Transcriptional profiling of macrophages in situ in metastatic melanoma reveals localization-dependent phenotypes and function

Modulation of immune function at the tumor site could improve patient outcomes. Here, we analyze patient samples of metastatic melanoma, a tumor responsive to T cell-based therapies, and find that tumor-infiltrating T cells are primarily juxtaposed to CD14+ monocytes/macrophages rather than melanoma cells. Using immunofluorescence-guided laser capture microdissection, we analyze transcriptomes of CD3+ T cells, CD14 + monocytes/macrophages, and melanoma cells in non-dissociated tissue. Stromal CD14+ cells display a specific transcriptional signature distinct from CD14+ cells within tumor nests. This signature contains LY75, a gene linked with antigen capture and regulation of tolerance and immunity in dendritic cells (DCs). When applied to TCGA cohorts, this gene set can distinguish patients with significantly prolonged survival in metastatic cutaneous melanoma and other cancers. Thus, the stromal CD14+ cell signature represents a candidate biomarker and suggests that reprogramming of stromal macrophages to acquire DC function may offer a therapeutic opportunity for metastatic cancers.

The STING activator c-di-AMP exerts superior adjuvant properties than the formulation poly(I:C)/CpG after subcutaneous vaccination with soluble protein antigen or DEC-205-mediated antigen targeting to dendritic cells

Vaccination is the most efficient strategy to protect from infectious diseases and the induction of a protective immune response not only depends on the nature of the antigen, but is also influenced by the vaccination strategy and the co-administration of adjuvants. Therefore, the precise monitoring of adjuvant candidates and their immune modulatory properties is a crucial step in vaccine development. Here, one central aspect is the induction of appropriate humoral and cellular effector mechanisms. In our study we performed a direct comparison of two promising candidates in adjuvant development, the STING activator bis-(3,5)-cyclic dimeric adenosine monophosphate (c-di-AMP) and the Toll-like receptor ligand formulation poly(I:C)/CpG. These were evaluated in C57BL/6 mice using the model antigen ovalbumin (OVA) in subcutaneous vaccination with soluble protein as well as in a dendritic cell (DC) targeting approach (αDEC-OVA). Strikingly, c-di-AMP as compared to poly(I:C)/CpG resulted in significantly higher antigen-specific IgG antibody levels when used in immunization with soluble OVA as well as in antigen targeting to DC. In vaccination with soluble OVA, c-di-AMP induced a significantly stronger CTL, Th1 and IFNγ-producing CD8⁺ memory T cell response than poly(I:C)/CpG. The response was CTL and Th1 cell dominated, a profile shared by both adjuvants. In the context of targeting OVA to DC, c-di-AMP induced significantly increased Th1 and Th2 cell responses as compared to poly(I:C)/CpG. Interestingly, the Th1 response dominated the overall T cell response only when c-di-AMP was used, indicating a distinct modulatory property of c-di-AMP when the DC targeting immunization approach was exploited. Taken together, we describe superior properties of c-di-AMP as compared to poly(I:C)/CpG in subcutaneous vaccination with soluble antigen as well as antigen targeting to DC. This indicates exceptionally effective adjuvant properties for c-di-AMP and provides compelling evidence of its potential for further adjuvant development, especially also when using DC targeting approaches.

Advancing immunomodulation by in vivo antigen delivery to DEC-205 and other cell surface molecules using recombinant chimeric antibodies

A targeted delivery of defined antigens in vivo allows for the probing of relevant functions of the immune system. Recombinant chimeric antibodies, produced by genetically modifying original monoclonal antibodies specific for molecules expressed on dendritic cells and other immune cells, have paved the way for the development of such strategies and have become reliable tools for achieving a specific immunomodulation. These antibodies have proven important in both basic research and clinical applications, extending data obtained in disease models of autoimmunity and cancer. Here we will describe the advances gained from the experimental and therapeutic strategies based on the targeting of the specific antigens by recombinant chimeric antibodies to the multilectin receptor DEC-205 and other cell surface molecules.

