Abstract: ADP-L-glycero-D-manno-heptose-6-epimerase encoded by rfaD gene was an enzyme essential for LOS synthesis. And it was confirmed as an important virulence factor of Haemophilus parasuis. In this study, the rfaD gene of H.parasuis serovar 4 strain clinical SC096 was amplified by PCR with a pair of specific primers based on the complete gene sequence of H.parasuis genome. And it was cloned into pMD19-T vector, then subsequently sub-cloned into expression vector pET-32a(+). SDS-PAGE and Western blotting analyses suggested that the recombinant BL21 (DE3) bacteria induced by IPTG were able to express the rfaD protein with molecular weight of 50 ku, which could react with the positive serum of H.parasuis serovar 4.

Key words: Haemophilus parasuis; rfaD gene; prokaryotic expression