Characterization of human rotavirus serotype G9 isolated in Japan and Thailand from 1995 to 1997

Epidemiology of gastroenteritis viruses in Japan: Prevalence, seasonality, and outbreak

Acute gastroenteritis has been recognized as one of the most common diseases in humans and continues to be a major public health problem worldwide. Several groups of viruses have been reported as the causative agents of acute gastroenteritis, including rotavirus, norovirus, sapovirus, human astrovirus, adenovirus, and an increasing number of others which have been reported more recently. The epidemiology, prevalence, seasonality, and outbreaks of these viruses have been reviewed in a number of studies conducted in Japan over three decades. Rotavirus and norovirus were the two most common viruses detected almost equally in children under 5 years of age who were suffering from acute gastroenteritis. Like many other countries, the main rotavirus strains circulating in pediatric patients in Japan are G1P[8], G2P[4], G3P[8], and G9P[8]. Norovirus GII.4 was involved in most outbreaks in Japan and found to be associated with the emergence of new variants Sydney_2012. The classic human astrovirus, MLB, and VA clades astroviruses were also commonly found in pediatric patients with acute diarrhea. The sapovirus and adenovirus have been identified as the minor viral causative agents for acute gastroenteritis in Japan.

Distribution of Human Rotaviruses, Especially G9 Strains, in Japan from 1996 to 2000

A 4-year (1996-2000) survey of rotavirus infection involving 2,218 diarrheal fecal specimens of children collected from five regions of Japan was conducted. A total of 642 (28.9%) specimens were found to be rotavirus positive. A changed prevalence pattern of rotavirus G serotype was found with an increase of G9 and G2 and a decrease of G1, although G1 remained the prevailing serotype. Serotype G9 was unexpectedly determined to be the prevailing serotype in Sapporo (62.5%) and Tokyo (52.9%) in 1998-1999, and in Saga (78.4%) in 1999-2000. G9 strains isolated from 1998-1999 belonged to the P[8]-NSP4-Wa-group with long RNA pattern, while, G9 strains isolated from 1999-2000 belonged to three groups, the P[8]-NSP4-Wa-group with long RNA pattern, the P[4]-NSP4-KUN-group with short RNA pattern and a mixed-type group (P[4]/P[8]-NSP4-KUN/Wa-group with long RNA pattern). Both sequence and immunological analysis of VP7 revealed that the G9 strains from 1999-2000 were much more closely related to the G9 strains isolated worldwide in the 1990s, including G9 strains found in Thailand in 1997. However, the G9 strains from 1998-1999 were distinct from these and more closely related to the G9 prototype strains F45, AU32 and WI61 discovered in Japan and the US in the 1980s. Thus the G9 strains isolated in 1998-1999 had progenitors common to the G9 prototype strains, while the strains isolated in 1999-2000 did not directly evolve from them but were related to global G9 strains that have emerged in recent years. These data supported our previous report that G9 rotavirus might exist as two or more subtypes with diverse RNA patterns, P-genotype and NSP4 genogroup combinations (Y.M. Zhou et al., J. Med. Virol. 65: 619-628, 2001) and suggested that G9 rotavirus prevalent in Japan during two successive years belonged to different subtypes. The nucleotide sequences presented in this paper were submitted to DDBJ, EMBL and GenBank nucleotide sequence databases. The accession numbers are: 00-Ad2863VP7 (AB091746), 00-OS2986VP7 (AB091747), 00-SG2509VP7 (AB091748), 00-SG2518VP7 (AB091749), 00-SG2541 (AB091750), 00-SG2864 (AB091751), 00-SP2737VP7 (AB091752), 99-SP1542VP7 (AB091753), 99-SP1904VP7 (AB091754), 99-TK2082VP7 (AB091755) and 99-TK2091VP7 (AB091756).

