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Thierry Boon

Publications and source records attributed to Thierry Boon.

At least 19 recordsLinked to original sources
PubMed2006

A new tumor-specific antigen encoded by MAGE-C2 and presented to cytolytic T lymphocytes by HLA-B44.

A panel of cytolytic T lymphocyte (CTL) clones was isolated from metastases and blood samples of a melanoma patient vaccinated with MAGE-3.A1-pulsed autologous dendritic cells. We report here the identification of a new antigen encoded by the MAGE-C2 cancer-germline gene. This antigen is recognized by some of these CTL on HLA-B*4403. The sequence of the peptide is SESIKKKVL. It is processed in various melanoma cell lines expressing MAGE-C2 and HLA-B*4403. Because of the expression pattern of gene MAGE-C2, this new antigen is strictly tumor-specific and could therefore be used for peptide-based antitumoral vaccination.

Amino Acid Sequence↗
PubMed2006

CD45RA on human CD8 T cells is sensitive to the time elapsed since the last antigenic stimulation.

The expression of CD45RA on CCR7- human CD8+ memory T cells is widely considered to be a marker of terminal differentiation. We studied the time course of CD45RA and CCR7 expression on human antitumoral cytotoxic T lymphocyte (CTL) clones and blood CD8+ T cells after antigenic stimulation. Our results indicate that CD45RA+ CCR7- CD8+ T cells are resting memory cells that, upon antigenic stimulation and during the next 10 days, proliferate, lose CD45RA, and transiently acquire CCR7. In the absence of further antigenic stimulation, they progressively re-express CD45RA and become CD45RA+ CCR7-. We conclude that the expression of CD45RA on these cells is indicative of the time elapsed since the last antigenic stimulation rather than the incapacity to proliferate or particularly high lytic potential. This concept leads to a reinterpretation of the significance of the presence of CD45RA+ CD8+ memory cells in patients affected by viral infections or by cancer.

Antigens, CD↗
PubMed2006

Lack of tumor recognition by cytolytic T lymphocyte clones recognizing peptide 195-203 encoded by gene MAGE-A3 and presented by HLA-A24 molecules.

Gene MAGE-A3 encodes tumor-specific antigenic peptides recognized by T cells on many tumors. MAGE-A3 peptides presented by HLA class I molecules have been identified using CD8 lymphocytes stimulated with cells that either expressed gene MAGE-A3 or were pulsed with candidate peptides. One antigen identified with the latter method is peptide MAGE-A3(195-203) IMPKAGLLI, presented by HLA-A24 molecules. It has been used to vaccinate advanced cancer patients. Here, we have used HLA/peptide tetramers to detect T cells recognizing this peptide. Their frequency was estimated to be 2 x 10(-8) of the blood CD8 cells in non-cancerous HLA-A24(+) individuals, which is tenfold lower than the reported frequencies of T cells against other MAGE peptides. In the blood of a patient vaccinated with MAGE-A3, the estimated frequency was 5 x 10(-7). Anti-MAGE-3.A24 cytolytic T cell clones were derived, that lysed peptide-pulsed cells with half-maximal effect at the low concentration of 500 pM. However, these CTL did not recognize a panel of HLA-A24(+) tumor cells that expressed MAGE-A3 at levels similar to those found in HLA-A1(+) tumor cells recognized by anti-MAGE-3.A1 CTLs. Furthermore, 293-EBNA cells transfected with MAGE-A3 and HLA-A24 constructs were hardly recognized by the anti-MAGE-3.A24 CTL clones. These results suggest that peptide MAGE-A3(195-203) is poorly processed and is not an appropriate target for cancer immunotherapy.

Antigen Presentation↗
PubMed2006

A point mutation in the NFYC gene generates an antigenic peptide recognized by autologous cytolytic T lymphocytes on a human squamous cell lung carcinoma.

