Expression of the major epitope regions of 2C integrated with the 3AB non-structural protein of foot-and-mouth disease virus and its potential for differentiating infected from vaccinated animals.

In recent years, the potential value of the non-structural proteins (NSP) 2C and 3ABC has been well documented for differentiation of animals infected with foot-and-mouth disease virus (FMDV) from vaccinated animals (DIVA). In order to develop a more sensitive approach to detect animals infected naturally in herds of FMDV-vaccinated animals, a 47.6 kD fusion protein named 2C3AB was expressed in bacteria which incorporated two major B-cell epitope regions of 2C and the whole 3AB within the NSP of FMDV. The product reacted specifically with sera from animals infected with FMDV, but did not react with sera from non-vaccinated and healthy animals. The performance of 2C3AB was compared further with the 3ABC fusion protein as the antigen in an indirect ELISA format for DIVA. The results showed that the 2C3AB-ELISA had an even stronger signal reaction in the indirect ELISA and showed higher sensitivity than the 3ABC-ELISA for DIVA purposes and for detection of early virus infection in animals. Therefore, it is expected that the recombinant protein 2C3AB could be a good candidate protein with which to develop more sensitive methods for DIVA and for surveillance of herds infected subclinically under conditions of vaccination. This study indicates that the 2C3AB-ELISA can be used to confirm the results of the 3ABC-ELISA to improve the performance of the 3ABC-ELISA DIVA test.