Clonal Evolution of a High-Grade Pediatric Glioma With Distant Metastatic Spread

Objective

High-grade glioma (HGG) rarely spreads outside the CNS. To test the hypothesis that the lesions were metastases originating from an HGG, we sequenced the relapsing HGG and distant extraneural lesions.

Methods

We performed whole-exome sequencing of an HGG lesion, its local relapse, and distant lesions in bone and lymph nodes.

Results

Phylogenetic reconstruction and histopathologic analysis confirmed the common glioma origin of the secondary lesions. The mutational profile revealed an IDH1/2 wild-type HGG with an activating mutation in EGFR and biallelic focal loss of CDKN2A (9p21). In the metastatic samples and the local relapse, we found an activating PIK3CA mutation, further copy number gains in chromosome 7 (EGFR), and a putative pathogenic driver mutation in a canonical splice site of FLNA.

Conclusions

Our findings demonstrate tumor spread outside the CNS and identify potential genetic drivers of metastatic dissemination outside the CNS, which could be leveraged as therapeutic targets or potential biomarkers.

Publisher Correction: Actively personalized vaccination trial for newly diagnosed glioblastoma

The additional author support information was erroneously omitted from the Supplementary Information. This has been corrected online.

Actively personalized vaccination trial for newly diagnosed glioblastoma

Patients with glioblastoma currently do not sufficiently benefit from recent breakthroughs in cancer treatment that use checkpoint inhibitors1,2. For treatments using checkpoint inhibitors to be successful, a high mutational load and responses to neoepitopes are thought to be essential3. There is limited intratumoural infiltration of immune cells4 in glioblastoma and these tumours contain only 30-50 non-synonymous mutations5. Exploitation of the full repertoire of tumour antigens-that is, both unmutated antigens and neoepitopes-may offer more effective immunotherapies, especially for tumours with a low mutational load. Here, in the phase I trial GAPVAC-101 of the Glioma Actively Personalized Vaccine Consortium (GAPVAC), we integrated highly individualized vaccinations with both types of tumour antigens into standard care to optimally exploit the limited target space for patients with newly diagnosed glioblastoma. Fifteen patients with glioblastomas positive for human leukocyte antigen (HLA)-A*02:01 or HLA-A*24:02 were treated with a vaccine (APVAC1) derived from a premanufactured library of unmutated antigens followed by treatment with APVAC2, which preferentially targeted neoepitopes. Personalization was based on mutations and analyses of the transcriptomes and immunopeptidomes of the individual tumours. The GAPVAC approach was feasible and vaccines that had poly-ICLC (polyriboinosinic-polyribocytidylic acid-poly-L-lysine carboxymethylcellulose) and granulocyte-macrophage colony-stimulating factor as adjuvants displayed favourable safety and strong immunogenicity. Unmutated APVAC1 antigens elicited sustained responses of central memory CD8+ T cells. APVAC2 induced predominantly CD4+ T cell responses of T helper 1 type against predicted neoepitopes.

Human tissue engineering allows the identification of active miRNA regulators of glioblastoma aggressiveness

Glioblastoma multiforme (GBM) is among the most aggressive cancers associated with massive infiltration of peritumoral parenchyma by migrating tumor cells. The infiltrative nature of GBM cells, the intratumoral heterogeneity concomitant with redundant signaling pathways likely underlie the inability of conventional and targeted therapies to achieve long-term remissions. In this respect, microRNAs (miRNAs), which are endogenous small non-coding RNAs that play a role in cancer aggressiveness, emerge as possible relevant prognostic biomarkers or therapeutic targets for treatment of malignant gliomas. We previously described a tissue model of GBM developing into a stem cell-derived human Engineered Neural Tissue (ENT) that allows the study of tumor/host tissue interaction. Combined with high throughput sequencing analysis, we took advantage of this human and integrated tissue model to understand miRNAs regulation. Three miRNAs (miR-340, -494 and -1293) active on cell proliferation, adhesion to extracellular matrix and tumor cell invasion were identified in GBM cells developing within ENT, and also confirmed in GBM biopsies. The components of miRNAs regulatory network at the transcriptional and the protein level have been also revealed by whole transcriptome analysis and Tandem Mass Tag in transfected GBM cells. Notably, miR-340 has a clinical relevance and modulates the expression of miR-494 and -1293, emphasizing its biological significance. Altogether, these findings demonstrate that human tissue engineering modeling GBM development in neural host tissue is a suitable tool to identify active miRNAs. Collectively, our study identified miR-340 as a strong modulator of GBM aggressiveness which may constitute a therapeutic target for treatment of malignant gliomas.

