T-cell Lines Research Articles

A survivin-responsive, conditionally replicating adenovirus induces potent cytocidal effects in adult T-cell leukemia/lymphoma

BackgroundAdult T-cell leukemia/lymphoma (ATL) is a peripheral T-cell malignancy caused by long-term human T-cell leukemia virus type I (HTLV-1) infection. Survivin-responsive, conditionally replicating adenoviruses regulated by multiple tumor-specific factors (Surv.m-CRAs), in which the expression of the adenoviral early region 1A gene is regulated by the survivin (BIRC5) promoter, can be used to treat several cancers. As survivin is overexpressed in ATL, we examined the effects of Surv.m-CRAs on ATL-selective replication and survival.MethodsWe tested two ATL cell lines and four HTLV-1-infected T-cell lines. The cells were subjected to infection with either E1-deleted, replication-defective adenoviruses or Surv.m-CRAs at various multiplicities of infection.ResultsStrong activation of survivin promoter was observed in all six cell lines. Moreover, the expression of the coxsackie and adenovirus receptor (CAR), which is important for adenoviral infection, was high in the cell lines. In contrast, we observed the absence of survivin promoter activity and a low expression of CAR in activated peripheral blood lymphocytes (PBLs) from healthy subjects. Surv.m-CRAs actively replicated and induced cytocidal effects in five out of six cell lines; conversely, we observed minimal viral replication and no marked cytotoxicity in normal activated PBLs.ConclusionsThis is the first report demonstrating that Surv.m-CRAs constitute attractive potential anti-ATL agents.

Modulation of MS-like disease by a multi epitope protein is mediated by induction of CD11c+CD11b+Gr1+ myeloid-derived dendritic cells

Specific neutralization of the pathogenic autoimmune cells is the ultimate goal in therapy of Multiple Sclerosis (MS). However, the pathogenic autoimmunity in MS, can be directed against several major target antigens, and therefore targeting pathogenic T-cells directed against a single target antigen is unlikely to be effective. To overcome this multiplicity and the potential complexity of pathogenic autoreactivities in MS, we have put forward the concept of concomitant multi-antigen/multi-epitope targeting as, a conceivably more effective approach to immunotherapy of MS. We constructed an (Experimental Autoimmune Encephalomeylitis (EAE)/MS-related synthetic human Target Autoantigen Gene (MS-shMultiTAG) designed to encode in tandem only EAE/MS related epitopes of all known encephalitogenic proteins. The MS–related protein product (designated Y-MSPc) was immunofunctional and upon tolerogenic administration, it effectively suppressed and reversed EAE induced by a single encephalitogenic protein. Furthermore, Y-MSPc also fully abrogated the development of “complex EAE” induced by a mixture of five encephalitogenic T-cell lines, each specific for a different encephalitogenic epitope of MBP, MOG, PLP, MOBP and OSP. Strikingly, Y-MSPc was consistently more effective than treatment with the single disease-specific peptide or with the peptide cocktail, both in suppressing the development of “classical” or “complex” EAE and in ameliorating ongoing disease. Overall, the modulation of EAE by Y-MSPc was associated with anergizing the pathogenic autoreactive T-cells, downregulation of Th1/Th17 cytokine secretion and upregulation of TGF-β secretion. Moreover, we show that both suppression and treatment of ongoing EAE by tolerogenic administration of Y-MSPc is associated also with a remarkable increase in a unique subset of dendritic-cells (DCs), CD11c+CD11b+Gr1+-myeloid derived DCs in both spleen and CNS of treated mice. These DCs, which are with strong immunoregulatory characteristics and are functional in down-modulation of MS-like-disease displayed increased production of IL-4, IL-10 and TGF-β and low IL-12. Functionally, these myeloid DCs suppress the in-vitro proliferation of myelin-specific T-cells and more importantly, the cells were functional in-vivo, as their adoptive transfer into EAE induced mice resulted in strong suppression of the disease, associated with a remarkable induction of CD4 + FoxP3+ regulatory cells.These results, which highlight the efficacy of “multi-epitope-targeting” agent in induction of functional regulatory CD11c+CD11b+Gr1+myeloid DCs, further indicate the potential role of these DCs in maintaining peripheral tolerance and their involvement in downregulation of MS-like-disease.

Development of a new monoclonal antibody specific to mouse Vγ6 chain.

