Pulsed Dendritic Cells Research Articles

ATIM-15. SUSTAINED COMPLETE RADIOGRAPHIC RESPONSE AND PROLONGED SYSTEMIC IMMUNE ACTIVATION IN A PATIENT WITH MGMT UNMETHYLATED MIDLINE GLIOBLASTOMA RECEIVING CMV pp65-LAMP RNA-PULSED DENDRITIC CELL VACCINES

Abstract BACKGROUND We initiated a Phase 2, randomized, placebo-controlled, clinical trial evaluating the efficacy of autologous CMV pp65-LAMP RNA pulsed dendritic cell vaccines mixed with GM-CSF and administered during cycles of adjuvant dose-intensified temozolomide (ATTAC II, NCT02465268). STUDY OBJECTIVE A patient with partially resected GBM experienced a sustained complete radiographic response after receiving five DC vaccines. Peripheral blood responses were characterized to examine possible immunologic biomarkers concordant with a sustained clinical response. METHODS Patients with newly diagnosed glioblastoma undergoing surgical resection are eligible and randomized 2:1 to DC vaccine arms vs placebo (PBMCs in saline). DC vaccines consist of CMV pp65 RNA conjugated either to the full-length lysosomal associated membrane protein (LAMP) or to the short LAMP signal sequence. Patients undergo leukapheresis for DC generation prior to standard chemoradiation and receive cycle 1 of dose-intensified temozolomide (100 mg/m^2 x 21 days) before first three biweekly intradermal DC vaccines admixed with GM-CSF. Subsequent DC vaccines (total of 10) are given monthly with each diTMZ cycle with an intradermal tetanus-diphtheria booster given 6-24hrs before the third, fifth, seventh, and ninth DC vaccines. PBMCs and serum are collected for immune monitoring. RESULTS A 58-year old white male with partially-resected, MGMT-unmethlyated, p53 mutant, H3.3 mutant, midline glioblastoma was enrolled on the ATTAC II study and experienced a complete radiographic response after the fifth DC vaccine that has been sustained > 10 months. Immune monitoring by Elispot, cytokine array, and single-cell RNA sequencing have revealed significant expansion of CMV pp65-specific immune responses, increased circulating IFNg, and marked systemic expansion of cytotoxic T cells and iNKT cells during vaccination. These responses were sustained through cycles of diTMZ despite profound lymphopenia. CONCLUSIONS CMV pp65-LAMP RNA-pulsed DC vaccination was associated with profound immunologic and clinical response in a patient with MGMT unmethylated midline glioblastoma.

Glycan modification of glioblastoma-derived extracellular vesicles enhances receptor-mediated targeting of dendritic cells

ABSTRACTGlioblastoma is the most prevalent and aggressive primary brain tumour for which total tumour lysate-pulsed dendritic cell vaccination is currently under clinical evaluation. Glioblastoma extracellular vesicles (EVs) may represent an enriched cell-free source of tumour-associated (neo-) antigens to pulse dendritic cells (DCs) for the initiation of an anti-tumour immune response. Capture and uptake of EVs by DCs could occur in a receptor-mediated and presumably glycan-dependent way, yet the glycan composition of glioblastoma EVs is unknown. Here, we set out to characterize the glycocalyx composition of glioblastoma EVs by lectin-binding ELISA and comprehensive immunogold transmission electron microscopy (immuno-TEM). The surface glycan profile of human glioblastoma cell line-derived EVs (50–200 nm) was dominated by α-2,3- and α-2,6 linked sialic acid-capped complex N-glycans and bi-antennary N-glycans. Since sialic acids can trigger immune inhibitory sialic acid–binding Ig-like lectin (Siglec) receptors, we screened for Siglec ligands on the EVs. Glioblastoma EVs showed significant binding to Siglec-9, which is highly expressed on DCs. Surprisingly, however, glioblastoma EVs lack glycans that could bind Dendritic Cell-Specific Intercellular adhesion molecule-3-Grabbing Non-integrin (DC-SIGN, CD209), a receptor that mediates uptake and induction of CD4+ and CD8+ T cell activation. Therefore, we explored whether modification of the EV glycan surface could reduce immune inhibitory Siglec binding, while enhancing EV internalization by DCs in a DC-SIGN dependent manner. Desialylation with a pan-sialic acid hydrolase led to reduction of sialic acid expression on EVs. Moreover, insertion of a high-affinity ligand (LewisY) for DC-SIGN resulted in a four-fold increase of uptake by monocyte-derived DCs. In conclusion, we show that the glycocalyx composition of EVs is a key factor of efficient DC targeting and that modification of the EV glycocalyx potentiates EVs as anti-cancer vaccine.

Selected commensal bacteria change profiles of Helicobacter pylori-induced T cells via dendritic cell modulation.

