AB0044 REDUCED PERIPHERAL BLOOD MYELOID CELLS IN PATIENTS WITH VEXAS SYNDROME

Background

Systemic inflammatory or dysimmune diseases (SIDDs) are encountered in up to a quarter of patients with myelodysplastic syndromes (MDS). Recently identified VEXAS (vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic) syndrome, associated with somatic mutations in UBA1, encompasses a range of severe inflammatory conditions along with hematologic abnormalities, including myelodysplasia. Only limited data are available on the pathophysiology of MDS-associated SIDDs, and especially about the role of different myeloid cell subsets.

Objectives

The aim of this study was to describe the phenotype of myeloid immune cells (dendritic cells and monocytes) in MDS patients with associated SIDDs, and to compare their distribution with MDS patients without SIDDs and controls.

Methods

Phenotype analysis by flow cytometry from PBMCs of 14 MDS patients with SIDDs, 23 MDS patients without SIDDs and 7 controls without MDS and SIDDs. Eight of the 14 MDS/SIDDs patients (57%) had a somatic UBA1 mutation.

Results

In this study analyzing peripheral blood myeloid immune cells in MDS patients with and without SIDDs, we observed a quantitative reduction of different DC and monocyte subsets in MDS/SIDDs patients, especially in patients with active SIDDs and above all in patients with newly described VEXAS syndrome.

Conclusion

Further functional studies are warranted to better understand the mechanisms and the consequences of the phenotypic modulations of immune myeloid cells in the pathophysiology of MDS-associated SIDDs, especially in VEXAS syndrome.

Disclosure of Interests

None declared

AB0161 CLONAL HEMATOPOIESIS IS INCREASED AND NOT RELATED TO AGING IN SYSTEMIC SCLEROSIS

Background:

Systemic sclerosis (SSc) is an autoimmune disease characterized by fibrosis, microangiopathy and immune dysfunctions including dysregulation of proinflammatory cytokines. Clonal hematopoiesis of indeterminate potential (CHIP) is defined by the acquisition of somatic mutations in hematopoietic stem cells leading to detectable clones in the blood. Recent data have shown a higher risk of cardiovascular disease in patients with CHIP resulting from increased production of proinflammatory cytokines and accelerated atherosclerosis. Eventual links between CHIP and autoimmune diseases are undetermined.

Objectives:

The aim of our study was to evaluate the prevalence of CHIP in SSc patients and its association with clinical phenotype.

Methods:

Forty-one genes frequently mutated in myeloid malignancies were sequenced in peripheral blood mononuclear cells from 90 SSc patients and from 44 healthy donors.

Results:

A total of 15 somatic variants was detected in 13/90 SSc patients (14%) and 4 somatic variants in 4/44 (9%) HD (p=0.58). The prevalence of CHIP was significantly higher in younger SSc patients than in HD: 25% (6/24) vs 4% (1/26) (p=0.045) under 50 years and 17% (7/42) vs 3% (1/38) (p=0.065) under 60 years. The prevalence of CHIP in patients over 70 years was similar in SSc patients and healthy donors

For SSc patients the most common mutations occurred inDNMT3A(7 variants). Other variants involvedATM,SF3B1, SETBP1, TET2,TP53,NF1orCBL. The distribution of gene mutations was overall comparable in SSc patients and in previously described CHIP series (3)

In most SSc patients, we identified a single CHIP mutation. Several mutations were detected in two SSc patients:SETBP1andNF1in one and,TET2andATMin the other Clonal mutations included missense (n=10), nonsense (n=3), frameshift (n=1) and a single splice site mutation. In all HD we detected a single CHIP mutation which occurred inDNMT3A, TP53 and CSF3R

Variant allele frequencies (VAF) of CHIP mutations ranged from 2 to 18.6% and did not differ between genes (DNMT3Aor others). Mean age was the same in patients withDNMT3Amutations or with other mutations. However, C>T transversions, that have been associated with ageing were more frequent inDNMT3Avariants than in other genes, suggesting distinct mechanisms for mutation acquisition or clonal selection No major differences in clinical and laboratory data were observed between SSc patients with or without CHIP. SSc subtypes, disease duration, different organ involvements and the prevalence of ischemic events were not associated with the presence of CHIP, except less frequent pyrosis in patients with CHIP than those without. SSc patients with CHIP had significantly more anti-RNA polymerase III antibodies than those without CHIP (p=0.045) At the time of analysis, 45 SSc patients had received a treatment for SSc which consisted in low-dose steroids, hydroxychloroquine, mycophenolate mofetil, cyclophosphamide or methotrexate. SSc patients with CHIP were significantly more exposed to cyclophosphamide (3/13 vs. 3/77) (p=0.04) (5, 6.5 and 11 gram respectively between 5 years to 8 years before the NGS sequencing analysis), but among these cyclophosphamide-exposed SSc the age was over 65 in 2/3 of them. When considering all immunosuppressive drugs (cyclophosphamide, methotrexate and mycophenolate mofetil) SSc patients with CHIP were not more exposed than those without CHIP (p=0.75) No patient developed any hematologic malignancy and no cytopenia during the median follow-up of 13 months (0-24 months). One SSc patients with CHIP developed a small lung cancer few months after NGS testing.

Conclusion:

Whether CHIP increases the risk to develop SSc or is a consequence of a SSc-derived modified bone marrow micro-environment remains to be explored.

