Vaccine-specific local T cell reactivity in immunotherapy-associated vitiligo in melanoma patients

The occurrence of vitiligo in patients with melanoma is especially reported for patients undergoing immunotherapy. While vitiligo in these patients is thought to be related to an immune response directed against melanoma cells, solid evidence is lacking. Here we report local cytotoxic T cell reactivity in three melanoma patients who developed vitiligo, after experimental immunotherapy using dendritic cell vaccinations. Tetramer analysis showed that vaccine-induced T cells recognizing gp100 and tyrosinase are present at the vitiligo lesions. These T cells secrete IFN-gamma and IL-2 upon peptide specific stimulation as well as upon recognition of the autologous tumor. We show that functional CD8(+) T cells specific for melanoma differentiation antigens used in a melanoma immunotherapy trial, do not only invade the tumor, but also the vitiligo lesions. This directly links vitiligo to the immuno-therapeutic intervention and supports the hypothesis that vitiligo is a marker of immunity against melanoma cells.

DCIR is endocytosed into human dendritic cells and inhibits TLR8-mediated cytokine production

C-type lectin receptors (CLRs) expressed on APCs play a pivotal role in the immune system as pattern-recognition and antigen-uptake receptors. In addition, they may signal directly, leading to cytokine production and immune modulation. To this end, some CLRs, like dectin-1 and dendritic cell immunoreceptor (DCIR), contain intracellular ITIMs or ITAMs. In this study, we explored expression and function of the ITIM-containing CLR DCIR on professional APCs. DCIR is expressed on immature and mature monocyte-derived DCs (moDC) but also on monocytes, macrophages, B cells, and freshly isolated myeloid and plasmacytoid DCs. We show that endogenous DCIR is internalized efficiently into human moDC after triggering with DCIR-specific mAb. DCIR internalization is clathrin-dependent and leads to its localization in the endo-/lysosomal compartment, including lysosome-associated membrane protein-1+ lysosomes. DCIR triggering affected neither TLR4- nor TLR8-mediated CD80 and CD86 up-regulation. Interestingly, it did inhibit TLR8-mediated IL-12 and TNF-alpha production significantly, and TLR2-, TLR3-, or TLR4-induced cytokine production was not affected. Collectively, the data presented characterize DCIR as an APC receptor that is endocytosed efficiently in a clathrin-dependent manner and negatively affects TLR8-mediated cytokine production. These data provide further support to the concept of CLR/TLR cross-talk in modulating immune responses.

Activation of human plasmacytoid dendritic cells by TLR9 impairs Fc gammaRII-mediated uptake of immune complexes and presentation by MHC class II

Human plasmacytoid dendritic cells (pDCs)(2) exploit Ag uptake receptors like CD32a for internalization of exogenous Ags. Activation of pDC by TLR9 ligand CpG-C induces strong maturation. Surprisingly, we observed that CpG-C-stimulated pDCs showed impaired Ag-specific T cell proliferation whereas the induction of allogeneic T cell proliferation was not affected. We demonstrated that signals from TLR9 caused a rapid down-regulation of the capacity of pDC to take-up Ab-Ag complexes without altering their CD32a expression, thus explaining the reduced Ag presentation. The recent contrasting biological responses that were observed upon TLR9 ligation in pDCs prompted us to study the effect of several TLR9 ligands. We observed that type I IFN-inducer CpG-A, localizing in the early endosomal compartment, did not affect CD32a function, whereas CpGs localizing in the late endosomes and inducing pDC maturation clearly inhibited CD32a-mediated Ag uptake and presentation. We conclude that TLR9 ligands not only determine the type of response, i.e., type I IFN production (innate immunity) or maturation (adaptive immunity), but also directly affect Ag presentation capacity of pDCs. We hypothesize that pDC, once activated via TLR9-ligands reaching the late endosomes, can only present initially sampled Ags and thus are protected from uptake and processing of additional potential self-Ags.

