Dendritic cell maturation: functional specialization through signaling specificity and transcriptional programming

Extracellular vesicles from virulent P. brasiliensis induce TLR4 and dectin-1 expression in innate cells and promote enhanced Th1/Th17 response

Extracellular vesicles (EVs) are membrane-enclosed nanoparticles that transport several biomolecules and are involved in important mechanisms and functions related to the pathophysiology of fungal diseases. EVs from Paracoccidioides brasiliensis, the main causative agent of Paracoccidioidomycosis (PCM), modulate the immune response of macrophages. In this study, we assessed the EVs proteome from a virulent P. brasiliensis isolated from granulomatous lesions and compared their immunomodulatory ability with EVs isolated from the fungus before the animal passage (control EVs) when challenging macrophages and dendritic cells (DCs). Proteome showed that virulent EVs have a higher abundance of virulence factors such as GP43, protein 14-3-3, GAPDH, as well as virulence factors never described in PCM, such as aspartyl aminopeptidase and a SidJ analogue compared with control EVs. Virulent extracellular vesicles induced higher expression of TLR4 and Dectin-1 than control EVs in macrophages and dendritic cells (DCs). In opposition, a lower TLR2 expression was induced by virulent EVs. Additionally, virulent EVs induced lower expression of CD80, CD86 and TNF-α, but promoted a higher expression of IL-6 and IL-10, suggesting that EVs isolated from virulent P. brasiliensis-yeast promote a milder DCs and macrophage maturation. Herein, we showed that EVs from virulent fungi stimulated a higher frequency of Th1/Tc1, Th17, and Treg cells, which gives new insights into fungal extracellular vesicles. Taken together, our results suggest that P. brasiliensis utilizes its EVs as virulence bags that manipulate the immune system in its favour, creating a milder immune response and helping with fungal evasion from the immune system.

Causal relationship between 731 immune cells and the risk of diabetic nephropathy: a two‑sample bidirectional Mendelian randomization study

OBJECTIVE

Previous observational studies have indicated associations between various immune cells and diabetic nephropathy (DN). However, the causality remains unclear. We aimed to further evaluate the causal association between immune cells and DN using bidirectional two-sample Mendelian randomization (MR) analysis.

METHOD

The DN data were retrieved from the IEU OpenGWAS Project database, while the data for 731 immune cells were sourced from GWAS summary statistics by Orru ̀ et al. The investigation into the causal relationship between immune cells and DN employed the inverse variance weighted (IVW), weighted median (WME), and MR-Egger methods. The stability and reliability of the findings underwent evaluation through Cochran's Q test, MR-Egger intercept's P-value, MR-PRESSO, and Leave-One-Out (LOO) method.

RESULT

The IVW estimates suggested a positive causal effect of CD25 on IgD-CD38dim B cell, CD25 on naive-mature B cell, CD127 on granulocyte, SSC-A on HLA DR + Natural Killer, HLA DR on plasmacytoid Dendritic Cell, and HLA DR on Dendritic Cell on DN. Conversely, the abundance of Myeloid Dendritic Cell, CD62L- Dendritic Cell %Dendritic Cell, CD86+ myeloid Dendritic Cell %Dendritic Cell, CD14- CD16-, CX3CR1 on CD14- CD16-, and SSC-A on CD4+ T cell had negative causal effects on DN. However, after correcting the P value for significant causality results using the FDR method, it was concluded that only Myeloid Dendritic Cells had a causal relationship with DN (FDR-p = 0.041), while the other immune cells showed no significant association with DN, so their relationship was suggestive. The results were stable with no observed horizontal pleiotropy and heterogeneity. Reverse MR analysis indicated no causal relationship between DN and the increased risk of positively identified immune cells.

CONCLUSION

This study provides an initial insight into the genetic perspective of the causal relationship between immune cells and DN. It establishes a crucial theoretical foundation for future endeavors in precision medicine and individualized treatment.

Impaired reprogramming of the autophagy flux in maturing dendritic cells from crohn disease patients with core autophagy gene-related polymorphisms

Crohn disease (CD) is an inflammatory bowel disease whose pathogenesis involves inappropriate immune responses toward gut microbiota on genetically predisposed backgrounds. Notably, CD is associated with single-nucleotide polymorphisms affecting several genes involved in macroautophagy/autophagy, the catabolic process that ensures the degradation and recycling of cytosolic components and microorganisms. In a clinical translation perspective, monitoring the autophagic activity of CD patients will require some knowledge on the intrinsic functional status of autophagy. Here, we focused on monocyte-derived dendritic cells (DCs) to characterize the intrinsic quantitative features of the autophagy flux. Starting with DCs from healthy donors, we documented a reprogramming of the steady state flux during the transition from the immature to mature status: both the autophagosome pool size and the flux were diminished at the mature stage while the autophagosome turnover remained stable. At the cohort level, DCs from CD patients were comparable to control in term of autophagy flux reprogramming capacity. However, the homozygous presence of ATG16L1 rs2241880 A>G (T300A) and ULK1 rs12303764 (G/T) polymorphisms abolished the capacity of CD patient DCs to reprogram their autophagy flux during maturation. This effect was not seen in the case of CD patients heterozygous for these polymorphisms, revealing a gene dose dependency effect. In contrast, the NOD2 rs2066844 c.2104C>T (R702W) polymorphism did not alter the flux reprogramming capacity of DCs. The data, opening new clinical translation perspectives, indicate that polymorphisms affecting autophagy-related genes can differentially influence the capacity of DCs to reprogram their steady state autophagy flux when exposed to proinflammatory challenges.Abbreviation: BAFA1: bafilomycin A1, CD: Crohn disease; DC: dendritic cells; HD: healthy donor; iDCs: immature DCs; IL: interleukin; J: autophagosome flux; LPS: lipopolysaccharide; MHC: major histocompatibility complex; nA: autophagosome pool size; SNPs: single-nucleotide polymorphisms; PCA: principal component analysis; TLR: toll like receptor; τ: transition time; TNF: tumor necrosis factor.

Impaired Proliferation of CD8+ T Cells Stimulated with Monocyte-Derived Dendritic Cells Previously Matured with Thapsigargin-Stimulated LAD2 Human Mast Cells

CD8+ T cells are essential for adaptive immunity against infection and tumors. Their ability to proliferate after stimulation is crucial to their functionality. Dendritic cells (DCs) are professional antigen-presenting cells that induce their proliferation. Here, we show that thapsigargin-induced LAD2 mast cell (MC) line-released products can impair the ability of monocyte-derived DCs to induce CD8+ T-cell proliferation and the generation of Th1 cytokine-producing T cells. We found that culture medium conditioned with LAD2 MCs previously stimulated with thapsigargin (thapsLAD2) induces maturation of DCs as determined by the maturation markers CD80, CD83, CD86, and HLA-DR. However, thapsLAD2-matured DCs produced no detectable TNFα or IL-12 during the maturation. In addition, although their surface expression of PD-L1 was comparable with the immature or TLR7/8-agonist (R848)-matured DCs, their TIM-3 expression was significantly higher than in immature DCs and even much higher than in R848-matured DCs. In addition, contrary to R848-matured DCs, the thapsLAD2-matured DCs only tended to induce enhanced proliferation of CD4+ T cells than immature DCs. For CD8+ T cells, this tendency was not even detected because thapsLAD2-matured and immature DCs comparably induced their proliferation, which contrasted with the significantly enhanced proliferation induced by R848-matured DCs. Furthermore, these differences were comparably recapitulated in the ability of the tested DCs to induce IFNγ- and IFNγ/TNFα-producing T cells. These findings show a novel mechanism of MC-mediated regulation of adaptive immune responses.

Potential mechanisms and targeting strategies of the gut microbiota in antitumor immunity and immunotherapy

BACKGROUND

Immunotherapies, notably immune checkpoints inhibitors that target programmed death 1/programmed death ligand 1(PD-1/PD-L1) and cytotoxic T lymphocyte-associated antigen 4 (CTLA-4), had profoundly changed the way advanced and metastatic cancers are treated and dramatically improved overall and progression-free survival.

AIMS

This review article aimed to explore the underlying molecular mechanisms by which the gut microbiota affects antitumor immunity and the efficacy of cancer immunotherapy.

METHODS

We summarized the latest knowledge supporting the associations among the gut microbiota, antitumor immunity, and immunotherapy. Moreover, we disscussed the therapeutic strategy for improving immunotherapy efficacy by modulating gut microbiota in cancer treatment.

RESULTS

The potential molecular mechanisms underlying these associations are explained in terms of four aspects: immunomodulation, molecular mimicry, mamps, and microbial metabolites.

CONCLUSION

The gut microbiota significantly impacts antitumor immunity and alters the effectiveness of cancer immunotherapy.

Modulating the gut microbiome in non-small cell lung cancer: Challenges and opportunities

Despite the efficacy of immunotherapy in non-small cell lung cancer (NSCLC), the majority of the patients experience relapse with limited subsequent treatment options. Preclinical studies of various epithelial tumors, such as melanoma and NSCLC, have shown that harnessing the gut microbiome resulted in improvement of therapeutic responses to immunotherapy. Is this review, we summarize the role of microbiome, including lung and gut microbiome in the context of NSCLC, provide overview of the mechanisms of microbiome in efficacy and toxicity of chemotherapies and immunotherapies, and address current ongoing clinical trials for NSCLC including fecal microbiota transplantation (FMT) and live biotherapeutic products (LBPs).