Acknowledgments:

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Disclosure of Interests:

None declared

Donor interleukin-22 and host type I interferon signaling pathway participate in intestinal graft-versus-host disease via STAT1 activation and CXCL10

Acute graft-versus-host disease (aGVHD) remains a major complication following allogeneic hematopoietic cell transplantation, limiting the success of this therapy. We previously reported that interleukin-22 (IL-22) participates to aGVHD development, but the underlying mechanisms of its contribution remain poorly understood. In this study, we analyzed the mechanism of the pathological function of IL-22 in intestinal aGVHD. Ex-vivo colon culture experiments indicated that IL-22 was able to induce Th1-like inflammation via signal transducer and activator of transcription factor-1 (STAT1) and CXCL10 induction in the presence of type I interferon (IFN). To evaluate a potential synergy between IL-22 and type I IFN in aGVHD, we transplanted recipient mice, either wild-type (WT) or type I IFN receptor deficient (IFNAR(-/-)), with bone marrow cells and WT or IL-22 deficient (IL-22(-/-)) T cells. We observed a decreased GVHD severity in IFNAR(-/-) recipient of IL-22(-/-) T cells, which was associated with a lower level of STAT1 activation and reduced CXCL10 expression in the large intestine. Finally, immunohistochemistry staining of STAT1 performed on gastrointestinal biopsies of 20 transplanted patients showed exacerbated STAT1 activation in gastrointestinal tissues of patients with aGVHD as compared with those without aGVHD. Thus, interfering with both IL-22 and type I IFN signaling may provide a novel approach to limit aGVHD.

Translational opportunities for targeting the Th17 axis in acute graft-vs.-host disease

Allogeneic stem cell transplantation (allo-SCT) is a curative therapy for different life-threatening malignant and non-malignant hematologic disorders. Acute graft-vs.-host disease (aGVHD) and particularly gastrointestinal aGVHD remains a major source of morbidity and mortality following allo-SCT, which limits the use of this treatment in a broader spectrum of patients. Better understanding of aGVHD pathophysiology is indispensable to identify new therapeutic targets for aGVHD prevention and therapy. Growing amount of data suggest a role for T helper (Th)17 cells in aGVHD pathophysiology. In this review, we will discuss the current knowledge in this area in animal models and in humans. We will then describe new potential treatments for aGVHD along the Th17 axis.

ATG-induced accelerated immune senescence: clinical implications in renal transplant recipients

Persistent ATG-induced CD4(+) T cell lymphopenia is associated with serious clinical complications. We tested the hypothesis that ATG induces accelerated immune senescence in renal transplant recipients (RTR). Immune senescence biomarkers were analyzed at transplant and one-year later in 97 incident RTR -62 patients receiving ATG and 35 receiving anti-CD25 mAb (α-CD25). This consisted in: (i) thymic output; (ii) bone marrow renewal of CD34(+) hematopoietic progenitor cells (CD34(+) HPC) and lymphoid (l-HPC) and myeloid (m-HPC) progenitor ratio; (iii) T cell phenotype; and (iv) measurement of T cell relative telomere length (RTL) and telomerase activity (RTA). Clinical correlates were analyzed with a 3 year follow-up. Thymic output significantly decreased one-year posttransplant in ATG-treated patients. ATG was associated with a significant decrease in l-HPC/m-HPC ratio. Late stage differentiated CD57(+) /CD28(-) T cells increased in ATG-treated patients. One-year posttransplant T cell RTL and RTA were consequently lower in ATG-treated patients. ATG is associated with accelerated immune senescence. Increased frequency of late differentiated CD4(+) T cell frequency at transplantation tended to be predictive of a higher risk of subsequent opportunistic infections and of acute rejection only in ATG-treated patients but this needs confirmation. Considering pretransplant immune profile may help to select those patients who may benefit from ATG to prevent severe infections and acute rejection.

Recovery of Lymphocyte and Dendritic Cell Subsets Following Reduced Intensity Allogeneic Bone Marrow Transplantation

Approaches using reduced conditioning regimens have been developed to obtain minimal procedure-related toxicity. Such novel therapeutic options are being explored with good preliminary results concerning feasibility and engraftment. However, many aspects remain under-evaluated and few data are available about immune and dendritic cell (DC) reconstitution after these highly immunosuppressive regimens. We present here our data in 20 patients receiving allogeneic bone marrow transplantation (allo-BMT) using a reduced preparative regimen. We evaluated in the first 3 months following allo-BMT, several immunological parameters including DC subsets, and compared these to historical results obtained in a group of myeloablative allo-BMT patients. We found an early recovery of leukocytes, CD8+ and NK lymphocytes. We also found a trend towards an improved B cell recovery. These results are somewhat in contrast to the altered immune recovery observed in the myeloablative setting. In addition, we found a significant early circulating DC recovery. Circulating blood DCs were also found to be of full donor origin as assessed by FISH in sex-mismatched pairs. Nevertheless, naive CD4 + CD45RA + T cells were found to be profoundly reduced following such regimens.Collectively, these data further enhance the overall benefits of reduced intensity regimens and the need for a stringent biological monitoring for assessment of the potential advantages of reduced intensity allo-BMT in comparison with conventional allo-BMT.

