IFN-gamma Secretion Research Articles

IFN-Gamma Secretion and IL-10 after Stimulation of ESAT-6-CFP-10 (EC610) Fusion Antigen in Patients with Active Tuberculosis and Latent Tuberculosis

Tuberculosis (TB) is an infectious disease caused by the bacterium Mycobacterium tuberculosis which is still a health problem in the world including in Indonesia. TB infection arises due to interference with the regulation of the body's defense system. Cellular immune system plays a role in fighting TB infection, namely the role of T lymphocytes that differentiate into Th1 cells secrete pro-inflammatory cytokines IFN-? and Th2 cells that secrete IL-10 anti-inflammatory cytokines. The EC610 fusion antigen is specific and has a strong antigenicity to T cell stimulation. The aim of the study was to determine differences in the mean levels of IFN-? and IL-10 after EC610 antigen stimulation in patients with active TB and latent TB. The design of this study was a quasi-in vitro experiment with PBMC culture stimulated by EC610 antigens in the active TB and latent TB groups. The research and examination were carried out at the South Sumatra Province SSR and the Health Research and Development Laboratory Center, Central Jakarta. There were 21 subjects with active TB and 28 subjects with latent TB who met the inclusion criteria. Measurement of IFN-levels? and IL-10 was performed using ELISA-Reader. The results showed the levels of IFN-? and IL-10 after EC610 antigen stimulation were higher in active TB than latent TB. High levels of IFN-? active TB patients showed protective immune responses against M.tb germs while high levels of IL-10 showed their role as anti-inflammatory. There is no significant difference in the average level of IFN-? in patients with active TB and latent TB (p = 0.769) and there was a significant difference in the level of IL-10 levels after EC610 antigen stimulation was higher in active TB than latent TB (p = 0,000).

Role of regulatory T cells and checkpoint inhibition in hepatocellular carcinoma.

Immune checkpoint inhibition suggests promising progress for the treatment of advanced hepatocellular carcinoma (HCC). However, the underlying cellular mechanisms remain unclear because liver cancer cells apparently do not upregulate inhibitory checkpoint molecules. Here, we analysed whether regulatory T cells (Tregs) can alternatively trigger checkpoint inhibition pathways in HCC. Using flow cytometry we analysed expression of checkpoint molecules (PD-1, PD-L1, CTLA-4, GITR, Tim-3) on peripheral CD4+CD25+Foxp3+ Tregs and their secretion of inhibitory mediators (IL-10, IL-35, TGF-beta, galectin-9) in 116 individuals (50 patients with HCC, 41 non-tumour bearing liver disease controls, 25 healthy controls). Functional activity of Tregs on T effector cells (IFN-gamma production, cytotoxicity) was characterized in vitro using a lectin-dependent cellular cytotoxicity (LDCC) assay against checkpoint inhibitor-negative P815 target cells. Unlike liver patients without malignancy and healthy controls, the frequency of checkpoint inhibitor-positive Tregs inversely correlated to age of patients with HCC (PD-L1, p = 0.0080; CTLA-4, p = 0.0029) and corresponded to enhanced numbers of Tregs producing IL-10 and IL-35 (p < 0.05 each). Tregs inhibited IFN-gamma secretion and cytotoxicity of CD8+ T cells when added to LDCC against P815 cells. Treg-induced inhibition of IFN-gamma secretion could be partially blocked by neutralizing PD-1 and PD-L1 antibodies specifically in HCC patients. In HCC peripheral Tregs upregulate checkpoint inhibitors and contribute to systemic immune dysfunction and antitumoural activity by several inhibitory pathways, presumably facilitating tumour development at young age. Blocking PD-L1/PD-1 interactions in vitro selectively interfered with inhibitory Treg -T effector cell interactions in the patients with HCC and resulted in improved antitumoural activity also against checkpoint inhibitor-negative tumour cells.

IMMU-07. CELLULAR IMMUNOTHERAPY TO OVERCOME TEMOZOLOMIDE INDUCED T CELL EXHAUSTION IN GLIOBLASTOMA

Abstract INTRODUCTION We have previously demonstrated that standard dose (SD) temozolomide results in T cell exhaustion in glioblastoma. In this study, we hypothesized that cellular immunotherapies will prevent T cell exhaustion. We tested temozolomide treatment with adoptive T cell transfer alone, dendritic cell (DC) vaccines alone and T cell transfer in combination with DC vaccines. METHOD GL-261-gp100 tumor-bearing mice were treated with SD (50 mg/kg for 5 days) or metronomic dose (MD) (25 mg/kg for 10 days) temozolomide. CD3+ T cells were isolated from Pmel mice and infused intravenously. Antigen-specific DC vaccines (gp-100) were given intradermally at the concentration of 50×104. Peripheral blood T cell populations were evaluated by flow cytometry. IFN-gamma secretion was measured for evaluation of T cells function. Survival was compared between groups. RESULTS Survival analysis demonstrated that naïve T cell transfer alone and DC vaccine alone add no survival benefit to temozolomide treatment for tumor-bearing animals. There were no significant differences in the expression of exhaustion markers of Tim-3 and Lag-3 on T cells of animals that received a combination of activated T cells and DC vaccines in the context of temozolomide therapy compared to the animals that just received temozolomide. Combination of activated T cell transfer and DC vaccines did not increase IFN-gamma secretion from T cells compared to temozolomide treated animals. Combination of naïve T cell transfer and two DC vaccines increased IFN-gamma secretion from T cells of GL-261 gp100 tumor-bearing animals. However, naïve T cell transfer and two DC vaccines in the context of temozolomide was not potent enough to extend the survival of these tumor-bearing animals. CONCLUSION Combinatorial treatment with naïve antigen-specific T cells and three dendritic cell vaccine boosters in the context of temozolomide is a promising approach to preserve T cell function and avoid T cell exhaustion.

