The relative frequencies of G serotypes of rotaviruses recovered from hospitalized children with diarrhea: A 10-year survey (1987-1996) in Japan with a review of globally collected data

Emergence of equine-like G3 strains as the dominant rotavirus among children under five with diarrhea in Sabah, Malaysia during 2018-2019

Rotavirus infection is a dilemma for developing countries, including Malaysia. Although commercial rotavirus vaccines are available, these are not included in Malaysia's national immunization program. A scarcity of data about rotavirus genotype distribution could be partially to blame for this policy decision, because there are no data for rotavirus genotype distribution in Malaysia over the past 20 years. From January 2018 to March 2019, we conducted a study to elucidate the rotavirus burden and genotype distribution in the Kota Kinabalu and Kunak districts of the state of Sabah. Stool specimens were collected from children under 5 years of age, and rotavirus antigen in these samples was detected using commercially available kit. Electropherotypes were determined by polyacrylamide gel electrophoresis of genomic RNA. G and P genotypes were determined by RT-PCR using type specific primers. The nucleotide sequence of the amplicons was determined by Sanger sequencing and phylogenetic analysis was performed by neighbor-joining method. Rotavirus was identified in 43 (15.1%) children with watery diarrhea. The male:female ratio (1.9:1) of the rotavirus-infected children clearly showed that it affected predominantly boys, and children 12-23 months of age. The genotypes identified were G3P[8] (74% n = 31), followed by G1P[8] (14% n = 6), G12P[6](7% n = 3), G8P[8](3% n = 1), and GxP[8] (3% n = 1). The predominant rotavirus circulating among the children was the equine-like G3P[8] (59.5% n = 25) with a short electropherotype. Eleven electropherotypes were identified among 34 strains, indicating substantial diversity among the circulating strains. The circulating genotypes were also phylogenetically diverse and related to strains from several different countries. The antigenic epitopes present on VP7 and VP4 of Sabahan G3 and equine-like G3 differed considerably from that of the RotaTeq vaccine strain. Our results also indicate that considerable genetic exchange is occurring in Sabahan strains. Sabah is home to a number of different ethnic groups, some of which culturally are in close contact with animals, which might contribute to the evolution of diverse rotavirus strains. Sabah is also a popular tourist destination, and a large number of tourists from different countries possibly contributes to the diversity of circulating rotavirus genotypes. Considering all these factors which are contributing rotavirus genotype diversity, continuous surveillance of rotavirus strains is of utmost importance to monitor the pre- and post-vaccination efficacy of rotavirus vaccines in Sabah.

Rotavirus infections in Detroit, USA, a region of low vaccine prevalence

After a sharp drop of rotavirus (RV) infections at Children's Hospital of Michigan, Detroit, USA in 2010 season, we noted an increase in the number of cases during the 2011 season including some RV vaccine (RVV) recipients. This study was conducted to determine the circulating genotypes during 2011 season and whether the increase in RV diarrhea was caused by replacement genotypes. G and P genotypes were determined by RT PCR and nucleotide sequencing of selected strains was performed. The vaccination rate among study patients was 24 %. RV strains from 68 stool samples were genotyped including 18 from vaccinated children and 50 from unvaccinated children. The predominant G genotype was G1 (58.8 %) followed by G9 (17.7 %) and G4 (15.5 %). P[8] was the predominant P genotype (68 %) followed by P[6] (17.6 %) and P[4] (3 %). All G9 strains were associated with P[6]. The most prevalent G-P combination was G1P[8] (56 %), followed by G9P[6] (17.6 %). Similar proportions of RV genotypes were found among vaccinated and unvaccinated children. Our local data suggest that 5 years after the introduction of RVV there has been no genotype replacement. Although a small increase in G9P[6] frequency was noted, G1P[8] remained the predominant strain of RV in our inner city community in the Midwestern USA.

A critical time for rotavirus vaccines: a review

Universal introduction of rotavirus vaccines into childhood immunization programs is expected to substantially reduce the mortality from rotavirus gastroenteritis in developing countries (currently estimated at 702,000 annual deaths among children less than 5 years of age). In addition, it is expected to virtually eliminate hospitalizations due to rotavirus gastroenteritis in developed countries. Two rotavirus vaccines, Rotarix (GlaxoSmithKline Biologicals, Belgium) and RotaTeq (Merck & Co., USA) have recently completed Phase III clinical trials, each involving more than 60,000 children. Both vaccines appear safe with respect to intussusception, and are highly efficacious in preventing severe gastroenteritis due to rotavirus strains carrying predominantly serotype G1. The monovalent human rotavirus vaccine Rotarix, possessing serotype P1A[8],G1, is being first introduced into developing countries, whereas the pentavalent bovine-human reassortant rotavirus vaccine RotaTeq, comprising G-types G1, G2, G3, G4 and P-type P1A[8], will be initially introduced into the USA and Europe. Current disease burden estimates and economic justification will be required wherever the vaccines are introduced. Confirmation of the safety of both vaccines will require extensive postlicensure evaluation in which it will be key to assure adherence to administration of the first dose of either vaccine before 3 months of age. Assessment of the ability of each vaccine to provide protection against an increasingly diverse population of rotavirus strains will crucially depend on continuous global strain surveillance. Finally, efforts to improve existing rotavirus vaccines and to develop alternative vaccines should continue, so as to ensure that the prerotavirus vaccine era is consigned to a historical context.