Tumor eradication by triplet therapy with BRAF inhibitor, TLR 7 agonist, and PD-1 antibody for BRAF-mutated melanoma

Programmed death 1 (PD-1)/programmed death-ligand 1 inhibitors are commonly used to treat various cancers, including melanoma. However, their efficacy as monotherapy is limited, and combination immunotherapies are being explored to improve outcomes. In this study, we investigated a combination immunotherapy involving an anti-PD-1 antibody that blocks the major adaptive immune-resistant mechanisms, a BRAF inhibitor that inhibits melanoma cell proliferation, and multiple primary immune-resistant mechanisms, such as cancer cell-derived immunosuppressive cytokines, and a Toll-like receptor 7 agonist that enhances innate immune responses that promote antitumor T-cell induction and functions. Using a xenogeneic nude mouse model implanted with human BRAF-mutated melanoma, a BRAF inhibitor vemurafenib was found to restore T-cell-stimulatory activity in conventional dendritic cells by reducing immunosuppressive cytokines, including interleukin 6, produced by human melanoma. Additionally, intravenous administration of the Toll-like receptor 7 agonist DSR6434 enhanced tumor growth inhibition by vemurafenib through stimulating the plasmacytoid dendritic cells/interferon-α/natural killer cell pathways and augmenting the T-cell-stimulatory activity of conventional dendritic cells. In a syngeneic mouse model implanted with murine BRAF-mutated melanoma, the vemurafenib and DSR6434 combination synergistically augmented the induction of melanoma antigen gp100-specific T cells and inhibited tumor growth. Notably, only triplet therapy with vemurafenib, DSR6434, and the anti-PD-1 antibody resulted in complete regression of SIY antigen-transduced BRAF-mutated melanoma in a CD8 T-cell-dependent manner. These findings indicate that a triple-combination strategy targeting adaptive and primary resistant mechanisms while enhancing innate immune responses that promote tumor-specific T cells may be crucial for effective tumor eradication.

Factor of time in dendritic cell (DC) maturation: short-term activation of DCs significantly improves type 1 cytokine production and T cell responses

Dendritic cells (DCs) have been intensively studied in correlation to tumor immunology and for the development DC-based cancer vaccines. Here, we present the significance of the temporal aspect of DC maturation for the most essential subsequent timepoint, namely at interaction with responding T cells or after CD40-Ligand restimulation. Mostly, DC maturation is still being achieved by activation processes which lasts 24 h to 48 h. We hypothesized this amount of time is excessive from a biological standpoint and could be the underlying cause for functional exhaustion. Indeed, shorter maturation periods resulted in extensive capacity of monocyte-derived DCs to produce inflammatory cytokines after re-stimulation with CD40-Ligand. This effect was most evident for the primary type 1 polarizing cytokine, IL-12p70. This capacity reached peak at 6 h and dropped sharply with longer exposure to initial maturation stimuli (up to 48 h). The 6 h maturation protocol reflected superiority in subsequent functionality tests. Namely, DCs displayed twice the allostimulatory capacity of 24 h- and 48 h-matured DCs. Similarly, type 1 T cell response measured by IFN-γ production was 3-fold higher when CD4+ T cells had been stimulated with shortly matured DC and over 8-fold greater in case of CD8+ T cells, compared to longer matured DCs. The extent of melanoma-specific CD8+ cytotoxic T cell induction was also greater in case of 6 h DC maturation. The major limitation of the study is that it lacks in vivo evidence, which we aim to examine in the future. Our findings show an unexpectedly significant impact of temporal exposure to activation signals for subsequent DC functionality, which we believe can be readily integrated into existing knowledge on in vitro/ex vivo DC manipulation for various uses. We also believe this has important implications for DC vaccine design for future clinical trials.

Dendritic Cells: A Bridge between Tolerance Induction and Cancer Development in Transplantation Setting

Dendritic cells (DCs) are a heterogeneous group of antigen-presenting cells crucial for fostering allograft tolerance while simultaneously supporting host defense against infections and cancer. Within the tumor microenvironment, DCs can either mount an immune response against cancer cells or foster immunotolerance, presenting a dual role. In immunocompromised individuals, posttransplant malignancies pose a significant health concern, with DCs serving as vital players in immune responses against cancer cells. Both recipient- and donor-derived DCs play a critical role in the rejection process, infiltrating the transplanted organ and sustaining T-cell responses. The use of immunosuppressive drugs represents the predominant approach to control this immunological barrier in transplanted organs. Evidence has shed light on the immunopharmacology of these drugs and novel strategies for manipulating DCs to promote allograft survival. Therefore, comprehending the mechanisms underlying this intricate microenvironment and the effects of immunosuppressive therapy on DCs is crucial for developing targeted therapies to reduce graft failure rates. This review will delve into the fundamental immunobiology of DCs and provide a detailed exploration of their clinical significance concerning alloimmune responses and posttransplant malignancies.

Antigen-specific immunotherapy via delivery of tolerogenic dendritic cells for multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous system resulting from loss of immune tolerance. Many disease-modifying therapies for MS have broad immunosuppressive effects on peripheral immune cells, but this can increase risks of infection and attenuate vaccine-elicited immunity. A more targeted approach is to re-establish immune tolerance in an autoantigen-specific manner. This review discusses methods to achieve this, focusing on tolerogenic dendritic cells. Clinical trials in other autoimmune diseases also provide learnings with regards to clinical translation of this approach, including identification of autoantigen(s), selection of appropriate patients and administration route and frequency.

Systematic dissection of tumor-normal single-cell ecosystems across a thousand tumors of 30 cancer types

The complexity of the tumor microenvironment poses significant challenges in cancer therapy. Here, to comprehensively investigate the tumor-normal ecosystems, we perform an integrative analysis of 4.9 million single-cell transcriptomes from 1070 tumor and 493 normal samples in combination with pan-cancer 137 spatial transcriptomics, 8887 TCGA, and 1261 checkpoint inhibitor-treated bulk tumors. We define a myriad of cell states constituting the tumor-normal ecosystems and also identify hallmark gene signatures across different cell types and organs. Our atlas characterizes distinctions between inflammatory fibroblasts marked by AKR1C1 or WNT5A in terms of cellular interactions and spatial co-localization patterns. Co-occurrence analysis reveals interferon-enriched community states including tertiary lymphoid structure (TLS) components, which exhibit differential rewiring between tumor, adjacent normal, and healthy normal tissues. The favorable response of interferon-enriched community states to immunotherapy is validated using immunotherapy-treated cancers (n = 1261) including our lung cancer cohort (n = 497). Deconvolution of spatial transcriptomes discriminates TLS-enriched from non-enriched cell types among immunotherapy-favorable components. Our systematic dissection of tumor-normal ecosystems provides a deeper understanding of inter- and intra-tumoral heterogeneity.

Involvement of autologous myeloid dendritic cells in the evaluation of immediate hypersensitivity reactions to betalactams

BACKGROUND

Amoxicillin (AX) and clavulanic acid (CLV) are the betalactam antibiotics (BLs) most used to treat bacterial infections, although they can trigger immediate hypersensitivity reactions (IDHRs). The maturation analysis of monocyte-derived dendritic cells (moDCs) and their capacity to induce proliferative response of lymphocytes are useful to test the sensitisation to a drug, although without optimal sensitivity. Nevertheless, this can be improved using directly isolated DCs such as myeloid DCs (mDCs).

METHODS

mDCs and moDCs were obtained from 28 allergic patients (AP), 14 to AX, 14 to CLV and from 10 healthy controls (HC). The expression of CCR7, CD40, CD80, CD83, and CD86 was analysed after stimulation with both BLs. We measured the capacity of these pre-primed DCs to induce drug-specific activation of different lymphocyte subpopulations, CD3+, CD4+, CD8+, CD4+Th1, and CD4+Th2, by flow cytometry.

RESULTS

Higher expression of CCR7, CD40, CD80, CD83, and CD86 was observed on mDCs compared to moDCs from AP after stimulating with the culprit BL. Similarly, mDCs induced higher proliferative response, mainly of CD4+Th2 cells, compared to moDCs, reaching up to 67% of positive results with AX, whereas of only 25% with CLV.

CONCLUSIONS

mDCs from selective AP efficiently recognise the culprit drug which trigger the IDHR. mDCs also trigger proliferation of lymphocytes, mainly those with a Th2 cytokine pattern, although these responses depend on the nature of the drug, mimicking the patient's reaction.

Crosstalking with Dendritic Cells: A Path to Engineer Advanced T Cell Immunotherapy

Crosstalk between dendritic cells (DCs) and T cells plays a crucial role in modulating immune responses in natural and pathological conditions. DC-T cell crosstalk is achieved through contact-dependent (i.e., immunological synapse) and contact-independent mechanisms (i.e., cytokines). Activated DCs upregulate co-stimulatory signals and secrete proinflammatory cytokines to orchestrate T cell activation and differentiation. Conversely, activated T helper cells "license" DCs towards maturation, while regulatory T cells (Tregs) silence DCs to elicit tolerogenic immunity. Strategies to efficiently modulate the DC-T cell crosstalk can be harnessed to promote immune activation for cancer immunotherapy or immune tolerance for the treatment of autoimmune diseases. Here, we review the natural crosstalk mechanisms between DC and T cells. We highlight bioengineering approaches to modulate DC-T cell crosstalk, including conventional vaccines, synthetic vaccines, and DC-mimics, and key seminal studies leveraging these approaches to steer immune response for the treatment of cancer and autoimmune diseases.

