Identification of tumour-associated T-cell epitopes for vaccine development

Cancer and immune response: old and new evidence for future challenges

Cancer may occur as a result of abnormal host immune system tolerance. Recent studies have confirmed the occurrence of spontaneous and induced antitumor immune responses expressed as the presence of tumor-infiltrating T cells in the tumor microenvironment in some cancer models. This finding has been recognized as a good prognostic factor in several types of tumors. Some chemotherapy agents, such as anthracyclines and gemcitabine, are effective boosters of the immune response through tumor-specific antigen overexpression after apoptotic tumor cell destruction. Other strategies, such as GM-CSF or interleukin-2, are pursued to increase immune cell availability in the tumor vicinity, and thus improve both antigen presentation and T-cell activation and proliferation. In addition, cytotoxic T lymphocyte antigen 4-blocking monoclonal antibodies enhance immune activity by prolonging T-cell activation. Strategies to stimulate the dormant immune system against tumors are varied and warrant further investigation of their applications to cancer therapy in the future.

Rapid tolerization of virus-activated tumor-specific CD8+ T cells in prostate tumors of TRAMP mice

To study T cell responses to tumors in an autochthonous model, we expressed a CD8 T cell epitope SIYRYYGL (SIY) in the prostate of transgenic adenocarcinoma (TRAMP) mice (referred to as TRP-SIY), which spontaneously develop prostate cancer. Naïve SIY-specific CD8 T cells adoptively transferred into TRP-SIY mice became tolerized in the prostate draining lymph nodes. Vaccination of TRP-SIY mice intranasally with influenza virus that expresses the SIY epitope resulted in generation of SIY-specific effector T cells in the lung-draining lymph nodes. These effector T cells expressed TNFalpha and IFNgamma, eliminated SIY peptide-loaded target cells in vivo, and infiltrated prostate tumors, where they rapidly lost the ability to produce effector cytokines. A population of these T cells persisted in prostate tumors but not in lymphoid organs and could be induced to re-express effector functions following cytokine treatment in vitro. These findings suggest that T cells of a given clone can be activated and tolerized simultaneously in different microenvironments of the same host and that effector T cells are rapidly tolerized in the tumors. Our model provides a system to study T cell-tumor interactions in detail and to test the efficacy of cancer immunotherapeutic strategies.

Autoantibodies as potential biomarkers for breast cancer

INTRODUCTION

Only a limited number of tumor markers for breast cancer are currently available. Antibodies to tumor-associated proteins may expand the number of available tumor markers for breast cancer and may be used together in a serum profile to enhance sensitivity and specificity.

METHODS

In the present study, we interrogated a breast cancer cDNA T7 phage library for tumor-associated proteins using biopan enrichment techniques with sera from normal individuals and from breast cancer patients. The enrichment of tumor-associated proteins after biopanning was tested using a plaque-lift assay and immunochemical detection. The putative tumor-associated phage clones were collected for PCR and sequencing analysis. Unique and open reading frame phage-expressed proteins were then used to develop phage protein ELISAs to measure corresponding autoantibodies using 87 breast cancer patients and 87 normal serum samples. A logistic regression model and leave-one-out validation were used to evaluate predictive accuracies with a single marker as well as with combined markers. Identities of those selected proteins were revealed through the sequence BLAST program.

RESULTS

We harvested 100 putative tumor-associated phage clones after biopan enrichment. Sequencing analysis revealed that six phage proteins were inframe and unique. Antibodies to these six phage-expressed proteins were measured by ELISAs, and the results showed that three of the phage clones had statistical significance in discriminating patients from normal individuals. BLAST results of the three proteins showed great matches to ASB-9, SERAC1, and RELT. Measurements of the three predictive phage proteins were combined in a logistic regression model that achieved 80% sensitivity and 100% specificity in prediction of sample status, whereas leave-one-out validation achieved 77.0% sensitivity and 82.8% specificity among 87 patient samples and 87 control samples. Receiver operating characteristic curve analysis and the leave-one-out method both showed that combined measurements of the three antibodies were more predictive of disease than any of the single antibodies studied, underscoring the importance of identifying multiple potential markers.

CONCLUSION

Serum autoantibody profiling is a promising approach for early detection and diagnosis of breast cancer. Rather than one autoantibody, a panel of autoantibodies appears preferable to achieve superior accuracy. Further refinements will need to be made to further improve the accuracy. Once refined, the assay must be applied to a prospective patient population to demonstrate applicability.

Efficient identification of a novel cancer/testis antigen for immunotherapy using three-step microarray analysis

Advanced technology in molecular biology has provided us powerful tools for the diagnosis and treatment for cancer. We herein adopted a new methodology to identify a novel cancer/testis (CT) antigen with high frequency of expression in colorectal cancer as follows: (a) combining laser microdissection and cDNA microarray was used to analyze the gene expression profile of colorectal cancer cells; (b) genes overexpressed in testis and underexpressed in normal colon epithelium were analyzed using cDNA microarray; and (c) the gene expression profile of colorectal cancer cells was compared with that of normal testis. Using this methodology, we selected 38 candidates for CT antigen. Among these genes, we identified a novel CT antigen, serine/threonine kinase 31 (STK31), which was previously reported as a gene expressed in spermatogonia. Reverse transcription-PCR analysis showed that STK31 gene expression levels in cancer samples were significantly higher (P < 0.0001) than those in normal samples. The STK31 gene was frequently expressed not only in colorectal cancer but also in gastric and esophageal cancer. Moreover, STK31 peptide was able to elicit specific CTLs and induced CTLs lysed either peptide-loading or endogenously STK31-expressing target cells. These results showed that the new methodology in this study facilitated identification of CT antigens and that STK31 may be a candidate for cancer immunotherapy against gastrointestinal cancer.

