Shift in the prevalent human rotavirus detected by ribonucleic acid segment differences

Development of rotavirus molecular epidemiology: electropherotyping

Early in the era of rotavirology it was realized that the characteristic patterns of bands produced in polyacrylamide gels following electrophoresis of genomic dsRNA were useful for checking the identity of rotavirus isolates. However it was Romilio Espejo who first proposed the use of this technique for epidemiology, although most others did not take the suggestion seriously because the technique was then rather specialized and RNA staining methods were not very sensitive. Using samples collected by Ruth Bishop in Melbourne following the original identification of human rotaviruses, Sue Rodger recorded the "electropherotypes" of all samples available to 1979 and painstakingly compared them, side by side (since minor variations in conditions, especially temperature, alter the relative migration distances of dsRNA bands). These efforts produced the first longitudinal, extensive study of human rotavirus strain variation. Since then, technical improvements have greatly increased the sensitivity of the procedures, and electropherotyping has been recognized as a powerful and economical method for epidemiological studies of rotaviruses.

Human rotavirus genomic RNA electropherotypes in Jeddah, Saudi Arabia from 1988 to 1992

Polyacrylamide gel electrophoresis was used to analyze the double-stranded RNA of rotavirus recovered from stool specimens collected between March 1988 and December 1992 from children with acute diarrhoea admitted to the central hospital in Jeddah, Saudi Arabia. Rotavirus was detected by ELISA in 523 specimens of the 1242 collected during the study, giving an overall prevalence of 42.2% for the 5 years of investigation. Out of 523 rotavirus-positive specimens, 263 (50.3%) were successfully electropherotyped. Eighteen different electropherotypes were observed, 12 long patterns and six short patterns. Eighty-seven per cent of the electropherotypes were of the long RNA pattern. The remaining were short electropherotypes. The predominant electropherotypes were two long patterns and maintained dominance over 5 years of the study. The third most predominant pattern was a short electropherotype. The remaining electropherotypes made minor contributions every year. These predominant electropherotypes were different from the predominant patterns detected in many countries. Temporal distribution was observed for 5 successive years for the predominant electropherotypes, with an increase in the incidence during the cooler months of the year.

Molecular epidemiology of rotaviruses associated with pediatric diarrhea in Bangkok, Thailand

Rotavirus diarrhea in 453 pediatric patients (29.8% of 1,518) was studied in greater Bangkok during 1985 to 1987. The disease persisted all year, increasing in incidence from August to January (30 to 50%). Polyacrylamide gel electrophoresis of rotavirus RNA from these patients and from an additional 46 patients of a 1982 to 1983 epidemic revealed 26 electropherotypes, 4 with short (S) and 22 with long (L) RNA profiles. Of the analyzed specimens, 85.5% were L forms. Only one or a few electropherotypes predominated in each epidemic, whereas others appeared sporadically at low frequencies. Shifts in the predominant electropherotypes were observed in every epidemic. Of these, 126 strains were tested for subgroup and serotype by monoclonal antibody enzyme immunoassay. Serotype 4 prevailed from 1982 to 1983, while serotype 1 was encountered more frequently than serotypes 2 and 4 from 1985 to 1987. A complete correlation was found between the electrophoretic migration of segments 10 and 11 and the serologically defined subgroup specificity. Distinct electropherotypes occurred within the same serotype, and strains with the identical electropherotype always showed the same serotype specificity. No specific electropherotype or serotype correlated with patient age. In this study, atypical rotaviruses and mixed infections with different rotaviruses were identified.

Diversity of rotavirus serotypes in Mexican infants with gastroenteritis

One hundred thirty-two stool specimens from infants with rotavirus gastroenteritis hospitalized in two Mexican cities (Mexico City and Mérida) were examined by serotype- and subgroup-specific enzyme immunoassays. Among them, 38 (29%) were serotype 1, 15 (11%) were serotype 2, 13 (10%) were serotype 3, 22 (17%) were serotype 4, none was serotype 5 or 6, and 44 (33%) could not be serotyped. By subgrouping, 121 specimens were characterized as follows: 24 (18%) were subgroup 1, 97 (74%) were subgroup 2, and none had both subgroup specificities. While serotype 1 rotavirus predominated in the Mexico City area for 4 consecutive years (1984 to 1987), serotype 4 predominated in Mérida during the single epidemic season studied (1985). These data demonstrate that all four primary human rotavirus serotypes circulated in Mexico, with serotype 1 being the most prevalent. The seroneutralization responses of 14 of the 22 patients infected with serotype 4 strains had been previously studied. Of these 14 infants, 11 appeared to have primary infections, as indicated by absence of neutralizing antibodies in the acute-phase sera and their young age (8 months on average) at the time of illness. Seven patients seroresponded to serotypes 1 and 4; two seroresponded to serotypes 1, 3, and 4; three seroresponded to serotype 1; and two had low-level seroresponses to serotype 3 or 4. These data indicate that heterotypic neutralizing antibody responses occur frequently following infection with serotype 4 rotaviruses.

