An In Vitro Model to Assess CRS Potential of CAR T Cells Using a Tumor Cell Line and Autologous Monocytes

Chimeric antigen receptor (CAR) T cell therapy is an engineered cell therapy where T cells are isolated and genetically modified to contain a synthetic CAR with specificity to a tumor cell antigen. Upon antigen binding, the CAR T cell will initiate signaling cascades that result in lysis of the associated tumor cell. Cytokine release syndrome (CRS) is the primary toxicity associated with CAR T cell therapy and remains a prominent safety issue with currently available commercial products. CRS is driven by interaction of the CAR T cells with endogenous monocytes and macrophages, which can lead to immune cell overactivation and an increase in certain cytokines to supraphysiological levels. Identifying the potential of any given CAR construct to drive toxicities in vivo should be assessed in preclinical models prior to human trials. While there are in vivo mouse models available for this purpose, these are often complex xenograft models available in few centers. Thus, there is a need to develop an in vitro assay for measuring the CRS potential of CAR T cells. The assay described here is a preclinical tool for assessing the propensity of any given CAR construct to produce potentially CRS-driving cytokines following tumor cell and monocyte interactions. This article provides a detailed protocol for target cell preparation and isolation of monocytes from peripheral blood mononuclear cells (PBMCs) autologous to the CAR T cells, as well as protocols for seeding the three cell types in a co-culture assay and collecting/analyzing the cytokines produced via an ELISA or multiplex bead array. © 2023 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Preparation of K562 target cells Basic Protocol 2: Isolation of monocytes from autologous PBMCs Basic Protocol 3: Seeding of CAR T cells, monocytes, and K562 cells in 96-well plates Basic Protocol 4: Analysis of co-culture supernatants by single-cytokine ELISA Alternate Protocol: Analysis of co-culture supernatants by multiplex cytokine bead array.

Genome-wide CRISPR/Cas9 library screening identified ATM signaling network genes as critical drivers for resistance to ATR inhibition in soft-tissue sarcomas: synthetic lethality and therapeutic implications

Soft-tissue sarcoma (STS) are a heterogeneous group of rare tumors with different biological behavior that are fatal in more than 40% of cases, due to their metastatic evolution and inadequate treatment options. ATR inhibition already showed an activity, even if modest, in broad pre-clinical models of STS. By using genome-wide CRISPR/Cas9 library screening, we identified ATM signaling network genes as critical drivers for resistance to the specific ATR inhibitor AZD6738. The role of such genes in resistance to AZD6738 was confirmed by using CRISPR/Cas9 knockout models. More strikingly, the ATM inhibitor AZD0156 works synergistically with AZD6738 in vitro and abolishes STS growth in vivo in our models of most frequent histotypes (such as dedifferentiated liposarcoma, leiomyosarcoma, and undifferentiated pleomorphic sarcoma among others). Moreover, the combination of AZD6738 and AZD0156 induced significantly higher levels of DNA damage than either drug used as single agent alone. In summary, our results demonstrate that targeting ATM is an effective approach to overcome resistance to ATR inhibition in different STS subtypes, including the most frequent histologies.

GSK3-beta as a candidate therapeutic target in soft tissue sarcomas

Soft tissue sarcoma (STS) is a predominantly fatal rare malignancy with inadequate treatment options. Glycogen synthase kinase 3β (GSK-3β) is an emerging target in human malignancies. Its therapeutic relevance in STS is unknown. We analyzed the prognostic impact of GSK-3β gene and protein expression in two independent cohorts of patients with STS. We then treated STS cell lines and mice xenografts with a novel GSK-3 inhibitor 9-ING-41 alone or in combination with chemotherapy. We demonstrated that 9-ING-41 treatment induced significant STS cells apoptosis and was synergistic in vivo when combined with chemotherapy. Mechanistically, 9-ING-41 induces significant apoptosis of STS cells via suppression of NF-κB-mediated X-linked inhibitor of apoptosis protein (XIAP) expression. These data support the inclusion of patients with STS in clinical studies of 9-ING-41 alone and in combination with chemotherapy.

T-cell intrinsic Toll-like receptor signaling: implications for cancer immunotherapy and CAR T-cells

Toll-like receptors (TLRs) are evolutionarily conserved molecules that specifically recognize common microbial patterns, and have a critical role in innate and adaptive immunity. Although TLRs are highly expressed by innate immune cells, particularly antigen-presenting cells, the very first report of a human TLR also described its expression and function within T-cells. Gene knock-out models and adoptive cell transfer studies have since confirmed that TLRs function as important costimulatory and regulatory molecules within T-cells themselves. By acting directly on T-cells, TLR agonists can enhance cytokine production by activated T-cells, increase T-cell sensitivity to T-cell receptor stimulation, promote long-lived T-cell memory, and reduce the suppressive activity of regulatory T-cells. Direct stimulation of T-cell intrinsic TLRs may be a relevant mechanism of action of TLR ligands currently under clinical investigation as cancer immunotherapies. Finally, chimeric antigen receptor (CAR) T-cells afford a new opportunity to specifically exploit T-cell intrinsic TLR function. This can be achieved by expressing TLR signaling domains, or domains from their signaling partner myeloid differentiation primary response 88 (MyD88), within or alongside the CAR. This review summarizes the expression and function of TLRs within T-cells, and explores the relevance of T-cell intrinsic TLR expression to the benefits and risks of TLR-stimulating cancer immunotherapies, including CAR T-cells.

Inefficient boosting of antitumor CD8(+) T cells by dendritic-cell vaccines is rescued by restricting T-cell cytotoxic functions

Dendritic cells (DCs) are powerful activators of primary and secondary immune responses and have promising activity as anticancer vaccines. However, various populations of immune cells, including natural killer cells, regulatory T cells and especially cytotoxic T lymphocytes (CTLs), can inhibit DC function through cytotoxic clearance. Spontaneous tumor-specific CTL responses are frequently observed in patients before immunotherapy, and it is unclear how such pre-existing responses may affect DC vaccines. We used an adoptive transfer model to show that DC vaccination fail to induce the expansion of pre-existing CTLs or increase their production of interferon γ (IFNγ). The expansion and effector differentiation of naïve host CD8⁺ T cells was also suppressed in the presence of CTLs of the same specificity. Suppression was caused by the cytotoxic functions of the adoptively transferred CTLs, as perforin-deficient CTLs could respond to DC vaccination by expanding and increasing IFNγ production. Proliferation and effector differentiation of host CD8⁺ T cells as well as resistance to tumor challenge were also significantly increased. Expression of perforin by antitumor CTLs was critical in regulating the survival of vaccine DCs, while FAS/FASL and TRAIL/DR5 had a significant, but comparatively smaller, effect. We conclude that perforin-expressing CTLs can suppress the activity of DC-based vaccines and prevent the expansion of naïve and memory CD8⁺ T cells as well as antitumor immune responses. We suggest that, paradoxically, temporarily blocking the cytotoxic functions of CTLs at the time of DC vaccination should result in improved vaccine efficiency and enhanced antitumor immunity.

