Isolation of human rotavirus subgroups 1 and 2 in cell culture

Reverse Genetics Approach for Developing Rotavirus Vaccine Candidates Carrying VP4 and VP7 Genes Cloned from Clinical Isolates of Human Rotavirus

Species A rotaviruses (RVs) are a leading cause of severe acute gastroenteritis in infants and children younger than 5 years. Currently available RV vaccines were adapted from wild-type RV strains by serial passage of cultured cells or by reassortment between human and animal RV strains. These traditional methods require large-scale screening and genotyping to obtain vaccine candidates. Reverse genetics is a tractable, rapid, and reproducible approach to generating recombinant RV vaccine candidates carrying any VP4 and VP7 genes that provide selected antigenicity. Here, we developed a vaccine platform by generating recombinant RVs carrying VP4 (P[4] and P[8]), VP7 (G1, G2, G3, G8, and G9), and/or VP6 genes cloned from human RV clinical samples using the simian RV SA11 strain (G3P[2]) as a backbone. Neutralization assays using monoclonal antibodies and murine antisera revealed that recombinant VP4 and VP7 monoreassortant viruses exhibited altered antigenicity. However, replication of VP4 monoreassortant viruses was severely impaired. Generation of recombinant RVs harboring a chimeric VP4 protein for SA11 and human RV gene components revealed that the VP8* fragment was responsible for efficient infectivity of recombinant RVs. Although this system must be improved because the yield of vaccine viruses directly affects vaccine manufacturing costs, reverse genetics requires less time than traditional methods and enables rapid production of safe and effective vaccine candidates.IMPORTANCE Although vaccines have reduced global RV-associated hospitalization and mortality over the past decade, the multisegmented genome of RVs allows reassortment of VP4 and VP7 genes from different RV species and strains. The evolutionary dynamics of novel RV genotypes and their constellations have led to great genomic and antigenic diversity. The reverse genetics system is a powerful tool for manipulating RV genes, thereby controlling viral antigenicity, growth capacity, and pathogenicity. Here, we generated recombinant simian RVs (strain SA11) carrying heterologous VP4 and VP7 genes cloned from clinical isolates and showed that VP4- or VP7-substituted chimeric viruses can be used for antigenic characterization of RV outer capsid proteins and as improved seed viruses for vaccine production.

Sensitive SYBR Green-Real Time PCR for the Detection and Quantitation of Avian Rotavirus A

Avian rotavirus A (ARtV-A) is a virus that affects young birds, causing acute diarrhea and economic losses in the poultry industry worldwide. The techniques used for the diagnosis of ARtV-A include electron microscopy, isolation in cell culture, and serology, as well as molecular techniques, such as the reverse transcription-polymerase chain reaction (RT-PCR). The objective of this work was to standardize a real-time RT-polymerase chain reaction (RT-qPCR) using SYBR Green chemistry for the rapid detection and quantification of ARtV-A from bird tissues and materials fixed on FTA cards on the basis of the nucleotide sequence of segment 6 (S6), which codes for the structural VP6 protein of ARtV-A. The results show the efficient amplification of the proposed target, with a limit of detection (LoD) of one copy gene (CG) per microliter of cDNA and a limit of quantification (LoQ) of 10 CGs per microliter. The efficiency of the primers was determined to be 95.66% using a standard curve, with an R² value of 0.999 and a slope of −3.43. The specificity was determined using samples coinfected with ARtV-A, the chicken parvovirus, the chicken astrovirus, and the avian nephritis virus as positive controls and commercially available vaccines of the infectious bronchitis virus, infectious bursa disease virus, avian reovirus and healthy organs as negative controls. This technique, which lacks nonspecific PCR products and dimers, demonstrated greater sensitivity and specificity than conventional RT-PCR, and it reduced the analysis time by more than 50%.

Porcine-like G3P[6] and G4P[6] rotavirus A strains detected from children with diarrhoea in Vietnam

Animal rotavirus A (RVA) strains can infect children and cause diarrhoea. We determined the full genome sequences of one G3P[6] strain (NT0001) and five G4P[6] strains (NT0042, NT0077, NT0205, NT0599, and NT0621) detected from children with diarrhoea in Vietnam in 2007-2008. Strain NT0001 had a genotype constellation of: G3-P[6]-I5-R1-C1-M1-A8-N1-T1-E1-H1, strain NT0042: G4-P[6]-I1-R1-C1-M1-A8-N1-T1-E1-H1, strain NT0077: G4-P[6]-I5-R1-C1-M1-A8-N1-T7-E1-H1, and strains NT0205, NT0599, and NT0621: G4-P[6]-I1-R1-C1-M1-A1-N1-T1-E1-H1. Sequence divergence data and phylogenetic analysis showed that they were different porcine RVA strains that independently and directly crossed the host species barrier to infect children.

Whole genome characterization of a G6P[5] rotavirus A strain isolated from a stray cat in Japan

The whole genome of an unusual G6P[5] rotavirus A strain named FRV537, which was isolated from a stray cat in Japan, was characterized to determine its species of origin. The genotype constellation of FRV537 was G6-P[5]-I2-R2-C2-M2-A13-N2- T6-E2-H3. No known feline rotavirus has this genotype constellation; the Japanese equine strain OH-4 is the only known strain that does. While FRV537 shares the same genotype with some feline rotaviruses in all genes except those encoding VP4 and NSP1, none of these genes are closely related to those of known feline rotaviruses. By contrast, G6P[5] is almost exclusively present in bovine rotaviruses. The VP7 and VP4 genes of FRV537 formed a lineage with typical bovine rotaviruses with high bootstrap values. As to the internal capsid and nonstructural gene constellation, three bovine rotavirus strains had a constellation identical to that of FRV537. Moreover, each of the genotypes of FRV537 was found to be a common bovine genotype. In addition to the high nucleotide sequence identities between FRV537 and bovine rotaviruses in each genome segment (≥95%), phylogenetic analysis revealed a close relationship to bovine/artiodactyl rotaviruses. Thus, the molecular and phylogenetic evidence suggests that FRV537 isolated from a stray cat was of bovine rotavirus origin.

