Small EV-based delivery of CpG ODNs for melanoma postsurgical immunotherapy

Blocking programmed cell death protein 1 (PD-1) is an effective therapeutic strategy for melanoma. However, patients often develop tumor recurrence postoperatively due to the low response rate to the anti-PD-1 antibody (aPD-1). In this study, we developed an in situ sprayable fibrin gel that contains cytosine-guanine oligodeoxynucleotides (CpG ODNs)-modified ovalbumin (OVA) antigen-expressing bone marrow dendritic cell (DC)-derived small extracellular vesicles (DC-sEVs) and aPD-1. CpG ODNs can activate DCs, which have potent immunostimulatory effects, by stimulating both the maturation and activation of tumor-infiltrating dendritic cells (TIDCs) and DCs in tumor-draining lymph nodes (TDLNs). In addition, DC-sEVs can deliver OVA to the same DCs, leading to the specific expression of tumor antigens by antigen-presenting cells (APCs). In brief, the unique synergistic combination of aPD-1 and colocalized delivery of immune adjuvants and tumor antigens enhances antitumor T-cell immunity, not only in the tumor microenvironment (TME) but also in TDLNs. This effectively attenuates local tumor recurrence and metastasis. Our results suggest that dual activation by CpG ODNs prolongs the survival of mice and decreases the recurrence rate in an incomplete tumor resection model, providing a promising approach to prevent B16-F10-OVA melanoma tumor recurrence and metastasis.

Biological effects triggered by chemical respiratory sensitizers on THP-1 monocytic cells

Respiratory sensitization encompasses a group of diseases that manifest through airway hyperresponsiveness and airflow limitation. Although the concerns regarding human health, to date there are still no validated methods for preclinical assessment of this class of toxicants once the chemical respiratory allergy mechanistic framework is not fully understood. As Dendritic Cells (DCs) are the bridging elements between innate and adaptative immune responses, we preliminarily investigated the biological alterations triggered by seven different LMW respiratory allergens in the DC model THP-1. The results have shown that exposure to respiratory allergens promoted alterations in DCs maturation/activation status and triggered pro-inflammatory changes in these cells through increased expression for the CD86/HLA-DR/CD11c surface biomarkers and enhancement in IL-8 and IL-6 production by exposed THP-1 cells. Therefore, evidence was found to support the startpoint for chemical respiratory allergy pathogenesis elucidation, subsidizing the contribution of dendritic cells in such pathomechanisms.

Superior low-immunogenicity of tilapia type I collagen based on unique secondary structure with single calcium binding motif over terrestrial mammals by inhibiting activation of DC intracellular Ca2+-mediated STIM1-Orai1/NF-кB pathway

The reason for low- or non-immunogenicity of fish collagens is still in doubt, which, to some extent, bottlenecks their production and clinical application as biomaterials. Employing bovine or porcine type I collagens (BCI or PCI) as controls in this paper, we intensively investigate the influence of tilapia type I collagens (TCI) on the function of dendritic cells (DCs) and T cells. From bio-informatic analyses, as well as data obtained in vitro and in vivo, we find the variations in amino acid sequences lead to only one calcium binding motif in the secondary structure of TCI, compared with three in BCI or PCI. So when TCI (together with the minor amount of Ca²⁺ they take) are uptaken, intracellular [Ca²⁺] remains stable and DCs maintain immature. On the contrary, those that have uptaken PCI or BCI experience not only increased [Ca²⁺] in the plasma but also phosphorylation of p65, resulting in activation of STIM1-Orai1/NF-кB signaling pathway and DC maturation. We fully prove our results on mice models, with no obvious cellular and humoral immune reactions. Our study primarily reveal the underlying mechanisms why TCI, different from BCI or PCI, show almost non-immunogenicity. Our findings are of great importance for the promotion and wide application of TCI in biomedicine.

The subunits of IL-12, originating from two distinct cells, can functionally synergize to protect against pathogen dissemination in vivo

Cytokines are typically single gene products, except for the heterodimeric interleukin (IL)-12 family. The two subunits (IL-12p40 and IL-12p35) of the prototype IL-12 are known to be simultaneously co-expressed in activated myeloid cells, which secrete the fully active heterodimer to promote interferon (IFN)γ production in innate and adaptive cells. We find that chimeric mice containing mixtures of cells that can only express either IL-12p40 or IL-12p35, but not both together, generate functional IL-12. This alternate two-cell pathway requires IL-12p40 from hematopoietic cells to extracellularly associate with IL-12p35 from radiation-resistant cells. The two-cell mechanism is sufficient to propel local T cell differentiation in sites distal to the initial infection and helps control systemic dissemination of a pathogen, although not parasite burden, at the site of infection. Broadly, this suggests that early secretion of IL-12p40 monomers by sentinel cells at the infection site may help prepare distal host tissues for potential pathogen arrival.

