The spectrum of subclonal TP53 mutations in chronic lymphocytic leukemia: A next generation sequencing retrospective study.

Chronic lymphocytic leukemia (CLL) is a hematological disorder with complex clinical and biological behavior. TP53 mutational status and cytogenetic assessment of the deletion of the corresponding locus (17p13.1) are considered the most relevant biomarkers associated with pharmaco-predictive response, chemo-refractoriness, and worse prognosis in CLL patients. The implementation of Next Generation Sequencing (NGS) methodologies in the clinical laboratory allows for comprehensively analyzing the TP53 gene and detecting mutations with allele frequencies ≤10%, that is, "subclonal mutations". We retrospectively studied TP53 gene mutational status by NGS in 220 samples from 171 CLL patients. TP53 mutations were found in 60/220 (27.3%) samples and 47/171 (27.5%) patients. Interestingly, subclonal mutations could be detected in 31/60 samples (51.7%) corresponding to 25 patients (25/47, 53.2%). We identified 44 distinct subclonal TP53 mutations clustered in the central DNA-binding domain of p53 protein (exons 5-8, codons 133-286). Missense mutations were predominant (>80%), whereas indels, nonsense, and splice site variants were less represented. All subclonal TP53 variants but one [p.(Pro191fs)] were already described in NCI and/or Seshat databases as "damaging" and/or "probably damaging" mutations (38/44, 86% and 6/44, 14%, respectively). Longitudinal samples were available for 37 patients. Almost half of them displayed at least one TP53 mutant subclone, which could be alone (4/16, 25%) or concomitant with other TP53 mutant clonal ones (12/16, 75%); different patterns of mutational dynamics overtimes were documented. In conclusion, utilization of NGS in our "real-life" cohort of CLL patients demonstrated an elevated frequency of subclonal TP53 mutations. This finding indicates the need for precisely identifying these mutations during disease since the clones carrying them may become predominant and be responsible for therapy failures.

L19-IL2 Immunocytokine in Combination with the Anti-Syndecan-1 46F2SIP Antibody Format: A New Targeted Treatment Approach in an Ovarian Carcinoma Model.

Epithelial ovarian cancer (EOC) is the fifth most common cancer affecting the female population. At present, different targeted treatment approaches may improve currently employed therapies leading either to the delay of tumor recurrence or to disease stabilization. In this study we show that syndecan-1 (SDC1) and tumor angiogenic-associated B-fibronectin isoform (B-FN) are involved in EOC progression and we describe the prominent role of SDC1 in the vasculogenic mimicry (VM) process. We also investigate a possible employment of L19-IL2, an immunocytokine specific for B-FN, and anti-SDC1 46F2SIP (small immuno protein) antibody in combination therapy in a human ovarian carcinoma model. A tumor growth reduction of 78% was obtained in the 46F2SIP/L19-IL2-treated group compared to the control group. We observed that combined treatment was effective in modulation of epithelial-mesenchymal transition (EMT) markers, loss of stemness properties of tumor cells, and in alleviating hypoxia. These effects correlated with reduction of VM structures in tumors from treated mice. Interestingly, the improved pericyte coverage in vascular structures suggested that combined therapy could be efficacious in induction of vessel normalization. These data could pave the way for a possible use of L19-IL2 combined with 46F2SIP antibody as a novel therapeutic strategy in EOC.

Mesenchymal Stromal Cells Induce Peculiar Alternatively Activated Macrophages Capable of Dampening Both Innate and Adaptive Immune Responses.