Detection of rotavirus from hospitalized diarrheic children in uttar pradesh, India

In the present study 220 stool samples collected from diarrheic children admitted to different hospitals and nursing homes of Uttar Pradesh and Uttarakhand were screened for rotavirus. Of 220 diarrheic samples screened 46 samples were found to be positive for rotavirus by RNA PAGE. All the isolates exhibited 4-2-3-2 migration pattern suggesting group A rotavirus. Both long and short electropherotypes were prevalent in these regions. Six different electropherotypes were detected in this study period. Male diarrheic children were found to be more susceptible to rotavirus infection (22.96 %) than that of the female ones (17.64 %). Viral RNA isolated from stool samples again subjected to VP4 gene amplification by RT-PCR using con2 and con3 primer which resulted 876 bp product suggesting group A rotavirus. Besides virus isolation was successfully done using MA104 cell line.

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

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

Identification by full-genome analysis of a bovine rotavirus transmitted directly to and causing diarrhea in a human child

The genome of rotaviruses consists of 11 segments of double-stranded RNA, and each genome segment has multiple genotypes. Thus, the genotype constellation of an isolate is often indicative of its host species. Albeit rarely, interspecies transmission occurs either by virions with nonreassorted or reassorted genomic segments. A rotavirus with the G6P[1] genotype, Ro8059, was isolated from the stool of a 1-year-old child during routine characterization of diarrheal specimens from a sentinel clinic in Israel in 1995. Since genotype G6P[1] is generally associated with bovine rotaviruses, and the child developed diarrhea within days of his first contact with calves at an urban farm, the aim of this study was to characterize the whole genomic constellation of Ro8059 and four G6P[1] bovine strains, BRV101, BRV105, BRV106, and CR231/39, by RNA-RNA hybridization and full genome sequencing to determine whether some or all of the segments were of bovine origin. The genome constellations of all four bovine G6P[1] strains were G6-P[1]-I2-R2-C2-M2-A3-N2-T6-E2-H3 for VP7-VP4-VP6-VP1-VP2-VP3-NSP1-NSP2-NSP3-NSP4-NSP5, respectively. Ro8059 shared the same genotype constellation with these bovine strains, with high nucleotide sequence identities (95.84 to 100%) for each of the 11 segments indicating that Ro8059 represented a direct interspecies whole-genome transmission of a nonreassorted rotavirus from a calf to a human infant. We conclude that this was the earliest example with a complete epidemiological link in which an entirely bovine rotavirus directly infected a human child and caused a symptomatic diarrheal illness. Thus, not all bovine rotaviruses are always naturally attenuated to the human host.

Molecular characterization of rotavirus strains detected during a clinical trial of a human rotavirus vaccine in Blantyre, Malawi

The human, G1P[8] rotavirus vaccine (Rotarix™) significantly reduced severe rotavirus gastroenteritis episodes in a clinical trial in South Africa and Malawi, but vaccine efficacy was lower in Malawi (49.5%) than reported in South Africa (76.9%) and elsewhere. The aim of this study was to examine the molecular relationships of circulating wild-type rotaviruses detected during the clinical trial in Malawi to RIX4414 (the strain contained in Rotarix™) and to common human rotavirus strains. Of 88 rotavirus-positive, diarrhoeal stool specimens, 43 rotaviruses exhibited identifiable RNA migration patterns when examined by polyacrylamide gel electrophoresis. The genes encoding VP7, VP4, VP6 and NSP4 of 5 representative strains possessing genotypes G12P[6], G1P[8], G9P[8], and G8P[4] were sequenced. While their VP7 (G) and VP4 (P) genotype designations were confirmed, the VP6 (I) and NSP4 (E) genotypes were either I1E1 or I2E2, indicating that they were of human rotavirus origin. RNA-RNA hybridization using 21 culture-adapted strains showed that Malawian rotaviruses had a genomic RNA constellation common to either the Wa-like or the DS-1 like human rotaviruses. Overall, the Malawi strains appear similar in their genetic make-up to rotaviruses described in countries where vaccine efficacy is greater, suggesting that the lower efficacy in Malawi is unlikely to be explained by the diversity of circulating strains.

DETECÇÃO E ISOLAMENTO DE ROTAVÍRUS CAPRINO DO GRUPO A

RESUMO Rotavírus é a principal causa de diarreia em animais jovens de várias espécies. Os rotavirus estão classificados na família Reoviridae e contêm um genoma formado por 11 segmentos de RNA de cadeia dupla, envolvidos em três camadas proteicas. Neste estudo, foi detectado rotavírus pela eletroforese em gel de poliacrilamida (PAGE) em amostras de fezes de caprinos, com 80 dias de idade, durante surto de diarreia em um rebanho leiteiro. O perfil eletroforético das amostras, denominadas cap01/2007 e cap02/2007, foi caracterizado no PAGE como sendo de rotavírus do grupo A. Para o isolamento viral, suspensão fecal a 20% em tampão tris 0,1M pH 7,3 foi filtrada e tratada com tripsina cristalina na concentração de 5mg/mL. A amostra caprina cap01/2007 foi inoculada em cultura de células MA104 (Rim de Macaco Rhesus). Foram testados dois tratamentos (T1 e T2): após adsorção (estufa 37º C por uma hora) adicionou-se meio de manutenção (Dulbecco-MEM) sem tripsina, mantendo o inóculo (T1). No tratamento 2 (T2), foi realizado o mesmo pro cedimento anterior, porém o inóculo foi dispensado. O efeito citopático foi observado na primeira passagem para ambos os tratamentos (T1 e T2) com 48 horas de inoculação e o isolamento viral foi confirmado no PAGE. O perfil de migração manteve-se inalterado após três passagens sucessivas. Este é o primeiro relato de isolamento de rotavírus em caprinos no Brasil.

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.

Lack of shedding of the RIX4414 live attenuated rotavirus vaccine administered to adult volunteers

Ten adult volunteers were given the RIX4414 rotavirus vaccine; one volunteer shed a small amount of virus antigen but not live virus. This suggests that parents of vaccinated children are unlikely to spread the vaccine.

