Decoding Antigen-specific Tolerance Mechanisms Imposed by an MHC-II targeted Nanobody-based Therapy for Multiple Sclerosis 2331736

Abstract Introduction We developed a therapy to induce antigen-specific tolerance in multiple sclerosis (MS). The MS therapy involves an antibody fragment, called a nanobody, that recognizes class II major histocompatibility complex antigens (VHHMHCII), conjugated to a myelin oligodendrocyte glycoprotein (MOG) peptide. MHC II is expressed by antigen presenting cells (APCs). When antigen presenting cells encounter antigen under non-inflammatory conditions, they are tolerogenic. Therefore, if MS-associated peptides are delivered to APCs, antigen-specific tolerance should be induced. The lab has demonstrated that a single dose of VHHMHCII-MOG provides enduring protection from induction of experimental autoimmune encephalitis (EAE). When VHHMHCII-MOG was conjugated to dexamethasone, a small molecule anti-inflammatory drug, this trimodal construct (VHHMHCII-MOG-DEX) effectively halted and reversed the severity of EAE. We are now investigating the mechanisms that explain the efficacy of this therapy. One major aim is to understand the therapeutic’s influence on the interaction between T-cells and APCs. Methods Using maleimide-thiol click chemistry and the theory of uLIPSTIC (universal labelling of immune partnerships by SorTagging intercellular contacts), we developed an ex-vivo strategy to look at immune cell interactions. Results Maleimide-thiol click chemistry can be used to label proteins at the cells surface, including T-cells which are functional post-labeling. We were able to monitor T-cell interactions with antigen-presenting cells ex vivo. We determined that LysM+ cells (e.g. macrophages) interact with MOG-specific T cells after incubation with VHHMHCII-MOG-DEX. Conclusion We will continue by investigating the interactions of antigen-specific T-cells with other APCs including dendritic cells and B-cells. Elucidating the treatment’s mechanism of action will enable further modification and improvement of MS treatments, and translation to other autoimmune diseases. Funding Source National Multiple Sclerosis Society Topic Categories Therapeutic Approaches to Autoimmunity (THER)