Evaluation of anti-citrullinated filaggrin antibodies as hallmarks for the diagnosis of rheumatic diseases

BACKGROUND

Anti-filaggrin antibodies (AFA) are among the most specific antibodies for rheumatoid arthritis, so procedures for their detection should be included in early biological diagnoses. AFA can be detected by indirect immunofluorescence (anti-keratin antibodies, AKA) or by new enzyme immunoassays (EIA). Their comparative performance needs to be established.

OBJECTIVE

To compare these technical procedures to optimise the serological diagnosis of rheumatoid arthritis.

METHODS

Results obtained using AKA and EIA were compared in 271 sera from 140 patients with rheumatoid arthritis at various stages, 98 patients with other autoimmune diseases, and 33 healthy subjects. EIA were successively undertaken with citrullinated linear filaggrin peptide (home made EIA) or cyclic citrullinated peptide (CCP2, commercial kits). Rheumatoid factor (RF) was assessed by EIA in all patients.

RESULTS

Anti-CCP2 kits showed the best sensitivity and specificity (65% and 96%, respectively). Among the 140 patients with rheumatoid arthritis, those with very recent disease (less than six months' duration, n = 21) were studied as a separate group. In this group, the sensitivity of anti-CCP2 kits decreased to approximately 50%. Nevertheless this assay remained the most accurate when compared with AKA or home made EIA using linear filaggrin peptides. The combination of anti-CCP2 and RF only slightly increased the sensitivity of the diagnosis of very early rheumatoid arthritis.

CONCLUSIONS

Kits using citrullinated cyclic peptides (CCP2) were more suitable than either AKA or EIA using linear filaggrin peptides for the diagnosis of early rheumatoid disease.

SSX antigens as tumor vaccine targets in human sarcoma

The efficacy of current standard therapies for the treatment of sarcoma remains limited. With the aim of identifying target antigens relevant to the development of vaccine-based immunotherapy of sarcoma, we have addressed the relevance of tumor-specific antigens encoded by genes belonging to the SSX family as vaccine targets in sarcoma tumors. Expression of SSX-1 to -5 was analyzed in a collection of sarcoma tumors of diverse histological subtypes and in sarcoma cell lines. We found expression of at least one SSX-encoded antigen in 42% of sarcoma tumors, including 5 of 7 different histological subtypes, and in 50% of sarcoma cell lines. SSX-1 was the most frequently expressed family member, followed by SSX-4, -2 and -5. Expression of SSX-3 was detected in only one sample. Importantly, most SSX positive samples co-expressed more than one family member. In addition, assessment of CD8+ T cell recognition of HLA-A2+ SSX-2+ sarcoma cells showed that the latter were efficiently recognized and lysed by SSX-2-specific CTLs. The results of this study indicate that SSX antigens are relevant targets for the development of vaccine-based immunotherapy of sarcoma and encourage the start of vaccination trials using SSX-derived immunogens in sarcoma patients.

Therapeutic cancer vaccines based on molecularly defined human tumor antigens

The results of numerous phases I and II clinical trials testing the safety and immunogenicity of various cancer vaccine formulations based on cytolytic T lymphocytes (CTLs)-defined tumor antigens have been reported recently. Specific T cell responses can be detected in only a fraction of immunized patients. A smaller but significant fraction of these patients have objective tumor responses. Efficient therapeutic vaccination should aim at boosting naturally occurring anti-tumor responses and at sustaining a large contingent of tumor antigen-specific and fully functional effector T cells at tumor sites.

