TCR Expression Research Articles

Deficiency of innate-like T lymphocytes in chronic obstructive pulmonary disease

BackgroundBased on the phenotypic and functional characteristics unconventional T-lymphocytes such as invariant natural killer T (iNKT) cells and mucosal-associated invariant T (MAIT) cells link the innate and adaptive immune responses. Up to now data are scarce about their involvement in pulmonary disorders including chronic obstructive pulmonary disease (COPD). This study explores simultaneously the frequencies of iNKT and MAIT cells in the peripheral blood and sputum of stable and exacerbating COPD patients.MethodsBy means of multicolor flow cytometry frequencies of total iNKT and MAIT cells and their subsets were enumerated in peripheral blood and sputum samples of healthy controls, and COPD patients. In addition, gene expression of TCR for iNKT, MAIT cells, and CD1d, MR1 were assessed by qPCR in the study cohorts.ResultsPercentages of total iNKT and MAIT cells were dramatically dropped in blood, and reduced numbers of iNKT cells were observed in the sputum of COPD patients. Furthermore decreased DN and increased CD4+ iNKT subsets, while increased DN and decreased CD8+ MAIT subpopulations were measured in the blood of COPD patients. Reduced invariant TCR mRNA levels in COPD patients had confirmed these previous findings. The mRNA expression of CD1d and MR1 were increased in stable and exacerbating COPD patients; however both molecules were decreased upon antibiotic and systemic steroid treatments.ConclusionsOur results support the notion that both invariant T-cell populations are affected in COPD. Further detailed analysis of invariant T cells could shed more light into the complex interactions of these lymphocyte groups in COPD pathogenesis.

Cytomegalovirus (CMV) Epitope-Specific CD4+ T Cells Are Inflated in HIV+ CMV+ Subjects.

Select CMV epitopes drive life-long CD8+ T cell memory inflation, but the extent of CD4 memory inflation is poorly studied. CD4+ T cells specific for human CMV (HCMV) are elevated in HIV+ HCMV+ subjects. To determine whether HCMV epitope-specific CD4+ T cell memory inflation occurs during HIV infection, we used HLA-DR7 (DRB1*07:01) tetramers loaded with the glycoprotein B DYSNTHSTRYV (DYS) epitope to characterize circulating CD4+ T cells in coinfected HLA-DR7+ long-term nonprogressor HIV subjects with undetectable HCMV plasma viremia. DYS-specific CD4+ T cells were inflated among these HIV+ subjects compared with those from an HIV- HCMV+ HLA-DR7+ cohort or with HLA-DR7-restricted CD4+ T cells from the HIV-coinfected cohort that were specific for epitopes of HCMV phosphoprotein-65, tetanus toxoid precursor, EBV nuclear Ag 2, or HIV gag protein. Inflated DYS-specific CD4+ T cells consisted of effector memory or effector memory-RA+ subsets with restricted TCRβ usage and nearly monoclonal CDR3 containing novel conserved amino acids. Expression of this near-monoclonal TCR in a Jurkat cell-transfection system validated fine DYS specificity. Inflated cells were polyfunctional, not senescent, and displayed high ex vivo levels of granzyme B, CX3CR1, CD38, or HLA-DR but less often coexpressed CD38+ and HLA-DR+ The inflation mechanism did not involve apoptosis suppression, increased proliferation, or HIV gag cross-reactivity. Instead, the findings suggest that intermittent or chronic expression of epitopes, such as DYS, drive inflation of activated CD4+ T cells that home to endothelial cells and have the potential to mediate cytotoxicity and vascular disease.

Cutting Edge: CD3 ITAM Diversity Is Required for Optimal TCR Signaling and Thymocyte Development.

For the αβ or γδTCR chains to integrate extracellular stimuli into the appropriate intracellular cellular response, they must use the 10 ITAMs found within the CD3 subunits (CD3γε, CD3δε, and ζζ) of the TCR signaling complex. However, it remains unclear whether each specific ITAM sequence of the individual subunit (γεδζ) is required for thymocyte development or whether any particular CD3 ITAM motif is sufficient. In this article, we show that mice utilizing a single ITAM sequence (γ, ε, δ, ζa, ζb, or ζc) at each of the 10 ITAM locations exhibit a substantial reduction in thymic cellularity and limited CD4-CD8- (double-negative) to CD4+CD8+ (double-positive) maturation because of low TCR expression and signaling. Together, the data suggest that ITAM sequence diversity is required for optimal TCR signal transduction and subsequent T cell maturation.