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

Rotavirus is a major cause of morbidity and mortality of infants and young children with diarrhea throughout the world. In Thailand, extensive studies of rotavirus infections have been reported continually and rotavirus diarrhea remains a common illness. To monitor the epidemiological situation of rotavirus in Chiang Mai, Thailand, surveillance of rotavirus circulating in pediatric patients was conducted. A total of 160 fecal specimens collected from children hospitalized with diarrhea were tested for rotaviruses groups A, B, and C by RT-PCR and their genotypes were identified by multiplex PCR and nucleotide sequencing. Group A rotavirus was detected at 29.4% but none of group B and C was found in this study. Molecular characterizations of G- and P-genotypes revealed three different G-P combinations, G1P[8] was the most predominant genotype with the prevalence of 72.3% followed by G2P[4] at 19.2%, and G3P[8] at 8.5%. Phylogenetic analyses of VP7 and VP4 genes of the representative strains detected in the present study, G1, G2, G3, and P[4] and P[8], respectively, revealed that G1 belonged to G1-Ic and G1-II, G2 belonged to G2-II, and G3 belonged to G3-III-S4 lineages while P[4] and P[8] were identified as P[4]-V and P[8]-III lineages. Analyses of VP6, NSP4, and NSP5 genes demonstrated that these representative strains belonged to genotypes I1 and I2, E1 and E2, and H1 and H2, respectively. Analyzing the association of G- and P-genotypes with I, E, H genotypes revealed unique patterns of genotypic linkage. The G1P[8] and G3P[8] were intimately linked with I1, E1, H1 genotypes and displayed the genetic features of G1-P[8]-I1-E1-H1 and G3-P[8]-I1-E1-H1, respectively, while G2P[4] was closely linked to I2, E2, H2 genotypes and showed the genetic pattern of G2-P[4]-I2-E2-H2. This study provides epidemiological information and insight into the genetic background of rotaviruses circulating in pediatric patients in Chiang Mai, Thailand.

Genotypic linkages of VP4, VP6, VP7, NSP4, NSP5 genes of rotaviruses circulating among children with acute gastroenteritis in Thailand

Rotavirus is the main cause of acute viral gastroenteritis in infants and young children worldwide. Surveillance of group A rotavirus has been conducted in Chiang Mai, Thailand since 1987 up to 2004 and those studies revealed that group A rotavirus was responsible for about 20-61% of diarrheal diseases in hospitalized cases. In this study, we reported the continuing surveillance of group A rotavirus in 2005 and found that group A rotavirus was detected in 43 out of 147 (29.3%) stool samples. Five different G and P genotype combinations were detected, G1P[8] (27 strains), G2P[4] (12 strains), G9P[8] (2 strains), G3P[8] (1 strain), and G3P[10] (1 strain). In addition, analysis of their genotypic linkages of G (VP7), P (VP4), I (VP6), E (NSP4), and H (NSP5) genotypes demonstrated that the rotaviruses circulating in Chiang Mai, Thailand carried 3 unique linkage patterns. The G1P[8], G3P[8], and G9P[8] strains carried their VP6, NSP4, NSP5 genotypes of I1, E1, H1, respectively. The G2P[4] strains were linked with I2, E2, H2 genotypes, while an uncommon G3P[10] genotype carried unique genotypes of I8, E3 and H6. These findings provide the overall picture of genotypic linkage data of rotavirus strains circulating in Chiang Mai, Thailand.

[Evolution of group A Rotavirus strains circulating in Tunisia over a 3-year period (2005-2007)]

BACKGROUND

Rotaviruses are the most frequent agents associated with diarrhoea in children worldwide. Analysis of mobility of the 11 segments of genomic RNA by polyacrylamide gel electrophoresis (PAGE) yields a pattern which is characteristic for a particular rotavirus isolate. The group A rotaviruses can be further characterized by analysis of VP7 and VP4 genes specificities, responsible for rotavirus classification into G and P genotypes, respectively. The aim of the present study was to determine the evolution of group A Rotavirus strains circulating in Tunisia over a 3-year period (2005-2007).

MATERIAL AND METHODS

A total of 1503 stool samples collected from children less than five years old, consulting or hospitalised in Tunisia for diarrhoea between 2005 and 2007, were screened for the presence of group A Rotaviruses. Rotavirus-positive specimens were further analyzed by PAGE and G/P-genotyped by multiplex semi-nested RT-PCR.

RESULTS

Rotaviruses were detected in 323 stool samples over 1503 (21 %). Long electropherotypes predominated in Tunisia during the whole period of study (N=158 vs N=82 short electropherotypes). VP7 genotyping showed the cocirculation of five different genotypes: G1, G2, G3, G4 and G9. VP4 typing detected four different P-genotypes: P[8], P[4], P[6] and P[11]. Rotavirus strains with G3P[8] specificity were predominating in Tunisia in 2005 and 2006, replaced by G2P[4] strains in 2007.

