New porcine rotavirus serotype antigenically related to human rotavirus serotype 3

Detection and genetic diversity of porcine rotavirus A, B and C in eastern Australian piggeries

Rotaviruses (RV) have a high prevalence in piggeries worldwide and are one of the major pathogens causing severe diarrhoea in young pigs. RV species A, B, and C have been linked to piglet diarrhoea in Australian pig herds, but their genetic diversity has not been studied in detail. Based on sequencing of the structural viral protein 7 (VP7) RVA G genotypes G3, G4 and G5, and RVC types G1, G3, G5, and G6 have been identified in Australian piggeries in previous studies. Although occurrence of RVB was reported in Australia in 1988, no further genetic analysis has been conducted. To improve health management decisions in Australian pig herds, more information on RV prevalence and genetic diversity is needed. Here, 243 enteric samples collected from 20 pig farms within Eastern Australia were analysed for the presence of RV in different age groups using a novel PCR-based multiplex assay (Pork MultiPath™ enteric panel). RVA, RVB, and RVC were detected in 10, 14, and 14 farms, respectively. Further sequencing of VP7 in selected RV-positive samples revealed G genotypes G2, G5, G9 (RVA), G6, G8, G14, G16, G20 (RVB), and G1, G3, G5, G6 (RVC) present. RVA was only detected in young (<10 weeks old) pigs whereas RVB and RVC were also detected in older animals (>11 weeks old). Interestingly, RVB and RVC G-type occurrence differed between age groups. In conclusion, this study provides new insights on the prevalence and diversity of different RV species in pig herds of Eastern Australia whilst demonstrating the ability of the Pork MultiPath™ technology to accurately differentiate between these RV species.

Porcine rotavirus C in pigs with gastroenteritis on Thai swine farms, 2011-2016

Swine are economically important food animals, but highly contagious porcine epidemic diarrhea virus (PEDV) and rotavirus can afflict pig herds and contribute significantly to piglet morbidity and mortality. While there have been studies on rotavirus group A (RVA) in Thailand, reports of rotavirus group C (RVC) are limited. Here, we aimed to identify the prevalence of RVC circulating on Thai commercial swine farms. We analyzed 769 feces and intestine mucosal contents of pigs affected with diarrhea between 2011 and 2016 using RT-PCR specific for the PEDV spike (S), rotavirus glycoprotein (G) VP7, and protease-sensitive protein (P) VP4 genes. We found that 6.6% (51/769) of samples tested positive for RVC, of which 11 samples were co-infected with RVA and four samples were co-infected with PEDV. Three samples tested positive for all three viruses. Phylogenetic analysis of the VP7 gene showed that the most frequent RVC genotype was G1, which grouped with the prototypic RVC Cowden strain. While G6 and G9 were also common, G3 was relatively rare. Analysis of the VP4 gene revealed that the most common P type was P[5], followed by P[4], P[7], and P[1]. In all, there were six G/P combinations (G6P[5], G1P[1], G1P[4], G1P[5], G9P[4], and G9P[7]), of which G6P[5] was the most predominant.

Identification of Equine Lactadherin-derived Peptides That Inhibit Rotavirus Infection via Integrin Receptor Competition

Human rotavirus is the leading cause of severe gastroenteritis in infants and children under the age of 5 years in both developed and developing countries. Human lactadherin, a milk fat globule membrane glycoprotein, inhibits human rotavirus infection in vitro, whereas bovine lactadherin is not active. Moreover, it protects breastfed infants against symptomatic rotavirus infections. To explore the potential antiviral activity of lactadherin sourced by equines, we undertook a proteomic analysis of milk fat globule membrane proteins from donkey milk and elucidated its amino acid sequence. Alignment of the human, bovine, and donkey lactadherin sequences revealed the presence of an Asp-Gly-Glu (DGE) α2β1 integrin-binding motif in the N-terminal domain of donkey sequence only. Because integrin α2β1 plays a critical role during early steps of rotavirus host cell adhesion, we tested a minilibrary of donkey lactadherin-derived peptides containing DGE sequence for anti-rotavirus activity. A 20-amino acid peptide containing both DGE and RGD motifs (named pDGE-RGD) showed the greatest activity, and its mechanism of antiviral action was characterized; pDGE-RGD binds to integrin α2β1 by means of the DGE motif and inhibits rotavirus attachment to the cell surface. These findings suggest the potential anti-rotavirus activity of equine lactadherin and support the feasibility of developing an anti-rotavirus peptide that acts by hindering virus-receptor binding.

Structural basis of rotavirus strain preference toward N-acetyl- or N-glycolylneuraminic acid-containing receptors

The rotavirus spike protein domain VP8* is essential for recognition of cell surface carbohydrate receptors, notably those incorporating N-acylneuraminic acids (members of the sialic acid family). N-Acetylneuraminic acids occur naturally in both animals and humans, whereas N-glycolylneuraminic acids are acquired only through dietary uptake in normal human tissues. The preference of animal rotaviruses for these natural N-acylneuraminic acids has not been comprehensively established, and detailed structural information regarding the interactions of different rotaviruses with N-glycolylneuraminic acids is lacking. In this study, distinct specificities of VP8* for N-acetyl- and N-glycolylneuraminic acids were revealed using biophysical techniques. VP8* protein from the porcine rotavirus CRW-8 and the bovine rotavirus Nebraska calf diarrhea virus (NCDV) showed a preference for N-glycolyl- over N-acetylneuraminic acids, in contrast to results obtained with rhesus rotavirus (RRV). Crystallographic structures of VP8* from CRW-8 and RRV with bound methyl-N-glycolylneuraminide revealed the atomic details of their interactions. We examined the influence of amino acid type at position 157, which is proximal to the ligand's N-acetyl or N-glycolyl moiety and can mutate upon cell culture adaptation. A structure-based hypothesis derived from these results could account for rotavirus discrimination between the N-acylneuraminic acid forms. Infectivity blockade experiments demonstrated that the determined carbohydrate specificities of these VP8* domains directly correlate with those of the corresponding infectious virus. This includes an association between CRW-8 adaption to cell culture, decreased competition by N-glycolylneuraminic acid for CRW-8 infectivity, and a Pro157-to-Ser157 mutation in VP8* that reduces binding affinity for N-glycolylneuraminic acid.

