Comparative analysis of the RVA VP7 and VP4 antigenic epitopes circulating in Iran and the Rotarix and RotaTeq vaccines

Abstract

Abstract Background Group A rotavirus is a leading cause of diarrheal disease, with its prevalence remaining high in low- and middle-income countries. In this study, circulating lineages of VP4 and VP7 proteins of human RVA isolates from children under 5 years of age were analyzed and their cytotoxic T cell and antigenic epitopes were compared to the RotaTeq and Rotarix vaccine strains. Methods Viral RNA was extracted from 51 positive samples and amplified using specific primers. Sequencing was performed and multiple sequence alignments were done in MEGA and phylogenetic trees were constructed. Similarity of VP7 and VP4 amino acids with the vaccine stains and structural analysis were performed using the UCSF Chimera-Molecular Modeling System. Results The Iranian strains clustered in the G1/II, G2/IV, G3/I, G4/I, G9/III, P[8]/III, P[4]/IV, and P[6]/I lineages. Comparative analysis of VP7 antigenic epitopes showed that G1/II strains are completely conserved, but G2/IV, G3/I, G4/I, G6, G9/III strains contained 2, 3-5, 2, 4 and 9 amino acids substitutions, respectively. P[8]/III genotypes differed by 3 amino acids, while P[6]/I genotypes had the most substitutions. CTL epitopes were completely conserved in G3/I strains, but other genotypes differed by 1-4 amino acids in comparison to the vaccine strains. Conclusions Considering the diversity of circulating RVA genotypes and the observed mutations in the neutralizing and CTL epitopes, immune escape by some of the strains is likely in Iran. This finding underscores the importance of evaluating the effect of rotavirus vaccines on local genotypes and related lineages before implementing the vaccination program.