New P serotype of group A human rotavirus closely related to that of a porcine rotavirus

Elucidating the conformational dynamics of histo-blood group antigens and their interactions with the rotavirus spike protein through computational lens

In the present study, we investigated the conformational dynamics of histo-blood group antigens (HBGAs) and their interactions with the VP8* domain of four rotavirus genotypes (P[4], P[6], P[19], and P[11]) utilizing all-atom molecular dynamics simulations in explicit water. Our study revealed distinct changes in the dynamic behavior of the same glycan due to linkage variations. We observed that LNFPI HBGA having a terminal β linkage shows two dominant conformations after complexation, whereas only one was obtained for LNFPI with a terminal α linkage. Interestingly, both variants displayed a single dominant structure in the free state. Similarly, LNT and LNnT show a shift in their dihedral linkage profile between their two terminal monosaccharides because of a change in the linkage from β(1-3) to β(1-4). The molecular mechanics generalized Born surface area (MM/GBSA) calculations yielded the highest binding affinity for LNFPI(β)/P[6] (-13.93 kcal/mol) due to the formation of numerous hydrogen bonds between VP8* and HBGAs. LNnT binds more strongly to P[11] (-12.88 kcal/mol) than LNT (-4.41 kcal/mol), suggesting a single change in the glycan linkage might impact its binding profile significantly. We have also identified critical amino acids and monosaccharides (Gal and GlcNAc) that contributed significantly to the protein-ligand binding through the per-residue decomposition of binding free energy. Moreover, we found that the interaction between the same glycan and different protein receptors within the same rotavirus genogroup influenced the micro-level dynamics of the glycan. Overall, our study helps a deeper understanding of the H-type HBGA and rotavirus spike protein interaction.Communicated by Ramaswamy H. Sarma.

G26P[19] rotavirus A strain causing acute gastroenteritis in the American continent

In Brazil, the rotavirus A genotype G26 was first identified in suckling piglets, while the P[19] genotype has not been identified in any animal species so far. This report details the genetic characterisation of a G26P[19] RVA strain detected from an eight year-old child, vaccinated with Rotarix^®, hospitalised with acute diarrhoeal disease in Rio de Janeiro in 2015. Most likely, the genome constellation (I5-R1-C1-M1-A8-N1-T1-E1-H1) observed in the G26P[19] Brazilian strain was a result of interspecies transmission events between humans and pigs. In addition, a rearrangement in the NSP5 gene was observed downstream of the 3’ non-coding region.

Complete genome sequence analysis of rare G4P[6] rotavirus strains from human and pig reveals the evidence for interspecies transmission

Two rare human rotavirus strains, RVA/Human-wt/THA/CMH-N016-10/2010/G4P[6] and RVA/Human-wt/THA/CMH-N014-11/2011/G4P[6], were detected during the surveillance of group A rotavirus (RVA) in Chiang Mai, Thailand. Complete genome sequences of both strains were analyzed in comparison with that of the representative porcine G4P[6] RVA strain (RVA/Pig-wt/THA/CMP-011-09/2009/G4P[6]) detected in the same geographical area. Human RVA strain CMH-N016-10 containing the genotype constellation of G4-P[6]-I1-R1-C1-M1-A8-N1-T1-E1-H1 was identical to that of porcine RVA strain CMP-011-09. Another human RVA strain (CMH-N014-11) was also contained the genotype constellation of ten segments identical to those of CMH-N016-10 and of porcine RVA strain CMP-011-09 except for genotype I of VP6 gene which contained I5 instead of I1. The genotype constellation of CMH-N014-11, G4-P[6]-I5-R1-C1-M1-A8-N1-T1-E1-H1 was a novel genotype constellation that has not been reported previously in both human and pig. Phylogenetic analysis of all 11 genome segments revealed that both strains of human RVA were more closely related to porcine and porcine-like human than to human RVA reference strains, particularly those reported from Thailand and other Asian countries with very high nucleotide sequence identities ranging from 91.1-100% except for NSP4 gene from 86.1-92.2%. Based on complete genome constellation and overall phylogenetic analyses suggested that these two human G4P[6] strains may have probably originated from porcine RVA strains of independent ancestor. This study provided an evidence for direct interspecies transmission of porcine RVA from pig to human.

Analysis of complete genome sequences of G9P[19] rotavirus strains from human and piglet with diarrhea provides evidence for whole-genome interspecies transmission of nonreassorted porcine rotavirus

Whole genomes of G9P[19] human (RVA/Human-wt/THA/CMH-S070-13/2013/G9P[19]) and porcine (RVA/Pig-wt/THA/CMP-015-12/2012/G9P[19]) rotaviruses concurrently detected in the same geographical area in northern Thailand were sequenced and analyzed for their genetic relationships using bioinformatic tools. The complete genome sequence of human rotavirus RVA/Human-wt/THA/CMH-S070-13/2013/G9P[19] was most closely related to those of porcine rotavirus RVA/Pig-wt/THA/CMP-015-12/2012/G9P[19] and to those of porcine-like human and porcine rotaviruses reference strains than to those of human rotavirus reference strains. The genotype constellation of G9P[19] detected in human and piglet were identical and displayed as the G9-P[19]-I5-R1-C1-M1-A8-N1-T1-E1-H1 genotypes with the nucleotide sequence identities of VP7, VP4, VP6, VP1, VP2, VP3, NSP1, NSP2, NSP3, NSP4, and NSP5 at 99.0%, 99.5%, 93.2%, 97.7%, 97.7%, 85.6%, 89.5%, 93.2%, 92.9%, 94.0%, and 98.1%, respectively. The findings indicate that human rotavirus strain RVA/Human-wt/THA/CMH-S070-13/2013/G9P[19] containing the genome segments of porcine genetic backbone is most likely a human rotavirus of porcine origin. Our data provide an evidence of interspecies transmission and whole-genome transmission of nonreassorted G9P[19] porcine RVA to human occurring in nature in northern Thailand.

Functional and Structural Characterization of P[19] Rotavirus VP8* Interaction with Histo-blood Group Antigens

Rotaviruses (RVs) of species A (RVA) are a major causative agent of acute gastroenteritis. Recently, histo-blood group antigens (HBGAs) have been reported to interact with human RVA VP8* proteins. Human P[19] is a rare P genotype of porcine origin that infects humans sporadically. The functional and structural characteristics of P[19] VP8* interaction with HBGAs are unknown. In this study, we expressed and purified the VP8* proteins of human and porcine P[19] RVs. In oligosaccharide and saliva binding assays, P[19] VP8* proteins showed obvious binding to A-, B-, and O-type saliva samples irrespective of the secretor status, implying broad binding patterns. However, they did not display specific binding to any of the oligosaccharides tested. In addition, we solved the structure of human P[19] VP8* at 2.4 Å, which revealed a typical galectin-like fold. The structural alignment demonstrated that P[19] VP8* was most similar to that of P[8], which was consistent with the phylogenetic analysis. Structure superimposition revealed the basis for the lack of binding to the oligosaccharides. Our study indicates that P[19] RVs may bind to other oligosaccharides or ligands and may have the potential to spread widely among humans. Thus, it is necessary to place the prevalence and evolution of P[19] RVs under surveillance.

