Development and characterisation of a fully recombinant competition ELISA for the diagnosis of foot-and-mouth disease virus infection.

Infection of livestock by foot-and-mouth disease (FMD) virus (FMDV) has serious economic implications due to productivity losses and trade restrictions. In countries that are free from foot and mouth disease, the World Organisation for Animal Health (WOAH) provides two proof of freedom from disease status categories; namely, FMD-free without using vaccination or FMD-free with use of vaccination. Serological surveillance of livestock after an incursion forms one part of a country's emergency disease response plan as it is an important condition in attaining a WOAH declaration of freedom from FMDV. The development of a competition enzyme-linked immunosorbent assay using recombinant antigen (FMDV 3B-maltose-binding protein fusion) and recombinant antibody (anti-FMDV 3B scFv-alkaline phosphatase fusion) reagents from two independently developed tests is described. The characteristics of the recombinant reagents and performance of the assay are presented and provide evidence of an improved, fully recombinant, competition ELISA suitable for sensitive and specific identification of antibodies to FMDV non-structural protein 3B in cattle sera, making it suitable for differentiating infected and vaccinated animals (DIVA).