Introduction of rotavirus vaccines in developing countries: remaining challenges

Rotavirus is the principal agent of severe, dehydrating gastro-enteritis in infants and young children worldwide. The main public health tool that can prevent hospitalisation and death from rotavirus is vaccination. One of two current rotavirus vaccines is now licensed in more than 80 countries and is incorporated into childhood immunisation schedules across several countries in the Americas and Europe. However, since the majority of childhood deaths from rotavirus occur in the developing countries of Africa and Asia, widespread use of vaccine in these two continents will be necessary before a major impact on global diarrhoea mortality is seen. Challenges in these latter settings which primarily relate to vaccine efficacy, safety and financing will be addressed within the next 3-5 years, and thus perhaps finally allow introduction of rotavirus vaccine into the populations in greatest need.

Continued Circulation of G12P[6] Rotaviruses Over 28 Months in Nepal: Successive Replacement of Predominant Strains

Rotavirus A causes severe diarrhoea in infants and young children worldwide. The migration pattern (electropherotype) of the double-stranded RNA genome upon polyacrylamide gel electrophoresis has been used to define "strains" in molecular epidemiology. In temperate countries, distinct electropherotypes (strains) appear after the annual, off-seasonal interruption of rotavirus circulation. In Nepal, rotavirus circulated year-round and an uncommon genotype G12P[6] predominated and persisted, providing a unique opportunity to examine whether the same electropherotype (the same strain) persisted or new electropherotypes (new strains) emerged successively under the same G12P[6] predominance. A total of 147 G12P[6] rotaviruses, collected from diarrhoeal children in Nepal between 2007 and 2010, were classified into 15 distinct electropherotypes (strains). Of these, three electropherotypes (strains), LP1, LP24, and LP27, accounted for 10%, 32% and 38% of the G12P[6] rotaviruses, respectively. Each of the three major strains successively appeared, dominated, and disappeared. This study provided new evidence for the hypothesis that rotavirus constantly changes its strains to predominate in the local population even under conditions where a single genotype predominates and persists. Such dynamic strain replacement, the constant takeover of one predominant strain by another, fitter strain, is probably gives a competitive edge to the survival of rotavirus in nature.

Emergence of human rotavirus genotype G9 in metropolitan Detroit between 2007 and 2009

Between January 2007 and April 2009, rotavirus (RV)-positive stool samples from 238 children with acute gastroenteritis, seen at Children's Hospital of Michigan in Detroit, USA, were collected and RV genotyping was performed. G and P genotypes were determined by RT-PCR and nucleotide sequencing was conducted on selected G9 and P[6] strains. Correlation between the severity of gastroenteritis episode and the infecting G genotype was done using a 14-point scoring system. The predominant G genotype was G9 (39.5 %), followed by G1 (35.3 %) and G4 (15.5 %), while P[8] was the most prevalent P genotype (66.5 %), followed by P[4] (21.9 %) and P[6] (11.2 %). The gene combinations G1P[8] and G9P[8] were the most prevalent (21.4 % and 20.6 %, respectively), followed by G4P[8] (13 %) and G9P[6] (8.8 %). Immunization data showed that only 17/238 (7.1 %) children received ≥one dose of RV vaccine (the pentavalent vaccine RotaTeq or the monovalent vaccine Rotarix) and that 10/17 were infected with G4P[8] strains. Severity of RV gastroenteritis episodes was not related to the infecting G genotype. Our results suggest a high proportion of genotype G9 strains in combination with P[8], P[6] and P[4] specificity circulating in the metropolitan Detroit area. While the protective efficacy of the RV vaccines has been demonstrated against G9P[8] strains, the level of cross-protection offered by the vaccines against G9 strains with P[6] and P[4] genotypes in the Detroit paediatric population remains to be determined.

Co-dominance of G1 and emerging G3 rotaviruses in Hong Kong: a three-year surveillance in three major hospitals

BACKGROUND

The World Health Organization recommends rotavirus vaccines be included in all national immunization programs as part of a strategy to control diarrhoeal diseases. Sentinel surveillance is advised to monitor impact post-vaccine introduction and to document changes in genotype distribution.

OBJECTIVES

To determine the molecular epidemiology of circulating rotaviruses in Hong Kong prior to implementation of universal rotavirus vaccination.

STUDY DESIGN

From December 2004 through December 2007, 830 rotavirus-positive stool samples from subjects admitted for acute diarrhea to three major hospitals in Hong Kong were examined. The electropherotypes, and the G and P genotypes of these rotaviruses were determined. Phylogenetic analysis of the VP7 gene was performed.

RESULTS

G3P[8] was the dominant genotype (46.1%), followed by G1P[8] (36.5%) and G9P[8] (9.2%). A total of 35 electropherotypes were identified. The G3 and G1 strains had high sequence similarities among themselves and were clustered with strains from Asia particularly mainland China. The G9 strains were clustered with the globally spreading strains. G12 and G4 were not found. The prevalence of rotavirus infection peaked in winter season when temperature was low, atmospheric pressure was high, relative humidity was low and rainfall was negligible.

CONCLUSIONS

Genotype G3 and G1 were the dominant rotaviruses circulating in Hong Kong between 2004 and 2007. Strains were mainly related with those from mainland China. Ongoing surveillance of circulating genotypes should continue in anticipation of universal rotavirus vaccine introduction.

