OBJECTIVETo obtain highly purified tetanus toxin fragment C (TTC) with good immunogenicity.

METHODSThe gene fragment encoding TTC was amplified from Clostridium tetani plasmid DNA by PCR, inserted into the vector pET43.1a (+) and expressed in E. coli BL21(DE3)plysS. After purification using Ni2+-chelate affinity chromatography, the expressed fusion protein was digested by thrombin and the resultant TTC protein was purified with Ni2+-chelate affinity chromatography followed by identification with SDS-PAGE and Western blotting. The purifed TTC protein was then used to immunize mice to test its immunogenecity.

RESULTSThe 1373-bp gene fragment encoding TTC was obtained, and the constructed recombinant expression vector pET43.1a (+)-TTC was successfully expressed in E. coli BL21(DE3)plysS. SDS-PAGE identified a recombinant fusion protein with relative molecular mass (Mr) of 117 000, which accounted for 22% of the total bacterial protein. The TTC protein with Mr of 50 000 was obtained after purification of the thrombin digestion products of the fusion protein, with a purity reaching 95.5%. Both the fusion protein and TTC protein could be recognized by anti-tetanus toxin antibody as shown by Western blotting. The titer of the anti-serum from mice immunized with the TTC protein was 1:25 600, and the anti-serum could specifically bind to tetanus toxin.

CONCLUSIONHighly purified and immunogenetic TTC protein has been successfully obtained, which provides a good model antigen for studying antigen presentation and immune responses in vivo.