We have identified an antigen recognized by cytolytic T lymphocytes (CTL) on the autologous tumor cells of a nonsmall cell lung cancer patient. The antigenic peptide, presented by HLA-B*5201 molecules, was encoded by a mutated sequence in the gene coding for the C subunit of transcription factor NF-Y. The mutation was present in the tumor sample from which the cell line was derived, and appeared to be unique to the tumor of this patient. In a lymph node draining the tumor, precursors of CTL recognizing the autologous tumor cells were detected at a frequency of about 1/30,000 of the CD8 cells, and 85% of them recognized the mutated NF-YC peptide, suggesting that the patient mounted a T cell response against this antigen. These results strengthened the notion that unique tumor-specific antigens are highly represented not only in melanoma but also in other types of tumors, like nonsmall cell lung cancer.

Antigens, Neoplasm↗
PubMed2006

Transient down-regulation of DNMT1 methyltransferase leads to activation and stable hypomethylation of MAGE-A1 in melanoma cells.

MAGE-A1 belongs to a group of germ line-specific genes that rely primarily on DNA methylation for repression in somatic tissues. In many types of tumors, the promoter of these genes becomes demethylated and transcription becomes activated. We showed previously that, although MZ2-MEL melanoma cells contain an active unmethylated MAGE-A1 gene, they lack the ability to induce demethylation of newly integrated MAGE-A1 transgenes that were methylated in vitro before transfection. In the same cells, unmethylated MAGE-A1 transgenes were protected against remethylation, and this appeared to depend on the level of transcriptional activity. We therefore proposed that hypomethylation of MAGE-A1 in tumors relies on a past demethylation event and on the presence of appropriate transcription factors that maintain the promoter unmethylated. Here, we tested this hypothesis further by examining whether induction of a transient demethylation phase in MZ2-MEL would suffice to convert a previously methylated MAGE-A1 transgene into a permanently hypomethylated and active one. For induction of the demethylation phase, we used antisense oligonucleotides targeting the three known human DNA methyltransferases. We found that down-regulation of DNMT1, but not of DNMT3A and DNMT3B, induces activation of the MAGE-A1 transgene, suggesting that DNMT1 has a predominant role for methylation maintenance in MZ2-MEL cells. By using a selectable MAGE-A1 transgene construct, we were able to isolate a cell population in which DNMT1 depletion had resulted in transgene activation. The promoter region of the transgene was almost completely unmethylated in these cells, and this active and unmethylated state was maintained for over 60 days after restoration of normal DNMT1 expression.

Antigens, Neoplasm↗
PubMed2006

Destructive cleavage of antigenic peptides either by the immunoproteasome or by the standard proteasome results in differential antigen presentation.

The immunoproteasome (IP) is usually viewed as favoring the production of antigenic peptides presented by MHC class I molecules, mainly because of its higher cleavage activity after hydrophobic residues, referred to as the chymotrypsin-like activity. However, some peptides have been found to be better produced by the standard proteasome. The mechanism of this differential processing has not been described. By studying the processing of three tumor antigenic peptides of clinical interest, we demonstrate that their differential processing mainly results from differences in the efficiency of internal cleavages by the two proteasome types. Peptide gp100(209-217) (ITDQVPSFV) and peptide tyrosinase369-377 (YMDGTMSQV) are destroyed by the IP, which cleaves after an internal hydrophobic residue. Conversely, peptide MAGE-C2(336-344) (ALKDVEERV) is destroyed by the standard proteasome by internal cleavage after an acidic residue, in line with its higher postacidic activity. These results indicate that the IP may destroy some antigenic peptides due to its higher chymotrypsin-like activity, rather than favor their production. They also suggest that the sets of peptides produced by the two proteasome types differ more than expected. Considering that mature dendritic cells mainly contain IPs, our results have implications for the design of immunotherapy strategies.

Amino Acid Sequence↗
PubMed2006

Human T cell responses against melanoma.