Mesenchymal stromal cells (MSCs) support hematopoiesis and exert immunoregulatory activities. Here, we analyzed the functional outcome of the interactions between MSCs and monocytes/macrophages. We showed that MSCs supported the survival of monocytes that underwent differentiation into macrophages, in the presence of macrophage colony-stimulating factor. However, MSCs skewed their polarization toward a peculiar M2-like functional phenotype (M(MSC) ), through a prostaglandin E2-dependent mechanism. M(MSC) were characterized by high expression of scavenger receptors, increased phagocytic capacity, and high production of interleukin (IL)-10 and transforming growth factor-ß. These cytokines contributed to the immunoregulatory properties of M(MSC) , which differed from those of typical IL-4-induced macrophages (M2). In particular, interacting with activated natural killer (NK) cells, M(MSC) inhibited both the expression of activating molecules such as NKp44, CD69, and CD25 and the production of IFNγ, while M2 affected only IFNγ production. Moreover, M(MSC) inhibited the proliferation of CD8(+) T cells in response to allogeneic stimuli and induced the expansion of regulatory T cells (Tregs). Toll-like receptor engagement reverted the phenotypic and functional features of M(MSC) to those of M1 immunostimulatory/proinflammatory macrophages. Overall our data show that MSCs induce the generation of a novel type of alternatively activated macrophages capable of suppressing both innate and adaptive immune responses. These findings may help to better understand the role of MSCs in healthy tissues and inflammatory diseases including cancer, and provide clues for novel therapeutic approaches. Stem Cells 2016;34:1909-1921.

Targeting Syndecan-1, a molecule implicated in the process of vasculogenic mimicry, enhances the therapeutic efficacy of the L19-IL2 immunocytokine in human melanoma xenografts.

Anti-angiogenic therapy of solid tumors has until now failed to produce the long lasting clinical benefits desired, possibly due to the complexity of the neoangiogenic process. Indeed, a prominent role is played by "vasculogenic" or "vascular" mimicry (VM), a phenomenon in which aggressive cancer cells form an alternative microvascular circulation, independently of endothelial cell angiogenesis. In this study we observed, in melanoma patient cell lines having vasculogenic/stem-cell like phenotype and in melanoma tumors, the syndecan-1 co-expression with VM markers, such as CD144 and VEGFR-2. We show that melanoma cells lose their ability to form tubule-like structures in vitro after blocking syndecan-1 activity by the specific human recombinant antibody, OC-46F2. Moreover, in a human melanoma xenograft model, the combined therapy using OC-46F2 and L19-IL2, an immunocytokine specific for the tumor angiogenic-associated B-fibronectin isoform(B-FN), led to a complete inhibition of tumor growth until day 90 from tumor implantation in 71% of treated mice, with statistically significant differences compared to groups treated with OC-46F2 or L19-IL2 as monotherapy. Furthermore, in the tumors recovered from mice treated with OC-46F2 either as monotherapy or in combination with L19-IL2, we observed a dramatic decrease of vascular density and loss of VM structures. These findings indicate for the first time a role of syndecan-1 in melanoma VM and that targeting syndecan-1, together with B-FN, could be promising in improving the treatment of metastatic melanoma.

NCR(+)ILC3 concentrate in human lung cancer and associate with intratumoral lymphoid structures.

Tertiary lymphoid structures (TLSs) are a common finding in non-small cell lung cancer (NSCLC) and are predictors of favourable clinical outcome. Here we show that NCR(+) innate lymphoid cell (ILC)-3 are present in the lymphoid infiltrate of human NSCLC and are mainly localized at the edge of tumour-associated TLSs. This intra-tumoral lymphocyte subset is endowed with lymphoid tissue-inducing properties and, on activation, produces IL-22, TNF-α, IL-8 and IL-2, and activates endothelial cells. Tumour NCR(+)ILC3 may interact with both lung tumour cells and tumour-associated fibroblasts, resulting in the release of cytokines primarily on engagement of the NKp44-activating receptor. In patients, NCR(+)ILC3 are present in significantly higher amounts in stage I/II NSCLC than in more advanced tumour stages and their presence correlate with the density of intratumoral TLSs. Our results indicate that NCR(+)ILC3 accumulate in human NSCLC tissue and might contribute to the formation of protective tumour-associated TLSs.

IL-1ß inhibits ILC3 while favoring NK-cell maturation of umbilical cord blood CD34(+) precursors.