Reproductive cycle-dependent expression of MHC and TCR in vaginal fluid and cells

Anti-HLA class I antibodies have been suggested as a possible cause of fetal and neonatal alloimmune thrombocytopenia (FNAIT). The aim of this study was to characterize maternal anti-HLA class I alloantibodies in suspected cases of FNAIT.The study population consisted of all nationwide referrals of neonates with suspected FNAIT to the National Unit for Platelet Immunology in Tromsø, Norway, during 1998–2009 (cases), and 250 unselected pregnancies originally included in a prospective study (controls). Inclusion criterion was a positive screening for maternal anti-HLA class I antibodies. Neonates with other identifiable causes of thrombocytopenia, including maternal anti-human platelet antigens (HPA) antibodies, were excluded. Ultimately, 50 cases with suspected FNAIT were compared with 60 controls.The median neonatal platelet count nadir among cases was 24 × 109/L (range 4–98 × 109/L). Five children (10%) were reported to have intracranial hemorrhage. Maternal and neonatal HLA class I genotype was available for 33 mother/child pairs (66%). Immunization was not tied to any particular HLA class I antigen. Using epitope mapping, we could demonstrate that the maternal anti-HLA class I antibodies were specific towards mismatched paternally-inherited fetal epitopes, with little reactivity towards any third-party epitopes. Antibody reactivity patterns were similar to those found among controls, although the mean fluorescence intensities (MFI) among cases were significantly higher.This study demonstrates the value of using data on HLA epitope expression, instead of HLA antigens, to examine alloimmune responses in connection with neonatal thrombocytopenia. Our findings support the idea that maternal anti-HLA class I antibodies are involved in FNAIT.

Cutting Edge: Dual TCRα Expression Poses an Autoimmune Hazard by Limiting Regulatory T Cell Generation.

Despite accounting for 10-30% of the T cell population in mice and humans, the role of dual TCR-expressing T cells in immunity remains poorly understood. It has been hypothesized that dual TCR T cells pose an autoimmune hazard by allowing self-reactive TCRs to escape thymic selection. We revisited this hypothesis using the NOD murine model of type 1 diabetes. We bred NOD mice hemizygous at both TCRα and β (TCRα+/- β+/-) loci, rendering them incapable of producing dual TCR T cells. We found that the lack of dual TCRα expression skewed the insulin-specific thymocyte population toward greater regulatory T (Treg) cell commitment, resulting in a more tolerogenic Treg to conventional T cell ratio and protection from diabetes. These data support a novel hypothesis by which dual TCR expression can promote autoimmunity by limiting agonist selection of self-reactive thymocytes into the Treg cell lineage.

Reduced circulating MAIT cells in obesity

Abstract Obesity is a major risk factor for certain types of cancer and the mechanisms by which obesity contributes to tumor metastasis are not well understood. Whereas the immune system is essential for fighting against tumors, in the context of obesity, systemic chronic inflammation with altered immune responses are found. Recent studies have revealed that the gut microbiota also contributes to obesity and the pathology associated with that disease. Mucosal-associated innate T (MAIT) cells are a unique subpopulation of T cells that are characterized by the expression of a semi-invariant TCR a chain (Vα19 in mice; Vα7.2 in humans). Although the development and maturation of MAIT cells require the gut microbiota and antigen presenting molecule MR1, the actual function of MAIT cells has not been well studied. We have found reduced circulating MAIT cells in obese patients as compared to age- and gender-matched healthy donors. Using real-time PCR to determine the expression levels of the invariant TCR of MAIT cells and classical T cell transcription factors, we found that, although no difference was observed in any gene expression analyzed between samples from obese patients or healthy donors, mRNA expression of the Vα7.2 TCR positively correlated with the transcription factor TBX21 (found in T helper 1 cells) and BCL6 (found in follicular helper T cells). Our work suggests that obesity alters the number of MAIT cells. The correlation of MAIT cell TCR gene expression with transcription factors of classical effector T cells, suggests there may be transcriptional pathways linking MAIT cells to the function of conventional T cells. Future work will focus on determining how obesity impacts the function of MAIT cells.