Abstract I11: Targeting pancreatic cancer with TCR-engineered T cells

We have been exploring in preclinical models and clinical trials methods to reproducibly provide therapeutic T-cell responses by transfer of genetically engineered T cells. Our largest clinical experience has been in treating human acute myelogenous leukemia (AML), in which we have utilized a high-affinity TCR specific for WT1, a protein associated with promoting leukemic transformation that is overexpressed in human leukemic stem cells, to genetically engineer CD8 T cells. We recently reported a study (Chapuis et al., Nat Med 2019) in which we treated leukemia patients at high risk of relapse (after hematopoietic cell transplant) that demonstrated all treated patients remain alive and relapse free at a median of 48 months, compared to a relapse rate of ~35% in the concurrent matched cohort (p<0.01). We have also been developing strategies to translate insights and technologies from this study to treatment of solid tumors. In a preclinical genetically engineered mouse model (KPC mice) of pancreatic cancer that faithfully replicates most aspects of human disease, we demonstrated (Stromnes et al., Cancer Cell 2015) that CD8 T cells engineered with a high-affinity TCR specific for mesothelin (Msln) can infiltrate pancreatic tumors, mediate antitumor activity, and provide therapeutic benefit. However, since the T cells are ultimately rendered dysfunctional in the tumor microenvironment (TME), prolonging survival has required repeated infusions of T cells to sustain antitumor activity. We have now isolated and validated a human high-affinity TCR specific for Msln for use in a planned clinical trial modeled after the approach successful in KPC mice. However, we would like to both enhance and sustain antitumor activity without requiring repeated infusions. In-depth analyses of the T cells, tumors, and the TME in treated KPC mice have illuminated strategies to potentially overcome the obstacles to tumor eradication, and we have been exploring molecular engineering approaches to achieve this. One approach has been to create synthetic immunomodulatory fusion proteins (IFPs) that have an ectodomain composed of the receptor for an inhibitory ligand encountered in the TME but, rather than the natural cytoplasmic tail that would deliver an inhibitory signal, the receptor has the tail of a costimulatory receptor and delivers an activation signal. Expression of such IFPs takes advantage of the inhibitory ligands commonly encountered in the TME by T cells by co-opting potential inhibitory signals and has resulted in enhanced T cell function, persistence/survival, and antitumor activity. Another major obstacle to sustained therapeutic activity appears to be the limited access in the TME to nutrients that effector T cells can utilize as an energy source. Analysis of the metabolites present in the TME and the transcriptional program in T cells has provided insights into genetic modifications that can be made to allow T cells to survive and function in the metabolically hostile TME. These and related studies will be discussed.

Citation Format: Philip D. Greenberg, Kristin G. Anderson, Dan Egan, Sunil R. Hingorani, Luigi Nezi, Teresa Manzo, Shannon K. Oda, Kelly G. Paulson, Rachel Perret, Leah Schmidt, Tom M. Schmitt, Ingunn M. Stromnes, Aude G. Chapuis. Targeting pancreatic cancer with TCR-engineered T cells [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2019 Sept 6-9; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2019;79(24 Suppl):Abstract nr I11.

Abstract IA17: Utilizing synthetic biology and high-dimensional probing to address therapeutic obstacles and empower engineered T cells with the capacity to eradicate tumors

We have been exploring in preclinical models and clinical trials methods to reproducibly provide therapeutic T cell responses by transfer of genetically engineered T cells. Our largest clinical experience is in treating human Acute Myelogenous Leukemia (AML). After identifying that WT1, a gene associated with promoting leukemic transformation, is over-expressed in human leukemic stem cells, and demonstrating in a clinical trial that in vitro expanded WT1-specific CD8 T cell clones can be safely transferred, exhibit anti-leukemic activity, and provide therapeutic benefit to AML patients, we extensively screened normal human repertoires and isolated a high affinity TCR specific for WT1 for genetically engineering CD8 T cells to reproducibly create cells with high avidity for leukemic cells. We have initially pursued this strategy in a 2 Arm trial for leukemia patients either at high risk of relapse (Arm 1) after hematopoietic cell transplant (HCT) or who have already relapsed after HCT (Arm 2). The prophylactic arm is now completed, with very encouraging results- all patients treated with engineered T cells remain alive and relapse free at a median of 38 months, compared to a relapse rate of ~50% in a concurrent matched cohort. Results in relapsed patients (Arm 2) have been less effective, and we have used high-dimensional analyses including single cell RNAseq both to elucidate the reasons for failure to eradicate the leukemia and to design strategies to overcome these obstacles. Our results have identified several mechanisms by which the leukemia escapes, and we have been testing approaches that employ further genetic modification of the T cells to enhance efficacy. The predominant reason for leukemia progression despite targeted therapy with T cells is the inability of the T cells to persist and maintain function in the context of encountering a rapidly proliferating myeloid leukemia. This reflects both engagement of pathways inhibitory to T cells by the leukemic cells, and apoptosis of the T cells from repetitive stimulation. We are addressing this issue by creating immuno-modulatory fusion proteins (IFPs) that have the ectodomain of an inhibitory or death receptor fused to a survival costimulatory domain. Results with two such IFPs will be discussed, a CD200R/CD28 fusion that binds the inhibitory ligand CD200 commonly expressed on leukemic cells but provides a CD28 costimulatory signal and a Fas/4-1BB fusion that binds FasL but rather than induce death promotes proliferation and survival. A more uncommon reason explaining progression is loss of expression of the WT1 epitope being targeted. This has occurred in 2 patients, but for distinct reasons. In one patient this reflected loss of a component of the immunoproteasome, and we have now isolated a TCR that recognizes an epitope not dependent on the immunoproteasome. In a second patient the level of WT1 expression declined- interestingly, this patient was treated with Vidaza, which can increase expression of WT1, and post-Vidaza the transferred T cells persisting in the patient’s bone marrow recognized and responded in vivo to the relapsing leukemia. The approaches and technologies we are developing and testing in leukemia are also applicable to solid tumors, and preclinical studies in pancreatic and ovarian cancers will be discussed.

Citation Format: Kristin G. Anderson, Dan Egan, Sunil R. Hingorani, Shannon K. Oda, Kelly Paulson, Rachel Perret, Leah Schmidt, Thomas Schmitt, Ingunn Stromnes, Aude Chapuis, Philip D. Greenberg. Utilizing synthetic biology and high-dimensional probing to address therapeutic obstacles and empower engineered T cells with the capacity to eradicate tumors [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr IA17.