Combinatorial peptide library-based identification of peptide ligands for tumor-reactive cytolytic T lymphocytes of unknown specificity

A novel approach for the identification of tumor antigen-derived sequences recognized by CD8(+) cytolytic T lymphocytes (CTL) consists in using synthetic combinatorial peptide libraries. Here we have screened a library composed of 3.1 x 10(11) nonapeptides arranged in a positional scanning format, in a cytotoxicity assay, to search the antigen recognized by melanoma-reactive CTL of unknown specificity. The results of this analysis enabled the identification of several optimal peptide ligands, as most of the individual nonapeptides deduced from the primary screening were efficiently recognized by the CTL. The results of the library screening were also analyzed with a mathematical approach based on a model of independent and additive contribution of individual amino acids to antigen recognition. This biometrical data analysis enabled the retrieval, in public databases, of the native antigenic peptide SSX-2(41-49), whose sequence is highly homologous to the ones deduced from the library screening, among the ones with the highest stimulatory score. These results underline the high predictive value of positional scanning synthetic combinatorial peptide library analysis and encourage its use for the identification of CTL ligands.

Interferon beta in multiple sclerosis: relationship between sustained serum IgG levels and clinical outcome

We investigated the effects of interferon beta-1a (IFN beta-1a) on specific response towards two immunodominant MBP peptides and on global production of IgG. We evaluated 54 sera from multiple sclerosis (MS) patients at baseline and 1 year after treatment. We did not observe any modification of immune response to the MBP peptides but we noted a significant decrease in mean IgG concentrations in patients with progression of the disease but not in stable patients. These results suggest that IFN beta1a restores or maintains a beneficial immune response.

Vaccination with a Melan-A peptide selects an oligoclonal T cell population with increased functional avidity and tumor reactivity

Both the underlying molecular mechanisms and the kinetics of TCR repertoire selection following vaccination against tumor Ags in humans have remained largely unexplored. To gain insight into these questions, we performed a functional and structural longitudinal analysis of the TCR of circulating CD8(+) T cells specific for the HLA-A2-restricted immunodominant epitope from the melanocyte differentiation Ag Melan-A in a melanoma patient who developed a vigorous and sustained Ag-specific T cell response following vaccination with the corresponding synthetic peptide. We observed an increase in functional avidity of Ag recognition and in tumor reactivity in the postimmune Melan-A-specific populations as compared with the preimmune blood sample. Improved Ag recognition correlated with an increase in the t(1/2) of peptide/MHC interaction with the TCR as assessed by kinetic analysis of A2/Melan-A peptide multimer staining decay. Ex vivo analysis of the clonal composition of Melan-A-specific CD8(+) T cells at different time points during vaccination revealed that the response was the result of asynchronous expansion of several distinct T cell clones. Some of these T cell clones were also identified at a metastatic tumor site. Collectively, these data show that tumor peptide-driven immune stimulation leads to the selection of high-avidity T cell clones of increased tumor reactivity that independently evolve within oligoclonal populations.

Toward synthetic combinatorial peptide libraries in positional scanning format (PS-SCL)-based identification of CD8+ Tumor-reactive T-Cell Ligands: a comparative analysis of PS-SCL recognition by a single tumor-reactive CD8+ cytolytic T-lymphocyte clone

The use of synthetic combinatorial peptide libraries in positional scanning format (PS-SCL) has emerged recently as an alternative approach for the identification of peptides recognized by T lymphocytes. The choice of both the PS-SCL used for screening experiments and the method used for data analysis are crucial for implementing this approach. With this aim, we tested the recognition of different PS-SCL by a tyrosinase 368-376-specific CTL clone and analyzed the data obtained with a recently developed biometric data analysis based on a model of independent and additive contribution of individual amino acids to peptide antigen recognition. Mixtures defined with amino acids present at the corresponding positions in the native sequence were among the most active for all of the libraries. Somewhat surprisingly, a higher number of native amino acids were identifiable by using amidated COOH-terminal rather than free COOH-terminal PS-SCL. Also, our data clearly indicate that when using PS-SCL longer than optimal, frame shifts occur frequently and should be taken into account. Biometric analysis of the data obtained with the amidated COOH-terminal nonapeptide library allowed the identification of the native ligand as the sequence with the highest score in a public human protein database. However, the adequacy of the PS-SCL data for the identification for the peptide ligand varied depending on the PS-SCL used. Altogether these results provide insight into the potential of PS-SCL for the identification of CTL-defined tumor-derived antigenic sequences and may significantly implement our ability to interpret the results of these analyses.