NK cells are innate lymphocytes characterized by the expression of nuclear factor interleukin 3 regulated (NFIL3 or E4BP4), eomesodermin (EOMES) transcription factors (TFs), and by the ability to exert cytolytic activity and release IFN-γ. In the haploidentical-hematopoietic stem cell transplantation (haplo-HSCT) setting, CD34(+) donor derived NK cells play a major role in the control of leukemic relapses. Therefore, it is important to better define cytokines that influence NK-cell differentiation from CD34(+) precursors. We analyzed the effects of IL-1ß on NK-cell differentiation from umbilical cord blood (UCB) CD34(+) cells. While IL-1ß inhibited CD161(+) CD56(+) cell proliferation, an increased expression of LFA-1, CD94/NKG2A, KIRs, and perforin on CD56(+) cells was detected. In addition, within the CD161(+) CD56(+) IL-1RI(+) LFA-1(-) cell fraction (representing group 3 innate lymphoid cells, ILC3-like cells), a significant increase of EOMES, NKp46, and CD94/NKG2A receptors, cytolytic granules, and IFN-γ was detected. This increase was paralleled by a decrease of related orphan receptors (RORγt) TF, NKp44 expression, and IL-22 production. These data suggest that IL-1ß inhibits ILC3- while favoring NK-cell maturation. Since in haplo-HSCT conditioning regimen, infections or residual leukemia cells may induce IL-1ß production, this may influence the NK/ILC3 development from donor-derived CD34(+) precursors.

Stromal cells from human decidua exert a strong inhibitory effect on NK cell function and dendritic cell differentiation.

Stromal cells (SC) are an important component of decidual tissues where they are in strict proximity with both NK and CD14(+) myelomonocytic cells that play a role in the maintenance of pregnancy. In this study we analyzed whether decidual SC (DSC) could exert a regulatory role on NK and CD14(+) cells that migrate from peripheral blood (PB) to decidua during pregnancy. We show that DSCs inhibit the IL15-mediated up-regulation of major activating NK receptors in PB-derived NK cells. In addition, the IL15-induced NK cell proliferation, cytolytic activity and IFN-γ production were severely impaired. DSCs sharply inhibited dendritic cells differentiation and their ability to induce allogeneic T cell proliferation. Indoleamine 2,3-dioxygenase (IDO) and prostaglandin E2 (PGE2) mediated the inhibitory effect of DSCs. Our results strongly suggest an important role of DSCs in preventing potentially dangerous immune response, thus contributing to maintenance of pregnancy.

Membrane transfer from tumor cells overcomes deficient phagocytic ability of plasmacytoid dendritic cells for the acquisition and presentation of tumor antigens.

The potential contribution of plasmacytoid dendritic cells (pDCs) in the presentation of tumor cell Ags remains unclear, and some controversies exist with regard to the ability of pDCs to phagocytose cell-derived particulate Ags and cross-present them to MHC class I-restricted T lymphocytes. In this study, we show that human pDCs, although inefficient in the internalization of cell membrane fragments by phagocytosis, can efficiently acquire membrane patches and associated molecules from cancer cells of different histotypes. The transfer of membrane patches to pDCs occurred in a very short time and required cell-to-cell contact. Membrane transfer also included intact HLA complexes, and the acquired Ags could be efficiently recognized on pDCs by tumor-specific CD8(+) T cells. Remarkably, pDCs isolated from human colon cancer tissues displayed a strong surface expression of epithelial cell adhesion molecule, indicating that the exchange of exogenous Ags between pDCs and tumor cells also can occur in vivo. These data demonstrate that pDCs are well suited to acquire membrane patches from contiguous tumor cells by a cell-to-cell contact-dependent mechanism that closely resembles "trogocytosis." This phenomenon may allow pDCs to proficiently present tumor cell-derived Ags, despite limited properties of endophagocytosis.

Characterization of human afferent lymph dendritic cells from seroma fluids.