Anticipating rotavirus vaccines in Brazil: Detection and molecular characterization of emerging rotavirus serotypes G8 and G9 among children with diarrhoea in Recife, Brazil

In 2006, Brazil will initiate universal immunization of its 4-million infants with a live attenuated serotype G1P[8] human rotavirus vaccine. In anticipation of the national immunization program, this study was undertaken to characterize rotavirus strains circulating among children in Recife, one of the largest cities in the northeast region of Brazil. Group A rotaviruses were detected in 102 (35%) of 290 faecal specimens collected from children under 5 years of age who presented with acute diarrhoea during a 1-year period between May 2004 and April 2005. In addition to the globally common G1P[8] serotype that accounted for 49% of strains, emerging rotavirus serotypes G8P[6] and G9P[8] represented 2% and 29% of strains, respectively. Following cell culture adaptation, RNA-RNA hybridization demonstrated that two Brazilian G8P[6] rotavirus strains shared a high level of genomic RNA homology with Malawian G8P[6] strains, and a Brazilian G9P[8] strain was related most closely to a G9P[8] strain from India. The results suggest that certain rotavirus strains have a much wider global circulation than generally appreciated. Continued global spread of such strains might challenge the efficacy of current rotavirus vaccines.

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.

Unexpected detection of simian SA11-human reassortant strains of rotavirus G3P[8] genotype from diarrhea epidemic among tribal children of Western India

This investigation is in continuation with the earlier studies on diarrhea epidemic due to rotavirus, that occurred at Jawhar western India, among tribal children during Dec 2000-Jan 2001 published by National Institute of Virology, Pune. Three rotavirus strains were isolated in cell culture from fecal specimens of affected children. Monoclonal antibody ELISA and RT-PCR typed the isolates as G3P [8]. Two isolates agglutinated guinea pig erythrocytes thereby indicating their animal origin. Antiserum against simian G3, SA11 neutralized both the isolates largely than antiserum against human G3 (YO). Nucleotide sequencing of VP7 gene, nested PCR product of three isolates, and two original fecal specimens showed 100% identity with both simian G3, SA11 prototype and ROSVP7, SA11 strains whereas, lower identity (82%) with human G3 (YO) strain. Partial sequence analysis of the VP4 gene of fecal specimen FS-006964 & isolate I-006964 showed 99% identity with G1P[8] strain, while 80% identity with simian G3P[2], SA11 strain. Thus, the strains appeared to be reassortants between human and simian origin. Serological studies further supported the identity of the causative agent as simian G3, SA11 like strains. Neutralizing antibody titers at very low level against simian G3, SA11 as well as human G3 (YO) strains among the population at Jawhar suggested an overall lack of immunity against the virus. Seroconversion against simian G3, SA11 was shown by six out of seven child patients. Thus, simian G3, SA11 like strains are claimed for the first time as etiological agents of diarrhea in humans.

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.

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

Since rotavirus vaccines aim to protect children from severe diarrhea, knowledge of the prevailing G serotypes among rotaviruses from hospitalized children is essential. Thus, we determined the G serotypes of rotaviruses collected from children with acute diarrhea in a local referral hospital in Akita, Japan, over the 10-year period between January 1987 and December 1996. Based on the assumption that rotaviruses with an identical electropherotype possess the same G serotype, the G serotypes of 488 rotavirus-positive specimens that were classified into 63 electropherotypes were determined by enzyme-linked immunosorbent assay with a supplementary use of G typing by reverse transcription-PCR. The relative frequencies over the 10-year period were 77.0 (G1), 14.5 (G2), 2.7 (G3) and 5.3% (G4), leaving the possibility that only 0.4% had G serotypes uncommon to human rotaviruses. Of 24,050 rotaviruses extracted by reviewing 63 serotyping studies in literature, the relative frequencies of the four major G serotypes were 50.6 (G1), 9.3 (G2), 7.2 (G3) and 11.6% (G4). As to uncommon G serotypes, only 0.9% were described as serotypes other than G1-4, and our estimate for potential uncommon serotypes were at most 8.1%. Thus, both this long-term study focusing on the rotaviruses only from severe cases in a single hospital in Japan and the global review of G serotypes published to date indicate that the primary target of any rotavirus vaccines should be rotaviruses possessing serotypes G1-4.

Isolation of a human rotavirus strain with a super-short RNA pattern and a new P2 subtype

Super-short rotavirus strains that have a rearranged gene segment 11 are rarely found in humans, and only five isolates, all from Southeast Asia, have been described in the literature. We report the first isolation in Japan from an infant with severe diarrhea of a rotavirus possessing a super-short RNA pattern. This strain, designated AU19, had a G1 VP7 and is also the first isolate in Japan that possesses a P2[6] VP4. Furthermore, the P2[6] VP4 carried by AU19 was divergent in the hypervariable region of the amino acid sequence from the P2A[6] VP4s carried by asymptomatic neonatal strains or from the P2B[6] VP4 carried by porcine rotavirus strain Gottfried. Thus, AU19 is likely to represent a new VP4 subtype, which we propose to call P2C. Given the recent emergence of the P2[6] VP4s in India, Brazil, and the United States and the role of VP4 in protective immunity, further scrutiny is justified to see whether the emergence of the previously underrepresented P2[6] VP4 serotype is related to this new P2 subtype.

Prophylaxis of rotavirus gastroenteritis using immunoglobulin

Oral inoculation of the human group A rotavirus MO strain (G serotype 3) into 5-day-old BALB/c mice causes gastroenteritis characterized by diarrhea. Using this small animal model, passive protection of suckling mice against human rotavirus infection was achieved with the use of immunoglobulin (IgY) from the yolks of eggs of rotavirus-immunized hens. When IgY against the rotavirus strain homotypic with the challenge virus (MO strain) was administered to mice, complete protection was achieved. After immunizing 8-month old pregnant Holstein cows with human rotavirus MO strain, colostrum containing neutralizing antibody to four different G serotypes of human rotavirus, designated Rota colostrum, was obtained. Rota colostrum completely protected suckling mice against rotavirus infection, and purified IgG obtained from Rota colostrum protected against infection with the homologous virus. After randomly grouping 20 infants from a baby care center, 10 infants received 20 ml of Rota colostrum for 2 weeks and 10 control infants received none. Rotavirus-associated diarrhea developed in 7 of the 10 infants in the control group. None of the three infants in the group daily receiving the Rota colostrum had such symptoms, and one of three infants in the group receiving treatment, every other day developed rotavirus-induced diarrhea. Oral administration of Rota colostrum seems to be an effective and safe means of preventing diarrhea caused by human rotavirus infection. Recently, the immunized cows were boosted by reinjection of 4 serotypes of human rotavirus into a superficial cervical lymph node two weeks after delivery, resulting in mass production of cow's milk containing a high-titered antibody to human rotavirus. Therefore, the hyperimmune cow's milk is a candidate for a "physiologically functional food" in Japan.