Many antigens recognized by autologous T lymphocytes have been identified on human melanoma. Melanoma patients usually mount a spontaneous T cell response against their tumor. But at some point, the responder T cells become ineffective, probably because of a local immunosuppressive process occurring at the tumor sites. Therapeutic vaccination of metastatic melanoma patients with these antigens is followed by tumor regressions only in a small minority of the patients. The T cell responses to the vaccines show correlation with the tumor regressions. The local immunosuppression may be the cause of the lack of vaccination effectiveness that is observed in most patients. In patients who do respond to the vaccine, the antivaccine T cells probably succeed in reversing focally this immunosuppression and trigger a broad activation of other antitumor T cells, which proceed to destroy the tumor.

Amino Acid Sequence↗
PubMed2005

Phase 1/2 study of subcutaneous and intradermal immunization with a recombinant MAGE-3 protein in patients with detectable metastatic melanoma.

The purpose of this phase 1/2 study was to evaluate toxicity, tumor evolution and immunologic response following administration of a fixed dose of a recombinant MAGE-3 protein by subcutaneous and intradermal routes in the absence of immunologic adjuvant. Thirty-two patients with detectable metastatic melanoma expressing gene MAGE-3 were included and 30 received at least one injection with a fixed dose of a ProtD-MAGE-3 fusion protein. The immunization schedule included 6 intradermal and subcutaneous injections at 3-week intervals. Afterward, patients without major tumor progression who required other treatments received additional vaccinations at increasing time intervals. The vaccine was generally well tolerated. Among the 26 patients who received at least 4 vaccinations, we observed 1 partial response and 4 mixed responses. For these 5 responding patients, time to progression varied from 3.5 to 51+ months. An anti-MAGE-3 CD4 T-lymphocyte response was detected in 1 out of the 5 responding patients. The majority of patients had no anti-MAGE-3 antibody response. The clinical and immunologic responses generated by the vaccine are rather limited. Nevertheless, given the potential antitumor efficacy and the very mild toxicity of vaccinations, further studies combining MAGE proteins and/or peptides with potent immunologic adjuvants are warranted, not only in metastatic melanoma, but also in the adjuvant setting.

Adult↗
PubMed2005

Analysis of a rare melanoma patient with a spontaneous CTL response to a MAGE-A3 peptide presented by HLA-A1.

We describe an HLA-A1 melanoma patient who has mounted a spontaneous cytolytic T cell (CTL) response against an antigenic peptide encoded by gene MAGE-A3 and presented by HLA-A1. The frequency of anti-MAGE-3.A1 CTLp was 5 x 10(-7) of the blood CD8 cells, with a dominant clonotype which was present in six out of seven independent anti-MAGE-3.A1 CTL clones. After vaccination with a recombinant poxvirus coding for the MAGE-3.A1 antigen, the blood frequency of anti-MAGE-3.A1 CTLp increased tenfold. Twenty-two independent CTL clones were derived. Surprisingly, only one of them corresponded to the dominant clonotype present before vaccination. Two new clonotypes were repeated 12 and 7 times, respectively. Our interpretation of these results is that the spontaneous anti-MAGE-3.A1 CTL response pre-existing to vaccination was polyclonal, and that the vaccine restimulated only some of these clones. To estimate the incidence of spontaneous anti-MAGE-3.A1 CTL responses in melanoma patients with a tumor expressing gene MAGE-A3, we measured the blood frequency of anti-MAGE-3.A1 T cells in 45 patients, and found only two clear responses.

Aged↗
PubMed2005

A new LAGE-1 peptide recognized by cytolytic T lymphocytes on HLA-A68 tumors.

