Maximizing dendritic cell migration in cancer immunotherapy

Enpp2 Expression by Dendritic Cells Is a Key Regulator in Migration

Enpp2 is an enzyme that catalyzes the conversion of lysophosphatidylcholine (LPC) to lysophosphatidic acid (LPA), which exhibits a wide variety of biological functions. Here, we examined the biological effects of Enpp2 on dendritic cells (DCs), which are specialized antigen-presenting cells (APCs) characterized by their ability to migrate into secondary lymphoid organs and activate naïve T-cells. DCs were generated from bone marrow progenitors obtained from C57BL/6 mice. Enpp2 levels in DCs were regulated using small interfering (si)RNA or recombinant Enpp2. Expression of Enpp2 in LPS-stimulated mature (m)DCs was high, however, knocking down Enpp2 inhibited mDC function. In addition, the migratory capacity of mDCs increased after treatment with rmEnpp2; this phenomenon was mediated via the RhoA-mediated signaling pathway. Enpp2-treated mDCs showed a markedly increased capacity to migrate to lymph nodes in vivo. These findings strongly suggest that Enpp2 is necessary for mDC migration capacity, thereby increasing our understanding of DC biology. We postulate that regulating Enpp2 improves DC migration to lymph nodes, thus improving the effectiveness of cancer vaccines based on DC.

Role of IL-6 in dendritic cell functions

Dendritic cells (DCs) are efficient antigen-presenting cells that serve as a link between the innate and adaptive immune systems. These cells are broadly involved in cellular and humoral immune responses by presenting antigens to initiate T cell reactions, cytokine and chemokine secretion, T cell differentiation and expansion, B cell activation and regulation, and the mediation of immune tolerance. The functions of DCs depend on their activation status, which is defined by the stages of maturation, phenotype differentiation, and migration ability, among other factors. IL-6 is a soluble mediator mainly produced by a variety of immune cells, including DCs, that exerts pleiotropic effects on immune and inflammatory responses through interaction with specific receptors expressed on the surface of target cells. Here, we review the role of IL-6, when generated in an inflammatory context or as derived from DCs, in modulating the biologic function and activation status of DCs and emphasize the importance of searching for novel strategies to target the IL-6/IL-6 signaling pathway as a means to diminish the inflammatory activity of DCs in immune response or to prime the immunogenic activity of DCs in immunosuppressive conditions.

Dendritic Cells and CCR7 Expression: An Important Factor for Autoimmune Diseases, Chronic Inflammation, and Cancer

Chemotactic cytokines-chemokines-control immune cell migration in the process of initiation and resolution of inflammatory conditions as part of the body's defense system. Many chemokines also participate in pathological processes leading up to and exacerbating the inflammatory state characterizing chronic inflammatory diseases. In this review, we discuss the role of dendritic cells (DCs) and the central chemokine receptor CCR7 in the initiation and sustainment of selected chronic inflammatory diseases: multiple sclerosis (MS), rheumatoid arthritis (RA), and psoriasis. We revisit the binary role that CCR7 plays in combatting and progressing cancer, and we discuss how CCR7 and DCs can be harnessed for the treatment of cancer. To provide the necessary background, we review the differential roles of the natural ligands of CCR7, CCL19, and CCL21 and how they direct the mobilization of activated DCs to lymphoid organs and control the formation of associated lymphoid tissues (ALTs). We provide an overview of DC subsets and, briefly, elaborate on the different T-cell effector types generated upon DC-T cell priming. In the conclusion, we promote CCR7 as a possible target of future drugs with an antagonistic effect to reduce inflammation in chronic inflammatory diseases and an agonistic effect for boosting the reactivation of the immune system against cancer in cell-based and/or immune checkpoint inhibitor (ICI)-based anti-cancer therapy.

The Tumour Vasculature as a Target to Modulate Leucocyte Trafficking

Simple Summary

Tumour blood vessels, characterised by abnormal morphology and function, create an immunosuppressive tumour microenvironment via restricting the appropriate leucocyte subsets trafficking. Strategies to trigger phenotypic alteration in tumour vascular system to resemble normal vascular system, named vascular normalisation, promote effective trafficking of leucocytes into tumours through enhancing the interactions between leucocytes and endothelial cells. This review specifically demonstrates how targeting tumour blood vessels modulates the critical steps of leucocyte trafficking. Furthermore, selective regulation of leucocyte subsets trafficking in tumours can be achieved by vasculature-targeting strategies, contributing to improved immunotherapy and thereby delayed tumour progression.

Abstract

The effectiveness of immunotherapy against solid tumours is dependent on the appropriate leucocyte subsets trafficking and accumulating in the tumour microenvironment (TME) with recruitment occurring at the endothelium. Such recruitment involves interactions between the leucocytes and the endothelial cells (ECs) of the vessel and occurs through a series of steps including leucocyte capture, their rolling, adhesion, and intraluminal crawling, and finally leucocyte transendothelial migration across the endothelium. The tumour vasculature can curb the trafficking of leucocytes through influencing each step of the leucocyte recruitment process, ultimately producing an immunoresistant microenvironment. Modulation of the tumour vasculature by strategies such as vascular normalisation have proven to be efficient in facilitating leucocyte trafficking into tumours and enhancing immunotherapy. In this review, we discuss the underlying mechanisms of abnormal tumour vasculature and its impact on leucocyte trafficking, and potential strategies for overcoming the tumour vascular abnormalities to boost immunotherapy via increasing leucocyte recruitment.

Dendritic Cells Generated in the Presence of Platelet Lysate Have a Reduced Type 1 Polarization Capacity

Previously, we have shown platelet lysate (PL) can be used as a non-xenogeneic serum supplement for generation of monocyte-derived dendritic cells (DCs). Since DC-based activation protocols are extremely sensitive to microenvironmental changes such as replacement of culture medium, we wanted to examine the behavior of DCs cultured in the presence of PL under various type-1 activation conditions and assess their type 1 polarization capacity. We compared the quality of DCs cultured in 10% PL-supplemented RPMI medium (plDCs) with clinical-grade DCs obtained using commercially available serum-free medium (sfDCs), frequently used in established DC vaccine protocols. The DC maturation protocols consisted of either monophosphoryl lipid A/IFN-γ, poly I:C/TNF-α/IFN-α or poly I:C/R848. In general, plDCs were inferior to sfDCs in most aspects of their functional type 1 polarization characteristics. After maturation, the expression of co-stimulatory, HLA class II and lymph node-homing molecules was strongly up-regulated, with some noticeable differences. The expression of CD80 and CD86 was more extensive on plDCs, which was particularly evident in case of CCR7. However, after observing their functional capacity, plDCs had significantly lower allo-stimulatory capacity both in terms of CD4⁺ and CD8⁺ T cell stimulation. The high expression of CCR7 corresponded to higher CCL-19 directed DC migration of plDCs compared to sfDCs. Finally, their capacity to induce granzyme B and IFN-γ production in CD8⁺ T cells was significantly reduced in comparison to sfDCs. Based on these findings, the use of PL as an alternative serum supplement for generation of monocyte-derived DC anti-tumor vaccines is questionable.Abbreviations: Ag: antigen; CCL: chemokine ligand; CCR: chemokine receptor; DC: dendritic cells; DC-SIGN: dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin; FBS: fetal bovine serum; GMP: good manufacturing practice; IFN: interferon; IL: interleukin; MPLA: monophosphoryl lipid A; PGE: prostaglandin E; pI:C: polyinosinic:polycytidylic acid; pl: platelet lysate; sf: serum free; TLR: toll-like receptor; TNF: tumor necrosis factor.