Blocking senescence and tolerogenic function of dendritic cells induced by γδ Treg cells enhances tumor-specific immunity for cancer immunotherapy

BACKGROUND

Regulatory T (Treg) cells are a key component in maintaining the suppressive tumor microenvironment and immune suppression in different types of cancers. A precise understanding of the molecular mechanisms used by Treg cells for immune suppression is critical for the development of effective strategies for cancer immunotherapy.

METHODS

Senescence development and tolerogenic functions of dendritic cells (DCs) induced by breast cancer tumor-derived γδ Treg cells were fully characterized using real-time PCR, flow cytometry, western blot, and functional assays. Loss-of-function strategies with pharmacological inhibitor and/or neutralizing antibody were used to identify the potential molecule(s) and pathway(s) involved in DC senescence and dysfunction induced by Treg cells. Impaired tumor antigen HER2-specific recognition and immune response of senescent DCs induced by γδ Treg cells were explored in vitro and in vivo in humanized mouse models. In addition, the DC-based HER2 tumor vaccine immunotherapy in breast cancer models was performed to explore the enhanced antitumor immunity via prevention of DC senescence through blockages of STAT3 and programmed death-ligand 1 (PD-L1) signaling.

RESULTS

We showed that tumor-derived γδ Treg cells promote the development of senescence in DCs with tolerogenic functions in breast cancer. Senescent DCs induced by γδ Treg cells suppress Th1 and Th17 cell differentiation but promote the development of Treg cells. In addition, we demonstrated that PD-L1 and STAT3 signaling pathways are critical and involved in senescence induction in DCs mediated by tumor-derived γδ Treg cells. Importantly, our complementary in vivo studies further demonstrated that blockages of PD-L1 and/or STAT3 signaling can prevent γδ Treg-induced senescence and reverse tolerogenic functions in DCs, resulting in enhanced HER2 tumor-specific immune responses and immunotherapy efficacy in human breast cancer models.

CONCLUSIONS

These studies not only dissect the suppressive mechanism mediated by tumor-derived γδ Treg cells on DCs in the tumor microenvironment but also provide novel strategies to prevent senescence and dysfunction in DCs and enhance antitumor efficacy mediated by tumor-specific T cells for cancer immunotherapy.

Concise review: The heterogenous roles of BATF3 in cancer oncogenesis and dendritic cells and T cells differentiation and function considering the importance of BATF3-dependent dendritic cells

The transcription factor, known as basic leucine zipper ATF-like 3 (BATF3), is a crucial contributor to the development of conventional type 1 dendritic cells (cDC1), which is definitely required for priming CD8 + T cell-mediated immunity against intracellular pathogens and malignancies. In this respect, BATF3-dependent cDC1 can bring about immunological tolerance, an autoimmune response, graft immunity, and defense against infectious agents such as viruses, microbes, parasites, and fungi. Moreover, the important function of cDC1 in stimulating CD8 + T cells creates an excellent opportunity to develop a highly effective target for vaccination against intracellular pathogens and diseases. BATF3 has been clarified to control the development of CD8α+ and CD103+ DCs. The presence of BATF3-dependent cDC1 in the tumor microenvironment (TME) reinforces immunosurveillance and improves immunotherapy approaches, which can be beneficial for cancer immunotherapy. Additionally, BATF3 acts as a transcriptional inhibitor of Treg development by decreasing the expression of the transcription factor FOXP3. However, when overexpressed in CD8 + T cells, it can enhance their survival and facilitate their transition to a memory state. BATF3 induces Th9 cell differentiation by binding to the IL-9 promoter through a BATF3/IRF4 complex. One of the latest research findings is the oncogenic function of BATF3, which has been approved and illustrated in several biological processes of proliferation and invasion.

Atypical cofilin signaling drives dendritic cell migration through the extracellular matrix via nuclear deformation

To mount an adaptive immune response, dendritic cells must migrate to lymph nodes to present antigens to T cells. Critical to 3D migration is the nucleus, which is the size-limiting barrier for migration through the extracellular matrix. Here, we show that inflammatory activation of dendritic cells leads to the nucleus becoming spherically deformed and enables dendritic cells to overcome the typical 2- to 3-μm diameter limit for 3D migration through gaps in the extracellular matrix. We show that the nuclear shape change is partially attained through reduced cell adhesion, whereas improved 3D migration is achieved through reprogramming of the actin cytoskeleton. Specifically, our data point to a model whereby the phosphorylation of cofilin-1 at serine 41 drives the assembly of a cofilin-actomyosin ring proximal to the nucleus and enhances migration through 3D collagen gels. In summary, these data describe signaling events through which dendritic cells deform their nucleus and enhance their migratory capacity.

Radical S-adenosyl methionine domain-containing 2, a potential target of D-tryptophan in asthma treatment, regulates T helper cell type 1/2 balance

Asthma is a common chronic respiratory disease. D-tryptophan (D-TRP) can inhibit allergic airway inflammation and T helper cell type 2 (Th2) immune response. RNA-sequencing results have indicated that radical S-adenosyl methionine domain-containing 2 (RSAD2) might be a potential molecular target of D-TRP in asthma treatment. Herein, we established a mouse model of asthma using ovalbumin (OVA) via intraperitoneal injection and inhalational challenge. Gain- and loss-of-function studies of RSAD2 were performed in mice following the intratracheal delivery of lentiviral vectors (3 × 106 TU/mL). Naïve CD-4+ T cells were isolated from the spleen and used to explore the effects of RSAD2 on Th2 cell differentiation. RSAD2 expression was higher in the asthma group than in the control group. RSAD2 knockdown alleviated inflammatory cell infiltration and reduced the number of goblet cells. Low RSAD2 expression decreased the levels of IgE, IL-25, IL-33, and TSLP, and it reduced the number of inflammatory cells in the bronchoalveolar lavage fluid. RSAD2 silencing suppressed Th2-related cytokine levels (such as IL-4, IL-5, and IL-13) and increased Th1-related cytokine levels (such as IFN-γ). Additionally, RSAD2 knockdown inhibited the phosphorylation of JAK1, JAK3, and STAT6, and downregulated GATA-3 expression. RSAD2 overexpression increased inflammatory cell infiltration and mucus secretion in the lung tissues of mice pretreated with D-TRP. D-TRP pretreatment reduced OVA-specific IgE content and IL-4 and IL-5 levels, and it increased the IFN-γ levels; however, RSAD2 overexpression reversed these effects. In conclusion, RSAD2 knockdown can mitigate OVA-induced asthma by regulating the Th2 immune response via JAK/STAT6 pathway inhibition.

Development of a Cytosolic DNA Sensor Agonist Using GALA Peptide-Conjugated DNA and Long Single-Stranded DNA

Cytosolic DNA sensors (CDSs) recognize DNA molecules that are abnormally located in the cytosol, thus leading to the activation of the stimulator of interferon genes (STING) and the induction of type 1 interferon. In turn, type 1 interferon evokes defensive reactions against viral infections and activates the immune system; therefore, the use of agonists of CDSs as cancer therapeutics and vaccine adjuvants is expected. Double-stranded DNA molecules with dozens to thousands of bases derived from bacteria and viruses are agonists of CDSs. However, DNA is a water-soluble molecule with a high molecular weight, resulting in poor cellular uptake and endosomal escape. In contrast, long single-stranded DNA (lssDNA) obtained by rolling circle amplification is efficiently taken up and localized to endosomes. Here we constructed a CDS-targeting lssDNA via the facilitation of its intracellular transport from endosomes to the cytosol. An endosome-disrupting GALA peptide was used to deliver the lssDNA to the cytosol. A peptide-oligonucleotide conjugate (POC) was successfully obtained via the conjugation of the GALA peptide with an oligonucleotide complementary to the lssDNA. By hybridization of the POC to the complementary lssDNA (POC/lssDNA), the CDS-STING pathway in dendritic cells was efficiently stimulated. GALA peptide-conjugated DNA seems to be a helpful tool for the delivery of DNA to the cytosol.