Potent costimulation of human CD8 T cells by anti-4-1BB and anti-CD28 on synthetic artificial antigen presenting cells

The in vitro generation of cytotoxic T lymphocytes (CTLs) for anticancer immunotherapy is a promising approach to take patient-specific therapy from the bench to the bedside. Two criteria must be met by protocols for the expansion of CTLs: high yield of functional cells and suitability for good manufacturing practice (GMP). The antigen presenting cells (APCs) used to expand the CTLs are the key to achieving both targets but they pose a challenge: Unspecific stimulation is not feasible because only memory T cells are expanded and not rare naïve CTL precursors; in addition, antigen-specific stimulation by cell-based APCs is cumbersome and problematic in a clinical setting. However, synthetic artificial APCs which can be loaded reproducibly with MHC-peptide monomers and antibodies specific for costimulatory molecules could resolve these problems. The purpose of this study was to investigate the potential of complex synthetic artificial APCs in triggering the costimulatory molecules CD28 and 4-1BB on the T cell. Anti-4-1BB antibodies were added to an established system of microbeads coated with MHC-peptide monomers and anti-CD28. Triggering via CD28 and 4-1BB resulted in strong costimulatory synergy. The quantitative ratio between these signals determined the outcome of the stimulation with optimal results when anti-4-1BB and anti-CD28 were applied in a 3:1 ratio. Functional CTLs of an effector memory subtype (CD45RA(-) CCR7(-)) were generated in high numbers. We present a highly defined APC platform using off-the-shelf reagents for the convenient generation of large numbers of antigen-specific CTLs.

Advances in specific immunotherapy for prostate cancer

OBJECTIVES

The absence of effective therapies for advanced prostate cancer has entailed an intensive search for novel treatments. This review presents an overview of specific immunotherapeutic strategies for prostate cancer.

METHODS

Current literature was reviewed regarding the identification of tumor antigens and the design of T-cell- and antibody-based immunotherapy for prostate cancer. The PubMed database was searched using the key words antibodies, clinical trials, dendritic cells, immunotherapy, prostate cancer, and T cells.

RESULTS

T cells and antibodies are powerful components of the specific antitumor immune response. CD8+ cytotoxic T lymphocytes (CTLs) efficiently destroy tumor cells. CD4+ T cells improve the antigen-presenting capacity of dendritic cells (DCs) and support the stimulation of tumor-reactive CTLs. Monoclonal antibodies exhibit their antitumor effects via antibody-dependent cellular cytotoxicity and complement activation. Consequently, much attention has been given to the identification of tumor antigens that represent attractive targets for specific immunotherapy. Several prostate cancer-related antigens were described and used in clinical trials. Such studies were based on the administration of peptides, proteins, or DNA. Furthermore, men with prostate cancer were vaccinated with peptide-, protein-, or RNA-loaded DCs, which display an extraordinary capacity to induce tumor-reactive T cells. Monoclonal antibodies directed against surface antigens were also used. Clinical trials revealed that immunotherapeutic strategies represent safe and feasible concepts for the induction of immunologic and clinical responses in men with prostate cancer.

CONCLUSIONS

Specific immunotherapy represents a promising treatment modality for prostate cancer. Further improvement of the current approaches is required and may be achieved by combining T-cell- and antibody-based vaccination strategies with radio-, hormone-, chemo-, or antiangiogenic therapy.

Redirecting adaptive immunity against foreign antigens to tumors for cancer therapy

Immunotherapy for cancer is often limited by weak immunogenicity of tumor antigens. However, immune systems are usually strong and effective against foreign invading antigens. To test whether the destructive effect of adaptive immunity against foreign antigens can be redirected to tumors for cancer therapy, we immunized mice with adenovector expressing LacZ (Ad/CMV-LacZ). Subcutaneous syngeneic tumors were then established in the immunized animals or in naïve animals. The immune response against adenovirus or LacZ was redirected to tumors by intratumoral injection of Ad/CMV-LacZ. We found that immunization and treatment with the adenovector dramatically reduced the tumor growth rate compared with intratumoral administration of adenovector in naïve mice. Complete tumor regression was observed in about 50% of the immunized animals but not in the naïve animals. Similar effects were observed when oncolytic vaccinia virus was used to immunize and treat tumors. Lymphocyte infiltration in tumors was dramatically increased in the immunized group when compared with other groups. Moreover, immunity against parental tumor cells was induced in the animals cured with immunization and treatment with Ad/CMV-LacZ, as evidenced by the lack of tumor growth when the mice were challenged with parental tumor cells. Taken together, these results suggest that redirecting adaptive immunity against foreign antigens is a potential approach for anticancer therapy and that pre-existing immunity could enhance virotherapy against cancers.

WHO grade associated downregulation of MHC class I antigen-processing machinery components in human astrocytomas: does it reflect a potential immune escape mechanism?

