Approaches to the Development of New Poliovirus Vaccines Based on Molecular Genetics

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Abstract
Complete nucleotide sequences of virion RNAs from immunologically distinct vaccine strains of poliovirus (i,e., Sabin strains 1,2, and 3) were determined by use of molecular cloning and rapid sequence analysis techniques. When the nucleotide sequences were compared, extensive sequence homology was observed among the virion RNAs in the 5' and 3' terminal regions. This result strongly suggested that the serotypes of poliovirus were derived from a putative prototype poliovirus and that the homologous sequences conservedthrough a long evolutionary processmay have essential roles for the replication and the viral functions of the virus. Many different amino acids, predicted from the nucleotide sequences, were located in polypeptidesPl-la, especially in PI-VPI, which is located on the surface of the virion and carries viral antigens. Locations of different amino acids, together with the calculated hydrophilicity values in PI-VPI, revealed possibleloci for type-specific antigenic determinants. Thesedata on functionally important conservedsequences and on possible locations of antigenic determinants will be useful in the construction of new polio vaccine strains.