Construction and preclinical evaluation of mmCT, a novel mutant cholera toxin adjuvant that can be efficiently produced in genetically manipulated Vibrio cholerae. Issue 18 (19th April 2016)

• Record Type: Journal Article
• Authors: Lebens, Michael; Terrinoni, Manuela; Karlsson, Stefan L.; Larena, Maximilian; Gustafsson-Hedberg, Tobias; Källgård, Susanne; Nygren, Erik; Holmgren, Jan
• Is Part Of: Vaccine. Volume 34:Issue 18(2016)
• Page Start: 2121
• Page End: 2128
• Publication Date: 2016-04-19
• Subjects: Adjuvant -- Cholera toxin -- Mucosal immunity -- Mucosal vaccine; Vaccines -- Periodicals; 615.372
• DOI: 10.1016/j.vaccine.2016.03.002
• Languages: English
• ISSNs: 0264-410X

Abstract

Highlights: Construction of a novel adjuvant mmCT, derived from cholera toxin (CT). Unlike dmLT, mmCT is produced in Vibrio cholerae and purified from growth medium. Like dmLT, mmCT lacks detectable enterotoxicity but retains adjuvant activity. Adjuvant activity for mucosal and systemic antibody and T cell responses. Enhances immune responses to oral cholera and intranasal influenza vaccines. Abstract: There is an urgent need for new adjuvants that are effective with mucosally administered vaccines. Cholera toxin (CT) is the most powerful known mucosal adjuvant but is much too toxic for human use. In an effort to develop a useful mucosal adjuvant we have generated a novel non-toxic mutant CT molecule that retains much of the adjuvant activity of native CT. This was achieved by making the enzymatically active A subunit (CTA) recalcitrant to the site-specific proteolytic cleavage ("nicking") required for toxicity, which was found to require mutations not only in the two residues rendering the molecule resistant to trypsin but also in neighboring sites protecting against cleavage by Vibrio cholerae proteases. This multiple-mutated CT (mmCT) adjuvant protein could be efficiently produced in and purified from the extracellular medium of CT-deleted V. cholerae. The mmCT completely lacked detectable enterotoxicity in an infant mouse model and had >1000-fold reduced cAMP inducing activity compared to native CT in a sensitive mammalian target cell system. It nonetheless proved to have potent adjuvant activity on mucosal and systemic antibody as well as cellular immune responses to mucosally co-administered antigens including oral cholera and intranasal influenza vaccines. We conclude that mmCT is an attractive novel non-toxic mucosal adjuvant for enhancing immune responses to co-administered mucosal vaccines.