Abstract IA02: Engineering T cells to eradicate tumors in the age of synthetic biology

Unlike cancer vaccines and immune modulators such as checkpoint inhibitors that seek to harness patient immune responses, adoptive therapy with genetically engineered T cells seeks to create responses that don’t exist in the patient’s immune system. Molecular technologies now make it feasible to not only create T cells with specificity for the tumor by introduction of a selected antigen-specific receptor, but also with qualities not naturally found, including improved function and resistance to immunosuppression. We have been exploring in preclinical models and clinical trials methods to reproducibly provide therapeutic T cell responses by transfer of genetically engineered T cells. For human acute myelogenous leukemia (AML), we have pursued targeting WT1, a gene overexpressed in human leukemic stem cells that is associated with promoting leukemic transformation. Preclinical studies performed in a mouse model demonstrated that CD8 T cells expressing a high affinity TCR specific for this oncogene can be safely administered, with no evidence of toxicity to the normal tissues known to express low but detectable levels of WT1. We have advanced this approach to a clinical trial in leukemia patients with poor prognostic factors that place them at high risk of relapse after hematopoietic cell transplant (HCT), using a high-affinity human TCR specific for WT1 to transduce CD8 cells and reproducibly create high-avidity T cells that recognize leukemic cells. Our clinical results demonstrate that such T cells can prevent leukemic relapse and sustain long-term remissions, and can mediate antileukemic activity in patients who have relapsed. This therapy is now being tested in AML patients who have minimal residual disease after induction therapy and are not candidates for HCT, as well as in solid tumors that similarly overexpress WT1.

Unfortunately, there are substantive obstacles in targeting established tumors that can preclude even a T cell expressing a high-affinity TCR from being effective. These impediments include the development of T cell dysfunction, particularly within the microenvironment of solid tumors, and we are using genetically engineered mouse models to elucidate the cellular and molecular pathways that need to be modulated to achieve meaningful therapeutic benefit in a variety of hematologic and solid tumor settings, including pancreatic and ovarian cancer. Our preclinical therapy studies reveal promising antitumor activity, but demonstrate that repeated infusions of functional T cells are required to sustain a therapeutic response in the context of the immunosuppressive tumor microenvironment, and we are engineering T cells to overcome these inhibitory signals and enhance efficacy. In place of current strategies that disrupt inhibitory pathways by systemic administration of blocking mAbs, which globally disrupt immune regulation and thus can have significant toxicity to the host, we are creating synthetic immunomodulatory fusion proteins that take advantage of the expression of inhibitory ligands by tumors by still binding the inhibitory ligand but alternatively delivering a costimulatory rather than inhibitory signal. Additionally, as the antitumor activity of CD8 T cells is enhanced by a concurrent CD4 T cell response, we are engineering CD4 T cells as well as CD8 T cells to create an orchestrated antitumor response. The results suggest that cancer therapy with engineered T cells can provide effective antitumor responses and will likely find an increasing role in the treatment of human cancers.

Citation Format: Philip D. Greenberg, Kristin G. Anderson, Dan Egan, Sunil R. Hingorani, Shannon K. Oda, Rachel Perret, Tom M. Schmitt, Ingunn M. Stromnes, Leah Schmidt, Aude G. Chapuis. Engineering T cells to eradicate tumors in the age of synthetic biology [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2017 Oct 1-4; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2018;6(9 Suppl):Abstract nr IA02.

Abstract IA18: Building better T cells for targeting and eliminating tumors

Effective cellular therapy for human malignancies requires first identifying and validating an appropriate antigenic target, and then establishing in each patient a tumor-reactive T cell response of high avidity and high magnitude that is not only safe but can infiltrate and retain function in the tumor microenvironment. We have used molecular expression profiling to detect antigens selectively or markedly over-expressed by tumors, and then used these antigens as stimuli to generate T cells from normal repertoires. We have developed a high throughput technology to identify those T cells that express high affinity TCRs, and to then isolate from these T cells the TCR genes, place them either directly or after affinity enhancement into shuttle vectors, and use these reagents to create recipient T cells with high avidity for tumor targets that can be administered in vivo. We have utilized in silico, in vitro, and preclinical mouse models to assess the safety and potential efficacy of T cells expressing such TCRs. We are currently pursuing targeting of 3 antigens that are expressed in both murine and human tumors and are pro-oncogenic, contributing to the malignant phenotype. This includes ongoing clinical trials that will be discussed in acute myelogenous leukemia and in non-small cell lung cancer or mesothelioma targeting WT1 with T cells transduced to express a high affinity TCR specific for WT1, as well as trials being designed to target Mesothelin (MSLN) with T cells transduced to express a high affinity TCR specific for MSLN in pancreatic and ovarian cancer that are anticipated to begin within 8-12 months.

Our clinical results in treatment of AML and preclinical results in mouse models of pancreatic and ovarian cancer appear very promising. However, the composite clinical data, as well as the results in the preclinical mouse models that drive our clinical trials, demonstrate substantial obstacles to sustaining T cell function in vivo after transfer, particularly in the context of solid tumors. Engineered T cells with specificity for tumor antigens appear to have the capacity to infiltrate and accumulate in solid tumors, and to initially mediate anti-tumor activity, but frequently become dysfunctional in the tumor microenvironment. Studies are being pursued to identify the critical obstacles to maintaining T cell function and achieving more reproducible tumor eradication, including modulating the tumor microenvironment and engineering T cells to express immunomodulatory fusion proteins (IFP) that recognize ligands for inhibitory signals but deliver an activation/costimulatory signal. Our data suggest that engineering T cells to acquire novel properties not naturally found in unmanipulated T cells has the potential to create effective therapies for human cancers.

Citation Format: Philip D. Greenberg, Aude Chapuis, Dan Egan, Ingunn Stromnes, Sunil Hingorani, Shannon Oda, Rachel Perret, Kristin Anderson, Tom Schmitt. Building better T cells for targeting and eliminating tumors. [abstract]. In: Proceedings of the AACR Precision Medicine Series: Targeting the Vulnerabilities of Cancer; May 16-19, 2016; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(1_Suppl):Abstract nr IA18.

Abstract IA01: Engineering T cell responses to tumors: Taking the immune system where no responses have gone before