Characterisation of gene-modified CD3-enhanced CD4+ T cells for cancer immunotherapy

Abstract TCR gene transfer is used to redirect the antigen specificity of T lymphocytes towards known tumour antigens. TCR gene therapies in murine studies have shown promising results. However, in the clinic they often generate sub-optimal responses, when compared to treatments with tumour infiltrating lymphocytes. Previous work to improve TCR gene therapy has demonstrated that transferring additional CD3 genes increases TCR expression of both endogenous and introduced TCR in CD4+ and CD8+ T cells. In vivo experiments demonstrated that CD8+ T cells, transduced with TCR and additional CD3 were more effective in tumour protection than T cells transduced with the TCR alone. Whilst, CD4+ T cells transduced with TCR and additional CD3 initially showed improved tumour protection, lethal toxicity, unrelated to tumour burden, was later observed. To investigate the effects of CD3 overexpression, CD3 genes only (no TCR genes) were transferred into purified CD4+ and CD8+ T cells. Following adoptive transfer, CD3-enhanced CD4+ T cells survived for longer and were recovered in higher percentages in spleen, lymph nodes, bone marrow and liver, compared to CD3-enhanced CD8+ T cells and mock transduced CD4+ T cells. The same trend was also seen in competition experiments where mice received a 1:1 ratio of CD3-enhanced CD4+ T cells and mock-transduced CD4+ T cells. Interestingly, this was observed despite a twofold downregulation of TCR levels in the CD3-enhanced CD4+ T cells, compared to their pre-transfer TCR levels. Current experiments are aimed at dissecting the mechanisms responsible for, and the physiological implications of the observed TCR downregulation.

Dual TCRα expression alters agonist selection, redirecting Treg-biased insulin-specific thymocytes into the conventional T cell lineage

Abstract Despite accounting for ~10% of the T cell population in mice and humans, the role of dual TCR-expressing T cells in immunity remains poorly understood. It has been hypothesized that dual TCR T cells pose an “autoimmune hazard” by allowing self-reactive TCRs to escape negative selection. We revisited this hypothesis using the non-obese diabetic (NOD) mouse model of type 1 diabetes (T1D). We bred NOD mice hemizygous at both TCRα and β (TCRα+/− β+/−) loci, rendering them incapable of producing dual TCR T cells. We found that NOD mice lacking dual TCRα expression were resistant to developing diabetes resulting from an increased insulin-specific Treg:Tconv ratio. Furthermore, early depletion of CD25-expressing cells was sufficient to induce diabetes in single TCR T cell NOD mice demonstrating that these mice are capable of developing diabetes and that Treg cells are responsible for their observed resistance to diabetes. Further investigation uncovered a previously-unrecognized impact of dual TCRα expression on agonist selection. Specifically, we found in single TCR T cell mice that single positive (SP) thymocytes had a higher Treg:CD4 ratio indicating increased Treg commitment, that insulin-specific thymocytes exhibited higher CD5 expression suggesting increased TCR signaling, and that deletion of SP thymocytes was reduced. Altogether these data demonstrate that dual TCRα expression perturbs agonist selection of the insulin-specific thymocyte subset, resulting in skewing of this population toward the diabetogenic conventional CD4+ T cell lineage and away from the regulatory T cell lineage. Thus, dual TCR expression can promote autoimmunity by reducing the ratio of protective Treg cells to pathogenic T cells.

Highlights of This Issue

Fc-gamma receptor (FCGR) genotypes have been shown to influence patient outcome following treatment with mAb-based immunotherapeutics in different cancer settings. Erbe and colleagues show that those FCGR SNP genotypes (FCGR2A, FCGR3A, and FCGR2C) related to greater FCGR function, associate with better response following treatment with IL2 (i.e., not an mAb-based immunotherapeutic) for metastatic renal cell carcinoma patients. This work raises important questions regarding endogenous antibody responses potentially involved, either in ADCC or in antibody facilitated antigen presentation, in a variety of therapies where a role for endogenous antibody influence was not previously considered.MYD88 mutations, notably the L265P variant, are a distinguishing feature of ABC subtype DLBCL. To explore the genomic profiles of MYD88 mutant DLBCL, Dubois and colleagues studied 361 DLBCL cases submitted to next generation sequencing, gene expression profiling, and clinical and prognostic analyses. Distinct genomic profiles for MYD88 L265P and non-L265P mutant DLBCL were highlighted; clustering analysis also segregated subgroups per associated alterations among patients with the same MYD88 mutation. Importantly, the survival of MYD88 L265P mutant ABC DLBCL was significantly improved by associated CD79B mutations. This study emphasizes the importance of genomic profiling to stratify patients for targeted therapy.Ren and colleagues established a method of high-efficient multiplex CRISPR/Cas9 editing to create triple-disrupted CAR T cells by electroporating the CAR T cells with RNA of CAS9 and gRNAs. The study shows the simultaneous and highly efficient disruption of the TCR and HLA expression so that universal CAR T cells can be produced. Checkpoint-resistant universal CAR T cells via additional disruption of PD1 showed improved antitumor efficacy in preclinical mouse models. The study shows highly efficient triple ablation (80%) in primary human T cells and that the efficiency of multiplex genetic editing has been sufficient to support future clinical trials.Cancer cells shape the microenvironment to promote malignancy by secreted factors. Tzeng and colleagues show that Rab37 small GTPase mediates the cross-talk between cancer cells and endothelial cells via exocytosis of antiangiogenic thrombospondin-1 (TSP1) for suppressing neoangiogenesis in esophageal squamous cell carcinoma (ESCC). Rab37-mediated exocytosis of TSP1 from cancer cells inhibited the activation of FAK/paxillin/ERK migration signaling in both cancer cells and their surrounding endothelial cells. Dysfunction of Rab37/TSP1 axis impaired the suppressive effects on tumor neovasculature and correlated with poor prognosis. The findings indicate a potential therapeutic value of targeting this pathway to treat ESCC.

