Nasal administration of CTB-insulin induces active tolerance against autoimmune diabetes in non-obese diabetic (NOD) mice

Abstract

SUMMARYNasal administration of beta cell-derived auto-antigens has been reported to suppress the development of autoimmune diabetes. We investigated the tolerogenic effects of insulin conjugated to the B subunit of cholera toxin (CTB). Nasal administration of 1 m g of CTB-insulin significantly delayed the incidence of diabetes in comparison to CTB treated mice. However, administration of 4 or 8 m g of the conjugate had no protective effect. Protection induced by CTB-insulin was transferred to naive recipients by splenic CD4+ T cells. This result favours an active cellular mechanism of regulation, which was lost using higher (4-8 m g) or lower (0·1-0·5 m g) amounts of the conjugate. When co-administered with diabetogenic T cells, splenic T cells from CTB-insulin-treated mice reduced the lymphocytic infiltration of the islets. Reverse transcription-polymerase chain reaction analysis of recipients' pancreatic glands revealed an increase of TGF-b and IL-10 transcripts after donor mice tolerization, while levels of IFNg and IL-4 RNAs were unchanged. We observed a significant increase of T cell proliferation after unspecific stimulation in the spleen and pancreatic lymph nodes 24 h after CTB-insulin administration in comparison to control treatment. Higher amounts of IL-4 and IFN-g were noticed in pancreatic lymph nodes of tolerized mice upon in vitro stimulation. Antigen-specific unresponsiveness after immunization and upon subsequent in vitro exposure to homologous antigen was obtained in nasally treated animals. Our results underlined the importance of nasal mucosa as an inducing site of tolerance and provided evidence for similar mechanisms of action to what has been described for the oral route, which favoured a CTB-insulin specific effect.

A plant-made cholera toxin B subunit enhances mucosal wound healing and protects against ulcerative colitis and colon cancer.

“…CTB has been shown to induce Tgfb1 expression in lymphoid cells in models of autoimmune diseases but a link to wound healing has not previously been explored (101)(102)(103). Consistent with the gene expression results, an in vitro wound healing assay using the Caco2 human colon epithelial cell line showed that CTBp could enhance TGFβ-mediated mucosal wound healing (Fig.…”

“…These data subsequently lead us to demonstrate that CTBp promotes wound healing in the colonic mucosa in vitro (Chapter 3). Although CTB was previously shown to upregulate TGFβ expression in B cells for IgA class switching (104) and induce Tgfb1 expression in lymphoid cells in models of autoimmune diseases (101)(102)(103), the present study showed for the first time that CTB can exert TGFβ-driven mucosal healing in the colon epithelia.…”

Autoantigen-Specific Immunotherapy

“…Further study investigating the protection mechanism indicated that administration of insulin could induce active tolerance against T1D (Aspord et al, 2002). Insulin-derived mutated proinsulin peptide B24-C36 was shown to induce antidiabetogenic regulatory T cells that block the adoptive transfer of T1D and protect the NOD mice from T1D (Fierabracci 2011).…”

Cytokine profile and insulin antibody IgG subclasses in patients with recent onset Type 1 diabetes treated with oral insulin

“…Animal models have been used to assess the ability of islet cell antigens administered via different routes (oral, intravenous, subcutaneous or nasal) to modulate the immune response and prevent or delay beta cell loss [4,5,6,7,8]. Animal models of Type 1 diabetes have demonstrated that the administration of diabetes-associated antigens, such as insulin or GAD, is effective in reducing or delaying the onset of disease [8,9]. These studies aimed to induce immune tolerance to beta cell antigens by promoting a deviation from a destructive Th1 response to a non-invasive/protective Th2/Th3 response.…”