Genetic variation in VP7 gene of human rotavirus serotype 2 (G2 type) isolated in Japan, China, and Pakistan

Sequence analysis of the gene encoding the major neutralization glycoprotein (VP7) was performed on sixteen human isolates of serotype 2 of rotavirus in Japan, China, and Pakistan and their genetic variations were examined. Comparative studies of their nucleotide and deduced amino acid sequences between the sixteen isolates and the HU5 strain revealed an overall homology of more than 94%. A higher degree of homology in nucleotides was observed among the sixteen isolates than between HU5 and the isolates. A total of thirteen amino acid residues frequently converted to another amino acid. Out of the thirteen, five amino acid residues belonging to the major neutralizing epitope regions (C, E, and F in this communication) converted frequently. From the amino acid sequences three subtypes, subtype 1, subtype 2, and intermediate, were suggested to be classified as previously reported for serotype 1 (Xin et al, Virology, 1993, 197: 813-816).

Molecular characterization of a human group A rotavirus isolated from an adult with severe dehydrating diarrhea and its relationship to strains concurrently circulating among children

BACKGROUND

While group A rotavirus is widely accepted as an important etiology of acute gastroenteritis in children, this agent rarely causes severe diarrhea in adults and, thus, is not considered by physicians to be an etiological agent for such diseases.

OBJECTIVES

None of the reports describing such rare cases in adults has examined the causative strains genetically in detail.

STUDY DESIGN

We determined the G type, the gene 4 genotype, the electropherotype, and the genomic RNA constellation (genogroup) of a group A rotavirus strain isolated from an adult with severe diarrhea. This patient, the first documented case of rotavirus diarrhea in adult in Japan, suffered from severe dehydrating diarrhea with 'rice-water' appearance, vomiting and little abdominal pain, presenting a clinical picture typical of cholera.

RESULTS

Rotavirus antigen and genomic RNA were detected in the stool but other enteric pathogens including Vibrio cholerae responsible for the disease were not isolated. Molecular characterization revealed that the patient was infected with a strain of the DS-1 genogroup with G2 and gene 4 genotype 4 which was circulating among children during the same period.

CONCLUSIONS

The result that the same group A rotavirus strain was isolated from children and an adult underlines the necessity of examining rotavirus in adults with acute diarrhea.

Recurrent circulation of single nonstructural gene substitution reassortants among human rotaviruses with a short RNA pattern

To determine the relative frequency of intergenogroup reassortants of rotavirus in nature, we analyzed the genetic composition of 22 electrophoretically distinct stool isolates which accounted for 95.2% of stool rotaviruses with a short RNA pattern collected during 10 rotavirus seasons. These strains all showed subgroup I and G2 specificities, but two distinct hybridization patterns were observed when the probes prepared from Wa (a member of the Wa genogroup) and KUN (a member of the DS-1 genogroup) were used. Genomic RNAs from 10 strains (accounting for 64% of the field rotaviruses with short RNA pattern) hybridized exclusively to the KUN probe, and thus belonged to the DS-1 genogroup. On the other hand, genomic RNAs of the remaining 12 strains (accounting for 36% of the field rotaviruses with short RNA pattern) formed one hybrid band with the Wa probe and 10 hybrid bands with the KUN probe. Thus, they were single gene substitution intergenogroup reassortants between members of the Wa and DS-1 genogroups. They had a similar genetic constellation in that a gene segment encoding either NS35 or NS34 from a Wa-like strain was introduced into a DS-1-like genome background.

Two G3 feline rotavirus strains lacking cross-neutralization reactions represent distinct subtypes of serotype G3

Two feline rotavirus strains, FRV-1 and FRV64, that have been shown to lack cross-neutralization reactions despite the sharing of serotype G3 were examined by plaque-reduction neutralization assays in relation to other G3 strains originating from cats, dogs, humans and monkeys. While FRV-1 and human G3 strains constituted one subtype (G3A), FRV64, canine strains and simian strains constituted another subtype (G3B).

Detection of viruses in environmental samples: suitability of commercial rotavirus and adenovirus test kits

Commercially marketed kits are now available for rapid viral assay of clinical specimens. This study was conducted to determine the suitability of these kits for use in environmental testing. Eight rotavirus kits and one enteric adenovirus kit were screened for sensitivity using simian rotavirus SA11, human rotavirus Wa, and adenovirus 41. The most sensitive rotavirus kit and the adenovirus kit were selected for further evaluation using virus-seeded and unseeded sewage samples. The selected rotavirus kit proved capable of detecting virus at the 10(1) PFU/ml level. The enteric adenovirus kit was similarly sensitive, detecting virus at the 10(1) TCID50/ml level. Neither kit was adversely affected by the presence of sewage. Kit assay revealed 3 of 30 unseeded sewage samples to be positive for rotavirus. Adenovirus positive samples were not detected among the 30 samples. These results were confirmed using electron microscopy. It was concluded that sensitive commercial kits could provide a reasonable alternative to cell culture for the presumptive testing of environmental samples.

Physical and chemical methods for enhancing rapid detection of viruses and other agents

Viral replication events can be enhanced by physical, chemical, or heat treatment of cells. The centrifugation of cells can stimulate them to proliferate, reduce their generation times, and activate gene expression. Human endothelial cells can be activated to release cyclo-oxygenase metabolites after rocking for 5 min, and mechanical stress can stimulate endothelial cells to proliferate. Centrifugation of virus-infected cultures can increase cytopathic effects (CPE), enhance the number of infected cells, increase viral yields, and reduce viral detection times and may increase viral isolation rates. The rolling of virus-infected cells also has an effect similar to that of centrifugation. The continuous rolling of virus-infected cultures at < or = 2.0 rpm can enhance enterovirus, rhinovirus, reovirus, rotavirus, paramyxovirus, herpesvirus, and vaccinia virus CPE or yields or both. For some viruses, the continuous rolling of infected cell cultures at 96 rpm (1.9 x g) is superior to rolling at 2.0 rpm for viral replication or CPE production. In addition to centrifugation and rolling, the treatment of cells with chemicals or heat can also enhance viral yields or CPE. For example, the treatment of virus-infected cells with dimethyl sulfoxide can enhance viral transformation, increase plaque numbers and plaque size, increase the number of cells producing antigens, and increase viral yields. The infectivity of fowl plague virus is increased by 80-fold when 4% dimethyl sulfoxide is added to culture medium immediately after infection. The heat shocking of virus-infected cells also has been shown to have a stimulatory effect on the replication events of cytomegalovirus, Epstein-Barr virus, and human immunodeficiency virus. The effects of motion, chemicals, or heat treatments on viral replication are not well understood. These treatments apparently activate cells to make them more permissive to viral infection and viral replication. Perhaps heat shock proteins or stress proteins are a common factor for this enhancement phenomenon. The utility of these treatments alone or in combination with other methods for enhancing viral isolation and replication in a diagnostic setting needs further investigation.