Differential capability of Bacillus thuringiensis Cry1Ac protoxin and toxin to induce in vivo activation of dendritic cells and B lymphocytes

The insecticidal Bacillus thuringiensis protein Cry1Ac is produced as a protoxin and becomes activated to a toxin when ingested by larvae. Both proteins are immunogenic and able to activate macrophages. The proposed mechanism of immunostimulation by Cry1Ac protoxin has been related to its capacity to activate antigen-presenting cells (APC), but its ability to activate dendritic cells (DC) has not been explored. Here we evaluated, in the popliteal lymph nodes (PLN), spleen and peritoneum, the activation of DC CD11c⁺ MHC-II⁺ following injection with single doses (50 μg) of Cry1Ac toxin or protoxin via the intradermal (i.d.) and intraperitoneal (i.p.) routes in C57BL/6 mice. In vivo stimulation with both Cry1Ac proteins induced activation of DC via upregulation of CD86, primarily in PLN 24 h after i. d. injection. Moreover, this activation was detected in DC, displaying CD103+, a typical marker of migratory DC, while upregulation of CD80 was uniquely induced by toxin. Tracking experiments showed that Cy5-labeled Cry1Ac proteins could rapidly reach the PLN and localize near DC, but some label remained in the footpad. When the capacity of Cry1Ac-activated DC to induce antigen presentation was examined, significant proliferation of naïve T lymphocytes was induced exclusively by the protoxin. The protoxin elicited a Th17-biased cytokine profile. Moreover, only the Cry1Ac toxin induced a pronounced proliferation of B cells from both untreated and Cry1Ac-injected mice, suggesting that it acts as a polyclonal activator. In conclusion, Cry1Ac protoxin and toxin show a distinctive capacity to activate APCs.

The human anti-CD40 agonist antibody mitazalimab (ADC-1013; JNJ-64457107) activates antigen-presenting cells, improves expansion of antigen-specific T cells, and enhances anti-tumor efficacy of a model cancer vaccine in vivo

Non-responders to checkpoint inhibitors generally have low tumor T cell infiltration and could benefit from immunotherapy that activates dendritic cells, with priming of tumor-reactive T cells as a result. Such therapies may be augmented by providing tumor antigen in the form of cancer vaccines. Our aim was to study the effects of mitazalimab (ADC-1013; JNJ-64457107), a human anti-CD40 agonist IgG1 antibody, on activation of antigen-presenting cells, and how this influences the priming and anti-tumor potential of antigen-specific T cells, in mice transgenic for human CD40. Mitazalimab activated splenic CD11c⁺ MHCII⁺ dendritic cells and CD19⁺ MHCII⁺ B cells within 6 h, with a return to baseline within 1 week. This was associated with a dose-dependent release of proinflammatory cytokines in the blood, including IP-10, MIP-1α and TNF-α. Mitazalimab administered at different dose regimens with ovalbumin protein showed that repeated dosing expanded ovalbumin peptide (SIINFEKL)-specific CD8⁺ T cells and increased the frequency of activated ICOS⁺ T cells and CD44^hi CD62L^- effector memory T cells in the spleen. Mitazalimab prolonged survival of mice bearing MB49 bladder carcinoma tumors and increased the frequency of activated granzyme B⁺ CD8⁺ T cells in the tumor. In the ovalbumin-transfected tumor E.G7-OVA lymphoma, mitazalimab administered with either ovalbumin protein or SIINFEKL peptide prolonged the survival of E.G7-OVA tumor-bearing mice, as prophylactic and therapeutic treatment. Thus, mitazalimab activates antigen-presenting cells, which improves expansion and activation of antigen-specific T cells and enhances the anti-tumor efficacy of a model cancer vaccine.

