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 × 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. Lethé, V. Corbière, I. Théate, N. van Baren, P.G. Coulie, and T. Boon. 2004. J. Exp. Med. 201:249–257)

C19orf48 encodes a minor histocompatibility antigen recognized by CD8+ cytotoxic T cells from renal cell carcinoma patients.

PURPOSE: Tumor regression has been observed in some patients with metastatic renal cell carcinoma (RCC) after nonmyeloablative allogeneic hematopoietic cell transplantation (HCT). Cellular and molecular characterization of antigens recognized by tumor-reactive T cells isolated from responding patients could potentially provide insight into the mechanisms of tumor regression. EXPERIMENTAL DESIGN: CD8+ CTL clones that recognized a novel RCC-associated minor histocompatibility (H) antigen presented by HLA-A*0201 were isolated from two patients with metastatic RCC who experienced tumor regression or stable disease following nonmyeloablative allogeneic HCT. These clones were used to screen a cDNA library and isolate the unique cDNA encoding the antigen. RESULTS: An alternative open reading frame in the C19orf48 gene located on chromosome 19q13 encodes the HLA-A*0201-restricted minor H antigen recognized by the RCC-reactive T cells. The differential T-cell recognition of donor- and recipient-derived target cells is attributable to a nonsynonymous single-nucleotide polymorphism within the nucleotide interval that encodes the antigenic peptide. Assays for gene expression and CTL recognition showed that the C19orf48-encoded peptide is widely expressed in renal tumors and solid tumors of other histologies. The antigenic peptide can be processed for CTL recognition via both TAP-dependent and TAP-independent pathways. CONCLUSIONS: Donor T-cell responses against the HLA-A*0201-restricted minor H antigen encoded by C19orf48 may contribute to RCC regression after MHC-matched allogeneic HCT

Subgroup II PAK-mediated phosphorylation regulates Ran activity during mitosis

Phosphorylation of the Ran GTPase on Serine-135 by PAK4 changes Ran’s association with its regulatory proteins and its ability to induce microtubule asters

Critically Ill Patients with Visceral Nocardia Infection, France and Belgium, 2004-2023.

peer reviewedWe studied 50 patients with invasive nocardiosis treated during 2004-2023 in intensive care centers in France and Belgium. Most (65%) died in the intensive care unit or in the year after admission. Nocardia infections should be included in the differential diagnoses for patients in the intensive care setting

Thrombocytopenia and platelet transfusions in ICU patients: an international inception cohort study (PLOT-ICU)

Purpose Thrombocytopenia (platelet count < 150 × 109/L) is common in intensive care unit (ICU) patients and is likely associated with worse outcomes. In this study we present international contemporary data on thrombocytopenia in ICU patients. Methods We conducted a prospective cohort study in adult ICU patients in 52 ICUs across 10 countries. We assessed frequencies of thrombocytopenia, use of platelet transfusions and clinical outcomes including mortality. We evaluated pre-selected potential risk factors for the development of thrombocytopenia during ICU stay and associations between thrombocytopenia at ICU admission and 90-day mortality using pre-specified logistic regression analyses. Results We analysed 1166 ICU patients; the median age was 63 years and 39.5% were female. Overall, 43.2% (95% confidence interval (CI) 40.4–46.1) had thrombocytopenia; 23.4% (20–26) had thrombocytopenia at ICU admission, and 19.8% (17.6–22.2) developed thrombocytopenia during their ICU stay. Non-AIDS-, non-cancer-related immune deficiency, liver failure, male sex, septic shock, and bleeding at ICU admission were associated with the development of thrombocytopenia during ICU stay. Among patients with thrombocytopenia, 22.6% received platelet transfusion(s), and 64.3% of in-ICU transfusions were prophylactic. Patients with thrombocytopenia had higher occurrences of bleeding and death, fewer days alive without the use of life-support, and fewer days alive and out of hospital. Thrombocytopenia at ICU admission was associated with 90-day mortality (adjusted odds ratio 1.7; 95% CI 1.19–2.42). Conclusion Thrombocytopenia occurred in 43% of critically ill patients and was associated with worse outcomes including increased mortality. Platelet transfusions were given to 23% of patients with thrombocytopenia and most were prophylactic.publishedVersio

[Antigenic peptides for peptide splicing in the proteosome].

These past years, we focused our researches on the identification of novel, potential peptide targets for cancer immunotherapy. Amongst the peptides we identified, two are composed of fragments originally distant in the parental protein and are produced by a novel mechanism termed peptide splicing. The peptide splicing reaction takes place in the proteasome and occurs by transpeptidation. Here, we describe the discovery of this new mechanism of production of antigenic peptides

Human Tumor Antigens and Cancer Immunotherapy

With the recent developments of adoptive T cell therapies and the use of new monoclonal antibodies against the immune checkpoints, immunotherapy is at a turning point. Key players for the success of these therapies are the cytolytic T lymphocytes, which are a subset of T cells able to recognize and kill tumor cells. Here, I review the nature of the antigenic peptides recognized by these T cells and the processes involved in their presentation. I discuss the importance of understanding how each antigenic peptide is processed in the context of immunotherapy and vaccine delivery