Antigens encoded by genes of the LAGE family, including LAGE-1 and NY-ESO-1, are of interest for cancer immunotherapy because they are tumor-specific and shared by tumors of different histological types. Several clinical trials are in progress with NY-ESO-1 peptides, protein, recombinant poxviruses, and dendritic cells pulsed with peptides. In this study, CD8 T lymphocytes from an individual without cancer were stimulated with dendritic cells infected with a recombinant avian poxvirus encoding a complete LAGE-1 protein. A CTL clone was isolated that recognized a new LAGE-1 peptide, ELVRRILSR, which corresponds to position 103-111 of the protein sequence. It is presented by HLA-A6801 molecules. When tumor cells expressing LAGE-1 were transfected with HLA-A68, they were lysed by the CTL clone, indicating that the peptide is processed in tumor cells. These results indicate that the LAGE-1.A68 peptide can be used for antitumoral vaccination. We observed also that specific T cells could be detected in a blood sample with a high sensitivity by using an A68/LAGE-1 fluorescent multimer.

Amino Acid Sequence↗
PubMed2005

Determination of cellularly processed HLA-A2402-restricted novel CTL epitopes derived from two cancer germ line genes, MAGE-A4 and SAGE.

PURPOSE: For identification of CTL epitopes useful for cancer vaccines, it is crucial to determine whether cognate epitopes are presented on the cell surface of target cancer cells through natural processing of endogenous proteins. For this purpose, we tried to use the cellular machinery of both mice and human to define naturally processed CTL epitopes derived from two "cancer germ line" genes, MAGE-A4 and SAGE. EXPERIMENTAL DESIGN: We vaccinated newly produced HLA-A2402 transgenic mice with DNA plasmids encoding target antigens. Following screening of synthesized peptides by splenic CD8(+) T cells of vaccinated mice, we selected candidate epitopes bound to HLA-A2402. We then examined whether human CD8(+) T cells sensitized with autologous CD4(+) PHA blasts transduced by mRNA for the cognate antigens could react with these selected peptides in an HLA-A2402-restricted manner. RESULTS: After DNA vaccination, murine CD8(+) T cells recognizing MAGE-A4(143-151) or SAGE(715-723) in an HLA-A2402-restricted manner became detectable. Human CTLs specific for these two peptides were generated after sensitization of HLA-A2402-positive CD8(+) T cells with autologous CD4(+) PHA blasts transduced with respective mRNA. CTL clones were cytotoxic toward tumor cell lines expressing HLA-A2402 and cognate genes. Taken together, these CTL epitopes defined in HLA-A24 transgenic mice are also processed and expressed with HLA-A2402 in human cells. The presence of SAGE(715-723)-specific precursors was observed in HLA-A2402-positive healthy individuals. CONCLUSIONS: Two novel HLA-A2402-restricted CTL epitopes, MAGE-A4(143-151) and SAGE(715-723), were identified. Our approach assisted by cellular machinery of both mice and human could be widely applicable to identify naturally processed CTL epitopes.

Animals↗
PubMed2005

Tumoral and immunologic response after vaccination of melanoma patients with an ALVAC virus encoding MAGE antigens recognized by T cells.

PURPOSE: To evaluate the toxicity, antitumoral effectiveness, and immunogenicity of repeated vaccinations with ALVAC miniMAGE-1/3, a recombinant canarypox virus containing a minigene encoding antigenic peptides MAGE-3(168-176) and MAGE-1(161-169), which are presented by HLA-A1 and B35 on tumor cells and can be recognized by cytolytic T lymphocytes (CTLs). MATERIALS AND METHODS: The vaccination schedule comprised four sequential injections of the recombinant virus, followed by three booster vaccinations with the MAGE-3(168-176) and MAGE-1(161-169) peptides. The vaccines were administered, both intradermally and subcutaneously, at 3-week intervals. RESULTS: Forty patients with advanced cancer were treated, including 37 melanoma patients. The vaccines were generally well tolerated with moderate adverse events, consisting mainly of transient inflammatory reactions at the virus injection sites. Among the 30 melanoma patients assessable for tumor response, a partial response was observed in one patient, and disease stabilization in two others. The remaining patients had progressive disease. Among the patients with stable or progressive disease, five showed evidence of tumor regression. A CTL response against the MAGE-3 vaccine antigen was detected in three of four patients with tumor regression, and in only one of 11 patients without regression. CONCLUSION: Repeated vaccination with ALVAC miniMAGE-1/3 is associated with tumor regression and with a detectable CTL response in a minority of melanoma patients. There is a significant correlation between tumor regression and CTL response. The contribution of vaccine-induced CTL in the tumor regression process is discussed in view of the immunologic events that could be analyzed in detail in one patient.

