Effect of intragenic rearrangement and changes in the 3' consensus sequence on NSP1 expression and rotavirus replication

The nonpolyadenylated mRNAs of rotavirus are templates for the synthesis of protein and the segmented double-stranded RNA (dsRNA) genome. During serial passage of simian SA11 rotaviruses in cell culture, two variants emerged with gene 5 dsRNAs containing large (1.1 and 0.5 kb) sequence duplications within the open reading frame (ORF) for NSP1. Due to the sequence rearrangements, both variants encoded only C-truncated forms of NSP1. Comparison of these and other variants encoding defective NSP1 with their corresponding wild-type viruses indicated that the inability to encode authentic NSP1 results in a small-plaque phenotype. Thus, although nonessential, NSP1 probably plays an active role in rotavirus replication in cell culture. In determining the sequences of the gene 5 dsRNAs of the SA11 variants and wild-type viruses, it was unexpectedly found that their 3' termini ended with 5'-UGAACC-3' instead of the 3' consensus sequence 5'-UGACC-3', which is present on the mRNAs of nearly all other group A rotaviruses. Cell-free assays indicated that the A insertion into the 3' consensus sequence interfered with its ability to promote dsRNA synthesis and to function as a translation enhancer. The results provide evidence that the 3' consensus sequence of the gene 5 dsRNAs of SA11 rotaviruses has undergone a mutation causing it to operate suboptimally in RNA replication and in the expression of NSP1 during the virus life cycle. Indeed, just as rotavirus variants which encode defective NSP1 appear to have a selective advantage over those encoding wild-type NSP1 in cell culture, it may be that the atypical 3' end of SA11 gene 5 has been selected for because it promotes the expression of lower levels of NSP1 than the 3' consensus sequence.

Molecular characterization of porcine rotaviruses from the southern region of Brazil: characterization of an atypical genotype G[9] strain

The G (VP7) and P (VP4) serotype distribution of Brazilian porcine rotaviruses was determined using reverse transcription-PCR genotyping methods. Common porcine G types G3, G4, and G5 were detected in combination with P types [6] and [7]. The detection of nonporcine G types and unusual G-P combinations and the characterization of an atypical virus indicated that interspecies transmission may contribute to the genetic diversity of porcine rotaviruses.

The stability of porcine rotavirus in feces

Rotaviruses are known as major causal agents of diarrhea in humans and animals. They affect young animals in intensive rearing and cause great economic losses. This study evaluated the infectivity of porcine rotavirus maintained for 32 months at approximately 10 degrees C in the original stool specimens. Thirty stool specimens of 1-4-week-old piglets from breeding farms located in the southwest of the State of Parana were selected for this study. They were randomly chosen from stool samples positive for rotavirus RNA by polyacrylamide gel electrophoresis (PAGE) at the time of collection. The thirty stool samples maintained for 32 months were re-tested by PAGE and 11 out of 30 were still positive showing physical integrity of the eleven segments of viral RNA. In order to demonstrate the maintenance of viral infectivity processed fecal homogenates were inoculated in MA-104 cell cultures. After an average of three blind passages 5 out of 11 samples demonstrated cytopathic effect similar to that of a simian rotavirus (SA-11) used as positive control. To confirm these findings an immunofluorescence test was performed and typical cytoplasmatic granular fluorescence was observed. Electron microscopy of stool samples showed that most of the virus particles were single-shelled and some were found to be in advanced state of degradation. The viral nucleic acid extracted from six fecal specimens out of those that showed physical integrity of rotavirus RNA by PAGE were also amplified when submitted to RT-PCR demonstrating stability of viral RNA. We therefore concluded that porcine rotavirus infectivity is maintained for a long period of time in stool specimens at low temperature.

Detection of porcine rotavirus type G9 and of a mixture of types G1 and G5 associated with Wa-like VP4 specificity: evidence for natural human-porcine genetic reassortment

Rotavirus type G5 is a primarily porcine pathogen that has caused frequent and widespread diarrhea in children in Brazil and in piglets elsewhere. Initial results on the rotavirus types circulating in diarrheic piglets in Brazil disclosed a high diversity of strains with distinct G types including G1, G4, G5, and G9 and the novelty of P[8], the predominant human P specificity type. Those results add strong evidence for the emergence of new strains through natural reassortment between rotaviruses of human and porcine origins.

Identification of two lineages (WA-like and F45-like) within the major rotavirus genotype P[8]

The fourth gene of a porcine (S8) and eight human rotavirus isolates possessing the major human VP4 specificity (P1A serotype and/or P[8] genotype) were partially sequenced and compared to other available P[8] sequences from rotaviruses types G1, G3, G5 and G9 specificities which had been originally recovered from children with diarrhea in Japan, Brazil and the USA. Brazilian rotavirus S8 represented the single known porcine rotavirus with this P specificity. Phylogenetic analysis revealed two lineages or subgenotypes within P[8] strains: the F45-like P subgenotype comprised most of the strains, including all the human G5 isolates analyzed, whereas the Wa- or S8-like subgenotype consisted of only a human isolate obtained in the same geographic region as S8 and an American strain with atypical RNA profile besides the prototypes Wa and S8 viruses. A conserved basic amino acid residue at position 131 in VP4 seemed characteristic of the F45-like P[8] subgenotype.