Passive immunizations of suckling mice and infants with bovine colostrum containing antibodies to human rotavirus

After immunizing 8-month pregnant Holstein cows with the human rotavirus MO strain, cow colostrum containing neutralizing antibody to four different serotypes of human rotavirus, designated Rota colostrum, was obtained. Oral inoculation of human rotavirus MO strain into 5-day-old BALB/c mice causes gastroenteritis characterized by diarrhea. Using this small animal model, passive protection of suckling mice against human rotavirus infection was achieved with the use of Rota colostrum. Rota colostrum completely protected against rotavirus infection, but purified IgG and IgA obtained from Rota colostrum were unable to protect against infection. After grouping randomly 20 infants from a baby care center, 10 infants received 20 ml of Rota colostrum per day for 2 weeks and 10 control infants did not. Rotavirus-associated diarrhea developed in 7 of 10 infants in the control group. None of the three infants in the every day recipient group of Rota colostrum had such symptoms, and one of three infants in the every other day recipient group developed rotavirus-induced diarrhea. All four infants who received Rota colostrum after symptoms appeared developed diarrhea. Oral administration of Rota colostrum seems to be an effective and safe means of preventing diarrhea caused by human rotavirus infection.

Human and bovine serotype G8 rotaviruses may be derived by reassortment

The origin of, and relationship between human and bovine serotype G8 rotaviruses were investigated by genomic hybridisation. Radiolabelled mRNAs of human G8 rotaviruses 69M (isolated in Indonesia) and HAL1271 (isolated in Finland), and bovine rotaviruses KK3 (G10) and NCDV (G6), were used as probes. The products of liquid hybridisation between the probes and the genomic RNA of human and bovine rotaviruses, including bovine G8 rotavirus 678 (isolated in Scotland) and two other Finnish human G8 rotaviruses HAL1166 and HAL8590, were examined by separation in polyacrylamide gels. The genomes of Finnish human G8 rotaviruses were similar to those of bovine G6 and G10 rotaviruses. Neither Indonesian human G8 nor bovine G8 viruses had high levels of similarity to each other or to other bovine and human rotaviruses. Thus these three epidemiologically distinct G8 rotaviruses have different origins and may be derived by reassortment with rotaviruses of a third, as yet unknown, host species. The similarity between the Finnish isolates and the bovine isolate NCDV suggests that they have diverged recently and that these human G8 rotaviruses may be derived from a zoonotic infection, or alternatively, from the live rotavirus vaccine of bovine origin which has been used to vaccinate Finnish children.

Isolation of an avianlike group A rotavirus from a calf with diarrhea

An atypical group A rotavirus (993/83) was isolated from a 3-day-old German calf with diarrhea. It differed from 35 conventional German bovine rotavirus isolates analyzed previously with respect to subgroup (strain 993/83 was non-subgroup I and non-subgroup II), serotype (strain 993/83 showed a two-way cross-reaction with serotype 7 and a one-way cross-reaction with serotype 3), and electropherotype (strain 993/83 showed comigrating gene segments 10 and 11). Isolate 993/83 reacted with only one of four monoclonal antibodies that recognized a common VP6 epitope(s). In addition, VP6 and VP2 of isolate 993/83 showed one-dimensional peptide maps that differed substantially from the peptide maps of VP6 and VP2 from all bovine rotavirus isolates. By RNA-RNA hybridization, the 993/83 probe failed to react with a panel of mammalian rotavirus strains, including bovine rotaviruses. It hybridized, however, to genomic RNA of an avian rotavirus strain. Isolate 993/83 could thus represent a candidate for a natural interspecies transmission of rotavirus between different classes of vertebrates.

Culture adaptation and characterization of group A rotaviruses causing diarrheal illnesses in Bangladesh from 1985 to 1986

Group A rotaviruses collected between 1985 and 1986 during comprehensive surveillance of treated diarrheal episodes occurring in a rural Bangladesh population were culture adapted and characterized by electropherotype, serotype, and subgroup. Of 454 episodes of rotavirus-associated diarrhea, rotaviruses were culture adapted from 381 (84%), and 335 contained 11 electrophoretically identical segments in unpassaged and cultured preparations. These 335 comprised 69 different electropherotypes with between 1 (32 isolates) and 79 representatives. The persistence of specific rotavirus strains within the study population, as defined by the detection of viruses with particular electropherotypes, was generally limited to a period of only a few months. All 335 isolates were serotyped by neutralization with hyperimmune antisera to prototype rotavirus strains representative of serotypes 1 to 4, i.e., Wa, DS-1, P, and ST-3. It was found that 80, 48, 119, and 88 isolates belonged to serotypes 1 to 4, respectively. The concentrations of hyperimmune antisera required to neutralize these isolates, however, were at least threefold greater than those needed to neutralize the homologous strains. Therefore, the isolates appeared to have altered neutralization epitopes from their prototype strains. Furthermore, the serotype 4 isolates were consistently shown to be much more closely related to the serotype 4B VA70 strain than the serotype 4A ST-3 strain. All but two isolates identified as serotypes 1, 3, or 4 had long electropherotypes and were subgroup II, and all but one serotype 2 isolate were subgroup I and had short electropherotypes. The three disparate strains appeared to be genetic reassortants. Evidence is presented that dual infections required for reassortant formation were not uncommon. Thus, formation of multiple reassortants may have been a cause for the observed rapid shift in viral strains within the study population.

