Immature Monocyte-derived Dendritic Cells Research Articles

Internalization of therapeutic antibodies into dendritic cells as a risk factor for immunogenicity.

Immunogenicity, the unwanted immune response triggered by therapeutic antibodies, poses significant challenges in biotherapeutic development. This response can lead to the production of anti-drug antibodies, potentially compromising the efficacy and safety of treatments. The internalization of therapeutic antibodies into dendritic cells (DCs) is a critical factor influencing immunogenicity. Using monoclonal antibodies, with differences in non-specific cellular uptake, as tools to explore the impact on the overall risk of immunogenicity, this study explores how internalization influences peptide presentation and subsequently T cell activation. To investigate the impact of antibody internalization on immunogenicity, untargeted toolantibodies with engineered positive or negative charge patches were utilized. Immature monocyte-derived DCs (moDCs), known for their physiologically relevant high endocytic activity, were employed for internalization assays, while mature moDCs were used for MHC-II associated peptide proteomics (MAPPs) assays. In addition to the lysosomal accumulation and peptide presentation, subsequent CD4+ T cell activation has been assessed. Consequently, a known CD4+ T cell epitope from ovalbumin was inserted into the tool antibodies to evaluate T cell activation on a single, shared epitope. Antibodies with positive charge patches exhibited higher rates of lysosomal accumulation and epitope presentation compared to those with negative charge patches or neutral surface charge. Furthermore, a direct correlation between internalization rate and presentation on MHC-II molecules could be established. To explore the link between internalization, peptide presentation and CD4+ T cell activation, tool antibodies containing the same OVA epitope were used. Previous observations were not altered by the insertion of the OVA epitope and ultimately, an enhanced CD4+ T cell response correlated with increased internalization in DCs and peptide presentation. These findings demonstrate that the biophysical properties of therapeutic antibodies, particularly surface charge, play a crucial role in their internalization into DCs. Antibodies internalized faster and processed by DCs, are also more prone to be presented on their surface leading to a higher risk of triggering an immune response. These insights underscore the importance of considering antibody surface charge and other properties that enhance cellular accumulation during the preclinical development of biotherapeutics to mitigate immunogenicity risks.

The Role of TIM-1 and CD300a in Zika Virus Infection Investigated with Cell-Based Electrical Impedance.

Orthoflaviviruses cause a major threat to global public health, and no antiviral treatment is available yet. Zika virus (ZIKV) entry, together with many other viruses, is known to be enhanced by phosphatidylserine (PS) receptors such as T-cell immunoglobulin mucin domain protein 1 (TIM-1). In this study, we demonstrate for the first time, using cell-based electrical impedance (CEI) biosensing, that ZIKV entry is also enhanced by expression of CD300a, another PS receptor. Furthermore, inhibiting CD300a in immature monocyte-derived dendritic cells partially but significantly inhibits ZIKV replication. As we have previously demonstrated that CEI is a useful tool to study Orthoflavivirus infection in real time, we now use this technology to determine how these PS receptors influence the kinetics of in vitro ZIKV infection. Results show that ZIKV entry is highly sensitive to minor changes in TIM-1 expression, both after overexpression of TIM-1 in infection-resistant HEK293T cells, as well as after partial knockout of TIM-1 in susceptible A549 cells. These results are confirmed by quantification of viral copy number and viral infectivity, demonstrating that CEI is highly suited to study and compare virus-host interactions. Overall, the results presented here demonstrate the potential of targeting this universal viral entry pathway.

Abstract 6743: Identifying new cellular adjuvants for cancer vaccines and immunotherapies

Abstract Background: Cancer vaccines represent a promising strategy for antitumor immunotherapy. Despite considerable research efforts and progress, the effectiveness of cancer vaccines remains a challenge. This is primarily due to relatively low immune responses against tumors, stemming from issues of poor immunogenicity and the immunosuppressive microenvironment commonly found in many solid tumors. Use of an optimal adjuvant can augment immune responses against tumor antigens and guide them towards a specific adaptive immune enhancement. Dendritic cells (DCs) play a primary role in initiating immunes response to vaccines, often through activation of toll-like receptors (TLRs). Identifying novel immunomodulatory proteins that regulate DCs or TLR activation can identify novel adjuvant candidates with applications for cancer immunotherapy. Methods: We constructed a Membrane Proteome Array (MPA) encompassing ~6,000 structurally intact human membrane proteins in their native conformation (94% of the entire membrane proteome) and used it to screen for cellular proteins that can modulate response to vaccination through DCs and TLRs. To identify proteins that interact with TLRs, the library was expressed in live TLR reporter cells, and these cells were tested for response to known activators. In addition, cells expressing the MPA were presented to DCs to identify membrane proteins that modulate DC activity. TLR-expressing cell activation was measuring using an NF-kB-activated luciferase reporter, while DC assays used upregulation of cell surface markers (CD80, CD83, and MHCII) to measure the activation of immature monocyte-derived dendritic cells. Results: Screening of TLR2, TLR3, and TLR5 reporter cell lines identified both known and novel regulators of TLR activation. Activators common to several TLRs were identified as well as activators unique to individual TLRs. Screening of primary human DCs likewise identified known regulators of activation (for example CD40L) and several novel targets. Putative novel regulators of DC activation are being further investigated to determine their biological significance. Conclusion: Discovering novel immunomodulatory targets and proteins that regulate DCs and TLR activation can identify novel adjuvant candidates with targeted immune outcomes, such as immune stimulating and anti-cancer responses. This study identified novel regulators of immune activation which are being further investigated as adjuvant candidates for cancer vaccines. Citation Format: Joseph Rucker, Nnenna Nwogu, Nicholas M. Molino, Ami Snyder, Jonathan T. Sullivan, Benjamin J. Doranz. Identifying new cellular adjuvants for cancer vaccines and immunotherapies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6743.

