Rational peptide-based tumour vaccine development and T cell monitoring

Cytolytic activity of the human papillomavirus type 16 E711-20 epitope-specific cytotoxic T lymphocyte is enhanced by heat shock protein 110 in HLA-A*0201 transgenic mice

Heat shock proteins (HSPs) have been successfully applied to a broad range of vaccines as biological adjuvants to enhance the immune response. The recently defined HSP110, in particular, exhibits strong protein binding affinity and is capable of enhancing the immunogenicity of protein antigens remarkably more than other HSP family members. In our previous study, we verified that murine HSP110 (mHSP110) significantly enhanced the immune response of a C57BL/6 mouse model to the H-2(d)-restricted human papillomavirus (HPV) E749-57 epitope (short peptide spanning the 49th to 57th amino acid residues in the E7 protein). To determine whether HSP110 similarly enhances the immunogenicity of human epitope peptides, we used the HLA-A2 transgenic mouse model to investigate the efficacy of the mHSP110 chaperone molecule as an immunoadjuvant of the human HLA-A2-restricted HPV16 E711-20 epitope vaccine. Results showed that mHSP110 efficiently formed a noncovalently bound complex with the E711-20 epitope. The mHSP110-E711-20 complex induced epitope-specific splenocyte proliferation and E711-20-specific gamma interferon (IFN-γ) secretion. Importantly, cytotoxic T lymphocytes primed by the mHSP110-E711-20 complex exerted strong cytolytic effects on target T2 cells pulsed with the E711-20 peptide or TC-1 cells transfected with the HLA-A2 gene. In addition, the mHSP110-E711-20 complex elicited stronger ex vivo and in vivo antitumor responses than either emulsified complete Freund's adjuvant or HSP70-chaperoned E711-20 peptide. These collective data suggest that HSP110 is a promising immunomodulator candidate for peptide-based human cancer vaccines, such as for the HLA-A2-restricted E711-20 epitope.

Minor histocompatibility antigen typing by DNA sequencing for clinical practice in hematopoietic stem-cell transplantation

In HLA-matched stem-cell transplantation (SCT), minor H antigens are key molecules driving allo-immune responses in both graft-versus-host disease (GvHD) and in graft-versus-leukemia (GvL) reactivity. Dissection of the dual function of minor H antigens became evident through their different modes of tissue and cell expression, i.e., hematopoietic system restricted or broad. Broadly expressed minor H antigens are the targets of immune responses in both arms of graft-versus-host (GvH) responses, i.e., both GvHD and GvL, whereas the immune responses against the hematopoietic system-specific minor H antigens are restricted to the GvL arm of SCT. Evidently, it is this latter group of minor H antigens that can function as curative tools for stem-cell (SC)-based immunotherapy of hematological malignancies and disorders. The HLA-matched patient/donor combinations, incompatible for one of the hematopoietic-specific minor H antigens, are suitable for minor H antigen immunotherapy (Goulmy, Immunol Rev 157:125-140, 1997). Information on the minor H antigen phenotype is therefore needed. Hereto, genomic typing for minor H antigens has been implemented in many HLA laboratories. Here, we firstly summarize the relevance of minor H antigens particularly in hematopoietic SCT. Secondly, we describe a method for typing the various polymorphic minor H antigens molecularly identified to date by DNA sequencing.

4-1BB-mediated expansion affords superior detection of in vivo primed effector memory CD8+ T cells from melanoma sentinel lymph nodes

We have been studying the re-activation of tumor-associated antigen (TAA)-specific CD8(+) T cells in sentinel lymph nodes (SLN) of melanoma patients upon intradermal administration of the CpG-B oligodeoxynucleotide PF-3512676. To facilitate functional testing of T cells from small SLN samples, high-efficiency polyclonal T cell expansion is required. In this study, SLN cells were expanded via classic methodologies with plate- or bead-bound anti-CD3/CD28 antibodies and with the K562/CD32/4-1BBL artificial APC system (K32/4-1BBL aAPC) and analyzed for responsiveness to common recall or TAA-derived peptides. K32/4-1BBL-expanded T cell populations contained significantly more effector/memory CD8(+) T cells. Moreover, recall and melanoma antigen-specific CD8(+) T cells were more frequently detected in K32/4-1BBL-expanded samples as compared with anti-CD3/CD28-expanded samples. We conclude that K32/4-1BBL aAPC are superior to anti-CD3/CD28 antibodies for the expansion of in vivo-primed specific CD8(+) T cells and that their use facilitates the sensitive monitoring of functional anti-tumor T cell immunity in SLN.