Circulating Tumor-reactive CD8(+) T cells in melanoma patients contain a CD45RA(+)CCR7(-) effector subset exerting ex vivo tumor-specific cytolytic activity

To defend the host from malignancies, the immune system can spontaneously raise CD8(+) T-cell responses against tumor antigens. Investigating the functional state of tumor-reactive cytolytic T cells in cancer patients is a key step for understanding the role of these cells in tumor immunosurveillance and for evaluating the potential of immunotherapeutic approaches of vaccination against cancer. In this study we identified a subset of circulating tumor-reactive CD8(+) T lymphocytes, which specifically secreted IFN-gamma after exposition to autologous tumor cell lines in stage IV metastatic melanoma patients. Additional phenotypic characterization using multicolor flow cytometry revealed that a significant fraction of these cells were CD45RA(+)CCR7(-), a phenotype that has been proposed recently to characterize cytolytic effectors potentially able to home into inflamed tissues. In the case of an HLA-A2-expressing patient, the antigen specificity of this population was identified by using HLA-A2/peptide multimers incorporating a tyrosinase-derived peptide. Consistently with their phenotypic characteristics, A2/tyrosinase peptide multimer(+) CD8(+) T cells, isolated by cell sorting, were directly lytic ex vivo and able to specifically recognize tyrosinase-expressing tumor cells. Overall, these results provide the first evidence that a proportion of melanoma patients have circulating tumor-reactive T cells, which are lytic effectors cells.

Discrepancy between ELISPOT IFN-gamma secretion and binding of A2/peptide multimers to TCR reveals interclonal dissociation of CTL effector function from TCR-peptide/MHC complexes half-life

Activation of CD8(+) cytolytic T lymphocytes (CTLs) by antigen is triggered by the interaction of clonotypic alphabeta T cell receptors (TCRs) with antigenic peptides bound to MHC class I molecules (pMHC complexes). Fluorescent multimeric pMHC complexes have been shown to specifically stain antigen-specific CTLs by directly binding the TCR. In tumor-infiltrating lymphocytes from a melanoma patient we found a high frequency of tyrosinase(368-376) peptide-specific cells as detected by IFN-gamma ELISPOT, without detectable staining with the corresponding A2/peptide multimers. Surprisingly, these T cells were able to lyse tyrosinase(368-376) peptide-pulsed target cells as efficiently as other specific T cells that were stained by multimers. Analysis of the staining patterns under different conditions of incubation time and temperature revealed that these results were explained by major differences in TCR-multimeric ligand interaction kinetics among the clones. Whereas no direct quantitative correlation between antigenic peptide concentration required for CTL effector functions and equilibrium multimer binding was observed interclonally, the latter was profoundly affected by the kinetics of TCR-ligand interaction. More importantly, our data indicate that similar levels of T cell activation can be achieved by independent CD8(+) T cell clonotypes displaying different TCR/pMHC complex dissociation rates.

Heterogeneous T-cell response to MAGE-A10(254-262): high avidity-specific cytolytic T lymphocytes show superior antitumor activity

MAGE-encoded antigens, which are expressed by tumors of many histological types but not in normal tissues, are suitable candidates for vaccine-based immunotherapy of cancers. Thus far, however, T-cell responses to MAGE antigens have been detected only occasionally in cancer patients. In contrast, by using HLA/peptide fluorescent tetramers, we have observed recently that CD8(+) T cells specific for peptide MAGE-A10(254-262) can be detected frequently in peptide-stimulated peripheral blood mononuclear cells from HLA-A2-expressing melanoma patients and healthy donors. On the basis of these results, antitumoral vaccination trials using peptide MAGE-A10(254-262) have been implemented recently. In the present study, we have characterized MAGE-A10(254-262)-specific CD8(+) T cells in polyclonal cultures and at the clonal level. The results indicate that the repertoire of MAGE-A10(254-262)-specific CD8(+) T cells is diverse both in terms of clonal composition, efficiency of peptide recognition, and tumor-specific lytic activity. Importantly, only CD8(+) T cells able to recognize the antigenic peptide with high efficiency are able to lyse MAGE-A10-expressing tumor cells. Under defined experimental conditions, the tetramer staining intensity exhibited by MAGE-A10(254-262)-specific CD8(+) T cells correlates with efficiency of peptide recognition so that "high" and "low" avidity cells can be separated by FACS. Altogether, the data reported here provide evidence for functional diversity of MAGE-A10(254-262)-specific T cells and will be instrumental for the monitoring of peptide MAGE-A10(254-262)-based clinical trials.