The effect of cortisol on equine monocyte–derived dendritic cell phenotype and cytokine production

AbstractBackgroundIncreased risk of infection in neonates, including foals, is associated with the naivety of the immune system and the immaturity of the endocrine system. Foal dendritic cells (DCs) are phenotypically and functionally less mature than adult horse DCs. Exposure of foal DCs to foal plasma alters DC phenotypic maturation, cytokine secretion and bacterial endocytosis. Specific plasma factors that impact equine DC activity are unknown. Endocrine dysfunction, resulting in altered cortisol availability, is common in foals. Cortisol impacts DC maturation and function in other species, but the effect of cortisol on equine DCs is not described. We hypothesized that exposure to cortisol would impact both the phenotype and function of equine monocyte–derived DCs (MoDCs), perpetuating an immature phenotype and altered cytokine profile.MethodsMoDCs were generated from foals (n = 8) on 1, 7 and 30 days of age and adult horses (n = 9). MoDCs were exposed to killed bacteria in the presence or absence of cortisol. The expression of surface markers (MHC class‐II, CD86 and CD14) was measured by flow cytometry. Supernatant cytokine concentrations (IL‐4, IL‐17, IFN‐γ and IL‐10) were quantified using a validated bead‐based immunoassay.ResultsCortisol exposure reduced the percentage of equine MoDCs expressing MHC class‐II and CD86 (p ≤ 0.03). Adult horse MoDCs exposed to bacteria and cortisol produced less IL‐4, IL‐17, IFN‐γ and IL‐10 than cells not treated with cortisol, and foal MoDCs secreted less IL‐10 and IL‐4 (p ≤ 0.009).ConclusionsIn sum, cortisol exposure perpetuates an immature MoDC phenotype and alters cytokine responses, which might impact the foal's susceptibility to infection.

Efficient material-induced activation of monocyte-derived dendritic cells releasing surface molecules, matrix metalloproteinases, and growth factors needed for regenerative tissue remodeling

New experimental approaches for tissue repair have recently been proposed and include the application of natural or synthetic biomaterials and immune cells. Herein, fully synthetic poly(glycidyl ether) (PGE) copolymer coatings are evaluated as bioinstructive materials for the in vitro culture and intrinsic activation of human immune cells. Immature monocyte-derived dendritic cells (moDCs) are exposed to PGE brush and gel coatings of varying copolymer composition, wettability, and deformability immobilized on polystyrene culture dishes. Compared to moDCs cultured on standard tissue culture-treated polystyrene, activation marker levels on the cell surface are strongly enhanced on PGE substrates. Thereby, moDCs undergo a distinct morphological change and reach levels of activation comparable to those achieved by toll-like receptor (TLR) ligand liposaccharide (LPS), specifically for the expression of costimulatory molecules CD86 and CD40 as well as human leukocyte antigen (HLA)-DR. In addition, PGE coatings induce a significantly enhanced level of programmed cell death ligands 1 and 2 (PD-L1/-L2) on the moDC surface, two molecules crucially involved in maintaining immune tolerance. In addition, an increased release of matrix metalloproteinases MMP-1 and MMP-7, as well as transforming growth factor (TGF)-β1 and epidermal growth factor (EGF) was observed in moDCs cultured on PGE substrates. As fully synthetic biomaterials, PGE coatings demonstrate intrinsic functional competence in instructing immature human moDCs for phenotypic activation in vitro, accompanied by the secretion of bioactive molecules, which are known to be crucial for tissue regeneration. Hence, PGE coatings hold strong potential for immune-modulating implant coatings, while PGE-activated moDCs are promising candidates for future clinical cell-based immunoengineering therapies.

Interleukin-27-induced HIV-resistant dendritic cells suppress reveres transcription following virus entry in an SPTBN1, autophagy, and YB-1 independent manner.