Adult↗
PubMed2005

A MAGE-1 antigenic peptide recognized by human cytolytic T lymphocytes on HLA-A2 tumor cells.

"Cancer-germline" genes such as those of the MAGE family are expressed in many tumors and in male germline cells, but are silent in normal tissues. They encode shared tumor-specific antigens that have been used in therapeutic vaccination trials of cancer patients. It was previously demonstrated that MAGE-1 peptide KVLEYVIKV was presented by HLA-A 0201 molecules on the surface of a human breast carcinoma cell line, but no human specific CTL had been isolated so far. Here, we have used HLA-A2/MAGE-1 fluorescent multimers to isolate from blood cells three human CTL clones that recognized the MAGE-1 peptide. These clones killed efficiently HLA-A2 tumor cells expressing MAGE-1, whether or not they were treated with IFN-gamma, suggesting that the MAGE-1 antigen is processed efficiently by both the standard proteasome and the immunoproteasome. These results indicate that the MAGE-1.A2 peptide can be used for antitumoral vaccination.

Amino Acid Sequence↗
PubMed2005

Monitoring of anti-vaccine CD4 T cell frequencies in melanoma patients vaccinated with a MAGE-3 protein.

Quantitative evaluation of T cell responses of patients receiving antitumoral vaccination with a protein is difficult because of the large number of possible HLA-peptide combinations that could be targeted by the response. To evaluate the responses of patients vaccinated with protein MAGE-3, we have developed an approach that involves overnight stimulation of blood T cells with autologous dendritic cells loaded with the protein, sorting by flow cytometry of the T cells that produce IFN-gamma, cloning of these cells, and evaluation of the number of T cell clones that secrete IFN-gamma upon stimulation with the Ag. An important criterion is that T cell clones must recognize not only stimulator cells loaded with the protein, but also stimulator cells transduced with the MAGE-3 gene, so as to exclude the T cells that recognize contaminants generated by the protein production system. Using this approach it is possible to measure T cell frequencies as low as 10(-6). We analyzed the frequencies of anti-vaccine CD4 T cells in five metastatic melanoma patients who had been injected with a MAGE-3 protein without adjuvant and showed evidence of tumor regression. Anti-MAGE-3 CD4 T cells were detected in one of the five patients. The frequency of the anti-MAGE-3 CD4 T cells was estimated at 1/60,000 of the CD4 T cells in postvaccination blood samples, representing at least an 80-fold increase in the frequency found before immunization. The frequencies of one anti-MAGE-3 CD4 T cell clonotype were confirmed by PCR analysis on blood lymphocytes. The 13 anti-MAGE-3 clones, which corresponded to five different TCR clonotypes, recognized the same peptide presented by HLA-DR1.

Amino Acid Sequence↗
PubMed2005

Contrasting frequencies of antitumor and anti-vaccine T cells in metastases of a melanoma patient vaccinated with a MAGE tumor antigen.

Melanoma patients have high frequencies of T cells directed against antigens of their tumor. The frequency of these antitumor T cells in the blood is usually well above that of the anti-vaccine T cells observed after vaccination with tumor antigens. In a patient vaccinated with a MAGE-3 antigen presented by HLA-A1, we measured the frequencies of anti-vaccine and antitumor T cells in several metastases to evaluate their respective potential contribution to tumor rejection. The frequency of anti-MAGE-3.A1 T cells was 1.5 x 10(-5) of CD8 T cells in an invaded lymph node, sixfold higher than in the blood. An antitumor cytotoxic T lymphocyte (CTL) recognizing a MAGE-C2 antigen showed a much higher enrichment with a frequency of approximately 10%, 1,000 times higher than its blood frequency. Several other antitumor T clonotypes had frequencies >1%. Similar findings were made on a regressing cutaneous metastasis. Thus, antitumor T cells were approximately 10,000 times more frequent than anti-vaccine T cells inside metastases, representing the majority of T cells present there. This suggests that the anti-vaccine CTLs are not the effectors that kill the bulk of the tumor cells, but that their interaction with the tumor generates conditions enabling the stimulation of large numbers of antitumor CTLs that proceed to destroy the tumor cells. Naive T cells appear to be stimulated in the course of this process as new antitumor clonotypes arise after vaccination.