Targeted Delivery of Toxoplasma gondii Antigens to Dendritic Cells Promote Immunogenicity and Protective Efficiency against Toxoplasmosis

Toxoplasmosis is a major public health problem and the development of a human vaccine is of high priority. Efficient vaccination against Toxoplasma gondii requires both a mucosal and systemic Th1 immune response. Moreover, dendritic cells play a critical role in orchestrating the innate immune functions and driving specific adaptive immunity to T. gondii. In this study, we explore an original vaccination strategy that combines administration via mucosal and systemic routes of fusion proteins able to target the major T. gondii surface antigen SAG1 to DCs using an antibody fragment single-chain fragment variable (scFv) directed against DEC205 endocytic receptor. Our results show that SAG1 targeting to DCs by scFv via intranasal and subcutaneous administration improved protection against chronic T. gondii infection. A marked reduction in brain parasite burden is observed when compared with the intranasal or the subcutaneous route alone. DC targeting improved both local and systemic humoral and cellular immune responses and potentiated more specifically the Th1 response profile by more efficient production of IFN-γ, interleukin-2, IgG2a, and nasal IgA. This study provides evidence of the potential of DC targeting for the development of new vaccines against a range of Apicomplexa parasites.

Enhanced contraception of canine zona pellucida 3 DNA vaccine via targeting DEC-205 in mice

Zona pellucida 3 (ZP3) is a potential antigen for the development of contraceptive vaccines to control animal population. In this study, we designed a canine ZP3 (CZP3) DNA vaccine through targeting DEC-205 (named as pcD-scFv-CZP3c) and investigated its contraceptive effect in mice. Female BALB/c mice were intramuscularly immunized 3 times at 2 weeks intervals. After immunization, humoral and cellular immune responses were detected by ELISA and flow cytometry. The results showed that pcD-CZP3 and pcD-scFv-CZP3c induced CZP3-specific antibody (Ab) responses both in serum and vaginal secretions compared to pcDNA3.1. Additionally, compared to pcD-CZP3, pcD-scFv-CZP3c increased the levels of CZP3-specific Abs after a third immunization. Abs induced by these two DNA vaccines could bind with mice and dogs oocytes. Moreover, pcD-scFv-CZP3c enhanced the activation of CD4⁺ T cells characterized by the increased frequencies of CD4⁺CD44⁺ T cells. Finally, the contraceptive effect was evaluated in the immunized mice. These two DNA vaccines significantly decreased a mean litter size of mice compared to pcDNA3.1, but pcD-scFv-CZP3c group showed the smallest mean litter size. The mean litter size of pcD-scFv-CZP3 were 3.2 ± 0.742 and 4.6 ± 1.118 in two mating tests, which were significantly lower than pcDNA3.1(P < 0.001 and P < 0.05). Our results suggest that the CZP3 DNA vaccine targeted with DEC-205 may be a potential strategy for developing a contraceptive DNA vaccine.

Targeting antigens to Dec-205 on dendritic cells induces a higher immune response in chickens: Hemagglutinin of avian influenza virus example

It is widely known that targeting a variety of antigens to the DEC-205 receptor on dendritic cells (DCs) significantly potentiate immunity. This communication reports the development of a new murine monoclonal antibody (mAb) against the chicken DEC-205, using as immunogen the carbohydrate recognition domain-2 (CRD-2) heterologously expressed. This mAb recognizes a protein band of 250kDa by immunoprecipitation analysis and shows strong cross-reactivity with human and pig DEC-205. Furthermore, the hemagglutinin (HA) of avian influenza H5N2 virus was cloned and expressed using insect cell-baculovirus expression system. We chemically conjugated the anti-chicken DEC-205 antibody with the highly purified HA to direct the antigen to the dendritic cells and evaluate the immune response elicited in vivo by this conjugate. A single dose of chemical conjugate was sufficient to elicit a strong immune response in chickens as early as fourteen days after priming. In addition, the conjugate induced an earlier and higher response compared to unconjugated HA. These results suggest that the strategy described here has potential to be used in the future design and development of successful vaccines against different chicken infectious diseases with direct impact in biotechnology and veterinary fields.

Mucosal expression of DEC-205 targeted allergen alleviates an asthmatic phenotype in mice

Considering the rising incidence of allergic asthma, the symptomatic treatments that are currently applied in most cases are less than ideal. Specific immunotherapy is currently the only treatment that is able to change the course of the disease, but suffers from a long treatment duration. A gene based immunization that elicits the targeting of allergens towards dendritic cells in a steady-state environment might have the potential to amend these difficulties. Here we used a replication deficient adenovirus to induce the mucosal expression of OVA coupled to a single-chain antibody against DEC-205. A single intranasal vaccination was sufficient to mitigate an OVA-dependent asthmatic phenotype in a murine model. Invasive airway measurements demonstrated improved lung function after Ad-Dec-OVA treatment, which was in line with a marked reduction of goblet cell hyperplasia and lung eosinophilia. Furthermore OVA-specific IgE titers and production of type 2 cytokines were significantly reduced. Together, the here presented data demonstrate the feasibility of mucosal expression of DEC-targeted allergens as a treatment of allergic asthma.

