A humanized IL-2 mutein expands Tregs and prolongs transplant survival in preclinical models
Orhan Efe, … , Thiago J. Borges, Leonardo V. Riella
Orhan Efe, … , Thiago J. Borges, Leonardo V. Riella
Published March 1, 2024
Citation Information: J Clin Invest. 2024;134(5):e173107. https://doi.org/10.1172/JCI173107.
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Research Article Immunology

A humanized IL-2 mutein expands Tregs and prolongs transplant survival in preclinical models

Abstract

Long-term organ transplant survival remains suboptimal, and life-long immunosuppression predisposes transplant recipients to an increased risk of infection, malignancy, and kidney toxicity. Promoting the regulatory arm of the immune system by expanding Tregs may allow immunosuppression minimization and improve long-term graft outcomes. While low-dose IL-2 treatment can expand Tregs, it has a short half-life and off-target expansion of NK and effector T cells, limiting its clinical applicability. Here, we designed a humanized mutein IL-2 with high Treg selectivity and a prolonged half-life due to the fusion of an Fc domain, which we termed mIL-2. We showed selective and sustainable Treg expansion by mIL-2 in 2 murine models of skin transplantation. This expansion led to donor-specific tolerance through robust increases in polyclonal and antigen-specific Tregs, along with enhanced Treg-suppressive function. We also showed that Treg expansion by mIL-2 could overcome the failure of calcineurin inhibitors or costimulation blockade to prolong the survival of major-mismatched skin grafts. Validating its translational potential, mIL-2 induced a selective and sustainable in vivo Treg expansion in cynomolgus monkeys and showed selectivity for human Tregs in vitro and in a humanized mouse model. This work demonstrated that mIL-2 can enhance immune regulation and promote long-term allograft survival, potentially minimizing immunosuppression.

Authors

Orhan Efe, Rodrigo B. Gassen, Leela Morena, Yoshikazu Ganchiku, Ayman Al Jurdi, Isadora T. Lape, Pedro Ventura-Aguiar, Christian LeGuern, Joren C. Madsen, Zachary Shriver, Gregory J. Babcock, Thiago J. Borges, Leonardo V. Riella

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Figure 1

Structure of mIL-2 including its Fc domain and interactions of IL-2 with CD122 (IL-2Rβ).

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Structure of mIL-2 including its Fc domain and interactions of IL-2 with...
(A) Illustration of the structure of mIL-2 including the mutations to increase Treg selectivity and developability and the fusion of a modified human antibody Fc to increase its half-life. (B) Quaternary structure of WT IL-2 and its interaction with the IL-2R by depiction of the electrostatic charges on the surface of CD122 (IL-2Rβ). IL-2 and CD132 (IL-2Rγ) molecules are shown in green and yellow, respectively. The electrostatic structure on the surface of CD122 is depicted by a red-to-blue color gradient representing a negative-to-positive charge gradient, respectively, while the white color represents a neutral charge or a hydrophobic surface. The H16 side chain of IL-2 undergoes protonation in the endosome due to acidic pH, and the positively charged H16 is expected to enhance the electrostatic interactions between IL-2 and CD122. (C) Quaternary structure of mIL-2 (H16L substitution) and its interaction with the IL-2R. The IL-2 surface residue H16L substitution is expected to have minimal impact on the secondary and tertiary structures of the IL-2 molecule since leucine also has a high α helix propensity. The H16L-IL-2 molecule is shown in green, and the receptors CD25 (IL2-Ra), CD122(IL2-Rβ) and CD132(IL-2Rγ) are shown in the semitransparent surface diagram in orange, cyan and yellow, respectively. The insert shows the molecular environment of the L16 residue of mIL-2, in which the hydrophobic side chain of L16 is proximal to the polar residues of CD122 (IL-2b), and this unfavorable molecular environment is responsible for the reduced affinity of mIL-2 for CD122 at physiological conditions. The reduced affinity of mIL-2 for CD122 in physiological conditions gives a better selectivity for CD25-expressing cells, whereas in the endosome, it enables enhanced recycling.