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

B cell profiles, antibody repertoire and reactivity reveal dysregulated responses with autoimmune features in melanoma

B cells are known to contribute to the anti-tumor immune response, especially in immunogenic tumors such as melanoma, yet humoral immunity has not been characterized in these cancers to detail. Here we show comprehensive phenotyping in samples of circulating and tumor-resident B cells as well as serum antibodies in melanoma patients. Memory B cells are enriched in tumors compared to blood in paired samples and feature distinct antibody repertoires, linked to specific isotypes. Tumor-associated B cells undergo clonal expansion, class switch recombination, somatic hypermutation and receptor revision. Compared with blood, tumor-associated B cells produce antibodies with proportionally higher levels of unproductive sequences and distinct complementarity determining region 3 properties. The observed features are signs of affinity maturation and polyreactivity and suggest an active and aberrant autoimmune-like reaction in the tumor microenvironment. Consistent with this, tumor-derived antibodies are polyreactive and characterized by autoantigen recognition. Serum antibodies show reactivity to antigens attributed to autoimmune diseases and cancer, and their levels are higher in patients with active disease compared to post-resection state. Our findings thus reveal B cell lineage dysregulation with distinct antibody repertoire and specificity, alongside clonally-expanded tumor-infiltrating B cells with autoimmune-like features, shaping the humoral immune response in melanoma.

Longitudinal analysis of DC subsets in patients with ovarian cancer: Implications for immunotherapy

Background

The use of circulating cDC1 to generate anti-cancer vaccines is among the most promising approaches to overcome the limited immunogenicity and clinical efficacy of monocyte-derived DC. However, the recurrent lymphopenia and the reduction of DC numbers and functionality in patients with cancer may represent an important limitation of such approach. In patients with ovarian cancer (OvC) that had received chemotherapy, we previously showed that cDC1 frequency and function were reduced.

Methods

We recruited healthy donors (HD, n=7) and patients with OvC at diagnosis and undergoing interval debulking surgery (IDS, n=6), primary debulking surgery (PDS, n=6) or at relapse (n=8). We characterized longitudinally phenotypic and functional properties of peripheral DC subsets by multiparametric flow cytometry.

Results

We show that the frequency of cDC1 and the total CD141+ DC capacity to take up antigen are not reduced at the diagnosis, while their TLR3 responsiveness is partially impaired in comparison with HD. Chemotherapy causes cDC1 depletion and increase in cDC2 frequency, but mainly in patients belonging to the PDS group, while in the IDS group both total lymphocytes and cDC1 are preserved. The capacity of total CD141+ DC and cDC2 to take up antigen is not impacted by chemotherapy, while the activation capacity upon Poly(I:C) (TLR3L) stimulation is further decreased.

Conclusions

Our study provides new information about the impact of chemotherapy on the immune system of patients with OvC and sheds a new light on the importance of considering timing with respect to chemotherapy when designing new vaccination strategies that aim at withdrawing or targeting specific DC subsets.

Combined Vaccination with NY-ESO-1 Protein, Poly-ICLC, and Montanide Improves Humoral and Cellular Immune Responses in Patients with High-Risk Melanoma

Given its ability to induce both humoral and cellular immune responses, NY-ESO-1 has been considered a suitable antigen for a cancer vaccine. Despite promising results from early-phase clinical studies in patients with melanoma, NY-ESO-1 vaccine immunotherapy has not been widely investigated in larger trials; consequently, many questions remain as to the optimal vaccine formulation, predictive biomarkers, and sequencing and timing of vaccines in melanoma treatment. We conducted an adjuvant phase I/II clinical trial in high-risk resected melanoma to optimize the delivery of poly-ICLC, a TLR-3/MDA-5 agonist, as a component of vaccine formulation. A phase I dose-escalation part was undertaken to identify the MTD of poly-ICLC administered in combination with NY-ESO-1 and montanide. This was followed by a randomized phase II part investigating the MTD of poly-ICLC with NY-ESO-1 with or without montanide. The vaccine regimens were generally well tolerated, with no treatment-related grade 3/4 adverse events. Both regimens induced integrated NY-ESO-1-specific CD4+ T-cell and humoral responses. CD8+ T-cell responses were mainly detected in patients receiving montanide. T-cell avidity toward NY-ESO-1 peptides was higher in patients vaccinated with montanide. In conclusion, NY-ESO-1 protein in combination with poly-ICLC is safe, well tolerated, and capable of inducing integrated antibody and CD4+ T-cell responses in most patients. Combination with montanide enhances antigen-specific T-cell avidity and CD8+ T-cell cross-priming in a fraction of patients, indicating that montanide contributes to the induction of specific CD8+ T-cell responses to NY-ESO-1.

Antibodies as biomarker candidates for response and survival to checkpoint inhibitors in melanoma patients

Background

Long-term survival of stage IV melanoma patients has improved significantly with the development of immune checkpoint inhibitors (CIs). Reliable biomarkers to predict response and clinical outcome are needed.

Methods

We investigated the role of melanoma-associated antibodies as predictive markers for CI therapy in two independent cohorts. In cohort 1, a prospective study, we measured specific antibodies before treatment, after one week and after six to nine weeks of treatment. Cohort 2 consisted of serum samples prior to CI therapy initiation. ELISA assays were performed to quantify specific IgG directed against melanocyte differentiation antigens tyrosinase-related proteins 1 and 2 (TRP1/TYRP1 and TRP2/TYRP2), glycoprotein 100 (gp100), MelanA/MART1, and the cancer-testis antigen NY-ESO-1. Response was defined as either complete or partial remission on CT scan according to RECIST 1.1.

Results

In cohort 1, baseline levels of these antibodies were higher in the responder group, although statistical significance was only reached for NY-ESO-1 (p = 0.007). In cohort 2, significantly higher antibody baseline levels for MelanA/MART1 (p = 0.003) and gp100 (p = 0.029) were found. After pooling the results from both cohorts, higher levels of MelanA/MART1 (p = 0.013), TRP1/TYRP1 (p = 0.048), TRP2/TYRP2 (p = 0.047) and NY-ESO-1 (p = 0.005) specific antibodies at baseline were independently associated with response.

Conclusions

Melanoma-associated antibodies may be candidate biomarkers for response and survival in metastatic melanoma patients being treated with CIs. These markers may be used to complement patient assessment, in combination with PD-L1 status, tumor-infiltrating lymphocytes and tumor mutational burden, with the aim to predict outcome of CI treatment in patients with metastatic melanoma.

Trial registration

Ethikkommission Ostschweiz, EKOS 16/079 https://ongoingprojects.swissethics.ch/runningProjects_list.php?q=%28BASECID~contains~2016-00998%29&orderby=dBASECID.

Electronic supplementary material

The online version of this article (10.1186/s40425-019-0523-2) contains supplementary material, which is available to authorized users.

Preclinical evaluation of a MAGE-A3 vaccination utilizing the oncolytic Maraba virus currently in first-in-human trials

Multiple immunotherapeutics have been approved for cancer patients, however advanced solid tumors are frequently refractory to treatment. We evaluated the safety and immunogenicity of a vaccination approach with multimodal oncolytic potential in non-human primates (NHP) (Macaca fascicularis). Primates received a replication-deficient adenoviral prime, boosted by the oncolytic Maraba MG1 rhabdovirus. Both vectors expressed the human MAGE-A3. No severe adverse events were observed. Boosting with MG1-MAGEA3 induced an expansion of hMAGE-A3-specific CD4⁺ and CD8⁺ T-cells with the latter peaking at remarkable levels and persisting for several months. T-cells reacting against epitopes fully conserved between simian and human MAGE-A3 were identified. Humoral immunity was demonstrated by the detection of circulating MAGE-A3 antibodies. These preclinical data establish the capacity for the Ad:MG1 vaccination to engage multiple effector immune cell populations without causing significant toxicity in outbred NHPs. Clinical investigations utilizing this program for the treatment of MAGE-A3-positive solid malignancies are underway (NCT02285816, NCT02879760).