Towards a standardized protocol for the generation of monocyte-derived dendritic cell vaccines

For more than one decade patients have been treated with dendritic cell (DC) immunotherapy against malignancies and infectious diseases. Proof of principle studies demonstrated immunogenicity and clinical responses were observed in a fraction of patients. Overlooking more than 200 publications one realizes, however, that it is almost impossible to compare many of these trials even in a given clinical setting or disease. This is primarily due to the fact that dendritic cell generation procedures are highly variable. There is a requirement for a standardized DC generation protocol which provides 'reference dendritic cells' to which other dendritic cells (e.g. differently matured ones) can be compared to in order to further optimize this promising vaccination approach. In this chapter, we describe in detail our standard DC generation protocols established during the last decade with over 200 melanoma patients treated and over 2,000 vaccinations applied in clinical studies at our hospital. We do not claim that these dendritic cells are the best ones, but the generation procedure is highly reliable and reproducible and provides a standardized reference DC vaccine.

HLA typing demands for peptide-based anti-cancer vaccine

Immunological treatment of cancer has made some very promising advances during the last years. Anti-cancer vaccination using peptides or peptide-pulsed dendritic cells and adoptive transfer of in vitro generated, epitope-specific T cells depend on a well-fitting interaction of HLA molecule and epitope. Accurate HLA-typing is a key factor for successful anti-cancer vaccination. No comprehensive data and no suggestion exist on the HLA-typing in this setting. We performed a systematic review of PubMed analyzing HLA-typing data in cancer vaccination trials over the last 4 years (2004-2007). Then, using the SYFPEITHI database, we calculated the peptide binding prediction of the eight most often used HLA-A*0201 binding epitopes. Finally, high-resolution typing [by sequence-specific primers (SSP)] data of a HLA-A*02 or HLA-A*24 positive population in Berlin, Germany, were analyzed. Forty-five cancer vaccination trials with 764 patients were included. Eighteen studies were performed in the USA, 13 in Europe, 12 in Asia (mainly Japan), and two in Australia. Most common diseases targeted were melanoma, prostate cancer, colorectal cancer, renal cell cancer, and breast cancer. The trials tested protocols using peptide plus adjuvants without DC or protocols using peptide-pulsed DC. In 38 trials (84%) HLA-A2 positive patients were vaccinated, in 11 studies (24%) HLA-A24 positive patients were vaccinated. Nineteen studies with 291 patients (38%) presented the HLA type as four-digit code (high-resolution), 26 studies with 473 patients (62%) presented the HLA-type in a low-resolution code. The method of HLA determination was given in six out of 45 trials (13%). Using the SYFPEITHI database we calculated the peptide binding prediction of the eight most often used HLA-A*0201 binding tumor antigen-derived epitopes for binding to HLA-A*0203. While the epitopes had a binding score of 17-28 for HLA-A*0201, the score for binding to HLA-A*0203 was zero in seven out of eight tested peptides. Only for one peptide the score was eight. Finally, we analyzed high-resolution data of HLA-A*02 and HLA-A*24 positive patients in Berlin, Germany. We found the HLA-A*0201 allele and HLA-A*2402 allele in 95%, respectively. HLA-A*0201 and HLA-A*2402 are most commonly used for peptide based vaccine in cancer. Data on HLA-typing given in the included cancer vaccine manuscripts are fractional. Only 13% report the method of HLA typing and most HLA types are given as low-resolution code. Looking at the binding of specific peptides to both the alleles, it is important to perform high-resolution typing. Further suggestions for immunogenetic laboratories and clinical tumor immunologists regarding HLA-typing for cancer vaccine trials and adoptive T cell transfer approaches are discussed.

