Abstract
Mucosal immunizations are convenient ways of vaccination, which do not require any trained personnel for administration. One of the major challenges for developing an effective mucosal vaccine is finding appropriate adjuvant. Bacillus subtilis endospores have been shown to help solving these obstacles while serving as a platform for presentation of both, antigens and adjuvants. In this study, we have successfully designed and constructed recombinant spores displaying an antigen/adjuvant chimeric protein. We have used a fragment of Clostridium difficile flagellar cap FliD protein as antigen and VQGEESNDK peptide, a fragment of human IL-1β, as adjuvant. Recombinant spores presenting FliD were able to elicit immune response in orally immunized mice which could be evaluated by detection of FliD-specific IgA antibodies in feces of immunized animals. Moreover, the presence of IL-1β fragment significantly changed characteristics of elicited immune response. Obtained results show that recombinant spores presenting an antigen/adjuvant chimeric protein exhibit both properties in mucosal immunization of mice. Moreover, IL-1β fragment could serve as valuable adjuvant in B. subtilis spore-based mucosal vaccines.
Highlights
The technology of heterologous proteins display on surface of Bacillus subtilis spores has been used in different applications since its invention almost 2 decades ago [1]
To obtain recombinant spores presenting an antigen/adjuvant chimera protein, we selected a fragment of C. difficile FliD as antigen and VQGEESNDK peptide encompassing 163–171 amino acid residues of human IL-1β as adjuvant
The gene encoding FliD fragment/Interleukin 1 (IL-1) peptide chimera was fused to the cotG spore coat protein, which retained its original promoter as in the BAN03 strain (CotG-FliD) [29]
Summary
The technology of heterologous proteins display on surface of Bacillus subtilis spores has been used in different applications since its invention almost 2 decades ago [1]. B. subtilis spores have been used for presentation of enzymes, fluorescent proteins, peptides, and antigens (reviewed in [2]). Second approach is based on the adsorption technique and enables presentation of native proteins on surface of spores produced by wild-type strains (reviewed in [3]). One of the most interesting applications of spores presenting heterologous proteins is the use as carriers of antigens in mucosal vaccines. Nonpathogenic status of B. subtilis, simplicity of construction of recombinant spores presenting heterologous protein, as well as efficient surface adsorption, combined with easiness of spores’ production and administration make them especially interesting carriers of antigens in mucosal vaccines
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