Antigens, Neoplasm↗
PubMed2005

High frequency of antitumor T cells in the blood of melanoma patients before and after vaccination with tumor antigens.

After vaccination of melanoma patients with MAGE antigens, we observed that even in the few patients showing tumor regression, the frequency of anti-vaccine T cells in the blood was often either undetectable or <10(-5) of CD8 T cells. This frequency being arguably too low for these cells to be sole effectors of rejection, we reexamined the contribution of T cells recognizing other tumor antigens. The presence of such antitumor T cells in melanoma patients has been widely reported. To begin assessing their contribution to vaccine-induced rejection, we evaluated their blood frequency in five vaccinated patients. The antitumor cytotoxic T lymphocyte (CTL) precursors ranged from 10(-4) to 3 x 10(-3), which is 10-10,000 times higher than the anti-vaccine CTL in the same patient. High frequencies were also observed before vaccination. In a patient showing nearly complete regression after vaccination with a MAGE-3 antigen, we observed a remarkably focused antitumoral response. A majority of CTL precursors (CTLp's) recognized antigens encoded by MAGE-C2, another cancer-germline gene. Others recognized gp100 antigens. CTLp's recognizing MAGE-C2 and gp100 antigens were already present before vaccination, but new clonotypes appeared afterwards. These results suggest that a spontaneous antitumor T cell response, which has become ineffective, can be reawakened by vaccination and contribute to tumor rejection. This notion is reinforced by the frequencies of anti-vaccine and antitumor CTLs observed inside metastases, as presented by Lurquin et al. (Lurquin, C., B. Lethe, V. Corbiere, I. Theate, N. van Baren, P.G. Coulie, and T. Boon. 2004. J. Exp. Med. 201:249-257).

Antigens, Neoplasm↗
PubMed2005

A polyclonal anti-vaccine CD4 T cell response detected with HLA-DP4 multimers in a melanoma patient vaccinated with MAGE-3.DP4-peptide-pulsed dendritic cells.

During the last few years, HLA class I tetramers have been successfully used to demonstrate anti-vaccine CD8 CTL proliferation in cancer patients vaccinated with tumor antigens. Frequencies of CTL as low as 10(-6) among CD8 cells were observed even in patients showing tumor regression. Little is known about the role of tumor-antigen-specific CD4 T cells in the context of these anti-vaccine responses. Therefore, we developed a very sensitive approach using fluorescent class-II-peptide multimers to detect antigen-specific CD4 T cells in vaccinated cancer patients. We produced HLA-DP4 multimers loaded with the MAGE-3(243-258) peptide and used them to stain ex vivo PBL from melanoma patients injected with dendritic cells pulsed with several class I and class II tumor antigenic peptides, including the MAGE-3(243-258) peptide. The multimer(+) CD4 T cells were sorted and amplified in clonal conditions; specificity was assessed by their ability to secrete IFN-gamma upon contact with the MAGE-3 antigen. We detected frequencies of about 1x10(-6) anti-MAGE-3.DP4 cells among CD4 cells. A detailed analysis of one patient showed an anti-MAGE-3.DP4 CD4 T cell amplification of at least 3000-fold upon immunization. TCR analysis of the clones from this patient demonstrated a polyclonal response against the MAGE-3 peptide.

Antibodies, Neoplasm↗