Condensate enabled delivery of Fas and IL-2 receptor agonists promotes T regulatory responses to alloantigens.

Abstract

FasL and IL-2 regulate two critical signaling pathways that are essential for maintaining immune homeostasis and tolerance to self-antigens. Combined use of these molecules has significant translational potential in autoimmune diseases and transplantation. However, systemic administration of these molecules is limited by rapid clearance and potential off-target effects that can cause adverse effects. To address these limitations, we herein established an injectable, biodegradable, lipid-encapsulated condensate (LipCon) platform for sustained delivery of a novel form of FasL (SA-FasL) and IL-2 to modulate alloreactive immune responses toward regulation. This dual-delivery platform combines two complementary immunomodulatory mechanisms to promote targeted immunomodulation: where SA-FasL induces apoptosis in activated T effectors (Teffs) and IL-2 drives the expansion of regulatory T cells (Tregs). LipCon showed 99% loading efficiency for IL-2 and 65% for SA-FasL. Both proteins demonstrated sustained in vitro release over a 30-day observation period. IL-2 retained full activity throughout, whereas SA-FasL activity declined by approximately 86% by day 6. In vivo, IL-2 showed sustained release with a half-life of ∼7 days, whereas SA-FasL showed rapid loss within ∼1 day, without evidence of acute toxicity. Importantly, LipCon-mediated co-delivery of IL-2 and SA-FasL significantly reduced the frequency of T effector cells (Teffs), while increasing T regulatory cells (Tregs), thereby shifting Teff/Treg balance toward immune regulation. Collectively, these findings establish LipCon as a versatile platform having robust IL-2 retention with transient SA-FasL bioavailability showing early immunomodulatory activity and significant translational potential.