Identifying baseline immune-related biomarkers to predict clinical outcome of immunotherapy

As cancer strikes, individuals vary not only in terms of factors that contribute to its occurrence and development, but as importantly, in their capacity to respond to treatment. While exciting new therapeutic options that mobilize the immune system against cancer have led to breakthroughs for a variety of malignancies, success is limited to a subset of patients. Pre-existing immunological features of both the host and the tumor may contribute to how patients will eventually fare with immunotherapy. A broad understanding of baseline immunity, both in the periphery and in the tumor microenvironment, is needed in order to fully realize the potential of cancer immunotherapy. Such interrogation of the tumor, blood, and host immune parameters prior to treatment is expected to identify biomarkers predictive of clinical outcome as well as to elucidate why some patients fail to respond to immunotherapy. To approach these opportunities for progress, the Society for Immunotherapy of Cancer (SITC) reconvened the Immune Biomarkers Task Force. Comprised of an international multidisciplinary panel of experts, Working Group 4 sought to make recommendations that focus on the complexity of the tumor microenvironment, with its diversity of immune genes, proteins, cells, and pathways naturally present at baseline and in circulation, and novel tools to aid in such broad analyses.

Melanoma: tumor microenvironment and new treatments

In the recent past years, many discoveries in the tumor microenvironment have led to changes in the management of melanoma and it is rising up hopes, specially, to those in advanced stages. FDA approved seven new drugs from 2011 to 2014. They are: Vemurafenib, Dabrafenib and Trametinib, kinases inhibitors used for patients that have BRAFV600E mutation; Ipilimumab (anti-CTLA4), Pembrolizumab (anti-PD-1) and Nivolumab (anti-PD-1), monoclonal antibodies that stimulate the immune system; and Peginterferon alfa-2b, an anti-proliferative cytokine used as adjuvant therapy. In this article, we will review the molecular bases for these new metastatic melanoma therapeutic agents cited above and also analyze new molecular discoveries in melanoma study, as Cancer-Testis antigens (CT). They are capable of induce humoral and cellular immune responses in cancer patients and because of this immunogenicity and their restrict expression in normal tissues, they are considered an ideal candidate for vaccine development against cancer. Among CT antigens, NY-ESO-1 is the best characterized in terms of expression patterns and immunogenicity. It is expressed in 20-40% of all melanomas, more in metastatic lesions than in primary ones, and it is very heterogeneous inter and intratumoral. Breslow index is associate with NY-ESO-1 expression in primary cutaneous melanomas, but its relation to patient survival remains controversial.

Origin and Role of a Subset of Tumor-Associated Neutrophils with Antigen-Presenting Cell Features in Early-Stage Human Lung Cancer

Based on studies in mouse tumor models, granulocytes appear to play a tumor-promoting role. However, there are limited data about the phenotype and function of tumor-associated neutrophils (TANs) in humans. Here, we identify a subset of TANs that exhibited characteristics of both neutrophils and antigen-presenting cells (APCs) in early-stage human lung cancer. These APC-like "hybrid neutrophils," which originate from CD11b(+)CD15(hi)CD10(-)CD16(low) immature progenitors, are able to cross-present antigens, as well as trigger and augment anti-tumor T cell responses. Interferon-γ and granulocyte-macrophage colony-stimulating factor are requisite factors in the tumor that, working through the Ikaros transcription factor, synergistically exert their APC-promoting effects on the progenitors. Overall, these data demonstrate the existence of a specialized TAN subset with anti-tumor capabilities in human cancer.

NY-ESO-1 specific antibody and cellular responses in melanoma patients primed with NY-ESO-1 protein in ISCOMATRIX and boosted with recombinant NY-ESO-1 fowlpox virus

Vaccination strategies based on repeated injections of NY-ESO-1 protein formulated in ISCOMATRIX particles (NY-ESO-1 ISCOMATRIX) have shown to elicit combined NY-ESO-1 specific antibody and T cell responses. However, it remains unclear whether heterologous prime-boost strategies based on the combination with NY-ESO-1 ISCOMATRIX with different NY-ESO-1 boosting reagents could be used to increase NY-ESO-1 CD8(+) or CD4(+) T cell responses. To address this question, we carried out a randomized clinical trial in 39 high-risk, resected melanoma patients vaccinated with NY-ESO-1 ISCOMATRIX, and then boosted with repeated injections of either recombinant fowlpox virus encoding full length NY-ESO-1 (rF-NY-ESO-1) (Arm A) or NY-ESO-1 ISCOMATRIX alone (Arm B). We have comprehensively analyzed NY-ESO-1 specific T cells and B cells response in all patients before and after vaccination for a total of seven time points per patient. NY-ESO-1 ISCOMATRIX alone elicited a strong NY-ESO-1 specific CD4(+) T cell and antibody response, which was maintained by both regiments at similar levels. However, CD8(+) T cell responses were significantly boosted in 3 out of 18 patients in Arm A after the first rF-NY-ESO-1 injection and such responses were maintained until the end of the trial, while no patients in Arm B showed similar CD8(+) T cell responses. In addition, our results clearly identified immunodominant regions in the NY-ESO-1 protein: NY-ESO-179-102 and NY-ESO-1115-138 for CD4+ T cells and NY-ESO-185-108 for CD8+ T cells in a large proportion of vaccinated patients. These regions of NY-ESO-1 protein should be considered in future clinical trials as immunodominant epitopes.

Resiquimod as an immunologic adjuvant for NY-ESO-1 protein vaccination in patients with high-risk melanoma

The Toll-like receptor (TLR) 7/8 agonist resiquimod has been used as an immune adjuvant in cancer vaccines. We evaluated the safety and immunogenicity of the cancer testis antigen NY-ESO-1 given in combination with Montanide (Seppic) with or without resiquimod in patients with high-risk melanoma. In part I of the study, patients received 100 μg of full-length NY-ESO-1 protein emulsified in 1.25 mL of Montanide (day 1) followed by topical application of 1,000 mg of 0.2% resiquimod gel on days 1 and 3 (cohort 1) versus days 1, 3, and 5 (cohort 2) of a 21-day cycle. In part II, patients were randomized to receive 100-μg NY-ESO-1 protein plus Montanide (day 1) followed by topical application of placebo gel [(arm A; n = 8) or 1,000 mg of 0.2% resiquimod gel (arm B; n = 12)] using the dosing regimen established in part I. The vaccine regimens were generally well tolerated. NY-ESO-1-specific humoral responses were induced or boosted in all patients, many of whom had high titer antibodies. In part II, 16 of 20 patients in both arms had NY-ESO-1-specific CD4⁺ T-cell responses. CD8⁺ T-cell responses were only seen in 3 of 12 patients in arm B. Patients with TLR7 SNP rs179008 had a greater likelihood of developing NY-ESO-1-specific CD8⁺ responses. In conclusion, NY-ESO-1 protein in combination with Montanide with or without topical resiquimod is safe and induces both antibody and CD4⁺ T-cell responses in the majority of patients; the small proportion of CD8⁺ T-cell responses suggests that the addition of topical resiquimod to Montanide is not sufficient to induce consistent NY-ESO-1-specific CD8⁺ T-cell responses.

Antibody-based therapy in colorectal cancer

Treatment in patients with nonresectable and resectable colorectal cancer at the advanced stage is challenging, therefore intensive strategies such as chemotherapy, signaling inhibitors and monoclonal antibodies (mAbs) to control the disease are required. mAbs are particularly promising tools owing to their target specificities and strong antitumor activities through multiple mechanisms, as shown by rituximab in B-cell non-Hodgkin's lymphoma and trastuzumab in breast cancer. Three mAbs (cetuximab, bevacizumab and panitumumab) have been approved for the treatment of colorectal cancer in the USA and many other mAbs are being tested in clinical trials. The potential of antibody therapy is associated with several mechanisms including interference of vital signaling pathways targeted by the antibody and immune cytotoxicity selectively directed against tumor cells by tumor-bound antibody through the Fc portion of the antibody, such as antibody-dependent cellular cytotoxicity and complement-dependent cytotoxicity. Moreover, recent experimental findings have shown that immune complexes formed by therapeutic mAbs with tumor-released antigens could augment the induction of tumor-specific cytotoxic CD8(+) T cells through activation of APCs. In addition, antibodies targeting immune checkpoints on hematopoietic cells have recently opened a new avenue for the treatment of cancer. In this review, we focus on mAb treatment in colorectal cancer and its immunological aspects.

