Engineered Nanobodies To Induce and Visualize Antigen-Specific Tolerance in Rheumatoid Arthritis 2260631

Abstract Introduction Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by synovial inflammation, progressive joint destruction, and systemic complications. Current therapies are not curative and rely on systemic immunosuppression. This alleviates symptoms but leaves patients vulnerable to opportunistic infections and increased risk of certain cancers. RA pathogenesis is characterized by the loss of T cell tolerance and expansion of pathogenic B cells, both driven by the presentation of autoantigens by MHCII. Delivery of antigens to antigen presenting cells (APCs) under non-inflammatory conditions can impose tolerance., Methods: We present a novel strategy to selectively silence autoreactive T and B cell immune responses in a collagen-induced RA mouse model. We fused two immunodominant collagen-derived T and B cell epitopes and the corticosteroid dexamethasone to a single-domain antibody fragment (VHHMHCII) that targets APCs via their MHCII molecules. Results A single therapeutic administration of the trimodal construct halted disease progression and prevented paw swelling. Treated mice had significantly reduced pathogenic autoantibody titers against type II collagen, rheumatoid factor, and cyclic citrullinated peptide. Histological and immunohistochemical analyses revealed less fibrosis, necrosis, and edema, as well as diminished infiltration of macrophages and neutrophils. We confirmed improved cartilage preservation and reduced infiltration of pro-inflammatory T and myeloid cells. We further functionalized VHHMHCII with radioactive 89Zr. Positron emission tomography (PET) imaging employing radiolabeled VHHMHCII detected specific accumulation in secondary lymphoid organs and inflamed joints. Conclusion This suggests that the trimodal adduct acts in the inflamed joint and draining lymph nodes to impose peripheral tolerance. Engineered nanobodies to reestablish antigen-specific tolerance may provide a safer and more effective alternative to broad-spectrum immunosuppressive therapies for RA. Funding Source Rheumatology Research Foundation Topic Categories Classical and Non-Classical Antigen Presenting Cells (APC)