Phylogeny of G9 rotavirus genotype: a possible explanation of its origin and evolution

BACKGROUND

G9 rotavirus genotype was isolated in the 1980s and re-emerged without a clear explanation in the mid-1990s as one of the most frequently occurring genotypes with distinct genetic and molecular characteristics.

OBJECTIVES

To study the G9 genotype sequence polymorphisms in Spain and compare them with the human and porcine G9 VP7 genes from the rest of the world. Complete phylogenetic analyses have been done to better characterize G9 genotypes, their relationships and evolution.

STUDY DESIGN

Twelve G9 VP7 genes from Spanish patients were sequenced and compared with 240 G genotype sequences. Nucleotide and amino acid sequence similarity percentages and neighbour-joining dendrograms were used to establish a new phylogenetic analysis.

RESULTS

Eight of the 12 Spanish sequenced samples had different nucleotide translated region sequences, which yielded only five different proteins. New nucleotide and amino acid sequence comparisons were made that differed from previously described results.

CONCLUSIONS

Spanish G9 genotype sequences have similar structure of those belonging to lineage III as the majority of the G9 sequences and share amino acid motifs with other sequences. The phylogenetic analyses of G9 genotypes confirmed the existence of 6 lineages, but did not confirm the 11 sublineages previously reported.

The VP7 genes of two G9 rotaviruses isolated in 1980 from diarrheal stool samples collected in Washington, DC, are unique molecularly and serotypically

In a retrospective study of archival diarrheal stool samples collected from 1974 to 1991 at Children's Hospital National Medical Center, Washington, DC, we detected three genotype G9P[8] viruses in specimens collected in 1980, which represented the earliest human G9 viruses ever isolated. The VP7 genes of two culture-adapted 1980 G9 viruses were phylogenetically related closely to the lineage 2 G9 virus VP7 gene. Unexpectedly, however, the VP7s of the 1980 G9 viruses were more closely related serotypically to lineage 3 VP7s than to lineage 2 VP7, which may be supported by amino acid sequence analyses of the VP7 proteins.

Group A rotavirus strains circulating in the eastern center of Tunisia during a ten-year period (1995-2004)

An epidemiological survey investigating rotavirus infections in children was undertaken in the Eastern Center of Tunisia between January 1995 and December 2004. A total of 982 faecal specimens collected from children less than 5 years in age were screened by enzyme-linked immunosorbent assay (ELISA) or latex agglutination assay for the presence of group A rotavirus antigen. Rotavirus-positive samples were used for G and P typing by multiplex semi-nested reverse transcription-PCR. Rotaviruses were detected in 22% (n = 220) of stools. Of these, 164 were typed for VP7: G genotypes found were G1 (59%), G2 (2%), G3 (9%), G4 (10%), G8 (1%), and G9 (1%). Sixteen specimens (9%) showed mixed G profiles. A total of 119 specimens were typed for VP4. P genotypes detected were P[8] (32%), P[6] (15%), and P[4] (13%). Mixed P profiles were also detected (6%). Although the distribution of the detected genotypes appeared to change annually, G1P[8] rotavirus strains always predominated during the 10-year period of study. This is the first report of rotaviruses in Tunisia with unconventional VP7 serotypes such as G8 and G9, highlighting the need for continual surveillance of emerging strains in Northern Africa. Indeed, the new commercial vaccines only contain the VP7 genes that dictate G1 or G1 to G4 specificities. These vaccines may protect less well against unusual strains circulating in countries planning to implement a rotavirus vaccine strategy.

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.

