Role In Activation Of Dendritic Cells Research Articles

Abnormal metabolism in melanocytes participates in the activation of dendritic cell in halo nevus

A comprehensive analysis of spatial transcriptomics was carried out to better understand the progress of halo nevus. We found that halo nevus was characterized by overactive immune responses, triggered by chemokines and dendritic cells (DCs), T cells, and macrophages. Consequently, we observed abnormal cell death, such as apoptosis and disulfidptosis in halo nevus, some were closely related to immunity. Interestingly, we identified aberrant metabolites such as uridine diphosphate glucose (UDP-G) within the halo nevus. UDP-G, accompanied by the infiltration of DCs and T cells, exhibited correlations with certain forms of cell death. Subsequent experiments confirmed that UDP-G was increased in vitiligo serum and could activate DCs. We also confirmed that oxidative response is an inducer of UDP-G. In summary, the immune response in halo nevus, including DC activation, was accompanied by abnormal cell death and metabolites. Especially, melanocyte-derived UDP-G may play a crucial role in DC activation.

Retinoic acid-inducible gene-1 knockdown induces immature properties in dendritic cells and prolongs the survival time of allograft mice

BackgroundThe mature state of dendritic cells (DCs) determines their ability to regulate immune responses. Retinoic acid-inducible gene-1 (RIG-1) plays a critical role in DC activation and maturation. RIG-1 activation triggers mitogen-activated protein kinase and nuclear factor-kappa B signal transduction. In this study, we aimed to investigate the effects of inhibiting RIG-1 expression in DCs and its potential in inducing immune tolerance. MethodsDCs were transduced with the recombinant lentiviral vector (Lv) to inhibit RIG-1 expression. A murine islet and skin transplantation model were constructed to find out whether DC-DDX58-RNAi could prolong allograft survival. The phenotypes of DCs and T-cells were analyzed using flow cytometry. Cytokines in serum were detected by the enzyme-linked immunosorbent assay. Protein levels were determined by Western blot. ResultsRIG-1-deficient DCs had low expression of costimulatory molecules and major histocompatibility complex and a strong phagocytic ability. DC-DDX58-RNAi induced regulatory T cell differentiation in the transplant recipient spleens. The DC-DDX58-RNAi-treated recipients showed satisfactory islet allograft function and longer survival time. ConclusionInhibition of RIG-1 with DDX58-RNAi prevented the activation and maturation of the DCs, affected T cell differentiation, protected the biological function of the allograft, and prolonged graft survival. These findings may have important therapeutic implications for new immunomodulatory regimens.

Role of miR-24-3p and miR-146a-5p in dendritic cells’ maturation process induced by contact sensitizers

MiRNAs are non-coding RNA molecules that regulate gene expression at the post-transcriptional level. Although allergic contact dermatitis has been studied extensively, few studies addressed miRNA expression and their role in dendritic cell activation. The main aim of this work was to investigate the role of miRNAs in the underlying mechanism of dendritic cell maturation induced by contact sensitizers of different potency. Experiments were conducted using THP-1-derived immature DCs (iDCs). Contact allergens of different potency were used: p-benzoquinone, Bandrowski’s base, and 2,4-dinitrochlorobenzene as extreme; nickel sulfate hexahydrate, diethyl maleate and 2-mercaptobenzothiazole as moderate; and α-hexyl cinnamaldehyde, eugenol, and imidazolidinyl urea as weak. Selective inhibitor and mimic miRNAs were then used and several cell surface markers was evaluated as targets. Also, patients patch tested with nickel were analyzed to determine miRNAs expression. Results indicate an important role of miR-24-3p and miR-146a-5p in DCs activation. miR-24-3p was up-regulated by extreme and weak contact allergens, while miR-146a-5p was up-regulated by weak and moderate contact allergens and down-regulated only by the extreme ones. Also, the involvement of PKCβ in contact allergen-induced miR-24-3p and miR-146a-5p expression was demonstrated. Furthermore, the expression of the two miRNAs maintains the same trend of expression in both in vitro and in human conditions after nickel exposure. Results obtained suggest the involvement of miR-24 and miR-146a in DCs maturation process in the proposed in vitro model, supported also by human evidences.

