-vaccine strains. Important amino acid differences were identified at position N242S in the VP7 genome segment of the three post-vaccine G9 strains compared to the other G9 strains. This substitution occurs at a neutralization epitope site and may slightly affect protein interaction at that position. These findings indicate that the Rwandan G9P[8] strains revealed a distinct sub-clustering pattern among post-vaccination study strains circulating in Rwanda, with changes at neutralization epitopes, which may play a role in neutralization escape from vaccine candidates. This emphasizes the need for continuous whole-genome surveillance to better understand the evolution and epidemiology of the G9P[8] strains post-vaccination.

Comparative whole genome analysis reveals re-emergence of human Wa-like and DS-1-like G3 rotaviruses after Rotarix vaccine introduction in Malawi

G3 rotaviruses rank among the most common rotavirus strains worldwide in humans and animals. However, despite a robust long-term rotavirus surveillance system from 1997 at Queen Elizabeth Central Hospital in Blantyre, Malawi, these strains were only detected from 1997 to 1999 and then disappeared and re-emerged in 2017, 5 years after the introduction of the Rotarix rotavirus vaccine. Here, we analysed representative twenty-seven whole genome sequences (G3P[4], n = 20; G3P[6], n = 1; and G3P[8], n = 6) randomly selected each month between November 2017 and August 2019 to understand how G3 strains re-emerged in Malawi. We found four genotype constellations that were associated with the emergent G3 strains and co-circulated in Malawi post-Rotarix vaccine introduction: G3P[4] and G3P[6] strains with the DS-1-like genetic backbone genes (G3-P[4]-I2-R2-C2-M2-A2-N2-T2-E2-H2 and G3-P[6]-I2-R2-C2-M2-A2-N2-T2-E2-H2), G3P[8] strains with the Wa-like genetic backbone genes (G3-P[8]-I1-R1-C1-M1-A1-N1-T1-E1-H1), and reassortant G3P[4] strains consisting of the DS-1-like genetic backbone genes and a Wa-like NSP2 (N1) gene (G3-P[4]-I2-R2-C2-M2-A2-N1-T2-E2-H2). Time-resolved phylogenetic trees demonstrated that the most recent common ancestor for each ribonucleic acid (RNA) segment of the emergent G3 strains was between 1996 and 2012, possibly through introductions from outside the country due to the limited genetic similarity with G3 strains which circulated before their disappearance in the late 1990s. Further genomic analysis revealed that the reassortant DS-1-like G3P[4] strains acquired a Wa-like NSP2 genome segment (N1 genotype) through intergenogroup reassortment; an artiodactyl-like VP3 through intergenogroup interspecies reassortment; and VP6, NSP1, and NSP4 segments through intragenogroup reassortment likely before importation into Malawi. Additionally, the emergent G3 strains contain amino acid substitutions within the antigenic regions of the VP4 proteins which could potentially impact the binding of rotavirus vaccine-induced antibodies. Altogether, our findings show that multiple strains with either Wa-like or DS-1-like genotype constellations have driven the re-emergence of G3 strains. The findings also highlight the role of human mobility and genome reassortment events in the cross-border dissemination and evolution of rotavirus strains in Malawi necessitating the need for long-term genomic surveillance of rotavirus in high disease-burden settings to inform disease prevention and control.

Reduction in Severity of All-Cause Gastroenteritis Requiring Hospitalisation in Children Vaccinated against Rotavirus in Malawi

Rotavirus is the major cause of severe gastroenteritis in children aged <5 years. Introduction of the G1P[8] Rotarix® rotavirus vaccine in Malawi in 2012 has reduced rotavirus-associated hospitalisations and diarrhoeal mortality. However, the impact of rotavirus vaccine on the severity of gastroenteritis presented in children requiring hospitalisation remains unknown. We conducted a hospital-based surveillance study to assess the impact of Rotarix® vaccination on the severity of gastroenteritis presented by Malawian children. Stool samples were collected from children aged <5 years who required hospitalisation with acute gastroenteritis from December 2011 to October 2019. Gastroenteritis severity was determined using Ruuska and Vesikari scores. Rotavirus was detected using enzyme immunoassay. Rotavirus genotypes were determined using nested RT-PCR. Associations between Rotarix® vaccination and gastroenteritis severity were investigated using adjusted linear regression. In total, 3159 children were enrolled. After adjusting for mid-upper arm circumference (MUAC), age, gender and receipt of other vaccines, all-cause gastroenteritis severity scores were 2.21 units lower (p < 0.001) among Rotarix®-vaccinated (n = 2224) compared to Rotarix®-unvaccinated children (n = 935). The reduction in severity score was observed against every rotavirus genotype, although the magnitude was smaller among those infected with G12P[6] compared to the remaining genotypes (p = 0.011). Each one-year increment in age was associated with a decrease of 0.43 severity score (p < 0.001). Our findings provide additional evidence on the impact of Rotarix® in Malawi, lending further support to Malawi's Rotarix® programme.

Genomic characterization of an African G4P[6] human rotavirus strain identified in a diarrheic child in Kenya: Evidence for porcine-to-human interspecies transmission and reassortment

Human rotavirus strains having the unconventional G4P[6] genotype have been sporadically identified in diarrheic patients in different parts of the world. However, the whole genome of only one human G4P[6] strain from Africa (central Africa) has been sequenced and analyzed, and thus the exact origin and evolutionary pattern of African G4P[6] strains remain to be elucidated. In this study, we characterized the full genome of an African G4P[6] strain (RVA/Human-wt/KEN/KCH148/2019/G4P[6]) identified in a stool specimen from a diarrheic child in Kenya. Full genome analysis of strain KCH148 revealed a unique Wa-like genogroup constellation: G4-P[6]-I1-R1-C1-M1-A1-N1-T7-E1-H1. NSP3 genotype T7 is commonly found in porcine rotavirus strains. Furthermore, phylogenetic analysis showed that 10 of the 11 genes of strain KCH148 (VP7, VP4, VP6, VP1-VP3, NSP1, and NSP3-NSP5) appeared to be of porcine origin, the remaining NSP2 gene appearing to be of human origin. Therefore, strain KCH148 was found to have a porcine rotavirus backbone and thus is likely to be of porcine origin. Furthermore, strain KCH148 is assumed to have been derived through interspecies transmission and reassortment events involving porcine and human rotavirus strains. To our knowledge, this is the first report on full genome-based characterization of a human G4P[6] strain from east Africa. Our observations demonstrated the diversity of human G4P[6] strains in Africa, and provide important insights into the origin and evolutionary pattern of zoonotic G4P[6] strains on the African continent.

Phylogenetic analysis of VP7 and VP4 genes of the most predominant human group A rotavirus G12 identified in children with acute gastroenteritis in Himachal Pradesh, India during 2013-2016

G12 strains are now considered to be the sixth most prevalent human rotaviruses globally. India has introduced rotavirus vaccine Rotavac® into the national immunization program in 2016 and Himachal Pradesh (HP) is the first state to launch it. During epidemiological rotavirus surveillance in HP, predominance of G12 rotaviruses was observed. This study investigated the genetic variability and evolution of HP G12 strains (n = 15) associated with P-genotypes P[6], P[4], and P[8] identified between 2013 and 2016. Phylogenetic analysis of VP7 gene revealed that all characterized G12 strains clustered in lineage-III and diversified into three subclusters indicating that these strains may have originated from three different ancestral G12 strains. The comparative sequence analysis of HP strains with Rotavac® and Rotarix® vaccine strains revealed various amino acid substitutions in epitope regions of VP7 and VP4 proteins especially at the antibody neutralization sites. Only 12/29 VP7 epitope residues and 2/25 VP4 epitope residues were found to be conserved between HP rotavirus strains and vaccine strains. Both long and short electropherotypes were observed in G12P[4] strains, while a single long electropherotype was observed in G12P[6] strains. Children of ≤11 months were significantly infected with G12 rotaviruses. The frequency of vomiting episodes (≥5/day) was significantly higher in children infected with G12 rotavirus strains as compared to non-G12 rotaviruses (p = 0.0405). Our study provides the comprehensive data on clinical characteristics and evolutionary pattern of the G12 rotavirus, the most prevalent strain in HP and emphasizes the need to monitor these strains for inclusion in future vaccine.