Molecular epidemiology of G9 rotaviruses in Taiwan between 2000 and 2002

Since the mid-1990s, novel G9 rotaviruses have been detected in many countries, suggesting that G9 is a globally important serotype. The molecular epidemiology of G9 rotaviruses in Taiwan from 2000 to 2002 was investigated in this study. G9 rotavirus first appeared in 2000 with 4 cases and constituted 33.8% and 54.8% of the rotavirus-positive samples in 2001 and 2002, respectively. These G9 strains belonged to P[8]G9, subgroup II, and long electropherotype, except one belonged to P[4]G9, subgroup II, and short electropherotype. Nucleotide sequencing and phylogenetic analysis of 52 Taiwanese G9 rotaviruses showed that the VP7 genes shared a high degree of identity to overseas G9 rotaviruses detected after 1993 and that the VP8* portions of the VP4 genes were more closely related to those of local rotaviruses of other G types. The two P[8]G9 strains with high nucleotide identities in the VP7 and the partial VP4 genes, 01TW591 of Taiwan from 2001 and 95H115 of Japan from 1995, varied in four genes, genes 2, 3, 7, and 8, which was revealed by RNA-RNA hybridization. Representative strains for different RNA patterns were also analyzed in the partial VP2 and VP3 genes; the nucleotide identities were high between Taiwanese G9 strains and local G3 or G2 strains. These results suggested that Taiwanese G9 rotaviruses possibly had evolved through reassortment between overseas G9 strains and circulating rotaviruses of other G types.

G-serotypes of group A rotaviruses in Pilsen region (Czechia)

A total of 260 feces samples from children with confirmed rotavirus infection collected during 1999-2002 were serotyped, using enzymoimmunoassay with VP7 specific monoclonal antibodies for G1-G4 serotypes. The serotypes were identified in 185 feces, i.e. 71.2 %. Individual serotypes occurred in 43, 2, 16 and 2 %; 8 % samples reacted with 2 type-specific monoclonal antibodies. The G1 serotype was prevalent over the whole period. The G3 type occurred with a statistically higher significance in children of up to 36 months (chi2 = 4.6, p = 0.028). In 4 children a different serotype was demonstrated in the first and second, or in the second and third stools, respectively. No dominant serotype was found in children with nosocomial infection.

Molecular Epidemiological Profile of Rotavirus in South Korea, July 2002 through June 2003: Emergence of G4P[6] and G9P[8] Strains

To determine the distribution of rotavirus strain genotypes in South Korea, rotavirus-positive stool specimens were collected from July 2002 through June 2003 at 8 hospitals in the Korean Rotavirus Strain Surveillance Network, and they were genotyped by means of reverse-transcription polymerase chain reaction. The globally uncommon G4P[6] type was the most prevalent type identified among strains (27% of strains), the newly emerging G9P[8] strain accounted for 11% of strains, and the globally common genotypes (i.e., G1P[8], G2P[4], G3P[8], and G4P[8]) constituted 55% of the strains characterized. Ninety percent of G4P[6] strains were detected in specimens obtained from neonates. Common genotypes were responsible for the rotavirus epidemic that began in January 2003 and ended in May 2003; however, an early peak in infections with the G4P[6] strain occurred from August through October 2002, and infections with this strain were detected throughout the remaining study period. G4P[6] strains were most commonly identified at 6 urban health care centers, but they were absent from 2 rural health care centers. The newly emerging strain G9P[8] represented a relatively greater proportion of strains identified at a hospital in the central region of Korea and at 2 hospitals in the southern region. The identification of novel rotavirus genotypes in this laboratory-based surveillance study underscores the importance to public health of continued strain surveillance among children for whom prevention of rotavirus infection by vaccination might be considered.

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 rotavirus G9 genotype in children hospitalized for rotavirus gastroenteritis in Belgium during 1999–2003

BACKGROUND

Group A rotavirus genotypes G1, G2, G3 and G4 are the main etiological agents of infantile diarrhea. The G9 rotavirus has recently emerged as a fifth important genotype all over the world.

OBJECTIVE

To characterize the VP7 gene of group A rotaviruses from gastroenteritis patients admitted to the Gasthuisberg University Hospital, Leuven, Belgium, during 1999-2003.

STUDY DESIGN

Rotavirus antigen was detected in stool specimens using an enzyme immunoassay. G-typing was performed by reverse transcriptase polymerase chain reaction (RT-PCR) amplification and sequencing of the complete VP7 gene.

RESULTS

The genotype distribution varied markedly over the four rotavirus years in Belgium. In the 1999-2000 rotavirus year, G1 was the predominating type (72%), and G9 was present in 5% of the rotavirus-positive patients. In the 2000-2001 and 2002-2003 years, G9 appeared as the dominating strain (45% and 53%, respectively). In the 2001-2002 year, between two G9 epidemic years, G1 was dominating (66%) but G9 was still present in 24%. All the G9 isolates were combined with P[8] and shared a high gene sequence similarity (<3% sequence divergence on the nucleotide and amino acid level). Phylogenetic analysis of the VP7 genes revealed that our Belgian G9 strains clustered together with recent G9 strains from all over the world, distinct from the prototype G9 strains isolated in the 1980s.