Oxidants and Antioxidants Synergistically Activate Immuno-Responses During Tumorgenesis

The human immune system possesses powerful surveillance functions to find and eliminate tumor cells. Several steps are involved, such as uptake and presentation of tumor antigens by dendritic cells (DCs) in order to activate T cells, trafficking and infiltration of the tumor with T cells and, finally, recognition and killing of tumor cells. Tumor cells release a number of soluble mediators that may disrupt these steps, thereby creating tolerance or immune escape. We previously published data on a rat animal model showing 1, 2-dimethylhydrazine (DMH) to inhibit DCs activation and enhance T regulatory cells (Treg) expression, ultimately inducing colon carcinogenesis. By feeding rats with mustard seeds (MS), the animals’ immune system shifted from a Th2 to a Th1 pattern, Tregs were inhibited and DCs activation enhanced. In the present study, we tried to isolate the functional fractions of MS and, to our surprise, we found that the oxidant and antioxidant fractions of MS showed synergistic effect on the activation of DCs and CD8+ effector T cells. Neither of the fractions alone, however, had any inhibitory effect on DMH-induced colon carcinogenesis. Differently from the antioxidant fraction, the oxidant fraction activated DCs (CD11c+CD80+, CD11c+CD86+), but not the CD8+ effector T cells. By adding Vitamin E, an acknowledged antioxidant, the oxidant fraction then became able to activate both spleenic DCs and effector T cells (CD8+CD28+). Taken together, these data suggest that the MS oxidant fraction might play an important role in activation of DCs, while also showing that oxidative signals may induce depletion of effector T cells. Addition of the antioxidant MS fraction, or Vitamin E, might restore the survival of effector T cells and eventually help eradicate tumor cells. Thus, MS oxidants, which normally are regarded as having negative effects, may actually function synergistically with antioxidants to prevent chemical-induced carcinogenesis. Keywords: Oxidants; Antioxidants; Immuno-responses; Mustard seeds; Colorectal cancer; Chemoprevention; T cells; Dendritic cells Abbreviations: AITC: Allyl Isothiocyanate; APCs: Antigen-Presenting Cells; CTLs: Cytotoxic T Lymphocytes; DCs: Dendritic Cells; DMH: 1, 2-Dimethylhydrazine; EGCG: Epigallocatechin Gallate; LPO: Lipid Peroxides ; MDA: Malondialdehyde; MHC: Major Histocompatibility Complex; MS: Mustard Seeds; MSE1: Ether Extract of Mustard Seeds; MSE2: Ethanolic Extract of Mustard Seeds; PBS: Phosphate-Buffered Saline; RBC: Red Blood Cell; ROS: Reactive Oxygen Species; TCRs: T Cell Receptors; Treg : T Regulatory Cells; VitE : Vitamin E

NG2, a common denominator for neuroinflammation, blood-brain barrier alteration, and oligodendrocyte precursor response in EAE, plays a role in dendritic cell activation.

In adult CNS, nerve/glial-antigen 2 (NG2) is expressed by oligodendrocyte progenitor cells (OPCs) and is an early marker of pericyte activation in pathological conditions. NG2 could, therefore, play a role in experimental autoimmune encephalomyelitis (EAE), a disease associated with increased blood–brain barrier (BBB) permeability, inflammatory infiltrates, and CNS damage. We induced EAE in NG2 knock-out (NG2KO) mice and used laser confocal microscopy immunofluorescence and morphometry to dissect the effect of NG2 KO on CNS pathology. NG2KO mice developed milder EAE than their wild-type (WT) counterparts, with less intense neuropathology associated with a significant improvement in BBB stability. In contrast to WT mice, OPC numbers did not change in NG2KO mice during EAE. Through FACS and confocal microscopy, we found that NG2 was also expressed by immune cells, including T cells, macrophages, and dendritic cells (DCs). Assessment of recall T cell responses to the encephalitogen by proliferation assays and ELISA showed that, while WT and NG2KO T cells proliferated equally to the encephalitogenic peptide MOG35-55, NG2KO T cells were skewed towards a Th2-type response. Because DCs could be responsible for this effect, we assessed their expression of IL-12 by PCR and intracellular FACS. IL-12-expressing CD11c+ cells were significantly decreased in MOG35-55-primed NG2KO lymph node cells. Importantly, in WT mice, the proportion of IL-12-expressing cells was significantly lower in CD11c+ NG2- cells than in CD11c+ NG2+ cells. To assess the relevance of NG2 at immune system and CNS levels, we induced EAE in bone-marrow chimeric mice, generated with WT recipients of NG2KO bone-marrow cells and vice versa. Regardless of their original phenotype, mice receiving NG2KO bone marrow developed milder EAE than those receiving WT bone marrow. Our data suggest that NG2 plays a role in EAE not only at CNS/BBB level, but also at immune response level, impacting on DC activation and thereby their stimulation of reactive T cells, through controlling IL-12 expression.Electronic supplementary materialThe online version of this article (doi:10.1007/s00401-016-1563-z) contains supplementary material, which is available to authorized users.

