The specialized roles of immature and mature dendritic cells in antigen cross-presentation

A review on polysaccharide-based tumor targeted drug nanodelivery systems

The tumor-targeted drug delivery system (TTDNS) uses nanocarriers to transport chemotherapeutic agents to target tumor cells or tissues precisely. This innovative approach considerably increases the effective concentration of these drugs at the tumor site, thereby enhancing their therapeutic efficacy. Many chemotherapeutic agents face challenges, such as low bioavailability, high cytotoxicity, and inadequate drug resistance. To address these obstacles, TTDNS comprising natural polysaccharides have gained increasing popularity in the field of nanotechnology owing to their ability to improve safety, bioavailability, and biocompatibility while reducing toxicity. In addition, it enhances permeability and allows for controlled drug delivery and release. This review focuses on the sources of natural polysaccharides and their direct and indirect mechanisms of anti-tumor activity. We also explored the preparation of various polysaccharide-based nanocarriers, including nanoparticles, nanoemulsions, nanohydrogels, nanoliposomes, nanocapsules, nanomicelles, nanocrystals, and nanofibers. Furthermore, this review delves into the versatile applications of polysaccharide-based nanocarriers, elucidating their capabilities for in vivo targeting, controlled release, and responsiveness to endogenous and exogenous stimuli, such as pH, reactive oxygen species, glutathione, light, ultrasound, and magnetic fields. This sophisticated design substantially enhances the chemotherapeutic efficacy of the encapsulated drugs at tumor sites and provides a basis for preclinical and clinical research. However, the in vivo stability, drug loading, and permeability of these preparations into tumor tissues still need to be improved. Most of the currently developed biomarker-sensitive polysaccharide nanocarriers are still in the laboratory stage, more innovative delivery mechanisms and clinical studies are needed to develop commercial nanocarriers for medical use.

Modified PEG-Lipids Enhance the Nasal Mucosal Immune Capacity of Lipid Nanoparticle mRNA Vaccines

BACKGROUND/OBJECTIVES

Omicron, the predominant variant of SARS-CoV-2, exhibits strong immune-evasive properties, leading to the reduced efficacy of existing vaccines. Consequently, the development of versatile vaccines is imperative. Intranasal mRNA vaccines offer convenient administration and have the potential to enhance mucosal immunity. However, delivering vaccines via the nasal mucosa requires overcoming complex physiological barriers. The aim of this study is to modify PEGylated lipids to enhance the mucosal immune efficacy of the vaccine.

METHODS

The PEGylated lipid component of lipid nanoparticle (LNP) delivery vectors was modified with chitosan or mannose to generate novel LNPs that enhance vaccine adhesion or targeting on mucosal surfaces. The impact of the mRNA encoding the receptor-binding domain of Omicron BA.4/BA.5 on the immune response was examined.

RESULTS

Compared to the unmodified LNP group, the IgG and IgA titers in the chitosan or mannose-modified LNP groups showed an increasing trend. The chitosan-modified group showed better effects. Notably, the PEGylated lipid with 1.5 mol% of chitosan modification produced high levels of IgG1 and IgG2a antibodies, promoting Th1/Th2 responses while also generating high levels of IgA, which can induce stronger cellular immunity, humoral immunity, and mucosal immunity.

CONCLUSIONS

The 1.5 mol% of chitosan-modified LNPs (mRNA-LNP-1.5CS) can serve as a safe and effective carrier for intranasal mRNA vaccines, offering a promising strategy for combating the Omicron variant.

Dendritic Cells and the Establishment of Fetomaternal Tolerance for Successful Human Pregnancy

Pregnancy is a remarkable event where the semi-allogeneic fetus develops in the mother's uterus, despite genetic and immunological differences. The antigen handling and processing at the maternal-fetal interface during pregnancy appear to be crucial for the adaptation of the maternal immune system and for tolerance to the developing fetus and placenta. Maternal antigen-presenting cells (APCs), such as macrophages (Mφs) and dendritic cells (DCs), are present at the maternal-fetal interface throughout pregnancy and are believed to play a crucial role in this process. Despite numerous studies focusing on the significance of Mφs, there is limited knowledge regarding the contribution of DCs in fetomaternal tolerance during pregnancy, making it a relatively new and growing field of research. This review focuses on how the behavior of DCs at the maternal-fetal interface adapts to pregnancy's unique demands. Moreover, it discusses how DCs interact with other cells in the decidual leukocyte network to regulate uterine and placental homeostasis and the local maternal immune responses to the fetus. The review particularly examines the different cell lineages of DCs with specific surface markers, which have not been critically reviewed in previous publications. Additionally, it emphasizes the impact that even minor disruptions in DC functions can have on pregnancy-related complications and proposes further research into the potential therapeutic benefits of targeting DCs to manage these complications.