Experience with serotyping rotavirus strains by reverse transcription and two-step polymerase chain reaction with generic and type-specific primers

Six VP7 serotypes or G types (G1-G4, G8 and G9) occur in group A human rotaviruses. Gouvea et al. recently reported a novel G-typing method based on reverse transcription (RT)-polymerase chain reaction (PCR) amplification of the VP7 gene with type-specific primers [Gouvea, V. et al. (1990). Journal of Clinical Microbiology 28, 276-82]. When we followed their protocol, 40 (89%) of 45 faecal rotavirus specimens were typed into G1-G4 and G9. The five specimens that were untypeable by the RT-PCR method contained three G2 and two G4 rotavirus specimens which were identified by an ELISA using G type-specific monoclonal antibodies. On the other hand, the RT-PCR typing assay was able to determine the G type of the seven isolates that were untypeable by the ELISA. Of 33 faecal rotaviruses that were typed by both assays, 100% agreement of the result was observed. In addition, when applied to some animal rotaviruses, the RT-PCR method identified G3 feline and canine rotavirus strains. We conclude that further refinement of the RT-PCR assay is desirable in order to more readily type G2 and G4 strains, although this assay displayed an applicability to epidemiologic studies comparable with ELISAs.

Protease inhibitors prevent the development of human rotavirus-induced diarrhea in suckling mice

Oral inoculation of human rotavirus MO strain (serotype 3) into 5-day-old BALB/c mice caused gastroenteritis characterized by diarrhea (90% on the average, on day 2). Using this animal model, preventive effect of antiviral agents on the development of rotavirus-induced diarrhea was examined. The infectivity of human rotavirus was enhanced by treatment with protease in vitro. A cysteine protease inhibitor, E-64-c, was given orally at 12 hr and 24 hr after MO infection. Oral administration of 0.3 mg of E-64-c decreased the diarrhea ratio to 17.5% on day 2 and to 10% on day 3. Oral administration of 0.15 mg of cysteine protease inhibitor, ovocystatin, completely prevented the diarrhea on day 2. Serine protease inhibitor, aprotinin (0.15 mg x 2), also prevented the diarrhea on day 2 to 14.3%. These protease inhibitors were nontoxic in vitro and to suckling mice. The histopathological changes in the small intestine due to infection recovered 2 days after MO infection in mice treated with E-64-c and ovocystatin. These results suggest that protease inhibitors are protective agents for human rotavirus infection by inhibiting proteases required for viral replication.

HT-29 cells: a new substrate for rotavirus growth

Susceptibilities of a continuous rhesus monkey kidney cell line (MA-104) and that of a human colon carcinoma cell line (HT-29) to infection by different human and animal rotavirus strains were compared. HT-29 cells appeared to be more sensitive to human rotavirus infection than MA-104 cells, whereas the latter cell line was more susceptible to animal rotavirus replication. The greater sensitivity to human rotavirus infection of HT-29 cells was confirmed by the successful, direct isolation of these viruses from faecal specimens. Human rotavirus infection of HT-29 cells was also followed by transmission electron microscopy. In ultra-thin sections, unenveloped particles of rotaviruses, representing infectious mature virions, were observed in large number. Moreover, many "double-shelled" particles were detected in negative-stained supernatants from infected cultures. Scanning electron microscopy of uninfected HT-29 cells showed that in the presence of Ca++, required for rotavirus growth, they are able to express some of the features of mature intestinal cells. In view of these results, HT-29 cells appear to be a useful in vitro model for the study of rotavirus infection.

Genetic diversity and similarity among mammalian rotaviruses in relation to interspecies transmission of rotavirus

To address the question whether there was any molecular evidence for interspecies transmission of rotaviruses from one animal species to another, genetic relationships among human and animal rotaviruses were examined by a series of hybridization experiments in which genomic RNAs from 14 rotavirus strains derived from seven different host species were hybridized with the [32P]-labelled transcription probes prepared from 11 strains representing rotaviruses from those seven host species. In general, higher level of homology among most, if not all, of the cognate gene segments that allowed classification into the same genogroup was shared among rotaviruses recovered from the same animal species but this level of homology was not found among rotavirus strains derived from different host species. However, such a high level of homology that was usually found among rotaviruses recovered from the same animal species was detected between feline rotavirus strain Cat97 and canine rotavirus strain K9 as well as between human rotavirus strain AU-1 and feline rotavirus strain FRV-1. The sharing of closely related genetic constellation of most of the 11 gene segments (genogroup) by rotaviruses recovered from different animal species provided molecular evidence that interspecies transmission of rotaviruses occurred in nature at least recently in the evolutionary history.

Molecular evidence for naturally occurring single VP7 gene substitution reassortant between human rotaviruses belonging to two different genogroups

Twenty four stool rotaviruses that comprised 22 distinct electropherotypes were selected for genome analysis from the collection of diarrheal specimens obtained over an eight-year period. These 22 electropherotypes were found in 46% of the total electropherotypes identified during the previous studies and represented 328 (64%) of rotavirus specimens in the collection. When genomic RNAs from these stool rotaviruses were hybridized to the 32P-labeled transcription probes prepared from prototypes representing three human rotavirus genogroups, Wa, DS-1, and AU-1, any one of the isolates showed a high degree of homology only with one of the three probes, which data confirmed and extended our previous observation on the existence of three distinct genogroups among human rotaviruses. Two stool rotaviruses which had an unusual combination of serotype (G1), subgroup (I) and RNA pattern (an identical short electropherotype), however, yielded the hybridization pattern indicative of an intergenogroupic single VP7 gene substitution reassortant. When they were cell culture adapted and analyzed by RNA-RNA hybridization, molecular evidence was obtained indicating that their VP7 gene derived from viruses belonging to the Wa genogroup whereas the remaining 10 genes hybridized with viruses belonging to the DS-1 genogroup. Interestingly, these natural reassortants emerged in the midst of the rotavirus season in which G1 strains predominated.

