Abstract: In order to obtain the protein expression product of Mycoplasma synoviae （MS） dihydrolipoamide dehydrogenase （PdhD） and analyze its immunogenicity, DNAStar Protean software was used to analyze the secondary structure and main antigen domain of PdhD. A at positions 593, 731, 1 712, and 1 833 nt of the PdhD gene was mutated to G, so that the successfully modified gene could be expressed correctly in Escherichia coli BL21;after induction with IPTG, a protein of approximately 70 ku was obtained. The secondary structure of PdhD protein was predicted for 622 amino acids. The Garnier Robson method predicted 18 alpha helix centers, 12 beta folding segments, and 17 T-corner segments. The Chou Fasman method predicted 24 alpha helix centers, 23 beta folding segments, and 37 T-corner segments. The Karplus Schulz method predicted 42 flexible regions. The main antigenic domain of PdhD was Gln27-Phe36,Vla38-Val51, Ala89-Ala99, Pro137-Asp159, Gly307-Ile336, Gly369-Gly386, Gly397-Gln416, Ala433-Val447, Ieu486-Tyr504, and Ala541-Asn549. Immunogenicity analysis revealed that PdhD recombinant protein could strongly react with rabbit-derived Anti-MS serum, but did not react with rabbit-derived Anti-MG serum or rabbit-derived serum Blank. PdhD had immunogenicity and could be used as a candidate antigen for the development of subunit vaccines.

Key words: Mycoplasma synoviae （MS）, dihydrolipoamide dehydrogenase, induced expression, immunogenicity analysis, biological characteristics