Sequence conservation and expression of the gene encoding the outer capsid glycoprotein among human group C rotaviruses of global distribution

Abstract

Group C rotaviruses have been identified recently from fecal samples of children with diarrhea in the United States. Using reverse transcriptasepolymerase chain reaction and sequence analysis, we sequenced gene 8s encoding VP7 from two U.S. strains (RI-1 and RI-2), and eight other strains isolated from patients on four continents, and compared these with the sequences of four published strains. The gene 8s of the 14 strains were remarkably conserved in size and in predicted primary and secondary structures. When the sequences of the human VP7s were compared with that of the prototype porcine Cowden strain, six regions were found variable in both deduced primary and predicted secondary structures, four of which were predicted to be hydrophilic and might determine serotype specificity. Gene 8 of the human S-1 strain was further characterized by expression in recombinant baculoviruses. The expressed product was immunogenic but failed to elicit neutralizing antibodies. Our sequence analysis indicates that all the human strains characterized to date belong to a single G genotype, which may constitute a single G serotype, pending further antigenic analysis. Whether the human strains and the Cowden strain are the same serotype remains to be determined.

Incidence of Group C Human Rotavirus in Central Australia and Sequence Variation of the VP7 and VP4 Genes

“…The genome segments, however, form basic groupings on polyacrylamide gels different from those of group A and the other serogroups of rotaviruses (17). The coding assignments of group C rotavirus genes also appear to differ from those of group A rotaviruses for several major structural proteins, including VP4, VP6, and VP7 (9).…”

“…Group A rotaviruses are the most common cause of severe diarrhea in infants and young children, but they also infect adults (10). Group C rotavirus infection in humans occurs both in children and adults, usually in sporadic cases or clustered outbreaks, and has now also been identified worldwide (1,3,8,9,11,12,(14)(15)(16)(17)20). However, compared to group A rotaviruses, the identification of group C rotaviruses has been far less common, and neither the overall disease burden nor the epidemiology of this group of rotaviruses is yet entirely clear (9).…”

“…Polyacrylamide gel electrophoresis (PAGE), which can be used to distinguish between different serogroups of rotavirus (17), and electron microscopy are not often used to detect rotavirus in stool specimens (9). Confirmatory tests, such as with reverse transcription-PCR (RT-PCR) with group C rotavirus-specific primers (5,8) and EIAs with group C rotavirusspecific reagents have not been widely used, usually only in reference laboratories (9).…”

“…Sequence variation is also evident between VP7 genes of human and animal group C rotaviruses, but among human group C rotavirus isolates themselves from many different parts of the world remarkable sequence conservation has been noted in this gene (1,3,6,9,11). A high degree of conservation has also been evident between the sequences of the VP4 genes of human group C rotavirus isolates from different parts of the world, but a greater difference was noted between these sequences and those of the VP4 genes of bovine and porcine group C rotavirus strains (1,4).…”

“…Type-specific monoclonal antisera, such as those available for group A rotaviruses, are not available for human group C rotaviruses. Relatedness between human group C rotaviruses has therefore thus far only been inferred from sequence analysis of (essentially) the VP7 genes (9).…”