Melanoma cells present a MAGE-3 epitope to CD4(+) cytotoxic T cells in association with histocompatibility leukocyte antigen DR11

Uncoupling CD4+ TIL-Mediated Tumor Killing from JAK-Signaling in Melanoma

PURPOSE

Impaired MHCI-presentation and insensitivity to immune effector molecules are common features of immune checkpoint blockade (ICB)-resistant tumors and can be, respectively, associated with loss of β2 microglobulin (B2M) or impaired IFNγ signaling. Patients with ICB-resistant tumors can respond to alternative immunotherapies, such as infusion of autologous tumor-infiltrating lymphocytes (TIL). CD4+ T cells can exert cytotoxic functions against tumor cells; however, it is unclear whether CD4+ T-cell responses can be exploited to improve the clinical outcomes of patients affected by ICB-resistant tumors.

EXPERIMENTAL DESIGN

Here, we exploited CRISPR (clustered regularly interspaced short palindromic repeats)/Cas9 gene editing to reproduce immune-resistant tumor phenotypes via gene knockout (KO). To determine the role of cytotoxic CD4+ TILs in ICB-resistant tumors, we investigated CD4+ TIL-mediated cytotoxicity in matched pairs of TILs and autologous melanoma cell lines, used as a model of patient-specific immune-tumor interaction. Around 40% of melanomas constitutively express MHC Class II molecules; hence, melanomas with or without natural constitutive MHC Class II expression (MHCIIconst+ or MHCIIconst-) were used.

RESULTS

CD4+ TIL-mediated cytotoxicity was not affected by B2M loss but was dependent on the expression of CIITA. MHCIIconst+ melanomas were killed by tumor-specific CD4+ TILs even in the absence of IFNγ-mediated MHCII upregulation, whereas IFNγ was necessary for CD4+ TIL-mediated cytotoxicity against MHCIIconst- melanomas. Notably, although tumor-specific CD4+ TILs did not kill JAK1KO MHCIIconst- melanomas even after IFNγ stimulation, sensitivity to CD4+ TIL-mediated cytotoxicity was maintained by JAK1KO MHCIIconst+ melanomas.

CONCLUSIONS

In conclusion, our data indicate that exploiting tumor-specific cytotoxic CD4+ TILs could help overcome resistance to ICB mediated by IFNγ-signaling loss in MHCIIconst+ melanomas. See related commentary by Betof Warner and Luke, p. 3829.

Design peptide and multi-epitope protein vaccine candidates against monkeypox virus using reverse vaccinology approach: an in-silico study

Monkeypox is a zoonotic virus that has recently affected different countries worldwide. On July 23, 2022, the WHO declared the outbreak of monkeypox as a public health emergency of international concern. Surveillance studies conducted in Central Africa in the 1980s and later during outbreaks in the same region showed smallpox vaccines to be clinically somewhat effective against Monkeypox virus. However, there is no specific vaccine against this virus. This research used bioinformatics techniques to establish a novel multi-epitope vaccine candidate against Monkeypox that can induce a strong immune response. Five well-known antigenic proteins (E8L, A30L, A35R, A29L, and B21R) of the virus were picked and assessed as possible immunogenic peptides. Two suitable peptide candidates were selected according to bio-informatics analysis. Based upon in silico evaluation, two multi-epitope vaccine candidates (ALALAR and ALAL) were built with rich-epitope domains consisting of high-ranking T and B-cell epitopes. After predicting and evaluating the 3D structure of the protein candidates, the most efficient 3D models were considered for docking studies with Toll-like receptor 4 (TLR4) and the HLA-A * 11:01, HLA-A*01:01, HLA-A*02:01, HLA-A*03:01, HLA-A*07:02, HLA-A*15:01, HLA-A*30:01 receptors. Subsequently, molecular dynamics (MD) simulation of up to 150 nanoseconds was employed to assess the durability of the interaction of the vaccine candidates with immune receptors. MD studies showed that M5-HLA-A*11:01, ALAL-TLR4, and ALALAR-TLR4 complexes were stable during simulation. Analysis of the in silico outcomes indicates that the M5 peptide and ALAL and ALALAR proteins may be suitable vaccine candidates against the Monkeypox virus.Communicated by Ramaswamy H. Sarma.

Progression of pre-rheumatoid arthritis to clinical disease of joints: Potential role of mesenchymal stem cells

Rheumatoid arthritis (RA) related autoimmunity is developed at mucosal sites due to the interplay between genetic risk factors and environmental triggers. The pre-RA phase that leads to anti-citrullinated protein antibodies, rheumatoid factor, and other autoantibodies spread in the systemic circulation may not affect articular tissue for years until a mysterious second hit triggers the localization of RA-related autoimmunity in joints. Several players in the joint microenvironment mediate the synovial innate and adaptive immunological processes, eventually leading to clinical synovitis. There still exists a gap in the early phase of RA pathogenesis, i.e., the progression of diseases from the systemic circulation to joints. The lack of better understanding of these events results in the inability to answer questions about why only after a certain point of time the disease appears in joints and why in some cases, it simply remains latent and doesn't affect joints at all. In the current review, we focused on the immunomodulatory and regenerative role of mesenchymal stem cells and associated exosomes in RA pathology. We also highlighted the age-related dysregulations in activities of mesenchymal stem cells and how that might trigger homing of systemic autoimmunity to joints.

Research progress in effects of MAGE-A family on gastric cancer

Gastric cancer (GC) is one of the most common malignant tumors worldwide, and most of the patients are diagnosed at the advanced stage. Most of the treating options are comprehensive treatment, in which immunotherapy plays more and more important role. Melanoma antigen-associated gene-A (MAGE-A) family is a kind of cancer testis antigens. Except in germ cells of testis and trophoblast cells of placenta, MAGE-A family is highly expressed in cancerous tissues and participates in a variety of biological processes, such as cancer cell proliferation, differentiation and metastasis. In addition, cancer testis antigen also possesses good immunogenicity, which can induce humoral and cellular immune responses, is a good target for immunotherapy, and has good application value in the diagnosis, treatment and prognosis of GC. A variety of targeted therapeutic drugs based on MAGE-A are in phase I or II clinical trials, it has good safety and potential clinical application value. With the continuous progress of clinical trials and basic research on MAGE-A targets in GC, it is expected to provide a theoretical basis for clinical transformation and immunotherapy of MAGE-A in the future.

Therapeutic Cancer Vaccines—Antigen Discovery and Adjuvant Delivery Platforms

For decades, vaccines have played a significant role in protecting public and personal health against infectious diseases and proved their great potential in battling cancers as well. This review focused on the current progress of therapeutic subunit vaccines for cancer immunotherapy. Antigens and adjuvants are key components of vaccine formulations. We summarized several classes of tumor antigens and bioinformatic approaches of identification of tumor neoantigens. Pattern recognition receptor (PRR)-targeting adjuvants and their targeted delivery platforms have been extensively discussed. In addition, we emphasized the interplay between multiple adjuvants and their combined delivery for cancer immunotherapy.