Serotype g12 rotaviruses, Lilongwe, Malawi

To assess diversity of rotavirus strains in Lilongwe, Malawi, we conducted a cross-sectional study of children with acute gastroenteritis, July 2005–June 2007. Serotype G12 was identified in 30 (5%) of 546 rotavirus-positive fecal specimens. The G12 strain possessed multiple electropherotypes and P-types, but their viral protein 7 sequences were closely related, indicating that reassortment has occurred.

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.

Molecular epidemiology of rotavirus diarrhea among children in Saudi Arabia: first detection of G9 and G12 strains

In anticipation of rotavirus vaccine introduction in Saudi Arabia, this study was undertaken to determine the distribution of the G and P genotypes of rotaviruses in order to examine whether there was any emerging serotype or unusual strain circulating in children in Saudi Arabia. Of 984 stool specimens collected between 17 April 2004 and 16 April 2005, rotavirus was detected by an enzyme-linked immunosorbent assay in 187 (19%) diarrheal children less than 5 years of age. Of these, 160 (86%) were classified into G and P genotypes as follows: G1P[8] (44%), G2P[4] (20%), G9P[8] (11%), G12P[8] (4%), and G3P[8] (4%). RNA polyacrylamide gel electrophoresis identified 94 (50%) specimens as long RNA patterns, 30 (16%) specimens as short RNA patterns, and 1 mixed infection. Only a single long RNA electropherotype was identified for seven specimens containing G12P[8] rotavirus. RNA-RNA hybridization demonstrated that the G12P[8] strains were similar in their genomic constellation to locally cocirculating strains and to a Nepalese G12P[8] strain. The Saudi Arabian G12 VP7 gene had a 99% nucleotide sequence identity with Nepalese and Indian G12 VP7 genes and belonged to the third lineage. This study is the first to describe the distribution of rotavirus G and P types and also the first to identify G9P[8] and G12P[8] strains in the country.

Vaccines against traveler's diarrhoea and rotavirus disease - a review

Diarrheal diseases constitute one of the most important health problems worldwide, preferentially in developing countries with a morbidity of estimated 5 billion and a mortality of 5 million cases per year. Children less than 5 years are particularly in danger with respect to the incidence and severity of the gastrointestinal symptoms. Travelers to developing countries are also at risk to develop diarrheal disorders; around 30-50% of them acquire so called "travelers's diarrhea" caused by bacteria, viruses or protozoa. It has been estimated that approximately 30-70% of diarrhea are due to bacteria, of which the most frequently detected enteric pathogens are non-invasive, enterotoxigenic Escherichia coli (ETEC). Their exotoxins, the heat stabile (ST) and the heat labile (LT) toxins are in large part responsible for the pathogenicity of the bacteria. About 20% of cases of traveler's diarrhea are caused by LT producing ETEC. This heat labile toxin exhibits a 80% sequence homology with cholera toxin. The presently available vaccine against cholera (Dukoral) contains inactivated Vibrio cholerae bacteria and the recombinant non-toxic B subunit of cholera toxin. Consequently, this vaccine displays also some efficacy against traveler's diarrhoea with up to 25% of travelers being protected against this disease. Rotaviruses are the leading recognized cause of diarrhoea-related illness and deaths among infants worldwide in developing and industrialized countries. Based on the high incidence of this disease two oral vaccines have been developed and will be available in Europe in 2006. Due to the impact of rotavirus diseases also in Austria vaccination against this disease has been already suggested in the Austrian vaccination schedules for infants from 6-24 weeks of age. One of the two vaccines, Rotarix, is an attenuated monovalent vaccine with a broad cross-reactivity against the most frequent serotypes. The second one, RotaTeq, is a pentavalent attenuated vaccine containing 5 human-bovine reassortants. Both vaccines display 85-98% efficacy against severe rotavirus disease and an excellent tolerability with no difference in side reactions to the placebo controls, particularly with respect to intussusceptions. With respect to increasing travel habits with infants and small children, particularly when visiting friends and relatives, vaccination against rotavirus infections will also be important in international travel.

Sequence analysis of the VP7 gene of human rotavirus G1 isolated in Japan, China, Thailand, and Vietnam in the context of changing distribution of rotavirus G-types

Over the last decade, rotavirus G1 has represented the most common genotype worldwide. Since 2000, the prevalence of rotavirus G1 has decreased in some countries such as Japan and China. To monitor the trend of the VP7 encoding gene of rotavirus G1, we performed a sequence analysis of 74 G1 rotavirus strains isolated in Japan, China, Thailand, and Vietnam during the period from 2002 to 2005. The phylogenetic tree showed that all of the studied G1 strains from the four countries clustered into lineage III, the same as the majority of the G1 strains isolated in China and Japan in 1990 and 1991. Examination of the deduced amino acid sequences of the G1 strains from China and Japan revealed an amino acid substitution at position 91 (Asn instead of Thr) in antigenic region A when compared to the G1 strains isolated in China and Japan in 1990, 1991, and global reference strains. For the G1 strains from Thailand and Vietnam, there were three amino acid substitutions, not belonging to any antigenic regions. The study showed that there have been no considerable changes of human rotavirus G1 isolated in Japan, China, Thailand, and Vietnam. Further studies need to be carried out for a better understanding of why such changes in the prevalence of rotavirus G1 occur in these countries.

