Killing Of Targets Research Articles

IFITM1 targets HIV-1 latently infected cells for antibody-dependent cytolysis.

HIV-1 persistence in latent reservoirs during antiretroviral therapy (ART) is the main obstacle to virus eradication. To date, there is no marker that adequately identifies latently infected CD4+ T cells in vivo. Using a well-established ex vivo model, we generated latently infected CD4+ T cells and identified interferon-induced transmembrane protein 1 (IFITM1), a transmembrane antiviral factor, as being overexpressed in latently infected cells. By targeting IFITM1, we showed the efficient and specific killing of a latently infected cell line and CD4+ T cells from ART-suppressed patients through antibody-dependent cytolysis. We hypothesize that IFITM1 could mark natural reservoirs, identifying an immune target for killing of latently infected cells. These novel insights could be explored to develop clinical therapeutic approaches to effectively eradicate HIV-1.

Tissue Dimensionality Influences the Functional Response of Cytotoxic T Lymphocyte-Mediated Killing of Targets.

Cytotoxic T lymphocyte (CTL)-mediated killing of virus infections and tumors occurs over a wide range of conditions. The spatial environments in which CTLs encounter target cells vary from narrow vessels, to two-dimensional epithelial tissues, to densely populated 3-dimensional (3D) T cell areas within lymphoid tissues. How such spatial environments alter the functional response of CTL-mediated killing, i.e., how the killing efficiency depends on cell densities, is unclear. In this study, we perform cellular Potts model simulations in different spatial configurations to investigate how the dimensionality of the space affects the functional response of CTL-mediated killing. Irrespective of the spatial configuration, the function with separate saturation constants for CTL and for target cell densities that we previously proposed can in all cases describe the response, demonstrating its generality. However, the tissue dimensionality determines at which cell densities the killing rate starts to saturate. We show that saturation in a fully 3D environment is stronger than in a “flat” 3D environment, which is largely due to accompanying differences in the CTL–target encounter rates.

Obama's War on Terror: “State Secrets Priviledge” and “Target Killing”

Obama's War on Terror: “State Secrets Priviledge” and “Target Killing”

From silent spring to silent night: Agrochemicals and the anthropocene

We are now living in the Anthropocene, the first time in Earth’s history when synthetic chemicals—created by humans—are damaging the planet and contributing to a major loss of biodiversity. Pesticides are a particular problem in this regard. Agricultural practices changed dramatically following World War II. Methods for the production of nitrogen for manufacturing explosives were adapted for use as fertilizer in agriculture. Further, chemicals used to combat insect vectors for disease during World War II were adapted for the control of insect pests in agriculture. Eventually, herbicides used as defoliants to destroy food supplies and aid in combating soldiers using forests as cover, were customized to control weeds in agriculture. The heavy use of pesticides in agriculture has resulted in global exposure to these chemicals. Travelling through water, air, and in migrating animals, pesticides can be found in drinking water reservoirs, the atmosphere, on mountain tops, and even in remote areas in the Arctic where they are not used. The widespread exposure to agrichemicals has altered landscapes and ecosystems around the world. In addition to directly killing non-target organisms, target and non-target organisms can evolve resistance to pesticides, resulting in altered gene pools. Further, emerging data demonstrate that even low— formerly considered “non-toxic”— concentrations of pesticides can impact health, physiology, reproduction and development through endocrine-disrupting effects. The development of genetically modified crops that are resistant to pesticides and that produce pesticides themselves, and the financial incentive of the chemical companies that produce the genetically modified organisms (GMOs) have resulted in increased pesticide applications. There is probably no place on earth that is not affected by pesticides. The solution is the adoption of integrated pest management practices that reduce the use of chemical pesticides and fertilizers in agriculture and the decoupling of the agrichemical and seed industry.

P3.01-041 Anti-Cancer Effect of Hyperoxia on Human Lung Cancer Cells through Oxidative Stress Mediated ERK Signaling: Topic: Functional Biology in Lung Cancer

Abnormal increases in reactive oxygen species (ROS) in cancer cells serves as a target for tumor-selective killing. Also, several experimental and clinical trials studied the effect of the hyperoxia condition by difference of response between normal cells and cancer cells. In this study, the hypothesis tested was that normobaric high oxygen concentration would have anti-cancer effects such as inducing apoptosis on human lung cancer cell line. Human bronchial epithelial cells (Beas-2b) and human alveolar adenocarcinoma cells (A549) were exposed with hyperoxia condition in a time-dependent manner. The changes in the cell morphology, viability and protein expressions such as p53 and ERK were examined after the exposure of hyperoxia (90% O2). In addition, to investigate whether hyperoxia condition affects the production of ROS and cell cycle regulation, cells were analyzed by a flow cytometry. Exposure to the hyperoxia caused morphologic changes such as atypical nuclei and numerous mitotic figures which inhibited the cell viability in a time-dependent manner in A549 (p <0.01). In addition, the colony formation was suppressed selectively in A549 exposed to hyperoxia. Although not statistically significant, A549 exposed to hyperoxia showed increases in the ROS levels compared with Beas-2b. Also, the hyperoxia condition caused a progression delay in the G2/M cell cycle significantly in A549 (p <0.01). In hyperoxia exposed A549 cells, the phosphorylation of ERK 1/2 (p-ERK 1/2) was reduced while the phosphorylation of p53 was increased. This study showed that hyperoxia may have anti-cancer effect by decreasing cell viability and the colony forming ability. ROS generation by hyperoxia may cause to suppress the p-ERK, it related with the activation of p53 and G2/M cell cycle arrest. In conclusion, our data suggests that the anti-cancer effect of hyperoxia may relate to the ROS through oxidative stress mediated ERK signaling and cell arrest.