High GILT Expression Is Associated with Improved Survival in Metastatic Melanoma Patients Treated with Immune Checkpoint Inhibition

Simple Summary

Skin cancer is the most common type of cancer, with melanoma being among the deadliest of skin cancers due to its propensity to metastasize. Immune checkpoint inhibitors (ICI) generate anti-tumor immune responses resulting in improved outcomes in patients with metastatic melanoma. However, only a subset of melanoma patients responds to these therapies, which are costly and come with a risk of adverse effects. Therefore, there is a need for biomarkers to predict which patients will respond to ICI. We found that ICI-treated metastatic melanoma patients with high GILT mRNA expression in bulk tumor samples had improved survival. Additionally, high GILT protein expression within metastatic melanoma cells was associated with improved survival in patients treated with ICI. This study suggests that GILT may serve as a biomarker to predict which patients will respond to ICI, which could improve patient care, reduce healthcare costs, and facilitate appropriate selection of therapies for patients with metastatic melanoma.

Abstract

Gamma-interferon-inducible lysosomal thiol reductase (GILT) is critical for MHC class II restricted presentation of multiple melanoma antigens. There is variable GILT protein expression in malignant melanocytes in melanoma specimens. High GILT mRNA expression in melanoma specimens is associated with improved overall survival, before the advent of immune checkpoint inhibitors (ICI). However, the association of GILT in metastatic melanoma with survival in patients treated with ICI and the cell type expressing GILT associated with survival have not been determined. Using RNA sequencing datasets, high GILT mRNA expression in metastatic melanoma specimens was associated with improved progression-free and overall survival in patients treated with ICI. A clinical dataset of metastatic melanoma specimens was generated and annotated with clinical information. Positive GILT immunohistochemical staining in antigen presenting cells and melanoma cells was observed in 100% and 65% of metastatic melanoma specimens, respectively. In the subset of patients treated with ICI in the clinical dataset, high GILT protein expression within melanoma cells was associated with improved overall survival. The association of GILT mRNA and protein expression with survival was independent of cancer stage. These studies support that high GILT mRNA expression in bulk tumor samples and high GILT protein expression in melanoma cells is associated with improved survival in ICI-treated patients. These findings support further investigation of GILT as a biomarker to predict the response to ICI.

T-cell subsets in the skin and their role in inflammatory skin disorders

T lymphocytes (T cells) are major players of the adaptive immune response. Naive T cells are primed in the presence of cytokines, leading to polarization into distinct T-cell subsets with specific functions. These subsets are classified based on their T-cell receptor profile, expression of transcription factors, surface cytokine and chemokine receptors, and their cytokine production, which together determine their specific function. This review provides an overview of the various T-cell subsets and their function in several inflammatory skin disorders ranging from allergic inflammation to skin tumors. Moreover, we highlight similarities of T-cell responses across different skin disorders, demonstrating the presence of similar and opposing functions for the different T-cell subsets. Finally, we discuss the effects of currently available and promising therapeutic approaches to harness T cells in inflammatory skin diseases for which efficacy next to unwanted side effects provide new insights into the pathophysiology of skin disorders.

High GILT Expression and an Active and Intact MHC Class II Antigen Presentation Pathway Are Associated with Improved Survival in Melanoma

The MHC class I Ag presentation pathway in melanoma cells has a well-established role in immune-mediated destruction of tumors. However, the clinical significance of the MHC class II Ag presentation pathway in melanoma cells is less clear. In Ag-presenting cells, IFN-γ-inducible lysosomal thiol reductase (GILT) is critical for MHC class II-restricted presentation of multiple melanoma Ags. Although not expressed in benign melanocytes of nevi, GILT and MHC class II expression is induced in malignant melanocytes in a portion of melanoma specimens. Analysis of The Cancer Genome Atlas cutaneous melanoma data set showed that high GILT mRNA expression was associated with improved overall survival. Expression of IFN-γ, TNF-α, and IL-1β was positively associated with GILT expression in melanoma specimens. These cytokines were capable of inducing GILT expression in human melanoma cells in vitro. GILT protein expression in melanocytes was induced in halo nevi, which are nevi undergoing immune-mediated regression, and is consistent with the association of GILT expression with improved survival in melanoma. To explore potential mechanisms of GILT's association with patient outcome, we investigated pathways related to GILT function and expression. In contrast to healthy skin specimens, in which the MHC class II pathway was nearly uniformly expressed and intact, there was substantial variation in the MHC class II pathway in the The Cancer Genome Atlas melanoma specimens. Both an active and intact MHC class II pathway were associated with improved overall survival in melanoma. These studies support a role for GILT and the MHC class II Ag presentation pathway in melanoma outcome.

Cellular immune responses against cancer-germline genes in cancers

BACKGROUND

Cancer-germline genes are a class of genes that are normally expressed in testis, trophoblast and few somatic tissues but abnormally expressed in tumor tissues. Their expression signature indicates that they can induce cellular immune responses, thus being applied as targets in cancer immunotherapy.

OBJECTIVES

To obtain the data of cellular immune responses against cancer-germline genes in cancer.

METHODS

We searched PubMed/Medline with the key words cancer-germline antigen, cancer-testis antigen, CD4+ T cell, CD8+ T cell and cancer.

RESULTS

About 40 cancer-germline genes have been shown to induce T cell specific responses in cancer patients. Melanoma, lung and breast cancer are among the mostly assessed cancer types. Several epitopes have been identified which can be used in immunotherapy of cancer.

CONCLUSION

Cellular immune responses against cancer-germline genes are indicative of appropriateness of these genes as therapeutic targets.

Tumor-Targeted Immunotherapy by Using Primary Adipose-Derived Stem Cells and an Antigen-Specific Protein Vaccine

Cancer is a leading cause of mortality and a major public health problem worldwide. For biological therapy against cancer, we previously developed a unique immunotherapeutic platform by combining mesenchymal stem cells with an antigen-specific protein vaccine. However, this system possesses a few limitations, such as improperly immortalized mesenchymal stem cells (MSCs) along with transfected oncogenic antigens in them. To overcome the limitations of this platform for future clinical application, we freshly prepared primary adipose-derived stem cells (ADSCs) and modified the E7' antigen (E7') as a non-oncogenic protein. Either subcutaneously co-inoculated with cancer cells or systemically administered after tumor growth, ADSC labeled with enhanced green fluorescent protein (eGFP) and combined with modified E7' (ADSC-E7'-eGFP) cells showed significant antitumor activity when combined with the protein vaccine in both colon and lung cancer in mice. Specifically, this combined therapy inhibited tumor through inducing cell apoptosis. The significantly reduced endothelial cell markers, CD31 and vascular endothelial growth factor (VEGF), indicated strongly inhibited tumor angiogenesis. The activated immune system was demonstrated through the response of CD4+ T and natural killer (NK) cells, and a notable antitumor activity might be contributed by CD8+ T cells. Conclusively, these evidences imply that this promising immunotherapeutic platform might be a potential candidate for the future clinical application against cancer.