CONCLUSION

Our study indicates that although the first introduction of G9 isolates in the Belgian population was recorded in 1997, G9 strains were able to establish themselves quickly as the predominant genotype. The emergence of G9 as an important pathogen in both developing as industrialized countries necessitates the urgent consideration of the G9 moiety in rotavirus vaccines.

Phylogenetic analyses of human rotavirus in central Taiwan in 1996, 2001 and 2002

BACKGROUND

Rotavirus epidemiology information is required for gastroenteritis disease control and prevention. Information gathered about the serotype distribution of rotaviruses isolated in Taiwan is of crucial significance, before a licensed rotavirus vaccine is introduced.

OBJECTIVES

The purpose of the present study is to investigate the epidemiological diversity of rotaviruses in Taiwan.

STUDY DESIGN

A total of 51 stool samples taken from cases of acute gastroenteritis were collected from three teaching hospitals in central Taiwan in 1996, 2001 and 2002. The samples were subjected to RT-PCR tests of VP7 gene of the human rotavirus group A, B, C.

RESULTS

A total of 16 stool samples were detected positive by RT-PCR and 10 were sequence analyzed and classified into G1, G3, and G9 types. Compared with other HRV strains: the sequences of CS96-40 of G1 are similar to MVD9816 (identity rate 97.15% and 96.09%, respectively, from Uruguay); the sequences of CS02-01 of G3 are similar to 98-B31 (identity rate 98.93% and 98.72%, respectively, from Japan); the sequences of CS01-05, CS01-06, CS01-07, CS01-09, CS01-13, CS02-02, CS02-03, CS02-04 are very similar to other established G9 rotaviruses sequences (identity rate 96.85-99.88%), especially between CS02-04 and SP2737 (from Japan) with an identity rate of 99.88% and 100% nucleotide and amino acid, respectively. Except for CS01-06 strain, it is VR3, but not VR5, VR7 or VR8, that found to be the most frequent mutated amino acid regions of VP7 in these strains.

CONCLUSIONS

Our findings are the first to document the high prevalence of G9 HRV strains in Taiwan, and suggest the re-emergence of G3 strains in central Taiwan since 1991. Epidemiological surveys carried out in this study suggest genotype shifts from type G1 before 1996, to G9 in 2001 and 2002 and the re-emergence of G3 type in 2002.

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.

Culture adaptation of serotype G6 human rotavirus strains from hospitalized diarrhea patients in India

During serotyping of fecal specimens positive for rotavirus from hospitalized diarrhea patients in Pune, India, about 10% showed multireactivity in enzyme immunoassay with monoclonal antibodies specific for serotypes G1-4, 6, 8, and 10. In order to characterize some of these, three fecal specimens from children and one from adult were culture adapted. All the isolates showed long RNA pattern, but three out of four isolates belonged to subgroup I and II and one, to subgroup I. The isolates were confirmed as G6 by neutralization assay and polymerase chain reaction. Nucleotide sequences of cDNA derived from the gene encoding the outer capsid protein, VP7 of two strains indicated >94% identity with G6, the serotype, generally associated with cattle. The isolates were more close to G6 RF strain, which is a bovine rotavirus, reported from France. This is a first report of isolation of bovine serotype, G6 from children as well as adults from India.

Evidence of rotavirus AU32 like G9 strains from nontypeable fecal specimens of Indian children hospitalized during 1993-1994

Serotyping of 432 rotavirus positive fecal specimens collected from hospitalized children during 1990-1997 was carried out at National Institute of Virology (NIV), Pune, India, using monoclonal antibodies (MAbs) directed against VP7 determinant of serotypes G1-G4, G6, G8, and G10. However, significant number of specimens, that is, 47.92% remained nontypeable. The aim of the present study was to culture adapt the nontypeable specimens and to characterize them further. Since the fecal specimens were not tested by MAb to G9 serotype, which has emerged as an important serotype infecting humans recently, presence of G9 serotype was expected in nontypeable specimens. Therefore, we selected specimens from those children, who showed higher neutralizing antibody (NAb) titer in their convalescent serum samples to G9 serotype than their mothers. Out of six isolates having long electropherotype, five isolates showed subgroup II, and one showed subgroup I, II. The isolates were confirmed as G9 by MAb based ELISA, neutralization assay, and PCR. The G9 specific nested PCR products of four isolates showed 96-99% identities to AU32 G9 strain reported from Japan. P type of four isolates was determined as P8. Besides isolates, four additional nontypeable fecal specimens were confirmed as G9 by MAb based ELISA. Thus, 10 (28.57%) out of 35 nontypeable specimens were identified as rotavirus serotype G9. The results indicate that serotype G9 may represent significant proportion of specimens, which were previously nontypeable.

