Ag-presenting CpG-activated pDCs prime Th17 cells that induce tumor regression

Plasmacytoid Dendritic Cells Mediate CpG-ODN-induced Increase in Survival in a Mouse Model of Lymphangioleiomyomatosis

Lymphangioleiomyomatosis (LAM) is a devastating disease primarily found in women of reproductive age that leads to cystic destruction of the lungs. Recent work has shown that LAM causes immunosuppression and that checkpoint inhibitors can be used as LAM treatment. Toll-like receptor (TLR) agonists can also reactivate immunity, and the TLR9 agonist CpG oligodeoxynucleotide (CpG-ODN) has been effective in treating lung cancer in animal models. In this study, we investigated the use of TLR9 agonist CpG-ODN as LAM immunotherapy in combination with checkpoint inhibitor anti-PD1 and standard of care rapamycin, and determined the immune mechanisms underlying therapeutic efficacy. We used survival studies, flow cytometry, ELISA, and histology to assess immune response and survival after intranasal treatment with CpG-ODN in combination with rapamycin or anti-PD1 therapy in a mouse model of metastatic LAM. We found that local administration of CpG-ODN enhances survival in a mouse model of LAM. We found that a lower dose led to longer survival, likely because of fewer local side effects, but increased LAM nodule count and size compared with the higher dose. CpG-ODN treatment also reduced regulatory T cells and increased the number of T-helper type 17 cells as well as cytotoxic T cells. These effects appear to be mediated in part by plasmacytoid dendritic cells because depletion of plasmacytoid dendritic cells reduces survival and abrogates T-helper type 17 cell response. Finally, we found that CpG-ODN treatment is effective in early-stage and progressive disease and is additive with anti-PD1 therapy and rapamycin. In summary, we have found that TLR9 agonist CpG-ODN can be used as LAM immunotherapy and effectively synergizes with rapamycin and anti-PD1 therapy in LAM.

Th17 cell function in cancers: immunosuppressive agents or anti-tumor allies?

T helper (Th) 17 cells, a distinct subset of Th lymphocytes, are known for their prominent interleukin (IL)-17 production and other pro-inflammatory cytokines. These cells exhibit remarkable plasticity, allowing them to exhibit different phenotypes in the cancer microenvironment. This adaptability enables Th17 cells to promote tumor progression by immunosuppressive activities and angiogenesis, but also mediate anti-tumor immune responses through employing immune cells in tumor setting or even by directly converting toward Th1 phenotype and producing interferon-gamma (IFN-γ). This dual role of Th17 cells in cancer makes it a double-edged sword in encountering cancer. In this review, we aim to elucidate the complexities of Th17 cell function in cancer by summarizing recent studies and, ultimately, to design novel therapeutic strategies, especially targeting Th17 cells in the tumor milieu, which could pave the way for more effective cancer treatments.

Contribution of m5C RNA Modification-Related Genes to Prognosis and Immunotherapy Prediction in Patients with Ovarian Cancer

Background

5-Methylcytosine (m5C) RNA modification is closely implicated in the occurrence of a variety of cancers. Here, we established a novel prognostic signature for ovarian cancer (OC) patients based on m5C RNA modification-related genes and explored the correlation between these genes with the tumor immune microenvironment.

Methods

Methylated-RNA immunoprecipitation sequencing helped us to identify candidate genes related to m5C RNA modification at first. Based on TCGA database, we screened the differentially expressed candidate genes related to the prognosis and constructed a prognostic model using LASSO Cox regression analyses. Notably, the accuracy of the model was evaluated by Kaplan-Meier analysis and receiver operator characteristic curves. Independent prognostic risk factors were investigated by Cox proportional hazard model. Furthermore, we also analyzed the biological functions and pathways involved in the signature. Finally, the immune response of the model was visualized in great detail.

Results

Totally, 2,493 candidate genes proved to be involved in m5C modification of RNA for OC. We developed a signature with prognostic value consisting of six m5C RNA modification-related genes. Specially, samples have been split into two cohorts with low- and high-risk scores according to the model, in which the low-risk OC patients exhibited dramatically better overall survival time than those with high-risk scores. Besides, not only was this model a prognostic factor independent of other clinical characteristics but it predicted the intensity of the immune response in OC. Significantly, the accuracy and availability of the signature were verified by ICGC database.

Conclusions

Our study bridged the gap between m5C RNA modification and the prognosis of OC and was expected to provide an effective breakthrough for immunotherapy in OC patients.