Interleukin (IL)-27, a member of the IL-12 family of cytokines, induces human immunodeficiency virus (HIV)-resistant monocyte-derived macrophages and T cells. This resistance is mediated via the downregulation of spectrin beta, non-erythrocytic 1 (SPTBN1), induction of autophagy, or suppression of the acetylation of Y-box binding protein-1 (YB-1); however, the role of IL-27 administration during the induction of immature monocyte-derived dendritic cells (iDC) is poorly investigated. In the current study, we investigated the function of IL-27-induced iDC (27DC) on HIV infection. 27DC inhibited HIV infection by 95 ± 3% without significant changes in the expression of CD4, CCR5, and SPTBN1 expression, autophagy induction and acetylation of YB-1 compared to iDC. An HIV proviral DNA copy number assay displayed that 27DC suppressed reverse transcriptase (RT) reaction without influencing the virus entry. A DNA microarray analysis was performed to identify the differentially expressed genes between 27DC and iDC. Compared to iDC, 51 genes were differentially expressed in 27DC, with more than 3-fold changes in four independent donors. Cross-reference analysis with the reported 2,214 HIV regulatory host genes identified nine genes as potential interests: Ankyrin repeat domain 22, Guanylate binding protein (GBP)-1, -2, -4, -5, Stabilin 1, Serpin family G member 1 (SERPING1), Interferon alpha inducible protein 6, and Interferon-induced protein with tetratricopeptide repeats 3. A knock-down study using si-RNA failed to determine a key factor associated with the anti-HIV activity due to the induction of robust amounts of off-target effects. Overexpression of each protein in cells had no impact on HIV infection. Thus, we could not define the mechanism of the anti-HIV effect in 27DC. However, our findings indicated that IL-27 differentiates monocytes into HIV-resistant DC, and the inhibitory mechanism differs from IL-27-induced HIV-resistant macrophages and T cells.

Engineered Human Dendritic Cell Exosomes as Effective Delivery System for Immune Modulation.

Exosomes (exos) contain molecular cargo of therapeutic and diagnostic value for cancers and other inflammatory diseases, but their therapeutic potential for periodontitis (PD) remains unclear. Dendritic cells (DCs) are the directors of immune response and have been extensively used in immune therapy. We previously reported in a mouse model of PD that custom murine DC-derived exo subtypes could reprogram the immune response toward a bone-sparing or bone-loss phenotype, depending on immune profile. Further advancement of this technology requires the testing of human DC-based exos with human target cells. Our main objective in this study is to test the hypothesis that human monocyte-derived dendritic cell (MoDC)-derived exos constitute a well-tolerated and effective immune therapeutic approach to modulate human target DC and T cell immune responses in vitro. MoDC subtypes were generated with TGFb/IL-10 (regulatory (reg) MoDCs, CD86lowHLA-DRlowPDL1high), E. coli LPS (stimulatory (stim) MoDCs, CD86highHLA-DRhighPDL1low) and buffer (immature (i) MoDCs, CD86lowHLA-DRmedPDL1low). Exosomes were isolated from different MoDC subtypes and characterized. Once released from the secreting cell into the surrounding environment, exosomes protect their prepackaged molecular cargo and deliver it to bystander cells. This modulates the functions of these cells, depending on the cargo content. RegMoDCexos were internalized by recipient MoDCs and induced upregulation of PDL1 and downregulation of costimulatory molecules CD86, HLADR, and CD80, while stimMoDCexos had the opposite influence. RegMoDCexos induced CD25+Foxp3+ Tregs, which expressed CTLA4 and PD1 but not IL-17A. In contrast, T cells treated with stimMoDCexos induced IL-17A+ Th17 T cells, which were negative for immunoregulatory CTLA4 and PD1. T cells and DCs treated with iMoDCexos were immune 'neutral', equivalent to controls. In conclusion, human DC exos present an effective delivery system to modulate human DC and T cell immune responses in vitro. Thus, MoDC exos may present a viable immunotherapeutic agent for modulating immune response in the gingival tissue to inhibit bone loss in periodontal disease.

Determination of Vaccine Immunogenicity Using Bovine Monocyte-Derived Dendritic Cells

Dendritic cells (DCs) are the most potent antigen-presenting cells (APCs) within the immune system. They patrol the organism looking for pathogens and play a unique role within the immune system by linking the innate and adaptive immune responses. These cells can phagocytize and then present captured antigens to effector immune cells, triggering a diverse range of immune responses. This paper demonstrates a standardized method for the in vitro generation of bovine monocyte-derived dendritic cells (MoDCs) isolated from cattle peripheral blood mononuclear cells (PBMCs) and their application in evaluating vaccine immunogenicity. Magnetic-based cell sorting was used to isolate CD14+ monocytes from PBMCs, and the supplementation of complete culture medium with interleukin (IL)-4 and granulocyte-macrophage colony-stimulating factor (GM-CSF) was used to induce the differentiation of CD14+ monocytes into naive MoDCs. The generation of immature MoDCs was confirmed by detecting the expression of major histocompatibility complex II (MHC II), CD86, and CD40 cell surface markers. A commercially available rabies vaccine was used to pulse the immature MoDCs, which were subsequently co-cultured with naive lymphocytes. The flow cytometry analysis of the antigen-pulsed MoDCs and lymphocyte co-culture revealed the stimulation of T lymphocyte proliferation through the expression of Ki-67, CD25, CD4, and CD8 markers. The analysis of the mRNA expression of IFN-γ and Ki-67, using quantitative PCR, showed that the MoDCs could induce the antigen-specific priming of lymphocytes in this in vitro co-culture system. Furthermore, IFN-γ secretion assessed using ELISA showed a significantly higher titer (**p < 0.01) in the rabies vaccine-pulsed MoDC-lymphocyte co-culture than in the non-antigen-pulsed MoDC-lymphocyte co-culture. These results show the validity of this in vitro MoDC assay to measure vaccine immunogenicity, meaning this assay can be used to identify potential vaccine candidates for cattle before proceeding with in vivo trials, as well as in vaccine immunogenicity assessments of commercial vaccines.

