FOOT-AND-MOUTH-DISEASE VIRUS-INFECTED BUT NOT VACCINATED CATTLE DEVELOP ANTIBODIES AGAINST RECOMBINANT 3AB1 NONSTRUCTURAL PROTEIN

Foot-and-mouth disease (FMD) vaccines induce antibodies against struct ural and some nonstructural proteins present in vaccine preparations. To differentiate between FMDV-infected and vaccinated animals, we deve loped immunochemical assays capable of detecting antibodies against a FMDV nonstructural protein. Recombinant nonstructural 3AB1 protein was expressed in E. coli and in insect cells and used to detect anti-3AB1 antibodies. ELISA and Western blot analysis showed that sera fi-om ca ttle infected with FMDV reacted with recombinant 3AB1 protein whereas sera from cattle which had been vaccinated against FMDV, mock-infected , or infected with different bovine viruses did not recognize the 3AB1 protein. In contrast, anti-virus infection associated antigen (VIAA) antibodies were present in both FMDV-infected and vaccinated animals. Detection of anti-3AB1 antibodies in sera of experimentally infected c attle obtained between 7 and 560 days postinfection indicated that imm unological tests based on the detection of recombinant 3AB1 protein co uld be used for the diagnosis of FMDV infection.