Survey of porcine rotavirus G and P genotype in Poland and the United States using RT-PCR

Porcine rotaviruses are a common cause of gastroenteritis. Several serotypes have been detected based on the two surface proteins VP4 (P-types) and VP7 (G-types). However, limited studies have been performed on the relative frequency of rotavirus types in diarrhetic pigs primarily because of the lack of availability of suitable methods. In this study, we describe a reverse transcriptase-polymerase chain reaction (RT-PCR) method for the typing of P and G types of rotavirus. This method allowed to detect G and P types in 96.8 and 87.1% of isolates collected in the United States, respectively and in 54.5 and 38.6% of isolates collected in Poland, respectively. Within the US specimens the G3, G4, G5, G9 and G10 types were detected in combination with P6 and P7 types while among Polish specimens only G3, G4 and G5 types in combination with P6 and P7 types were identified. In both instances the G4 and G5 were the most prevalent types. These studies show that a RT-PCR typing method is suitable for molecular epidemiological studies and that there is more diversity among porcine rotavirus than previously reported.

Selection of rotavirus VP4 cell receptor binding domains for MA104 cells using a phage display library

Rotavirus infection of host cells, like other viruses, is a complex process that has not been fully elucidated, and much attention has been focused on the regions of the viral attachment protein, VP4, that are involved in binding to the cellular receptor. In this study, phage display technology was employed to generate a g3p VP4 gene-targeted phage display peptide library using the porcine rotavirus strain CRW8, and a method was optimised for panning this library on adherent MA104 cells to identify receptor binding domains. Recombinant phage that displayed expressed peptides from both the rotavirus VP4 trypsin cleavage products VP8* and VP5* were selected, and while some of the phage clones contained insert sequences from regions of VP4 implicated previously in cell binding and infection, new domains were also identified. In all, four regions within VP8* and six regions of VP5* were selected by panning. To our knowledge, this paper is the first description of using a gene-targeted phage display library to identify receptor binding domains on viral proteins.

Rotavirus VP7 epitope mapping using fragments of VP7 displayed on phages

cDNA copies of the complete porcine rotavirus CRW-8 VP7 gene were randomly digested to fragments of about 30-60 or 30-500 base pairs by DNase1 in the presence of Mn(2+). The fragments were cloned and expressed in a filamentous phage fd-tet-derived vector to create specific-gene-related peptide libraries. Polyclonal antibodies were then used to pan the SGRP libraries for antibody-binding phages. Analysis of the phage isolates revealed that the majority (86%) of them only had a single insert. However, phages displaying composite inserts containing the VP7 antigenic regions A, B, and C, originally defined by neutralising monoclonal antibody escape mutants, were also isolated. Inserts containing A or C region peptide were found to contain extra sequences from the C region, while the B region epitope was linear and had additional sequence from either upstream or downstream. In addition a dominant and possibly non-neutralising VP7 epitope was identified around amino acids 263-270. One of the recreated antigenic epitopes has also been fused to the outer membrane protein A (OmpA) of Escherichia coli and shown to maintain its antigenicity. The results in this study may have significant implication for recreation of conformational epitopes and vaccine development.

Bacterial expression of the major antigenic regions of porcine rotavirus VP7 induces a neutralizing immune response in mice

The outer capsid protein of rotavirus, VP7, is a major neutralization antigen. A chimeric protein comprising Escherichia coli (E. coli) outer membrane protein A (OmpA) and part of porcine rotavirus VP7 containing all three antigenic regions (217 amino acids) was expressed in Salmonella and E. coli as an outer-membrane associated protein. Mice immunized intraperitoneally or orally, respectively, with live E. coli or Salmonella cells expressing this chimeric protein produced antibodies against native VP7 as determined by enzyme-linked immunosorbent assays and neutralization tests. This indicates that the VP7 fragment from a porcine rotavirus which is antigenically similar to human rotavirus serotype 3, when expressed in bacteria as a chimeric protein, can form a structure resembling its native form at least in some of the major neutralization domains. These results indicate that the use of a live bacterial vector expressing rotavirus VP7 may represent a strategy for the development of vaccines against rotavirus-induced diarrhoea in infants.

Single point mutations may affect the serotype reactivity of serotype G11 porcine rotavirus strains: a widening spectrum?

A panel of single and double neutralization-resistant escape mutants of serotype G11 porcine rotavirus strains A253 and YM, selected with G11 monotype- and serotype-specific neutralizing monoclonal antibodies (MAbs) to VP7, was tested in neutralization assays with hyperimmune sera raised against rotavirus strains of different serotypes. Escape mutants with an amino acid substitution in antigenic region A (amino acids [aa] 87 to 101) resulting in a residue identical or chemically similar to those present at the same positions in serotype G3 strains, at positions 87 for strain A253 and 96 for strain YM, were significantly more sensitive than the parental strains to neutralization with sera against some serotype G3 strains. Also, one YM antigenic variant (YM-5E6.1) acquired reactivity by enzyme-linked immunosorbent assay with MAbs 159, 57/8, and YO-1E2, which react with G3 strains, but not with the serotype G11 parental strain YM. Cross-adsorption studies suggested that the observed cross-neutralization by the G3-specific sera was due to the sera containing antibodies reactive with the parental strain plus antibodies reactive with the epitope(s) on the antigenic variant that mimick the serotype G3 specific one(s). Moreover, antibodies reactive with antigenic region F (aa 235 to 242) of VP7 might also be involved since cross-reactivity to serotype G3 was decreased in double mutants carrying an additional mutation, which creates a potential glycosylation site at position 238. Thus, single point mutations can affect the serotype reactivity of G11 porcine rotavirus strains with both monoclonal and polyclonal antibodies and may explain the origin of rotavirus strains with dual serotype specificity based on sequence divergence of VP7.

Serological and genomic characterization of porcine rotaviruses in Thailand: detection of a G10 porcine rotavirus

A total of 557 fecal specimens collected from piglets with diarrhea in Thailand were examined for rotavirus RNA by polyacrylamide gel electrophoresis. Twenty-three, one, and two samples were positive for group A, group B, and group C rotaviruses, respectively. Two samples exhibited two segments found in picobirnavirus RNA. RNA electropherotyping of 23 group A rotaviruses showed that they were classified into five patterns. By serotyping by enzyme-linked immunosorbent assay and PCR, viruses in 3 and 14 specimens were found to be serotype G3 and serotype G10, respectively. For one specimen, containing a serotype G10 virus (strain P343), virus was isolated in MA-104 cells, and the nucleotide sequences of the VP7 and VP4 genes were determined. Comparative sequence analysis and cross-neutralization tests showed that strain P343 has B223-like G10 and UK-like P7 serotype (or VP4 genotype 5) specificities. Rotaviruses having such antigenic specificities have not been detected in piglets. Thus, the interspecies transmission of rotaviruses between cows and pigs was suggested.