α-Galactosylceramide-activated murine NK1.1(+) invariant-NKT cells in the myometrium induce miscarriages in mice

Innate immunity, which is unable to discriminate self from allo‐antigens, is thought to be important players in the induction of miscarriages. Here, we show that the administration of IL‐12 to syngeneic‐mated C57BL/6 mice on gestation day 7.5 (Gd 7.5), drives significant miscarriages in pregnant females. Furthermore, the administration on Gd 7.5 of α‐galactosylceramide (α‐GalCer), which is known to activate invariant natural killer T (iNKT) cells, induced miscarriages in both syngeneic‐mated C57BL/6 mice and allogeneic‐mated mice (C57BL/6 (♀) × BALB/c (♂)). Surprisingly, the percentages of both DEC‐205⁺ DCs and CD1d‐restricted NK1.1⁺ iNKT cells were higher in the myometrium of pregnant mice treated i.p. with α‐GalCer than in the decidua. IL‐12 secreted from α‐GalCer‐activated DEC‐205⁺ DCs stimulated the secretion of cytokines, including IL‐2, IL‐4, IFN‐γ, TNF‐α, perforin, and granzyme B, from the NK1.1⁺ iNKT cells in the myometrium, leading to fetal loss in pregnant mice. Finally, the i.p. administration of IL‐12 and/or α‐GalCer in iNKT‐deficient Jα18(‐/‐) (Jα18 KO) mice did not induce miscarriages. This study provides a new perspective on the importance of the myometrium, rather than the decidua, in regulating pregnancy and a mechanism of miscarriage mediated by activated DEC‐205⁺ DCs and NK1.1⁺ iNKT cells in the myometrium of pregnant mice.

Targeting Antigens to Dec-205 on Dendritic Cells Induces Immune Protection in Experimental Colitis in Mice

The endocytotic c-type lectin receptor DEC-205 is highly expressed on immature dendritic cells. In previous studies, it was shown that antigen-targeting to DEC-205 is a useful tool for the induction of antigen-specific Foxp3⁺ regulatory T cells and thereby can prevent inflammatory processes. However, whether this approach is sufficient to mediate tolerance in mucosal tissues like the gut is unknown. In this study, we established a new mouse model in which the adoptive transfer of naive hemagglutinin (HA)-specific CD4⁺Foxp3^– T cells into VILLIN-HA transgenic mice leads to severe colitis. To analyze if antigen-targeting to DEC-205 could protect against inflammation of the gut, VILLIN-HA transgenic mice were injected with an antibody–antigen complex consisting of the immunogenic HA_110–120 peptide coupled to an α-DEC-205 antibody (DEC-HA) before adoptive T cell transfer. DEC-HA-treated mice showed significantly less signs of intestinal inflammation as was demonstrated by reduced loss of body weight and histopathology in the gut. Strikingly, abrogated intestinal inflammation was mediated via the conversion of naive HA-specific CD4⁺Foxp3^– T cells into HA-specific CD4⁺Foxp3⁺ regulatory T cells. In this study, we provide evidence that antigen-targeting to DEC-205 can be utilized for the induction of tolerance in mucosal organs that are confronted with large numbers of exogenous antigens.

Targeting of rotavirus VP6 to DEC-205 induces protection against the infection in mice