654 Monitoring malignant T-cell clones by direct TCR expression assay in patients with leukemic cutaneous T-cell lymphoma over extracorporeal photopheresis

654 Monitoring malignant T-cell clones by direct TCR expression assay in patients with leukemic cutaneous T-cell lymphoma over extracorporeal photopheresis

A new mechanism shapes the naïve CD8+ T cell repertoire: the selection for full diversity.

During thymic T cell differentiation, TCR repertoires are shaped by negative, positive and agonist selection. In the thymus and in the periphery, repertoires are also shaped by strong inter-clonal and intra-clonal competition to survive death by neglect. Understanding the impact of these events on the T cell repertoire requires direct evaluation of TCR expression in peripheral naïve T cells. Several studies have evaluated TCR diversity, with contradictory results. Some of these studies had intrinsic technical limitations since they used material obtained from T cell pools, preventing the direct evaluation of clonal sizes. Indeed with these approaches, identical TCRs may correspond to different cells expressing the same receptor, or to several amplicons from the same T cell. We here overcame this limitation by evaluating TCRB expression in individual naïve CD8+ T cells. Of the 2269 Tcrb sequences we obtained from 13 mice, 99% were unique. Mathematical analysis of the data showed that the average number of naïve peripheral CD8+ T cells expressing the same TCRB is 1.1 cell. Since TCRA co-expression studies could only increase repertoire diversity, these results reveal that the number of naïve T cells with unique TCRs approaches the number of naïve cells. Since thymocytes undergo multiple rounds of divisions after TCRB rearrangement and 3-5% of thymocytes survive thymic selection events the number of cells expressing the same TCRB was expected to be much higher. Thus, these results suggest a new repertoire selection mechanism, which strongly selects for full TCRB diversity.