Relationship among serotype G3P5A rotavirus strains isolated from different host species

The relationship among G3P5A rotavirus strains was analysed by restriction endonuclease assay of the VP4, VP6 and VP7 encoding genes, neutralization assay and phylogenetic analysis. The restriction patterns of the capsid encoding genes were species specific allowing the differentiation among the strains of different origin. The VP7 profiles differentiated human from animal strains more efficiently. The phylogenetic analysis of the VP4 gene demonstrated that HCR3A and K9 are closer related to each other than to other P5A strains. The same occurs to strains Ro1845 and Cat 97. The CU-1 virus appears to be an ancestor of the P5A strains by neutralization and phylogenetic analysis. The results placed the RRV strain definitely in a separate VP4 serotype and genotype from that of P5A strains. Restriction endonuclease assay of the capsid encoding genes seems to be a useful tool to identify the host species of rotavirus strains belonging to the same serotype and/or genotype.

Detection of rotavirus types G8 and G10 among Brazilian children with diarrhea

Characterization of 49 rotavirus-positive stool specimens from children with diarrhea in the state of Rio de Janeiro, Brazil, in 1996 and 1997 revealed a great diversity of rotavirus G types. Conventional types G1 and G3 accounted for 27 and 12% of the infections, respectively, whereas 60% of the infections were caused by unconventional types G5 (25%), G10 (16%), and G8 (4%) and mixed G types (16%).

Hepatitis E virus: complete genome sequence and phylogenetic analysis of a Nepali isolate

The complete nucleotide sequence of the Nepali strain TK15/92 of hepatitis E (HEV) was determined. It showed the highest sequence homology with the Burmese B1 strain, but closer evolutionary relatedness to the Indian strains. Difficulties in reverse-transcribing and amplifying the hypervariable region in ORF1 suggested that strong secondary structures might be intrinsically responsible for the high mutational rate observed in this region of the HEV genome.

Genotyping of hepatitis E virus in clinical specimens by restriction endonuclease analysis

The genomic variability of hepatitis E virus (HEV) was examined by restriction endonuclease analysis (REA) of four genomic cDNA copies comprising a 499 bp segment of the putative polymerase gene, a 264 bp segment of the helicase gene, and two, 680 bp and 448 bp, segments of the capsid gene. Analysis of the deduced restriction sites of all 27 HEV sequences currently available in the GenBank, and digestion of reverse-transcribed and nested PCR amplified segments obtained from six Nepali isolates were used to devise and test a REA genotyping assay. The assay allowed easy discrimination between the Mexico and Asian genotypes, and the classification of the Asian genotypes into three, or perhaps four subgenotypes. In addition, endonucleases identifiers of individual isolate or clusters of isolates were found. This assay permits rapid identification of a large number of HEV isolates directly from clinical specimens for studies on the molecular epidemiology and evolution of HEV.

Identification of hepatitis E virus in clinical specimens: amplification of hydroxyapatite-purified virus RNA and restriction endonuclease analysis

A multi-site nested reverse transcription and polymerase chain reaction (RT-PCR) followed by restriction endonuclease analysis (REA) was developed to identify hepatitis E virus (HEV) in clinical specimens. Four sets of primers were selected to amplify regions in the HEV genome supposed to encode the helicase, polymerase, and parts of the viral capsid protein. Digestion of the nested PCR products with HinfI, HaeII, AvaII, BglI, KpnI, SmaI, or EcoRI generated readily recognizable profiles that confirm the HEV sequences and/or distinguish the unique Mexico genotype (our positive control) from all other isolates (Asian genotype). In addition, the hydroxyapatite (HA) adsorption method was compared to other adsorption and extraction methods widely used to purify viral RNA from clinical specimens for RT-PCR. All methods presented the same sensitivity of recovery of HEV RNA, but only the adsorption methods efficiently removed fecal enzymatic inhibitors. The HA method gave the best results and was the most economic in terms of time, cost, manipulations and reagents. The method was validated by screening a small number of serum and fecal specimens available from patients with acute non-A,B,C hepatitis in Nepal. HEV RNA was identified in half (5/11) of the fecal specimens obtained from patients with evidence of recent HEV infection, but in none of the 14 patients without a serological marker for hepatitis E.