Intratumoral rhIL-12 administration in head and neck squamous cell carcinoma patients induces B cell activation

The objectives of this study were to investigate the effects of intratumorally (i.t.) administered recombinant human interleukin-12 (rhIL-12) on the distribution and function of B cells in the primary tumors, the locoregional lymph nodes and peripheral blood of head and neck squamous cell carcinoma (HNSCC) patients. The initial characterization of the patients participating in the phase Ib and phase II studies has previously been reported. After rhIL-12 treatment, fewer secondary follicles with a broader outer region of the mantle zones and an increase in interfollicular B-blasts were seen in the enlarged lymph nodes compared with control HNSCC patients. The size of the germinal center (GC) was diminished, partly due to a decrease in the number of CD57+ GC cells that have been associated with immune suppression. These changes did not correlate with signs of apoptosis or CXCR5 expression by B cells. Strikingly, in 3 out of 4 IL-12 treated patients, increased IFN-gamma mRNA expression by B cells was detected. In addition, a highly significant IgG subclass switch was seen in the plasma with more IgG1, less IgG2 and more IgG4, indicating a switch to T helper 1 phenotype. Finally, peritumoral B cell infiltration was a positive prognostic sign for overall survival in the 30 HNSCC patients investigated, irrespective of IL-12 treatment. In conclusion, these data indicate that after i.t. IL-12 treatment in HNSCC, significant activation of the B cell and the B cell compartment occurred and that the presence of tumor infiltrating B cells correlated with overall survival of HNSCC patients.

Maximizing dendritic cell migration in cancer immunotherapy

BACKGROUND

The success of dendritic cell (DC)-based immunotherapy in inducing cellular immunity against tumors is highly dependent on accurate delivery and trafficking of the DC to T-cell-rich areas of secondary lymphoid tissues.

OBJECTIVE

To provide an overview of DC migration in vivo and how migration to peripheral lymph nodes might be improved to optimize DC therapy.

METHODS

We focused on DC migration in preclinical models and human skin explants and on clinical vaccination trials studying migration of in vitro-generated DC.

RESULTS/CONCLUSIONS

DC migration requires an intricate interplay between the cell and its environment. To maximize migration for cellular therapy, it is important to optimize the generation of migratory DC as well as treatment strategies.

Toll-like receptor signalling on Tregs: to suppress or not to suppress?

To balance self-tolerance and immunity against pathogens or tumours, the immune system depends on both activation mechanisms and down-regulatory mechanisms. Immunologists have long been focusing on activation mechanisms, and a major breakthrough was the identification of the Toll-like receptor (TLR) family of proteins. TLRs recognize conserved molecular patterns present on pathogens, including bacteria, viruses, fungi and protozoa. Pathogen recognition via TLRs activates the innate as well as the adaptive immune response. The discovery of a suppressive T-cell subset that constitutively expresses the interleukin (IL)-2 receptor alpha-chain (CD25) has boosted efforts to investigate the negative regulation of immune responses. It is now well appreciated that these regulatory T cells (Tregs) play a pivotal role in controlling immune function. Interestingly, recent studies revealed that TLR2 signalling affects Treg expansion and function. This review will focus on the presence and influence of different TLRs on T lymphocytes, including Tregs, and their role in cancer.