There are seven Vγ gene segments in the TCR γ chain loci of mice. We developed monoclonal antibodies (mAbs) specific to the Vγ6 chain (Heilig & Tonegawa nomenclature). By immunizing Vγ4/6 KO mice with complementarity-determining region peptides in Vγ6 chains, we generated three hybridomas. These hybridomas produced mAbs capable of cell surface staining of Vγ6/Vδ1 gene-transfected T-cell line lacking TCR as well as of Vγ1- Vγ4- Vγ5- Vγ7- γδ T cells and the CD3high TCRδint γδ T cells in various organs. The location of Vγ6+ γδ T cells, which peaked in the newborn thymus, was associated with mTEC. In vivo administration of clone 1C10-1F7 mAb impaired protection against Klebsiella pneumoniae infection but ameliorated psoriasis-like dermatitis induced by imiquimod treatment. These new mAbs are useful to elucidate the development, location, and functions of Vγ6 γδ T cells in mice.

Naturally processed HLA-DR3-restricted HHV-6B peptides are recognized broadly with polyfunctional and cytotoxic CD4 T-cell responses.

Human herpes virus 6B (HHV-6B) is a widespread virus that infects most people early in infancy and establishes a chronic life-long infection with periodic reactivation. CD4 Tcells have been implicated in control of HHV-6B, but antigenic targets and functional characteristics of the CD4 T-cell response are poorly understood. We identified 25 naturally processed MHC-II peptides, derived from six different HHV-6B proteins, and showed that they were recognized by CD4 T-cell responses in HLA-matched donors. The peptides were identified by mass spectrometry after elution from HLA-DR molecules isolated from HHV-6B-infected Tcells. The peptides showed strong binding to matched HLA alleles and elicited recall T-cell responses in vitro. T-cell lines expanded in vitro were used for functional characterization of the response. Responding cells were mainly CD3+ CD4+ , produced IFN-γ, TNF-α, and low levels of IL-2, alone or in combination, highlighting the presence of polyfunctional Tcells in the overall response. Many of the responding cells mobilized CD107a, stored granzyme B, and mediated specific killing of peptide-pulsed target cells. These results highlight a potential role for polyfunctional cytotoxic CD4 Tcells in the long-term control of HHV-6B infection.

Optimization of the T2 HLA-A2 shift assay for testing of the biological activity of immunotherapies

Abstract T2 is a lymphoma-derived cell line that express low amounts of HLA-A2 on the cell surface due to TAP deficiency and can only present exogenous peptides. Binding of exogenous peptides to HLA-A2 stabilizes the HLA-A2- peptide complexes and can be detected using immunofluorescence staining. The T2 cell line is commonly used for identification and analysis of novel HLA-A2-restricted CTL epitopes in the assay known as T2 shift. In this study we evaluated parameters that may influence the T2 shift assay performance and considered new applications of this method for testing of the biological activity of peptide-based immunotherapies. Method optimization was performed using HLA-A2-restricted peptide SurA2.M alone and in the context of a peptide-based immunotherapy drug, DPX-Survivac. DPX-Survivac is a lipid nanoparticle-based formulation that contains five peptides aiming to elicit a CTL response against tumor cells presenting the survivin peptides on HLA class I molecules. Results indicated that performance of the T2 shift assay was highly sensitive to cell passaging intervals, pH variations, cell concentrations and β2-microglobulin concentrations. Discrimination of the T2 cells by either size or granularity did not affect the results for the T2 shift assay. We determined the linear response range for the SurA2.M peptide to be 30-110 μg/mL in the T2 shift assay. The T2 shift assay can detect SurA2.M within the DPX-Survivac matrix. In conclusion, we found that optimal culturing conditions of T2 cells are critical for the T2 shift assay reproducibility and linearity and should be carefully considered if the assay is to be used for quantitative or semi-quantitative evaluation of the peptide activity alone or as a part of an immunotherapeutic drug.

In T-cell lines dually sensitized with antigens from EBV and CMV or from EBV and WT1 the T-cells specific for CMV or WT1 are often restricted by hla alleles that differ from those restricting T-cells specific for EBV