Defects of major histocompatibility complex (MHC) class I antigen-processing machinery (APM) components have been shown to contribute to immune escape of malignant cells. We investigated the expression of APM components in astrocytomas without detectable defects in HLA class I antigen expression and correlated it with grade of malignancy. Quantitative immunohistochemical analysis of astrocytomas revealed reduced expression of the cytosolic proteasome subunit low molecular weight protein 2 (LMP2), the endoplasmatic reticulum (ER) transporter associated with antigen processing-1 (TAP1), and the ER chaperone beta2-microglobulin (beta2m) in astrocytoma cells when compared to astrocytes from nonpathological brain. Among human WHO grade II-IV astrocytomas, downregulation of LMP2, TAP1 and beta2m correlated with grade of malignancy. Furthermore, astrocytoma cell lines (n = 12) expressed all APM components analyzed at levels comparable to dendritic cells (DC), which were used for comparative purposes. However, upregulation of beta2m after stimulation with inflammatory cytokines was significantly lower in astrocytoma cell lines than in control cells. Our results support the hypothesis that coordinated downregulation or impaired upregulation of certain HLA class I APM components may serve as a mechanism for astrocytoma cells to evade the host's immune response, even if HLA class I antigen surface expression is not altered.

Exploiting dendritic cells for active immunotherapy of cancer and chronic infections

Dendritic cells (DCs) are important antigen-presenting cells (APCs) that can prime naive T cells and control adaptive immune responses with respect to magnitude, memory and self-tolerance. Understanding the biology of these cells is central to the development of new generation immunotherapies for cancer and chronic infections. This review presents a brief overview of DC biology and of the preparation and use of DC-based vaccines.

Initiation of adaptive immune responses by transcutaneous immunization

The development of new, effective, easy-to-use and lower-cost vaccination approaches for the combat against malignant and infectious diseases is a pre-eminent need: cancer is a leading cause of morbidity in the Western World; there are numerous pathogenic diseases for which we still have no protective or therapeutic cure; and the financial limitations of developing countries to fight these diseases. In this mini-review we focus on transcutaneous immunization (TCI), a relatively new route for antigen delivery. TCI protocols appear to be particularly promising by gaining access to skin resident APC, which are highly efficient for the initiation of humoral and/or cellular immune responses. Consisting of an adjuvant as a stimulus in combination with an antigen which defines the target, TCI offers a most attractive immunization strategy to mount highly specific full-blown adaptive immune responses. As a topically applicable cell-free adjuvant/antigen mixture, TCI might be suitable to improve patient compliance, as well as feasible economically for the use in Third World countries. In addition, this non-invasive procedure might increase the safety of vaccinations by eliminating the risk of infections related to the recycling and improper disposal of needles. The dissection of antigen and adjuvant is important because it allows "free" combinations in contrast to classical immunizations which are based on application of the pathogen of interest. The most relevant ways and means to find new, effective pathogenic target antigens are "reverse vaccinology" and the direct peptide-epitope identification from MHC molecules with mass-spectrometry. Due to these efficient approaches the variety of antigenic epitopes for potential protective/therapeutic use is perpetually expanding. The most studied adjuvants in TCI approaches are cholera toxin (CT) and its less toxic relative, the heat-labile enterotoxin (LT). Both CT and LT can serve as antigen as well. In contrast to these large proteins, which can only penetrate "pre-treated" skin barrier, the immune response modifier, TLR7 agonist R-837 (Imiquimod) is a small compound adjuvant that easily passages non-disrupted epidermis. It remains currently elusive which cells of the complex-structured "skin-associated lymphoid tissue" (SALT) respond to the adjuvant and which APC carries the antigen to the draining lymphnodes for subsequent initiation of adaptive immune responses.

Dendritic cell vaccine strategies for renal cell carcinoma

Dendritic cell (DC) vaccines are an important experimental immunotherapy for renal cell carcinomas. DC vaccines have proven safe, but only minimal clinical efficacy has been observed to date. DC vaccine strategies reflect the continually evolving understanding of DC biology. The use of mature DCs is particularly important to avoid the induction of regulatory T cells. Better defined sources of immunizing antigens and more efficient antigen-loading will contribute to DC vaccines of better quality. Improved clinical efficacy may also be achieved using DCs that secrete biologically active IL-12, which fosters innate immunity and polarizes T helper type 1 responses that contribute to optimal antitumor immunity. Furthermore, combination therapies that treat systemic immune suppression will be crucial for obtaining improved clinical responses to DC vaccines in patients with advanced disease.

The polycomb group proteins, BMI-1 and EZH2, are tumour-associated antigens

We used SEREX technology to identify novel tumour-associated antigens in patients with primary hepatocellular carcinoma and found serological responses to the polycomb group (PcG) protein BMI-1, which is overexpressed in a range of different tumour types. Further studies identified T-cell responses to both BMI-1 and another PcG protein, EZH2, in cancer patients and at relatively lower levels in some normal donors. We next identified several CD8+ T-cell epitopes derived from BMI-1 and EZH2 and demonstrated that EZH2-derived peptides elicited more significant interferon-gamma (IFN-gamma) release than BMI-1-derived peptides. That CD8(+) T cells were responsible for the observed responses was confirmed for EZH2 by both IFN-gamma capture assays and tetramer staining using an HLA-A0201-restricted, EZH2-derived YMSCSFLFNL (aa 666-674) epitope. The ability of YMSCSFLFNL (aa 666-674) to stimulate the in vitro expansion of specific T cells from peripheral blood lymphocytes was greatly enhanced when the CD25(+) T-cell population was depleted. EZH2-specific cytotoxic T lymphocyte clones specific for two HLA-A0201 epitopes were generated and found to recognise endogenously processed EZH2 in both HLA-matched fibroblasts and tumour cell lines. Given the widespread overexpression of PcG proteins in cancer and their critical role in oncogenesis, these data suggest that they may be useful targets for cancer immunotherapy.