Selective cancer-germline gene expression in pediatric brain tumors

Cancer-germline genes (CGGs) code for immunogenic antigens that are present in various human tumors and can be targeted by immunotherapy. Their expression has been studied in a wide range of human tumors in adults. We measured the expression of 12 CGGs in pediatric brain tumors, to identify targets for therapeutic cancer vaccines. Real Time PCR was used to quantify the expression of genes MAGE-A1, MAGE-A2, MAGE-A3, MAGE-A4, MAGE-A6, MAGE-A10, MAGE-A12, MAGE-C2, NY-ESO-1 and GAGE-1,2,8 in 50 pediatric brain tumors of different histological subtypes. Protein expression was examined with immunohistochemistry. Fifty-five percent of the medulloblastomas (n = 11), 86% of the ependymomas (n = 7), 40% of the choroid plexus tumors (n = 5) and 67% of astrocytic tumors (n = 27) expressed one or more CGGs. Immunohistochemical analysis confirmed qPCR results. With exception of a minority of tumors, the overall level of CGG expression in pediatric brain tumors was low. We observed a high expression of at least one CGG in 32% of the samples. CGG-encoded antigens are therefore suitable targets in a very selected group of pediatric patients with a brain tumor. Interestingly, glioblastomas from adult patients expressed CGGs more often and at significantly higher levels compared to pediatric glioblastomas. This observation is in line with the notion that pediatric and adult glioblastomas develop along different genetic pathways.

Phenotypic and functional characterization of mature dendritic cells from pediatric cancer patients

BACKGROUND

Dendritic cells (DCs) are the most potent antigen-presenting cells of the immune system. Clinical trials have demonstrated that mature DCs loaded with tumor-associated antigens can induce tumor-specific immune responses. Theoretically, pediatric patients are excellent candidates for immunotherapy since their immune system is more potent compared to adults. We studied whether sufficient amounts of mature monocyte-derived DCs can be cultured from peripheral blood of pediatric cancer patients.

PROCEDURE

DCs from 15 pediatric patients with an untreated primary tumor were cultured from monocytes and matured with clinical grade cytokines. Phenotype and function were tested with flow cytometry, mixed lymphocyte reaction (MLR), and an in vitro migration assay. DCs of children with a solid tumor were compared with monocyte-derived DCs from age-related non-malignant controls.

RESULTS

Ex vivo-generated monocyte-derived DCs from pediatric patients can be generated in numbers sufficient for DC vaccination trials. Upon cytokine stimulation the DCs highly upregulate the expression of the maturation markers CD80, CD83, and CD86. The mature DCs are six times more potent in inducing T cell proliferation compared to immature DCs. Furthermore, mature DCs, but not immature DCs, express the chemokine receptor CCR7 and have the capacity to migrate in vitro.

CONCLUSIONS

These data indicate that mature DCs can be generated ex vivo to further optimize DC-vaccination trials in pediatric cancer patients.

Dendritic-cell immunotherapy: from ex vivo loading to in vivo targeting

The realization that dendritic cells (DCs) orchestrate innate and adaptive immune responses has stimulated research on harnessing DCs to create more effective vaccines. Early clinical trials exploring autologous DCs that were loaded with antigens ex vivo to induce T-cell responses have provided proof of principle. Here, we discuss how direct targeting of antigens to DC surface receptors in vivo might replace laborious and expensive ex vivo culturing, and facilitate large-scale application of DC-based vaccination therapies.

Sensitivity of magnetic resonance imaging of dendritic cells for in vivo tracking of cellular cancer vaccines

Success of immunotherapy with dendritic cells (DC) to treat cancer is highly dependent on their interaction with and activation of antigen specific T cells. To maximize DC-T cell contact accurate delivery of the therapeutic cells into the lymph node, or efficient trafficking of DC to the lymph nodes of the patient is essential. Since responses are seen in some patients but not in others, monitoring of the injected cells may be of major importance. Tracking of cells with magnetic resonance (MR) imaging is a non-invasive method that provides detailed anatomical information and is therefore more informative for the evaluation of the localization of therapeutic cells after injection than e.g. scintigraphic imaging. To challenge the sensitivity of this novel technique, we investigated the minimum amount of label and the number of cells required for MR imaging and the effect of labeling on DC function. DC were labeled with different concentrations of a clinically approved MR contrast agent consisting of superparamagnetic iron oxide particles and were imaged at both 3 and 7 T. Our results demonstrate the following: (i) When loaded with 30 (+/-4) pg Fe/cell, cell numbers as low as 1,000 cells/mm3 at 3 T and 500 cells/mm3 at 7 T could be readily imaged; (ii) Labeling does not affect cell viability and function; (iii) Because of its high spatial resolution and sensitivity, MRI is ideally suited to track therapeutic cells in vivo.

