DETECTION OF VIRUS INFECTION-ASSOCIATED ANTIGEN AND 3D ANTIBODIES IN CATTLE VACCINATED AGAINST FOOT-AND-MOUTH-DISEASE

The analysis of sera obtained from animals vaccinated or revaccinated with inactivated vaccines against foot and mouth disease (FMD) virus s howed that these vaccines induced antibodies against the virus infecti on-associated (VIA) antigen, detectable by agar gel immunodiffusion (A GID). The present study evaluates the antibody response to protein 3D and the VIA antigen (VIAA) of FMD virus induced by different vaccines in a group of 51 calves. This response was detected using AGID and a l iquid-phase blocking sandwich enzyme-linked immunosorbent assay (ELISA ) for anti-3D antibodies (ELlSA-3D). No anti-VIAA or anti-3D antibodie s were detected after the initial vaccination. Following revaccination , animals giving positive results were detected by both methods. This immune response disappeared 60-120 days post-revaccination (dprv) acco rding to the AGID method, and 90-180 dprv when ELISA-3D was used. Samp les of oesophageal-pharyngeal fluid obtained from animals that remaine d positive for anti-VIAA antibodies at 90-120 dprv gave negative resul ts for viral isolation, indicating that the transitional antibody resp onse induced by the vaccine was due to the presence of non-structural antigens in the Vaccine and not to viral infection. These results indi cate that the ELISA-3D method could be used as a complementary method for sero-epidemiological studies as an indirect indicator of viral act ivity, as long as the age and vaccination status of the animals being sampled are taken into consideration.