IgG reactivity against citrullinated myelin basic protein in multiple sclerosis

An increased level of citrullinated myelin basic protein (MBP-C8) has been reported in the brains of multiple sclerosis (MS) patients. However, the involvement of the immune response to post-translational modified MBP in the pathophysiology of MS remains speculative. The aim of this study was to compare the levels of immunoglobulin G antibodies to several MBP epitopes, before and after citrullination, in the cerebrospinal fluid (CSF) and sera of MS patients using enzyme-linked immunosorbent assay (ELISA). We analyzed antibody reactivity against various MBP-peptides in the CSF and sera of 60 MS patients, and 30 patients with other neurological diseases (OND) as controls. The peptides tested were: MBP(75-98) (peptide 1), native (peptide 2) and citrullinated (peptide 3) MBP(108-126) (ARG(122)-->Cit(122)), and native (peptide 4) and citrullinated (peptide 5) MBP(151-170) (ARG(159, 170)-->Cit(159, 170)). All selected peptides could support an immune reactivity in CSF and sera of MS and OND patients. A higher reactivity against peptide 4 was found in the CSF of MS patients compared with OND patients (P<0.0001), but not against citrullinated peptides (peptides 3 and 5). However, we observed that the citrullination state of peptide 2 modified the patterns of immune reactivity more markedly in MS patients (P<0.0001) than in OND patients (P<0.02). Although some MBP epitopes could be a potential target in MS, our data did not demonstrate any difference of antibody response to MBP peptides in their citrullinated forms.

Combinatorial peptide libraries as an alternative approach to the identification of ligands for tumor-reactive cytolytic T lymphocytes

The recent identification of molecularly defined human tumor antigens recognized by autologous CTLs has opened new opportunities for the development of antigen-specific cancer vaccines. Despite extensive work, however, the number of CTL-defined tumor antigens that are suitable targets for generic vaccination of cancer patients is still limited, mostly because of the painstaking and lengthy nature of the procedures currently used for their identification. A novel approach is based on the combined use of combinatorial peptide libraries in positional scanning format (positional scanning synthetic combinatorial peptide libraries, PS-SCLs) and tumor-reactive CTL clones. To validate this approach, we herein analyzed in detail the recognition of PS-SCLs by Melan-A-specific CTL clones. Our results indicate that, at least for some clones, most of the amino acids composing the native antigenic peptide can be identified through the use of PS-SCLs. Interestingly, this analysis also allowed the identification of peptide analogues with increased antigenic activity as well as agonist peptides containing multiple amino-acid substitutions. In addition, biometrical analysis of the data generated by PS-SCL screening allowed the identification of the native ligand in a public database. Overall, these data demonstrate the successful use of PS-SCLs for the identification and optimization of tumor-associated CTL epitopes.

CD8+ T-cell response to NY-ESO-1: relative antigenicity and in vitro immunogenicity of natural and analogue sequences

We have shown previously that HLA-A*0201 melanoma patients can frequently develop a CTL response to the cancer testis antigen NY-ESO-1. In the present study, we have analyzed in detail the relative antigenicity and in vitro immunogenicity of natural and modified NY-ESO-1 peptide sequences. The results of this analysis revealed that, although suboptimal for binding to the HLA-A*0201 molecule, peptide NY-ESO-1 157-165 is, among natural sequences, very efficiently recognized by specific CTL clones derived from three melanoma patients. In contrast, peptides NY-ESO-1 157-167 and NY-ESO-1 155-163, which bind very strongly to HLA-A*0201, are recognized less efficiently. In agreement with previous data, substitution of peptide NY-ESO-1 157-165 COOH-terminal C with various other amino acids resulted in a significantly increased binding to HLA-A*0201 molecules as well as in an increased CTL recognition, although variable at the clonal level. Among natural peptides, NY-ESO-1 157-165 and NY-ESO-1 157-167 exhibited good in vitro immunogenicity, whereas peptide NY-ESO-1 155-163 was poorly immunogenic. The fine specificity of interaction between peptide NY-ESO-1 C165A, HLA-A*0201, and T-cell receptor was analyzed at the molecular level using a series of variant peptides containing single alanine substitutions. The findings reported here have significant implications for the formulation of NY-ESO-1-based vaccines as well as for the monitoring of either natural or vaccine-induced NY-ESO-1-specific CTL responses in cancer patients.

