Ultrastructural and functional studies of the interaction between IL-12 and IL-2 for the generation of lymphokine-activated killer cells

Immunotherapy for neuroblastoma by hematopoietic cell transplantation and post-transplant immunomodulation

Neuroblastoma represents a relatively common childhood tumor that imposes therapeutic difficulties. High risk neuroblastoma patients have poor prognosis, display limited response to radiochemotherapy and may be treated by hematopoietic cell transplantation. Allogeneic and haploidentical transplants have the distinct advantage of reinstitution of immune surveillance, reinforced by antigenic barriers. The key factors favorable to ignition of potent anti-tumor reactions are transition to adaptive immunity, recovery from lymphopenia and removal of inhibitory signals that inactivate immune cells at the local and systemic levels. Post-transplant immunomodulation may further foster anti-tumor reactivity, with positive but transient impact of infusions of lymphocytes and natural killer cells both from the donor, the recipient or third party. The most promising approaches include introduction of antigen-presenting cells in early post-transplant stages and neutralization of inhibitory signals. Further studies will likely shed light on the nature and actions of suppressor factors within tumor stroma and at the systemic level.

Tumor mRNA-transfected dendritic cells stimulate the generation of CTL that recognize neuroblastoma-associated antigens and kill tumor cells: immunotherapeutic implications

Several observations suggest a potential role of T-cell-mediated immunity in the control of neuroblastoma (NB). However, the generation of NB-specific cytotoxic T lymphocytes (CTL) on T-cell priming with tumor mRNA-transfected dendritic cells (DC) has never been investigated before. In the present study, the feasibility of this strategy has been analyzed, both in healthy donors and in NB patients. Monocyte-derived DC were raised from three human leukocyte antigen (HLA) A2+ NB patients and seven HLA-A1+ or HLA-A2+ healthy donors transfected with mRNA from four NB cell lines and cocultured with autologous CD8+ lymphocytes. Expanded CTL expressed an effector/memory phenotype and a T cytotoxic 1-like profile of cytokine secretion. CTL specificity was demonstrated by interferon-gamma release on incubation with HLA-matched NB cell lines. The latter cell lines, but not autologous T-cell blasts, were lysed by CTL in an HLA-restricted manner. Cytotoxicity was found to involve the release of granzyme B. When tested for reactivity against NB-associated antigens, CTL from normal individuals recognized anaplastic lymphoma-associated kinase (ALK) and preferentially expressed antigen of melanoma (PRAME) peptides only, whereas patients' CTL reacted also to survivin, telomerase, and tyrosine hydroxylase peptides. This study demonstrates that DC transfected with NB mRNA induce the generation of patients' CTL specific for different NB-associated antigens, supporting the feasibility of NB T-cell immunotherapy.

T cell mediated immune responses to Toxoplasma gondii in pregnant women with primary toxoplasmosis

The aim of this study was to investigate T cell immunity to Toxoplasma gondii (Tg) in pregnant women with primary toxoplasmosis. This issue has never been addressed before in humans and available information derives from murine models. Peripheral blood mononuclear cells (PBMC) from pregnant women with primary Tg infection were stimulated with Tg tachyzoites, excretory-secretory antigens (ESA) or recombinant surface antigen-1 (rSAG-1), and tested for proliferation, immunophenotype, cytokine production and antigen specific cytotoxic activity. Pregnant women with primary toxoplasmosis displayed a significant decrease of the CD4/CD8 T cell ratio and a significant increase of circulating T cell receptor (TCR) gammadelta+ cells as compared to their uninfected counterparts. T cells from Tg infected pregnant women proliferated to Tg tachyzoites, ESA or rSAG-1. Most tachyzoite and ESA specific T cell blasts were CD4+, whereas SAG-1 specific blasts were CD4+ and CD8+. ESA and tachyzoite specific T cell blasts displayed a Th1 or Th0 cytokine profile with overexpression of IFN-gamma. This pattern was unchanged upon in vitro exposure of T cells to progesterone, tested at a concentration close to that reached in vivo at the maternal-fetal interface. Finally, tachyzoite or ESA specific T cell blasts lysed, through a granule exocytosis dependent mechanism, autologous lymphoblastoid cell lines presenting Tg antigens. In conclusion, pregnant women with primary toxoplasmosis mounted in vitro Tg-specific Th1/Th0 responses whose impact on neonatal infection warrants further investigation.

Multiple defects of the antigen-processing machinery components in human neuroblastoma: immunotherapeutic implications

Low expression of human leukocyte antigen (HLA) class I in human tumors may be related to defects of the antigen-processing machinery (APM) components. Neuroblastoma cells are virtually HLA class I negative, but (i) the underlying mechanisms are unknown, and (ii) expression of the APM components has never been investigated. Here we have used a panel of novel monoclonal antibodies to proteasomal and immunoproteasomal components, chaperons and transporter associated with antigen processing (TAP) to characterize 24 stroma-poor neuroblastoma tumors and six neuroblastoma cell lines. Primary tumors showed defects in the expression of zeta, tapasin, TAP1 or TAP2, HLA class I heavy chain and beta2 microglobulin, LMP2 and LMP7, as compared to normal adrenal medulla. Neuroblastoma cell lines displayed roughly similar patterns of APM expression in comparison to primary tumors. Incubation of neuroblastoma cell lines with interferon-gamma caused upregulation of HLA class I molecules and reduced lysis by killer inhibitory receptor HLA ligand-matched NK cells. Defects in APM components explain reduced peptide loading on HLA class I molecules, their instability and failure to be expressed on the cell surface. HLA class I upregulation by interferon-gamma, although enhancing neuroblastoma cell recognition by cytotoxic T cells, dampens their susceptibility to NK cells.

