Real-World Insights on the Management of Immune-Mediated Thrombotic Thrombocytopenic Purpura (iTTP) With Caplacizumab

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Le mode de vaccination des patients avec un antigène tumoral influence la différenciation des lymphocytes T CD8 anti-vaccinaux

The identification in 1991 of antigens recognized on human tumor cells by cytolytic T lymphocytes (CTL) opened new prospects for cancer immunotherapy. Several small scale clinical trials of vaccination with MAGE antigens have been conducted in metastatic melanoma patients with measurable disease. Tumor regressions have been observed in 15-20% of the patients, and a third of these regressions corresponded to 'partial responses' or better. These clinical results are similar whatever the vaccine modality (peptide, protein, recombinant virus, or dendritic cells). Vaccination with peptide MAGE-A3(168-176) under different modalities induced low level anti-vaccine CTL responses in the blood, reached between 10-5 and 10-3 of the CD8+ T cells. These responses were detectable after in vitro restimulation in limiting dilution condition, followed by labeling the responder cells with the HLA-A1/MAGE-A3(168-176) tetramer. The anti-vaccine CTL responses were correlated with the tumor regressions, suggesting a causative link. It is however surprising that so few anti-vaccine CTL could by themselves eliminate one or several metastases, leading in some cases to complete remission. Several hypotheses could explain this paradox, and this work consisted in exploring two of them. The low level anti-vaccine CTL responses could be associated to other anti-vaccine CTL responses, possibly of high magnitude, but not detectable by our methodology. Indeed, labeling the microcultures with the HLA-A1/MAGE-A3(168-176) tetramer, we were not able to detect T lymphocytes recognizing peptide MAGE-A3(168-176) presented by other HLA molecules than HLA-A1. I used two approaches to reasonably exclude this possibility: a screening of the microcultures with a cytokine secretion assay instead of a tetramer, and an in vitro assessment of the binding of peptide MAGE-A3(168-176) to other recombinant class I HLA molecules. I obtained negative results, strengthening the hypothesis that the low level anti-MAGE-A3(168-176)/HLA-A1 CTL responses detected in some patients played a crucial role in the tumor regressions. Anti-vaccine CTL could have functional properties that could explain their anti-tumoral effect, even in low numbers. As the low blood frequencies of anti-vaccine T cells prevented robust ex vivo functional analyses, I analyzed a representative set of 15 anti-MAGE-A3(168-176)/HLA-A1 CTL clones derived from 8 melanoma patients who displayed tumor regression. Using gene expression profiling, I observed that the expression levels of about 20 genes distinguished the anti-MAGE-A3(168-176)/HLA-A1 CTL clones derived from patients vaccinated with peptide alone or with a recombinant poxvirus containing MAGE minigenes, and the anti-MAGE-A3(168-176)/HLA-A1 CTL clones derived from patients vaccinated with peptide-pulsed dendritic cells. These results indicated that the vaccination modality with a MAGE tumor-specific antigen influences the differentiation of anti-vaccine CTL. This might impact on their capacity to trigger tumor regression. In addition they suggest that it might be important to carry out the immunological monitoring of vaccinated cancer patients with methods that do not only evaluate quantitative aspects of the response, but that can also compare the functional properties of the detected anti-vaccine T lymphocytes.La découverte d’antigènes tumoraux, reconnus à la surface des cellules tumorales par des lymphocytes T