Personalized T cell therapy for metastatic colon cancer.

e15183 Background: Current immunotherapies fail to benefit patients with colon cancer, largely due to high molecular heterogeneity and low frequencies of tumor infiltrating lymphocytes. In this study, we are addressing this limitation via a novel technology to expand patient tumor specific T cells ex-vivo, using patient’s matched tumor and peripheral blood mononuclear cells (PBMCs). This technology utilizes tumor membrane vesicles (TMVs) made from excised tumor tissue, as a source of tumor associated antigens, and further modified to express IL-12 and B7-1 for ex-vivo expansion of tumor specific T cells. Additionally, the T cells are cultured with PI3K delta inhibitor (idelalisib) and vasoactive intestinal peptide antagonist (VIPhyb) to increase yield, polyfunctionality and in-vivo persistence. Methods: Matched tumor and blood were collected from consented colon cancer patients. TMVs were prepared from excised tumors by homogenizing and centrifuging the tumor over a sucrose gradient. TMVs were then made to express glycosyl phosphatidylinositol (GPI) linked IL-12 and B7-1 (decorated TMV) via a proprietary protein transfer technology. PBMCs isolated from matched blood were cultured in media with 10ug/ml decorated TMV with/without VIPhyb(3uM) and idelalisib (100nM) for 14 days. T cells were then phenotyped for percentage of IFN gamma secreting CD4+ and CD8+ T cells and injected into PDX mice bearing matched tumors (2 doses of 1 million and 4 million cells, 20 days apart). Results: 14 days after expansion, T cells expanded with decorated TMVs+VIPhyb+idelalisib (TMVs+drugs) resulted in significantly increased number of IFN gamma secreting CD8+ T cells (25% of T cells), when compared to T cells treated with decorated TMVs without VIPhyb and idelalisib (13% of T cells). Further, when injected to PDX mice bearing matched tumors, and followed for differences in tumor growth, we observed that on day 30 after T cell injection, while the tumor volumes increased 4.5-fold in the untreated group, the tumors in the TMVs+drugs group only increased 2.8-fold. Conclusions: In this study, we have thus developed a novel technology to expand patient tumor specific T cells ex-vivo, for adoptive T cell therapy against metastatic colon cancer.

Improving T cell functionality for adoptive T cell therapy in metastatic colorectal cancer

Abstract Adoptive T cell therapy in solid tumors such as colorectal cancers are challenging due the low frequency of tumor infiltrating T cells and high molecular tumor heterogeneity. In this study, we are proposing to address this issue by developing a novel technology to expand patient tumor specific T cells ex-vivo, using patient’s matched tumor and PBMCs. Published data from our group shows T cells isolated from heavily treated lymphoma patients when treated with inhibitors of PI3K delta (idelalisib) and vasoactive intestinal peptide (VIPhyb) signaling results in decreased levels of senescent T cells and increased persistence in-vivo in NSG mice. Additionally, we have demonstrated that tumor membrane vesicles (TMVs) prepared from human tumor cells decorated with IL-12 and B7-1 (decorated TMVs), stimulate expansion of tumor antigen specific T cells with increased IFN gamma release. This study thus combines both strategies to obtain tumor antigen specific T cells with enhanced anti-tumor activity and in-vivo persistence. Preliminary data was generated with PBMCs obtained from consented colon cancer patients expanded with decorated TMVs with/without VIPhyb and idelalisib. Results showed that on day 14 of T cell expansion, T cells expanded with decorated TMVs + VIPhyb + idelalisib resulted in significantly increased number of IFN gamma secreting CD8+ T cells (25% of T cells), when compared to T cells treated with decorated TMVs without VIPhyb and idelalisib (13% of T cells). On the other hand, in the absence of decorated TMVs, there were less IFN gamma secreting T cells, both in the CD4 and CD8 compartment. Further experiments are underway to test the persistence and efficacy of the expanded T cells in PDX mice with matched human colon cancer.

Systemic proinflammation after Mycobacterium tuberculosis infection was correlated to the gut microbiome in HIV-uninfected humans.

