Antigenic structure of chimeras of type 1 and type 3 poliovirus involving antigenic site 1

Chimeric polioviruses have been prepared in which part of the antigenic site 1-encoding sequence of the Sabin strain of type 1 poliovirus has been replaced by sequences based on those found in the homologous region of the Sabin type 3 strain. The chimeras were analysed for their reaction with polyclonal and monoclonal antibodies raised against type 1 and type 3 viruses, and with polyclonal antipeptide sera, as well as for their immunogenicity in animals. The effectiveness with which the type 3 site was presented antigenically varied in ways which were partially predictable, based on the behaviour of type 3 mutants with monoclonal antibodies. However, other factors were implicated which may include conformational effects and other components of the site in addition to those altered in the chimeras. The ability of the chimeras to induce antibodies reacting with type 3 polioviruses paralleled their antigenic reactivity, and evidence is presented for the induction of strain-specific antibodies.