Transendothelial migration (TEM) of in vitro generated dendritic cell vaccine in cancer immunotherapy

Many efforts have been made to improve the efficacy of dendritic cell (DC) vaccines in DC-based cancer immunotherapy. One of these efforts is to deliver a DC vaccine more efficiently to the regional lymph nodes (rLNs) to induce stronger anti-tumor immunity. Together with chemotaxis, transendothelial migration (TEM) is believed to be a critical and indispensable step for DC vaccine migration to the rLNs after administration. However, the mechanism underlying the in vitro-generated DC TEM in DC-based cancer immunotherapy has been largely unknown. Currently, junctional adhesion molecules (JAMs) were found to play an important role in the TEM of in vitro generated DC vaccines. This paper reviews the TEM of DC vaccines and TEM-associated JAM molecules.

Interactions Between Nanoparticles and Dendritic Cells: From the Perspective of Cancer Immunotherapy

Dendritic cells (DCs) are the primary antigen-presenting cells and play key roles in the orchestration of the innate and adaptive immune system. Targeting DCs by nanotechnology stands as a promising strategy for cancer immunotherapy. The physicochemical properties of nanoparticles (NPs) influence their interactions with DCs, thus altering the immune outcome of DCs by changing their functions in the processes of maturation, homing, antigen processing and antigen presentation. In this review, we summarize the recent progress in targeting DCs using NPs as a drug delivery carrier in cancer immunotherapy, the recognition of NPs by DCs, and the ways the physicochemical properties of NPs affect DCs' functions. Finally, the molecular pathways in DCs that are affected by NPs are also discussed.

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

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

Cytokines Produced by Dendritic Cells Administered Intratumorally Correlate with Clinical Outcome in Patients with Diverse Cancers

Purpose: Dendritic cells (DC) initiate adaptive immune responses through the uptake and presentation of antigenic material. In preclinical studies, intratumorally injected activated DCs (aDCs; DCVax-Direct) were superior to immature DCs in rejecting tumors from mice.Experimental Design: This single-arm, open-label phase I clinical trial evaluated the safety and efficacy of aDCs, administered intratumorally, in patients with solid tumors. Three dose levels (2 million, 6 million, and 15 million aDCs per injection) were tested using a standard 3 + 3 dose-escalation trial design. Feasibility, immunogenicity, changes to the tumor microenvironment after direct injection, and survival were evaluated. We also investigated cytokine production of aDCs prior to injection.Results: In total, 39 of the 40 enrolled patients were evaluable. The injections of aDCs were well tolerated with no dose-limiting toxicities. Increased lymphocyte infiltration was observed in 54% of assessed patients. Stable disease (SD; best response) at week 8 was associated with increased overall survival. Increased secretion of interleukin (IL)-8 and IL12p40 by aDCs was significantly associated with survival (P = 0.023 and 0.024, respectively). Increased TNFα levels correlated positively with SD at week 8 (P < 0.01).Conclusions: Intratumoral aDC injections were feasible and safe. Increased production of specific cytokines was correlated with SD and prolonged survival, demonstrating a link between the functional profile of aDCs prior to injection and patient outcomes. Clin Cancer Res; 24(16); 3845-56. ©2018 AACR.

Upregulation of heme oxygenase-1 in Kupffer cells blocks mast cell degranulation and inhibits dendritic cell migration in vitro

Kupffer cells (KCs) influence liver allografts by interacting with other non‑parenchymal cells. However, the exact mechanism remains unclear. Upregulation of heme oxygenase-1 (HO-1) in KCs upon interaction with mast cells (MCs), and the effects on dendritic cell (DC) function, were investigated in the present study. KCs, MCs and DCs were prepared from 8‑10‑week‑old C57BL/6 mice. KCs were pretreated with PBS, dimethyl sulfoxide, hemin (50 µM; HO‑1 inducer), and zinc protoporphyrin (50 µM; HO‑1 inhibitor) for 8 h. Reverse transcription‑polymerase chain reaction and western blotting was performed to determine HO‑1 mRNA and protein levels in KCs, respectively. C‑C motif chemokine receptor 7 (CCR7) surface molecules were measured using flow cytometry, and prostaglandin E2 (PGE2), C‑C motif chemokine ligand (CCL) 19 and CCL21 were measured by ELISA. The Transwell model was used to investigate the migration of DCs. Pretreatment of KCs with hemin induced HO‑1 transcription and protein expression, and interacted with and stabilized MC membranes. When co‑cultured with MCs, the expression of CCR7 on DCs was reduced, and PGE2, CCL19 and CCL21 were similarly decreased. DC migration was also impaired. Upregulation of HO‑1 in KCs blocked MC degranulation and reduced DC migration.

Tracking dendritic cell migration into lymph nodes by using a novel PET probe 18F-tetrafluoroborate for sodium/iodide symporter

BACKGROUND

Recently, ¹⁸F-tetrafluoroborate (TFB) was used as a substrate for the human sodium/iodide symporter (hNIS) reporter gene. This study evaluated the feasibility of performing molecular-genetic imaging by using the new radiotracer (¹⁸F-TFB) for the hNIS gene, to track dendritic cell (DC) migration in live mice. A murine dendritic cell line (DC2.4) co-expressing the hNIS and effluc genes (DC/NF) was established. To confirm the functional cellular expression of both effluc and NIS in the inoculated DC/NF cells by bio-medical imaging, combined bioluminescence imaging (BLI) and ¹⁸F-TFB positron emission tomography/computed tomography (PET/CT) imaging was performed after intramuscular injection with parental DCs and DC/NF cells. For DC-tracking, parental DCs or DC/NF cells were injected in the left or right mouse footpad, respectively, and ¹⁸F-TFB PET/CT and BLI were performed to monitor these cells in live mice.

RESULTS

In vivo PET/CT and BLI showed a clear signal in DC/NF injection sites but not in parental DC injection sites. The signal intensity in DC/NF cells was correlated with time. In vivo ¹⁸F-TFB PET/CT imaging showed higher radiotracer activity in the draining popliteal lymph nodes (DPLNs) in DC/NF injection sites than those in DC injection sites on day 2. BLI also showed DC/NF cell migration to the DPLNs on day 2 after the injection.