Cross-reactive, serotype- and monotype-specific neutralization epitopes on VP7 of serotype G3 and G5 porcine rotavirus strains

VP7 specific monoclonal antibodies raised against serotype G5 porcine rotavirus strains isolated in Venezuela showed either a serotype G5- or monotype-specific pattern of reactivity by neutralization against a panel of 53 group A rotavirus isolates representative of all established G serotypes. Monoclonal antibodies raised against two G3 porcine strains were either specific for a subset of porcine G3 strains or reactive with another subset of porcine G3 strains and with most G5 strains. Neither were reactive with G3 strains from other species. Analysis of neutralization resistant mutants selected with these monoclonal antibodies indicated that epitopes defined by cross-reactive, serotype- and monotype-specific monoclonal antibodies overlap functionally and that binding and neutralization by these antibodies depended on specific amino acid residues in the region A or C of VP7. Results indicate that a high degree of monotypic variation occurs among G5 and G3 porcine rotavirus strains and the existence of at least one common epitope shared by G5 and G3 porcine strains, in the major neutralization domain of these VP7s.

Prevalence of neutralizing antibodies to 9 rotavirus strains representing 7 G-serotypes in sheep sera

Neutralizing antibodies to 9 rotavirus strains representing serotypes G1, G3, G5, G6, G8, G9, and G10 were investigated in 212 ovine serum samples from 3 age groups, 1-week-old lambs, 2- to 3-months-old lambs and adult sheep. All sera from 1-week-old lambs had neutralizing antibodies to all 9 rotavirus strains. Both neutralizing antibody titers and prevalences to all 9 strains markedly decreased in the 2- to 3-months-old lamb group and increased again in the adult sheep group. Also, adult sheep sera neutralized a larger number of rotavirus strains than 2- to 3-months-old lamb sera. The highest neutralizing antibody titers and prevalences were found to strains B223 and K923, representing serotype G10, to strain RRV, representing serotype G3, and to strain NCDV, representing serotype G6, indicating that these could be the predominant 3 rotavirus serotypes in Spanish sheep. The rotavirus serotypes infecting sheep observed by us differ from those described for cattle, where G6 is the most prevalent serotype followed by G10, and G3 has been seldom found. Very low prevalences were observed for strains WA and OSU representing serotypes G1 and G5 respectively, suggesting that they probably do not infect sheep and neutralizing antibodies found are derived from heterotypic responses to other serotypes. Intermediate prevalences and titers were found to strains UK (serotype G6), 69M (serotype G8) and WI61 (serotype G9). Neutralizing antibodies distinguished between different strains sharing their VP7 specificity: B223 and K923, a bovine and an ovine serotype G10 strains, and NCDV and UK, two serotype G6 bovine rotavirus strains with different VP4 antigen.

Comparative amino acid sequence analysis of the major outer capsid protein (VP7) of porcine rotaviruses with G3 and G5 serotype specificities isolated in Venezuela and Argentina

Seven porcine group A rotavirus strains isolated in Venezuela were shown to be antigenically related to serotype G3 (five strains) or to serotype G5 (two strains), whereas two strains isolated in Argentina were classified as serotype G5. The serological classification of eight of these strains was confirmed by sequence analysis of the gene encoding the VP7 glycoprotein. A high degree of homology was observed among strains belonging to the same G serotype, although some variations in the serotype-specific regions were detected among different strains. Comparison with the published VP7 amino acid sequences of serotype G3 indicated that most porcine rotavirus strains are more closely related to each other and to human rotavirus strains than to rotavirus strains isolated from other species. Amino acid sequence comparison among serotype G5 porcine strains revealed that Venezuelan porcine isolates were more closely related to the American strain OSU, while the Argentinian strains had a higher similarity to the Australian strain TRF-41. This report confirms the worldwide distribution of these G serotypes among the porcine population.

Subgroup determination of group A rotaviruses recovered from piglets in Nigeria

Subgroup analysis using subgroup-specific monoclonal ELISA revealed a preponderance of subgroup 2-specific antigens of group A porcine rotaviruses over subgroup 1. Of 113 polyacrylamide gel electrophoresis-positive test samples, obtained from 4 States of Nigeria, 31 (27.4%) and 45 (39.8%) were determined to have subgroup 1 and 2 specificities, respectively. However, 37 (32.7%) test samples could not be classified into any of the known group A rotavirus subgroups. These "unclassifiable" samples probably had neither subgroup 1 nor 2 specificities in ELISA or could belong to a third subgroup unknown or not investigated in this study. In all age groups investigated, subgroup 1 and 2 specific antigens were prevalent. This was also observed after yearly analysis of subgroup specificity; however, a higher prevalence of subgroup 2 specificity was observed in 1990 and 1991. Subgroup 1 rotaviruses were found in all the 4 States sampled (Plateau, Benue, Oyo, and Cross River), whereas subgroup 2 rotaviruses were detected only in Plateau State. All rotaviruses recovered in this study had long genome electrophoretic migration patterns, irrespective of subgroup. Thus genomic diversity of group A rotaviruses does not necessarily reflect antigenic diversity, as there is no mandatory correlation between genome electropherotype pattern and subgroup specificity.

Prevalence of P types among porcine rotaviruses using subgenomic VP4 gene probes

Nucleic acid probes were developed to differentiate VP4 (P) types among porcine rotaviruses. These probes were then used to determine the relative prevalence of P types 6 (Gottfried-like) and 7 (OSU-like) in cultivated rotaviruses and field specimens. The variable regions between bases 205-551 of the VP4 gene of rotavirus strains OSU and Gottfried were amplified by the polymerase chain reaction and radiolabeled with 32P by random primer extension. Radiolabeled probes were tested in a dot blot hybridization assay. The subgenomic probes prepared from VP4 gene detected as little as 5 ng oF rotavirus RNA and were specific for differentiating the two porcine rotavirus P types. The probes were used to determine the P type of several reference rotavirus strains and recently cultivated porcine rotavirus strains. Eight of the 10 cultivated, previously untyped, rotaviruses isolates tested were of P type 7 (OSU-like). Two rotavirus strains neither reacted with OSU nor with the Gottfried probe, therefore, their P type could not be determined. Seventeen out of the 26 rotavirus (65.4%) field samples tested had a P type 6 (Gottfried-like) whereas 5 out of 26 (19.2%) had a P type 7 (OSU-like). Four of the 26 samples (15.4%) reacted neither with the OSU nor with the Gottfried probe and possibly represent previously unrecognized P types in swine. Data in this study suggests that (1) rotaviruses with P type 7 are most common among the cultivated rotaviruses, (2) rotaviruses with P type 6 are the most abundant type of rotavirus in natural infections and (3) rotaviruses with additional P types are also associated with diarrheic swine.