Development and validation of DNA microarray for genotyping group A rotavirus VP4 (P[4], P[6], P[8], P[9], and P[14]) and VP7 (G1 to G6, G8 to G10, and G12) genes

Previously, we reported the development of a microarray-based method for the identification of five clinically relevant G genotypes (G1 to G4 and G9) (V. Chizhikov et al., J. Clin. Microbiol. 40:2398-2407, 2002). The expanded version of the rotavirus microarray assay presented herein is capable of identifying (i) five clinically relevant human rotavirus VP4 genotypes (P[4], P[6], P[8], P[9], and P[14]) and (ii) five additional human rotavirus VP7 genotypes (G5, G6, G8, G10, and G12) on one chip. Initially, a total of 80 cell culture-adapted human and animal reference rotavirus strains of known P (P[1] to P[12], P[14], P[16], and P[20]) and G (G1-6, G8 to G12, and G14) genotypes isolated in various parts of the world were employed to evaluate the new microarray assay. All rotavirus strains bearing P[4], P[6], P[8], P[9], or P[14] and/or G1 to G6, G8 to G10, or G12 specificity were identified correctly. In addition, cross-reactivity to viruses of genotype G11, G13, or G14 or P[1] to P[3], P[5], P[7], P[10] to P[12], P[16], or P[20] was not observed. Next, we analyzed a total of 128 rotavirus-positive human stool samples collected in three countries (Brazil, Ghana, and the United States) by this assay and validated its usefulness. The results of this study showed that the assay was sensitive and specific and capable of unambiguously discriminating mixed rotavirus infections from nonspecific cross-reactivity; the inability to discriminate mixed infections from nonspecific cross-reactivity is one of the inherent shortcomings of traditional multiplex reverse transcription-PCR genotyping. Moreover, because the hybridization patterns exhibited by rotavirus strains of different genotypes can vary, this method may be ideal for analyzing the genetic polymorphisms of the VP7 or VP4 genes of rotaviruses.

Molecular epidemiology of rotavirus diarrhea among children and adults in Nepal: detection of G12 strains with P[6] or P[8] and a G11P[25] strain

In anticipation of a rotavirus vaccine in Nepal, this study was undertaken to determine the distribution of the G and P serotypes and electropherotypes of rotaviruses in order to examine if there is any emerging serotype or unusual strain circulating in children and adults in Nepal. Of 1,315 diarrheal stool specimens, rotavirus was detected by an enzyme-linked immunosorbent assay in 116 (17%) of 666 patients less than 5 years of age, in 18 (7%) of 260 patients 5 to 14 years of age, and in 19 (5%) of 358 patients 15 years of age and older. Approximately 75% of rotavirus diarrhea occurred in children less than 5 years of age. Approximately 70% of rotaviruses found in each of the three age groups belonged to serotype G1P[8]. Interestingly, there were 29 (20%) G12 rotaviruses carrying either P[8] or P[6] and one (0.7%) G11 rotavirus carrying an unusual P[25] genotype. RNA polyacrylamide gel electrophoresis discriminated 19 strains (electropherotypes), among which there were three codominant strains carrying G1P[8] and long RNA patterns. Five electropherotypes were discriminated among G12 rotaviruses, all of which had long RNA patterns. The fact that 20% of rotaviruses were G12 strains carrying either P[8] or P[6] and had multiple electropherotypes suggest that G12 strains are not more rare strains but that they pose an emerging challenge to current and future vaccines. The presence of multiple strains as defined by electropherotypes suggests the richness of the rotavirus gene pool in Nepal, where unusual strains may continue to emerge.

Molecular characterization of rotavirus gastroenteritis strains, Iraqi Kurdistan

Of 260 children with acute diarrhea in Erbil, Iraqi Kurdistan, 96 (37%) were infected with rotavirus. Reverse transcription-polymerase chain reaction identified G1, G4, G2, G9, P[8], P[6], and P[4] as the most common genotypes. Eight G/P combinations were found, but P[8]G1 and P[4]G2 accounted for >50% of the strains.

Rotavirus vaccines: current prospects and future challenges

Rotavirus is the most common cause of severe diarrhoea in children worldwide and diarrhoeal deaths in children in developing countries. Accelerated development and introduction of rotavirus vaccines into global immunisation programmes has been a high priority for many international agencies, including WHO and the Global Alliance for Vaccines and Immunizations. Vaccines have been developed that could prevent the enormous morbidity and mortality from rotavirus and their effect should be measurable within 2-3 years. Two live oral rotavirus vaccines have been licensed in many countries; one is derived from an attenuated human strain of rotavirus and the other combines five bovine-human reassortant strains. Each vaccine has proven highly effective in preventing severe rotavirus diarrhoea in children and safe from the possible complication of intussusception. In developed countries, these vaccines could substantially reduce the number and associated costs of child hospitalisations and clinical visits for acute diarrhoea. In developing countries, they could reduce deaths from diarrhoea and improve child survival through programmes for childhood immunisations and diarrhoeal disease control. Although many scientific, programmatic, and financial challenges face the global use of rotavirus vaccines, these vaccines-and new candidates in the pipeline-hold promise to make an immediate and measurable effect to improve child health and survival from this common burden affecting all children.