Overcoming regulatory T-cell suppression by a lyophilized preparation of Streptococcus pyogenes

Cancer vaccines have yet to yield clinical benefit, despite the measurable induction of humoral and cellular immune responses. As immunosuppression by CD4(+) CD25(+) regulatory T (Treg) cells has been linked to the failure of cancer immunotherapy, blocking suppression is therefore critical for successful clinical strategies. Here, we addressed whether a lyophilized preparation of Streptococcus pyogenes (OK-432), which stimulates Toll-like receptors, could overcome Treg-cell suppression of CD4(+) T-cell responses in vitro and in vivo. OK-432 significantly enhanced in vitro proliferation of CD4(+) effector T cells by blocking Treg-cell suppression and this blocking effect depended on IL-12 derived from antigen-presenting cells. Direct administration of OK-432 into tumor-associated exudate fluids resulted in a reduction of the frequency and suppressive function of CD4(+) CD25(+) Foxp3(+) Treg cells. Furthermore, when OK-432 was used as an adjuvant of vaccination with HER2 and NY-ESO-1 for esophageal cancer patients, NY-ESO-1-specific CD4(+) T-cell precursors were activated, and NY-ESO-1-specific CD4(+) T cells were detected within the effector/memory T-cell population. CD4(+) T-cell clones from these patients had high-affinity TCRs and recognized naturally processed NY-ESO-1 protein presented by dendritic cells. OK-432 therefore inhibits Treg-cell function and contributes to the activation of high-avidity tumor antigen-specific naive T-cell precursors.

Intracellular Tumor-Associated Antigens Represent Effective Targets for Passive Immunotherapy

Monoclonal antibody (mAb) therapy against tumor antigens expressed on the tumor surface is associated with clinical benefit. However, many tumor antigens are intracellular molecules that generally would not be considered suitable targets for mAb therapy. In this study, we provide evidence challenging this view through an investigation of the efficacy of mAb directed against NY-ESO-1, a widely expressed immunogen in human tumors that is expressed intracellularly rather than on the surface of cells. On their own, NY-ESO-1 mAb could neither augment antigen-specific CD8+ T-cell induction nor cause tumor eradication. To facilitate mAb access to intracellular target molecules, we combined anti-NY-ESO-1 mAb with anticancer drugs to accentuate the release of intracellular NY-ESO-1 from dying tumor cells. Strikingly, combination therapy induced a strong antitumor effect that was accompanied by the development of NY-ESO-1–specific effector/memory CD8+ T cells that were not elicited by single treatments alone. The combinatorial effect was also associated with upregulation of maturation markers on dendritic cells, consistent with the organization of an effective antitumor T-cell response. Administration of Fc-depleted F(ab) mAb or combination treatment in Fcγ receptor–deficient host mice abolished the therapeutic effect. Together, our findings show that intracellular tumor antigens can be captured by mAbs and engaged in an efficient induction of CD8+ T-cell responses, greatly expanding the possible use of mAb for passive cancer immunotherapy. Cancer Res; 72(7); 1672–82. ©2012 AACR.

Integrated NY-ESO-1 antibody and CD8+ T-cell responses correlate with clinical benefit in advanced melanoma patients treated with ipilimumab

Ipilimumab, a monoclonal antibody against cytotoxic T lymphocyte antigen 4 (CTLA-4), has been shown to improve survival in patients with advanced metastatic melanoma. It also enhances immunity to NY-ESO-1, a cancer/testis antigen expressed in a subset of patients with melanoma. To characterize the association between immune response and clinical outcome, we first analyzed NY-ESO-1 serum antibody by ELISA in 144 ipilimumab-treated patients with melanoma and found 22 of 140 (16%) seropositive at baseline and 31 of 144 (22%) seropositive following treatment. These NY-ESO-1-seropositive patients had a greater likelihood of experiencing clinical benefit 24 wk after ipilimumab treatment than NY-ESO-1-seronegative patients (P = 0.02, relative risk = 1.8, two-tailed Fisher test). To understand why some patients with NY-ESO-1 antibody failed to experience clinical benefit, we analyzed NY-ESO-1-specific CD4(+) and CD8(+) T-cell responses by intracellular multicytokine staining in 20 NY-ESO-1-seropositive patients and found a surprising dissociation between NY-ESO-1 antibody and CD8 responses in some patients. NY-ESO-1-seropositive patients with associated CD8(+) T cells experienced more frequent clinical benefit (10 of 13; 77%) than those with undetectable CD8(+) T-cell response (one of seven; 14%; P = 0.02; relative risk = 5.4, two-tailed Fisher test), as well as a significant survival advantage (P = 0.01; hazard ratio = 0.2, time-dependent Cox model). Together, our data suggest that integrated NY-ESO-1 immune responses may have predictive value for ipilimumab treatment and argue for prospective studies in patients with established NY-ESO-1 immunity. The current findings provide a strong rationale for the clinical use of modulators of immunosuppression with concurrent approaches to favor tumor antigen-specific immune responses, such as vaccines or adoptive transfer, in patients with cancer.

Human Langerhans cells capture measles virus through Langerin and present viral antigens to CD4⁺ T cells but are incapable of cross-presentation

Langerhans cells (LCs) are a subset of DCs that reside in the upper respiratory tract and are ideally suited to sense respiratory virus infections. Measles virus (MV) is a highly infectious lymphotropic and myelotropic virus that enters the host via the respiratory tract. Here, we show that human primary LCs are capable of capturing MV through the C-type lectin Langerin. Both immature and mature LCs presented MV-derived antigens in the context of HLA class II to MV-specific CD4(+) T cells. Immature LCs were not susceptible to productive infection by MV and did not present endogenous viral antigens in the context of HLA class I. In contrast, mature LCs could be infected by MV and presented de novo synthesized viral antigens to MV-specific CD8(+) T cells. Notably, neither immature nor mature LCs were able to cross-present exogenous UV-inactivated MV or MV-infected apoptotic cells. The lack of direct infection of immature LCs, and the inability of both immature and mature LCs to cross-present MV antigens, suggest that human LCs may not be directly involved in priming MV-specific CD8(+) T cells. Immune activation of LCs seems a prerequisite for MV infection of LCs and subsequent CD8(+) T-cell priming via the endogenous antigen presentation pathway.

ISCOMATRIX adjuvant combines immune activation with antigen delivery to dendritic cells in vivo leading to effective cross-priming of CD8+ T cells

Cancer vaccines aim to induce CTL responses against tumors. Challenges for vaccine design are targeting Ag to dendritic cells (DCs) in vivo, facilitating cross-presentation, and conditioning the microenvironment for Th1 type immune responses. In this study, we report that ISCOM vaccines, which consist of ISCOMATRIX adjuvant and protein Ag, meet these challenges. Subcutaneous injection of an ISCOM vaccine in mice led to a substantial influx and activation of innate and adaptive immune effector cells in vaccine site-draining lymph nodes (VDLNs) as well as IFN-γ production by NK and NKT cells. Moreover, an ISCOM vaccine containing the model Ag OVA (OVA/ISCOM vaccine) was efficiently taken up by CD8α(+) DCs in VDLNs and induced their maturation and IL-12 production. Adoptive transfer of transgenic OT-I T cells revealed highly efficient cross-presentation of the OVA/ISCOM vaccine in vivo, whereas cross-presentation of soluble OVA was poor even at a 100-fold higher concentration. Cross-presenting activity was restricted to CD8α(+) DCs in VDLNs, whereas Langerin(+) DCs and CD8α(-) DCs were dispensable. Remarkably, compared with other adjuvant systems, the OVA/ISCOM vaccine induced a high frequency of OVA-specific CTLs capable of tumor cell killing in different tumor models. Thus, ISCOM vaccines combine potent immune activation with Ag delivery to CD8α(+) DCs in vivo for efficient induction of CTL responses.

Efficient in vivo priming by vaccination with recombinant NY-ESO-1 protein and CpG in antigen naive prostate cancer patients

PURPOSE

NY-ESO-1, one of the most immunogenic tumor antigens, is expressed in 15% to 25% of metastatic prostate cancers. The immunological and clinical effects of vaccination with recombinant NY-ESO-1 protein combined with CpG as adjuvant were evaluated.

EXPERIMENTAL DESIGN

In a phase I clinical study, patients with advanced prostate cancer were vaccinated with recombinant NY-ESO-1 protein (100 μg) mixed with CpG 7909 (2.5 mg) every 3 weeks intradermally for 4 doses. Objectives of the study were the safety of the vaccine and changes of specific humoral and cellular immunological responses to NY-ESO-1 in relation to detectable NY-ESO-1 expression in the individual tumor.