Serotypic differentiation of rotaviruses in field samples from diarrheic pigs by using nucleic acid probes specific for porcine VP4 and human and porcine VP7 genes

Of 216 fecal and intestinal samples collected from nursing or weaned diarrheic pigs in the United States and Canada, 57 were identified as group A rotavirus positive by RNA electrophoresis and silver staining. Fifty-seven and 52 rotavirus-positive samples were analyzed by hybridization with Gottfried and OSU PCR-derived gene 9 and 4 probes, respectively. Only 17 samples were identified with either homologous VP4 (P)- or VP7 (G)-coding genes or both. One rotavirus identified as G4 and P7 was similar to the previously characterized interserotype rotavirus, SB-1A. Additional hybridization analyses were performed with PCR-derived probes prepared from gene 9 cDNA of the human rotaviruses Wa (G1), DS-1 (G2), and P (G3) and of the porcine rotavirus YM (G11). Eleven of 52 samples collected and analyzed from swine in Ohio, California, and Nebraska were identified as G11. No samples with G1-, G2-, or G3-type specificities were detected among the 25 of 57 rotavirus-positive samples analyzed with human rotavirus-derived probes. Further investigations with a PCR-derived gene 4 probe prepared from porcine rotavirus YM revealed hybridization specificities similar to those of the OSU gene 4 probe.

Characterization of the neutralizing epitopes of VP7 of the Gottfried strain of porcine rotavirus

The neutralization epitopes of the outer capsid protein VP7 of a porcine group A rotavirus were studied by using neutralizing monoclonal antibodies (N-MAbs). Six N-MAbs which were specific for the VP7 protein of the Gottfried strain of porcine rotavirus (serotype G4) were used for analyzing the antigenic sites of VP7. Three different approaches were used for this analysis: testing the serological reactivity of each N-MAb against different G serotypes of human and animal rotaviruses, analyzing N-MAb-resistant viral antigenic variants, and performing a nucleotide sequence analysis of the VP7 gene of each of the viral antigenic variants generated. From the serological analyses, three different reactivity patterns were recognized by plaque reduction virus neutralization and cell culture immunofluorescence tests. A single MAb (RG36H9) reacted with animal rotavirus serotypes G3 and G4 but not with human serotypes G3 and G4. The MAb 57/8 (D. A. Benfield, E. A. Nelson, and Y. Hoshino, p. 111, in Abstr. VIIth Internat. Congr. Virol., 1987, and E. R. Mackow, R. D. Shaw, S. M. Matsui, P. T. Vo, D. A. Benfield, and H. B. Greenberg, Virology 165:511-517, 1988) reacted with animal and human rotavirus serotypes G3 and G4 and also with human serotype G9 and bovine serotype G6. The other four MAbs reacted only with the porcine rotavirus serotype G4. The epitope defined by MAb 57/8 and the epitope defined by the other five MAbs appeared to be partially overlapping or close to each other, as identified by viral antigenic variant analysis. However, data from nucleotide and deduced amino acid sequence analyses of the VP7 of each of the viral antigenic variants showed that these two epitopes constituted a large, single neutralization domain.

Isolation and characterization of a novel reassortant between avian Ty-1 and simian RRV rotaviruses

A reassortant, TyRh, was isolated after coinfection of MA104 cells with avian Ty-1 and simian RRV rotaviruses. Hybridization and serological studies showed that the reassortant's 4th gene, which encodes Vp4, was derived from the simian RRV rotavirus parent, whereas the remaining 10 genes were derived from the avian Ty-1 rotavirus parent.

Characterization of full-length and polymerase chain reaction-derived partial-length Gottfried and OSU gene 4 probes for serotypic differentiation of porcine rotaviruses

To determine the VP4 (P type) specificity of porcine rotaviruses, full- and partial-length gene 4 probes were produced from cloned Gottfried and OSU porcine rotavirus genomic segment 4 cDNAs. The gene 4 segments from the prototype Gottfried (VP7 serotype 4) and OSU (VP7 serotype 5) porcine rotavirus strains were selected for study because of their distinct P types and the occurrence of rotaviruses with similar serotypes among swine. Partial-length gene 4 cDNAs were produced and amplified by the polymerase chain reaction (PCR) and encompassed portions of the variable region (nucleotides 211 to 612) of VP8 encoded by genomic segment 4. The hybridization stringency conditions necessary for optimal probe specificity and sensitivity were determined by dot or Northern (RNA) blot hybridizations against a diverse group of human and animal rotaviruses of heterologous group A serotypes and against representative group B and C porcine rotaviruses. The PCR-derived gene 4 probes were more specific than the full-length gene 4 probes but demonstrated equivalent sensitivity. The Gottfried PCR-derived probe hybridized with Gottfried, SB2, SB3, and SB5 G serotype 4 porcine rotaviruses. The OSU PCR-derived probe hybridized with OSU, EE, A580, and SB-1A porcine rotaviruses and equine H1 rotavirus. Results of the hybridization reactions of the PCR-derived gene 4 probes with selected porcine rotavirus strains agreed with previous serological or genetic analyses, indicating their suitability as diagnostic reagents.

A variant serotype G3 rotavirus isolated from an unusually severe outbreak of diarrhoea in piglets

About 80% of faecal samples from severe outbreak of porcine diarrhoea (scours) were positive for rotavirus. Rotavirus positive samples were analyzed for their antigenic properties and amino acid sequences of the glycoprotein genes. These viruses could not be assigned to any serotypes using serotyping monoclonal antibodies (MAbs) developed for porcine rotaviruses [Nagesha and Holmes: Journal of Medical Virology 35:206-211, 1991b]. When two such viruses were isolated in cell culture and analyzed by neutralization tests using hyperimmune sera they showed only one way antigenic relation with both human and porcine viruses belonging to serotype G3. In addition none of the serotyping MAbs neutralized these two virus isolates. There was no base variation between VP7 genes of faecal and cell culture isolates. Predicted amino acid sequences of the VP7 gene showed marked epitope variation from other porcine type G3 isolates with amino acid substitutions and an additional glycosylation site at residue 238. This antigenic variation seen in rotaviruses appears similar to that of influenza viruses undergoing antigenic drift.

