Dose-response evaluation of a genetically engineered foot-and-mouth disease virus polypeptide immunogen in cattle.

: Four groups of 9 cattle each were vaccinated with 10, 50, 250, or 1,250 micrograms of foot-and-mouth disease (FMD) virus A12 VP1 fusion protein that was produced in Escherichia coli and emulsified in an oil adjuvant. The groups given the 10 and 50 micrograms of antigen were revaccinated at 15 weeks and were challenge exposed at 30 weeks; 5 of 9 and 7 of 9 cattle, respectively, were protected from FMD virus infection. The remaining 2 groups, vaccinated with 250 or 1,250 micrograms of antigen, were revaccinated at 32 weeks and were challenge exposed at 45 weeks; 8 of 9 and 9 of 9 cattle, respectively, were protected. The results indicated that the biosynthetic polypeptide FMD vaccine was effective using vaccination intervals frequently followed with conventional whole-virus vaccines.