Naturally occurring serotype 2/subgroup II rotavirus reassortants in northern Brazil

Nine serotype 2 human rotavirus strains were isolated in a community-based longitudinal study in Northern Brazil. Five of these strains had a 'long' RNA electrophoretic pattern and all five strains were determined to belong to subgroup II by ELISA assay, in contrast to properties common to serotype 2 human rotaviruses previously characterized. Hybridization studies of one of these unusual strains with 32P-labelled mRNAs derived from the prototype human strains Wa (serotype 1, subgroup II) and S2 (serotype 2, subgroup I) suggested that it was generated by a reassortment event in nature, in which a subgroup II, 'long' electropherotype rotavirus exchanged its serotype-specific gene and gene number 10 for the equivalent genes from a serotype 2, 'short' electropherotype virus.

Detailed structural analysis of a genome rearrangement in bovine rotavirus

A genome rearrangement involving RNA segment 11 of a bovine rotavirus has been analysed by molecular cloning and sequencing. This revealed that the rearranged genome segment was generated by a head to tail concatemerisation of two almost full length copies of segment 11. The upstream copy of the gene has lost its 3' end and the downstream copy its 5' end. The truncation of the upstream copy of the gene occurs within the termination codon for VP11 converting it from a UAG to a UGA, the rearranged gene is therefore still able to encode a normal VP11. The possible mechanisms by which this rearrangement may have been generated are discussed.

Sequences of VP9 genes from short and supershort rotavirus strains

Segment 10 genes from a short (RV-5, serotype G2) and a supershort (B37, a new G serotype) strain were cloned and their sequences compared to the (corresponding) segment 11 sequences of Wa, SA11, and UK rotaviruses. The determined nucleotide sequences were 817 (RV-5) and 947 (B37) bases in length and showed extensively conserved 5' noncoding and protein coding regions. The major open reading frame codes for a protein of 200 (RV-5) or 198 (B37) amino acids, and the newly proposed second open reading frame can code for a protein of 92 amino acids. Compared to long strain gene segments, the base sequences of the short and supershort strains were found to contain extended, AT-rich 3' noncoding regions which were not significantly homologous to each other, to other parts of the VP9 gene, or to other rotavirus genes that have been sequenced. The function(s) of these 3' regions is not apparent.

Four-year study of rotavirus electropherotypes from cases of infantile diarrhea in Rome

Rotavirus infections were detected in 210 of 675 children with acute diarrhea admitted to a major pediatric hospital in Rome from January 1982 through December 1985. Most of the patients with rotavirus infections were admitted during the winter season in both 1982 and 1985, whereas during the two intermediate years, cases occurred in all months. Among 84 rotavirus samples examined, 14 different electropherotypes were recognized, 2 of which largely predominated over the others. The two electropherotypes were particularly frequent in the 2 epidemic years, altogether accounting for 70.2% of the samples typed, and circulated in distinct periods. None of the viruses showed a short pattern of electrophoretic migration of the genome, indicating a minor involvement of subgroup I rotaviruses in hospitalization-requiring diarrheas occurring in the area surveyed.

Evidence of duplication and deletion in super short segment 11 of rabbit rotavirus Alabama strain

The complete nucleotide sequence of genome segment 11, of the Alabama strain of rabbit rotavirus, was determined by sequencing dsRNA and mRNA using the dideoxy chain termination method. This strain has a "super short" RNA pattern. Its segment 11 is 1036 bp in length, 369 nucleotides longer than that reported for rotavirus strains with a "long" electropherotype. Sequence analysis indicated that the shift in genome segment 11 of Alabama strain to a "super short" RNA pattern results from a simple duplication followed by a simple deletion. The positive strand of segment 11 contains two non-overlapping open reading frames of 594 bases (198 amino acids) starting at base 22 and a second of 273 bases (91 amino acids) starting at base 712. The polypeptide from the latter reading frame is the result of a partial duplication of the nucleotide sequence encoding amino acids 110 to 198 of gene 11.

Temporal variation of Malaysian rotavirus electropherotypes

An analysis of rotavirus electropherotypes circulating in Kuala Lumpur, Malaysia, over 7 years showed that all except 1 of the 360 electropherotypes encountered were characteristic of group A rotaviruses. The long electropherotype predominated annually, and there was a rarity of short electropherotypes. Extensive genome variability and cocirculation of different electropherotypes were observed annually. A sequential appearance of the predominant electropherotype was observed in all years of the study, except for 1985 and 1988, when one electropherotype predominated throughout the study periods. There was no shift in the predominant electropherotype over a 6-year period.