CONCLUSIONS

Migration of DCs to the lymph nodes was successfully monitored using ¹⁸F-TFB PET/CT imaging of the NIS gene and optical imaging of the effluc gene in live mice. These data support the feasibility of using ¹⁸F-TFB as a substrate for hNIS reporter gene imaging to track the migration of DCs to the lymph nodes in live animals. The use of ¹⁸F-TFB may facilitate enhanced PET imaging of the hNIS reporter gene in small animals and humans in future studies.

Glycyrrhiza uralensis water extract enhances dendritic cell maturation and antitumor efficacy of HPV dendritic cell-based vaccine

Licorice has been used as herbal medicine and natural sweetener. Here, we prepared Glycyrrhiza uralensis water extract (GUWE) and investigated the effect of GUWE on the maturation and function of dendritic cells (DCs) and its adjuvant effect on DC-based vaccine. We observed that GUWE dose-dependently promoted DC maturation and cytokine secretion through TLR4 signaling pathway. The capacity of DC to stimulate allogenic splenocyte proliferation was also enhanced by GUWE treatment. Compared with control group, GUWE treated DCs pulsed with human papillomavirus (HPV)-16 E6/E7 peptides significantly inhibited the tumor growth in both early and late therapeutic groups. In early therapeutic group, the frequencies of induced regulatory T cells (iTregs: CD4⁺CD25⁻Fopx3⁺) and CD4⁺ and CD8⁺ T cells were significantly decreased and increased, respectively. HPV-16-specific CD8⁺ T cell responses were significantly induced and negatively correlated with iTreg frequencies and tumor weight. These results indicated the immunoregulatory activities of licorice.

Immunotherapy with Dendritic Cells Modified with Tumor-Associated Antigen Gene Demonstrates Enhanced Antitumor Effect Against Lung Cancer

BACKGROUND: Immunotherapy using dendritic cell (DC) vaccine has the potential to overcome the bottleneck of cancer therapy. METHODS: We engineered Lewis lung cancer cells (LLCs) and bone marrow–derived DCs to express tumor-associated antigen (TAA) ovalbumin (OVA) via lentiviral vector plasmid encoding OVA gene. We then tested the antitumor effect of modified DCs both in vitro and in vivo. RESULTS: The results demonstrated that in vitro modified DCs could dramatically enhance T-cell proliferation (P < .01) and killing of LLCs than control groups (P < .05). Moreover, modified DCs could reduce tumor size and prolong the survival of LLC tumor-bearing mice than control groups (P < .01 and P < .01, respectively). Mechanistically, modified DCs demonstrated enhanced homing to T-cell–rich compartments and triggered more naive T cells to become cytotoxic T lymphocytes, which exhibited significant infiltration into the tumors. Interestingly, modified DCs also markedly reduced tumor cells harboring stem cell markers in mice (P < .05), suggesting the potential role on cancer stem-like cells. CONCLUSION: These findings suggested that DCs bioengineered with TAA could enhance antitumor effect and therefore represent a novel anticancer strategy that is worth further exploration.

Magnetic Enrichment of Dendritic Cell Vaccine in Lymph Node with Fluorescent-Magnetic Nanoparticles Enhanced Cancer Immunotherapy

Dendritic cell (DC) migration to the lymph node is a key component of DC-based immunotherapy. However, the DC homing rate to the lymphoid tissues is poor, thus hindering the DC-mediated activation of antigen-specific T cells. Here, we developed a system using fluorescent magnetic nanoparticles (α-AP-fmNPs; loaded with antigen peptide, iron oxide nanoparticles, and indocyanine green) in combination with magnetic pull force (MPF) to successfully manipulate DC migration in vitro and in vivo. α-AP-fmNPs endowed DCs with MPF-responsiveness, antigen presentation, and simultaneous optical and magnetic resonance imaging detectability. We showed for the first time that α-AP-fmNP-loaded DCs were sensitive to MPF, and their migration efficiency could be dramatically improved both in vitro and in vivo through MPF treatment. Due to the enhanced migration of DCs, MPF treatment significantly augmented antitumor efficacy of the nanoparticle-loaded DCs. Therefore, we have developed a biocompatible approach with which to improve the homing efficiency of DCs and subsequent anti-tumor efficacy, and track their migration by multi-modality imaging, with great potential applications for DC-based cancer immunotherapy.

The combination of Pleurotus ferulae water extract and CpG-ODN enhances the immune responses and antitumor efficacy of HPV peptides pulsed dendritic cell-based vaccine

Our previous study reported that the combination of Pleurotus ferulae water extract (PFWE) and CpG (PFWE+CpG) enhanced the maturation and function of dendritic cells (DCs). Here, we investigated the effects of PFWE+CpG on the immune responses and antitumor efficacy of DC-based vaccine. We observed that all of HPV E6 and E7 peptides pulsed DCs (HPV-immature DCs, HPV+PFWE-, +CpG- or +PFWE+CpG-DCs) induced antigen-specific CD8(+) T cell responses and HPV+PFWE+CpG-DCs induced highest level of CD8(+) T cell responses. The antitumor efficacy of HPV-DCs vaccines was evaluated in TC-1 tumor mouse model. The early therapeutic study showed that HPV+PFWE-, +CpG- and +PFWE+CpG-DCs greatly inhibited tumor growth. Moreover, HPV+PFWE+CpG-DCs controlled tumor growth at a faster rate compared to other groups. These three groups induced HPV-specific CD8(+) T cell responses and significantly decreased the frequencies of induced regulatory T cells (iTregs: CD4(+)CD25(-)Fopx3(+)). However, only HPV+PFWE+CpG-DCs significantly decreased the frequency of natural Tregs (nTregs: CD4(+)CD25(+)Fopx3(+)). Furthermore, HPV+PFWE+CpG-DCs also significantly inhibited tumor growth in the late therapeutic study. The results showed that PFWE+CpG enhanced the immune responses and antitumor efficacy of DC-based vaccine, suggesting that PFWE+CpG might be the potential candidate for the generation of clinical-grade mature DCs.

Unexpected impairment of TNF-α-induced maturation of human dendritic cells in vitro by IL-4

Background

An efficient strategy for programing dendritic cells (DCs) for cancer immunotherapy is the optimization of their maturation so that they can efficiently stimulate cancer-specific T cell responses. Interleukin (IL)-4 has appeared as an essential cytokine, widely used in vitro with granulocyte macrophage-colony stimulating factor (GM-CSF) to differentiate monocytes into immature DCs (iDC) and to prevent macrophage formation. Conflicting data have been published regarding the effect of IL-4 on functional DC maturation. To further understand IL-4’s effects on DC maturation and function in vitro, we choose the most commonly used maturation factor tumor necrosis factor (TNF)-α.

Methods

Human monocyte-derived iDC were treated for 48 h with GM-CSF and TNF-α in the presence (IL-4⁺-DC) or absence (IL-4⁻-DC) of IL-4 and functions of both DC populations were compared.