Oleic acid nanoemulsion for nasal vaccination: Impact on adjuvanticity based immune response

Subunit vaccine formulations with enhanced potency are vital to improve immune response against weak antigens and also promote dose sparing of adjuvant and antigens that may cause undesirable side effects. Recently particulate delivery systems are under exploration to enhance antigen specific immunity. Oleic acid a potential biomaterial in terms of penetration is used for formulating nanoemulsion for nasal vaccination. In this study influence of oleic acid nanoemulsion on antigen uptake and role in dendritic cells activation is studied. Formulation conditions were optimized to produce a stable nanoemulsion at lowest surfactant concentration (2%). Penetration enhancement of oleic acid nanoemulsion was evaluated using cell uptake study by Fluorescein isothiocyanate conjugated OVA on A549 cell line. Here, we report strong class switched, high avidity humoral and cellular (cytokine) immune response elicited by vaccine delivery system with antigen and adjuvant. Flowcytometry analysis showed enhanced expression of activated dendritic cells on 45th day compared to soluble antigen. These data suggest that oleic acid formulation enhances penetration, sustain release of antigen and stimulates both cellular and humoral immune response.

Lack of transglutaminase 2 diminished T‐cell responses in mice

Transglutaminase 2 (TG2) has been reported to play a role in dendritic cell activation and B-cell differentiation after immunization. Its presence and role in T cells, however, has not been explored. In the present study, we determined the expression of TG2 on mouse T cells, and evaluated its role by comparing the behaviours of wild-type and TG2(-/-) T cells after activation. In our results, naive T cells minimally expressed TG2, expression of which was increased after activation. T-cell proliferation, expression of activation markers such as CD69 and CD25, and secretions of interleukin-2 and interferon-γ were suppressed in the absence of TG2, presumably due, in part, to diminished nuclear factor-κB activation. These effects on T cells seemed to be reflected in the in vivo immune response, the contact hypersensitivity reaction elicited by 2,4-dinitro-1-fluorobenzene, with lowered peak responses in the TG2(-/-) mice. When splenic T cells from mice immunized with tumour lysate-loaded wild-type dendritic cells were re-challenged ex vivo with the same antigen, the profile of surface markers including CD44, CD62L, and CD127 strongly indicated lesser generation of memory CD8(+) T cells in TG2(-/-) mice. In the TG2(-/-) CD8(+) T cells, moreover, Eomes expression was markedly decreased. These results indicate possible roles of TG2 in CD8(+) T-cell activation and CD8(+) memory T-cell generation.

Kruppel-Like Factor 2 Regulates Dendritic Cell Activation in Patients with Acute Coronary Syndrome

Objective: Dendritic cells (DCs) activation is important in atherosclerosis and coronary heart disease, but the mechanisms regulating activation of dendritic cells remain largely unclear. The aim of this study was to evaluate the effect of transcription factor Kruppel-like factor 2 (KLF2) in the proinflammatory activation of DCs in acute coronary syndrome. Methods and Results: In this study, the expression of CD80 and KLF2 was detected in DCs in normal health controls, patients with stable angina (SA), and acute coronary syndrome (ACS). Our study found that compared with normal control and SA, KLF2 expression in DCs is reduced in patients with ACS. Moreover, the surface expression of CD80 was increased in ACS. In vitro experiment, we found that ox-LDL could increase CD80 expression and decrease KLF2 expression. Furthermore, down-regulated KLF2 could in turn increase CD80 expression via NF-κB pathway. Conclusions: These observations identify KLF2 as a novel negative regulator of DC function and it may play an essential role in DC activation in ACS.