Vaccination of hormone-refractory prostate cancer patients with peptide cocktail-loaded dendritic cells: results of a phase I clinical trial

BACKGROUND

Immunotherapies might represent promising alternatives for the treatment of patients with hormone-refractory prostate cancer (HRPC). In a Phase I clinical trial, we evaluated a vaccination with dendritic cells (DCs) loaded with a cocktail consisting of HLA-A*0201-restricted peptides derived from five different prostate cancer-associated antigens [prostate-specific antigen (PSA), prostate-specific membrane antigen (PSMA), survivin, prostein, transient receptor potential p8 (trp-p8)].

METHODS

Eight HRPC patients received a total of four vaccinations every other week. Clinical and immunological responses were monitored by the determination of the serum PSA levels and by enzyme linked immunospot (ELISPOT) analyses, respectively.

RESULTS

Apart from local skin reactions no side effects were noted. One patient displayed a partial response (PR; PSA decrease >50%) and three other patients showed stable PSA values or decelerated PSA increases. In ELISPOT analyses, three of four PSA responders also showed antigen-specific CD8+ T-cell activation against prostein, survivin, and PSMA.

CONCLUSIONS

The described protocol represents a safe and feasible concept for the induction of clinical and immunological responses. The application of a peptide cocktail-derived from different antigens as a novel treatment modality is supposed to allow for the genetic and biologic heterogeneity of PCa.

Some considerations on the use of peptides and mRNA for therapeutic vaccination against cancer

Active immunization against existing cancer is a field that is currently in development and is associated with a number of problems. The potential use of peptides as minimal essential T-cell antigens and of mRNA as a novel form of antigen with advantages is discussed, with special consideration of practical aspects.

Vaccines for tumour prevention

Despite tremendous progress in basic and epidemiological research, effective prevention of most types of cancer is still lacking. Vaccine use in cancer therapy remains a promising but difficult prospect. However, new mouse models that recapitulate significant features of human cancer progression show that vaccines can keep precancerous lesions under control and might eventually be the spearhead of effective and reliable ways to prevent cancer.

Identification of a naturally processed T cell epitope derived from the glioma-associated protein SOX11

The development of T cell-based immunotherapies of cancer depends on the identification of tumor-associated antigens capable of eliciting tumor-directed cytotoxic T cell responses. In malignant glioma the number of well-defined target antigens for cytotoxic T lymphocytes (CTLs) is still very limited. Recently, we demonstrated the abundant and specific overexpression of the transcription factor SOX11 in malignant glioma. Here, we describe the SOX11-derived peptide LLRRYNVAKV which is capable of inducing human leukocyte antigen-A*0201-restricted and tumor-reactive CTLs. This novel CTL epitope may serve as an attractive candidate for a T cell-based immunotherapy of glioma.

Upregulation of meiosis-specific genes in lymphoma cell lines following genotoxic insult and induction of mitotic catastrophe

Background

We have previously reported that p53 mutated radioresistant lymphoma cell lines undergo mitotic catastrophe after irradiation, resulting in metaphase arrest and the generation of endopolyploid cells. A proportion of these endopolyploid cells then undergo a process of de-polyploidisation, stages of which are partially reminiscent of meiotic prophase. Furthermore, expression of meiosis-specific proteins of the cancer/testis antigens group of genes has previously been reported in tumours. We therefore investigated whether expression of meiosis-specific genes was associated with the polyploidy response in our tumour model.

Methods

Three lymphoma cell lines, Namalwa, WI-L2-NS and TK6, of varying p53 status were exposed to a single 10 Gy dose of gamma radiation and their responses assessed over an extended time course. DNA flow cytometry and mitotic counts were used to assess the kinetics and extent of polyploidisation and mitotic progression. Expression of meiotic genes was analysed using RT-PCR and western blotting. In addition, localisation of the meiotic cohesin REC8 and its relation to centromeres was analysed by immunofluorescence.

Results

The principal meiotic regulator MOS was found to be significantly post-transcriptionally up-regulated after irradiation in p53 mutated but not p53 wild-type lymphoma cells. The maximum expression of MOS coincided with the maximal fraction of metaphase arrested cells and was directly proportional to both the extent of the arrest and the number of endopolyploid cells that subsequently emerged. The meiotic cohesin REC8 was also found to be up-regulated after irradiation, linking sister chromatid centromeres in the metaphase-arrested and subsequent giant cells. Finally, RT-PCR revealed expression of the meiosis-prophase genes, DMC1, STAG3, SYCP3 and SYCP1.

Conclusion

We conclude that multiple meiotic genes are aberrantly activated during mitotic catastrophe in p53 mutated lymphoma cells after irradiation. Furthermore, we suggest that the coordinated expression of MOS and REC8 regulate the extent of arrested mitoses and polyploidy.