Hepatitis E virus in Nepal: similarities with the Burmese and Indian variants

Hepatitis E has been the predominant type of acute hepatitis in Nepal both in adults and children, in sporadic and epidemic forms. We examined six hepatitis E virus (HEV) isolates obtained during an 8-year period, from 1987 to 1995, in the Kathmandu valley of Nepal. Analysis of portions of the putative helicase, polymerase and capsid genes demonstrated close genetic relatedness among themselves (> 96.4% identity) and with the Burmese (> 95.5%) and Indian (> 95.3%) isolates, and less so with the African (> 94.4%) and the Chinese (> 91%) isolates within the Asian genotype. Phylogenetic analysis placed the Nepali isolates in the Burma-India evolutionary branch and showed that the oldest isolate, TK78/87 was more similar to the Burmese isolates whereas the most recent isolates were closer to the Indian ones. Assuming no frameshifts, the Nepali isolates showed high amino acid conservation, but also unique changes when compared to other HEV isolates. Amino acid residue 614 of the capsid protein was identified as a possible marker to distinguish the Burma-Nepal-India from the China-Central Asian Republics subgenotype, and the Mexico genotype.

A novel human rotavirus serotype with dual G5-G11 specificity

Rotavirus serotype G5 isolates were recently recovered from children with diarrhoea in Brazil. Like most human strains, they exhibited long electropherotypes and subgroup II and Wa-like VP4 specificity. We report the successful propagation and the molecular and antigenic characterization of one of these isolates (IAL-28). Cross-neutralization of IAL-28 and a single gene reassortant, UK x IAL-28, which contains the gene encoding the IAL-28 VP7 in the UK genomic background, with prototype G1 to G14 rotaviruses demonstrated that IAL-28 has antigenic determinants specific for both G5 and G11 serotypes. Sequence analysis of the gene encoding VP7 suggested that one or two amino acid substitutions at positions 96 and 100 on IAL-28 VP7 were possibly responsible for the additional G11 specificity. G5 rotaviruses are found in horses and predominate in piglets, whereas G11 has been identified exclusively as a swine pathogen.

Detection of group C rotavirus in infants with extrahepatic biliary atresia

The purpose of this retrospective study was to examine liver tissue from patients with cholestatic disease for the presence of group C rotavirus RNA. The reverse transcriptase-polymerase chain reaction (PCR) for genes 5 and 6 was used, and the PCR products were subjected to liquid hybridization with a 32P-labeled probe. A second amplification with nested primers was also used. Samples from 32 subjects (20 with biliary atresia or choledochal cyst and 12 controls) were tested. Ten of 20 biliary atresia patients were positive for group C rotavirus RNA; no controls were positive (P < .003). Three of the positive patients were positive for both genes 5 and 6. Six of the 10 had > 1 sample that was positive. These data suggest a possible relationship between group C rotavirus and extrahepatic biliary atresia in the 10 patients in whom virus RNA was detected.

Outbreak of severe gastroenteritis in adults and children associated with type G2 rotavirus. Study Group on Diarrhea of the Instituto Adolfo Lutz

An outbreak of severe gastroenteritis affecting 132 adults and children occurred in the small city of Mirassol, São Paulo, Brazil, in 1992. The outbreak of diarrhoeal disease had an abrupt onset and afflicted all age segments of the population. Group A rotavirus was the only pathogen associated with the epidemic. It was detected in 12 of the 27 (44%) stool specimens analyzed and was identified as serotype G2 rotavirus. Severe dehydration was common among adults and older children, and 35% of all the notified cases were hospitalized for parenteral rehydration. Contamination of the main water supply was the most likely source.

Evaluation of the protective efficacy of a serotype 1 bovine-human rotavirus reassortant vaccine in infants

The objective of this study was to evaluate the efficacy of a live, attenuated bovine (strain WC3) x human (strain WI79, serotype G1) rotavirus reassortant (WI79-9) virus vaccine for prevention of symptomatic rotavirus gastroenteritis in infants. The study was a prospective, randomized, double-blind, placebo-controlled trial, conducted over a single rotavirus season in 325 infants who were 2 to 8 months old at enrollment. Subjects were randomized to receive either placebo or WI79-9 virus vaccine at 10(7.3) plaque-forming units in three oral doses each separated by 2 months. Subjects were followed for 7 days after each dose for occurrence of adverse events and during the subsequent winter for development of rotavirus gastroenteritis. Administration of WI79-9 virus vaccine was well-tolerated, and the rates of low grade fever after each dose were no higher in vaccine recipients (8 to 21%) than in placebo recipients (14 to 19%). The protective efficacy of the WI79-9 vaccine during a subsequent epidemic of predominantly serotype G1 rotavirus was 87.0% (95% confidence limits, 62.6 to 95.5%) against relatively severe rotavirus gastroenteritis (rotavirus gastroenteritis with a clinical severity score of > 8) and was 64.1% (95% confidence limits 35.9 to 79.9%) against all symptomatic rotavirus episodes. The WI79-9 vaccine was safe and effective in prevention of homotypic human rotavirus infection in infants. Further studies of reassortant vaccines based on the bovine WC3 rotavirus should be performed.

Is rotavirus a population of reassortants?

Rotaviruses appear to exist as heterogeneous populations of reassortants and related variants. This phenomenon is consistent with the quasispecies concept of RNA viruses, and suggests that gene reassortment is a crucial evolutionary mechanism for this segmented virus. It also explains puzzling epidemiological findings and controversial results of vaccine-efficacy studies.