Immunomodulatory role of metalloproteases in cancers: Current progress and future trends

Metalloproteinases (MPs) is a large family of proteinases with metal ions in their active centers. According to the different domains metalloproteinases can be divided into a variety of subtypes mainly including Matrix Metalloproteinases (MMPs), A Disintegrin and Metalloproteases (ADAMs) and ADAMs with Thrombospondin Motifs (ADAMTS). They have various functions such as protein hydrolysis, cell adhesion and remodeling of extracellular matrix. Metalloproteinases expressed in multiple types of cancers and participate in many pathological processes involving tumor genesis and development, invasion and metastasis by regulating signal transduction and tumor microenvironment. In this review, based on the current research progress, we summarized the structure of MPs, their expression and especially immunomodulatory role and mechanisms in cancers. Additionally, a relevant and timely update of recent advances and future directions were provided for the diagnosis and immunotherapy targeting MPs in cancers.

Anti-hepatoma Effect of DC2.4 Cells Transfected with Tumor-Associated Antigen Cdc25C In Vitro

OBJECTIVE

Cell division cyclin 25 homolog C (Cdc25C) is a tumor-associated antigen candidate gene, and this may be used as an effective target in cancer treatment. The present study aims to evaluate the lysis effect of cytotoxic T lymphocytes (CTLs) induced by dendritic cell line DC2.4 overexpressing Cdc25C, and the feasibility of Cdc25C as a component in hepatoma immunotherapy.

METHODS

The mouse Cdc25C gene was ligated into a lentiviral vector, and transfected into DC2.4 cells. The DC2.4 cell phenotype and cytokine secretion were determined by flow cytometry and ELISA, respectively. CD8⁺ T cells were sorted from the spleens of C57BL/6 mice using a magnetic bead sorting kit obtained from Miltenyi Biotech, Germany, and co-cultured with DC2.4 cells for one week as effector cells. Then, IL-2, granzyme B and perforin were detected in the CTL culture medium by ELISA. Next, time-resolved fluorescence immunoassay was used to detect the immune killing effect of Cdc25C-specific CTLs on target cells. Meanwhile, the effect of blocking MHC-I sites on target cells with a monoclonal anti-MHC-I antibody was evaluated.

RESULTS

The results revealed that Cdc25C could be stably overexpressed in DC2.4 cells by LV-Cdc25C infection. DC2.4 cells transfected with LV-Cdc25C secreted more IL-6, IL-12, TNF-α and IFN-γ, and had higher expression levels of CD40, CD86, CCR7 and MHC-II than unaltered DC2.4 cells. The elevated Cdc25C in dendritic cells also further increased the secretion of IL-2, granzyme B and perforin to elicit Cdc25C-specific CTLs, and induced the higher cytotoxicity in Hepa1-6 cell lines (P<0.05), but this had no effect on the target cells when MHC-I monoclonal antibodies were blocked.

CONCLUSION

DC2.4 cells transfected with LV-Cdc25C can induce specific CTLs, and result in a strong cellular immune response. The dendritic cells that overexpress Cdc25C may be useful for hepatoma immunotherapy.

Identification of Profound Metabolic Alterations in Human Dendritic Cells by Progesterone Through Integrated Bioinformatics Analysis

Maintaining the homeostasis of the decidual immune microenvironment at the maternal-fetal interface is essential for reproductive success. Dendritic cells (DCs) are the professional antigen-presenting cells and dominate this balance of immunogenicity and tolerance. Progesterone (P4) is highlighted as the “hormone of pregnancy” in most eutherian mammals because of its regulatory role in immune-endocrine behavior during pregnancy. Recent studies have shown that P4 is associated with the differentiation and function of DCs, however, the underlying mechanisms remain unidentified. In addition, while progress in the field of immunometabolism has highlighted the intimate connections between the metabolism phenotype and the immunogenic or tolerogenic fate of DCs, whether P4 can affect DCs metabolism and thus exert a functional manipulation has not yet been explored. In this study, we acquired human peripheral blood monocyte-derived DCs and conducted RNA sequencing (RNA-seq) on immature DCs (iDCs), P4-treated DCs (pDCs), and mature DCs (mDCs), aiming to comprehensively assess the effects of P4 on DCs. Our results showed pDCs performed a distinct differentially expressed genes (DEGs) profile compared with iDCs or mDCs. Further functional enrichment and weighted gene co-expression network (WGCNA) analysis found that these DEGs were related not only to the cellular components but also to the significant metabolic activities, including mitochondrial oxidative phosphorylation (OXPHOS) and fatty acid metabolism. In addition, these changes may be involved in the activation of various signaling pathways of PI3K/Akt/mTOR, AMPK/PGC1-α, and PPAR-γ. In summary, our work suggested that P4 induced profound metabolic alterations of mitochondrial OXPHOS and fatty acid metabolism in DCs. Our findings may provide new insights into the role of P4 in DCs.