Results

On mixed lymphocyte reaction assay, IL-4⁺-DC were less potent than IL-4⁻-DC at inducing the proliferation of allogeneic CD4⁺ T cells and the proportion of activated T cells expressing CD69 and/or CD25 was smaller. Interleukin-4 reduced the cell-surface expression of TNF-α-induced DC maturation markers CD83, CD86, HLA-DR and CD25 and generated a heterogeneous population of DCs. IL-4⁺-DC secreted less IL-12 and more IL-10 than IL-4⁻-DC following activation by soluble CD40L, and IL-4⁺-DC-activated T cells secreted lesser amounts of T helper (Th) 1 cytokines (IL-2 and interferon-γ). Importantly, IL-4 impaired the in vitro migratory capacity of DCs in response to CCL21 and CCL19 chemokines. This effect was related to reduced expression of CCR7 at both mRNA and protein levels.

Conclusion

Interleukin-4 used with GM-CSF and TNF-α during the maturation of DCs in vitro impaired DC functions and disturbed the maturation effect of TNF-α. Finally, our study reinforces the view that the quality of the DC maturation stimulus, which regulates DC migration and cytokine production, may be a decisive feature of the immunogenicity of DCs.

Immature human dendritic cells enhance their migration through KCa3.1 channel activation

Migration capacity is essential for dendritic cells (DCs) to present antigen to T cells for the induction of immune response. The DC migration is supposed to be a calcium-dependent process, while not fully understood. Here, we report a role of the KCa3.1/IK1/SK4 channels in the migration capacity of both immature (iDC) and mature (mDC) human CD14(+)-derived DCs. KCa3.1 channels were shown to control the membrane potential of human DC and the Ca(2+) entry, which is directly related to migration capacities. The expression of migration marker such as CCR5 and CCR7 was modified in both types of DCs by TRAM-34 (100nM). But, only the migration of iDC was decreased by use of both TRAM-34 and KCa3.1 siRNA. Confocal analyses showed a close localization of CCR5 with KCa3.1 in the steady state of iDC. Finally, the implication of KCa3.1 seems to be limited to the migration capacities as T cell activation of DCs appeared unchanged. Altogether, these results demonstrated that KCa3.1 channels have a pro-migratory effect on iDC migration. Our findings suggest that KCa3.1 in human iDC play a major role in their migration and constitute an attractive target for the cell therapy optimization.

The immunoregulatory effects of Chinese herbal medicine on the maturation and function of dendritic cells

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional Chinese herbal medicine (CHM) has a long-history for treatment of various human diseases including tumors, infection, autoimmune diseases in Asian countries, especially in China, Japan, Korea and India. CHM was traditionally used as water extracts and many Chinese herbs were considered to be good for health, which can regulate immune system to protect host from diseases. With the progress of technology, the components of CHM were identified and purified, which included polysaccharides, saponins, phenolic compounds, flavonoids and so on. Recently, accumulating evidence indicates that CHM and its components can regulate immune system through targeting dendritic cells (DCs). We hereby reviewed the immunoregulatory effects of CHM on the maturation, cytokine production and function of DCs. This should help to shed light on the potential mechanism of CHM to improve the usage and clinical efficacy of CHM.

MATERIALS AND METHODS

Literatures about the effects of CHM on DCs were searched in electronic databases such as Pubmed, Google Scholar and Scopus from 2000 to 2014. 'CHM', 'DC' or 'immune' were used as keywords for the searches. We only reviewed literatures published in English.

RESULTS

Over 600 publications were found about 'CHM&immune' and around 120 literatures about 'CHM&DC' were selected and reviewed in this paper. All publications are backed by preclinical or clinical evidences both in vitro and in vivo. Some CHM and its components promote the maturation, pro-inflammatory cytokine production and function of DCs and as the adjuvant enhance immune responses against tumor and infection. In contrast, other CHM and its components suppress the activation status of DCs to induce regulatory T cells, inhibit allergic and inflammatory responses, ameliorate autoimmune diseases, and prolong the allograft survival. A large body of evidence shows that CHM and its components regulate the activation status of DCs through TLRs, NF-κB, MAPK signaling pathways.

CONCLUSION

This review provides useful information for understanding the mechanism of CHM on the treatment of diseases, which facilitates to improve the efficacy of CHM. Based on the immunoregulatory effects of CHM on DCs, it indicated that some CHM and its components could be use to develop adjuvant to enhance antigen-specific immune responses or tolerogenic adjuvant to generate antigen-specific immune tolerance.

Functional manipulation of dendritic cells by photoswitchable generation of intracellular reactive oxygen species

Reactive oxygen species (ROS) play an important role in cellular signaling as second messengers. However, studying the role of ROS in physiological redox signaling has been hampered by technical difficulties in controlling their generation within cells. Here, we utilize two inert components, a photosensitizer and light, to finely manipulate the generation of intracellular ROS and examine their specific role in activating dendritic cells (DCs). Photoswitchable generation of intracellular ROS rapidly induced cytosolic mobilization of Ca(2+), differential activation of mitogen-activated protein kinases, and nuclear translocation of NF-κB. Moreover, a transient intracellular ROS surge could activate immature DCs to mature and potently enhance migration in vitro and in vivo. Finally, we observed that intracellular ROS-stimulated DCs enhanced antigen specific T-cell responses in vitro and in vivo, which led to delayed tumor growth and prolonged survival of tumor-bearing mice when immunized with a specific tumor antigen. Therefore, a transient intracellular ROS surge alone, if properly manipulated, can cause immature DCs to differentiate into a motile state and mature forms that are sufficient to initiate adaptive T cell responses in vivo.

Dendritic cell-based vaccine efficacy: aiming for hot spots

Many approaches for cancer immunotherapy have targeted dendritic cells (DCs), directly or indirectly, for the induction of antitumor immune responses. DC-based vaccines have been developed using a wide variety of ex vivo DC culture conditions, antigen (Ag) source and loading strategies, maturation agents, and routes of vaccination. Adjuvants are used to activate innate immune cells at the vaccine injection site, to promote Ag transport to the draining lymph nodes (LNs) and to model adaptive immune responses. Despite years of effort, the effective induction of strong and durable antitumor T-cell responses in vaccinated patients remains a challenge. The study of vaccine interactions with other immune cells in the LNs and, more recently, in the injection site has opened new doors for understanding antitumor effector T-cell licensing and function. In this review, we will briefly discuss the relevant sites and up-to-date facts regarding possible targets for antitumor vaccine refinement. We will focus on the processes taking place at the injection site, adjuvant combinations and their role in DC-based vaccines, LN homing, and modeling vaccine-induced immune responses capable of controlling tumor growth and generating immune memory.