Potential of long non-coding RNAs in cancer patients: From biomarkers to therapeutic targets.

Because of high specificity and easy detection in the tissues, serum, plasma, urine and saliva, interest in exploring the potential of long non-coding RNAs (lncRNAs) in cancer patients continues to increase. LncRNAs have shown potential as a biomarker in the diagnosis and prognosis of bladder cancer, prostate cancer, gastric cancer, pancreatic cancer, breast cancer and many other cancer types. Some lncRNAs have also been used as adjunct to improve the specificity and sensitivity of existing biomarkers. The molecular tools such as RNA-seq, RNA-FISH, ic-SHAPE and quantitative real-time PCR have been used for examining the lncRNAs' potential. Some lncRNAs such as PCA3 is now routinely used in the clinic for the diagnosis of prostate cancer. Single nucleotide polymorphisms (SNPs) in lncRNAs can also be used as a predictor of cancer risk. Although ongoing studies continue to unravel the underlying mechanism, some lncRNAs have been used as therapeutic targets for the selective killing of cancer cells in patients. Thus lncRNAs are emerging as convenient and minimally invasive diagnostic/prognostic markers, and also as therapeutic target. Companies such as the Curna Inc., MiNA Therapeutics Ltd. and RaNA Therapeutics Inc. have been taking steps to develop lncRNA based strategies against cancer. In this review, we discuss the potential of lncRNAs as biomarkers and therapeutic targets in cancer patients.

Cross-Presentation Is a Source of Tumor Antigens for Multiple Myeloma Immunotherapy

IntroductionMultiple myeloma (MM) remains incurable and accounts for 20% of deaths from hematologic malignancies. Immune modulating drugs and immunotherapy have been shown to be beneficial in MM patients, highlighting the importance of the immune system in MM. The success of these interventions relies on the unique ability of the immune system to specifically distinguish between MM and normal cells. One example involves the use of cytotoxic T-lymphocytes (CTL) that eliminate cancer cells by recognizing tumor specific antigens (TSA) that are presented on human leukocyte antigen (HLA) class I molecules on the tumor cells. TSA are presented on HLA class I via the canonical antigen-processing pathway, which causes the tumor cells to become targets for killing by CTL. On the other hand, exogenous antigens are typically presented on HLA class II molecules. Through cross-presentation, exogenous antigens are taken up and presented on HLA class I molecules. We have recently identified cross-presentation as a mechanism by which tumor cells, including MM, present exogenous antigens, leading to an expanded repertoire of possible tumor antigens that can be targeted. Here we demonstrate that targeting cross-presented antigens is a feasible immunotherapeutic strategy in MM. To this end, we used the anti-PR1/HLA-A2 antibody, 8F4, which effectively eliminates PR1/HLA-A2-expressing tumor cells, and identified novel cross-presented antigens.Experimental designNSG mice were sublethally irradiated with 200 Rad. After 24 hours, 2x106 U266 cells transduced with luciferase/GFP were IV injected. Engraftment was confirmed by measuring human IgE in the mouse serum by ELISA and bioluminescent imaging (BLI). Mice were treated with 8F4 (10 mg/kg), IgG isotype control (10 mg/kg) or PBS. Mice were sacrificed on week 9, bone marrow was harvested and analyzed by flow cytometry.To identify novel cross-presented antigens, polymorphonuclear cells (PMN) were isolated from HLA-A2- healthy donors. PMN were lysed and cultured with U266 cells for 24 hours at a 2:1 PMN:U266 cell ratio. U266 cells were lysed, incubated with anti-HLA-ABC antibody and protein-A/G-sepharose beads. Immunoprecipitated proteins were recovered by mild acid elution and peptides were discovered using tandem mass spectrometry. HLA-A2 specific peptides with strong predicted in silico binding were analyzed using the HLArestrictor 1.2 algorithm.Antigen processing machinery (APM) of primary patient samples were analyzed using western blots.Results8F4 treated mice showed a 2 fold decrease in the percent of U266 in the bone marrow compared to isotype and untreated mice (P<0.05) (Figure 1). ELISA demonstrated approximately a 3-fold decrease in human IgE ng/mL in serum of mice treated with 8F4 (P<0.001). BLI quantification showed approximately a 0.5 fold decrease in total flux (p/s) in mice treated with 8F4 compared to isotype and untreated mice. In addition to illustrating the therapeutic potential of targeting PR1, we also sought to identify other cross-presented MM peptides. Initially, over 4x103 total peptides were discovered by mass spectrometry (Figure 2). Using our reality score indexing and bioinformatics we identified approximately 5x102 unique, high confidence, cross-presented peptides. Our top candidate peptides have predicted HLA-A2 binding affinities of <18 nM, ion scores >21, retention time >30.42 minutes, and are rank 1 for their spectral matches. Since we have demonstrated the capability of MM to cross-present antigens, we investigated whether the APM was dysregulated in MM patients. Patients show dysregulation in tapasin, LMP2/7, and calnexin by western blot analysis.ConclusionCollectively, our data demonstrate that the MM antigen repertoire is much larger than previously appreciated, and that there is a new catalogue of potential immunotherapeutic targets in MM derived from exogenous antigens. [Display omitted] [Display omitted] DisclosuresSergeeva:Astellas Pharma: Patents & Royalties. Molldrem:Astellas Pharma: Patents & Royalties.

