Differential presentation of a soluble exogenous tumor antigen, NY-ESO-1, by distinct human dendritic cell populations

NY-ESO-1 protein formulated in ISCOMATRIX adjuvant is a potent anticancer vaccine inducing both humoral and CD8+ t-cell-mediated immunity and protection against NY-ESO-1+ tumors

NY-ESO-1 is a 180 amino-acid human tumor antigen expressed by many different tumor types and belongs to the family of "cancer-testis" antigens. In humans, NY-ESO-1 is one of the most immunogenic tumor antigens and NY-ESO-1 peptides have been shown to induce NY-ESO-1-specific CD8(+) CTLs capable of altering the natural course of NY-ESO-1-expressing tumors in cancer patients. Here we describe the preclinical immunogenicity and efficacy of NY-ESO-1 protein formulated with the ISCOMATRIX adjuvant (NY-ESO-1 vaccine). In vitro, the NY-ESO-1 vaccine was readily taken up by human monocyte-derived dendritic cells, and on maturation, these human monocyte-derived dendritic cells efficiently cross-presented HLA-A2-restricted epitopes to NY-ESO-1-specific CD8(+) T cells. In addition, epitopes of NY-ESO-1 protein were also presented on MHC class II molecules to NY-ESO-1-specific CD4(+) T cells. The NY-ESO-1 vaccine induced strong NY-ESO-1-specific IFN-gamma and IgG2a responses in C57BL/6 mice. Furthermore, the NY-ESO-1 vaccine induced NY-ESO-1-specific CD8(+) CTLs in HLA-A2 transgenic mice that were capable of lysing human HLA-A2(+) NY-ESO-1(+) tumor cells. Finally, C57BL/6 mice, immunized with the NY-ESO-1 vaccine, were protected against challenge with a B16 melanoma cell line expressing NY-ESO-1. These data illustrate that the NY-ESO-1 vaccine represents a potent therapeutic anticancer vaccine.

Mature human Langerhans cells derived from CD34+ hematopoietic progenitors stimulate greater cytolytic T lymphocyte activity in the absence of bioactive IL-12p70, by either single peptide presentation or cross-priming, than do dermal-interstitial or monocyte-derived dendritic cells

The emerging heterogeneity of dendritic cells (DCs) mirrors their increasingly recognized division of labor at myriad control points in innate and acquired cellular immunity. We separately generated blood monocyte-derived DCs (moDCs), as well as Langerhans cells (LCs) and dermal-interstitial DCs (DDC-IDCs) from CD34(+) hematopoietic progenitor cells. Differential expression of CD11b, CD52, CD91, and the CD1 isoforms proved useful in distinguishing these three DC types. All mature DCs uniformly expressed comparable levels of HLA-DR, CD83, CD80, and CD86, and were potent stimulators of allogeneic T cells after exposure either to recombinant human CD40L trimer or a combination of inflammatory cytokines with PGE(2). moDCs, however, required 0.5-1 log greater numbers than LCs or DDC-IDCs to stimulate comparable T cell proliferation. Only moDCs secreted the bioactive heterodimer IL-12p70, and moDCs phagocytosed significantly more dying tumor cells than did either LCs or DDC-IDCs. LCs nevertheless proved superior to moDCs and DDC-IDCs in stimulating CTL against a recall viral Ag by presenting passively loaded peptide or against tumor Ag by cross-priming autologous CD8(+) T cells. LCs also secreted significantly more IL-15 than did either moDCs or DDC-IDCs, which is especially important to the generation of CTL. These findings merit further comparisons in clinical trials designed to determine the physiologic relevance of these distinctions in activity between LCs and other DCs.