cytolytiques, a ouvert en 1991 de nouvelles perspectives pour l’immunothérapie anti-cancéreuse. Plusieurs études cliniques de vaccination avec des antigènes codés par les gènes MAGE ont été conduites chez des patients atteints de mélanome. Des régressions tumorales ont été observées dans 15-20% des cas. Un tiers d’entre elles constituent des réponses cliniques au minimum partielles. Ces résultats cliniques sont similaires quelle que soit la modalité vaccinale (peptides, protéines, virus recombinants, cellules dendritiques). La vaccination avec le peptide MAGE-3(168-176), administré sous différentes formes, induit de faibles réponses CTL anti-MAGE-A3(168-176)/HLA-A1 qui atteignent des fréquences entre 10-5 et 10-3 des lymphocytes T CD8+ du sang. Ces réponses ne sont donc généralement détectables qu’après restimulation in vitro des CTL circulants en condition de dilution limite, suivie par l’analyse des microcultures avec le tétramère HLA-A1/MAGE-A3(168-176). Ces réponses CTL anti-vaccinales sont corrélées aux régressions tumorales. Nous en déduisons qu’elles ont probablement joué un rôle dans les réponses cliniques survenant après vaccination. Il est surprenant que des lymphocytes T cytolytiques aussi rares puissent déclencher un processus de régression tumorale, menant parfois à une rémission complète. Ce paradoxe apparent pourrait s’expliquer de plusieurs manières. Mon travail a consisté à évaluer deux d’entre elles. Ces réponses immunologiques de faible amplitude pourraient être fréquemment associées à d’autres réponses lymphocytaires T cytolytiques contre le vaccin, potentiellement de forte amplitude, mais qui ne soient pas identifiables par notre méthodologie. En effet, par le marquage des microcultures avec le tétramère HLA-A1/MAGE-A3(168-176), nous ne pouvons pas détecter des lymphocytes T qui reconnaîtraient le peptide vaccinal MAGE-A3(168-176) présenté par un autre HLA qu’HLA-A1. Afin d’exclure raisonnablement cette hypothèse, j’ai utilisé deux méthodes indépendantes : analyser les microcultures par un test de sécrétion de cytokine à la place du tétramère et tester directement la liaison du peptide MAGE-A3(168-176) à certains HLA recombinants de classe 1. Les résultats négatifs obtenus confortent l’hypothèse que les faibles réponses CTL anti-MAGE-A3(168-176)/HLA-A1 détectées chez certains patients ont joué un rôle crucial dans les régressions tumorales observées. Les lymphocytes T cytolytiques anti-vaccinaux pourraient exprimer des propriétés particulières qui expliqueraient leur rôle dans les régressions tumorales, m��me en faible nombre. Après avoir éliminé raisonnablement ma première hypothèse, j’ai cherché à mieux caractériser ces réponses lymphocytaires T identifiées. Leur faible amplitude m’a empêché de réaliser une étude fonctionnelle ex vivo. C’est pourquoi, j’ai réalisé mes expériences sur une batterie de 15 clones CTL anti-MAGEA3(168-176)/HLA-A1 dérivés de 8 patients qui ont présenté une régression tumorale suite à la vaccination. Le niveau d’expression d’environ 20 gènes fut fortement différent entre les clones CTL dérivés de patients vaccinés avec le peptide antigénique seul ou avec ALVACminiMAGE-1/3 et les clones CTL dérivés de patients vaccinés avec des cellules dendritiques incubées avec le peptide vaccinal. Ces résultats indiquent que la modalité de vaccination avec un antigène spécifique de tumeur influence la voie de différenciation des lymphocytes T CD8 anti-vaccinaux. Cela pourrait avoir un impact sur leur capacité à initier un rejet tumoral. De plus, cette observation suggère qu’une analyse immunologique uniquement quantitative telle que pratiquée en vaccinologie humorale est probablement insuffisante en vaccinologie anti-tumorale.(SBIM 3) -- UCL, 200

