Treatment of multiple sclerosis with peptide-coupled red blood cells induces antigen-specific T regulatory cells

Inducing antigen-specific immune tolerance is a long-standing aim in organ-specific autoimmune diseases including multiple sclerosis (MS). We developed a therapy based on autologous red blood cells (RBCs) as tolerizing carriers of autoantigens and tested these in an open-label, dose-escalation, phase Ib clinical trial with clinical, imaging, and mechanistic readouts. RBCs coupled with seven immunodominant myelin peptides (pcRBCs) were safe and well tolerated. Several clinical and imaging readouts remained stable, which was supported by a reduction of neurofilament light chain indicating reduced tissue inflammation in the brain. Single-cell RNA sequencing identified expansion of antigen-specific CD4+ memory T cells with regulatory phenotypes and loss of proinflammatory cells three months after a single administration of pcRBCs. This was corroborated by a reduction of autoreactive CD4+ T cell responses and an early increase of IL-10, Tr1 regulatory T cells and tolerogenic monocytes and plasmacytoid dendritic cells. Biodistribution studies in mice and humans demonstrate that pcRBCs are rapidly processed by Kupffer cells in the liver and by marginal zone macrophages in the spleen. In summary, pcRBCs are a promising autologous cell therapy for achieving antigen-specific immune tolerance in MS.