We have entered a new and exciting era in cancer therapy, in which immunotherapeutic strategies are achieving unprecedented successes and are increasingly becoming incorporated into standard of care regimens. Checkpoint blockade is dependent on inducing and/or reactivating or sustaining responses to the tumor by T cells already in the patient. Similarly, vaccines attempt to generate and/or expand responses of T cells naturally present in the normal repertoire. However, these strategies require that functional tumor-reactive T cells exist in the patient's repertoire and that the method pursued can harness those T cells to create a potent response that will function in the tumor microenvironment, which limits the settings in which these approaches will prove effective. Adoptive T cell therapy, in which patient T cells can be expanded to large numbers ex vivo before infusion, provides a means to bypass or overcome these obstacles, particularly with the advent of genetic engineering that now makes it possible to create T cells not only with specificity for the tumor but also with qualities not naturally found, including improved function and resistance to immunosuppression. We have been exploring in preclinical models and clinical trials methods to reproducibly provide therapeutic T cell responses by transfer of genetically engineered T cells. The first issue is to identify tumor antigens that can be safely, effectively, and reproducibly targeted. We have used analyses of differential gene expression to search for antigenic targets that are either uniquely expressed in a tumor or are differentially expressed at high levels in the tumor with much lower and limited expression in normal tissues, and that preferentially are associated with the malignant phenotype to reduce the risk of antigen loss by the tumor. In our search for targets in acute myelogenous leukemia (AML), we found that WT1, a gene known to be associated with promoting leukemic transformation, is expressed in comparative abundance in human leukemic stem cells. The next step is to generate T cells specific for the target antigen that can recognize and eliminate malignant cells expressing the antigen. Extensive screening of normal human repertoires revealed a high affinity TCR specific for WT1 that can recognize leukemic cells, and that could be inserted into CD8 T cells to reproducibly produce high avidity T cells for use in therapy. Preclinical studies performed in a mouse model demonstrated that CD8 T cells specific for this oncogene expressing a high affinity TCR can be safely administered, with no evidence of toxicity to the normal tissues known to express low but detectable levels of WT1. We have advanced this approach targeting WT1 to an initial clinical trial in leukemia patients with poor prognostic factors that make them at high risk of relapse after hematopoietic cell transplant (HCT). The Vα and Vβ genes of the human WT-1 specific TCR were codon optimized to enhance expression, modified by a point mutation in each chain to create an interchain disulfide bond that minimizes the potential problem of mispairing of the introduced TCR chains with the endogenous TCR chains, and inserted these TCR genes into a lentiviral vector. Preliminary results of this trial, which has provided evidence that such T cells can prevent leukemic relapse and sustain long-term remissions, will be discussed. This therapy is now being advanced for use in AML patients who are not HCT candidates. We have also now initiated additional trials with this TCR for treatment of patients with non-small cell lung cancer (NSCLC) or mesothelioma, as WT1 is commonly overexpressed in NSCLC as well as many other malignancies. For many candidate target antigens that are also normal self-antigens, isolation of high affinity TCRs may not be readily achieved from normal repertoires. However, it is now feasible to engineer TCRs that have higher affinities than normally exist for their antigen target. We have developed strategies to enhance the affinity of isolated TCRs with retention of specificity, including saturation mutagenesis of CDR3 regions and an in vitro thymic selection system that allows for capture of a more diverse set of high affinity specific TCRs during TCR gene rearrangement. These approaches induce modifications to the TCR region that predominantly makes contacts with the peptide epitope rather than MHC, which is necessary to minimize the risk of off-target toxicity from promiscuous peptide/MHC recognition. However, it remains essential that such modified TCRs do not induce unanticipated tissue damage, and we are using bioinformatics, functional screening, and modeling in the mouse to uncover any potential for off-target toxicity. Unfortunately, providing a high avidity T cell response does not necessarily result in tumor eradication, as there are other substantive obstacles that can preclude even a T cell expressing a high affinity TCR from being effective. These impediments include the development of T cell dysfunction, particularly within the microenvironment of solid tumors, and we are using genetically engineered mouse models to elucidate the cellular and molecular pathways that need to be modulated to achieve meaningful therapeutic benefit in a variety of solid tumor settings, including pancreatic and ovarian cancer. Our preclinical therapy studies, particularly in a pancreatic ductal adenocarcinoma (PDA) model, already appear very promising, as we have demonstrated that T cells expressing a high affinity TCR targeting a tumor antigen expressed by PDA cells can infiltrate the tumor, mediate tumor lysis, modify the tumor stroma, and provide therapeutic benefit. We have now identified high affinity human TCRs specific for this tumor antigen, and plan to use the insights derived from these studies to initiate within the next year clinical trials in human pancreatic and ovarian cancers. The genetically-engineered mouse models of spontaneously developing tumors we are using, which recapitulate many aspects of the analogous human cancer, are also making it possible to assess strategies to improve the efficacy of T cell therapy. These models have helped elucidate the importance of not only cell extrinsic mechanisms of regulation and dysfunction that render T cells unresponsive, particularly via inhibitory cells commonly present in the tumor microenvironment that interfere with an effector response, such as the accumulation of regulatory CD4 T cells (Treg), myeloid derived suppressor cells (MDSC), and tumor-associated macrophages (TAM), but also the cell intrinsic mechanisms that derive in large part from persistent stimulation by the tumor antigen and ultimately can render T cells progressively dysfunctional, leading to epigenetic modifications that eventuallly result in non-responsive cells that cannot be readily rescued. These cumulative mechanisms highlight the difficulties eliciting and/or sustaining responses to tumor antigens. Strategies to disrupt inhibitory pathways by systemic administration of mAbs or cytokines are currently being pursued clinically, but such reagents globally disrupt inhibitory pathways and thus can have significant toxicity to the host. Therefore, we are evaluating strategies to sustain function and anti-tumor activity by genetically modifying T cells to enhance function and to be resistant to obstacles that prevent tumor eradication. As different tumor types exhibit unique characteristics and are capable of engaging distinct inhibitory pathways, improved understanding of the immunobiology of the tumor type to be treated will likely prove essential for designing effective therapies. However, the relatively straightforward means to use synthetic biology to genetically engineer T cells to acquire novel capacities to overcome inhibitory signals and function in the tumor microenvironment suggests that cancer therapy with engineered T cells will likely find an increasing role in the treatment of human cancers.

Citation Format: Philip D. Greenberg, Kristin G. Anderson, Dan Egan, Sunil R. Hingorani, Shannon K. Oda, Rachel Perret, Andrea Schietinger, Tom M. Schmitt, Ingunn M. Stromnes, Alec Wilkens, Aude G. Chapuis. Engineering T cell responses to tumors: Taking the immune system where no responses have gone before [abstract]. In: Proceedings of the Second CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; 2016 Sept 25-28; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(11 Suppl):Abstract nr IA01.

Expanding the scope of WT1- and cyclin A1-specific TCR gene therapy for AML and other cancers

TCR gene therapy hastens the reproducible generation of tumor-specific T cells from patients, creating a promising avenue for treating hematological and solid tumors. Several hurdles remain to making this a broadly effective modality, including variable target antigen expression, risk of tumor antigenic escape, and current therapies limited almost exclusively to HLA-A0201+ patients. We previously characterized WT1 and cyclin A1 as favorable T cell immunotherapy targets, based on high expression in malignant versus normal cells and roles in oncogenesis, reducing likelihood of loss variants. We currently have a high-affinity HLA-A0201/WT1-specific TCR in Phase I trials for the treatment of AML and NSCLC, and are now focused on developing WT1- and cyclin A1-specific TCRs for ~7 common HLA types, aiming to cover >90% of patients. T cell lines were generated by stimulating donor PBMC with overlapping peptide libraries to identify new reactive epitopes, and the highest affinity T cell clones for each HLA/antigen combination identified by tetramer binding strength. TCRs were then cloned into lentiviral vectors for expression in CD8 T cells. We are currently in the process of selecting the best HLA-A0201/cyclin A1-specific TCR with which to proceed to clinical development. We are also continuing to optimize our epitope discovery protocol for the improved selection of TCRs for other HLA alleles. Safety and efficacy of selected TCRs are rigorously tested using bioinformatic screens, in vitro assays, and humanized MHC-I mouse models. Our goal is to create a molecular toolbox of off-the-shelf TCR reagents to facilitate rapid treatment of patients, using T cell immunotherapies targeted to their particular tumor antigenic profile and HLA type.

