Molecular epidemiology of human P[8],G9 rotaviruses in Hungary between 1998 and 2001

Increasing numbers of studies have documented the widespread distribution of human G9 rotaviruses and demonstrated that these strains may represent a fifth epidemiologically important G serotype. Serotype G9 strains were identified in Hungary for the first time in the 1997-1998 rotavirus season. Contrary to numerous surveys that reported several unexpected P-G combinations among recent G9 isolates (e.g. genotypes P[4], P[6] and P[19]), all Hungarian strains characterized to date possess the globally most common P-type, P[8], which was found among the first G9 isolates that were identified during the 1980s in the USA (WI61) and Japan (F45). To study the genetic variability within Hungarian G9 strains, RNA profile analysis and nucleotide sequencing were performed on a subset of samples that were collected between 1998 and 2001. These strains could be classified into four major RNA profiles, of which two were characteristic for epidemiologically major and two for epidemiologically minor G9 strains. Phylogenetic analysis demonstrated substantial sequence differences between the VP7 gene of Hungarian G9 strains and early strains that were isolated in the USA (WI61), Japan (F45) and India (116E) and a few recently identified isolates, e.g. from China (97'SZ37) and the USA (OM67) (< 90 % nucleotide sequence similarity). In contrast, the VP7 genes of Hungarian G9 strains were related very closely to the vast majority of G9 strains that were isolated in a variety of countries over the last several years (> 96 % nucleotide sequence similarity). With respect to the VP4 gene, Hungarian G9 rotaviruses fell into two of the major genetic lineages of genotype P[8], one corresponding to the epidemic strains (lineage II; P-like) and the other for two unique strains (lineage I; Wa-like), suggesting independent introduction of distinct P[8],G9 strains into Hungary or genetic reassortment between locally circulating P[8] strains and descendants of G9 isolates that were imported into the country at an earlier time. The unexpected heterogeneity found for G9 VP7 genes from several countries suggests that genetic variation among these strains has not yet been fully explored.