Rotavirus serotype G9 strains belonging to VP7 gene phylogenetic sequence lineage 1 may be more suitable for serotype G9 vaccine candidates than those belonging to lineage 2 or 3

A safe and effective group A rotavirus vaccine that could prevent severe diarrhea or ameliorate its symptoms in infants and young children is urgently needed in both developing and developed countries. Rotavirus VP7 serotypes G1, G2, G3, and G4 have been well established to be of epidemiologic importance worldwide. Recently, serotype G9 has emerged as the fifth globally common type of rotavirus of clinical importance. Sequence analysis of the VP7 gene of various G9 isolates has demonstrated the existence of at least three phylogenetic lineages. The goal of our study was to determine the relationship of the phylogenetic lineages to the neutralization specificity of various G9 strains. We generated eight single VP7 gene substitution reassortants, each of which bore a single VP7 gene encoding G9 specificity of one of the eight G9 strains (two lineage 1, one lineage 2 and five lineage 3 strains) and the remaining 10 genes of bovine rotavirus strain UK, and two hyperimmune guinea pig antisera to each reassortant, and we then analyzed VP7 neutralization characteristics of the eight G9 strains as well as an additional G9 strain belonging to lineage 1; the nine strains were isolated in five countries. Antisera to lineage 1 viruses neutralized lineage 2 and 3 strains to at least within eightfold of the homotypic lineage viruses. Antisera to lineage 2 virus neutralized lineage 3 viruses to at least twofold of the homotypic lineage 2 virus; however, neutralization of lineage 1 viruses was fourfold (F45 and AU32) to 16- to 64-fold (WI61) less efficient. Antisera to lineage 3 viruses neutralized the lineage 2 strain 16- to 64-fold less efficiently, the lineage 1 strains F45 and AU32 8- to 128-fold less efficiently, and WI61 (prototype G9 strain) 128- to 1024-fold less efficiently than the homotypic lineage 3 viruses. These findings may have important implications for the development of G9 rotavirus vaccine candidates, as the strain with the broadest reactivity (i.e., a prime strain) would certainly be the ideal strain for inclusion in a vaccine.

Genetic and antigenic characterization of rotavirus serotype G9 strains isolated in Australia between 1997 and 2001

Rotavirus serotype G9 is recognized as the most widespread of the emerging serotypes, emerging since 1996 as a frequent cause of severe acute gastroenteritis in children from many countries covering all continents of the world. This study characterized serotype G9 strains collected in three widely separated Australian centers from 1997 to 2001. All G9 strains possessed the VP4 P[8] and VP6 subgroup II genes. The overall prevalence of the G9 strains increased in Australia, from 0.6% of the strains found in 1997 to 29% of the strains found in 2001. The prevalence of G9 relative to all other serotypes varied from year to year and with geographic location. In Melbourne (representing east coast urban centers), G9 made up 11 to 26% of all of the strains found from 1999 to 2001. In Perth (representing west coast urban centers), G9 made up less than 2% of the strains found in 1997 to 2000 but increased to 18.6% of the strains found in 2001. In Alice Springs (representing widely dispersed settlements in northern arid regions), G9 made up 0 to 5% of the strains found from 1997 to 2000 and was the dominant strain in 2001, making up 68.9% of all of the strains found. Three distinct antigenic groups based on reaction with neutralizing monoclonal antibodies (N-MAbs) were identified, including a dominant group (63%) that cross-reacted with the serotype G4 N-MAb. Phylogenetic analysis of the VP7-encoding gene from Australian strains, compared with a worldwide collection of G9 strains, showed that the Australian G9 strains made up a genetic group distinct from other serotype G9 strains identified in the United States and Africa. Future epidemiological studies of the occurrence of G9 strains should combine reverse transcription-PCR and typing with G1 to G4 and G9 N-MAbs to determine the extent of G9 and G4 cross-reactions among rotavirus strains, in order to assess the need to incorporate G9 strains into new candidate vaccines.

