Attempts at potency testing of foot-and-mouth disease vaccines by evaluation of the complement fixing capacity of eluates.

A method has been developed to evaluate the amount of antigen in foot-and-mouth disease vaccines by complement fixation after elution from aluminum hydroxide. The 12 S antigen is eliminated by treatment with Arcton 119 so that only the 140 S antigen may be determined. The concentration of 140 S antigen eluted from the vaccine is compared with the degree of protection conferred to cattle. 333 heads of cattle were vaccinated with 111 vaccines containing detectable amounts of 140 S antigen. Only one animal was not protected. In a repeated test of the questionable vaccine with 6 animals all were found to be protected. From 32 vaccines the amount of eluted 140 S antigen was compared with the PD50 in guinea pigs. Ten vaccines from 11 without detectable 140 S antigen had a PD50 value in guinea pigs lower than the limit indicating a satisfying potency for cattle.