Survey of rotavirus G and P types associated with human gastroenteritis in São Paulo, Brazil, from 1986 to 1992

Rotavirus strains causing gastroenteritis in Brazilian children were characterized by PCR-based typing assays. In addition to strains bearing the major human G and P types, large numbers of strains bearing P3 (M37-like), P6 (HCR3-like), untypeable P and G types, and complex mixtures of P and G types not previously recognized were present in the community.

Identification of Norwalk virus in artificially seeded shellfish and selected foods

A rotavirus dsRNA purification protocol was adapted to extract Norwalk ssRNA from artificially contaminated shellfish, and a sensitive reverse transcription-polymerase chain reaction assay for Norwalk virus was devised to identify an estimated 20-200 genomic copies. The technique includes deproteinization with guanidinium isothiocyanate, adsorption of RNA to hydroxyapatite, and sequential precipitation with cetyltrimethylammonium bromide and ethanol. The protocol allows high recovery of viral RNA free of enzymatic inhibitors from oysters, clams, and a variety of food matrices. Norwalk virus sequences were copied and amplified by using primers selected from the polymerase gene. Digestion of the amplified products with restriction enzymes ensured the specificity of the test. This rapid and sensitive assay may significantly improve the prospect for the routine screening of the uncultivatable Norwalk virus in food stuffs.

Comparative analysis of VP8* sequences from rotaviruses possessing M37-like VP4 recovered from children with and without diarrhoea

Rotavirus strains belonging to G types 1 to 4 and having a P3 genotype (M37-like VP4) were recovered from children with symptomatic and asymptomatic infections. Partial sequences of their VP4 genes were determined in an attempt to characterize these strains further. The genomic regions encoding VP8*, the connecting and putative fusion peptides and three other regions in VP5* were sequenced. The deduced amino acid sequences were compared with rotavirus strains belonging to different P genotypes that had been previously reported. High degrees of identity were found between the VP8* fragment of all human P3 strains (92.7 to 99.7%) suggesting that they belong to the same genotype, regardless of differences in their virulence. Furthermore, based on comparative sequence analysis, we did not identify any amino acid(s) that differ appreciably between symptomatic and asymptomatic strains and could therefore be associated with virulence. The results suggest that the P3 genotype, although frequently associated with asymptomatic infections, may not be the single determining factor in attenuation of symptoms.

Identification of bovine and porcine rotavirus G types by PCR

A new seminested PCR typing assay has been extended to identify the important veterinary rotavirus serotypes G5, G6, G10, and G11, as well as the rare human serotype G8. The specificity of the method was evaluated with 30 standard laboratory strains of the G1 to G6 and G8 to G11 types. Rotavirus strain types G6 and G8, not previously recognized in pigs, were identified in field specimens of porcine origin.

Rotavirus serotype G5 associated with diarrhea in Brazilian children

Rotavirus serotype G5 in fecal specimens of 38 Brazilian children with diarrhea was identified by PCR and enzyme immunoassays. The strains exhibited long RNA electropherotypes and either subgroup II or nonsubgroup I-nonsubgroup II specificities. Serotype G5 has been found in piglets and horses but not yet in humans.

VP4 typing of bovine and porcine group A rotaviruses by PCR

A PCR typing assay was developed to identify rotavirus P types (VP4 specificity) of bovine NCDV, UK, and B223 strains and porcine OSU and Gottfried strains. Thirty-nine human and animal strains representing all known, and some undefined, rotavirus P types were used to develop and evaluate the specificity of the method. No cross-amplification was observed. The PCR results agreed with previous characterizations by monoclonal antibodies, sequence analysis, and hybridization assays, except for the Gottfried strain, which showed a P type distinct from the human asymptomatic strains. Analysis of a small number of field specimens suggested a high level of VP4 polymorphism among porcine strains. The assay should be of value in typing field isolates and tracing interspecies infections.

Improved method for purification of viral RNA from fecal specimens for rotavirus detection

An improved procedure to recover and purify double-stranded RNA (dsRNA) from fecal specimens is described. Guanidine isothiocyanate, hydroxyapatite, and cetyltrimethylammonium bromide were used to extract and purify rotavirus dsRNA from fecal specimens. The method is very efficient and easy to perform, and precludes the use of toxic substances such as phenol, chloroform, and Freon. It yields RNA free of enzymatic inhibitors, permitting its detection by reverse transcription-polymerase chain reaction assays. In addition, it was demonstrated that during initial clarification of the fecal suspension, the pellet must be washed at least twice to avoid massive losses of virus, viral protein, or viral nucleic acid retained in the solid debris.

VP4 genotyping of human rotavirus in the United States

The VP4 (P) and VP7 (G) types of 171 rotavirus isolates obtained from children with diarrhea in the United States were characterized by PCR typing assays. Strains P1G1 predominated (71%); this was followed by strains P1G3 (20%) and P2G2 and P1G4 (2% each). Mixed types were identified in five (3%) specimens. Two (1%) strains bearing the P3 genotype (P3G1 and P3G2) were found in children with severe dehydrating diarrhea, although the P3 genotype has been regarded as a possible marker for virus attenuation.