Extracellular vesicles from Mycobacterium tuberculosis-infected neutrophils induce maturation of monocyte-derived dendritic cells and activation of antigen-specific Th1 cells.

Tuberculosis remains one of the leading public health problems in the world. The mechanisms that lead to the activation of the immune response against Mycobacterium tuberculosis have been extensively studied, with a focus on the role of cytokines as the main signals for immune cell communication. However, less is known about the role of other signals, such as extracellular vesicles, in the communication between immune cells, particularly during the activation of the adaptive immune response. In this study, we determined that extracellular vesicles released by human neutrophils infected with M. tuberculosis contained several host proteins that are ectosome markers. In addition, we demonstrated that extracellular vesicles released by human neutrophils infected with M. tuberculosis released after only 30 min of infection carried mycobacterial antigens and pathogen-associated molecular patterns, and we identified 15 mycobacterial proteins that were consistently found in high concentrations in extracellular vesicles released by human neutrophils infected with M. tuberculosis; these proteins contain epitopes for CD4 T-cell activation. We found that extracellular vesicles released by human neutrophils infected with M. tuberculosis increased the expression of the costimulatory molecule CD80 and of the coinhibitory molecule PD-L1 on immature monocyte-derived dendritic cells. We also found that immature and mature dendritic cells treated with extracellular vesicles released by human neutrophils infected with M. tuberculosis were able to induce IFN-γ production by autologous M. tuberculosis antigen-specific CD4 T cells, indicating that these extracellular vesicles acted as antigen carriers and transferred mycobacterial proteins to the antigen-presenting cells. Our results provide evidence that extracellular vesicles released by human neutrophils infected with M. tuberculosis participate in the activation of the adaptive immune response against M. tuberculosis.

Effects of Magnetic Nanoparticles on the Functional Activity of Human Monocytes and Dendritic Cells.

The use of nanoparticles in medicine is sometimes hampered by their potential to activate immune cells, eliciting inflammation or allergy. We investigated whether magnetic nanoparticles (MNPs) or biomimetic magnetic nanoparticles (BMNPs) affect relevant activities of human monocytes. We found that the nanoparticles neither elicited the production of pro-inflammatory mediators IL-6 and TNFα by resting monocytes (when BMNP dose &lt; 300 μg/mL) nor enhanced their secretion induced by R848, a molecule engaging virus-recognizing receptors, or bacterial lipopolysaccharide (LPS). MNPs and BMNPs neither induced the generation of reactive oxygen species (ROS), nor affected the ROS production elicited by the NADPH oxidase activator phorbol myristate acetate (PMA) or the fungal derivative β-glucan. BMNPs, but not MNPs, caused an up-regulation of the maturation markers CD80, CD83, and CD86 in immature monocyte-derived dendritic cells (DCs), whereas both nanoparticles did not affect the LPS-induced expression of these markers. Moreover, the nanoparticles were greedily ingested by monocytes and DCs without altering their viability. Therefore, these nanoparticles are candidates for medical applications because they do not activate pro-inflammatory activities of monocytes. Furthermore, their ability to stimulate DC maturation could be used for the design of vaccines. Moreover, harmlessly engulfed nanoparticles could be vehicles to carry molecules inside the immune cells to regulate the immune response.

Monocyte-derived immature dendritic cells negatively regulate hepatic stellate cells in vitro by secreting IL-10

The development of liver fibrosis is associated with inflammatory responses resulting from chronic liver disease. Immature dendritic cells (imDCs) play an important role in modulating the inflammatory environment of the liver. This study investigated the effects of imDCs on the regulation of hepatic stellate cells (HSCs) during liver fibrosis. We isolated and induced imDCs from monocytes of healthy volunteers, activated LX-2 cells with TGF-β to establish in vivo liver fibrosis HSCs model, and then set up a cell co-culture system with transwell membranes. imDC surface markers and apoptosis rates of LX-2 cells were detected by flow cytometry. The concentration of IL-10 secreted by imDC was measured through ELISA. The expression of α-SMA in LX-2 after co-culture was examined by qRT‑PCR. Proliferation of LX-2 cells were detected by CCK-8. The western blot was used to illustrate the LX-2 activation-related proteins such as Smad3/7 and TGF-β1. The imDCs co-culture group and the interleukin-10 (IL-10) treatment group had similar results, as they were both able to increase apoptosis, inhibit proliferation, downregulate α-SMA mRNA, and reduce TGF-β1 and Smad3 protein expression in LX-2 cells. Additionally, the Smad7 protein level was increased after treatment with imDC and IL-10. However, the results in the IL-10 antagonist group showed the opposite trend to that of imDCs and IL-10 groups. Thus, these results suggest that imDC secretion of IL-10 negatively regulates activated LX-2 cells, probably via inhibition of the TGF-β1/Smad3 pathway and increased expression of Smad7 protein. This may be a potential therapeutic target for liver fibrosis.