Tumor-infiltrating BRAFV600E-specific CD4+ T cells correlated with complete clinical response in melanoma

T cells specific for neoantigens encoded by mutated genes in cancers are increasingly recognized as mediators of tumor destruction after immune checkpoint inhibitor therapy or adoptive cell transfer. Unfortunately, most neoantigens result from random mutations and are patient specific, and some cancers contain few mutations to serve as potential antigens. We describe a patient with stage IV acral melanoma who achieved a complete response following adoptive transfer of tumor-infiltrating lymphocytes (TILs). Tumor exome sequencing surprisingly revealed fewer than 30 nonsynonymous somatic mutations, including oncogenic BRAFV600E. Analysis of the specificity of TILs identified rare CD4+ T cells specific for BRAFV600E and diverse CD8+ T cells reactive to nonmutated self-antigens. These specificities increased in blood after TIL transfer and persisted long-term, suggesting they contributed to the effective antitumor immune response. Gene transfer of the BRAFV600E-specific T cell receptor (TCR) conferred recognition of class II MHC-positive cells expressing the BRAF mutation. Therapy with TCR-engineered BRAFV600E-specific CD4+ T cells may have direct antitumor effects and augment CD8+ T cell responses to self- and/or mutated tumor antigens in patients with BRAF-mutated cancers.

Isolation and Characterization of an HLA-DPB1*04: 01-restricted MAGE-A3 T-Cell Receptor for Cancer Immunotherapy

Long-term tumor regressions have been observed in patients following the adoptive transfer of autologous tumor-infiltrating lymphocytes or genetically modified T cells expressing MHC class I-restricted T-cell receptors (TCRs), but clinical trials have not evaluated responses to genetically modified T cells expressing antitumor MHC class II-restricted TCRs. As studies carried out in a murine tumor model system have demonstrated that the adoptive transfer of CD4 T cells could lead to the regression of established tumors, we plan to test the hypothesis that CD4 T cells can also induce tumor regressions in cancer patients. In this study, 2 MAGE-A3-specific TCRs were isolated from a regulatory T-cell clone (6F9) and an effector clone (R12C9), generated from the peripheral blood of 2 melanoma patients after MAGE-A3 vaccination. The results indicated that T cells transduced with 6F9 TCR mediated stronger effector functions than R12C9 TCR. The 6F9 TCR specifically recognized MAGE-A3 and the closely related MAGE-A6 gene product, but not other members of the MAGE-A family in the context of HLA-DPB1*04:01. To test the feasibility of a potential clinical trial using this TCR, a clinical-scale procedure was developed to obtain a large number of purified CD4 T cells transduced with 6F9 TCR. Because HLA-DPB1*04:01 is present in ∼60% of the Caucasian population and MAGE-A3 is frequently expressed in a variety of cancer types, this TCR immunotherapy could potentially be applicable for a significant portion of cancer patients.

Immune targets and neoantigens for cancer immunotherapy and precision medicine

Harnessing the immune system to eradicate malignant cells is becoming a most powerful new approach to cancer therapy. FDA approval of the immunotherapy-based drugs, sipuleucel-T (Provenge), ipilimumab (Yervoy, anti-CTLA-4), and more recently, the programmed cell death (PD)-1 antibody (pembrolizumab, Keytruda), for the treatment of multiple types of cancer has greatly advanced research and clinical studies in the field of cancer immunotherapy. Furthermore, recent clinical trials, using NY-ESO-1-specific T cell receptor (TCR) or CD19-chimeric antigen receptor (CAR), have shown promising clinical results for patients with metastatic cancer. Current success of cancer immunotherapy is built upon the work of cancer antigens and co-inhibitory signaling molecules identified 20 years ago. Among the large numbers of target antigens, CD19 is the best target for CAR T cell therapy for blood cancer, but CAR-engineered T cell immunotherapy does not yet work in solid cancer. NY-ESO-1 is one of the best targets for TCR-based immunotherapy in solid cancer. Despite the great success of checkpoint blockade therapy, more than 50% of cancer patients fail to respond to blockade therapy. The advent of new technologies such as next-generation sequencing has enhanced our ability to search for new immune targets in onco-immunology and accelerated the development of immunotherapy with potentially broader coverage of cancer patients. In this review, we will discuss the recent progresses of cancer immunotherapy and novel strategies in the identification of new immune targets and mutation-derived antigens (neoantigens) for cancer immunotherapy and immunoprecision medicine.

Tumor antigen-specific CD4+ T cells in cancer immunity: from antigen identification to tumor prognosis and development of therapeutic strategies

CD4(+) T cells comprise a large fraction of tumor infiltrating lymphocytes and it is now established that they may exert an important role in tumor immune-surveillance. Several CD4(+) T cell subsets [i.e. T helper (Th)1, Th2, T regulatory (Treg), Th17, Th22 and follicular T helper (Tfh)] have been described and differentiation of each subset depends on both the antigen presenting cells responsible for its activation and the cytokine environment present at the site of priming. Tumor antigen-specific CD4(+) T cells with different functional activity have been found in the blood of cancer patients and different CD4(+) T cell subsets have been identified at the tumor site by the expression of specific transcription factors and the profile of secreted cytokines. Importantly, depending on the subset, CD4(+) T cells may exert antitumor versus pro-tumor functions. Here we review the studies that first identified the presence of tumor-specific CD4(+) T cells in cancer patients, the techniques used to identify the tumor antigens recognized, the role of the different CD4(+) T cell subsets in tumor immunity and in cancer prognosis and the development of therapeutic strategies aimed at activating efficient antitumor CD4(+) T cell effectors.

Immunologic hierarchy, class II MHC promiscuity, and epitope spreading of a melanoma helper peptide vaccine

Immunization with a combination melanoma helper peptide (6MHP) vaccine has been shown to induce CD4(+) T cell responses, which are associated with patient survival. In the present study, we define the relative immunogenicity and HLA allele promiscuity of individual helper peptides and identify helper peptide-mediated augmentation of specific CD8(+) T cell responses. Thirty-seven participants with stage IIIB-IV melanoma were vaccinated with 6MHP in incomplete Freund's adjuvant. The 6MHP vaccine is comprised of 6 peptides representing melanocytic differentiation proteins gp100, tyrosinase, Melan-A/MART-1, and cancer testis antigens from the MAGE family. CD4(+) and CD8(+) T cell responses were assessed in peripheral blood and in sentinel immunized nodes (SIN) by thymidine uptake after exposure to helper peptides and by direct interferon-γ ELIspot assay against 14 MHC class I-restricted peptides. Vaccine-induced CD4(+) T cell responses to individual epitopes were detected in the SIN of 63 % (22/35) and in the peripheral blood of 38 % (14/37) of participants for an overall response rate of 65 % (24/37). The most frequently immunogenic peptides were MAGE-A3281-295 (49 %) and tyrosinase386-406 (32 %). Responses were not limited to HLA restrictions originally described. Vaccine-associated CD8(+) T cell responses against class I-restricted peptides were observed in 45 % (5/11) of evaluable participants. The 6MHP vaccine induces both CD4(+) and CD8(+) T cell responses against melanoma antigens. CD4(+) T cell responses were detected beyond reported HLA-DR restrictions. Induction of CD8(+) T cell responses suggests epitope spreading and systemic activity mediated at the tumor site.

A melanoma helper peptide vaccine increases Th1 cytokine production by leukocytes in peripheral blood and immunized lymph nodes

Background

Cancers produce soluble and cell-associated molecules that can suppress or alter antitumor immunity. Preclinical studies suggest the disease burden may alter the cytokine profile of helper T cell responses to cancer antigens. We studied cytokine production by helper T cells responding to vaccination with 6 melanoma helper peptides (6MHP) in blood and lymph nodes.