Fibrinogen-like protein 1 (FGL1): the next immune checkpoint target

Immune checkpoint therapy has achieved significant efficacy by blocking inhibitory pathways to release the function of T lymphocytes. In the clinic, anti-programmed cell death protein 1/programmed cell death ligand 1 (PD-1/PD-L1) monoclonal antibodies (mAbs) have progressed to first-line monotherapies in certain tumor types. However, the efficacy of anti-PD-1/PD-L1 mAbs is still limited due to toxic side effects and de novo or adaptive resistance. Moreover, other immune checkpoint target and biomarkers for therapeutic response prediction are still lacking; as a biomarker, the PD-L1 (CD274, B7-H1) expression level is not as accurate as required. Hence, it is necessary to seek more representative predictive molecules and potential target molecules for immune checkpoint therapy. Fibrinogen-like protein 1 (FGL1) is a proliferation- and metabolism-related protein secreted by the liver. Multiple studies have confirmed that FGL1 is a newly emerging checkpoint ligand of lymphocyte activation gene 3 (LAG3), emphasizing the potential of targeting FGL1/LAG3 as the next generation of immune checkpoint therapy. In this review, we summarize the substantial regulation mechanisms of FGL1 in physiological and pathological conditions, especially tumor epithelial to mesenchymal transition, immune escape and immune checkpoint blockade resistance, to provide insights for targeting FGL1 in cancer treatment.

Withaferin A inhibits lymphocyte proliferation, dendritic cell maturation in vitro and prolongs islet allograft survival

The immunosuppressive regimen for clinical allogeneic islet transplantation uses beta cell–toxic compounds such as tacrolimus that cause islet graft loss. Previously we reported that the plant-derived steroidal lactone Withaferin A (WA) can protect islet grafts by inhibiting nuclear factor-kappa B (NF-κB). Since the NF-κB signaling pathway is essential for T-cell activation, we hypothesized that long-term WA administration may also provide an immunosuppressive effect. Treatment of BALB/c donor islets and C57BL/6N recipients with WA alone resulted in 80% islet graft long-term survival vs. 40% in low-dose FK506-treated mice. In vitro, WA significantly blocked mouse and human T-cell proliferation by CD3/CD28 bead stimulation and in mixed lymphocyte reaction assay. Treatment of immature dendritic cells with WA prevented their maturation in response to inflammatory stimuli, as seen by decreased expression of CD83 and human leukocyte antigen–DR isotype. Exosomes released by islets treated with WA contained significantly fewer proinflammatory molecules interleukin-6, interleukin-8, monocyte chemoattractant protein-1, interferon-gamma-induced protein-10, inducible nitric oxide synthase, and cyclooxygenase-2. In conclusion, WA treatment not only reduced inflammation but also prolonged allograft survival, possibly through suppression of dendritic cell maturation and T-cell proliferation. WA has the potential to inhibit both the innate and adaptive immune response to prolong allograft survival.

Tropomodulin1 Expression Increases Upon Maturation in Dendritic Cells and Promotes Their Maturation and Immune Functions

Dendritic cells (DCs) are the most potent antigen-presenting cells. Upon maturation, DCs express costimulatory molecules and migrate to the lymph nodes to present antigens to T cells. The actin cytoskeleton plays key roles in multiple aspects of DC functions. However, little is known about the mechanisms and identities of actin-binding proteins that control DC maturation and maturation-associated functional changes. Tropomodulin1 (Tmod1), an actin-capping protein, controls actin depolymerization and nucleation. We found that Tmod1 was expressed in bone marrow-derived immature DCs and was significantly upregulated upon lipopolysaccharide (LPS)-induced DC maturation. By characterizing LPS-induced mature DCs (mDCs) from Tmod1 knockout mice, we found that compared with Tmod1+/+ mDCs, Tmod1-deficient mDCs exhibited lower surface expression of costimulatory molecules and chemokine receptors and reduced secretion of inflammatory cytokines, suggesting that Tmod1 deficiency retarded DC maturation. Tmod1-deficient mDCs also showed impaired random and chemotactic migration, deteriorated T-cell stimulatory ability, and reduced F-actin content and cell stiffness. Furthermore, Tmod1-deficient mDCs secreted high levels of IFN-β and IL-10 and induced immune tolerance in an experimental autoimmune encephalomyelitis (EAE) mouse model. Mechanistically, Tmod1 deficiency affected TLR4 signaling transduction, resulting in the decreased activity of MyD88-dependent NFκB and MAPK pathways but the increased activity of the TRIF/IRF3 pathway. Rescue with exogenous Tmod1 reversed the effect of Tmod1 deficiency on TLR4 signaling. Therefore, Tmod1 is critical in regulating DC maturation and immune functions by regulating TLR4 signaling and the actin cytoskeleton. Tmod1 may be a potential target for modulating DC functions, a strategy that would be beneficial for immunotherapy for several diseases.

