Suppression of experimental myasthenia gravis by a B-cell epitope-free recombinant acetylcholine receptor.
Myasthenia gravis (MG) and experimental autoimmune MG (EAMG) are antibody-mediated autoimmune diseases in which the nicotinic acetylcholine receptor (AChR) is the major autoantigen. Previously we have revealed that oral treatment with the less native recombinant fragment of the extracellular domain of the human AChR (Halpha1-205) suppressed ongoing EAMG, whereas the more native recombinant Trx-Halpha1-210 exacerbated EAMG. In this study, we speculated on the role of B-cell epitopes in oral tolerogens for the induction of oral tolerance in EAMG. We developed a B-cell epitope-free AChR fragment (BF-AChR) by removing two major B-cell epitopes (67-76 and 129-145) from Trx-Halpha1-210. BF-AChR exhibited a poor response to EAMG sera and to AChR-specific B- and T-cells while its parent fragment, Trx-Halpha1-210, showed much higher reactivity. Oral administration of BF-AChR ameliorated the symptoms in ongoing myasthenic rats accompanied by a significant decrease in AChR-specific humoral and Th1 cellular responses. The underlying mechanism for BF-AChR-induced oral tolerance was mediated by a shift from Th1 to regulatory T-cell (IL-10(+), CD4(+) TGF-beta(+) or Foxp3(+)) responses. This shift was assessed by changes in the cytokine profile and a deviation in the anti-AChR IgG isotypes from IgG2a/IgG2b to IgG1. Our results suggest that the removal of pathogenic B-cell epitopes from AChR fragments increases tolerogenicity by reducing the activation and proliferation of autoreactive B- and T-cells. Collectively, careful consideration of the immunogenicity of a tolerogen is necessary to induce successful oral tolerance in autoimmune disorders.
Yi
Hwa-Jung
HJ
Department of Life Sciences, Gwangju Institute of Science and Technology (GIST), 1 Oryong-dong, Buk-gu, Gwangju 500-712, Republic of Korea.
Chae
Chang-Suk
CS
So
Jae-Seon
JS
Tzartos
Socrates J
SJ
Souroujon
Miriam C
MC
Fuchs
Sara
S
Im
Sin-Hyeog
SH
D000284:Administration, Oral; D000818:Animals; D001323:Autoantibodies / Q000276:immunology; D001402:B-Lymphocytes / Q000187:drug effects / Q000276:immunology; D016207:Cytokines / Q000276:immunology; D015536:Down-Regulation / Q000187:drug effects; D018985:Epitopes, B-Lymphocyte / Q000276:immunology*; D005260:Female; D007074:Immunoglobulin G / Q000276:immunology; D007150:Immunohistochemistry; D018836:Inflammation Mediators / Q000276:immunology; D020720:Myasthenia Gravis, Autoimmune, Experimental / Q000097:blood / Q000188:drug therapy* / Q000276:immunology*; D051381:Rats; D011917:Rats, Inbred Lew; D011950:Receptors, Cholinergic / Q000008:administration & dosage / Q000276:immunology*; D011994:Recombinant Proteins / Q000494:pharmacology / Q000627:therapeutic use*; D017384:Sequence Deletion; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology; D018417:Th1 Cells / Q000187:drug effects / Q000276:immunology
D001323:Autoantibodies; D016207:Cytokines; D018985:Epitopes, B-Lymphocyte; D007074:Immunoglobulin G; D018836:Inflammation Mediators; D011950:Receptors, Cholinergic; D011994:Recombinant Proteins