Background & Aim Virus-specific T-cells generated from transplant or 3rd party donors can induce durable remissions of post-transplant severe infections or EBV lymphomas. T-cells simultaneously sensitized with antigens from multiple viruses have also shown promise. We hypothesized that in any individual donor, immunogenic peptides from different viruses might elicit T-cell responses restricted by different HLA alleles. In HLA non-identical patients, the T-cells, specific for one virus or tumor antigen will be effective only if they are restricted by an HLA allele shared by the patient. Methods, Results & Conclusion We analyzed HLA restrictions (HLA-R) of 42 CTL lines generated by dual sensitization with either autologous EBV-transformed B-cells (BLCL) loaded with a pool of overlapping 15-mer peptides spanning the sequence of CMVpp65 (BLCL/CMV CTL) (n=20) or autologous BLCL loaded with a pool of 15-mers spanning the oncofetal protein WT-1 (BLCL/WT1 CTL) (n=22). EBV CTL lines were generated by sensitization with BLCL alone. The HLA-R of the CMVpp65-specific T-cells(CMV-T), WT1 specific T cells (WT1-T) and EBV specific T cells (EBV-T) in each T cell product were assessed by their cytotoxic activity against a panel of Cr51 labeled peptide-loaded dendritic cells and BLCL sharing a single HLA allele with the T cell donor. In 13/20 BLCL/CMV CTL(65%) and 17/22 BLCL/WT1 CTL(77%) the CMV-T or WT1-T were restricted by single HLA alleles. In 10/20(50%) BLCL/CMV CTL, CMV-T and EBV-T in the same line were restricted by the same HLA allele. However, in the other 10(50%) the CMV-T were restricted by an HLA allele different from that of the EBV-T. Similarly, in 13/22(59%) BLCL/WT1 CTL, WT1-T and EBV-T in the same line were restricted by different HLA alleles. In 2/4 BLCL/CMV CTL and 2/5 BLCL/WT1 CTL, in which the HLA-R of CMV-T or WT1-T differed from that of EBV-T in the same culture, the HLA allele differentially presenting CMV or WT1 antigen but not an EBV antigen was a prominent restricting allele of EBV-T in the EBV CTL of the same origin. This suggests that while immunodominant EBV and CMV epitopes presented by certain prevalent HLA alleles such as HLA B0702 or HLA A0201 often induce responses to both viruses, in certain dual-sensitized cultures, immunogenic epitopes from different antigens may compete for presentation by a specific HLA allele or differ in their potential to induce a dominant T-cell response.

Plexin B1 expression on human Treg cells is required for regulation of their phenotypic stability by semaphorin 4A

Abstract We previously reported that neuroimmune semaphorin (Sema) 4A regulates the severity of experimental allergic asthma and increases regulatory T-cell (Treg) numbers in vivo, however the mechanisms of Sema4A action remain unknown. It was also reported that Sema4A controls murine Treg cell function and survival acting through Neuropilin 1 (NRP-1) receptor. To clarify Sema4A action on human T cells, we employed T-cell lines, HuT78 and HuT102, as well as human PBMCs and CD4+ T cells in phenotypic and functional assays. We found that HuT78 demonstrated a T-effector-like phenotype (CD4+CD25lowFoxp3-), while HuT102 expressed a Treg-like phenotype (CD4+CD25hi Foxp3+). Neither cell line expressed NRP-1. However, HuT102 cells expressed high levels of the Sema4A-counter receptor, Plexin B1 whereas HuT78 cells demonstrated high cell-surface expression of Sema4A. All human peripheral blood CD4+ T cells, including Treg cells, expressed PlexinB1 and lacked both, NRP-1 and −2. Culture of HuT cells with soluble Sema4A led to an upregulation of CD25 and Foxp3 markers on HuT102 cells. Addition of soluble Sema4A increased the relative numbers of CD4+CD25+Foxp3+ cells in PBMC and CD4+ T cells which did not express NRP-1 but were PlexinB1+, suggesting the role of this receptor in Treg cell stability. The inclusion of anti-PlexinB1 blocking Ab in cultures before rSema4A addition significantly decreased Treg cell numbers as compared to cultures with rSema4A alone. Sema4A was as effective as TGF-b in iTreg induction from CD4+CD25depleted cells but did not affect Treg cell suppressive activity in vitro. These results suggest strategies for the development of new Sema4A-based therapeutic measures to combat allergic inflammatory diseases.

Evaluation of anticancer activity of α-defensins purified from neutrophils trapped in leukoreduction filters

AimsThe α-defensins or human neutrophil peptides (HNP 1–3) that exist in azurophilic granules are found to have anticancer activity. The pattern of disulfide bonds in α-defensins is crucial for the functional properties. Therefore, synthesis using the chemical and recombinant approaches is a challenging. A safe source for the production of α-defensins can be the use of leukoreduction filters in blood banks that contain large quantities of neutrophils and are discarded after use. The aim of this study was to purify α-defensins from neutrophils trapped in leukofilters and to investigate its anticancer activity. Materials and methodsImmunoprecipitation was performed to purify α-defensins and the presence of protein was confirmed by Western Blot. The Jurkat T-cell line was incubated with different concentrations (5, 10 and 15 μg/ml) of purified HNP1–3 for 16 h. Cell viability was measured using a WST-1 assay and apoptosis was analyzed for Annexin V/PI markers. Caspase-3/7 activity was determined using fluorescence assay. The effects of purified α-defensins were compared to commercial HNP 1–3. Key findingsPurified HNP 1–3 decreased the viability at 10 and 15 μg/ml and commercial HNP 1–3 at 15 μg/ml concentrations. Following to the purified HNP1–3 treatment, the percentage of Annexin V positive population and caspase-3 activity were significantly increased compared to control (p = 0.000 and p = 0.001, respectively) and commercial HNP1–3 (p = 0.034 and p = 0.018, respectively). SignificanceResults indicated the anticancer activity of HNP1–3 which can be used as future chemotherapeutic drugs. Furthermore, leukofilters can be considered as economic source for purifying these peptides.