Nanomedicine

The intricate problems associated with the delivery and various unnecessary in vivo transitions of proteins and drugs needs to be tackled soon to be able to exploit the myriad of putative therapeutics created by the biotechnology boom. Nanomedicine is one of the most promising applications of nanotechnology in the field of medicine. It has been defined as the monitoring, repair, construction and control of human biological systems at the molecular level using engineered nanodevices and nanostructures. These nanostructured medicines will eventually turn the world of drug delivery upside down. PEGylation (i.e. the attachment of polyethylene glycol to proteins and drugs) is an upcoming methodology for drug development and it has the potential to revolutionise medicine by drastically improving the pharmacokinetic and pharmacodynamic properties of the administered drug. This article provides a total strategy for improving the therapeutic efficacy of various biotechnological products in drug delivery. This article also presents an extensive analysis of most of the PEGylated proteins, peptides and drugs, together with extensive clinical data. Nanomedicines and PEGylation, the latest offshoots of nanotechnology will definitely pave a way in the field of drug delivery where targeted delivery, formulation, in vivo stability and retention are the major challenges.

A Novel Strategy for the Discovery of MHC Class II–Restricted Tumor Antigens: Identification of a Melanotransferrin Helper T-Cell Epitope

CD4+ helper T cells play a critical role in orchestrating host immune responses, including antitumor immunity. The limited availability of MHC class II-associated tumor antigens is still viewed as a major obstacle in the use of CD4+ T cells in cancer vaccines. Here, we describe a novel approach for the identification of MHC class II tumor-associated antigens (TAAs). By combining two-dimensional liquid chromatography and nanoelectrospray ionization tandem mass spectrometry, we developed a highly sensitive method for the detection of human leukocyte antigen (HLA)-DR-associated peptides of dendritic cells upon exposure to necrotic tumor cells. This approach led to the identification of a novel MHC class II-restricted TAA epitope derived from melanotransferrin. The epitope stimulated T cells derived from melanoma patients and healthy individuals and displayed promiscuity in HLA-DR restriction. Moreover, the same peptide was also presented by MHC class II-positive melanoma cells. This strategy may contribute to increase the number of tumor epitopes presented by MHC class II molecules and may support the development of more efficacious vaccines against cancer.

Using protein microarray as a diagnostic assay for non-small cell lung cancer

RATIONALE

Phenotypic and genotypic heterogeneity of lung cancer likely precludes the identification of a single predictive marker and suggests the importance of identifying and measuring multiple markers.

OBJECTIVES

We describe the use of a fluorescent protein microarray to identify and measure multiple non-small cell lung cancer-associated antibodies and show how simultaneous measurements can be combined into a single diagnostic assay.

METHODS

T7 phage cDNA libraries of non-small cell lung cancer were first biopanned with plasma samples from normal subjects and patients with non-small cell lung cancer to enrich the component of tumor-associated proteins, and then applied to microarray slides. Two hundred twelve immunogenic phage-expressed proteins were identified from roughly 4,000 clones, using high-throughput screening with patient plasmas and assayed with 40 cancer and 41 normal plasma samples. Twenty patient and 21 normal plasma samples were randomly chosen and used for statistical determination of the predictive value of each putative marker. Statistical analysis identified antibody reactivity to seven unique phage-expressed proteins that were significantly different (p < 0.01) between patient and normal groups. The remaining 20 patient and 20 normal plasma samples were used as an independent test of the predictive ability of the selected markers.

MAIN RESULTS

Measurements of the 5 most predictive phage proteins were combined in a logistic regression model that achieved 90% sensitivity and 95% specificity in prediction of patient samples, whereas leave-one-out statistical analysis achieved 88.9% diagnostic accuracy among all 81 samples.

CONCLUSION

Our data indicate that antibody profiling is a promising approach that could achieve high diagnostic accuracy for non-small cell lung cancer.

Immunostimulatory neem leaf preparation acts as an adjuvant to enhance the efficacy of poorly immunogenic B16 melanoma surface antigen vaccine

Immunogenecity of the poorly immunogenic B16 melanoma cell surface antigen (B16MelSAg) was enhanced by combining B16MelSAg with NLP in C57BL/6 mice, as evidenced by ELISA and flow cytometry. NLP was as effective as Freund's complete and incomplete adjuvant to generate antibodies recognizing the B16MelSAg. The NLP generated antibody was a gamma globulin with a subtype of IgG1. Splenic lymphocytes from B16MelSAg+NLP treated mice proliferated more rapidly in vitro when stimulated by specific (B16MelSAg) and nonspecific (ConA) stimulators, in comparison to the proliferation detected in B16MelSAg and NLP treated groups. Vaccination of mice with B16MelSAg+NLP more efficiently prevented the growth of B16 melanoma tumor than mice immunized with B16MelSAg or NLP alone. In another experiment, the immune sera (B16MelSAg+NLP) was mixed with B16Mel tumors and injected subcutaneously into syngenic C57BL/6 mice. Tumor burden was less in mice receiving a tumor along with B16MelSAg+NLP generated immune sera than other groups. The B16MelSAg+NLP generated immune sera induced antibody dependent cellular cytotoxicity specifically towards B16Mel tumor cells in vitro. We concluded that NLP might be a potential immune adjuvant for inducing active immunity towards tumor antigens.