IMPORTANCE

Human P[19] is a rare P genotype of porcine origin. Based on phylogenetic analysis of VP8* sequences, P[19] was classified in the P[II] genogroup, together with P[4], P[6], and P[8], which have been reported to interact with HBGAs in a genotype-dependent manner. In this study, we explored the functional and structural characteristics of P[19] VP8* interaction with HBGAs. P[19] VP8* showed binding to A-, B-, and O-type saliva samples, as well as saliva of nonsecretors. This implies that P[19] has the potential to spread among humans with a broad binding range. Careful attention should be paid to the evolution and prevalence of P[19] RVs. Furthermore, we solved the structure of P[19] VP8*. Structure superimposition indicated that P[19] may bind to other oligosaccharides or ligands using potential binding sites, suggesting that further investigation of the specific cell attachment factors is warranted.

Novel porcine-like human G26P[19] rotavirus identified in hospitalized paediatric diarrhoea patients in Ho Chi Minh City, Vietnam

During a hospital-based diarrhoeal disease study conducted in Ho Chi Minh City, Vietnam from 2009 to 2010, we identified four symptomatic children infected with G26P[19] rotavirus (RV) – an atypical variant that has not previously been reported in human gastroenteritis. To determine the genetic structure and investigate the origin of this G26P[19] strain, the whole genome of a representative example was characterized, revealing a novel genome constellation: G26–P[19]–I5–R1–C1–M1–A8–N1–T1–E1–H1. The genome segments were most closely related to porcine (VP7, VP4, VP6 and NSP1) and Wa-like porcine RVs (VP1–3 and NSP2–5). We proposed that this G26P[19] strain was the product of zoonotic transmission coupled with one or more reassortment events occurring in human and/or animal reservoirs. The identification of such strains has potential implications for vaccine efficacy in south-east Asia, and outlines the utility of whole-genome sequencing for studying RV diversity and zoonotic potential during disease surveillance.

Rotavirus associated gastroenteritis in Thailand

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

Genetic diversity and novel combinations of G4P[19] and G9P[19] porcine rotavirus strains in Thailand

Several epidemiological studies reported the detection of rotavirus strains bearing unusual combinations of genetic background of human and porcine rotaviruses. This observation supports the hypothesis of interspecies transmission of rotaviruses in humans and pigs. The aims of this study were to investigate the genotypes and molecular characteristics of rotaviruses in piglets with diarrhea in several farms from two provinces in Thailand. A total of 207 fecal specimens collected from diarrheic piglets were screened for the presence of groups A, B, and C rotaviruses. Group A rotaviruses were detected in 41 out of 207 (19.8%) fecal specimens tested. A wide variety of G-P combination rotavirus strains were detected in this study. The G4P[6] was identified as the most prevalent genotype (39.0%), followed by G4P[23] (12.2%), G3P[23] (7.3%), G4P[19] (7.3%), G3P[6] (4.9%), G3P[13] (4.9%), G3P[19] (4.9%), G9P[13] (4.9%), G9P[19] (4.9%), G5P[6], and G5P[13] each of 2.4%. Furthermore, G5 and G9 in combinations with P-nontypeable strains were also found at each consisting of 2.4% (n=1) of the collection. It was interesting to note that among diversified porcine rotavirus strains, novel combinations of G4P[19] and G9P[19] strains were detected for the first time in this study. Nucleotide sequences of VP4 and VP7 of these strains were closely related to human rotaviruses reported previously. The data implies that these porcine rotaviruses were probably generated in nature from the reassortment between the viruses of human and porcine origin. This study provides valuable epidemiological information and molecular characteristics of porcine rotaviruses circulating in piglets with diarrhea in northern Thailand.

Diverse origin of P[19] rotaviruses in children with acute diarrhea in Taiwan: Detection of novel lineages of the G3, G5, and G9 VP7 genes

We previously reported the detection of genotype P[19] rotavirus strains from children hospitalized with acute dehydrating diarrhea during a 5-year surveillance period in Taiwan. The characterization of five P[19] strains (0.4% of all typed), including three G3P[19], a novel G5P[19], and a unique G9P[19] genotype is described in this study. Phylogenetic analysis of the VP4, VP7, VP6, and NSP4 genes was performed, which demonstrated novel lineages for respective genotypes of the VP4 and the VP7 genes. The sequence similarities of the P[19] VP4 gene among Taiwanese human strains was higher (nt, 91.5-96.2%; aa, 93.7-97.6%) than to other P[19] strains (nt, 83.5-86.6%; aa, 89.4-94.1%) from different regions of the world. The VP7 gene of the three G3P[19] Taiwanese strains shared up to 93.4% nt and 97.5% aa identity to each other but had lower similarity to reference strain sequences available in GenBank (nt, <90.1%; aa, <95.6%). Similarly, the VP7 gene of the novel G5P[19] strain was only moderately related to the VP7 gene of reference G5 strains (nt, 82.2-87.3%; aa, 87.0-93.1%), while the VP7 gene of the single G9P[19] strain was genetically distinct from other known human and animal G9 rotavirus strains (nt, ≤ 92.0%; aa, ≤ 95.7%). Together, these findings suggest that the Taiwanese P[19] strains originated by independent interspecies transmission events. Synchronized surveillance of human and animal rotaviruses in Taiwan should identify possible hosts of these uncommon human rotavirus strains.

Detection and characterisation of group A rotavirus in asymptomatic piglets in southern Ireland

Porcine group A rotaviruses (GARV) are causative agents of enteritis in piglets and are a large reservoir of genetic material for the diversification of human GARVs. Accumulation of information on the genetic heterogeneity of porcine viruses is pivotal for readily characterising unusual human strains. Screening of 292 fecal samples, collected from 4-5- to 8-9-week-old asymptomatic pigs from four herds in Ireland between 2005 and 2007 resulted in 19 (6.5%) samples testing positive by reverse-transcription PCR (RT-PCR) for GARV. The strains were molecularly characterized to collate data on the VP7 and partial VP4 outer capsid genes. By sequence analysis of the VP7 gene, the Irish strains were identified as G2, G4, G5, G9 and G11 viruses. The G11 strains were closely related to other human and porcine G11 strains, while the G2 strains resembled porcine G2 viruses detected recently in Europe and southern Asia. The G4 strains were distantly related to other G4 human and animal strains, constituting a separate G4 VP7 lineage. Analysis of the G5 strains revealed that they were similar to a selection of G5 human and porcine strains, while the G9 strains resembled other porcine G9 viruses. By sequence analysis of the VP8* fragment of the VP4, the Irish viruses were characterised as P[6], P[7], P[13], P[13]/[22], P[26] and P[32].