Human viral gastroenteritis

During the last 15 years, several different groups of fastidious viruses that are responsible for a large proportion of acute viral gastroenteritis cases have been discovered by the electron microscopic examination of stool specimens. This disease is one of the most prevalent and serious clinical syndromes seen around the world, especially in children. Rotaviruses, in the family Reoviridae, and fastidious fecal adenoviruses account for much of the viral gastroenteritis in infants and young children, whereas the small caliciviruses and unclassified astroviruses, and possibly enteric coronaviruses, are responsible for significantly fewer cases overall. In addition to electron microscopy, enzyme immunoassays and other rapid antigen detection systems have been developed to detect rotaviruses and fastidious fecal adenoviruses in the stool specimens of both nonhospitalized patients and those hospitalized for dehydration and electrolyte imbalance. Experimental rotavirus vaccines have also been developed, due to the prevalence and seriousness of rotavirus infection. The small, unclassified Norwalk virus and morphologically similar viruses are responsible for large and small outbreaks of acute gastroenteritis in older children, adolescents, and adults. Hospitalization of older patients infected with these viruses is usually not required, and their laboratory diagnoses have been limited primarily to research laboratories.

Molecular characterization of three rabbit rotavirus strains

We report biochemical (RNA and protein patterns and gene-coding assignments) and serologic (serotype and subgroup) properties of three strains of rabbit rotaviruses--Ala C11 and R2. The RNA electropherotypes were a standard "short" pattern for R2, an unusual "short" pattern for Ala, and an unusual "long" pattern for C11. Serologic studies indicated that these viruses were all group A serotype 3 rotaviruses. In addition, the Ala and C11 viruses were found to possess subgroup I specificity, whereas the R2 virus possessed subgroup II specificity. In contrast to their distinctive RNA patterns, the polypeptide patterns of the rabbit viruses were similar to those of SA11. To identify cognate genes and determine gene-coding assignments for the rabbit rotaviruses, cDNA probes of individual SA11 genes were hybridized to rabbit rotaviral genomic RNA segments that had been separated by polyacrylamide gel electrophoresis and transferred to filters (Northern blots). The order of genome segments 7-11 for each of the rabbit rotaviruses was unique and differed from that of SA11 genes. These differences were possibly due to rearrangements of the RNA sequences within these individual genome segments. Sequence analysis of the individual RNA segments will confirm whether genome rearrangements are the molecular basis for these novel migration patterns.

Molecular epidemiology of rotavirus in black infants in South Africa

The molecular epidemiology of rotavirus infections in black infants in Ga-Rankuwa, South Africa, was investigated by polyacrylamide gel electrophoresis. Between 1983 and 1986, 14 different RNA electrophoretic patterns were observed for children with acute gastroenteritis. These electrophoretypes showed a sequential pattern of appearance, with a limited number being present at any one time. In contrast, for neonates only one RNA electrophoretype was detected, which persisted for at least 3 years.

Heterogeneity of genome rearrangements in rotaviruses isolated from a chronically infected immunodeficient child

Rotaviruses with genome rearrangements, isolated from a chronically infected immunodeficient child, were adapted to growth in BSC-1 cells. Preparations of viral RNA from fecal extracts showed a mixed atypical rotavirus RNA profile, which was due to the presence of at least 12 subpopulations of viruses grossly differing in genotype. Besides various forms of genome rearrangements involving segment 8-, 10-, and 11-specific sequences, reassortment in vivo was likely to have occurred during the emergence of these viruses. The protein products of viral genomes with various forms of segmental rearrangements seemed to be largely unaltered. Genome rearrangement is proposed to be a third mechanism directing the evolution of rotaviruses.

Antigenic characterization of rotaviruses isolated in Kenya from 1982 to 1983

The electropherotypes of human rotavirus RNAs from 100 diarrheic stool specimens collected in two major districts of Kenya from 1982 to 1983 were previously reported (Y. Chiba, C. Miyazaki, Y. Makino, L. N. Mutanda, A. Kibue, E. O. Lichenga, and P. M. Tukei, J. Clin. Microbiol. 19:579-582, 1984). Of these specimens, 25 that contained rotaviruses with different RNA electropherotypes were subjected to a virus isolation experiment with MA-104 cells, and 16 rotavirus strains were isolated. The use of an enzyme-linked immunosorbent assay with subgroup-specific monoclonal antibodies enabled us to successfully subgroup 15 isolates: 4 in subgroup I and 11 in subgroup II. By fluorescent-focus-neutralization test with serotype-specific rabbit antisera, 13 isolates could be serotyped: 7 as serotype 1, 4 as serotype 2, and 2 as serotype 3. Of the remaining three isolates, F153, F247, and G402, the former was doubly neutralizable with serotype 1 and serotype 4 antisera and the latter two were neutralizable with serotype 3 and serotype 4 antisera. Detailed analysis with the antisera against F153 and F247 and four serotype-specific, VP7-directed monoclonal antibodies suggested that F153 is a serotypic mosaic strain with serotype 4-specific VP3 and serotype 1-specific VP7 outer capsid proteins and F247 and G402 are possibly antigenic mosaic strains with serotype 3 and serotype 4 antigens. On the basis of the correspondence of the rotavirus isolate serotypes determined in this study to the electropherotypes reported previously, it was inferred that serotype 1 strains were most prevalent in two districts of Kenya from 1982 to 1983, followed by any type of serotypic mosaic strains.