Amino acid sequence similarity of the VP7 protein of human rotavirus HCR3 to that of canine and feline rotaviruses

The sequence of the VP7 gene of human rotavirus strain HCR3 was determined and its predicted amino acid sequence was compared with that of other rotavirus strains. The VP7 gene is 1062 nucleotides long and contains a single open reading frame of 981 nucleotides capable of encoding a protein of 326 amino acids. The VP7 amino acid sequence similarity of strain HCR3 to those of various human and animal G3 serotypes ranged from 88.7 to 99.4%, and from 60.4 to 88.3% to strains representing each of the other 13 G serotypes. Alignment of four variable regions [VR4, VR5(A), VR7(B) and VR8(C)] of HCR3 with those of G3 strains of different host species showed that HCR3 possesses a sequence almost identical to that of canine rotaviruses and feline rotavirus strain CAT97 in all four regions. A considerable divergence in regions VR4, VR7(B) and VR8(C) was found with strains of human, mouse, monkey, horse and rabbit rotaviruses. This observation together with results of our previous study on VP4 indicated that human rotavirus HCR3 is genetically more closely related to animal rotaviruses than to other human rotaviruses.

Nucleotide sequence of the VP4-encoding gene of an unusual human rotavirus (HCR3)

Human rotavirus strain HCR3 was isolated from the stool of a clinically normal infant and identified as a serotype G3 rotavirus; however, it could not be grouped into any known human VP4 genetic groups by a polymerase chain reaction assay. The fourth gene of strain HCR3, which encodes the outer capsid protein VP4, was sequenced. This gene is 2362 nucleotides in length and contains one open reading frame capable of encoding a protein of 776 amino acids. The VP4 protein of strain HCR3 shared 67.5-73.5% amino acid identity with those of strains KU, RV-5, 1076, and K8, representing four human genetic groups, and relatively high homology (84.7%) with a fifth genetic group represented by strain 69M, whose VP4 shows more similarity to animal than to human strains. Strain HCR3 shared higher VP4 amino acid homology with various animal rotaviruses, ranging from 74.5 to 89.4%. These observations suggest that the VP4 outer capsid protein of strain HCR3 represents a new VP4 genetic group that is more closely related to animal rotaviruses than to human rotaviruses.

Rotavirus-specific humoral and cellular immune response after primary, symptomatic infection

The humoral and cellular immune response after symptomatic, primary rotavirus infection was examined in 8 children < 2 years old. Rotavirus-specific IgA, rotavirus-specific helper T (Th) cells, and neutralizing antibody responses were evaluated at the time of illness, 2-8 weeks later, and 3-5 months later. In addition, rotavirus strains associated with infection were tested by polymerase chain reaction analysis using oligonucleotide primers specific for genes 4 (P type) and 9 (G type). The absence of rotavirus-specific IgA or rotavirus-specific helper T cell activity at the time of illness was consistent with a primary infection in 7 of 8 children. Two children were infected with serotype 1 (P type 1, G type 1), 3 with serotype 3 (P type 1, G type 3), and 3 with serotype 4 (P type 1, G type 4) strains. Neutralizing antibodies were directed against the gene 4 (P type) protein product (vp4). Because all infecting strains were P type 1, convalescent antisera did not distinguish among different rotavirus G types. Rotavirus-specific IgA responses were detected in 6 of 8 and rotavirus-specific Th cell responses in 7 of 8 children during convalescence.

Restriction endonuclease analysis of the vp7 genes of human and animal rotaviruses

The vp7 genes of 194 strains of group A rotaviruses representing all known G types were analyzed with three restriction enzymes by direct digestion of amplified cDNA copies or by deduction of the restriction patterns from known sequences. Mammalian rotavirus strains were classified into 28 restriction patterns consisting of combinations of the 6 profiles (s1 to s6) obtained by digestion with Sau96I endonuclease, 9 profiles (h1 to h9) obtained with HaeIII, and 15 profiles (b1 to b15) obtained with BstYI. Digestion with Sau96I and HaeIII identified restriction sites common to all, or almost all, rotavirus strains studied, whereas BstYI was the most discriminating among rotavirus strains. A clear correlation between some restriction patterns or individual profiles and G type and/or host species of origin was found. Several discriminatory restriction sites consisted of type-specific nucleic acid sequences that encoded conserved amino acid residues. Although not directly involved in antigenic diversity, these sites appear to indicate the G type of the isolate. The technique permits rapid comparison of a large number of virus isolates directly from fecal specimens and provides useful markers for investigating the evolution of rotavirus vp7 genes and tracing vaccine virus and interspecies transmission.