Relevance of DC-SIGN in DC-induced T cell proliferation

The role of dendritic cell-specific ICAM-3-grabbing nonintegrin (DC-SIGN) in DC-T cell communication was assessed by analyzing the effect of DC-SIGN-blocking mAb in MLR. The results show that the degree of inhibition by DC-SIGN and LFA-1 mAb depends on the magnitude of the MLR and the maturation status of the DC. Addition of DC-SIGN mAb at several time-points during MLR showed that DC-SIGN is involved early on in DC-T cell contacts. This initial role is masked by strong adhesive and costimulatory mechanisms, indicating a short-lived effect of DC-SIGN in DC-T cell interactions. To examine this concept in more detail, the percentage of PBL capable of binding DC-SIGN was determined. Analysis of several donors revealed that 1-20% PBL bind to beads coated with recombinant DC-SIGN, and the DC-SIGN-binding cells comprised all major cell subsets found in blood. PBL isolated from a donor with high DC-SIGN-binding capacity were more prone to blocking by DC-SIGN mAb in MLR than PBL from a donor with low DC-SIGN-binding capacity. This study indicates an initial and transient role for DC-SIGN in T cell proliferation, which becomes apparent when T cell proliferation is low and when the percentage of DC-SIGN binding PBL is high.

Plasmacytoid dendritic cells of melanoma patients present exogenous proteins to CD4+ T cells after Fc gamma RII-mediated uptake

Plasmacytoid dendritic cells (pDCs) contribute to innate antiviral immune responses by producing type I interferons. Although human pDCs can induce T cell responses upon viral infection, it remains unclear if pDCs can present exogenous antigens. Here, we show that human pDCs exploit FcgammaRII (CD32) to internalize antigen-antibody complexes, resulting in the presentation of exogenous antigen to T cells. pDCs isolated from melanoma patients vaccinated with autologous monocyte-derived peptide- and keyhold limpet hemocyanin (KLH)-loaded dendritic cells, but not from nonvaccinated patients or patients that lack a humoral response against KLH, were able to stimulate KLH-specific T cell proliferation. Interestingly, we observed that internalization of KLH by pDCs depended on the presence of serum from vaccinated patients that developed an anti-KLH antibody response. Anti-CD32 antibodies inhibited antigen uptake and presentation, demonstrating that circulating anti-KLH antibodies binding to CD32 mediate KLH internalization. We conclude that CD32 is an antigen uptake receptor on pDCs and that antigen presentation by pDCs is of particular relevance when circulating antibodies are present. Antigen presentation by pDCs may thus modulate the strength and quality of the secondary phase of an immune response.

Development of 111In-labeled tumor-associated antigen peptides for monitoring dendritic-cell-based vaccination

Dendritic cells (DC) are professional antigen-presenting cells capable of inducing potent immune responses. In our ongoing clinical trials, human leukocyte antigen (HLA)-A2.1+ melanoma patients are vaccinated with mature DC, presenting tumor-derived peptides in major histocompatibility complexes (MHC) to naive T cells. Previously, we have shown that both intradermally and intranodally injected (111)In-labeled mature DC migrate to draining lymph nodes. However, little is known about the fate of the MHC-peptide complex after injection of these peptide-loaded DC. The aim of the present study was to develop radiolabeled, tumor-derived peptides to monitor their binding to MHC Class I.

METHODS

The HLA-A2.1 binding peptide gp100:154-162mod (gp100:154m) was conjugated with diethylenetriamine pentaacetic acid (DTPA) either at the N-terminus (alpha-DTPA-gp100:154m) or at the epsilon amino group of the Lys(154) residue (epsilon-DTPA-gp100:154m) and labeled with (111)In.

