3.3 The BLAST and phylogenetic analyses of the VP7 and VP4 genes of the G8P[8] strains
The VP7 and VP4 genes of 14 G8P[8] strains were first subjected to nucleotide sequencing and phylogenetic analysis. According to the BLAST analysis, the VP7 gene of the G8 strains had nucleotide sequence similarity of 100% with a Thai RVA/Human-wt/CMH-ST260-18/2018/G8P[8] strain. Phylogenetically, the VP7 gene of G8 strains included in this analysis were divided into at least 6 lineages (I-VI) (Figure 2A). All 14 G8 strains (or called “Chiang Rai strain”), together with DS-1-like G8P[8] reference strains (labelled with □) from several countries such as China, the Czech Republic, Japan, Korea, Singapore, Taiwan, Thailand, and Vietnam, belonged to the same lineage VI. The G8 strains detected in this study formed a single sublineage A, most closely related to 11 G8P[8] strains previously detected in Thailand in 2017-2019 and two G8P[8] strains in China in 2021 with nucleotide sequence similarity of 98.7-100%.
The BLAST analysis revealed that the VP4 gene of 14 P[8] strains had nucleotide sequence similarity of 100% with various Thai G3P[8], G8P[8], and G9P[8] strains formerly reported in 2018-2019, such as RVA/Human-wt/THA/B5117/2018/G3P[8], RVA/Human-wt/THA/CMH-N004-19/2019/G8P[8], RVA/Human-wt/THA/B4982/2018/G8P[8], RVA/ Human-wt/THA/DBM2018-291/2018/G9P[8], and RVA/Human-wt/THA/CMH-ST139-18/ 2018/G9P[8]. Phylogenetically, the VP4 gene of P[8] strains included in the present study were divided into at least 5 lineages (I-V) (Figure 2B). All 14 P[8] strains, together with DS-1-like G8P[8] reference strains (labelled with □) and many other P[8] strains combined with different G-genotypes: G1, G2, G3, G6, G8, G9, and G12, belonged to the same lineage V.