Whole Genome Analysis of African G12P[6] and G12P[8] Rotaviruses Provides Evidence of Porcine-Human Reassortment at NSP2, NSP3, and NSP4

Group A rotaviruses (RVA) represent the most common cause of pediatric gastroenteritis in children <5 years, worldwide. There has been an increase in global detection and reported cases of acute gastroenteritis caused by RVA genotype G12 strains, particularly in Africa. This study sought to characterize the genomic relationship between African G12 strains and determine the possible origin of these strains. Whole genome sequencing of 34 RVA G12P[6] and G12P[8] strains detected from the continent including southern (South Africa, Zambia, Zimbabwe), eastern (Ethiopia, Uganda), central (Cameroon), and western (Togo) African regions, were sequenced using the Ion Torrent PGM method. The majority of the strains possessed a Wa-like backbone with consensus genotype constellation of G12-P[6]/P[8]-I1-R1-C1-M1-A1-N1-T1-E1-H1, while a single strain from Ethiopia displayed a DS-1-like genetic constellation of G12-P[6]-I2-R2-C2-M2-A2-N2-T2-E2-H2. In addition, three Ethiopian and one South African strains exhibited a genotype 2 reassortment of the NSP3 gene, with genetic constellation of G12-P[8]-I1-R1-C1-M1-A1-N1-T2-E1-H1. Overall, 10 gene segments (VP1–VP4, VP6, and NSP1–NSP5) of African G12 strains were determined to be genetically related to cognate gene sequences from globally circulating human Wa-like G12, G9, and G1 strains with nucleotide (amino acid) identities in the range of 94.1–99.9% (96.5–100%), 88.5–98.5% (93–99.1%), and 89.8–99.0% (88.7–100%), respectively. Phylogenetic analysis showed that the Ethiopian G12P[6] possessing a DS-1-like backbone consistently clustered with G2P[4] strains from Senegal and G3P[6] from Ethiopia with the VP1, VP2, VP6, and NSP1–NSP4 genes. Notably, the NSP2, NSP3, and NSP4 of most of the study strains exhibited the closest relationship with porcine strains suggesting the occurrence of reassortment between human and porcine strains. Our results add to the understanding of potential roles that interspecies transmission play in generating human rotavirus diversity through reassortment events and provide insights into the evolutionary dynamics of G12 strains spreading across selected sub-Saharan Africa regions.

Genomic constellation of human Rotavirus A strains identified in Northern Brazil: a 6-year follow-up (2010-2016)

Surveillance of Rotavirus A (RVA) throughout the national territory is important to establish a more complete epidemiological-molecular scenario of this virus circulation in Brazil. The aim of the present study was to investigate the genetic diversity of RVA strains circulating in Tocantins State (Northern Brazil) during six years of post-vaccination follow-up (2010-2016). A total of 248 stool samples were screened by next generation sequencing and 107 (43.1%) nearly full length RVA genome sequences were obtained; one sample was co-infected with two RVA strains (G2/G8P[4]). Six G and P genotypes combinations were detected: G12P[8] strains (78.6%), as well as the G3P[8] (9.3%) and G1P[8] (0.9%) were associated with a Wa-like genogroup backbone. All G2P[4] (5.6%) and G8P[4] (2.8%) strains, including the mixed G2/G8P[4] infection (0.9%) showed the DS-1-like genetic background. The two G12P[4] strains (1.9%) were associated with distinct genetic backbones: Wa-like and DS-1-like. The phylogenetic analysis revealed the circulation of lineages G1-I, G2-IV, G3-III, G8-I and G12-III, and P[4]-V and P[8]-III of the VP7 and VP4 genes, respectively. Conserved clustering pattern and low genetic diversity were observed regarding VP1-VP3 and VP6, as well as NSP1-5 segments. We identified the same RVA circulation pattern reported in other Brazilian regions in the period of 2010-2016, suggesting that rural and low-income areas may not have a different RVA genotypic distribution compared to other parts of the country. The unique presentation of whole-genome data of RVA strains detected in the Tocantins State provides a baseline for monitoring variations in the genetic composition of RVA in this area.

The origins of G12P[6] rotavirus strains detected in Lebanon

The G12 rotaviruses are an increasingly important cause of severe diarrhoea in infants and young children worldwide. Seven human G12P[6] rotavirus strains were detected in stool samples from children hospitalized with gastroenteritis in Lebanon during a 2011-2013 surveillance study. Complete genomes of these strains were sequenced using VirCapSeq-VERT, a capture-based high-throughput viral-sequencing method, and further characterized based on phylogenetic analyses with global RVA and vaccine strains. Based on the complete genomic analysis, all Lebanese G12 strains were found to have Wa-like genetic backbone G12-P[6]-I1-R1-C1-M1-A1-N1-T1-E1-H1. Phylogenetically, these strains fell into two clusters where one of them might have emerged from Southeast Asian strains and the second one seems to have a mixed backbone between North American and Southeast Asian strains. Further analysis of these strains revealed high antigenic variability compared to available vaccine strains. To our knowledge, this is the first report on the complete genome-based characterization of G12P[6] emerging in Lebanon. Additional studies will provide important insights into the evolutionary dynamics of G12 rotaviruses spreading in Asia.

Report of the 1st African Enteric Viruses Genome Initiative (AEVGI) Data and Bioinformatics Workshop on whole-genome analysis of some African rotavirus strains held in Bloemfontein, South Africa

The University of the Free State - Next Generation Sequencing (NGS) Unit, Bloemfontein, South Africa, hosted a data and bioinformatics workshop from 19 to 22 June 2018. The workshop was coordinated by the African Enteric Viruses Genome Initiative (AEVGI) with support from the Bill & Melinda Gates Foundation. The event introduced technologies in NGS and data analysis with focus on the rotavirus (RV) genome. The workshop fostered interactions and networking between professionals, scientific experts, technicians and students. The courses provided an overview of RV diarrhoea and its burden in Africa, while highlighting the key resources and methodologies in NGS and advanced bioinformatics in deciphering vaccine impact. It was concluded that, despite the reported significant decline in RV associated-diarrhoea mortality and morbidity in Africa due to RV vaccine impact, the need for continuous surveillance and genomic characterization to better understand the ever-changing dynamics of RV strains is imperative.

Generation of Simian Rotavirus Reassortants with VP4- and VP7-Encoding Genome Segments from Human Strains Circulating in Africa Using Reverse Genetics

Human rotavirus A (RVA) causes acute gastroenteritis in infants and young children. The broad use of two vaccines, which are based on RVA strains from Europe and North America, significantly reduced rotavirus disease burden worldwide. However, a lower vaccine effectiveness is recorded in some regions of the world, such as sub-Saharan Africa, where diverse RVA strains are circulating. Here, a plasmid-based reverse genetics system was used to generate simian RVA reassortants with VP4 and VP7 proteins derived from African human RVA strains not previously adapted to cell culture. We were able to rescue 1/3 VP4 mono-reassortants, 3/3 VP7 mono-reassortants, but no VP4/VP7 double reassortant. Electron microscopy showed typical triple-layered virus particles for the rescued reassortants. All reassortants stably replicated in MA-104 cells; however, the VP4 reassortant showed significantly slower growth compared to the simian RVA or the VP7 reassortants. The results indicate that, at least in cell culture, human VP7 has a high reassortment potential, while reassortment of human VP4 from unadapted human RVA strains with simian RVA seems to be limited. The characterized reassortants may be useful for future studies investigating replication and reassortment requirements of rotaviruses as well as for the development of next generation rotavirus vaccines.