Isolation and characterization of two distinct human rotavirus strains with G6 specificity

Two new human rotavirus (HRV) strains, PA151 and PA169, with subgroup I specificity and a long RNA pattern, yet with a serotype G (VP7) specificity different from those of any of the six well-established HRV serotypes (G1 to G4, G8, and G9), were isolated 3 months apart from two children with acute gastroenteritis in Sicily, southern Italy, in the winter season of 1987 and 1988. The HRV isolates were adapted to growth in cell cultures and were then characterized by neutralization and RNA-RNA (Northern blot) hybridization. Cross-neutralization studies with type-specific immune sera to RV serotypes 1 to 10 showed the antigenic relatedness of the two strains with serotype 6 bovine strains UK and NCDV. Monoclonal antibodies to VP7 of UK were able to recognize UK and NCDV strains as well as both HRV isolates. Cross-hybridization studies showed a genetic relatedness of PA151 and PA169 to bovine strains for all genes except gene 4. Gene 4 of PA151 appeared to be genetically related to that of AU228 (a human strain of subgroup I and with serotype G3 specificity that belongs to a feline genogroup), whereas gene 4 of PA169 appeared to be unique, yet it was related to gene 4 of two recently reported subgroup I HRV strains, one (PA710) with serotype G3 specificity and the other (HAL1271) with serotype G8 specificity. The new HRV strains must be taken into consideration when deciding strategies for the development of an effective RV vaccine.

Molecular and serological analyses of two bovine rotaviruses (B-11 and B-60) causing calf scours in Australia

Fecal specimens from 78 calves involved in outbreaks of calf diarrhea which occurred in three farms in Victoria, Australia, in 1988 were analyzed for rotaviruses. Thirty-eight samples were positive for group A virus antigen by enzyme-linked immunosorbent assay, and 20 of these contained viral double-stranded RNAs that could be detected by polyacrylamide gel electrophoresis. Two major electropherotypes could be observed, and a representative isolate of each electropherotype (isolates B-11 and B-60) was successfully adapted to grow in MA104 cells. Sequencing of the VP7 genes directly from RNA transcripts of fecal and cell culture-adapted viruses demonstrated that no base changes occurred in this gene upon adaptation to growth in MA104 cells. Sequencing also revealed that the VP7 protein of B-60 was closely related to G serotype 6 (G6) strains, whereas the B-11 sequence was significantly different from all previously published sequences except the recently reported VP7 sequences of bovine isolates 61A and B223, particularly across the antigenic regions A, B, and C. The other strains most closely related to B-11 by VP7 amino acid sequence analysis were G4 porcine strains BMI-1 and BEN-144 and G8 human strain 69M. Serotyping of B-11 and B-60 gave results that were in good agreement with the sequencing data. Hyperimmune typing sera clearly identified B-60 as a member of G6, whereas the B-11 strain reacted to moderate titers only with antisera to some G10 strains. Antiserum raised against B-11 neutralized some strains of G10 cross-reacted with porcine G4 type isolates BMI-1 and BEN-144 but not with other G4 strains or with rotaviruses of other mammalian G serotypes. Northern blot hybridization showed that B-11 was closely related to the recently reported bovine G10 strain B223, and they both possessed a similar segment 4 that was different from that of either UK bovine or NCDV rotavirus.

Relation of VP7 amino acid sequence to monoclonal antibody neutralization of rotavirus and rotavirus monotype

The neutralization epitopes of the VP7 of human rotavirus RV-4 were studied by using five neutralizing mouse monoclonal antibodies to select virus variants resistant to neutralization by each of the antibodies. Antibody resistance patterns and sequence analysis of the RV-4 variants revealed that at least four sites on VP7, located at amino acids 94 (region A), 147 to 148 (region B), 213 (region C), and 291, are involved in neutralization of the human G1 rotavirus RV-4. The A-region site elicited antibody cross-reactive between G types and showed species-restricted immunodominance not related to carbohydrate attachment. The monotype 1b rotavirus M37 lacked this site. The B region contained strain-specific and cross-reactive sites, absent in monotype 1c rotaviruses. The C-region site was present in all G1 rotaviruses tested. Monotype 1a rotaviruses contained all these sites of neutralization. Virus monotype and sensitivity to monoclonal antibody neutralization usually related to the presence of a particular amino acid(s) at or next to the positions at which the mutations were selected in the virus variants.

Direct serotyping of porcine rotaviruses using VP7-specific monoclonal antibodies by an enzyme immunoassay

Employing a serotyping EIA test using MAbs both cell culture adapted and faecal porcine rotaviruses were classified into serotypes G3, G3/5, G4, and G5. The MAbs have confirmed and extended the serotyping results obtained using polyclonal antisera. These MAbs are therefore potential reagents for serotyping of porcine rotaviruses. Using subgroup specific MAbs serotypes G3, G3/5, and G5 were found to contain subgroup I antigens while G4 rotaviruses contained either subgroup II or subgroup I antigens.

Protection of agammaglobulinemic piglets from porcine rotavirus infection by antibody against simian rotavirus SA-11

Rotavirus, a double-stranded RNA virus, has been implicated as a diarrhea-provoking agent in a variety of animal species. Several previous reports have shown that immunization with a single serotype may result in increased in vitro neutralization titers against serotypes not represented in the immunogen. This study was undertaken to determine whether antibody from cows immunized against simian rotavirus strain SA-11 (which is alien to pigs) could protect neonatal piglets from infection with a North Carolina isolate of porcine rotavirus. Accordingly, cows were immunized with SA-11 and an immunoglobulin G (IgG)-rich fraction was isolated from their colostrum. An IgG-rich fraction was similarly isolated from colostrum of nonimmunized cows. At equal concentrations, IgG from SA-11-immunized cows had two- to fourfold higher neutralization titers to seven of eight test strains of rotavirus, including SA-11 (serotype 3); human rotavirus serotypes 1, 3, and 4; North Carolina porcine rotavirus (serotype undetermined); Ohio State porcine rotavirus (serotype 5); and bovine rotavirus (serotype 6). The IgG-rich fractions were fed as dietary supplements to agammaglobulinemic piglets infected with the North Carolina porcine rotavirus. IgG from the SA-11-immunized cows was about eightfold more effective in protecting piglets than was IgG from nonimmunized cows.

VP4 monotype specificities among porcine rotavirus strains of the same VP4 serotype

The porcine rotavirus OSU strain was used to produce monoclonal antibodies (MAbs) directed against the outer capsid protein VP4. From two separate fusions, eight MAbs that inhibited hemagglutination activity of the OSU strain were selected. All MAbs immunoprecipitated both the OSU VP4 protein derived from a lysate of infected MA104 cells and the OSU VP4 protein expressed in Sf9 cells by a recombinant baculovirus. By immunoprecipitation of in vitro-translated OSU gene 4 transcripts of different length, the eight MAbs were found to be specific for the VP8 subunit of VP4. All MAbs neutralized the OSU strain but failed to neutralize human, bovine, and simian rotavirus strains. Antiserum to the expressed OSU VP4 protein was used to study the distribution of VP4 antigenicity among porcine rotaviruses. At least two distinct specificities were identified among 14 rotavirus strains that had been previously assigned to four distinct VP7 serotypes. Five groups of monotype specificities of the VP4 protein were identified by the eight anti-VP4 MAbs among 11 porcine strains that share the same VP4 serotype.

