Evidence for conformational changes of poliovirus precursor particles during virus morphogenesis.

Antisera raised against isolated structural polypeptides VP1, VP2 and VP3 of poliovirus type 1, strain Mahoney, reveal a differential reaction against mature virus and its precursor particles. During virus morphogenesis antigenic sites recognized by VP1 and VP2 antisera are lost stepwise from the surface of precursor particles. These sites are cross-reacting between serotypes and are also lost from precursor particles of type 2 (MEF-1) and type 3 (Saukett). They are absent on the surface of mature virus of all three serotypes. In contrast, the VP3 antiserum recognizes sites expressed maximally on the surface of infectious virus of type 1 (Mahoney). This antiserum did not show significant intertypic cross-reactions with virus particles, empty capsids or 14S particles of poliovirus types 2 and 3. However, it does recognize intertypic cross-reacting sites, like the VP1 and VP2 antisera, on denatured polypeptides and 5S particles of each serotype.