Phase II clinical trial of adoptive cell therapy for patients with metastatic melanoma with autologous tumor-infiltrating lymphocytes and low-dose interleukin-2.

Adoptive cell therapy using autologous tumor-infiltrating lymphocytes (TIL) has shown significant clinical benefit, but is limited by toxicities due to a requirement for post-infusion interleukin-2 (IL-2), for which high dose is standard. To assess a modified TIL protocol using lower dose IL-2, we performed a single institution phase II protocol in unresectable, metastatic melanoma. The primary endpoint was response rate. Secondary endpoints were safety and assessment of immune correlates following TIL infusion. Twelve metastatic melanoma patients were treated with non-myeloablative lymphodepleting chemotherapy, TIL, and low-dose subcutaneous IL-2 (125,000 IU/kg/day, maximum 9-10 doses over 2 weeks). All but one patient had previously progressed after treatment with immune checkpoint inhibitors. No unexpected adverse events were observed, and patients received an average of 6.8 doses of IL-2. By RECIST v1.1, two patients experienced a partial response, one patient had an unconfirmed partial response, and six had stable disease. Biomarker assessment confirmed an increase in IL-15 levels following lymphodepleting chemotherapy as expected and a lack of peripheral regulatory T-cell expansion following protocol treatment. Interrogation of the TIL infusion product and monitoring of the peripheral blood following infusion suggested engraftment of TIL. In one responding patient, a population of T cells expressing a T-cell receptor Vß chain that was dominant in the infusion product was present at a high percentage in peripheral blood more than 2 years after TIL infusion. This study shows that this protocol of low-dose IL-2 following adoptive cell transfer of TIL is feasible and clinically active. (ClinicalTrials.gov identifier NCT01883323.).

Inflammation rapidly reorganizes mouse bone marrow B cells and their environment in conjunction with early IgM responses.

Systemic inflammation perturbs the bone marrow environment by evicting resident B cells and favoring granulopoiesis over lymphopoiesis. Despite these conditions, a subset of marrow B cell remains to become activated and produce potent acute immunoglobulin M (IgM) responses. This discrepancy is currently unresolved and a complete characterization of early perturbations in the B-cell niche has not been undertaken. Here, we show that within a few hours of challenging mice with adjuvant or cecal puncture, B cells accumulate in the bone marrow redistributed away from sinusoid vessels. This response correlates with enhanced sensitivity to CXC chemokine ligand 12 (CXCL12) but not CXCL13 or CC chemokine ligand 21. Concurrently, a number of B-cell survival and differentiation factors are elevated to produce a transiently supportive milieu. Disrupting homing dynamics with a CXC chemokine receptor 4 inhibitor reduced the formation of IgM-secreting cells. These data highlight the rapidity with which peripheral inflammation modifies the marrow compartment, and demonstrate that such modifications regulate acute IgM production within this organ. Furthermore, our study indicates that conversion to a state of emergency granulopoiesis is temporally delayed, allowing B cells opportunity to respond to antigen.

CD4+ T cell plasticity engenders robust immunity in response to cytokine therapy.

CD4+ T cells represent an entire arm of the immune system that has hitherto been incompletely understood, but their potential to act as both helper and effector may make them optimal protagonists in immunotherapeutic approaches to treat cancer. Cytokine therapy can activate this population in a manner that ensures maximal diversification of effector function for a robust immune response.

Murine splenic CD4⁺ T cells, induced by innate immune cell interactions and secreted factors, develop antileukemia cytotoxicity.

Inciting the cellular arm of adaptive immunity has been the fundamental goal of cancer immunotherapy strategies, specifically focusing on inducing tumor antigen-specific responses by CD8(+) cytotoxic T lymphocytes (CTL). However, there is an emerging appreciation that the cytotoxic function of CD4(+) T cells can be effective in a clinical setting. Harnessing this potential will require an understanding of how such cells arise. In this study, we use an IL12-transduced variant of the 70Z/3 leukemia cell line in a B6D2F1 (BDF1) murine model system to reveal a novel cascade of cells and soluble factors that activate anticancer CD4(+) killer cells. We show that natural killer T cells play a pivotal role by activating dendritic cells in a contact-dependent manner; soluble products of this interaction, including MCP-1, propagate the activation signal, culminating in the development of CD4(+) CTLs that directly mediate an antileukemia response while also orchestrating a multipronged attack by other effector cells. A more complete picture of the conditions that induce such a robust response will allow us to capitalize on CD4(+) T-cell plasticity for maximum therapeutic effect.

IL-12 immunotherapy of murine leukaemia: comparison of systemic versus gene modified cell therapy.

The ability of IL-12 to initiate anti-leukaemia immune responses has been well established; however clinical outcomes fail to recapitulate the therapeutic benefits observed in the laboratory. To address this, we compared two systems of IL-12 therapy that elicit protective immune responses against the murine acute lymphoblastic leukaemia (ALL) cell line, 70Z/3. These systems differ in the method of IL-12 administration and ultimately result in leukaemia clearance by distinct mechanisms, emphasizing the importance of treatment vehicle. Injecting low-dose IL-12 was sufficient to elicit long-term protective immunity against an established leukaemia burden, mediated by both CD4(+) and CD8(+) T cells. These findings agree with the standard model of IL-12 activity. We compared this protocol to a cell-based approach in which a novel lentiviral vector (LV) expressing murine IL-12 was created, 70Z/3 cells transduced, and clones selected that stably secrete different amounts of IL-12. We found that only a small proportion (1%) of IL-12 secreting cells were required for rejection but that the amount of IL-12 produced per cell was critical for successful therapy. Importantly, the levels of IL-12 required were found to be higher than the levels reported to date in the human clinical trial literature. We found that the cell-based approach led to protective immunity that was both long-term and specific but dependent primarily on a CD4(+) cellular subset alone. Our results highlight that the mode of IL-12 delivery has a distinct impact on the immune response initiated, leading to leukaemia clearance by disparate mechanisms. We also establish a new and critical parameter, IL-12 production/cell, which may have significant implications for future therapeutic design.