HLA-A2 expression, stage, and survival in colorectal cancer

INTRODUCTION

Most cancer vaccination trials have been performed in human leukocyte antigen (HLA)-A2 positive populations. Some studies have used HLA-A2 negative patients as control group. However, HLA-type and HLA-expression can interact with tumor biology and possibly affect prognosis. HLA-A2 negative patients might constitute an inadequate control group.

MATERIALS AND METHODS

Patients with colorectal cancer were serologically analyzed for HLA-A2 expression. Patients were evaluated for tumor stage, grading, tumor location. Overall survival (OAS) of HLA-A2 positive and HLA-A2 negative patients was compared.

RESULTS

One hundred forty-four patients were evaluable (50% HLA-A2+). Median age was 62 years. UICC stage III or IV: 45.8%. Gender, location, and UICC stage were equally distributed between HLA-A2 subgroups. HLA-A2 positive patients more frequently had grade 3 histology (27.8% vs 13.9%) and chemotherapy (62.9% vs 45.6%). At a median follow-up of 75.8 months, median OAS for the entire study population was 123.3 months, 5-year OAS was 77.5%. No statistically significant difference in OAS was observed between HLA-A2 positive and negative patients (116.5 vs 157 months, 5-year-OAS 74.1+/-11.6% vs 81+/-11.6%, p=0.46). Expectedly, patients with UICC stage I and II disease lived significantly longer than patients with stage III and IV (5-year OAS 94.3% vs 53.4%; p<0.001). A significantly superior OAS was also found for women, independent of stage or HLA status.

CONCLUSION

HLA-A2 positive patients exhibit poorer tumor differentiation. This might account for a non-significant difference in OAS. The use of HLA-A2 negative patients as control cohort in CRC vaccinations would rather underestimate potential treatment-related survival effects. Therefore, we suggest they constitute a valid auxiliary control group.

Experimental discovery of T-cell epitopes: combining the best of classical and contemporary approaches

T cells specifically recognize antigens as peptide epitope-MHC complexes on the surface of target cells. The inherent complexities of antigen processing and presentation, the polygenic and polymorphic nature of MHC and the technical hurdles in working with T cells have made epitope discovery challenging. Here, we review significant experimental advances in recent years. These include new and sensitive assays and the availability of human cells and high numbers of synthetic peptides for screening, which have allowed for the first time comprehensive analysis of antigens and whole virus genomes. Such studies have provided important insights into the immunobiology of a number of diseases. The newly gathered detailed information on T-cell epitopes will aid vaccine design and immunological monitoring in clinical trials.

Preventive and therapeutic vaccination with PAP-3, a novel human prostate cancer peptide, inhibits carcinoma development in HLA transgenic mice

Conventional treatment of recurrent and metastasized prostate cancer (CaP) remains inadequate; this fact mandates development of alternative therapeutic modalities, such as specific active or passive immunotherapy. Previously, we reported the identification of a novel highly immunogenic HLA-A*0201-restricted Prostatic Acid Phosphatase-derived peptide (PAP-3) by a two-step in vivo screening in an HLA-transgenic (HHD) mouse system. In the present study we aimed at elucidating the efficiency of PAP-3-based vaccine upon active antitumor immunization. To this end we established preventive and therapeutic carcinoma models in HHD mice. The 3LL murine Lewis lung carcinoma clone D122 transduced to express HLA-A*0201 and PAP served as a platform for these models. The HLA-A*0201-PAP-3 complex specific recombinant single chain scFV-PAP-3 antibodies were generated and used to confirm an endogenous PAP processing resulting in PAP-3 presentation by HLA-A*0201. PAP-3 based vaccines significantly decreased tumor incidence in a preventive immunization setting. Therapeutic vaccination of HHD mice with PAP-3 led to rejection of early established tumors and to increase of mouse survival. These results strongly support a therapeutic relevance of the identified CTL epitope upon active antitumor immunization. The newly established carcinoma model presented herein might be a useful tool for cancer vaccine design and optimization.