Identification of an immunodominant H-2D(b)-restricted CTL epitope of human PSA

BACKGROUND

Human prostate specific antigen (PSA) is expressed selectively in prostate epithelium and is a potential target for the immunotherapy against prostate cancer. Various PSA-based vaccines have been reported to induce cytotoxic T lymphocyte (CTL) responses in animal models. Here, we present the identification and validation of an immunodominant CTL epitope of PSA in C57Bl/6 mice (H-2(b)).

METHODS

PSA-specific CTLs were induced by immunization with a plasmid expressing PSA. Epitope specificity of the CTLs was determined by their reactivity against a panel of C-terminus truncated or mutated PSA proteins and use of bioinformatical prediction with the SYFPEITHI algorithm.

RESULTS

The majority of PSA-specific CTLs were directed against a single H-2D(b) restricted epitope corresponding to the amino acid residues 65-74 (HCIRNKSVIL) of the protein. The CTLs had similar functional avidity against two putative H-2D(b) binding peptides: a 9-aa-long psa65-73 (HCIRNKSVI) and a 10-aa-long psa65-74 (HCIRNKSVIL).

CONCLUSIONS

We demonstrate that the psa65-73 peptide can be used for reactivation of PSA-specific CTLs in vitro and ex vivo, and H-2D(b) pentamers assembled with this peptide are an efficient tool for monitoring of PSA-specific CTL responses after DNA vaccination.

Identification of Noncanonical Melanoma-Associated T Cell Epitopes for Cancer Immunotherapy

The identification of tumor-associated T cell epitopes has contributed significantly to the understanding of the interrelationship of tumor and immune system and is instrumental in the development of therapeutic vaccines for the treatment of cancer. Most of the known epitopes have been identified with prediction algorithms that compute the potential capacity of a peptide to bind to HLA class I molecules. However, naturally expressed T cell epitopes need not necessarily be strong HLA binders. To overcome this limitation of the available prediction algorithms we established a strategy for the identification of T cell epitopes that include suboptimal HLA binders. To this end, an artificial neural network was developed that predicts HLA-binding peptides in protein sequences by taking the entire sequence context into consideration rather than computing the sum of the contribution of the individual amino acids. Using this algorithm, we predicted seven HLA A*0201-restricted potential T cell epitopes from known melanoma-associated Ags that do not conform to the canonical anchor motif for this HLA molecule. All seven epitopes were validated as T cell epitopes and three as naturally processed by melanoma tumor cells. T cells for four of the new epitopes were found at elevated frequencies in the peripheral blood of melanoma patients. Modification of the peptides to the canonical sequence motifs led to improved HLA binding and to improved capacity to stimulate T cells.

Cancer/testis antigens and gametogenesis: a review and "brain-storming" session

Genes expressed both in normal testis and in malignancies (Cancer/ Testis associated genes - CTA) have become the most extensively studied antigen group in the field of tumour immunology. Despite this, many fundamentally important questions remain unanswered: what is the connection between germ-cell specific genes and tumours? Is the expression of these genes yet another proof for the importance of genome destabilisation in the process of tumorigenesis?, or maybe activation of these genes is not quite random but instead related to some programme giving tumours a survival advantage?This review collates most of the recent information available about CTAs expression, function, and regulation. The data suggests a programme related to ontogenesis, mostly to gametogenesis. In the "brain-storming" part, facts in conflict with the hypothesis of random CTA gene activation are discussed. We propose a programme borrowed from organisms phylogenetically much older than humans, which existed before the differentiation of sexes. It is a programme that has served as a life cycle with prominent ploidy changes, and from which, as we know, the germ-cell ploidy cycle - meiosis - has evolved. Further work may show whether this hypothesis can lead to a novel anti-tumour strategy.

Spontaneous tumor-specific humoral and cellular immune responses to NY-ESO-1 in hepatocellular carcinoma

PURPOSE

Hepatocellular carcinoma (HCC) is the fifth most common cancer around the world. Although several therapeutic approaches for treatment of HCC are available, survival rates for HCC patients are still very poor because of inefficient treatment options. For HCC, as well as other tumors, antigen-specific immunotherapy remains a viable approach that is dependent on the definition of tumor-associated antigens. NY-ESO-1, a member of the cancer testis antigen family, is one possible candidate for a tumor-specific antigen in HCC. The aim of this study was to show the relevance of NY-ESO-1 in hepatocellular carcinoma.

EXPERIMENTAL DESIGN

Sera samples from 189 HCC patients were analyzed for NY-ESO-1-specific antibodies. Forty-nine HCC patients were screened for NY-ESO-1 mRNA expression in HCC tissue. Selected patients were followed for up to 3 years to correlate their immune response with their clinical course of events. NY-ESO-1-specific CD4+ and CD8+ T-cell responses from NY-ESO-1 seropositive patients were analyzed and a NY-ESO-1+ specific cytotoxic T-cell line was generated.

RESULTS

Twelve of 49 analyzed tumor samples expressed NY-ESO-1 mRNA and 23 of 189 patients showed NY-ESO-1-specific antibody responses. These humoral immune responses were accompanied by NY-ESO-1-specific functional CD4+ and CD8+ T-cell responses. Finally, NY-ESO-1 humoral responses were dependent on the presence of NY-ESO-1-expressing tumors.

CONCLUSIONS

This is the first report of a spontaneous immune response in HCC patients to a known tumor-specific antigen, NY-ESO-1 protein. Our data favor the possibility of immunotherapeutic strategies for the treatment of HCC.

