FIG 1.

Expression of Tcd169 in the nontoxigenic C. difficile CCUG37785 (designated NTCD). (A) Tcd169 was constructed by fusing the glucosyltransferase domain (GT), the cysteine proteinase domains (CPD) and the receptor binding domain (RBD) of TcdB with the RBD of TcdA. Two-point mutations were made in the GT of TcdB and one point mutation was made in the CPD of TcdB, which essentially eliminates the toxicity of Tcd169. (B) Western blot analysis of Tcd169 expression in supernatants and pellets of strains NTCD_Tcd169 and NTCD using anti-TcdA or anti-TcdB antibodies.