Abstract SY31-03: Employing TCRs in engineered T cells to develop therapeutic reagents for effectively targeting malignancies

Effective cellular therapy for human malignancies requires first identifying and validating an appropriate antigenic target, and then establishing in each patient a tumor-reactive T cell response of high avidity and high magnitude that is safe and can infiltrate and retain function in the tumor microenvironment. We have been exploring in preclinical models and clinical trials methods to reproducibly provide such responses by transfer of genetically engineered T cells that acquire target specificity by virtue of an introduced high affinity TCR. To identify candidate antigens in leukema, we examined purified human leukemic stem cells for over-expression of genes based on comparisons to purified human hematopoietic stem cells as well as normal somatic tissues. Our analysis revealed that WT1, a gene known to be associated with promoting leukemic transformation, is expressed in comparative abundance in human leukemic stem cells. Preclinical studies were then performed in a mouse model, and revealed that CD8 T cells specific for this oncogene with even higher avidity than can be detected in normal repertoires could be safely administered, with no evidence of toxicity to the normal tissues known to express low but detectable levels of WT1. For our initial clinical trial, poor prognosis leukemia patients who relapsed after hematopoietic cell transplant (HCT) were treated with transfer of WT1-specific CD8 T cells clones isolated and expanded in vitro from the HCT donor. This study demonstrated that such T cells were safe, mediated in vivo anti-leukemic activity, and were associated with maintenance of long-term remissions in some patients, but generating sufficient numbers of WT1-specific CD8 T cells with high avidity for the target in each patient represented a substantive problem. Therefore, to create a more predictably effective standardized reagent for treatment of patients with a tumor that expresses the target antigen and shares the associated MHC restricting allele, we pursued methods to genetically engineer patient T cells to acquire high avidity for the tumor target. This requires identifying a high affinity TCR and producing a vector that can achieve high-level expression of the genes encoding the Vα and Vβ genes of a TCR demonstrated to have high affinity for the target epitope. Therefore, we screened a large number of normal repertoires for the presence of high avidity WT1-specific CD8 T cells, and selected the T cell clone expressing the highest affinity TCR. We then incorporated changes in the TCR genes such as codon optimization to enhance expression, and introduced a point mutation in each chain to create a disulfide bond that minimizes the potential problem of mispairing of the introduced TCR chains with the endogenous TCR chains. We have now have now initiated a trial in which this high affinity, WT1-specific, HLA-A2-restricted TCR is being introduced into patient CD8 T cells with a lentiviral vector and the transduced cells are being infused into the patient. The early results from this trial appear promising in terms of both evidence of antileukemic activity and the capacity for the transferred cells to persist in patients, and we plan to begin very shortly another trial in patients with non-small cell lung cancer (NSCLC) utilizing this same TCR, as WT1 is also commonly overexpressed in NSCLC as well as many other malignancies.

For many candidate target antigens that are also normal self-antigens, isolating high affinity TCRs may not be readily achieved from normal repertoires. Therefore, we have developed strategies to enhance the affinity of isolated TCRs with retention of specificity, including saturation mutagenesis of CDR3 regions and an in vitro thymic selection system that allows for capture of a more diverse set of high affinity specific TCR genes during TCR gene rearrangement. These approaches induce modifications to the TCR region that predominantly makes contacts with the peptide epitope rather than MHC, which is necessary to minimize the risk of off-target toxicity from promiscuous peptide/MHC recognition. However, it remains essential that such modified TCRs do not induce unanticipated tissue damage, and we are using bioinformatics as well as modeling in the mouse to uncover any potential for off-target toxicity.

Unfortunately, providing a high avidity T cell response does not necessarily result in tumor eradication, as there are other substantive obstacles that can preclude even a T cell expressing a high affinity TCR from being effective. These impediments include the development of T cell dysfunction, particularly within the microenvironment of solid tumors, and we are using genetically engineered mouse models to elucidate the cellular and molecular pathways that need to be modulated to achieve meaningful therapeutic benefit in a variety of solid tumor settings, including pancreatic and ovarian cancer. Our preclinical therapy studies, particularly in a pancreatic ductal adenocarcinoma (PDA) model, already appear very promising, as we have demonstrated that T cells expressing a high affinity TCR targeting a tumor antigen expressed by PDA cells can infiltrate the tumor, mediate tumor lysis, modify the tumor stroma, and provide therapeutic benefit. We have already identified high affinity human TCRs specific for this tumor antigen, and plan to use the insights derived from these studies to initiate within the next 1-2 years clinical trials in human pancreatic and ovarian cancers.

The genetically-engineered mouse models of spontaneously developing tumors we are using, which recapitulate many aspects of the analogous human cancer, are also making it possible to assess strategies to improve the efficacy of T cell therapy. These models have helped elucidate the importance of not only cell extrinsic mechanisms of regulation and dysfunction that render T cells unresponsive, particularly via inhibitory cells commonly present in the tumor microenvironment that interfere with an effector response such as the accumulation of regulatory CD4 T cells (Treg), myeloid derived suppressor cells (MDSC), and tumor-associated macrophages (TAM), but also the cell intrinsic mechanisms that derive in large part from persistent stimulation by the tumor antigen and ultimately can render T cells progressively dysfunctional, leading to epigenetic modifications that eventually result in non-responsive cells that cannot be readily rescued. These cumulative mechanisms highlight the difficulties eliciting and/or sustaining responses to tumor antigens. Strategies to disrupt inhibitory pathways by systemic administration of mAbs or cytokines are currently being pursued clinically, but such reagents globally disrupt inhibitory pathways which can have significant toxicity to the host. Therefore, we are evaluating strategies to sustain function and anti-tumor activity by genetically modifying T cells to enhance function and to be resistant to obstacles that prevent tumor eradication. As different tumor types exhibit unique characteristics and are capable of engaging distinct inhibitory pathways, improved understanding of the immunobiology of the tumor type to be treated will likely prove essential for designing effective therapies. However, the relatively straightforward means to use synthetic biology to genetically engineer T cells to acquire novel capacities to overcome inhibitory signals and function in the tumor microenvironment suggests that cancer therapy with engineered T cells will likely find an increasing role in the treatment of human cancers.

Citation Format: Philip D. Greenberg, Tom M. Schmitt, Andrea Schietinger, Ingunn M. Stromnes, Sunil R. Hingorani, Shannon K. Oda, Rachel Perret, Kristin G. Anderson, Merav Bar, Aude G. Chapuis. Employing TCRs in engineered T cells to develop therapeutic reagents for effectively targeting malignancies. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr SY31-03. doi:10.1158/1538-7445.AM2015-SY31-03

iNKT/CD1d-antitumor immunotherapy significantly increases the efficacy of therapeutic CpG/peptide-based cancer vaccine

Background

Therapeutic cancer vaccines aim to boost the natural immunity against transformed cancer cells, and a series of adjuvants and co-stimulatory molecules have been proposed to enhance the immune response against weak self-antigens expressed on cancer cells. For instance, a peptide/CpG-based cancer vaccine has been evaluated in several clinical trials and was shown in pre-clinical studies to favor the expansion of effector T versus Tregs cells, resulting in a potent antitumor activity, as compared to other TLR ligands. Alternatively, the adjuvant activity of CD1d-restricted invariant NKT cells (iNKT) on the innate and adaptive immunity is well demonstrated, and several CD1d glycolipid ligands are under pre-clinical and clinical evaluation. Importantly, additive or even synergistic effects have been shown upon combined CD1d/NKT agonists and TLR ligands. The aim of the present study is to combine the activation and tumor targeting of activated iNKT, NK and T cells.

