Low-dose interleukin-2 therapy in systemic lupus erythematosus

Preclinical characterization of MTX-101: a novel bispecific CD8 Treg modulator that restores CD8 Treg functions to suppress pathogenic T cells in autoimmune diseases

Introduction

Regulatory CD8 T cells (CD8 Treg) are responsible for the selective killing of self-reactive and pathogenic CD4 T cells. In autoimmune disease, CD8 Treg may accumulate in the peripheral blood but fail to control the expansion of pathogenic CD4 T cells that subsequently cause tissue destruction. This CD8 Treg dysfunction is due in part to the expression of inhibitory killer immunoglobulin-like receptors (KIR; KIR2DL isoforms [KIR2DL1, KIR2DL2, and KIR2DL3]); these molecules serve as autoimmune checkpoints and limit CD8 Treg activation.

Methods

Here we describe the pre-clinical characterization of MTX-101, a bispecific antibody targeting inhibitory KIR and CD8. Using human peripheral blood mononuculear cells (PBMC) derived from healthy donors and autoimmune patients, humanized mouse models, and human derived tissue organoids, we evaluated the molecular mechanisms and functional effects of MTX-101.

Results

By binding to KIR, MTX-101 inhibited KIR signaling that can restore CD8 Treg ability to eliminate pathogenic CD4 T cells. MTX-101 bound and activated CD8 Treg in human peripheral blood mononuclear cells (PBMC), resulting in increased CD8 Treg cytolytic capacity, activation, and prevalence. Enhancing CD8 Treg function with MTX-101 reduced pathogenic CD4 T cell expansion and inflammation, without increasing pro-inflammatory cytokines or activating immune cells that express either target alone. MTX-101 reduced antigen induced epithelial cell death in disease affected tissues, including in tissue biopsies from individuals with autoimmune disease (i.e., celiac disease, Crohn's disease). The effects of MTX-101 were specific to autoreactive CD4 T cells and did not suppress responses to viral and bacterial antigens. In a human PBMC engrafted Graft versus Host Disease (GvHD) mouse model of acute inflammation, MTX-101 bound CD8 Treg and delayed onset of disease. MTX-101 induced dose dependent binding, increased prevalence and cytolytic capacity of CD8 Treg, as well as increased CD4 T cell death. MTX-101 selectively bound CD8 Treg without unwanted immune cell activation or increase of pro-inflammatory serum cytokines and exhibited an antibody-like half-life in pharmacokinetic and exploratory tolerability studies performed using IL-15 transgenic humanized mice with engrafted human lymphocytes, including CD8 Treg at physiologic ratios.

Conclusion

Collectively, these data support the development of MTX-101 for the treatment of autoimmune diseases.

Cutting Edge: Low-dose Recombinant IL-2 Treatment Prevents Autoantibody Responses in Systemic Lupus Erythematosus via Regulatory T Cell-independent Depletion of T Follicular Helper Cells

The expansion of T follicular helper (Tfh) cells correlates with disease progression in human and murine systemic lupus erythematosus (SLE). Unfortunately, there are no therapies to deplete Tfh cells. Importantly, low-dose rIL-2-based immunotherapy shows potent immunosuppressive effects in SLE patients and lupus-prone mice, primarily attributed to the expansion of regulatory T cells (Tregs). However, IL-2 can also inhibit Tfh cell differentiation. In this study, we investigate the potential of low-dose rIL-2 to deplete Tfh cells and prevent autoantibody responses in SLE. Our data demonstrate that low-dose rIL-2 efficiently depletes autoreactive Tfh cells and prevents autoantibody responses in lupus-prone mice. Importantly, this immunosuppressive effect was independent of the presence of Tregs. The therapeutic potential of eliminating Tfh cells was confirmed by selectively deleting Tfh cells in lupus-prone mice. Our findings demonstrate the critical role of Tfh cells in promoting autoantibody responses and unveil, (to our knowledge), a novel Treg-independent immunosuppressive function of IL-2 in SLE.

Nanoparticles loaded with IL-2 and TGF-β promote transplantation tolerance to alloantigen

We have previously reported that nanoparticles (NPs) loaded with IL-2 and TGF-β and targeted to T cells induced polyclonal T regulatory cells (Tregs) that protected mice from graft-versus-host disease (GvHD). Here, we evaluated whether administration of these NPs during alloantigen immunization could prevent allograft rejection by converting immunogenic responses to tolerogenic ones. Using C57BL/6 mice and BALB/c mice as either donors or recipients of allogeneic splenocytes, we found that treatment with the tolerogenic NPs in both strains of mice resulted in a marked inhibition of mixed lymphocyte reaction (MLR) to donor cell alloantigen but not to third-party control mouse cells after transfer of the allogeneic cells. The decreased alloreactivity associated with a four- to fivefold increase in the number of CD4+ and CD8+ T regulatory cells (Tregs) and the acquisition of a tolerogenic phenotype by recipient dendritic cells (DCs) in NP-treated mice. As allogeneic cells persisted in NP-treated mice, these findings suggest that tolerogenic NPs can induce alloantigen-specific Tregs and tolerogenic DCs promoting tolerogenic responses to alloantigen. By inhibiting reactivity to allotransplant, this approach could help reduce the need for immune suppression for the maintenance of allografts.

Novel therapeutic strategies targeting abnormal T-cell signaling in systemic lupus erythematosus

Therapeutic strategies for autoimmune diseases have been based on the use of glucocorticoids and immunosuppressive agents that broadly suppress immune responses. Therefore, organ damage from long-term use and infections due to immunocompromised status have been significant issues. Safer immunosuppressants and biological agents are now available, but there is still an urgent need to develop specific drugs to replace glucocorticoids. T-lymphocytes, central players in immune responses, could be crucial targets in the treatment of autoimmune diseases. Extensive research has been conducted on the phenotypic changes of T-cells in systemic lupus erythematosus, which has led to the discovery of various therapeutic strategies. In this comprehensive review, we discuss novel treatment approaches and target molecules with expected effectiveness in humans and mice, based on research for lymphocytes involved in autoimmune diseases, especially T-cells in SLE.