A standardized methodical approach to characterize the influence of key parameters on the in vitro efficacy of extracorporeal photopheresis.

Extracorporeal photopheresis (ECP) is an autologous immunomodulatory cell therapy that consists of the ex vivo collection of mononuclear cells (MNCs), which are irradiated with UVA in the presence of the photosensitizing agent 8-methoxypsoralen (8-MOP) to induce cell apoptosis. This photoactivated cell preparation is then reinfused into the patient. While the clinical benefits of ECP are well-demonstrated, no study has yet characterized the influence of variations in the composition of the cell preparation on the efficacy of ECP in vitro. Here, we describe a standardized methodology for the in vitro assessment of ECP that uses the human lymphoma T-cell line and mimics the clinical procedure. By quantifying cell apoptosis, inhibition of cell proliferation, and 8-MOP consumption, we used this approach to characterize the specific influence of key variables on the cellular response to ECP. We found that (i) increases in hematocrit and plasma concentrations attenuated the cellular response to ECP; (ii) plasma concentration was the only variable tested that influenced 8-MOP consumption; and (iii) the loss of efficacy due to variations in the concentration of certain blood components could be counteracted by modulating the UVA dose. This methodology may enable evaluation of other leukapheresis preparation protocols and better determination of the optimal working parameters for ECP.

Cells of adult T-cell leukemia evade HTLV-1 Tax/NF-κB hyperactivation–induced senescence

AbstractHuman T-cell leukemia virus type 1 (HTLV-1) is the etiological agent of adult T-cell leukemia/lymphoma (ATL). The HTLV-1 viral trans-activator/oncoprotein Tax is a major driver of ATL, yet it induces rapid p21Cip1/Waf1 (p21)- and p27Kip1-mediated cellular senescence through constitutive activation (hyperactivation) of NF-κB. Although constitutive NF-κB activation is a common feature of T/B-cell leukemia/lymphoma, including ATL, it is not known how ATL cells maintain chronic NF-κB activation without undergoing senescence. Here, we demonstrate that, in contrast to HTLV-1− T-cell lines, ATL cell lines no longer undergo Tax-induced senescence. Although Tax+ and Tax− ATL cell lines showed signatures of constitutive NF-κB activation, their ability to progress through the cell cycle was unaffected. In some cases, ATL cell lines continued to proliferate despite significant upregulation of p21; additionally, many cell lines displayed altered expression of G1 and G1/S cyclins, particularly overexpression of cyclin D2. We propose that, during the course of ATL development, leukemia cells acquire genetic/epigenetic changes that can mitigate the senescence response triggered by NF-κB hyperactivation. Restoring the NF-κB–induced senescence response would likely help to control the development and progression of ATL and similar lymphoid malignancies.

P114 MCH LINKS IMMUNOMETABOLSIM TO INTESTINAL INFLAMMATION

Melanin concentrating hormone (MCH) was first identified as a hypothalamic neuropeptide regulating feeding behavior and energy balance. The MCH receptor, MCHR1, is present in brain as well as in several peripheral tissues including the gastrointestinal tract where its role is yet to be established. Increased MCH and MCHR1 expression in the mucosa of patients with inflammatory bowel disease (IBD) implies a role of MCH in disease pathogenesis. Our previous studies have shown that MCH-deficient mice develop attenuated colitis, a phenotype that was recapitulated when mice were treated with an anti-MCH antibody. The exact mechanisms by which MCH exerts proinflammatory effects remain under investigation, as well as the cell types involved and have been the focus of the present study. We found MCHR1 upregulation in CD4+ T cells isolated from the lamina propria of patients with Crohn’s disease, in contrast to those derived from peripheral blood. In vitro, MCHR1 was induced upon activation of CD4+ T-cells. Furthermore, treatment with MCH of mucosal explants from patients with IBD resulted in increased cytokine secretion in the culture supernatant (IFNg, IL-17, IL-2, IL-6, IL8, MCP1, TNFa). Most importantly, metabolomics analysis of Jurkat cells, a T-cell line expressing high basal levels of MCHR1 receptor, revealed that treatment with MCH increased glutamine, glutamate and a-ketoglutarate levels 4-, 2.5-, and 3.5-fold, respectively, as well as those of acetyl-CoA (3-fold) while glycolytic intermediates remained unaltered. These findings imply engagement of a “reductive carboxylation” cycle in the presence of MCH, the fuel of which is a-ketoglutarate instead of glucose. The role of a-ketoglutarate in driving T-effector activation and differentiation is well established. In further support of these observations, stimulation with MCH resulted in upregulation of the glutamine transporter SLC1A5 that determines intracellular glutamine levels, as well those of its metabolites glutamate and a-ketoglutarate. In relation to the immune phenotype, MCH-induced metabolic shifts correlated with increased proliferation and reduced apoptosis of Jurkat cells, as well as increased IL-2 secretion. In a more relevant context, treatment of isolated CD4+ T cells with MCH under polarized conditions resulted in 70% increase of IL-17+ cells, in contrast to 32% decrease of IL-4+ and 25% decrease of Foxp3+ cells. Collectively, these findings further support a deleterious effect of aberrant MCH signaling in IBD and potentially illustrate a new target in IBD therapeutics.

