Determining Cellular and Molecular Mechanisms of Multivalent Soluble Antigen Arrays that Contribute to Therapeutic Efficacy Against a Murine Model of Multiple Sclerosis

Abstract

A pressing need exists for antigen-specific immunotherapies (ASIT) that induce selective tolerance in autoimmune disease while avoiding deleterious global immunosuppression. Multivalent soluble antigen arrays (SAgAPLP:LABL), consisting of a hyaluronic acid (HA) linear polymer backbone co-grafted with multiple copies of autoantigen (PLP) and cell adhesion inhibitor (LABL) peptides, are designed to induce tolerance to a specific multiple sclerosis (MS) autoantigen. Previous in vivo studies established that SAgAPLP:LABL was therapeutic in experimental autoimmune encephalomyelitis (EAE), a murine model of MS. This dissertation sought to elucidate SAgA therapeutic cellular mechanisms while identifying therapeutic molecular properties. In Chapter 2, the role of two-signal co-delivery was explored by evaluating EAE in vivo results in conjunction with in silico molecular dynamics simulations and nanomaterial properties for various covalent and physical combinations of HA, PLP, and LABL. We found that co-delivery of both primary autoantigen and secondary inhibitory signal was necessary for therapeutic efficacy against EAE. In Chapters 3 and 4, the SAgAPLP:LABL cellular mechanism was investigated in a model B cell system by evaluating binding, specificity, and signaling modulation in vitro. Here, we developed click-conjugated cSAgAPLP:LABL which, unlike SAgAPLP:LABL, employed a non-hydrolyzable linker chemistry to conjugate PLP and LABL to HA. cSAgAPLP:LABL exhibited significantly enhanced in vivo efficacy compared to hydrolyzable SAgAPLP:LABL. We found that cSAgAPLP:LABL acted through high avidity, antigen-specific B cell binding, targeting the B cell receptor (BCR) to dampen BCR-mediated signaling. Our conclusions point to induction of antigen-specific B cell anergy as the cSAgAPLP:LABL therapeutic mechanism and present a promising option for ASIT.