Enhancement of dendritic cell activation via CD40 ligand-expressing γδ T cells is responsible for protective immunity toPlasmodiumparasites

Previous reports have shown that γδ T cells are important for the elimination of malaria parasites in humans and mice. However, how γδ T cells are involved in protective immunity against blood-stage malaria remains unknown. We infected γδ T-cell-deficient (TCRδ-KO) mice and control wild-type mice with Plasmodium berghei XAT, which is a nonlethal strain. Although infected red blood cells were eliminated within 30 d after infection, TCRδ-KO mice could not clear the infected red blood cells, showed high parasitemia, and eventually died. Therefore, γδ T cells are essential for clearance of the parasites. Here, we found that γδ T cells play a key role in dendritic cell activation after Plasmodium infection. On day 5 postinfection, γδ T cells produced IFN-γ and expressed CD40 ligand during dendritic cell activation. These results suggest that γδ T cells enhance dendritic cell activation via IFN-γ and CD40 ligand-CD40 signaling. This hypothesis is supported strongly by the fact that in vivo induction of CD40 signaling prevented the death of TCRδ-KO mice after infection with P. berghei XAT. This study improves our understanding of protective immunity against malaria and provides insights into γδ T-cell-mediated protective immunity against various infectious diseases.

Anti–IL6-receptor-alpha (tocilizumab) does not inhibit human monocyte-derived dendritic cell maturation or alloreactive T-cell responses

AbstractSignificant comorbidites and lethality complicate GVHD and its treatment. Targeting the cytokine milieu may improve GVHD control; and IL6 is an attractive candidate, given its role in dendritic cell activation and T-cell differentiation. Tocilizumab is a humanized mAb to IL6-receptor-α (IL6R-α), which is Food and Drug Administration–approved for treatment of rheumatoid arthritis. Mouse transplant models have demonstrated that IL6 blockade also improves GVHD scores and survival. Definitive immunologic effects of IL6 inhibition have not emerged given inconsistent alterations in regulatory T cells (Tregs) and suppression of T-cell proliferation. Despite on-target suppression of IL6R-α signaling in human monocyte-derived dendritic cells (moDCs) and T cells, our data show no effect on moDC maturation/activation, alloreactive T-cell proliferation, Treg expansion, or allogeneic Th1/Th17 responses in vitro. These findings merit attention in any clinical trials of tocilizumab for GVHD prevention or treatment and provide a rationale for evaluating more specific inhibitors of downstream JAK2/STAT3 signaling as well.

Influence of Interleukin-13 in 5-HT Synthesis and Severity of Experimental Colitis

BACKGROUND: Mucosal inflammation in conditions ranging from infective acute enteritis or colitis to inflammatory bowel disease is accompanied by alteration in serotonin (5hydroxytryptamine, 5-HT) content in the gut. In our previous studies, we have shown that 5-HT plays an important role in the pathogenesis of experimental colitis. Dendritic cells (DC) are important innate immune cells and play a key role in the activation of the immune response and generation of gut inflammation. DCs express the 5-HT7 receptor, and we have recently demonstrated that 5-HT plays an important role in DC activation in relation to gut inflammation. In this study, we have evaluated the effect of inhibiting 5-HT signaling by using a 5-HT7 receptor antagonist or 5-HT7 receptor knockout mice in experimental colitis. METHODS: Mice (C57BL/6) were treated with selective 5-HT7 receptor antagonist SB266970 (40mg/kg, ip) or vehicle (saline) starting one day prior to administration of 5% dextran sulfate sodium (DSS) in drinking water and were sacrificed on day 5 post-DSS to assess the extent of colitis, myeloperoxidase (MPO) activity and pro-inflammatory cytokines. Colitis was also induced in 5-HT7 receptor deficient mice on C57BL/6 background (5HT7KO) and wild type mice either by 5% DSS or intrarectal administration of dinitrobenzene sulfonic acid (DNBS, 5mg/mouse) and were sacrificed on day 5 post-DSS and day 3 postDNBS to assess the extent of colitis, MPO activity and pro-inflammatory cytokines. RESULTS: Inhibition of 5-HT signaling by blocking 5-HT7 receptor function with a 5-HT7 antagonist ameliorated DSS-induced colitis. Compared to saline treated mice, we observed significantly lower macroscopic (4.0±0.28 vs. 2.6±0.43) and histological damage scores (4.8±0.59 vs. 2.4±0.54) in antagonist treated mice on day 5 post-DSS. This was associated with downregulation of MPO activity (16.9±0.88 vs. 12.32±1.21, P<0.05) and lower production of IL-1β, TNF-α and IL-6 (P<0.05) post-DSS. There were also significantly lower histological scores, MPO and pro-inflammatory cytokine levels in 5-HT7KOmice as compared to controls post-DSS. DCs isolated from 5-HT7KO mice post-DSS produced lower levels of IL-12 and IL-1β when stimulated with LPS as compared to wild-type mice (P<0.05). We also observed significant reduction in severity of colitis in 5-HT7KO mice following induction of DNBScolitis. CONCLUSION: These results demonstrate that disruption of 5-HT7 receptor function reduces the severity of gut inflammation and identifies a key role of 5-HT7 receptor mediated signaling in the pathogenesis of experimental colitis. These observations provide us with novel information on the role of the 5-HT7 receptor in gut inflammation and highlight the potential benefit of targeting this receptor to alleviate disease severity in intestinal inflammatory conditions including inflammatory bowel disease.

