Sequence analysis of VP4 genes of wild type and culture adapted human rotavirus G1P[8] strains

Objective: To conduct a comparative analysis of the VP4 gene sequences of Indian wild type (06361, 0613158, 061060 and 0715880) and cell culture adapted (06361-CA, 0613158-CA, 061060-CA and 0715880-CA) G1P[8] rotavirus strains. Methods: Full-length VIM genes of each of the four wild type G1P[8] rotavirus strains and their cell culture adapted counterparts displaying consistent cytopathic effect were subjected to RT-PCR amplification and nucleotide sequencing. Results: All four cell culture adapted G1P[8] rotavirus strains showed nucleotide and amino acid substitutions in the VP4 gene as compared to their wild type strains. The number of substitutions however, varied from 1-64 and 1-13 respectively. The substitutions were distributed in both VP5* and VP8* subunits of VP4 gene respectively of permeabilization and hemagglutinating activity. The presence of unique amino acid substitutions was identified in two of the four wild type (V377G, S387N in 061060 and 16441, in 0715880) and all four cell culture adapted (A46V in 0613158-CA, T60R in 0636I-CA, 1.237V, G389V and Q480H in 061060-CA and S615G and T625P in 0715880-CA) strains for the first time in the VP4 gene of P[8] specificity. Amino acid substitutions generated increase in the hydrophilicity in the cell culture adapted rotavirus strains as compared to their corresponding wild type strains. Conclusions: Amino acid substitutions detected in the VP4 genes of G1p[8] rotavirus strains front this study together with those from other studies highlight occurrence of only strain and/or host specific substitutions during cell culture adaptation. Further evaluation of such substitutions for their role in attenuation, immunogenicity and conformation is needed for the development of newer rotavirus vaccines.