DEVELOPMENT OF A HUMANISED DELIVERY SYSTEM FOR INTERLEUKIN 2 TO TREAT TRAUMATIC BRAIN INJURY

Neuroinflammation is a major driver of secondary injury and long-term neurological sequelae following traumatic brain injury (TBI). While inflammatory responses are essential for initiation of repair, dysregulated immune activity within the central nervous system (CNS) promotes sustained glial activation, tissue damage, and impaired recovery. Regulatory T cells (Tregs) are critical modulators of immune homeostasis and have emerged as key regulators of neuroinflammatory processes after CNS injury. However, endogenous expansion of Tregs within the CNS is constrained by low local availability of interleukin-2 (IL-2), a cytokine that is indispensable for Treg survival, stability, and suppressive function.
Across a series of studies, we developed a CNS-targeted, humanised AAV9 gene delivery platform designed to enhance local IL-2 availability specifically at sites of neuroinflammation. The vector selectively targets astrocytes to secrete a human IL-2 mutein engineered to preferentially support Treg expansion while minimising activation of pro-inflammatory immune populations. To further enhance therapeutic precision, IL-2 expression is under pharmacological control using a minocycline-inducible system, enabling temporal regulation of biologic activity. Flow cytometric analyses demonstrate robust and selective expansion of brain-resident Tregs, with the IL-2 mutein achieving significantly greater enrichment than wild-type IL-2 (mean 35% vs. 28% of CD4⁺ T cells; AAV9.GFP controls 9%; at 1×10¹⁰ vg/mouse). Consistent with enhanced bioactivity, the mutein also increased IL-2 production within the brain (1 pg/ml vs. 0.5 pg/ml; at 1×10¹⁰ vg/mouse).
Together, these data support a CNS-targeted, regulatable IL-2 gene delivery approach to expand brain-resident Tregs and modulate neuroinflammation after injury.