Differentiating Diagnosis Of Animals Naturally Infected And Vaccinated With Foot-and-Mouth Disease Virus Using The Non-structural Protein Of Foot-and-Mouth Disease Virus

Foot-and-mouth disease (FMD) is a highly contacting infectious disease, affecting international trade, and is ranked one of the most important infectious disease by OIE. The control and eradication of FMD including immunity and slaughter shadiness droves. In vaccinated droves, the antibodies to the structural protein were positive, thereby, naturally infected animals were difficultly distinguished from vaccinated ones through some diagnosis methods to the non-structural protein.According to published literatures, 3ABC and 3AB were good antigens to distinguish naturally infected animals from vaccinated ones, but antibodies to 3A of few vaccinated cow were detected, because the 3A protein remained in the process of preparing vaccines or some crossing antigens. In conclusion, they may affect the specificity of detecting tests to 3ABC or 3AB, but a special test to the conservative epitope domain F5 in protein 3ABC was used to overcome their problems.Using recombinant DNA technology, the epitope domain F5 was amplified though Plasmid pM18T-3ABC, then the segment and vector pET-28a(+)were enzymed by Bgl II and HindIII, and conducted each other ,transformed into the bacteria TG1. The expression plasmid containing six F5 segment in series was named pET-28a-F5 (+6) which was induced to expression. The expression product was analyzed by SDS-PAGE and DOT-ELISA. The results indicated the F5 segment was highly expressed in dissoluble form and had immunity. The F5 (+6) -EL ISA was established using the purified protein, the results revealed optimal dilution of serum, through detecting 307 negative serum of FMDV. The specificity, preliminary sensitivity of the ELISA were 96% and 100% respectively which suggested F5 (+6 ) -EL ISA was used for diagnosis of FMD.The ELISA using NS-3AB antigen is a credible method to distinguish naturally infected animals from vaccinated ones. The specificity results of detecting NS-3 AB-ELIS A by the standard negative and positive sera was 100%. The type of "O" FMD killed concentrated vaccines was used in some Shanghai cow farms. 852 cows were detected though NS-3AB-ELISA and IHA which revealed the type of "O" FMD killed concentrated vaccines contained infinitesimal NS antigen.