Activation of dendritic cells by polymorphonuclear neutrophils

The obsolete view describing neutrophils as innate immune cells that respond rapidly to microbial invasion and then rapidly die by apoptosis is now challenged by several data. In both human and mice, there are now evidences that neutrophils play a role in dendritic cell activation, a critical step for the outcome of the specific T cell response.

HMOX1 and NQO1 Genes are Upregulated in Response to Contact Sensitizers in Dendritic Cells and THP-1 Cell Line: Role of the Keap1/Nrf2 Pathway

Electrophilicity is one of the most common features of skin contact sensitizers and is necessary for protein haptenation. The Keap1 (Kelch-like ECH-associated protein 1)/Nrf2 -signaling pathway is dedicated to the detection of electrophilic stress in cells leading to the upregulation of genes involved in protection or neutralization of chemical reactive species. Signals provided by chemical stress could play an important role in dendritic cell activation and the aim of this work was to test whether contact sensitizers were specific activators of the Keap1/Nrf2 pathway. CD34-derived dendritic cells (CD34-DC) and the THP-1 myeloid cell line were treated by a panel of sensitizers (Ni, 1-chloro 2,4-dinitrobenzene, cinnamaldehyde, 7-hydroxycitronellal, 1,4-dihydroquinone, alpha-methyl-trans-cinnamaldehyde, 2-4-tert-(butylbenzyl)propionaldehyde or Lilial, and 1,4-phenylenediamine), irritants (sodium dodecyl sulfate, benzalkonium chloride), and a nonsensitizer molecule (chlorobenzene). Three well-known Nrf2 activators (tert-butylhydroquinone, lipoic acid, sulforaphane) were also tested. Expression of hmox1 and nqo1 was measured using real-time PCR and cellular accumulation of Nrf2 was assessed by Western blot. Our results showed an increased expression at early time points of hmox1 and nqo1 mRNAs in response to sensitizers but not to irritants. Accumulation of the Nrf2 protein was also observed only with chemical sensitizers. A significant inhibition of the expression of hmox1 and nqo1 mRNAs and CD86 expression was found in 1-chloro 2,4-dinitrobenzene-treated THP-1 cells preincubated with N-acetyl cysteine, a glutathione precursor. Altogether, these data suggested that the Keap1/Nrf2-signaling pathway was activated by electrophilic molecules including sensitizers in dendritic cells and in the THP-1 cell line. Monitoring of this pathway may provide new biomarkers (e.g., Nrf2, hmox1) for the detection of the sensitization potential of chemicals.

