Vaccination against type F botulinum toxin using attenuated Salmonella enterica var Typhimurium strains expressing the BoNT/F H(C) fragment.

The utility of the htrA, pagC and nirB promoters to direct the expression of the carboxy-terminal (H(C)) fragment of botulinum toxin F (FH(C)) in Salmonella enterica var Typhimurium has been evaluated. Only low levels of serum antibody were induced after immunisation, and some protection against botulinum toxin type F was demonstrated after oral immunisation of mice with two doses of any of these recombinant Salmonella. Immunisation with two doses of recombinant Salmonella expressing FH(C) from the htrA promoter gave the greatest protection, against up to 10,000 mouse lethal doses of botulinum toxin type F. These results demonstrate the feasibility of an orally delivered vaccine against botulinum toxin type F.