Rotavirus A (RVA) is a dominant causative agent of acute gastroenteritis in children worldwide. G2P[4] is one of the most common genotypes among human rotavirus (HRV) strains, and has been persistently prevalent in South Asia including Bangladesh. In the present study, whole genome sequences of a total of 16 G2P[4] HRV strains (8 strains each in 2010 and 2013) detected in Mymensingh, north-central Bangladesh were determined. These strains had typical DS-1-like genotype constellation. Most of gene segments from DS-1 genogroup exhibited high level sequence identities to each other (>98%), while slight diversity was observed for VP1, VP3, and NSP4 genes. By phylogenetic analysis, individual RNA segments were classified into one (V) or two-three lineages (V-VI or V-VII). In terms of lineages (sublineages) of 11 gene segments, the 16 Bangladeshi strains could be further classified into four clades (A-D) containing 8 lineage constellations, revealing the presence of three clades (A-C) with three lineage constellations in 2010, and a single clade (D) with four constellations in 2013. Therefore, co-existence of multiple G2P[4] HRV strains with different lineage constellations, and change in clades for the study period were demonstrated. Although amino acids in the antigenic regions on VP7 and VP4 were mostly identical to those of global G2P[4] strains after 2000, VP4 of clade D RVAs in 2013 had alanine and proline at positions 88 and 114, respectively, which are novel substitutions compared with recent global G2P[4] strains. Replacement of lineage constellations associated with unique amino acid changes in the antigenic region in VP4 suggested continuous genetic evolutionary state for emerging new G2P[4] rotavirus strains in Bangladesh.
Keywords: Evolution; Genetics; Microbiology.