IL-22 deficiency in donor T cells attenuates murine acute graft-versus-host disease mortality while sparing the graft-versus-leukemia effect

Acute graft-versus-host disease (aGVHD) remains a major complication following allogeneic hematopoietic cell transplantation (allo-HCT), limiting the success of this therapy. Many proinflammatory cytokines secreted following the conditioning regimen have been linked to aGVHD initiation. Interleukin-22 (IL-22) is a cytokine related to IL-10 for its structure and is secreted by T helper type 17 (TH17) cells and innate immune cells. Given the paradoxical role of IL-22 in inflammation with both protective or proinflammatory functions, we investigated whether IL-22 could have a role in aGVHD pathophysiology in a mouse allo-HCT model. In this study, we show that IL-22 deficiency in donor T cells can decrease the severity of aGVHD, while limiting systemic and local inflammation in aGVHD target organs. In addition, we found that Foxp3+ regulatory T cells (Treg cells) were increased in recipient mice that received IL-22-deficient T cells, suggesting that Treg were involved in the reduced severity of GVHD. Finally, we found that the graft-versus-leukemia (GVL) effect mediated by donor T cells was preserved in the absence of IL-22. Overall, these data suggest that targeting of IL-22 may represent a valid approach towards decreasing aGVHD severity after allo-HCT while preserving the GVL effect.

Plasmacytoid dendritic cells and Th17 immune response contribution in gastrointestinal acute graft-versus-host disease

The contribution of Th17 cells in acute graft-versus-host disease (aGVHD) has been demonstrated in aGVHD mouse models. However, their contribution in human gastrointestinal aGVHD remains unclear. We evaluated Th17 cells in a cohort of 23 patients at diagnosis of aGVHD. In this study, we have shown that the absolute number of Th17 cells using the CCR6 and CD161 markers were significantly higher in the intestinal mucosa of patients with aGVHD compared with intestinal mucosa of patients without aGVHD. Moreover, in keeping with the increase of CCR6+ and CD161+ T cells, RORγt the key transcription factor that orchestrates the differentiation of Th17 cells, was significantly increased in the intestinal mucosa of patients with aGVHD compared with intestinal mucosa of patients without aGVHD (P=0.01). Since plasmacytoid dendritic cells (PDCs) have been reported to drive the differentiation of the Th17 subset, we quantified PDCs in these patients. PDC CD123+ cells were increased in the intestinal mucosa of patients with aGVHD. Furthermore, the number of CD123+ PDCs paralleled the histological grade of aGVHD, providing evidence for a role of Th17-mediated responses and a potential new pathophysiological link between PDCs and Th17 in human aGVHD.

Impact of plasmacytoid dendritic cells on outcome after reduced-intensity conditioning allogeneic stem cell transplantation

The reconstitution of the plasmacytoid dendritic cells (PDCs) compartment might influence outcome after allogeneic stem cell transplantation (allo-SCT). Thus, we investigated the impact of blood PDCs measured at the third month after reduced-intensity conditioning (RIC) in 54 patients who received an HLA-identical sibling allo-SCT. The absence of grade II-IV acute graft-versus-host-disease (GVHD) was associated with an improved PDC count at 3 months after RIC-allo-SCT (P=0.003; OR=6.4; 95% CI, 1.9-22). The CD34+ stem cell dose and other lymphoid subsets infused with the allograft did not affect PDC recovery. Although PDC count could not predict death from progression or relapse, patients with a "high" PDC recovery profile had an improved overall survival (OS; P=0.03), in contrast to patients with a "low" PDC recovery profile who had an increased incidence of nonrelapse mortality (GVHD, infections) (P=0.03). The overall incidence of late infections (viral, fungal and bacterial) was significantly higher in the "low" PDC recovery group as compared to the "high" PDC recovery group (59 vs 19%; P=0.002). In a multivariate analysis, only a "high" PDC count was significantly predictive of a decreased risk of death (P=0.04; RR=0.34; 95% CI, 0.12-0.96). Monitoring of PDCs at 3 months after RIC-allo-SCT may be a useful indicator predictor of long-term outcome.

Cytomegalovirus-specific immune recovery following allogeneic HLA-identical sibling transplantation with reduced-intensity preparative regimen

Cytomegalovirus (CMV) represents a major cause of morbidity after allogeneic stem cell transplantation (allo-SCT). Using interferon-gamma-enzyme-linked immunospot (ELISPOT) assay and HLA-peptide tetramers, we analysed 54 patients who received a reduced-intensity conditioning regimen, including fludarabine, busulphan and antithymocyte globulin (ATG), with the aim of defining essential elements of protective immunity to CMV. The cumulative incidence of CMV positive antigenaemia was 37% occurring at a median of 43 days (range, 7-104) after allo-SCT. In univariate analysis, conditioning regimen (ATG dose) and graft characteristics (graft source and CD3+ T-cell dose) significantly influenced CMV-specific immune recovery. A significant correlation (P=0.000002) was found between CMV-specific T cells detected by IFN-gamma ELISPOT assay and pp65-specific CD8+ T-cell frequency quantified by tetramers. CMV-specific CD8+ T cells presented a phenotype of effector cells (perforin and 2B4 positive). In multivariate analysis, bone marrow (BM) as a graft source was the only variable associated with an increased risk of CMV positive antigenaemia (P=0.0001) in line with the ELISPOT assay showing a higher frequency of functional CMV-specific effectors within peripheral blood stem cell grafts as compared to BM. Thus, early monitoring of CMV-specific immune recovery using sensitive new tools might prove useful for patient management after allo-SCT.

