Comparative sequence analysis of the VP7 genes of G6, G8 and G10 bovine group A rotaviruses and further characterization of G6 subtypes

We previously reported the relatively high prevalence ( 15 %) of bovine G6 subtypes (G6s) in the field using RT-PCR and restriction fragment length po lymorphism (RFLP) analysis (Chang et al., Arch. Virol. 141: 1727-39). In th e present study, we report the nucleotide and antigenic characterization of a G6s strain (C-8336). We also sequenced the VP7 genes of four additional bovine rotavirus (BRV) strains: another G6s (MC27), G6 (IND), G8 (C-8008) a nd G10 (2292B) and compared these with other bovine and human rotavirus str ains. The C-8336 and MC27 strains were confirmed as P[11]G6s by RT-PCR and RFLP analysis. The VP7 genes of the C-8336 and MC27 strains showed high hom ology to each other (similar to 98%) and with other bovine G6s strains (gre ater than 95% homology in nucleotide and amino acid sequence with KN-4{P[ll ]G6s}) and also showed lower, but substantial sequence homology with human G6s strains and prototype G6 BRV (79-87% in nucleotide and 88-919% in amino acid). Serologic analysis of the cell culture adapted C-8336 strain showed that it was neutralized by a G6 monoclonal antibody (MAb IC3) to similar t iters as the reference NCDV and IND G6 strains. In two-way cross-neutraliza tion tests, strain C-8336 showed 4- to 16-fold differences in antibody tite rs with NCDV and IND G6 BRV. Moreover polyclonal antiserum against strain C -8336 neutralized the NCDV and IND strains weakly. Genetic variability was also observed among G8 and G10 bovine and human group A rotaviruses: the VP 7 genes of the bovine C-8008 (P[5]G8) and 2292 B (P[11]G10) strains showed from 10 to 17% nucleotide divergence with those of Cody 1801 (P[1]G8, bovin e), A5 (P[I]GS, bovine), 69 M (P[10]G8, human) and Hal 1166 (P[14]G8, human ), and I321(P[11]G10, human) and MC35 (P[14]G10, human) rotaviruses, respec tively. The divergence of VP7 genes among bovine and human G6, G8 and G10 s trains appears related to host species origin and their combination with VP 4 (P type). The data presented in this report confirms the genetic variabil ity among homotypic bovine and human strains and highlights the importance of continued monitoring of BRV G and P types circulating in the field for t he future development and monitoring of effective vaccines.