A lack of significant association between the electropherotype or G-serotype of the infecting strain and disease severity of rotavirus gastroenteritis

Despite many previous studies, the question has not been settled as to whether some human rotavirus strains are more virulent than others. Since disease severity is most clearly reflected by the hospitalization status of the infected children, we examined whether there was any difference in the distribution of dominant strains between inpatient and outpatient groups. The study population comprised 763 children with acute diarrhea who were treated at a general hospital in Honjo City, Akita, Japan, during 1986-1997. Rotaviruses from stool specimens were classified into 77 electropherotypes using polyacrylamide gel electrophoresis. A single dominant strain or two co-dominant strains circulated simultaneously with some infrequent strains in most rotavirus seasons. Over the 11 rotavirus seasons, there was no significant difference in the relative frequencies of 15 rotavirus strains between the inpatient and the outpatient groups when strains of rotavirus were defined by their electropherotypes in polyacrylamide gel electrophoresis. However, infection with one G1 strain that co-dominated with a G4 strain carrying an identical electropherotype except the VP7 gene resulted in a statistically significantly reduced risk of hospitalization. There was no significant difference in the relative frequencies of four major G-serotypes or long/short RNA pattern. We conclude that the virulence or disease-causing potential of human rotavirus is not substantially different in the majority of strains.

Isolation and molecular characterization of a naturally occurring non-structural protein 5 (NSP5) gene reassortant of group A rotavirus of serotype G2P[4] with a long RNA pattern

We report here two unusual strains of group A rotavirus, AU85 and AU102, isolated from children with diarrhea. These strains showed an unusual combination of serotype G2 and a long RNA pattern. RNA-RNA hybridization assays showed that these strains are reassortants in which a single genome segment 11 (the NSP5 gene) was derived from a Wa genogroup strain, while other 10 genome segments from a DS-1 genogroup strain. Phylogenetic analysis showed that the NSP5 gene of strain AU85 did not form cluster with Wa strain, while it belonged to the cluster of YM and other porcine strains. Phylogenetic analysis also showed that NSP5 and VP7 genes of AU85 were derived from the rotavirus circulating in the area. Both co-electrophoresis and RNA-RNA hybridization showed that AU85 and AU102 are identical strains. Moreover, the nucleotide sequence comparison between these two strains revealed that they had 100% identical NSP4, NSP5, and VP7 genes. These results suggest that AU85 was a reassortant formed relatively recently between rotaviruses belonging to the Wa and the DS-1 genogroup.

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.

Predominance of rotavirus genotype G9 during the 1999, 2000, and 2002 seasons among hospitalized children in the city of Salvador, Bahia, Brazil: implications for future vaccine strategies

Two hundred eight of 648 (32%) diarrheal stool samples collected from hospitalized children under 5 years of age during a 3-year period (1999, 2000, and 2002) in the city of Salvador, in the state of Bahia, Brazil, were rotavirus positive. One hundred sixty-four of 208 (78.8%) rotavirus-positive samples had genotype G9 specificity, predominantly in association with P[8]. Other specificities detected were G1 (12.0%) and G4 (1.4%). Viruses with G2, G3, or P[4] specificity were not detected. Rotavirus genotype G9 predominated during each of the three seasons studied; it represented 89.2% of rotavirus strains detected in 1999, 85.3% in 2000, and 74.5% in 2002. G1 viruses (the globally most common G type) have a unique epidemiological characteristic of maintaining predominance during multiple consecutive rotavirus seasons. We have shown in this study for the first time that the G9 viruses also have a similar epidemiological characteristic, albeit for a shorter period of surveillance. The next generation of rotavirus vaccines will need to provide adequate protection against disease caused by G9 viruses.

Porcine rotavirus strain Gottfried-based human rotavirus candidate vaccines: Construction and characterization

Rotavirus gastroenteritis remains the leading cause of severe diarrheal disease in infants and young children worldwide, and thus, a safe and effective rotavirus vaccine is urgently needed in both developing and developed countries. Various candidate rotavirus vaccines that were developed by us and others have been or are being evaluated in different populations in various parts of the world. We have recently confirmed that a porcine rotavirus Gottfried strain bears a P (VP4) serotype (P2B[6]) closely related to human rotavirus P serotype 2A[6] which is of epidemiologic importance in some regions of the world. Based on the modified Jennerian approach to immunization, we have constructed 11 Gottfried-based single VP7 or VP4 gene substitution reassortant vaccine candidates which could provide: (i) an attenuation phenotype of a porcine rotavirus in humans; and (ii) antigenic coverage for G serotypes 1-6 and 8-10 and P serotype 1A[8], 1B[4] and 2A[6]. In addition, following immunization of guinea pigs with Gottfried VP4, we found low but consistent levels of neutralizing antibodies to VP4 with P1A[8] or P1B[4] specificity, both of which are of global epidemiologic importance. Thus, porcine-based VP7 reassortant rotavirus vaccines may provide an advantage over rhesus- or bovine-based VP7 reassortant vaccines since the VP4s of the latter vaccines do not evoke antibodies capable of neutralizing the viruses bearing P1A[8], P1B[4] or P2A[6] VP4.

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.