Methods

Twenty-three patients with stage IIIB-IV melanoma received a 6MHP vaccine. Antigen-reactive T cells from blood and draining lymph nodes were cultured, exposed to antigen, and then supernatants (days 2 and 5) were assayed for Th1 and Th2 cytokines. Results from 4 time points were compared to pre-vaccine levels.

Results

Cytokine responses to vaccinating peptides were observed in 83% of patients. Th1 favoring responses were most common (17 of 19 responders). The most abundant cytokines produced were IFN-γ and IL-5 in the PBMC’s. IL-2 responses predominated in cells obtained from draining lymph nodes in 2-day culture but not in 5-day cultures. Patients with clinically measurable disease produced similar levels of total cytokine and similar degree of Th1 polarization as patients with no evidence of disease (NED).

Conclusions

The MHC class II-associated peptides used in this study induced helper T cells with a Th1-biased cytokine response in both PBMC and sentinel immunized nodes. Most patients can mount a Th1 dominant response to these peptides. Future studies are needed to test newer vaccine adjuvants in combination with these peptides.

Trial registration

CDR0000378171, Clinicaltrials: NCT00089219.

T-cell epitope vaccine design by immunoinformatics

Vaccination is generally considered to be the most effective method of preventing infectious diseases. All vaccinations work by presenting a foreign antigen to the immune system in order to evoke an immune response. The active agent of a vaccine may be intact but inactivated ('attenuated') forms of the causative pathogens (bacteria or viruses), or purified components of the pathogen that have been found to be highly immunogenic. The increased understanding of antigen recognition at molecular level has resulted in the development of rationally designed peptide vaccines. The concept of peptide vaccines is based on identification and chemical synthesis of B-cell and T-cell epitopes which are immunodominant and can induce specific immune responses. The accelerating growth of bioinformatics techniques and applications along with the substantial amount of experimental data has given rise to a new field, called immunoinformatics. Immunoinformatics is a branch of bioinformatics dealing with in silico analysis and modelling of immunological data and problems. Different sequence- and structure-based immunoinformatics methods are reviewed in the paper.

In silico analysis and experimental validation of Mycobacterium tuberculosis -specific proteins and peptides of Mycobacterium tuberculosis for immunological diagnosis and vaccine development

Comparative analyses of the Mycobacterium tuberculosis genome with the genomes of other mycobacteria have led to the identification of several genomic regions of difference (RDs) between M. tuberculosis and M. bovis BCG. The identification of immunodominant and HLA-promiscuous antigens and peptides encoded by these RDs could be useful for diagnosis and the development of new vaccines against tuberculosis. The analysis of RD proteins and peptides by in silico methods (using computational programs to predict major and HLA-promiscuous antigenic proteins and peptides) and experimental validations (using peripheral blood mononuclear cells and sera from tuberculosis patients and BCG-vaccinated healthy subjects to assess antigen-specific cellular and humoral immune responses in vitro) identified several major antigens and peptides. To evaluate the in vivo potentials, the genes of immunodominant antigens were cloned and expressed in DNA vaccine vectors. Immunizations of experimental animals with the recombinant constructs induced antigen-specific cellular responses. Further experiments showed that each of these proteins had several T and B cell epitopes scattered throughout their sequence, which confirmed their strong immunogenicity. In conclusion, the bioinformatics-based in silico identification of promiscuous antigens and peptides of M. tuberculosis is a useful approach to identify new candidates important for diagnosis and vaccine applications.

Profound tumor-specific Th2 bias in patients with malignant glioma

Background

Vaccination against tumor-associated antigens is one promising approach to immunotherapy against malignant gliomas. While previous vaccine efforts have focused exclusively on HLA class I-restricted peptides, class II-restricted peptides are necessary to induce CD4⁺ helper T cells and sustain effective anti-tumor immunity. In this report we investigated the ability of five candidate peptide epitopes derived from glioma-associated antigens MAGE and IL-13 receptor α2 to detect and characterize CD4⁺ helper T cell responses in the peripheral blood of patients with malignant gliomas.

Methods

Primary T cell responses were determined by stimulating freshly isolated PBMCs from patients with primary glioblastoma (GBM) (n = 8), recurrent GBM (n = 5), meningioma (n = 7), and healthy controls (n = 6) with each candidate peptide, as well as anti-CD3 monoclonal antibody (mAb) and an immunodominant peptide epitope derived from myelin basic protein (MBP) serving as positive and negative controls, respectively. ELISA was used to measure IFN-γ and IL-5 levels, and the ratio of IFN-γ/IL-5 was used to determine whether the response had a predominant Th1 or Th2 bias.

Results

We demonstrate that novel HLA Class-II restricted MAGE-A3 and IL-13Rα2 peptides can detect T cell responses in patients with GBMs as well as in healthy subjects. Stimulation with a variety of peptide antigens over-expressed by gliomas is associated with a profound reduction in the IFN-γ/IL-5 ratio in GBM patients relative to healthy subjects. This bias is more pronounced in patients with recurrent GBMs.

Conclusions

Therapeutic vaccine strategies to shift tumor antigen-specific T cell response to a more immunostimulatory Th1 bias may be needed for immunotherapeutic trials to be more successful clinically.

Enhancing cancer immunotherapy by intracellular delivery of cell-penetrating peptides and stimulation of pattern-recognition receptor signaling

The importance of T-cell-mediated antitumor immunity has been demonstrated in both animal models and human cancer immunotherapy. In the past 30 years, T-cell-based immunotherapy has been improved with an objective clinical response rate of up to 72%. Identification of MHC class I- and II-restricted tumor antigens recognized by tumor-reactive T cells has generated a resurgence of interest in cancer vaccines. Although clinical trials with cancer peptide/protein vaccines have only met a limited success, several phase II/III clinical trials are either completed or ongoing with encouraging results. Recent advances in immunotherapy have led to the approval of two anticancer drugs (sipuleucel-T vaccine and anti-CTLA-4 antibody) by the US FDA for the treatment of metastatic castration-resistant prostate cancer and melanoma, respectively. Intracellular delivery of antigenic peptides into dendritic cells (DCs) prolongs antigen presentation of antigen-presenting cells to T cells, thus further improving clinical efficacy of peptide/protein cancer vaccines. Because innate immune responses are critically important to provide sensing and initiating of adaptive immunity, combined use of cell-penetrating peptide vaccines with stimulation of innate immune signaling may produce potent antitumor immune responses. We will discuss the recent progress and novel strategies in cancer immunotherapy.