Variable Immunogenic Potential of Wheat: Prospective for Selection of Innocuous Varieties for Celiac Disease Patients via in vitro Approach.

Celiac Disease (CD) is a multifactorial, autoimmune enteropathy activated by cereal proteins in genetically predisposed individuals carrying HLA DQ2/8 genes. A heterogenous gene combination of the cereal prolamins is documented in different wheat genotypes, which is suggestive of their variable immunogenic potential. In the current study, four wheat varieties (C591, C273, 9D, and K78) identified via in silico analysis were analyzed for immunogenicity by measuring T-cell proliferation rate and levels of inflammatory cytokines (Interferon-γ and Tumor Necrosis Factor-α). Peripheral Blood Mononuclear Cells and biopsy derived T-cell lines isolated from four CD patients in complete remission and two controls were stimulated and cultured in the presence of tissue transglutaminase activated pepsin-trypsin (PT) digest of total gliadin extract from test varieties. The immunogenicity was compared with PBW 621, one of the widely cultivated wheat varieties. Phytohaemagglutinin-p was taken as positive control, along with unstimulated cells as negative control. Rate of cell proliferation (0.318, 0.482; 0.369, 0.337), concentration of IFN- γ (107.4, 99.2; 117.9, 99.7 pg/ml), and TNF- α (453.8, 514.2; 463.8, 514.2 pg/ml) was minimum in cultures supplemented with wheat antigen from C273, when compared with other test varieties and unstimulated cells. Significant difference in toxicity levels among different wheat genotypes to stimulate celiac mucosal T-cells and PBMC's was observed; where C273 manifested least immunogenic response amongst the test varieties analyzed.

Alterations in cellular and viral microRNA and cellular gene expression in Marek's disease virus-transformed T-cell lines treated with sodium butyrate.

A shared feature of herpesviruses is their ability to enter a latent state following an initially lytic infection. Marek's disease virus serotype 1 (MDV-1) is an oncogenic avian herpesvirus. Small RNA profiling studies have suggested that microRNAs (miRNAs) are involved in viral latency. Sodium butyrate treatment is known to induce herpesvirus reactivation. The present study was undertaken to determine transcriptome and miRNome changes induced by sodium butyrate in 2 MDV-transformed cell lines, RP2 and CU115. In the first 24 h post-treatment, microarray analysis of transcriptional changes in cell lines RP2 and CU115 identified 137 and 114 differentially expressed genes, respectively. Small RNA deep-sequencing analysis identified 17 cellular miRNAs that were differentially expressed. The expression of MDV-encoded miRNAs was also altered upon treatment. Many of the genes and miRNAs that are differentially expressed are involved in regulation of the cell cycle, mitosis, DNA metabolism, and lymphocyte differentiation.