RESULTS

The maximum specific activity for both peptides was 13 GBq/micromol. The IC50 of the alpha-[(111)In]DTPA-gp100:154m peptide was >75 microM. The IC50 of the (111)In-labeled epsilon-DTPA-gp100:154m was 3 microM, similar to the unconjugated peptide. MHC binding studies showed specific binding of the epsilon-[(111)In]DTPA-gp100:154m peptide to the JY cells at 4 degrees C. Interestingly, no specific binding was observed for the alpha-[(111)In]DTPA-gp100:154m peptide. In contrast to the alpha-[(111)In]DTPA-gp100:154m peptide, the epsilon-[(111)In]DTPA-gp100:154m peptide was recognized by cytotoxic T cells.

CONCLUSION

When DTPA was conjugated to the epsilon NH2 group of the Lys(154) residue, MHC binding of the peptide was preserved and could still be recognized by cytotoxic T cells. These studies allow the noninvasive determination of the behavior of MHC-peptide complexes on DC in vivo.

Cancer-germline gene expression in pediatric solid tumors using quantitative real-time PCR

Cancer-germline genes (CGGs) code for immunogenic antigens that are present on various human tumors but not on normal tissues. The importance of CGGs in cancer immunotherapy has led to detailed studies of their expression in a range of human tumors. We measured the levels of expression of 12 CGGs in various pediatric solid tumors to identify targets for therapeutic cancer vaccines. Quantitative real-time PCR (qPCR) was used to measure the expression of 8 MAGE genes and of genes LAGE-2/NY-ESO-1 and GAGE-1, 2, 8 in 9 osteosarcomas, 10 neuroblastomas, 12 rhabdomyosarcomas and 18 Ewing's sarcomas. Nine tumors were also examined by immunohistochemistry with monoclonal antibodies specific for the MAGE-A1, MAGE-A4 and NY-ESO-1 proteins. All osteosarcoma and 80% of neuroblastoma samples expressed several CGGs at high levels. Six of 12 rhabdomyosarcomas and 11 of 18 Ewing's sarcomas expressed at least one CGG. Immunohistochemistry data correlated well with qPCR results and showed a homogeneous protein distribution pattern in most positive tumors. No correlation was found between the levels of CGG expression in the tumors and clinicopathological parameters of the patients. Pediatric solid tumors express several CGGs, which encode antigens that could be targeted in therapeutic vaccination trials. Several CGGs of the MAGE, GAGE and LAGE families are coexpressed in a large proportion of osteosarcoma and neuroblastoma samples. Some rhabdomyosarcomas express several of these genes at high levels. Ewing's sarcomas have an overall low CGG expression.

Magnetic resonance tracking of dendritic cells in melanoma patients for monitoring of cellular therapy

The success of cellular therapies will depend in part on accurate delivery of cells to target organs. In dendritic cell therapy, in particular, delivery and subsequent migration of cells to regional lymph nodes is essential for effective stimulation of the immune system. We show here that in vivo magnetic resonance tracking of magnetically labeled cells is feasible in humans for detecting very low numbers of dendritic cells in conjunction with detailed anatomical information. Autologous dendritic cells were labeled with a clinical superparamagnetic iron oxide formulation or (111)In-oxine and were co-injected intranodally in melanoma patients under ultrasound guidance. In contrast to scintigraphic imaging, magnetic resonance imaging (MRI) allowed assessment of the accuracy of dendritic cell delivery and of inter- and intra-nodal cell migration patterns. MRI cell tracking using iron oxides appears clinically safe and well suited to monitor cellular therapy in humans.

Immunomonitoring tumor-specific T cells in delayed-type hypersensitivity skin biopsies after dendritic cell vaccination correlates with clinical outcome

PURPOSE

Tumor-specific immunomonitoring is essential to evaluate the efficacy of vaccination against cancer. In this study, we investigated the predictive value of the presence or absence of antigen-specific T cells in biopsies from delayed-type hypersensitivity (DTH) sites.