The development of a novel cancer immunotherapeutic platform using tumor-targeting mesenchymal stem cells and a protein vaccine

An ideal anticancer strategy should target only the malignant cells but spare the normal ones. In this regard, we established a platform, consisting of an antigen-delivering vehicle and a protein vaccine, for developing an immunotherapeutic approach with the potential for eliminating various cancer types. Mesenchymal stem cells (MSCs) have been demonstrated capable of targeting tumors and integrating into the stroma. Moreover, we have developed a protein vaccine PE(ΔIII)-E7-KDEL3 which specifically recognized E7 antigen and elicited immunity against cervical cancer. Taking advantage of tumor-homing property of MSCs and PE(ΔIII)-E7-KDEL3, we used E6/E7-immortalized human MSCs (KP-hMSCs) as an E7 antigen-delivering vehicle to test if this protein vaccine could effectively eliminate non-E7-expressing tumor cells. Animals which received combined treatment of KP-hMSCs and PE(ΔIII)-E7-KDEL3 demonstrated a significant inhibition of tumor growth and lung-metastasis when compared to PE(ΔIII)-E7-KDEL3 only and KP-hMSCs only groups. The efficiency of tumor suppression correlated positively to the specific immune response induced by PE(ΔIII)-E7-KDEL3. In addition, this combined treatment inhibited tumor growth via inducing apoptosis. Our findings indicated that KP-hMSCs could be used as a tumor-targeting device and mediate antitumor effect of PE(ΔIII)-E7-KDEL3. We believe this strategy could serve as a platform for developing a universal vaccine for different cancer types.

The present and future of peptide vaccines for cancer: single or multiple, long or short, alone or in combination?

Peptide vaccines incorporate one or more short or long amino acid sequences as tumor antigens, combined with a vaccine adjuvant. Thus, they fall broadly into the category of defined antigen vaccines, along with vaccines using protein, protein subunits, DNA, or RNA. They remain one of the most immunogenic approaches, based on measures of T-cell response in the blood or in draining lymph nodes. However, existing peptide vaccines have had limited success at inducing clinical tumor regressions, despite reliable induction of T-cell responses. Several new developments offer promise for improving peptide vaccines, including use of long peptides, optimization of adjuvants including toll-like receptor agonists, and combination with systemic therapies that may reduce tumor-associated immune dysfunction, such as blockade of PD-1/PD-L1 interactions. To apply these new approaches optimally, it will be critical to study their effects in the context of defined antigens, for which peptide vaccines are optimal.

Immunization delivered by lentiviral vectors for cancer and infectious diseases

The increasing level of understanding of the lentivirus biology has been instrumental in shaping the design strategy of creating therapeutic lentiviral delivery vectors. As a result, lentiviral vectors have become one of the most powerful gene transfer vehicles. They are widely used for therapeutic purposes as well as in studies of basic biology, due to their unique characteristics. Lentiviral vectors have been successfully employed to mediate durable and efficient antigen expression and presentation in dendritic cells both in vitro and in vivo, leading to the activation of cellular immunity and humoral responses. This capability makes the lentiviral vector an ideal choice for immunizations that target a wide range of cancers and infectious diseases. Further advances into optimizing the vector system and understanding the relationship between the immune system and diseases pathogenesis will only augment the potential benefits and utility of lentiviral vaccines for human health.

A long peptide from MELOE-1 contains multiple HLA class II T cell epitopes in addition to the HLA-A*0201 epitope: an attractive candidate for melanoma vaccination

CD4(+) T cells contribute importantly to the antitumor T cell response, and thus, long peptides comprising CD4 and CD8 epitopes may be efficient cancer vaccines. We have previously identified an overexpressed antigen in melanoma, MELOE-1, presenting a CD8(+) T cell epitope, MELOE-1(36-44), in the HLA-A*0201 context. A T cell repertoire against this epitope is present in HLA-A*0201+ healthy subjects and melanoma patients and the adjuvant injection of TIL containing MELOE-1 specific CD8(+) T cells to melanoma patients was shown to be beneficial. In this study, we looked for CD4(+) T cell epitopes in the vicinity of the HLA-A*0201 epitope. Stimulation of PBMC from healthy subjects with MELOE-1(26-46) revealed CD4 responses in multiple HLA contexts and by cloning responsive CD4(+) T cells, we identified one HLA-DRβ1*1101-restricted and one HLA-DQβ1*0603-restricted epitope. We showed that the two epitopes could be efficiently presented to CD4(+) T cells by MELOE-1-loaded dendritic cells but not by MELOE-1+ melanoma cell-lines. Finally, we showed that the long peptide MELOE-1(22-46), containing the two optimal class II epitopes and the HLA-A*0201 epitope, was efficiently processed by DC to stimulate CD4(+) and CD8(+) T cell responses in vitro, making it a potential candidate for melanoma vaccination.

MAGE-A3 and MAGE-A4 specific CD4(+) T cells in head and neck cancer patients: detection of naturally acquired responses and identification of new epitopes

Frequent expression of cancer testis antigens (CTA) has been consistently observed in head and neck squamous cell carcinomas (HNSCC). For instance, in 52 HNSCC patients, MAGE-A3 and -A4 CTA were expressed in over 75% of tumors, regardless of the sites of primary tumors such as oral cavity or hypopharynx. Yet, T-cell responses against these CTA in tumor-bearing patients have not been investigated in detail. In this study, we assessed the naturally acquired T-cell response against MAGE-A3 and -A4 in nonvaccinated HNSCC patients. Autologous antigen-presenting cells pulsed with overlapping peptide pools were used to detect and isolate MAGE-A3 and MAGE-A4 specific CD4(+) T cells from healthy donors and seven head and neck cancer patients. CD4(+) T-cell clones were characterized by cytokine secretion. We could detect and isolate MAGE-A3 and MAGE-A4 specific CD4(+) T cells from 7/7 cancer patients analyzed. Moreover, we identified six previously described and three new epitopes for MAGE-A3. Among them, the MAGE-A3(111-125) and MAGE-A3(161-175) epitopes were shown to be naturally processed and presented by DC in association with HLA-DP and DR, respectively. All of the detected MAGE-A4 responses were specific for new helper epitopes. These data suggest that naturally acquired CD4(+) T-cell responses against CT antigens often occur in vivo in HNSCC cancer patients and provide a rationale for the development of active immunotherapeutic approaches in this type of tumor.

A TCR targeting the HLA-A*0201-restricted epitope of MAGE-A3 recognizes multiple epitopes of the MAGE-A antigen superfamily in several types of cancer

Adoptive immunotherapy using TCR-engineered PBLs against melanocyte differentiation Ags mediates objective tumor regression but is associated with on-target toxicity. To avoid toxicity to normal tissues, we targeted cancer testis Ag (CTA) MAGE-A3, which is widely expressed in a range of epithelial malignancies but is not expressed in most normal tissues. To generate high-avidity TCRs against MAGE-A3, we employed a transgenic mouse model that expresses the human HLA-A*0201 molecule. Mice were immunized with two HLA-A*0201-restricted peptides of MAGE-A3: 112-120 (KVAELVHFL) or MAGE-A3: 271-279 (FLWGPRALV), and T cell clones were generated. MAGE-A3-specific TCR α- and β-chains were isolated and cloned into a retroviral vector. Expression of both TCRs in human PBLs demonstrated Ag-specific reactivity against a range of melanoma and nonmelanoma tumor cells. The TCR against MAGE-A3: 112-120 was selected for further development based on superior reactivity against tumor target cells. Interestingly, peptide epitopes from MAGE-A3 and MAGE-A12 (and to a lesser extent, peptides from MAGE-A2 and MAGE-A6) were recognized by PBLs engineered to express this TCR. To further improve TCR function, single amino acid variants of the CDR3 α-chain were generated. Substitution of alanine to threonine at position 118 of the α-chain in the CDR3 region of the TCR improved its functional avidity in CD4 and CD8 cells. On the basis of these results, a clinical trial is planned in which patients bearing a variety of tumor histologies will receive autologous PBLs that have been transduced with this optimized anti-MAGE-A3 TCR.