Enhanced antigen-specific CD8 T cells contribute to early protection against FMDV through swine DC vaccination

Foot-and-mouth disease virus (FMDV) remains a challenge for cloven-hooved animals. The currently licensed FMDV vaccines induce neutralizing antibody (NAb)-mediated protection but show defects in the early protection. Dendritic cell (DC) vaccines have shown great potency in inducing rapid T-cell immunity in humans and mice. Whether DC vaccination could enhance early protection against FMDV has not been elaborately explored in domestic pigs. In this study, we employed DC vaccination as an experimental approach to study the roles of cellular immunity in the early protection against FMDV in pigs. Autologous DCs were differentiated from the periphery blood mononuclear cells of each pig, pulsed with inactivated FMDV (iFMDV-DC) and treated with LPS, and then injected into the original pigs. The cellular immune responses and protective efficacy elicited by the iFMDV-DC were examined by multicolor flow cytometry and tested by FMDV challenge. The results showed that autologous iFMDV-DC immunization induced predominantly FMDV-specific IFN-γ-producing CD4+ T cells and cytotoxic CD8+ T cells (CTLs), high NAb titers, compared to the inactivated FMDV vaccine, and accelerated the development of memory CD4 and CD8 T cells, which was concomitantly associated with early protection against FMDV virulent strain in pigs. Such early protection was associated with the rapid proliferation of secondary T-cell response after challenge and significantly contributed by secondary CD8 effector memory T cells. These results demonstrated that rapid induction of cellular immunity through DC immunization is important for improving early protection against FMDV. Enhancing cytotoxic CD8+ T cells may facilitate the development of more effective FMDV vaccines.IMPORTANCEAlthough the currently licensed FMDV vaccines provide NAb-mediated protection, they have defects in early immune protection, especially in pigs. In this study, we demonstrated that autologous swine DC immunization augmented the cellular immune response and induced an early protective response against FMDV in pigs. This approach induced predominantly FMDV-specific IFN-γ-producing CD4+ T cells and cytotoxic CD8+ T cells, high NAb titers, and rapid development of memory CD4 and CD8 T cells. Importantly, the early protection conferred by this DC immunization is more associated with secondary CD8+ T response rather than NAbs. Our findings highlighted the importance of enhancing cytotoxic CD8+ T cells in early protection to FMDV in addition to Th1 response and identifying a strategy or adjuvant comparable to the DC vaccine might be a future direction for improving the current FMDV vaccines.

Single-cell transcriptomics reveals the role of antigen presentation in liver metastatic breast cancer

Liver metastasis (LM) is the primary cause of cancer-related mortality in late-stage breast cancer (BC) patients. Here we report an in-depth analysis of the transcriptional landscape of LM of 11 patients with secondary hepatic carcinoma at single-cell resolution. Our study reveals that terminally exhausted CD4+ and dysfunctional CD8+ T cells were enriched in LM along with low antigen presentation. We also found that macrophages were associated with the tumor infiltrating CD4+ T cells, while FCN3+ macrophages, type 1 conventional dendritic cells (cDC1) and LAMP3+ DC regulated T cell functions, probably via antigen processing and presentation. Major histocompatibility complex expression in FCN3+ macrophage, cDC1 and LAMP3+ DC was reduced in LM compared to those in normal tissues and primary BC. Malfunctioned antigen presentation in these cells is linked to a worse prognosis in invasive BC and hepatocellular carcinoma. Our results provide valuable insights into the role of tumor infiltrating T cells in LM.

Immune cell early activation, apoptotic kinetic, and T-cell functional impairment in domestic pigs after ASFV CADC_HN09 strain infection

African swine fever (ASF) caused by the African swine fever virus (ASFV) is a fatal and highly contagious disease of domestic pigs characterized by rapid disease progression and death within 2 weeks. How the immune cells respond to acute ASFV infection and contribute to the immunopathogenesis of ASFV has not been completely understood. In this study, we examined the activation, apoptosis, and functional changes of distinct immune cells in domestic pigs following acute infection with the ASFV CADC_HN09 strain using multicolor flow cytometry. We found that ASFV infection induced broad apoptosis of DCs, monocytes, neutrophils, and lymphocytes in the peripheral blood of pigs over time. The expression of MHC class II molecule (SLA-DR/DQ) on monocytes and conventional DCs as well as CD21 expression on B cells were downregulated after ASFV infection, implying a potential impairment of antigen presentation and humoral response. Further examination of CD69 and ex vivo expression of IFN-γ on immune cells showed that T cells were transiently activated and expressed IFN-γ as early as 5 days post-infection. However, the capability of T cells to produce cytokines was significantly impaired in the infected pigs when stimulated with mitogen. These results suggest that the adaptive cellular immunity to ASFV might be initiated but later overridden by ASFV-induced immunosuppression. Our study clarified the cell types that were affected by ASFV infection and contributed to lymphopenia, improving our understanding of the immunopathogenesis of ASFV.

Radiation-Detoxified Form of Endotoxin Effectively Activates Th1 Responses and Attenuates Ragweed-Induced Th2-Type Airway Inflammation in Mice

Urbanization with reduced microbial exposure is associated with an increased burden of asthma and atopic symptoms. Conversely, environmental exposure to endotoxins in childhood can protect against the development of allergies. Our study aimed to investigate whether the renaturation of the indoor environment with aerosolized radiation-detoxified lipopolysaccharide (RD-LPS) has a preventative effect against the development of ragweed-induced Th2-type airway inflammation. To explore this, cages of six-week-old BALB/c mice were treated daily with aerosolized native LPS (N-LPS) or RD-LPS. After a 10-week treatment period, mice were sensitized and challenged with ragweed pollen extract, and inflammatory cell infiltration into the airways was observed. As dendritic cells (DCs) play a crucial role in the polarization of T-cell responses, in our in vitro experiments, the effects of N-LPS and RD-LPS were compared on human monocyte-derived DCs (moDCs). Mice in RD-LPS-rich milieu developed significantly less allergic airway inflammation than mice in N-LPS-rich or common environments. The results of our in vitro experiments demonstrate that RD-LPS-exposed moDCs have a higher Th1-polarizing capacity than moDCs exposed to N-LPS. Consequently, we suppose that the aerosolized, non-toxic RD-LPS applied in early life for the renaturation of urban indoors may be suitable for the prevention of Th2-mediated allergies in childhood.

Nanomaterial-encapsulated STING agonists for immune modulation in cancer therapy

The cGAS-STING signaling pathway has emerged as a critical mediator of innate immune responses, playing a crucial role in improving antitumor immunity through immune effector responses. Targeting the cGAS-STING pathway holds promise for overcoming immunosuppressive tumor microenvironments (TME) and promoting effective tumor elimination. However, systemic administration of current STING agonists faces challenges related to low bioavailability and potential adverse effects, thus limiting their clinical applicability. Recently, nanotechnology-based strategies have been developed to modulate TMEs for robust immunotherapeutic responses. The encapsulation and delivery of STING agonists within nanoparticles (STING-NPs) present an attractive avenue for antitumor immunotherapy. This review explores a range of nanoparticles designed to encapsulate STING agonists, highlighting their benefits, including favorable biocompatibility, improved tumor penetration, and efficient intracellular delivery of STING agonists. The review also summarizes the immunomodulatory impacts of STING-NPs on the TME, including enhanced secretion of pro-inflammatory cytokines and chemokines, dendritic cell activation, cytotoxic T cell priming, macrophage re-education, and vasculature normalization. Furthermore, the review offers insights into co-delivered nanoplatforms involving STING agonists alongside antitumor agents such as chemotherapeutic compounds, immune checkpoint inhibitors, antigen peptides, and other immune adjuvants. These platforms demonstrate remarkable versatility in inducing immunogenic responses within the TME, ultimately amplifying the potential for antitumor immunotherapy.

Dendritic cell therapy for neurospoagioma: Immunomodulation mediated by tumor vaccine

Neurospagioma, arising from different glial cells such as astrocytes, oligodendrocytes, and ependymal cells, stands as the prevalent intracranial tumor within the central nervous system. Among its variants, glioblastoma (GBM) represents the most aggressive form, characterized by a notably high occurrence rate and a discouragingly low survival prognosis. The formidable challenge posed by glioblastoma underscores its critical importance as a life-threatening ailment. Currently, clinical approaches often involve surgical excision along with a combination of radiotherapy and chemotherapy. However, these treatments frequently result in a notable recurrence rate, accompanied by substantial adverse effects that significantly compromise the overall prognosis. Hence, there is a crucial need to investigate novel and dependable treatment strategies. Dendritic cells (DCs), being specialized antigen-presenting cells (APCs), hold a significant position in both innate and adaptive immune responses. Presently, DC vaccines have gained widespread application in the treatment of various tumors, including neurospoagioma. In this review, we summarize the immunomodulatory effects and related mechanisms of DC vaccines in neurospoagioma as well as the progress of clinical trials to propose possible challenges of DC vaccines and new development directions.

Fecal microbiota transplantation regulates the microbiota-gut-spinal cord axis to promote recovery after spinal cord injury

Spinal cord injury (SCI) is devastating for patients, and currently lacks effective treatments. Dysbiosis commonly occurs after SCI and has significant immunomodulatory effects, but its impact on recovery remains unclear. The current study investigated the effects and mechanisms of fecal microbiota transplantation (FMT) in SCI. FMT was administered in a rat model of SCI and spinal pathology, inflammatory cytokines, and gut microbiome composition were assessed. Flow cytometry identified a source of interleukin (IL)-17 in spinal cord tissues, and carboxyfluorescein succimidyl ester labeling tracked γδ T cell migration. In vitro coculture was used to analyze the regulatory mechanisms of γδ T cells. Seahorse analysis was used to profile dendritic cell (DC) metabolism. Here we show that FMT improved spinal pathology and dampened post-injury inflammation. It also corrected post-SCI dysbiosis, increasing levels of the beneficial bacterium Akkermansia. The therapeutic effects of FMT were mediated by IL-17 produced by γδ T cells. FMT regulated γδ T cells via DC-T regulatory cell interaction, and induced metabolic reprogramming in DCs. These findings suggest that FMT represents a promising therapeutic approach for SCI, with potential to target IL-17+ γδ T cells. Elucidating the interconnected pathways between microbiota, immunity, and the spinal cord may facilitate novel treatment strategies.

