Characteristics of single-radial-diffusion and autoradiographic zone size enhancement (ZE) techniques for poliovirus...

The reactions of polioviruses in single-radial-immuno diffusion (SRD) tests were investigated with a view to developing accurate and sensitive antigen assay systems. In direct SRD tests, employing high concentrations of immune poliovirus serum in agarose gels, poliovirus D antigens produced D antigens produced clear reaction zones demonstrated by protein staining. The reactions were type specific for polioviruses of types 1, 2 and 3 but the tests were of low sensitivity being applicable only to the assay of virus concentrates. A novel autoradiographic zone size enhancement (ZE) test was developed which increased the sensitivity of the SRD assay 40--100 fold. The ZE test was dependent upon the ability of unlabelled poliovirus to co-migrate with the radioactive marker virus and so enhance the zone-size detected autoradiographically. The areas of the autoradiographic zones were directly proportional to the concentration of unlabelled antigen. The ZE test was capable of detecting poliovirus D antigens in diluted cell culture fluid harvests in amounts corresponding to 103.3 - 104.3 TCD50 of infectious virus.