GILT accelerates autoimmunity to the melanoma antigen tyrosinase-related protein 1

Melanocyte differentiation Ags, including tyrosinase-related protein (TRP) 1, are relevant to both autoimmune skin depigmentation (vitiligo) and tumor immunity, because they are expressed by both benign melanocytes and many malignant melanomas. Melanoma patients generate CD4(+) T cells that specifically recognize these proteins. TRP1 contains internal disulfide bonds and is presented by MHC class II molecules. Gamma-IFN-inducible lysosomal thiol reductase (GILT) facilitates the generation of class II-binding peptides by the endocytic reduction of protein disulfide bonds. We show in this study that GILT is required for efficient MHC class II-restricted processing of a TRP1 epitope in vitro and accelerates the onset of vitiligo in TRP1-specific TCR transgenic mice. The presence of GILT confers a small increase in the percentage of autoreactive T cells with an effector memory phenotype that may contribute to earlier disease onset. The onset of vitiligo is associated with a greater increase in the percentage of autoreactive T cells with an effector memory phenotype. Given that many self and tumor Ags have disulfide bonds and are presented on MHC class II, GILT is likely to be important in the pathogenesis of other CD4(+) T cell-mediated autoimmune diseases and for the development of effective cancer immunotherapy.

The CD4+ T-cell epitope-binding register is a critical parameter when generating functional HLA-DR tetramers with promiscuous peptides

Detection of CD4(+) T cells specific for tumor-associated antigens is critical to investigate the spontaneous tumor immunosurveillance and to monitor immunotherapy protocols in patients. We investigated the ability of HLA-DR 1101 multimers to detect CD4(+) T cells specific for three highly promiscuous MAGE-A3 derived peptides: MAGE-A3(191-205) (p39), MAGE-A3(281-295) (p57) and MAGE-A3(286-300) (p58). Tetramers stained specific CD4(+) T cells only when loaded with p39, although all peptides activated the specific T cells when presented by plastic-bound HLA-DR 1101 monomers. This suggested that tetramer staining ability was determined by the mode rather than the affinity of peptide binding to HLA-DR 1101. We hypothesized that peptides should bear a single P1 anchor residue to bind all arms of the multimer in a homogeneous register to generate peptide-HLA-DR conformers with maximal avidity. Bioinformatics analysis indicated that p39 contained one putative P1 anchor residue, whereas the other two peptides contained multiple ones. Designing p57 and p58 analogues containing a single anchor residue generated HLA-DR 1101 tetramers that stained specific CD4(+) T cells. Producing HLA-DR 1101 monomers linked with the optimized MAGE-A3 analogues, but not with the original epitopes, further improved tetramer efficiency. Optimization of CD4(+) T-cell epitope-binding registers is thus critical to generate functional HLA-DR tetramers.

A Mage3/Heat Shock Protein70 DNA vaccine induces both innate and adaptive immune responses for the antitumor activity

Heat shock proteins (HSPs) are highly effective and versatile molecules in promoting antitumor immune responses. We tested whether a HSP-based DNA vaccine can induce effective immune response against Mage3, a cancer testis (CT) antigen frequently expressed in many human tumors, thereby controlling the Mage3-expressing tumor. The vaccine was constructed by linking human inducible HSP70 to the C-terminus of a modified Mage3 gene (sMage3) that was attached at its N-terminus with the signal leader sequence of the human RANTES for releasing the expressed fusion protein from the transduced cells. Intramuscular injection of sMage3Hsp DNA induced CD4(+)/CD8(+) T cell and antibody responses. Vaccination with sMage3Hsp DNA was more effective in inhibiting Mage3-expressing TC-1 tumors. When we dissected the antitumor activity of CD4(+) and CD8(+) T cells by immunizing CD4(+) and CD8(+) knockout mice with sMage3Hsp DNA, we found that both CD8(+) T and CD4(+) T cells played a role in control of inoculated tumor, but did not constitute the whole of immune protection in the prophylactic immunization. Instead, depletion of natural killer (NK) cells led to a major loss of antitumor activity in the immunized mice. These results indicate that the HSP-based Mage3 DNA vaccine can more effectively inhibit tumor growth by inducing both the innate immune responses and Mage3-specific adaptive immune responses via the Hsp-associated adjuvant function.

Characterization of preexisting MAGE-A3-specific CD4+ T cells in cancer patients and healthy individuals and their activation by protein vaccination

Vaccination with cancer/testis Ag MAGE-A3 in the form of recombinant protein often induces specific humoral and cellular immune responses. Although Ag-specific CD4+ T cells following vaccination are detectable by cytokine production after a single in vitro stimulation, their detection before vaccination is difficult because of low frequency. In this study, we have applied a sensitive method using CD154 (CD40L) staining to detect MAGE-A3-specific CD4+ T cells. MAGE-A3-specific T cell responses were analyzed in four healthy donors, two lung cancer patients with spontaneous serum Abs to MAGE-A3, and two baseline seronegative lung cancer patients throughout vaccination with MAGE-A3 protein. MAGE-A3-specific CD4+ T cells were detected in all individuals tested, at low frequency in healthy donors and seronegative cancer patients and higher frequency in patients seropositive for MAGE-A3. Polyclonal expansion of CD154-expressing CD4+ T cells after cell sorting generated a large number of MAGE-A3-specific CD4+ T cell lines from all individuals tested, enabling full characterization of peptide specificity, HLA-restriction, and avidity. Application of this method to cancer patients vaccinated with MAGE-A3 protein with or without adjuvant revealed that protein vaccination induced oligoclonal activation of MAGE-A3-specific CD4+ T cells. It appeared that MAGE-A3 protein vaccination in the presence of adjuvant selectively expanded high avidity CD4+ T cells, whereas high avidity T cells disappeared after multiple vaccinations with MAGE-A3 protein alone.

Vaccination with recombinant NY-ESO-1 protein elicits immunodominant HLA-DR52b-restricted CD4+ T cell responses with a conserved T cell receptor repertoire

PURPOSE

ESO is a tumor-specific antigen with wide expression in human tumors of different histologic types and remarkable spontaneous immunogenicity. We have previously shown that specific T(H)1 and antibody responses can be elicited in patients with no detectable preexisting immune responses by vaccination with rESO administered with Montanide ISA-51 and CpG ODN 7909. The purpose of the present study was to characterize vaccine-induced ESO-specific CD4(+) T cell responses.

EXPERIMENTAL DESIGN

We generated CD4(+) T cell clones from patient C2, who had the highest CD4(+) T cell response to the vaccine, and analyzed their fine specificity and HLA class II restriction to determine the recognized epitope. We then assessed the response to the identified epitope in all vaccinated patients expressing the corresponding HLA class II allele.