VP4 relationships between porcine and other rotavirus serotypes

VP4 relationship of Australian porcine rotaviruses were identified using genetic reassortants and MAbs. All porcine virus isolates except BEN-144 appeared to share VP4 antigenicity with OSU virus. VP4 and BEN-144 virus (Gottfried-like virus) showed some antigenic relationships with the human neonatal viruses ST-3 and RV-3. In addition, VP4 of porcine CRW-8 showed antigenic relationships with simian SA-11. RRV and also canine K9 viruses, while that of porcine TFR-41 showed at least one way VP4 antigenic relatedness with UK bovine rotavirus. Furthermore, BMI-1 virus which is antigenically similar to an American virus SB1-A (a naturally occurring reassortant) may have arisen similarly by gene reassortment in nature in Australia.

Serotypic differentiation of group A rotaviruses with porcine rotavirus gene 9 probes

The serotypic specificities of Gottfried and OSU porcine rotavirus gene 9 probes were investigated in a dot hybridization assay. The probes were reacted with homologous and heterologous serotypes of group A rotaviruses of human and animal origin. Hybridizations were conducted under relatively low-stringency (52 degrees C, no formamide, 5 x SSC) and high-stringency (52 degrees C, 50% formamide, formamide, 5 x SSC) conditions (1 x SSC is 0.15 M NaCl plus 0.015 M sodium citrate). Under conditions of relatively low stringency, the Gottfried and OSU gene 9 probes demonstrated broad cross-reactivity and were useful in the detection of homologous and heterologous serotypes of group A rotaviruses. Under conditions of relatively high stringency, the Gottfried and OSU gene 9 probes were serotype specific. The Gottfried gene 9 probe (serotype 4) hybridized with homologous Gottfried porcine rotavirus as well as the serotype 4 human rotaviruses ST3 and VA70. The OSU gene 9 probe (serotype 5) hybridized with homologous OSU porcine rotavirus and the serotype 5 equine rotavirus H1. Hybridization was not observed with the antigenically distinct group B and C porcine rotaviruses or with other porcine enteric viruses, including calicivirus and a coronavirus, transmissible gastroenteritis virus, regardless of stringency conditions. Analysis of 14 group A rotavirus-positive field samples resulted in the serotypic differentiation, collectively, of six serotype 4 or 5 porcine rotaviruses. No field samples reacted with both the Gottfried and OSU gene 9 probes.

Some infectious causes of diarrhea in young farm animals

Escherichia coli, rotaviruses, and Cryptosporidium parvum are discussed in this review as they relate to enteric disease in calves, lambs, and pigs. These microorganisms are frequently incriminated as causative agents in diarrheas among neonatal food animals, and in some cases different strains or serotypes of the same organism cause diarrhea in humans. E. coli causes diarrhea by mechanisms that include production of heat-labile or heat-stable enterotoxins and synthesis of potent cytotoxins, and some strains cause diarrhea by yet undetermined mechanisms. Rotaviruses and C. parvum induce various degrees of villous atrophy. Rotaviruses infect and replicate within the cytoplasm of enterocytes, whereas C. parvum resides in an intracellular, extracytoplasmic location. E. coli, rotavirus, and C. parvum infections are of concern to producers, veterinarians, and public health officials. These agents are a major cause of economic loss to the producer because of costs associated with therapy, reduced performance, and high morbidity and mortality rates. Moreover, diarrheic animals may harbor, incubate, and act as a source to healthy animals and humans of some of these agents.

Development of specific nucleic acid probes for the differentiation of porcine rotavirus serotypes

A dot blot hybridization assay is described for the detection and differentiation of porcine rotavirus serotypes. Recombinant complementary DNA (cDNA) representing gene 9 (the gene encoding the neutralization antigens in VP7 glycoprotein) from OSU (porcine rotavirus serotype 1) and Gottfried (porcine rotavirus serotype 2) strains were used to determine the optimal hybridization conditions which allow specific detection of group A porcine rotaviruses. Probes were prepared by excision of the inserts from the recombinant plasmids and radiolabeling of cDNA with 32P by the random primer extension method. Probes were hybridized at various stringencies with viral RNA from different rotavirus serotypes bound to nylon membranes. Hybridization at low stringency (26% base pair mismatch for stable hybrid formation) had high sensitivity but low specificity. Hybridization at high stringency (16% base pair mismatch for stable hybrid formation) produced high specificity but decreased the sensitivity observed at low stringency. Probes were specific for rotavirus at both stringencies and did not hybridize with nucleic acids from other porcine viruses. Subgenomic gene 9 fragments were then tested to provide more specific probes. A 322 bp fragment from OSU gene 9 between nucleotides 382 and 704 and a 266 bp fragment from Gottfried gene 9 between nucleotides 230 and 496 were found to be specific as hybridization probes. These studies demonstrated the feasibility of the dot blot hybridization assay using subgenomic fragments of gene 9 to detect and differentiate serotypes of porcine rotavirus. Additional studies are warranted to further evaluate the sensitivity and the capability of these probes to detect porcine field isolates of the same serotype.

Porcine rotaviruses antigenically related to human rotavirus serotypes 1 and 2

Fecal samples from rotavirus-infected piglets were characterized by a serotyping enzyme-linked immunosorbent assay (ELISA) by using monoclonal antibodies (MAbs) specific to human serotypes 1, 2, 3, and 4 (D. O. Matson, M. K. Estes, J. W. Burns, H. B. Greenberg, K. Taniguchi, and S. Urasawa, submitted for publication). Rotavirus in 19 of 25 specimens tested from two herds of pigs from Buenos Aires province, Argentina, were classified antigenically as follows: one serotype 1, four serotype 2, two serotype 3, and no serotype 4. Six specimens reacted with both serotype 1 and 2 MAbs, and viruses in six specimens probably belonged to other serotypes because they reacted only with a VP7 common epitope MAb. Two porcine rotavirus fecal samples found to contain both serotype 1 and 2 viruses by the MAb-based test and one found to contain a serotype 2 virus were grown in tissue culture. When plaque-purified preparations of these tissue culture-adapted viruses were analyzed in the serotyping ELISA, the C60 and C86 preparations reacted only as serotype 1 viruses, indicating that the original fecal samples, which showed multiple VP7 reactivities, were heterogeneous and apparently contained two types of viruses. Testing of plaque-purified C134 virus confirmed its serotype 2 reactivity. The MAb-based serotype designations of these viruses also were confirmed by using a neutralization immunoperoxidase focus reduction assay. This is the first report of the occurrence of serotype 1 and 2 rotaviruses in animals. The MAbs originally developed to serotype human rotaviruses can be utilized to type animal rotaviruses.

