Soluble antigen arrays disarm antigen-specific B cells to promote lasting immune tolerance in experimental autoimmune encephalomyelitis

Abstract

Autoreactive lymphocytes that escape central immune tolerance may be silenced via an endogenous peripheral tolerance mechanism known as anergy. Antigen-specific therapies capable of inducing anergy may restore patients with autoimmune diseases to a healthy phenotype while avoiding deleterious side effects associated with global immunosuppression. Inducing anergy in B cells may be a particularly potent intervention, as B cells can contribute to autoimmune diseases through multiple mechanisms and offer the potential for direct antigen-specific targeting through the B cell receptor (BCR). Our previous results suggested autoreactive B cells may be silenced by multivalent 'soluble antigen arrays' (SAgAs), which are polymer conjugates displaying multiple copies of autoantigen with or without a secondary peptide that blocks intracellular cell-adhesion molecule-1 (ICAM-1). Here, key therapeutic molecular properties of SAgAs were identified and linked to the immunological mechanism through comprehensive cellular and in vivo analyses. We determined non-hydrolyzable 'cSAgAs' displaying multivalent 'click'-conjugated antigen more potently suppressed experimental autoimmune encephalomyelitis (EAE) compared to hydrolyzable SAgAs capable of releasing conjugated antigen. cSAgAs restored a healthy phenotype in disease-specific antigen presenting cells (APCs) by inducing an anergic response in B cells and a subset of B cells called autoimmune-associated B cells (ABCs) that act as potent APCs in autoimmune disease. Accompanied by a cytokine response skewed towards a Th2/regulatory phenotype, this generated an environment of autoantigenic tolerance. By identifying key therapeutic molecular properties and an immunological mechanism that drives SAgA efficacy, this work guides the design of antigen-specific immunotherapies capable of inducing anergy.

Soluble Antigen Arrays Displaying Mimotopes Direct the Response of Diabetogenic T Cells

“…6 SAgAs have been designed to bundle peptides / proteins together for more efficient uptake in vivo and, in some cases, achieve multivalent engagement of B cells. 7,8 In addition, SAgA uptake results in epitope presentation to targeted T cells in the absence of costimulation or proinflammatory cytokines, which may induce antigen-specific immune tolerance as a way to treat T1D. SAgAs are constructed using a hydrophilic linear polymer, hyaluronic acid (HA), grafted with multiple repeating epitopes from an autoantigen.…”

Designing Multivalent Ligands to Control Biological Interactions: From Vaccines and Cellular Effectors to Targeted Drug Delivery

“…In a follow‐up study, Hartwell et al . elucidated the immunological mechanisms responsible for the development of tolerance to the PLP autoantigen.…”

“…[43,44] Building upon this work, Berkland and co-workers [45] next replaced the hydrolysable oxime bond (used to synthesize SA-gA PLP:LABL )w ith ah ydrolyticallys table covalent "Click" attachment (via Copper-catalyzed Azide-Alkyne Cycloaddition) to synthesize cSAgA PLP:LABL .T heir hypothesis was that this modification would help enhance and maintain the molecule'sa ction at the APC surfacet oi mprovee fficacy.T hey indeed saw that cSAgA PLP:LABL achieved efficacy equivalent to that of hydrolysable SAgA PLP:LABL at one-quarter of the dose when tested in a preclinical model for encephalomyelitis (EAE). [45] In af ollow-up study,H artwell et al [46] elucidatedt he immunological mechanisms responsible for the development of tolerancet ot he PLP autoantigen. They found that multivalent cSAgA PLP:LABL induced an anergic response in Bc ells and particularly as ubset of Bc ells-auto-immune associated Bc ells (ABCs)-that acted as potent APCs in auto-immune diseases.…”

Engineering Immune Tolerance with Biomaterials

“…Another approach harnessing multivalent delivery of self‐antigens to promote tolerance involves using low molecular weight polymers presenting self‐antigens to directly modulate interactions with B cells, termed “soluble antigen arrays.” B cells require antigen recognition of the B cell receptor to trigger B cell activation. However, repeated signaling through the B cell receptor (BCR) in the absence of a costimulatory signal can promote functional exhaustion or anergy.…”