Disruption of IL-33 Signaling Limits Early CD8+ T Cell Effector Function Leading to Exhaustion in Murine Hemophagocytic Lymphohistiocytosis

Macrophage Activation Syndrome

Macrophage activation syndrome (MAS) is a state of immune hyperactivation that can result in life-threatening multisystem end-organ dysfunction. Often termed a "cytokine storm," MAS occurs among the rheumatic diseases most typically in Still's disease but also in systemic lupus erythematosus and Kawasaki disease. MAS can also accompany infection, malignancy, and inborn errors of immunity. This review provides a practical, evidence-based guide to the understanding, recognition, and management of MAS in children and adults, with a primary focus on MAS complicating Still's disease.

Phase I/II Study of Adaptive Manufactured Lentiviral Anti-CD20/Anti-CD19 Chimeric Antigen Receptor T Cells for Relapsed, Refractory Mantle Cell Lymphoma

PURPOSE

Mantle cell lymphoma (MCL) is an aggressive B-cell malignancy characterized by t(11;14) and bright CD20 expression. To improve outcomes from single targeted CD19 chimeric antigen receptor (CAR) T cells, we used dual targeted lentiviral anti-CD20/anti-CD19 (LV20.19) CAR T cells as part of a phase I/II clinical trial in relapsed, refractory (R/R) MCL (ClinicalTrials.gov identifier: NCT04186520).

METHODS

Patients with MCL who had failed two lines of therapy or relapsed post-transplant were eligible. LV20.19 CAR T cells were manufactured on-site via CliniMACS Prodigy using an adaptive 8- to 12-day process to optimize the final CAR product for increased numbers of naïve and stem-cell memory (SCM) like T cells.

RESULTS

Seventeen patients with R/R MCL received a single dose of LV20.19 CAR T cells at 2.5 × 106 cells/kg (phase I = three patients; phase II = 14 patients). The best overall response rate (ORR) was 100% (complete response [CR] = 88%; partial response = 12%) and the phase II efficacy threshold for day-90 CR rate was exceeded. Two patients have relapsed as of the data cutoff and neither the median progression-free survival nor overall survival has been reached with a median follow-up of 15.8 months. Ninety-four percent (n = 16) experienced cytokine release syndrome, all grade 1-2. Eighteen percent (n = 3) had immune effector cell-associated neurotoxicity syndrome in the first 28-days, two with reversible grade 3 toxicity. Three patients had nonrelapse mortality events; all occurred in the setting of ongoing B-cell aplasia. The final LV20.19 CAR products were enriched for higher percentages of T-SCM/T-naïve cells and most patients received CAR T cells within 8 days of apheresis.

CONCLUSION

In conclusion, we demonstrate that on-site adaptive manufactured LV20.19 CAR T cells are feasible, safe, and efficacious for R/R MCL with best ORR of 100%, a favorable safety profile, and few relapses to date.

IL-1 Family Blockade in Cytokine Storm Syndromes

Interleukin-1 is a prototypic proinflammatory cytokine that is elevated in cytokine storm syndromes (CSSs), such as secondary hemophagocytic lymphohistiocytosis (sHLH) and macrophage activation syndrome (MAS). IL-1 has many pleotropic and redundant roles in both innate and adaptive immune responses. Blockade of IL-1 with recombinant human interleukin-1 receptor antagonist has shown efficacy in treating CSS. Recently, an IL-1 family member, IL-18, has been demonstrated to be contributory to CSS in autoinflammatory conditions, such as in inflammasomopathies (e.g., NLRC4 mutations). Anecdotally, recombinant IL-18 binding protein can be of benefit in treating IL-18-driven CSS. Lastly, another IL-1 family member, IL-33, has been postulated to contribute to CSS in an animal model of disease. Targeting of IL-1 and related cytokines holds promise in treating a variety of CSS.

CXCL9 inhibition does not ameliorate disease in murine models of both primary and secondary hemophagocytic lymphohistiocytosis

Hemophagocytic Lymphohistiocytosis (HLH) is a group of disorders culminating in systemic inflammation and multi-organ failure with high incidence of hepatic dysfunction. Overproduction of IFN-γ is the main immunopathological driver in this disorder. Monokine induced by IFN-γ (CXCL9) serves as a biomarker for disease activity and response to treatment in this disorder. However, very little is understood about the actual functional role of CXCL9 in pathogenesis in HLH. In the current study, we sought to determine the role of CXCL9 in pathogenesis in murine models of both Familial HLH (prf1^-/-) and Toll Like Receptor (TLR) 9 repeated stimulation induced Macrophage Activation Syndrome (MAS), a form of secondary HLH. FHL and MAS were induced in both CXCL9 genetically deficient mice (cxcl9^-/-) and controls as well as using AMG487, a pharmacological antagonist of the CXCL9 receptor, CXCR3. Results showed that CXCL9 genetic deficiency did not improve disease parameters or hepatitis in both models. Consistent with genetic ablation of CXCL9, inhibition of its receptor, CXCR3, by AMG487 did not show any significant effects in the FHL model. Taken together, inhibition of CXCL9-CXCR3 interaction does not ameliorate HLH physiology in general, or hepatitis as a classical target organ of disease.

