Cell Stimulatory Capacity Research Articles

TCR Repertoire Clonality Analysis and Transcriptome Analyses of Immune Infiltrates in Patients with Langerhans Cell Histiocytosis Can Define Prognostic Biomarkers for Future Therapeutic Development

Langerhans Cell Histiocytosis (LCH) is a myeloproliferative disorder, most common in children, with an incidence of approximately 5 cases per million children and 1/10,000 live births per year - similar to the frequency of Hodgkin's lymphoma and AML in children. LCH lesions are comprised of clonal pathologic CD207+ dendritic cells (DCs) harboring mutually exclusive genomic alterations of MAPK pathway members along with a large inflammatory infiltrate comprised of macrophages, multinucleated giant cells, lymphocytes, and eosinophils that do not carry MAPK mutations. Mass cytometry revealed that in systemic LCH lesions, T lymphocytes are the most abundant cellular subsets among immune infiltrates and exhibit an exhausted phenotype characterized by expression of immune inhibitory receptors. Since inflammatory infiltrate composed of cells without MAPK pathway mutation is characteristic of LCH, it is likely that the pathogenic DCs in LCH mediate some of the pathologic manifestations through DC-T cell interactions. However, properties of tumor infiltrating T lymphocytes (TILs) in LCH are poorly understood, In this study we performed Bulk TCR alpha/ beta repertoire profiling using the SMARTer TCR a/b Profiling Kit (Takara Bio ) to identify the CDR3 and full length clonotypes in sorted CD8, CD4 and CD4 CD25 compartments isolated from lesions that were stimulated as well the repertoire from the matching white blood cells. We found that in the sorted CD8 cells and CD4 cells from all patient lesions, there was a characteristic clonality shift where-in the repertoire in the lesions were clonally expanded, and interestingly some of the V, J genes were shared among the patient lesions, In addition to changes in the TCR repertoire, we performed bulk Transcriptome analyses to characterize the functional nature of the T-cell infiltrates, and we find that genes responsible for calcium mobilization and mitochondrial metabolism are significantly downregulated in LCH TILs, even after TCR stimulation. RANKL (encoding receptor activator of nuclear factor kappa-B ligand or tumor necrosis factor ligand superfamily member 11) expression, which is solely dependent on TCR activation‐induced calcium mobilization, is also downregulated in the LCH TILs. RANKL is widely known as a modulator of immune cell function by virtue of influencing the survival and T cell-stimulatory capacity of DCs. Impaired calcium mobilization and mitochondrial metabolism might explain the exhausted phenotype we observe in the LCH TILs. We are currently investigating whether the clonal signatures identified by TCR sequencing in the LCH TILs can be used for prognostic purposes, and the T cell functional states can also be exploited to identify biomarkers that can be used to stratify LCH patients for therapy. Disclosures No relevant conflicts of interest to declare.

The Culture Dish Surface Influences the Phenotype and Cytokine Production of Human Monocyte-Derived Dendritic Cells.

Monocyte-derived dendritic cells (moDC) are an important scientific and clinical source of functional dendritic cells (DC). However, the optimization of the generation process has to date mainly been limited to the variation of soluble factors. In this study, we investigated the impact of the cell culture dish surface on phenotype and cytokine profile. We compared a standard cell culture dish to a non-adherent culture dish for two immunogenic maturation conditions, two tolerogenic conditions, and an unstimulated control. Phenotype, cytokine profile and T cell stimulatory capacity were determined after a 3-day culture. Light microscopy revealed an increase in homotypic cluster formation correlated with the use of non-adherent surfaces, which could be reduced by using blocking antibodies against CD18. All surface markers analyzed showed moderate to strong differences depending on the culture dish surface, including significantly decreased expression of key maturation markers such as CD80, CD86, and CCR7 as well as PD-L1 on cells stimulated with the Jonuleit cytokine cocktail cultured on a non-adherent surface. Significant differences in the secretion of many cytokines were observed, especially for cells stimulated with LPS, with over 10-fold decreased secretion of IL-10, IL12-p40, and TNF-α from the cells cultured on the non-adherent surface. All immunogenic moDC populations showed similar capacity to induce antigen-specific T cells. These results provide evidence that the DC phenotype depends on the surface used during moDC generation. This has important implications for the optimization of DC-based immunotherapy development and underlines that the local surrounding can interfere with the final DC population beyond the soluble factors.