Low molecular weight hyaluronan-pulsed human dendritic cells showed increased migration capacity and induced resistance to tumor chemoattraction

We have shown that ex vivo pre-conditioning of bone marrow-derived dendritic cells (DC) with low molecular weight hyaluronan (LMW HA) induces antitumor immunity against colorectal carcinoma (CRC) in mice. In the present study we investigated the effects of LMW HA priming on human-tumor-pulsed monocytes-derived dendritic cells (DC/TL) obtained from healthy donors and patients with CRC. LMW HA treatment resulted in an improved maturation state of DC/TL and an enhanced mixed leucocyte reaction activity in vivo. Importantly, pre-conditioning of DC/TL with LMW HA increased their ability to migrate and reduced their attraction to human tumor derived supernatants. These effects were associated with increased CCR7 expression levels in DC. Indeed, a significant increase in migratory response toward CCL21 was observed in LMW HA primed tumor-pulsed monocyte-derived dendritic cells (DC/TL/LMW HA) when compared to LWM HA untreated cells (DC/TL). Moreover, LMW HA priming modulated other mechanisms implicated in DC migration toward lymph nodes such as the metalloproteinase activity. Furthermore, it also resulted in a significant reduction in DC migratory capacity toward tumor supernatant and IL8 in vitro. Consistently, LMW HA dramatically enhanced in vivo DC recruitment to tumor-regional lymph nodes and reduced DC migration toward tumor tissue. This study shows that LMW HA--a poorly immunogenic molecule--represents a promising candidate to improve human DC maturation protocols in the context of DC-based vaccines development, due to its ability to enhance their immunogenic properties as well as their migratory capacity toward lymph nodes instead of tumors.

Taking the lymphatic route: dendritic cell migration to draining lymph nodes

In contrast to leukocyte migration through blood vessels, trafficking via lymphatic vessels (LVs) is much less well characterized. An important cell type migrating via this route is antigen-presenting dendritic cells (DCs), which are key for the induction of protective immunity as well as for the maintenance of immunological tolerance. In this review, we will summarize and discuss current knowledge of the cellular and molecular events that control DC migration from the skin towards, into, and within LVs, followed by DC arrival and migration in draining lymph nodes. Finally, we will discuss potential strategies to therapeutically target this migratory step to modulate immune responses.

In-chip fabrication of free-form 3D constructs for directed cell migration analysis

Free-form constructs with three-dimensional (3D) microporosity were fabricated by two-photon polymerization inside the closed microchannel of an injection-molded, commercially available polymer chip for analysis of directed cell migration. Acrylate constructs were produced as woodpile topologies with a range of pore sizes from 5 × 5 μm to 15 × 15 μm and prefilled with fibrillar collagen. Dendritic cells seeded into the polymer chip in a concentration gradient of the chemoattractant CCL21 efficiently negotiated the microporous maze structure for pore sizes of 8 × 8 μm or larger. The cells migrating through smaller pore sizes made significantly more turns than those through larger pores. The introduction of additional defined barriers in the microporous structure resulted in dendritic cells making more turns while still being able to follow the chemoattractant concentration gradient.

Reducing cell number improves the homing of dendritic cells to lymph nodes upon intradermal vaccination

Dendritic cell (DC)-based vaccines require the cells to relocate to lymph nodes (LNs). Unfortunately, however, DC migration rates are typically very poor. We investigated strategies to increase the migration efficacy of DC-based vaccines. Surprisingly, a reduction in DC number, but not the conditioning of the injection site, improved LN targeting.

Dendritic cell based PSMA immunotherapy for prostate cancer using a CD40-targeted adenovirus vector

Human prostate tumor vaccine and gene therapy trials using ex vivo methods to prime dendritic cells (DCs) with prostate specific membrane antigen (PSMA) have been somewhat successful, but to date the lengthy ex vivo manipulation of DCs has limited the widespread clinical utility of this approach. Our goal was to improve upon cancer vaccination with tumor antigens by delivering PSMA via a CD40-targeted adenovirus vector directly to DCs as an efficient means for activation and antigen presentation to T-cells. To test this approach, we developed a mouse model of prostate cancer by generating clonal derivatives of the mouse RM-1 prostate cancer cell line expressing human PSMA (RM-1-PSMA cells). To maximize antigen presentation in target cells, both MHC class I and TAP protein expression was induced in RM-1 cells by transduction with an Ad vector expressing interferon-gamma (Ad5-IFNγ). Administering DCs infected ex vivo with CD40-targeted Ad5-huPSMA, as well as direct intraperitoneal injection of the vector, resulted in high levels of tumor-specific CTL responses against RM-1-PSMA cells pretreated with Ad5-IFNγ as target cells. CD40 targeting significantly improved the therapeutic antitumor efficacy of Ad5-huPSMA encoding PSMA when combined with Ad5-IFNγ in the RM-1-PSMA model. These results suggest that a CD-targeted adenovirus delivering PSMA may be effective clinically for prostate cancer immunotherapy.

A large-scale (19)F MRI-based cell migration assay to optimize cell therapy

Adoptive transfer of cells for therapeutic purposes requires efficient and precise delivery to the target organ whilst preserving cell function. Therefore, therapeutically applied cells need to migrate and integrate within their target tissues after delivery, e.g. dendritic cells (DCs) need to migrate to lymph nodes to elicit an antigen-specific immune response. Previous studies have shown that inappropriate cell delivery can hinder DC migration and result in insufficient immune induction. As migration can be extremely difficult to study quantitatively in vivo, we propose an in vitro assay that reproduces key in vivo conditions to optimize cell delivery and migration in vivo. Using DC migration along a chemokine gradient, we describe here a novel (19)F MR-based, large-scale, quantitative assay to measure cell migration in a three-dimensional collagen scaffold. Unlike conventional migration assays, this set-up is amenable to both large and small cell numbers, as well as opaque tissue samples and the inclusion of chemokines or other factors. We labeled primary human DCs with a (19)F label suitable for clinical use; (0.5-15) × 10(6) cells in the scaffolds were imaged sequentially, and migration was assessed using two independent methods. We found no migration with larger numbers of cells, but up to 3% with less than one million cells. Hence, we show that the cell density in cell bolus injections has a decisive impact on migration, and this may explain the limited migration observed using large cell numbers in the clinic.

Effect of administration of apoptotic blebs on disease development in lupus mice

INTRODUCTION

Systemic lupus erythematosus (SLE) is an autoimmune disease characterised by the formation of autoantibodies against nuclear components. Disturbed apoptosis and reduced clearance of apoptotic material have been assigned a role in the pathogenesis of SLE. During apoptosis, apoptotic blebs are formed, in which SLE autoantigens are clustered. In vitro, apoptotic blebs can induce maturation of dendritic cells (DC), which in turn can stimulate IL-17 production by T cells. Here, we investigated the effects of administration of apoptotic blebs, separate or in combination with dendritic cells, on disease progression and autoantibody production in lupus and normal mice.

METHODS

A preparation of apoptotic blebs, with or without DC, was intravenously administered to MRL/lpr and CBA mice at weeks 7, 9, and 11 of age. T-cell responses against autoantigens present in blebs were examined by delayed type hypersensitivity reactions. Disease progression of the mice was evaluated by determining proteinuria and the titers of anti-DNA, anti-histone, and anti-nucleosome autoantibodies in plasma.