Methods

Activation and tumor targeting of iNKT cells via recombinant α-galactosylceramide (αGC)-loaded CD1d-anti-HER2 fusion protein (CD1d-antitumor) is combined or not with OVA peptide/CpG vaccine. Circulating and intratumoral NK and H-2Kb/OVA-specific CD8 responses are monitored, as well as the state of activation of dendritic cells (DC) with regard to activation markers and IL-12 secretion. The resulting antitumor therapy is tested against established tumor grafts of B16 melanoma cells expressing human HER2 and ovalbumin.

Results

The combined CD1d/iNKT antitumor therapy and CpG/peptide-based immunization leads to optimized expansion of NK and OVA-specific CD8 T cells (CTLs), likely resulting from the maturation of highly pro-inflammatory DCs as seen by a synergistic increase in serum IL-12. The enhanced innate and adaptive immune responses result in higher tumor inhibition that correlates with increased numbers of OVA-specific CTLs at the tumor site. Antibody-mediated depletion experiments further demonstrate that in this context, CTLs rather than NK cells are essential for the enhanced tumor inhibition.

Conclusions

Altogether, our study in mice demonstrates that αGC/CD1d-antitumor fusion protein greatly increases the efficacy of a therapeutic CpG-based cancer vaccine, first as an adjuvant during T cell priming and second, as a therapeutic agent to redirect immune responses to the tumor site.

Electronic supplementary material

The online version of this article (doi:10.1186/s40425-014-0039-8) contains supplementary material, which is available to authorized users.

Adjuvants that improve the ratio of antigen-specific effector to regulatory T cells enhance tumor immunity

Antitumor immunity is strongly influenced by the balance of tumor antigen-specific effector T cells (Teff) and regulatory T cells (Treg). However, the impact that vaccine adjuvants have in regulating the balance of antigen-specific T-cell populations is not well understood. We found that antigen-specific Tregs were induced following subcutaneous vaccination with either OVA or melanoma-derived peptides, with a restricted expansion of Teffs. Addition of the adjuvants CpG-ODN or Poly(I:C) preferentially amplified Teffs over Tregs, dramatically increasing the antigen-specific Teff:Treg ratios and inducing polyfunctional effector cells. In contrast, two other adjuvants, imiquimod and Quil A saponin, favored an expansion of antigen-specific Tregs and failed to increase Teff:Treg ratios. Following therapeutic vaccination of tumor-bearing mice, high ratios of tumor-specific Teffs:Tregs in draining lymph nodes were associated with enhanced CD8(+) T-cell infiltration at the tumor site and a durable rejection of tumors. Vaccine formulations of peptide+CpG-ODN or Poly(I:C) induced selective production of proinflammatory type I cytokines early after vaccination. This environment promoted CD8(+) and CD4(+) Teff expansion over that of antigen-specific Tregs, tipping the Teff to Treg balance to favor effector cells. Our findings advance understanding of the influence of different adjuvants on T-cell populations, facilitating the rational design of more effective cancer vaccines.

MicroRNA-155 is required for effector CD8+ T cell responses to virus infection and cancer

MicroRNAs (miRNAs) regulate the function of several immune cells, but their role in promoting CD8(+) T cell immunity remains unknown. Here we report that miRNA-155 is required for CD8(+) T cell responses to both virus and cancer. In the absence of miRNA-155, accumulation of effector CD8(+) T cells was severely reduced during acute and chronic viral infections and control of virus replication was impaired. Similarly, Mir155(-/-) CD8(+) T cells were ineffective at controlling tumor growth, whereas miRNA-155 overexpression enhanced the antitumor response. miRNA-155 deficiency resulted in accumulation of suppressor of cytokine signaling-1 (SOCS-1) causing defective cytokine signaling through STAT5. Consistently, enforced expression of SOCS-1 in CD8(+) T cells phenocopied the miRNA-155 deficiency, whereas SOCS-1 silencing augmented tumor destruction. These findings identify miRNA-155 and its target SOCS-1 as key regulators of effector CD8(+) T cells that can be modulated to potentiate immunotherapies for infectious diseases and cancer.

CD1d-antibody fusion proteins target iNKT cells to the tumor and trigger long-term therapeutic responses

Despite the well-established antitumor activity of CD1d-restricted invariant natural killer T lymphocytes (iNKT), their use for cancer therapy has remained challenging. This appears to be due to their strong but short-lived activation followed by long-term anergy after a single administration of the CD1d agonist ligand alpha-galactosylceramide (αGC). As a promising alternative, we obtained sustained mouse iNKT cell responses associated with prolonged antitumor effects through repeated administrations of tumor-targeted recombinant sCD1d-antitumor scFv fusion proteins loaded with αGC. Here, we demonstrate that CD1d fusion proteins bound to tumor cells via the antibody fragment specific for a tumor-associated antigen, efficiently activate human iNKT cell lines leading to potent tumor cell lysis. The importance of CD1d tumor targeting was confirmed in tumor-bearing mice in which only the specific tumor-targeted CD1d fusion protein resulted in tumor inhibition of well-established aggressive tumor grafts. The therapeutic efficacy correlated with the repeated activation of iNKT and natural killer cells marked by their release of TH1 cytokines, despite the up-regulation of the co-inhibitory receptor PD-1. Our results demonstrate the superiority of providing the superagonist αGC loaded on recombinant CD1d proteins and support the use of αGC/sCD1d-antitumor fusion proteins to secure a sustained human and mouse iNKT cell activation, while targeting their cytotoxic activity and cytokine release to the tumor site.

Markers of effective anti-tumor CTL populations for adoptive cell therapy (165.5)

Adoptive transfer of in vitro activated, tumor-specific CTL is a useful strategy for cancer immunotherapy. We compared in vitro culture conditions for ability to generate tumor-specific CTL that reject tumours in vivo, and for expression of molecular markers associated with effective anti-tumor activity. Specific CTL were obtained in short-term in vitro cultures of naïve CD8+ T cells and bone marrow DC loaded with peptide antigen, and were expanded in IL-2 for 2 days before transfer in vivo. The conditions of DC activation did not appear to affect the recovery, phenotype or effector function of cultured CTL, but had a substantial effect on the CTL’s ability to prevent tumour growth in vivo. Proteomic analysis of the total and surface proteome of different CTL populations was carried out using liquid chromatography and tandem mass spectrometry. Among more than 1,000 identified proteins, several were expressed with different abundance in CTL populations with varying anti-tumour activity. The functional significance of proteins showing the greatest differential expression is currently being examined using a combination of gene silencing and in vivo transfer studies. The identification of markers associated with effective anti-tumor function will provide useful means to understand and predict the functional activity of CTL populations for in vivo transfer.

Memory T cells in cancer immunotherapy: which CD8 T-cell population provides the best protection against tumours?