Oxidized base 8-oxoguanine, a product of DNA repair processes, contributes to dendritic cell activation

A growing body of evidence suggests that elevated levels of reactive oxygen species (ROS) in the airways caused by exposure to gas phase pollutants or particulate matter are able to activate dendritic cells (DCs); however, the exact mechanisms are still unclear. When present in excess, ROS can modify macromolecules including DNA. One of the most abundant DNA base lesions is 7,8-dihydro-8-oxoguanine (8-oxoG), which is repaired by the 8-oxoguanine DNA glycosylase 1 (OGG1)-initiated base excision repair (BER) (OGG1-BER) pathway. Studies have also demonstrated that in addition to its role in repairing oxidized purines, OGG1 has guanine nucleotide exchange factor activity when bound to 8-oxoG. In the present study, we tested the hypothesis that exposure to 8-oxoG, the specific product of OGG1-BER, induces functional changes of DCs. Supporting our hypothesis, transcriptome analysis revealed that in mouse lungs, out of 95 genes associated with DCs' function, 22 or 42 were significantly upregulated after a single or multiple intranasal 8-oxoG challenges, respectively. In a murine model of allergic airway inflammation, significantly increased serum levels of ovalbumin (OVA)-specific IgE antibodies were detected in mice sensitized via nasal challenges with OVA+8-oxoG compared to those challenged with OVA alone. Furthermore, exposure of primary human monocyte-derived DCs (moDC) to 8-oxoG base resulted in significantly enhanced expression of cell surface molecules (CD40, CD86, CD83, HLA-DQ) and augmented the secretion of pro-inflammatory mediators IL-6, TNF and IL-8, whereas it did not considerably influence the production of the anti-inflammatory cytokine IL-10. The stimulatory effects of 8-oxoG on human moDCs were abolished upon siRNA-mediated OGG1 depletion. Collectively, these data suggest that OGG1-BER-generated 8-oxoG base-driven cell signaling activates DCs, which may contribute to initiation of both the innate and adaptive immune responses under conditions of oxidative stress.

Inhibition of fatty acid metabolism by etomoxir or TOFA suppresses murine dendritic cell activation without affecting viability

Objective: Dendritic cells (DCs) are important players in immunity against pathogens, but overactive DCs have been implicated in autoimmune diseases, like lupus, in which a paucity of targeted therapies remains. Recent research shows that DCs upregulate their immunometabolism when activating. We explored whether modulating fatty acid (FA) metabolism needed for oxidative phosphorylation can affect the activation of two main DC subsets. Material and methods: Sorted murine plasmacytoid DCs (pDCs) and conventional DCs (cDCs), generated in FLT3-L medium, were treated with etomoxir, an inhibitor of FA oxidation, or TOFA, an inhibitor of FA synthesis, then stimulated with TLR9 agonist CpGA. Surface activation markers and viability were analyzed by flow cytometry, cytokine, and chemokine production and were measured by ELISA. Results: Modulation of FA metabolism suppressed the upregulation of costimulatory molecules and the production of proinflammatory cytokine IL-6 and type I Interferon-dependent chemokine CXCL10 by both subsets of DCs, without affecting DC viability, neither of resting DCs or upon activation. Etomoxir inhibited pDCs at lower doses than cDCs, suggesting that pDCs may be more susceptible to FA metabolic modulation. Conclusions: Both cDCs, the primary antigen presenting cell, and pDCs, the primary type I IFN producer, exhibit a suppressed ability to activate but normal viability when their FA metabolism is inhibited by etomoxir or TOFA. Our findings indicate that FA metabolism plays an important role in the activation of both pDCs and cDCs and suggest that its modulation is an exploitable therapeutic target to suppress DC activation in inflammation or autoimmunity.

Monitoring Dendritic Cell Activation and Maturation

Since the 1997 discovery that the first identified human homolog of Drosophila Toll could activate the innate immune system, the innate arm of immunity has rapidly taken on a new light as an important player in the recognition of pathogens and damaged self. The recognition of danger by dendritic cells (DC) is a crucial step in activating the adaptive immune system. Different DC express varied subsets of pattern recognition receptors (PRR), enabling both overlap and exclusivity in the recognition of danger signals by DC. PRR-mediated DC maturation and activation can be measured by changes in the surface expression of costimulatory as well as coinhibitory molecules, changes in size and shape of the DC and by their production of different cytokines.

Mycobacterium tuberculosis protein Rv2220 induces maturation and activation of dendritic cells

Tuberculosis remains a serious health problem worldwide. Characterization of the dendritic cell (DC)-activating mycobacterial proteins has driven the development of effective TB vaccine candidates besides improving the understanding of immune responses. Some studies have emphasized the essential role of protein Rv2220 from M. tuberculosis in mycobacterial growth. Nonetheless, little is known about cellular immune responses to Rv2220. In this study, our aim was to test whether protein Rv2220 induces maturation and activation of DCs. Rv2220-activated DCs appeared to be in a mature state with elevated expression of relevant surface molecules and proinflammatory cytokines. DC maturation caused by Rv2220 was mediated by MAPK and NF-κB signaling pathways. Specifically, Rv2220-matured DCs induced the expansion of memory CD62L^lowCD44^highCD4⁺ T cells in the spleen of mycobacteria-infected mice. Our results suggest that Rv2220 regulates host immune responses through maturation of DCs, a finding that points to a new vaccine candidate against tuberculosis.