The dysbiosis of gut microbiome and interaction with host immunity after Mycobacterium tuberculosis (MTB) infection are under investigation. We had found fatigue symptom concurrent with dysbiosis by decreasing the ratio of Firmicutes to Bacteroidetes (F/B ratio) in active tuberculosis (TB). The study aims to assess the inflammatory biomarkers and their interaction with gut microbiome in active TB and latent TB infection before starting anti-TB regimens. Interleukin-1 beta (IL-1B), IL-4, IL-6, IL-10, CD3+, CD4+, CD8+ T cells and interferon-gamma (IFN-γ) releasing assay (IGRA) were measured in 25 active TB patients, 32 LTBI subjects and 23 healthy controls (HC). Gut microbiome profiles were obtained using 16S rRNA MiSeq sequencing method. The leucocytosis (7032±387 cell/cum, P<0.05), increase in IL-6 (229.7±104µg/dL, P<0.05), and decrease in IL-4 (0.27µg/dL±0.1, P<0.05) were presented in active TB. The proportion of polymorphic neutrophil (PMN) in peripheral blood was positively related to the relative abundance of Bacteroidetes in LTBI and active TB (R2 =0.23, P<0.05). The F/B ratio was positively related to the detectable IL-1B in TB (R2 =0.97, P<0.01) and to the IL-4 in LTBI (R2 =0.27, P<0.05). In LTBI, the relative abundances of Coriobacteriaceae were positively related to the secretion of IFN-gamma against MTB-antigens more likely associated with of CD4+ T cell (R2 =0.42, P<0.05). In active TB, dysbiosis with higher relative abundances of Bacteroidetes in stool and low F/B ratio was related to systemic proinflammation. In LTBI, dose-response relationship between peripheral PMN and relative abundances of Bacteroidetes was remained but not leads to systemic inflammation.

Abstract A124: Preclinical characterization of AB154, a fully humanized anti-TIGIT antibody, for use in combination therapies

Abstract TIGIT (T-cell immunoreceptor with Ig and ITIM domains) is an inhibitory receptor that is expressed on natural killer (NK) cells, CD8+ T-cells, and immunosuppressive regulatory T-cells (Treg). DNAM-1 (DNAX Accessory Molecule-1; CD226) is an activating receptor found on NK cells, monocytes and a subset of T-cells. TIGIT and DNAM-1 are paired receptors that compete for shared ligands CD155 (PVR) and CD112 (Nectin-2) expressed by tumor and antigen-presenting cells. TIGIT binding to CD155 or CD112 results in immune suppression, whereas binding of DNAM-1 to the same ligands mediates immune activation. As malignancies progress, high TIGIT expression often occurs alongside the upregulation of other immune checkpoint proteins and markers of T-cell exhaustion such as PD-1 (Programmed Death-1). We have developed AB154 to inhibit TIGIT and shift the balance in the tumor microenvironment towards a more productive anticancer response. Blockade of multiple immune checkpoint proteins can confer effective and durable responses in the treatment of cancer. Data assembled from TCGA (The Cancer Genome Atlas) identified numerous tumor types in which TIGIT is co-expressed with PD-1. In these tumors, TIGIT and PD-1 were significantly upregulated compared to normal adjacent tissue. Immunophenotyping performed on human tumor infiltrating lymphocytes demonstrated a strong correlation between TIGIT and PD-1 co-expression on specific immune cells including CD8+ T-cells and Treg cells. AB154 is a fully humanized antibody that blocks human TIGIT with sub-nanomolar affinity, as determined using a CHO.hTIGIT over-expressing cell line and primary human T-cells. Functional consequences of blocking TIGIT/CD155 interactions in combination with anti-PD-1 or anti-PD-L1 were evaluated using mixed lymphocyte reactions (MLR). Briefly, we show here that co-cultures of GM-CSF/IL-4-differentiated CD155+ PD-L1+ monocytes and TIGIT+ CD4+ T-cells, in the presence of AB154, significantly increased IFN-gamma secretion when combined with anti-PD-1 or anti-PD-L1 blocking antibodies relative to each monotherapy. Understanding pharmacokinetic (PK) and pharmacodynamic (PD) relationships enables the choice of a dosing regimen that provides adequate target coverage. To evaluate the PD effects of AB154 in clinical samples, we developed a multicolor flow cytometry-based assay that utilizes an anti-TIGIT antibody that is competitive with AB154 to determine receptor occupancy. In human whole blood, ex vivo addition of AB154 achieved complete inhibition of TIGIT. Analysis of blood mononuclear cells, including CD8+ and CD4+ T-cells, Treg and NK cells, demonstrated target engagement by AB154 suitable for clinical development. In addition, we examined TIGIT receptor occupancy of AB154 (added to whole blood ex vivo) in a small cohort of non-small cell lung cancer (NSCLC) patients treated with anti-PD-1 antibody pembrolizumab. In these samples, TIGIT receptor occupancy by AB154 was comparable to that obtained with healthy donor blood samples. The data presented here provide: 1) rationale for combining AB154 with our in-house developed anti-PD-1 antibody (AB122) in upcoming clinical trials, and 2) methodology to evaluate TIGIT receptor occupancy in the upcoming AB154 dose escalation studies. AB154 is expected to enter clinical trials in 2018. Citation Format: Amy E. Anderson, Annette Becker, FangFang Yin, Hema Singh, Xiaoning Zhao, Lisa Seitz, Rick Stanton, Nigel P.C. Walker, Joanne B.L. Tan. Preclinical characterization of AB154, a fully humanized anti-TIGIT antibody, for use in combination therapies [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 A124.

In-depth characterization of the neuroinflammatory reaction induced by peripheral surgery in an animal model.