Development of a mRNA Lipid Nanoparticle (mRNA-LNP) Cancer Vaccine to Prevent Leukemia Relapse after Stem Cell Transplant

Introduction The most common acute leukemia in adults is acute myeloid leukemia (AML). Approximately 20,050 new cases and 11,540 deaths are expected for 2022 in the US. Allogeneic stem cell transplant (alloSCT) remains the only cure for high-risk AML. AlloSCTs leverage the immune system to kill leukemic cells through a graft-versus-leukemia (GVL) response mediated by donor CD4+ and CD8+ T cells that recognize recipient leukemic minor histocompatibility antigens (mHAs) as foreign. Unfortunately, transplantation failure related to relapse is common. We postulate that proper targeting of mHAs could enhance leukemia-specific immune responses without off-target effects, improving relapse rates. Using computational modeling, we predicted a series of GVL mHAs, confirmed our first GVL mHA (UNC-GRK4-V) through targeted mass spectrometry, and generated a high-affinity T cell receptor (TCR) against it. Using UNC-GRK4-V as our target, we developed a novel mHA mRNA lipid nanoparticle (LNP) vaccine that we hypothesized could induce an antigen-specific immune response. Methods A custom mRNA was ordered from TriLink that encoded the UNC-GRK4-V peptide linked to an MHC Class I trafficking domain (MITD) and was modified with a 5' cap and polyadenylated tail. We created mRNA LNPs by mixing an ethanol lipid solution made of ionizable lipid (SS-OP, SM-102, or MC3)/ DOPE/Cholesterol/DMG-PEG 2000 with an aqueous solution of mRNA (eGFP or UNC-GRK4-V mRNA) dissolved in a citrated buffer solution. We measured mRNA LNP sizes with a Malvern ZS90 and quantified encapsulation rates using a Quant-it RiboGreen RNA assay kit. Immature monocyte-derived dendritic cells (mo-DCs) were differentiated from monocytes collected from fresh blood and transfected with mRNA LNPs. As a control, we measured eGFP mRNA LNP transfection rates of mo-DCs using flow cytometry. CD8+ T cells were transduced with a retroviral supernatant containing a high-affinity UNC-GRK4-V T-cell receptor and stimulated. We co-cultured mRNA LNP transfected mo-DCs with transduced CD8+ T cells. IFN-g was measured from the co-culture supernatant using IFN-g ELISA assays. We used flow cytometry to determine the cytotoxic killing of transfected mo-DCs by transduced CD8+ T cells. Results To identify the most efficient ionizable lipid platform for mRNA delivery and transfection, we tested three commercially available ionizable lipids: SS-OP, SM-102, and MC3. We found that all three ionizable lipids were easily reproducible with SS-OP 75.2nm ± SD 14.8, MC3 97.0nm ± SD 5.4, SM-102 102.1nm ± SD 0.651. The encapsulation rates of mRNA were 75.4% ± SD 6.3% for SS-OP, 70.5% ± SD 2.6% for MC3, and 73.7% ± SD 0.1% for SM-102. The transfection rate of mo-DCs using eGFP mRNA LNPs were 0.48%, 19.3%, and 62.5% for SS-OP, MC3, and SM-102, respectively. Based on poor transfection rates with SS-OP, we used MC3 and SM-102 LNP formulations to study cytokine expression and cytotoxic killing using a co-culture model of transfected mo-DC with transduced CD8+ T cells. We found a 16.8-fold increase in IFN-g release for the SM-102 based LNPs compared to control empty LNPs (p < 0.0001) and a 4.1-fold increase in IFN-g release for the MC3 based LNPs compared to control empty LNPs (p < 0.0001). We then evaluated SM-102 LNPs for cytotoxic killing as they demonstrated the highest IFN-g release. SM-102 demonstrated increased cell death of 13.5% versus 3.5% for control (empty SM-102) after being normalized for background mo-DC death. Conclusions The SM-102 based UNC-GRK4-V mRNA LNP vaccine elicits robust, antigen-specific T-cell responses and could be a potent therapeutic for decreasing relapse rates post-alloSCT. Furthermore, advances in alloSCT have created regimens that eliminate traditional long-term calcineurin inhibitor use in post-alloSCT, allowing therapeutic cancer vaccines to be given much earlier after transplant.