The mechanisms of downregulation of protective immunity against Helicobacter pylori (Hp) infection strongly depend on dendritic cell (DC)-induced T-lymphocyte differentiation pattern. Lactic acid bacteria (LAB) strains can modulate Hp-induced immunoresponse by changes in DC activation profiles. Here, we want to find out if the LAB-pulsed DCs will change Hp-induced T-cell responsiveness patterns. The naive peripheral CD4+ T cells were co-cultured with Hp CagA+pulsed monocyte-derived DCs (DC/CD4+ T cell) in the presence/absence of the feces-derived probiotics: antagonistic or non-antagonistic to Hp (Lactobacillus rhamnosus 900, Lr, Lactobacillus paracasei 915, Lp, respectively), as assessed by the agar slab method. The regulatory T-cell (Treg) population was assessed by flow cytometry, and IFN-γ, IL-12p70, IL-10, and IL-17A levels were evaluated by ELISA method. The Hp-pulsed DC/CD4+ T-cell co-cultures were characterized by high IL-10, decreased IL-12p70 and IFN-γ levels, and elevated Treg population. In contrast, Lr-pulsed DC/CD4+ T-cell co-cultures expressed low IL-10, high IL-12p70 and IFN-γ levels and declined Treg population; this responsiveness pattern was not changed by Hp. The responsiveness pattern of the Lp/Hp-pulsed DC/CD4+ T-cell co-cultures did not differ from those pulsed with Hp alone. In contrast to Lp, Lr probiotic strain overcomes Hp-mediated immune profile in the DC/T-cell co-cultures toward Th1 pattern and limited generation of Tregs in vitro. Lr may therefore be used as a component of anti-Hp treatment.

Abstract 1420: Novel expansion of CD8+PD1+ spleen cells for therapeutic intent in pancreatic adenocarcinoma cancer

Abstract Pancreatic ductal adenocarcinoma (PDAC) is a devastating disease with poor prognosis and overall survival. In 2018 it is estimated that there will be 44,333 deaths making PDAC the 3rd cause of cancer related deaths. A distal pancreatomy for PDAC in the body/tail of the pancreas usually includes a splenectomy, with current practice to discard the spleen post-surgery. Spleens can provide a large number of lymphocytes, including CD8+ T-cells with potential to be utilized for adoptive cellular therapy. Our studies have focused on spleen from this patient population, which we posit (and show herein) provides a large number of CD8+PD1+ cells for expansion and the first clinical strategy to expand activated, tumor specific T-cells for subsequent infusion with therapeutic intent. In our studies we used Milteny magnetic bead isolation of CD8+PD1+ T-cells from the spleens of PDAC patients with disease in the distal pancreas. The purity of the cells was 98% with a yield of 79% providing 9x108 CD8+PD1+ cells from an idealized 160 gm spleen. CD8 expansion was undertaken with various growth factor cocktails incorporating combinations of three interleukins (IL); IL-7, IL-15, and IL-21 at varying concentrations. IL-7 supports T-cell survival and proliferation, IL-15 is a potent T-cell growth factor and promotes naïve and memory T-cell survival, and IL-21 limits T-cell exhaustion in response to chronic stimulation. The optimized cocktail incorporated IL-7, IL-15, and IL-21 at 40 ng/mL, which demonstrated maximum T-cell expansion, based on cellularity and cell viability. The predominant T-cell memory phenotype of the CD8+PD1+ cells following expansion was transitional memory (TTM) T-cells that increased from 35.6 ± 4.3 to 52 ± 3%. This memory T-cell phenotype has a high proliferative potential while retaining effector function. Following six days of culture with the three interleukins we observed a 10 fold increase in CD8+PD1+ cells such that 9x109 cells are obtained from the 160 gm spleen. These cells, based on ELISPOT analysis with autologous tumor lysate pulsed dendritic cells retained tumor specificity. In conclusion, CD8+PD1+ cells can be isolated from resected spleen, expanded with retention of tumor specificity and potentially used for adoptive cellular therapy. Citation Format: Kathryn Cole, Quan P. Ly, Jesse L. Cox, Michael A. Hollingsworth, James C. Padussis, Jason M. Foster, Luciano M. Vargas, James E. Talmadge. Novel expansion of CD8+PD1+ spleen cells for therapeutic intent in pancreatic adenocarcinoma cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1420.