Autologous tumor rejection in humans: trimming the myths

There is overwhelming evidence that the human immune system can keep in check the growth of autologous tumors. Yet, this phenomenon is rare and most often tumors survive striking a balance with the host's immune system. The well-documented coexistence of immune cells that can recognize cancer and their targets within the same host is reminiscent of chronic allograft rejection well-controlled by immune suppression or of a lingering tissue-specific autoimmune reaction. In this review, we argue that autologous tumor rejection represents a distinct form of tissue-specific rejection similar to acute allograft rejection or to flares of autoimmunity. Here we discuss similarities within the biology of these phenomena that may converge into a common immunological constant of rejection. The purpose is to simplify the basis of immune rejection to its bare bones critically dissecting the significance of those components proposed by experimental models as harbingers of this final outcome.

Immune monitoring of T-cell responses in cancer vaccine development

Monitoring cellular immune responses is one prerequisite for rational development of cancer vaccines. The primary objective of immune monitoring is to determine the efficacy of a vaccine to induce or augment a specific T-cell response. Further questions relate to the prevalence and functional relevance of spontaneous tumor-directed immune responses, the functional characteristics of T-cell responses, and, finally and most importantly, the relationship between immune monitoring assay results and clinical end points. The issue of T-cell monitoring has become more complex as different types and generations of assays have been adopted during the past decade and both standardization and validation of assays have often been insufficient. Because the development of assays parallel the clinical development of cancer vaccines, technical advances have been achieved simultaneously with broadening understanding of cancer immunity. Suitable animal models for immune monitoring are, however, lacking, because preclinical vaccine development in rodents does not allow serial immune monitoring of the peripheral blood, as is commonly used in patients. The current situation is characterized by a lack of universal standards for T-cell assessment, uncertainty about the association between immune monitoring assay results and clinical antitumor end points, and lack of knowledge regarding the contribution of different aspects of T-cell function to clinical efficacy. It is acknowledged that T-cell monitoring will have to be validated in large trials with clinically effective vaccines, but this necessity should not discourage the current application of novel assays within clinical trials of all stages.

From pathogen to medicine: HIV-1-derived lentiviral vectors as vehicles for dendritic cell based cancer immunotherapy

Over the years, the unique capacity of dendritic cells (DC) for efficient activation of naive T cells has led to their extensive use in cancer immunotherapy protocols. In order to be able to fulfil their role as antigen-presenting cells, the antigen of interest needs to be efficiently introduced and subsequently correctly processed and presented by the DC. For this purpose, a variety of both viral and non-viral antigen-delivery systems have been evaluated. Amongst those, HIV-1-derived lentiviral vectors have been used successfully to transduce DC. This review considers the use of HIV-1-derived lentiviral vectors to transduce human and murine DC for cancer immunotherapy. Lentivirally transduced DC have been shown to present antigenic peptides, prime transgene-specific T cells in vitro and elicit a protective cytotoxic T-lymphocyte (CTL) response in animal models. Different parameters determining the efficacy of transduction are considered. The influence of lentiviral transduction on the DC phenotype and function is described and the induction of immune responses by lentivirally transduced DC in vitro and in vivo is discussed in detail. In addition, direct in vivo administration of lentiviral vectors aiming at the induction of antigen-specific immunity is reviewed. This strategy might overcome the need for ex vivo generation and antigen loading of DC. Finally, future perspectives towards the use of lentiviral vectors in cancer immunotherapy are presented.

Immunological monitoring of cancer vaccine therapy

Immunological treatment of malignant diseases in humans aiming at the induction and proliferation of antigen-specific T cells has made rapid progress in recent years. A growing number of tumour-associated antigens, potentially synergistic combinations with adjuvants, and various routes of application provide new opportunities for cancer vaccination. Therefore, a highly accurate assessment of vaccine-induced T cell responses is required. Three T cell assays (tetramers, intracellular cytokine flow cytometry and ELISPOT assay) have emerged as first-line methods for monitoring T cell induction during vaccination. These assays are relatively easy to perform, reliable, sensitive and allow an ex vivo T cell analysis at the single cell level. Although at this stage assays are not a defined surrogate marker for clinical efficacy, they already provide information concerning the immunological potency of a given vaccine. In particular, comparing immune responses under various treatment conditions will help to develop more clinically efficient tumour vaccination. Novel assays, such as CD107 staining, human leukocyte antigen/green fluorescent protein-antigen-presenting cells or microarrays, and assays determining functions, such as proliferation assays, are beginning to complement first-line monitoring assays.