CD137L-DCs, Potent Immune-Stimulators-History, Characteristics, and Perspectives.

Dendritic cell (DC)-based immunotherapies are being explored for over 20 years and found to be very safe. Most often, granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-4 (IL-4)-induced monocyte-derived DCs (moDCs) are being used, which have demonstrated some life-prolonging benefit to patients of multiple tumors. However, the limited clinical response and efficacy call for the development of more potent DCs. CD137L-DC may meet this demand. CD137L-DCs are a novel type of monocyte-derived inflammatory DCs that are induced by CD137 ligand (CD137L) agonists. CD137L is expressed on the surface of antigen-presenting cells, including monocytes, and signaling of CD137L into monocytes induces their differentiation to CD137L-DCs. CD137L-DCs preferentially induce type 1 T helper (Th1) cell polarization and strong type 1 CD8+ T cell (Tc1) responses against tumor-associated viral antigens. The in vitro T cell-stimulatory capacity of CD137L-DCs is superior to that of conventional moDCs. The transcriptomic profile of CD137L-DC is highly similar to that of in vivo DCs at sites of inflammation. The strict activation dependence of CD137 expression and its restricted expression on activated T cells, NK cells, and vascular endothelial cells at inflammatory sites make CD137 an ideally suited signal for the induction of monocyte-derived inflammatory DCs in vivo. These findings and their potency encouraged a phase I clinical trial of CD137L-DCs against Epstein–Barr virus-associated nasopharyngeal carcinoma. In this review, we introduce and summarize the history, the characteristics, and the transcriptional profile of CD137L-DC, and discuss the potential development and applications of CD137L-DC.

Recognition of Class II MHC Peptide Ligands That Contain β-Amino Acids.

Proteins are composed of α-amino acid residues. This consistency in backbone structure likely serves an important role in the display of an enormous diversity of peptides by class II MHC (MHC-II) products, which make contacts with main chain atoms of their peptide cargo. Peptides that contain residues with an extra carbon in the backbone (derived from β-amino acids) have biological properties that differ starkly from those of their conventional counterparts. How changes in the structure of the peptide backbone affect the loading of peptides onto MHC-II or recognition of the resulting complexes by TCRs has not been widely explored. We prepared a library of analogues of MHC-II-binding peptides derived from OVA, in which at least one α-amino acid residue was replaced with a homologous β-amino acid residue. The latter contain an extra methylene unit in the peptide backbone but retain the original side chain. We show that several of these α/β-peptides retain the ability to bind tightly to MHC-II, activate TCR signaling, and induce responses from T cells in mice. One α/β-peptide exhibited enhanced stability in the presence of an endosomal protease relative to the index peptide. Conjugation of this backbone-modified peptide to a camelid single-domain Ab fragment specific for MHC-II enhanced its biological activity. Our results suggest that backbone modification offers a method to modulate MHC binding and selectivity, T cell stimulatory capacity, and susceptibility to processing by proteases such as those found within endosomes where Ag processing occurs.

Cord blood granulocytic myeloid-derived suppressor cells impair monocyte T cell stimulatory capacity and response to bacterial stimulation.

Neonatal sepsis is a leading cause of perinatal morbidity and mortality. In comparison to adults, neonates exhibit a higher susceptibility to infections. Myeloid-derived suppressor cells (MDSCs) are myeloid cells with suppressive activity on other immune cells accumulating during foetal life and controlling inflammation in neonates. Most studies investigating the mechanisms for MDSC-mediated immune suppression have been focused on T-cells. Thus far, little is known about the role of MDSC for monocyte function. The impact of human cord blood MDSCs (CB-MDSCs) on monocytes was investigated in an in vitro model. CB-MDSCs were co-cultured with peripheral blood mononuclear cells and monocytes were analysed for expression of surface markers, T cell stimulatory and phagocytic capacity, as well as the production of intracellular cytokines by flow cytometry. CB-MDSCs increased the expression of co-inhibitory molecules and decreased the expression of major histocompatibility complex class II molecules on monocytes, leading to an impaired T-cell stimulatory capacity. Upon bacterial stimulation, expression of phagocytosis receptors, phagocytosis rates and production of tumor necrosis factor-α by monocytes was diminished by CB-MDSCs. We show that CB-MDSCs profoundly modulate monocyte functions, thereby indirectly impairing T-cell activation. Further research is needed to figure out if MDSCs could be a therapeutic target for inflammatory diseases in neonates like neonatal sepsis.