IFN-gamma enables cross-presentation of exogenous protein antigen in human Langerhans cells by potentiating maturation

We compared monocyte-derived dendritic cells and transforming growth factor-beta1-induced Langerhans-like cells (LCs) for their capacity to cross-present exogenous NY-ESO-1 protein/antibody immune complexes to an NY-ESO-1-specific CD8+ T cell clone. In contrast to dendritic cells, LCs were not able to cross-present NY-ESO-1 to the T cell clone constitutively but did so after treatment with IFN-gamma. Remarkably, this IFN-gamma-inducible characteristic was due neither to enhanced antigen uptake nor to facilitated antigen processing in LCs. Rather, IFN-gamma acted at least in part by potentiating the maturation of otherwise refractory LCs, enabling in turn exogenous antigen to reach the processing machinery. This model of conditional cross-presentation establishes an original level of action for IFN-gamma as an effective immune modulator and supports the use of IFN-gamma in protein vaccination strategies targeting LCs.

A novel mechanism of alternative promoter and splicing regulates the epitope generation of tumor antigen CML66-L

This report describes the difference in the epitope generation of two isoforms of self-tumor Ag CML66 and the regulation mechanism. We identified a new CML66 short isoform, termed CML66-S. The previously identified long CML66 is referred to as CML66-L. CML66-S shares the C terminus with CML66-L but has its unique N terminus. CML66-S is predominantly expressed in testis, but is also expressed in very low levels in tumor cells, whereas CML66-L is expressed in tumor cells and testis. Differential expression of CML66-L and CML66-S in tumor cells resulted from regulation at transcription, although alternative splicing also participated in the generation of the isoforms. In addition, Ab titers to a CML66-L peptide were significantly higher than that to CML66-S peptide in the sera from patients with tumors. Finally, the Abs to full-length CML66-L in the sera from patients with tumors were correlated with the Abs in the sera from these patients to CML66-L-38, which is a fusion protein with a CML66-L-specific N terminus. This suggests that the CML66-L isoform is mainly responsible for the epitope generation. Our studies have identified the alternative promoter in combination with alternative splicing as a novel mechanism for regulation of the epitope generation of a self-tumor Ag.

A vaccine prepared by fusion of H22 cells with the spleen-drived dendritic cells

AIM: To prepare a cancer vaccine (H₂₂-DC) based on fusion of hepatocarcinoma cells (H₂₂) with dendritic cells (DC) of mice and to analyze the biological characteristics, tumorigenicity and specific CTL activity of H₂₂-DC.

METHODS: DCs were fused with H₂₂ cells and fusion cells were marked with CD11c MicroBeads. The teachniques of cell culture, immunocytochemistry and light microscopy were used to test the characteristics of growth morphology of H₂₂-DC in vitro. As an immunogen, H₂₂-DC was inoculated subcutaneously into the right armpit of Balb/C mice, and their tumorigenicity in vivo was observed. MTT was used to test the CTL activity of murine spleen in vitro.

RESULTS: H₂₂-DC was able to divide and prolifterate in vitro,but its activity of proliferation was significantly decreased as compared with H₂₂ cells and its growth curve was flatter than that of H₂₂ cells. The spleen CTL activity against H₂₂ cells in mice implanted with fresh H₂₂-DC was significantly higher than that in control groups (P < 0.01).

CONCLUSION: H₂₂-DC can significantly stimulate the specific CTL activity of murine spleen. The DC vaccine is likely to become a helpful approach in immunotherapy of hepatocellular carcinoma.

Survey of naturally occurring CD4+ T cell responses against NY-ESO-1 in cancer patients: correlation with antibody responses

