We propose to continue and greatly extend our studies on the molecular biology of picornaviruses, particularly on poliovirus. We shall study aspects of viral protein synthesis (initiation and processing of polypeptides) and the intriguing problem of viral RNA replication. We will use recombinant DNA technology to define gene function (in vitro recombination, site specific mutagenesis) and we plan to characterize the surface properties of the virion (neutralizing epitopes, virus-cell attachment sites). Our studies may lead to the development of new vaccines and drugs directed against picornavirus infection.