The application of machine learning methods to the prediction of novel ligands for RORγ/RORγT receptors

In this work, we developed and applied a computational procedure for creating and validating predictive models capable of estimating the biological activity of ligands. The combination of modern machine learning methods, experimental data, and the appropriate setup of molecular descriptors led to a set of well-performing models. We thoroughly inspected both the methodological space and various possibilities for creating a chemical feature space. The resulting models were applied to the virtual screening of the ZINC20 database to identify new, biologically active ligands of RORγ receptors, which are a subfamily of nuclear receptors. Based on the known ligands of RORγ, we selected candidates and calculate their predicted activities with the best-performing models. We chose two candidates that were experimentally verified. One of these candidates was confirmed to induce the biological activity of the RORγ receptors, which we consider proof of the efficacy of the proposed methodology.

Targeting the dendritic cell-T cell axis to develop effective immunotherapies for glioblastoma

Glioblastoma is an aggressive primary brain tumor that has seen few advances in treatments for over 20 years. In response to this desperate clinical need, multiple immunotherapy strategies are under development, including CAR-T cells, immune checkpoint inhibitors, oncolytic viruses and dendritic cell vaccines, although these approaches are yet to yield significant clinical benefit. Potential reasons for the lack of success so far include the immunosuppressive tumor microenvironment, the blood-brain barrier, and systemic changes to the immune system driven by both the tumor and its treatment. Furthermore, while T cells are essential effector cells for tumor control, dendritic cells play an equally important role in T cell activation, and emerging evidence suggests the dendritic cell compartment may be deeply compromised in glioblastoma patients. In this review, we describe the immunotherapy approaches currently under development for glioblastoma and the challenges faced, with a particular emphasis on the critical role of the dendritic cell-T cell axis. We suggest a number of strategies that could be used to boost dendritic cell number and function and propose that the use of these in combination with T cell-targeting strategies could lead to successful tumor control.

Immunostimulatory DNA Hydrogel Enhances Protective Efficacy of Nanotoxoids against Bacterial Infection

While vaccines have been highly successful in protecting against various infections, there are still many high-priority pathogens for which there are no clinically approved formulations. To overcome this challenge, researchers have explored the use of nanoparticulate strategies for more effective antigen delivery to the immune system. Along these lines, nanotoxoids are a promising biomimetic platform that leverages cell membrane coating technology to safely deliver otherwise toxic bacterial antigens in their native form for antivirulence vaccination. Here, in order to further boost their immunogenicity, nanotoxoids formulated against staphylococcal α-hemolysin are embedded into a DNA-based hydrogel with immunostimulatory CpG motifs. The resulting nanoparticle-hydrogel composite is injectable and improves the in vivo delivery of vaccine antigens while simultaneously stimulating nearby immune cells. This leads to elevated antibody production and stronger antigen-specific cellular immune responses. In murine models of pneumonia and skin infection caused by methicillin-resistant Staphylococcus aureus, mice vaccinated with the hybrid vaccine formulation are well-protected. This work highlights the benefits of combining nanoparticulate antigen delivery systems with immunostimulatory hydrogels into a single platform, and the approach can be readily generalized to a wide range of infectious diseases.

The protective and pathogenic role of Th17 cell plasticity and function in the tumor microenvironment

At the turn of the century, researchers discovered a unique subtype of T helper cells that secretes IL-17 and defined it as Th17. The latest study found that Th17 cells play both positive and negative definitive roles in the regulation of antitumor immune responses. Although the function of Th17 in the tumor microenvironment remains poorly understood, more and more studies have shown that this paradoxical dual role is closely related to the plasticity of Th17 cells in recent decades. Further understanding of the characteristics of Th17 cells in the tumor microenvironment could yield novel and useful therapeutic approaches to treat cancer. In this review, we further present the high plasticity of Th17 cells and the function of Th17-producing IL-17 in tumor immunity.

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.

Th17 Cells: Orchestrators of Mucosal Inflammation and Potential Therapeutic Targets

T helper 17 (Th17) cells represent a specialized subgroup of effector CD4+ T cells known for their role in provoking neutrophil-driven tissue inflammation, particularly within mucosal tissues. Although they are pivotal for defending the host against extracellular bacteria and fungi, they have also been associated with development of various T cell-mediated inflammatory conditions, autoimmune diseases, and even cancer. Notably, Th17 cells exhibit a dual nature, with different Th17 cell subtypes showcasing distinct effector functions and varying capacities to incite autoimmune tissue inflammation. Furthermore, Th17 cells exhibit significant plasticity, which carries important functional implications, both in terms of their expression of cytokines typically associated with other effector T cell subsets and in their interactions with regulatory CD4+ T cells. The intricate balance of Th17 cytokines can also be a double-edged sword in inflammation, autoimmunity, and cancer. Within this article, we delve into the mechanisms that govern the differentiation, function, and adaptability of Th17 cells. We culminate with an exploration of therapeutic potentials in harnessing the power of Th17 cells and their cytokines. Targeted interventions to modulate Th17 responses are emerging as promising strategies for autoimmunity, inflammation, and cancer treatment. By precisely fine-tuning Th17-related pathways, we may unlock new avenues for personalized therapeutic approaches, aiming to restore immune balance, alleviate the challenges of these disorders, and ultimately enhance the quality of life for individuals affected by them.