Prevalent patterns of serotype-specific seroconversion in Mexican children infected with rotavirus

The level of neutralizing antibodies to rotaviruses belonging to serotypes 1, 3, and 4 was determined in acute- and convalescent-phase sera from 36 Mexican children with rotaviral diarrhea. Most of the infants who seroconverted fell into one of the following three patterns: single seroconversion to serotype 1; seroconversion to serotypes 1 and 4; or seroconversion to all three serotypes tested. The heterotypic neutralizing antibody responses to rotavirus infections are discussed.

Development of a monoclonal antibody specific for serotype 3 rotavirus strains

Monoclonal antibodies were prepared against serotype 3 simian rotavirus SA11. Antigenic analysis of 18 hybridoma cell lines secreting monoclonal antibodies by radioimmunoprecipitation and Western blot revealed that seven monoclonals were directed against the major inner capsid protein VP6, four against VP3, an outer capsid protein with hemagglutinating activity, and one against VP7, the main outer capsid protein of the virus. The specificity of six monoclonals could not be determined. One monoclonal (1P14E2) directed against VP3 showed serotype 3-specific neutralizing activity. This monoclonal, which recognized only serotype 3 viruses in an enzyme-linked immunosorbent assay, could be useful in assays for serotyping rotavirus directly in stool samples.

Electropherotype heterogeneity within serotypes of human rotavirus strains circulating in Italy. Brief report

Using solid-phase immune electron microscopy, 126 of 129 human rotavirus (HRV) strains could be serotyped directly in stools collected in Italy during the period 1981-1985. Prevalence was 70.5 per cent for serotype 1, and 13.2 per cent for each of serotypes 2 and 4. No serotype 3 strain was detected. In parallel, for 39 of 61 HRV strains tested the electropherotype of genomic RNA was successfully determined. Different electropherotypes were detected among strains of the same serotype, whereas the same electropherotype was found in HRV strains of different serotypes. Serotyping and electropherotyping of HRV strains appear to be complementary to each other, and both should be used in conjunction for epidemiological surveys.

Comparison between children treated at home and those requiring hospital admission for rotavirus and other enteric pathogens associated with acute diarrhea in Melbourne, Australia

The etiology of acute diarrhea in children less than 42 months of age attending one pediatric hospital in Melbourne, Australia, was studied during a 7-month period encompassing the winter of 1984. Pathogens identified in 157 children treated as outpatients with mild disease were compared with those in 232 children hospitalized with severe disease. The pathogens (and frequencies among outpatients and inpatients, respectively) detected were rotaviruses (32.5 and 50.9%), enteric adenoviruses (8.9 and 7.4%), Campylobacter jejuni (7.2 and 1.3%), and Salmonella sp. (4.0 and 1.7%). Electropherotypes of rotavirus strains from outpatients and inpatients were compared. Two strains predominated during the 7 months of this study and were observed with equal frequency from outpatients and inpatients. Rotaviruses of the same electropherotype caused a wide spectrum of disease, with symptoms ranging from mild to severe, life-threatening diarrhea. The similarity of etiological agents identified from children with mild and severe forms of acute diarrhea suggests that the etiology of community enteric illness can be reasonably inferred from the etiology of inpatient disease in children in the same geographic area. During the winter epidemic period, the severity of symptoms associated with rotavirus infection in young children is likely to be determined by the inherent susceptibility of the host rather than by genetic differences in the strains of infecting rotaviruses.

Characterization of rotaviruses and subgroup F adenoviruses from acute summer gastroenteritis in South Africa

Six hundred and sixteen specimens were collected from black children hospitalised with acute gastroenteritis during the summer and autumn of 1982-1983 (October to May). Eighty-five children (13.8%) shed rotavirus and at least 40 (6.5%) shed adenovirus (Ad) type 40 or 41 belonging to subgroup F. The highest monthly prevalence of shedding subgroup F adenoviruses (10.1%) coincided with a peak in admissions in midsummer, whereas the highest monthly prevalence of shedding rotaviruses (41.9%) coincided with a peak in admissions in autumn. There were at least five genome types of rotavirus, at least three genome types of Ad40, and at least five genome types of Ad41 circulating in the Johannesburg-Soweto area during the study period. The high rate of rotavirus shedding in autumn could not be attributed to an upsurge in infections by any particular rotavirus strain.