NY-ESO-1 is one of the most immunogenic proteins described in human cancers, based on its capacity to elicit simultaneous antibody and CD8+ T cell responses in vivo. Although HLA class II restricted epitopes from NY-ESO-1 have been identified, no broad survey has yet established the status of natural CD4+ T cell responses in cancer patients in relation to CD8+ and antibody responses. We used a recently developed general strategy for monitoring CD4+ responses that overcomes the need for prior knowledge of epitope or HLA restriction to analyze a series of 31 cancer patients and healthy donors for the presence of CD4+ T cells to NY-ESO-1, and related this response to NY-ESO-1 expression in tumor cells and serum antibodies to NY-ESO-1. None of the 18 patients that tested seronegative for NY-ESO-1 had detectable CD4+ T cell responses. On the contrary, 11 of 13 cancer patients with serum antibodies to NY-ESO-1 had polyclonal CD4+ T cell responses directed against various known and previously undescribed NY-ESO-1 epitopes. NY-ESO-1 peptide 80-109 was the most immunogenic, with 10 of 11 patients responding to this peptide. We show here that 12-mer determinants from NY-ESO-1 eliciting a CD4+ T cell response were peptide 87-98 with promiscuous HLA class II presentation, peptide 108-119 restricted by HLA-DP4, and peptides 121-132 and 145-156, both shorter epitopes from previously described HLA-DR4 peptides, also presented by HLA-DR7. This study represents the next step in compiling a comprehensive picture of the adaptive immune response to NY-ESO-1, and provides a general strategy for analyzing the CD4+ T cell response to other tumor antigens eliciting a humoral immune response.

Against the self: dendritic cells versus cancer

The role of host defense in cancer is highly variable. Although there are cases where spontaneous cures of cancer appear to be mediated by immunologic mechanisms, malignant disease generally progresses even in patients where tumor-specific immunity can be demonstrated. It is apparent that there are complex interactions between tumor cells and dendritic cells, the dominant antigen-presenting cells of the immune system. Through their inhibitory actions upon dendritic cells, tumor cells can negatively regulate priming of tumor-specific immunity. Recent work has also shown that dendritic cells have direct cytotoxic effects upon tumor cells. These interactions may impact on the efficacy of current strategies using dendritic cell-based vaccines for tumor immunotherapy.

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Failure of monocytes of trauma patients to convert to immature dendritic cells is related to preferential macrophage-colony-stimulating factor-driven macrophage differentiation

Following trauma, increased inflammatory monokine activation and depressed APC function can occur simultaneously. These contradictory monocyte (Mphi) dysfunctions could result if postinjury Mphi differentiation preferentially favored inflammatory macrophage (Mac) differentiation over development into the most potent APC, dendritic cells (DC). In this report, Mphi of trauma patients with a depressed MLR induction capacity are, for the first time, shown to be unable to differentiate in vitro to immature CD1a(+) DC under the influence of GM-CSF and IL-4. Trauma patient Mphi that retained MLR-inducing capacity had a nonsignificant reduction in DC differentiation capacity. Only patient Mphi populations with depressed differentiation to immature DC (iDC) demonstrated depressed IL-12 and IL-15 production and a continued reduced MLR induction capacity. Neither increased IL-10 production nor decreased CD11c(+) DC precursor numbers correlated with depressed Mphi-to-DC differentiation. Instead, these patients' APC-dysfunctional Mphi populations had increased expression of inflammatory Mac phenotypes (CD64(+), CD86(low), HLA-DR(low)) and up-regulated secretion of M-CSF. M-CSF combined with IL-6 inhibits Mphi-to-iDC differentiation and promotes Mphi-to-Mac differentiation by down-regulating GM-CSFR expression and increasing DC apoptosis. Both depressed GM-CSFR expression and increased Mphi iDC apoptosis, as well as increased expression of CD126 (IL-6R) and CD115 (M-CSFR), were detected in APC-defective patient Mphi. In vitro addition of anti-M-CSF enhanced the IL-4 plus GM-CSF-induced Mphi-to-DC differentiation of these patients. This suggests that, in trauma patients, enhanced Mphi-to-Mac differentiation with concomitant inhibited iDC development is partially due to increased circulating Mphi sensitivity to and production of M-CSF and contributes to postinjury immunoaberrations.

The use of dendritic cells in cancer immunotherapy

A novel approach to vaccination against cancer is to exploit dendritic cells (DCs) as "nature's adjuvants" and actively immunize cancer patients with a sample of their own DCs primed with tumor antigens. DC vaccination is, however, still at an early stage, slowed in part by the need to carry out research in humans. Nevertheless, valuable proofs of concept have been obtained with respect to the capacity of DCs to expand cancer-directed immune responses. The methods for preparing DCs are being improved continuously, and there are many opportunities to improve efficacy at the level of DC biology. An increased number of Phase I, II and III studies will drive this new area of human research.