Cancer immunotherapy strategies often fail because of immunosuppressive mechanisms present in the tumour-bearing host. Adoptive T-cell transfer therapy circumvents this problem by activating tumour-specific CD8(+) T cells in vitro and transferring them back into the patient. Classically, effector T cells have been used in these studies because of their potent anti-tumour activity. However, it is becoming apparent that highly activated effector cells may become terminally differentiated, display impaired proliferation and survival in vivo, and mediate short-term anti-tumour effects. In contrast to effector cells, memory cells have enhanced proliferative potential and survival, and the potential to provide more robust and enduring protection against tumours. Here, we discuss key studies in the field of adoptive T-cell transfer, along with some of our own results relating to this area. Based on the body of existing research, it is clear that CD8(+) T cells with memory potential are superior to terminally differentiated effectors in mediating successful tumour clearance. Opinions remain divided as to whether the central memory or effector memory T-cell subset is capable of providing the best protection against tumours. We propose that as these cell types have different but complementary benefits for the anti-tumour immune response, the ideal cell population to use for adoptive T-cell transfer should consist of a heterogeneous mixture of memory cells.

Effector lymphoid tissue and its crucial role in protective immunity

It is often argued that T cell-mediated immunity to secondary infection is dependent on the 'accelerated' responses of memory T cells in lymph nodes. However, new evidence points to a crucial role for effector memory T cells, which are resident in peripheral tissues, in immune protection. These T cells, which reside in peripheral tissues, are not necessarily bound by an anatomical structure and can be present at many sites. Collectively, they represent a third functional tissue of the immune system, uniquely specialized to mediate protective immunity. We propose that the paradigm 'effector lymphoid tissue' needs to be articulated and developed as a focus of new research to describe and understand the unique role this tissue has in protective immunity.

Microheterogeneity of serum glycoproteins in patients with chronic alcohol abuse compared with carbohydrate-deficient glycoprotein syndrome type I

BACKGROUND

Chronic alcohol abuse alters the normal N-glycosylation of transferrin, producing the carbohydrate-deficient transferrin isoforms. This alteration could be similar to that present in patients with carbohydrate-deficient glycoprotein syndrome type 1 (CDG1). We thus compared the alterations of N-glycans present in patients with alcoholism and patients with CDG1.

METHODS

The N-glycans of serum glycoproteins were compared in sera of patients with alcoholism, patients with CDG1, and controls by two-dimensional electrophoresis, neuraminidase, peptide:N-glycosidase F, and endoglycosidase F2 treatments. A specific antibody directed against the amino acid sequence surrounding the N-432 N-glycosylation site of transferrin was prepared (SZ-350 antibody).

RESULTS

In patients with alcoholism, the abnormal transferrin and alpha(1)-antitrypsin isoforms were devoid of a variable number of entire N-glycan moieties and were identical with those present in CDG1. In the serum of patients with alcoholism, this finding was less pronounced than in CDG1. In contrast to CDG1, there was no decrease in clusterin or serum amyloid P in patients with alcoholism. The SZ-350 antibody recognized only transferrin isoforms with one or no N-glycan moieties.

CONCLUSION

Antibodies directed against specific N-glycosylation sites of glycoproteins could be useful for developing more specific immunochemical tests for the diagnosis of chronic alcohol abuse.

Is carbohydrate-deficient transferrin a specific marker for alcohol abuse? A study in patients with chronic viral hepatitis

Carbohydrate-deficient transferrin, a transferrin isoform, is hailed as a new marker of chronic alcohol abuse, but its specificity is, however, not unequivocally accepted. The aim of the present study was therefore to determine carbohydrate-deficient transferrin levels in patients with chronic hepatitis B and C with or without documented chronic alcohol intake. Carbohydrate-deficient transferrin was measured using a double-antibody radioimmunoassay (CDTect, Pharmacia) in serum samples from 66 patients (45 males and 21 females; mean age: 39 years) with chronic viral hepatitis B (n = 20) or C (n = 46). Diagnosis of the underlying liver disease was established by liver biopsy. Carbohydrate-deficient transferrin levels were raised in 15 patients [23%; hepatitis B (n = 2) and hepatitis C (n = 13)]. In patients with chronic hepatitis B, the carbohydrate-deficient transferrin level was raised in two abstainers. In the 46 patients with chronic hepatitis C, 10 (22%) patients with an alcohol consumption of < 60 g/day for the men and 30 g/day for the women had raised carbohydrate-deficient transferrin levels. The overall specificity of carbohydrate-deficient transferrin for chronic alcohol abuse was thus 78%, suggesting an association between elevated carbohydrate-deficient transferrin levels and the presence of chronic viral hepatitis. Carbohydrate-deficient transferrin levels were not correlated with the histological grading or staging of chronic hepatitis B and C, or with biological markers of hepatic synthesis and cellular damage. Thus, an increased carbohydrate-deficient transferrin level may occur in patients with chronic viral hepatitis in the absence of chronic alcohol abuse. This fact should be kept in mind by physicians when using this marker to detect alcohol abuse.

Colchicum autumnale agglutinin activates all murine T-lymphocytes but does not induce the proliferation of all activated cells

Plant lectins with mitogenic properties for T-lymphocytes have been particularly useful for the study of T-cell activation and effector functions. In the search for mitogenic lectins possessing activation features different from the ones associated with the already known mitogens, we found that an agglutinin isolated from Colchicum autumnale tubers, Colchicum autumnale agglutinin (CAA), possesses interesting properties. First, contrasting with the classical mitogens, CAA induces the proliferation of a fraction of the CD4+ and CD8+ mouse T-lymphocytes. Second, the CAA-induced proliferation requires MHC class II and CD4 molecules. Third, although only a fraction of T-cells enters into the cell cycle, all T-lymphocytes are activated and express high levels of the activation markers CD69 and CD44. Finally, CAA-stimulation is characterized by a particular pattern of the cytokine gene expression, reflected by the transcription of the IL2, IL5, and IFN-gamma genes, while the IL4 and IL10 genes remained silent. Taken together these data demonstrate that CAA activation does not conform to the pathway of T-cell triggering observed with classical mitogenes and represents a new tool for the analysis of T-cell activation.

Opposite effects of interleukin-4 on memory T helper cell development depend on interleukin-2

We previously reported that cyclosporin A (CSA) promotes the generation of T helper memory cells during antigenic priming of murine spleen cells in vitro. More recently, we have demonstrated that interleukin-2 (IL2) has a downmodulating effect on T helper memory cell generation. The present data address the role of the other T cell growth factor, IL4, upon induction of these cells. The data presented here show that IL4 can interfere with this process: addition of rIL4 to immunosuppressed priming cultures leads to a considerable decrease in the helper activity of the recovered cells. However, in standard cultures, in which IL2 is normally produced, no effect of IL4 on T helper memory cell generation was found. Addition of IL4 has important consequences for cytokines produced upon antigenic restimulation. In standard cultures, IL4 primes for cells expressing high levels of IL2 and IL4 mRNA. Strikingly, in immunosuppressed priming cultures, IL4 counterbalances the CSA-induced blockade of the IFN gamma gene. Taken together, our results suggest that the unique role of IL4 is to drive T helper memory precursors into an IL4 production differentiation pathway. However, IL4 has a downmodulating effect on memory T helper cell induction when IL2 is not produced. These results confirm that synergy between IL2 and IL4 is mandatory for the directive role of IL4 upon IL4-producing cells. Furthermore, the finding that IL4 promotes the induction of IFN gamma in a CSA-resistant pathway represents a new tool for analysis of regulation of the IFN gamma gene.

