Orcutt-Jahns et al. profiled the signaling specificity effects of 13 engineered cytokine variations, including cytokines with affinity-altering mutations and different Fc-fusion formats. Using a multivalent binding model, they found that Fc fusion valency was an important factor in cell-type specificity, and that the effect of cytokine multivalency was based on altered surface receptor binding avidity, with higher valency formats predicted to confer greater specify towards certain immune cell types. This analysis was validated with the design of two tetravalent IL-2 muteins, in both symmetric and asymmetric formats, with biased avidity and enhanced Treg signaling selectivity.
Contributed by Lauren Hitchings
ABSTRACT: The cytokine interleukin-2 (IL-2) has the potential to treat autoimmune disease but is limited by its modest specificity toward immunosuppressive regulatory T (Treg) cells. IL-2 receptors consist of combinations of α, β, and γ chains of variable affinity and cell specificity. Engineering IL-2 to treat autoimmunity has primarily focused on retaining binding to the relatively Treg-selective, high-affinity receptor while reducing binding to the less selective, low-affinity receptor. However, we found that refining the designs to focus on targeting the high-affinity receptor through avidity effects is key to optimizing Treg selectivity. We profiled the dynamics and dose dependency of signaling responses in primary human immune cells induced by engineered fusions composed of either wild-type IL-2 or mutant forms with altered affinity, valency, and fusion to the antibody Fc region for stability. Treg selectivity and signaling response variations were explained by a model of multivalent binding and dimer-enhanced avidity-a combined measure of the strength, number, and conformation of interaction sites-from which we designed tetravalent IL-2-Fc fusions that had greater Treg selectivity in culture than do current designs. Biasing avidity toward IL2Rα with an asymmetrical multivalent design consisting of one α/β chain-binding and one α chain-binding mutant further enhanced Treg selectivity. Comparative analysis revealed that IL2Rα was the optimal cell surface target for Treg selectivity, indicating that avidity for IL2Rα may be the optimal route to producing IL-2 variants that selectively target Tregs.
Author Info: (1) Department of Bioengineering, University of California, Los Angeles, Los Angeles, CA 90095, USA. (2) Department of Bioengineering, University of California, Los Angeles, Los An
Author Info: (1) Department of Bioengineering, University of California, Los Angeles, Los Angeles, CA 90095, USA. (2) Department of Bioengineering, University of California, Los Angeles, Los Angeles, CA 90095, USA. (3) Department of Bioengineering, University of California, Los Angeles, Los Angeles, CA 90095, USA. (4) Department of Bioengineering, University of California, Los Angeles, Los Angeles, CA 90095, USA. (5) Department of Bioengineering, University of California, Los Angeles, Los Angeles, CA 90095, USA. Jonsson Comprehensive Cancer Center, University of California, Los Angeles, Los Angeles, CA 90095, USA. Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California, Los Angeles, Los Angeles, CA 90095, USA.