Abundant expression of fibronectin is a major feature of leukemic dendritic cells differentiated from patients with acute myeloid leukemia

Dendritic cells (DCs) are the most potent antigen-presenting cells responsible for the initiation of primary immune responses, playing a key role in eliciting effective antitumor immune responses. We reported previously that leukemic blasts from selected patients with acute myeloid leukemia (AML) were able to differentiate in vitro into cells with DC features. In order to identify genes differentially expressed in leukemia-derived DCs (AML-DCs), a polymerase chain reaction (PCR)-based subtraction approach was applied using cDNA from AML-DCs and monocyte-derived DCs from healthy donors as competitors. In the 548 sequences analyzed, 80% corresponded to fibronectin (FN) gene fragments. Overexpression of FN in AML-DCs was demonstrated both by semiquantitative PCR analysis and by immunostaining. In addition, we could show that FN was secreted by AML-DCs. Indeed, FN overexpression was already detectable in AML blasts of M4 and M5 subtype, and was significantly induced during DC differentiation after culture. Although the molecular events leading to overexpression of FN and the in vivo relevance of this phenomenon remain to be resolved, leukemic DCs appear to have specific patterns of differentiation, warranting stringent biological and cellular monitoring for the development and testing of leukemic DC-based immunotherapeutic strategies.

Dendritic cells: interfaces with immunobiology and medicine. A report from the Keystone Symposia Meeting held in Keystone, 3-8 March 2003

Dendritic cells (DCs) are the most potent antigen-presenting cells in vitro and in vivo. They play a key role in the initiation of the immune response and are considered promising targets for immunotherapy. The recent DC Keystone Symposia, organized by Ralph M Steinman, Anne O'Garra and Jacques Banchereau, was held on 3-8 March 2003 in Keystone (CO, USA). This multidisciplinary meeting developed various areas related to the DC biology including: (i) DC and the control of immunity vs tolerance; (ii) DC maturation and manipulation for immunotherapy in vivo; and (iii) antigen capture by DC in situ and interactions with microbial pathogens. The aim of this report is to present some of the highlights developed during the meeting and debated among the DC community.

Identification of precursors of leukemic dendritic cells differentiated from patients with acute myeloid leukemia

Dendritic cells (DC) can facilitate immune responses that might help in the induction of effective antitumor T cell responses. We reported previously that leukemic blasts from selected patients with acute myeloid leukemia (AML) were able to differentiate in vitro into cells with mature DC features. However, despite the use of a wide variety of cytokine combinations, leukemic DC could not be obtained from all AML patients. In this study, we investigated in a wide range of AML patients (n = 30), the nature and functional characteristics of the blast compartment that can be induced to acquire DC features in vitro. Our results demonstrate that leukemic DC generated in the presence of GM-CSF, IL-4 and matured with CD40L, are composed of two major subsets: DC derived from CD14(+) leukemic cells and leukemic DC derived from in vivo expanded circulating blood myeloid DC (MDC). Leukemic DC of both subsets exhibited DC morphology, had a phenotype of mature DC, and could induce a potent proliferative response of naive CD4(+) T cells. Moreover, both subsets produced large amounts of IL-12p70 and leukemic CD14(+)-derived DC could induce a potent Th1 response. These results can be considered as a prerequisite before the design of vaccine immunotherapy protocols for the adjuvant treatment of AML patients.

Leukemic dendritic cells: potential for therapy and insights towards immune escape by leukemic blasts

Dendritic cells (DCs) are a system of potent antigen-presenting cells (APCs) specialized to initiate primary immune responses. DCs are considered important elements in the induction of specific antitumor cytotoxic effectors. At present, because of potential therapeutic implications, the critical role of DCs in cancer patients is under intensive investigation. Interactions between DCs and acute myeloid leukemia cells represent an attractive model for the study of DC physiology. Moreover, DCs can be a valuable therapeutic tool for the adjuvant treatment of leukemic patients. However, DC subsets in vivo may also be affected by leukemogenesis and may contribute to the escape of leukemia from immune control. The aim of this review is to shed further light on this paradoxical picture where the line between immune tolerance and immune defense is narrow.

Features of large granular lymphocytes (LGL) expansion following allogeneic stem cell transplantation: a long-term analysis

Large granular lymphocyte (LGL) proliferation typically follows a chronic course during which major features are cytopenia and immune abnormalities. Elevated numbers of LGL were reported in a few cases following allogeneic stem cell transplantation (allo-SCT). In this report, we present a retrospective analysis of LGL cases that occurred following allo-SCT in a cohort of 201 consecutive patients transplanted over a period of 7 years. Six cases were identified and LGL expansion occurred more frequently following a reduced fludarabine and anti-T lymphocyte globulin-based preparative regimen (4 cases/49), than after a conventional myeloablative regimen (2 cases/152). Expansion of LGL was seen between 3 and 15 months following allo-SCT. Hematopoiesis, with mild to severe cytopenia, was a favored target for LGL. Autoimmune manifestations including polyarthritis and hypergammaglobulinemia were also observed. LGL proliferation was observed in the context of chronic antigenic stimulation associated with recurrent viral infections especially CMV. Moreover, five out of these six high risk patients achieved a long-term complete remission concomitant or following LGL expansion. These data suggest that LGL might be a subset of effector lymphocytes which may participate to the graft-versus-tumor effect.