HLA Class I Antigen Down-Regulation in Primary Ovary Carcinoma Lesions: Association with Disease Stage

Purpose: To investigate TAP1, TAP2, and HLA class I antigen expression in primary ovarian carcinoma lesions and to assess the clinical significance of defects in the expression of these molecules.

Experimental Design: Fifty-one formalin-fixed, paraffin-embedded primary ovarian carcinoma lesions were stained with affinity-purified rabbit anti-TAP1 and anti-TAP2 antibodies and with anti-HLA class I heavy chain monoclonal antibody (mAb) HC-10 using the immunoperoxidase reaction. The results of immunohistochemical staining were correlated with the histopathologic characteristics of the lesions and with patients' survival.

Results: Ovarian surface epithelium, thecal cells of follicles, and stromal cells were stained by anti-TAP1, anti-TAP2, and anti-HLA class I antigen xenoantibodies with a homogeneous pattern. In contrast, no staining of lutheinic cells by these antibodies was detected. Forty-one and 32 out of 51 primary ovarian carcinoma lesions were stained by anti-TAP1 and anti-TAP2 xenoantibodies and by anti-HLA class I antigen mAb HC-10, respectively. The staining patterns by anti-TAP1 and anti-TAP2 xenoantibodies were completely concordant, but did not correlate with that by anti-HLA class I heavy chain mAb HC-10. TAP1 and TAP2 expression was associated neither with the histopathologic characteristics of the lesions nor with clinical variables. On the other hand, HLA class I antigen down-regulation was associated with disease stage: the odds ratio of stage III for HLA class I antigen negative patients was 7.6 (95% confidence interval, 1.9-30.5; P= 0.007), whereas for TAP negative patients was 5.1 (95% confidence interval, 0.9-28.4; P = 0.07). Follow up was available for 39 out of the 51 patients. Multivariate analysis showed that both grading and staging were associated with a higher risk of death, whereas TAP and HLA class I antigen phenotypes were not.

Conclusions: The lack of association between TAP and HLA class I antigen expression is compatible with the possibility that multiple mechanisms underlie HLA class I antigen down-regulation in primary ovarian carcinoma lesions. The potential role of immunologic events in the clinical course of ovarian carcinoma suggests that the association between HLA class I antigen down-regulation and disease progression may reflect the escape of tumor cells from immune recognition and destruction.

T-cell-based immunotherapy of melanoma: what have we learned and how can we improve?

The lack of effective treatment for advanced stage melanoma by conventional therapies, such as radiation and chemotherapy, has highlighted the need to develop alternative therapeutic strategies. Among them, immunotherapy has attracted much attention because of the potential role played by immunological events in the clinical course of melanoma and the availability of well-characterized melanoma antigens to target melanoma lesions with immunological effector mechanisms. In recent years, T-cell-based immunotherapy has been emphasized, in part because of the disappointing results of the antibody-based trials conducted in the early 1980s, and in part because of the postulated major role played by T-cells in tumor growth control. In this review, the characteristics of antibody and T-cell-defined melanoma antigens will first be described, with emphasis on those used in clinical trials. Following a review of the current immunization and immunomonitoring strategies, the results from the T-cell-based immunotherapy clinical trials conducted to date will be reviewed.

Multiepitope Trojan antigen peptide vaccines for the induction of antitumor CTL and Th immune responses

We describe in this study a strategy to produce synthetic vaccines based on a single polypeptide capable of eliciting strong immune responses to a combination CTL and Th epitopes with the purpose of treating malignancies or preventing infectious diseases. This strategy is based on the capacity of Trojan Ags to deliver exogenous Ags into the intracellular compartments, where processing into MHC-binding peptides takes place. Our previous work demonstrated that Trojan Ags containing a CTL epitope localized to intracellular compartments, where MHC class I-binding peptides were generated in a TAP-independent fashion by the action of various exopeptidases and the endopeptidase furin. In this study, we report that Trojan Ags containing several CTL epitopes joined via furin-sensitive linkers generated all of the corresponding MHC class I-binding peptides, which were recognized by CTL. However, Trojan Ags prepared with furin-resistant linkers failed to produce the MHC class I-binding peptides. We also present data indicating that Trojan Ags bearing both CTL and Th epitopes can generate the corresponding MHC class I- and II-binding peptides, which are capable of stimulating T cell responses. Most significantly, in vivo vaccination of mice with a single injection of multiepitope Trojan Ags resulted in strong CTL and Th responses that translated into significant antitumor responses in a model of malignant melanoma. The overall results indicate that Trojan Ags prepared with furin-sensitive linkers are ideal candidates for producing synthetic multiepitope vaccines for the induction of CTL and Th responses that could be used against a variety of diseases, including cancer.