Rotavirus (RV) is the primary etiologic agent of severe gastroenteritis in human infants. Although two attenuated RV-based vaccines have been licensed to be applied worldwide, they are not so effective in low-income countries, and the induced protection mechanisms have not been clearly established. Thus, it is important to develop new generation vaccines that induce long lasting heterotypic immunity. VP6 constitutes the middle layer protein of the RV virion. It is the most conserved protein and it is the target of protective T-cells; therefore, it is a potential candidate antigen for a new generation vaccine against the RV infection. We determined whether targeting the DEC-205 present in dendritic cells (DCs) with RV VP6 could induce protection at the intestinal level. VP6 was cross-linked to a monoclonal antibody (mAb) against murine DEC-205 (αDEC-205:VP6), and BALB/c mice were inoculated subcutaneously (s.c.) twice with the conjugated containing 1.5 μg of VP6 in the presence of polyinosinic-polycytidylic acid (Poly I:C) as adjuvant. As controls and following the same protocol, mice were immunized with ovalbumin (OVA) cross-linked to the mAb anti-DEC-205 (αDEC-205:OVA), VP6 cross-linked to a control isotype mAb (Isotype:VP6), 3 μg of VP6 alone, Poly I:C or PBS. Two weeks after the last inoculation, mice were orally challenged with a murine RV. Mice immunized with α-DEC-205:VP6 and VP6 alone presented similar levels of serum Abs to VP6 previous to the virus challenge. However, after the virus challenge, only α-DEC-205:VP6 induced up to a 45% IgA-independent protection. Memory T-helper (Th) cells from the spleen and the mesenteric lymph node (MLN) showed a Th1-type response upon antigen stimulation in vitro. These results show that when VP6 is administered parenterally targeting DEC-205, it can induce protection at the intestinal level at a very low dose, and this protection may be Th1-type cell dependent.

Design, expression, and characterization of a novel dendritic cell-targeted proteins

In vivo approaches to inducing an effective immune response focus on targeted antigen (Ag) delivery to dendritic cells (DCs). In this study, we developed a new method of targeting plasmid DNA and/or the antigen (Ag)-antibody (Ab) complex to DCs via the DC receptor DEC-205, also known as cluster of differentiation CD205. We cloned and expressed a recombinant protein composed of mouse DEC-205-specific single-chain fragment variable region (mDEC-205-scFv), the streptococcal protein G (SPG) IgG-binding domain and cationic peptide (CP), which named mDEC205-scFv-SPG-CP (msSC). In vitro, the recombinant protein msSC can specifically bind to DCs through the section of mDEC-205-scFv, and bound the Ag-Ab complex via SPG as well as plasmid DNA through electrostatic bonding with CP in vitro. In addition, msSC functioned in a manner similar to anti-DEC-205 monoclonal Ab and bound to mouse bone marrow-derived DCs. It was demonstrated in vivo that msSC can target plasmid DNA to DCs, resulting in efficient uptake and expression. Moreover, msSC can form a complex with pGL3-CMV and transport it to draining lymph nodes when injected in vivo. These results indicate that msSC can be used as a carrier protein for vaccine delivery to DCs via formation of plasmid DNA-Ag-Ab ternary complexes.

Imbalance between CD205 and CD80/CD86 in dendritic cells in patients with immune thrombocytopenia. Thromb Res. 2015;135:352-361. [PMID: 25554498 DOI: 10.1016/j.thromres.2014.11.042]

INTRODUCTION

CD205(DEC-205), a tolerance-associated receptor, is a member of the macrophage mannose receptor family of C-type lectin receptors. Antigen uptake via CD205 induces regulatory T cells, thereby regulating peripheral immune tolerance. However, the contribution of CD205 to autoimmune diseases has not been elucidated. Immune thrombocytopenia (ITP) is an autoimmune disorder characterized by overdestruction of platelets. A previous study by the present authors found that CD205 expression in dendritic cells (DCs) was upregulated during induction of immune tolerance in patients with ITP.

METHODS

CD205 expression in monocyte-derived DCs and spleens from patients with ITP was analysed prior to and after high-dose dexamethasone (HD-DXM) treatment. Expression of CD80, CD86 and HLA-DR was also analysed in order to identify and define the maturation status of the DCs more precisely.

RESULTS

In patients with ITP, CD205 expression was found to be significantly decreased in DCs, and rare or absent in the border region of the spleen. However, the expression of CD80 and CD86 was increased in both monocyte-derived DCs and spleens in patients with ITP compared with controls. HD-DXM treatment may upregulate CD205 expression and downregulate CD80/CD86 expression, then rebalance the expression of CD205 and CD80/CD86 in DCs in patients with ITP.

CONCLUSION

Imbalance between CD205 and CD80/CD86 may contribute to the development of ITP. Therapies that aim to restore the balance between CD205 and CD80/CD86 may help to re-establish tolerance in patients with ITP.