Zoonotic aspects of rotaviruses

Rotaviruses are important enteric pathogens of humans and animals. Group A rotaviruses (GARVs) account for up to 1 million children deaths each year, chiefly in developing countries and human vaccines are now available in many countries. Rotavirus-associated enteritis is a major problem in livestock animals, notably in young calves and piglets. Early in the epidemiological GARV studies in humans, either sporadic cases or epidemics by atypical, animal-like GARV strains were described. Complete genome sequencing of human and animal GARV strains has revealed a striking genetic heterogeneity in the 11 double stranded RNA segments across different rotavirus strains and has provided evidence for frequent intersections between the evolution of human and animal rotaviruses, as a result of multiple, repeated events of interspecies transmission and subsequent adaptation.

Molecular characterization of a rare G1P[19] rotavirus strain from India: evidence of reassortment between human and porcine rotavirus strains

This study pertains to the characterization of a human rotavirus strain (NIV929893) with a rare specificity of G1P[19]. Three structural genes (VP4, VP6 and VP7) and one non-structural gene (NSP4) of strain NIV929893 were subjected to RT-PCR for amplification of entire coding regions. All of the amplicons were sequenced to carry out phylogenetic analysis. The complete amino acid sequences of the VP7 and VP4 gene products showed clustering of the VP7 gene with G1 strains of human origin and the VP4 gene with P[19] strains of porcine origin. The two viral proteins VP6 and NSP4, described previously as genetically linked proteins, were shown to be subgroup II and genotype B of human and porcine origins, respectively. The findings of this study provide evidence of reassortment between VP7/VP6 genes of humans and VP4/NSP4 genes of porcine species and an independent segregation of VP6 and NSP4 genes in a group A human rotavirus strain with G1P[19] specificity.

Characterization of full-length VP4 genes of OP354-like P[8] human rotavirus strains detected in Bangladesh representing a novel P[8] subtype

The G1 and G9 rotavirus strains MMC71 and MMC38 (subgroup II, NSP4 genogroup B), respectively, isolated from children in Bangladesh, were analyzed genetically. Full-length VP4 genes of these strains had 98.9% identity to each other and showed 83.9-89.4% identity to those of the P[4] and P[8] rotaviruses. Phylogenetic analysis of VP4 nucleotide sequences revealed that strains MMC38 and MMC71 were located in a lineage of P[8] strains. However, the cluster was highly divergent from the previously established P[8] strains. The VP8* portions of strains MMC38 and MMC71 showed more than 93.9% nucleotide sequence identity to OP354-like P[8] strains, and these strains were clustered into the same lineage. These findings indicate that the VP4 of these strains should be classified into a subtype of the P[8] genotype (P[8]b) that is distinct from that of common P[8] rotaviruses (P[8]a).

Full genomic analysis of a human group A rotavirus G9P[6] strain from Eastern India provides evidence for porcine-to-human interspecies transmission

Deduced amino acid sequence and phylogenetic analyses of a group A rotavirus G9P[6] strain (designated as mcs/13-07), detected from a 3-year-old child in Eastern India, revealed a VP8* closely related to porcine P[6] strains (P[6] sublineage 1D), and the VP7 clustered with G9 lineage-III strains. To our knowledge, this is the first report of human P[6] strain clustering in sublineage Id. Thus, to further characterize the evolutionary diversity of strain mcs/13-07, all gene segments were analyzed. VP6 and NSP4 exhibited genetic relatedness to Wa-like human subgroup II strains, while VP1-3, NSP1-3 and NSP5 were closely related to porcine strains. Based on the new classification system of rotaviruses, mcs/13-07 revealed a G9-P[6]-I1-R1-C1-M1-A8-N1-T1-E1-H1 genotype with close similarity to human Wa-like and porcine Gottfried strains. Therefore, considering the porcine-like or porcine origin of multiple gene segments, it might be tempting to assume that strain mcs/13-07 represents a rare instance of whole-virus transmission from pig to human, after which the virus evolved with time. Alternatively, it is possible that strain mcs/13-07 resulted from multiple reassortment events involving human subgroup II and porcine P[6] strains. Nevertheless, detection of strain mcs/13-07 provides further evidence for complex interspecies transmission events, which are frequent in developing countries.

Characterization ofVP7andVP4genes of rotavirus strains: 1990–1994 and 2000–2002

A total of 90 rotavirus-positive faecal specimens collected from patients hospitalized with diarrhoea in 1990–1994 (n=77) and 2000–2002 (n=13) were investigated for VP7 and VP4 genotypes. The specimens included 21 typable and 69 non-reactive or multireactive rotavirus strains as monitored by monoclonal antibody-based serotyping ELISA. Genotyping was carried out by multiplex PCR/sequencing using primers specific for bothVP7andVP4genes. The contribution of common genotypes (G1P[8], G2P[4], G3P[8], G4P[8]) in causing rotavirus diarrhoea was 79·2% and 92·3% in the years 1990–1994 and 2000–2002, respectively, while G9P[8] infections were detected at lower levels (1·3% and 7·7%) at both time-points. There was a predominance of G1P[8] in 1990–1994 and of G2P[4] in 2000–2002. The detection of unusual rotavirus strains (G1P[6], G1P[4], G1P[19], G2P[8], G3P[4], G4P[6]) in 19·5% of the patients indicated a significant contribution of reassortants in causing diarrhoea in western India.

Detection of a porcine-like rotavirus in a child with enteritis in Italy

During a 1-year rotavirus surveillance of children hospitalized with acute gastroenteritis in Brescia Hospital, Italy, a chimerical rotavirus strain, G3P[6], was detected, displaying the VP7 and VP4 genes of porcine origin and the NSP4 and VP6 genes of human origin. The reassortant nature of the virus rules out a direct zoonotic event.

Changing profile of rotavirus in Ireland: predominance of P[8] and emergence of P[6] and P[9] in mixed infections

Six hundred and thirty three fecal specimens were collected from patients under 6 years, suffering from non-bacterial, putative viral gastroenteritis in the south of Ireland, between 2003 and 2006. Following laboratory identification of rotavirus as the aetiological agent in 558 specimens, reverse transcriptase polymerase chain reaction was employed to amplify the VP7 and VP4 gene segments of 249 and 245 samples, respectively. G and P typing was subsequently carried out on these amplicons. G1 (65.1%), and G3 (16.1%) were found to be the most prevalent circulating G types over the course of the study. Both G2 (1.2%) and G9 (3.6%), were also found to be circulating, however, these types were less frequently detected. Mixed G type infections were found to account for 41 samples (14%). P typing was carried out on 245 samples. P[8] was the most commonly detected P type over the course of the study (93.5%). Both P[6] and P[9], which had not previously been detected in the Irish population, were detected during this investigation. P[6] was detected in both single and mixed P type infections, while P[9] was detected as part of mixed infections only. The key findings of this study were the emergence of P[6] and P[9] as epidemiologically important rotavirus strains in the Irish population. The profile of rotavirus is changing continuously in Ireland, and continued surveillance of the circulating strains is needed to detect the appearance of new strains, or new variants which could escape immune protection induced by an outdated vaccine.