Abstract 2403: Targeting 4-1BB in tumors enhances anti-tumor immune responses

Abstract 4-1BB (CD137) is a co-stimulatory receptor expressed on activated T cells and other immune cells and is associated with enhanced T cell proliferation, survival, and increased cytokine production upon engagement with its ligand (4-1BBL). We have previously shown that addition of agonistic 4-1BB antibody to tumor fragments increased tumor infiltrating lymphocyte (TIL) expansion in human melanoma and pancreatic tumors. Furthermore, agonistic 4-1BB antibody led to increased expression of maturation markers in resident dendritic cells (DCs) present within tumor fragments. While the role of 4-1BB in T cell biology is well described, little is known about 4-1BB signaling in tumor-resident DCs. We hypothesized that 4-1BB agonism in tumor-resident DCs would promote anti-tumor T cell immune responses. To evaluate the role of 4-1BB signaling on dendritic cells, murine bone marrow derived-DCs were cultured with agonistic 4-1BB antibody and loaded with OVA protein. Treatment with agonistic 4-1BB in vitro led to increased OVA-FITC uptake by DCs (32.6% compared to 15.9% in DCs treated with control antibody). DCs treated with agonistic 4-1BB antibody demonstrated increased T cell stimulatory capacity upon co-culture with OVA-specific OT-I and OT-II T cells. We next compared systemic and intralesional (IL) treatment with agonistic 4-1BB antibody. For the systemic model, mice were injected subcutaneously (SC) with B16 melanoma or Panc02 pancreatic tumor cells and treated by intraperitoneal injection of control or anti-4-1BB antibodies. Mice treated systemically with agonistic 4-1BB antibody exhibited a minimal reduction in tumor growth. In contrast, IL injection of agonistic 4-1BB antibody led to dramatic decreases in tumor growth. Next, we wanted to determine whether IL treatment with agonistic 4-1BB antibody would improve DC stimulatory capacity. Mice bearing B16 or Panc02 tumors were treated IL with normal control or anti-4-1BB antibody. After 7 days, tumor-resident CD11b+ DCs exhibited enhanced in vivo antigen uptake. In addition, an increased number of CD8+ T cells was measured within tumors treated with agonistic 4-1BB antibody (28.1% compared to 20% in NrIgG-treated Panc02OVA tumors and 19.45% compared to 7.3% in NrIgG treated B16-OVA tumors; p=0.0059). Together, these studies demonstrate that agonistic 4-1BB can enhance the ability of DCs to stimulate T cells and IL administration of agonistic 4-1BB antibody can significantly reduce tumor growth. This suggests that IL treatment of agonistic 4-1BB may yield greater efficacy than systemic therapy in patients with melanoma or pancreatic cancer. Citation Format: Amy Mackay Weber, Patrick Innamarato, Jennifer Morse, Scott Kidd, Sarah Asby, Amod Sarnaik, Shari Pilon-Thomas. Targeting 4-1BB in tumors enhances anti-tumor immune responses [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 2403.

MicroRNA-155 Controls T Helper Cell Activation During Viral Infection.

MicroRNA (miR) 155 has been implicated in the regulation of innate and adaptive immunity as well as autoimmune processes. Importantly, it has been shown to regulate several antiviral responses, but its contribution to the immune response against cytopathic viruses such as vesicular stomatitis virus (VSV) infections is not known. Using transgenic/recombinant VSV expressing ovalbumin, we show that miR-155 is crucially involved in regulating the T helper cell response against this virus. Our experiments indicate that miR-155 in CD4+ T cells controls their activation, proliferation, and cytokine production in vitro and in vivo upon immunization with OVA as well as during VSV viral infection. Using intravital multiphoton microscopy we analyzed the interaction of antigen presenting cells (APCs) and T cells after OVA immunization and found impaired complex formation when using miR-155 deficient CD4+ T cells compared to wildtype CD4+ T cells ex vivo. In contrast, miR-155 was dispensable for the maturation of myeloid APCs and for their T cell stimulatory capacity. Our data provide the first evidence that miR-155 is required for efficient CD4+ T cell activation during anti-viral defense by allowing robust APC-T cell interaction required for activation and cytokine production of virus specific T cells.