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.

VP7 gene polymorphism of serotype G9 rotavirus strains and its impact on G genotype determination by PCR

Rotaviruses are the single most important etiologic agents of severe diarrhea of infants and young children worldwide. Surveillance of rotavirus serotypes/genotypes (both VP7[G] and VP4[P]) is in progress globally in which polymerase chain reaction (PCR) has been the assay of choice. We investigated polymorphism of the VP7 gene of serotype G9 rotavirus strains and its impact on the determination of VP7 gene genotype by PCR assay. By VP7 gene sequence analysis, we and others have previously shown that the G9 rotavirus strains belong to one of three VP7 gene lineages. By PCR assay using three different sets of commonly used primers specific for G1-4, 8 and 9, 23 Brazilian G9 strains and 5 well-characterized prototype G9 strains which collectively represented all three VP7 gene lineages were typed as: (i) G3; (ii) G4; (iii) G9; (iv) G3 and G9; or (v) G9 and G4 depending on a primer pool employed. This phenomenon appeared to be due to: (i) a VP7 gene lineage-specific polymorphism, more specifically mutation(s) in the primer binding region of the VP7 gene of G9 strain; and (ii) the magnitude of difference in nucleotide homology at respective primer binding site between homotypic (G9) and heterotypic (G3 or G4) primers present in a primer pool employed.

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.

Genogroup characterization of reemerging serotype G9 human rotavirus strain 95H115 in comparison with earlier G9 and other human prototype strains

Serotype G9 human rotaviruses have emerged globally since the mid-1990s. The 95H115 strain was derived from a stool specimen collected in Japan in the 1994-95 season, thus it is the earliest of the globally reemerging G9 human rotaviruses that were adapted to cell culture. Genogrouping by RNA-RNA hybridization was performed to examine the genetic background of 95H115. The 95H115 strain belonged to the Wa genogroup, the most common human rotavirus genogroup, and it had a high degree of homology with AU32 and WI61, the prototype G9 isolates in the 1980s. However, the divergent genomic RNA constellation as indicated by the aberrant hybridization patterns between 95H115 and earlier G9 strains served as further evidence that 95H115 was not a direct descendant of the prototype strains in the '80s.

Rotavirus vaccines--an update

Rotavirus vaccines offer the best hope to reduce the toll of acute rotaviral gastroenteritis in both developed and developing countries. An association with intussusception (IS) led to the withdrawal of the first licensed rotavirus vaccine in the USA in 1999, forcing a re-evaluation of the safety profile of potentially lifesaving vaccines. Development of new rotavirus vaccine candidates has continued, with a bovine-human reassortant vaccine and an attenuated human monovalent vaccine commencing Phase III trials. Several other candidates are in early Phase I and II clinical trials. The creation of innovative funding strategies to support vaccine development and production, specifically in developing countries, aim to make vaccines available where rotavirus causes the greatest impact.

VP7 gene polymorphism of serotype G9 rotavirus strains and its impact on G genotype determination by PCR

Rotaviruses are the single most important etiologic agents of severe diarrhea of infants and young children worldwide. Surveillance of rotavirus serotypes/genotypes (both VP7[G] and VP4[P]) is in progress globally in which polymerase chain reaction (PCR) has been the assay of choice. We investigated polymorphism of the VP7 gene of serotype G9 rotavirus strains and its impact on the determination of VP7 gene genotype by PCR assay. By VP7 gene sequence analysis, we and others have previously shown that the G9 rotavirus strains belong to one of three VP7 gene lineages. By PCR assay using three different sets of commonly used primers specific for G1-4, 8 and 9, 23 Brazilian G9 strains and 5 well-characterized prototype G9 strains which collectively represented all three VP7 gene lineages were typed as: (i). G3; (ii). G4; (iii). G9; (iv). G3 and G9; or (v). G9 and G4 depending on a primer pool employed. This phenomenon appeared to be due to: (i). a VP7 gene lineage-specific polymorphism, more specifically mutation(s) in the primer binding region of the VP7 gene of G9 strain; and (ii). the magnitude of difference in nucleotide homology at respective primer binding site between homotypic (G9) and heterotypic (G3 or G4) primers present in a primer pool employed.