Expansion and functional maturation of human tumor antigen-specific CD8+ T cells after vaccination with antigenic peptide

Peptide-based vaccines are currently being tested for their ability to induce or augment tumor antigen (Ag)-specific CD8+ T-cell responses in cancer patients. Here we report that the frequency of circulating CD8+ T cells directed against the Melan-A/MART-1 Ag increased >20-fold in an HLA-A2 melanoma patient immunized repeatedly with the corresponding antigenic peptide, as assessed by staining with HLA-A2/peptide tetramers. Multiparameter flow cytometric analysis demonstrated that the increase in total Melan-A-specific cell number was accompanied by a marked increase in the proportion of the cells that expressed an activated/memory surface phenotype. As assessed by ELISPOT assays and intracellular staining, the absolute number of Melan-A-specific cells able to secrete IFN-gamma increased >50-fold upon vaccination. When tested directly after cell sorting on the basis of tetramer staining, Melan-A-specific cells were weakly cytolytic but became highly active after in vitro restimulation. Altogether, these results indicate that large numbers of functionally active tumor Ag-specific CD8+ T cells can be obtained and maintained at high levels after in vivo activation by repeated peptide-based vaccination.

Melanoma patients respond to a cytotoxic T lymphocyte-defined self-peptide with diverse and nonoverlapping T-cell receptor repertoires

HLA-A2+ melanoma patients develop naturally a strong CD8+ T cell response to a self-peptide derived from Melan-A. Here, we have used HLA-A2/peptide tetramers to isolate Melan-A-specific T cells from tumor-infiltrated lymph nodes of two HLA-A2+ melanoma patients and analyzed their TCR beta chain V segment and complementarity determining region 3 length and sequence. We found a broad diversity in Melan-A-specific immune T-cell receptor (TCR) repertoires in terms of both TCR beta chain variable gene segment usage and clonal composition. In addition, immune TCR repertoires selected in the patients were not overlapping. In contrast to previously characterized CD8+ T-cell responses to viral infections, this study provides evidence against usage of highly restricted TCR repertoire in the natural response to a self-differentiation tumor antigen.

Frequent cytolytic T-cell responses to peptide MAGE-A10(254-262) in melanoma

MAGE genes encode tumor-specific shared antigens that are among the most interesting candidates for cancer vaccines. Despite extensive studies, however, CD8+ T-cell responses to MAGE-derived epitopes have been detected only occasionally in cancer patients, even after vaccination. In contrast with these findings, we report here that HLA-A2 melanoma patients respond frequently to the recently identified peptide MAGE-A10(254-262). Indeed, as assessed by staining with fluorescent HLA-A2/peptide MAGE-A10(254-262) tetramers, CD8+ T cells directed against this peptide were readily detectable in a large proportion of HLA-A2+ melanoma patients. These results provide new insight into the immunogenicity of MAGE antigens and underline the potential usefulness of MAGE-A10 peptide-based cancer vaccines.