RESULTS

All 12 baseline sero-negative patients developed high-titer NY-ESO-1 antibody responses. B-cell epitope mapping identified NY-ESO-1 p91-110 to be recognized most frequently by vaccine-induced antibodies. Two patients developed significant antibody titers against the adjuvant CpG. NY-ESO-1-specific CD4+ and/or CD8+ T-cell responses were induced in 9 patients (69%). Five of these 9 patients did not express NY-ESO-1 in the autologous tumor. Postvaccine CD8+ T-cell clones recognized and lyzed HLA-matched tumor cell lines in an antigen-specific manner.

CONCLUSION

Our data provide clear evidence for the capacity of NY-ESO-1 protein/CpG vaccine to induce integrated antigen-specific immune responses in vivo and to efficiently prime CD8+ T-cell responses in NY-ESO-1 antigen-negative patients. Our results may also support further clinical vaccination protocols with NY-ESO-1 protein not only focused on the treatment of existing cancer, but also to prevent further development of NY-ESO-1 positive cancers in vivo.

Processing and cross-presentation of individual HLA-A, -B, or -C epitopes from NY-ESO-1 or an HLA-A epitope for Melan-A differ according to the mode of antigen delivery

The ability of dendritic cells (DCs) to cross-present protein tumor antigens to cytotoxic T lymphocytes (CTLs) underpins the success of therapeutic cancer vaccines. We studied cross-presentation of the cancer/testis antigen, NY-ESO-1, and the melanoma differentiation antigen, Melan-A by human DC subsets. Monocyte-derived DCs (MoDCs) efficiently cross-presented human leukocyte associated (HLA)-A2-restricted epitopes from either a formulated NY-ESO-1/ISCOMATRIX vaccine or when either antigen was mixed with ISCOMATRIX adjuvant. HLA-A2 epitope generation required endosomal acidification and was proteasome-independent for NY-ESO-1 and proteasome-dependent for Melan-A. Both MoDCs and CD1c(+) blood DCs cross-presented NY-ESO-1-specific HLA-A2(157-165)-, HLA-B7(60-72)-, and HLA-Cw3(92-100)-restricted epitopes when formulated as an NY-ESO-1/ISCOMATRIX vaccine, but this was limited when NY-ESO-1 and ISCOMATRIX adjuvant were added separately to the DC cultures. Finally, cross-presentation of NY-ESO-1(157-165)/HLA-A2, NY-ESO-1(60-72)/HLA-B7, and NY-ESO-1(92-100)/HLA-Cw3 epitopes was proteasome-dependent when formulated as immune complexes (ICs) but only proteasome-dependent for NY-ESO-1(60-72)/HLA-B7-restricted cross-presentation facilitated by ISCOMATRIX adjuvant. We demonstrate, for the first time, proteasome-dependent and independent cross-presentation of HLA-A-, B-, and C-restricted epitopes within the same full-length tumor antigen by human DCs. Our findings identify important differences in the capacities of human DC subsets to cross-present clinically relevant, full-length tumor antigens and how vaccine formulation impacts CTL responses in vivo.

Prolonged antigen survival and cytosolic export in cross-presenting human gammadelta T cells

Human blood Vgamma9Vdelta2 T cells respond to signals from microbes and tumors and subsequently differentiate into professional antigen-presenting cells (gammadelta T-APCs) for induction of CD4(+) and CD8(+) T cell responses. gammadelta T-APCs readily take up and degrade exogenous soluble protein for peptide loading on MHC I, in a process termed antigen cross-presentation. The mechanisms underlying antigen cross-presentation are ill-defined, most notably in human dendritic cells (DCs), and no study has addressed this process in gammadelta T-APCs. Here we show that intracellular protein degradation and endosomal acidification were significantly delayed in gammadelta T-APCs compared with human monocyte-derived DCs (moDCs). Such conditions are known to favor antigen cross-presentation. In both gammadelta T-APCs and moDCs, internalized antigen was transported across insulin-regulated aminopeptidase (IRAP)-positive early and late endosomes; however, and in contrast to various human DC subsets, gammadelta T-APCs efficiently translocated soluble antigen into the cytosol for processing via the cytosolic proteasome-dependent cross-presentation pathway. Of note, gammadelta T-APCs cross-presented influenza antigen derived from virus-infected cells and from free virus particles. The robust cross-presentation capability appears to be a hallmark of gammadelta T-APCs and underscores their potential application in cellular immunotherapy.

Granzymes in cancer and immunity

Cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells are indispensable factors in the body's ongoing defence against viral infection and tumor development. CTL/NK cells recognize and kill infected or aberrant target cells by two major pathways: either through introduction of a battery of proteases - called granzymes - to the target cell cytosol, or through TNF superfamily-dependent killing. During granzyme-dependent killing, target cell death is quick and efficient and is mediated by multiple granzymes, acting via redundant cell death pathways. Although granzyme-mediated cell death has been intensively studied, recent work has also hinted at an alternative, proinflammatory role for these enzymes. Thus, in addition to their well-established role as intracellular effectors of target cell death, recent data suggest that granzymes may have an extracellular role in the propagation of immune signals. In this study, we discuss the role of granzymes as central factors in antitumor immunity, as well possible roles for these proteases as instigators of inflammation.

Development of prophylactic and therapeutic vaccines using the ISCOMATRIX adjuvant

Adjuvants are components that when added to subunit antigen (Ag) vaccines boost their immunogenicity and thus immune efficacy. However, there are few adjuvants that are approved for clinical use resulting in a critical need for the development of safe and effective adjuvants for use in both prophylactic and therapeutic vaccines. The paucity of appropriate adjuvants is more chronic for the development of therapeutic vaccines for cancer and chronic infectious disease, which need to induce cytotoxic T-cell responses via cross-presentation of the vaccine Ag by dendritic cells. The ISCOMATRIX adjuvant represents a unique adjuvant system that facilitates Ag delivery and presentation as well as immunomodulation to provide enhanced and accelerated immune responses. The immune responses generated are of broad specificity to the vaccine Ag, and include robust antibody responses of multiple subclasses as well as both CD4(+) and CD8(+) T-cell responses. Here we discuss our understanding of the mechanisms of action by which ISCOMATRIX adjuvant may facilitate these integrated immune responses and touch on insights gained through its clinical experience.

ISCOMATRIX adjuvant induces efficient cross-presentation of tumor antigen by dendritic cells via rapid cytosolic antigen delivery and processing via tripeptidyl peptidase II

Cancer vaccines aim to induce antitumor CTL responses, which require cross-presentation of tumor Ag to CTLs by dendritic cells (DCs). Adjuvants that facilitate cross-presentation of vaccine Ag are therefore key for inducing antitumor immunity. We previously reported that human DCs could not efficiently cross-present the full-length cancer/testis Ag NY-ESO-1 to CTL unless formulated as either an immune complex (NY-ESO-1/IC) or with ISCOMATRIX adjuvant. We now demonstrate that NY-ESO-1/ICs induce cross-presentation of HLA-A2- and HLA-Cw3-restricted epitopes via a proteasome-dependent pathway. In contrast, cross-presentation of NY-ESO-1/ISCOMATRIX vaccine was proteasome independent and required the cytosolic protease tripeptidyl peptidase II. Trafficking studies revealed that uptake of ICs and ISCOMATRIX vaccine by DCs occurred via endocytosis with delivery to lysosomes. Interestingly, ICs were retained in lysosomes, whereas ISCOMATRIX adjuvant induced rapid Ag translocation into the cytosol. Ag translocation was dependent on endosomal acidification and IL-4-driven differentiation of monocytes into DCs. This study demonstrates that Ag formulation determines Ag processing and supports a role for tripeptidyl peptidase II in cross-presentation of CTL epitopes restricted to diverse HLA alleles.

Monoclonal antibodies for cancer immunotherapy

Monoclonal antibodies are effective treatments for many malignant diseases. However, the ability of antibodies to initiate tumour-antigen-specific immune responses has received less attention than have other mechanisms of antibody action. We describe the rationale and evidence for the development of antibodies that can stimulate host tumour-antigen-specific immune responses. Such responses can be induced through the induction of antibody-dependent cellular cytotoxicity, promotion of antibody-targeted cross-presentation of tumour antigens, or by triggering of the idiotypic network. Future treatment modifications or combinations might be able to prolong, amplify, and shape these immune responses to increase the clinical benefits of antibody therapy for human cancer.