Dendritic cells (DCs) migrate from peripheral tissues to secondary lymphoid organs (SLOs) through the afferent lymph. Owing to limitations in investigating human lymph, DCs flowing in afferent lymph have not been properly characterized in humans until now. In this study, DCs present in seroma, an accrual of human afferent lymph occurring after lymph node surgical dissection, were isolated and analyzed in detail. Two main DC subsets were identified in seroma that corresponded to the migratory DC subsets present in lymph nodes, that is, CD14(+) and CD1a(+). The latter also included CD1a(bright) Langerhans cells. The two DC subsets appeared to share the same monocytic precursor and to be developmentally related; both of them spontaneously released high levels of TGF-ß and displayed similar T cell-activating and -polarizing properties. In contrast, they differed in the expression of surface molecules, including TLRs; in their phagocytic activity; and in the expression of proteins involved in Ag processing and presentation. It is worth noting that although both subsets were detected in seroma in the postsurgical inflammatory phase, only CD1a(+) DCs migrated via afferent lymph under steady-state conditions. In conclusion, the high numbers of DCs contained in seroma fluids allowed a proper characterization of human DCs migrating via afferent lymph, revealing a continuous stream of DCs from peripheral regions toward SLOs under normal conditions. Moreover, we showed that, in inflammatory conditions, distinct subsets of DCs can migrate to SLOs via afferent lymph.

A novel human anti-syndecan-1 antibody inhibits vascular maturation and tumour growth in melanoma.

INTRODUCTION: Syndecan-1 is a cell membrane protein that, after its shedding by heparanase enzymes, is accumulated in the extracellular matrix of some tumours, e.g. myeloma and lung carcinoma, where it modulates several key processes of tumourigenesis such as cancer cell proliferation and apoptosis, angiogenesis and metastasis. Few studies have focused on syndecan-1 in malignant melanoma, a tumour for which new therapeutic targets are desperately needed. We aimed to investigate the role of syndecan-1 in melanoma and to evaluate the potential therapeutic efficacy of a novel fully human anti-syndecan-1 recombinant antibody in this deadly disease. METHODS: The OC-46F2 recombinant antibody was generated by selecting a human antibody phage display library on human melanoma cells and by its expression in mammalian cells. The specific antigen recognised by the antibody was identified by mass spectrometry. Murine models of human melanoma and ovarian carcinoma were used in the pre-clinical in vivo experiments. RESULTS: The fully human antibody OC-46F2, specific for the extracellular domain of syndecan-1, inhibited vascular maturation and tumour growth in an experimental human melanoma model. The therapeutic efficacy of this antibody was also demonstrated in an experimental ovarian carcinoma model. A co-distribution of syndecan-1 with vascular endothelial growth factor receptor 2 (VEGFR2) observed in the intratumour melanoma microenvironment was absent in the tumours from mice treated with OC-46F2 scFv. CONCLUSION: These findings highlight the role of syndecan-1 as a potential therapeutic target in melanoma and ovarian carcinoma and provide a new tool able to block vessel maturation, one of the mechanisms that underpin the angiogenic process essential for solid tumour growth.

Human NK cells at early stages of differentiation produce CXCL8 and express CD161 molecule that functions as an activating receptor.

Human natural killer (NK) cell development is a step-by-step process characterized by phenotypically identified stages. CD161 is a marker informative of the NK cell lineage commitment, whereas CD56, CD117, and CD94/NKG2A contribute to define discrete differentiation stages. In cells undergoing in vitro differentiation from CD34(+) umbilical cord blood (UCB) progenitors, LFA-1 expression allowed to discriminate between immature noncytolytic CD161(+)CD56(+)LFA-1(-) and more differentiated cytolytic CD161(+)CD56(+)LFA-1(+) NK cells. CD161(+)CD56(+)LFA-1(-) NK cells produce large amounts of CXCL8 after phorbol myristate acetate (PMA) or cytokine treatment. Remarkably, CXCL8 mRNA expression was also detected in fresh stage III immature NK cells isolated from tonsils and these cells expressed CXCL8 protein on PMA stimulation. Within in vitro UCB-derived CD161(+)CD56(+)LFA-1(-) NK cells, CXCL8 release was also induced on antibody-mediated cross-linking of NKp44 and CD161. Such unexpected activating function of CD161 was confined to the CD161(+)CD56(+)LFA-1(-) subset, because it did not induce cytokine release or CD107a expression in CD161(+)CD56(+)LFA-1(+) cells or in mature peripheral blood NK cells. Anti-CXCL8 neutralizing antibody induced a partial inhibition of NK cell differentiation, which suggests a regulatory role of CXCL8 during early NK cell differentiation. Altogether, these data provide novel information that may offer clues to optimize NK cell maturation in hematopoietic stem cell transplantation.