Induction of Antigen-Specific Immune Suppression Using Biodegradable Nanoparticles Containing Antigen and Dexamethasone

Abstract Dexamethasone (Dex) is known to reduce inflammation and autoimmunity by modulating dendritic cell (DC) function, maturation, and differentiation. Nanoparticles (NPs) prepared using biodegradable and biocompatible poly(lactic-co-glycolic acid) (PLGA) can be used to target-delivery vehicles to DCs. In the present study, PLGA nanoparticles containing ovalbumin (OVA) and Dex (NP[OVA+Dex]) were prepared by W1/O/W2 double emulsion solvent evaporation method, and evaluated their antigen-specific immune tolerizing effects. DCs treated with NP[OVA+Dex] were decreased in the expression of MHC class II (I-Ab) and co-stimulatory molecules (CD80 and CD86), and increased in the proportion of CD86−PD-L1+ cell population. DCs treated with NP[OVA+Dex] were reduced in the production of pro-inflammatory cytokine, such as IL-1β, IL-6, IL-12p40 and TNF-α, whereas the production of immunosurpressive cytokine IL-10 was enhanced. Treatment of DCs with NP[OVA+Dex] were diminished in MHC class II-restricted OVA presentation and allogenic T cell stimulatory capacity. NP[OVA+Dex]-treated DCs induced CD4+CD25+FoxP3+ regulatory T cell differentiation from CD4+CD25− T cells isolated from normal, or OT-II mice. Mice injected i.v., or i.g. with NP[OVA+Dex] were suppressed in both inducing OVA-specific CTL responses and producing OVA-specific IgG. The present study demonstrates that NPs encapsulated with antigen and Dex are useful tools in inducing antigen-specific immune tolerance.

Characterization of Antigen-Presenting Cell Subsets in Human Liver-Draining Lymph Nodes.

T-cell immunity in the liver is tightly regulated to prevent chronic liver inflammation in response to antigens and toxins derived from food and intestinal bacterial flora. Since the main sites of T cell activation in response to foreign components entering solid tissues are the draining lymph nodes (LN), we aimed to study whether Antigen-Presenting Cell (APC) subsets in human liver lymph-draining LN show features that may contribute to the immunologically tolerant liver environment. Healthy liver LN, iliac LN, spleen and liver perfusates were obtained from multi-organ donors, while diseased liver LN were collected from explanted patient livers. Inguinal LN were obtained from kidney transplant recipients. Mononuclear cells were isolated from fresh tissues, and immunophenotypic and functional characteristics of APC subsets were studied using flowcytometry and in ex vivo cultures. Healthy liver-draining LN contained significantly lower relative numbers of CD1c+ conventional dendritic cells (cDC2), plasmacytoid DC (PDC), and CD14+CD163+DC-SIGN+ macrophages (MF) compared to inguinal LN. Compared to spleen, both types of LN contained low relative numbers of CD141hi cDC1. Both cDC subsets in liver LN showed a more activated/mature immunophenotype than those in inguinal LN, iliacal LN, spleen and liver tissue. Despite their more mature status, cDC2 isolated from hepatic LN displayed similar cytokine production capacity (IL-10, IL-12, and IL-6) and allogeneic T cell stimulatory capacity as their counterparts from spleen. Liver LN from patients with inflammatory liver diseases showed a further reduction of cDC1, but had increased relative numbers of PDC and MF. In steady state conditions human liver LN contain relatively low numbers of cDC2, PDC, and macrophages, and relative numbers of cDC1 in liver LN decline during liver inflammation. The paucity of cDC in liver LN may contribute to immune tolerance in the liver environment.

Regulation of Dendritic Cell Immune Function and Metabolism by Cellular Nutrient Sensor Mammalian Target of Rapamycin (mTOR).

