Heteropentameric Cholera Toxin B Subunit Chimeric Molecules Genetically Fused to a Vaccine Antigen Induce Systemic and Mucosal Immune Responses: a Potential New Strategy To Target Recombinant Vaccine Antigens to Mucosal Immune Systems

Abstract

Noninvasive mucosal vaccines are attractive alternatives to parenteral vaccines. Although the conjugation of vaccine antigens with the B subunit of cholera toxin (CTB) is one of the most promising strategies for vaccine delivery to mucosal immune systems, the molecule cannot tolerate large-protein fusion, as it severely impairs pentamerization and loses affinity for GM1-ganglioside. Here we report a new strategy, in which steric hindrance between CTB-antigen fusion subunits is significantly reduced through the integration of unfused CTB "molecular buffers" into the pentamer unit, making them more efficiently self-assemble into biologically active pentamers. In addition, the chimeric protein took a compact configuration, becoming small enough to be secreted, and one-step affinity-purified proteins, when administered through a mucosal route, induced specific immune responses in mice. Since our results are not dependent on the use of a particular expression system or vaccine antigen, this strategy could be broadly applicable to bacterial enterotoxin-based vaccine design.

Oral immunogenicity and protective efficacy in mice of transgenic rice plants producing a vaccine candidate antigen (As16) of Ascaris suum fused with cholera toxin B subunit

“…The level of expression in our system is lower by a factor of twenty, probably because of the burden imposed on CTB at the molecular level. This markedly reduces its pentamerization and thus often results in low production levels (Harakuni et al 2005). Non-use of codon optimization for As16 antigen gene could be another factor.…”

Cholera toxin B subunit acts as a potent systemic adjuvant for HIV-1 DNA vaccination intramuscularly in mice

“…CTB has been exploited as a DNA vaccine adjuvant, for instance, genetically fused CTB gene to a DNA vaccine 16 or coadministered in intradermal with a DNA vaccine. 17 However, CTB has rarely been reported as an adjuvant co-inoculated with DNA vaccine intramuscularly.…”

Plasmodium vivax Ookinete Surface Protein Pvs25 Linked to Cholera Toxin B Subunit Induces Potent Transmission-Blocking Immunity by Intranasal as Well as Subcutaneous Immunization

“…2a for details). Each conjugation sample was analyzed by GM1-enzyme-linked immunosorbent assay (GM1-ELISA) as described previously (11). Briefly, 5 g of monosialoganglioside GM1 (Sigma-Aldrich, St. Louis, MO)/ml, a receptor for CT, diluted with bicarbonate buffer (15 mM Na 2 CO 3 , 35 mM NaHCO 3 [pH 9.6]; 50 l/well) was coated onto a 96-well microtiter plate (Sumitomo Bakelite Co., Ltd., Tokyo, Japan), and the plate was incubated at 4°C overnight.…”