Abstract 375: Integrin β4-targeted cancer immunotherapies

Abstract Integrins are heterodimeric cell surface receptors that mediate interaction of cells with extracellular matrix components. Integrin β4 (ITGB4) has been reported by other investigators as a marker of cancer stem cells (CSCs). Immunological targeting of CSCs utilizing ITGB4 as a biomarker represnets a novel therapeutic opportunity to improve the efficacy of current cancer treatment. We previously reported the use of ALDH as a marker to isolate CSCs from multiple tumor types, including both human and animal tumors. In this study, we used two murine tumor models: triple-negative breast cancer (TNBC) 4T1 tumor syngeneic to Balb/c mice and SCC7 tumor which is a spontaneously arising head and neck squamous cell cancer syngeneic to C3H mice. 4T1 cells highly express ITGB4 (about 90%) in unsorted, ALDHhigh and ALDHlow cell populations. In contrast, SCC7 cells preferentially express ITGB4 on ALDHhigh CSCs because ITGB4 cell-surface abundance on ALDHhigh SCC7 cells is approximately 2-fold higher than that on ALDHlow SCC7 cells. We tested two different approaches for ITGB4-targeted immunotherapy: using ITGB4 protein as antigen to pulse dendritic cells (DC) to prepare ITGB4-DC for vaccination, or coating tumor-draining lymph node (TDLN) T cells with anti-CD3 x anti-ITGB4 bispecific antibody (ITGB4BiAb) to prepare ITGB4BiAb-T cells for adoptive transfer. We found that for the tumor which expresses ITGB4 on all the tumor cells at high level (4T1), ITGB4-targeted immunotherapies could inhibit both local tumor growth and metastasis; for the tumor which preferentially expresses ITGB4 on ALDHhigh CSCs (SCC7), ITGB4-targeted immunotherapies inhibited the tumor growth in the lung, with partial effect on local tumor. Co-current administration of anti-PD-L1 mAb significantly enhanced the therapeutic effectiveness of both approches. Our immune monitoring studies in vitro revealed that splenetic T cells harvested from mice treated with ITGB4-DC vaccine or ITGB4BiAb armed T cells mediated significant cytotoxicity against 4T1 cells and SCC7 cells, especially to ALDHhigh CSCs. In addition, ITGB4-DC vaccine or ITGB4BiAb armed T cells conferred significant host anti-ITGB4 humoral immunity as evident by produced antibodies that specifically bind and kill 4T1 cells and SCC7 cells, especially the ALDHhigh CSC population. As a result, both immunotherapeutic approaches significantly reduced the number of ALDHhigh CSCs in the residual tumor subjected to immunotherapies. In conclusion, ITGB4-targeted immunotherapies alone or combined with PD-L1 blockade demonstrated significant antitumor immunity via targeting CSCs. This may provide novel therapeutic strategies for the treatment of ITGB4-positive cancers, such as breast cancer, head and neck squamous cell carcinoma and other soilid tumors. Citation Format: Shasha Ruan, Ming Lin, Yongshun Chen, Elaine Hurt, Alfred E. Chang, Max S. Wicha, Qiao Li. Integrin β4-targeted cancer immunotherapies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 375.

Abstract 1451: HER2 peptide pulsed dendritic cell vaccine induce senescence and eliminates disseminated cancer cells in a preventive model of transgenic HER2/neu breast cancer

Abstract HER-2/neu overexpression plays a critical role in breast cancer development, and its expression in ductal carcinoma in situ (DCIS) is associated with development of invasive breast cancer. The detection of disseminated cancer cells (DCCs) in early-stage DCIS likely to become invasive and manifests prominent role in metastasis and recurrence. The HER2-positive DCCs can easily escape targeted therapies and become a source of tumor recurrence suggesting that targeting these cells may provide eminent benefits in HER2 positive breast cancer patients. Unfortunately, the conventional therapies that target these DCCs are limited. Previous studies from our lab have shown that HER2 peptide pulsed-DC1 (HER2-DC1) vaccine induced 30% complete response (pCR) in DCIS patients. However, little is known about the effect of HER2-DC1 vaccine on DCCs. Here, we investigated the efficacy of HER2-DC1 vaccine on DCCs in a transgenic HER2 mammary cancer model (neuT). The key features of this model are each one of ten mammary glands develops an independent carcinoma that slowly progresses from a microscopic lesion to an invasive tumor and metastasis is mainly driven by DCCs. Since this model mimics some of the most critical features of human disease, we evaluated the efficacy of HER2-DC1 vaccine on DCCs. Mice received six doses of HER2-DC1 vaccine subcutaneously twice a week. The spontaneous tumor development in the mammary glands of NeuT mice was examined once a week by ultrasound until the age of week 16. HER2-DC1 vaccine significantly prevented spontaneous tumor growth in NeuT mice. Remarkably, HER2-DC1 vaccine treatment significantly decreased HER2+CYT8/18+Ki-67+ proliferative DCCs (2%, p<0.002) in the bone marrow (BM-DCCs) compared to untreated mice (6%) by flow cytometry. We also observed increased senescent DCCs (82%, p<0.0001 compared to untreated mice, 37%) by a β-gal assay. BM-DCCs in HER2-DC1 vaccinated mice had reduced expression of Ki-67 compared to untreated mice. Multicolor flow cytometry demonstrated elevated levels of CD4 T cells (2 fold increase) and CD8 T cells (1 fold increase) in the bone marrow after HER2-DC1 vaccination compared to untreated mice. Importantly, accumulation of CD4 T cells (5 fold increase), CD8 T cells (19 fold increase) and B cells (100 fold increase) was observed in the mammary glands of HER2-DC1 vaccinated mice with strong anti-HER2 Th1 immune responses. Notably, HER2-DC1 vaccine led to an increased in the M1 macrophage phenotype (3 fold increase) and decreased M2 type (8 fold decrease) at the tumor site. Treatment of DCCs with Th1 cytokines, IFN-γ or TNF-α significantly induced senescence (76.3%, p<0.0001) in cultured DCCs compared to untreated cells (26%) in vitro. These results describe the novel role of HER2-DC1 vaccine in targeting DCCs and a possible role in prevention of metastasis and recurrence. Citation Format: Ganesan Ramamoorthi, Krithika Kodumudi, Colin Synder, William Dominguez-Viqueira, Scott Kidd, Shari Pilon-Thomas, Brian Czerniecki. HER2 peptide pulsed dendritic cell vaccine induce senescence and eliminates disseminated cancer cells in a preventive model of transgenic HER2/neu breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1451.