The alarmin interleukin-33 promotes the expansion and preserves the stemness of Tcf-1+ CD8+ T cells in chronic viral infection

T cell factor 1 (Tcf-1) expressing CD8⁺ T cells exhibit stem-like self-renewing capacity, rendering them key for immune defense against chronic viral infection and cancer. Yet, the signals that promote the formation and maintenance of these stem-like CD8⁺ T cells (CD8⁺SL) remain poorly defined. Studying CD8⁺ T cell differentiation in mice with chronic viral infection, we identified the alarmin interleukin-33 (IL-33) as pivotal for the expansion and stem-like functioning of CD8⁺SL as well as for virus control. IL-33 receptor (ST2)-deficient CD8⁺ T cells exhibited biased end differentiation and premature loss of Tcf-1. ST2-deficient CD8⁺SL responses were restored by blockade of type I interferon signaling, suggesting that IL-33 balances IFN-I effects to control CD8⁺SL formation in chronic infection. IL-33 signals broadly augmented chromatin accessibility in CD8⁺SL and determined these cells' re-expansion potential. Our study identifies the IL-33-ST2 axis as an important CD8⁺SL-promoting pathway in the context of chronic viral infection.

Familial hemophagocytic lymphohistiocytosis hepatitis is mediated by IFN-γ in a predominantly hepatic-intrinsic manner

Interferon gamma (IFN-γ) is the main cytokine driving organ dysfunction in Familial Hemophagocytic Lymphohistiocytosis (FHL). Blockade of IFN-γ pathway ameliorates FHL hepatitis, both in animal models and in humans with FHL. Hepatocytes are known to express IFN-γ receptor (IFN-γ-R). However, whether IFN-γ induced hepatitis in FHL is a lymphocyte or liver intrinsic response to the cytokine has yet to be elucidated. Using a IFNgR-/- bone marrow chimeric model, this study showed that non-hematopoietic IFN-γ response is critical for development of FHL hepatitis in LCMV-infected Prf1-/- mice. Lack of hepatic IFN-γ responsiveness results in reduced hepatitis as measured by hepatomegaly, alanine aminotransferase (ALT) levels and abrogated histologic endothelial inflammation. In addition, IFN-γ non-hematopoietic response was critical in activation of lymphocytes by soluble interleukin 2 receptor (sIL-2r) and recruitment of CD8+ effector T lymphocytes (CD8+ CD44hi CD62Llo) (Teff) and inflammatory monocytes. Lastly, non-hematopoietic IFN-γ response results in increased hepatic transcription of type 1 immune response and oxidative stress response pathways, while decreasing transcription of genes involved in extracellular matrix (ECM) production. In summary, these findings demonstrate that there is a hepatic transcriptional response to IFN-γ, likely critical in the pathogenesis of FHL hepatitis and hepatic specific responses could be a therapeutic target in this disorder.

Understanding of cytokines and targeted therapy in macrophage activation syndrome

Macrophage activation syndrome (MAS) is a potentially life-threatening complication of systemic autoinflammatory/autoimmune diseases, generally systemic juvenile idiopathic arthritis and adult-onset Still's disease. It is characterized by an excessive proliferation of macrophages and T lymphocytes. Recent research revealed that cytokine storm with elevated pro-inflammatory cytokines, including IFN-γ, IL-18, and IL-6, may be central to the pathogenesis of MAS. Though the mainstream of MAS treatment remains corticosteroids and cyclosporine, targeted therapies with anti-cytokine biologics are reported to be promising for controlling systemic inflammation in MAS.

Highways to hell: Mechanism-based management of cytokine storm syndromes

Since the first textbook devoted to cytokine storm syndromes (CSSs) was published in 2019, the world has changed dramatically and the term’s visibility has broadened. Herein, we define CSSs broadly to include life/organ-threatening systemic inflammation and immunopathology regardless of the context in which it occurs, recognizing that the indistinct borders of such a definition limit its utility. Nevertheless, we are focused on the pathomechanisms leading to CSSs, including impairment of granule-mediated cytotoxicity, specific viral infections, excess IL-18, and chimeric antigen receptor T-cell therapy. These mechanisms are often reflected in distinct clinical features, functional tests, and/or biomarker assessments. Moreover, these mechanisms often indicate specific, definitive treatments. This mechanism-focused organization is vital to both advancing the field and understanding the complexities in individual patients. However, increasing evidence suggests that these mechanisms interact and overlap. Likewise, the utility of a broad term such as “cytokine storm” is that it reflects a convergence on a systemic inflammatory phenotype that, regardless of cause or context, may be amenable to “inflammo-stabilization.” CSS research must improve our appreciation of its various mechanisms and their interactions and treatments, but it must also identify the signs and interventions that may broadly prevent CSS-induced immunopathology.