Dendritic cells in pregnancy and pregnancy-associated diseases

Dendritic cells (DCs) play a critical immuno-modulating role in pregnancy, which requires the maternal immune system to tolerate semiallogeneic fetus and at the same time to maintain adequate defense against pathogens. DCs interact closely with other immune components such as T cells, natural killer cells and macrophages, as well as the endocrine system to keep a pregnancy-friendly environment. Aberrant DC activities have been related to various pregnancy-associated diseases such as recurrent spontaneous abortion, preterm birth, pre-eclampsia, peripartum cardiomyopathy and infectious pregnancy complications. These findings make DCs an attractive candidate for prevention or therapy on the pregnancy-associated diseases. Here, we review recent findings that provide new insights into the roles of DCs in pregnancy and the related diseases. We also discuss the medical potentials to manipulate DCs in clinics. Whereas this is an emerging area with much work remaining, we anticipate that a better understanding of the role of DCs in maternal-fetal immunotolerance and a therapeutic manipulation of DCs will help women suffering from the pregnancy-associated diseases.

Intradermal Phleum pratense allergoid immunotherapy. Double-blind, randomized, placebo-controlled trial

Background

In allergology, the intradermal approach is generally used to establish an aetiological diagnosis, with limited experience in specific allergen immunotherapy.

Objective

To evaluate the efficacy and safety of immunotherapy with an allergen extract of glutaraldehyde‐polymerized Phleum pratense, administered intradermally, in patients with rhinoconjunctivitis sensitized to grass pollen.

Methods

Multicentre, randomized, double‐blind, placebo‐controlled clinical trial in patients from 12 to 65 years of age with rhinitis or rhinoconjunctivitis, with or without asthma, due to grass pollen allergy. Patients were divided into three groups and received a total of six doses in a weekly interval, of either placebo; 0.03 or 0.06 μg of protein per dose of P pratense allergoid. The primary objective was to evaluate the combined symptoms and medication consumption score (CSMS). The secondary objectives were symptoms and medication, tolerance to the conjunctival provocation test, specific IgE and IgG4 antibodies and the safety profile according to the WAO scale.

Results

The dose of 0.06 μg of protein proved to be effective versus the placebo by significantly reducing CSMS and increasing tolerance to the allergenic extract in the conjunctival provocation test, after the first pollen season. This group showed a significant reduction in specific IgE after the second pollen season relative to the baseline. There were no variations in IgG4 levels. Only one grade 2 systemic reaction was recorded.

Conclusion & Clinical Relevance

Intradermal immunotherapy with P pratense allergoid has been shown to be effective and safe, reducing CSMS, increasing tolerance to the conjunctival provocation test and reducing IgE levels.

Activated γδ T Cells Promote Dendritic Cell Maturation and Exacerbate the Development of Experimental Autoimmune Uveitis (EAU) in Mice

Our previous study reveals that gamma delta (γδ) T cells were activated and dendritic cells (DCs) underwent maturation during the inflammation phase in experimental autoimmune uveitis (EAU) mice, and the interaction between DCs and γδ T cells may significantly exacerbate the development of EAU. However, the interactions between DCs and γδ T cells that can affect DCs maturation to influence EAU development must be further addressed. In this study we showed that mature DC numbers in TCR-δ^-/- (KO) EAU mice were lower than those in wild-type (WT) C57BL/6 (B6) mice. The γδ T cells harvested from WT EAU mice secreted more interferon-γ (IFN-γ), however, after blocking IFN-γ, the maturation of DCs was significantly downregulated. By contrast, the percentage of IFN-γ- and IL-17-producing CD4⁺ T cells in KO EAU mice decreased to a greater extent than that in WT EAU mice during the inflammatory phase. Additionally, the levels of IFN-γ/IL-17 in serum were in agreement with those of CD4⁺ T cells. Furthermore, after activated γδ T cells injection, the inflammatory symptoms of EAU mice were more aggravated. In vitro co-cultures of both cell types showed that activated γδ T cells may induce DCs to generate higher levels of intracellular cell adhesion molecule-1 (ICAM-1/CD54), CD80, CD83, and CD86. Moreover, co-culture of the two cells may induce the activation of CD4⁺ T cells. Taken together, our results demonstrated that activated γδ T cells may promote DCs maturation and further enhance the generation of Th1/Th17 cells in EAU mice, resulting in exacerbated EAU.