Exosomes secreted by ST3GAL5high cancer cells promote peritoneal dissemination by establishing a premetastatic microenvironment

Peritoneal dissemination of cancer affects patient survival. The behavior of peritoneal mesothelial cells (PMCs) and immune cells influences the establishment of a microenvironment that promotes cancer cell metastasis in the peritoneum. Here, we investigated the roles of lactosylceramide alpha-2,3-sialyltransferase (ST3G5; also known as ST3GAL5 and GM3 synthase) in the exosome-mediated premetastatic niche in peritoneal milky spots (MSs). Exosomes secreted from ST3G5high cancer cells (ST3G5high -cExos) were found to contain high levels of hypoxia-inducible factor 1-alpha (HIF1α) and accumulated in MSs via uptake in macrophages (MΦs) owing to increased expression of sialic acid-binding Ig-like lectin 1 (CD169; also known as SIGLEC1). ST3G5high -cExos induced pro-inflammatory cytokines and glucose metabolic changes in MΦs, and the interaction of these MΦs with PMCs promoted mesothelial-mesenchymal transition (MMT) in PMCs, thereby generating αSMA+ myofibroblasts. ST3G5high -cExos also increased the expression of immune checkpoint molecules and T-cell exhaustion in MSs, which accelerated metastasis to the omentum. These events were prevented following ST3G5 depletion in cancer cells. Mechanistically, ST3G5high -cExos upregulated chemokines, including CC-chemokine ligand 5 (CCL5), in recipient MΦs and dendritic cells (DCs), which induced MMT and immunosuppression via activation of signal transducer and activator of transcription 3 (STAT3). Maraviroc, a C-C chemokine receptor type 5 (CCR5) antagonist, prevented ST3G5high -cExo-mediated MMT, T-cell suppression, and metastasis in MSs. Our results suggest ST3G5 as a suitable therapeutic target for preventing cExo-mediated peritoneal dissemination.

Decoding immunogenic cell death from a dendritic cell perspective

Dendritic cells (DCs) are myeloid cells bridging the innate and adaptive immune system. By cross-presenting tumor-associated antigens (TAAs) liberated upon spontaneous or therapy-induced tumor cell death to T cells, DCs occupy a pivotal position in the cancer immunity cycle. Over the last decades, the mechanisms linking cancer cell death to DC maturation, have been the focus of intense research. Growing evidence supports the concept that the mere transfer of TAAs during the process of cell death is insufficient to drive immunogenic DC maturation unless this process is coupled with the release of immunomodulatory signals by dying cancer cells. Malignant cells succumbing to a regulated cell death variant called immunogenic cell death (ICD), foster a proficient interface with DCs, enabling their immunogenic maturation and engagement of adaptive immunity against cancer. This property relies on the ability of ICD to exhibit pathogen-mimicry hallmarks and orchestrate the emission of a spectrum of constitutively present or de novo-induced danger signals, collectively known as damage-associated molecular patterns (DAMPs). In this review, we discuss how DCs perceive and decode danger signals emanating from malignant cells undergoing ICD and provide an outlook of the major signaling and functional consequences of this interaction for DCs and antitumor immunity.

A mechanistic marker-based screening tool to predict clinical immunogenicity of biologics

BACKGROUND

The efficacy and safety of therapeutic proteins are undermined by immunogenicity driven by anti-drug antibodies. Immunogenicity risk assessment is critically necessary during drug development, but current methods lack predictive power and mechanistic insight into antigen uptake and processing leading to immune response. A key mechanistic step in T-cell-dependent immune responses is the migration of mature dendritic cells to T-cell areas of lymphoid compartments, and this phenomenon is most pronounced in the immune response toward subcutaneously delivered proteins.

METHODS

The migratory potential of monocyte-derived dendritic cells is proposed to be a mechanistic marker for immunogenicity screening. Following exposure to therapeutic protein in vitro, dendritic cells are analyzed for changes in activation markers (CD40 and IL-12) in combination with levels of the chemokine receptor CXCR4 to represent migratory potential. Then a transwell assay captures the intensity of dendritic cell migration in the presence of a gradient of therapeutic protein and chemokine ligands.

RESULTS

Here, we show that an increased ability of the therapeutic protein to induce dendritic cell migration along a gradient of chemokine CCL21 and CXCL12 predicts higher immunogenic potential. Expression of the chemokine receptor CXCR4 on human monocyte-derived dendritic cells, in combination with activation markers CD40 and IL-12, strongly correlates with clinical anti-drug antibody incidence.

CONCLUSIONS

Mechanistic understanding of processes driving immunogenicity led to the development of a predictive tool for immunogenicity risk assessment of therapeutic proteins. These predictive markers could be adapted for immunogenicity screening of other biological modalities.

Lactobacillus johnsonii N5 from heat stress-resistant pigs improves gut mucosal immunity and barrier in dextran sodium sulfate-induced colitis

Developing effective strategies to prevent diarrhea and associated-gut disorders in mammals has gained great significance. Owing to the many health benefits provided by the commensal microbiota of the intestinal tract, such as against environmental perturbation, we explored the host phenotype-associated microbes and their probiotic potential. Based on the observations that the chronic heat stress-exposed weaned piglets present as heat stress-susceptible (HS-SUS) or heat stress-resistant (HS-RES) individuals, we confirmed the phenotypic difference between the two on growth performance (P < 0.05), diarrhea index (P < 0.001), intestinal heat shock protein 70 (HSP70) regulation (P < 0.01), and inflammatory responses (P < 0.01). By comparing the gut microbiome using 16S rRNA gene sequencing and KEGG functional analysis, we found that Lactobacillus johnsonii exhibited significantly higher relative abundance in the HS-RES piglets than in the HS-SUS ones (P < 0.05). Further experiments using a mouse model for chemical-induced inflammation and intestinal injury demonstrated that oral administration of a representative L. johnsonii N5 (isolated from the HS-RES piglets) ameliorated the clinical and histological signs of colitis while suppressing intestinal pro-inflammatory cytokines TNF-α and IL-6 production (P < 0.05). We found that N5 treatment enhanced tight junction proteins ZO-1 and occludin and cytoprotective HSP70 levels under physiological condition and restored their mucosal expressions in colitis (P < 0.05). In support of the high production of the anti-inflammatory cytokine IL-10, N5 promoted the intestinal Peyer's patches MHCII+ and CD103+ dendritic cell populations (P < 0.05), increased the regulatory T (Treg) cell numbers (P < 0.05), and decreased the Th17 population and its IL-17a production under physiological condition and during colitis (P < 0.01). Our results shed light on understanding the interaction between commensal Lactobacillus and the host health, and provide L. johnsonii N5 as an alternative to antibiotics for preventing diarrhea and intestinal diseases.

Anti-CD1d treatment suppresses immunogenic maturation of lung dendritic cells dependent on lung invariant natural killer T cells in asthmatic mice

Our previous findings show that invariant natural killer T (iNKT)cells can promote immunogenic maturation of lung dendritic cells (LDCs) to enhance Th2 cell responses in asthma. It has been accepted that recognition of glycolipid antigens presented by CD1d molecules by the T cell receptors of iNKT cells leads to iNKT cell activation. Therefore, we examine the immunoregulatory influences of anti-CD1d treatment on Th2 cell response and immunogenic maturation of LDCs and subsequently explored whether these influences were dependent on lung iNKT cells in asthmatic mice. We discoveredthat in wild-type mice sensitized and challenged with house dust mite or ovalbumin (OVA), anti-CD1d treatment inhibited Th2 cell response and immunogenic maturation of LDCs. LDCs from asthmatic mice with anti-CD1d treatment had a markedly decreased influence on Th2 cell responses in vivo and in vitro. Furthermore, anti-CD1d treatment reduced the abundance and activation of lung iNKT cells in asthmatic mice. Moreover, in asthmatic iNKT cell-deficient Jα18-/- mice, anti-CD1d treatment did not influence Th2 cell responses and immunogenic maturation of LDCs. Meanwhile, the quantity of CD40L+ iNKT cells in asthmatic mice was significant decreased by anti-CD1d treatment. Finally, the inhibition of anti-CD1d treatment on LDC immunogenic maturation and Th2 cell responses in asthmatic mice was reversed by anti-CD40 treatment. Our data suggest that anti-CD1d treatment can suppress Th2 cell responses through inhibiting immunogenic maturation of LDCs dependent on lung iNKT cells, which couldbe partially related to the downregulation of CD40L expression on lung iNKT cells in asthmatic mice.

