A collaborative study on the use of single radial immunodiffusion for the assay of rabies virus glycoprotein

The single radial immunodiffusion (SRD) technique has been applied to the assay of the glycoprotein content of rabies vaccines produced in cell cultures. Fourteen laboratories in seven countries participated in a collaborative study to evaluate the reproducibility of the SRD technique; some laboratories also examined vaccines in the mouse protection (NIH) test and by enzyme immunoassay. Good agreement was found between potency estimates using the SRD technique: the geometric coefficients of variation for combined potency estimates of all laboratories were about 10%. SRD assays appear to have a role for the in vitro assay of antigen content of vaccine and could complement results obtained in in vivo assays which are subject to wide variability.