Association of viral replication capacity with the pathogenicity of enterovirus 71.

Enterovirus 71 (EV71) is a major cause of hand-foot-and-mouth disease, which is associated with fatal neurological disease. The mechanism of EV71 pathogenesis remains obscure. We compared the replication capacity of the severe and mild enterovirus 71 isolates. The replication kinetics of EV71 in RD cells and ICR mice was determined by qRT-PCR. The lung, muscular, brain, intestine tissues were used for histopathological and immunohistochemical assays. The growth curves of EV71 strains in RD cells showed that the severe EV71 strains (SDLY107 and SDLY52) replicated faster and generated more viral RNA than the mild EV71 strains (SDLY11 and SDLY1). The mice infected by the severe EV71 strains (SDLY107) showed more severe clinical symptoms, pathological changes and higher viral load than the mice infected by the mild EV71 strains (SDLY11). These results suggest that there was a difference in replication capacity between the severe and mild EV71 strains, which was possibly associated with EV71 pathogenesis.