The preparation of specific immune sera against type 3 poliovirus D-antigen and C-antigen and the demonstration of two C-antigenic components in vaccine strain populations.

Animals were immunized with purified D-antigen or C-antigen of type 3 poliovirus to produce specific antisera which were used to analyse the antigenic characteristics of the progeny virus in harvests from poliovirus type 3-infected cells. An examination of the virus progeny present at 24 h p.i. of cells with Sabin type 3 vaccine strain virus revealed a large population of particles sedimenting at a slightly lower rate (130S) than infectious virus (155S) in addition to slowly sedimenting (80S) empty capsids. Such 130S particles were not detected in the progeny from cells infected with strains genetically unrelated to the Sabin vaccine strains. They were non-infectious, contained RNA in an RNase-resistant form unless heated, and lacked the virion protein VP4. They expressed C-antigen rather than the D-antigen of infectious virus, and, therefore, had the properties previously described for poliovirus particles eluted from cells. The amount of incorporation of radio-isotope into the proteins or nucleic acids of such particles varied from 15 to 20% to 300% of the amount incorporated into infectious virus depending on the cells and virus strains studied. Virus strains genetically related to Sabin type 3 vaccine virus which were isolated from cases of paralytic poliomyelitis produced the particles in either low or undetectable quantities.