Genetic recombination of poliovirus in a cell-free system.

Genetic recombination of plus-strand RNA viruses is an important process for promoting genetic variation. By using genetically marked poliovirus RNAs, we have demonstrated that genetic recombination can occur in a cell-free system that generates infective virus from added poliovirus RNA. Recombinant polioviruses were isolated, and the region of crossing over was roughly mapped. Recombinants could be isolated even under conditions where the yield of viruses from one of the parental RNAs was depressed to levels comparable to or less than the yield of recombinant viruses, an observation suggesting that only one of the recombining RNAs needs to be replication-competent. The generation of poliovirus recombinants in a cell-free system offers new possibilities for studying recombination and evolution of RNA viruses.