Dendritic cell (DC) activation is characterized by an acute increase in glucose metabolic flux that is required to fuel the high anabolic rates associated with DC activation. Inhibition of glycolysis significantly attenuates most aspects of DC immune effector function including antigen presentation, inflammatory cytokine production, and T cell stimulatory capacity. The cellular nutrient sensor mammalian/mechanistic Target of Rapamycin (mTOR) is an important upstream regulator of glycolytic metabolism and plays a central role in coordinating DC metabolic changes and immune responses. Because mTOR signaling can be activated by a variety of immunological stimuli, including signaling through the Toll-like Receptor (TLR) family of receptors, mTOR is involved in orchestrating many aspects of the DC metabolic response to microbial stimuli. It has become increasingly clear that mTOR's role in promoting or attenuating inflammatory processes in DCs is highly context-dependent and varies according to specific cellular subsets and the immunological conditions being studied. This review will address key aspects of the complex role of mTOR in regulating DC metabolism and effector function.

Staphylococcus aureus PSM Peptides Modulate Human Monocyte-Derived Dendritic Cells to Prime Regulatory T Cells.

Staphylococcus aureus (Sa), as one of the major human pathogens, has very effective strategies to subvert the human immune system. Virulence of the emerging community-associated methicillin-resistant Sa (CA-MRSA) depends on the secretion of phenol-soluble modulin (PSM) peptide toxins e.g., by binding to and modulation of innate immune cells. Previously, by using mouse bone marrow-derived dendritic cells we demonstrated that PSMs in combination with various Toll-like receptor (TLR) ligands induce a tolerogenic DC phenotype (tDC) characterized by the production of IL-10 and impaired secretion of pro-inflammatory cytokines. Consequently, PSM-induced tDCs favored priming of CD4+CD25+FoxP3+ Tregs with suppressor function while impairing the Th1 response. However, the relevance of these findings for the human system remained elusive. Here, we analyzed the impact of PSMα3 on the maturation, cytokine production, antigen uptake, and T cell stimulatory capacity of human monocyte-derived DCs (moDCs) treated simultaneously with either LPS (TLR4 ligand) or Sa cell lysate (TLR2 ligand). Herein, we demonstrate that PSMs indeed modulate human moDCs upon treatment with TLR2/4 ligands via multiple mechanisms, such as transient pore formation, impaired DC maturation, inhibited pro- and anti-inflammatory cytokine secretion, as well as reduced antigen uptake. As a result, the adaptive immune response was altered shown by an increased differentiation of naïve and even CD4+ T cells from patients with Th1/Th17-induced diseases (spondyloarthritis and rheumatoid arthritis) into CD4+CD127−CD25hiCD45RA−FoxP3hi regulatory T cells (Tregs) with suppressor function. This Treg induction was mediated most predominantly by direct DC-T-cell interaction. Thus, PSMs from highly virulent Sa strains affect DC functions not only in the mouse, but also in the human system, thereby modulating the adaptive immune response and probably increasing the tolerance toward the bacteria. Moreover, PSMα3 might be a novel peptide for tolerogenic DC induction that may be used for DC vaccination strategies.

Differentially Tolerized Mouse Antigen Presenting Cells Share a Common miRNA Signature Including Enhanced mmu-miR-223-3p Expression Which Is Sufficient to Imprint a Protolerogenic State.

Dendritic cells (DCs) are pivotal for the induction and maintenance of antigen-specific tolerance and immunity. miRNAs mediate post-transcriptional gene regulation and control in part the differentiation and stimulation-induced immunogenic function of DCs. However, the relevance of miRNAs for the induction and maintenance of a tolerogenic state of DCs has scarcely been highlighted yet. We differentiated mouse bone marrow cells to conventional/myeloid DCs or to tolerogenic antigen presenting cells (APCs) by using a glucocorticoid (dexamethasone) or interleukin-10, and assessed the miRNA expression patterns of unstimulated and LPS-stimulated cell populations by array analysis and QPCR. Differentially tolerized mouse APCs convergingly down-regulated a set of miRNA species at either state of activation as compared with the corresponding control DC population (mmu-miR-9-5p, mmu-miR-9-3p, mmu-miR-155-5p). These miRNAs were also upregulated in control DCs in response to stimulation. In contrast, miRNAs that were convergingly upregulated in both tolerized APC groups at stimulated state (mmu-miR-223-3p, mmu-miR-1224-5p) were downregulated in control DCs in response to stimulation. Overexpression of mmu-miR-223-3p in DCs was sufficient to prevent stimulation-associated acquisition of potent T cell stimulatory capacity. Overexpression of mmu-miR-223-3p in a DC line resulted in attenuated expression of known (Cflar, Rasa1, Ras) mRNA targets of this miRNA species shown to affect pathways that control DC activation. Taken together, we identified sets of miRNAs convergingly regulated in differentially tolerized APCs, which may contribute to imprint stimulation-resistant tolerogenic function as demonstrated for mmu-miR-223-3p. Knowledge of miRNAs with protolerogenic function enables immunotherapeutic approaches aimed to modulate immune responses by regulating miRNA expression.