PATIENTS AND METHODS

In our ongoing clinical trials, HLA-A2.1+ melanoma patients were vaccinated with mature dendritic cells (DC) pulsed with melanoma-associated peptides (gp100 and tyrosinase) and keyhole limpet hemocyanin.

RESULTS

After intradermal administration of a DTH challenge with gp100- and tyrosinase peptide-loaded DC, essentially all patients showed a positive induration. In clinically responding patients, T cells specific for the antigen preferentially accumulated in the DTH site, as visualized by in situ tetramer staining. Furthermore, significant numbers of functional gp100 and tyrosinase tetramer-positive T cells could be isolated from these DTH biopsies, in accordance with the applied antigen in the DTH challenge. We observed a direct correlation between the presence of DC vaccine-related T cells in the DTH biopsies of stage IV melanoma patients and a positive clinical outcome (P = .0012).

CONCLUSION

These findings demonstrate the potency of this novel approach in the monitoring of vaccination studies in cancer patients.

Migration of dendritic cell based cancer vaccines: in vivo veritas?

Ex vivo generated cancer vaccines based on dendritic cells (DCs) are currently applied in the clinic. The migration of DCs from the tissues to the lymph nodes is tightly controlled and involves many different mediators and their receptors. A recent study demonstrated that the rate of migration of antigen-bearing DCs in situ from the skin to the lymph node is 100-fold higher than previously estimated. The migration of ex vivo generated DCs is rather inefficient but can be improved by pre-conditioning of the vaccine injection site with inflammatory cytokines. An alternative approach that is currently being explored is to target tumor antigens directly to DCs in situ, thereby exploiting the intricate migratory capacity of DCs in vivo. Recent advances have been made in understanding DC migration in the context of DC-based vaccines.

Intratumoral recombinant human interleukin-12 administration in head and neck squamous cell carcinoma patients modifies locoregional lymph node architecture and induces natural killer cell infiltration in the primary tumor

The objective of this study was to evaluate the histologic and immunohistopathologic effects of intratumorally given recombinant human interleukin-12 on the immune cells in the primary tumors and regional lymph nodes. Ten previously untreated patients with head and neck squamous cell carcinoma (HNSCC) were injected in the primary tumor twice to thrice, once weekly, at two dose levels of 100 or 300 ng/kg, before surgery. These patients were compared with 20 non-IL-12-treated control HNSCC patients. In the primary tumor, the number of CD56+ natural killer (NK) cells was increased in IL-12-treated patients compared with control patients. In some IL-12-treated patients, an impressive peritumoral invasion of CD20+ B cells was noticed. No differences were seen in the CD8+ or CD4+ T lymphocytes. Interestingly, major differences were apparent in the architecture of the enlarged lymph nodes of IL-12-treated patients; in particular, the distribution of B cells differed and fewer primary and secondary follicles with smaller germinal centers were observed. In addition, a decrease of dendritic cell lysosyme-associated membrane glycoprotein-positive cells in the paracortex was noted, resulting in a reduction of paracortical hyperplasia. In the lymph nodes, especially the CD56+ NK cells but also the CD8+ and CD4+ T lymphocytes, produced a high amount of IFN-gamma. Patients, irrespectively of IL-12 treatment, with a high number of CD56+ cells in the primary tumor had a better overall survival than those with a low number. In conclusion, after i.t. IL-12 treatment in HNSCC patients, the largest effect was seen on the NK cells, with a higher number in the primary tumor and a high IFN-gamma mRNA expression in the lymph nodes. Significant effects were noted on B cells, with altered lymph node architecture in every IL-12-treated patient and excessive peritumoral infiltration in some patients.

