Diversity in the VP7 encoding genes of rotavirus strains isolated from adolescent and adult cases of acute gastroenteritis

A study was conducted to examine the diversity in the VP7 genes of rotavirus strains circulating in adolescent and adult cases of acute gastroenteritis during two different time periods, 1993-1996 and 2004-2007. The multiplex RT-PCR carried out on 131 rotavirus positive fecal specimens detected 65 (49.6%) single and 48 (36.6%) mixed infections of VP7 genotypes that included 43G1 (38.1%), 37G2 (32.7%), 8G3 (7.1%), 15G4 (13.3%), and 10G9 (8.8%) specificities. Sequencing and phylogenetic analysis of the VP7 gene amplicons revealed the presence of G1-IA (4.7%), G1-IB (69.8%), and G1-IC (25.5%) lineages within the G1 strains, G2-IIb1 (70.3%) and G2-IIb2 (29.7%) lineages within G2 strains, G3-3S1 (12.5%) and G3-3S4 (87.5%) lineages within G3 strains, G4-Ia (6.7%) and G4-Ib (93.3%) lineages within G4 strains, and G9-III lineage within G9 strains. The variability within VP7 genotypes was evident by 1.4-8.0% and 1.3-3.9% amino acid divergence respectively from the prototype strains and between the groups of strains at the two time points. This is the first report describing the phylogenetic analysis of VP7 genes of rotaviruses from adolescent and adult cases of acute gastroenteritis in India. Since adults infected with rotavirus could act as a source of infection and affect the epidemiology of rotaviruses in children, genetic analysis of the rotavirus strains circulating in adults is required. The intragenotypic diversity within VP7 genes demonstrated by the present study highlights the need for constant surveillance of rotavirus infections to understand better the evolution and transmission of group A rotaviruses in the community.