An anti-DEC-205 monoclonal antibody stimulates binding of thymocytes to rat thymic dendritic cells and promotes apoptosis of thymocytes

DEC-205, a transmembrane receptor responsible for cross-presentation of apoptotic cell-derived antigens, is expressed by cortical thymic epithelial cells (TEC) and thymic dendritic cells (TDC) in humans and mice, but its function in T-cell development is still unclear. In this work we have studied for the first time the expression of DEC-205 in the rat thymus by HD83 monoclonal antibody (mAb) and immunohistochemistry, as well as the ability of this mAb to modulate thymocyte – TDC interactions in vitro. We showed the positivity of cortical TEC in situ, including thymic nurse cells (TNC) in suspension, and TDC, whereas subcapsular, perivascular and medullary TEC were negative. All examined DEC-205 positive and DEC-205 negative structures were MHC class II positive. HD83 mAb increased apoptosis of thymocytes in co-culture with TDC in vitro and the process was associated with increased binding of thymocytes to TDC in a rosette form. Since negative selection of thymocytes by clonal deletion (apoptosis) was mediated predominantly by TDC, our results suggest the possible indirect effect of the DEC-205 molecule in these mechanisms.

Targeting human dendritic cells via DEC-205 using PLGA nanoparticles leads to enhanced cross-presentation of a melanoma-associated antigen

Targeting antigen to dendritic cells (DCs) is a powerful and novel strategy for vaccination. Priming or loading DCs with antigen controls whether subsequent immunity will develop and hence whether effective vaccination can be achieved. The goal of our present work was to increase the potency of DC-based antitumor vaccines by overcoming inherent limitations associated with antigen stability and cross-presentation. Nanoparticles prepared from the biodegradable polymer poly(lactic-co-glycolic acid) have been extensively used in clinical settings for drug delivery and are currently the subject of intensive investigation as antigen delivery vehicles for vaccine applications. Here we describe a nanoparticulate delivery system with the ability to simultaneously carry a high density of protein-based antigen while displaying a DC targeting ligand on its surface. Utilizing a targeting motif specific for the DC-associated surface ligand DEC-205, we show that targeted nanoparticles encapsulating a MART-1_27–35 peptide are both internalized and cross-presented with significantly higher efficiency than isotype control-coated nanoparticles in human cells. In addition, the DEC-205-labeled nanoparticles rapidly escape from the DC endosomal compartment and do not colocalize with markers of early (EEA-1) or late endosome/lysosome (LAMP-1). This indicates that encapsulated antigens delivered by nanoparticles may have direct access to the class I cytoplasmic major histocompatibility complex loading machinery, overcoming the need for “classical” cross-presentation and facilitating heightened DC stimulation of anti-tumor CD8⁺ T-cells. These results indicate that this delivery system provides a flexible and versatile methodology to deliver melanoma-associated antigen to DCs, with both high efficiency and heightened potency.

CD8+ dendritic cell-mediated tolerance of autoreactive CD4+ T cells is deficient in NOD mice and can be corrected by blocking CD40L

DCs are important mediators of peripheral tolerance for the prevention of autoimmunity. Chimeric αDEC-205 antibodies with attached antigens allow in vivo antigen-specific stimulation of T cells by CD8(+) DCs, resulting in tolerance in nonautoimmune mice. However, it is not clear whether DC-mediated tolerance induction occurs in the context of ongoing autoimmunity. We assessed the role of CD8(+) DCs in stimulation of autoreactive CD4(+) T cells in the NOD mouse model of type 1 diabetes. Targeting of antigen to CD8(+) DCs via αDEC-205 led to proliferation and expansion of β-cell specific BDC2.5 T cells. These T cells also produced IL-2 and IFN-γ and did not up-regulate FoxP3, consistent with an activated rather than tolerant phenotype. Similarly, endogenous BDC peptide-reactive T cells, identified with I-A(g7) tetramers, did not become tolerant after antigen delivery via αDEC-205: no deletion or Treg induction was observed. We observed that CD8(+) DCs from NOD mice expressed higher surface levels of CD40 than CD8(+) DCs from C57BL/6 mice. Blockade of CD40-CD40L interactions reduced the number of BDC2.5 T cells remaining in mice, 10 days after antigen targeting to CD8 DCs, and blocked IFN-γ production by BDC2.5 T cells. These data indicate that the ability of autoreactive CD4(+) T cells to undergo tolerance mediated by CD8(+) DCs is defective in NOD mice and that blocking CD40-CD40L interactions can restore tolerance induction.