Coding-Gene Coevolution Analysis of Rotavirus Proteins: A Bioinformatics and Statistical Approach

Rotavirus remains a major cause of diarrhea in infants and young children worldwide. The permanent emergence of new genotypes puts the potential effectiveness of vaccines under serious question. The distribution of unusual genotypes subject to viral fitness is influenced by interactions among viral proteins. The present work aimed at analyzing the genetic constellation and the coevolution of rotavirus coding genes for the available rotavirus genotypes. Seventy-two full genome sequences of different genetic constellations were analyzed using a genetic algorithm. The results revealed an extensive genome-wide covariance network among the 12 viral proteins. Altogether, the emergence of new genotypes represents a challenge to the outcome and success of vaccination and the coevolutionary analysis of rotavirus proteins may boost efforts to better understand the interaction networks of proteins during viral replication/transcription.

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

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

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

BACKGROUND

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

OBJECTIVES

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

METHODS

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

FINDINGS

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

MAIN CONCLUSIONS

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

Emergence of Double- and Triple-Gene Reassortant G1P[8] Rotaviruses Possessing a DS-1-Like Backbone after Rotavirus Vaccine Introduction in Malawi

To combat the high burden of rotavirus gastroenteritis, multiple African countries have introduced rotavirus vaccines into their childhood immunization programs. Malawi incorporated a G1P[8] rotavirus vaccine (Rotarix) into its immunization schedule in 2012. Utilizing a surveillance platform of hospitalized rotavirus gastroenteritis cases, we examined the phylodynamics of G1P[8] rotavirus strains that circulated in Malawi before (1998 to 2012) and after (2013 to 2014) vaccine introduction. Analysis of whole genomes obtained through next-generation sequencing revealed that all randomly selected prevaccine G1P[8] strains sequenced (n = 32) possessed a Wa-like genetic constellation, whereas postvaccine G1P[8] strains (n = 18) had a DS-1-like constellation. Phylodynamic analyses indicated that postvaccine G1P[8] strains emerged through reassortment events between human Wa- and DS-1-like rotaviruses that circulated in Malawi from the 1990s and hence were classified as atypical DS-1-like reassortants. The time to the most recent common ancestor for G1P[8] strains was from 1981 to 1994; their evolutionary rates ranged from 9.7 × 10⁻⁴ to 4.1 × 10⁻³ nucleotide substitutions/site/year. Three distinct G1P[8] lineages chronologically replaced each other between 1998 and 2014. Genetic drift was the likely driver for lineage turnover in 2005, whereas replacement in 2013 was due to reassortment. Amino acid substitution within the outer glycoprotein VP7 of G1P[8] strains had no impact on the structural conformation of the antigenic regions, suggesting that it is unlikely that they would affect recognition by vaccine-induced neutralizing antibodies. While the emergence of DS-1-like G1P[8] rotavirus reassortants in Malawi was therefore likely due to natural genotype variation, vaccine effectiveness against such strains needs careful evaluation.

IMPORTANCE The error-prone RNA-dependent RNA polymerase and the segmented RNA genome predispose rotaviruses to genetic mutation and genome reassortment, respectively. These evolutionary mechanisms generate novel strains and have the potential to lead to the emergence of vaccine escape mutants. While multiple African countries have introduced a rotavirus vaccine, there are few data describing the evolution of rotaviruses that circulated before and after vaccine introduction. We report the emergence of atypical DS-1-like G1P[8] strains during the postvaccine era in Malawi. Three distinct G1P[8] lineages circulated chronologically from 1998 to 2014; mutation and reassortment drove lineage turnover in 2005 and 2013, respectively. Amino acid substitutions within the outer capsid VP7 glycoprotein did not affect the structural conformation of mapped antigenic sites, suggesting a limited effect on the recognition of G1-specific vaccine-derived antibodies. The genes that constitute the remaining genetic backbone may play important roles in immune evasion, and vaccine effectiveness against such atypical strains needs careful evaluation.

Rotavirus A strains obtained from children with acute gastroenteritis in Mozambique, 2012-2013: G and P genotypes and phylogenetic analysis of VP7 and partial VP4 genes

In Mozambique rotavirus (RV) was shown to be the greatest cause of acute diarrhoea in infants from 0 to 11 months, and in 2015, national rotavirus vaccination was introduced. As with other developing countries, there is very limited active strain characterisation. Rotavirus positive clinical specimens, collected between 2012 and 2013, have now provided information on the genotypes circulating in southern Mozambique prior to vaccine introduction. Genotypes G2 (32.4%), G12 (28.0%), P[4] (41.4%) and P[6] (22.9%) (n = 157) strains were commonly detected with G2P[4] (42.3%) RVs being predominant, specifically during 2013. Phylogenetic evaluation of the VP7 and VP8* encoding genes showed, for the majority of the Mozambican strains, that they clustered with other African strains based on genotype. RVA/Human-wt/MOZ/0153/2013/G2P[4], RVA/Human-wt/MOZ/0308/2012/G2P[4] and RVA/Human-wt/MOZ/0288/2012/G12P[8] formed separate clusters from the other Mozambican strains with similar genotypes, suggesting possible reassortment. Amino acid substitutions in selected epitope regions also supported phylogenetic clustering. As expected, the VP7 and VP8* genes from the Mozambican strains differed from both the RotaTeq^® (SC2-9) G2P[5] and Rotarix^® (A41CB052A) G1P[8] genes. This study provides information on the genetic diversity of rotavirus strains prior to vaccine introduction and generates baseline data for future monitoring of any changes in rotavirus strains in response to vaccine pressure.

Whole genome analysis of selected human and animal rotaviruses identified in Uganda from 2012 to 2014 reveals complex genome reassortment events between human, bovine, caprine and porcine strains

Rotaviruses of species A (RVA) are a common cause of diarrhoea in children and the young of various other mammals and birds worldwide. To investigate possible interspecies transmission of RVAs, whole genomes of 18 human and 6 domestic animal RVA strains identified in Uganda between 2012 and 2014 were sequenced using the Illumina HiSeq platform. The backbone of the human RVA strains had either a Wa- or a DS-1-like genetic constellation. One human strain was a Wa-like mono-reassortant containing a DS-1-like VP2 gene of possible animal origin. All eleven genes of one bovine RVA strain were closely related to those of human RVAs. One caprine strain had a mixed genotype backbone, suggesting that it emerged from multiple reassortment events involving different host species. The porcine RVA strains had mixed genotype backbones with possible multiple reassortant events with strains of human and bovine origin.Overall, whole genome characterisation of rotaviruses found in domestic animals in Uganda strongly suggested the presence of human-to animal RVA transmission, with concomitant circulation of multi-reassortant strains potentially derived from complex interspecies transmission events. However, whole genome data from the human RVA strains causing moderate and severe diarrhoea in under-fives in Uganda indicated that they were primarily transmitted from person-to-person.

Whole-genome characterisation of G12P[6] rotavirus strains possessing two distinct genotype constellations co-circulating in Blantyre, Malawi, 2008

Rotavirus A strains detected in diarrhoeal children commonly possess any one of the genotypes G1, G2, G3, G4, and G9, with a recent increase in G12 detection globally. G12P[6] strains possessing short RNA (DS-1-like) and long RNA (Wa-like) migration patterns accounted for 27 % of the strains circulating in Blantyre, Malawi, between 2007 and 2008. To understand how the G12P[6] strains with two distinct genetic backgrounds emerged in Malawi, we conducted whole-genome analysis of two long-RNA and two short-RNA strains. While the former had a typical Wa-like genotype constellation of G12-P[6]-I1-R1-C1-M1-A1-N1-T1-E1-H1, the latter was found to have G12-P[6]-I2-R2-C2-M1-A2-N2-T2-E2-H2: a VP3 gene mono-reassortant on the DS-1-like backbone. Phylogenetic and Bayesian Markov chain Monte Carlo analyses showed that the short-RNA G12P[6] strains were generated around 2006 by reassortment between an African Wa-like G12P[6] strain donating three genes (the VP7, VP4, and VP3 genes) and a G2P[4] strain similar to the one circulating in Thailand or the United States of America that donated the remaining eight genes. On the other hand, the long-RNA strains were generated as a result of reassortment events within Wa-like G12 and non-G12 strains commonly circulating in Africa; only the VP4 gene was from a Malawian G8P[6] strain. In conclusion, this study uncovered the evolutionary pathways through which two distinct G12P[6] strains emerged in Malawi.