Effective induction of naive and recall T-cell responses by targeting antigen to human dendritic cells via a humanized anti-DC-SIGN antibody

Current dendritic cell (DC)-based vaccines are based on ex vivo-generated autologous DCs loaded with antigen prior to readministration into patients. A more direct and less laborious strategy is to target antigens to DCs in vivo via specific surface receptors. Therefore, we developed a humanized antibody, hD1V1G2/G4 (hD1), directed against the C-type lectin DC-specific intercellular adhesion molecule 3-grabbing nonintegrin (DC-SIGN) to explore its capacity to serve as a target receptor for vaccination purposes. hD1 was cross-linked to a model antigen, keyhole limpet hemocyanin (KLH). We observed that the chimeric antibody-protein complex (hD1-KLH) bound specifically to DC-SIGN and was rapidly internalized and translocated to the lysosomal compartment. To determine the targeting efficiency of hD1-KLH, monocyte-derived DCs and peripheral blood lymphocytes (PBLs) were obtained from patients who had previously been vaccinated with KLH-pulsed DCs. Autologous DCs pulsed with hD1-KLH induced proliferation of patient PBLs at a 100-fold lower concentration than KLH-pulsed DCs. In addition, hD1-KLH-targeted DCs induced proliferation of naive T cells recognizing KLH epitopes in the context of major histocompatibility complex (MHC) classes I and II. We conclude that antibody-mediated targeting of antigen to DCs via DC-SIGN effectively induces antigen-specific naive as well as recall T-cell responses. This identifies DC-SIGN as a promising target molecule for DC-based vaccination strategies.

Phenotypical and functional characterization of clinical-grade dendritic cells

Dendritic cells (DC) are the most potent antigen-presenting cells and form a promising new treatment modality. Fully activated DC loaded with antigen are very useful in stimulating immune responses, in particular those to combat cancer. Immature DC can either cause immunological tolerance or induce regulatory T-cells, opening up future application in transplantation, autoimmunity, and perhaps chronic inflammation. For these clinical applications, generation of DC under Good Manufacturing Practice conditions and without the use of animal products is a main prerequisite. To date, there are many different DC culture protocols, which subsequently lead to different types of DC. Protocols differ not only in DC preparation techniques, but also many other variables, like maturation status, dose and timing interval, route of administration, and antigen loading. DC vaccination, although very promising, is far from standardized. In this chapter we discuss the usefulness of standardized clinical and immunological criteria and the need for careful study design to further optimize the use of dendritic cells and to unequivocally prove their efficacy.

Dendritic cell immunotherapy: mapping the way

Dendritic cells (DCs) are the professional antigen-presenting cells of the immune system, with the potential to either stimulate or inhibit immune responses. Exploiting the immune-regulatory capacities of dendritic cells holds great promise for the treatment of cancer, autoimmune diseases and the prevention of transplant rejection. Although early clinical trials indicate that DC vaccines can induce immune responses in some cancer patients, careful study design and use of standardized clinical and immunological criteria are needed.

Maturation of dendritic cells is a prerequisite for inducing immune responses in advanced melanoma patients

PURPOSE

We have investigated the capacity of immature and mature monocyte-derived DCs pulsed with melanoma-associated peptides (gp100 and tyrosinase) to induce a primary cytotoxic T-lymphocyte response in vivo.

EXPERIMENTAL DESIGN

Advanced HLA-A2.1(+) melanoma patients were vaccinated with peptide- and keyhole limpet hemocyanin (KLH)-pulsed DCs, either immature (9 patients) or matured by monocyte-conditioned medium/tumor necrosis factor alpha/prostaglandin E(2) (10 patients).