FGL2 regulates IKK/NF-κB signaling in intestinal epithelial cells and lamina propria dendritic cells to attenuate dextran sulfate sodium-induced colitis

Inflammatory bowel disease (IBD) is an autoimmune disease characterized by an abnormal immune response. Fibrinogen-like protein 2 (FGL2) is known to have immunoregulatory and anti-inflammatory activity. The level of FGL2 is elevated in patients with IBD; however, its comprehensive function in IBD is almost unknown. In our study, we explored the effect of FGL2 on dextran sulfate sodium (DSS)-induced colitis in mice and on NF-κB signaling in intestinal epithelial cells (IECs) and lamina propria dendritic cells (LPDCs). We founded that FGL2^-/- mice in the colitis model showed more severe colitis manifestations than WT mice did, including weight loss, disease activity index (DAI), and colon histological scores. FGL2^-/- mice treated with DSS produced more proinflammatory cytokines (IL-1β, IL-6, TNF-α) in serum than WT mice did and demonstrated upregulated expression of TNF-α and inflammatory marker enzymes, inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (Cox-2) in the colon tissue. Our data suggested that DSS-treated FGL2^-/- mice showed stronger activation of NF-κB signaling, especially in IECs. Next, we demonstrated that recombinant FGL2 (rFGL2) inhibited the production of proinflammatory cytokines and the expression of inflammatory marker enzymes by downregulating the NF-κB signaling in HT-29 cells. Finally, we discovered that LPDCs from the colon of DSS-treated FGL2^-/- mice showed significantly upregulated expression of surface maturation co-stimulatory molecules, including CD80, CD86, CD40, and MHC class II molecules compared with that in WT mice. In addition, LPDCs in FGL2^-/- treated with DSS exhibited excessive NF-κB activity and the administration of rFGL2 to FGL2^-/- mice could rescue the aggravated results of FGL2^-/- mice. Taken together, our findings demonstrated that FGL2 might be a target for further therapy of IBD.

Miniaturized High-Throughput Multiparameter Flow Cytometry Assays Measuring In Vitro Human Dendritic Cell Maturation and T-Cell Activation in Mixed Lymphocyte Reactions

Enhancing antitumor activities of the human immune system is a clinically proven approach with the advent of monoclonal antibodies recognizing programmed cell death protein-1 (PD1) receptors on immune cell surfaces. Historically, using flow cytometry as a means to assess next-generation agent activities was underused, largely due to limits on cell number and assay sensitivity. Here, we leveraged an IntelliCyt high-throughput flow cytometry platform to monitor human dendritic cell maturation and lymphocyte proliferation in mixed lymphocyte reactions. Specifically, we established flow cytometry-based immunophenotyping and screening methodologies capable of measuring T-cell activation as a result of cell-associated antigens presented on dendritic cell surfaces, as indicated by cell proliferation, cytokine secretion, and surface marker expression. Together, the overall novelty of this 384-well platform is its capability to measure multiple functional readouts in one well and consistently evaluate large numbers of compounds in a single study, as well as its ability to show increased assay sensitivity requiring considerably fewer primary cells and less reagents compared to more traditional 96-well flow cytometry methods.

Type I Interferon-Independent Dendritic Cell Priming and Antitumor T Cell Activation Induced by a Mycoplasma fermentans Lipopeptide

Mycoplasma fermentans-derived diacylated lipoprotein M161Ag (MALP404) is recognized by human/mouse toll-like receptor (TLR) 2/TLR6. Short proteolytic products including macrophage-activating lipopeptide 2 (MALP2) have been utilized as antitumor immune-enhancing adjuvants. We have chemically synthesized a short form of MALP2 named MALP2s (S-[2,3-bis(palmitoyloxy)propyl]-CGNNDE). MALP2 and MALP2s provoke natural killer (NK) cell activation in vitro but only poorly induce tumor regression using in vivo mouse models loading NK-sensitive tumors. Here, we identified the functional mechanism of MALP2s on dendritic cell (DC)-priming and cytotoxic T lymphocyte (CTL)-dependent tumor eradication using CTL-sensitive tumor-implant models EG7 and B16-OVA. Programmed death ligand-1 (PD-L1) blockade therapy in combination with MALP2s + ovalbumin (OVA) showed a significant additive effect on tumor growth suppression. MALP2s increased co-stimulators CD80/86 and CD40, which were totally MyD88-dependent, with no participation of toll-IL-1R homology domain-containing adaptor molecule-1 or type I interferon signaling in DC priming. MALP2s + OVA consequently augmented proliferation of OVA-specific CTLs in the spleen and at tumor sites. Chemokines and cytolytic factors were upregulated in the tumor. Strikingly, longer duration and reinvigoration of CTLs in spleen and tumors were accomplished by the addition of MALP2s + OVA to α-PD-L1 antibody (Ab) therapy compared to α-PD-L1 Ab monotherapy. Then, tumors regressed better in the MALP2s/OVA combination than in the α-PD-L1 Ab monotherapy. Hence, MALP2s/tumor-associated antigens combined with α-PD-L1 Ab is a good therapeutic strategy in some mouse models. Unfortunately, numerous patients are still resistant to PD-1/PD-L1 blockade, and good DC-priming adjuvants are desired. Cytokine toxicity by MALP2s remains to be settled, which should be improved by chemical modification in future studies.