Identification of group A rotavirus gene 4 types by polymerase chain reaction

Five genetically distinct human rotavirus (HRV) gene 4 groups have been described on the basis of comparative nucleotide sequencing and the predicted amino acid sequences, and at least four of them represent distinct VP4 antigenic types. To identify each gene 4 type and investigate its distribution in HRV isolates from patients with diarrhea, we developed a polymerase chain reaction (PCR) typing method using sequence information available for four genetically distinct gene 4 types. Rotavirus double-stranded RNAs (dsRNAs) isolated from stool samples were first reverse transcribed and amplified by PCR by using two oligonucleotide primers that correspond to regions that are highly conserved among all known HRV gene 4 types. The 876-bp dsDNA products were then reamplified by PCR in the presence of a cocktail containing one conserved plus-sense primer and four type-specific minus-sense primers (selected from the hypervariable region of gene 4), resulting in products of 345, 483, 267, and 391 bp corresponding to gene 4 types 1, 2, 3, and 4, respectively. This method reliably identified the gene 4 types of 16 well-characterized HRV isolates. Our results were independently confirmed for all 16 strains by reverse transcription and PCR amplification of HRV dsRNA in the presence of alternate type-specific primer pairs. For direct gene 4 typing of HRV in stool samples, we developed a method to extract rotavirus dsRNA from stool specimens by using glass powder. Our results suggest that gene 4 typing will be useful in providing more a complete characterization of HRV strains of epidemiologic or vaccine-related interest.

Distribution of serotypes of human rotavirus in different populations

Serotyping is a useful tool to study the epidemiologic characteristics of rotaviruses in large populations and to assess the need for a vaccine to protect against all strains. By using an enzyme immunoassay with serotype-specific monoclonal antibodies to the four most common rotavirus serotypes, we analyzed 1,183 rotavirus-positive specimens from 16 stool collections in eight countries on four continents that were obtained from 1978 to 1989. Of the 926 strains (78%) that could be serotyped, 48% were serotype 1, 8% were serotype 2, 15% were serotype 3, and 7% were serotype 4. Twenty-two percent had insufficient numbers of double-shelled virus particles to react with the monoclonal antibody of the VP4 rotavirus protein and therefore could not be serotyped. Our results indicate that vaccines being developed must provide the greatest coverage against serotype 1 and that the serotype distribution cannot be predicted currently by the geographic area or prevalence in the preceding year.

Coding assignments of the genome of adult diarrhea rotavirus

Adult diarrhea rotavirus (ADRV) has caused epidemics of diarrhea in China since 1982 and remains the only group B rotavirus associated with widespread disease in humans. We recently characterized the proteins of ADRV and have now proceeded to identify the gene segments encoding each protein. Viral RNA transcripts were synthesized in vitro with the endogenous viral RNA polymerase and separated by electrophoresis in agarose. The individual transcripts were translated in a cell-free system using nuclease-treated rabbit reticulocyte lysates. The translation products were compared with polypeptides found in purified virus and were characterized by SDS-PAGE, immunoprecipitation, and Western blot analysis using antisera to double- and single-shelled virions, virus cores, and monoclonal antibodies. Furthermore, individual RNA transcripts were hybridized to total dsRNA to determine their genomic origin. Based on this analysis, the core polypeptides VP1, VP2 and VP3 are encoded by segments 1, 2, and 3, respectively. The main polypeptides in the inner capsid, VP6, and the outer capsid, VP4 and VP7, are encoded by segments 6, 4, and 8 respectively. Segments 5, 7, and 9 code for 60, 45, and 30 kDa nonstructural polypeptides. Two other nonstructural polypeptides (24 and 25 kDa) are derived from gene segment 11. Gene segment 10 codes for a 26 kDa polypeptide that is precipitated with serum to ADRV and may be a structural protein VP9. With this exception, gene coding assignments of ADRV are comparable to those of the group A rotaviruses. Our results have clear implications for further work in cloning, sequencing, and expression genes of ADRV and can provide direction towards understanding the origin and the evolution of this virus.

Detection of group B and C rotaviruses by polymerase chain reaction

We adapted the polymerase chain reaction (PCR) to detect the noncultivatable group B and C rotaviruses and introduced a simple and convenient technique to purify viral RNA from stool specimens. Double-stranded RNA present in stool extracts was purified by adsorption to hydroxyapatite and was used as the template for reverse transcription and polymerase amplification. Primer pairs specific for group B (gene 8) and group C (gene 6) rotaviruses were selected to amplify group-characteristic sizes of cDNA copies readily identifiable in ethidium bromide-stained agarose gels. These primer pairs were used separately in individual PCR assays or were pooled with a primer pair specific for group A rotavirus (gene 9) in a combined PCR assay for the simultaneous detection of all three rotavirus groups. The method was very sensitive and was used to identify both human and porcine strains of group B and C rotaviruses in stool specimens. A second PCR amplification with internal group-specific primers served to increase further the sensitivity of the test and to confirm the diagnostic results obtained in the first amplification.