A porcine rotavirus strain with dual VP7 serotype specificity

Porcine rotavirus MDR-13, which on original isolation showed a two-way antigenic relationship with human rotavirus RV-3, shows VP7 relationships with serotype G5 as well as G3 viruses upon gene reassortment. Analysis of porcine MDR-13 and the MD-UK reassortant revealed marked nucleotide and amino acid similarity of VP7 genes of these viruses with those of both serotype G3 and G5 viruses. Evolution of such a strain, possibly by sequential mutations in the VP7 gene, is discussed.

Further antigenic characterization of porcine rotavirus YM

We recently reported that the serotype specificity of YM, a group A porcine rotavirus, is different from those of the previously established rotavirus serotypes, 1 to 6 (A. M. Ruiz, I. V. Lopez, S. Lopez, R. T. Espejo, and C. F. Arias, J. Virol. 62:4331-4336, 1988). Here we demonstrate by cross-neutralization studies that rotavirus YM is also antigenically distinct from prototype rotavirus strains of serotypes 7 (Ty1), 8 (69M), 9 (WI61), and 10 (B223). A comparison of the serotype-determining amino acid regions of the YM surface glycoprotein, VP7, with the reported homologous sequences of rotavirus strains Gottfried, 69M, B37, F45, and WI61 further supported the serotypic individuality of the rotavirus YM VP7 protein.

Rotavirus gene structure and function

Knowledge of the structure and function of the genes and proteins of the rotaviruses has expanded rapidly. Information obtained in the last 5 years has revealed unexpected and unique molecular properties of rotavirus proteins of general interest to virologists, biochemists, and cell biologists. Rotaviruses share some features of replication with reoviruses, yet antigenic and molecular properties of the outer capsid proteins, VP4 (a protein whose cleavage is required for infectivity, possibly by mediating fusion with the cell membrane) and VP7 (a glycoprotein), show more similarities with those of other viruses such as the orthomyxoviruses, paramyxoviruses, and alphaviruses. Rotavirus morphogenesis is a unique process, during which immature subviral particles bud through the membrane of the endoplasmic reticulum (ER). During this process, transiently enveloped particles form, the outer capsid proteins are assembled onto particles, and mature particles accumulate in the lumen of the ER. Two ER-specific viral glycoproteins are involved in virus maturation, and these glycoproteins have been shown to be useful models for studying protein targeting and retention in the ER and for studying mechanisms of virus budding. New ideas and approaches to understanding how each gene functions to replicate and assemble the segmented viral genome have emerged from knowledge of the primary structure of rotavirus genes and their proteins and from knowledge of the properties of domains on individual proteins. Localization of type-specific and cross-reactive neutralizing epitopes on the outer capsid proteins is becoming increasingly useful in dissecting the protective immune response, including evaluation of vaccine trials, with the practical possibility of enhancing the production of new, more effective vaccines. Finally, future analyses with recently characterized immunologic and gene probes and new animal models can be expected to provide a basic understanding of what regulates the primary interactions of these viruses with the gastrointestinal tract and the subsequent responses of infected hosts.

Reactivity of VP4-specific monoclonal antibodies to a serotype 4 porcine rotavirus with distinct serotypes of human (symptomatic and asymptomatic) and animal rotaviruses

Thirteen hybridomas secreting VP4-specific monoclonal antibodies against the Gottfried strain of porcine rotavirus (serotype 4) were produced and characterized. Nine of the hybridomas secreted neutralizing monoclonal antibodies (N-MAbs) against Gottfried rotavirus. These N-MAbs were divided into five distinct groups (groups I to V) according to their patterns of reactivity with different serotypes of human and animal rotaviruses. Group I N-MAbs (n = 3) were cross-reactive with five different serotypes of human rotavirus examined by a plaque reduction virus neutralization test. Group II N-MAbs (n = 3) neutralized all symptomatic human rotavirus serotypes tested and asymptomatic human rotavirus serotype 4 to a low titer. The single group III N-MAb neutralized mainly symptomatic human rotavirus serotypes 2 and 9 and none of the asymptomatic human rotavirus serotypes. The one N-MAb in group IV reacted at low titers with only asymptomatic human rotavirus serotypes 1 through 4. A group V N-MAb recognized serotype 4 porcine rotaviruses (Gottfried and SB-2) but no other human or animal rotaviruses examined. None of the N-MAbs recognized any animal rotaviruses tested (SA-11, RRV, OSU, NCDV, and B223), except for the Gottfried and SB-2 rotaviruses. The failure of N-MAbs (groups I to IV) to react with any animal rotaviruses tested but their ability to react variably with all human rotaviruses tested suggest that neutralizing epitopes on the VP4 protein are highly conserved between the Gottfried porcine and human rotaviruses. The Gottfried rotavirus may possibly represent a naturally occurring reassortant between pig and human rotaviruses or a rotavirus which is human in origin but pathogenic for swine.

Comparative sequence analysis of VP7 genes from five Australian porcine rotaviruses

The genes coding for the rotavirus major neutralizing protein, VP7, from 5 Australian porcine rotaviruses representing glycoprotein (i.e. VP7 or G) serotypes 3, 4, and 5, were sequenced. The genes were each 1,062 nucleotides long with two long open reading frames for proteins of either 326 or 297 amino acids and containing only one potential glycosylation site at amino acid position 69. When compared to the corresponding genes of human viruses, the porcine genes showed very high nucleotide and deduced amino acid homology. Sequence comparison also revealed that Australian porcine rotaviruses of G serotype 4 and 5 were similar to the corresponding porcine strains found in the U.S.A. and U.K., while G serotype 3 and 4 porcine rotaviruses were closely related to human G serotype 3 strain, RV-3 and serotype 4 strain, ST-3, respectively. These Australian rotavirus VP7 sequences were found to correlate with serological data we reported previously.

Subgroup and serotype distributions of human, bovine, and porcine rotavirus in Thailand

The subgroup and serotype specificities of human, bovine, and porcine group A rotaviruses in stool specimens collected in Thailand were examined by an enzyme-linked immunosorbent assay by using subgroup- and serotype-specific monoclonal antibodies. A clear yearly change was observed in the serotype distribution of human rotavirus. Between 1983 and 1984, serotype 4 was the most prevalent, while the highest frequency of serotype 2 was found between 1987 and 1988. All the bovine and porcine rotaviruses examined showed subgroup I specificities and long RNA patterns. It was of note that serotype 3 porcine rotaviruses were found at a high frequency.