Preclinical Analyses Support Clinical Investigation of Combined Anti-CD19 CAR-T Cell, JCAR017 with Ibrutinib for the Treatment of Chronic Lymphocytic Leukemia

Chronic lymphocytic leukemia (CLL) drives systemic immune suppression and T cell dysfunction in patients, highlighting an important consideration in this setting for the manufacturing and efficacy of adoptive cell therapies using autologous T cells. In clinical studies, anti-CD19 CAR-T cells produce durable and complete responses in leukemic and some lymphomatous B cell malignancies. While preconditioning with cyclophosphamide (Cy) and fludarabine (Flu) has improved CAR-T responses in CLL patients, reported complete response rates still have been below 50%; additional therapeutic strategies likely will be required.Ibrutinib, an irreversible inhibitor of BTK, has been approved as a frontline treatment option for patients with CLL. The potent off-BTK activity of ibrutinib on ITK and TEC family kinases could affect CAR T cell biology. Recent work highlighted the ability of ibrutinib to restore CLL patient T cell functionality, enhance CAR-T production and potentially improve clinical efficacy. Additional preclinical work demonstrated improved tumor clearance when anti-CD19 CAR T cells were combined with ibrutinib in several murine tumor models. A preclinical evaluation of the combination between the anti-CD19 CAR-T product, JCAR017, and ibrutinib was performed to determine feasibility for clinical use in CLL. JCAR017 is a second generation CAR-T cell product candidate that contains a 41BB costimulatory endo-domain and is currently in phase 1 trials for non-Hodgkin lymphoma (NHL).A series of in vitro studies assessed the functional activity of JCAR017 cells (derived from 3 healthy donors), in combination with ibrutinib (500-0.05nM), across a dose range covering the cMax and cMin. Cytolytic activity was monitored by co-culturing CAR-T cells with ibrutinib-resistant K562 CD19 tumor cells at an effector-to-target ratio of 2.5:1. Ibrutinib, at concentrations tested, did not inhibit the cytolytic function of JCAR017 cells. For cells derived from some donors, addition of ibrutinib appeared to increase % target killing. To address ibrutinib effects on JCAR017 activation, cell surface markers and cytokines were tracked over 4 days following stimulation with irradiated K562 CD19 cells. We observed no significant effect on JCAR017 surface expression of CD25, CD38, CD39, CD95, CD62L, CCR7, or CD45RO, or of EGFRt, a surrogate transduction marker. With addition of ibrutinib, we observed a modest decrease in the percentage of cells expressing CD69, CD107a and PD-1. With 5 and 50nM of ibrutinib, there was a 19.5% (p<0.01) average increase in IFNγ production. At supraphysiological concentrations (500nM) we observed a 20% (p<0.05) decrease in IL-2 production, suggesting ibrutinib at high concentrations may dampen T cell activation. CAR-T cell expansion after repeated antigen stimulation has been shown to be a predictor of in vivo efficacy. JCAR017 cells stimulated every 3-4 days with irradiated target cells in the presence of ibrutinib showed no inhibition of initial growth. However, after 5 rounds of stimulation, JCAR017 + ibrutinib cells from 1 donor had enhanced proliferation compared to control, untreated cells (p<0.05). Interestingly, after 5 rounds of serial stimulation, we observed an increased proportion of CD4+CXCR3+CRTh2- Th1 cells with 500nM ibrutinib treatment compared to control (p<0.01).We assessed the in vivo anti-tumor activity of JCAR017 in combination with ibrutinib using NSG mice injected with 5x105 Nalm6-luciferase cells. After tumor engraftment, a suboptimal dose (5x105) of JCAR017 cells was transferred to mice and ibrutinib (25 mg/kg qd) was administered for the duration of the study. Ibrutinib treatment alone had no effect on tumor burden compared to vehicle treatment. Mice treated with a suboptimal JCAR017 dose + ibrutinib showed decreased tumor burden (p<0.05) and increased median survival from 44 days to >80 days (p<0.001) compared to the group receiving the suboptimal JCAR017 dose + vehicle. Similar effects were seen in replicate studies using JCAR017 cells produced from multiple donors. Ex vivo evaluation for CAR-T quantitation and immunophenotyping was also performed.Taken together, the results suggest that ibrutinib enhances intrinsic JCAR017 activity and may improve outcomes in CLL patients treated with anti-CD19 CAR T therapy, irrespective of BTK mutational status. A Phase 1b study of JCAR017 in combination with ibrutinib for BTKi R/R CLL is planned. DisclosuresQin:Juno Therapeutics: Employment. Baturevych:Juno Therapeutics: Employment. Mudri:Juno Therapeutics: Employment, Equity Ownership. Salmon:Juno Therapeutics: Employment. Ports:Juno Therapeutics: Employment.

ZW38, a Novel Azymetric Bispecific CD19-Directed CD3 T Cell Engager Antibody Drug Conjugate with Controlled T Cell Activation and Improved B Cell Cytotoxicity

