Differences in the amino acid composition of the antigen epitopes of the VP7 protein of Russian rotaviruses with the G9 genotype and the vaccine strains RotaTeq, Rotavac, and Rotarix

Abstract

Introduction. Rotaviruses of group A (RVA) with genotype G9P[8] are a common cause of acute gastroenteritis in children in Russia. In Nizhny Novgorod, the part of G9P[8] among all RVA strains reached 63.1% during 20162017 epidemic season. Two live rotavirus vaccines, RotaTeq and Rotarix have been successfully introduced into the national immunization programs worldwide. In addition, the Indian vaccine Rotavac, based on the strain with G9P[8] genotype, is used on a regional level. The parent strains for all mentioned vaccines were isolated more than 30 years ago. There is no data about phylogenetic analysis and comparative analysis of antigenic epitopes of Russian G9P[8] wild-type isolates and vaccine strains. In the present study, for the first time, we provide a comparative phylogenetic analysis and research of the amino acid composition of the B- and T-cell epitopes of the VP7 protein between Russian rotaviruses with the G9 genotype and the vaccine strains in RotaTeq, Rotarix and Rotavac composition. Materials and methods. The nucleotide and amino acid sequences of the VP7 gene of RVA with genotype G9 were studied. The rotaviruses had been previously isolated from children hospitalized with acute gastroenteritis in the infectious hospital in Nizhny Novgorod during 20112016. Results. A phylogenetic analysis of the nucleotide sequences of the VP7 gene showed that the Nizhny Novgorod strains belong to the G9-III allele. Based on the amino acid sequences VP7, three B-cell epitopes (71a, 71b and 72) and two T-cell epitopes (1628 aa and 4052 aa) were analyzed. The smallest number of substitutions was found in the RotaTeq vaccine registered in Russia: from 0 to 3 aa differences at the epitope. The same (from 0 to 3 aa differences at the epitope) was found between the wild-type strains RVA and the Rotavac vaccine. The largest number of amino acid differences was found between the vaccine strain Rotarix and the Nizhny Novgorod G9 strains (from 3 to 10 aa at the epitope). Conclusion. In the present work, based on nucleotide sequences VP7 gene, we provide phylogenetic and comparative analyses of the amino acid composition of antigenic epitopes of G9 RVA isolated in Russia vs rotavirus strains in vaccines RotaTeq, Rotavac and Rotarix. The accumulation of mutations in antigenic epitopes can help the virus to escape the immune response. Continuous molecular monitoring of wild-type RVA strains is necessary for estimation of the possible impact of vaccines on the genotype diversity of the rotavirus population in the wild and to monitor the emergence of novel antigenic variants.