Delirium is a common complication seen after surgery and anesthesia, in particular in older patients. Although the etiology of postoperative delirium is only incompletely understood, various lines of evidence suggest that proinflammatory signaling from the peripheral site of inflammation to central nervous system results in a decrease of cerebral acetylcholine (ACh) levels thereby inducing neuroinflammation. To corroborate this theory, we applied an animal model for characterization of the neuroinflammatory response after partial hepatectomy (HPx). In this model, the surgery-induced decrease in cerebral ACh levels can be prevented by intraoperative application of physostigmine. Thus, ACh-associated changes in the expression and secretion of inflammation-related compounds can be assessed by comparing the results obtained after surgery, in physostigmine-treated and untreated controls. This way we were able to show that the decrease of cerebral ACh triggers increased secretion of IL-1β, IL-6, TNFα, MIP-2 (CCL3), RANTES, MCP1, IFNgamma, and IP-10. A gene array covering the expression of 370 inflammation-related genes indicated 13 candidates that are induced upon cerebral ACh decrease after HPx. Quantification of the changes in the expression of these candidates by the comparative CT method revealed a significant increase (> 1.5-fold) in the expression of IL-1β, IL-6, TNFα, MIP2, RANTES, MCP1, TLR2, TLR4, HMGB1, TNFSF6, TNFSF12, IL1R1 and ILR6. Thus, our results suggest that peripheral surgery induces a reduction of cerebral ACh levels which trigger a complex neuroinflammatory response. From a clinical point of view, manipulating cerebral ACh levels by procholinergic drugs such as physostigmine could become an option to therapeutically target this kind of neuroinflammation.

Abstract 4559: KY-B602, a humanized anti-human OX40 antibody, enhances CD4+T cell activation and inhibits tumor growth in a syngeneic model

Abstract OX40, a member of the tumor necrosis factor (TNF) receptor superfamily, is mainly expressed on activated T cells. As a secondary costimulatory molecule, activated OX40 can increase effector T-cell survival, proliferation, and memory. Anti-OX40 monoclonal antibodies have shown anti-tumor efficacy. Recent preclinical studies further support the potential synergistic effects of agonist OX40 immunotherapy in combination with cancer vaccination or in sequential co-administration with PD1 antibody to revert PD1 resistance. Several anti-OX40 agonistic monoclonal antibodies are currently tested in early phase cancer clinical trials either in monotherapy or in combination with other immune modulators. KY-B602 is a novel humanized IgG1 anti-OX40 antibody under pre-clinical development. It was generated from hybridoma and humanized by CDR grafting and structure simulation. KY-B602 specifically binds to the extracellular domain of human OX40 with high affinity (KD = 5.1 nM, determined by Biacore). FACS study showed KY-B602 also binds to both human and cynomolgus monkey OX40 over-expressed on 293T cells (EC50 =4.6nM, EC50=6.1nM, respectively). Another, in HT1080 cell reporter assay, KY-B602 significantly increased IL-8 secretion through OX40 pathway. In addition, KY-B602 dose-dependently augmented IL-2 and IFN-gamma secretion from CD4+T cells, that were pre-stimulated with IL-2 and PHA. However, in FACS competition assay, KY-B602 did not affect OX40L binding to OX40, suggesting that KY-B602 binds to a different epitope with that of OX40L. Moreover, KY-B602 inhibits in vivo tumor growth in MC38 syngeneic model. In summary, the current data of KY-B602 support its potency for cancer therapy. Citation Format: feng hao, feng he, mingxuan ning, zhaoshuai bai, jinying ning. KY-B602, a humanized anti-human OX40 antibody, enhances CD4+T cell activation and inhibits tumor growth in a syngeneic model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4559.

IMMU-27. Re-MATCH PROTOCOL: PHASE I STUDY OF AUTOLOGOUS TUMOR SPECIFIC LYMPHOCYTE TRANSFER (ALT) + DC VACCINE (DCV) DURING RECOVERY FROM MYELOABLATIVE CHEMOTHERAPY (MAC) AND AUTOLOGOUS STEM CELL RESCUE (HDC + ASCR) OR NON-MYELOABLATIVE CHEMOTHERAPY (NMAC) IN PATIENTS WITH RECURRENT CENTRAL PNETs (r-PNET)

We performed a phase I study to assess feasibility, safety, and efficacy of ALT+DCV following HDC +ASCR (group A) or NMAC (group B) in pts with r-PNET. Eligible pts underwent surgery to confirm diagnosis and obtain tumor for vaccine preparation. Pts with local (group A) or metastatic (group B) recurrence received 4 cycles of cytoreductive chemotherapy prior to either MAC (carboplatin + thiotepa + etoposide) (group A) or NMAC (cyclophosphamide + Fludarabine) (group B). Two dose levels of ALT were evaluated [3 x 106 or 3 x 107 cells/kg] with 3 intradermal biweekly DCVs (107cells each). Safety evaluation for DLT assessment was 2 weeks past third DCV with monthly vaccines thereafter as available. Correlative studies for immune response included TCR sequencing and measurement of serum cytokines Ten pts (M5; F5) were treated on protocol (group A 1, group B 9). Nine evaluable pts received immunotherapy; DCV [median 3 doses (3-9)] + ALT [3 x106/kg (n=4) or 3 x 107/kg (n=5)]. There were no DLTs observed. At median of 21 months follow-up, 3 pts are alive with (n=2) or without (n=1) disease 33-42 months following treatment. TCR RNA sequencing demonstrates massive clonal expansion of T cells following ALT+DCV and positive correlation with clinical outcomes. Persistence of tumor-reactive (IFN-gamma secreting) T cell clones in the peripheral blood was observed 4 months after treatment in a patient with long-term disease control. ALT+DCV is feasible, safe, and shows signs of biologic and clinical activity in some pts with r-PNET.