Although blinatumomab is an approved treatment for Philadelphia chromosome negative relapsed or refractory (r/r) precursor-B cell ALL and is under development for r/r B cell NHL, blinatumomab has several limitations impacting fuller therapeutic utility. For instance, blinatumomab therapy requires continuous infusion due to its rapid clearance owing to its size and lack of an antibody Fc and has been associated with potentially life-threatening CNS toxicities and cytokine release syndrome (Viardot A et al, Blood 2016; Goebeler ME et al, J Clin Oncol 2016; Topp et al, Lancet Oncol 2015). In addition, blinatumomab treatment is associated with higher incidence of relapse in patients with high disease burden, and its T cell redirected killing is limited by T cell immunosuppression (e.g. PD-1/PD-L1 up-regulation [Köhnke et al, J Hematol & Oncol 2015]; Treg suppression [Duell et al, ASH abstract 2014]). ZW38 is designed to address each of these limitations and represents a best in class CD19-directed CD3 T cell engager and a novel class of bispecific antibody drug conjugate (ADC).ZW38 contains an Azymetric IgG1-like Fc that carries mutations in the CH2 domain preventing FcgR dependent ADCC and ADCP and exhibits typical IgG1-like PK in rodent studies. Transient expression in mammalian CHO cells demonstrate ZW38 can be expressed at a titre of hundreds mg/L and can be purified using conventional IgG antibody methods and resins with typical IgG step purification yields and high heterodimer purity. Additionally, ZW38 has been conjugated to a microtubule inhibitor that lacks bystander killing.ZW38 antibody paratopes have been engineered to favor T cell-B cell functional engagement and selective target B cell cytotoxicity. In vitro studies demonstrated that ZW38 binds to human CD19+ B cells with >30-fold higher affinity than to human CD3+ T cells. Similar to blinatumomab, ZW38 can redirect the killing of target cancer B cells via T cell subtypes from human PBMC and its cytotoxicity is target B cell dependent. At concentrations that result in efficacious B cell depletion, ZW38 does not overly activate T cells. ZW38 is specifically engineered to induce more ’controlled’ T cell activation than blinatumomab while still mediating sufficient T cell redirected target B cell depletion. ZW38 mediates T cell activation, cytokine release, and proliferation at nanomolar potency. By design, the sufficient, lower cytokine levels necessary for B cell killing may reduce the risk of cytokine release syndrome and T cell anergy. ZW38 exhibited potent growth inhibition in a panel of different B cell ALL and NHL cancer lines including but not limited to: G2, Nalm-6, RS4-11, Daudi, SUDHL-4 and SUDHL-6. In comparison to blinatumomab, ZW38 exhibits superior target B cell depletion in in vitro co-cultures of Raji lymphoma cells and human PBMC (ZW38 depletes > 90% B cells; blinatumomab depletes 20-90% B cells depending on the PBMC donor). In addition, ZW38 was effective in killing target B cells in PBMC cultures in which PD-1 has been up-regulated, which were resistant to blinatumomab killing in this assay. The dual mechanisms of action of ZW38, redirected T cell cytotoxicity and ADC cytotoxicity, may prolong and/or boost response rates, lower the incidence of relapse, and reduce the likelihood of acquired resistance while its ’controlled’ T cell activation profile may reduce the risk of life-threatening and potentially fatal neurotoxicity and CRS. DisclosuresNg:Zymeworks: Employment, Patents & Royalties. Spreter:Zymeworks: Employment, Patents & Royalties. Davies:Zymeworks Biopharmaceuticals: Employment. Wickman:Zymeworks: Employment.

CD16-IL15-CD33 Trispecific Killer Engager (TriKE) Overcomes Cancer-Induced Immune Suppression and Induces Natural Killer Cell-Mediated Control of MDS and AML Via Enhanced Killing Kinetics

Although adoptive transfer of NK cells with IL-2 can induce complete remissions in 30-50% of patients with refractory AML, efficacy is limited by IL-2 mediated induction of Tregs and by lack of antigen specificity. Thus we generated a 161533 trispecific killer engager (TriKE) molecule containing an anti-CD16 scFv to engage NK cells, an anti-CD33 scFv to engage myeloid targets (including myelodysplastic syndrome [MDS]), and a modified IL-15 linker. We have previously shown that this molecule is superior to a 1633 bispecific killer engager (BiKE) in killing of AML targets and that it promotes enhanced survival and in vivo expansion of NK cells. We questioned the mechanism for the increased potency of the 161533 TriKE and if the TriKE could activate the dysfunctional and suppressed NK cells found in patients with MDS. Cryopreserved mononuclear cells (obtained from the NMDP Sample Repository) collected from 8 patients with advanced MDS were tested to investigate how the TriKE might enhance functionality in this setting. Previously we reported that MDS patients have significantly decreased frequencies of NK cells due to increased CD33+ myeloid derived suppressor cells. Our 161533 TriKE enhanced the function of NK cells derived from MDS patients against acute promyelocytic CD33+ leukemia HL-60 tumor targets (Figure 1A), when compared to 1633 BiKE, in a flow cytometry assay measuring NK cell degranulation (% CD107a: 41.8±3.8 vs. 30.3±3.2, p=0.004), and inflammatory cytokine production (% IFNg: 40.7±5.0 vs. 30.0±4.9, p=0.009; % TNFa: 36.9±5.5 vs. 28.4±4.8, p=0.009). State of the art microchip-based live cell imaging was then employed to evaluate NK cell function and contact-to-target dynamics (Figure 1B). Briefly, resting NK cells and HL-60 target cells were stained with distinct dyes and then co-incubated in the presence of BiKE or TriKE in microwells at 37°C and 5% CO2. Cells were then imaged for 12 hours using a Zeiss 880 microscope and analyzed by Matlab. In contrast to those incubated with BiKE, NK cells cultured in the presence of TriKE had augmented cytotoxicity (37%±6% vs. 59%±6%, p=0.02) and killed their targets remarkably faster (time to first target kill = 148±30 min vs. 75±26 min, p< 0.0001). In addition, NK cell serial killers were more common in the presence of TriKE compared to BiKE (number of killed targets ≥3: 18%±7% vs. 9%±1%, p=0.04). Having shown the robust killing dynamics of TriKE primed NK cells, we next designed an in vivo dose escalation study to evaluate HL-60 tumor control in our xenogeneic mouse model. NSG (NOD scid gamma) mice were conditioned with a sub-lethal dose of radiation (275 cGy) and engrafted with 750,000 HL-60luc cells, which allow for tracking of tumor growth using bioluminescent imaging (BLI). Mice were infused with 1 million fresh healthy donor human NK cells and treated daily with recombinant IL-15 (5 ug/injection), 20-200 ug of 161533 TriKE, or left untreated. Higher doses of TriKE provided better tumor control (6.3x109±2.9x109 [200 ug 1615133] vs. 1.6 x1010±2.7x109 [20 ug 161533] p/sec/cm2/sr) demonstrating dose responsiveness at days 14 and 21 This was not due to increased proliferation of effectors (NK cell numbers) induced by the IL-15 segment of the TriKE as the absolute PBNK cell counts in mice were not different across the TriKE concentrations. However, the day 14 and 21 absolute PBNK counts were higher in all of the TriKE groups when compared to the IL-15 treated mice, including in the 20 ug 161533 TriKE group which best matched the 5 ug IL-15 dose. These data indicated that the TriKE molecule mediates superior NK cell expansion or maintenance in vivo. Taken together the in vivo data suggests that 161533 TriKE not only mediates tumor control by inducing NK cell proliferation and survival in a methodology that exceeds signals provided by IL-15 alone, but also increases tumor killing through enhanced killing kinetics. In summary, we have shown that the 161533 TriKE can rescue dysfunctional NK cells suppressed in patients with MDS and can mediate potent in vivo tumor killing presumably through better NK cell maintenance and enhanced killing kinetics This is of translational importance and demonstrates that the cancer induced immune suppression is reversible by the activating signals induced by the TriKE molecule. The 161533 TriKE represents a promising modality to maximizing NK cell based immunotherapies against MDS and AML and will be in phase I clinical testing the first half of 2017. [Display omitted] DisclosuresCooley:Fate Therapeutics: Research Funding. Vallera:Oxis Biotech: Consultancy, Membership on an entity's Board of Directors or advisory committees. Miller:Fate Therapeutics: Consultancy, Research Funding; Oxis Biotech: Consultancy, Other: SAB.