Unbiased whole-genome deep sequencing of human and porcine stool samples reveals circulation of multiple groups of rotaviruses and a putative zoonotic infection

Coordinated and synchronous surveillance for zoonotic viruses in both human clinical cases and animal reservoirs provides an opportunity to identify interspecies virus movement. Rotavirus (RV) is an important cause of viral gastroenteritis in humans and animals. In this study, we document the RV diversity within co-located humans and animals sampled from the Mekong delta region of Vietnam using a primer-independent, agnostic, deep sequencing approach. A total of 296 stool samples (146 from diarrhoeal human patients and 150 from pigs living in the same geographical region) were directly sequenced, generating the genomic sequences of sixty human rotaviruses (all group A) and thirty-one porcine rotaviruses (thirteen group A, seven group B, six group C, and five group H). Phylogenetic analyses showed the co-circulation of multiple distinct RV group A (RVA) genotypes/strains, many of which were divergent from the strain components of licensed RVA vaccines, as well as considerable virus diversity in pigs including full genomes of rotaviruses in groups B, C, and H, none of which have been previously reported in Vietnam. Furthermore, the detection of an atypical RVA genotype constellation (G4-P[6]-I1-R1-C1-M1-A8-N1-T7-E1-H1) in a human patient and a pig from the same region provides some evidence for a zoonotic event.

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.

Complete genotyping of unusual species A rotavirus G12P[11] and G10P[14] isolates and evidence of frequent in vivo reassortment among the rotaviruses detected in children with diarrhea in Kolkata, India, during 2014

Species A rotaviruses (RVA) are the most important cause of acute gastroenteritis in the young of humans and many animal species globally. G1P[8], G2P[4], G3P[8], G4P[8], G9P[6/8] and G12P[6/8] are the predominantly isolated genotypes throughout the world including India. Unusual genotypes from different host species such as G5, G6, G8, G10 and G11 have also been reported in humans with low frequency. In the present study, among >650 RVA positive stool samples collected from children with diarrhea in Kolkata, India, during 2014, two isolates each of the genotype G12P[11] and G10P[14] were obtained and their genomes completely sequenced. The full genotype constellations were G12-P[11]-I1-R1-C1-M2-A1-N1-T2-E1-H1 and G12-P[11]-I1-R1-C1-M1-A5-N1-T1-E1-H1 for G12P[11] viruses, suggesting several reassortments between Wa- and DS-1-like human RVA strains, including possible reassortment of a simian NSP1 gene. The G10P[14] viruses (G10-P[14]-I2-R2-C2-M2-A11-N2-T6-E2-H3) were found to contain multiple genes closely related to RVAs of artiodactyl origin, highlighting the role of inter-host species transmissions of RVAs. From the G/P constellation of all RVA isolates, it could be concluded that approximately one quarter had likely arisen from reassortment events in vivo among RVAs of 'usual' genotypes.

Epidemiology of rotavirus A diarrhea in Chókwè, Southern Mozambique, from February to September, 2011

Acute diarrhea disease caused by Rotaviruses A (RVA) is still the leading cause of morbidity and mortality in children ≤5 years old in developing countries. An exploratory cross-sectional study was conducted between February and September, 2011 to determine the proportion of acute diarrhea caused by RVA. A total of 254 stool specimens were collected from children ≤5 years old with acute diarrhea, including outpatients (222 children) and inpatients (32 children), in three local health centers in Chókwè District, Gaza Province, South of Mozambique. RVA antigens were detected using enzyme immunoassay (EIA); the RVA G (VP7) and P (VP4) genotypes were determined by RT-PCR or analysis sequencing. Sixty (24%) out of 254 fecal specimens were positive for RVA by EIA; being 58 (97%) from children ≤2 years of age. RVA prevalence peaks in June and July (coldest and drier months) and the G[P] binary combination observed were G12P[8] (57%); G1P[8] (9%); G12P[6] (6%); and 2% for each of the following genotypes: G1P[6], G2P[6] G4P[6], and G9P[8]. Non-Typeable (NT) G and/or P genotypes were observed as follows: G12P [NT] (6%); G1P [NT], G3P[NT] and GNTP[NT] (4%). Considering the different GP combinations, G12 represented 67% of the genotypes. This is the first data showing the diversity of RVA genotypes in Mozambique highlighting the epidemiological importance of these viruses in acute diarrhea cases in children ≤2 years old. In addition, these findings will provide a baseline data before the introduction of the RVA monovalent (Rotarix(®) ) vaccine in the National Immunization Program in September 2015. J. Med. Virol. 88:1751-1758, 2016. © 2016 Wiley Periodicals, Inc.

Engineering and expression of a human rotavirus candidate vaccine in Nicotiana benthamiana

BACKGROUND

Human rotaviruses are the main cause of severe gastroenteritis in children and are responsible for over 500 000 deaths annually. There are two live rotavirus vaccines currently available, one based on human rotavirus serotype G1P[8], and the other a G1-G4 P[8] pentavalent vaccine. However, the recent emergence of the G9 and other novel rotavirus serotypes in Africa and Asia has prompted fears that current vaccines might not be fully effective against these new varieties.

RESULTS

We report an effort to develop an affordable candidate rotavirus vaccine against the new emerging G9P[6] (RVA/Human-wt/ZAF/GR10924/1999/G9P[6]) strain. The vaccine is based on virus-like particles which are both highly immunogenic and safe. The vaccine candidate was produced in Nicotiana benthamiana by transient expression, as plants allow rapid production of antigens at lower costs, without the risk of contamination by animal pathogens. Western blot analysis of plant extracts confirmed the successful expression of two rotavirus capsid proteins, VP2 and VP6. These proteins assembled into VLPs resembling native rotavirus particles when analysed by transmission electron microscopy (TEM). Expression of the rotavirus glycoprotein VP7 and the spike protein VP4 was also tried. However, VP7 expression caused plant wilting during the course of the time trial and expression could never be detected for either protein. We therefore created three fusion proteins adding the antigenic part of VP4 (VP8*) to VP6 in an attempt to produce more appropriately immunogenic particles. Fusion protein expression in tobacco plants was detected by western blot using anti-VP6 and anti-VP4 antibodies, but no regular particles were observed by TEM, even when co-expressed with VP2.

CONCLUSION

Our results suggest that the rotavirus proteins produced in N. benthamiana are candidates for a subunit vaccine specifically for the G9P[6] rotavirus strain. This could be more effective in developing countries, thereby possibly providing a higher overall efficacy for the existing vaccines. The production of rotavirus proteins in plants would probably result in lower manufacturing costs, making it more affordable for developing countries. Further investigation is required to evaluate the immunogenic potential of the VLPs and fusion proteins created in this study.

Multiplexed one-step RT-PCR VP7 and VP4 genotyping assays for rotaviruses using updated primers

The current two-step VP7 and VP4 genotyping RT-PCR assays for rotaviruses have been linked consistently to genotyping failure in an estimated 30% of RVA positive samples worldwide. We have developed a VP7 and VP4 multiplexed one-step genotyping assays using updated primers generated from contemporary VP7 and VP4 sequences. To determine assay specificity and sensitivity, 17 reference virus strains, 6 non-target gastroenteritis viruses and 725 clinical samples carrying the most common VP7 (G1, G2, G3, G4, G9, and G12) and VP4 (P[4], P[6], P[8], P[9] and P[10]) genotypes were tested in this study. All reference RVA strain targets yielded amplicons of the expected sizes and non-target genotypes and gastroenteritis viruses were not detected by either assay. Out of the 725 clinical samples tested, the VP7 and VP4 assays were able to assigned specific genotypes to 711 (98.1%) and 714 (98.5%), respectively. The remaining unassigned samples were re-tested for RVA antigen using EIA and qRT-PCR assays and all were found to be negative. The overall specificity, sensitivity and limit of detection of the VP7 assay were in the ranges of 99.0-100%, 94.0-100% and 8.6×10(1) to 8.6×10(2) copies of RNA/reaction, respectively. For the VP4 assay, the overall specificity, sensitivity and limit of detection assay were in the ranges of 100%, 94.0-100% and ≤1 to 8.6×10(2) copies of RNA/reaction, respectively. Here we report two highly robust, accurate, efficient, affordable and documentable gel-based genotyping systems which are capable of genotyping 97.8% of the six common VP7 and 98.3% of the five common VP4 genotypes of RVA strains which are responsible for approximately 88.2% of all RVA infections worldwide.

