A cholera toxoid-insulin conjugate as an oral vaccine against spontaneous autoimmune diabetes

Abstract

Mucosally induced immunological tolerance is an attractive strategy for preventing or treating illnesses resulting from untoward inf lammatory immune reactions against self-or non-self-antigens. Oral administration of relevant autoantigens and allergens has been reported to delay or suppress onset of clinical disease in a number of experimental autoimmune and allergic disorders. However, the approach often requires repeated feeding of large amounts of tolerogens over long periods and is only partly effective in animals already systemically sensitized to the ingested antigen such as in animals already harboring autoreactive T cells, and thus presumably also in humans with an autoimmune disease. We have recently shown that oral administration of microgram amounts of antigen coupled to cholera toxin B subunit (CTB), can effectively suppress systemic T cell reactivity in naive as well as in immune animals. We now report that feeding small amounts (2-20 g) of human insulin conjugated to CTB can effectively suppress beta cell destruction and clinical diabetes in adult nonobese diabetic (NOD) mice. The protective effect could be transferred by T cells from CTBinsulin-treated animals and was associated with reduced lesions of insulitis. Furthermore, adoptive co-transfer experiments involving injection of Thy-1,2 recipients with diabetogenic T cells from syngeneic mice and T cells from congenic Thy-1,1 mice fed with CTB-insulin demonstrated a selective recruitment of Thy-1,1 donor cells in the peripancreatic lymph nodes concomitant with reduced islet cell infiltration. These results suggest that protection against autoimmune diabetes can be achieved by feeding minute amounts of a pancreas islet cell autoantigen linked to CTB and appears to involve the selective migration and retention of protective T cells into lymphoid tissues draining the site of organ injury.

Oral Tolerance Induction with Antigen Conjugated to Cholera Toxin B Subunit Generates Both Foxp3+CD25+ and Foxp3−CD25− CD4+ Regulatory T Cells

“…administration of OVA/CTB conjugate effectively induces OVA-specific peripheral immunological tolerance, whether tested in normal BALB/c mice, OVA TCR Tg (DO11.10) mice, or in either BALB/c mice or Rag1 Ϫ/Ϫ mice transferred with OVA TCR Tg T cells. Consistent with our previous findings in other systems (17)(18)(19)(20)(21)(22), oral tolerance induction with Ag/CTB conjugate was superior to that induced with free Ag both in markedly increasing the efficacy of tolerization and in dramatically decreasing the effective amounts of Ag. The oral tolerance by i.g.…”

Restraint of Proinflammatory Cytokine Biosynthesis by Mitogen-Activated Protein Kinase Phosphatase-1 in Lipopolysaccharide-Stimulated Macrophages

“…9), an immune-modulatory agent (30,31). Coupled to relevant auto antigens, CTB has been shown to effectively prevent the development of T cell-mediated autoimmune diseases, including encephalomyelitis, arthritis, and type I diabetes, in animal models (32)(33)(34). Recently, it has been reported that pretreatment of macrophages and monocytes with CTB diminishes the LPS-induced proinflammatory response, leading to a significant decrease in the production of TNF-␣ and IL-6 (30,31).…”

“…It has been shown that in addition to functioning as a carrier for the cholera toxin A subunit to target adenylate cyclase, CTB can exert immune-modulating effects independent of the A subunit (30,31). CTB has been reported to suppress the onset of T cell-dependent autoimmune diseases and to potentiate tolerance of the adaptive immune response (32)(33)(34). Pretreatment of macrophages with CTB has been reported to suppress the LPS-induced production of TNF-␣ and IL-6 (30, 31).…”

No effect of oral insulin on residual beta-cell function in recent-onset Type I diabetes (the IMDIAB VII)

“…As the addition of oral insulin does not influence metabolic control, higher doses of oral insulin should possibly be tested. The use of an adjuvant carrier to increase the tolerogen capacity of insulin is also worth consideration for tolerance induction, with implications for clinical use [15].…”