Rotavirus surveillance in the city of Rio de Janeiro-Brazil during 2000-2004: Detection of unusual strains with G8P[4] or G10P[9] specificities

Rotavirus diarrhea is a potentially life-threatening disease that affects millions of children annually around the world. Because protection against rotavirus disease is thought to be type specific, continuous rotavirus surveillance before and after implementation of a vaccine is still of essential importance. Rotavirus surveillance has been conducted in the city of Rio de Janeiro, Brazil since 1982. In the present study, we report rotavirus surveillance data in Rio de Janeiro city from 2000 to 2004. One hundred twenty nine of 1,568 (8.2%) stool samples, collected from children with acute diarrhea between January 2000 and July 2004 were rotavirus-positive. One hundred twenty eight of the 129 (99.2%) rotavirus-positive samples were genotyped for G and/or P specificity. G1 was the predominant strain (49.6%, 64/129) followed by G9 (30.2%, 39/129), and G4 (17.8%, 23/129); G2 and G3 viruses were not detected. One sample (0.8%) was non-typeable. P genotypes were determined for 124 of the 129 (96%) samples, and P[8] was the predominant genotype (90.6%, 117/129). Genotypes P[4] and P[9] were detected in two (1.6%) samples each; one (0.8%) sample presented P[6] genotype; and five (3.8%) samples were non-typeable. Two samples (1.6%) presented mixed P genotypes (P[6] + P[8]). Two unusual strains were isolated: a G8P[4] strain isolated from a non-hospitalized child with diarrhea and a G10P[9] strain isolated from a hospitalized child with diarrhea.

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.

An outbreak of gastroenteritis during school trip caused by serotype G2 group A rotavirus

Between May14 and 18, 2001, there was an outbreak of acute gastroenteritis involving 45 school children out of a total of 107 (aged 11-12 years) attending a 3-day school trip. The epidemic curve characterized by a rapid onset and decline with a single peak incidence over a 5-day period resembled the pattern typical of a food-borne gastroenteritis outbreak. Epidemiological and virological investigations concluded, however, that this outbreak was caused by a single strain of serotype G2 group A rotavirus spreading to schoolmates from the primary case-pupil who had already been ill at the start of the trip. Efficient person-to-person transmission was likely to have occurred due to prolonged and close contacts under the conditions typical of such school trips. This study emphasizes the importance of including group A rotavirus infection as a possible cause of gastroenteritis outbreaks even in older children and adults.

Diversity of enteric viruses detected in patients with gastroenteritis in a tertiary referral paediatric hospital

The genetic diversity of enteric viruses co-circulating in a cohort of patients with viral gastroenteritis in a large tertiary paediatric hospital in London, UK, was determined. Multiple strains of noroviruses (NV), sapoviruses (SV) and astroviruses (HAsV) were detected in these patients, indicating the likelihood of multiple introductions from different sources, possible sub-clinical infections and simultaneous infection with different viruses in immunocompromised and other patients. Routine screening of immunocompromised patients and infection control procedures are important to prevent nosocomial infection.

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.

Assessment of the epidemic potential of a new strain of rotavirus associated with the novel G9 serotype which caused an outbreak in the United States for the first time in the 1995-1996 season

Rotavirus causes severe morbidity in developed countries and frequent deaths (> or = 500,000 per year) in less-developed countries. Historically, four serotypes--G1, G2, G3, and G4-have predominated; they are distinguished by one of two surface neutralization antigens (VP7). However, in 1983 and 1984 we described a new rotavirus serotype, designated G9, in five children hospitalized for diarrhea in Philadelphia, Pa. G9 rotavirus was not identified again in the Western Hemisphere until it caused ca. 50% of the rotavirus disease detected in Philadelphia in the 1995-1996 season. This outbreak allowed us to question whether a rotavirus strain completely new to a well-studied community would target either very young infants or older children, cause especially severe disease, or completely displace previously extant serotypes. We observed a significant excess of G9 infections in younger infants (especially in those < 6 months old) that might be attributed to the lack of G9-specific antibodies in mothers. Of further note, six of the seven oldest patients with rotavirus diarrhea were infected with the G9 strains (not significant). However, the age distribution of children with rotavirus did not differ over a 5-year study period regardless of the infecting serotype. Patients with diarrhea associated with G9 strains did not have disease more severe than that caused by the G1, G2, or G3 serotype. G9 strains did not displace the other serotypes but were virtually completely replaced by G1 or G2 serotypes in the three subsequent rotavirus seasons. We conclude that the abrupt appearance of this novel rotavirus serotype did not present a special threat to public health in the community.

Human rotavirus strains bearing VP4 gene P[6] allele recovered from asymptomatic or symptomatic infections share similar, if not identical, VP4 neutralization specificities

A rotavirus VP4 gene P[6] allele has been documented in a number of countries to be characteristically associated with an endemic predominantly asymptomatic infection in neonates in maternity hospital nurseries. The mechanisms underlying the endemicity and asymptomatic nature of such neonatal infections remain unknown. Rotavirus strains sharing this same P genotype, however, have more recently been recovered from an increasing number of symptomatic diarrheal episodes in infants and young children in various parts of the world. Previously, we have shown that an asymptomatic P[6] rotavirus neonatal infection is not associated with a unique VP7 (G) serotype but may occur in conjunction with various G types. Although amino acid sequence comparisons of the VP4 gene between selected "asymptomatic" and "symptomatic" P[6] rotavirus strains have been reported and yielded information concerning their VP4 genotypes, serotypic comparisons of the outer capsid spike protein VP4 of such viruses have not been studied systematically by two-way cross-neutralizations. We determined the VP4 neutralization specificities of four asymptomatic and four symptomatic P[6] strains: two each of asymptomatic and symptomatic strains by two-way tests, and two each of additional asymptomatic and symptomatic strains by one-way tests. Both asymptomatic and symptomatic P[6] strains were shown to bear similar, if not identical, VP4 neutralization specificities. Thus, P[6] rotavirus strains causing asymptomatic or symptomatic infections did not appear to belong to unique P (VP4) serotypes. In addition, a close VP4 serotypic relationship between human P[6] rotavirus strains and the porcine P[6] rotavirus Gottfried strain was confirmed.