Genetic heterogeneity, evolution and recombination in emerging G9 rotaviruses

G9 rotavirus is recognized as the emerging genotype spreading around the world. The rapidly increasing detection of this virus in association with the genetic heterogeneity raises questions regarding its origin and epidemiological importance. A total of 380 sequences of rotavirus G9 strains including our sequence data from Vietnam and Japan, which were detected from 1983 to 2006 in five different continents, were collected from GenBank to investigate their heterogeneity and evolution. A novel nomenclature for G9 rotaviruses is proposed, in which these viruses are clustered into 6 lineages with 11 sublineages. Multiple amino acid substitutions of VP7 specific for lineages and sublineages were found. Interestingly, six short amino acid motifs correctly defined phylogenetic lineages and sublineages. Another interesting finding was the identification of recombinant G9 rotavirus, bearing different genotype sequence. In view of rotavirus evolution, this report is an additional evidence to support the notion that there might exist a genomic relatedness between human and porcine rotaviruses.

Novel porcine rotavirus of genotype P[27] shares new phylogenetic lineage with G2 porcine rotavirus strain

A novel and unusual strain of porcine rotavirus (PoRV) CMP034 was isolated from a 7-week-old piglet during the epidemiological survey of porcine rotavirus infection in Chiang Mai province, Thailand from June 2000 to July 2001. Molecular characterization of gene VP4 by sequence analysis showed a low level of amino acid sequence identity, ranging from 56.7% to 76.6%, while comparison of VP8* portion showed 41.8% to 69.9% identity, with the 26 P genotypes recognized to date. Phylogenetic analysis of the VP4 sequence revealed that CMP034 was only distantly related to the other 26 P genotypes and was located in a separate branch. Sequence analysis of gene VP7 showed the highest level of amino acid identity (94.7%) with the PoRV G2-like reference strain 34461-4 but a lower level of identity with those of human G2 rotaviruses, ranging from 87.7% to 88.0%. Phylogenetic analysis of gene VP7 revealed two major lineages among G2 rotavirus strains based on the host origin. PoRV strain CMP034 clustered exclusively with G2-like PoRV strain 34461-4 in a novel lineage that is distinct from the major G2 human lineage. Moreover, strain CMP034 displayed a porcine-like VP6 and NSP5/6 with subgroup I specificity, while bearing an NSP4 with some genetic group B human-like characteristics. These findings provide evidence that CMP034 should be considered as a novel VP4 genotype P[27].

Molecular characterization of rare G3P[9] rotavirus strains isolated from children hospitalized with acute gastroenteritis

In 2004, an epidemiological survey of human rotavirus infection in Chiang Mai, Thailand detected two uncommon human rotavirus strains (CMH120/04 and CMH134/04) bearing AU-1-like G3P[9] genotypes in 1 year old children hospitalized with acute gastroenteritis. The CMH120/04 and CMH134/04 rotavirus strains were characterized by molecular analyses of their VP6, VP7, VP8*, and NSP4 gene segments as well as the determination of RNA patterns by polyacrylamide gel electrophoresis (PAGE). Analysis of the VP8* gene revealed a high level of amino acid sequence identities with those of P[9] rotavirus reference strains, ranging from 94.9% to 98.3%. The highest identities were shared with the human rotavirus AU-1 strain at 97.8% and 98.3% for CMH120/04 and CMH134/04 strains, respectively. Analysis of the VP7 gene sequence revealed the highest identities with G3 human rotavirus strain KC814 at 96.6% and 96.2% for CMH120/04 and CMH134/04 strains, respectively. Based on the analyses of VP7 and VP8* genes, CMH120/04 and CMH134/04 belonged to G3P[9] genotypes. In addition, analyses of VP6 and NSP4 sequences revealed a VP6 subgroup (SG) I, with NSP4 genetic group C specificities. Moreover, both strains displayed a long RNA electrophoretic pattern. The finding of uncommon G3P[9] rotaviruses in pediatric patients provided additional evidence of the genetic/antigenic diversities of human group A rotaviruses in the Chiang Mai area of Thailand.

Changing pattern of rotavirus G genotype distribution in Chiang Mai, Thailand from 2002 to 2004: Decline of G9 and reemergence of G1 and G2

Group A rotaviruses are the most common cause of acute viral diarrhea in humans and animals throughout the world. Previous surveillance studies of group A rotaviruses in Thailand indicated that the dominant types of rotaviruses were changing from time to time. During 2000 and 2001, the G9 rotavirus emerged as the most prevalent genotype, with an exceptionally high frequency (91.6%) in Chiang Mai, Thailand. In the year 2002-2004, group A rotavirus was detected in 98 out of 263 (37.3%) fecal specimens collected from children hospitalized with diarrhea. Of these, 40 (40.8%) were G9P[8], 33 (33.7%) were G1P[8], 23 (23.5%) were G2P[4], and 2 (2.0%) were G3P[9]. The G9P[8] was found to be the most predominant strain in 2002, but the prevalence rate abruptly decreased during the period 2003-2004. In addition, G2P[4] reemerged in the epidemic season of 2003, whereas G1P[8] became the most predominant strain in the following year (2004). Phylogenetic analysis of the VP7 genes revealed that G1, G2, and G9 rotavirus strains clustered together with recently circulating strains, which were isolated from different regional settings in Thailand. In conclusion, the study demonstrated a decrease of incidence of G9P[8] and reemergence of G1P[8] and G2P[4] rotaviruses in Chiang Mai, Thailand during the period 2002-2004. These data imply that the distribution of group A rotavirus genotypes circulating in Chiang Mai, Thailand, changes over time.

Identification of group A porcine rotavirus strains bearing a novel VP4 (P) Genotype in Italian swine herds

The VP4 gene of a G5 Italian porcine rotavirus strain, 344/04-1, was nontypeable by PCR genotyping. The amino acid sequence of the full-length VP4 protein had low identity (<or=76.6%) with the homologous sequences of representative strains of the remaining P genotypes, providing evidence for a novel P genotype.

Detection of rare G3P[19] porcine rotavirus strains in Chiang Mai, Thailand, provides evidence for origin of the VP4 genes of Mc323 and Mc345 human rotaviruses

Among 175 fecal specimens collected from diarrheic piglets during a surveillance of porcine rotavirus (PoRV) strains in Chiang Mai, Thailand, 39 (22.3%) were positive for group A rotaviruses. Of these, 33.3% (13 of 39) belonged to G3P[19], which was a rare P genotype seldom reported. Interestingly, their VP4 nucleotide sequences were most closely related to human P[19] strains (Mc323 and Mc345) isolated in 1989 from the same geographical area where these PoRV strains were isolated. These P[19] PoRV strains were also closely related to another human P[19] strain (RMC321), isolated from India in 1990. The VP4 sequence identities with human P[19] were 95.4% to 97.4%, while those to a porcine P[19] strain (4F) were only 87.6 to 89.1%. Phylogenetic analysis of the VP4 gene revealed that PoRV P[19] strains clustered with human P[19] strains in a monophyletic branch separated from strain 4F. Analysis of the VP7 gene confirmed that these strains belonged to the G3 genotype and shared 97.7% to 98.3% nucleotide identities with other G3 PoRV strains circulating in the regions. This close genetic relationship was also reflected in the phylogenetic analysis of their VP7 genes. Altogether, the findings provided peculiar evidence that supported the porcine origin of VP4 genes of Mc323 and Mc345 human rotaviruses.

