Genetic variation in the VP7 gene of rotavirus G1P[8] strains isolated in Vietnam, 1998–2009

► We examined genetic variation in VP7 gene of rotavirus G1P[8] strains in Vietnam. ► VP7 gene of 1998–1999 strains clusters in lineage I with different sublineages. ► VP7 gene of the G1 strains from 2008 to 2009 is homogeneous, clustered in lineage IIC. ► Between lineages, 13 substitutions were found including in antigenic region A and C. Group A rotavirus genotype G1P[8] is the most common strain affecting humans around the world over the past few decades. In this study, we examined genetic variation in the VP7 gene of rotavirus G1P[8] strains, detected in children of four major cities of Vietnam during three different rotavirus seasons: 1998–1999, 2007–2008 and 2008–2009 in order to assess the evolution of the virus over 11 years. Fecal samples (n=73) from children hospitalized for gastroenteritis caused by G1P[8] rotavirus were analyzed by DNA sequencing of gene 9 encoding the VP7 capsid protein. Phylogenetic analyses indicated that VP7 gene of the G1 strains from 1999 contained a lineage I, while rotaviruses from 2009 clustered in lineage II. Both of these lineages were found co-circulating in 2007–2008 season. While different sublineages of lineage I and II co-circulated in the 1998–1999 and 2007–2008 seasons, almost all strains in 2009 belonged to sub-lineage II-C. In the analysis using selected 10 strains, the VP4 genes of these 2 VP7-G1 lineages were all grouped in F45-like cluster. Deduced amino acid analyses indicated that there were thirteen amino acid substitutions between strains of two lineages. Of those, two were found in antigenic regions A and C, implying possible antigenic differences between these two lineages. The G1P[8] strains in Vietnam are very genetically diverse and dynamic, implying the frequent monitoring on evolution of rotavirus will be important to assess efficacy of rotavirus vaccine in Vietnam.