Serotypes and electropherotypes of human rotavirus in the USA: 1987-1989

The epidemiology of rotavirus gastroenteritis was investigated for two consecutive seasons (1987-1988 and 1988-1989) in seven locales in the continental USA. The 281 representative fecal samples obtained from children with diarrhea were electropherotyped and serotyped by an enzyme immunoassay with serotype-specific monoclonal antibodies and a new amplification typing technique (polymerase chain reaction typing). Serotype 1 was predominant in both years, particularly in the North and East; serotype 3 was second in frequency and found most often in the South; serotype 2 was detected only occasionally; serotypes 4, 8, and 9 were never found. Rotavirus strains were grouped into five major electropherotypes, each corresponded to a single serotype, and the relative migration of the gene segments 7-9 could be used to distinguish serotype 1 from serotype 3. The amplification typing technique proved to be of great value in typing the 17% of rotavirus-positive specimens untypable by the serologic technique.

Viral agents of gastroenteritis. Public health importance and outbreak management

Each year, infectious gastroenteritis causes greater than 210,000 children in the United States to be hospitalized and 4-10 million children to die worldwide. Since the mid-1970s, knowledge has increased dramatically concerning the viral agents that are responsible for much of this public health burden. Rotavirus, the most common cause of diarrhea among children, infects virtually every child in the United States by the age of 4 years and causes potentially lethal dehydration in 0.75% of children less than 2 years of age. Other recently identified pathogens include the enteric adenoviruses, calicivirus, astrovirus, and the Norwalk family of agents. Conclusive diagnosis of these viruses requires electron microscopic examination of stool specimens, a laboratory technique that is available only at a few large centers, including CDC. Stool samples from an outbreak that are submitted to CDC for detection of viral pathology should be collected in bulk from 10 ill persons during their first 48 hours of illness, while feces are still liquid, and should be stored at 4 C (not frozen). Acute- and convalescent-phase serum samples should be collected from the same persons, plus from an equal number of controls, during the first week of illness and 3 weeks thereafter. Control measures for outbreaks of viral gastroenteritis should focus on the removal of an ongoing common source of infection (e.g., an ill food handler or the contamination of a water supply) and on the interruption of person-to-person transmission that can perpetuate an outbreak in a population after the common source has been removed. Because improvements in environmental hygiene may not be accompanied by reductions of endemic diarrhea caused by viruses, immunization may play an important role in future control; vaccine trials for rotavirus are in progress. In anticipation of vaccine development and use, CDC recently began national surveillance for the viral agents of gastroenteritis. Health-care facilities involved in the detection of rotavirus or the other viral agents of diarrhea can participate.

Polymerase chain reaction amplification and typing of rotavirus nucleic acid from stool specimens

The rotavirus gene segment coding for the major outer capsid glycoprotein vp7 was amplified directly from stool specimens by the polymerase chain reaction (PCR). Double-stranded RNA extracted from stool samples was used as the template for reverse transcription, which was followed immediately and in the same reaction mix with amplification, using the Taq polymerase. Various conditions were examined to optimize the yield of the amplified gene. The concentrations of MgCl2, dimethyl sulfoxide, and template RNA were critical. The choice of primer pairs allowed amplification of the entire segment or specific portions. By using type-specific primers derived from distinct regions on the gene, we devised a PCR typing method in which each human serotype virus produced a characteristic segment size, readily identifiable in agarose gels. The PCR typing method was applied to 10 rotavirus reference strains, including all 6 known human serotypes (serotypes 1, 2, 3, 4, 8, and 9), and to 34 stool specimens previously serotyped by an enzyme immunoassay with monoclonal antibodies. An absolute correlation was found between the molecular and serologic methods. In addition, 14 stool specimens nonserotypable by an enzyme immunoassay with monoclonal antibodies could be typed by the PCR method. Besides the application for rotavirus detection and typing directly from stools, the PCR method provides a rapid and efficient means of obtaining large quantities of cDNA suitable for sequencing, cloning, and other genetic studies, precluding the need for cell culture and virus purification.

Protective effect of WC3 vaccine against rotavirus diarrhea in infants during a predominantly serotype 1 rotavirus season

We used a double-blind, placebo-controlled trial to study the efficacy of WC3 rotavirus vaccine administered to 104 infants (ages, three to 12 months) before the rotavirus season. Forty-nine infants received vaccine; 55 received placebo. Rotavirus disease during this season was predominantly caused by a serotype 1 strain. In placebo recipients there were 14 cases of rotavirus diarrhea (attack rate, 25%); 11 were moderate to severe (attack rate, 20%). Vaccinees experienced only three cases of rotavirus disease (attack rate, 6.1%), all mild. When all cases (whether associated with rotavirus or not) of clinically significant diarrhea (CSD) were evaluated, WC3 vaccine provided statistically significant (P less than .01) protection against the total number of episodes of CSD and reduced the number of days of CSD-associated diarrhea, vomiting, fever, or illness. Seventy-one percent of the WC3-vaccinated infants had serum antibody responses to the vaccine. The 14 placebo recipients who experienced natural disease predominantly had antibody responses to serotype 1. Sera taken after the rotavirus season revealed a nearly identical rate (40%) of natural rotavirus infection in the vaccinated and placebo groups.