Preclinical Assessment of CAR T-Cell Therapy Targeting the Tumor Antigen 5T4 in Ovarian Cancer.

Chimeric antigen receptor (CAR) T cells represent a novel targeted approach to overcome both quantitative and qualitative shortfalls of the host immune system relating to the detection and subsequent destruction of tumors. The identification of antigens expressed specifically on the surface of tumor cells is a critical first step in the ability to utilize CAR T cells for the treatment of cancer. The 5T4 is a tumor-associated antigen which is expressed on the cell surface of most solid tumors including ovarian cancer. Matched blood and tumor samples were collected from 12 patients with ovarian cancer; all tumors were positive for 5T4 expression by immunohistochemistry. Patient T cells were effectively transduced with 2 different anti-5T4 CAR constructs which differed in their affinity for the target antigen. Co-culture of CAR T cells with matched autologous tumor disaggregates resulted in antigen-specific secretion of IFN-gamma. Furthermore, assessment of the efficacy of anti-5T4 CAR T cells in a mouse model resulted in therapeutic benefit against established ovarian tumors. These results demonstrate proof of principle that 5T4 is an attractive target for immune intervention in ovarian cancer and that patient T cells engineered to express a 5T4-specific CAR can recognize and respond physiologically to autologous tumor cells.

Development of improved therapeutic mesothelin-based vaccines for pancreatic cancer.

Pancreatic cancer is the 5th leading cause of cancer deaths, and there are no effective treatments. We developed a poxvirus platform vaccine with improved immunogenicity and inserted the mesothelin gene to create an anti-mesothelin cancer vaccine. Mesothelin expression is mostly restricted to tumors in adult mammals and thus may be a good target for cancer treatment. We show here that the modified vaccinia virus Ankara (MVA) virus expressing mesothelin and the enhanced MVA virus missing the immunosuppressive A35 gene and expressing mesothelin were both safe in mice and were able to induce IFN-gamma secreting T cells in response to mesothelin expressing tumor cells. In addition, the MVA virus has oncolytic properties in vitro as it can replicate in and kill Panc02 pancreatic adenocarcinoma cell line tumor cells, even though it is unable to replicate in most mammalian cells. Deletion of the A35 gene in MVA improved T cell responses as expected. However, we were unable to demonstrate inhibition of Panc02 tumor growth in immunocompetent mice with pre-vaccination of mice, boosts, or even intratumoral injections of the recombinant viruses. Vaccine efficacy may be limited by shedding of mesothelin from tumor cells thus creating a protective screen from the immune system.

Irradiated haploidentical donor leukocyte infusions as an adoptive immunotherapy strategy to induce host-versus-tumor effects.

Previous research has shown that irradiated splenocytes preserve the antitumor effect and induce relatively weaker graft-versus-host disease in parent C57BL/6~CB6F1 transplantation. The present study was designed to investigate the antitumor effect of 5-Gy-irradiated haploidentical donor leukocyte infusions (DLI) without prior bone marrow transplantation and the possibly involved mechanism in (H-2d/k)~(H-2b/d) infusion model systems. Hepa 1-6 tumor-bearing mice were used to evaluate the antitumor effect and the possible mechanism of irradiated haploidentical DLI treatment. Changes in tumor volume, lymphocyte proliferation and cytotoxicity, IFN-gamma and IL-2 secretion and donor cell survival in vivo were analyzed. After irradiated haploidentical DLI treatment of the poorly immunogeneic Hepa 1-6 tumor mouse model, the donor cells were rejected and disappeared within 4 days. Surprisingly, an antitumor response was still observed. The infusion treatment effectively inhibited tumor growth and prolonged the survival of recipients, and this effect could be enhanced by combined treatment with cyclophosphamide and impaired by deleting donor-derived T cells. Moreover, the infusion treatment increased the levels of type 1 cytokines including IFN-gamma and IL-2, and enhanced the proliferation of lymphocyte subsets, particularly CD8 + T and NK cells. Specifically, multiple infusions proved to enhance the antitumor effect without inducing graft-versus-host disease. As an adoptive therapy, irradiated haploidentical DLI without bone marrow transplantation might be a promising and safe treatment for cancer.

Flow cytometry: An efficient method for antigenicity measurement and particle characterization on an adjuvanted vaccine candidate H4-IC31 for tuberculosis

We have developed an accurate, precise and stability-indicating flow cytometry (FC) based assay to directly measure antigenicity of H4 protein (also known as HyVac4) in a vaccine formulation of H4-IC31, without desorbing the H4 protein from the IC31 adjuvant. This method involves immuno-staining of H4-IC31 complex with anti-H4 monoclonal antibodies (mAbs) followed by FC analysis. The assay is not only able to consistently measure H4 antigenicity levels in H4-IC31 stored under normal condition at 2–8°C, but also able to detect changes in H4 antigenicity after H4-IC31 undergoes heat stress or freeze-thawing. In addition, the FC method is able to characterize particle morphology while measuring antigenicity. The biological relevance of the changes in H4 antigenicity detected by the FC assay was supported by an in vitro cell based functional assay using human PBMCs to measure IFN-gamma (IFN-γ) secretion upon re-stimulation with H4-IC31. Our results show that the FC based antigenicity assay can efficiently monitor the biological and physicochemical properties of H4-IC31 and is an indicator for adjuvanted vaccine product stability.