Abstract A031: Engineering antigen density sensors for T-cell immunotherapy

Abstract T-cells can be redirected to kill tumor cells via synthetic T-cell receptors known as chimeric antigen receptors (CARs); this approach is becoming a highly promising therapeutic strategy for cancer treatment. Current CAR T-cells, while effective at killing cells expressing the target antigen, fail to discriminate between cells expressing high and low levels of common antigens. Potential target antigens are often also found on normal cells at lower expression levels, and CAR T-cells get activated even by low amounts of target antigen, resulting in potentially deadly toxic effects. We are approaching this problem of antigen density discrimination by using common biochemical mechanisms for cooperative recognition to design new synthetic T-cell receptors. CAR T-cells are highly sensitive to even low densities of the target antigen. Current strategies for generating CAR T-cells consist of selecting antibodies with high affinity since previous studies have shown that the CAR T-cell activity is inversely correlated with the antibody’s affinity. However, these CARs are unable to discriminate between cancer and normal cells based on antigen density. Recent studies suggest that lowering the receptor affinity on a CAR T-cell could increase its selectivity against targeT-cells with different antigen densities. Nevertheless, lowering the affinity is unlikely to provide a sharp density threshold of activation. Instead for a sharp threshold transition from off to on, one would require cooperativity and nonlinear recognition. We have designed a two-step recognition-activation circuit that involves two receptors. In this circuit an initial recognition event alters the potency of a subsequent response. We combined a weak receptor that turns on the activity of a high-affinity receptor that fully activates the cell. For this circuits we have made used of a new class of modular receptors called synthetic notch receptors (SynNotch). SynNotch receptors use antibody-based domains to recognize a target antigen, but when activated, they control transcription via a cleaved transcriptional domain. We have designed and expressed several synNotch/CAR circuits and have tested in vitro their ability to achieve antigen density sensing. These circuits use a synNotch receptor to control the expression of a CAR—all recognizing the same Her2 ligand. The constructs are introduced into T-cells via standard lentiviral infection, and sorted for receptor expression using flow cytometry (anti-myc stain). We have screened candidate receptors for expression and activation response in the human Jurkat T-cell line and human primary CD4+ and CD8+ T-cells from several donors, using standard flow-based assays (e.g. CD69 Activation, T-cell proliferation) and cytokine assays (e.g., IL-2, INF-γ). We are now taking the best circuit candidate and proceeding in mouse models. We have first characterized the growth curves of tumors made by engineered targeT-cells to measure the baseline tumor growth and then I have tested either conventional CAR T-cells or my new engineered T-cells in bilateral tumors into NSG immunocompromised mice, in which one side contains a low-density Her2 K562 tumor, and the other side will contain a higher-density Her2 K562 tumor. The engineered T-cells are injected into the tail vein, and allowed to traffic freely to either tumor. We are monitoring tumor size by caliper over the course of 4 weeks, and tracking the differential clearance of the high- and low-density tumors. We have confirmed that when using a fixed affinity standard CAR T-cell, then cells kill either high- or low-expression-level Her2 tumors with equal efficiency. I have begun parallel mouse experiments with the two receptor circuits that show improved antigen density discrimination in vitro. While still in progress, preliminary results look promising. Citation Format: Rogelio A. Hernandez-Lopez, Wendell A. Lim, Wei Yu. Engineering antigen density sensors for T-cell immunotherapy [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 A031.

P114 MCH LINKS IMMUNOMETABOLSIM TO INTESTINAL INFLAMMATION

Melanin concentrating hormone (MCH) was first identified as a hypothalamic neuropeptide regulating feeding behavior and energy balance. The MCH receptor, MCHR1, is present in brain as well as in several peripheral tissues including the gastrointestinal tract where its role is yet to be established. Increased MCH and MCHR1 expression in the mucosa of patients with inflammatory bowel disease (IBD) implies a role of MCH in disease pathogenesis. Our previous studies have shown that MCH-deficient mice develop attenuated colitis, a phenotype that was recapitulated when mice were treated with an anti-MCH antibody. The exact mechanisms by which MCH exerts proinflammatory effects remain under investigation, as well as the cell types involved and have been the focus of the present study. We found MCHR1 upregulation in CD4+ T cells isolated from the lamina propria of patients with Crohn’s disease, in contrast to those derived from peripheral blood. In vitro, MCHR1 was induced upon activation of CD4+ T-cells. Furthermore, treatment with MCH of mucosal explants from patients with IBD resulted in increased cytokine secretion in the culture supernatant (IFNg, IL-17, IL-2, IL-6, IL8, MCP1, TNFa). Most importantly, metabolomics analysis of Jurkat cells, a T-cell line expressing high basal levels of MCHR1 receptor, revealed that treatment with MCH increased glutamine, glutamate and a-ketoglutarate levels 4-, 2.5-, and 3.5-fold, respectively, as well as those of acetyl-CoA (3-fold) while glycolytic intermediates remained unaltered. These findings imply engagement of a “reductive carboxylation” cycle in the presence of MCH, the fuel of which is a-ketoglutarate instead of glucose. The role of a-ketoglutarate in driving T-effector activation and differentiation is well established. In further support of these observations, stimulation with MCH resulted in upregulation of the glutamine transporter SLC1A5 that determines intracellular glutamine levels, as well those of its metabolites glutamate and a-ketoglutarate. In relation to the immune phenotype, MCH-induced metabolic shifts correlated with increased proliferation and reduced apoptosis of Jurkat cells, as well as increased IL-2 secretion. In a more relevant context, treatment of isolated CD4+ T cells with MCH under polarized conditions resulted in 70% increase of IL-17+ cells, in contrast to 32% decrease of IL-4+ and 25% decrease of Foxp3+ cells. Collectively, these findings further support a deleterious effect of aberrant MCH signaling in IBD and potentially illustrate a new target in IBD therapeutics.