Janus Kinase Inhibitor Baricitinib Modulates Human Innate and Adaptive Immune System.

The purpose of this study was to elucidate the mechanism of action of baricitinib on Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signaling, which involves in human innate and adaptive immune system. The effects of baricitinib were evaluated using human monocyte-derived dendritic cells (MoDCs), plasmacytoid dendritic cells (pDCs), B cells, and T cells. Baricitinib concentration-dependently suppressed the expression of CD80/CD86 on MoDCs and the production of type-I interferon (IFN) by pDCs. Baricitinib also suppressed the differentiation of human B cells into plasmablasts by B cell receptor and type-I IFN stimuli and inhibited the production of interleukin (IL)-6 from B cells. Human CD4+ T cells proliferated after T cell receptor stimulation with anti-CD3 and anti-CD28 antibody; however, such proliferation was suppressed by baricitinib in a concentration-dependent manner. In addition, baricitinib inhibited Th1 differentiation after IL-12 stimulation and Th17 differentiation by TGF-β1, IL-6, IL-1β, and IL-23 stimulation. Tofacitinib showed similar effects in these experiments. In naive CD4+ T cells, IFN-α and IFN-γ induced phosphorylation of STAT1, which was inhibited by baricitinib and tofacitinib. Furthermore, IL-6-induced phosphorylation of STAT1 and STAT3 was also inhibited by JAK inhibitors. In conclusion, the results indicated that baricitinib suppresses the differentiation of plasmablasts, Th1 and Th17 cells, as well as innate immunity, such as the T cell stimulatory capacity of dendritic cells. Thus, JAK inhibitors can be potentially clinically effective not only in rheumatoid arthritis but other immune-related diseases.

2173 RNA-nanoparticles to enhance and track dendritic cell migration

OBJECTIVES/SPECIFIC AIMS: Despite aggressive chemotherapy, surgical resection, and radiation therapy, glioblastoma remains almost universally fatal. In a pilot, randomized, and blinded clinical trial, we recently demonstrated that administration of RNA-loaded DC vaccines was associated with significantly improved progression-free and overall survival in patients with glioblastoma (Mitchell et al., Nature, 2015). Furthermore, clinical outcomes correlated with DC migration to vaccine-site draining lymph nodes measured by Indium-111 labeling of RNA-loaded DCs and SPECT/CT imaging. Although these studies demonstrated that tracking DC migration may be an important clinical biomarker for response to DC vaccination, the complexity and regulatory requirements associated with nuclear labelling to track DC migration limits widespread application of this technique. We have therefore developed RNA-loaded magnetic nanoparticles (RNA-NPs) to enhance DC migration to LNs and track that migration with a widely available imaging modality (i.e., MRI). METHODS/STUDY POPULATION: Cationic liposomes were loaded with iron oxide nanoparticles with or without cholesterol. The resulting nanoparticles were complexed with RNA and used to transfect DCs ex vivo. RNA-NP-loaded DsRed+ DCs were then injected intradermally into mice and tracked noninvasively with T2-weighted 11T MRI before excision and quantification with flow cytometry. RESULTS/ANTICIPATED RESULTS: In vitro experiments demonstrate that iron oxide loading does not reduce RNA-NP-mediated transfection of DCs. Additionally, replacement of cationic lipids with cholesterol increased RNA-NP transfection of the DC2.4 cell line and enhanced the T cell stimulatory capacity of treated bone marrow-derived dendritic cells (BMDCs). Compared to electroporation, RNA-NPs enhanced DC migration to lymph nodes and reduced T2 MRI intensity in DC-bearing lymph nodes. DISCUSSION/SIGNIFICANCE OF IMPACT: This data suggests that iron oxide-loaded RNA-NPs enable noninvasive cell tracking with MRI and enhance DC migration to lymph nodes. We have further shown that inclusion of cholesterol in RNA-NPs augments the stimulatory capacity of transfected DCs. Future work will consider effects of RNA-NPs on antitumor immune responses and the utility of MRI-detected DC migration as a biomarker of vaccine efficacy.