Abstract 2622: Two new TLR9 agonists for cancer immunotherapy: Combination with checkpoint inhibitors

Abstract Introduction TLR9 agonists are developed as anti-cancer therapies based on their broad activation of the innate and adaptive immune system. Single-stranded oligodeoxynucleotides (ODN) containing non-methylated CG-motifs activate TLR9. Previously, chemical modification was used to prevent their degradation by exonucleases. To avoid the off-target effects observed with chemical modifications, new TLR9 agonists containing only natural DNA were stabilized by structural components. The dSLIM® family of TLR9 agonists is protected from exonucleolytic degradation by its covalently-closed dumbbell-shaped structure. It contains an immunomodulatory sequence with CG-motifs in its loops. The linear single-stranded EnanDIM® family of TLR9 agonists utilizes L-deoxyribonucleotides (natural enantiomers of D-deoxyribonucleotides) at their 3’-ends to prevent degradation. Since the mode-of-action of TLR9 agonists starts upstream of the targets of checkpoint inhibitors anti-PD-1/anti-PD-L1 a combinatory approach may support synergistic immune activation and thus enhanced anti-tumor effects. Methods The impact of dSLIM2006 and EnanDIM-1 on T cell responses was analyzed employing an in vitro assay using human peripheral blood mononuclear cells (PBMC). PBMC were treated with peptides selected from HLA class I-restricted T-cell epitopes of recall-antigens (CMV, EBV, Flu = CEF), TLR9 agonists and anti-PD-1 as checkpoint inhibitor. In addition, in vivo studies were used to investigate the anti-tumor effect of dSLIM2006 and EnanDIM-1 in combination with anti-PD-1 in a syngeneic murine CT26 tumor model. Results The IFN-gamma secretion of human PBMC after stimulation of CEF peptides was roughly 5-fold increased by EnanDIM-1 and dSLIM2006, whereas treatment with anti-PD-1 resulted barely in a two-fold increase. The combination of the TLR9 agonists and anti-PD-1 further enforced IFN-gamma secretion by about 7-fold. In the murine colon cancer model CT26 the subcutaneous injection of EnanDIM-1 or intraperitoneal injection of anti-PD-1 had a moderate effect on the tumor growth when used in monotherapy (28.3% or 57.0% tumor growth inhibition, TGI). Notably, a combination of EnanDIM-1 and anti-PD-1 further reduced tumor growth (74.7% TGI). Intratumoral injection of dSLIM2006 in combination with intraperitoneal injection of anti-PD-1 reduced tumor growth (54.2% TGI) whereas the single components had more limited effects (dSLIM2006: 18.7%, anti-PD-1: no inhibition). Combined treatment with TLR9 agonists and anti-PD-1 prolonged survival of the mice in comparison to single treatments. Conclusions The TLR9 agonists and immune surveillance reactivators (ISR) EnanDIM-1 and dSLIM2006 enhance T cell responses and anti-tumor effects of the anti-PD-1 checkpoint inhibitor. These data show their promising potential not only for monotherapeutic but also combinatory approaches. Citation Format: Kerstin Kapp, Barbara Volz, Detlef Oswald, Burghardt Wittig, Manuel Schmidt. Two new TLR9 agonists for cancer immunotherapy: Combination with checkpoint inhibitors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2622. doi:10.1158/1538-7445.AM2017-2622

Abstract 2667: In vitro properties and pre-clinical activity of PF-06801591, a high-affinity engineered anti-human PD-1

Abstract Monoclonal-antibody-based therapies targeting the immune checkpoint receptors have become the new standard of care in many cancers. Antibodies that specifically target programmed death receptor-1 (PD-1) or its cognate ligand, programmed death receptor ligand-1 (PD-L1), alone or in combination, have yielded clinical benefits and durable responses in patient subsets with various cancers (including metastatic melanoma, NSCLC, RCC, urothelial cancer, cHL and others). Here we report on the biophysical characteristics and non-clinical antagonistic activities of PF-06801591. PF-06801591 is a humanized anti-PD-1 antibody of human IgG4 isotype, that binds selectively and with similar potency to human and cynomolgus monkey PD-1 receptor (EC50 ~50 pM) and blocks its interaction with its cognate ligands PD-L1 and PD-L2 (IC50 &amp;lt; 1 nM) with no detectable Fc effector function. The interaction of PF-06801591 to PD-1 rescues T cell suppression and exhaustion that translates into NFAT activation, IL-2 and IFN-gamma secretion and T cell proliferation both in vitro cultures and in vivo using an acute xeno GvHD model with human PBMC transfer. Binding of PF-068001591 to human and cynomolgus PD-1 is characterized by the formation of a very stable complex (T1/2 = 2 h) as measured by SPR at 37 C, resulting in high affinity (KD ~20 pM) as measured in solution by KinExA at 23 C. In addition, we explored therapeutic potential of anti-PD-1 in combination with other immunotherapy agents using surrogate antibodies in non-clinical tumor models. The data presented here support future development of PF-06801591 as a single agent or in combination with other immunotherapies. Citation Format: Sawsan Youssef, Yasmina Abdiche, HoangKim Nguyen, Joyce Chou, Sherman Michael Chin, Cris Kamperschroer, Patricia A. Schneider, Eugenia Kraynov, Heike I. Krupka, Arvind Rajpal, John Lin. In vitro properties and pre-clinical activity of PF-06801591, a high-affinity engineered anti-human PD-1 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2667. doi:10.1158/1538-7445.AM2017-2667