A Novel Bioluminescent Mouse Model for Optimization of Adoptive T Cell Therapy

Adoptive T cell therapy (ATT) is a promising option for the treatment of solid cancers. However, various defense mechanisms acquired by the tumor during evolution prevent transferred T cells (TC) to unfold their full potential. A combination of ATT with accessory therapeutic approaches including checkpoint inhibition and targeted therapy could lift TC inhibition and efficiently shift the immune balance towards tumor rejection. An in-vivo analysis of the impact of combination strategies on the outcome of ATT would greatly enhance the search for an optimal accessory to ATT therapy.We generated the transgenic mouse line BLITC (bioluminescence imaging of T cells) expressing an NFAT (nuclear factor of activated T cell)-dependent Click-beetle luciferase (Na et. al, 2010) and a constitutive Renilla Luciferase, allowing us to monitor migration and activation of transferred TCs in vivo. In order to analyze crucial ATT parameters in a clinically relevant tumor model, BLITC mice were crossed to the two HY-TCR transgenic mice Marilyn (CD4: H-2Ab-Dby) and MataHari (CD8: H-2Db-Uty) to generate TCs that could be monitored for in-vivo infiltration, local activation and rejection of established (> 0,5 cm x 0,5 cm / ≥10 days growth) H-Y expressing MB49 tumors. In order to better reflect the clinical situation, we lymphodepleted tumor-bearing immunocompetent albino B6 mice with fludarabine (FLu) and/or cyclophosphamide (CTX) prior to ATT. Transferred TCs were FACSorted and injected after an optional culture expansion phase.As shown before for freshly injected tumor cells (Perez-Diez, 2007), we observed a superior response of tumor-antigen specific CD4+ TCs compared to CD8+ TCs against established tumors. Whereas 5*106 CD8+ T cells hardly attenuated tumor growth, even as few as 5000 H-Y TCR-transgenic CD4+ T cells rejected tumors in most mice, depending on the lymphodepleting treatment (Figure A - remission rates in parentheses). Tumor infiltration and activation of adoptively transferred TCs was monitored in-vivo by the respective bioluminescent reporters. Around day 4 and 6, CD4+ TCs migrated from tumor-draining lymph nodes into the tumor environment and persisted until rejection. Interestingly, activation of CD4+ TCs was only transient (between days 4 and 7) in all mice, independent of therapy outcome (in Figure B shown for refractory tumor). Whereas loss of activation signal during remission was correlated with tumor clearance and decline of effector function, in refractory tumors it suggests a rapid inactivation of infiltrating TCs by the tumor microenvironment. Our data indicate that the failure of tumor rejection is not caused by impaired peripheral expansion or tumor homing but rather by inhibition of TC effector function. Responsible mechanisms and counter-acting therapeutic interventions are the focus of ongoing studies.In summary, the BLITC reporter system facilitates analysis of therapeutic parameters for ATT in a well-established solid tumor model. Using BLITC mice for transduction with TCR or CAR expression cassettes could allow rapid monitoring of on-target as well as undesired off-target effects in virtually any tumor setting. Future experiments will focus on the beneficial effects of combination treatments on the activation of adoptively transferred TCs. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Phase II Study of the Combination of Interleukin-2 with Zoledronic Acid As Maintenance Therapy Following Autologous Stem Cell Transplant in Patients with Multiple Myeloma

Background:Multiple myeloma is still today an incurable disease. The many therapeutic techniques and new therapies proposed in recent years have extended survival but did not allow for healing. Further study allowed to demonstrate that a maintenance could be useful to control the progression of disease. However, there is no clear indication for which maintenance has to be used after a first line of induction therapy. The technique of allograft, used in patients at highest risk, demonstrates that the immune response to the residual disease plays a key role in the success of this technique. Among the major players in response to myeloma, in allogeneic stem cell transplantation, gamma delta lymphocytes play a significant action: complete response after allogeneic few months later (also the molecular level) happen in parallel with the presence in the bone marrow of a significant proportion of lymphocytes with gamma delta oligoclonal expression of TCR rearrangements.Zoledronic acid induces proliferation of these cells by the production of several cytokines, in particular interleukin-2 (IL-2). Furthermore, T lymphocytes Vdelta2 are proved to be crucial antineoplastic mediators and, after expansion in vitro, capable of controlling tumor growth in animal models. These data confirm the hypothesis that gammadelta lymphocytes have a role in controlling the growth of myeloma plasma cells and can be active on the residual disease after autologous stem cell transplant. We planned to evaluate the role of the association of Zoledronate and IL-2 in vivo as post ASCT maintenance therapy in patients with newly diagnosed multiple myeloma (NDMM).Methods:This is a single arm phase II multicenter ongoing study of the combination of IL-2 with zoledronic acid as maintenance therapy for NDMM patients post ASCT. The primary objective was to establish safety and efficacy of IL-2 as maintenance therapy. The secondary objective was to evaluate the immunological expansion of gamma delta lymphocytes. Eligible patients had undergone ASCT, with melphalan as a preparative regimen. At July 2016, forty two patients in very good partial remission (VGPR) have been enrolled in the study (total planned enrollment: 43 pts) and started maintenance therapy 90-180 days post ASCT.Maintenance schedule included IL2 and zoledronic acid. IL2 was administered at a fixed dose of 2 x 106UI from day 1 to day 7 for the first cycle and with the maximum tolerated dose (up to a max of 8 x 106UI) from day 1 to day 7 for subsequent cycles (dose escalation of 25% in each cycle in the absence of toxicity). Zoledronic acid was infused 4 mg iv on day 2. This dosing regimen is repeated every 28 days until disease progression. Adverse events were graded by NCI-CTCAE v4. Response was assessed by the modified International Uniform Response Criteria.Results and toxicity:42 patients (pts) have been enrolled with a median age of 59 (range 42-72); 50% were male and 50% female. All the 42 pts have received a median of 11 cycles (range 1-23). Of the 42 pts 21 remain on therapy (data at July 2016), 21 pts are off study: 9 due to progressive disease (PD) and 12 due to consent withdrawal. Among the 9 pts with PD, the median PFS post ASCT was 12 months (2-18 months). Of the 42 pts, 33 (79%) not progressed after a median of 13 months (range 1-33) and the median PFS has not been reached. 7/42 patients (17%) reached complete remission. Peripheral and bone marrow analysis of gamma delta lymphocytes expansion to evaluate the level of immune response is still under examination.Grade 1/2 hematologic adverse events (AEs) included: grade 1 (G1) anemia (3 pts), G1 neutropenia (3). Grade 1/2 drug-related non-hematologic AEs included: G1 fever (25) G2 fever (8); G2 constitutional symptoms (joint pains) (20); G2 constipation (4); G1/2 nausea (10); G1 fatigue (15), G1/2 cutaneous rash (2).Conclusions:Long term administration of combination of IL-2/zoledronate as maintenance therapy post ASCT is feasible. The incidence of non hematologic adverse events (in particular fever) were manageable with no dose escalation of IL-2 over 5 x 106UI. This immunological approach, without any chemotherapeutic drug, seems to be able to control the disease and to obtain the complete remission in a subgroup of myeloma patients. DisclosuresNo relevant conflicts of interest to declare.