Molecular epidemiology of rotavirus infections in Uppsala, Sweden, 1981: disappearance of a predominant electropherotype

The molecular epidemiology of rotavirus infections was studied in children with acute gastroenteritis in Uppsala, Sweden, during 1981. Altogether 118 virus strains were investigated by analysis of the RNA migration pattern in silver-stained polyacrylamide gels. Six different electropherotypes were seen: two with "short" and four with "long" RNA migration patterns. Forty-two strains (36%) exhibited "short" patterns. The seasonal distribution showed that strains with "long" and "short" RNA patterns cocirculated in equal frequency during the first seven months of the year, until the predominant "short" RNA electropherotype suddenly disappeared. More than 11 RNA segments were seen in two stool specimens. A complete correlation was found between the electrophoretic migration of segments 10 and 11 and the serological defined subgroup specificity.

Genomic variations and antigenic relationships among cytopathic rotavirus strains isolated in Quebec dairy herds

Twelve isolates of bovine rotavirus, originating from eight dairy herds in Quebec known to have frequent epizootics of diarrhea in young calves in the last five years, were successfully propagated in cell cultures. The 12 isolates produced clear-cut plaques in BSC-1 cells and, except for one isolate, agglutinated human group "O" erythrocytes to an higher titer than bovine erythrocytes. Antisera to each isolate were produced in rabbits and used to study their antigenic relationships. All the isolates shared the group-specific immunofluorescent antigen and were antigenically related as demonstrated by the seroneutralization and hemagglutination-inhibition tests. However, the relationships to the Nebraska rotavirus was quite weak in cases of two Quebec isolates. When the genomes of the various isolates were compared by polyacrylamide gel electrophoresis, at least three different reproducible fractionation patterns could be identified.

Detection of rotavirus by a latex agglutination test, Rotalex: comparison with electron microscopy, immunofluorescence, polyacrylamide gel electrophoresis, and enzyme linked immunosorbent assay

A commercially available latex agglutination test, Rotalex (Orion Diagnostics, Finland), for detecting rotaviruses was evaluated in comparison with four other tests (electron microscopy, immunofluorescence, polyacrylamide gel electrophoresis, and enzyme linked immunosorbent assay) routinely used in our laboratories. Although Rotalex was the least complex method, it showed lack of specificity and sensitivity when carried out according to the manufacturer's instructions. Four basic modifications of Rotalex are described. These include the use of Hank's balanced salt solution, increasing the incubation time to 20 min, reading the agglutination result by an experienced observer, and the use of 50 mm square glass plates. The modified procedure gave results which were comparable with those obtained by electron microscopy, immunofluorescence, polyacrylamide gel electrophoresis, and enzyme linked immunosorbent assay. The latter techniques, when used to detect rotavirus, all gave similar results.

Epidemiology of rotavirus electropherotypes determined by a simplified diagnostic technique with RNA analysis

The incidence and RNA electropherotypes of rotavirus in stools or rectal swabs of children with diarrhea were studied for three rotavirus seasons (1981 through 1984) in Philadelphia, Pa. We used a simplified RNA analysis method involving polyacrylamide gel electrophoresis followed by silver staining. Phosphate-buffered saline suspensions of the stools and swab eluates were examined directly by polyacrylamide gel electrophoresis-silver staining analysis and enzyme-linked immunoadsorbent assay (Rotazyme; Abbott Laboratories); electron microscopy was performed on solid stool specimens. The RNA analysis results were compared with electron microscopy and enzyme-linked immunosorbent assay results and exhibited a sensitivity and specificity greater than or equal to that of electron microscopy or the enzyme-linked immunosorbent assay. Ten different electropherotypes were detected among the 68 rotavirus RNA-positive specimens examined over the 3-year study. The predominant electropherotype was different in each season. Our results indicate that the polyacrylamide gel electrophoresis-silver nitrate strain RNA analysis of simple unextracted stool suspensions is a uniquely useful diagnostic technique; it rapidly provides both a definitive positive result and immediate determination of the RNA electropherotype, which is of value for epidemiological study.