Human tumor-specific T lymphocytes: does function matter more than number?

In recent years, several clinical trials have involved the vaccination of cancer patients with tumor-specific antigens that are recognized by T lymphocytes. Anti-vaccine T-cell responses in these patients have been monitored on the assumption that their magnitude would correlate with clinical efficacy. Although analysis of these data show that such a correlation is emerging, detailed analyses of the few patients who benefit clinically from the vaccinations suggest that the function of the anti-vaccine T cells might be more important than their number. Recent studies show that in cancer patients numerous tumor-specific T cells appear to be quiescent in the presence of the tumor. Understanding how an efficient vaccine interferes with this coexistence is one of the current challenges of cancer immunotherapy

Retroperitoneal fibrosis and multiple myeloma: fortuitous association?

We report a 59-year-old man presenting with retroperitoneal fibrosis (RF) associated with IgG lambda multiple myeloma. Recent clinical and immunohistochemical findings suggest that RF might be a particular expression of plasma cell/lymphoid dyscrasia, and that this association is not merely fortuitous. We review the pathophysiological evidence supporting this hypothesis

Dominant TCR Valpha usage by virus and tumor- reactive T cells with wide affinity ranges for their specific antigens

International audienceWe have studied the TCR features and functional responses of three sets of human cytolytic T cell (CTL) clones, recognizing antigenic peptides presented by HLA-A2 and derived from the Epstein-Barr virus proteins BMLF1 and BRLF1 and from the melanoma protein Melan-A/MART-1. Within each set, a majority of clones used a recurrent V alpha region, even though they expressed highly diverse TCR beta chains and V(D)J junctional sequences. Functional assays and peptide/MHC multimer binding studies indicated that this restricted V alpha usage was not associated with the affinity/avidity of the CTL clones. The V alpha dominance, which may be a frequent feature of antigen-specific T cells, likely reflects a restricted geometry of TCR/peptide/MHC complexes, primarily determined by V alpha CDR

Functions of Anti-MAGE T-Cells Induced in Melanoma Patients under Different Vaccination Modalities.

Tumor regressions have been observed in a small proportion of melanoma patients vaccinated with a MAGE-A3 peptide presented by HLA-A1, administered as peptide, ALVAC canarypox virus containing a MAGE-A3 minigene, or peptide-pulsed dendritic cells (DC). There was a correlation between tumor regression and the detection of anti-MAGE-3.A1 CTL responses. These responses were monoclonal and often of a very low magnitude after vaccination with peptide or ALVAC, and usually polyclonal and of a higher magnitude after DC vaccination. These results suggested that, at least in some patients, surprisingly few anti-MAGE-3.A1 T-cells could initiate a tumor regression process. To understand the role of these T cells, we carried out a functional analysis of anti-MAGE-3.A1 CTL clones derived from vaccinated patients who displayed tumor regression. The functional avidities of these CTL clones, evaluated in lysis assays, were surprisingly low, suggesting that high avidity was not part of the putative capability of these CTL to trigger tumor rejection. Most anti-MAGE-3.A1 CTL clones obtained after DC vaccination, but not after peptide or ALVAC vaccination, produced interleukin 10. Transcript profiling confirmed these results and indicated that approximately 20 genes, including CD40L, prostaglandin D2 synthase, granzyme K, and granzyme H, were highly differentially expressed between the anti-MAGE-3.A1 CTL clones derived from patients vaccinated with either peptide-ALVAC or peptide-pulsed DC. These results indicate that the modality of vaccination with a tumor-specific antigen influences the differentiation pathway of the antivaccine CD8 T-cells, which may have an effect on their capacity to trigger a tumor rejection response. [Cancer Res 2008;68(10):3931-40]

Monoclonal Anti-MAGE-3 CTL Responses in Melanoma Patients Displaying Tumor Regression after Vaccination with a Recombinant Canarypox Virus

SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Cytolytic T-cell responses of cancer patients vaccinated with a MAGE antigen

'Cancer-germline' genes such as the MAGE gene family are expressed in many tumors and in male germline cells but not in normal tissues. They encode shared tumor-specific antigens, which have been used in therapeutic vaccination trials of metastatic melanoma patients. To establish whether there is a correlation between tumoral regressions and T-cell responses against the vaccine antigen, we evaluated the responses of patients vaccinated with a MAGE-3 antigenic peptide or a recombinant virus coding for the peptide. Blood lymphocytes were stimulated with antigenic peptide followed by detection with tetramer, T-cell cloning, and TCR analysis. In 4/9 regressor patients and in 1/14 progressors we found a low level, usually monoclonal cytolytic T lymphocyte response against the MAGE-3 peptide