RESULTS

All patients vaccinated with mature DCs showed a pronounced proliferative T-cell and humoral response against KLH. By contrast, KLH responses were absent in most of the patients vaccinated with immature DCs. Delayed-type hypersensitivity (DTH) reactions against antigen-pulsed DCs were only observed in patients vaccinated with mature DCs and not in patients vaccinated with immature DCs. MHC-peptide tetramer staining of DTH-derived T cells revealed the presence of specific T cells recognizing the melanoma-associated peptides in 1 patient. In a second patient, DTH-derived T cells showed specific lysis of tumor cells expressing the antigens used for DC pulsing. Only patients vaccinated with mature DCs showed objective clinical responses. Interestingly, both patients with long-term progression-free survival (22 and >40 months) were both vaccinated with mature DCs and demonstrated antigen-specific T-cell reactivity of DTH-derived T cells.

CONCLUSIONS

We conclude that mature DC are superior to immature DC in the induction of immunological responses in melanoma patients, which may translate into improved clinical results.

Vaccination of patients with metastatic renal cell carcinoma with autologous dendritic cells pulsed with autologous tumor antigens in combination with interleukin-2: a phase 1 study

Dendritic cells (DC) have been recognized as the most potent antigen presenting cells (APC) of the immune system. We performed a phase 1 study in twelve patients with metastatic renal cell carcinoma (RCC) using autologous immature DC loaded with autologous tumorlysate (TuLy) as a vaccine based on our earlier in vitro observations that such DC can activate tumor-specific cytotoxic T-lymphocytes. The treatment was combined with low-dose interleukin (IL)-2, as this has shown benefit in DC-based therapies. Patients received three intradermal vaccinations at two weekly intervals, and, after each vaccination, IL-2 was administered for 5 consecutive days. In six patients, keyhole-limpet hemocyanin (KLH) was added to the DC culture for immunologic monitoring purposes. In general, DC phenotype was CD14(low), CD86(high), CD40(high), CD80(low), and CD83(low). We noticed that the number of CD14+ cultured DC increased during treatment. Nevertheless, ovalbumin uptake remained high, underlining that these cells were still functional immature DC. The vaccine was able to elicit cellular anti-KLH responses, emphasizing the ability of the injected DC to mount an immunologic response. However, proliferative responses against TuLy were not detected, and humoral responses against TuLy or KLH were absent. Objective clinical responses were not observed, but extended stable disease was noted. The absence of cellular, humoral, or clinical antitumor responses suggests that the vaccination strategy with immature DC has little benefit for patients with advanced RCC. Nevertheless, this study shows the feasibility of a completely autologous DC and tissue culture methodology for the generation of TuLy pulsed DC.

Phenotypical and functional characterization of clinical grade dendritic cells

Dendritic cells (DC) are the professional antigen presenting cells of the immune system. Therefore, several clinical studies have been initiated in which tumor antigen-loaded DC are used as a vaccine to boost an immune response against malignant tumors in patients with cancer. A prerequisite for DC used in these vaccination studies is not only that they are grown under "Good Manufacturing Practice" but equally important that they retain their functional properties. In an extensive study, various conditions were tested to optimize the maturation and yield of DC grown for clinical use. DC grown in XVIVO-15 medium supplemented with 5% HS yielded the best results, morphologically and phenotypically. Mature DC expressed significant amounts of mature DC markers (CD83) and the costimulatory molecules CD80 and CD86. It was shown that mature and immature DC can be frozen and retain their phenotype and function after thawing. These clinical grade DC secreted high levels of the chemokines dendritic cell chemokine 1 (DC-CK1), interleukin-8 (IL-8), macrophage-derived chemokine (MDC), and thymus and activation-regulated chemokine (TARC). This implicates that these DC can attract naïve T and B cells as well as natural killer cells and memory T cells. Finally, to test their migratory capacity in vivo, (111)In-labeled DC were injected into tumor-free lymph nodes of patients with melanoma. Autoradiographic analysis of the dissected lymph nodes indicated that these DC could migrate into the T cell area of adjacent lymph nodes. In conclusion, a culture procedure was established to generate large numbers of monocyte-derived immature and mature DC that retain their morphologic, phenotypic, and functional characteristics in vitro and can be visualized in situ.