Phenotypic and genomic characterization of human coxsackievirus A16 strains with distinct virulence in mice.

Human coxsackievirus A16 (CA16) infection results in hand, foot, and mouth disease (HFMD) along with other severe neurological diseases in children and poses an important public health threat in Asian countries. During an HFMD epidemic in 2009 in Guangdong, China, two CA16 strains (GD09/119 and GD09/24) were isolated and characterized. Although both strains were similar in plaque morphology and growth properties in vitro, the two isolates exhibited distinct pathogenicity in neonatal mice upon intraperitoneal or intracranial injection. Complete genome sequences of both CA16 strains were determined, and the possible virulence determinants were analyzed and predicted. Phylogenetic analysis revealed that these CA16 isolates from Guangdong belonged to the B1b genotype and were closely related to other recent CA16 strains isolated in mainland China. Similarity and bootscanning analyses of these CA16 strains detected homologous recombination with the EV71 prototype strain BrCr in the non-structural gene regions and the 3'-untranslated regions. Together, the phenotypic and genomic characterizations of the two clinical CA16 isolates circulating in China were compared in detail, and the potential amino acid residues responsible for CA16 virulence in mice were predicted. These findings will help explain the evolutionary relationship of the CA16 strains circulating in China, warranting future studies investigating enterovirus virulence.