Identification of the scavenger receptors SREC-I, Cla-1 (SR-BI), and SR-AI as cellular receptors for Tamm-Horsfall protein

Tamm-Horsfall protein (THP) is expressed exclusively in the kidney and constitutes the most abundant protein in urine. An important role for THP in antibacterial host defense but also in inflammatory disorders of the urogenital tract has been suggested. In line with this, THP has been shown recently to potently activate macrophages and dendritic cells (DC) via the toll-like receptor 4 (TLR4) pathway. We show here that THP interacts specifically with surface structures on DC and provides evidence that they are distinct from TLR4. Using retroviral expression cloning, we have identified one such receptor as the scavenger receptor (SR) expressed by endothelial cells I (SREC-I). In addition, we found that two other receptors for acetylated low-density lipoprotein (AcLDL), namely scavenger receptors AI (SR-AI) and Cla-1 (SR-BI), also serve as receptors for THP. SREC-I/THP interaction is of high affinity (16.8+/-6.8 nM), whereas Cla-1 and SR-AI have lower affinities for THP (396 nM+/-114 nM and 802 nM+/-157 nM, respectively). The interaction of THP with these molecules is fully blocked by AcLDL. However, AcLDL only partially blocks binding of THP to DC, and a series of experiments did not support a role in DC activation for SR interacting with THP and AcLDL. Thus, our data point to the existence of additional receptors for THP, which mediate TLR4-dependent DC activation. Interaction and up-take of THP by SR might play an important role in local host defense and could contribute to inflammatory kidney diseases associated with THP-specific antibody responses.

NF-κB Plays a Major Role in the Maturation of Human Dendritic Cells Induced by NiSO4 but not by DNCB

Dendritic cell (DC) activation is a critical event for the induction of an immune response to haptens. Although signaling pathways such as mitogen-activated protein kinase (MAPK) family members have been reported to play a role in DC activation by haptens, little is known about the implication of the nuclear factor kappa B (NF-kappaB) pathway. In this work, we showed that NiSO(4) induced the expression of HLA-DR, CD83, CD86, and CD40 and the production of interleukin (IL)-8, IL-6, and IL-12p40 in human DCs, whereas DNCB induced mainly the expression of CD83 and CD86 and the production of IL-8. NiSO(4) but not DNCB was able to activate the degradation of IkappaB-alpha leading to the binding of the p65 subunit of NF-kappaB on specific DNA probes. Inhibition of the NF-kappaB pathway using BAY 11-7085 prevents both CD40 and HLA-DR expression and cytokine production induced by NiSO(4). However, BAY 11-7085 only partially inhibited CD86 and CD83 expression induced by NiSO(4). In addition, p38 MAPK and NF-kappaB were independently activated by NiSO(4) since SB203580 did not inhibit NF-kappaB activation by NiSO(4). Interestingly, we also showed that DNCB inhibited the degradation of IkappaB-alpha induced by tumor necrosis factor-alpha leading to alteration of CD40, HLA-DR, and CD83 expression but not of CD86 and CCR7. Extensive modifications of DC phenotype by NiSO(4) in comparison to DNCB are probably the consequence of NF-kappaB activation by NiSO(4) but not by DNCB.

665. Enhanced Transgene Delivery to Activated Vascular Endothelial Cells In Vitro and In Vivo Using a Novel Strategy To Modify Adenovirus Tropism