Immune responses of mature chicken bone-marrow-derived dendritic cells infected with Newcastle disease virus strains with differing pathogenicity

Infection of chickens with virulent Newcastle disease virus (NDV) is associated with severe pathology and increased morbidity and mortality. The innate immune response contributes to the pathogenicity of NDV. As professional antigen-presenting cells, dendritic cells (DCs) play a unique role in innate immunity. However, the contribution of DCs to NDV infection has not been investigated in chickens. In this study, we selected two representative NDV strains, i.e., the velogenic NDV strain Chicken/Guangdong/GM/2014 (GM) and the lentogenic NDV strain La Sota, to investigate whether NDVs could infect LPS-activated chicken bone-derived marrow DCs (mature chicken BM-DCs). We compared the viral titres and innate immune responses in mature chicken BM-DCs following infection with those strains. Both NDV strains could infect mature chicken BM-DC, but the GM strain showed stronger replication capacity than the La Sota strain in mature chicken BM-DCs. Gene expression profiling showed that MDA5, LGP2, TLR3, TLR7, IFN-α, IFN-β, IFN-γ, IL-1β, IL-6, IL-18, IL-8, CCL5, IL-10, IL-12, MHC-I, and MHC-II levels were altered in mature DCs after infection with NDVs at all evaluated times postinfection. Notably, the GM strain triggered stronger innate immune responses than the La Sota strain in chicken BM-DCs. However, both strains were able to suppress the expression of some cytokines, such as IL-6 and IFN-α, in mature chicken DCs at 24 hpi. These data provide a foundation for further investigation of the role of chicken DCs in NDV infection.

Encapsulation of Hydrophilic and Hydrophobic Peptides into Hollow Mesoporous Silica Nanoparticles for Enhancement of Antitumor Immune Response

Codelivery of combinational antigenic peptides and adjuvant to antigen presenting cells is expected to amplify tumor specific T lymphocytes immune responses while minimizing the possibility of tumor escaping and reducing immune tolerance to single antigenic peptide. However, the varied hydrophobicities of these multivariant derived short antigenic peptides limit their codelivery efficiency in conventional delivery systems. Here, a facile yet effective route is presented to generate monodisperse and stable hollow mesoporous silica nanoparticles (HMSNs) for codelivering of HGP100_25-33 and TRP2_180-188 , two melanoma-derived peptides with varied hydrophobicities. The HMSNs with large pore size can improve the encapsulation efficiency of both HGP100 and TRP2 after NH₂ modification on the inner hollow core and COOH modification in the porous channels. HGP100 and TRP2 loaded HMSNs (HT@HMSNs) are further enveloped within monophosphoryl lipid A adjuvant entrapped lipid bilayer (HTM@HMLBs), for improved stability/biocompatibility and codelivery efficiency of multiple peptides, adjuvant, and enhanced antitumor immune responses. HTM@HMLBs increase uptake by dendritic cells (DCs) and stimulate DCs maturation efficiently, which further induce the activation of both tumor specific CD8⁺ and CD4⁺ T lymphocytes. Moreover, HTM@HMLBs can significantly inhibit tumor growth and lung metastasis in murine melanoma models with good safety profiles. HMSNs enveloped with lipid bilayers (HMLBs) are believed to be a promising platform for codelivery of multiple peptides, adjuvant, and enhancement of antitumor efficacy of conventional vaccinations.

Early dengue virus interactions: the role of dendritic cells during infection

Dengue is an acute infectious disease caused by dengue virus (DENV) that affects approximately 400 million people annually, being the most prevalent human arthropod-borne disease. DENV infection causes a wide variety of clinical manifestations that range from asymptomatic to dengue fever, and in some cases may evolve to the more severe dengue hemorrhagic fever and dengue shock syndrome. The exact reasons why some patients do not have symptoms while others develop the severe forms of disease are still elusive, but gathered evidence showed correlation between a secondary infection with a heterologous DENV serotype and the occurrence of severe symptoms. Despite several advances, the mechanisms of DENV infection are still not completely elucidated, and efforts have been made to understand the development of immunity and/or pathology to DENV. When a mosquito transmits DENV, the virus is initially deposited in the skin, where mononuclear phagocytic cells, such as dendritic cells (DCs), become infected. DCs play a critical role in the induction of immune responses, as they are able to rapidly detect pathogen-associated molecular patterns, endocytose and process antigens, and efficiently activate naïve-T and B cells. Recent findings have shown that DCs serve as DENV targets, but they are also important mediators of immunity against the virus. In this review, we will briefly discuss DENV infection pathogenesis, and introduce DCs as central players in the induction of anti-DENV immune responses. Then, we will review in more detail how DENV interacts with and is sensed by DCs, with particular emphasis in two classes of receptors implicated in viral entry.