Safety of nivolumab in combination with dendritic cell vaccines in recurrent high-grade glioma.

e13526 Background: Recurrence of high-grade glioma (HGG) (WHO grade III-IV) is a nearly universal phenomenon and necessitates the development of new therapeutic modalities. Two possible immunotherapeutic modalities are checkpoint blockade with agents such as nivolumab, a blocking antibody against the inhibitory checkpoint programmed cell death-1 (PD-1), and dendritic cell (DC) vaccination. We have shown in phase 1 and 2 trials that DC vaccination against the glioblastoma (GBM)-associated antigen human cytomegalovirus pp65-lysosomal-associated membrane protein (CMVpp65) is safe and possesses potential benefit. We hypothesized that nivolumab-induced immune checkpoint blockade could enhance efficacy of DC vaccination. Therefore, we undertook a phase 1 study to evaluate safety of nivolumab in combination with CMVpp65 mRNA pulsed DC vaccination in subjects with first or second recurrence of resectable HGG. Methods: We performed a phase 1, single-center, randomized study of nivolumab alone versus nivolumab + DC vaccination prior to planned surgical resection for both groups. We administered nivolumab 3 mg/kg IV q2weeks for 8 weeks followed by surgery and planned continuation of nivolumab. For the group receiving nivolumab + DC vaccination, we administered 3 vaccines before surgical resection with both groups receiving 5 planned post-resection DC vaccines. Primary endpoint was safety assessment using NCI-CTCAE 4.03. Results: We enrolled 6 subjects (4: GBM, 1: anaplastic astrocytoma, 1: anaplastic oligodendroglioma) with 3 receiving nivolumab alone and 3 receiving nivolumab + DC vaccination. Age range was 45-63 years subjects. We documented similar adverse events in both groups with most common grade 1-2 toxicities being fatigue (2 subjects, nivolumab alone) and thrombocytopenia (2 subjects, nivolumab + DC vaccine). Grade 4 toxicities included wound infection (2 subjects, nivolumab + DC vaccine) and meningitis (1 subject, nivolumab + DC vaccine). While we designed the study to enroll 66 subjects, we terminated the study early in light of CheckMate 143 phase III data showing nivolumab did not improve overall survival in recurrent GBM. Conclusions: Safety of nivolumab + DC vaccination in recurrent HGG is similar to nivolumab alone. Continued evaluation of new therapeutics including immunotherapy is underway for this patient population. Clinical trial information: NCT02529072.

Frequency determination of breast tumor-reactive CD4 and CD8 T cells in humans: unveiling the antitumor immune response

ABSTRACT As cancer immunotherapy gains importance, the determination of a patient’s ability to react to his/her tumor is unquestionably relevant. Though the presence of T cells that recognize specific tumor antigens is well established, the total frequency of tumor-reactive T cells in humans is difficult to assess, especially due to the lack of broad analysis techniques. Here, we describe a strategy that allows this determination, in both CD4 and CD8 compartments, using T cell proliferation induced by tumor cell-lysate pulsed dendritic cells as the readout. All 12 healthy donor tested had circulating CD4 and CD8 tumor cell-reactive T cells. The detection of these T cells, not only in the naïve but also in the memory compartment, can be seen as an evidence of tumor immunosurveillance in humans. As expected, breast cancer patients had higher frequencies of blood tumor-reactive T cells, but with differences among breast cancer subtypes. Interestingly, the frequency of blood tumor-reactive T cells in patients did not correlate to the frequency of infiltrating tumor-reactive T cells, highlighting the danger of implying a local tumor response from blood obtained data. In conclusion, these data add T cell evidence to immunosurveillance in humans, confirm that immune parameters in blood may be misleading and describe a tool to follow the tumor-specific immune response in patients and, thus, to design better immunotherapeutic approaches.

Use of modified peptides for live tracking of peptide-MHCII complexes during antigenspecific T cell-dendritic cell interactions

Abstract The recognition of peptide-MHC class II complexes (pMHCII) presented by dendritic cells (DCs) is critical for the activation of CD4+ T cells, and proper detection of such complexes is essential for understanding T cell-DC interactions. However, current detection methods for pMHCII complexes using antibodies may block cellular interactions, limiting their use, while conventional tags, such as GFP, are too large to be loaded onto MHCII without disrupting its function. To probe pMHCII complexes, we constructed a variant of the ovalbumin peptide (OVA323–339) linked to a tetracysteine tag (CCPGCC), which can be treated with organoarsenic compounds to induce fluorescence. This modified peptide retained its functionality as it was able to stimulate T cells to the same degree as the unmodified peptide. We also analyzed signal specificity both at the pMHCII level, by using MHCII−/− APCs, and at a broader level by quenching endogenous tetracysteine expression, and confirmed that our fluorescent signal was derived from the peptide modification. We then used microscopy to visualize pMHCII movement after interaction of pulsed DCs with OVA-specific T cells in vitro and subsequently in vivo, and detected a gradual increase of pMHCII complexes at the synapse. Interestingly, we also observed a transfer of fluorescent signal from DCs to antigen-specific T cells, but not to polyclonal T cells, indicating acquisition of pMHCII, which we were able to quantify. Taken together, our results show a non-disruptive approach to assay pMHCII, and provide a window to observe intricate T cell-DC interactions in real-time.

