Differentiating infection from vaccination in foot-and-mouth-disease: evaluation of an ELISA based on recombinant 3ABC.

Recent devastating outbreaks of foot-and-mouth disease (FMD) in Europe have reopened the discussion about the adequacy of the non-vaccination strategy implemented by the EU in 1991. Here we describe the evaluation of a new commercially available test kit for the discrimination between vaccination and infection. The test is based on the detection of antibodies against the recombinant non-structural (NS) protein 3ABC. In contrast to immunization with vaccines free of 3ABC, these antibodies are elicited as a consequence of infection. Testing more than 3600 negative sera from several countries revealed a specificity of > 99% for bovine, ovine, and porcine samples. Antibodies specific for 3ABC can be detected as soon as 10 days post-infection. As compared with the occurrence of antibodies against structural proteins of FMDV, anti-3ABC antibodies can be detected 5-10 days later, depending on the species. No anti-3ABC antibodies were detected in sera from vaccination experiments or in field sera from vaccinated animals. However, anti-3ABC antibodies can be detected in vaccinated animals upon challenge. These results provide evidence that this test can facilitate the use of vaccines in new strategies against FMD.