RESULTS

Repeated administration of apoptotic blebs, with or without DC, had no effect on the course of proteinuria or on anti-DNA, anti-histone and anti-nucleosome autoantibody levels in MRL/lpr mice. Intravenous injections of apoptotic blebs resulted in a decrease in the DTH response towards s.c. administered blebs in MRL/lpr mice and in reduced anti-nucleosome antibody titers in CBA mice. These tolerizing effects were lost when apoptotic blebs were administered together with syngeneic DC after 2 hours of co-incubation.

DISCUSSION AND CONCLUSIONS

In contrast to previous studies with apoptotic cells, and deviating from our in vitro findings with apoptotic blebs, we observed no stimulating effect of the administration of apoptotic blebs on disease progression in MRL/lpr lupus mice. The tolerogenic effects that were observed may be associated with rapid removal of i.v. administered blebs by phagocytes in an immune-silencing way.

Simultaneous in vivo tracking of dendritic cells and priming of an antigen-specific immune response

We report the fabrication of a one-pot antigen system that delivers antigen to dendritic cells (DCs) and tracks their in vivo migration after injection. Multifunctional polymer nanoparticles containing ovalbumin protein, magnetic resonance imaging contrast agents (iron oxide nanoparticles), and near-infrared fluorophores (indocyanine green, ICG), MPN-OVA, were prepared using a double emulsion method. The MPN-OVA was efficiently taken up by the dendritic cells and subsequently localized in the lysosome. Flow cytometry analysis revealed an increase in the uptake of OVA antigen by MPN-OVA at 37 °C, when compared with soluble OVA protein. We found that MPN-OVA had no effect on DC surface expression of MHC class I, costimulatory (CD80, CD86) or adhesion (CD54) molecules or the ability of DCs to mature in response to LPS. Following the uptake of MPN-OVA, exogenous OVA antigen was delivered to the cytoplasm, and OVA peptides were presented on MHC class I molecules, which enhanced OVA antigen-specific cross-presentation to OT-1 T cells and CD8OVA1.3 T cell hybridoma in vitro. The immunization of mice with MPN-OVA-treated DCs induced OVA-specific CTL activity in draining lymph nodes. The presence of MPN allowed us to monitor the migration of DCs via lymphatic drainage using NIR fluorescence imaging, and the homing of DCs into the lymph nodes was imaged using MRI. This system has potential for use as a delivery system to induce T cell priming and to image DC-based immunotherapies.

Carcinoma-derived interleukin-8 disorients dendritic cell migration without impairing T-cell stimulation

Background

Interleukin-8 (IL-8, CXCL8) is readily produced by human malignant cells. Dendritic cells (DC) both produce IL-8 and express the IL-8 functional receptors CXCR1 and CXCR2. Most human colon carcinomas produce IL-8. IL-8 importance in malignancies has been ascribed to angiogeneis promotion.

Principal Findings

IL-8 effects on human monocyte-derived DC biology were explored upon DC exposure to recombinant IL-8 and with the help of an IL-8 neutralizing mAb. In vivo experiments were performed in immunodeficient mice xenografted with IL-8-producing human colon carcinomas and comparatively with cell lines that do not produce IL-8. Allogenic T lymphocyte stimulation by DC was explored under the influence of IL-8. DC and neutrophil chemotaxis were measured by transwell-migration assays. Sera from tumor-xenografted mice contained increasing concentrations of IL-8 as the tumors progress. IL-8 production by carcinoma cells can be modulated by low doses of cyclophosphamide at the transcription level. If human DC are injected into HT29 or CaCo2 xenografted tumors, DC are retained intratumorally in an IL-8-dependent fashion. However, IL-8 did not modify the ability of DC to stimulate T cells. Interestingly, pre-exposure of DC to IL-8 desensitizes such cells for IL-8-mediated in vitro or in vivo chemoattraction. Thereby DC become disoriented to subsequently follow IL-8 chemotactic gradients towards malignant or inflamed tissue.

Conclusions

IL-8 as produced by carcinoma cells changes DC migration cues, without directly interfering with DC-mediated T-cell stimulation.

Chemokines: can effector cells be redirected to the site of the tumor?

Chemokines (ie, chemoattractant cytokines) are a family of small secreted molecules that mediate leukocyte migration. It is becoming increasingly more evident that chemokines play an integral role in the initiation of a specific immune response. With respect to cancer, chemokines are being studied for both their role in tumor biology and as promising immunotherapy candidates. We review several areas of chemokine importance in tumor immunity and discuss the experimental evidence that is leading to the clinical use of this cytokine family in new treatment approaches for patients with cancer.

Dendritic cells matured by a prostaglandin E2-containing cocktail can produce high levels of IL-12p70 and are more mature and Th1-biased than dendritic cells treated with TNF-α or LPS

Dendritic cells (DCs) play a crucial role in the initiation of an immune response. As maturation is critical for effective antigen presentation, different methods have been used to generate mature DCs (mDCs) ex vivo. The use of a maturation cocktail (MC) consisting of IL-1β, IL-6, TNF-α, and prostaglandin E2 (PGE2) initially showed promising results, but then was challenged because of low production of IL-12p70 and the potential for induction of Th2-type immune responses. To investigate this contention, we compared two of the most commonly used maturation factors, TNF-α and LPS, with MC. Maturation cocktail was superior to TNF-α and LPS with respect to enhancement of mDC-specific surface marker expression (CD83, CD86, and HLA-DR), induction of T cell proliferation by mDCs, and directional motility of mDCs toward CCL19. These results were supported by increased expression of a significant number of additional maturation-related genes by MC in comparison to TNF-α and LPS. In addition, we did not observe a Th2-biased shift in the gene expression profile of mDCs generated by MC. Conversely, MC induced more Th1-promoting transcriptional changes than LPS or TNF-α, including increased transcript levels of Th1-type cytokines such as IL-15, IL-12β, and EBI3 (IL-27β) and MHC class I molecules, Th1-promoting changes in the transcripts of CXCL16, CCL13, and CCL18, and reduced transcript levels of MHC class II molecules. More interestingly, the Th1-promoting characteristics of MC-mDCs were confirmed by their potential to produce large amounts of IL-12p70 after effective stimulation simulating in vivo events.

A novel (19)F agent for detection and quantification of human dendritic cells using magnetic resonance imaging

Monitoring of cell therapeutics in vivo is of major importance to estimate its efficacy. Here, we present a novel intracellular label for (19)F magnetic resonance imaging (MRI)-based cell tracking, which allows for noninvasive, longitudinal cell tracking without the use of radioisotopes. A key advantage of (19)F MRI is that it allows for absolute quantification of cell numbers directly from the MRI data. The (19)F label was tested in primary human monocyte-derived dendritic cells. These cells took up label effectively, resulting in a labeling of 1.7 ± 0.1 × 10(13) (19)F atoms per cell, with a viability of 80 ± 6%, without the need for electroporation or transfection agents. This results in a minimum detection sensitivity of about 2,000 cells/voxel at 7 T, comparable with gadolinium-labeled cells. Comparison of the detection sensitivity of cells labeled with (19)F, iron oxide and gadolinium over typical tissue background showed that unambiguous detection of the (19)F-labeled cells was simpler than with the contrast agents. The effect of the (19)F agent on cell function was minimal in the context of cell-based vaccines. From these data, we calculate that detection of 30,000 cells in vivo at 3 T with a reasonable signal to noise ratio for (19)F images would require less than 30 min with a conventional fast spin echo sequence, given a coil similar to the one used in this study. This is well within acceptable limits for clinical studies, and thus, we conclude that (19)F MRI for quantitative cell tracking in a clinical setting has great potential.