Circulating blood dendritic cells from myeloid leukemia patients display quantitative and cytogenetic abnormalities as well as functional impairment

Dendritic cells (DCs) are responsible for the initiation of immune responses. Two distinct subsets of blood DCs have been characterized thus far. Myeloid DCs (MDCs) and plasmacytoid monocytes (PDCs) were shown to be able to promote polarization of naive T cells. This study shows a dramatic quantitative imbalance in both circulating blood DC subsets in 37 patients with acute myeloid leukemias. Eleven patients (30%) displayed a normal quantitative profile (MDC mean, 0.37% +/- 0.21%; range, 0.01% to 0.78%; PDC mean, 0.21% +/- 0.24%; range, 0.04% to 0.62%), whereas 22 (59%) showed a tremendous expansion of MDCs (9 patients: mean, 16.76% +/- 14.03%; range, 1.36% to 41%), PDCs (4 patients: mean, 7.28% +/- 6.84%; range, 1% to 14%), or both subsets (9 patients: MDC mean, 10.86% +/- 12.36%; range, 1.02% to 37.1%; PDC mean, 4.25% +/- 3.78%; range, 1.14% to 13.04%). Finally, in 4 patients (11%), no DC subsets were detectable. Both MDC and PDC subsets exhibited the original leukemic chromosomal abnormality. Ex vivo, leukemic PDCs, but not leukemic MDCs, had impaired capacity for maturation and decreased allostimulatory activity. Also, leukemic PDCs were altered in their ability to secrete interferon-alpha. These data provide evidence that DC subsets in vivo may be affected by leukemogenesis and may contribute to leukemia escape from immune control.

Large granular lymphocytes (LGL) following non-myeloablative allogeneic bone marrow transplantation: a case report

We report here the first case of large granular lymphocytes (LGL) expansion following non-myeloablative allo-BMT for chronic myeloid leukemia. We characterized the morphologic, phenotypic and functional features of the LGL subset amplified in vivo 14 months after allo-BMT. Our results indicate that LGL can mediate in vitro a cytolytic activity on tumor cells. In vivo, the timing of the LGL expansion was associated with a sustained complete molecular remission. These observations suggest that LGL are a subset with the properties of effector lymphocytes which may contribute to the graft-versus-tumor effect.

Human acute myeloid leukemia CD34+/CD38- progenitor cells have decreased sensitivity to chemotherapy and Fas-induced apoptosis, reduced immunogenicity, and impaired dendritic cell transformation capacities

The destruction of cells capable of initiating and maintaining leukemia challenges the treatment of human acute myeloid leukemia. Recently, CD34+/CD38- leukemia progenitors have been defined as new leukemia-initiating cells less mature than colony-forming cells. Here we show that CD34+/CD38- leukemia precursors have reduced in vitro sensitivity to daunorubicin, a major drug used in leukemia treatment, in comparison with the CD34+/CD38+ counterpart, and increased expression of multidrug resistance genes (mrp/lrp). These precursors show lower expression of Fas/Fas-L and Fas-induced apoptosis than CD34+/CD38+ blasts. Moreover, the CD34+/CD38- leukemic subpopulation induces a weaker mixed leukocyte reaction of responding T-lymphocytes than the CD34+/CD38+ leukemic counterpart, either in a MHC-unmatched or MHC-matched settings. This weaker immunogenicity could be linked to lower expression on CD34+/CD38- leukemia precursors of major immune response molecules (MHC-DR, LFA-3, B7-1, or B7-2) than CD34+/CD38+ leukemic cells. Nonetheless, the susceptibility of the immature CD38- precursors to cytotoxicity was not different from the sensitivity of the CD38+ counterpart. Finally, CD34+/CD38- leukemia precursors, in contrast with CD38+ precursors, failed, under appropriate conditions, to differentiate into dendritic cells, a central step for antigen recognition. This is to our knowledge the first demonstration that the very immature phenotype of CD34+/CD38- leukemic progenitors confers both chemotherapy resistance and decreased capacities to induce an immune response. Because the susceptibility of the immature leukemia cells as cytotoxic targets is maintained, our data underline the importance of improving the initial steps of leukemia recognition, more particularly by defining optimal conditions of dendritic cell transformation of the very immature hematopoietic precursors.

A new antigen recognized by cytolytic T lymphocytes on a human kidney tumor results from reverse strand transcription

By stimulating blood lymphocytes from a renal cell carcinoma patient in vitro with the autologous tumor cells, we obtained cytolytic T lymphocyte (CTL) clones that killed several autologous and allogeneic histocompatibility leukocyte antigen (HLA)-B7 renal carcinoma cell lines. We identified the target antigen of these CTLs by screening COS cells transfected with the HLA-B7 cDNA and with a cDNA library prepared with RNA from the tumor cells. The antigenic peptide recognized by the CTLs has the sequence LPRWPPPQL and is encoded by a new gene, which we named RU2. This gene is transcribed in both directions. The antigenic peptide is not encoded by the sense transcript, RU2S, which is expressed ubiquitously. It is encoded by an antisense transcript, RU2AS, which starts from a cryptic promoter located on the reverse strand of the first intron and ends up on the reverse strand of the RU2S promoter, which contains a polyadenylation signal. This mechanism of antigen expression is unprecedented and further illustrates the notion that many peptides recognized by T cells cannot be predicted from the primary structure of the major product of the encoding gene. Antisense transcript RU2AS is expressed in a high proportion of tumors of various histological types. It is absent in most normal tissues, but is expressed in testis and kidney, and, at lower levels, in urinary bladder and liver. Short-term cultures of normal epithelial cells from the renal proximal tubule expressed significant levels of RU2AS message and were recognized by the CTLs. Therefore, this antigen is not tumor specific, but corresponds to a self-antigen with restricted tissue distribution.