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.

Construction and characterization of rhesus monkey rotavirus (MMU18006)- or bovine rotavirus (UK)-based serotype G5, G8, G9 or G10 single VP7 gene substitution reassortant candidate vaccines

Group A rotaviruses are the single most important etiologic agents of severe diarrhea of infants and young children worldwide and have been estimated to be responsible for approximately 650,000-800,000 deaths annually in children <5-year-old in the developing countries. Thus, the development of a safe and effective rotavirus vaccine has been a global public health goal. Epidemiologic surveillance of rotavirus VP7 (G) serotypes-genotypes conducted in various populations throughout the world has repeatedly shown that approximately 90% of the typeable rotavirus isolates belong to G1-G4. For these reasons, we have developed a rhesus rotavirus (RRV)-based or bovine rotavirus (UK)-based quadrivalent vaccine which is designed to provide antigenic coverage for G1-G4. More recently, G serotypes-genotypes other than G1-G4, including G5, G8-G10, have been detected in various parts of the world. Although the occurrence of such uncommon G types, except for G9, has been focal, still, in order to "be ready and prepared", we have constructed and characterized eight additional reassortant rotavirus vaccines, each of which bears a single human or bovine VP7 gene encoding G serotype 5, 8, 9 or 10 specificity and the remaining 10 genes of RRV strain MMU18006 or bovine rotavirus strain UK. These candidate vaccines could be evaluated singly in special populations or in combination with a RRV- or an UK-based quadrivalent vaccine to broaden its G serotype specificity.

Excretion of serotype G1 rotavirus strains by asymptomatic staff: a possible source of nosocomial infection

This study supports the hypothesis that feces from asymptomatic adults may provide a vehicle for the transmission of rotavirus, in addition to aerosols, hands, and fomites. The observed preferential carriage of serotype G1 strains in the adult gastrointestinal tract may explain G1 predominance and persistence in epidemiologic studies worldwide.

Increased prevalence of G1P[4] genotype among children with rotavirus-associated gastroenteritis in metropolitan Detroit

The G and P genotypes of rotavirus stool isolates from 100 children were determined by reverse transcription-PCR and nucleotide sequencing. G1P[4] was the most prevalent genotype(41%), followed by G1P[8] (16%) and G4P[4] (14%). The G genoypes detected were G1 (73%), G4 (17.4%), G9 (6.3%), and G2 (2.8%). The P genotypes were P[4] (71%) and P[8] (29%). Coinfection with more than one G genotype occurred in 12 patients, and coinfection with more than one P genotype occurred in 11 patients.

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.

Generation and characterization of six single VP4 gene substitution reassortant rotavirus vaccine candidates: each bears a single human rotavirus VP4 gene encoding P serotype 1A[8] or 1B[4] and the remaining 10 genes of rhesus monkey rotavirus MMU18006 or bovine rotavirus UK

The global disease burden of rotavirus diarrhea in infants and young children has stimulated interest in the biological and clinical characteristics of these agents, leading to intensive efforts to develop a vaccine. A rhesus rotavirus (RRV)-based quadrivalent vaccine ("RotaShield") was licensed and administered to about 1 million infants and found to be highly effective. However, it was withdrawn because of a link with intussusception. This vaccine was developed according to a modified "Jennerian" approach in which one of the two major outer capsid proteins (VP7) shares neutralization specificity with one of the four epidemiologically important human rotavirus serotypes. The other outer capsid protein (VP4) is derived solely from RRV and is distinct from the VP4 of the four human rotavirus serotypes of epidemiologic importance. In an effort to further increase the immunogenicity of the existing VP7-based RRV quadrivalent vaccine, we generated three single VP4 gene substitution reassortant rotavirus candidate vaccines, each of which bears a single human rotavirus VP4 gene encoding P serotype 1A[8] or 1B[4] specificity while the remaining 10 genes are derived from the rhesus rotavirus. By incorporating one or two of these strains into the quadrivalent vaccine, a pentavalent or hexavalent RRV-based vaccine could be formulated thus providing antigenic coverage not only for VP7 serotype 1, 2, 3 and 4 but also for VP4 serotype 1A[8] or 1B[4], thus possibly augmenting its immunogenicity. Similarly, three single VP4 gene (P1A[8] or P1B[4]) substitution reassortants have also been generated in a background of 10 bovine (UK) rotavirus genes for addition to a second generation UK-based quadrivalent vaccine.

Rotavirus vaccines: development, current issues and future prospects

The potential benefit of safe and effective rotavirus vaccination in reducing morbidity and especially mortality from rotavirus gastroenteritis among children in developing countries has long been recognised. More recently, the focus of attention shifted to developed countries, where cost-effectiveness analyses justified the routine introduction of rotavirus vaccines into childhood immunisation schedules. The recent withdrawal in the U.S.A. of the first licensed rotavirus vaccine (the tetravalent rhesus reassortant rotavirus vaccine), following investigation into reports of intussusception among a number of vaccinees, has directed attention once more towards rotavirus vaccine use in developing countries. However, issues relating to vaccine safety, efficacy, and cost, remain to be overcome before widespread introduction of rotavirus vaccines can be anticipated.

