Fig. 1.

A schematic description of vaccine vector. a Linear depiction of the three major domains identified within C. difficile TcdA and TcdB. Note: ED; Enzymatic Domain; HD: Hydrophobic Translocation Domain; RBD: Receptor Binding Domain; IVS: Synthetic intron. b Schematic depiction of the vaccine gene sequence as inserted into the eukaryotic expression vector, pIRES. c Protein expression from vaccine vectors following transient transfection of COS7 cells. Immunoblot of COS7 cell lysates and supernatants following transient transfection with pTA (line1), pTB (line2) and pTAB (line3) for detection of expressed protein products. Supernatant was clarified at 18,000 × g for 30 min prior to the procedure. The expected size of TcdA-RBD is 35 kDa, TcdB-RBD is 60 kDa