Molecular epidemiology of human rotavirus infections

Recognition of rotaviruses as a major aetiological agent of acute gastroenteritis in infants and young children has prompted the investigation of their epidemiology by molecular techniques. Genome analysis by electrophoretic separation of the RNA segments has been widely used to distinguish virus isolates and to monitor patterns of virus transmission. Examination of virus isolates from different epidemics has clearly demonstrated the existance of extensive genomic variation in viruses circulating in large communities; with the co-circulation of a number of viruses of differing electrophoretype. Preliminary studies using the more advanced techniques of oligonucleotide mapping and hybridization analysis have suggested that variation among the viruses may occur by processes involving both "drift" and "shift". Because of their ease and specificity the new hybridization analysis techniques should greatly facilitate both the rapid diagnosis of rotavirus infections, and the solution of many epidemiological and evolutionary questions. Continued and expanded use of molecular techniques for the study of the epidemiology of rotavirus infections will be required to manage future outbreaks and to effect long term control measures.

Detection of human rotavirus by nucleic acid analysis in comparison to enzyme-linked immunoassay and electron microscopy

The results of RNA analysis for the detection of rotavirus were compared with those of a standard enzyme-linked immunosorbent assay (ELISA) and electron microscopy using 212 faecal specimens obtained from 200 children with gastroenteritis. Rotavirus was extracted directly from faecal specimens and RNA segments were made visible by polyacrylamide gel electrophoresis using a silver staining technique. Of the 212 faecal specimens 137 were found to be positive in ELISA, 125 in RNA analysis and 121 in both methods. Forty-nine of the 212 specimens were also investigated by electron microscopy. Thirty-five were positive when examined by electron microscopy, 37 were positive in ELISA and 33 in RNA analysis. RNA analysis of 119 faecal samples in outbreaks and sporadic cases of rotavirus infection yielded 42 different rotavirus electrophoretypes. The results indicated that no one method was sufficient to detect all positive specimens and that RNA analysis is useful in epidemiological studies.

Biochemical techniques for the genetic and phenotypic analysis of viruses: 'molecular epidemiology'

New technologies now enable virologists to study small genetic and antigenic differences between field isolates of animal viruses at a higher level of discrimination than has been possible using conventional serological techniques. The most important of the laboratory techniques revolve around the use of monoclonal antibodies, peptide mapping, fingerprinting of whole RNA virus genomes, RNA:RNA hybridization, ‘electropherotyping’ of virus RNA or polypeptides, restriction enzyme analysis of virus DNA genomes, cloning of genes and rapid sequencing of viral DNAs and RNAs, in the latter case using primer extension techniques (reviewed by Palese & Roizman, 1980). From a practical point of view, genetic and phenotypic heterogeneity among viruses may be of considerable importance in attempts to control certain virus diseases by chemo- or immunoprophylaxis.

Double-stranded RNAs that encode killer toxins in Saccharomyces cerevisiae: unstable size of M double-stranded RNA and inhibition of M2 replication by M1

The sizes of M1 and M2 (but not L) change rapidly with growth, varying by perhaps as much as 33%. Size variation is seen within 76 generations. In addition, the exclusion of M2 by M1 or L-A-E [( EXL]) is mediated by inhibition of replication or segregation, not by enhanced degradation of preexisting molecules.

Double-stranded RNAs that encode killer toxins in Saccharomyces cerevisiae: unstable size of M double-stranded RNA and inhibition of M2 replication by M1

The sizes of M1 and M2 (but not L) change rapidly with growth, varying by perhaps as much as 33%. Size variation is seen within 76 generations. In addition, the exclusion of M2 by M1 or L-A-E [( EXL]) is mediated by inhibition of replication or segregation, not by enhanced degradation of preexisting molecules.

Subgrouping of human rotavirus strains by complement fixation, indirect double-antibody sandwich enzyme-linked immunosorbent assay and solid-phase immune electron microscopy

Complement fixation (CF), indirect double-antibody sandwich (DAS) enzyme-linked immunosorbent assay (ELISA) and solid-phase immune electron microscopy (SPIEM) were compared for their ability to subgroup 73 human rotavirus (HRV) strains from infants and young children with gastroenteritis admitted to one or the other of two different hospitals of Northern Italy. By both indirect DAS ELISA and SPIEM all 73 HRV strains were classified into one or the other of two subgroups. By CF only 67 strains could be subgrouped, as six HRV-positive stools showed anticomplementary activity which could not be eliminated. Indirect DAS ELISA required subgroup-specific, unabsorbed antisera from two different animal species. For SPIEM two antisera from a single animal species were needed, but they had to be absorbed with single-shelled bovine rotavirus for HRV subgrouping to be reliable. Indirect DAS ELISA appeared to be the technique most suitable for extensive application in epidemiological studies of HRV infections by different subgroups. However, SPIEM allowed rapid subgrouping of HRV in stool specimens showing anticomplementary activity in the CF test or non-specific reactions in the ELISA test. In one area of Northern Italy the prevalence of subgroup I HRV infections was 7.8 per cent, while in another it reached 68.1 per cent in the same period.