CD19 chimeric antigen receptor–redirected T cells combined with epidermal growth factor receptor pathway substrate 8 peptide–derived dendritic cell vaccine in leukemia

BackgroundChimeric antigen receptor (CAR)–T cell therapy opens a new era for cancer treatment. However, in prolonged follow-up, relapse has emerged as one of the major obstacles. Dendritic cell (DC) vaccination is a promising treatment to eradicate tumor cells and prevent relapse. The epidermal growth factor receptor (EGFR) pathway substrate 8 (Eps8) gene is involved in regulating cancer progression and is considered an attractive target for specific cancer immunotherapy. The purpose of this study was to explore a combinatorial therapy using CAR-T cells and a DC vaccine such as Eps8-DCs to increase leukemia treatment efficacy. MethodsWe pulsed DCs with Eps8-derived peptides to generate Eps8-DCs, engineered T cells to express a second-generation CAR specific for CD19, and analyzed the effects of the Eps8-DCs on the in vitro expansion, phenotype and effector functions of the CD19 CAR-T cells. ResultsThe Eps8-DCs significantly reduced the activation-induced cell death and enhanced the proliferative potential of CAR-T cells during in vitro expansion. In addition, the expanded T cells co-cultured with the Eps8-DCs exhibited an increased percentage of central memory T cells (Tcms) and a decreased percentage of effector memory T cells (Tems). The Eps8-DCs enhanced CD19 CAR-T cell immune functions, including cytokine production, CD107a degranulation activity and cytotoxicity. DiscussionThis study demonstrates that Eps8-DCs exert synergistic effect on CD19 targeting CAR-T cells and paves the way for clinical trials using the combination of DC vaccination and engineered T cells in relapsed leukemia.

A Characterization of Dendritic Cells and Their Role in Immunotherapy in Glioblastoma: From Preclinical Studies to Clinical Trials

Glioblastoma (GBM) is the most common and fatal primary central nervous system malignancy in adults with a median survival of less than 15 months. Surgery, radiation, and chemotherapy are the standard of care and provide modest benefits in survival, but tumor recurrence is inevitable. The poor prognosis of GBM has made the development of novel therapies targeting GBM of paramount importance. Immunotherapy via dendritic cells (DCs) has garnered attention and research as a potential strategy to boost anti-tumor immunity in recent years. As the “professional” antigen processing and presenting cells, DCs play a key role in the initiation of anti-tumor immune responses. Pre-clinical studies in GBM have shown long-term tumor survival and immunological memory in murine models with stimulation of DC activity with various antigens and costimulatory molecules. Phase I and II clinical trials of DC vaccines in GBM have demonstrated some efficacy in improving the median overall survival with minimal to no toxicity with promising initial results from the first Phase III trial. However, there remains no standardization of vaccines in terms of which antigens are used to pulse DCs ex vivo, sites of DC injection, and optimal adjuvant therapies. Future work with DC vaccines aims to elucidate the efficacy of DC-based therapy alone or in combination with other immunotherapy adjuvants in additional Phase III trials.

Abstract A119: Combating primary and secondary checkpoint blockade resistance using immunostimulatory CD40L/4-1BBL-encoding oncolytic virotherapy for melanoma

Abstract In recent years, cancer immunotherapies significantly advanced the clinical management of metastatic melanoma. In particular, treatment with immune checkpoint inhibitors increased survival rates compared with standard therapy. However, not all patients benefit from checkpoint blockade. Primary treatment resistance is connected to poor T-cell infiltration in the tumors. This can be due to limited activation of antigen-presentation cells such as dendritic cells (DCs) and the high threshold of activating low-affinity T-cells that may respond to the tumor antigens. CD27 signaling in T-cells during activation lowers the T-cell receptor signaling threshold, which may be important to activate tumor-targeting T-cells. Secondary resistance to checkpoint blockade therapy includes loss of MHC-I on the tumor cells. Hence, inducing natural killer (NK) cell activation in parallel to antitumor T-cells may be crucial. LOAd703 was designed to optimize antitumor immune activation. LOAd703 is an oncolytic adenovirus (serotype Ad5/35) carrying two immunostimulatory transgenes; a trimerized membrane-bound CD40 ligand (TMZ-CD40L) and the full-length 4-1BB ligand (4-1BBL) (patent filed: PCT/EP2015/057489). The viral replication is restricted to tumor cells with a hyperphosphorylated retinoblastoma pathway due to a deletion in E1A, but transgenes are expressed under the control of a cytomegalovirus (CMV) promoter, which enables transgene expression even in the surrounding tumor microenvironment. Herein, we investigated LOAd703 in a melanoma model and its immunostimulatory effect on DC maturation to induce antigen-specific T-cell responses. LOAd703 infected the human melanoma cell line 526-mel and efficiently induced tumor cell death as evaluated by MTS viability assay. The viability of infected cells was reduced to 15% at 72 hours post infection compared to uninfected cells. Transgene expression of both TMZ-CD40L and 4-1BBL was confirmed by flow cytometry post infection. To evaluate the immunostimulatory capacity of LOAd703, immature DCs were differentiated from CD14+ monocytes using granulocyte-macrophage colony-stimulating factor and interleukin-4 and infected with virus. LOAd703-infected DCs upregulated the expression of maturation markers, such as CD83, CD86 and MHC molecules as analyzed by flow cytometry. Interestingly, CD70 that is required for CD27 stimuli of T-cells was highly upregulated on the DCs using LOAd703. Furthermore, the chemokine receptor CCR7 and the adhesion molecule ICAM-1 were increased upon LOAd703 infection, which are crucial for lymph node homing and the initiation of a systemic response. Next, the functional capacity of LOAd703-matured DCs to induce antigen-specific T-cell responses was assessed in a CMV model, in which CMV-peptide pulsed DCs are utilized to induce expansion of CMV-specific T-cells. LOAd703-matured DCs from CMV+ donors were pulsed with CMV-peptide and co-cultured with autologous peripheral blood mononuclear cells for 11 days. LOAd703-matured DCs were able to expand CMV-specific T-cells, but to a lower degree than the positive control Poly I:C matured DCs. However, the CMV-specific T-cells expanded from the positive control had higher expression of PD-1 compared to the LOAd703 group, indicating that LOAd703 leads to the expansion of less exhausted and potentially more functional T-cells. Moreover, LOAd703 also induced a massive expansion of NK cells, which is probably driven by 4-1BBL. In conclusion, LOAd703 killed human melanoma cells by oncolysis and induced the expression of TMZ-CD40L and 4-1BBL in infected cells. Furthermore, LOAd703 infection activated DCs to express costimulatory molecules including high levels of CD70 and CCR7, which in turn could promote the expansion of antigen-specific T-cells with low PD-1 expression, as well as the potent expansion of NK cells. Citation Format: Jessica Wenthe, Mantas Šilanskas, Emma Eriksson, Angelica Loskog. Combating primary and secondary checkpoint blockade resistance using immunostimulatory CD40L/4-1BBL-encoding oncolytic virotherapy for melanoma [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 A119.