Abstract 3746: Plasma membrane spanning and linker-domains from tumor necrosis factor receptor superfamily (TNFRSF) proteins provide novel functionality to chimeric antigen receptors (CARs) expressed in human T cells

Abstract Chimeric antigen receptor T cells redirected to the B cell antigen CD19 (CAR19) have shown efficacy in the treatment of B-lineage acute lymphocytic leukemia, and are being evaluated in other hematologic malignancies as well. The prevalent configuration of CAR19 for clinical application is comprised of the extracellular single chain targeting domain (scFv) derived from the FMC63 antibody, a CD8 linker and transmembrane domain, a CD137 signaling domain, and a CD3-zeta signaling domain. Transmembrane domains from other immunologically-active proteins, including CD3, CD28, or CD4, and spacer domains from IgG have been employed as structural components of CARs as well. The relationship between the composition of the CAR linker and transmembrane domain and CAR T function is, however, poorly understood. We hypothesized that CAR transmembrane and linker domains derived from proteins of the tumor necrosis factor receptor superfamily (TNFRSF), whose expression is associated with normal T cell functions, may optimize the anti-tumor activity of CAR19. Therefore, primary human T cells were transduced with lentiviral expression vectors (LV) expressing new combinations of linker and transmembrane sequences encoded by various TNFRSF members. Specifically, the linker:transmembrane domain combinations were: CD8:CD4, CD8:TNFRSF19, TNFRSF19:TNFRSF19, truncated TNFRSF19:TNFRSF19, TNFRSF9:TNFRSF9 and TNFRSF16:TNFRSF16. We found that CAR T cells comprised of transmembrane domains derived from either TNFRSF19 or TNFRSF9 were superior to the CD8 transmembrane CAR 19 in tumor killing, and in the induction of IFN gamma, TNF alpha, IL-2, and GM-CSF cytokine secretion in vitro, upon co-culture with leukemia cell line targets. Moreover, TNFRSF19-expressing CAR19 T cells were superior to the CD8 transmembrane CAR19 in the elimination of engrafted Raji cells (a Burkitt’s lymphoma line) in an NSG leukemia mouse model. On the other hand, the transmembrane domain derived from TNFRSF16/LNGFR, a low affinity neurotrophin receptor, created a CAR19 construct that had no functional activity either in vitro or in vivo, despite high levels of surface CAR expression in human T cells. In conclusion, the magnitude of CAR T response can be enhanced by the use of novel linker and transmembrane domains derived from TNFRSF19 and TNFRSF9. Thus, the transmembrane domain can play a determining role in CAR T function beyond a direct topographical connection between the extracellular and the intracellular domains of the chimeric protein. Studies are underway to elucidate the mechanistic role of TNFRSF-derived linker and transmembrane domains in CAR T function. Citation Format: Dina Schneider, Ying Xiong, Darong Wu, Boro Dropulic, Rimas Orentas. Plasma membrane spanning and linker-domains from tumor necrosis factor receptor superfamily (TNFRSF) proteins provide novel functionality to chimeric antigen receptors (CARs) expressed in human T cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3746. doi:10.1158/1538-7445.AM2017-3746

Abstract 4606: Preclinical characterization of a novel fully human IgG1 anti-PD-L1 mAb CK-301

Abstract Antibodies targeting Programmed Death-1 (PD-1), or its ligand, PD-L1, have demonstrated remarkable efficacy in subsets of cancer patients, with inhibition of the interaction between PD-1 on T-cells and PD-L1 on tumor cells leading to the recovery of anti-tumor immune response and immune-mediated eradication of tumors. However, not all patients respond to existing PD-1 and PD-L1 targeting agents and relapses to therapy still occur. Therefore, there exists a need to identify additional therapeutics and approaches to engage the immune system to enhance the efficacy of current anticancer therapies. Using phage and yeast display approaches, we have discovered and optimized a novel, fully human, PD-L1 specific IgG1 antibody, CK-301, which exhibits subnanomolar binding affinity for PD-L1. CK-301 blocks binding of PD-L1 to both PD-1 and B7-1 in enzyme-linked immunosorbent assays (ELISA) and cell-based competition assays. Using an assay measuring inhibition of a nuclear factor of activated T-cells (NFAT) reporter caused by PD-L1 binding to PD-1, we demonstrate that CK-301 completely reverses reporter inhibition at concentration of less than 1 µg/ml, IC50 of the dose response curve is 80ng/ml. CK-301 enhances IFN-gamma secretion in allogeneic mixed lymphocyte reaction (MLR) using primary human T-cells and immature dendritic cells. CK-301 can also trigger antibody-dependent cell-mediated cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC) mediated killing of PD-L1+ cell lines, including lymphoma cells. CK-301 has similar subnanomolar affinity for cynomolgus monkey PD-L1 as for human PD-L1, hence we chose Macaca fascicularis for pre-clinical toxicology and safety pharmacology studies. Single-dose administration of CK-301 to monkeys up to the highest tested dose of 100 mg/kg was shown to be safe and demonstrated linear dose-dependent pharmacokinetic (PK) properties over the dose range from 1 to 100 mg/kg with a half-life of 15 days at 100 mg/kg. A first-in-human Phase 1 study of CK-301 is planned to commence in mid-2017. Citation Format: Leonid Gorelik, George Avgerinos, Yune Kunes, Wayne A. Marasco. Preclinical characterization of a novel fully human IgG1 anti-PD-L1 mAb CK-301 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4606. doi:10.1158/1538-7445.AM2017-4606