Identification of a novel VP4 genotype carried by a serotype G5 porcine rotavirus strain

Rotavirus genome segment 4, encoding the spike outer capsid VP4 protein, of a porcine rotavirus (PoRV) strain, 134/04-15, identified in Italy was sequenced, and the predicted amino acid (aa) sequence was compared to those of all known VP4 (P) genotypes. The aa sequence of the full-length VP4 protein of the PoRV strain 134/04-15 showed aa identity values ranging from 59.7% (bovine strain KK3, P8[11]) to 86.09% (porcine strain A46, P[13]) with those of the remaining 25 P genotypes. Moreover, aa sequence analysis of the corresponding VP8* trypsin cleavage fragment revealed that the PoRV strain 134/04-15 shared low identity, ranging from 37.52% (bovine strain 993/83, P[17]) to 73.6% (porcine strain MDR-13, P[13]), with those of the remaining 25 P genotypes. Phylogenetic relationships showed that the VP4 of the PoRV strain 134/04-15 shares a common evolutionary origin with porcine P[13] and lapine P[22] rotavirus strains. Additional sequence analyses of the VP7, VP6, and NSP4 genes of the PoRV strain 134/04-15 revealed the highest VP7 aa identity (95.9%) to G5 porcine strains, a porcine-like VP6 within VP6 genogroup I, and a Wa-like (genotype B) NSP4, respectively. Altogether, these results indicate that the PoRV strain 134/04-15 should be considered as prototype of a new VP4 genotype, P[26], and provide further evidence for the vast genetic and antigenic diversity of group A rotaviruses.

Identification of the novel lapine rotavirus genotype P[22] from an outbreak of enteritis in a Hungarian rabbitry

Application of improved molecular techniques in the detection and characterization of rotavirus strains has led to the recent description of several new combinations, specificities, and genetic variants of the outer capsid genes, VP7 and VP4. In spite of the enormous diversity of mammalian rotavirus strains, the few lapine rotaviruses characterized to date, appear to carry a narrow range of such antigen combinations; only P[14], G3 and, based on a more recent study, P[22], G3 rotaviruses have proved to be epidemiologically important in rabbits. In the present study, we characterized a lapine group A rotavirus with a super-short electropherotype detected in an outbreak of fatal enteritis in a Hungarian commercial rabbitry. Based on sequence and phylogenetic analysis of the VP7, VP4, and NSP4 genes, our lapine strain is a P[22], G3 rotavirus that carries the NSP4 genotype shared by most lapine rotaviruses. Although the P[22] VP4 specificity has been newly identified, the relatively high sequence variation between our strain and those identified in Italy (89.1-90.4% nucleotide identity; region VP8*) implies that these strains diversified far before they were described for the first time, strongly suggesting that this genotype may have circulated in rabbitries or in nature without prior detection. We conclude that genotype P[22] lapine rotaviruses show a wider geographical dispersal than previously thought, although understanding their true epidemiological significance needs further investigation.

Serotype diversity and reassortment between human and animal rotavirus strains: implications for rotavirus vaccine programs

The development of rotavirus vaccines that are based on heterotypic or serotype-specific immunity has prompted many countries to establish programs to assess the disease burden associated with rotavirus infection and the distribution of rotavirus strains. Strain surveillance helps to determine whether the most prevalent local strains are likely to be covered by the serotype antigens found in current vaccines. After introduction of a vaccine, this surveillance could detect which strains might not be covered by the vaccine. Almost 2 decades ago, studies demonstrated that 4 globally common rotavirus serotypes (G1-G4) represent >90% of the rotavirus strains in circulation. Subsequently, these 4 serotypes were used in the development of reassortant vaccines predicated on serotype-specific immunity. More recently, the application of reverse-transcription polymerase chain reaction genotyping, nucleotide sequencing, and antigenic characterization methods has confirmed the importance of the 4 globally common types, but a much greater strain diversity has also been identified (we now recognize strains with at least 42 P-G combinations). These studies also identified globally (G9) or regionally (G5, G8, and P2A[6]) common serotype antigens not covered by the reassortant vaccines that have undergone efficacy trials. The enormous diversity and capacity of human rotaviruses for change suggest that rotavirus vaccines must provide good heterotypic protection to be optimally effective.

Characterization of a novel P[25],G11 human group a rotavirus

A novel rotavirus strain (Dhaka6) isolated from a 21-year-old Bangladeshi male patient was characterized by sequence analysis of its VP7 and VP4 gene segments. Phylogenetic analysis of the VP7 gene of the Dhaka6 strain revealed a common evolutionary lineage with porcine G11 rotavirus strains. This isolate is the first reported G11 rotavirus strain infecting a human host. Comparison of the VP4 gene sequences with all currently recognized 24 different P genotypes revealed only low nucleotide (54 to 71%) and amino acid (52 to 76%) sequence identities. This lack of high sequence similarity in the VP4 gene indicates that the Dhaka6 isolate represents a new group A rotavirus P genotype, to which we propose assignment of the designation P[25].

Changing distribution of group A rotavirus G-types and genetic analysis of G9 circulating in Japan

A total of 1,797 fecal specimens from infants and children with acute gastroenteritis in Japan from July 2000 to June 2003 were tested for group A rotavirus by ELISA, RT-PCR, RNA-PAGE and latex agglutination methods. Of these, 439 were found to be positive for group A rotavirus and this presented 24.4%. In 2000-2001, G1 was the most prevalent (45.5%) followed by G2 (32.5%), G3 (12.3%), G9 (5.9%) and G4 (2.6%). However, G2 was found predominant with 40% in the following year (2001-2002). Interestingly, G9 had a rapid increase of infection up to 17.8%. In 2002-2003, G3 dominated over other G-types with 34%. Another interesting feature of the study was the demonstration of great genetic diversity among G9 strains in Japan. Worth of note was the first prevalence pattern of rotavirus G-types with an increase of G2, G3 as well as G9 and a decrease of G1 during the 20 year-survey of rotavirus infection in Japan.