Immunotherapy for the treatment of canine transmissible venereal tumor based in dendritic cells pulsed with tumoral exosomes

Context: Exosomes secreted by tumor cells are a good source of cellular components that stimulate the immune response, such as alarmins (mRNA, tetraspanins (CD9, CD63, CD81), heat-shock proteins, major histocompatibility complex class I molecules) and tumor-associated antigens. These properties permit to pulsed dendritic cells in the immunotherapy for many cancers types. The aim of this study was to demonstrate the use of exosomes derived from canine transmissible venereal tumor (CTVT) as an antigen to pulsed dendritic cells and its administration in dogs with CTVT as treatment against this disease.Material and methods: From primary culture of CTVT cells the exosomes were isolated and characterized by scanning electron microscopy assay, dot blot and protein quantification. The monocytes of each patient were differentiated to dendritic cells (DC) and pulsed with CTVT exosomes (CTVTE). Phagocytosis, tumor size, populations of lymphocytes and IFN-c levels were evaluated.Results: The CTVTE showed a size around 90 nm. CD81, CD63, CD9 and Hsp70 were expressed. Monocytes showed an expression of 85.71% for CD14+, 12.3% for CD80+, 0.1% for CD83+ and 0.8% for DLA-II. In DC 5.1% for CD14+, 86.7% for CD80+, 90.1% for CD83+ and 92.6% for DLA-II and a phagocytosis of 63% was obtained by FITC Dextran test. No side effects were observed in the experimental groups with our therapy. Tumor regression was of 100% at the seventh week, as well as an increase in the level of IFN-γ (142 pg/ml), and CD4+ (28%) and CD8+ (34%) cell percentage.Discusion and conclusion: These results have shown that DC pulsed with tumor exosomes induce regression of the TVT in dogs.

Development of Acute Myeloid Leukemia Cell Membrane Coated Nanoparticles (AMCNPs) for Cancer Vaccination Immunotherapy

Acute Myeloid Leukemia (AML) is the most common acute leukemia in adults and has a five-year survival rate under 50%. Most patients will relapse even after complete remission is achieved through standard chemotherapy. Thus, one barrier in current AML therapy is how to target the minimal residual disease during remission. Recent developments in understanding cancer cell antigen presentation and immunosuppression have revealed the promise of cancer immunotherapy in activating immune responses to target residual disease. Each leukemia patient has a unique spectrum of cell surface antigens, which are mostly uncharacterized. If these antigens can be efficiently presented to the patient's immune system, immune responses to fight the leukemia can be significantly enhanced. We therefore sought to develop and characterize an AML cell membrane-coated nanoparticle (AMCNP) platform with nanoparticles (NPs) carrying the same surface antigens as the source leukemic cells for use as an anti-cancer vaccine.To demonstrate that our AMCNP vaccines enhance leukemia-specific antigen dendritic cell (DC) presentation and T-cell responses, we modified the C1498 murine AML cell line to express membrane-bound chicken ovalbumin (C1498-mOVA) as a model antigen. We confirmed that the C1498-mOVA line presents the OVA MHC class-I “SIINFEKL” antigen through flow-cytometry and LacZ B3Z T-cell activation assays. The C1498-mOVA line remained leukemogenic when injected into C57BL/6 mice, with survival times between 30 and 55 days.We generated both C1498 and C1498-mOVA membrane-coated nanoparticles, that were packaged with CpG oligo-deoxynucleotides (CpG) as an immune-stimulatory adjuvant. The final AMCNPs exhibit a core-shell structure with uniform coating as shown by transmission electron microscopy. The C1498-mOVA AMCNPs retained mOVA antigen. To confirm that the C1498-mOVA AMCNPs can effectively stimulate DC OVA MHC class I cross-presentation, we pulsed primary bone marrow derived DCs with C1498 AMCNPs or C1498-mOVA AMCNPs; only the C1498-mOVA AMCNP pulsed DCs specifically elicited OVA MHC class-I T-cell activation in lacZ B3Z T-cell activation assays.To verify that the AMCNPs can elicit antigen-specific immune responses in vivo, we vaccinated C57BL/6 mice with C1498 AMCNPs, C1498-mOVA AMCNPs, or equivalent amounts of whole cell lysates. When stimulated ex vivo with OVA peptide, immune-cell preparations from the C1498-mOVA AMCNP vaccinated mice showed significantly enhanced production of OVA-specific T-cells and IFN-γ, demonstrating increased immune responses. To assess if the enhanced cellular immunity afforded by the C1498-mOVA AMCNP formula can translate into functional rejection of leukemia cells, we performed a prophylactic study using the C1498-mOVA model. Mice vaccinated with the C1498-mOVA AMCNPs all survived beyond 120 days post C1498-mOVA cell challenge, compared to mock treated control mice which had a median survival of 60 days.Collectively, we developed an AMCNP platform that carries AML surface antigens and can be packaged with immunostimulatory adjuvants. These AMCNPs retained AML specific antigens, elicited enhanced antigen specific immune responses after in vivo vaccination, and improved immunity against AML challenge. Therefore, using AML cell membrane coated NPs to enhance anticancer immunity is a feasible strategy for AML vaccination immunotherapy. DisclosuresKline:iTeos: Research Funding; Merck: Honoraria, Research Funding.