Efficient simultaneous presentation of NY-ESO-1/LAGE-1 primary and nonprimary open reading frame-derived CTL epitopes in melanoma

Recent studies have shown that CTL epitopes derived from tumor-associated Ags can be encoded by both primary and nonprimary open reading frames (ORF). In this study we have analyzed the HLA-A2-restricted CD8(+) T cell response to a recently identified CTL epitope derived from an alternative ORF product of gene LAGE-1 (named CAMEL), and the highly homologous gene NY-ESO-1 in melanoma patients. Using MHC/peptide tetramers we detected CAMEL(1-11)-specific CD8(+) T cells in peptide-stimulated PBMC as well as among tumor-infiltrated lymph node cells from several patients. Sorting and expansion of tetramer(+) CD8(+) T cells allowed the isolation of tetramer(bright) and tetramer(dull) populations that specifically recognized the peptide Ag with high and low avidity, respectively. Remarkably, only high avidity CAMEL-specific CTL were able to recognize Ag-expressing tumor cells. A large series of HLA-A2-positive melanoma cell lines was characterized for the expression of LAGE-1 and NY-ESO-1 mRNA and protein and tested for recognition by CAMEL-specific CTL as well as CTL that recognize a peptide (NY-ESO-1(157-165)) encoded by the primary ORF products of the LAGE-1 and NY-ESO-1 genes. This analysis revealed that tumor-associated CD8(+) T cell epitopes are simultaneously and efficiently generated from both primary and nonprimary ORF products of LAGE-1 and NY-ESO-1 genes and, importantly, that this occurs in the majority of melanoma tumors. These findings underscore the in vivo immunological relevance of CTL epitopes derived from nonprimary ORF products and support their use as candidate vaccines for inducing tumor specific cell-mediated immunity against cancer.

Naturally occurring human lymphocyte antigen-A2 restricted CD8+ T-cell response to the cancer testis antigen NY-ESO-1 in melanoma patients

Cancer testis (CT) antigens are particularly interesting candidates for cancer vaccines. However, T-cell reactivity to CT antigens has been detected only occasionally in cancer patients, even after vaccination. A new group of CT antigens has been recently identified using the SEREX technique based on immunoscreening of tumor cDNA expression libraries with autologous sera. We have used fluorescent HLA-A2/peptide tetramers containing an optimized antigenic peptide to directly identify HLA-A2-restricted CD8+ T cells specific for the SEREX-defined CT antigen NY-ESO-1 in melanoma patients. High frequencies of NY-ESO-1-specific CD8+ T cells were readily detected in peptide-stimulated peripheral blood mononuclear cells as well as in lymphocytes infiltrating melanoma lesions from patients with measurable antibody responses to NY-ESO-1. NY-ESO-1-specific CD8+ T cells were also detectable in peptide-stimulated peripheral blood mononuclear cells from some seronegative patients. Whereas the frequencies of NY-ESO-1-specific CD8+ T cells in circulating lymphocytes were usually below the limit of detection by tetramer staining, the presence of NY-ESO-1 CD8+ T cells displaying a memory phenotype was clearly detectable ex vivo in blood from a seropositive patient over an extended period of time. These results indicate that sustained CD8+ T-cell responses to CT antigens can naturally occur both locally and systemically in melanoma patients.

Tetramer-guided analysis of TCR beta-chain usage reveals a large repertoire of melan-A-specific CD8+ T cells in melanoma patients

The assessment of the TCR repertoire expressed by tumor-specific CD8+ T lymphocytes has been hampered to date by the difficulty of targeting the analysis to lymphocytes directed against a single epitope. In the present study we have used fluorescent A2/Melan-A tetramers in conjunction with anti-CD8 and anti-TCR beta-chain variable (BV) mAbs to analyze by flow cytometry the BV segment usage by Melan-A-specific CD8+ T cells in tumor-infiltrated lymph nodes (TILN) and tumor-infiltrating lymphocytes (TIL) from A2 melanoma patients. Analysis of TILN populations revealed small proportions of A2/Melan-A tetramer+ cells expressing many different BV together with over-representation of A2/Melan-A tetramer+ cells expressing certain BVs. The BV usage by A2/Melan-A tetramer+ lymphocytes in TIL was more restricted than that in TILN. Moreover, the predominant BV segments were quite distinct in populations derived from different patients. A2/Melan-A tetramer+ cells expressing the dominant BVs found in TILN could also be found in the corresponding peptide-stimulated autologous PBMC, although A2/Melan-A tetramer+ lymphocytes expressing additional BVs were also identified. Together, these results suggest that a large and diverse repertoire of Melan-A-specific T cells using different BV TCR segments is available in A2 melanoma patients.