A Novel Humanised ROR1 Bi-Specific T-Cell Engager Molecule for the Treatment of Chronic Lymphocytic Leukaemia

Bispecific T-cell Engagers (BiTEs) are a promising immunotherapeutic approach, usually consisting of two single chain variable fragments (scFv) linked in tandem. One arm binds to tumour-associated antigens, whilst the other binds CD3 on T-cells, facilitating the formation of cytotoxic synapses leading to killing of tumour targets in a MHC and co-stimulatory molecule independent manner. Blinatumomab, the most advanced BiTE in clinic targets CD19 and has shown impressive results in patients with relapsed/refractory B cell acute lymphoid leukaemia but results in elimination of normal and malignant B lymphocytes.Receptor Tyrosine Kinase Like Orphan receptor is a surface antigen expressed on a range of haematological and solid malignancies, including Chronic Lymphocytic Leukaemia (CLL), Acute Lymphoblastic Leukaemia (ALL), and cancer stem cell-like cells (CSC). It is however expressed at low or undetectable levels in normal tissues making it an attractive target for immunotherapy approaches. We generated a panel of novel fully humanised ROR1 antibodies and selected an optimal scFv based on ROR1 binding to use in our BiTE format.Our ROR1 BiTE (ROR1xCD3), at low concentrations, was efficient inducing T-cell mediated cytotoxicity and consequent inflammatory cytokine secretion against a panel of haematopoietic cell lines with constitutive ROR1 expression in vitro. Importantly cytotoxicity was comparable to that seen with a control CD19 BITE. Moreover, ROR1xCD3 led to significant and selective cytotoxicity of primary CLL samples. We transitioned our in vitro studies to animal models and showed that our ROR1xCD3 is able to retard growth of established SKW cells engrafted in immunocompromised mice, as detected by bioluminescence imaging. Additionally ROR1xCD3 improved survival, with the ROR1xCD3 treated cohort showing improved median survival of 50 days compared to control mice of 18 days despite only receiving a single infusion of T-cells.In summary, we have developed a novel ROR1 BiTE able to target an array of haematopoietic malignancies. Our ROR1 BiTE induces T-cell cytotoxicity against ROR1 positive cell lines in vitro and in vivo as well as primary CLL cells and has the potential to be a beneficial therapeutic for CLL. DisclosuresGohil:UCL Business: Patents & Royalties: ROR1 based immunotherapies. Paredes-Moscosso:UCL Business: Patents & Royalties: ROR1 based immunotherapies. Nathwani:UCL Business: Patents & Royalties: ROR1 based Immunotherapies. Della Peruta:UCL Business: Patents & Royalties: ROR1 based immunotherapies.

