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

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.

RvD1 treatment during primary infection modulates memory response increasing viral load during respiratory viral reinfection.

Resolvin D1 (RvD1), which is biosynthesized from essential long-chain fatty acids, is involved in anti-inflammatory activity and modulation of T cell response. Memory CD8+ T cells are important for controlling tumor growth and viral infections. Exacerbated inflammation has been described as impairing memory CD8+ T cell differentiation. This study aimed to verify the effects of RvD1 on memory CD8+ T cells in vitro and in vivo in a respiratory virus infection model. Peripheral blood mononuclear cells were treated at different time points with RvD1 and stimulated with anti-CD3/anti-CD28 antibodies. Pre-treatment with RvD1 increases the expansion of memory CD8+ T cells. The IL-12 level, a cytokine described to control memory CD8+ T cells, was reduced with RvD1 pre-treatment. When the mTOR axis was inhibited, the IL-12 levels were restored. In a respiratory virus infection model, Balb/c mice were treated with RvD1 before infection or after 7 days after infection. RvD1 treatment after infection increased the frequency of memory CD8+ T cells in the lung expressing II4, II10, and Ifng. During reinfection, RvD1-treated and RSV-infected mice present a high viral load in the lung and lower antibody response in the serum. Our results show that RvD1 modulates the expansion and phenotype of memory CD8+ T cells but contributed to a non-protective response after RSV reinfection.

PD-L1:CD80 Cis-Heterodimer Triggers the Co-stimulatory Receptor CD28 While Repressing the Inhibitory PD-1 and CTLA-4 Pathways.

Combined immunotherapy targeting the immune checkpoint receptors cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and programmed cell death 1 (PD-1), or CTLA-4 and the PD-1 ligand (PD-L1) exhibits superior anti-tumor responses compared with single-agent therapy. Here, we examined the molecular basis for this synergy. Using reconstitution assays with fluorescence readouts, we found that PD-L1 and the CTLA-4 ligand CD80 heterodimerize in cis but not trans. Quantitative biochemistry and cell biology assays revealed that PD-L1:CD80 cis-heterodimerization inhibited both PD-L1:PD-1 and CD80:CTLA-4 interactions through distinct mechanisms but preserved the ability of CD80 to activate the T cell co-stimulatory receptor CD28. Furthermore, PD-L1 expression on antigen-presenting cells (APCs) prevented CTLA-4-mediated trans-endocytosis of CD80. Atezolizumab (anti-PD-L1), but not anti-PD-1, reduced cell surface expression of CD80 on APCs, and this effect was negated by co-blockade of CTLA-4 with ipilimumab (anti-CTLA-4). Thus, PD-L1 exerts an immunostimulatory effect by repressing the CTLA-4 axis; this has implications to the synergy of anti-PD-L1 and anti-CTLA-4 combination therapy.