Inhibition of TREM-2 Markedly Suppresses Joint Inflammation and Damage in Experimental Arthritis.

The triggering receptors expressed on myeloid cells (TREMs) are a family of activating immune receptors that regulate the inflammatory response. TREM-1, which is expressed on monocytes and/or macrophages and neutrophils, functions as an inflammation amplifier and plays a role in the pathogenesis of rheumatoid arthritis (RA). Unlike TREM-1, the role in RA of TREM-2, which is expressed on macrophages, immature monocyte-derived dendritic cells, osteoclasts, and microglia, remains unclear and controversial. TREM-2 ligands are still unknown, adding further uncertainty to our understanding of TREM-2 function. Previously, we demonstrated that TREM-1 blockade, using a ligand-independent TREM-1 inhibitory peptide sequence GF9 rationally designed by our signaling chain homooligomerization (SCHOOL) model of cell signaling, ameliorates collagen-induced arthritis (CIA) severity in mice. Here, we designed a TREM-2 inhibitory peptide sequence IA9 and tested it in the therapeutic CIA model, either as a free 9-mer peptide IA9, or as a part of a 31-mer peptide IA31 incorporated into lipopeptide complexes (IA31-LPC), for targeted delivery. We demonstrated that administration of IA9, but not a control peptide, after induction of arthritis diminished release of proinflammatory cytokines and dramatically suppressed joint inflammation and damage, suggesting that targeting TREM-2 may be a promising approach for the treatment of RA.

Podocalyxin Expressed in Antigen Presenting Cells Promotes Interaction With T Cells and Alters Centrosome Translocation to the Contact Site.

Podocalyxin (PODXL), a cell surface sialomucin expressed in diverse types of normal and malignant cells, mediates cellular adhesion to extracellular matrix and cell-to-cell interaction. A previous study reported the expression of PODXL protein on monocytes undergoing macrophage differentiation, yet the expression of this molecule in other antigen presenting cells (APCs) and its function in the immune system still remain undetermined. In this study, we report that PODXL is expressed in human monocyte-derived immature dendritic cells at both the mRNA and protein levels. Following dendritric cells maturation using pro-inflammatory stimuli, PODXL expression level decreased substantially. Furthermore, we found that PODXL expression is positively regulated by IL-4 through MEK/ERK and JAK3/STAT6 signaling pathways. Our results revealed a polarized distribution of PODXL during the interaction of APCs with CD4+ T cells, partially colocalizing with F-actin. Notably, PODXL overexpression in APCs promoted their interaction with CD4+ T cells and CD8+ T cells and decreased the expression of MHC-I, MHC-II, and the costimulatory molecule CD86. In addition, PODXL reduced the translocation of CD4+ T-cell centrosome toward the APC-contact site. These findings suggest a regulatory role for PODXL expressed by APCs in immune responses, thus representing a potential target for therapeutic blockade in infection and cancer.

Immune activation of the monocyte-derived dendritic cells using patients own circulating tumor cells.

Dendritic cell (DC) therapy counts to the promising strategies how to weaken and eradicate cancer disease. We aimed to develop a good manufacturing practice (GMP) protocol for monocyte-derived DC (Mo-DC) maturation using circulating tumor cells lysates with subsequent experimental T-cell priming in vitro. DC differentiation was induced from a population of immunomagnetically enriched CD14 + monocytes out of the leukapheresis samples (n = 6). The separation was provided automatically, in a closed bag system, using CliniMACS Prodigy® separation protocols (Miltenyi Biotec). For differentiation and maturation of CD14 + cells, DendriMACs® growing medium with supplements (GM-CSF, IL-4, IL-6, IL-1B, TNFa, PGE) was used. Immature Mo-DCs were loaded with autologous circulating tumor cell (CTCs) lysates. Autologous CTCs were sorted out by size-based filtration (MetaCell®) of the leukapheresis CD14-negative fraction. A mixture of mature Mo-DCs and autologous non-target blood cells (NTBCs) was co-cultured and the activation effect of mature Mo-DCs on T-cell activation was monitored by means of multimarker gene expression profiling. New protocols for mMo-DC production using automatization and CTC lysates were introduced including a feasible in vitro assay for mMo-DC efficacy evaluation. Gene expression analysis revealed elevation for following genes in NTBC (T cells) subset primed by mMo-DCs: CD8A, CD4, MKI67, MIF, TNFA, CD86, and CD80 (p ≤ 0.01). Summarizing the presented data, we might conclude mMo-DCs were generated using CliniMACS Prodigy® machine and CTC lysates in a homogenous manner showing a potential to generate NTBC activation in co-cultures. Identification of the activation signals in T-cell population by simple multimarker-qPCRs could fasten the process of effective mMo-DC production.