Shifts in the electrophoretic pattern on the RNA genome of rotaviruses under different electrophoretic conditions

Substantial differences in the RNA electrophoretic patterns of rotaviruses were observed when the conditions for gel electrophoresis were varied. Electropherotypes which seem alike under one set of conditions, may appear significantly different under other conditions such as distinct proportions of acrylamide and bisacrylamide or different running buffer. Different patterns were observed for the same rotavirus RNA sample even when different voltages were applied to otherwise identical runs; these differences were probably caused by the increasing amount of heat generated at higher voltage. Although the conditions of electrophoresis did not have as pronounced an effect on 'double-stranded' as on 'single-stranded' RNA, precautions should be taken to obtain comparable and reproducible results. A standard methodology for 'electropherotyping' of rotaviruses is therefore suggested.

Molecular epidemiology of human rotaviruses. Analysis of outbreaks of acute gastroenteritis in Glasgow and the west of Scotland 1981/82 and 1982/83

The molecular epidemiology of rotavirus infections in Glasgow and the west of Scotland during 1981/82 and 1982/83 was investigated by electron microscopy, ELISA testing and RNA migration pattern analysis. In 1981/82, rotaviruses of both the 'long' and the 'short' electropherotype (in different variants) co-circulated from the onset throughout the winter peak of the outbreak. Approximately 80% of the children were infected during the first year of life. No differences in incidence were found between sexes. In 1982/83 the isolated rotaviruses were almost exclusively of the 'long' electropherotype (in different variants) and 36% of the children were infected beyond the first year of life. Rotaviruses of the 'long' electropherotype serologically were of subgroup II and serotype 1 and those of the 'short' electropherotype of subgroup I and serotype 2.

Serotyping of cell culture-adapted subgroup 2 human rotavirus strains by neutralization

Nine human rotavirus strains from stools of infants with gastroenteritis were serially propagated in MA-104 cell cultures. All strains were identified as subgroup 2 rotaviruses by RNA gel electrophoresis, complement fixation, and enzyme-linked immunosorbent assay. The human rotavirus strains were propagated for 15 to 20 passages and then used for immunization of guinea pigs and rabbits. Animal antisera were also raised against a subgroup 1 human strain purified from stools and against the cell culture-adapted Wa strain, a reference subgroup 2 rotavirus of human origin. Cross-neutralization studies revealed the existence of two distinct serotypes within the cell culture-adapted subgroup 2 human rotaviruses: strains related and unrelated to strain Wa were classified as serotypes 1 and 3, respectively. Results with convalescent-phase sera from infants with primary rotavirus infections confirmed the existence of two serotypes within subgroup 2, and the serotypes responsible for primary subgroup 2 infections could be determined on the basis of the neutralizing reactivity of convalescent sera.

Rapid serotyping of human rotavirus strains by solid-phase immune electron microscopy

Nine cell culture-adapted, as well as 30 clinical, human rotavirus (HRV) strains from fecal extracts of children with primary HRV infection were typed by rapid solid-phase immune electron microscopy with protein A and absorbed DS-1 (HRV serotype 2), Wa (serotype 1), and VA70 (assumed serotype 3) rabbit immune sera. As a reference typing test for cell culture-adapted strains, the neutralization assay was used, whereas for noncultivatable strains typing was done for comparison, indirectly, based upon the differential neutralization reactivity of convalescent-phase serum samples from patients with primary HRV infection versus the three reference HRV serotypes. Typing results by solid-phase immune electron microscopy for all strains examined were in complete agreement with those obtained by the neutralization assay, both on cell culture-adapted strains with the three reference rabbit antisera and on three reference HRV strains with human convalescent-phase serum samples. Since adaptation to growth in cell cultures of clinical HRV strains from stool specimens is a time-consuming procedure and is often unsuccessful, solid-phase immune electron microscopy is preferred over the neutralization assay, giving results in about 16 h and also allowing typing of HRV strains from stool specimens low in virus particles. In addition, HRV strains reacting differently from the three reference serotypes may be easily selected by solid-phase immune electron microscopy for further characterization, as was the case for one strain in this study.

RNA electropherotypes of human rotaviruses from North and South America

Between April 1979 and December 1982, viral agents were found in 231 of 695 children admitted to the Texas Children's Hospital with gastroenteritis. Electron microscopic analysis showed that rotaviruses were the most common viral agents, and a seasonal pattern of rotavirus disease was observed. The migration patterns of the RNA segments of these rotaviruses on electrophoresis in polyacrylamide gels were compared with those of rotaviruses collected from other areas of the United States of America and from Argentina, Colombia and Mexico. A number of different RNA electropherotypes were found, including some patterns not previously reported.