Rotavirus landscape in Africa-Towards prevention and control: A report of the 8th African rotavirus symposium, Livingstone, Zambia

The 8th African Rotavirus Symposium was held in Livingstone, Zambia from the 12-13 June 2014. Over 130 delegates from 35 countries - 28 from African nations - participated in this symposium, which included scientists, clinicians, immunisation managers, public health officials, policymakers and vaccine manufacturers. The theme for the symposium was Rotavirus Landscape in Africa-Towards Prevention and Control. At the time of the symposium, a total of 21 African countries had introduced the rotavirus vaccine into their national immunisation schedules. This meeting was particularly timely and relevant to review early data on vaccine adoption and impact from these countries. The concluding panel discussion proposed several recommendations for areas of focus moving forward in rotavirus advocacy and research.

Chimaeric virus-like particles derived from consensus genome sequences of human rotavirus strains co-circulating in Africa

Rotavirus virus-like particles (RV-VLPs) are potential alternative non-live vaccine candidates due to their high immunogenicity. They mimic the natural conformation of native viral proteins but cannot replicate because they do not contain genomic material which makes them safe. To date, most RV-VLPs have been derived from cell culture adapted strains or common G1 and G3 rotaviruses that have been circulating in communities for some time. In this study, chimaeric RV-VLPs were generated from the consensus sequences of African rotaviruses (G2, G8, G9 or G12 strains associated with either P[4], P[6] or P[8] genotypes) characterised directly from human stool samples without prior adaptation of the wild type strains to cell culture. Codon-optimised sequences for insect cell expression of genome segments 2 (VP2), 4 (VP4), 6 (VP6) and 9 (VP7) were cloned into a modified pFASTBAC vector, which allowed simultaneous expression of up to four genes using the Bac-to-Bac Baculovirus Expression System (BEVS; Invitrogen). Several combinations of the genome segments originating from different field strains were cloned to produce double-layered RV-VLPs (dRV-VLP; VP2/6), triple-layered RV-VLPs (tRV-VLP; VP2/6/7 or VP2/6/7/4) and chimaeric tRV-VLPs. The RV-VLPs were produced by infecting Spodoptera frugiperda 9 and Trichoplusia ni cells with recombinant baculoviruses using multi-cistronic, dual co-infection and stepwise-infection expression strategies. The size and morphology of the RV-VLPs, as determined by transmission electron microscopy, revealed successful production of RV-VLPs. The novel approach of producing tRV-VLPs, by using the consensus insect cell codon-optimised nucleotide sequence derived from dsRNA extracted directly from clinical specimens, should speed-up vaccine research and development by by-passing the need to adapt rotaviruses to cell culture. Other problems associated with cell culture adaptation, such as possible changes in epitopes, can also be circumvented. Thus, it is now possible to generate tRV-VLPs for evaluation as non-live vaccine candidates for any human or animal field rotavirus strain.

Whole genomic analysis of human G12P[6] and G12P[8] rotavirus strains that have emerged in Kenya: identification of porcine-like NSP4 genes

G12 rotaviruses are globally emerging rotavirus strains causing severe childhood diarrhea. However, the whole genomes of only a few G12 strains have been fully sequenced and analyzed, of which only one G12P[4] and one G12P[6] are from Africa. In this study, we sequenced and characterized the complete genomes of three G12 strains (RVA/Human-tc/KEN/KDH633/2010/G12P[6], RVA/Human-tc/KEN/KDH651/2010/G12P[8], and RVA/Human-tc/KEN/KDH684/2010/G12P[6]) identified in three stool specimens from children with acute diarrhea in Kenya, Africa. On whole genomic analysis, all three Kenyan G12 strains were found to have a Wa-like genetic backbone: G12-P[6]-I1-R1-C1-M1-A1-N1-T1-E1-H1 (strains KDH633 and KDH684) and G12-P[8]-I1-R1-C1-M1-A1-N1-T1-E1-H1 (strain KDH651). Phylogenetic analysis showed that most genes of the three strains examined in this study were genetically related to globally circulating human G1, G9, and G12 strains. Of note is that the NSP4 genes of strains KDH633 and KDH684 appeared to be of porcine origin, suggesting the occurrence of reassortment between human and porcine strains. Furthermore, strains KDH633 and KDH684 were very closely related to each other in all the 11 gene segments, indicating derivation of the two strains from a common origin. On the other hand, strain KDH651 consistently formed distinct clusters of 10 of the 11 gene segments (VP1-2, VP4, VP6-7, and NSP1-5), indicating a distinct origin of strain KDH651 from that of strains KDH633 and KDH684. To our knowledge, this is the first report on whole genome-based characterization of G12 strains that have emerged in Kenya. Our observations will provide important insights into the evolutionary dynamics of emerging G12 rotaviruses in Africa.

Genetic diversity of porcine group A rotavirus strains in the UK

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This is the first study of rotavirus genotypes circulating in UK pigs.

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Rotavirus transmission between pigs and humans is not thought to be common in the UK.

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Human rotavirus genotype P[8] found in a UK pig.

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The uncommon rotavirus genotype P[32] is widespread in UK pig herds.

Rotavirus is endemic in pig farms where it causes a loss in production. This study is the first to characterise porcine rotavirus circulating in UK pigs. Samples from diarrheic pigs with rotavirus enteritis obtained between 2010 and 2012 were genotyped in order to determine the diversity of group A rotavirus (GARV) in UK pigs. A wide range of rotavirus genotypes were identified in UK pigs: six G types (VP7); G2, G3, G4, G5, G9 and G11 and six P types (VP4); P[6], P[7], P[8], P[13], P[23], and P[32]. With the exception of a single P[8] isolate, there was less than 95% nucleotide identity between sequences from this study and any available rotavirus sequences.

The G9 and P[6] genotypes are capable of infecting both humans and pigs, but showed no species cross-over within the UK as they were shown to be genetically distinct, which suggested zoonotic transmission is rare within the UK. We identified the P[8] genotype in one isolate, this genotype is almost exclusively found in humans. The P[8] was linked to a human Irish rotavirus isolate in the same year. The discovery of human genotype P[8] rotavirus in a UK pig confirms this common human genotype can infect pigs and also highlights the necessity of surveillance of porcine rotavirus genotypes to safeguard human as well as porcine health.

Rotavirus surveillance in Kisangani, the Democratic Republic of the Congo, reveals a high number of unusual genotypes and gene segments of animal origin in non-vaccinated symptomatic children

Group A rotavirus (RVA) infections form a major public health problem, especially in low-income countries like the Democratic Republic of the Congo (COD). However, limited data on RVA diversity is available from sub-Saharan Africa in general and the COD in particular. Therefore, the first aim of this study was to determine the genetic diversity of 99 RVAs detected during 2007–2010 in Kisangani, COD. The predominant G-type was G1 (39%) and the most predominant P-type was P[6] (53%). A total of eight different G/P-combinations were found: G1P[8] (28%), G8P[6] (26%), G2P[4] (14%), G12P[6] (13%), G1P[6] (11%), G9P[8] (4%), G4P[6] (2%) and G8P[4] (1%). The second aim of this study was to gain insight into the diversity of P[6] RVA strains in the COD. Therefore, we selected five P[6] RVA strains in combination with the G1, G4, G8 (2x) or G12 genotype for complete genome analysis. Complete genome analysis showed that the genetic background of the G1P[6] and G12P[6] strains was entirely composed of genotype 1 (Wa-like), while the segments of the two G8P[6] strains were identified as genotype 2 (DS-1-like). Interestingly, all four strains possessed a NSP4 gene of animal origin. The analyzed G4P[6] RVA strain was found to possess the unusual G4-P[6]-I1-R1-C1-M1-A1-N1-T7-E1-H1 constellation. Although the majority of its genes (if not all), were presumably of porcine origin, this strain was able to cause gastro-enteritis in humans. The high prevalence of unusual RVA strains in the COD highlights the need for continued surveillance of RVA diversity in the COD. These results also underline the importance of complete genetic characterization of RVA strains and indicate that reassortments and interspecies transmission among human and animal RVAs strains occur regularly. Based on these data, RVA vaccines will be challenged with a wide variety of different RVA strain types in the COD.