Peptides produits par épissage peptidique dans le proteasome

These past years, we focused our researches on the identification of novel, potential peptide targets for cancer immunotherapy. Amongst the peptides we identified, two are composed of fragments originally distant in the parental protein and are produced by a novel mechanism termed peptide splicing. The peptide splicing reaction takes place in the proteasome and occurs by transpeptidation. Here, we describe the discovery of this new mechanism of production of antigenic peptides

Antigenic peptides produced by peptide splicing in the proteasome

La lignée LG2-MEL est une lignée tumorale dérivée d’une métastase ganglionnaire du patient LG2 atteint de mélanome malin. Différents variants tumoraux ont été obtenus in vitro et utilisés pour stimuler des lymphocytes du sang du patient LG2. Ceci nous a permis d’obtenir différents clones lymphocytes T cytolytiques (CTL) qui reconnaissent spécifiquement les variants de la tumeur LG2. Le peptide reconnu par un de ces CTL a été précédemment identifié : il correspond à un nonapeptide présenté par le HLA-B*3503 et qui dérive de la tyrosinase, une protéine de différenciation des mélanocytes. Ce travail de doctorat nous a permis d’identifier trois nouveaux peptides antigéniques exprimés par le mélanome LG2 et reconnus par des CTL autologues. Parmi les nouveaux peptides identifiés, l’un est présenté par le HLA-B*4403 et dérive d’une mutation ponctuelle dans le gène S_OS-9. Un second peptide est encodé par la protéine de différenciation gp100PMEL17 et est présenté par le HLA-B*3503. Le troisième peptide, qui est présenté par le HLA-A*3201, dérive également de la protéine gp100PMEL17, mais, étonnamment, est composé de deux fragments non-contigus de la protéine. La production de ce peptide nécessite l’excision d’un fragment de 4 acides aminés, et l’épissage des produits libérés. Nous avons étudié en détail ce mécanisme d’épissage peptidique. Nos résultats indiquent que l’épissage peptidique se produit à l’intérieur du protéasome, qu’il est étroitement lié au processus de protéolyse, et qu’il implique la formation d’un intermédiaire acyl-enzyme. Un deuxième projet, réalisé en collaboration avec le Dr. Warren du Fred Hutchinson Research Center à Seattle, a permis d’identifier un autre peptide produit par épissage peptidique, et qui correspond à un antigène mineur d’histocomptabilité présenté par le HLA-A-0301, et dérivant d’un polymorphisme mononucléotidique (SNP) au sein du gène SP110. le peptide antigénique identifié est composé de deux fragments non-contigus de la protéine SP110 qui sont assemblés en orientation inverse par rapport à la séquence génétique. Comme dans le cas du peptide dérivé de gp100, nos résultats suggèrent que ce phénomène de réarrangement peptidique se produit dans la protéasome par un mécanisme similaireMelanoma line LG2-MEL was derived from a lymph node metastasis of patient LG2. Various tumor clones were obtained in vitro, which were used to stimulate blood lymphocytes of patient LG2. Several cytolytic T lymphocyte clones (CTL) recognizing specifically LG2-MEL variants have been isolated. The peptide recognized by one of these CTL has been previously identified: it corresponds to a nonapeptide restricted by HLA-B*3503 and which is derived from melanocyte differentiation protein tyrosinase. During this thesis work, we have identified three other antigenic peptides expressed on LG2-MEL and recognized by autologous CTL. One of these peptides is presented by HLA-B*4403 and is derived from a point mutation in ubiquitously expressed gene OS-9. A second peptide is restricted by HLA-B*3503, and is produced from differentiation protein gp100PMEL17. The third peptide, which is presented by HLA-A*3201 and derived from gp100PMEL17, proved very interesting as it is composed of two non-contiguous fragments of the protein. The production of this peptide requires the excision of a 4-amino acid fragment and the splicing of the products. We have studied in more detail the mechanism of this peptide splicing, which had not been described before. Our results indicate that the splicing process occurs in the proteasome, is tightly coupled to the proteolytic process, and results from a transpeptidation reaction involving an acyl-enzyme intermediate. In the frame of a collaboration with Dr.Warren in Fred Hutchinson Research Center in Seattle, we have identified another spliced peptide, which is a minor histocompatibility antigen presented by HLA-A*0301 and derived from a small nuclear polymorphism (SNP) in gene SP110. The antigenic peptide is also composed of two non-contiguous fragments of the SP110 protein, but these fragments are spliced together in the reverse orientation, leading to the disruption of the linear correspondence between the peptide and the encoding genetic segment. As for the gp100 epitope, our results suggest that this rearrangement occurs in the proteasome by a similar mechanism.Thèse de doctorat en sciences biomédicales (SBIM 3)--UCL, 200

Processing and presentation of antigenic peptides recognized by cytolytic T lymphocytes on tumors

Processing and presentation of antigenic peptides recognized by cytolytic T lymphocytes on tumor