Reprogramming the lipid metabolism of dendritic cells in tumor immunomodulation and immunotherapy

Dendritic cells (DCs) are the most potent antigen-presenting cells in the human body. They detect and process environmental signals and communicate with T cells to bridge innate and adaptive immunity. Cell activation, function, and survival are closely associated with cellular metabolism. An increasing number of studies have revealed that lipid metabolism affects DC activation as well as innate and acquired immune responses. Combining lipid metabolic regulation with immunotherapy can strengthen the ability of antigen-presentation and T-cell activation of DCs, improve the existing anti-tumor therapy, and overcome the defects of DC-related therapies in the current stage, which has great potential in cancer therapy. This review summarizes the lipid metabolism of DCs under physiological conditions, analyzes the role of reprogramming the lipid metabolism of DCs in tumor immune regulation, and discusses potential immunotherapeutic strategies.

CAR-T cells and CAR-Tregs targeting conventional type-1 dendritic cell suppress experimental autoimmune encephalomyelitis

Conventional type 1 dendritic cells (DC1) contribute to the development of pathogenic T helper type 1 (Th1) cells in part via the production of the proinflammatory cytokine interleukin-12. Thus, depletion of DC1 has the potential to dampen autoimmune responses. Here, we developed X-C motif chemokine receptor 1 (XCR1)-specific chimeric antigen receptor (CAR)-T cells and CAR-Tregs that specifically targeted DC1. XCR1 CAR-T cells were successfully generated as CD4+ and CD8+ T cells, expressed XCR1 CAR efficiently, and induced XCR1-dependent activation, cytokine production and proliferation. XCR1 CAR-T cells selectively depleted DC1 when transferred into RAG2-/- mice with a compensatory increase in conventional type 2 DC (DC2) and plasmacytoid DC (pDC). XCR1 CAR-T cell-mediated depletion of DC1 modestly suppressed the onset of Th1-driven experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis. Diphtheria toxin-mediated DC1 depletion in XCR1-diphtheria toxin receptor mice also suppressed EAE, suggesting that DC1 depletion was responsible for EAE suppression. XCR1 CAR-Tregs were successfully generated and suppressed effector T cells in the presence of XCR1+ cells. Therapeutic treatment with XCR1 CAR-Tregs suppressed Th1-driven EAE. Therefore, we conclude that depletion of DC1 with XCR1 CAR-T cells or immune suppression with XCR1 CAR-Tregs can modestly suppress Th1-driven EAE.

A Bidens pilosa L. Non-Polar Extract Modulates the Polarization of Human Macrophages and Dendritic Cells into an Anti-Inflammatory Phenotype

Different communities around the world traditionally use Bidens pilosa L. for medicinal purposes, mainly for its anti-inflammatory, antinociceptive, and antioxidant properties; it is used as an ingredient in teas or herbal medicines for the treatment of pain, inflammation, and immunological disorders. Several studies have been conducted that prove the immunomodulatory properties of this plant; however, it is not known whether the immunomodulatory properties of B. pilosa are mediated by its ability to modulate antigen-presenting cells (APCs) such as macrophages (MØs) and dendritic cells (DCs) (through polarization or the maturation state, respectively). Different polar and non-polar extracts and fractions were prepared from the aerial part of B. pilosa. Their cytotoxic and immunomodulatory effects were first tested on human peripheral blood mononuclear cells (PBMCs) and phytohemagglutinin (PHA)-stimulated PBMCs, respectively, via an MTT assay. Then, the non-cytotoxic plant extracts and fractions that showed the highest immunomodulatory activity were selected to evaluate their effects on human MØ polarization and DC maturation (cell surface phenotype and cytokine secretion) through multiparametric flow cytometry. Finally, the chemical compounds of the B. pilosa extract that showed the most significant immunomodulatory effects on human APCs were identified using gas chromatography coupled with mass spectrometry. The petroleum ether extract and the ethyl acetate and hydroalcoholic fractions obtained from B. pilosa showed low cytotoxicity and modulated the PHA-stimulated proliferation of PBMCs. Furthermore, the B. pilosa petroleum ether extract induced M2 polarization or a hybrid M1/M2 phenotype in MØs and a semi-mature status in DCs, regardless of exposure to a maturation stimulus. The immunomodulatory activity of the non-polar (petroleum ether) extract of B. pilosa on human PBMC proliferation, M2 polarization of MØs, and semi-mature status in DCs might be attributed to the low-medium polarity components in the extract, such as phytosterol terpenes and fatty acid esters.

Dendritic cell vaccine of gliomas: challenges from bench to bed

Gliomas account for the majority of brain malignant tumors. As the most malignant subtype of glioma, glioblastoma (GBM) is barely effectively treated by traditional therapies (surgery combined with radiochemotherapy), resulting in poor prognosis. Meanwhile, due to its "cold tumor" phenotype, GBM fails to respond to multiple immunotherapies. As its capacity to prime T cell response, dendritic cells (DCs) are essential to anti-tumor immunity. In recent years, as a therapeutic method, dendritic cell vaccine (DCV) has been immensely developed. However, there have long been obstacles that limit the use of DCV yet to be tackled. As is shown in the following review, the role of DCs in anti-tumor immunity and the inhibitory effects of tumor microenvironment (TME) on DCs are described, the previous clinical trials of DCV in the treatment of GBM are summarized, and the challenges and possible development directions of DCV are analyzed.

Recent Advances in Antitumor Dendritic Cell Vaccines

Background: Dendritic cells (DCs) are the most important antigen-presenting cells in the body and play a key role in antigen recognition, uptake, processing, and presentation and mediate nonspecific immunity and specific immunity. Purpose: To summarize the main findings that DC vaccines are a new immunotherapy scheme combining the strengths of tumor antigens and DCs that can boost the body's identification and clearance of tumors. Methods: In this review, the authors focus on the biological characteristics of DCs, recent advances in the understanding of antitumor mechanisms, and the classification of DC vaccines. Results: The current progress of DC-based vaccine immunotherapy for common tumors with high morbidity or mortality in China were systematically summarize. Conclusions: The DC vaccines combining the strengths of tumor antigens will provide directions to explore reasonable, safe, and effective combination immunotherapy strategies for tumors in the future.

The development and function of human monocyte-derived dendritic cells regulated by metabolic reprogramming

Human monocyte-derived dendritic cells (moDCs) that develop from monocytes play a key role in innate inflammatory responses as well as T cell priming. Steady-state moDCs regulate immunogenicity and tolerogenicity by changing metabolic patterns to participate in the body's immune response. Increased glycolytic metabolism after danger signal induction may strengthen moDC immunogenicity, whereas high levels of mitochondrial oxidative phosphorylation were associated with the immaturity and tolerogenicity of moDCs. In this review, we discuss what is currently known about differential metabolic reprogramming of human moDC development and distinct functional properties.

Tumor-derived interleukin-1 receptor antagonist exhibits immunosuppressive functions and promotes pancreatic cancer

BACKGROUND

Pancreatic ductal adenocarcinoma (PDA) is a pernicious disease characterized by an immunosuppressive milieu that is unresponsive to current immunotherapies. Interleukin-1 receptor antagonist (IL-1Ra) is a natural anti-inflammatory cytokine; however, its contribution to cancer pathogenesis and immunosuppression remains elusive. In this research, we investigated the role and mechanism of IL-1Ra in malignant progression of PDA.

RESULTS

Through analyzing clinical dataset and examining the pathological tumor tissues and serum samples, we have demonstrated that IL-1Ra expression is elevated in human PDA and positively associated with malignant progression of PDA. To study the biological function of IL-1Ra in tumors, we generated a set of mouse pancreatic cancer cell lines with a knockout (KO) of the Il1rn gene, encoding IL-1Ra, and compared the tumor growth rates in immune-competent and immune-deficient mice. We found that the Il1rn KO cells exhibited greater tumor inhibition in immune-competent mice, highlighting the crucial role of a functional immune system in Il1rn KO-mediated anti-tumor response. Consistently, we found an increase in CD8+ T cells and a decrease in CD11b+Ly6G- immunosuppressive mononuclear population in the tumor microenvironment of Il1rn KO-derived tumors. To monitor the inhibitory effects of IL-1Ra on immune cells, we utilized a luciferase-based reporter CD4+ T cell line and splenocytes, which were derived from transgenic mice expressing ovalbumin-specific T cell receptors in CD8+ T cells, and mice immunized with ovalbumin. We showed that IL-1Ra suppressed T cell receptor signaling and inhibited antigen-specific interferon-γ (IFN-γ) secretion and cytolytic activity in splenocytes.

CONCLUSIONS

Our findings illustrate the immunosuppressive properties of the natural anti-inflammatory cytokine IL-1Ra, and provide a rationale for considering IL-1Ra-targeted therapies in the treatment of PDA.

