Anti-4-1BB-based immunotherapy for autoimmune diabetes: lessons from a transgenic non-obese diabetic (NOD) model

Various therapeutic strategies have been developed to tolerize autoreactive T cells and prevent autoimmune pathology in type 1 diabetes. 4-1BB, a member of the tumor necrosis factor receptor (TNFR) superfamily, is a costimulatory receptor primarily expressed on activated T cells. The administration of an agonistic anti-4-1BB antibody (2A) dramatically reduced the incidence and severity of experimental autoimmune encephalomyelitis (EAE). Treatment with the same antibody in Fas-deficient MRL/lpr mice blocked lymphadenopathy and lupus-like autoimmune processes. Paradoxically, transgenic non-obese diabetic (NOD) mice overexpressing membrane-bound agonistic single-chain anti-4-1BB Fv in pancreatic beta cells developed more severe diabetes than their non-transgenic littermates, with earlier onset, faster diabetic processes, and higher mortality. Forty percent of transgenic mice developed diabetes by 4 weeks of age, compared with their control littermates, which first exhibited diabetes at 14 weeks. The frequency of diabetes in female transgenics reached 70% by 8 weeks of age. Most female transgenic mice died around 12 weeks. Consistent with this, transgenic mice developed earlier and more severe insulitis and showed stronger GAD-specific T-cell responses, compared with age-matched control littermates. Our results indicate an adverse effect of transgenic anti-4-1BB scFv in NOD mice and suggest a potential risk of this anti-4-1BB-based immunotherapy for autoimmune diseases.