MD-1 deficiency attenuates dextran sodium sulfate (DSS)-induced colitis through modulating the function of colonic lamina propria dendritic cells

Available evidence suggests that both dysregulated innate and adaptive immune pathways contribute to the aberrant intestinal inflammatory response in patients with inflammatory bowel disease (IBD). Myeloid Differentiation 1 (MD-1), also known as Lymphocyte Antigen 86 (Ly86), a secreted protein interacting with radioprotective 105 (RP105), plays an important role in Toll-like receptor 4 (TLR4) signaling pathway. Previous studies showed that MD-1 may be involved in the (patho) physiological regulation of the innate immune system and inflammation. In this study, we reported for the first time that MD-1 mRNA expression was up-regulated in both human IBD patients and DSS-treated WT mice. We showed that MD-1(-/-) mice were less susceptible to the development of colitis than WT controls as demonstrated by significantly reduced weight loss, disease activity index, colon histological scores, cellular infiltration and expression of inflammatory mediators. In addition, mucosal barrier function seemed to be intact in response to the loss of MD-1. Finally, lamina propria dendritic cells (LPDCs) from the colon of MD-1(-/-) mice after DSS exposure not only decreased in number but also significantly down-regulated the expression of surface maturation co-stimulatory molecules MHC-II, CD40 and CD86 compared with those from WT mice. Taken together, our results reveal that MD-1 deficiency is of critical importance in down-regulating induction and progression of DSS colitis, thereby suggesting that MD-1 might be a target for future interventional therapies of IBD.

Tumor-infiltrating dendritic cells exhibit defective cross-presentation of tumor antigens, but is reversed by chemotherapy

Cross-presentation defines the unique capacity of an APC to present exogenous Ag via MHC class I molecules to CD8(+) T cells. DCs are specialized cross-presenting cells and as such have a critical role in antitumor immunity. DCs are routinely found within the tumor microenvironment, but their capacity for endogenous or therapeutically enhanced cross-presentation is not well characterized. In this study, we examined the tumor and lymph node DC cross-presentation of a nominal marker tumor Ag, HA, expressed by the murine mesothelioma tumor AB1-HA. We found that tumors were infiltrated by predominantly CD11b(+) DCs with a semimature phenotype that could not cross-present tumor Ag, and therefore, were unable to induce tumor-specific T-cell activation or proliferation. Although tumor-infiltrating DCs were able to take up, process, and cross-present exogenous cell-bound and soluble Ags, this was significantly impaired relative to lymph node DCs. Importantly, however, systemic chemotherapy using gemcitabine reversed the defect in Ag cross-presentation of tumor DCs. These data demonstrate that DC cross-presentation within the tumor microenvironment is defective, but can be reversed by chemotherapy. These results have important implications for anticancer therapy, particularly regarding the use of immunotherapy in conjunction with cytotoxic chemotherapy.

Thymus-deriving natural regulatory T cell generation in vitro: role of the source of activation signals

In this research we have examined different sources of activation signals in order to optimize culture conditions for in vitro generation of thymus-deriving natural regulatory T cells (nTregs). We have established a novel model using JAWS II dendritic cell line of immature phenotype and compared it to commonly used methods for the generation of Tregs from peripheral lymphoid organs or blood T cells. In our model the first activation signal is provided by anti-CD3 monoclonal antibodies while the second is delivered by costimulatory molecules expressed on JAWS II cells. The presence of JAWS II cells co-cultured in vitro with unsorted thymocytes directly isolated from the thymus gland creates environment favoring SP CD4+ differentiation, provides the apoptotic cells clearance, maintains the survival of thymocytes and facilitate nTreg generation. Moreover the usage of immature dendritic cells stimuli enables to conduct research on agents affecting nTreg survival, proliferation and development in conditions of cell-to-cell contact of undifferentiated thymocytes with dendritic cells.

Rice bran feruloylated oligosaccharides activate dendritic cells via Toll-like receptor 2 and 4 signaling

This work presents the effects of feruloylated oligosaccharides (FOs) of rice bran on murine bone marrow-derived dendritic cells (BMDCs) and the potential pathway through which the effects are mediated. We found that FOs induced phenotypic maturation of DCs, as shown by the increased expression of CD40, CD80/CD86 and MHC-I/II molecules. FOs efficiently induced maturation of DCs generated from C3H/HeN or C57BL/6 mice with normal toll-like receptor 4 (TLR-4) or TLR-2 but not DCs from mice with mutated TLR4 or TLR2. The mechanism of action of FOs may be mediated by increased phosphorylation of ERK, p38 and JNK mitogen-activated protein kinase (MAPKs) and increased NF-κB activity, which are important signaling molecules downstream of TLR-4 and TLR-2. These data suggest that FOs induce DCs maturation through TLR-4 and/or TLR-2 and that FOs might have potential efficacy against tumor or virus infection or represent a candidate-adjuvant approach for application in immunotherapy and vaccination.

