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The release of soluble ligands of activating Natural Killer (NK) cell receptors may represent a regulatory mechanism of NK cell function both in physiologic and in pathologic conditions. Here, we identified the extracellular matrix protein Nidogen-1 (NID1) as a ligand of NKp44, an important activating receptor expressed by activated NK cells. When released as soluble molecule, NID1 regulates NK cell function by modulating NKp44-induced IFN-γ production or cytotoxicity. In particular, it also modulates IFN-γ production induced by Platelet-Derived Growth Factor (PDGF)-DD following NKp44 engagement. We also show that NID1 may be present at the cell surface. In this form or when bound to a solid support (bNID1), NID1 fails to induce NK cell cytotoxicity or cytokine release. However, analysis by mass spectrometry revealed that exposure to bNID1 can induce in human NK cells relevant changes in the proteomic profiles suggesting an effect on different biological processes.

Chimeric antigen receptor (CAR) T-cell therapy has been shown to be dramatically effective in the treatment of B-cell malignancies. However, there are still substantial obstacles to overcome, before similar responses can be achieved in patients with solid tumors. We evaluated both in vitro and in a preclinical murine model the efficacy of different 2nd and 3rd generation CAR constructs targeting GD2, a disial-ganglioside expressed on the surface of neuroblastoma (NB) tumor cells. In order to address potential safety concerns regarding clinical application, an inducible safety switch, namely inducible Caspase-9 (iC9), was also included in the vector constructs. Our data indicate that a 3rd generation CAR incorporating CD28.4-1BB costimulatory domains is associated with improved anti-tumor efficacy as compared with a CAR incorporating the combination of CD28.OX40 domains. We demonstrate that the choice of 4-1BB signaling results into significant amelioration of several CAR T-cell characteristics, including: 1) T-cell exhaustion, 2) basal T-cell activation, 3) in vivo tumor control and 4) T-cell persistence. The fine-tuning of T-cell culture conditions obtained using IL7 and IL15 was found to be synergic with the CAR.GD2 design in increasing the anti-tumor activity of CAR T cells. We also demonstrate that activation of the suicide gene iC9, included in our construct without significantly impairing neither CAR expression nor anti-tumor activity, leads to a prompt induction of apoptosis of GD2.CAR T cells. Altogether, these findings are instrumental in optimizing the function of CAR T-cell products to be employed in the treatment of children with NB.

We demonstrated that γδ T cells of patients given HLA-haploidentical HSCT after removal of αβ + T cells and CD19 + B cells are endowed with the capacity of killing leukemia cells after ex vivo treatment with zoledronic acid (ZOL). Thus, we tested the hypothesis that infusion of ZOL in patients receiving this type of graft may enhance γδ T-cell cytotoxic activity against leukemia cells. ZOL was infused every 28 d in 43 patients; most were treated at least twice. γδ T cells before and after ZOL treatments were studied in 33 of these 43 patients, till at least 7 mo after HSCT by high-resolution mass spectrometry, flow-cytometry, and degranulation assay. An induction of Vδ2-cell differentiation, paralleled by increased cytotoxicity of both Vδ1 and Vδ2 cells against primary leukemia blasts was associated with ZOL treatment. Cytotoxic activity was further increased in Vδ2 cells, but not in Vδ1 lymphocytes in those patients given more than one treatment. Proteomic analysis of γδ T cells purified from patients showed upregulation of proteins involved in activation processes and immune response, paralleled by downregulation of proteins involved in proliferation. Moreover, a proteomic signature was identified for each ZOL treatment. Patients given three or more ZOL infusions had a better probability of survival in comparison to those given one or two treatments (86% vs. 54%, respectively, p = 0.008). Our data indicate that ZOL infusion in pediatric recipients of αβ T- and B-cell-depleted HLA-haploidentical HSCT promotes γδ T-cell differentiation and cytotoxicity and may influence the outcome of patients.