Tumor-Derived Microvesicles Enhance Cross-Processing Ability of Clinical Grade Dendritic Cells.

Tumor cells release extracellular microvesicles (MVs) in the microenvironment to deliver biological signals to neighboring cells as well as to cells in distant tissues. Tumor-derived MVs appear to play contradictory role promoting both immunosuppression and tumor growth and both evoking tumor specific immune response. Recent evidences indicate that tumor-derived MVs can positively impact Dendritic Cells (DCs) immunogenicity by reprogramming DC antigen processing machinery and intracellular signaling pathways, thus promoting anti-tumor response. DCs are considered pivot cells of the immune system due to their exclusive ability to coordinate the innate and acquired immune responses, cross-present exogenous antigens, and prime naïve T cells. DCs are required for the induction and maintenance of long-lasting anti-tumor immunity and their exploitation has been extensively investigated for the design of anti-tumor vaccines. However, the clinical grade culture conditions that are required to generate DCs for therapeutic use can strongly affect their functions. Here, we investigated the immunomodulatory impact of MVs carrying the MUC1 tumor glycoantigen (MVsMUC1) as immunogen formulation on clinical grade DCs grown in X-VIVO 15 (X-DCs). Results indicated that X-DCs displayed reduced performance of the antigen processing machinery in term of diminished phagocytosis and acidification of the phagosomal compartment suggesting an altered immunogenicity of clinical grade DCs. Pulsing DCs with MVsMUC1 restored phagosomal alkalinization, triggering ROS increase. This was not observed when a soluble MUC1 protein was employed (rMUC1). Concurrently, MVsMUC1 internalization by X-DCs allowed MUC1 cross-processing. Most importantly, MVsMUC1 pulsed DCs activated IFNγ response mediated by MUC1 specific CD8+ T cells. These results strongly support the employment of tumor-derived MVs as immunogen platforms for the implementation of DC-based vaccines.

Total tumor RNA pulsed dendritic cells plus adoptive transfer of ex-vivo enriched autologous T-lymphocytes in the treatment of children with primary brain tumors

Total tumor RNA pulsed dendritic cells plus adoptive transfer of ex-vivo enriched autologous T-lymphocytes in the treatment of children with primary brain tumors

Immunogenic potential of three transmissible venereal tumor cell lysates to prime canine-dendritic cells for cancer immunotherapy

Whole tumor cell lysates consist of a mixture of tumor antigens and danger associated molecular patterns (DAMPs) that can be used for dendritic cell maturation and consequently for the activation of a polyclonal T cell-specific tumor response. We evaluated the in vitro efficacy of three different preparations of canine transmissible venereal tumor (TVT) cell lysates: hypochlorous acid-whole tumor cell lysates (HOCl-L), heat shock-whole tumor cell lysates (HS-L), and freeze-thaw cycles-whole tumor cell lysates (FT-L) for the maturation of canine-derived dendritic cells. Our results showed calreticulin, HSP70, and HSP90 release in the three tumor lysates preparations (HOCl-L, HS-L, and FT-L); however, HMGB1 was detected only in HOCl-L and FT-L. Additionally, the uptake by HOCl-L pulsed dendritic cell (DC) increased compared to HS-L and FT-L pulsed DC; and dendritic cell maturation was confirmed by the appropriate cell surface markers (CD11c, CD80, CD83, and MHCII). Furthermore, dendritic cells pulsed with HOCl-L, HS-L or FT-L were cultured with canine lymphocytes. There was an increase of Th1-type cytokines (IL-12, TNF-α, and IFN-γ), in all the tumor cell lysates co-cultures, this correlates with T lymphocyte activation and cytotoxic response. Our data confirm that TVT cell lysates can induce functional canine-DC and that HOCl-L is the most effective one. This preparation of TVT cell lysates with HOCl is an attractive approach that allows the recognition of neoantigens as potential tumor targets and DC priming and therefore could be used for cancer immunotherapy against TVT.