Bigger, Stronger, Faster: Chimeric Antigen Receptor T Cells Are Olympic Killers

Chimeric antigen receptor T cells (CAR T) re-directed to CD19, have induced remarkable responses in clinical trials for patients with B-cell malignancies. Patients have responded to therapy with a CAR T dose which is a fraction of the pre-existing tumor burden. Explanations for this observation include studies which show the proliferative potential of the CAR T cells (Kalos M et al Sci Transl Med 2011), as well as our recent study which showed that individual CAR T cells can serial kill tumor cells (Davenport AJ et al CIR 2015, Figure 6). Using our dual antigen receptor model (OT-I T cell receptor and 2nd generation HER-2 CAR in the same T cell, termed CAR.OTI cells), we also observed a reproducible and significantly shorter time from CAR- vs TCR-mediated activation to detachment from dying tumor cells (Davenport AJ et al CIR 2015, Figure 4D)suggesting that CAR-mediated individual killing events are actually faster. To explore how this may occur, we examined the immune synapse structure at 20 minutes of CAR.OTI CTL co-culture with tumor cells expressing the cognate antigen for either the CAR or TCR. At this timepoint, CAR.OTI CTL, activated via the TCR, formed a conventional bull's eye immune synapse with accumulation of LCK and actin clearance (Figure 1). Surprisingly, CAR.OTI CTL activated via their CAR had an immune synapse with no or diffuse LCK and small actin rings (Figure 1). At the same timepoint, CAR-activated CAR.OTI CTL conjugates with tumor cells were characterized by a microtubule organizing center (MTOC) distant from the immune synapse LCK accumulation. In contrast TCR activated CAR.OTI CTL conjugates consistently had the MTOC proximal to the LCK accumulation (Figure 2A). Despite this, CAR-mediated CAR.OTI CTL killing of tumor targets was inhibited by a protein kinase C zeta inhibitor and is, therefore, MTOC dependent (Figure 2B). The MTOC circumnavigates the activated CTL nucleus and moves to the immune synapse, bringing cytotoxic granules with it. Using time lapse live video (TLLV) microscopy, we compared CAR.OTI CTL cytotoxic granule movement when the CAR.OTI were activated via the TCR vs CAR. We showed that following CAR vs TCR activation, CAR.OTI cytotoxic granules moved with a significantly higher velocity, and had a shorter time lapse to reach the immune synapse following activation (Ca2+ flux), and a significantly shorter time to detachment from the dying tumor cell (Figure 2C).We then re-examined immune synapse formation at an earlier timepoint, to explore whether the data from Figures 1-2 could be explained by a more rapid CTL response following CAR-mediated signaling. In contrast to our observations at 20 minutes, at five minutes we showed CAR-activated CAR.OTI CTL formed conjugates with tumor targets and the immune synapse showed distinct LCK accumulation and actin clearance (Figure 3A). Finally, we explored CAR.OTI CTL signaling and showed that CAR-mediated activation induced a significantly lower number of Ca2+ fluxes, however each Ca2+ flux amplitude was not different (Figure 3B). We also examined changes in proximal (phospho-LCK, pLCK) and distal (phospho-ERK, pERK) signals in CAR- versus TCR- activated CAR.OTI cells, and showed that CAR-mediated activation induced more rapid proximal and distal activation signals (Figure 3C). In conclusion, this study showed that compared to activation by TCR ligation, T cells respond to CAR ligation with faster phospho-protein signaling, Ca2+ flux, formation of an immune synapse and a more rapid movement of the MTOC and delivery of the cytotoxic granules to kill the tumor cells. Furthermore, LFA-1 did not accumulate at the immune synapse following CAR activation, therefore, reduced adhesion may facilitate the observed rapid detachment from the dying tumor cell, and enable the CAR T to rapidly move onto the next tumor target for 'bigger, stronger, faster' killing. [Display omitted] [Display omitted] [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Continuous IL-15 Signaling Leads to Functional Exhaustion of Human Natural Killer Cells through Metabolic Changes That Alters Their In Vivo Anti-Tumor Activity

Natural Killer (NK) cells represent an exciting immunotherapeutic approach to treat cancer. We have shown that in vivo expansion and activation of donor NK cells supported by administration of IL-2 induces remission in patients with refractory AML. Recent clinical studies by our group have shown that IL-15 is superior to IL-2 to support NK cell persistence 14 days after adoptive transfer. However, only 36% of patients treated with 12 consecutive days of IL-15 had NK cell expansion to the level of ≥100 donor derived NK cells/µL blood compared to 10% in subjects treated with IL-2 (p=0.02). This leads us to conclude that we might not know the optimal route and interval to administer in vivo IL-15. We hypothesized that daily uninterrupted IL-15 dosing could lead to exhaustion or NK cellular stress. Therefore we designed an in vitro model system in which enriched NK cells are treated with three 3-day cycles of continuous IL-15 (IL-15cont) or were rested with a "gap" (skipping the middle cycle [IL-15gap]) before returning to the last cycle of IL-15. IL-15cont treatment yielded more proliferation and higher cell numbers compared to IL-15gap (4.8±0.44 vs. 1.9±0.26 million cells/ml, p < 0.0001) when cells were analyzed at the end of the three cycles (on day 9, where all in vitro measurements were taken). However, NK cell death, measured by flow cytometry, in the IL-15cont group was higher (18.9±2.2 vs 14.9±1.7 % cell death, p = 0.035) and this group also had an enrichment in genes involved in cell cycle checkpoint/ arrest, perhaps indicating more cellular stress in the IL-15cont. In an in vitro flow cytometric functional assay, the IL-15cont group had decreased activation when compared to the IL-15 gap group against K562 targets (43.6±2.1 vs 55.6±2.7 % CD107a [degranulation], p < 0.0001; 1.9±0.41 vs 7.1±0.93 % IFNg [inflammatory cytokine production], p = 0.0055). The decrease in NK cell activation correlated with a strong decrease in tumor target killing in an in vitro chromium release assay (Figure 1A) measuring killing of acute promyelocytic leukemia (HL-60) cell targets, in which the IL-15cont NK cells were potently outperformed by the IL-15gap cells (6.4±2.6 vs 51.5±4.8 % killing at 2.5:1 effector:target ratio, p < 0.0001). We used an in vivo xenogeneic model of AML, where conditioned NSG (NOD scid gamma) mice are engrafted with HL-60luc tumor targets 3 days prior to infusion with nothing, IL-15cont or IL-15gap human NK cells prepared within our 9 day culture system. Only the IL-15gap NK group mediated statistically significant tumor control when compared to tumor alone at two weeks following NK cell infusion (Figure 1B). To probe deeper into the functional defect we evaluated signaling after these treatments and noted decreased phosphorylation of several proteins in the IL-15cont group. These data led us to explore proteins involved in metabolism and we noted that CPT1A, a critical enzyme involved in fatty acid oxidation (FAO), was strongly increased in the IL-15gap treated NK cells (protein MFI of 15,759±2,603 [IL-15gap] vs 5,273±744 [IL-15cont], p = 0.009). Metabolic analysis using a Seahorse XFe24 analyzer showed an increased mitochondrial spare respiratory capacity (SRC) in the IL-15gap group, denoting better capability of the IL-15gap NK cells to respond to energetic demands (Figure 1C). In a separate experiment the groups were treated with etomoxir to inhibit CPT1A, and the SRC phenotype was reversed, with the IL-15gap group containing lower SRC than the IL-15cont group. To test these findings in a functional assay we repeated the IL-15cont treatment in combination with rapamycin, which can induce CPT1A through inhibition of mTORC1, and saw restoration of function to levels similar to IL-15gap (40.8±2.0 vs 49.3±2.9 % CD107a in the IL-15cont vs IL-15cont + rapamycin, p = 0.005; 2.4±0.47 vs 4.8±1.0 % IFNg in the IL-15cont vs IL-15cont + rapamycin, p = 0.03). These data indicate that NK cell functional exhaustion via continuous IL-15 signaling is mediated by a decrease in FAO. Intermittent IL-15 dosing or altering metabolism through other mechanisms may overcome this competition. These findings could impact ongoing clinical trials through simple alterations in dosing strategies in order to minimize NK cell exhaustion in the immunotherapeutic setting. [Display omitted] DisclosuresCooley:Fate Therapeutics: Research Funding. Miller:Oxis Biotech: Consultancy, Other: SAB; Fate Therapeutics: Consultancy, Research Funding.