Predominance of porcine rotavirus G9 in Japanese piglets with diarrhea: close relationship of their VP7 genes with those of recent human G9 strains

Type G9 of group A rotavirus (GAR) was shown to be predominant in a survey of VP7 (G) and VP4 (P) genotypes among porcine GARs associated with outbreaks of diarrhea in young pigs in Japan between 2000 and 2002. Comparison of the G9 VP7 gene sequences showed that the porcine G9 strains were more closely related to human G9 strains reemerging globally since the mid-1990s than to those from the mid-1980s. The VP7 gene sequences of porcine G9 strains from different farms were divergent (6.1 to 7.2% difference in nucleotides), suggesting that these G9 VP7 genes were not the result of recent introduction into the porcine population. Regarding the P genotype specificities of porcine G9 strains, while the majority of strains were close to unusual porcine P types (P[13] and P[23]), two strains were of the P[6] type, which has closer sequence identity with the human AU19 strain than with the porcine Gottfried strain. These unexpected results suggest that G9 GARs in the porcine population have spread more widely than previously thought and that the VP7 genes of porcine G9 strains and those of some human G9 strains detected recently may have a common progenitor.

Typing of human rotaviruses: nucleotide mismatches between the VP7 gene and primer are associated with genotyping failure

Background

Rotavirus genotyping is performed by using reverse transcription PCR with type-specific-primers. Because the high rotavirus mutation rate generates an extensive genomic variation, different G-type-specific primer sets are applied in different geographical locations. In Bangladesh, a significant proportion (36.9%) of the rotavirus strains isolated in 2002 could not be G-typed using the routinely used primer set. To investigate the reason why the strains were untypeable, nucleotide sequencing of the VP7 genes was performed.

Results

Four nucleotide substitutions at the G1 primer-binding site of the VP7 gene of Bangladeshi G1 rotaviruses rendered a major proportion of circulating strains untypeable using the routine primer set. Using an alternative primer set, we could identify G1 rotaviruses as the most prevalent genotype (44.8%), followed by G9 (21.7%), G2 (15.0%) and G4 (13.8%).

Conclusion

Because of the natural variation in the rotaviral gene sequences, close monitoring of rotavirus genotyping methods is important.

Global distribution of rotavirus serotypes/genotypes and its implication for the development and implementation of an effective rotavirus vaccine

A safe and effective rotavirus vaccine is urgently needed, particularly in developing countries. Critical to vaccine development and implementation is a knowledge base concerning the epidemiology of rotavirus G and P serotypes/genotypes throughout the world. The temporal and geographical distribution of human rotavirus G and P types was reviewed by analysing a total of 45571 strains collected globally from 124 studies reported from 52 countries on five continents published between 1989 and 2004. Four common G types (G1, G2, G3 and G4) in conjunction with P[8] or P[4] represented over 88% of the strains analysed worldwide. In addition, serotype G9 viruses associated with P[8] or P[6] were shown to have emerged as the fourth globally important G type with the relative frequency of 4.1%. When the global G and/or P type distributions were divided into five continents/subcontinents, several characteristic features emerged. For example, the P[8]G1 represented over 70% of rotavirus infections in North America, Europe and Australia, but only about 30% of the infections in South America and Asia, and 23% in Africa. In addition, in Africa (i) the relative frequency of G8 was as high as that of the globally common G3 or G4, (ii) P[6] represented almost one-third of all P types identified and (iii) 27% of the infections were associated with rotavirus strains bearing unusual combinations such as P[6]G8 or P[4]G8. Furthermore, in South America, uncommon G5 virus appeared to increase its epidemiological importance among children with diarrhea. Such findings have (i) confirmed the importance of continued active rotavirus strain surveillance in a variety of geographical settings and (ii) provided important considerations for the development and implementation of an effective rotavirus vaccine (e.g. a geographical P-G type adjustment in the formulation of next generation multivalent vaccines).

A porcine G9 rotavirus strain shares neutralization and VP7 phylogenetic sequence lineage 3 characteristics with contemporary human G9 rotavirus strains

Of five globally important VP7 (G) serotypes (G1-4 and 9) of group A rotaviruses (the single most important etiologic agents of infantile diarrhea worldwide), G9 continues to attract considerable attention because of its unique natural history. Serotype G9 rotavirus was isolated from a child with diarrhea first in the United States in 1983 and subsequently in Japan in 1985. Curiously, soon after their detection, G9 rotaviruses were not detected for about a decade in both countries and then reemerged in both countries in the mid-1990s. Unexpectedly, however, such reemerged G9 strains were distinct genetically and molecularly from those isolated in the 1980s. Thus, the origin of the reemerged G9 viruses remains an enigma. Sequence analysis has demonstrated that the G9 rotavirus VP7 gene belongs to one of at least three phylogenetic lineages: lineage 1 (strains isolated in the 1980s in the United States and Japan), lineage 2 (strains first isolated in 1986 and exclusively in India thus far), and lineage 3 (strains that emerged/reemerged in the mid-1990s). Currently, lineage 3 G9 viruses are the most frequently detected G9 strains globally. We characterized a porcine rotavirus (A2 strain) isolated in the United States that was known to belong to the P[7] genotype but had not been serotyped by neutralization. The A2 strain was found to bear serotype G9 and P9 specificities as well as NSP4 [B] and subgroup I characteristics. By VP7-specific neutralization, the porcine G9 strain was more closely related to lineage 3 viruses than to lineage 1 or 2 viruses. Furthermore, by sequence analysis, the A2 VP7 was shown to belong to lineage 3 G9. These findings raise intriguing questions regarding possible explanations for the emergence of variations among the G9 strains.

Emergence of human G9 rotavirus with an exceptionally high frequency in children admitted to hospital with diarrhea in Chiang Mai, Thailand

Among 315 fecal specimens collected from children hospitalized with diarrhea in Chiang Mai, Thailand, in 2000-2001, group A rotavirus was detected in 107 (34.0%). Of these, 98 (91.6%) were G9, 6 (5.6%) were G3 and 3 (2.8%) were G2, respectively. Identification of their P-types demonstrated that 103 (96.3%) were P[8], 3 (2.8%) were P[4], and 1 (0.9%) was P[3] genotypes. Determination of G- and P-type combination revealed that all of G9 isolates were associated with P[8]. G9P[8] was the most predominant genotype and accounted for the majority (91.6%) of rotaviruses detected in this study. Molecular characterization of these G9 isolates demonstrated that all had long electropherotype, 96 of 98 (98.0%) belonged to subgroup II, one belonged to subgroup I and the other one was subgroup unidentifiable. All of G9 isolates possessed NSP4 genetic group B except for one isolate that showed dual genetic group specificities, B and C. The full-length VP7 gene nucleotide sequences among 15 representatives of these G9 strains were found to be highly homologous with percent identities of 99.3%-100%. Comparison with other G9 strains recently isolated showed that their nucleotide sequences were closely related to those of the US strain, US1205 (98.7%-99.0%) and Thai strain, 97CM108 (98.1%-99.0%). Interestingly, they were most closely related to the Japanese strain, 00-SG2509VP7, isolated in the same epidemic season, with percent nucleotide sequence identity of 99.4%-99.8%. The data imply that G9 strains isolated in this study and a G9 strain isolated in Japan in the year 2000 might have descended from the same ancestor.