Soluble flagellin coimmunization attenuates Th1 priming to Salmonella and clearance by modulating dendritic cell activation and cytokine production

Soluble flagellin (sFliC) from Salmonella Typhimurium (STm) can induce a Th2 response to itself and coadministered antigens through ligation of TLR5. These properties suggest that sFliC could potentially modulate responses to Th1 antigens like live STm if both antigens are given concurrently. After coimmunization of mice with sFliC and STm there was a reduction in Th1 T cells (T-bet(+) IFN-γ(+) CD4 T cells) compared to STm alone and there was impaired clearance of STm. In contrast, there was no significant defect in the early extrafollicular B-cell response to STm. These effects are dependent upon TLR5 and flagellin expression by STm. The mechanism for these effects is not related to IL-4 induced to sFliC but rather to the effects of sFliC coimmunization on DCs. After coimmunization with STm and sFliC, splenic DCs had a lower expression of costimulatory molecules and profoundly altered kinetics of IL-12 and TNFα expression. Ex vivo experiments using in vivo conditioned DCs confirmed the effects of sFliC were due to altered DC function during a critical window in the coordinated interplay between DCs and naïve T cells. This has marked implications for understanding how limits in Th1 priming can be achieved during infection-induced, Th1-mediated inflammation.

Minor genomic differences between related B6 and B10 mice affect severity of schistosome infection by governing the mode of dendritic cell activation

Infection with the helminth Schistosoma mansoni results in hepatointestinal granulomatous inflammation mediated by CD4 T cells directed against parasite eggs. The severity of disease varies greatly in humans and mice; however, the genetic basis of such a heterogenous immune response remains poorly understood. Here we show that, despite their close genetic relationship, C57BL/10SnJ (B10) mice developed significantly more pronounced immunopathology and higher T helper 17 cell responses than C57BL/6J (B6) mice. Similarly, live egg-stimulated B10-derived dendritic cells (DCs) produced significantly more IL-1β and IL-23, resulting in higher IL-17 production by CD4 T cells. Gene expression analysis disclosed a heightened proinflammatory cytokine profile together with a strikingly lower expression of Ym1 in B10 versus B6 mice, consistent with failure of B10 DCs to attain alternative activation. To genetically dissect the differential response, we developed and analyzed congenic mouse strains that capture major regions of allelic variation, and found that the level of inflammation was controlled by a relatively small number of genes in a locus mapping to chromosome 4 117-143 MB. Our study has thus identified novel genomic regions that regulate the severity of the schistosome infection by way of controlling the mode of DC activation and consequent CD4 T-cell subset development.

Induction of suppressive phenotype in monocyte-derived dendritic cells by leukemic cell products and IL-1β

Professional antigen-presenting cells, dendritic cells (DCs) play an important role in controlling tumors. It is known that solid tumor cell products inhibit DC differentiation. Recently a similar effect produced by leukemic cell products has been demonstrated. In this case, leukemic cell products induced the secretion of IL-1β by monocytes undergoing differentiation. The aim of the present work was to characterize and to compare the development of monocyte-derived DCs under the influence of leukemic cell products (K562 supernatant) or exogenous IL-1β. It became clear that leukemic cell products and IL-1β differentially modulate some of the parameters studied on monocytes stimulated to differentiate into DCs. In the presence of K562 supernatant, the expression of the macrophage markers CD16 and CD68 were higher than in immature DCs control. Contrasting with IL-1β, leukemic cell products possibly favor the development of cells with macrophage markers. In addition, CD80 and CD83 expressions were also higher in the presence of tumor supernatant whereas HLA-DR was lower. In the presence of IL-1β, only CD80 was increased. Furthermore, it was observed that when monocytes were induced to differentiate into DCs in the presence of tumor supernatant and then activated, they expressed less CD80 and CD83 than activated DCs control. A reduced expression of CD83 following activation was also seen in cells differentiated with IL-1β. TGF-β and VEGF were found in the tumor supernatants. Moreover, the exposure to tumor supernatant or IL-1β stimulated IL-10 production while decreased IL-12 production by activated DCs. Finally, these results suggest that the addition of products released by leukemic cells or, more discreetly, the addition of IL-1β affects DC differentiation, inducing a suppressive phenotype.