Artificial Thymic Organoids Permit Allelic Exclusion and Efficient Generation of Naïve TCR-Engineered T-Cells from Human Hematopoietic Stem Cells In Vitro

Engineered adoptive immunotherapies have shown unprecedented activity in the treatment of cancer and chronic viral infections. Current approaches rely on individualized ex vivo genetic modification of autologous T cells due to the risk of graft-versus-host disease from allogeneic T cells. These processes furthermore require activation and prolonged expansion of T cells, which may reduce in vivo efficacy and persistence. Direct in vitro differentiation of engineered T cells from hematopoietic stem and progenitor cells (HSPCs) may overcome these problems by permitting the suppression of endogenous TCR expression through allelic exclusion, and the de novo generation of naïve antigen-specific T cells. Existing methods of in vitro human T cell differentiation are subject to wide experimental variability and do not adequately support the positive selection of immature T cell precursors to mature T cells, and thus have not been suitable for clinical-scale production of engineered T cells.We report here the preclinical development of an artificial thymic organoid (ATO) system using off-the-shelf, serum-free components and a standardized stromal cell line that supports highly efficient in vitro differentiation and positive selection of native and TCR-engineered human T cells from cord blood (CB), bone marrow, and mobilized peripheral blood CD34+ HSPCs, and purified CD34+CD38- hematopoietic stem cells. ATOs closely recapitulated thymic T cell commitment and differentiation, resulting in greater than 80% CD7+CD5+ T-lineage cells and 50% CD4+CD8+ double positive (DP) T cell precursors by 4 weeks. By 6 weeks, 30-40% of ATO cells were CD3+TCRαβ+ T cells, of which 20-30% were mature CD8 single positive (SP) T cells. CD4SP cells were generated at a lower frequency and later in culture (2-14% of CD3+TCRαβ+ cells). ATO-derived T cells exhibited a naïve CD45RA+CD27+CCR7+CD62L+ phenotype, a diverse, thymic-like TCR repertoire, and robust TCR-dependent cytokine release and proliferation.Transduction of CB CD34+ HSPCs with an HLA-A*02:01-restricted αβ TCR specific for NY-ESO-1 resulted in a markedly increased cell output per ATO (>400-fold, relative to input HSPCs) and enhanced generation of naïve CD3+TCRαβ+CD8αβ+ conventional T cells, the majority of which were antigen-specific by tetramer staining. Positive selection of TCR-engineered naïve T cells could be further enhanced by expression of cognate HLA-A*02:01 in ATO stromal cells. ATO-derived TCR-engineered T cells exhibited a near complete lack of endogenous TCR Vβ expression, consistent with induction of allelic exclusion by the exogenous TCR during T cell development. ATO-derived engineered T cells underwent antigen-specific cytotoxic priming, polyfunctional cytokine release, and proliferation in response to artificial APCs; and exhibited antigen-specific killing of NY-ESO-1+ tumor cells in vitro and in vivo.ATOs thus present a highly efficient off-the-shelf platform for the generation of clinically relevant numbers of naïve and potentially non-alloreactive engineered T cells for adoptive immunotherapy. Clinical translation of the ATO system will be aided by its simplicity, scalability, use of serum-free components, and compatibility with irradiated stromal cells. In addition, genetic manipulation of stem or stromal cell components can be easily incorporated into the system to further enhance downstream T cell engraftment or function. DisclosuresSeet:Kite Pharma: Patents & Royalties: Kite Pharma holds an exclusive license to certain intellectual property. Montel-Hagen:Kite Pharma: Patents & Royalties: Kite Pharma holds an exclusive license to certain intellectual property. Crooks:Kite Pharma: Patents & Royalties: Kite Pharma holds an exclusive license to certain intellectual property, Research Funding.