Characterization of rotavirus electropherotypes excreted by symptomatic and asymptomatic infants

Human rotavirus isolates from 1100 stool samples were analyzed by polyacrylamide gel electrophoresis, and 48 different migration patterns were detected. Heterogeneity in the migration of segment 10 was observed in both long and short electropherotypes in which three long and two short patterns were identified. In spite of these variations all short and long electropherotypes were subgrouped by enzyme immunoassay as subgroups I and II respectively. Mixed infections were detected in 17% of cases and the subgrouping correlated with the corresponding electropherotypes. The same electropherotypes were present in severe, mild and asymptomatic cases and no electropherotype was particularly associated with greater virulence. Furthermore, the electropherotypes isolated from nosocomial asymptomatic cases were the same as those detected from those admitted with severe diarrhea. It seems unlikely that electropherotyping can be used to identify more virulent strains of rotavirus.

Presence of three P types (VP4 serotypes) and two G types (VP7 serotypes) among bovine rotavirus strains

Cross neutralization tests with a panel of rotavirus strains representing previously described nine VP7 (G) serotypes revealed that bovine rotavirus strain KK-3, a prototype Japanese bovine serotype 2, belonged to a new serotype (G10), confirming and extending the recent report of Snodgrass et al. [J. Clin. Microbiol. 28: 504-507 (1990)] which showed that hyperimmune serum to the KK-3 strain neutralized the B223 strain, a proposed type strain of G10. Further antigenic characteristics of the KK-3 strain, as well as the 0510 strain (a G6 strain isolated in Japan), were examined in terms of their VP4 (P) specificity. For the characterization of P types, we employed genetic reassortants that possess VP4 gene for UK and VP7 gene for D (G1), VP4 gene for NCDV and VP7 gene for SA11 (G3), or VP4 gene for SA11 and VP7 gene for NCDV (G6) in the plaque reduction neutralization assay with hyperimmune sera against these two Japanese strains and the prototype bovine rotavirus NCDV strain. While the 0510 strain had UK-like P and NCDV-like G types, the KK-3 strain had a distinct set of P and G types. Thus, at least three P types (NCDV-, UK-, and KK-3-like) and two G types (G6 and G10) are present among bovine rotavirus strains.

Gastroenteritis in suckling mice caused by human rotavirus can be prevented with egg yolk immunoglobulin (IgY) and treated with a protein-bound polysaccharide preparation (PSK)

Oral inoculation of human rotavirus MO strain (serotype 3) into 5-day-old BALB/c mice cause gastroenteritis characterized by diarrhea. Clinical symptoms, histopathological changes in the small intestine, and the detection of rotavirus antigen in enterocytes were all characteristic of rotavirus-induced gastroenteritis. Using this small animal model, passive protection of suckling mice against human rotavirus infection was achieved with the use of immunoglobulin (IgY) from the yolks of eggs of rotavirus-immunized hens. When IgY against a rotavirus strain homotypic to the challenge virus (MO strain) was administered in the mice, complete protection against rotavirus infection was achieved. On the other hand, with oral administration of IgY against a heterotypic strain (serotype 1, Wa strain), a lower protective effect was nevertheless obtained. The four different strains of human rotavirus (Wa, KUN, MO, and ST3) were inactivated in vitro by treatment with PSK, a protein-bound polysaccharide preparation, in a dose-dependent manner. Oral administration of 2.5 mg of PSK caused a therapeutic effect on experimentally MO-infected suckling mice. The antiviral effect of PSK was indicated by the reduction of the duration of diarrhea.

Molecular identification by RNA-RNA hybridization of a human rotavirus that is closely related to rotaviruses of feline and canine origin

With a few exceptions subgroup I group A human rotavirus strains have short RNA patterns, whereas most animal rotavirus strains belong to subgroup I and have long RNA patterns. Thus, new isolates of subgroup I human rotaviruses with long RNA patterns are considered to have a high likelihood of being animal rotaviruses. A group of human rotaviruses represented by the AU-1 strain has recently been shown to be genetically related to a feline rotavirus (FRV-1) isolated in Japan. A human rotavirus, strain Ro1845, which is similar to the AU-1 strain in its subgroup (I), serotype (3), and electropherotype (long), was compared with various human and animal strains by RNA-RNA hybridization to determine its genogroup, a term proposed to classify rotaviruses based on their gene homology. The Ro1845 strain did not show a significant level of homology with AU-1, FRV-1, or other human strains, indicating that the Ro1845 strain is different in its genogroup not only from the AU-1 strain but also from other human strains. However, the Ro1845 strain showed a high degree of homology with another feline rotavirus (Cat97) isolated previously in Australia, suggesting that the Ro1845 strain might originate from a feline rotavirus that is genetically distinct from the Japanese FRV-1 strain. Furthermore, the Ro1845 strain as well as the Cat97 strain were related genetically to the canine rotavirus RS15 strain. Taken together, these results indicate that at least two genogroups are present in feline rotaviruses, one resembling the AU-1 strain and the other resembling the Ro1845 strain as well as canine rotaviruses.

Molecular characterization by RNA-RNA hybridization of a serotype 8 human rotavirus with "super-short" RNA electropherotype

A human rotavirus isolate (the 69M strain) with a "super-short" RNA electropherotype has been classified as serotype 8, a new human serotype [Matsuno et al., 1985]RNA-RNA hybridization using 32P-labeled transcription probes was used to assess the genetic relatedness of the 69M strain to a panel of human and animal rotaviruses. The 69M strain showed a medium level of homology with subgroup 1, serotype 2 human rotaviruses with short RNA electropherotypes. However, the 69M strain was not significantly related to any other human rotavirus strains tested in this study, including recently identified serotype 9 strains (represented by the WI61 strain) and subgroup 1 human rotaviruses with long RNA electropherotypes (represented by the AU-1 strain) that are shown to be genetically distinct from other human rotavirus strains. Unexpectedly, a medium level of homology was also found between the 69M probe and the double-stranded RNAs from bovine rotavirus strains (represented by the NCDV strain).

Isolation and molecular characterization of a serotype 9 human rotavirus strain

A human rotavirus strain, designated AU32, that belongs to serotype 9 was isolated and was compared by RNA-RNA hybridization with recently established two serotype 9 strains (WI61 and F45) as well as other prototype human strains. These three strains exhibited a very high degree of homology with one another and shared a high degree of homology with strains belonging to the Wa genogroup but not with strains belonging to either the DS-1 or AU-1 genogroup. These results suggest that genetic constellation of the serotype 9 strains is similar to that of the commonest human rotavirus despite the recent recognition of this serotype.

