The present invention relates to immunogenic compositions comprising isolated Clostridium difficile CDTb and/or CDTa protein. In particular the isolated Clostridium difficile CDTb protein is suitably a truncated CDTb protein comprising the receptor binding domain or a mutated CDTb protein incapable of binding to CDTa, and the isolated Clostridium difficile CDTa protein is suitably a truncated CDTa protein which does not comprise the C-terminal domain. In particular the invention also relates to fusion proteins comprising a CDTa protein and a CDTb protein and also fusion proteins between an isolated Clostridium difficile toxin A protein and/or an isolated Clostridium difficile toxin B protein fused to a CDTb protein. The invention further relates to compositions comprising fragments or variants of SEQ ID NO:3, SEQ ID NO:7, SEQ ID NO:16, SEQ ID NO:9, SEQ ID NO:51, SEQ ID NO:34, SEQ ID NO:36, SEQ ID NO:50, SEQ ID NO:14, SEQ ID NO:15, SEQ ID NO:46, SEQ ID NO:48, SEQ ID NO:52, SEQ ID NO:54, SEQ ID NO:40, SEQ ID NO:41 or SEQ ID NO:42 or SEQ ID NO:43 or SEQ ID NO:44 or SEQ ID NO:45.