The use of dendritic cells (DC) loaded with tumor-associated antigens (TAA) for therapeutic cancer vaccines is particularly attractive because of the central role that DCs play in immunity as antigen presenting cells (APCs). Efficient and specific loading of the DCs with TAA genes is needed for therapeutic cancer vaccines to be successful. Defining ways to target DCs would potentially lesson the amount of vector needed for an effective dose, decrease adverse reactions and/or damage to healthy cells, and lower production costs. DCs are extremely refractory to Ad infection due to the low levels of the primary Ad receptor, coxsackievirus-adenovirus receptor (CAR) on their surface. In this regard, we have successfully augmented the transduction of DCs by re-routing the Ad vector to CD40 that is expressed at relatively high levels on the DC surface. Angiotensin-converting enzyme (ACE), a zinc-metalloprotease with broad substrate specificity, is generally known as an important regulator of blood pressure, fluid, and electrolyte homeostasis. We have also reported a high level of ACE expression in DCs [Danilov, 2003, Exp. Hematol, 31: 1301]. Therefore, we evaluated adenovirus (Ad) targeting of human monocyte-derived DCs via the angiotensin-converting enzyme (ACE, CD143) surface marker. Surface and mRNA expression of ACE were analyzed by flow cytometry and real time PCR, then compared to that of CD40, a well-characterized DC marker. Targeting proteins were developed that have two binding specificities. One part of the targeting protein binds to the fiber of the Ad vector and the other part binds to the ACE expressed on the surface of DCs. Ad vectors were then complexed with the targeting proteins. The resulting ACE-targeted Ad was then used to infect human monocyte-derived DCs. We screened transductional and transcriptional activity of ACE-targeted adenovirus that has luciferase reporter genes under the control of the cytomegarovirus promoter in ΔE1 region (AdCMVLuc) in vitro. ACE surface expression levels were greater than CD40 levels in immature DCs (iDC), however, were less in mature DCs (mDC). The results of luciferase assay demonstrated that ACE-targeting significantly (4-fold) increased the Ad transduction efficiency of iDCs compared to untargeted Ad. This vector approach may thus mediate not only high efficiency gene delivery but also serve a proactive role in DC activation. These results illustrate a novel surface marker on DCs that may be utilized for the therapeutic cancer vaccines.

Induction of dendritic cell costimulator molecule expression is suppressed by T cells in the absence of antigen-specific signalling: role of cluster formation, CD40 and HLA-class II for dendritic cell activation.

Full activation of T lymphocytes by dendritic cells (DC) during antigen presentation is known to require the interaction of several inducible receptor-ligand pairs. We have postulated that the reciprocal activation of DC by T lymphocytes is also important. Potential signalling molecules that might increase the stimulatory capacity of DC during antigen presentation to T lymphocytes were tested using an in vitro model. Fresh human blood DC were cocultured with CD4+ and CD8+ allogeneic or with autologous T lymphocytes plus Staphylococcus superantigen A (SEA). Surprisingly, costimulator expression on DC cocultured with T lymphocytes was reduced in comparison to DC cultured alone. However, the minority (10-30%) of DC clustering with T lymphocytes showed antigen-specific up-regulation of the CD40, CD80 and CD86 costimulator molecules, whereas the non-clustered DC (70-90%) had less up-regulation than control DC cultured alone and did not respond to antigen-specific triggering. Monoclonal antibodies (mAb) to CD40 ligand (CD40L) and human leucocyte antigen (HLA)-DR, but not lymphocyte function-associated antigen-1 (LFA-1), LFA-3 or HLA-class I, significantly inhibited the T-lymphocyte induction of DC costimulator expression. Since HLA-class II, but not HLA-class I mAb, inhibited allogeneic T-lymphocyte-mediated activation of DC, CD4 T lymphocytes appear to be the main subset activating DC in the mixed lymphocyte reaction. Cross-linking of CD40, but not HLA-class II, up-regulated DC or B-cell costimulator expression. Although direct class II signalling does not appear to play a role in DC activation, antigen-specific T-cell recognition contributes via other mechanisms to regulate DC activation.

Maturation of Dendritic Cells Accompanies High-Efficiency Gene Transfer by a CD40-Targeted Adenoviral Vector

Important therapeutic applications of genetically modified dendritic cells (DC) have been proposed; however, current vector systems have demonstrated only limited gene delivery efficacy to this cell type. By means of bispecific Abs, we have dramatically enhanced gene transfer to monocyte derived DC (MDDC) by retargeting adenoviral (Ad) vectors to a marker expressed on DC, CD40. Adenovirus targeted to CD40 demonstrated dramatic improvements in gene transfer relative to untargeted Ad vectors. Fundamental to the novelty of this system is the capacity of the vector itself to modulate the immunological status of the MDDC. This vector induces DC maturation as demonstrated phenotypically by increased expression of CD83, MHC, and costimulatory molecules, as well as functionally by production of IL-12 and an enhanced allostimulatory capacity in a MLR. In comparing this vector to other Ad-based gene transfer systems, we have illustrated that the features of DC maturation are not a function of the Ad particle, but rather a consequence of targeting to the CD40 marker. This vector approach may thus mediate not only high-efficiency gene delivery but also serve a proactive role in DC activation that could ultimately strengthen the utility of this vector for immunotherapy strategies.