Characterizing the function of the CD300e immunoregulatory molecule.

Abstract The CD300 molecules are a family of immunoglobulin-like molecules that have immune regulatory functions. It includes both inhibitory and triggering members, which are highly conserved within the family as well as across species. CD300e, the most restricted member of the family, is expressed in low amounts in most of tissue, whereas its expression is upregulated in different cancers, such as, colorectal, stomach, liver, ovarian and pancreatic cancer. CD300e is highly expressed on CD14+ monocytes. Differentiation of monocytes into dendritic cells (DCs) and macrophages down regulated their CD300e expression. As no monoclonal antibodies are available yet to mouse CD300e, we generated a CD300e knock-out (KO) mouse as an alternative approach to study its biology. We have characterized the changes in immune cells populations resulting from CD300e deletion. The CD300eKO mice are in general fit and reproductively healthy. Mice with CD300e deficiency has a significantly reduction in their circulating leukocytes compared to wild type mice. Hematopoietic stem cells from CD300eKO mice were capable of differentiating in vitro into DC or macrophages with normal antigen uptake and T cell stimulatory capacity. We are using CD300eKO mice to elucidate CD300e function by further testing a variety of functions in monocytic cells.

MRNA-nanoparticles to enhance and track dendritic cell migration.

72 Background: Despite aggressive clinical interventions, glioblastoma (GBM) remains almost universally fatal. In a pilot, randomized, and blinded clinical trial, we recently demonstrated that administration of RNA-loaded dendritic cell (DC) vaccines was associated with significantly improved progression-free and overall survival in patients with GBM (Mitchell et al, Nature 2015). Furthermore, clinical outcomes correlated with migration of Indium-111-labeled DCs to vaccine-site draining lymph nodes (LNs) measured by SPECT/CT imaging. While these studies demonstrated that DC migration may be an important clinical biomarker for response to DC vaccination, the complexity and regulatory requirements associated with nuclear labeling to track DC migration limits widespread application of this technique. We have therefore developed RNA-loaded magnetic nanoparticles (RNA-NPs) to enhance DC migration to LNs and track that migration with a widely available imaging modality (i.e. MRI). Methods: Cationic liposomes were loaded with iron oxide nanoparticles with or without cholesterol modification. The resulting nanoparticles were complexed with RNA and used to transfect DCs ex vivo. RNA-NP-loaded DsRed+ DCs were then injected intradermally into mice and tracked noninvasively with T2-weighted 11T MRI before excision and quantification with flow cytometry. Results: In vitro experiments demonstrate that iron oxide loading does not reduce RNA-NP-mediated transfection of DCs. Additionally, replacement of cationic lipids with cholesterol increased RNA-NP transfection of the DC2.4 cell line and enhanced the T cell stimulatory capacity of treated bone marrow-derived dendritic cells (BMDCs). Compared to electroporation, RNA-NPs enhanced DC migration to lymph nodes and reduced T2 MRI intensity in DC-bearing lymph nodes. Conclusions: This data suggests that iron oxide-loaded RNA-NPs enable noninvasive cell tracking with MRI and enhance DC migration to lymph nodes. We have further shown that inclusion of cholesterol in RNA-NPs augments the stimulatory capacity of transfected DCs. Future work will consider effects of RNA-NPs on antitumor immune responses and the utility of MRI-detected DC migration as a biomarker of vaccine efficacy.

Friend virus limits adaptive cellular immune responses by imprinting a maturation-resistant and T helper type 2-biased immunophenotype in dendritic cells.