Human acute myeloblastic leukemia cells differentiate in vitro into mature dendritic cells and induce the differentiation of cytotoxic T cells against autologous leukemias

An immune response is involved in the control of leukemias as demonstrated by allogeneic bone marrow transplantation, by the eradication of residual leukemic cells by cytotoxic T cells and finally by the identification of tumor antigens which are recognized by effector T cells. Dendritic cells (DC) are professional antigen-presenting cells (APC) able to present antigens in the context of co-stimulatory signals necessary for T cell activation. Although tumor cells may express tumor antigens, they are usually unable to elicit an immune response since they are devoid of co-stimulatory capacities. To overcome this problem, engineering tumors to provide APC function could potentially result in polyvalent immunization to multiple tumor antigens. We have tested the differentiation of AML-5 (monoblastic, promonocytic and monocytic) leukemia cells and demonstrated that eight out of the ten fresh human acute myeloid leukemia populations tested can differentiate in vitro into bona fide APC. Leukemic cells acquire in vitro DC morphology, mature DC markers such as CD83, the up-regulation of MHC and co-stimulatory molecules and the ability to produce IL-12 upon maturation, while retaining their characteristic caryotypic abnormalities. However, we could not obtain an immature DC phenotype. They also acquire the ability to induce the differentiation of allogeneic naive cord blood CD4 and CD8 T cells as well as resting autologous cytotoxic T cells. These results demonstrate that some tumor cells acquire APC phenotype and functions and can thereby induce a potent autologous immune response that will be a valuable tool for detection of new tumor antigens and for in vivo immunization.

[Tumor antigens recognized by T-lymphocytes in human cancers. New advances and therapeutic perspectives]

The melanoma antigen coded by the MAGE-1 gene was the first tumor antigen described in human cancer. Genetic, biochemical, and "candidate peptide" strategies have been used to identify antigenic peptides presented to T-cells by class I major histocompatibility complex antigens. Antigens have now been characterized in a wide variety of tumor types. Five categories have been described based on expression profile. These antigens are detailed in this review. Among the tumor antigens produced as a result of intratumoral mutations, some are of special interest because of their potentially oncogenic effects. These new data can be expected to lead to the development of novel anticancer treatments based on specific immunotherapy. Pilot clinical studies are ongoing.

An antigen recognized by autologous CTLs on a human bladder carcinoma

By stimulating blood lymphocytes with autologous bladder carcinoma cells that had been transfected with B7-1, we obtained a panel of CTL clones which lyse specifically the bladder tumor cells in an MHC class I-restricted fashion. Based on inhibition with anti-HLA Abs and the recognition of allogeneic tumor cells, we could distribute our clones in three groups that recognized three distinct Ags. We characterized one of these Ags by screening a cDNA library prepared with the RNA from this bladder tumor line. This new tumor Ag is a peptide presented by HLA-B4403 molecules. It is produced by a point mutation in a gene that is recorded in databases under the name KIAA0205, is ubiquitously expressed, and whose function is unknown. We also found this mutation in the tumor sample that was originally resected from this patient, but the mutation was not found in the 100 or more independent tumors of various histologic types that were tested. This report is the first to describe the isolation of CTL clones directed against human bladder cancer and the molecular characterization of a bladder tumor Ag.

Renal-cell carcinoma-specific lysis by cytotoxic T-lymphocyte clones isolated from peripheral blood lymphocytes and tumor-infiltrating lymphocytes

Melanoma and renal-cell carcinoma (RCC) are generally considered to be relatively immunogenic tumor types in humans. In the case of melanoma, many major histocompatibility complex (MHC) class I-restricted tumor-specific cytotoxic T lymphocytes (CTL) have been isolated from either tumor-infiltrating lymphocytes (TIL) or autologous peripheral blood lymphocytes (PBL). In contrast, such CTL have only incidentally been described in the case of RCC. It has often been reported that TIL lines isolated from RCC display non-MHC-restricted and non-specific activity. Here, we report the isolation and characterization of tumor-specific CTL from PBL of one RCC patient and from TIL of another RCC patient. CTL clones 263/17 and 263/45, isolated from the PBL of patient LE-9211, were restricted by HLA-B7. CTL clone 5E, isolated from the TIL of patient LE-8915, was restricted by HLA-B37. The autologous RCC cell lines were efficiently lysed by the CTL clones, whereas normal epithelial cells of the proximal tubuli matched for the restriction element and K562 were not. From a panel of allogeneic RCC cell lines, CTL 5E recognized MZ-1940-RCC. Reactivity to allogeneic RCC sharing HLA-B7 was also observed with CTL 263/17 and 263/45, both of which could lyse the HLA-B7-positive cell line MZ-1851-RCC. Our data provide evidence that common tumor antigens are recognized by CTL on RCC.