Downregulation and/or release of NKG2D ligands as immune evasion strategy of human neuroblastoma

Neuroblastoma (NB) is a pediatric extracranial tumor characterized by downregulation of human leukocyte antigen class I and defects of the antigen processing machinery, two features that make it an appropriate target for natural killer (NK)-mediated lysis. NKG2D is an activating immunoreceptor expressed by cytotoxic T lymphocytes and NK cells. The ligands for NKG2D are the major histocompatibility complex class I-related chain (MIC)A and MICB glycoproteins, and the UL-16-binding proteins (ULBPs). Here, the expression of NKG2D ligands was investigated in human primary NB tumors and cell lines because scanty information is available on this issue. MICA, MICB, and ULBP transcripts were found in most tumors and cell lines. MICA protein was detected in some NB cell lines but not in primary tumors. A soluble form of MICA (sMICA) was identified in most patient sera and in some cell line supernatants. sMICA downregulated surface NKG2D in normal peripheral blood CD8(+) cells and decreased NK-mediated killing of MICA(+) NB cells. MICB was detected exclusively in the cytosol of primary tumors and cell lines. Approximately 50% of primary tumors expressed ULBP-2, but not ULBP-1 or -3. ULBP-3 was expressed in 5 of 9 cell lines, ULBP-2 in 2 of 9, whereas ULBP-1 was never detected. These studies delineate novel potential pathways of tumor escape and immunodeficiency in NB.

IL-12/IL-2 combination cytokine therapy for solid tumours: translation from bench to bedside

A broad range of approaches are under active investigation for the biological therapy of cancer, in particular, strategies directed at host immune response potentiation. These efforts have been fuelled by studies demonstrating the presence of an endogenous, but ineffective, host antitumour immune response and a greater understanding of the key factors which regulate this response. These mechanisms involve complex interactions between various effector cell populations, soluble factors and the tumour itself and are determined by the timing and relative intensity of positive and negative autoregulatory pathways, as well as a variety of immunosuppressive effects capable of mediating tumour self-defence. Based on these observations, immunotherapeutic regimens have been developed to potentiate antigen-specific sensitisation of effector cells with tumour vaccines/adjuvants, expand and amplify the number and function of effector cells, and to counteract suppressive pathways engaged by tumour cells themselves. Significant effort has focused on evaluating the use of exogenous cytokines, administered either systemically or locally into the tumour site via gene therapy. Several cytokines have demonstrated unique activity in the preclinical setting, including IL-2 and IFN-alpha -inducing cytokines such as IL12 and IL18. Most notably, later studies have now attempted to build on the clinical efficacy of IL-2 alone, to define combinations of agents with synergistic immunoregulatory and/or antitumour efficacy. Several lines of evidence suggest that IL-12 and IL-2 provide complementary immunoregulatory signals and have now shown that in combination, these two cytokines mediate synergistic antitumour activity in preclinical tumour models. This paper will review existing data regarding mechanisms of interaction between IL-2 and IL-12 in vitro and in preclinial models and describe future opportunities for the investigation of these potentially promising cytokines in the treatment of cancer.

Interleukin-12 induces efficient lysis of natural killer-sensitive and natural killer-resistant human osteosarcoma cells: the synergistic effect of interleukin-2

Previously we demonstrated that some osteosarcoma cell lines varied greatly in their susceptibility to natural killer (NK) cell lysis in vitro. The expression of CD54 and CD58 adhesion molecules on their surface appeared to influence their vulnerability, and the tumour necrosis factor-alpha (TNF-alpha)-induced positive modulation of CD54 increased osteosarcoma susceptibility in vitro. This study investigated whether peripheral blood mononuclear cells from normal healthy donors could be activated by interleukin (IL)-12 and IL-2, separately or in combination, to lyse osteosarcoma cell lines in vitro, as evaluated by using a microcytotoxicity test. In addition, we analysed (by flow cytometry) whether this function correlated with modifications of the CD2, CD11a, CD11b and CD18 molecules, which are involved in the adhesion of effector cells to the counter-receptors (CD54 and CD58) on osteosarcomas. This study demonstrates that incubation with IL-12 and/or IL-2 triggered NK cell cytolytic activity against osteosarcoma targets and that cytolytic activity was enhanced to a greater extent when lymphocytes were incubated simultaneously with a combination of IL-12 and IL-2. The density of CD18 and CD2 molecules involved in NK adhesion was also up-modulated following cytokine incubation. These changes in the density of adhesion molecules can be involved in the increased lytic activity of effector lymphocytes and in the modification of their binding capacity to osteosarcoma target cells.