RESULTS

We found that ESO-specific CD4(+) T cell clones from patient C2 recognize peptide ESO(119-143) (core region 123-137) presented by HLA-DR52b (HLA-DRB3*0202), a MHC class II allele expressed by about half of Caucasians. Importantly, following vaccination, all patients expressing DR52b developed significant responses to the identified epitope, accounting for, on average, half of the total CD4(+) T cell responses to the 119-143 immunodominant region. In addition, analysis of ESO-specific DR52b-restricted CD4(+) T cells at the clonal level revealed significant conservation of T cell receptor usage among different individuals.

CONCLUSIONS

The identification of a DR52b-restricted epitope from ESO that is immunodominant in the context of vaccine-elicited immune responses is instrumental for the immunologic monitoring of vaccination trials targeting this important tumor antigen.

Helper T-cell responses and clinical activity of a melanoma vaccine with multiple peptides from MAGE and melanocytic differentiation antigens

PURPOSE

A phase I/II trial was performed to evaluate the safety and immunogenicity of a novel melanoma vaccine comprising six melanoma-associated peptides defined as antigenic targets for melanoma-reactive helper T cells. Source proteins for these peptides include MAGE proteins, MART-1/MelanA, gp100, and tyrosinase.

PATIENTS AND METHODS

Thirty-nine patients with stage IIIB to IV melanoma were vaccinated with this six-peptide mixture weekly at three dose levels, with a preceding phase I dose escalation and subsequent random assignment among the dose levels. Helper T-lymphocyte responses were assessed by in vitro proliferation assay and delayed-type hypersensitivity skin testing. Patients with measurable disease were evaluated for objective clinical response by Response Evaluation Criteria in Solid Tumors.

RESULTS

Vaccination with the helper peptide vaccine was well tolerated. Proliferation assays revealed induction of T-cell responses to the melanoma helper peptides in 81% of patients. Among 17 patients with measurable disease, objective clinical responses were observed in two patients (12%), with response durations of 1 and 3.9+ years. Durable stable disease was observed in two additional patients for periods of 1.8 and 4.6+ years.

CONCLUSION

Results of this study support the safety and immunogenicity of a vaccine comprised of six melanoma helper peptides. There is also early evidence of clinical activity.

Identification of human CD4 T-cell epitopes on the VP1 capsid protein of enterovirus 71

The identification of human CD4 T-cell epitopes within a protein vaccine candidate is of great interest,as it provides a better understanding of the mechanisms involved in protective immunity and may therefore help in the design of effective vaccines and diagnostic tools. The entire amino acid sequence of the VP1 capsid protein from enterovirus 71 (EV 71) strain 41 was submitted to analysis by the ProPred algorithm for the identification of potential promiscuous human CD4 T-cellepitopes. Three regions spanning amino acids 66-77, 145-159, and 247-261 of VP1 were predicted to bind more than 25 HLA-DR alleles. The corresponding synthetic peptides (SP1 to SP3) were then tested for their abilities to induce proliferation of CD4 T cells isolated from five human volunteers screened positive for previous EV 71 exposure and one EV 71-negative volunteer. Upon stimulation with either peptide, CD4 T-cell proliferative responses were observed for all EV 71-positive volunteers,indicating the presence of EV 71-specific memory CD4 T cells. The amplitude of the proliferative responses was peptide- and HLA-DR-dependent, and correlated well with the ProPredpredicted binding efficiencies. Moreover, CD4 T cells from EV 71-positive volunteers produced significant levels of IL-2 and IFN- upon stimulation, indicative of a T-cell differentiation into Th-1-type subset. Among the three peptides, SP2 induced the highest proliferative response and cytokine production. Moreover, SP2-induced proliferative response could be inhibited with anti-major histocompatibility complex (MHC) class II antibody, indicating that SP2 represents a MHC class II-restricted CD4 T-cell epitope. This study demonstrates that the ProPred algorithm can accurately predict the presence of human CD4 T-cell epitopes within the VP1 capsid protein of EV 71, and therefore represents a useful tool for the design of subunit vaccines against EV 71.

Human CD4+ T lymphocytes recognize a vascular endothelial growth factor receptor-2-derived epitope in association with HLA-DR

PURPOSE

Given the multiple escape mechanisms of tumor cells, immunotherapy targeting tumor-dependent stroma may be an effective cancer treatment strategy. Animal models indicate that inducing immunity to tumor endothelia engenders potent antitumor effects without significant pathology. Recently, the first human tumor endothelial antigen vascular endothelial growth factor receptor-2 (VEGFR-2) recognized by HLA class I-restricted CD8(+) T cells has been characterized. In this study, we sought to investigate specific recognition of this molecule by human CD4(+) T cells.

EXPERIMENTAL DESIGN

To identify HLA-DR-restricted antigenic peptides on VEGFR-2 recognized by CD4(+) T cells of healthy donors and cancer patients.

RESULTS

Nine candidate VEGFR-2 peptides with high binding probability to six common HLA-DRB1 alleles were synthesized using the SYFPEITHI algorithm. One 15-mer peptide (EKRFVPDGNRISWDS), mapping to the 167-181 region of VEGFR-2, stimulated CD4(+) T cells in association with several HLA-DR alleles, including DR4 and DR7. Importantly, the epitope could be naturally processed and presented both by HLA-DR-matched antigen-expressing proliferating endothelial cells and by dendritic cells loaded with the native antigen. Furthermore, circulating VEGFR-2-specific CD4(+) T cells were detected in 4 of 10 healthy donors and 12 of 40 cancer patients even after single-round peptide stimulation in short-term culture. Patient's T cells could recognize antigen-expressing proliferating endothelial cells in a HLA-DR-restricted fashion.

CONCLUSION

These findings indicate an important role for the 167-181 region of VEGFR-2 in the stimulation of CD4(+) T cell responses to VEGFR-2 protein, and may be instrumental both for the development and monitoring of upcoming antitumor vessel vaccines against different cancers based on VEGFR-2 immunogens.

Differential pattern of CD4+ and CD8+ T-cell immunity to MAGE-A1/A2/A3 in patients with monoclonal gammopathy of undetermined significance (MGUS) and multiple myeloma

The factors that determine progression from monoclonal gammopathy of undetermined significance (MGUS) to multiple myeloma are unclear but may include the breakdown of immune surveillance. Cancer testis antigens (CTAgs) are expressed by the majority of myelomas and MGUS tumors and are a potential immune target. We have characterized CD4(+) and CD8(+) T-cell immune responses to MAGE-A1/A2/A3 in these patients. CD4(+) T-cell immunity to MAGE proteins is stronger and more frequent in MGUS compared with myeloma with a predominantly CD45RA(-)CCR7(-) effector memory profile and cytotoxicity against MAGE-positive cell lines. In contrast CD8(+) T-cell immune responses were present almost exclusively in patients with multiple myeloma, correlating with disease, with a CD45RA(+)CCR7(-) memory phenotype, localizing poorly to the bone marrow but were able to lyse myeloma cell lines in vitro. This suggests that the CD4(+) CTAg-specific immune response may play a role in controlling tumor growth, whereas the efficacy of the CD8(+) T-cell response appears to be limited in vivo. Despite this, patients with evidence of a CTAg-specific immune response had a 53% reduction in mortality over a median follow-up of 4 years. These findings have important implications for clinical approaches to CTAg-specific immunotherapy in patients with cancer.