Dok-1 and Dok-2 Regulate the Formation of Memory CD8+ T Cells.

Diverse signals received by CD8+ T cells are integrated to achieve the required magnitude of cell expansion and the appropriate balance of effector/memory CD8+ T cell generation. Notably, the strength and nature of TCR signaling influence the differentiation and functional capacity of effector and memory CD8+ T cells. Dok-1 and Dok-2, the two members of the Dok family expressed in T cells, negatively regulate TCR signaling in vitro. However, the role of Dok proteins in modulating T cell function in vivo has not yet studied. We studied the function of Dok-1 and Dok-2 proteins in the regulation of the CD8+ T cell response to vaccinia virus infection. Comparison of responses to vaccinia virus expressing OVA peptide SIINFEKL by wild-type and Dok-1/2-/- CD8+ OT-I cells showed that the absence of Dok-1 and Dok-2 slightly reduced the magnitude of virus-specific effector CD8+ T cell expansion. This was not due to reduced proliferation or enhanced apoptosis of effector CD8+ T cells. Dok-1/2-deficient effector CD8+ T cells showed increased cell surface TCR expression following virus infection in vivo and increased expression of granzyme B and TNF upon stimulation with peptide Ag ex vivo. Finally, Dok-1/2-deficient effector CD8+ T had a severe defect in survival that resulted in impaired generation of memory CD8+ T cells. These results reveal the critical involvement of Dok-1 and Dok-2 in a negative-feedback loop that prevents overactivation of CD8+ T cells and promotes memory formation.

Rapid identification and expression of human TCRs in retrogenic mice

Single-cell paired TCR identification is a powerful tool, but has been limited in its previous incompatibility with further functional analysis. The current protocol describes a method to clone and functionally evaluate in vivo TCRs derived from single antigen-responsive human T cells and monoclonal T cell lines. We have improved upon current PCR-based TCR sequencing protocols by developing primers that allow amplification of human TCRα and TCRβ variable regions, while incorporating specific restriction cut sites for direct subcloning into the template retroviral vector. This streamlined approach for generating human:mouse chimeric TCR vectors allows for rapid TCR expression in humanized-retrogenic (hu-Rg) mice through retroviral mediated stem cell gene transfer. Using widely available techniques and equipment, this method is easily adaptable by most laboratories. This is the first TCR identification protocol that is efficiently combined with subsequent in vivo TCR expression.

Abstract 2309: T-cell development from T cell-derived induced pluripotent stem cell

Abstract The ability to differentiate T cells of defined specificity and function from T-cell derived induced pluripotent stem cells (TiPSC) may be useful for the treatment of a range of pathologies, including cancer, infection and immune deficits. We recently reported that genetic engineering of TiPSC to express a Chimeric Antigen Receptor (CAR) is an effective strategy to combine the unlimited availability of TiPSC and facilitate reprogramming of the T cell specificity and functional potential. In vivo, CD19-retargeted human TiPS-derived CAR T cells (CARTiPSC-T) display therapeutic potency in a lymphoma model. Surprisingly, despite expression of the endogenous αβ TCR, the CARTiPSC-T cells possessed innate-like phenotype and function, most similar to γδ T cells. Although innate T cells have anti-tumor activity, they lack some vital features for therapeutic efficacy including long-term memory and in vivo persistence, which characterize mature CD8+ and CD4+ αβ TCR T cells. Additional research into the mechanisms underlying in vitro T cell differentiation of TiPSC is required to improve the development of mature TCRαβ T cells and facilitate the employment of their therapeutic potential. T cell lineage determination depends in part on the balance between Notch and TCR signaling, we are investigating their respective roles, as well as that of the CAR, in determining lineage commitment. We hypothesize that the combined CAR and early CD3/TCRαβ expression disrupts the TCR/Notch signaling balance, prohibiting mature TCRαβ T cell development. To study the effects of the different Notch ligands, TiPSC were differentiated on OP9 cells expressing one of four Notch ligands (DLL1, DLL4, Jagged-1 or Jagged-2). Preliminary data suggests that DLL4 is able to facilitate T cell development to CD4/CD8 double positive (DP) stage, however, this is hindered by CAR expression. To determine the role of early TCRαβ expression, elimination of TCRαβ expression was facilitated by targeted disruption of the TCRα constant region using the CRISPR/Cas9 system. Elimination of early TCRαβ expression showed improved development towards DP stage of TiPSC on OP9-DLL1. TiPSC are a valuable system for the study of human T cell differentiation. In addition, and most importantly they are further amenable to genetic engineering with TCRs or CARs, which may be useful for the generation of therapeutic “off-the-shelf”, antigen-specific T cells. Citation Format: Sjoukje J.C. van der Stegen, Maria Themeli, Justin Eyquem, Jorge Mansilla-Soto, Michel Sadelain. T-cell development from T cell-derived induced pluripotent stem cell. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2309.