Long-lasting cross-presentation of tumor antigen in human DC

DC cross-present exogenous antigens on MHC class I molecules, a process required for the onset of anti-tumor immune responses. In order to study the cross-presentation of tumor antigens by human DC, we compared the pathways of cross-presentation of long peptides requiring internalization and intracellular processing with the direct presentation of short peptides, which does not require intracellular processing. We found that, after brief incubations with DC, short peptides were presented to CD8(+) T cells with higher efficiencies than long peptides. After longer times of chase in the absence of peptide, however, the efficiency of presentation of the two types of peptides was reversed. After 2-3 days, DC pulsed with long peptides still activated T cells efficiently, while DC pulsed with short peptides failed to do so. Long-lasting presentation of the long peptides was, at least in part, due to a stored persistent pool of antigen, which was still available for loading on MHC class I molecules after several days of chase. These results show that the use of long synthetic peptides allows the efficient, long-lasting, presentation of tumor antigens, suggesting that long peptides represent an interesting approach for active anti-tumor vaccination.

Humoral immune responses in patients vaccinated with 1-146 HER2 protein complexed with cholesteryl pullulan nanogel

The CHP-HER2 vaccine, comprising truncated 146HER2 protein complexed with nanogels of cholesteryl pullulan (CHP), is a novel protein antigen vaccine that elicits 146HER2-specific CD8(+) and CD4(+) T-cell immune responses in patients with HER2-expressing tumors. We analyzed the humoral responses in patients vaccinated with CHP-HER2 and those with CHP-HER2 plus granulocyte-macrophage colony-stimulating factor (GM-CSF). The vaccine was injected subcutaneously at a dose of 300 microg protein. Nine patients received the vaccine alone over the first four injections, followed by CHP-HER2 with GM-CSF or OK-432, whereas six received CHP-HER2 plus GM-CSF from the first cycle. 146HER2-specific IgG antibodies were induced in 14 patients, who were negative at baseline. The antibodies became detectable after the second or third vaccination and reached plateau levels after the third or fourth cycle in patients vaccinated with CHP-HER2 plus GM-CSF. In contrast, the antibodies appeared only after the third to sixth vaccination and the plateau appeared after the fourth to eighth cycle in patients vaccinated with the CHP-HER2 vaccine alone over the first four cycles. The antibodies induced by the vaccine were not reactive with HER2 antigen expressed on the cell surface in any of the patients. Epitope analysis using overlapping peptides revealed a single region in the 146HER2 protein, amino acids 127-146, in eight patients who were initially vaccinated with CHP-HER2 alone. Similarly, the same HER2 region was recognized dominantly in patients vaccinated with GM-CSF. Our results indicate that CHP-HER2 induced HER2-specific humoral responses in patients with HER2-expressing tumors and that GM-CSF seems to accelerate the responses.

Induction of regulatory T cell–resistant helper CD4+ T cells by bacterial vector

Salmonella typhimurium engineered to deliver cancer/testis antigen NY-ESO-1 through type III secretion (S typhimurium–NY-ESO-1) was shown to be an efficient cancer vaccine construct in mice and to stimulate NY-ESO-1–specific CD8+/CD4+ T cells in vitro in patients with cancer with NY-ESO-1 spontaneous immunity. We also showed that individuals without spontaneous immunity to NY-ESO-1 had specific CD4+ T-cell precursors with high avidity to NY-ESO-1 under tight control by CD4+CD25+ regulatory T (Treg) cells. We now found that in healthy donors and patients with melanoma without NY-ESO-1 spontaneous immunity, S typhimurium–NY-ESO-1 elicits CD4+ T helper 1 (Th1) cells in vitro recognizing naturally processed antigen from these high-avidity NY-ESO-1–specific naive precursors. In contrast to peptide stimulation, induction of specific Th1 cells with S typhimurium–NY-ESO-1 did not require in vitro depletion of CD4+CD25+ Treg cells, and this prevailing effect was partially blocked by disruption of interleukin-6 or glucocorticoid-induced TNF receptor (GITR) signals. Furthermore, S typhimurium–induced Th1 cells had higher GITR expression than peptide-induced Th1 cells and were resistant to suppression by CD4+CD25+ Treg cells in a GITR-dependent fashion. We propose that S typhimurium–NY-ESO-1 induces antigen-specific T-cell responses that are resistant to suppression by CD4+CD25+ Treg cells.

Booster vaccination of cancer patients with MAGE-A3 protein reveals long-term immunological memory or tolerance depending on priming

We previously reported results of a phase II trial in which recombinant MAGE-A3 protein was administered with or without adjuvant AS02B to 18 non-small-cell lung cancer (NSCLC) patients after tumor resection. We found that the presence of adjuvant was essential for the development of humoral and cellular responses against selected MAGE-A3 epitopes. In our current study, 14 patients that still had no evidence of disease up to 3 years after vaccination with MAGE-A3 protein with or without adjuvant received an additional four doses of MAGE-A3 protein with adjuvant AS02B. After just one boost injection, six of seven patients originally vaccinated with MAGE-A3 protein plus adjuvant reached again their peak antibody titers against MAGE-A3 attained during the first vaccination. All seven patients subsequently developed even stronger antibody responses. Furthermore, booster vaccination widened the spectrum of CD4(+) and CD8(+) T cells against various new and known MAGE-A3 epitopes. In contrast, only two of seven patients originally vaccinated with MAGE-A3 protein alone developed high-titer antibodies to MAGE-A3, and all these patients showed very limited CD4(+) and no CD8(+) T cell reactivity, despite now receiving antigen in the presence of adjuvant. Our results underscore the importance of appropriate antigen priming using an adjuvant for generating persistent B and T cell memory and allowing typical booster responses with reimmunization. In contrast, absence of adjuvant at priming compromises further immunization attempts. These data provide an immunological rationale for vaccine design in light of recently reported favorable clinical responses in NSCLC patients after vaccination with MAGE-A3 protein plus adjuvant AS02B.

Cross-presentation of NY-ESO-1 cytotoxic T lymphocyte epitope fused to human heat shock cognate protein 70 by dendritic cells

The cancer-testis antigen NY-ESO-1 has been implicated as one of the most attractive candidates for a cancer vaccine. However, a protein vaccine generally meets inefficient antigen presentation to CD8(+) T cells, which could be overcome by combination with an appropriate adjuvant. Heat shock protein is a natural adjuvant and activates the antigen-presenting cells to channel exogenous antigens into the classical major histocompatibility complex class I antigen-processing pathway (cross-presentation). Therefore, we genetically fused a minigene encompassing the NY-ESO-1 cytotoxic T lymphocyte (CTL) epitope 157-165 (ESO p157-165) to the human heat shock cognate protein 70 (hsc70) and expressed the resulting fusion proteins in Escherichia coli. By using a human leukocyte antigen-A*0201-restricted NY-ESO-1-specific CTL clone, the cross-presentation of ESO p157-165 by monocyte-derived dendritic cells (mo-DC) pulsed with the fusion protein was evaluated. The fusion protein-pulsed mo-DC activates the CTL clone much more efficiently than the free NY-ESO-1 protein-pulsed mo-DC. Moreover, the magnitude of the CTL activity was comparable between ESO p157-165 and the fusion protein of hsc70 and ESO p157-165 (hsc70-ESO p157-165 fusion protein). In addition, the CTL activation induced by the fusion protein, but not by the epitope, was inhibited by paraformaldehyde fixation of the mo-DC and by treatment with lactacystin, a specific inhibitor for the proteasome. Finally, the hsc70-ESO p157-165 fusion protein-pulsed DC was able to induce an antigen-specific T-cell response. These results suggest that the hsc70-ESO p157-165 fusion protein is therefore considered to be a promising candidate as a cancer vaccine.

Both Langerhans cells and interstitial DC cross-present melanoma antigens and efficiently activate antigen-specific CTL

Dendritic cells (DC) have a unique capacity to present external antigens to CD8(+) T cells, i.e. cross-presentation. However, it is not fully established whether the ability to cross-presentation is restricted to a unique subset of DC in humans. Here, we show that two major myeloid DC subsets, i.e. Langerhans cells (LC) and interstitial DC (Int-DC), have the ability to cross-present antigens to CD8(+) T cells in vitro. LC and Int-DC were obtained from DC generated by culturing human CD34(+)-hematopoietic progenitor cells with GM-CSF, FLT3-L, and TNF-alpha (CD34-DC). Both DC subsets were able to capture necrotic/apoptotic allogeneic melanoma cells and present antigens to CD8(+) T cells, resulting in efficient priming of naive CD8(+) T cells into CTL capable of killing melanoma cells. Strikingly, a single stimulation with either subset (LC or Int-DC) or total CD34-DC loaded with necrotic/apoptotic melanoma cells was sufficient to activate melanoma-specific memory CD8(+) T cells obtained from patients with metastatic melanoma to become effective CTL. Thus, this study provides the rationale to use CD34-DC loaded with necrotic/apoptotic allogeneic melanoma cells in a clinical trial.