ISCOMs/MPLA-Adjuvanted SDAD Protein Nanoparticles Induce Improved Mucosal Immune Responses and Cross-Protection in Mice

The epidemics caused by the influenza virus are a serious threat to public health and the economy. Adding appropriate adjuvants to improve immunogenicity and finding effective mucosal vaccines to combat respiratory infection at the portal of virus entry are important strategies to boost protection. In this study, a novel type of core/shell protein nanoparticle consisting of influenza nucleoprotein (NP) as the core and NA1-M2e or NA2-M2e fusion proteins as the coating antigens by SDAD hetero-bifunctional crosslinking is exploited. Immune-stimulating complexes (ISCOMs)/monophosphoryl lipid A (MPLA) adjuvants further boost the NP/NA-M2e SDAD protein nanoparticle-induced immune responses when administered intramuscularly. The ISCOMs/MPLA-adjuvanted protein nanoparticles are delivered through the intranasal route to validate the application as mucosal vaccines. ISCOMs/MPLA-adjuvanted nanoparticles induce significantly strengthened antigen-specific antibody responses, cytokine-secreting splenocytes in the systemic compartment, and higher levels of antigen-specific IgA and IgG in the local mucosa. Meanwhile, significantly expanded lung resident memory (RM) T and B cells (TRM /BRM ) and alveolar macrophages population are observed in ISCOMs/MPLA-adjuvanted nanoparticle-immunized mice with a 100% survival rate after homogeneous and heterogeneous H3N2 viral challenges. Taken together, ISCOMs/MPLA-adjuvanted protein nanoparticles could improve strong systemic and mucosal immune responses conferring protection in different immunization routes.

The Unfolded Protein Response Sensor IRE1 Regulates Activation of In Vitro Differentiated Type 1 Conventional DCs with Viral Stimuli

Type 1 conventional dendritic cells (cDC1s) are leukocytes competent to coordinate antiviral immunity, and thus, the intracellular mechanisms controlling cDC1 function are a matter of intense research. The unfolded protein response (UPR) sensor IRE1 and its associated transcription factor XBP1s control relevant functional aspects in cDC1s including antigen cross-presentation and survival. However, most studies connecting IRE1 and cDC1 function are undertaken in vivo. Thus, the aim of this work is to elucidate whether IRE1 RNase activity can also be modeled in cDC1s differentiated in vitro and reveal the functional consequences of such activation in cells stimulated with viral components. Our data show that cultures of optimally differentiated cDC1s recapitulate several features of IRE1 activation noticed in in vivo counterparts and identify the viral analog Poly(I:C) as a potent UPR inducer in the lineage. In vitro differentiated cDC1s display constitutive IRE1 RNase activity and hyperactivate IRE1 RNase upon genetic deletion of XBP1s, which regulates production of the proinflammatory cytokines IL-12p40, TNF-α and IL-6, Ifna and Ifnb upon Poly(I:C) stimulation. Our results show that a strict regulation of the IRE1/XBP1s axis regulates cDC1 activation to viral agonists, expanding the scope of this UPR branch in potential DC-based therapies.

Multifunctional Nanoparticles Precisely Reprogram the Tumor Microenvironment and Potentiate Antitumor Immunotherapy after Near-Infrared-II Light-Mediated Photothermal Therapy

Mild-temperature photothermal therapy (mild PTT) is a safe and efficient antitumor therapy. However, mild PTT alone usually fails to activate the immune response and prevent tumor metastasis. Herein, a photothermal agent, copper sulfide@ovalbumin (CuS@OVA), with an effective PTT effect in the second near-infrared (NIR-II) window, is developed. CuS@OVA can optimize the tumor microenvironment (TME) and evoke an adaptive immune response. Copper ions are released in the acidic TME to promote the M1 polarization of tumor-associated macrophages. The model antigen OVA not only acts as a scaffold for nanoparticle growth but also promotes the maturation of dendritic cells, which primes naive T cells to stimulate adaptive immunity. CuS@OVA augments the antitumor efficiency of the immune checkpoint blockade (ICB) in vivo, which suppresses tumor growth and metastasis in a mouse melanoma model. The proposed therapeutic platform, CuS@OVA nanoparticles, may be a potential adjuvant for optimizing the TME and improving the efficiency of ICB as well as other antitumor immunotherapies. STATEMENT OF SIGNIFICANCE: Mild-temperature photothermal therapy (mild PTT) is a safe and efficient antitumor therapy, but usually fails to activate the immune response and prevent tumor metastasis. Herein, we develop a photothermal agent, copper sulfide@ovalbumin (CuS@OVA), with an excellent PTT effect in the second near-infrared (NIR-II) window. CuS@OVA can optimize the tumor microenvironment (TME) and evoke an adaptive immune response by promoting the M1 polarization of tumor-associated macrophages and the maturation of dendritic cells. CuS@OVA augments the antitumor efficiency of the immune checkpoint blockade (ICB) in vivo, suppressing tumor growth and metastasis. The platform may be a potential adjuvant for optimizing the TME and improving the efficiency of ICB as well as other antitumor immunotherapies.

Two Modes of Th1 Polarization Induced by Dendritic-Cell-Priming Adjuvant in Vaccination

Viral infections are usually accompanied by systemic cytokinemia. Vaccines need not necessarily mimic infection by inducing cytokinemia, but must induce antiviral-acquired immunity. Virus-derived nucleic acids are potential immune-enhancers and particularly good candidates as adjuvants in vaccines in mouse models. The most important nucleic-acid-sensing process involves the dendritic cell (DC) Toll-like receptor (TLR), which participates in the pattern recognition of foreign DNA/RNA structures. Human CD141+ DCs preferentially express TLR3 in endosomes and recognize double-stranded RNA. Antigen cross-presentation occurs preferentially in this subset of DCs (cDCs) via the TLR3-TICAM-1-IRF3 axis. Another subset, plasmacytoid DCs (pDCs), specifically expresses TLR7/9 in endosomes. They then recruit the MyD88 adaptor, and potently induce type I interferon (IFN-I) and proinflammatory cytokines to eliminate the virus. Notably, this inflammation leads to the secondary activation of antigen-presenting cDCs. Hence, the activation of cDCs via nucleic acids involves two modes: (i) with bystander effect of inflammation and (ii) without inflammation. In either case, the acquired immune response finally occurs with Th1 polarity. The level of inflammation and adverse events depend on the TLR repertoire and the mode of response to their agonists in the relevant DC subsets, and could be predicted by assessing the levels of cytokines/chemokines and T cell proliferation in vaccinated subjects. The main differences in the mode of vaccine sought in infectious diseases and cancer are defined by whether it is prophylactic or therapeutic, whether it can deliver sufficient antigens to cDCs, and how it behaves in the microenvironment of the lesion. Adjuvant can be selected on a case-to-case basis.

Activation, Amplification, and Ablation as Dynamic Mechanisms of Dendritic Cell Maturation

T cell responses to cognate antigens crucially depend on the specific functionality of dendritic cells (DCs) activated in a process referred to as maturation. Maturation was initially described as alterations of the functional status of DCs in direct response to multiple extrinsic innate signals derived from foreign organisms. More recent studies, conducted mainly in mice, revealed an intricate network of intrinsic signals dependent on cytokines and various immunomodulatory pathways facilitating communication between individual DCs and other cells for the orchestration of specific maturation outcomes. These signals selectively amplify the initial activation of DCs mediated by innate factors and dynamically shape DC functionalities by ablating DCs with specific functions. Here, we discuss the effects of the initial activation of DCs that crucially includes the production of cytokine intermediaries to collectively achieve amplification of the maturation process and further precise sculpting of the functional landscapes among DCs. By emphasizing the interconnectedness of the intracellular and intercellular mechanisms, we reveal activation, amplification, and ablation as the mechanistically integrated components of the DC maturation process.

LXR signaling controls homeostatic dendritic cell maturation

Dendritic cells (DCs) mature in an immunogenic or tolerogenic manner depending on the context in which an antigen is perceived, preserving the balance between immunity and tolerance. Whereas the pathways driving immunogenic maturation in response to infectious insults are well-characterized, the signals that drive tolerogenic maturation during homeostasis are still poorly understood. We found that the engulfment of apoptotic cells triggered homeostatic maturation of type 1 conventional DCs (cDC1s) within the spleen. This maturation process could be mimicked by engulfment of empty, nonadjuvanted lipid nanoparticles (LNPs), was marked by intracellular accumulation of cholesterol, and was highly specific to cDC1s. Engulfment of either apoptotic cells or cholesterol-rich LNPs led to the activation of the liver X receptor (LXR) pathway, which promotes the efflux of cellular cholesterol, and repressed genes associated with immunogenic maturation. In contrast, simultaneous engagement of TLR3 to mimic viral infection via administration of poly(I:C)-adjuvanted LNPs repressed the LXR pathway, thus delaying cellular cholesterol efflux and inducing genes that promote T cell-mediated immunity. These data demonstrate that conserved cellular cholesterol efflux pathways are differentially regulated in tolerogenic versus immunogenic cDC1s and suggest that administration of nonadjuvanted cholesterol-rich LNPs may be an approach for inducing tolerogenic DC maturation.

TIPE2 deficiency prolongs mouse heart allograft survival by inhibiting immature DCs-induced Treg generation

It has been reported that deletion of tumor necrosis factor-α-induced protein-8 like 2 (TNFAIP8L2, TIPE2) facilitates the activation of T-cell receptors. However, the role of TIPE2 in T-cell-mediated acute transplant rejection remains unclear. To illustrate the underlying cellular mechanisms, we transplanted BALB/c hearts into C57BL/6 wild-type C57BL/6 mice or mice deficient for TIPE2 (TIPE2^-/-) and found that TIPE2^-/- recipient mice showed significantly prolonged survival of heart allografts and suppressed maturation of CD11c⁺ dendritic cells (DCs), which largely abolished the activation and proliferation of alloreactive T cells and their cytotoxic activity. TIPE2^-/- DCs increased CD4⁺Foxp3⁺CD127^- Treg generation, likely by inhibiting DCs maturation and CD80 and CD86 expression. Administration of anti-CD25 abolished the allograft survival induced by TIPE2 deficiency. Moreover, TIPE2 deficiency increased IL-10 production in T cells and in recipient serum and allografts. Mechanistic studies revealed that TIPE2^-/- restrained the maturation of DCs via inhibition of PI3K/AKT phosphorylation during alloantigen stimulation. Taken together, TIPE2 deficiency in recipient mice inhibited acute rejection by increasing Tregs generated by immature DCs. Thus, TIPE2 could be a therapeutic target for suppressing rejection in organ transplantation.