Induction of protective cellular immune responses against experimental visceral leishmaniasis mediated by dendritic cells pulsed with the N-terminal domain of Leishmania infantum elongation factor-2 and CpG oligodeoxynucleotides

Leishmania elongation factor 2 (EF-2) has been previously identified as a TH1-stimulatory protein. In this study, we assayed the protective potential of the N-terminal domain of EF-2 (N-LiEF-2, 1–357 aa) that has been predicted to contain several overlapping MHC class I and II-restricted epitopes injected in the form of dendritic cell (DC)-based vaccine. Ex vivo pulsing of DCs with the recombinant N-LiEF-2 domain along with CpG oligodeoxynucleotides (ODNs) resulted in their functional differentiation. BALB/c vaccinated with CpG-triggered DCs pulsed with N-LiEF-2 were found to be the most immune-reactive in terms of induction of DTH responses, increased T cell proliferation and IL-2 production. Moreover, vaccination induced antigen-specific TH1 type immune response as evidenced by increased IFN-γ and TNFα levels followed by a significant increase of nitrite (NO) and reactive oxygen species (ROS) in splenocyte cultures. Vaccinated mice showed a pronounced decrease in parasite load in spleen and liver when challenged with L. infantum, increased expression of Stat1 and Tbx21 mRNA transcripts versus reduced expression of Foxp3 transcripts and were able to produce significantly elevated levels of IL-2, IFN-γ and TNFα but not IL-10 compared to non-vaccinated mice. Both antigen and parasite-specific CD4+ T and CD8+ T cells contributed to the IFN-γ production indicating that both subtypes contribute to the resistance to infection and correlated with robust nitrite generation, critical in controlling Leishmania infection. Together, these findings demonstrated the immunogenic as well as protective potential of the N-terminal domain of Leishmania EF-2 when given with CpG-triggered DCs representing a basis for the development of rationalized vaccine against leishmaniasis.

Plant-derived polysaccharides activate dendritic cell-based anti-cancer immunity.

Today, cancers pose a major public health burden. Although a myriad of cancer treatments are available, only a few have achieved clinical efficacy. This is partly attributed to cancers capability to evade host immunity by converting dendritic cells (DCs) from potent stimulators to negative modulators of immunity. Dendritic cell-based immunotherapy attempts to resolve this problem by manipulating the functional characteristics of DCs. Plant-derived polysaccharides (PDPs) can stimulate the maturation of DCs conferring on them the capacity to present internalised tumorigenic antigens to naïve T cells and subsequently priming T cells to eliminate tumours. PDPs have been used as immune modulators and later as anti-cancer agents by Traditional Chinese Medicine practitioners for centuries. They are abundant in nature and form a large group of heterogeneous though structurally related macromolecules that exhibit diverse immunological properties. They can induce antigen pulsed DCs to acquire functional characteristics in vitro which can subsequently be re-introduced into cancer patients. They can also be used as adjuvants in DC-based vaccines or independently for their intrinsic anti-tumour activities. Clinically, some in vitro generated DCs have been shown to be both safe and immunogenic although their clinical application is limited in part by unsatisfactory functional maturation as well as impaired migration to draining lymph nodes where T cells reside. We review the relative potencies of individual PDPs to induce both phenotypic and functional maturation in DCs, their relative abilities to activate anti-cancer immunity, the possible mechanisms by which they act and also the challenges surrounding their clinical application.

Enhanced cytotoxic activity of effector T-cells against cholangiocarcinoma by dendritic cells pulsed with pooled mRNA.

Cholangiocarcinoma is a malignancy of bile duct epithelia with an increasing in incidence rate worldwide. Surgery is the only curative treatment, while adjuvant chemotherapy and radiotherapy render poor responses. Cell-based immunotherapy is a potential strategy for cholangiocarcinoma treatment. However, variation of tumor antigens in cholangiocarcinoma leads to the ineffectiveness of cell-based immunotherapy. In this study, we examined the activation of effector T-cells by dendritic cells pulsed with protein lysate or total RNA from cholangiocarcinoma cell lines for their cytolytic activity against cholangiocarcinoma. Broad-spectrum antigen types with respect to RNA antigen sources were obtained from combination of three cholangiocarcinoma cell lines (KKU-213, KKU-100, and KKU-055). Compared with protein lysate-pulsed dendritic cells, total RNA-pulsed dendritic cells induced anti-tumor effector T-cell response with higher killing ability to KKU-100 and KKU-213 cells compared with protein lysate-pulsed dendritic cells. Moreover, pooled messenger RNA from three cholangiocarcinoma cell lines significantly increased the specific killing capacity of activated lymphocytes against KKU-213 cells. These results suggest that activation of anti-tumor effector T-cells against cholangiocarcinoma by RNA-pulsed dendritic cells is more effective than that by protein lysate-pulsed dendritic cells. In addition, pulsing dendritic cells with pooled messenger RNA from multiple cell lines enhanced the efficacy of a cellular immune response against cholangiocarcinoma.