A new gene coding for an antigen recognized by autologous cytolytic T lymphocytes on a human renal carcinoma

Previous reports have described antigens that are recognized on human melanoma cells by autologous cytolytic T lymphocytes (CTL). The genes coding for a number of these antigens have been identified. Here we report the cloning of a gene that codes for an antigen recognized by autologous CTL on a human renal carcinoma cell line. This antigen is presented by HLA-B7 and is encoded by a new gene that we have named RAGE1. No expression of RAGE1 was found in normal tissues other than retina. RAGE1 expression was found in only one of 57 renal cell carcinoma samples, and also in some sarcomas, infiltrating bladder carcinomas, and melanomas. This represents the first identification of an antigen recognized by autologous CTL on a renal tumor.

A tyrosinase nonapeptide presented by HLA-B44 is recognized on a human melanoma by autologous cytolytic T lymphocytes

The human tyrosinase gene has been reported previously to code for two distinct antigens recognized on HLA-A2 melanoma cells by autologous cytolytic T lymphocytes (CTL). By stimulating lymphocytes of melanoma patient MZ2 with a subclone of the tumor cell line of this patient, we obtained a CTL clone that lysed this subclone but did not lyse other subclones of the same melanoma cell line. The sensitive melanoma subclone was found to express a much higher level of tyrosinase than the others, suggesting that the antigen recognized by the CTL might be encoded by tyrosinase. Transfection of a tyrosinase cDNA demonstrated that the CTL clone indeed recognized a tyrosinase product presented by HLA-B*4403. The relevant antigenic peptide corresponds to residues 192-200 of the tyrosinase protein. Lymphoblastoid cells of the B*4402 subtype were not recognized by the CTL following incubation with the peptide. Nevertheless, by stimulating in vitro lymphocytes of a healthy HLA-B*4402 donor with autologous adherent cells pulsed with the same peptide, we obtained a CTL clone which recognized tumor cells expressing tyrosinase and HLA-B*4402. As HLA-B44 is expressed in 24% of Caucasians, the tyrosinase-B44 antigen may constitute a useful target for specific immunotherapy of melanoma.

A new family of genes coding for an antigen recognized by autologous cytolytic T lymphocytes on a human melanoma

Human melanoma MZ2-MEL expresses several distinct antigens that are recognized by autologous cytolytic T lymphocytes (CTL). Some of these antigens are encoded by genes MAGE-1, MAGE-3, and BAGE, which are expressed in a large fraction of tumors of various histological types but are silent in normal adult tissues with the exception of testis. We report here the identification of the gene coding for MZ2-F, another antigen recognized by autologous CTL on MZ2-MEL cells. This gene, which was named GAGE-1, is not related to any presently known gene. It belongs to a family of genes that are expressed in a variety of tumors but not in normal tissues, except for the testis. Antigenic peptide YRPRPRRY, which is encoded by GAGE-1, is recognized by anti-MZ2-F CTL on class I molecule HLA-Cw6. The two genes of the GAGE family that code for this peptide, namely GAGE-1 and GAGE-2, are expressed in a significant proportion of melanomas (24%), sarcomas (25%), non-small cell lung cancers (19%), head and neck tumors (19%), and bladder tumors (12%). About 50% of melanoma patients carry on their tumor at least one of the presently defined antigens encoded by the MAGE, BAGE, and GAGE genes.

Human gene MAGE-3 codes for an antigen recognized on a melanoma by autologous cytolytic T lymphocytes

Human melanoma cell line MZ2-MEL expresses several antigens recognized by autologous cytolytic T lymphocyte (CTL) clones. We reported previously the identification of a gene, named MAGE-1, that codes for one of these antigens named MZ2-E. We show here that antigen MZ2-D, which is present on the same tumor, is encoded by another member of the MAGE gene family named MAGE-3. Like MAGE-1, MAGE-3 is composed of three exons and the large open reading frame is entirely located in the third exon. Its sequence shows 73% identity with MAGE-1. Like MZ2-E, antigen MZ2-D is presented by HLA-A1. The antigenic peptide of MZ2-D is a nonapeptide that is encoded by the sequence of MAGE-3 that is homologous to the MAGE-1 sequence coding for the MZ2-E peptide. Competition experiments using single Ala-substituted peptides indicated that amino acid residues Asp in position 3 and Tyr in position 9 were essential for binding of the MAGE-1 peptide to HLA-A1. Gene MAGE-3 is expressed in many tumors of several types, such as melanoma, head and neck squamous cell carcinoma, lung carcinoma and breast carcinoma, but not in normal tissues except for testes. It is expressed in a larger proportion of melanoma samples than MAGE-1. MAGE-3 encoded antigens may therefore have a wide applicability for specific immunotherapy of melanoma patients.