The role of dendritic cells in radiation-induced immune responses

Dendritic cells perform critical functions in bridging innate and adaptive immunity. Their ability to sense adjuvant signals in their environment, migrate on maturation, and cross-present cell-associated antigens enables these cells to carry antigen from tissue sites to lymph nodes, and thereby prime naïve T cells that cannot enter tissues. Despite being an infrequent cell type in tumors, we discuss how dendritic cells impact the immune environment of tumors and their response to cancer therapies. We review how radiation therapy of tumors can impact dendritic cells, through transfer of cell associated antigens to dendritic cells and the release of endogenous adjuvants, resulting in increased antigen presentation in the tumor-draining lymph nodes. We explore how tumor specific factors can result in negative regulation of dendritic cell function in the tumor, and the impact of direct radiation exposure to dendritic cells in the treatment field. These data suggest an important role for dendritic cell subpopulations in activating new T cell responses and boosting existing T cell responses to tumor associated antigens in tumor draining lymph nodes following radiation therapy. It further justifies a focus on the needs of the lymph node T cells to improve systemic anti-immunity following radiation therapy.

CTCF controls three-dimensional enhancer network underlying the inflammatory response of bone marrow-derived dendritic cells

Dendritic cells are antigen-presenting cells orchestrating innate and adaptive immunity. The crucial role of transcription factors and histone modifications in the transcriptional regulation of dendritic cells has been extensively studied. However, it is not been well understood whether and how three-dimensional chromatin folding controls gene expression in dendritic cells. Here we demonstrate that activation of bone marrow-derived dendritic cells induces extensive reprogramming of chromatin looping as well as enhancer activity, both of which are implicated in the dynamic changes in gene expression. Interestingly, depletion of CTCF attenuates GM-CSF-mediated JAK2/STAT5 signaling, resulting in defective NF-κB activation. Moreover, CTCF is necessary for establishing NF-κB-dependent chromatin interactions and maximal expression of pro-inflammatory cytokines, which prime Th1 and Th17 cell differentiation. Collectively, our study provides mechanistic insights into how three-dimensional enhancer networks control gene expression during bone marrow-derived dendritic cells activation, and offers an integrative view of the complex activities of CTCF in the inflammatory response of bone marrow-derived dendritic cells.

Effect of cigarette smoke on mucosal vaccine response with activation of plasmacytoid dendritic cells: The outcomes of in vivo and in vitro experiments

Mucosal vaccines offer several advantages over transdermal vaccines, including the ability to acquire systemic and mucosal immunities. Smoking is a huge public health threat and major risk factor for various diseases that exacerbate or prolong respiratory symptoms and conditions. However, its impact on the efficacy of mucosal vaccines remains partially explored. Thus, this study investigates the effects of smoking on mucosal vaccine reactivity by assessing the induction of Th1 immunity, a vital response in infection defense. Cigarette smoke condensate was prepared as a substitute for mainstream smoke. We intranasally administered diphtheria toxoid as an antigen and natural CpG oligonucleotide G9.1, which enhances the Th1-type antibody (Ab) response in a plasmacytoid dendritic cells (pDCs) dependent manner, as an adjuvant to mice to assess the effect of cigarette smoke condensate on Ab responses. The mechanism of its effect was evaluated using human peripheral blood mononuclear cells and their pDC-rich fraction cultured with or without G9.1. In mice, cigarette smoke condensate tended to decrease diphtheria toxoid-specific Ab response, with a higher reduction in Th1-type IgG2 Ab response than in Th2-type IgG1 Ab response. In human peripheral blood mononuclear cells, cigarette smoke condensate significantly reduced the induction of IFN-α production by G9.1. Moreover, G9.1-induced increases in the CD83 expression in pDCs and the CD80 expression in DCs were suppressed via treatment with cigarette smoke condensate. Among the mechanisms suggested were decreased expression of toll-like receptor 9 mRNA, decreased expression of mRNA for IFN regulatory factor 7, and increased CpG methylation of its promoter region. The analysis of Tbet and GATA3 expressions revealed that cigarette smoke condensate exhibits Th1-directed immunostimulatory activity at a steady state but becomes more Th2-directed under G9.1 stimulation. In conclusion, smoking could reduce mucosal vaccine responses by decreasing pDC activation and, consequently, Th1-dominant immunity.

Vibrio cholerae Porin OmpU Activates Dendritic Cells via TLR2 and the NLRP3 Inflammasome

OmpU is one of the major porins of Vibrio cholerae, a Gram-negative human pathogen. Previously, we showed that OmpU stimulates host monocytes and macrophages and induces the production of proinflammatory mediators via activation of the Toll-like receptor 1/2 (TLR1/2)-MyD88-dependent pathways. In the present study, we show that OmpU activates murine dendritic cells (DCs) via activation of the TLR2-mediated pathway and the NLRP3 inflammasome, leading to the production of proinflammatory cytokines and DC maturation. Our data reveal that although TLR2 plays an important role in providing both priming and the activation signal for the NLRP3 inflammasome in OmpU-activated DCs, OmpU is capable of activating the NLRP3 inflammasome, even in the absence of TLR2, if a priming signal is given. Furthermore, we show that the OmpU-mediated interleukin-1β (IL-1β) production in DCs depends on calcium flux and mitochondrial reactive oxygen species (mitoROS) generation. Interestingly, both OmpU translocation to the mitochondria of DCs as well as calcium signaling contribute to mitoROS production and prompt NLRP3 inflammasome activation. We also demonstrate that OmpU induces downstream signaling via activation of phosphoinositide-3-kinase (PI3K)-AKT, protein kinase C (PKC), mitogen-activated protein kinases (MAPKs), and transcription factor NF-κB. Furthermore, our data reveal that OmpU-mediated activation of TLR2 induces signaling via PKC, MAPKs p38 and extracellular signal-regulated kinase (ERK), and transcription factor NF-κB; however, PI3K and MAPK Jun N-terminal protein kinase (JNK) are activated in TLR2 independent manner.

Heterogeneity of adherent and non‑adherent JAWS II dendritic cells

Dendritic cells (DCs) are crucial in the development of immune responses. DC JAWS II is a murine cell line frequently used in DC studies. These cells are grown in two cell fractions: Adherent and non-adherent. The present study aimed to compare these two fractions in both immature and lipopolysaccharide (LPS)-activated JAWS II cells. The present study analysed the condition, phenotype, antigen uptake capability, signalling properties and the influence on the activity of T cells using flow cytometry, mixed cell reaction and ELISA methods. Adherent immature JAWS II cells exhibited increased endocytosis and decreased activation of the Pi3K signalling pathway. After LPS activation, adherent JAWS II cells exhibited increased expression levels of CD80 and CD86 costimulatory molecules, increased endocytosis and an elevated ability to induce T cell proliferation, compared with non-adherent cells. These results demonstrated that the two fractions of JAWS II adherent and non-adherent cells exhibited different properties and this should be taken into account in the planning of research.

Nanoparticle vaccines can be designed to induce pDC support of mDCs for increased antigen display

Cancer vaccine immunotherapy facilitates the immune system's recognition of tumor-associated antigens, and the biomolecular design of these vaccines using nanoparticles is one important approach towards obtaining strong anti-tumor responses. Following activation of dendritic cells (DCs), a robust CD8+ T cell-mediated adaptive immune response is critical for tumor elimination. While the role of efficient antigen-presenting myeloid DCs (mDCs) is conventionally attributed towards vaccine efficacy, participation by highly cytokine-producing plasmacytoid DCs (pDCs) is less understood and is often overlooked. We examined vaccines based on the E2 protein nanoparticle platform that delivered encapsulated TLR9 agonist bacterial-like DNA (CpG1826 or CpG1018) or TLR7 agonist viral ssRNA to determine their efficacy over free agonists in activating both mDCs and pDCs for antigen presentation. Although mDCs were only activated by nanoparticle-encapsulated TLR9 agonists, pDCs were activated by all the individually tested constructs, and CpG1826 was shown to induce pDC cytokine production. Transfer of secreted factors from pDCs that were stimulated with a vaccine formulation comprising peptide antigen and CpG1826 enhanced mDC display of the antigen, particularly when delivered in nanoparticles. Only when treated with nanoparticle-conjugated vaccine could pDCs secrete factors to induce antigen display on naïve mDCs. These results reveal that pDCs can aid mDCs, highlighting the importance of activating both pDCs and mDCs in designing effective cancer vaccines, and demonstrate the advantage of using nanoparticle-based vaccine delivery.