S1P analogues SEW2871, BAF312 and FTY720 affect human Th17 and Treg generation ex vivo

Multiple Sclerosis is an immune-mediated neurodegenerative disease. IL-23-mediated signaling and Th17 cells play critical roles in disease pathogenesis in murine models of disease and humans. Sphingosine 1 phosphate (S1P) regulates migration of several types of immune cells including Th17 cells. S1P analogues (fingolimod (FTY720) and Siponimod (BAF312)) have been approved and currently used for MS treatment. Immunomodulatory roles for FTY720 have been defined, however, how different S1P analogues impact human Th17 and Treg cell generation and cytokine production, and IL-23-mediated signaling have not yet been explored in detail. In the current study, we investigated the effects of S1P receptor 1 (S1P1) specific S1P analogue SEW2871, S1P1 and S1P5 specific BAF312, and non-selective FTY720 on human Th17 and Treg differentiation and IL-23-mediated signaling. All three S1P analogues directly inhibited Th17 cell differentiation ex vivo while increasing Treg differentiation from naive CD4 + T cells. All three S1P analogues suppressed IL-23-mediated STAT4, NF-kB and AKT activation. Lastly, all three S1P analogues also inhibited Dectin-1 expression by both mature and immature monocyte-derived dendritic cells (moDCs) and in turn curdlan-mediated production of IL-23p19, p40, IL-6 and IL-1β cytokines. Our results provide novel insight into the immunomodulatory roles of different S1P analogues on human Th17 and Treg cell biology.

Antiviral effects of deoxynojirimycin (DNJ)-based iminosugars in dengue virus-infected primary dendritic cells

Dendritic cells (DCs) are important targets for dengue virus (DENV) infection and play a significant role in the early immune response. Antiviral effects of iminosugars against DENV in primary cells have been demonstrated previously in monocyte-derived macrophages (MDMΦs). Given the important role played by DCs in innate immune defense against DENV, the antiviral effects of three deoxynojirimycin (DNJ) derivatives (NN-DNJ, EOO-DNJ and 2THO-DNJ) and a deoxygalactonojirimycin (DGJ) negative control were evaluated in DENV-infected primary human monocyte-derived immature DCs (imDCs). DNJ- but not DGJ-derivatives elicited antiviral activity in DENV-infected imDCs, similar to that observed in MDMΦs. The DNJ-derivatives inhibited DENV secretion in a dose-dependent manner. Endoplasmic reticulum (ER) α-glucosidase I inhibition by DNJ-derived iminosugars, at concentrations of 3.16 μM, correlated with a reduction in the specific infectivity of virions that were still secreted, as well as a reduction in DENV-induced tumour necrosis factor alpha secretion. This suggests iminosugar-mediated ER α-glucosidase I inhibition may give rise to further benefits during DENV infection, beyond the reduction in viral secretion associated with ER α-glucosidase II inhibition.

Genomic Multiple Sclerosis Risk Variants Modulate the Expression of the ANKRD55-IL6ST Gene Region in Immature Dendritic Cells.

Intronic single-nucleotide polymorphisms (SNPs) in the ANKRD55 gene are associated with the risk for multiple sclerosis (MS) and rheumatoid arthritis by genome-wide association studies (GWAS). The risk alleles have been linked to higher expression levels of ANKRD55 and the neighboring IL6ST (gp130) gene in CD4+ T lymphocytes of healthy controls. The biological function of ANKRD55, its role in the immune system, and cellular sources of expression other than lymphocytes remain uncharacterized. Here, we show that monocytes gain capacity to express ANKRD55 during differentiation in immature monocyte-derived dendritic cells (moDCs) in the presence of interleukin (IL)-4/granulocyte-macrophage colony-stimulating factor (GM-CSF). ANKRD55 expression levels are further enhanced by retinoic acid agonist AM580 but downregulated following maturation with interferon (IFN)-γ and lipopolysaccharide (LPS). ANKRD55 was detected in the nucleus of moDC in nuclear speckles. We also analyzed the adjacent IL6ST, IL31RA, and SLC38A9 genes. Of note, in healthy controls, MS risk SNP genotype influenced ANKRD55 and IL6ST expression in immature moDC in opposite directions to that in CD4+ T cells. This effect was stronger for a partially correlated SNP, rs13186299, that is located, similar to the main MS risk SNPs, in an ANKRD55 intron. Upon analysis in MS patients, the main GWAS MS risk SNP rs7731626 was associated with ANKRD55 expression levels in CD4+ T cells. MoDC-specific ANKRD55 and IL6ST mRNA levels showed significant differences according to the clinical form of the disease, but, in contrast to healthy controls, were not influenced by genotype. We also measured serum sgp130 levels, which were found to be higher in homozygotes of the protective allele of rs7731626. Our study characterizes ANKRD55 expression in moDC and indicates monocyte-to-dendritic cell (Mo–DC) differentiation as a process potentially influenced by MS risk SNPs.

Immunomodulatory Effects of Extract of Lingzhi or Reishi Medicinal Mushroom Ganoderma lucidum (Agaricomycetes) Basidiocarps Cultivated on Alternative Substrate.