Emergence of G3 and G9 rotavirus and increased incidence of mixed infections in the southern region of Ireland 2001-2004

Two hundred and thirty fecal specimens were collected from children (up to 5 years of age) admitted with suspected rotaviral gastroenteritis at four Irish hospitals (Cork University Hospital, Mercy Hospital, Cork, Waterford Regional Hospital, and Kerry General Hospital) in the southern region of Ireland, between 2001 and 2004. Following laboratory confirmation of the aetiological agent, the rotavirus G-type was determined in all positive samples by reverse transcriptase-polymerase chain reaction (RT-PCR). The distribution of the G-types (n=230) over the 3 year period was G1 (31%), G9 (21.8%), G3 (8.7%), G4 (6.5%), and G2 (3.5%). There were many mixed infections which accounted for 28.5% of the collection. G9 emerged as the most prevalent G type (30.1%) in 2001-2002, whilst G3 first emerged in 2002-2003 and accounted for 15.8% of the collection. Notably, G2 strains were present at a very low frequency (3.5%) during 2001-2004, compared to an earlier study (1997-1999), where they accounted for 28.5% of the specimens. A smaller subset of the study collection was similarly P-typed (n=139). P[8]-type was identified as the most prevalent P-type, accounting for 97.4% (n=186), while P[4] accounted for just 2.6% (n=5) of the collection. The low frequency of P[4] coincided with the decrease in G2 strains in circulation. The key finding in this study was the emergence of G3- and G9-serotypes as epidemiologically important rotavirus strains since 1999, and the low prevalence of the previously common G2 strains in Ireland. The profile of rotavirus is changing continuously in Ireland and the implications for a successful vaccination program are discussed.

Human infection with a P[14], G3 lapine rotavirus

Group A rotaviruses are the main cause of severe diarrhoea in humans and animals throughout the world. We report the first description of a clinically apparent infection with a P[14], G3 rotavirus (strain B4106) in a hospitalized 6-year-old child. The VP7 gene of the B4106 strain had the closest sequence similarity (94% and 97% on the nucleotide and amino acid level, respectively) with strain 30/96 (P[14], G3), a lapine rotavirus isolated in an Italian rabbit in 1996 while the VP4 gene had the closest similarity with strain 30/96 on the nucleotide level (96%), and with lapine strains C-11 (P[14], G3) and Alabama (P[14], G3), isolated in the United States in the 1980s on the amino acid level (99%). The host restriction determinant gene NSP4 of B4106 was also most similar to lapine strain Alabama (95% nt identity and 97% aa identity). Phylogenetic analysis showed that the VP4, VP7, and NSP4 genes of the B4106 strain share a common evolutionary lineage with those of lapine rotavirus strains. We therefore hypothesize that a lapine rotavirus was able to cross the host species barrier and caused disease in a new host. The increasing detection of strains in humans that were previously believed to be restricted to animals raises questions whether interspecies transmission of rotaviruses is a common event in nature.

Eight-year survey of human rotavirus strains demonstrates circulation of unusual G and P types in Hungary

Between 1992 and 2000, a total of 4173 rotavirus-positive samples were collected from two areas of Hungary. Of these, 2020 specimens (48.4%) were analyzed for G serotype, using monoclonal antibody-based immunoassay and reverse transcription-PCR. By the two methods, 1789 samples were specified as G1 (62%), G2 (12.2%), G3 (1.4%), G4 (6.4%), G6 (1.0%), G9 (2.9%), or mixed infection (2.6%), and the remaining 231 (11.4%) could not be G typed. The linkage between G and P type, subgroup specificity, and RNA profile was investigated with a sample subset. Among these specimens, we identified both the four globally common strains (P[8],G1 subgroup II (sgII); P[4],G2 sgI; P[8],G3 sgII; and P[8],G4 sgII) and six uncommon strains (P[6],G4 sgII; P[9],G3 sgI; P[9],G6 sgI; P[14],G6 sgI; P[8],G9 sgII; and P[8],G9 sgI). All strains with P[8], P[6], P[9], and P[14] specificities had a long electropherotype, whereas most of those carrying a P[4] specificity were associated with a short electropherotype. Although once considered to be rare, P[9],G6 and P[8],G9 rotavirus strains represent potentially important new serotypes in Hungary.

Serologic and genomic characterization of a G12 human rotavirus in Thailand

The G and P type specificity of the human rotavirus strain T-152 (G12P[9]) isolated in Thailand was serologically confirmed with G12-specific monoclonal antibodies prepared in this study by using a reference G12 strain, L26, as an immunizing antigen and a P[9]-specific monoclonal antibody, respectively. The genomic relationship of strain T-152 with representative human rotavirus strains was examined by means of Northern blot analysis. The results showed that T152 is closely related to strain AU-1 (G3P[9]). Gene 5 (NSP1 gene) of T152, which did not hybridize with those of any other strains examined, was characterized by sequence determination. The T152 NSP1 gene is 1,652 nucleotides in length, encodes 493 amino acids, and exhibits low identity to those of representative human and animal rotaviruses.

Genetic variability of human rotavirus strains isolated from Eastern and Northern India

An epidemiological study was conducted in Eastern and Northern India to determine the genomic diversity of rotaviruses in these parts of the country. In 2001, a total of 126 Group A rotavirus positive samples were detected from children below 4 years of age with diarrhoea from Kolkata, Dibrugarh and Bhubaneswar in Eastern India, and Chandigarh, a city in Northern India. All the samples were genotyped for VP7 (G-type) and VP4 (P-type) gene by reverse transcription (RT) and multiplex PCR using different type specific primers. The strains with G1P[8] (32.5%) was predominant as reported earlier [Das et al. (2002) J Clin Microbiol 40:146-149] followed by G2P[4](4.7%) and only one sample was of G4P[8] specificity. Along with these common types some rare strains like G1P[6], G2P[8], G2P[6], G4P[4], and G4P[6] were also detected in 14.3% of cases. Thirty percent of samples in this study were mixed infections and 21 (16.7%) specimens remained untypeable either for the VP7 or for the VP4 gene. After sequencing of the VP7 gene, two G9 strains (RMC321 and ISO-3) were identified with P[8] and P[19] specificities. Sequence analysis revealed that they have much lower homology to the G9 strains (116E, INL1, and G16) isolated earlier from Indian subcontinent, but have much higher homology to isolates from Argentina, Brazil, Malawi, Taiwan, and USA suggesting a separate progenitor for these strains.

A novel type of VP4 carried by a porcine rotavirus strain

The gene encoding the VP8* trypsin-cleavage product of the VP4 protein of porcine rotavirus strain A34 was sequenced, and the predicted amino acid (aa) sequence was compared to the homologous region of all known P genotypes. The aa sequence of the VP8* of strain A34 shared low identity, ranging from 39% (bovine strain B223, P8[11]) to 76% (human strain 69M, P4[10]), with the homologous sequences of representative strains of the remaining 21 P genotypes. Phylogenetic relationships showed that the VP8* of strain A34 shares a common evolutionary lineage with those of human 69M (P4[10]) and equine H-2 (P4[12]) strains. Hyperimmune sera raised to strain A34 and to a genetic reassortant strain containing the VP4 gene from strain A34, both with high homologous neutralization titer via VP4, failed to neutralize strains representative of 15 different P genotypes. These results indicate that strain A34 should be considered as prototype of a new P genotype and serotype (P14[23]) and provide further evidence for the vast genetic and antigenic diversity of group A rotaviruses.