Vaccination with an NY-ESO-1 peptide of HLA class I/II specificities induces integrated humoral and T cell responses in ovarian cancer

NY-ESO-1 is a "cancer-testis" antigen expressed in epithelial ovarian cancer (EOC) and is among the most immunogenic tumor antigens defined to date. The NY-ESO-1 peptide epitope, ESO(157-170), is recognized by HLA-DP4-restricted CD4+ T cells and HLA-A2- and A24-restricted CD8+ T cells. To test whether providing cognate helper CD4+ T cells would enhance the antitumor immune response, we conducted a phase I clinical trial of immunization with ESO(157-170) mixed with incomplete Freund's adjuvant (Montanide ISA51) in 18 HLA-DP4+ EOC patients with minimal disease burden. NY-ESO-1-specific Ab responses and/or specific HLA-A2-restricted CD8+ and HLA-DP4-restricted CD4+ T cell responses were induced by a course of at least five vaccinations at three weekly intervals in a high proportion of patients. There were no serious vaccine-related adverse events. Vaccine-induced CD8+ and CD4+ T cell clones were shown to recognize NY-ESO-1-expressing tumor targets. T cell receptor analysis indicated that tumor-recognizing CD4+ T cell clones were structurally distinct from non-tumor-recognizing clones. Long-lived and functional vaccine-elicited CD8+ and CD4+ T cells were detectable in some patients up to 12 months after immunization. These results confirm the paradigm that the provision of cognate CD4+ T cell help is important for cancer vaccine design and provides the rationale for a phase II study design using ESO(157-170) epitope or the full-length NY-ESO-1 protein for immunotherapy in patients with EOC.

Vaccination with NY-ESO-1 protein and CpG in Montanide induces integrated antibody/Th1 responses and CD8 T cells through cross-priming

The use of recombinant tumor antigen proteins is a realistic approach for the development of generic cancer vaccines, but the potential of this type of vaccines to induce specific CD8(+) T cell responses, through in vivo cross-priming, has remained unclear. In this article, we report that repeated vaccination of cancer patients with recombinant NY-ESO-1 protein, Montanide ISA-51, and CpG ODN 7909, a potent stimulator of B cells and T helper type 1 (Th1)-type immunity, resulted in the early induction of specific integrated CD4(+) Th cells and antibody responses in most vaccinated patients, followed by the development of later CD8(+) T cell responses in a fraction of them. The correlation between antibody and T cell responses, together with the ability of vaccine-induced antibodies to promote in vitro cross-presentation of NY-ESO-1 by dendritic cells to vaccine-induced CD8(+) T cells, indicated that elicitation of NY-ESO-1-specific CD8(+) T cell responses by cross-priming in vivo was associated with the induction of adequate levels of specific antibodies. Together, our data provide clear evidence of in vivo cross-priming of specific cytotoxic T lymphocytes by a recombinant tumor antigen vaccine, underline the importance of specific antibody induction for the cross-priming to occur, and support the use of this type of formulation for the further development of efficient cancer vaccines.

Cross-presentation of antigens from apoptotic tumor cells by liver sinusoidal endothelial cells leads to tumor-specific CD8+ T cell tolerance

Development of tumor-specific T cell tolerance contributes to the failure of the immune system to eliminate tumor cells. Here we report that hematogenous dissemination of tumor cells followed by their elimination and local removal of apoptotic tumor cells in the liver leads to subsequent development of T cell tolerance towards antigens associated with apoptotic tumor cells. We provide evidence that liver sinusoidal endothelial cells (LSEC) remove apoptotic cell fragments generated by induction of tumor cell apoptosis through hepatic NK1.1+ cells. Antigen associated with apoptotic cell material is processed and cross-presented by LSEC to CD8+ T cells, leading to induction of CD8+ T cell tolerance. Adoptive transfer of LSEC isolated from mice challenged previously with tumor cells promotes development of CD8+ T cell tolerance towards tumor-associated antigen in vivo. Our results indicate that hematogenous dissemination of tumor cells, followed by hepatic tumor cell elimination and local cross-presentation of apoptotic tumor cells by LSEC and subsequent CD8+ T cell tolerance induction, represents a novel mechanism operative in tumor immune escape.

NY-ESO-1 immunotherapy for multiple myeloma

Most patients with poor-prognosis myeloma (abnormal metaphase cytogenetics) achieve excellent responses with tandem transplants, but the remissions are not durable. Novel interventions such as immunotherapy may eradicate the residual chemotherapy-resistant disease. Immunotherapy targeting weak antigens such as myeloma idiotype or tumor lysate has failed to produce clinically meaningful responses. We previously reported that the NY-ESO-1 antigen is expressed in >60% of poor-prognosis myeloma at diagnosis. Since NY-ESO-1 is highly immunogenic and is not expressed in most normal tissues, it is an ideal target for anti-myeloma immunotherapy. NY-ESO-1 based therapies are already being tested in clinical trials for a multitude of tumors. This review discusses the potential of NY-ESO-1 immunotherapy to improve outcome for myeloma.

Dendritic cells loaded with killed allogeneic melanoma cells can induce objective clinical responses and MART-1 specific CD8+ T-cell immunity

Dendritic cells (DCs) loaded with killed allogeneic tumors can cross-prime tumor-specific naive CD8 T cells in vitro, thereby providing an option to overcome human leukocyte antigen restriction inherent to loading DC vaccines with peptides. We have vaccinated 20 patients with stage IV melanoma with autologous monocyte-derived DCs loaded with killed allogeneic Colo829 melanoma cell line. DCs were generated by culturing monocytes with granulocyte macrophage-colony stimulating factor (granulocyte macrophage-colony stimulating factor) and interleukin (IL-4) and activated by additional culture with tumor necrosis factor and CD40 ligand. A total of 8 vaccines were administered at monthly intervals. The first patient was accrued December 2002 and the last November 2003. Fourteen patients were alive at 12 months, 9 patients were alive at 24 months, and 8 patients are alive as of January 2006. The estimated median overall survival is 22.5 months with a range of 2 to 35.5 months. Vaccinations were safe and tolerable. They induced, in 2 patients who failed previous therapy, durable objective clinical responses, 1 complete regression (CR) and 1 partial regression (PR) lasting 18 and 23 months, respectively. Three out of 13 analyzed patients showed T-cell immunity to melanoma antigen recognized by autologous T cells (MART-1) tissue differentiation antigen. Two of 3 patients showed improved immune function after vaccinations demonstrated by improved secretion of interferon (IFN)-gamma or T-cell proliferation in response to MART-1 derived peptides. In one of these patients, vaccination led to elicitation of CD8 T-cell immunity specific to a novel peptide-derived from MART-1 antigen, suggesting that cross-priming/presentation of melanoma antigens by DC vaccine had occurred. Thus, the present results justify the design of larger follow-up studies to assess the clinical response to DC vaccines loaded with killed allogeneic tumor cells in patients with metastatic melanoma.

An unconventional antigen translated by a novel internal ribosome entry site elicits antitumor humoral immune reactions

Self-tumor Ags that elicit antitumor immune responses in responses to IFN-alpha stimulation remain poorly defined. We screened a human testis cDNA library with sera from three polycythemia vera patients who responded to IFN-alpha and identified a novel Ag, MPD6. MPD6 belongs to the group of cryptic Ags without conventional genomic structure and is encoded by a cryptic open reading frame located in the 3'-untranslated region of myotrophin mRNA. MPD6 elicits IgG Ab responses in a subset of polycythemia vera patients, as well as patients with chronic myelogenous leukemia and prostate cancer, suggesting that it is broadly immunogenic. The expression of myotrophin-MPD6 transcripts was up-regulated in some tumor cells, but only slightly increased in K562 cells in response to IFN-alpha treatment. By using bicistronic reporter constructs, we showed that the translation of MPD6 was mediated by a novel internal ribosome entry site (IRES) upstream of the MPD6 reading frame. Furthermore, the MPD6-IRES-mediated translation, but not myotrophin-MPD6 transcription, was significantly up-regulated in response to IFN-alpha stimulation. These findings demonstrate that a novel IRES-mediated mechanism may be responsible for the translation of unconventional self-Ag MPD6 in responsive to IFN-alpha stimulation. The eliciting antitumor immune response against unconventional Ag MPD6 in patients with myeloproliferative diseases suggests MPD6 as a potential target of novel immunotherapy.