Clinical evaluation of a single oral dose of human-bovine (UK) reassortant rotavirus vaccines Wa x UK (P1A[8],G6) and Wa x (DS-1 x UK) (P1A[8],G2)

The safety, infectivity, and immunogenicity of two human-bovine reassortant rotavirus candidate vaccines were evaluated in adults, children, and infants. One of these, Wa x UK, contained a single human rotavirus gene from the Wa strain that encoded VP4 P1A specificity in a background of 10 bovine genes including the VP7 gene that encodes G6 specificity, whereas the other, Wa x (DS-1 x UK), possessed the human rotavirus VP4 gene from the Wa strain as well as the human VP7 gene from strain DS-1 that encoded G2 specificity. Each of these vaccines appeared to be well-tolerated and immunogenic in infants less than 6 months of age following a single oral dose, and therefore should be evaluated further as vaccine candidates.

Distribution of rotavirus G and P types in north and south Indian children with acute diarrhoea in 1998-99

VP7 and VP4 genotypes of 82 rotavirus strains from children with acute diarrhoea during November 1998-January 1999, in 4 Indian towns, were determined by reverse-transcription PCR. Overall, 68/82 (83%) could be VP7- and 52/82 (63%) VP4-typed. Geographical differences in rotavirus circulation have implications for future vaccination strategies.

Apparent re-emergence of serotype G9 in 1995 among rotaviruses recovered from Japanese children hospitalized with acute gastroenteritis

Serotype G9 rotaviruses have been detected in about 0.5% of the circulating strains worldwide. However, G9 strains emerged globally in the middle of the 90s and thereafter. A rotavirus, contained in stool specimen 95H115, possessing a G9 VP7 emerged in Japan in the 1994-1995 season for the first time after a 9-year interval since prototype G9 strains AU32 and F45 were discovered in the 1985-1986 season. In comparison with other G9 VP7 genes thus far published, the sequencing of the VP7 genes of AU32 and 95H115 revealed that the 95H115 VP7 gene did not directly evolve from the AU32 VP7 gene but was much more closely related to the contemporary G9 VP7 genes found in the United States of America. Thus, recently emerging G9 VP7 genes were not direct descendants of the VP7 genes of the prototype strains in the 80s, rather they evolved independently into 4 phylogenetic clusters from a common ancestor.

Rotavirus infection and intussusception: a view from retrospect

A live orally-administrable rhesus rotavirus (RRV) tetravalent (TV) vaccine, licensed in the U.S.A. and the European Union, was recalled from the market because it was suspected to increase the risk of intussusception during the week following immunization. In contrast, natural rotavirus infection is generally believed not to cause intussusception. Because my experience contributed to the first paper that linked intussusception with rotavirus infection, I have re-examined our own data published 22 years ago and other studies on this issue. I also made a case study of adenovirus and intussusception as a paradigm to establish an etiological association of viral infection and intussusception. My hypothesis postulated in this review is that natural infection of susceptible (or predisposed) infants with some rotavirus strains, probably serotype G3 rotaviruses, will result in an appreciable fraction of idiopathic intussusception. Thus, the number of rotavirus-induced intussusception cases may change reflecting the relative frequency of G3 strains, which I believe was much higher in the 70s than during the last two decades. The epidemiological data indicate that the RRV-TV vaccine triggers intussusception at a rate significantly higher than the background incidence rate following the week of vaccination, particularly after the first dose. In contrast, the data do not suggest that the cumulative incidence among the vaccine recipients increases accordingly, implicating that the risk of intussusception attributable to the RRV-TV vaccine may be minimal.

Rotavirus strain diversity in Blantyre, Malawi, from 1997 to 1999

In a 2-year study of viral gastroenteritis in children in Blantyre, Malawi, the diversity of rotavirus strains was investigated by using electropherotyping, reverse transcription-PCR amplification of the VP7 and VP4 genes (G and P genotyping), and nucleotide sequencing. Of 414 rotavirus strains characterized, the following strain types were identified: P[8], G1 (n = 111; 26.8%); P[6], G8 (n = 110; 26.6%); P[8], G3 (n = 93; 22.5%); P[4], G8 (n = 31; 7.5%); P[8], G4 (n = 21; 5.1%); P[6], G3 (n = 12; 2.9%); P[6], G1 (n = 7; 1.7%); P[6], G9 (n = 3; 0.7%); P[6], G4 (n = 3; 0.7%); P[4], G3 (n = 1; 0.2%); and mixed (n = 15; 3.6%). While all strains could be assigned a G type, seven strains (1.7%) remained P nontypeable. The majority of serotype G8 strains and all serotype G9 strains had short electropherotype profiles. All remaining typeable strains had long electropherotypes. Divergent serotype G1 rotaviruses, which contained multiple base substitutions in the 9T-1 primer binding site, were commonly identified in the second year of surveillance. Serotype G2 was not identified. Overall, G8 was the most frequently identified VP7 serotype (n = 144; 34.8%) and P[8] was the most frequently detected VP4 genotype (n = 227; 54.8%). Partial sequence analysis of the VP4 gene of genotype P[8] rotaviruses identified three distinct clusters, which predominantly (but not exclusively) comprised strains belonging to a distinct VP7 serotype (G1, G3, or G4). As a result of mutations in the 1T-1 primer binding site, strains belonging to each cluster required a separate primer for efficient typing. One cluster, represented by P[8], G4 strain OP354, was highly divergent from the established Wa and F45 VP4 P[8] lineages. As is the case for some other countries, the diversity of rotaviruses in Malawi implies that rotavirus vaccines in development will need to protect against a wider panel of serotypes than originally envisioned.