Abstract B137: Preclinical evaluation of a Wilms’ tumor protein 1-targeted interleukin-15 dendritic cell vaccine: T-cell activity and batch production

Abstract Encouraging results from clinical trials demonstrate that dendritic cell (DC) vaccination is a valuable tool in cancer immunotherapy. Empowering DC vaccine immunogenicity to improve clinical outcome is at center stage in the rapidly evolving immunotherapeutic landscape. Developing a unique type of DC vaccine, so-called interleukin (IL)-15 DCs generated with IL-15 and strong immune stimulating maturation signals, we could demonstrate superior in vitro activities at both adaptive as well as innate immunity as compared to gold-standard IL-4 DCs. In this light, IL-15 DCs are capable of activating NK cells and gamma-delta T-cells, whereas IL-4 DCs are not. Designed to induce durable antitumor T-cell immunity, this pre-clinical research focuses on the improvement of Wilms’ Tumor protein 1 (WT1)-targeted T-cell activity. The WT1 antigen is overexpressed in a wide variety of human cancers and thus appears to fulfill the criteria of a universal tumor-associated antigen. The capacity of our novel IL-15 DCs to induce WT1-specific immunity is assessed using two in-house developed tumor antigen-specific T-cell assays. The first series of experiments demonstrate in a head-to-head comparison that WT1 mRNA-electroporated IL-15 DCs perform at least as well as IL-4 DCs in triggering a WT1 T-cell receptor (TCR)-transfected T-cell line. Using an autologous primary TCR-engineered CD8+ T-cell approach, we are now comparing their WT1-specific antitumor function. With its unique characteristics, including IL-15-transpresentation and interferon-gamma secretion, IL-15 DCs are expected to significantly promote WT1-specific T-cell-mediated tumor cell killing. Enabling its clinical application, we also evaluated the upscaled IL 15 DC vaccine production and cryopreservation processes. We were able to employ the three-day culture protocol in clinically suitable culture flasks. In addition, the use of an optimized cryopreservation medium results in a pre- to-post cryopreservation yield of 81.3 ± 7.4 % with a preserved phenotype and functionality. High-scale production and cryopreservation allows for the implementation of DC vaccination in multimodal treatment schedules. Underscoring the tumor antigen-specific T-cell-stimulating capacity among previously described superior characteristics and warranting batch production of patient-specific DC vaccines, further strengthens the impetus to bring WT1-loaded IL-15 DCs to the clinic. Citation Format: Maarten Versteven, David Damoiseaux, Diana Campillo-Davo, Heleen Van Acker, Hans De Reu, Sébastien Anguille, Zwi N Berneman, Evelien L Smits, Viggo F Van Tendeloo, Eva Lion. Preclinical evaluation of a Wilms’ tumor protein 1-targeted interleukin-15 dendritic cell vaccine: T-cell activity and batch production [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 B137.

Antigen Production After Latency Reversal and Expression of Inhibitory Receptors in CD8+ T Cells Limit the Killing of HIV-1 Reactivated Cells.

The so-called shock and kill therapies aim to combine HIV-1 reactivation by latency-reversing agents (LRA) with immune clearance to purge the HIV-1 reservoir. The clinical use of LRA has demonstrated detectable perturbations in the HIV-1 reservoir without measurable reductions to date. Consequently, fundamental questions concerning the limitations of the recognition and killing of LRA-reactivated cells by effector cells such as CD8+ T cells remain to be answered. Here, we developed a novel experimental framework where we combine the use of cytotoxic CD8+ T-cell lines and ex vivo CD8+ T cells from HIV-1-infected individuals with functional assays of LRA-inducible reactivation to delineate immune barriers to clear the reservoir. Our results demonstrate the potential for early recognition and killing of reactivated cells by CD8+ T cells. However, the potency of LRAs when crossing the barrier for antigen presentation in target cells, together with the lack of expression of inhibitory receptors in CD8+ T cells, are critical events to maximize the speed of recognition and the magnitude of the killing of LRA-inducible provirus. Taken together, our findings highlight direct limitations in LRA potency and CD8+ T cell functional status to succeed in the cure of HIV-1 infection.

Chemically modified peanut extract shows increased safety while maintaining immunogenicity.