Genetic variability among serotype G6 human rotaviruses: identification of a novel lineage isolated in Hungary

Rotavirus serotype G6 has been demonstrated to be a rare cause of gastroenteritis in man. To date, only a few well characterized strains have been described from Italy, Australia, and the United States. Nucleotide sequencing of G6 VP7 genes shows that these strains belong to two distinct G6 lineages, one for strains of serotype P11[14],G6 (PA169-like strains) and one for strains of serotype P3[9],G6 (PA151-like strains). In this study, we sequenced the VP7 genes and VP8* gene fragments of human rotavirus G6 strains detected in Hungary. Phylogenetic analysis demonstrated that the VP7 genes of Hungarian G6 strains fell into three lineages, represented by a single PA169-like strain, three PA151-like strains, and two novel G6 strains, respectively. The amino acid sequence identity of VP7 was 97.2-100% within each lineage and 92-93.9% between any two lineages. The sequence analysis of VP8* revealed that the single PA169-like Hungarian G6 strain belonged to genotype P[14] and was phylogenetically closely related to P11[14],G6 strains characterized previously. In contrast, the VP8* of PA151-like Hungarian G6 strains clustered in accordance with their VP7 genes representing genetically distinguishable variants of genotype P[9]. This finding raises the possibility that Hungarian genotype P[9],G6 strains might have been generated through independent reassortment events. Serotype G6-specific primers for each human G6 lineage were also developed. The use of these primers in reverse-transcription polymerase chain reaction genotyping may help determine the epidemiological role of G6 strains in humans.

Characterization of serotype G9 rotavirus strains isolated in the United States and India from 1993 to 2001

The emergence of rotavirus serotype G9 as a possible fifth globally common serotype in the last decade, together with its increasing detection in association with various genome constellations, raises questions about the origins and epidemiological importance of recent G9 isolates. We examined a collection of 40 G9 strains isolated in the United States from 1996 to 2001 and in India since 1993 to determine their VP7 gene sequences, P types, E types, subgroup specificities, and RNA-RNA hybridization profiles. With the exception of two U.S. strains, all of the study strains shared high VP7 gene sequence homology (<2.5% sequence divergence on both the nucleotide and amino acid levels) and were more closely related to other recent isolates than to the first G9 strains isolated in the 1980s. The VP7 gene sequence and RNA-RNA hybridization profiles of the long-E-type strains showed greater variation than the short-E-type strains, suggesting that the latter strains are the result of a relatively recent reassortment event of the G9 VP7 gene into a short-E-type lineage. No evidence for reassortment of genes other than VP4 and VP7 between major human rotavirus genogroups was observed. Except for Om46 and Om67, which formed a distinct clade, phylogenetic analysis showed that most of the study strains grouped together, with some subgroups forming according to genetic constellation, geographic location, and date of isolation. The high potential of G9 strains to generate different P and G serotype combinations through reassortment suggests that it will be important to determine if current vaccines provide heterotypic protection against these strains and underscores the need for continued surveillance for G9 and other unusual or emerging rotavirus strains.

Genetic characterization of a novel, naturally occurring recombinant human G6P[6] rotavirus

A binary classification system has been established for group A rotaviruses, with the viral capsid protein VP7 defining G types and VP4 defining P types. At least 15 G types and 21 P types have been isolated globally with various G and P combinations. Most of the currently circulating human rotaviruses belong to G1P[8], G2P[4], G3P[8], and G4P[8]. We report a human rotavirus strain (B1711) with a novel genotypic VP7/VP4 combination of G6P[6]. This unique rotavirus was isolated from a 13-month-old human immunodeficiency virus (HIV)- negative child of an HIV-seropositive Malian mother that was hospitalized with severe diarrhea in Belgium after returning from a trip to Mali. The VP7 and VP4 genes of the rotavirus strain were sequenced, and phylogenetic trees were constructed. Nucleotide and amino acid sequence comparisons with 15 known G genotypes indicated that the VP7 sequence of strain B1711 was most closely related to an American (Se584) and an Italian (PA151) human G6 strain (95 to 96% nucleotide and 98% amino acid identity). Comparison of the VP4 sequence with 21 P types showed the closest similarity to P[6] genotypes, with greatest similarity to a G8P[6] Malawi strain (mw131) (97% nucleotide and 98% amino acid identity). The B1711 strain is the first reported rotavirus isolate with a G6P[6] genotypic combination. The discovery and surveillance of novel human and nonhuman rotavirus G or P types or of novel G/P combinations is essential for the design of future rotavirus vaccines and for our understanding of rotavirus diversity and evolution.

Epidemiological features of rotavirus infection among hospitalized children with gastroenteristis in Ho Chi Minh City, Vietnam

An epidemiological study of the G serotype and P genotype distribution of group A rotaviruses by using ELISA and/or RT-PCR was conducted in children (aged 1 month to 15 years) with diarrhea that were admitted to the General Children's Hospital No. 1, Ho Chi Minh City, Vietnam from December 1999 to November 2000. The results showed that rotavirus is associated with 65.6% (889/1355) of diarrheal admissions. Rotavirus infection mostly affected children under 2 years of age with a peak incidence in children 1 to 2 years of age (75.7%) and it occurs year round with a slight seasonal pattern; 99.5% of the specimens could be G-typed: G1 was predominant (68.7%), followed by G4 (15.4%), G2 (12.3%), G3 (0.6%), and G9 (0.5%). High identities of VP7 nucleotide (96.3 to 96.9%) and deduced amino acid (98.1 to 98.4%) were found between two Vietnamese G9 strains and also the recent emergence of G9 strains US 1205, Brazilian R143, and Malawian MW69. Mixed infections were identified in 17 (2.0%), and 5 strains (0.5%) remained untypable. The four most common worldwide strains, G1P[8], G2P[4], G3P[8], and G4P[8], constituted 81.1% of all rotaviruses typed with G1P[8] being the most prevalent type (58.2%). Unusual G/P combinations (11 strains) were detected in 11.7% of all strains, of which, G1P[4] was the most prevalent, accounting for 5.6% of the total. Several combinations of G and P types were observed in this study, suggesting a complex rotavirus infection pattern in Vietnam. This study has provided for the first time clear indication on the circulating G and P genotypes among hospitalized children in Ho Chi Minh City, Vietnam. The results suggest that these viral infections are prevalent among hospitalized children and that the four most common worldwide G types as well as the four most common G-P combinations were also infecting children in Ho Chi Minh City, Vietnam. This result could have important implications for rotavirus vaccine programs and for understanding the epidemiological characteristics of human rotavirus in Ho Chi Minh City, Vietnam.