CD8αα+MHC Class II+ Cell with the Capacity To Terminate Autoimmune Inflammation Is a Novel Antigen-Presenting NK-like Cell in Rats.

Discovery of immune tolerance mechanisms, which inhibit pre-existing autoimmune inflammation, may provide us with new strategies for treating autoimmune diseases. We have identified a CD8αα+MHC class II+ cell with professional APC capacity during our investigation on spontaneous recovery from autoimmune glomerulonephritis in a rat model. This cell actively invades inflamed target tissue and further terminates an ongoing autoimmune inflammation by selective killing of effector autoreactive T cells. In this study, we show that this cell used a cytotoxic machinery of Ly49s+ NK cells in killing of target T cells. Thus, this CD8αα+MHC class II+ cell was a dually functional Ag-presenting NK-like (AP-NK) cell. Following its coupling with target T cells through Ag presentation, killing stimulatory receptor Ly49s6 and coreceptor CD8αα on this cell used rat nonclassic MHC class I C/E16 on the target T cells as a ligand to initiate killing. Thus, activated effector T cells with elevated expression of rat nonclassic MHC class I C/E16 were highly susceptible to the killing by the CD8αα+ AP-NK cell. Granule cytolytic perforin/granzyme C from this cell subsequently mediated cytotoxicity. Thus, inhibition of granzyme C effectively attenuated the killing. As it can recognize and eliminate effector autoreactive T cells in the inflamed target tissue, the CD8αα+ AP-NK cell not only represents a new type of immune cell involved in immune tolerance, but it also is a potential candidate for developing a cell-based therapy for pre-existing autoimmune diseases.

Kinase Regulation of Human MHC Class I Molecule Expression on Cancer Cells.

The major histocompatibility complex I (MHC-1) presents antigenic peptides to tumor-specific CD8+ T cells. The regulation of MHC-I by kinases is largely unstudied, even though many patients with cancer are receiving therapeutic kinase inhibitors. Regulators of cell-surface HLA amounts were discovered using a pooled human kinome shRNA interference-based approach. Hits scoring highly were subsequently validated by additional RNAi and pharmacologic inhibitors. MAP2K1 (MEK), EGFR, and RET were validated as negative regulators of MHC-I expression and antigen presentation machinery in multiple cancer types, acting through an ERK output-dependent mechanism; the pathways responsible for increased MHC-I upon kinase inhibition were mapped. Activated MAPK signaling in mouse tumors in vivo suppressed components of MHC-I and the antigen presentation machinery. Pharmacologic inhibition of MAPK signaling also led to improved peptide/MHC target recognition and killing by T cells and TCR-mimic antibodies. Druggable kinases may thus serve as immediately applicable targets for modulating immunotherapy for many diseases. Cancer Immunol Res; 4(11); 936-47. ©2016 AACR.

A novel anti-CD40 antibody prevents activation of alloreactive T cells and prolongs skin allograft survival

Abstract Targeting the CD40-CD154 pathway to induce transplantation tolerance has been of interest to transplantation immunologists for over two decades. The efficacy of anti-CD154 antibody (Ab) observed in murine and non-human primate models for preventing allograft rejection and suppressing autoimmunity, generated great interest in the development of this antibody for clinical use. However, clinical trials with anti-CD154 Ab resulted in thromboembolic complications in patients as a result of CD154 expression by human platelets and limited the clinical application. To develop an alternative approach to anti-CD154 Ab, recent efforts have focused on targeting its receptor, CD40. In this study we evaluated the effects of a novel murine antagonistic antibody to CD40 (BI CD40-1) on alloreactive immune responses. Costimulation blockade consisting of donor splenocytes (DST) and BI CD40-1 reduced activation of alloreactive CD8 T cells as shown by inhibition of expansion, decreased cytokine production and decreased killing of allogeneic targets using an in vivo cytotoxicity assay. Moreover DST/BI CD40-1 treatment significantly prolonged skin graft survival in a BALB/c to B6 MHC mismatch model. The efficacy of BI CD40-1 in preventing alloreactive T cell responses was similar to anti-CD154 Ab. These results indicate that anti-CD40 Ab is an attractive candidate for translation to clinical application.