Dendritic cell surface calreticulin is a receptor for NY-ESO-1: direct interactions between tumor-associated antigen and the innate immune system

How the immune system recognizes endogenously arising tumors and elicits adaptive immune responses against nonmutated tumor-associated Ags is poorly understood. In search of intrinsic factors contributing to the immunogenicity of the tumor-associated Ag NY-ESO-1, we found that the NY-ESO-1 protein binds to the surface of immature dendritic cells (DC), macrophages, and monocytes, but not to that of B cells or T cells. Using immunoprecipitation coupled with tandem mass spectrometry, we isolated DC surface calreticulin as the receptor for NY-ESO-1. Calreticulin Abs blocked NY-ESO-1 binding on immature DC and its cross-presentation to CD8+ T cells in vitro. Calreticulin/NY-ESO-1 interactions provide a direct link between NY-ESO-1, the innate immune system, and, potentially, the adaptive immune response against NY-ESO-1.

NY-ESO-1: review of an immunogenic tumor antigen

In the 9 years since its discovery, cancer-testis antigen NY-ESO-1 has made one of the fastest transitions from molecular, cellular, and immunological description to vaccine and immunotherapy candidate, already tested in various formulations in more than 30 clinical trials worldwide. Its main characteristic resides in its capacity to elicit spontaneous antibody and T-cell responses in a proportion of cancer patients. An overview of immunological findings and immunotherapeutic approaches with NY-ESO-1, as well the role of regulation in NY-ESO-1 immunogenicity, is presented here.

The dominant role of CD8+ dendritic cells in cross-presentation is not dictated by antigen capture

Mouse spleens contain three populations of conventional (CD11c(high)) dendritic cells (DCs) that play distinct functions. The CD8(+) DC are unique in that they can present exogenous antigens on their MHC class I molecules, a process known as cross-presentation. It is unclear whether this special ability is because only the CD8(+) DC can capture the antigens used in cross-presentation assays, or because this is the only DC population that possesses specialized machinery for cross-presentation. To solve this important question we examined the splenic DC subsets for their ability to both present via MHC class II molecules and cross-present via MHC class I using four different forms of the model antigen ovalbumin (OVA). These forms include a cell-associated form, a soluble form, OVA expressed in bacteria, or OVA bound to latex beads. With the exception of bacterial antigen, which was poorly cross-presented by all DC, all antigenic forms were cross-presented much more efficiently by the CD8(+) DC. This pattern could not be attributed simply to a difference in antigen capture because all DC subsets presented the antigen via MHC class II. Indeed, direct assessments of endocytosis showed that CD8(+) and CD8(-) DC captured comparable amounts of soluble and bead-associated antigen, yet only the CD8(+) DC cross-presented these antigenic forms. Our results indicate that cross-presentation requires specialized machinery that is expressed by CD8(+) DC but largely absent from CD8(-) DC. This conclusion has important implications for the design of vaccination strategies based on antigen targeting to DC.

Influence of CD4+CD25+ regulatory T cells on low/high-avidity CD4+ T cells following peptide vaccination

We have recently reported that NY-ESO-1-specific naive CD4+ T cell precursors exist in most individuals but are suppressed by CD4+CD25+ regulatory T cells (Tregs), while memory CD4+ T cell effectors against NY-ESO-1 are found only in cancer patients with spontaneous Ab responses to NY-ESO-1. In this study, we have analyzed mechanisms of CD4+ T cell induction following peptide vaccination in relation to susceptibility to Tregs. Specific HLA-DP4-restricted CD4+ T cell responses were elicited after vaccination with NY-ESO-1(157-170) peptide (emulsified in IFA) in patients with NY-ESO-1-expressing epithelial ovarian cancer. These vaccine-induced CD4+ T cells were detectable from effector/memory populations without requirement for in vitro CD4+CD25+ T cell depletion. However, they were only able to recognize NY-ESO-1(157-170) peptide but not naturally processed NY-ESO-1 protein and had much lower avidity compared with NY-ESO-1-specific pre-existing naive CD4+CD25- T cell precursors or spontaneously induced CD4+ T cell effectors of cancer patients with NY-ESO-1 Ab. We propose that vaccination with NY-ESO-1(157-170) peptide recruits low-avidity T cells with low sensitivity to Tregs and fails to modulate the suppressive effect of Tregs on high-avidity NY-ESO-1-specific T cell precursors.

Cross-presentation of HLA class I epitopes from influenza matrix protein produced in Saccharomyces cerevisiae

Here we report that genetically engineered yeast of the strain Saccharomyces cerevisiae expressing full-length influenza matrix protein (IMP) attached to the yeast cell wall are a very versatile host for antigen delivery. Feeding of dendritic cells with either intact yeast expressing IMP protein or soluble IMP protein cleaved off the cell wall resulted in protein uptake, processing and cross-presentation of IMP-derived peptides. This process was analysed using previously established T-cell lines recognizing the immuno-dominant 58-66 peptide when presented by HLA-A2*0201 complexes. In addition, IMP(58-66)/HLA-A2*0201-specific antibodies were selected from a naive phage library which confirmed that peptide presentation was an active process of endocellular uptake and not just a result of external peptide loading. Moreover, MHC peptide antibodies could block the recognition of peptide-presenting dendritic cells by IMP(58-66)-specific T-cells in a dose dependent manner. There was no difference in T-cell recognition when either intact yeast or yeast cell extracts were used for DC feeding. Together, these data demonstrate that yeast derived proteins either in their soluble form or as part of a whole yeast vaccine are taken up, processed and presented by dendritic cells in HLA class I context.

Heat Shock Protein–Based Cancer Vaccines

The ability to duplicate the remarkable success of infectious disease vaccines in cancer, with durably robust and highly specific antitumor immune responses, has been long held as one of the keys in developing true "magic bullet" cancer therapies. This article attempts to explain why cancer vaccines have failed (so far), delineate the increasingly complex barriers that prevent the eliciting of effective antitumor immunity and examines the ability of heat shock protein-based vaccines to overcome these barriers. This article is not a definitive compendium of the huge body of relevant literature but rather focuses on the major concepts underlying active specific immunotherapy in general and heat shock protein vaccines in particular.

Langerhans cells cross-present antigen derived from skin

Dendritic cells (DC) efficiently cross-present exogenous antigen on MHC class I molecules to CD8+ T cells. However, little is known about cross-presentation by Langerhans cells (LC), the DCs of the epidermis. Therefore, we investigated this issue in detail. Isolated murine LCs were able to cross-present soluble ovalbumin protein on MHC-class I molecules to antigen-specific CD8+ T cells, albeit less potently than the CD8+ DC subsets from spleen. Furthermore, LCs cross-presented cell-associated ovalbumin peptide and protein expressed by neighboring keratinocytes. Use of transporter associated with antigen processing (TAP-1)-deficient mice suggested a TAP-dependent pathway. Similar observations were made with migratory LC. Antigen expressed in the epidermis was ingested by LCs during migration from the epidermis and presented to antigen-specific T cells in vitro. Cross-presentation of ovalbumin protein by LCs induced IFN-gamma production and cytotoxicity in antigen-specific CD8+ T cells. Additionally, epicutaneous application of ovalbumin protein induced in vivo proliferation of OT-I T cells in the draining lymph nodes; this was markedly enhanced when antigen was applied to inflamed, barrier-disrupted skin. Thus, LCs cross-present exogenous antigen to CD8+ T cells and induce effector functions, like cytokine production and cytotoxicity, and may thereby critically contribute in epicutaneous vaccination approaches.

