1. Department of Microbiology, University of Reading, London Road, Reading RG1 5AQ, UK
2. ^*National Institute for Biological Standards and Control, Blanche Lane, South Mimms, Potters Bar, Hertfordshire EN6 3QG, UK

Abstract

Polioviruses occur as three distinct serotypes, 1, 2 and 3, and are composed of a single-stranded positive-sense RNA genome of 7,450 nucleotides enclosed in an icosahedral particle of diameter 27 nm. The three-dimensional crystallographic structure of poliovirus type 1 has been determined at 2.9 Å resolution, providing a detailed knowledge of the folding and arrangement of the individual virus proteins, VP1–VP4¹. From this and the charac-terization of monoclonal antibody-resistant mutants^2–7, the amino acids contributing to antigenic sites have been identified and located on the surface of the virus particle. Here we describe the construction and characterization of a poliovirus chimaera having a defined region of type 3 inserted into type 1. This virus has composite antigenicity and the substitute site is immunogenic in small animals and primates. The ability to construct such viruses has implications for the design of improved poliovirus vaccine strains or vaccines against other picornaviruses, such as hepatitis A.