Generation of recombinant antibody fragments that target canine dendritic cells by phage display technology

One of the main goals in cancer immunotherapy is the efficient activation of the host immune system against tumour cells. Dendritic cells (DCs) can induce specific anti-tumour immune responses in both experimental animal models and humans. However, most preclinical studies using small animal models show only limited correlation with studies carried out in clinical settings, whereas laboratory dogs naturally develop tumours that are biologically and histopathologically similar to their human counterparts. Here, we describe the generation and characterization of recombinant antibodies against canine DCs, isolated using the Tomlinson phage display system. We successfully isolated highly specific single-chain variable fragment (scFv) antibodies in a sequential three-step panning strategy involving depletion on canine peripheral blood mononuclear cells followed by positive selection on native canine DCs. This provides the basis for an antibody-based method for the immunological detection and manipulation of DCs and for monitoring antigen-specific immune responses.

Imaging of cellular therapies

Cellular therapy promises to revolutionize medicine, by restoring tissue and organ function, and combating key disorders including cancer. As with all major developments, new tools must be introduced to allow optimization. For cell therapy, the key tool is in vivo imaging for real time assessment of parameters such as cell localization, numbers and viability. Such data is critical to modulate and tailor the therapy for each patient. In this review, we discuss recent work in the field of imaging cell therapies in the clinic, including preclinical work where clinical examples are not yet available. Clinical trials in which transferred cells were imaged using magnetic resonance imaging (MRI), nuclear scintigraphy, single photon emission computed tomography (SPECT), and positron emission tomography (PET) are evaluated from an imaging perspective. Preclinical cell tracking studies that focus on fluorescence and bioluminescence imaging are excluded, as these modalities are generally not applicable to clinical cell tracking. In this review, we assess the advantages and drawbacks of the various imaging techniques available, focusing on immune cells, particularly dendritic cells. Both strategies of prelabeling cells before transplant and the use of an injectable label to target cells in situ are covered. Finally, we discuss future developments, including the emergence of multimodal imaging technology for cell tracking from the preclinical to the clinical realm.

Exogenous dendritic cell homing to draining lymph nodes can be boosted by mast cell degranulation

Dendritic cells (DCs), as potent antigen presenting cells, are increasingly used for immunotherapeutic approaches, predominantly in oncology. Low efficiency of injected Ag-pulsed DC homing to draining lymph nodes (DLNs) is one of the factors that affect the efficacy of therapy. As Langerhans cell emigration was enhanced after skin mast cell degranulation, we investigated the effect of local mast cell activation on exogenous bone marrow-derived DCs (BM-DCs) homing to DLNs. Product of activated MC/9 mast cells enhanced chemotaxis of BM-DCs to CCL21 in vitro. Intradermal injection of compound 48/80 (c48/80) induced local skin mast cell obvious degranulation and boosted exogenous BM-DC homing to DLNs. Both Ag-specific lymphocyte proliferation and TH1/TH2 cytokine production increased after HBsAg-pulsed BM-DC was injected into c48/80 pretreated mice. These results suggest that transferred DC homing to DLNs promoted by local mast cell degranulation may have potential application to improve DC-based immunotherapy.

Targeting MARCO can lead to enhanced dendritic cell motility and anti-melanoma activity

We reported that murine tumor lysate-pulsed dendritic cells (TP-DC) could elicit tumor-specific CD4(+) and CD8(+) T cells in vitro and in vivo. In some limited cases, TP-DC treatments in vivo could also result in regression of established subcutaneous tumors and lung metastases. By gene array analysis, we reported a high level of expression of a novel member of the cell surface class A scavenger receptor family, MARCO, by murine TP-DC compared to unpulsed DC. MARCO is thought to play an important role in the immune response by mediating binding and phagocytosis, but also in the formation of lamellipodia-like structures and dendritic processes. We have now examined the biologic and therapeutic implications of MARCO expressed by TP-DC. In vitro exposure of TP-DC to a monoclonal anti-MARCO antibody resulted in a morphologic change of rounding with disappearance of dendritic-like processes. TP-DC remained viable after anti-MARCO antibody treatment; had little, if any, change in production of IL-10, IL-12p70 and TNF-alpha; but demonstrated enhanced migratory capacity in a microchemotaxis assay. The use of a selective inhibitor showed MARCO expression to be linked to the p38 mitogen-activated protein kinase (MAPK) pathway. In vivo, anti-MARCO antibody treated TP-DC showed better trafficking from the skin injection site to lymph node, enhanced generation of tumor-reactive IFN-gamma producing T cells, and improved therapeutic efficacy against B16 melanoma. These results, coupled with our finding that human monocyte-derived DC also express MARCO, could have important implications to human clinical DC vaccine trials.

Enhanced migration of human dendritic cells expressing inducible CD40

Dendritic cells (DC) are the most potent antigen-presenting cells for priming and activating naïve CD4(+) and CD8(+) T lymphocytes. This property has led to their use as a cellular vaccine in a number of clinical trials with promising results. However, the clinical efficacy of DC vaccines in patients has been unsatisfactory, probably because of a number of key deficiencies, including limited migration of ex vivo generated DCs to the secondary lymphoid tissues. To enhance human DC-based vaccines, we used the combination of an inducible CD40 receptor (iCD40) along with TLR-4 ligation. The iCD40 receptor permits targeted, reversible activation of CD40. Using iCD40 in combination with lipopolysaccharides (LPS), we enhanced DCs migration in vitro upon escalation of the AP1903 dimerizer drug doses. This result suggests that the use of iCD40-modified and LPS-stimulated DCs is a potent strategy in DC-based cancer immunotherapies.

Short-term cultured, interleukin-15 differentiated dendritic cells have potent immunostimulatory properties

Background

Optimization of the current dendritic cell (DC) culture protocol in order to promote the therapeutic efficacy of DC-based immunotherapy is warranted. Alternative differentiation of monocyte-derived DCs using granulocyte macrophage colony-stimulating factor (GM-CSF) and interleukin (IL)-15 has been propagated as an attractive strategy in that regard. The applicability of these so-called IL-15 DCs has not yet been firmly established. We therefore developed a novel pre-clinical approach for the generation of IL-15 DCs with potent immunostimulatory properties.

