Molecular epidemiology of G9 rotaviruses in Taiwan between 2000 and 2002

Abstract

Since the mid-1990s, novel G9 rotaviruses have been detected in many countries, suggesting that G9 is a globally important serotype. The molecular epidemiology of G9 rotaviruses in Taiwan from 2000 to 2002 was investigated in this study. G9 rotavirus first appeared in 2000 with 4 cases and constituted 33.8% and 54.8% of the rotavirus-positive samples in 2001 and 2002, respectively. These G9 strains belonged to P[8]G9, subgroup II, and long electropherotype, except one belonged to P[4]G9, subgroup II, and short electropherotype. Nucleotide sequencing and phylogenetic analysis of 52 Taiwanese G9 rotaviruses showed that the VP7 genes shared a high degree of identity to overseas G9 rotaviruses detected after 1993 and that the VP8* portions of the VP4 genes were more closely related to those of local rotaviruses of other G types. The two P[8]G9 strains with high nucleotide identities in the VP7 and the partial VP4 genes, 01TW591 of Taiwan from 2001 and 95H115 of Japan from 1995, varied in four genes, genes 2, 3, 7, and 8, which was revealed by RNA-RNA hybridization. Representative strains for different RNA patterns were also analyzed in the partial VP2 and VP3 genes; the nucleotide identities were high between Taiwanese G9 strains and local G3 or G2 strains. These results suggested that Taiwanese G9 rotaviruses possibly had evolved through reassortment between overseas G9 strains and circulating rotaviruses of other G types.

FIG. 1.

Monthly G type distribution of rotavirus strains between 2000 and 2002.

FIG. 2.

Age distribution of patients infected with G9 and non-G9 rotavirus between 2001 and 2002.

FIG. 3.

PAGE of rotavirus RNA. The viral RNAs were analyzed by electrophoresis in a 10% polyacrylamide gel and visualized by silver staining. The RNA patterns were compared in the same PAGE. Six RNA patterns (a to f) were determined for the G9 strains isolated at NTUH from 2000 to 2002. Representative Taiwanese G9 strains were used in the analysis: 01TW591 for RNA pattern a, 02TW1532 for RNA pattern b, 02TW498 for RNA pattern c, 02TW569 for RNA pattern d, 01TW1640 for RNA pattern e, and 01TW1288 for RNA pattern f.

FIG. 4.

Phylogenetic analysis of the nucleotide sequences of the VP7 gene (nt 73 to 942) of G9 strains isolated in Taiwan recently and G9 strains from different parts of the world. A phylogenetic tree was constructed based on the neighbor-joining method within the MEGA package. Percent bootstrap values above 70% are shown at branch nodes. The branch length for a 2% nucleotide difference is indicated at the bottom. For each strain, the P genotype (where available), the country of origin, and the year isolated are shown. Taiwanese strains are indicated by boldface italic type.

FIG. 5.

Phylogenetic analysis of the nucleotide sequences of the VP8* portions of the VP4 genes (nt 70 to 813). A phylogenetic tree was constructed based on the neighbor-joining method within the MEGA package. Percent bootstrap values above 70% are shown at branch nodes. The branch length for a 2% nucleotide difference is indicated at the bottom. For each strain, the P and G genotypes and the country of origin are shown. Taiwanese G9 strains are indicated by boldface italic type, and Taiwanese strains with other G types are indicated by italic type. In addition to one representative G9 strain for each RNA pattern listed in Table 2, a Taiwanese G9 strain, 01TW1465, with RNA pattern c was also included in the analysis.

FIG. 6.

Phylogenetic analysis of the nucleotide sequences of the partial VP2 genes (nt 490 to 997 of KU strain). A phylogenetic tree was constructed based on the neighbor-joining method within the MEGA package. Percent bootstrap values above 70% are shown at branch nodes. The branch length for a 2% nucleotide difference is indicated at the bottom. For each strain, the P and G genotypes (where available) and the country of origin are shown. Taiwanese G9 strains are indicated by boldface italic type, and Taiwanese strains with other G types are indicated by italic type.

FIG. 7.

Phylogenetic analysis of the nucleotide sequences of the partial VP3 genes (nt 1959 to 2563). A phylogenetic tree was constructed based on the neighbor-joining method within the MEGA package. Percent bootstrap values above 70% are shown at branch nodes. The branch length for a 5% nucleotide difference is indicated at the bottom. For each strain, the P and G genotypes and the country of origin are shown. Taiwanese G9 strains are indicated by boldface italic type, and Taiwanese strains with other G types are indicated by italic type.