Clostridium difficile recombinant toxin A repeating units as a carrier protein for conjugate vaccines: Studies of pneumococcal type 14, Escherichia coli K1, and Shigella flexneri type 2a polysaccharides in mice

Unlike the native protein, a nontoxic peptide (repeating unit of the native toxin designated rARU) from Clostridium difficile toxin A (CDTA) afforded an antigen that could be bound covalently to the surface polysaccharides of pneumococcus type 14, Shigella flexneri type 2a, and Escherichia coli K1. The yields of these polysaccharide-protein conjugates were significantly in creased by prior treatment of rARU with succinic anhydride. Conjugates, pre pared with rARU or succinylated (rARUsucc), were administered to mice by a clinically relevant dosage and immunization scheme. All conjugates elicited high levels of serum immunoglobulin G both to the polysaccharides and to C DTA. Conjugate-induced anti-CDTA had neutralizing activity in vitro and pro tected mice challenged with CDTA, similar to the rARU alone. Conjugates pre pared with succinylated rARU, therefore, have potential for serving both as effective carrier proteins for polysaccharides and for preventing enteric disease caused by C. difficile.