Assessment of CD8 involvement in T cell clone avidity by direct measurement of HLA-A2/Mage3 complex density using a high-affinity TCR like monoclonal antibody

Peptide affinity for MHC molecules determines the number of MHC/peptide complexes stabilized at the cell surface in in vitro tests or in vaccination protocols. We isolated a high affinity monoclonal antibody specific for the HLA-A2/Mage3 complex that enables an equilibrium binding assay to be performed on T2 cell line loaded with a range of Mage3 peptides. Binding of Mage3 to the HLA-A2 molecule can be modeled by a standard receptor-ligand interaction characterized by an affinity constant. This model enables the measurement of the affinity of other immunogenic peptides for HLA-A2 by a competition test and the calculation of the density of complexes stabilized at the T2 cell surface for all peptide concentrations. Quantification of the HLA-A2/Mage3 complexes at target cell surfaces was used to estimate the number of complexes required to reach cytotoxicity ED50 of human T cell clones sorted from an unprimed repertoire. We confirm with this antibody the direct relationship between clone avidity and TCR affinity, and the moderate contribution of the CD8 co-receptor in the reinforcement of TCR-MHC/peptide contact. Nevertheless, CD8 plays a critical role in the amplification of the specific signal to establish an efficient T cell response at low specific complex densities found in physiological situations.

Immunotherapy of cancer through targeting of minor histocompatibility antigens

Minor histocompatibility antigens are allogeneic targets of T-cell mediated graft-versus-tumour effects following allogeneic stem cell transplantation. Recent research has identified several minor histocompatibility antigens as tumour proteins and has also disclosed their unique properties in both the induction and the effector phase of graft-versus-tumour effects. Targeting tumour-specific minor histocompatibility antigens by adoptive immunotherapy will battle against tumour tolerance and evoke allo-immune responses, thereby enhancing graft-versus-tumour effects against leukaemia and solid tumours. Recently acquired knowledge of the role of donor immunisation status, new techniques in the generation of minor histocompatibility antigen-specific cytotoxic T lymphocytes in vitro, and innovative principles in vaccination will help to design clinical trials that exploit minor histocompatibility antigens in the immunotherapy of cancer.

Vaccination with T cell-defined antigens

Tumour immunology encompasses a broad array of biological phenomena including interactions between neoplastic cells and the innate and adaptive immune response. Among immune cells, T cells have taken the centre stage because they can be easily demonstrated to specifically recognise autologous cancer cells. As most tumour-associated antigens are intracellular proteins, T cells appear to be the most suitable tool for cancer-specific attack, as antibodies do not cross the cell membrane and the innate immune response lacks the same level of specificity. Finally, the relative ease in which T cells can be educated through antigen-specific immunisation to recognise cancer cells has elevated them to an even higher stature. In this review, it will be argued that T cells represent a unique anticancer agent, characterised by absolute specificity. Although other therapeutic modalities (antibody-based) have been effectively implemented, a comparison of T cell-based approaches with other modalities goes beyond the purposes of this review and will not be included in the discussion. However, it is obvious that the role of the T cell is limited and other components of the immune response (effector mononuclear phagocytes, natural killer cells, cytokines, chemokines, soluble factors), genetic background and tumour heterogeneity are likely to be necessary for the completion of cancer rejection.