Melanoma cells inhibit natural killer cell function by modulating the expression of activating receptors and cytolytic activity.

Natural killer (NK) cells play a key role in tumor immune surveillance. However, adoptive immunotherapy protocols using NK cells have shown limited clinical efficacy to date, possibly due to tumor escape mechanisms that inhibit NK cell function. In this study, we analyzed the effect of coculturing melanoma cells and NK cells on their phenotype and function. We found that melanoma cells inhibited the expression of major NK receptors that trigger their immune function, including NKp30, NKp44, and NKG2D, with consequent impairment of NK cell-mediated cytolytic activity against various melanoma cell lines. This inhibitory effect was primarily mediated by indoleamine 2,3-dioxygenase (IDO) and prostaglandin E2 (PGE2). Together, our findings suggest that immunosuppressive barriers erected by tumors greatly hamper the antitumor activity of human NK cells, thereby favoring tumor outgrowth and progression.

Identification of a novel cell binding site of periostin involved in tumour growth.

INTRODUCTION: Periostin (PN), a member of the fasciclin family of proteins, is a TGF-ß-induced extracellular matrix protein involved in cell survival, angiogenesis, invasion and metastasis. It is considered a potent angiogenic factor and a marker of tumour progression in many types of human cancer. Many different kinds of cells bind to PN by means of the integrins αvß3 and αvß5, but the periostin epitope recognised by these integrins is not formally demonstrated. The aim of our study was to identify which domain of PN could be involved in cell adhesion and its potential role in tumour growth. METHODS: We generated the monoclonal antibody OC-20 (mAb OC-20) by hybridoma technology. Different PN recombinant fragments were used to characterise the periostin epitope recognised by the mAb OC-20 and to localise a new cell binding site of the protein. A murine model of human melanoma was used in the preclinical in vivo experiments. RESULTS: We formally demonstrate that the periostin epitope recognised by OC-20 is a new binding site for the integrins αvß3 and αvß5, localised in the second FAS1 domain (FAS1-2) of the protein. Moreover the in vivo use of this antibody significantly inhibits tumour growth and angiogenesis. CONCLUSION: Our results show that the FAS1-2 domain of PN plays a role in tumour progression. Moreover this novel antibody may likewise prove to be very useful in clarifying the role of PN in angiogenesis and may contribute to the design of novel anti-angiogenesis drugs.

CD34+ hematopoietic precursors are present in human decidua and differentiate into natural killer cells upon interaction with stromal cells.

Natural killer (NK) cells are the main lymphoid population in the maternal decidua during the first trimester of pregnancy. Decidual NK (dNK) cells display a unique functional profile and play a key role in promoting tissue remodeling, neoangiogenesis, and immune modulation. However, little information exists on their origin and development. Here we discovered CD34(+) hematopoietic precursors in human decidua (dCD34(+)). We show that dCD34(+) cells differ from cord blood- or peripheral blood-derived CD34(+) precursors. The expression of IL-15/IL-2 receptor common ß-chain (CD122), IL-7 receptor α-chain (CD127), and mRNA for E4BP4 and ID2 transcription factors suggested that dCD34(+) cells are committed to the NK cell lineage. Moreover, they could undergo in vitro differentiation into functional (i.e., IL-8- and IL-22-producing) CD56(bright)CD16(-)KIR(+/-) NK cells in the presence of growth factors or even upon coculture with decidual stromal cells. Their NK cell commitment was further supported by the failure to undergo myeloid differentiation in the presence of GM-CSF. Our findings strongly suggest that decidual NK cells may directly derive from CD34(+) cell precursors present in the decidua upon specific cellular interactions with components of the decidual microenvironment.

