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

Genetic diversity and novel combinations of G4P[19] and G9P[19] porcine rotavirus strains in Thailand

Several epidemiological studies reported the detection of rotavirus strains bearing unusual combinations of genetic background of human and porcine rotaviruses. This observation supports the hypothesis of interspecies transmission of rotaviruses in humans and pigs. The aims of this study were to investigate the genotypes and molecular characteristics of rotaviruses in piglets with diarrhea in several farms from two provinces in Thailand. A total of 207 fecal specimens collected from diarrheic piglets were screened for the presence of groups A, B, and C rotaviruses. Group A rotaviruses were detected in 41 out of 207 (19.8%) fecal specimens tested. A wide variety of G-P combination rotavirus strains were detected in this study. The G4P[6] was identified as the most prevalent genotype (39.0%), followed by G4P[23] (12.2%), G3P[23] (7.3%), G4P[19] (7.3%), G3P[6] (4.9%), G3P[13] (4.9%), G3P[19] (4.9%), G9P[13] (4.9%), G9P[19] (4.9%), G5P[6], and G5P[13] each of 2.4%. Furthermore, G5 and G9 in combinations with P-nontypeable strains were also found at each consisting of 2.4% (n=1) of the collection. It was interesting to note that among diversified porcine rotavirus strains, novel combinations of G4P[19] and G9P[19] strains were detected for the first time in this study. Nucleotide sequences of VP4 and VP7 of these strains were closely related to human rotaviruses reported previously. The data implies that these porcine rotaviruses were probably generated in nature from the reassortment between the viruses of human and porcine origin. This study provides valuable epidemiological information and molecular characteristics of porcine rotaviruses circulating in piglets with diarrhea in northern Thailand.

Molecular characterization of unusual human G5P[6] rotaviruses identified in China

BACKGROUND

We found an unusual human rotavirus, LL36755 of G5P[6] genotype, in a stool sample collected in Lulong County, Hebei Province, China. This is the first detection of rotavirus serotype G5 in Asia.

OBJECTIVES

To identify and characterize G5 rotaviruses in 988 stool samples collected from children under 5 years old with acute gastroenteritis.

STUDY DESIGN

We analyzed 459 rotavirus-positive samples with RT-PCR using G5 genotype-specific primers. The G5 strains were sequenced.

RESULTS

Two additional G5-positive samples (LL3354 and LL4260) were identified. VP7, VP4, VP6 and NSP4 genes of LL3354, LL4260 and LL36755 strains were sequenced. The VP4 sequences formed a group with porcine P[6] strains. The VP6 sequences of strains LL3354 and LL36755 were phylogenetically close to the major clusters of SGI and SGII rotaviruses, respectively. The deduced VP6 protein of strain LL4260 had characteristics of both SGI and SGII strains, but best fit with a cluster of atypical SGI viruses. In addition, based on NSP4 sequences, the three G5 strains belonged to genogroup B and were closest to human strain Wa.

CONCLUSION

These results indicate a dynamic interaction of human and porcine rotaviruses and suggest that reassortment could result in the stable introduction and successful spread of porcine gene alleles into human rotaviruses.

Prevalence of G and P serotypes among equine rotaviruses in the faeces of diarrhoeic foals

Variant types of VP4 and VP7 gene segments of faecal rotaviruses from diarrhoeic foals were identified by restriction endonuclease digestion of reverse transcription/polymerase chain reaction (RT/PCR) products. The variants observed were correlated with serotypes by determination of the sequence of representative RT/PCR products (entire coding sequence for VP7 and the VP8 region of VP4) and comparison to published sequences of equine G and P serotype genes. Both G and P serotypes could be predicted for 95/116 (82%) strains, P serotype only for a further 8 (7%) strains and G serotype only for 1 (1%) strain. All characterised strains belonged to the same P serotype, P12, although minor sequence variations were observed. Of those strains able to be assigned to G serotypes, 84/96 (87.5%) belonged to serotype G3A, and 12/96 (12.5%) belonged to serotype G14. Comparison of G serotyping by ELISA to the RT/PCR method showed that serotyping equine rotaviruses by currently available ELISA methods was prone to error. This study establishes the restricted serotypic diversity of equine rotaviruses, and the significance of serotype G14.

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.

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.

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.