Vaccination with a synthetic nonapeptide expressed in human tumors prevents colorectal cancer liver metastases in syngeneic rats

In previous studies, the antigen CSH-275 (RTNKEASIC) was found expressed in tissue specimens from colorectal cancer but not in normal colonic mucosa. It was also naturally expressed in the DHD-K12 experimental colorectal cancer in BDIX rats. In this study, we describe the effect of vaccination with the synthetic nonapeptide CSH-275 in preventing tumor growth in a model closely mimicking the clinical situation of liver metastases, after surgical resection of primary colorectal cancer. A vaccination protocol using CSH-275, conjugated with complete or incomplete Freund's adjuvant, was carried out to determine the effect in preventing the progression of liver metastases induced by DHD-K12 cells injected in the splenic vein (preventive vaccine). An additional vaccination procedure was carried out to determine the effect on s.c. tumor growth (therapeutic vaccine). A significant improvement in survival along with the prevention of liver metastases formation and reduced growth of s.c. tumor were observed. CSH-275 vaccination resulted in a significant increase in CTL activity against autologous DHD-K12 cells in DHD-K12 tumor-bearing rats and the generation of a CTL response against DHD-K12 cells in DHD-K12 naive rats. Vaccination also induced massive infiltration of CD8(+) cells in tumor. These results demonstrate that CSH-275 is a new molecular target for colorectal cancer immunotherapy; it is also an excellent candidate for preclinical studies because it is naturally expressed on tumors in a fully competent syngeneic animal, which reproduces the clinical pattern of cancer progression.

Novel therapeutic agents under investigation for malignant melanoma

Malignant melanoma presents a therapeutic challenge. Patients at high risk for recurrence (stage III) are eligible for adjuvant treatment with IFN-alpha or may enrol in a clinical trial. Both options offer no meaningful survival advantage. Patients with metastatic disease (stage IV) have a 5-year survival of < 10% and have no effective treatment options. Despite aggressive investigations into vaccine therapy, no vaccine has yet received FDA approval. Biological therapies with IFN-alpha and IL-2 have demonstrated a real but minimal effect. Chemotherapeutic options are even more dismal. Single-agent chemotherapy yields a 15-20% response rate of short lived duration. Combination chemotherapy alone or with immunological adjuvants yields response rates of 35-45% but with significant toxicity and no significant improvement in survival. Novel treatment agents that target metabolic pathways, angiogenesis inhibitors, antisense therapies, gene therapies and innovative vaccines may offer hope for an otherwise grave disease.

Tumor-associated antigen profiling in breast and ovarian cancer: mRNA, protein or T cell recognition?

PURPOSE

The absence of tumor-associated antigens (TAA) which might elicit an immune response is one reason for the disappointing results of therapeutical vaccines in cancer patients. Moreover, impaired expression of MHC class-I and components involved in antigen processing, such as TAP-1, -2, LMP-2, -7, and MECL-1, may lead to tumor escape from immune recognition. Expression profiling of TAA is one approach towards the design of well-defined and individualized anti-tumor vaccines.

METHODS

Quantitative polymerase chain reaction (qRT-PCR) is the method of choice to characterize immunologically relevant properties of individual tumors. However, the application of qRT-PCR as a surrogate parameter for the expression of TAAs depends upon the assumption that the level of an mRNA species correlates with the cellular level of the protein it encodes. Therefore, we additionally analyzed TAA expression by immunofluorescence and T cell recognition.

RESULTS

In the present study we were unable to confirm that impaired TAP-1 or -2 (transporter associated with antigen processing) expression characterized at the mRNA level is an appropriate surrogate parameter for down-regulated MHC class-I expression in breast cancer. In addition, we analyzed the expression pattern of TAAs in breast and ovarian cancer cell lines. Besides the well-known over-expression of HER-2/neu, CEA, and MUC-1, multiple antigens of the MAGE-family were frequently co-expressed. We investigated whether detection of TAAs by qRT-PCR correlates with monoclonal antibody staining, and which method could predict T cell recognition. We demonstrated a correlation between tumor cell lysis by HLA-A*0201-restricted, MUC-1-specific CTL and threshold levels of MUC-1-specific mRNA.

CONCLUSION

MUC-1 is an example that TAA profiling by RT-PCR and flow cytometry can fail to correlate with each other and are of limited value in the prediction of T cell recognition.

Cancer/testis-associated genes: identification, expression profile, and putative function

Cancer/testis-associated genes (CTAs) are a subgroup of tumor antigens with a restricted expression in testis and malignancies. During the last decade, many of these immunotherapy candidate genes have been discovered using various approaches. Most of these genes are localized on the X-chromosome, often as multigene families. Methylation status seems to be the main, but not the only regulator of their specific expression pattern. In testis, CTAs are exclusively present in cells of the germ cell lineage, though there is a lot of variation in the moment of expression during different stages of sperm development. Likewise, there is also a lot of heterogeneity in the expression of CTAs in melanoma samples. Clues regarding functionality of CTAs for many of these proteins point to a role in cell cycle regulation or transcriptional control. Better insights in the function of these genes may shed light on the link between spermatogenesis and tumor growth and could be of use in anti-tumor therapies. This review outlines the CTA family and focuses on their expression and putative function during male germ cell development and melanocytic tumor progression.

The future of vaccination as a treatment strategy in dermatological diseases

Vaccination approaches are increasingly explored as means for both prevention and therapy of skin diseases. These development are boosted by the rapidly accumulating knowledge of the molecular and cellular bases of these disease and the antigens involved, on the one hand, and of the components and mechanisms of cellular and humoral immune responses, on the other. In a number of cases these newly developed vaccination strategies are already tested in clinical trials. Although most of them are still in very early stages of the development, it is foreseeable that vaccination will emerge as an important option for prevention and treatment of infectious skin diseases as well as of cancer, allergies and maybe, auto-immune disorders.