The immune inhibitory receptor LAIR-1 is highly expressed by plasmacytoid dendritic cells and acts complementary with NKp44 to control IFNα production.

Plasmacytoid dendritic cells (pDCs) are a subset of dendritic cells endowed with the capacity of producing large amounts of IFNα. Here we show that the Leukocyte-Associated Ig-like Receptor-1 (LAIR-1) is abundantly expressed on pDCs (the highest expression among all leukocytes) and its cross-linking inhibits IFNα production in response to Toll-like receptor ligands. Remarkably, LAIR-1 expression in pDCs is down-regulated in the presence of interleukin (IL)-3, thus indicating coordinated functions with NKp44, another pDC inhibitory receptor, which is conversely induced by IL-3. Nevertheless, the expression of NKp44 in pDCs isolated from secondary lymphoid organs, which is thought to be influenced by IL-3, is not coupled to a decreased expression of LAIR-1. Interestingly, pDCs isolated from peripheral blood of systemic lupus erithematosus (SLE) patients express lower levels of LAIR-1 while displaying slight but consistent expression of NKp44, usually undetectable on pDCs derived from healthy donors. Using sera derived from SLE patients, we show that LAIR-1 and NKp44 display synergistic inhibitory effects on IFNα production by interleukin IL-3 cultured pDCs stimulated with DNA immunocomplexes. In conclusion, our results indicate that the inhibitory function of LAIR-1 may play a relevant role in the mechanisms controlling IFNα production by pDCs both in normal and pathological innate immune responses.

CD56brightCD16- killer Ig-like receptor- NK cells display longer telomeres and acquire features of CD56dim NK cells upon activation.

Human NK cells can be divided into CD56(dim)CD16(+) killer Ig-like receptors (KIR)(+/-) and CD56(bright)CD16(-) KIR(-) subsets that have been characterized extensively regarding their different functions, phenotype, and tissue localization. Nonetheless, the developmental relationship between these two NK cell subsets remains controversial. We report that, upon cytokine activation, peripheral blood (PB)-CD56(bright) NK cells mainly gain the signature of CD56(dim) NK cells. Remarkably, KIR can be induced not only on CD56(bright), but also on CD56(dim) KIR(-) NK cells, and their expression correlates with lower proliferative response. In addition, we demonstrate for the first time that PB-CD56(dim) display shorter telomeres than PB- and lymph node (LN)-derived CD56(bright) NK cells. Along this line, although human NK cells collected from nonreactive LN display almost no KIR and CD16 expression, NK cells derived from highly reactive LN, efferent lymph, and PB express significant amounts of KIR and CD16, implying that CD56(bright) NK cells could acquire these molecules in the LN during inflammation and then circulate through the efferent lymph into PB as KIR(+)CD16(+) NK cells. Altogether, our results suggest that CD56(bright)CD16(-) KIR(-) and CD56(dim)CD16(+)KIR(+/-) NK cells correspond to sequential steps of differentiation and support the hypothesis that secondary lymphoid organs can be sites of NK cell final maturation and self-tolerance acquisition during immune reaction.

The tryptophan catabolite L-kynurenine inhibits the surface expression of NKp46- and NKG2D-activating receptors and regulates NK-cell function.

Tryptophan (Trp) catabolism mediated by indoleamine 2,3-dioxygenase (IDO) plays a central role in the regulation of T-cell-mediated immune responses. In this study, we also demonstrate that natural killer (NK)-cell function can be influenced by IDO. Indeed, l-kynurenine, a Trp-derived catabolite resulting from IDO activity, was found to prevent the cytokine-mediated up-regulation of the expression and function of specific triggering receptors responsible for the induction of NK-cell-mediated killing. The effect of l-kynurenine appears to be restricted to NKp46 and NKG2D, while it does not affect other surface receptors such as NKp30 or CD16. As a consequence, l-kynurenine-treated NK cells display impaired ability to kill target cells recognized via NKp46 and NKG2D. Instead, they maintain the ability to kill targets, such as dendritic cells (DCs), that are mainly recognized via the NKp30 receptor. The effect of l-kynurenine, which is effective at both the transcriptional and the protein level, can be reverted, since NK cells were found to recover their functional competence after washing.