Patterns and etiology of diarrhea in three clinical settings

Acute diarrhea of young children was studied from September 1978 to April 1981 to determine age and time patterns, clinical characteristics and microbial association in two pediatric practices and in a hospital population in southern Michigan. The practice population sizes were estimated so that rates of diarrhea could be determined. Care was sought for about 0.85 episodes per child in the first year of life and 0.4 episodes in the second year of life. Bacterial pathogens were rarely identified in the practices and were identified in only 5% of hospitalized patients. Rotavirus was identified in 16% of the episodes in children under two years of age in the practices. These rotavirus diarrheas occurred mainly in the winter and were clearly more severe than nonrotavirus diarrheas. The rotavirus-infected patients did not, however, have more frequent respiratory symptoms. Respiratory symptom frequency was related to practice setting and income but not etiology. In the fall, before the rotavirus seasonal peak, a peak of nonrotaviral, nonbacterial diarrhea was seen in the practices. The symptoms were mild and a corresponding peak was not seen in hospital patients. The total direct costs of diarrheal illness to society were estimated to be due more to hospitalization than to outpatient care.

In vitro characterization of an avian reovirus vaccine strain

In vitro studies were performed to characterize the vaccine strain, designated P100, derived from the arthrogenic reovirus isolate, S1133, by cold adaptation. P100 appeared to be temperature sensitive, shown by a marked drop in titer and efficiency of plaquing after incubation at 41 degrees. Studies indicated that genomic double-stranded RNA and protein synthesis were severely restricted at the elevated temperature. Differences in the growth behavior of P100 and S1133 at 37 degrees were also noted. The vaccine strain seemed to be more cell associated than S1133. Three outer coat proteins of P100 grown at 37 degrees displayed mobilities different from those of S1133 by PAGE. It is possible that alterations in these proteins may have some relationship to the growth characteristics observed for the P100 strain.

Pathogenicity of avian reoviruses: examination of six isolates and a vaccine strain

Six avian reovirus isolates and a vaccine reovirus strain were compared for invasiveness, virulence, and pathological characteristics upon infection of day-old specific-pathogen-free chicks by the footpad, subcutaneous, and oral routes of inoculation. No significant differences were noted regarding the ability of individual isolates to infect target tissues. However, virulence (measured as the 50% lethal dose) among the isolates varied markedly from 2 x 10(5) to less than 10 PFU per chick for the most virulent isolate; between the parental wild-type virus and the derivative vaccine virus strain, a million-fold (10(6)) difference in virulence was demonstrated. All strains revealed, with considerable variation, arthrogenic potential.

Avian reovirus polypeptides: analysis of intracellular virus-specified products, virions, top component, and cores

Avian reovirus-specified polypeptides can be separated into three size classes: large (lambda), medium (mu), and small (sigma), similar to those of the mammalian reoviruses. A nomenclature has been proposed to indicate the individual polypeptides within each size class by progressive alphabetical subscripts. Three lambda polypeptides (lambda(A), lambda(B), and lambda(C)) are found in infectious viral particles and have molecular weights of 145,000, 130,000, and 115,000, respectively. All are present in core preparations, and two (lambda(A) and lambda(B)) appear to be exposed at the surface of the virion. Two mu polypeptides can be distinguished in purified virus (mu(A), 72,000 daltons; mu(B), 70,000 daltons), and another is occasionally evident by immunoprecipitation from infected-cell extracts (mu(NS)). mu(B) represents the major outer capsid protein and is structurally homologous to mu(1C) of the mammalian reoviruses. No additional mu proteins can be detected, and there is no evidence for a product-precursor relationship among these proteins. Three major sigma proteins are evident in viral particles. sigma(C) has the lowest molecular weight, is part of the outer capsid of the virion, and appears homologous to the mammalian sigma(1) protein. Interestingly, it demonstrates the greatest polymorphism of all the polypeptides among the different avian reoviruses examined. sigma(B) (36,000 daltons) is a major constituent of the outer capsid and, like sigma(C), is exposed to the surface of the virion. sigma(A) (39,000 daltons) appears to be an internal protein. An additional polypeptide band in the sigma class having an apparent molecular weight of 34,000 to 35,000 can be seen under three different conditions: (i) in some S1133 reovirus preparations, particularly after prolonged storage, a new band (sigma(B')) appears with a reduction in intensity of sigma(B), suggesting that sigma(B') is a degradation product of sigma(B); (ii) in polypeptides immunoprecipitated from infected-cell extracts, a major band (sigma(NS)) is apparent migrating just ahead of sigma(B); (iii) in top component preparations from all avian reoviruses examined, a band (sigma(TC)) with mobility identical to that of sigma(NS) represents a major constitutent and appears to be incorporated within the particle itself. The relationship among these three bands is not currently known. Avian reovirus polypeptides are thus in general similar to those found in mammalian reoviruses, but differences do exist which may be important for understanding viral structure and assembly.