Predicting Intra- and Intertypic Recombination in Enterovirus 71

Enteroviruses are well known for their ability to cause neurological damage and paralysis. The model enterovirus is poliovirus (PV), the causative agent of poliomyelitis, a condition characterized by acute flaccid paralysis. A related virus, enterovirus 71 (EV-A71), causes similar clinical outcomes in recurrent outbreaks throughout Asia. Retrospective phylogenetic analysis has shown that recombination between circulating strains of EV-A71 produces the outbreak-associated strains which exhibit increased virulence and/or transmissibility. While studies on the mechanism(s) of recombination in PV are ongoing in several laboratories, little is known about factors that influence recombination in EV-A71. We have developed a cell-based assay to study recombination of EV-A71 based upon previously reported assays for poliovirus recombination. Our results show that: (1) EV-A71 strain-type and RNA sequence diversity impacts recombination frequency in a predictable manner that mimics the observations found in nature; (2) recombination is primarily a replicative process mediated by the RNA-dependent RNA polymerase (RdRp); (3) a mutation shown to reduce recombination in PV (L420A) similarly reduces EV-A71 recombination suggesting conservation in mechanism(s); and (4) sequencing of intertypic recombinant genomes indicates that template-switching is by a mechanism that requires some sequence homology at the recombination junction and that the triggers for template-switching may be sequence independent. The development of this recombination assay will permit further investigation on the interplay between replication, recombination and disease.