A liposomal inverse vaccine protects mice from arthritis and experimental autoimmune encephalomyelitis

Chronic autoinflammatory diseases such as rheumatoid arthritis and multiple sclerosis lack curative therapies, and current immunosuppressive treatments often cause systemic off-target effects. To address this unmet need, we previously developed an "inverse vaccine" based on anionic phosphatidylglycerol liposomes carrying a disease-specific peptide antigen conjugated to dexamethasone. Here, we assess the therapeutic efficacy and immunomodulatory mechanisms of this platform in two murine models of autoimmunity. In the proteoglycan-induced arthritis model, a single administration of liposomal dexamethasone-human proteoglycan peptide (Dex-K4-hPG) markedly slowed arthritis progression compared to an equivalent dose of free Dex-K4-hPG. Long-term follow-up showed that two injections provided superior protection over a single dose, whereas a third injection yielded no additional benefit. Flow cytometry of paw draining lymph nodes revealed reduced RORγt⁺CD4⁺ T cells in mice receiving multiple doses indicating a shift toward less pro-inflammatory T-cell responses. Histological staining of the knees of mice also revealed less damage to the joints of mice receiving 2 or 3 injections of liposomes. To evaluate the versatility of this platform, we generated a novel Dex-peptide conjugate by replacing hPG for myelin oligodendrocyte glycoprotein (MOG). The resulting Dex-K4-MOG conjugate was encapsulated in the liposomes at high encapsulation efficiency (∼60%), demonstrating platform modularity. In an experimental autoimmune encephalomyelitis mouse model, two injections of Dex-K4-MOG liposomes (one before disease induction and one after) strongly suppressed disease development compared with controls. Together, these findings demonstrate that antigen-specific inverse vaccination using anionic liposomes offers a modular and broadly applicable strategy for inducing long-term protection in multiple autoimmune disease models. The platform elicits regulatory immune signatures and suppresses pathogenic Th17 responses, supporting its potential as a tolerogenic therapeutic approach.