Dendritic cell-mediated immunization in macroglobulinemia

Dendritic cells (DCs) are professional antigen-presenting cells (APCs) specialized to initiate immunity and are critical targets for all vaccines. New methods to generate large quantities of these cells in the laboratory and load them with tumor antigens allows novel approaches targeting these APCs in the clinic. Injection of antigen loaded DCs can boost tumor-specific immunity in patients. Studies in myeloma suggest that the use of autologous tumor as a source of antigen may be the preferred approach. Boosting antitumor immunity may be a useful strategy to prevent tumor progression in patients with asymptomatic macroglobulinemia.

Cross-presentation of HLA class I epitopes from exogenous NY-ESO-1 polypeptides by nonprofessional APCs

NY-ESO-1, a germ cell Ag often detected in tumor tissues, frequently elicits Ab and CD8(+) T cell responses in cancer patients. Overlapping long peptides spanning the NY-ESO-1 sequence have been used to map HLA class I-restricted epitopes recognized by NY-ESO-1-specific CD8(+) T lymphocytes. To address the antigenicity of long peptides, we analyzed two synthetic 30-mer peptides from NY-ESO-1, polypeptides 80-109 and 145-174, for their capacity to be processed by APCs and to stimulate CD8(+) T cells. By incubating APCs with polypeptides at different temperatures or in the presence of protease inhibitors, we found that NY-ESO-1 polypeptides were rapidly internalized by B cells, T2 cells, or PBLs and submitted to cellular proteolytic action to yield nonamer epitopes presented by HLA class I. Polypeptides were also immunogenic in vitro and stimulated the expansion of CD8(+) T cells against naturally processed NY-ESO-1 epitopes in the context of three different HLA class I alleles. Polypeptides can thus serve as exogenous Ags that are cross-presented on HLA class I without requiring the action of professional APCs. These findings support innovative vaccination strategies using NY-ESO-1 polypeptides that would circumvent current limitations of HLA class I peptide vaccination, i.e., HLA eligibility criteria and knowledge of epitope, while allowing for facilitated immunogenicity in the presence of helper epitopes.

CD8(+) T cell responses against a dominant cryptic HLA-A2 epitope after NY-ESO-1 peptide immunization of cancer patients

NY-ESO-1 is a germ cell antigen aberrantly expressed in different tumor types that elicits strong humoral and cellular immune responses in cancer patients. Monitoring spontaneous CD8(+) T cell responses against NY-ESO-1 peptides 157-165 (S9C) and 157-167 (S11L) in a series of HLA-A2(+) cancer patients showed that these two peptides had overlapping antigenic profiles and were equally immunogenic. However, discrepancies between S9C and S11L reactivities were observed upon vaccination with both peptides to generate or boost T cell responses to NY-ESO-1 in cancer patients. We here analyze the fine specificity of these responses and describe an HLA-A2-restricted epitope, NY-ESO-1 peptide 159-167 (L9L), which is strongly recognized by CD8(+) T cells as a result of peptide vaccination of cancer patients. Responses to L9L were stimulated by S11L and appeared early in the course of vaccination, independently of S9C responses. However, L9L-specific CD8(+) T cells failed to recognize tumor cells naturally expressing NY-ESO-1 or B lymphoblastoid cells transduced with NY-ESO-1. Processing of L9L could be rescued after IFN-gamma treatment of tumor cells or by dendritic cells pulsed with NY-ESO-1 protein/antibody immune complexes. The present results demonstrate a dual specificity within peptide S11L, with S9C as the natural antigenic tumor epitope, and L9L as a cryptic epitope with dominant immunogenicity upon vaccination that diverts the immune response from tumor recognition. These unanticipated findings raise questions about the use of S11L in the clinic and emphasize the importance of analyzing the fine specificity of vaccine-induced T cell responses in patients as a basis for constructing effective cancer vaccines.