G1P[8] Rotavirus in children with severe diarrhea in the post-vaccine introduction era in Brazil: Evidence of reassortments and structural modifications of the antigenic VP7 and VP4 regions.

Worldwide rotaviruses A (RVA) are responsible for approximately 215,000 deaths annually among children aged <5 years. RVA G1P[8] remains associated with >50% of gastroenteritis cases in this age group. The aim of this study was to assess the genetic variability of G1P[8] strains detected in children with severe diarrhea in Belém, Pará, Brazil, during the post-rotavirus vaccine introduction era. Phylogenetic analysis clustered the VP4 and VP7 genes of 40 samples selected between 2009 and 2011 into lineages found to be different from the Rotarix® vaccine strain. A detailed investigation of their complete genotype constellations identified 2 reassortant viruses (5%), resulting from reassortments between the genogroups Wa-like and DS-1-like (G1-P[8]-I1-R2-C1-M1-A1-N1-T2-E1-H1) and Wa-like and AU-1-like (G1-P[8]-I1-R3-C1-M1-A1-N1-T1-E1-H1) genotype constellations. A comparison of the amino acid residues presents in the antigenic epitopes of VP7 and VP4, showed differences in the electrostatic charges distribution, between wild type Brazilian strains and the Rotarix® and RotaTeq® vaccine strains. These findings reflect the structural analyses of the antigenic regions of VP7 and VP4 of the RVA G1P[8] in children with gastroenteritis in Northern Brazil raising the hypothesis that structural modifications at these sites over time may account for the emergence of new strains that could possibly pose a challenge to current vaccines.