Evaluation of functional heterogeneity in the CD8 subset with T cells from T cell receptor-transgenic mice

The question of functional differentiation within the CD8 subset has been addressed in a model of TcR-transgenic (TcR-tg) mice expressing a TcR specific for H-2Kb (Ti). CD8+ Ti+ T cells present in the periphery of these mice have no cytotoxic T lymphocyte (CTL) activity unless they are stimulated with H-2Kb-expressing cells. In contrast to T cells from normal H-2k littermates, alloantigen induction of CTL from TcR-tg mice is independent of CD4+ T helper (Th) cells and is accompanied by high level secretion of interleukin-(IL)-2 by Ti+ CD8+ T cells. Precursor frequency analysis performed on CD8+ cells from TcR-tg mice revealed a high frequency of Th as compared to CTL precursors. This raised the possibility of the existence of distinct subpopulations within CD8+ precursors with different requirements for differentiation to functional CTL. FACS analyses (performed on resting and on in vitro stimulated T cells from normal and TcR-tg mice) demonstrated a heterogeneous expression of Ly-6C on CD8+ cells with a large enrichment of Ly-6C- cells among the Ti+ cells which persisted after stimulation with H-2b cells in conditions that led to a homogeneous expression of the activation markers pgp-1 and CD69. The possibility that Ly-6C expression could mark functionally different subpopulations in CD8+ T cells was investigated. Stimulation of sorted populations of Ly-6C- and Ly-6C+ cells allowed detection of CTL precursors in both these subsets and the majority of limiting dilution wells containing one pCTL also scored positive for IL-2 secretion. Thus, for CD8+ T cells expressing the same TcR, differentiation led to acquisition of both IL-2 secretion and CTL function and there was no evidence for the existence of a distinct population of helper-dependent CTL precursors.

Evidence for quantitative and qualitative differences in functional activation of Mls-reactive T cell clones and hybridomas by antigen or TcR/CD3 antibodies

In this study, we demonstrated that some V beta 6+, CD4+, Mls-1a-specific T cell clones had cytolytic activity when stimulated with anti-T cell receptor(TcR)/CD3 monoclonal antibodies (mAb), but not with targets expressing Mls-1a, although they produced lymphokines (interleukin 2 and interferon-gamma) in response to both types of stimuli. To examine the possibility that lack of cytolysis resulted from expression of the Mls-1a antigen on merely a fraction of splenic B blasts, we (a) used the B cell lymphoma LBB.3.4.16 and (b) measured esterase secretion which is generally concurrent with cytotoxic T lymphocyte (CTL) activity. The B cell lymphoma maximally stimulated the T cell clone for interferon-gamma production when responding and stimulating cells were incubated at a 1:1 ratio, but it was never killed by the Mls-1a-specific T cell clone unless TcR/CD3-specific mAb were added. Furthermore, a fivefold excess of the Mls-1a B cell lymphoma did not induce any secretion of esterase, which was observed only in the presence of the TcR/CD3-specific mAb. Comparison of the reactivity of two Mls-1a-specific T cell hybridomas expressing the same TcR at similar surface density, revealed both quantitative and qualitative differences between CD3-specific mAb and Mls stimulation of the hybridomas. A small quantitative difference in the sensitivity of hybridoma FJ22.5 to stimulation with V beta 6 or CD3-specific mAb resulted in a marked decrease in efficiency of stimulation by Mls-1a for interleukin 2 production and to inability to detect growth inhibition by Mls-expressing cells. A qualitative difference was observed when analyses of inositol phosphate production were performed under optimal conditions of stimulation of the highly responsive T cell hybridoma (FJ8.1): only stimulation with CD3-specific mAb, but not Mls-expressing cells, could induce detectable inositol phosphate production. Lack of cytolysis of Mls-1a class II-expressing B cells may have evolutionary significance in view of the recent mapping of Mls to mouse mammary tumor virus genes.

Isolation of homologous and heterologous complexes between catalytic and regulatory components of adenylate cyclase by forskolin-Sepharose

Homologous and heterologous complexes between catalytic and GTP-binding components can be isolated by means of immobilized succinyldeacetylforskolin (forskolin-Sepharose). A heterologous complex is formed by reconstitution of forskolin-Sepharose bound catalytic function from rabbit myocardial membranes with the homogenous [3H]methyl-GTP-binding protein from duck erythrocyte membranes. Analysis of the reconstituted complex by sodium dodecyl sulfate polyacrylamide gelelectrophoresis reveals that only the Mr 42 000 component of the GTP-binding protein's Mr 42 000/Mr 35 000 heterodimer contributes to the formation of active adenylate cyclase.

Inhibition of NS-protein-stimulated human-platelet adenylate cyclase by epinephrine and stable GTP analogs

The influence of purified, preactivated NS protein, mediating adenylate cyclase stimulation by hormones and guanine nucleotides, was studied on adenylate cyclase activity in membranes of human platelets. The preactivated coupling protein caused a large increase in platelet enzyme activity. The activation occurred after a short lag phase and exhibited saturation. NS protein increased the V of the platelet adenylate cyclase without change in the enzyme's affinity for the substrate, MgATP, whereas the apparent affinity for Mg2+ was increased by more than one order of magnitude. The NS-protein-activated human platelet adenylate cyclase was inhibited by the hormone, epinephrine, and by the stable GTP analogs, guanosine 5'-[beta, gamma-imido]triphosphate and guanosine 5'-[gamma-thio]triphosphate. The stable GTP analog or hormone-induced adenylate cyclase inhibition was not competitive with regard to the concentration of NS protein. Inhibition of NS-protein-stimulated platelet adenylate cyclase caused by stable GTP analogs appeared to be persistent, was amplified by epinephrine and was accompanied by a large decrease in the enzyme's apparent affinity for Mg2+. The data suggest that the hormone-sensitive adenylate cyclase is regulated by two guanine-nucleotide-binding sites, NS and Ni, mediating enzyme stimulation and inhibition, respectively, by hormones and guanine nucleotides, and that the two coupling components interact in a non-competitive manner with the adenylate cyclase, exhibiting high and low affinity for Mg2+ when affected by NS and Ni, respectively.