Ganoderma lucidum is a medicinal mushroom exhibiting numerous health benefits primarily based on strong immunostimulatory effects. The study aimed to investigate if there were differences in effects of extracts of commercially (GC) and alternatively (wheat straw) (GA) cultivated G. lucidum basidiocarps on properties of peritoneal macrophages (PM) and monocyte-derived dendritic cells (MoDCs). Differences in immunomodulatory effects of GC/GA extracts were studied. The viability of treated PMs, their adhesive and phagocytic capability, and their capacity to produce reactive oxygen species (ROS) and NO were tested. Immature MoDCs generated from human monocytes were treated with poly I:C (10.0 μg/ml) and loxoribine (34.0 μg/ml), a selective TLR3 and TLR7 agonists, respectively, and with/without GC/GA extract (100.0 μg/ml). The effect of each combination on phenotypic properties, cytokines production by MoDCs, and their proliferation and Th polarizing capacity was studied. GA extract stimulated the metabolic and phagocytic activity of PMs, their adhesion capability, and ability to produce ROS and NO more strongly compared to GC. Both tested extracts significantly increased allostimulatory and Th1 polarization capacity of simultaneous TLR3 and TLR7-activated MoDCs, but GA extract was more effective. The extract of alternatively cultivated G. lucidum basidiocarps increased production of ROS and NO by TLR4 stimulated PMs and upregulated production of certain cytokines as well as allostimulatory and Th1 polarization capacity of MoDCs. GA extract could be a potent immunostimulatory agent for activation of MoDCs with the simultaneous engagement of TLRs, which seems to be a promising strategy for the preparation of DC-based anti-tumor vaccines.

Abstract 1846: DuoBody-CD40×4-1BB (GEN1042) induces dendritic-cell maturation and enhances T-cell activation and effector functions in vitro by conditional CD40 and 4-1BB agonist activity

Abstract The clinical success of immune checkpoint inhibitor monoclonal antibodies (mAbs) has demonstrated potential for re-activation of anti-tumor immunity in cancer treatment. DuoBody®-CD40×4-1BB (GEN1042) is a first-in-class bispecific agonistic antibody that combines targeting of costimulatory molecules CD40 and 4-1BB, resulting in priming and (re-)activation of tumor-specific immunity. We previously showed that DuoBody-CD40×4-1BB induces CD40 and 4-1BB agonist activity that is conditional, i.e., dependent on crosslinking of CD40- and 4-1BB-expressing cells. Here we further elucidate the preclinical mechanism of action of DuoBody-CD40×4-1BB in a broad range of functional immune cell assays. Fixed cell microscopy and live cell imaging of the immune synapse was performed using co-cultures of activated T cells and monocyte-derived dendritic cells (DC). DuoBody-CD40×4-1BB co-localized with LFA-1 at the interface between DC and activated T cells. By binding to both targets, DuoBody-CD40×4-1BB enhanced DC/T cell interactions and increased the contact duration between these cells compared to the combination of monovalent CD40- and 4-1BB-specific antibodies. In mixed lymphocyte reactions (MLR) comprised of naïve CD8+ T cells co-cultured with immature (iDC) or LPS-matured monocyte-derived DCs (mDC), DuoBody-CD40×4-1BB induced DC maturation and increased T cell functionality, shown by a dose-dependent increase in HLA-DR/CD86 expression and production of IFNγ, CXCL10 and granzyme B. DC maturation induced by DuoBody-CD40×4-1BB was also observed in monocultures of iDCs expressing both targets, and was associated with a concurrent dose-dependent increase in TNFα production. Furthermore, in antigen-specific T-cell assays (CLDN6-TCR+CD8+ T cells co-cultured with CLDN6+CD40+ DCs), DuoBody-CD40×4-1BB conditionally enhanced T-cell proliferation and production of IFNγ and TNFα, and induced upregulation of the degranulation marker CD107a and granzyme B. Finally, DuoBody-CD40×4-1BB enhanced clonal expansion of human TILs derived from non-small cell lung and colon cancer patients ex vivo in a dose-dependent manner. In conclusion, by enhancing the formation of the immune synapse between CD40+ DC and 4-1BB+ T cells, DuoBody-CD40×4-1BB induced conditional activation of both cell types, resulting in DC maturation, T-cell activation and effector functions in vitro. Thereby, DuoBody-CD40×4-1BB provides a unique combination of priming and enhancing existing anti-tumor immunity. DuoBody-CD40×4-1BB is currently being evaluated in patients with advanced solid tumors in a first-in-human trial (NCT04083599). Citation Format: Alexander Muik, Rachelle Kosoff, Friederike Gieseke, Isil Altintas, Kristina Schödel, Saskia Burm, Eliana Stanganello, Fulvia Vascotto, Aras Toker, Homer Adams, III, Esther Breij, Mustafa Diken, Tahamtan Ahmadi, Kate Sasser, Özlem Türeci, Mark Fereshteh, Ugur Sahin, Maria Jure-Kunkel. DuoBody-CD40×4-1BB (GEN1042) induces dendritic-cell maturation and enhances T-cell activation and effector functions in vitro by conditional CD40 and 4-1BB agonist activity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1846.