CAR-engineered precursor T cells (preTs) for leukemia control after hematopoietic stem cell transplantation

Background: Co-transplanted CAR-engineered preTs are an attractive tool for preventing leukemia relapse. The impact on endogenous TCR expression and thereby thymic selection processes remains unclear.

Dual T cell receptor-expressing CD8 T cells potentiate autoreactivity

Abstract Central tolerance serves to eliminate newly developing T cells that express strongly autoreactive T cell receptors. Although central tolerance is efficient in deleting high avidity autoreactive T cells, some lower avidity autoreactive T cells escape negative selection to cause autoimmune diseases. Although tight allelic exclusion limits thymocytes to expressing a single TCRbeta chain, rearrangement of the TCRalpha chain continues unabated until halted by positive selection, enabling thymocytes to express up to two TCRalpha chains and thus two TCRs. Moreover, it has been postulated that pathogenic low avidity autoreactive CD8 T cells may escape central tolerance through expression of a secondary benign TCR that mediates positive selection. To determine the role of dual TCR expressing CD8 T cells in autoreactivity and autoimmunity, we have compared CD8 T cell autoreactivity against the model autoantigen ovalbumin between T cells capable of expressing two TCRs (TCRalpha+/+) versus T cells capable of expressing a single TCR (TCRalpha+/−). TCRalpha+/− CD8 T cells exhibited reduced proliferative capacity upon OVA stimulation relative to TCRalpha+/+ CD8 T cells. In addition, a lower frequency of TCRalpha+/− CD8 T cell effectors produced IFN-gamma upon activation with OVA compared to TCRalpha+/+ CD8 T cell effectors. Taken together, we shown that dual TCR expression by CD8 T cells reduces the efficiency of T cell tolerance and may potentiate T cell autoreactivity. We are investigating whether dual TCR-expressing T cells are key to the pathogenesis of autoimmune diabetes in our mouse model system. Our results will provide valuable insight into the escape mechanisms exploited by pathogenic autoreactive CD8 T cells.

Characterizing the anti-tumor response of T cell receptor gene-modified invariant natural killer T cells

Abstract Human invariant NKT cells represent a distinct lymphocyte population that co-express an invariant antigen receptor and NK surface markers. Classic NKT cells express a restricted T cell receptor that recognizes lipids, such as α-Galactosylceramide (α-GalCer), in the context of CD1d. Activated iNKT cells produce a high level of cytokines, such as IFN- γ, thereby bridging innate and acquired immunity through the activation of other effector cells including dendritic cells (DCs), CD8 T cells, and NK cells. One major hurdle to studying the anti-tumor activity of iNKT cells is that they do not recognize antigens presented by classical MHC molecules and they have unknown tumor antigen specificity. Therefore, we expressed the MHC class I-restricted TIL 1383I TCR in human NKT cells to characterize their biology and tumor antigen-specific response. The 1383I TCR is a CD8 independent, high affinity TCR that recognizes the melanoma antigen, tyrosinase, presented by HLA-A2. Here, we report the expression and function of TIL 1383I TCR transduced human iNKT cells. iNKT cells stimulated with α-GalCer- pulsed DCs are transduced with the retroviral vector encoding the TIL1383I TCR. After confirming TIL 1383I TCR expression in iNKT cells by flow cytometry, we assess their anti-tumor activity and polyfunctionality by intracellular cytokine staining. TIL 1383I TCR transduced iNKT cells produced IFN-γ in response to tyrosinase loaded T2 cells and HLA-A2+/tyrosinase+ melanoma. These findings indicate that genetically engineered iNKT cells are useful to study their biology in the context of antigen specificity, as well as to generate new effector populations for the treatment of cancer patients.