Utilizing previously identified in vitro correlates of protection to predict the efficacy of a novel vaccine candidate against the intracellular bacterium Francisella tularensis

Abstract Francisella tularensis (Ft) is an intracellular bacterium that causes tularemia, a disease with a low incidence in US. The only available vaccine, the Live Vaccine Strain (LVS), is investigational and is derived from Type B Ft, not the more virulent Type A Ft. Previous work produced potential correlates to predict successful vaccination. These were determined by in vitro stimulation of murine Ft LVS-immune cells and analyses of their gene expression. We used this approach to investigate correlates of protection for the novel ΔclpB vaccine, derived from Type A Ft SchuS4. Mice were vaccinated with ΔclpB as well as LVS-derived vaccines and subsequently challenged with a lethal dose of LVS, after which all mice vaccinated with ΔclpB and LVS survived. The in vivo survival data was compared with in vitro data obtained from PBLs and splenocytes from vaccinated mice. In general, the in vitro functions of leukocytes from ΔclpB-vaccinated mice were comparable or exceeded those of leukocytes from LVS-vaccinated mice, including control of LVS intramacrophage replication, IFN-gamma secretion, and NO production. Correlates up-regulated in cells from mice vaccinated with ΔclpB included IFN-gamma, IL-21, Nos2, LTA, T-bet, IL-12rbeta2, CCL5 and GzmB; in some cases up-regulation was higher than that from LVS-derived PBLs. Other genes were up-regulated in ΔclpB-derived but not LVS-derived leukocytes, suggesting that improved protection stimulated by the ΔclpB vaccine may be related to the change in strain and/or to stronger immune responses. Hence, this panel of correlates could contribute to the screening of new vaccine candidates, bridging from animal models to humans, and augmenting clinical trials.

Hypomethylating treatment induces tumor specific CD8+ T-cell recognition to osteosarcoma

Objective To investigate feasible immunotherapy strategy using tumor specific cell against osteosarcoma, and to analyze the therapeutic effect of adoptive cellular infusion therapy on osteosarcoma. Methods Decitabine (DAC) was employed as a hypomethylating agent for the treatment in osteosarcoma cell lines HOS and U2OS. After treatment, the expression of cancer-testis antigen (CTA) was evaluated by PCR and Western Blot. In animal studies, human osteosarcoma cell line HOS, which was transfected by luciferase and HLA-A0201 in previous, was inoculated into immune deficient NOD-SCID mice to establish osteosarcoma xenografts. Ex-vivo expanded CTA specific homo CD8+ T-ells were labeled with DiR and injected into the mice via the tail vein. In vivo imaging system was utilized to detect the distribution of administrated CD8+ T-cells. In addition, the progression of tumor xenografts was monitored. Moreover, mouse K7M2 osteosarcoma cell line was used to establish animal models in immune competent BALB/c mice. Immune competent models were utilized to evaluate the effectiveness of hypomethylating treatment in regarding to spontaneous immune attack against tumors. Flow cytometry was used to analyze the proportion of intratumoral lymphocytes and the status of these effector antitumor immune cells, and to reveal the effect of hypomethylating treatment in facilitating lymphocyte infiltration and activation. Results The expression of all the evaluated cancer/testis antigens were elevated in HOS and U2OS osteosarcoma cell lines after hypomethylating treatment with DAC. The proliferation of in vitro cultured osteosarcoma cells can be significantly suppressed after at least 5 d treatment with DAC. Besides, DAC alone controlled osteosarcoma cell proliferation. In immune deficient mouse models, hypomethylating pre-treatment resulted in successful T-cell homing to tumor sites. Moreover, the combination treatment with DAC and CTA specific T-cell adoptive transfer significantly suppressed tumor proliferation. In immune competent mouse models, hypomethylating treatment with DAC improved autologous T-cell infiltration into the tumor, and strengthened the activity of intratumoral CD8+ T-cells, elevated the secretion of IFN-gamma, granzyme B and perforin by CD8+ T-cells. Conclusion Hypomethylating treatment is able to suppress osteosarcoma cell proliferation, improve the expression of CTA in osteosarcoma cells, and consequently provide optimal environment for CTA specific T-cell adoptive therapy. Key words: Osteosarcoma; Cell line, tumor; Animal experimentation