[Multiple viral transmission chains of human enterovirus 71 co-circulated in Gansu Province in 2008]

Abstract

Objective: To study the molecular evolution of Human enterovirus 71 (HEV71) isolated from clinical specimens of Hand, Foot and Mouth Disease (HFMD)patients in Gansu in 2008.

Methods: Clinical samples including stools, throat swabs and vesicle fluids were collected from HFMD patients in outpatient service in Gansu province and then viral isolation was performed. Reverse Transcription-Polymerase Chain Reactions (RT-PCR) specific for HEV71 were performed with the viral isolates. Then 20 HEV71 isolates were selected randomly for entire VP1 coding gene amplification and sequencing, finally phylogenetic tree was constructed among these 20 Gansu HEV71 strains and 38 HEV71 representative strains of known genotypes and subgenotypes.

Results: The nucleotide acid and amino acid of 20 Gansu HEV71 strains were closed to HEV71 strains isolated in Mainland China since 1998, especially has the highest homology to HEV71 stains circulated in mainland China in 2008 and it showed that all strains clustered within the C4b evolution branch of C4 Subgenotype. But there was some difference in the nucleotide and the amino acid in VP1 region among the 20 Gansu HEV71 strains, the homology were 92.5%-100.0% and 96.9%-100% respectively. 20 HEV71 strains lie in several lineages in the phylogenetic tree, and it revealed that these strains belonged to at least 7 viral transmission chains.

Conclusions: The HEV71 strains circulated in Gansu province in 2008 were all belong to C4b evolution branch of C4 subgenotype. Phylogenetic analysis revealed these HEV71 strains located in different lineages,and a close phylogenetic and chronological relationship with HEV71 isolated in other provinces in mainland China had been observed in 2008. This confirmed Gansu HEV71 strains had not evolved independently, but coevolved with the HEV71 strains in other provinces in mainland China.