Evaluation of ELISA based on the conserved and functional middle region of nucleocapsid protein to detect distemper infection in dogs

A 287 bp fragment from the middle region of the nucleocapsid protein of canine distemper virus (CDV) was amplified from the conjunctival samples of distemper-infected dogs and was cloned into pRSET B vector. The recombinant protein was expressed as a 16-kDa-fusion protein with histidine tag in E. coli. Sera of distemper-infected and vaccinated dogs contained IgG antibodies against the purified recombinant protein as observed by enzyme linked immunosorbent assays (ELISA) and showed a strong correlation (r = 0.882, p < 0.0001 at 95% CI) and good agreement (kappa = 0.718) with the conventional tissue culture viral antigen based ELISA. Further, the results of recombinant protein based ELISA and Western blotting with the sera from the infected and vaccinated dogs correlated well (kappa = 0.8226). These findings recommend the use of the recombinant protein in the serodiagnosis of canine distemper virus infection in dogs.