Germination-independent induction of cellular immune response by Bacillus subtilis spores displaying the C fragment of the tetanus toxin

Bacillus subtilis spores displaying the tetanus toxin fragment C (TTFC) on their surface have been previously shown to induce the production of specific IgG and secretory IgA in mice immunized through the oral or nasal route. Aim of this study was to analyze whether these spores were also able to induce cellular immunity, and whether such immune response was dependent on spore germination in the animal gastrointestinal tract (GIT). We first developed a germination defective strain of B. subtilis unable to produce viable cells inside the mouse GIT. Germination-defective and conaenic wild-type spores both expressing TTFC on their surface were then used to orally immunize Balb/C mice. Both types of spores induced spleen and mesenteric lymph nodes cell proliferation as well as production of IFN gamma but not of IL-4 and IL-10 in both districts. Our results indicate that recombinant spores preferentially induce a strong cell-mediated immune response with a Th I phenotype, independently from their ability to germinate in the GIT. (c) 2006 Elsevier Ltd. All rights reserved.