Comparative genome-wide screens reveal novel regulators of Cytotoxic Lymphocyte-mediated cell death.

Abstract Cytotoxic Lymphocytes (CLs) are key players in the effector branch of the immune response, detecting and eliminating transformed and pathogen-infected cells. While the physiological roles of CL-mediated apoptosis are well established, many regulators of these apoptotic pathways in target cells remain poorly understood. We performed comparative genome-wide haploid genetic screens in a human cell culture model for CL killing and resistance in order to identify positive and negative regulators of target cell survival during CL-mediated killing. These regulators include genes encoding glycosylphosphatidylinositol (GPI) anchor synthesis enzymes and immune surveillance receptors. In order to identify further potential components of these pathways, we performed an additional resistance screen in a GPI-anchored protein deficient haploid cell line. We identified both common and disparate regulators between unaltered target cells and GPI-anchored protein deficient target cells. These disparate regulators underline the importance of GPI-anchored proteins in CL target recognition and killing. Some gene knockouts enriched by CL-mediated killing in both screens are also mutated in cancer. Further study of the regulators identified by these screens will advance our understanding of how the many killing pathways used by CLs shape the interaction between the immune system and cancer.

CD16-IL15-CD33 Trispecific Killer Engager (TriKE) induces NK cell expansion, persistence, and myeloid blast antigen specific killing.

Abstract NK cell infusions induce complete remissions in 30–50% of patients with refractory AML when combined with lymphodepleting chemotherapy and IL-2. NK cell therapy is limited by lack of antigen specificity and by IL-2 mediated induction of Tregs. To overcome these limitations we developed a 161533 trispecific killer engager (TriKE) molecule containing an anti-CD16 scFv, to engage NK cells, an anti-CD33 scFv, to engage AML targets, and an IL-15 molecule. We have shown previously that a 1633 bispecific killer engager (BiKE) is capable of creating an immunologic synapse between NK cells and AML targets leading to target killing. These molecules generate higher affinity interactions than natural CD16 binding to Fc portions of therapeutic antibodies, resulting in increased NK cell functionality. Addition of IL-15 in the TriKE molecule is meant to enhance NK cell priming, proliferation, and maintenance without inducing Tregs. Cytotoxicity assays and cytokine secretion assessment of NK cells incubated with CD33+ HL-60 target cells indicated that the TriKE induced greater NK cell activation than the BiKE or no molecule control. The TriKE was able to induce potent NK cell proliferation and survival when compared to the BiKE. Interestingly, when compared to recombinant IL-15 the TriKE induced less proliferation of T cells while inducing similar proliferation of NK cells from healthy donors, indicating specificity. The TriKE was capable of rescuing NK cell function of post-transplant patients. In vivo functionality was tested in an NSG xenogeneic model engrafted with HL-60-luc targets and NK cells. TriKE treatment resulted in reduced tumor burden and NK cell maintenance at day 21, displaying the immunotherapeutic potential of the molecule.

A Leukocyte Immune-Type Receptor Subset Is a Marker of Antiviral Cytotoxic Cells in Channel Catfish, Ictalurus punctatus.

Channel catfish, Ictalurus punctatus, leukocyte immune type receptors (LITRs) represent a multigene family that encodes Ig superfamily proteins that mediate activating or inhibitory signaling. In this study, we demonstrate the use of mAb CC41 to monitor viral cytotoxic responses in catfish and determine that CC41 binds to a subset of LITRs on the surface of catfish clonal CTLs. Homozygous gynogenetic catfish were immunized with channel catfish virus (CCV)-infected MHC-matched clonal T cells (G14D-CCV), and PBL were collected at various times after immunization for flow cytometric analyses. The percentage of CC41(+) cells was significantly increased 5 d after primary immunization with G14D-CCV and at 3 d after a booster immunization as compared with control fish only injected with G14D. Moreover, CC41(+) cells magnetically isolated from the PBL specifically killed CCV-infected targets as measured by (51)Cr release assays and expressed messages for CD3γδ, perforin, and at least one of the CD4-like receptors as analyzed by RNA flow cytometry. When MLC effector cells derived from a G14D-CCV-immunized fish were preincubated with CC41 mAb, killing of G14D-CCV targets was reduced by ∼40%, suggesting that at least some LITRs have a role in target cell recognition and/or cytotoxicity. The availability of a LITR-specific mAb has allowed, to our knowledge for the first time, functional characterization of LITRs in an autologous system. In addition, the identification of an LITR subset as a cytotoxic cell marker will allow for more effective monitoring of catfish immune responses to pathogens.

Cutting Edge: Enhanced Clonal Burst Size Corrects an Otherwise Defective Memory Response by CD8+ Recent Thymic Emigrants.

The youngest peripheral T cells (recent thymic emigrants [RTEs]) are functionally distinct from naive T cells that have completed postthymic maturation. We assessed the RTE memory response and found that RTEs produced less granzyme B than their mature counterparts during infection but proliferated more and, therefore, generated equivalent target killing in vivo. Postinfection, RTE numbers contracted less dramatically than those of mature T cells, but RTEs were delayed in their transition to central memory, displaying impaired expression of CD62L, IL-2, Eomesodermin, and CXCR4, which resulted in impaired bone marrow localization. RTE-derived and mature memory cells expanded equivalently during rechallenge, indicating that the robust proliferative capacity of RTEs was maintained independently of central memory phenotype. Thus, the diminished effector function and delayed central memory differentiation of RTE-derived memory cells are counterbalanced by their increased proliferative capacity, driving the efficacy of the RTE response to that of mature T cells.