Peanuts are most responsible for food-induced anaphylaxis in adults in developed countries. An effective and safe immunotherapy is urgently needed. The aim of this study was to investigate the immunogenicity, allergenicity, and immunotherapeutic efficacy of a well-characterized chemically modified peanut extract (MPE) adsorbed to Al(OH)3 . Peanut extract (PE) was modified by reduction and alkylation. Using sera of peanut-allergic patients, competitive IgE-binding assays and mediator release assays were performed. The immunogenicity of MPE was evaluated by measuring activation of human PE-specific T-cell lines and the induction of PE-specific IgG in mice. The safety and efficacy of MPE adsorbed to Al(OH)3 was tested in two mouse models by measuring allergic manifestations upon peanut challenge in peanut-allergic mice. Compared to PE, the IgE-binding and capacity to induce allergic symptoms of MPE were lower in all patients. PE and MPE displayed similar immunogenicity invivo and invitro. In mice sensitized to PE, the threshold for anaphylaxis (drop in BT) upon subcutaneous challenge with PE was 0.01mg, while at 0.3mg MPE no allergic reaction occurred. Anaphylaxis was not observed when PE and MPE were fully adsorbed to Al(OH)3 . Both PE and MPE+Al(OH)3 showed to be efficacious in a model for immunotherapy. In our studies, an Al(OH)3 adsorbed MPE showed reduced allergenicity compared to unmodified PE, while the efficacy of immunotherapy is maintained. The preclinical data presented in this study supports further development of modified peanut allergens for IT.

Leukoreduction system chambers are a reliable cellular source for the manufacturing of T-cell therapeutics.

Following solid organ or hematopoietic cell transplantation, refractory opportunistic viral reactivations are a significant cause of morbidity and mortality but can effectively be controlled by virus-specific T-cell transfer. Among effective and safe strategies is the use of "third-party" (neither from the transplant donor nor recipient) virus-specific T cells that can be manufactured from healthy donors and used as "off-the-shelf" therapies. Leukoreduction system chambers (LRSCs), recovered after routine plateletpheresis, were evaluated as a potential source of peripheral blood mononuclear cells (PBMCs) for the manufacturing of clinical-scale virus-specific T cell. PBMCs from the same donors obtained either from LRSCs or peripheral blood were compared, focusing on T-cell function and phenotype as well as the potential to generate cytomegalovirus (CMV)-specific T-cell lines from both CMV seropositive and seronegative donors. PBMCs from both sources were comparable except for a transient downregulation of CD62L expression on freshly extracted PBMCs from LRSCs. Both nonspecific stimulation using anti-CD3/CD28 antibodies and CMV peptides revealed that LRSCs or blood T cells were equivalent in terms of expansion, differentiation, and function. Moreover, PBMCs from LRSCs can be used to generate autologous monocyte-derived dendritic cells to prime and expand CMV-specific T cells from seronegative donors. LRSCs are a reliable source of PBMCs for the generation of virus-specific T cells for immunotherapy. These findings have implications for the development of third-party therapeutic T-cell products from well-characterized blood product donors.

Alternative to Animal Use for Detecting Biologically Active Staphylococcal Enterotoxin Type A.

Staphylococcal enterotoxins (SEs) are a food safety concern. Existing methods for biologically active SE detection rely on the emetic response in live kittens or monkeys. This method suffers from low sensitivity, poor reproducibility, and causes ethical concerns regarding the use of experimental animals. The Lautenberg Chemical Safety Act encourages the development and adoption of alternatives to testing on animals for chemical toxicity methodologies. In this study, we utilized the superantigenic effect of SE type A (SEA) and used an ex vivo bioassay as an alternative to live animal testing. We found that interleukin-2 (IL-2) secreted by splenocyte can be utilized for quantifiable detection of SEA in food products. To avoid food matrix interference and attenuation of signal, we separated SEA from spiked food products by employing immunomagnetic beads that were coated with an anti-SEA antibody. This ex vivo method has achieved the detection of 1 ng mL−1 of SEA, which is 107 times more sensitive than the existing live animal testing methods. However, this ex vivo bioassay requires sacrificing of mice. To overcome this limitation, we established a cell based in vitro assay using CCRF-CEM, a human CD4+ T-cell line, for the quantitative detection of SEA. Incubation of SEA with CCRF-CEM human T-cells and Raji cells led to quantifiable and dose dependent secretion of IL-2. This novel cell-based assay is highly specific to biologically active SEA, compared with the related SE toxin subtypes B, D, and E or heat inactivated SEA, which produce no secretion of IL-2. This is the first demonstration of an alternative assay that completely eliminates the use of animals for quantitative detection of active SEA.