Identification of rotaviruses by dot-blot hybridization using an alkaline phosphatase-conjugated synthetic oligonucleotide probe

We have evaluated a recently-developed dot-blot hybridization assay for the detection of human rotaviruses using an alkaline-phosphatase conjugated oligonucleotide probe. The lower detection limit of this assay was 1 ng (approximately 5 x 10(7) copies) of the double-stranded (ds) RNA, when a purified preparation from serotype 1 human rotavirus was used but appeared to be much higher when applied on clinical specimens. This assay could detect dsRNA from rotavirus strains belonging to serotypes 1 through 6, 8 and 9. A total of 235 stool specimens were used to evaluate the oligonucleotide probe assay in comparison with polyacrylamide gel electrophoresis and latex agglutination assay (Rotalex). When polyacrylamide gel electrophoresis was used as a gold standard, sensitivity, specificity and positive and negative predictive values of the probe assay were 84, 100, 100 and 89%, respectively. These values were slightly better than those of Rotalex assay which is commonly used in clinical laboratories in Japan. Although the probe assay requires more hands-on time than the immunoassays, the high specificity of this probe assay recommends it as a confirmatory test in the clinical laboratory setting.

Identification of rotavirus genogroups by RNA-RNA hybridization

The genetic relatedness of various human rotavirus strains was examined by RNA-RNA hybridization in which 32P-labelled single stranded RNAs produced by in vitro transcription from viral RNAs were used as probes. Denatured genomic double stranded RNAs were hybridized to the probes under highly stringent conditions and the resulting hybrids were fractionated by polyacrylamide gel electrophoresis. Based on the hybridization patterns obtained with probes made from prototype strains Wa (subgroup II, long RNA electropherotype), DS-1 (subgroup I, short RNA electropherotype) and AU-1 (subgroup I, long RNA electropherotype), we have observed that human rotaviruses fall into three distinct gene groups which we have termed 'genogroups'. Identification of genogroups among rotavirus isolates will prove to be a valuable asset for the analysis of naturally occurring reassortants, to trace interspecies transmission of animal rotaviruses to man or vice versa and to identify rotaviruses from environmental sources with regard to their original host species. Furthermore, such an approach will contribute to our understanding of the evolution of rotavirus genes.

Efficiency of isolation of human rotavirus in primary African green monkey kidney cells

Out of 212 human rotavirus (HRV) containing fecal specimens, 173 (81.6%) yielded virus on first passage in primary African Green monkey kidney cells (AGMK), while additional 34 specimens, did not yield virus on first passage. However, following blind passages, 18 of the 34 yielded virus in passage levels 2-8, thus raising the overall isolation rate to 90.1%. The isolation rate of HRV strains obtained in embryonic Rhesus monkey kidney cell line (MA-104), was only 41.4%. ELISA tests performed on fluids from infected cell cultures proved to be an efficient tool to measure virus replication. No differences were encountered in the isolation rates between subgroup I and II strains, while viruses lacking the antigenic determinants of both subgroups did not grow at all. However, one of those unusual group A strains was isolated and grew well in AGMK cells. Primary AGMK and MA-104 cells supported the growth of tissue culture adapted virus most efficiently when compared with six human and primate cell types.

Comparison of human, simian, and bovine rotaviruses for requirement of sialic acid in hemagglutination and cell adsorption

Human rotaviruses (Wa, KUN, MO) showed hemagglutination (HA) only with fixed 1-day-old chicken erythrocytes, and their HA activities were completely destroyed by trypsin activation of virions. Simian SA-11 and bovine NCDV had HA activities not only against fixed erythrocytes but also against fresh erythrocytes from various species. Their HA activities against fixed erythrocytes were also inhibited by trypsin activation, but those against fresh erythrocytes were not. Neuraminidase treatment of fixed erythrocytes did not inhibit HA by trypsin-untreated rotaviruses. In contrast, HA of fresh human erythrocytes by SA-11 and NCDV was completely inhibited by neuraminidase treatment of erythrocytes or glycophorin A, the major erythrocyte sialoglycoprotein. Adsorption and infection of SA-11 and NCDV to monkey kidney MA104 cells were also inhibited by neuraminidase treatment of cells. Adsorption and infection of human rotaviruses were not, however, affected by treatment of cells with neuraminidase from Vibrio cholerae or Arthrobacter ureafaciens or with potassium periodate. Therefore, HA of fixed chicken erythrocytes by trypsin-untreated human and animal rotaviruses may be independent of sialic acids, whereas that of fresh erythrocytes by SA-11 and NCDV is sialic acid dependent and probably mediated by glycophorin A. Sialic acids also constitute an essential part of the cellular receptors for SA-11 and NCDV, whereas those for human rotaviruses were quite resistant to treatments known to destroy major types of sialic acids.

Use of alkaline northern blot hybridization for the identification of genetic relatedness of the fourth gene of rotaviruses

A recently developed alkaline northern blot hybridization assay (Li, J. K. K., Parker, B. & Kowalik, T., Analytical Biochemistry 163, 210-18, 1987) was used to assess the genetic relatedness of the fourth gene of human rotavirus strains recovered from children with diarrhea and from asymptomatic neonates. Genomic double stranded (ds) RNAs of the rotavirus strains were separated by polyacrylamide gel electrophoresis and were blotted to nylon membranes (Gene Screen Plus or Zeta Probe membranes). The blotted RNAs were then probed with 32P-labelled single-stranded (ss) RNA probes prepared by in vitro transcription from single-shelled particles of the different strains. When analysed under a condition of high stringency (52 degrees C, 2.5 x SSC, 50% formamide) that allowed up to 21% of nucleotide mismatch, a high degree of the fourth gene homology was observed among strains recovered from asymptomatic neonates (asymptomatic rotaviruses) or among strains recovered from infants and children with diarrhea (symptomatic rotaviruses), while the homology of the fourth gene between the asymptomatic and symptomatic strains was considerably lower. It is of particular interest that the fourth gene of the AU-1 and AU228 strains recovered from children with diarrhea failed to hybridize to the corresponding gene of either asymptomatic or symptomatic rotavirus strains but showed a high degree of homology with the fourth gene of a feline rotavirus recovered from an apparently healthy cat. These data indicate that a new group of the fourth gene is present among symptomatic rotaviruses and that the fourth gene of this group is genetically related to the corresponding gene of a feline rotavirus.