Whole-genome analyses of DS-1-like human G2P[4] and G8P[4] rotavirus strains from Eastern, Western and Southern Africa

Group A rotaviruses (RVAs) with distinct G and P genotype combinations have been reported globally. We report the genome composition and possible origin of seven G8P[4] and five G2P[4] human RVA strains based on the genetic evolution of all 11 genome segments at the nucleotide level. Twelve RVA ELISA positive stool samples collected in the representative countries of Eastern, Southern and West Africa during the 2007-2012 surveillance seasons were subjected to sequencing using the Ion Torrent PGM and Illumina MiSeq platforms. A reference-based assembly was performed using CLC Bio's clc_ref_assemble_long program, and full-genome consensus sequences were obtained. With the exception of the neutralising antigen, VP7, all study strains exhibited the DS-1-like genome constellation (P[4]-I2-R2-C2-M2-A2-N2-T2-E2-H2) and clustered phylogenetically with reference strains having a DS-1-like genetic backbone. Comparison of the nucleotide and amino acid sequences with selected global cognate genome segments revealed nucleotide and amino acid sequence identities of 81.7-100 % and 90.6-100 %, respectively, with NSP4 gene segment showing the most diversity among the strains. Bayesian analyses of all gene sequences to estimate the time of divergence of the lineage indicated that divergence times ranged from 16 to 44 years, except for the NSP4 gene where the lineage seemed to arise in the more distant past at an estimated 203 years ago. However, the long-term effects of changes found within the NSP4 genome segment should be further explored, and thus we recommend continued whole-genome analyses from larger sample sets to determine the evolutionary mechanisms of the DS-1-like strains collected in Africa.

Analysis of human rotaviruses from a single location over an 18-year time span suggests that protein coadaption influences gene constellations

Rotaviruses (RVs) are 11-segmented, double-stranded RNA viruses that cause severe gastroenteritis in children. In addition to an error-prone genome replication mechanism, RVs can increase their genetic diversity by reassorting genes during host coinfection. Such exchanges allow RVs to acquire advantageous genes and adapt in the face of selective pressures. However, reassortment may also impose fitness costs if it unlinks genes/proteins that have accumulated compensatory, coadaptive mutations and that operate best when kept together. To better understand human RV evolutionary dynamics, we analyzed the genome sequences of 135 strains (genotype G1/G3/G4-P[8]-I1-C1-R1-A1-N1-T1-E1-H1) that were collected at a single location in Washington, DC, during the years 1974 to 1991. Intragenotypic phylogenetic trees were constructed for each viral gene using the nucleotide sequences, thereby defining novel allele level gene constellations (GCs) and illuminating putative reassortment events. The results showed that RVs with distinct GCs cocirculated during the vast majority of the collection years and that some of these GCs persisted in the community unchanged by reassortment. To investigate the influence of protein coadaptation on GC maintenance, we performed a mutual information-based analysis of the concatenated amino acid sequences and identified an extensive covariance network. Unexpectedly, amino acid covariation was highest between VP4 and VP2, which are structural components of the RV virion that are not thought to directly interact. These results suggest that GCs may be influenced by the selective constraints placed on functionally coadapted, albeit noninteracting, viral proteins. This work raises important questions about mutation-reassortment interplay and its impact on human RV evolution.

IMPORTANCE

Rotaviruses are devastating human pathogens that cause severe diarrhea and kill >450,000 children each year. The virus can evolve by accumulating mutations and by acquiring new genes from other strains via a process called reassortment. However, little is known about the relationship between mutation accumulation and gene reassortment for rotaviruses and how it impacts viral evolution. In this study, we analyzed the genome sequences of human strains found in clinical fecal specimens that were collected at a single hospital over an 18-year time span. We found that many rotaviruses did not reassort their genes but instead maintained them as specific sets (i.e., constellations). By analyzing the encoded proteins, we discovered concurrent amino acid changes among them, which suggests that they are functionally coadapted to operate best when kept together. This study increases our understanding of how rotaviruses evolve over time in the human population.

Whole genome analyses of G1P[8] rotavirus strains from vaccinated and non-vaccinated South African children presenting with diarrhea

Group A rotaviruses (RVAs) are the leading cause of severe gastroenteritis and eventually death among infants and young children worldwide, and disease prevention and management through vaccination is a public health priority. In August 2009, Rotarix™ was introduced in the South African Expanded Programme on Immunisation. As a result, substantial reductions in RVA disease burden have been reported among children younger than 5 years old. Rotavirus strain surveillance post-vaccination is crucial to, inter alia, monitor and study the evolution of vaccine escape strains. Here, full-genome sequence data for the 11 gene segments from 11 South African G1P[8] rotavirus strains were generated, including 5 strains collected from non-vaccinated children during the 2004-2009 rotavirus seasons and 6 strains collected from vaccinated children during the 2010 rotavirus season. These data were analyzed to gain insights into the overall genetic makeup and evolution of South African G1P[8] rotavirus strains and to compare their genetic backbones with those of common human Wa-like RVAs from other countries, as well as with the Rotarix™ and RotaTeq™ G1P[8] vaccine components. All 11 South African G1P[8] strains revealed a complete Wa-like genotype constellation of G1-P[8]-I1-R1-C1-M1-A1-N1-T1-E1-H1. On the basis of sequence similarities, the South African G1P[8] strains (with the exception of strain RVA/Human-wt/ZAF/1262/2004/G1P[8]) were closely related to each other (96-100% identity in all gene segments). Comparison to the Rotarix™ and RotaTeq™ G1P[8] vaccine components revealed a moderate nucleotide identity of 89-96% and 93-95%, respectively. The results indicated that none of the gene segments of these 11 South African G1P[8] strains were vaccine-derived. This study illustrates that large-scale next generation sequencing will provide crucial information on the influence of the vaccination program on evolution of rotavirus strains. This is the first report to describe full genomic analyses of G1P[8] RVA strains collected from both non-vaccinated and vaccinated children in South Africa.

Genetic diversity of rotavirus genome segment 6 (encoding VP6) in Pretoria, South Africa

BACKGROUND

Rotavirus viral protein 6 (VP6), encoded by genome segment (GS) 6, is the primary target for rotavirus diagnosis by serological and some molecular techniques. Selected full length nucleotide sequences of GS 6 of rotavirus strains from South Africa were sequenced and analysed to determine genetic diversity and variations within the circulating rotaviruses.

FINDINGS

The VP6 amplicons were sequenced using the Sanger ABI 3130xl. Phylogenetic and pairwise analysis revealed that the VP6 genes of the study strains belonged to two different VP6 [I] genotypes. Five sequences were assigned genotype I1 and seven as genotype I2. Comparison of the group specific antigenic regions of the South African strains to the reference strains, shows that the South African VP6 sequences belonging to the VP6 genotype I2 were highly conserved, with only two amino acids changes at positions 239 (T›N) and 261(I›V). On the other hand, South African VP6 sequences belonging to I1 genotypes revealed several amino acid variations mostly within the antigenic region III.

CONCLUSIONS

Rotavirus strains with I1 and I2 genotype are predominantly circulating within the South African communities of which the later seems to be more conserved within the antigenic regions. The observed genetic variations observed within GS 6 of rotaviruses analysed in the current study are unlikely to impact negatively on the performance of the current VP6-based detection methods. Nevertheless, investigators should continually consider this diversity and adapt the primer design for the detection and characterization of the VP6 gene accordingly.

