CTA1-DD-Immune Stimulating Complexes: a Novel, Rationally Designed Combined Mucosal Vaccine Adjuvant Effective with Nanogram Doses of Antigen

Abstract

Mucosally active vaccine adjuvants that will prime a full range of local and systemic immune responses against defined antigenic epitopes are much needed. Cholera toxin and lipophilic immune stimulating complexes (ISCOMS) containing Quil A can both act as adjuvants for orally administered Ags, possibly by targeting different APCs. Recently, we have been successful in separating the adjuvant and toxic effects of cholera toxin by constructing a gene fusion protein, CTA1-DD, that combines the enzymatically active CTA1-subunit with a B cell-targeting moiety, D, derived from Staphylococcus aureus protein A. Here we have extended this work by combining CTA1-DD with ISCOMS, which normally target dendritic cells and/or macrophages. ISCOMS containing a fusion protein comprising the OVA323–339 peptide epitope linked to CTA1-DD were highly immunogenic when given in nanogram doses by the s.c., oral, or nasal routes, inducing a wide range of T cell-dependent immune responses. In contrast, ISCOMS containing the enzymatically inactive CTA1-R7K-DD mutant protein were much less effective, indicating that at least part of the activity of the combined vector requires the ADP-ribosylating property of CTA1. No toxicity was observed by any route. To our knowledge, this is the first report on the successful combination of two mechanistically different principles of adjuvant action. We conclude that rationally designed vectors consisting of CTA1-DD and ISCOMS may provide a novel strategy for the generation of potent and safe mucosal vaccines.

Mucosal Immunization with Recombinant Fusion Protein DnaJ-ΔA146Ply Enhances Cross-Protective Immunity against Streptococcus pneumoniae Infection in Mice via Interleukin 17A

“…Vibrio cholerae cholera toxin (CT) and Escherichia coli heat-labile enterotoxin (LT) and their subunits are known to readily induce immune responses and have been widely used (39,40). However, neither of them can be used for human vaccine in their native form because of their intrinsic toxic effect.…”

Simultaneous presentation and cross‐presentation of immune‐stimulating complex‐associated cognate antigen by antigen‐specific B cells

“…First, it is likely that the frequency of antigen-specific B cells will be expanded in previously immunised animals, meaning that ISCOMS-based vaccines could bind to and cross-link sufficient specific B cells to generate their dual adjuvant effects when used as a booster strategy. Secondly, we have shown previously that ISCOMS can be targeted to polyclonal populations of B cells in vivo by incorporation of CTA1-DD, generating strong CD4 + T cell-dependent immunity [15,16]. Genosys (Cambridge, UK).…”

The Combined CTA1-DD/ISCOMs Vector Is an Effective Intranasal Adjuvant for Boosting PriorMycobacterium bovisBCG Immunity toMycobacterium tuberculosis

“…does not cause inflammation or accumulate in the nervous tissues (13). This combined adjuvant vector, CTA1-DD/ISCOMs, has proven exceptionally potent as a mucosal immunoenhancer of a wide range of immune responses, including specific antibodies, CD4 T-cell priming, and effective cytotoxic T lymphocytes (25,28).…”

“…does not cause inflammation or accumulate in the nervous tissues (13). This combined adjuvant vector, CTA1-DD/ISCOMs, has proven exceptionally potent as a mucosal immunoenhancer of a wide range of immune responses, including specific antibodies, CD4 T-cell priming, and effective cytotoxic T lymphocytes (25,28).The fusion protein Ag85B-ESAT-6 has been demonstrated in a range of animal models to be a successful candidate for use in s.c.-delivered subunit vaccines against TB (24,29,31). Therefore, we have evaluated the immunoenhancing properties of the mucosal combined adjuvant vector CTA1-DD/ ISCOMs in a formulation for i.n.…”

“…We have constructed a combined adjuvant vector composed of immune-stimulating complexes (ISCOMs) and the cholera toxin-derived fusion protein CTA1-DD. The CTA1-DD/ ISCOMs vector is a rationally designed mucosal adjuvant that was developed in order to incorporate the distinctive properties of the individual adjuvant components in a synergistic manner and thereby further enhance mucosal immune responses (25,28). CTA1-DD is a construct based on a gene fusion protein between the enzymatically active CTA1 protein A (2).…”