Epidemiology of human rotaviruses as determined by electrophoresis of genome RNA

An epidemiological survey was made of rotavirus infection in a children's hospital by determining changes in rotaviral genome patterns by means of polyacrylamide gel electrophoresis. In 180 fecal samples collected between December 1978 and June 1981, 53 distinct patterns were obtained belonging to 13 different types. Two of these patterns dominated in endemic nosocomial infections of neonates until 1981, when one of them was replaced by a third pattern. Two epidemics of diarrhea in the neonatal wards were associated with an endemic and an exogenic rotavirus strain respectively. The latter was not established as an endemic strain. Three patterns were found exclusively in isolates from infants with nosocomial infection and one pattern was found with a doubled fifth segment, suggesting a double infection. The latter findings support the conjecture that there is reassortment of rotavirus genomic segments in vivo.

Analysis of human rotavirus mixed electropherotypes

Mixed human rotavirus electropherotypes were detected in stool samples from patients with acute gastroenteritis in Santiago, Chile. These electropherotypes accounted for 10% of 149 samples studied. The finding of extra RNA fragments with respect to the regular 11 genome segments suggests the possibility of simultaneous or sequential infection by more than one electropherotype in a single diarrhea event or occurrence of modification in the length of the RNA segments during an infection. These possibilities arose from gel electrophoretic analysis of unique and sequential samples of human rotavirus genome RNA.

Electrophoretic study of the genome of human rotaviruses from Rio de Janeiro, São Paulo and Pará, Brazil

Human rotaviruses from the states of Rio de Janeiro, São Paulo and Pará of Brazil were analysed by RNA electrophoresis. At least some bands characteristic of rotavirus double-stranded RNA were detected in 138 (86.8%) of 159 faecal samples in which the presence of rotavirus had been demonstrated by enzyme immunoassay. Of the RNA-positive samples, 18 (13.0%) were classified as subgroup 1, 94 (68.1%) as subgroup 2, and 26 (18.8%) could not be classified due to absence of visible bands 10 and 11. Subgroup 2 was more frequent in the three states. All strains of subgroup 1 detected in Rio de Janeiro were associated with a single short-lived school outbreak. All strains of subgroup 1 resembled each other in electrophoretic pattern, irrespective of geographical origin, although minor differences could be detected by co-electrophoresis. Subgroup 2, on the other hand, showed a great degree of electrophoretic heterogeneity and could be divided into several sub-categories.

Characterization of rotaviral RNA isolated from children with gastroenteritis in two hospitals in Rotterdam

Rotavirus RNA was extracted from stools collected from children with gastroenteritis in two hospitals in Rotterdam. Electrophoresis of the RNAs showed that at least 19 different electropherotypes were isolated from stools collected in the period from 1977 to 1982. It was possible to identify the index case in some hospital-acquired cases of rotaviral gastroenteritis.

Cocirculation of different rotavirus strains in a local outbreak of infantile gastroenteritis: monitoring by rapid and sensitive nucleic acid analysis

Rotaviruses isolated from 22 patients during a local outbreak of infantile gastroenteritis in October/November 1981 were genotyped by establishing their RNA migration patterns on polyacrylamide gels. A highly sensitive silver staining procedure was used to visualize the RNAs. It was found that strains with at least four different RNA patterns cocirculated and also showed serological differences.

Genetic heterogeneity within individual bovine rotavirus isolates

The genomic RNA patterns of six different bovine rotavirus isolates were analyzed on high-percentage polyacrylamide gels (12.5, 13.6, and 17.5%). In contrast to the RNA patterns exhibited by conventional gel systems, those on the high-percentage gels showed an improvement in segment resolution which consequently aided in the detection of extensive band splitting in these patterns. The ability to clone out various electrophoretically distinct virus subpopulations from each of the six isolates provided an explanation for the band splitting detected by the high-resolution gels. The significance of the coexistence of genetically distinct rotavirus populations within a single host is discussed.

Three human rotavirus serotypes demonstrated by plaque neutralization of isolated strains

Human rotaviruses were isolated directly from stool specimens of gastroenteritis patients in MA-104 cells in the presence of trypsin. For the plaque assay of the isolated strains, the optimal composition of overlay medium was determined. The antigenicity of the isolated strains was investigated by a plaque neutralization method, using antisera prepared against six strains having different electropherotypes of viral RNA, and three different neutralization serotypes were demonstrated.

Epidemiology of rotavirus diarrhea in Yogyakarta, Indonesia, as revealed by electrophoresis of genome RNA

Nine different electropherotypes of rotaviruses occurred among 85 children with rotavirus diarrhea in Yogyakarta, Indonesia. Eighty percent of the electropherotypes had a "long" RNA pattern characteristic of human subgroup 2.