Geldanamycin-mediated inhibition of heat shock protein 90 partially activates dendritic cells, but interferes with their full maturation, accompanied by impaired upregulation of RelB

Background

The chaperon heat shock protein 90 (HSP90) constitutes an important target for anti-tumor therapy due to its essential role in the stabilization of oncogenes. However, HSP90 is ubiquitously active to orchestrate protein turnover, chemotherapeutics that target HSP90 may affect immune cells as a significant side effect. Therefore, we asked for potential effects of pharmacological HSP90 inhibition at a therapeutically relevant concentration on human dendritic cells (DCs) as main inducers of both cellular and humoral immune responses, and on human CD4⁺ T cells as directly activated by DCs and essential to confer B cell help.

Methods

Unstimulated human monocyte-derived DCs (MO-DCs) were treated with the prototypical HSP90 inhibitor geldanamycin (GA). Based on dose titration studies performed to assess cytotoxic effects, GA was applied at a rather low concentration, comparable to serum levels of clinically used HSP90 inhibitors. The immuno-phenotype (surface markers, cytokines), migratory capacity, allo T cell stimulatory and polarizing properties (proliferation, cytokine pattern) of GA-treated MO-DCs were assessed. Moreover, effects of GA on resting and differentially stimulated CD4⁺ T cells in terms of cytotoxicity and proliferation were analysed.

Results

GA induced partial activation of unstimulated MO-DCs. In contrast, when coapplied in the course of MO-DC stimulation, GA prevented the acquisition of a fully mature DC phenotype. Consequently, this MO-DC population exerted lower allo CD4⁺ T cell stimulation and cytokine production. Furthermore, GA exerted no cytotoxic effect on resting T cells, but abrogated proliferation of T cells stimulated by MO-DCs at either state of activation or by stimulatory antibodies.

Conclusion

HSP90 inhibitors at clinically relevant concentrations may modulate adaptive immune responses both on the level of DC activation and T cell proliferation. Surprisingly, unstimulated DCs may be partially activated by that agent. However, due to the potent detrimental effects of HSP90 inhibitors on stimulated CD4⁺ T cells, as an outcome a patients T cell responses might be impaired. Therefore, HSP90 inhibitors most probably are not suitable for treatment in combination with immunotherapeutic approaches aimed to induce DC/T cell activation.

Clitocybe nuda Activates Dendritic Cells and Acts as a DNA Vaccine Adjuvant

This work represents the first evaluation of the effects of water extract of C. nuda (WE-CN), an edible mushroom, on murine bone marrow-derived dendritic cells (BMDCs) and the potential pathway through which the effects are mediated. Our experimental results show that WE-CN could induce phenotypic maturation of DCs, as shown by the increased expression of MHC and costimulatory molecules. In addition, it also induced the proinflammatory cytokines expression on DCs and enhanced both the proliferation and IFN- γ secretion of allogenic T cells. Therefore, since WE-CN did not induce maturation of DCs generated from mice with mutated TLR-4 or TLR-2, suggesting that TLR4 and TLR2 might function as membrane receptors for WE-CN. Moreover, the mechanism of action of WE-CN may be mediated by increased phosphorylation of ERK, p38, and JNK mitogen-activated protein kinase (MAPK) and increased NF- κ B p65 activity, which are important signaling molecules downstream of TLR-4 and TLR-2. Finally, coimmunization of mice with WE-CN and a HER-2/neu DNA vaccine induced a HER-2/neu-specific Th1 response that resulted in significant inhibition of HER-2/neu overexpressing mouse bladder tumor (MBT-2) growth. These data suggest that WE-CN induces DC maturation through TLR-4 and/or TLR-2 and that WE-CN can be used as an adjuvant in cancer vaccine immunotherapy.

Dendritic cell apoptosis and the pathogenesis of dengue

Dengue viruses and other members of the Flaviviridae family are emerging human pathogens. Dengue is transmitted to humans by Aedes aegypti female mosquitoes. Following infection through the bite, cells of the hematopoietic lineage, like dendritic cells, are the first targets of dengue virus infection. Dendritic cells (DCs) are key antigen presenting cells, sensing pathogens, processing and presenting the antigens to T lymphocytes, and triggering an adaptive immune response. Infection of DCs by dengue virus may induce apoptosis, impairing their ability to present antigens to T cells, and thereby contributing to dengue pathogenesis. This review focuses on general mechanisms by which dengue virus triggers apoptosis, and possible influence of DC-apoptosis on dengue disease severity.