Evidence of recombination among enteroviruses

Human enteroviruses consist of more than 60 serotypes, reflecting a wide ra nge of evolutionary divergence. They have been genetically classified into four clusters on the basis of sequence homology in the coding region of the single-stranded RNA genome. To explore further the genetic relationships b etween human enteroviruses and to characterize the evolutionary mechanisms responsible for variation, previously sequenced genomes were subjected to d etailed comparison. Bootstrap and genetic similarity analyses were used to systematically scan the alignments of complete genomic sequences. Bootstrap analysis provided evidence from an early recombination event at the juncti on of the 5' noncoding and coding regions of the progenitors of the current clusters. Analysis within the genetic clusters indicated that enterovirus prototype strains include intraspecies recombinants. Recombination breakpoi nts were detected in all genomic regions except the capsid protein coding r egion. Our results suggest that recombination is a significant and relative ly frequent mechanism in the evolution of enterovirus genomes.