Protein-engineered molecules carrying GAD65 epitopes and targeting CD35 selectively down-modulate disease-associated human B lymphocytes

Abstract

Summary Type 1 diabetes mellitus is an autoimmune metabolic disorder characterized by chronic hyperglycemia, the presence of autoreactive T and B cells and autoantibodies against self‐antigens. A membrane‐bound enzyme on the pancreatic beta‐cells, glutamic acid decarboxylase 65 (GAD65), is one of the main autoantigens in type 1 diabetes. Autoantibodies against GAD65 are potentially involved in beta‐cell destruction and decline of pancreatic functions. The human complement receptor type 1 (CD35) on B and T lymphocytes has a suppressive activity on these cells. We hypothesized that it may be possible to eliminate GAD65‐specific B cells from type 1 diabetes patients by using chimeric molecules, containing an anti‐CD35 antibody, coupled to peptides resembling GAD65 B/T epitopes. These molecules are expected to selectively bind the anti‐GAD65 specific B cells by the co‐cross‐linking of the immunoglobulin receptor and CD35 and to deliver a suppressive signal. Two synthetic peptides derived from GAD65 protein (GAD65 epitopes) and anti‐CD35 monoclonal antibody were used for the construction of two chimeras. The immunomodulatory activity of the engineered antibodies was tested in vitro using peripheral blood mononuclear cells (PBMCs) from type 1 diabetes patients. A reduction in the number of anti‐GAD65 IgG antibody‐secreting plasma cells and increased percentage of apoptotic B lymphocytes was observed after treatment of these PBMCs with the engineered antibodies. The constructed chimeric molecules are able to selectively modulate the activity of GAD65‐specific B lymphocytes and the production of anti‐GAD65 IgG autoantibodies by co‐cross‐linking of the inhibitory CD35 and the B cell antigen receptor (BCR). This treatment presents a possible way to alter the autoimmune nature of these cells.

hMSCs Migrate under the Chemotaxis of CXCL-13 and Enhance Islet B Cell Activity through p-AKT Signaling Pathway in High-Glucose Environment

“…e mechanism of the development of type 2 diabetes is that long-term chronic hyperglycemia significantly inhibits the activity of islet B cells and promotes the apoptosis of islet B cells [2,3]. e decrease in islet B cells number leads to decreased function of islet B cells [4].…”

Selective Silencing of Disease-Associated B Lymphocytes from Hashimoto’s Thyroiditis Patients by Chimeric Protein Molecules

“…The features of these epitopes suggest that HT development might be associated with the unmasking of cryptic epitopes, and whose antigen presentation would break the tolerance to Tg [ 21 ]. Similar overlapping of T-cell epitopes within the frame of B-cell epitopes and presentation by autoreactive B cells resulted in blocking or inhibition of antigen-presentation to the respective T-cell clones in a model of human diabetes mellitus type 1 [ 18 , 22 ].…”

“…These engineered antibodies consist of multiple peptide epitopes recognized in SLE and T1DM and coupled to an anti-human CD35 monoclonal antibody that crosslinks their inhibitory CD35 with BCRs. The administration of SLE- or T1DM-chimeric molecules resulted in a significant reduction in anti-dsDNA or anti-GAD65 IgG antibody-producing plasma cells, inhibition of disease-associated cell proliferation, induction of B- and T-lymphocyte apoptosis as well as reduction in proteinuria and glomerular deposition of human IgG immune complexes in humanized immunodeficient SCID mice reconstituted with PBMCs from SLE patients [ 16 , 17 , 18 ].…”

“…A potential candidate for this purpose is the human complement receptor (CR1, CD35), which provides a strong inhibitory signal to B lymphocytes [ 14 , 15 ]. We have shown in a previous work how to provide the specificity of B-cell targeting by engineered protein chimeric molecules which crosslink the surface antigen-binding receptors with the inhibitory B-cell receptors [ 16 , 17 , 18 ]. These engineered molecules contain a monoclonal antibody specific to CD35 conjugated to peptide epitopes derived from basic autoantigens.…”

Utilization of complement receptors in immune cell–microbe interaction

“…Previously, our group was the first to show that in human system CR1 is a potent inhibitor of BCR-dependent B-cell activationsuch as proliferation, cytokine and antibody production of cellsin both physiological and pathological conditions [9][10][11][12]. Since then the inhibitory function of CR1 was confirmed by others, using in vivo model systems as well [143][144][145].…”