Interleukin-2 down-modulates memory T helper lymphocyte development during antigenic stimulation in vitro

Using an in vitro antigenic stimulation model of murine spleen cells in the presence of the immunosuppressor cyclosporin A (CSA) we have previously reported that not only does this drug not interfere with the differentiation of T lymphocytes into memory cells it appears to favor this differentiation (Motta, I. et al., Eur. J. Immunol. 1991. 21:551). Because CSA blocks interleukin-2 (IL-2) gene expression, we have analyzed the effect of this cytokine on memory T helper cell development. Murine splenic cells were primed for 6 days with sheep red blood cells (SRBC) in protocols in which either IL-2 was not produced or its biological activity was neutralized by anti-IL-2 receptor (R) antibodies. The helper function of the recovered T cells was revealed by their capacity to help virgin B splenocytes produce anti-SRBC antibodies upon challenge in vitro. We found that CD4+ cells primed in the absence of IL-2, provoked either by IL-2 gene transcription blockade by CSA or by treatment with anti-IL-2R antibodies, afford the best helper functions. These cells exhibit a memory-type phenotype characterized by the low expression of the MEL-14 marker and the high expression of the CD44 marker. Evidence is also presented that memory T helper cells originate in part from naive subset displaying the MEL-14hi phenotype. The pattern of expression of the genes encoding different cytokines (IL-2, IL-4, IL-5 and interferon-gamma) following a secondary antigenic stimulation shows that the helper function of the cells primed in the absence of IL-2 correlates with the up-regulation of the IL-2 and the IL-5 genes. From these data, we conclude that IL-2 plays a major role in the control of memory T helper cell induction.

[Diagnosis of hydroxyapatite disease]

The possibility of detecting hydroxyapatite crystals in synovia in a routine setting has been studied prospectively. Coloration of the crystals with alizarin red-S was the method of choice. The diagnostic results were markedly improved by simultaneous observation of a freshly prepared positive control synovia.

Hybrid polypeptide heavy chains produced by two hybridoma lines

Two anti-TNP antibodies exhibiting unusual features are described. They were obtained in two independent fusions. Spleen cells from CB20 mice sensitized with TNP-Ficoll and challenged with TNP-LPS were fused with SP2/0 myeloma cells. One of these hybridomas, CBT3, secretes antibodies which react with both monospecific anti-gamma 2b and anti-gamma 3 anti-isotypic sera; the second hybridoma, CBT4, secretes antibodies reacting with monospecific anti-mu and anti-gamma 2b sera. Only one type of immunoglobulin is secreted by each hybridoma, ruling out the hypothesis of hybrid molecules formed by distinct heavy chains. These results imply that the two heavy chains are made up from elements encoded by gamma 3 and gamma 2b genes in CBT3 and by gamma 2b and mu genes in CBT4. The molecular mechanisms underlying the production of these singular heavy chains are discussed.

The expression of the sIgD isotype in wild-derived mice

IgD and IgM are concomitantly expressed on the surface of most mouse B lymphocytes and both molecules serve as receptor for antigen. In this communication we report that in contrast to IgM, which is expressed in a constant manner on the surface of spleen B lymphocytes of different laboratory and wild-derived mice, IgD expression is variable among the spleen cells of wild-derived mice. SPE, SEI, and SFM mice belonging to the Mus 3 subgroup show a fluorescence profile characterized by a marked diminution in the population of B lymphocytes expressing the IgD isotype; in addition, these cells have a low sIgD density on their membranes. These findings were confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of the iodinated membrane proteins. Polyclonal in vitro activation with lipopolysaccharide increases the frequency of surface IgD (sIgD)-bearing spleen cells and sIgD density in the SPE strain but decreases both the frequency and the density of IgD bearing cells in the BALB/c strain. This result suggests that delta gene expression is regulated differently in SPE and BALB/c mice. In addition, genetic analysis of sIgD expression in (BALB/c X SPE)F1 hybrids suggests that the proportion of sIgD-bearing cells and sIgD density are independently regulated.

The expression of the sIgD isotype in wild-derived mice

IgD and IgM are concomitantly expressed on the surface of most mouse B lymphocytes and both molecules serve as receptor for antigen. In this communication we report that in contrast to IgM, which is expressed in a constant manner on the surface of spleen B lymphocytes of different laboratory and wild-derived mice, IgD expression is variable among the spleen cells of wild-derived mice. SPE, SEI, and SFM mice belonging to the Mus 3 subgroup show a fluorescence profile characterized by a marked diminution in the population of B lymphocytes expressing the IgD isotype; in addition, these cells have a low sIgD density on their membranes. These findings were confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of the iodinated membrane proteins. Polyclonal in vitro activation with lipopolysaccharide increases the frequency of surface IgD (sIgD)-bearing spleen cells and sIgD density in the SPE strain but decreases both the frequency and the density of IgD bearing cells in the BALB/c strain. This result suggests that delta gene expression is regulated differently in SPE and BALB/c mice. In addition, genetic analysis of sIgD expression in (BALB/c X SPE)F1 hybrids suggests that the proportion of sIgD-bearing cells and sIgD density are independently regulated.

Compression of the right pulmonary artery by aortic aneurysms: CT demonstration

Two cases are presented in which compression of the right pulmonary artery by thoracic aortic aneurysm was demonstrated using dynamic CT. The patients initially presented with symptoms suggestive of pulmonary embolus and were found to have unilateral absence of perfusion on isotope lung scan. Computed tomography was useful in demonstrating pulmonary artery compression by aortic aneurysm as the cause in both cases, and in demonstrating an aortic dissection in one case.

A new approach to immunological memory using thymus-independent antigens

Contrary to what has been reported of thymus-independent antigens, we recently demonstrated that trinitrophenylated lipopolysaccharide (TNP-LPS), a class 1 thymus-independent antigen, elicited an anti-TNP anamnestic response in C57BL/6 mice. The question of whether or not class 2 thymus-independent antigens (DNP-Ficoll and DNP-dextran) could also induce immunological memory in this mouse strain was examined. Evidence induce immunological memory in this mouse strain was examined. Evidence is presented that priming with either of these class 2 thymus-independent antigens resulted in the induction of memory B lymphocytes. However, while the memory cells generated by these two antigens were able to be activated by TNP-LPS, they were not triggered by class 2 thymus-independent antigens. Genetic analysis of the capacity of different mouse strains to mount a secondary response to TNP-LPS revealed that major histo-compatibility-associated genes did not play an essential role, but that IgH-V or closely linked gene(s) controlled the immunological memory to TNP-LPS. These findings are discussed in terms of regulatory phenomena which govern the expression of memory response to thymus-independent antigens.

Differences in helper T-cell sensitivity to anti-thy-1.2 alloantiserum or monoclonal antibody

A Thy-1 alloantigen recognized by a monoclonal antibody which is not present in all strains of mice carrying the Thy-1b allele is reported. Indeed, helper and memory T cells of DBA/2 strain are not eliminated by the monoclonal antibody used in this study.