Molecular epidemiology of contemporary G2P[4] human rotaviruses cocirculating in a single U.S. community: footprints of a globally transitioning genotype

Group A rotaviruses (RVs) remain a leading cause of childhood gastroenteritis worldwide. Although the G/P types of locally circulating RVs can vary from year to year and differ depending upon geographical location, those with G1P[8], G2P[4], G3P[8], G4P[8], G9P[8], and G12P[8] specificities typically dominate. Little is known about the evolution and diversity of G2P[4] RVs and the possible role that widespread vaccine use has had on their increased frequency of detection. To address these issues, we analyzed the 12 G2P[4] RV isolates associated with a rise in RV gastroenteritis cases at Vanderbilt University Medical Center (VUMC) during the 2010-2011 winter season. Full-genome sequencing revealed that the isolates had genotype 2 constellations typical of DS-1-like viruses (G2P[4]-I2-R2-C2-M2-A2-N2-T2-E2-H2). Phylogenetic analyses showed that the genome segments of the isolates were comprised of two or three different subgenotype alleles; this enabled recognition of three distinct clades of G2P[4] viruses that caused disease at VUMC in the 2010-2011 season. Although the three clades cocirculated in the same community, there was no evidence of interclade reassortment. Bayesian analysis of 328 VP7 genes of G2 viruses isolated in the last 39 years indicate that existing G2 VP7 gene lineages continue to evolve and that novel lineages, as represented by the VUMC isolates, are constantly being formed. Moreover, G2 lineages are characteristically shaped by lineage turnover events that introduce new globally dominant strains every 7 years, on average. The ongoing evolution of G2 VP7 lineages may give rise to antigenic changes that undermine vaccine effectiveness in the long term.

IMPORTANCE

Little is known about the diversity of cocirculating G2 rotaviruses and how their evolution may undermine the effectiveness of rotavirus vaccines. To expand our understanding of the potential genetic range exhibited by rotaviruses circulating in postvaccine communities, we analyzed part of a collection of rotaviruses recovered from pediatric patients in the United States from 2010 to 2011. Examining the genetic makeup of these viruses revealed they represented three segregated groups that did not exchange genetic material. The distinction between these three groups may be explained by three separate introductions. By comparing a specific gene, namely, VP7, of the recent rotavirus isolates to those from a collection recovered from U.S. children between 1974 and 1991 and other globally circulating rotaviruses, we were able to reconstruct the timing of events that shaped their ancestry. This analysis indicates that G2 rotaviruses are continuously evolving, accumulating changes in their genetic material as they infect new patients.

Novel NSP1 genotype characterised in an African camel G8P[11] rotavirus strain

Animal-human interspecies transmission is thought to play a significant role in influencing rotavirus strain diversity in humans. Proving this concept requires a better understanding of the complete genetic constellation of rotaviruses circulating in various animal species. However, very few whole genomes of animal rotaviruses, especially in developing countries, are available. In this study, complete genetic configuration of the first African camel rotavirus strain (RVA/Camel-wt/SDN/MRC-DPRU447/2002/G8P[11]) was assigned a unique G8-P[11]-I2-R2-C2-M2-A18-N2-T6-E2-H3 genotype constellation that has not been reported in other ruminants. It contained a novel NSP1 genotype (genotype A18). The evolutionary dynamics of the genome segments of strain MRC-DPRU447 were rather complex compared to those found in other camelids. Its genome segments 1, 3, 7-10 were closely related (>93% nucleotide identity) to those of human-animal reassortant strains like RVA/Human-tc/ITA/PA169/1988/G6P[14] and RVA/Human-wt/HUN/Hun5/1997/G6P[14], segments 4, 6 and 11 shared common ancestry (>95% nucleotide identity) with bovine rotaviruses like strains RVA/Cow-wt/CHN/DQ-75/2008/G10P[11] and RVA/Cow-wt/KOR/KJ19-2/XXXX/G6P[7], whereas segment 2 was closely related (94% nucleotide identity) to guanaco rotavirus strain RVA/Guanaco-wt/ARG/Rio_Negro/1998/G8P[1]. Its genetic backbone consisted of DS-1-like, AU-1-like, artiodactyl-like and a novel A18 genotype. This suggests that strain MRC-DPRU447 potentially emerged through multiple reassortment events between several mammalian rotaviruses of at least two genogroups or simply strain MRC-DPRU447 display a unique progenitor genotypes. Close relationship between some of the genome segments of strain MRC-DPRU447 to human rotaviruses suggests previous occurrence of reassortment processes combined with interspecies transmission between humans and camels. The whole genome data for strain MRC-DPRU447 adds to the much needed animal rotavirus data from Africa which is limited at the moment.

Consensus sequence determination and elucidation of the evolutionary history of a rotavirus Wa variant reveal a close relationship to various Wa variants derived from the original Wa strain

The consensus nucleotide sequence of a human rotavirus Wa strain, with only a partially known passage history, was determined with sequence-independent amplification and next generation 454® pyrosequencing. This rotavirus Wa strain had the expected genome constellation of G1-P[8]-I1-R1-C1-M1-A1-N1-T1-E1-H1 and was designated RVA/Human-tc/USA/WaCS/1974/G1P[8]. Phylogenetic analyses revealed a close relationship to four human rotavirus Wa variants (Wag5re, Wag7/8re, ParWa and VirWa) derived from the original 1974 human isolate. There were rearrangements in the Wag5re- and Wag7/8re variants in genome segments 5 (Wag5re) and 7 and 8 (Wag7/8re), which were not present in WaCS. Pairwise comparisons and a combined molecular clock for the Wa rotavirus genome indicated a close relationship between WaCS and ParWa and VirWa. These results suggest that WaCS is most probably an early cell culture adapted variant from the initial gnotobiotic pig passaged Wa isolate. Evolutionary pressure analysis identified a possible negative selected amino acid site in VP1 (genome segment 1) and a likely positive selected site in VP4 (genome segment 4). The WaCS may be more appropriate as a rotavirus Wa reference sequence than the current composite Wa reference genome.

Phylogenetic analysis of G1P[6] group A rotavirus strains detected in Northeast Brazilian children fully vaccinated with Rotarix™

In 2009 the World Health Organization recommended the use of group A rotavirus (RVA) vaccines in all national immunization programs (NIPs) in order to control severe RVA gastroenteritis disease. In Brazil, Rotarix™ was introduced in the NIP in March 2006, and a significant reduction in mortality rates among children ≤ 5 years old was observed, especially in the Northern and Northeastern Brazil. In the current study the 11 gene segments of six Brazilian G1P[6] RVA strains, isolated in 2009 and 2010 from vaccinated children, were analyzed in order to investigate if the genetic composition of these strains might help to elucidate why they were able to cause acute gastroenteritis in vaccinated children. All six Brazilian RVA strains revealed a complete Wa-like genotype constellation: G1-P[6]-I1-R1-C1-M1-A1-N1-T1-E1-H1. Phylogenetic analysis showed that all six strains were nearly identical and showed a close genetic relationship with contemporary typical human Wa-like RVA strains. These results suggests that the fact that these strains were able to cause acute gastroenteritis in vaccinated children is likely not due to the genetic background of the strains, but rather to other factors such as host relating factors, co-infecting pathogens or vaccine efficacy. P[6] RVA strains are detected rather occasionally in humans in most regions of the world, except for South Asia and Sub-Saharan Africa. However, recently two studies conducted in Brazil showed the circulation of G12P[6] and G2P[6]. This is the first report on the detection and complete genome analyses of G1P[6] RVA strains in Brazil. Surveillance studies will be crucial to further investigate the prevalence of this genotype in the Brazilian population, and the efficacy of current licensed vaccines, which do not contain the P[6] genotype.