Methods

Human CD14⁺ monocytes were differentiated with GM-CSF and IL-15 into immature DCs. Monocyte-derived DCs, conventionally differentiated in the presence of GM-CSF and IL-4, served as control. Subsequent maturation of IL-15 DCs was induced using two clinical grade maturation protocols: (i) a classic combination of pro-inflammatory cytokines (tumor necrosis factor-α, IL-1β, IL-6, prostaglandin E₂) and (ii) a Toll-like receptor (TLR)7/8 agonist-based cocktail (R-848, interferon-γ, TNF-α and prostaglandin E₂). In addition, both short-term (2-3 days) and long-term (6-7 days) DC culture protocols were compared. The different DC populations were characterized with respect to their phenotypic profile, migratory properties, cytokine production and T cell stimulation capacity.

Results

The use of a TLR7/8 agonist-based cocktail resulted in a more optimal maturation of IL-15 DCs, as reflected by the higher phenotypic expression of CD83 and costimulatory molecules (CD70, CD80, CD86). The functional superiority of TLR7/8-activated IL-15 DCs over conventionally matured IL-15 DCs was evidenced by their (i) higher migratory potential, (ii) advantageous cytokine secretion profile (interferon-γ, IL-12p70) and (iii) superior capacity to stimulate autologous, antigen-specific T cell responses after passive peptide pulsing. Aside from a less pronounced production of bioactive IL-12p70, short-term versus long-term culture of TLR7/8-activated IL-15 DCs resulted in a migratory profile and T cell stimulation capacity that was in favour of short-term DC culture. In addition, we demonstrate that mRNA electroporation serves as an efficient antigen loading strategy of IL-15 DCs.

Conclusions

Here we show that short-term cultured and TLR7/8-activated IL-15 DCs fulfill all pre-clinical prerequisites of immunostimulatory DCs. The results of the present study might pave the way for the implementation of IL-15 DCs in immunotherapy protocols.

Targeting of epidermal Langerhans cells with antigenic proteins: attempts to harness their properties for immunotherapy

Langerhans cells, a subset of skin dendritic cells in the epidermis, survey peripheral tissue for invading pathogens. In recent functional studies it was proven that Langerhans cells can present exogenous antigen not merely on major histocompatibility complexes (MHC)-class II molecules to CD4+ T cells, but also on MHC-class I molecules to CD8+ T cells. Immune responses against topically applied antigen could be measured in skin-draining lymph nodes. Skin barrier disruption or co-application of adjuvants was required for maximal induction of T cell responses. Cytotoxic T cells induced by topically applied antigen inhibited tumor growth in vivo, thus underlining the potential of Langerhans cells for immunotherapy. Here we review recent work and report novel observations relating to the potential use of Langerhans cells for immunotherapy. We investigated the potential of epicutaneous immunization strategies in which resident skin dendritic cells are loaded with tumor antigen in situ. This contrasts with current clinical approaches, where dendritic cells generated from progenitors in blood are loaded with tumor antigen ex vivo before injection into cancer patients. In the current study, we applied either fluorescently labeled protein antigen or targeting antibodies against DEC-205/CD205 and langerin/CD207 topically onto barrier-disrupted skin and examined antigen capture and transport by Langerhans cells. Protein antigen could be detected in Langerhans cells in situ, and they were the main skin dendritic cell subset transporting antigen during emigration from skin explants. Potent in vivo proliferative responses of CD4+ and CD8+ T cells were measured after epicutaneous immunization with low amounts of protein antigen. Targeting antibodies were mainly transported by langerin+ migratory dendritic cells of which the majority represented migratory Langerhans cells and a smaller subset the new langerin+ dermal dendritic cell population located in the upper dermis. The preferential capture of topically applied antigen by Langerhans cells and their ability to induce potent CD4+ and CD8+ T cell responses emphasizes their potential for epicutaneous immunization strategies.

Lymphoid-tissue-specific homing of bone-marrow-derived dendritic cells

Because of their potent immunoregulatory capacity, dendritic cells (DCs) have been exploited as therapeutic tools to boost immune responses against tumors or pathogens, or dampen autoimmune or allergic responses. Murine bone marrow-derived DCs (BM-DCs) are the closest known equivalent of the blood monocyte-derived DCs that have been used for human therapy. Current imaging methods have proven unable to properly address the migration of injected DCs to small and deep tissues in mice and humans. This study presents the first extensive analysis of BM-DC homing to lymph nodes (and other selected tissues) after intravenous and intraperitoneal inoculation. After intravenous delivery, DCs accumulated in the spleen, and preferentially in the pancreatic and lung-draining lymph nodes. In contrast, DCs injected intraperitoneally were found predominantly in peritoneal lymph nodes (pancreatic in particular), and in omentum-associated lymphoid tissue. This uneven distribution of BM-DCs, independent of the mouse strain and also observed within pancreatic lymph nodes, resulted in the uneven induction of immune response in different lymphoid tissues. These data have important implications for the design of systemic cellular therapy with DCs, and in particular underlie a previously unsuspected potential for specific treatment of diseases such as autoimmune diabetes and pancreatic cancer.

In vitro end points for the assessment of cellular immune response-modulating drugs

BACKGROUND

The concept of immunotoxicology and the development of a battery of immune-function assays to screen potential immunotoxic compounds have been increasingly used in the past. Immunotoxic outcome generally seems appropriate to evaluate the risk in drug development. Improving this approach is possible, by using methods now available, to study the effect of a chemical compound on the immune system.

OBJECTIVE

The goal of this review is to provide an overview of the current and recent methodologies for testing the immunological effect and immunotoxic risks in drug candidates.

METHODS

The methodological details here discussed include a synthetic description of the immunocompetent cells in cell-mediated immunity and the choice of the most appropriate assay (bioassays, immunoassays, molecular biology techniques, flow cytometry).

CONCLUSION

This review offers an assessment of in vitro models to study the toxic impact of (bio)pharmaceuticals on cellular immune system and aid drug scientists in understanding the significance and the methods to approach immunotoxicology.

Dendritic cells: a critical player in cancer therapy?

Cancer immunotherapy seeks to mobilize a patient's immune system for therapeutic benefit. It can be passive, that is, transfer of immune effector cells (T cells) or proteins (antibodies), or active, that is, vaccination. Early clinical trials testing vaccination with ex vivo generated dendritic cells (DCs) pulsed with tumor antigens provide a proof-of-principle that therapeutic immunity can be elicited. Yet, the clinical benefit measured by regression of established tumors in patients with stage IV cancer has been observed in a fraction of patients only. The next generation of DC vaccines is expected to generate large numbers of high avidity effector CD8 T cells and to overcome regulatory T cells and suppressive environment established by tumors, a major obstacle in metastatic disease. Therapeutic vaccination protocols will combine improved DC vaccines with chemotherapy to exploit immunogenic chemotherapy regimens. We foresee adjuvant vaccination in patients with resected tumors but at high risk of relapse to be based on in vivo targeting of DCs with fusion proteins containing anti-DCs antibodies, antigens from tumor stem/propagating cells, and DC activators.