Characterization of the σB-encoding genes of muscovy duck reovirus: σC–σB-ELISA for antibodies against duck reovirus in ducks

The σB/σC-encoding genes of muscovy duck reovirus (DRV) S12 strain were cloned, sequenced, and expressed in Escherichia coli. The σC-encoding gene of DRV showed only 21–22% identity to that of avian reovirus (ARV) at both nucleotide and amino acid level. The σB-encoding gene of DRV comprised 1163 bp with one open reading frame (ORF). The ORF comprised 1104 bp and encoded 367 amino acids with a predicted molecular mass of 40.44 kDa. A zinc-binding motif and a basic amino acid motif were found within the predicted amino acid sequence of σB. The identities between the S12 and ARV were 59.3–64.0% and 60.9–62.5%, respectively, at the nucleotide and deduced amino acid levels. Phylogenetic analysis of the σB-encoding gene sequence indicated that S12 separated as a distinct virus relative to other avian strains. The expressed σB/σC fusion proteins in E. coli could be detected, approximately 45 and 50 kDa, respectively, by duck anti-reovirus polyclonal serum. In addition, an ELISA (σB–σC-ELISA) using the expressed σB–σC proteins as coating antigen for detection of antibodies to DRV in ducks was developed. In comparison with the virus neutralization test and agar gel immuno-diffusion test (AGID), the σB–σC-ELISA showed perfect specificity and sensitivity. The σB–σC-ELISA did not react with the antisera to other duck pathogens, implying that these two proteins were specific in recognition of DRV antibodies. Taken together, the results demonstrated that σB–σC-ELISA was a sensitive and accurate method for detecting antibodies to DRV.