G8 rotaviruses with conserved genotype constellations detected in Malawi over 10 years (1997-2007) display frequent gene reassortment among strains co-circulating in humans

Rotavirus A, the most common cause of severe diarrhoea in children worldwide, occurs in five major VP7 (G) and VP4 (P) genotype combinations, comprising G1P[8], G2P[4], G3P[8], G4P[8] and G9P[8]. However, G8, a common bovine rotavirus genotype, has been reported frequently among children in African countries. Surveillance of rotavirus gastroenteritis conducted in a sentinel hospital in Blantyre, Malawi between 1997 and 2007 provided a rare opportunity to examine the whole genotype constellation of G8 strains and their evolution over time. A sample of 27 (9.0 %) of 299 G8 strains was selected to represent each surveillance year and a range of P genotypes, which shifted in predominance from P[6] to P[4] and P[8] during the study period. Following cell culture adaptation, whole genome sequencing demonstrated that the genetic background of 26 strains possessed the DS-1 genotype constellation. A single G8P[6] strain was a reassortant in which both NSP2 and NSP5 genes from strains with the Wa genotype constellation had been inserted into a strain with the DS-1 genotype background. Phylogenetic analysis suggested frequent reassortment among co-circulating strains with the DS-1 genotype constellation. Little evidence was identified to suggest the introduction of contemporary bovine rotavirus genes into any of the 27 G8 strains examined. In conclusion, Malawian G8 strains are closely related to other human strains with the DS-1 genotype constellation. They have evolved over the last decade through genetic reassortment with other human rotaviruses, changing their VP4 genotypes while maintaining a conserved genotype constellation for the remaining structural and non-structural proteins.

Characterization of human rotaviruses circulating in Iraq in 2008: atypical G8 and high prevalence of P[6] strains

Fecal samples from 976 children with gastroenteritis were collected and analyzed for group A rotavirus (RVA), in three different cities in Iraq between January 2008 and December 2008. RVA antigen was detected in 394 (40%) of the samples, and 98 samples were available for further genotype analyses using multiplex RT-PCR and sequence analyses for untypeable strains. The G/P-genotype combination was determined for 69 samples, and 19, 2 and 8 samples remained P-untypeable, G-untypeable and G/P-untypeable (UT), respectively. The most prevalent genotype was G2 (40%, 39/98) most often associated with P[6]. G1 was the second most common genotype (16%, 16/98) mainly associated with P[8] and P[UT]. G3, G4 and G9 were detected at a lower prevalence (3%, 11%, 3%, respectively), mainly associated with P[6]. Surprisingly, five G8P[6], and seven G12 RVA strains in combination with P[6] and P[8] were also detected for the first time in Iraq. Overall, a striking high prevalence of 47% of the analyzed samples possessed the P[6] genotype (65% of the P-typed RVA strains). Atypical genotype combinations such as G1P[4], G1P[6], G2P[8] or strains with mixed G-types were detected sporadically. The detection of unusual G8P[6] RVA strains prompted us to further analyze the NSP2, NSP3, NSP4 and NSP5 gene segments of three selected G8P[6] strains, resulting in their designation to the N2, T2, E2 and H2 genotypes, respectively. The VP7, VP4, NSP2, NSP3 and NSP5 gene segments clustered closely with common human RVA strains, whereas the NSP4 gene sequences were found to cluster with animal derived RVA strains, suggesting a potential reassortment event. The high prevalence of RVA strains with the G8, G12 and P[6] genotypes in combination with a DS-1-like genotype constellation in Iraq, needs to be monitored closely as these RVA strains might challenge the effectiveness of current RVA vaccines.

Whole-genome consensus sequence analysis of a South African rotavirus SA11 sample reveals a mixed infection with two close derivatives of the SA11-H96 strain

Whole-genome, sequence-independent amplification and 454(®) pyrosequencing of a rotavirus SA11 cell culture sample with an unknown passage history yielded consensus sequences of twelve complete genome segments. Two distinct sequences for genome segment 8 (encoding NSP2) were present, indicating a mixed infection with two rotavirus SA11 strains. The genotypes of the viruses were G3-P[2]-I2-R2-C5-M5-A5-Nx-T5-E2-H5, where x was either 5 or 2. The strains were named RVA/Simian-tc/ZAF/SA11-N5/1958/G3P[2] and RVA/Simian-tc/ZAF/SA11-N2/1958/G3P[2]. The genotype (N2) and sequence of genome segment 8 of RVA/Simian-tc/ZAF/SA11-N2/1958/G3P[2] were identical to that of the bovine rotavirus O agent. Five novel amino acids were detected in minor population variants of three genome segments. Genome segment 1 (VP1) has a high nucleotide substitution rate, but the substitutions are synonymous. Distance matrices and Bayesian molecular clock phylogenetics showed that SA11-N2 is a reassortant containing genome segment 8 from the O agent, whereas SA11-N5 is a very close derivative of the prototype SA11-H96.

Complete genetic characterization of human G2P[6] and G3P[6] rotavirus strains

During the 2008-2009 rotavirus season, 10 G3P[6] rotavirus strains were isolated for the first time in Belgium, while an outbreak of G2P[6] strains occurred in the USA in 2005-2006. Partial sequencing of the 11 genome segments of the 10 Belgian G3P[6] strains revealed a clonal origin. Two of these strains, and a G2P[6] strain representative of the American outbreak, were selected and sequenced completely to analyze their evolutionary relationships. Genetic analysis revealed that all strains possessed a DS-1-like genotype constellation. The 2 Belgian G3P[6] strains showed >99% sequence identity at the nucleotide level and the American G2P[6] strain was phylogenetically closely related to the Belgian P[6] strains. These data suggest that reassortment(s) involving VP7 occurred recently, and that the prevalence of DS-1-like P[6] rotavirus strains need to be closely monitored because the currently licensed RVA vaccines contain neither the P[6] genotype nor strains with a complete human DS-1 genotype constellation.

Rotavirus in diarrheal children in rural Burkina Faso: high prevalence of genotype G6P[6]

Group A rotavirus (RVA) is the most common cause of severe gastroenteritis in young children globally, and responsible for a significant number of deaths in African countries. While vaccines are available, trials have shown a lesser efficacy in Africa. One of the reasons could be the prevalence and/or emergence of unusual or novel RVA strains, as many strains detected in African countries remain uncharacterized. In this study, we characterized RVA positive specimens from two remote rural areas in Burkina Faso, West Africa. In total 56 RVA positive specimens were subgrouped by their VP6 gene, and G-and P typed by PCR and/or sequencing of the VP7 and VP4 genes, respectively. Notably, we found a high prevalence of the unusual G6P[6]SGI strains (23%). It was the second most common constellation after G9P[8]SGII (32%); and followed by G1P[8]SGII (20%) and G2P[4]SGI (9%). We also detected a G8P[6]SGI strain, for the first time in Burkina Faso. The intra-genetic diversity was high for the VP4 gene with two subclusters within the P[8] genotype and three subclusters within the P[6] genotype which were each associated with a specific G-type, thereby suggesting a genetic linkage. The G6P[6]SGI and other SGI RVA strains infected younger children as compared to SGII strains (p<0.05). To conclude, in this study we observed the emergence of unusual RVA strains and high genetic diversity of RVA in remote rural areas of Burkina Faso. The results highlight the complexity of RVA epidemiology which may have implication for the introduction of rotavirus vaccines currently being evaluated in many African countries.

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.

Genotype constellation and evolution of group A rotaviruses infecting humans

Numerous rotavirus group A (RVA) strains with distinct G-genotype and P-genotype combinations have been described infecting humans worldwide. However, the increasing amount of complete RVA genome data which have become available, suggest that only RVA strains with 2 discrete genotype constellations have been successful in sustaining infection of humans worldwide over longer periods of time. Those genotype constellations have been designated I1-R1-C1-M1-A1-N1-T1-E1-H1 and I2-R2-C2-M2-A2-N2-T2-E2-H2 and are also known as Wa-like and DS-1-like, respectively. RVAs of other genotype constellations which were able to spread to a limited extent in the human population are AU-1-related RVA strains (I3-R3-C3-M3-A3/A12-N3-T3-E3-H3/H6) in combination with G3P[9] or G12P[9], and neonatal G10P[11] RVA strains in India (bovine×human Wa-like reassortants). On the basis of the analysis of complete genomes, it is suggested that the overall genetic diversity of epidemiologically widespread human RVA strains is more limited than generally assumed. This conclusion has consequences for how we look at host range restriction and the criteria according to which the effectiveness of RVA universal mass vaccination programs is assessed.