An evalutation of some methods of assay of foot-and-mouth disease antigen for vaccines.

The relative merits of various in vitro assay systems for the measurement of the quality and quantity of foot-and-mouth disease virus vaccine antigen will be discussed. The assay systems include : viral infectivity, complement fixing activity, particle counts, radial diffusion titre and single radial haemolysis titre. The predictive value of the tests for the immunogenicity of the final vaccine product will be evaluated against the results of 50% Protective Dose titres determined in guinea pigs and cattle by antibody assay and by challenge.