Synthetic CD4+ T cell-targeted antigen-presenting cells elicit protective antitumor responses

CD4(+) helper T cells are critical for protective immune responses and yet suboptimally primed in response to tumors. Cell-based vaccination strategies are under evaluation in clinical trials but limited by the need to derive antigen-presenting cells (APC) from patients or compatible healthy donors. To overcome these limitations, we developed CD4(+) T cell-targeted synthetic microbead-based artificial APC (aAPC) and used them to activate CD4(+) T lymphocytes specific for a tumor-associated model antigen (Ag) directly from the naive repertoire. In vitro, aAPC specifically primed Ag-specific CD4(+) T cells that were activated to express high levels of CD44, produced mainly interleukin 2, and could differentiate into Th1-like or Th2-like cells in combination with polarizing cytokines. I.v. administration of aAPC led to Ag-specific CD4(+) T-cell activation and proliferation in secondary lymphoid organs, conferred partial protection against subcutaneous tumors, and prevented the establishment of lung metastasis. Taken together, our data support the use of cell-free, synthetic aAPC as a specific and versatile alternative to expand peptide-specific CD4(+) T cells in adoptive and active immunotherapy.

Endosomal proteases influence the repertoire of MAGE-A3 epitopes recognized in vivo by CD4+ T cells

Little is known about the repertoire of MAGE-A3 CD4(+) T-cell epitopes recognized in vivo by neoplastic patients and how antigen processing influences epitope formation. Here, we first show that MAGE-A3-specific CD4(+) T cells are present in the blood of advanced melanoma patients. MAGE-A3(111-125), MAGE-A3(191-205), and MAGE-A3(281-300) were recognized by 7, 6, and 5 of the 11 patients tested, respectively. MAGE-A3(146-160) and MAGE-A3(171-185) were also recognized in two and one cases, whereas no recognition of MAGE-A3(161-175) and MAGE-A3(243-258) was observed. Cytokines produced were mainly interleukin 5 and/or granulocyte macrophage colony-stimulating factor, suggesting impairment of productive polarized Th1 responses. Secondly, proteases inhibitors were used to modulate in vitro the recognition by CD4(+) T-cells clones of dendritic cells loaded with MAGE-A3-expressing cell lysates. We found that formation of MAGE-A3(111-125) depended on both leupeptin-sensitive and pepstatin-sensitive proteases. In contrast, we found that MAGE-A3(161-175), which was never recognized ex vivo, was formed by leupeptin but destroyed by pepstatin-sensitive proteases. Collectively, our results show that (a) anti-MAGE-A3 CD4(+) T-cell immunity develops in vivo in neoplastic patients and is focused toward immunodominant epitopes, (b) the response in advanced disease is skewed toward a Th2 type, and (c) endosomal/lysosomal proteases in dendritic cells influence the repertoire of the epitopes recognized.

MAGE-A3(161-175) contains an HLA-DRbeta4 restricted natural epitope poorly formed through indirect presentation by dendritic cells

We report here that HLA-DRbeta4*01 restricted MAGE-A3(161-175 )specific CD4(+) T cells from a healthy donor recognize a naturally processed epitope formed through the exogenous but not the endogenous pathway. However, the intensity of recognition of the native epitope by MAGE-A3(161-175 )specific CD4(+) T cells strongly depends on the antigen presenting cells and the amount of protein available for processing. EBV-transformed lymphoblastoid cells (LCLs) and melanoma cells engineered to express MAGE-A3 in the endosomal/lysosomal compartment were strongly recognized while autologous dendritic cells loaded with lysate from MAGE-A3 expressing cells were, although significantly, poorly recognized. To prove that the amount of antigen available for processing was a key factor determining the different response LCLs were sorted by MAGE-A3 expression. The response intensity correlated with the amount of MAGE-A3 expressed by the cells. Collectively, these results suggest that different antigen presenting cells with different amount of antigen available for processing as well as protease activity are important factors in determining the epitope repertoire produced in vivo, and therefore reliable tools should be used when testing recognition of native epitopes by peptide specific CD4(+) T cells.

Searching for borrelial T cell epitopes associated with antibiotic-refractory Lyme arthritis

Antibiotic-refractory Lyme arthritis is believed to result from an infection-induced autoimmune response triggered by the spirochete Borrelia burgdorferi (Bb). Disease susceptibility is associated with the HLA alleles DRB1*0101, 0401, 0402, 0404, 0405 and DRB5*0101, and all these MHC molecules bind the Bb epitope OspA(163-175.) However, not all patients have a proliferative response to this epitope. To identify other possible Bb epitopes involved in this disease process, the algorithm TEPITOPE was used to scan 17 immunogenic Bb proteins for potential T cell epitopes with a refractory arthritis-associated MHC binding profile, and the Bb proteome was searched for peptides with sequence homology to OspA(165-173). Sixteen promising T epitopes were identified and their MHC binding profiles to 13 MHC molecules were verified using in vitro MHC/peptide binding assays. One peptide, BBK32(392-404), had a strong refractory arthritis-associated MHC binding profile, and another GK(297-306) shared sequence homology to OspA(165-173). However, patient cells did not proliferate in response to either peptide making it highly unlikely they were involved in a refractory course. A comparison of the in silico and in vitro results revealed that TEPITOPE correctly predicted 74% of the in vitro binding peptides, but it incorrectly predicted that 44% of the in vitrononbinding peptides would bind. For a particular MHC molecule, concordance between the in silico and in vitro results varied anywhere between 33% and 100%. Therefore, while additional Bb epitopes may be involved in the development of antibiotic-refractory Lyme arthritis, recognition of OspA(163-175) remains the only known Bb epitope associated with this disease course.

A HLA-DQ5 restricted Melan-A/MART-1 epitope presented by melanoma tumor cells to CD4+ T lymphocytes

Melan-A/MART1 is a melanocytic differentiation antigen expressed by tumor cells of the majority of melanoma patients and, as such, is considered as a good target for melanoma immunotherapy. Nonetheless, the number of class I and II restricted Melan-A epitopes identified so far remains limited. Here we describe a new Melan-A/MART-1 epitope recognized in the context of HLA-DQa1*0101 and HLA-DQb1*0501, -DQb1*0502 or -DQb1*0504 molecules by a CD4+ T cell clone. This clone was obtained by in vitro stimulation of PBMC from a healthy donor by the Melan-A51-73 peptide previously reported to contain a HLA-DR4 epitope. The Melan-A51-73 peptide, therefore contains both HLA-DR4 and HLA-DQ5 restricted epitope. We further show that Melan-A51-63 is the minimal peptide optimally recognized by the HLA-DQ5 restricted CD4+ clone. Importantly, this clone specifically recognizes and kills tumor cell lines expressing Melan-A and either HLA-DQb1*0501, -DQb1*0504 or -DQb1*0502 molecules. Moreover, we could detect CD4+ T cells secreting IFN-gamma in response to Melan-A51-63 and Melan-A51-73 peptides among tumor infiltrating and blood lymphocytes from HLA-DQ5+ patients. This suggests that spontaneous CD4+ T cell responses against this HLA-DQ5 epitope occur in vivo. Together these data significantly increase the fraction of melanoma patients susceptible to benefit from a Melan-A class II restricted vaccine approach.