In vitro Stimulation of CD8 and CD4 T Cells by Dendritic Cells Loaded with a Complex of Cholesterol-Bearing Hydrophobized Pullulan and NY-ESO-1 Protein: Identification of a New HLA-DR15–Binding CD4 T-Cell Epitope

PURPOSE

NY-ESO-1 belongs to a class of cancer/testis antigens and has been shown to be immunogenic in cancer patients. We synthesized a complex of cholesterol-bearing hydrophobized pullulan and NY-ESO-1 protein (CHP/ESO) and investigated the in vitro stimulation of CD8 and CD4 T cells from peripheral blood mononuclear cells in healthy donors with autologous CHP/ESO-loaded dendritic cells as antigen-presenting cells.

EXPERIMENTAL DESIGN

In vitro stimulation of CD8 or CD4 T cells was determined by IFNgamma ELISPOT assays against autologous EBV-B cells infected with vaccinia/NY-ESO-1 recombinant virus or wild-type vaccinia virus as targets and by ELISA measuring secreted IFNgamma.

RESULTS

NY-ESO-1-specific CD8 and CD4 T cells were induced. In a donor expressing HLA-A2, CD8 T cells stimulated with CHP/ESO-loaded dendritic cells recognized naturally processed NY-ESO-1(157-165), an HLA-A2-binding CD8 T cell epitope. NY-ESO-1 CD4 T cells were Th1-type. We identified a new HLA-DR15-binding CD4 T cell epitope, NY-ESO-1(37-50).

CONCLUSIONS

These findings indicate that CHP/ESO is a promising polyvalent cancer vaccine targeting NY-ESO-1.

Protein transduction of dendritic cells for NY-ESO-1-based immunotherapy of myeloma

Myeloma vaccines, based on dendritic cells pulsed with idiotype or tumor lysate, have been met with limited success, probably in part due to insufficient cross-priming of myeloma antigens. A powerful method to introduce myeloma-associated antigens into the cytosol of dendritic cells is protein transduction, a process by which proteins fused with a protein transduction domain (PTD) freely traverse membrane barriers. NY-ESO-1, an immunogenic antigen by itself highly expressed in 60% of high-risk myeloma patients, was purified to near homogeneity both alone and as a recombinant fusion protein with a PTD, derived from HIV-Tat. Efficient entry of PTD-NY-ESO-1 into dendritic cells, confirmed by microscopy, Western blotting, and intracellular flow cytometry, was achieved without affecting dendritic cell phenotype. Experiments with amiloride, which inhibits endocytosis, and N-acetyl-l-leucinyl-l-norleucinal, a proteasome inhibitor, confirmed that PTD-NY-ESO-1 entered dendritic cells by protein transduction and was degraded by the proteasome. Tetramer analysis indicated superior generation of HLA-A2.1, CD8+ T lymphocytes specific for NY-ESO-1(157-165) with PTD-NY-ESO-1 compared with NY-ESO-1 control protein (44% versus 2%, respectively). NY-ESO-1-specific T lymphocytes generated with PTD-NY-ESO-1 secreted IFN-gamma indicative of a Tc1-type cytokine response. Thus, PTD-NY-ESO-1 accesses the cytoplasm by protein transduction, is processed by the proteasome, and NY-ESO-1 peptides presented by HLA class I elicit NY-ESO-1-specific T lymphocytes.

Identification of B cell epitopes recognized by antibodies specific for the tumor antigen NY-ESO-1 in cancer patients with spontaneous immune responses

Expression of the germ line antigen NY-ESO-1 in adult somatic tissues other than testis is strictly found in association with cancer. Patients bearing NY-ESO-1 expressing tumors often develop integrated specific immune responses to the antigen, encompassing T cell and antibody responses. Hence, detection of NY-ESO-1 specific antibody responses can be considered as a cancer biomarker of great interest. Here, we used synthetic peptides spanning the sequence of the NY-ESO-1 protein to assess antibody responses in cancer patients. This approach allowed the identification of peptides containing linear B cell epitopes. Some peptides were recognized by the majority of seropositive patients thus identifying several distinct regions of the protein containing frequently recognized B cell epitopes. The results of this study provide the first appraisal of the diversity of naturally-occurring NY-ESO-1 specific antibodies and could be instrumental in the monitoring of therapy-induced antibody responses in cancer patients receiving NY-ESO-1-based vaccines.

Phase I trial of a murine antibody to MUC1 in patients with metastatic cancer: evidence for the activation of humoral and cellular antitumor immunity

BACKGROUND

BrevaRex mAb-AR20.5 is a murine anti-MUC1 monoclonal antibody generated to induce MUC1 antigen-specific immune responses through the formation of immune complexes with circulating MUC1 and/or MUC1-expressing tumor cells that may target these immune complexes (IC) to receptors on dendritic cells (DCs).

PATIENTS AND METHODS

A phase I study focusing on safety and immunology evaluated 1, 2 and 4-mg doses. Seventeen patients with MUC1-positive cancers received intravenous infusions of the antibody over 30 min on weeks 1, 3, 5, 9, 13 and 17 of treatment.

RESULTS

mAb-AR20.5 was well-tolerated, not associated with dose-limiting toxicity, and did not induce hypersensitivity reactions. Overall, five of 15 evaluable patients developed human anti-mouse antibodies (HAMA), five developed anti-idiotypic antibodies (Ab2) and seven developed anti-MUC1 antibodies. Immune responses were most prominent in the 2-mg dose cohort for all parameters tested, and treatment-emergent MUC1-specific T-cell responses were detected in five of 10 evaluable patients treated with mAb-AR20.5.

CONCLUSIONS

The injection of a murine antibody to MUC1 induces MUC1-specific immune responses in advanced cancer patients. Anti-MUC1 antibody increases correlated with decrease or stabilization of CA15.3 levels (P=0.03). The 2-mg dose of mAb-AR20.5 showed strongest biological activity, and will be evaluated in future efficacy trials.

Tumor antigen processing and presentation depend critically on dendritic cell type and the mode of antigen delivery

Dendritic cells (DCs) are being evaluated for cancer immunotherapy due to their unique ability to induce tumor-directed T-cell responses. Here we report that the type of human DC, the mode of activation, and the strategy for delivery of antigen are 3 critical factors for efficient stimulation of tumor-specific CD8+ and CD4+ T cells. Only CD1c+ blood DCs and monocyte-derived DCs (MoDCs) were capable of presenting epitopes of the full-length tumor antigen NY-ESO-1 on both major histocompatibility complex (MHC) class I (cross-presentation) and MHC II, whereas plasmacytoid DCs were limited to MHC II presentation. Cross-presentation was inefficient for soluble protein, but highly efficient for antigen-antibody immune complexes (NY-ESO-1/IC) and for protein formulated with ISCOMATRIX adjuvant (NY-ESO-1/IMX). DC activation with CD40L further enhanced cross-presentation efficiency. The mode of antigen delivery was found to be a determining factor for cytosolic proteolysis by DCs. Immune complexes (ICs) targeted a slow, proteasome-dependent cross-presentation pathway, whereas ISCOMATRIX (IMX) targeted a fast, proteasome-independent pathway. Both cross-presentation pathways resulted in a long-lived, T-cell stimulatory capacity, which was maintained for several days longer than for DCs pulsed with peptide. This may provide DCs with ample opportunities for sensitizing tumor-specific T cells against a broad array of tumor antigen epitopes in lymph nodes.

Selective blockade of inhibitory Fcgamma receptor enables human dendritic cell maturation with IL-12p70 production and immunity to antibody-coated tumor cells

The final differentiation or maturation of dendritic cells (DCs) in response to environmental stimuli influences their ability to both initiate immunity and determine the quality of the response to antigens. Circulating immune complexes and cell-bound immunoglobulins present in normal human sera represent a potential stimulus for inadvertent DC activation in the steady state and during autoimmunity. Here, we show that selective blockade of the inhibitory Fcgamma receptor (FcgammaR) FcgammaRIIb with recently developed monoclonal antibodies leads to maturation of human monocyte-derived DCs, which depends on the presence of IgG in normal human plasma. Plasma, in the presence of an FcgammaRIIb blockade, caused the DCs to up-regulate the expression of costimulatory molecules and to produce the inflammatory mediator IL-12p70. FcgammaRIIb blockade of DCs loaded with tumor cells led to increased tumor-specific T cell immunity without the need for exogenous stimuli other than human plasma. Therefore, the activation status of DCs in the presence of normal human serum depends on the balance between activating and inhibitory FcgammaRs and can be enhanced by new antibodies that react selectively with FcgammaRIIb. These data suggest an approach for modifying this balance to enhance immunity to immune complexes and antibody-coated tumor cells and to silence DC activation by immune complexes in autoimmune states.