Immunogenic detoxified mutant e. coli lt-a toxin

Abstract

An immunogenic detoxified protein is provided which comprises the amino acid sequence of subunit A of an E. coli heat labile toxin (LT-A) or a fragment thereof in which at least amino acid Ala-72 of the A subunit is mutated, preferably by substitution with Arg. The toxoid is useful as vaccine against an enterotoxigenic strain of E. coli and is produced by recombinant DNA means by site-directed mutagenesis. It is also an effective adjuvant.

Description

[0001] The present invention relates to immunogenic detoxified heat labile toxin proteins (LT) produced by enterotoxigenic strains of Escherichia coli (E.coli) wherein at least amino acid Ala-72 of the A subunit is mutated, and to their use in vaccines which are useful in the prevention or treatment of enterotoxigenic E.coli infections and as adjuvants for other immunogenic proteins. Toxoids of the invention can be suitably produced using recombinant DNA techniques by site-directed mutagenesis of DNA encoding the wild-type toxins.BACKGROUND TO THE INVENTION[0002] Heat-labile enterotoxin (LT), produced by enterotoxigenic strains of E. coli, and cholera toxin (CT), produced by V.cholerae strains, are the causative agents of traveller's diarrhoea and cholera, respectively [Spangler (1992) Microbiol Rev 56:622]. LT and CT show 80% homology in the primary structure and an identical tertiary structure. They are composed of two functionally distinct domains: the enzymatically-active A subu...

AI Technical Summary

Benefits of technology

[0016] As used herein, the term "residual toxicity" means that the detoxified immunogenic protein may retain a measurable toxicity. More particularly the level of toxicity may be optimised in a benefit / side-effect trade-off to maximise immunogenicity and / or adjuvanticity whilst maintaining a sufficiently low toxicity to be tolerated by the subject after administration.

[0017] Thus, although these proteins are detoxified in the sense of having a much lower toxicity than the wild-type protein, traces of the enzymatic activity responsible for toxicity may remain. The mutation causes a decrease in toxicity of which makes the toxoid suitable for human use.

Problems solved by technology

(1993) Vaccine 11:1316], but their toxicity has precluded their use in humans.

In relation to adjuvanticity, much data has been generated but many questions remain unanswered.

Some studies have suggested that LT-B and CT-B have adjuvant activity, but the conclusions drawn have been compromised by contamination with active toxin [Wilson et al.

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