Neutralizing monoclonal antibodies against three serotypes of porcine rotavirus

Using three serotypes (four strains) of cultivable porcine rotavirus as immunizing antigens, 10 neutralizing monoclonal antibodies were characterized. One VP4-specific monoclonal antibody directed against porcine rotavirus BEN-144 (serotype G4) neutralized human rotavirus strain ST-3 in addition to the homologous porcine virus. All nine VP7-specific monoclonal antibodies were highly specific for viruses of the same serotype as the immunizing rotavirus strain. One exception was the VP7-specific monoclonal antibody C3/1, which neutralized both serotype G3 and G5 rotaviruses. However, this monoclonal antibody did not neutralize the porcine rotavirus AT/76, also of serotype G3, nor mutants of SA-11 virus (serotype G3) which were selected with monoclonal antibody A10/N3 and are known to have mutations affecting the C antigenic region.

The VP7 gene of a new G serotype of human rotavirus (B37) is similar to G3 proteins in the antigenic c region

The human rotavirus isolate B37 has a characteristic "super-short" RNA electropherotype and has been shown to represent a new VP7 serotype (M. J. Albert, L. E. Unicomb, and R. F. Bishop, 1987, J. Clin. Microbiol. 25, 183-185). The VP7 gene was cloned, and its nucleotide and predicted amino acid sequences were compared to other published VP7 gene sequences. Consistent with the serological evidence, two major antigenic regions of the B37 VP7 (i.e., regions A and B) differ in sequence from those of other G serotypes. Unexpectedly, the C antigenic region shows close similarity to G3 rotaviruses, but we were unable to detect a serological relationship using serotype 3 monoclonal antibodies.

Antigenic characterization of swine rotaviruses in Argentina

Fecal samples from 156 diarrheic piglets were collected from several herds located in two main breeding areas of Argentina. Rotaviruses were detected in 60 samples (38.4%) by polyacrylamide gel electrophoresis and in 55 samples by a group A-specific enzyme-linked immunosorbent assay (ELISA). All samples which were positive by polyacrylamide gel electrophoresis and negative by ELISA had elicited atypical electropherotypes resembling those of group B or C. ELISA-positive samples showing genome rearrangements were also detected (R.C. Bellinzoni, N.M. Mattion, O.R. Burrone, S.A. González, J.L. La Torre, and E.A. Scodeller, J. Clin. Microbiol. 25:952-954, 1987; N.M. Mattion, S.A. González, O.R. Burrone, R.C. Bellinzoni, J.L. La Torre, and E.A. Scodeller, J. Gen. Virol. 69:695-698, 1988). By subgrouping with monoclonal antibodies, it was found that of 32 positive samples, 13 belonged to subgroup I, 2 belonged to subgroup II, 2 samples had both specificities, and 15 samples were neither subgroup I nor subgroup II (non-I/II). In addition, 10 samples were adapted to grow in tissue culture, cloned, and serotyped by means of neutralization assays. Two samples were classified as serotype 5, and none of them were classified as serotype 4. The other strains showed only a one-way relationship with serotype 5 and can be tentatively classified as new porcine serotypes. Two samples with rearranged genomes had a one-way relationship with antiserum to human strain 69M, which displays a supershort electropherotype and was classified as a new human serotype (S. Matsuno, A. Hasegawa, A. Mukoyama, and S. Inouye, J. Virol. 54:623-624, 1985). At one farm, similar rearranged strains were detected during three successive years. Serotype changes were found between the isolates of the first and the second year, suggesting that a high degree of antigenic variability went on during continuous circulation of these strains in the field.

Molecular and antigenic characterization of porcine rotavirus YM, a possible new rotavirus serotype

In 1983, we isolated a porcine rotavirus (strain YM) that was prevalent in several regions of Mexico, as judged by the frequency of its characteristic electropherotype. By a focus reduction neutralization test, rotavirus YM was clearly distinguished from prototype rotavirus strains belonging to serotypes 1 (Wa), 2 (S2), 3 (SA11), 4 (ST3), 5 (OSU), and 6 (NCDV). Minor, one-way cross-neutralization (1 to 5%) was observed when antisera to the various rotavirus strains were incubated with rotavirus YM. In addition, the YM virus was not neutralized by neutralizing monoclonal antibodies with specificity to serotypes 1, 2, 3, and 5. The subgroup of the virus was determined to be I by enzyme-linked immunosorbent assay. To characterize the serotype-specific glycoprotein of the virus at the molecular level, we cloned and sequenced the gene coding for VP7. Comparison of the deduced amino acid sequence with reported homologous sequences from human and animal rotavirus strains belonging to six different serotypes further supported the distinct immunological identity of the YM VP7 protein.

Nucleotide sequence of UK bovine rotavirus segment 4: possible host restriction of VP3 genes

The bovine UK and simian SA11 rotaviruses are commonly used VP7-type reference strains. Since the surface protein VP3 is a significant neutralization antigen, it is important to fully characterize the VP3 types associated with current reference strains. Here we present the complete nucleotide and predicted amino acid sequence of VP3 from UK rotavirus (VP7 type 6) and compare it to the published sequences of SA114fm and RV-5. We also compare the deduced amino acid sequence covering the trypsin cleavage region of UK VP3 to 25 other available sequences. The UK protein is clearly different from that of bovine NCDV (another commonly used VP7 type 6 strain) and represents a second VP3 type associated with bovine rotaviruses. Our SA11 sequence differs from that determined by Lopez et al. [1985, Virology 144, 11-19; later referred to as SA114fM by Lopez et al. (1986, Virology 154, 224-227], their sequence being very similar to the published sequence of NCDV VP3. The significance of these results with regard to virus serotypes is discussed. Finally, in analyzing the nucleotide sequence surrounding the initiation codon, a potential hairpin-loop structure was identified which may be involved in translational regulation.

Atypical rotaviruses in Australian pigs

Atypical rotaviruses of two different electropherotypes were identified by PAGE in 16 out of 237 (5.3%) diarrhoeic faecal samples from piglets. A cDNA probe derived from a group B rotavirus hybridized strongly to two samples (of 3 tested) with electropherotypes suggestive of groups B or E, identifying them as group B. The electropherotype(s) of seven samples were typical of group C. By immunofluorescence, antibodies to group B, C, and E rotaviruses have been detected in sera from Australian sows, so it appears that atypical rotaviruses belonging to three different groups occur in pigs in this country.