The murine Friend virus (FV) retrovirus model has been widely used to study anti-viral immune responses, and virus-induced cancer. Here we analyzed FV immune evasion mechanisms on the level of dendritic cells (DC) essential for the induction of primary adaptive immune responses. Comparative quantitative proteome analysis of FV-infected DC (FV-DC) of different genotypes (BALB/c, C57BL/6) and non-infected DC revealed numerous genotype-independently regulated proteins rergulating metabolic activity, cytoskeletal rearrangements, and antigen processing/presentation. These alterations may promote virion production in FV-DC. Stimulation of FV-DC with LPS resulted in strongly enhanced IL-10 production which was partially responsible for their attenuated T cell (CD4+, CD8+) stimulatory capacity. Stimulated FV-DC induced less IFN-γ production in T cells required for cellular anti-viral responses, but more T helper cell type 2 (Th2)-associated cytokines (IL-4, IL-5, IL-13). We conclude that FV reprograms DC to promote viral spreading and immune deviation by imprinting a largely maturation-resistant, Th2-biased immunophenotype.

MIF inhibition interferes with the inflammatory and T cell-stimulatory capacity of NOD macrophages and delays autoimmune diabetes onset

Macrophages contribute in the initiation and progression of insulitis during type 1 diabetes (T1D). However, the mechanisms governing their recruitment into the islets as well as the manner of retention and activation are incompletely understood. Here, we investigated a role for macrophage migration inhibitory factor (MIF) and its transmembrane receptor, CD74, in the progression of T1D. Our data indicated elevated MIF concentrations especially in long-standing T1D patients and mice. Additionally, NOD mice featured increased MIF gene expression and CD74+ leukocyte frequencies in the pancreas. We identified F4/80+ macrophages as the main immune cells in the pancreas expressing CD74 and showed that MIF antagonism of NOD macrophages prevented their activation-induced cytokine production. The physiological importance was highlighted by the fact that inhibition of MIF delayed the onset of autoimmune diabetes in two different diabetogenic T cell transfer models. Mechanistically, macrophages pre-conditioned with the MIF inhibitor featured a refractory capacity to trigger T cell activation by keeping them in a naïve state. This study underlines a possible role for MIF/CD74 signaling pathways in promoting macrophage-mediated inflammation in T1D. As therapies directed at the MIF/CD74 pathway are in clinical development, new opportunities may be proposed for arresting T1D progression.

NO donors exhibit anti-inflammatory properties by modulating inflammatory signatures and by regulating the life cycle of dendritic cells.

NO mediates a variety of physiologic processes and is considered an important intracellular messenger in different cellular systems. Because of its complex regulation and multiple molecular and cellular targets, NO provides both stimulatory and suppressive properties in the immune system. Dendritic cells (DCs) are considered the most potent APCs, whose regulation has important implications in the induction of an effective immune response. In this study, we analyzed the effect of the compound NCX 2057, a new class of NO-releasing derivatives of ferulic acid, on activation and functional properties of DCs. NCX 2057 was able to modulate the inflammatory program, the cytokines production, and the cellular life cycle but not the maturation markers and the T cells stimulatory capacity of DCs in the presence or absence of LPS. The results indicate that NCX 2057 may modulate different aspects of the activation of DCs and suggest novel applications of NO donors in the contest of inflammatory response modulation through the life cycle regulation of DCs.

CD40 ligation on antigen presenting cells (APCs) enhances properdin production

Gene silencing using small interfering ribonucleic acids (siRNA) is a powerful method to interfere with gene expression, allowing for the functional exploration of specific genes. siRNA interference can be applied in both cell lines, as well as in primary, non-dividing cell types like dendritic cells. However, the efficacy in different cell types is variable and requires optimization. Here, we showed that the type of culture medium used during lipid-based siRNA-mediated transfection acts as a critical factor, affecting dendritic cell activation. Transfection of immature monocyte-derived dendritic cells in RPMI medium, but not in IMDM, showed increased transcript levels of pro-inflammatory cytokines. Moreover, the expression of co-stimulatory molecules was enhanced, thereby increasing the T cell stimulatory capacity. Our data demonstrates that the choice of medium should be critically examined as one of the variables while optimizing cell transfection.