Workshop on Cancer Biometrics: Identifying Biomarkers and Surrogates of Cancer in Patients

The current excitement about molecular targeted therapies has driven much of the recent dialog in cancer diagnosis and treatment. Particularly in the biologic therapy of cancer, identifiable antigenic T-cell targets restricted by MHC molecules and the related novel stress molecules such as MICA/B and Letal allow a degree of precision previously unknown in cancer therapy. We have previously held workshops on immunologic monitoring and angiogenesis monitoring. This workshop was designed to discuss the state of the art in identification of biomarkers and surrogates of tumor in patients with cancer, with particular emphasis on assays within the blood and tumor. We distinguish this from immunologic monitoring in the sense that it is primarily a measure of the tumor burden as opposed to the immune response to it. Recommendations for intensive investigation and targeted funding to enable such strategies were developed in seven areas: genomic analysis; detection of molecular markers in peripheral blood and lymph node by tumor capture and RT-PCR; serum, plasma, and tumor proteomics; immune polymorphisms; high content screening using flow and imaging cytometry; immunohistochemistry and tissue microarrays; and assessment of immune infiltrate and necrosis in tumors. Concrete recommendations for current application and enabling further development in cancer biometrics are summarized. This will allow a more informed, rapid, and accurate assessment of novel cancer therapies.

Understanding the response to immunotherapy in humans

Whether the efforts of the last decade aimed at the development of vaccines against tumor-specific antigens encountered success or failure is a matter of expectations. On the bright side, we could optimistically observe that anti-cancer-vaccines stand as an outstanding example of the successful implementation of modern biotechnology tools for the development of biologically sound therapeutics. In particular, vaccines against melanoma (the prototype model of tumor immunology in humans) can reproducibly induce cytotoxic T cell (CTL) responses exquisitely specific for cancer cells. This achievement trespasses the specificity of any other anti-cancer therapy. The skeptics, on the other end, might point out that immunization only rarely leads to cancer regression, labeling, therefore, this approach is ineffective. In our opinion this judgment stems from the naïve expectation that CTL induction is sufficient for an effective immune response. Here we propose that more needs to be understood about the mechanisms required for the induction of a therapeutically relevant immune response in humans. In particular, we will discuss the variables related to cancer heterogeneity, the weight of individual patients' polymorphism(s), the role of the T cell activation and differentiation and, finally, the complex relationship between immune and cancer cells within the tumor microenvironment.

T cell responses against tumor associated antigens and prognosis in colorectal cancer patients

INTRODUCTION: Spontaneous T cell responses against specific tumor-associated antigens (TAA) are frequently detected in peripheral blood of tumor patients of various histiotypes. However, little is known about whether these circulating, spontaneously occurring, TAA-reactive T cells influence the clinical course of disease. METHODS: Fifty-four HLA-A2 positive colorectal cancer patients had been analyzed for the presence of T cell responses against epitopes derived from the TAA Ep-CAM, her-2/neu, and CEA either by ELISPOT assay or by intracellular cytokine staining. Then, Kaplan-Meier survival analysis was performed comparing T-cell-responders and T-cell-non-responders. For comparison, a group of T-cell-non-responders was compiled stringently matched to T-cell-responders based on clinical criteria and also analyzed for survival. RESULTS: Sixteen out of 54 patients had a detectable T cell response against at least one of the three tested TAA. Two out of 21 patients (9.5%) with limited stage of disease (UICC I and II) and 14 out of 33 patients (42.4%) with advanced disease (UICC III and IV) were T cell response positive. Comparing all T-cell-responders (n = 16) and all T-cell-non-responders (n = 38), no survival difference was found. In an attempt to reduce the influence of confounding clinical factors, we then compared 16 responders and 16 non-responders in a matched group survival analysis; and again no survival difference was found (p = 0.7). CONCLUSION: In summary, we found no evidence that spontaneous peripheral T cell responses against HLA-A2-binding epitopes of CEA, her-2/neu and Ep-CAM are a strong prognostic factor for survival.

Overview of melanoma vaccines and promising approaches

It is difficult to envision anything better than melanoma vaccines to exemplify the effectiveness of modern biotechnology in developing biologically rational therapeutics. Melanoma vaccines can reproducibly induce cytotoxic T lymphocyte (CTL) responses better than any other anticancer therapy. Anticancer vaccines have been labeled by some as ineffective for the simple reason that they only rarely lead to cancer regression. This oxymoron stems from the naïve expectation that CTLs are all that is needed to reject cancer. Little is known about requirements for CTL localization and effector function within the tumor microenvironment. In the future, more attention should be given to events downstream of immunization (afferent arm of immune response) to identify combination therapies likely to facilitate localization and activation of CTL at the receiving end (efferent arm).