Abstract
In animals, oral administration of the cholera toxin B (CTB) subunit conjugated to the autoantigen insulin enhances the specific immune-unresponsive state. This is called oral tolerance and is capable of suppressing autoimmune type 1 diabetes (T1D). However, the process by which the CTB-insulin (CTB-INS) protein works as a therapy for T1D in vivo remains unclear. Here, we successfully expressed a green fluorescent protein- (GFP-) tagged CTB-Ins (CTB-Ins-GFP) fusion protein in silkworms in a pentameric form that retained the native ability to activate the mechanism. Oral administration of the CTB-Ins-GFP protein induced special tolerance, delayed the development of diabetic symptoms, and suppressed T1D onset in nonobese diabetic (NOD) mice. Moreover, it increased the numbers of CD4⁺CD25⁺Foxp3⁺ T regulatory (Treg) cells in peripheral lymph tissues and affected the biological activity of spleen cells. This study demonstrated that the CTB-Ins-GFP protein produced in silkworms acted as an oral protein vaccine, inducing immunological tolerance involving CD4⁺CD25⁺Foxp3⁺ Treg cells in treating T1D.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Administration, Oral
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Adoptive Transfer / methods
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Animals
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Autoantigens / administration & dosage
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Autoantigens / immunology
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Baculoviridae
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Blotting, Western
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Bombyx
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Cholera Toxin / administration & dosage
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Cholera Toxin / immunology*
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Diabetes Mellitus, Type 1 / immunology*
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Diabetes Mellitus, Type 1 / mortality
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Diabetes Mellitus, Type 1 / pathology
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Diabetes Mellitus, Type 1 / prevention & control
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Diabetes Mellitus, Type 1 / therapy
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Disease-Free Survival
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Female
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Genetic Vectors
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Green Fluorescent Proteins / genetics
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Green Fluorescent Proteins / immunology
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Green Fluorescent Proteins / metabolism
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Immune Tolerance*
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Immunization
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Insulin / administration & dosage
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Insulin / immunology*
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Mice
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Mice, Inbred NOD
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Mice, SCID
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Recombinant Fusion Proteins / administration & dosage
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Recombinant Fusion Proteins / biosynthesis
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Recombinant Fusion Proteins / immunology*
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Spleen / immunology
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Spleen / metabolism
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Spleen / pathology
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T-Lymphocytes, Regulatory / immunology*
Substances
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Autoantigens
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Insulin
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Recombinant Fusion Proteins
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Green Fluorescent Proteins
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Cholera Toxin