Developments in foot-and-mouth disease vaccines.

The current status of foot-and-mouth disease (FMD) vaccine production is reviewed. The production of antigen in bovine tongue epithelium (Frenkel culture) is described and improvements in monolayer and suspension cultures of cell lines are outlined. Inactivation of viral antigen and safety tests are discussed. A 'minimum safety level' is recommended: at the end of the inactivation process, antigen batches of any size should contain less than one virus particle. After inactivation the antigen can be formulated into a vaccine or purified and concentrated for storage at ultra-low temperatures in a vaccine bank. Vaccines prepared with the adjuvants Al(OH)3 and saponin are compared with (double) oil emulsion vaccines. Because oil vaccines can protect both cattle and pigs and induce long-term protection, they are most suitable for use in ring vaccinations. A new generation of vaccines, based on constructed modified-live viruses or (bio-) synthetic peptides, is briefly reviewed.