Molecular characterization of coxsackievirus A21 in Shandong, China.

Coxsackievirus A21 (CV-A21) is a rarely detected serotype belonging to the species Enterovirus C (EV-C). In this study, we report the isolation and genetic characterization of CV-A21 in Shandong Province, China, during 1997 to 2013. A total of 13 strains were obtained from surveillance of cases of acute flaccid paralysis (AFP) (n = 9) and from environmental sewage (n = 4). Sequence comparison of the VP1 genes revealed high nucleotide sequence similarity (94.1 % to 99.8 % identity) among these Shandong strains during the period of 17 years and 75.8 % to 98.5 % sequence identity to foreign strains. Bayesian phylodynamic evolutionary analysis of Shandong and global CV-A21 VP1 sequences revealed that the inferred CV-A21 ancestral sequence dated back to 1750 (1643-1841) and evolved with 2.943 × 10(-3) substitutions per site per year. Alignment of the deduced VP1 amino acid sequences revealed changes that might alter the hydropathicity of the encoded protein. The complete genome of one strain from 2013 was sequenced and evidence of recombination was detected by similarity plot and bootscanning analyses. This study describes the complete genome characterization and molecular epidemiology of CV-A21 in China and gives further insight into CV-A21 evolution.