Molecular and functional characterization of NKG2D, NKp80, and NKG2C triggering NK cell receptors in rhesus and cynomolgus macaques: monitoring of NK cell function during simian HIV infection.

An involvement of innate immunity and of NK cells during the priming of adaptive immune responses has been recently suggested in normal and disease conditions such as HIV infection and acute myelogenous leukemia. The analysis of NK cell-triggering receptor expression has been so far restricted to only NKp46 and NKp30 in Macaca fascicularis. In this study, we extended the molecular and functional characterization to the various NK cell-triggering receptors using PBMC and to the in vitro-derived NK cell populations by cytofluorometry and by cytolytic activity assays. In addition, RT-PCR strategy, cDNA cloning/sequencing, and transient transfections were used to identify and characterize NKp80, NKG2D, CD94/NKG2C, and CD94/NKG2A in M. fascicularis and Macaca mulatta as well as in the signal transducing polypeptide DNAX-activating protein DAP-10. Both M. fascicularis and M. mulatta NK cells express NKp80, NKG2D, and NKG2C molecules, which displayed a high degree of sequence homology with their human counterpart. Analysis of NK cells in simian HIV-infected M. fascicularis revealed reduced surface expression of selected NK cell-triggering receptors associated with a decreased NK cell function only in some animals. Overall surface density of NK cell-triggering receptors on peripheral blood cells and their triggering function on NK cell populations derived in vitro was not decreased compared with uninfected animals. Thus, triggering NK cell receptor monitoring on macaque NK cells is possible and could provide a valuable tool for assessing NK cell function during experimental infections and for exploring possible differences in immune correlates of protection in humans compared with cynomolgus and rhesus macaques undergoing different vaccination strategies.

Identification of 4Ig-B7-H3 as a neuroblastoma-associated molecule that exerts a protective role from an NK cell-mediated lysis.

In this study, in an attempt to identify neuroblastoma-associated surface antigens, we generated mAbs against the ACN neuroblastoma cell line. A mAb was selected (5B14) that reacted with all neuroblastoma cell lines analyzed and allowed detection of tumor cell infiltrates in bone marrow aspirates from neuroblastoma patients. In cytofluorimetric analysis, unlike anti-disialoganglioside mAb, 5B14 mAb did not display reactivity with normal bone marrow hematopoietic cell precursors, thus representing a highly specific marker for identifying neuroblastoma cells. Molecular analysis revealed that the 5B14 mAb-reactive surface glycoprotein corresponded to the recently identified 4Ig-B7-H3 molecule. Remarkably, mAb-mediated masking of the 4Ig-B7-H3 molecule on cell transfectants or on freshly isolated neuroblastoma cells resulted in enhancement of natural killer-mediated lysis of these target cells. These data suggest that 4Ig-B7-H3 molecules expressed at the tumor cell surface can exert a protective role from natural killer-mediated lysis by interacting with a still undefined inhibitory receptor expressed on natural killer cells.

Expression and crystallographic characterization of the extracellular domain of human natural killer cell triggering receptor NKp46.

Human natural killer (NK) cells are regulated in their cytolytic activity by a delicate interplay between activating and inhibitory signals related to distinct families of triggering and inhibitory receptor proteins. NKp46 is a major NK cell-specific triggering receptor involved in the recognition and lysis of human and murine tumour and virally infected cells. It consists of an extracellular portion, composed of two Ig-like domains, a transmembrane segment and a small cytoplasmic domain. To shed light on the molecular-recognition events involved in NK cytotoxicity triggering mechanisms, the NKp46 extracellular region was cloned, overexpressed, refolded and crystallized. X-ray diffraction data could be collected to a resolution limit of 1.93 A. Crystals of the NKp46 extracellular region belong to the hexagonal space group P6(1) (or P6(5)), with unit-cell parameters a = b = 85.48, c = 59.91 A, gamma = 120 degrees; the asymmetric unit contains one protein chain (197 amino acids).