The impact on colostrum oxidative stress, cytokines, and immune cells composition after SARS-CoV-2 infection during pregnancy

Background

Limited data are available regarding the differences between immunological, biochemical, and cellular contents of human colostrum following maternal infection during pregnancy with coronavirus 2 disease (COVID-19).

Objective

To investigate whether maternal COVID-19 infection may affect immunological, biochemical, and cellular contents of human colostrum.

Methods

Using a case-control study design, we collected colostrum from 14 lactating women with a previous diagnosis of COVID-19 during pregnancy and 12 without a clear diagnosis during September 2020 to May 2021. Colostrum samples were analysed for some enzymes and non-enzymatic oxidative stress markers (SOD, CAT, GPx, MDA, GSH, GSSG, H2O2, MPO) and for IL-1β, IL-6, tumour necrosis factor (TNF)-α, protein induced by interferon gamma (IP)-10, IL-8, IFN-λ1, IL12p70, IFN-α2, IFN-λ2/3, granulocyte macrophage colony stimulating factor (GM-CSF), IFN-β, IL-10 and IFN-γ, along with IgA and IgG for the SARS-CoV-2 S protein. We perform immunophenotyping to assess the frequency of different cell types in the colostrum.

Results

Colostrum from the COVID-19 symptomatic group in pregnancy contained reduced levels of H2O2, IFN-α2, and GM-CSF. This group had higher levels of GSH, and both NK cell subtypes CD3-CD56brightCD16-CD27+IFN-γ+ and CD3-CD56dimCD16+CD27- were also increased.

Conclusion

The present results reinforce the protective role of colostrum even in the case of mild SARS-Cov-2 infection, in addition to demonstrating how adaptive the composition of colostrum is after infections. It also supports the recommendation to encourage lactating women to continue breastfeeding after COVID-19 illness.

Dendritic Cell-Based Vaccines Against Cancer: Challenges, Advances and Future Opportunities

As the most potent professional antigen presenting cells, dendritic cells (DCs) have the ability to activate both naive CD4 and CD8 T cells. Recognized for their exceptional ability to cross-present exogenous antigens to prime naive antigen-specific CD8 T cells, DCs play a critical role in generating CD8 T cell immunity, as well as mediating CD8 T cell tolerance to tumor antigens. Despite the ability to potentiate host CD8 T cell-mediated anti-tumor immunity, current DC-based cancer vaccines have not yet achieved the promised success clinically with the exception of FDA-approved Provenge. Interestingly, recent studies have shown that type 1 conventional DCs (cDC1s) play a critical role in cross-priming tumor-specific CD8 T cells and determining the anti-tumor efficacy of cancer immunotherapies including immune checkpoint blockade (ICB). Together with promising clinical results in neoantigen-based cancer vaccines, there is a great need for DC-based vaccines to be further developed and refined either as monotherapies or in combination with other immunotherapies. In this review, we will present a brief review of DC development and function, discuss recent progress, and provide a perspective on future directions to realize the promising potential of DC-based cancer vaccines.

Plasmacytoid Dendritic Cells, a Novel Target in Myeloid Neoplasms

Plasmacytoid dendritic cells (pDC) are the main type I interferon producing cells in humans and are able to modulate innate and adaptive immune responses. Tumor infiltration by plasmacytoid dendritic cells is already well described and is associated with poor outcomes in cancers due to the tolerogenic activity of pDC. In hematological diseases, Blastic Plasmacytoid Dendritic Cells Neoplasm (BPDCN), aggressive leukemia derived from pDCs, is well described, but little is known about tumor infiltration by mature pDC described in Myeloid Neoplasms (MN). Recently, mature pDC proliferation (MPDCP) has been described as a differential diagnosis of BPDCN associated with acute myeloid leukemia (pDC-AML), myelodysplastic syndrome (pDC-MDS) and chronic myelomonocytic leukemia (pDC-CMML). Tumor cells are myeloid blasts and/or mature myeloid cells from related myeloid disorders and pDC derived from a clonal proliferation. The poor prognosis associated with MPDCP requires a better understanding of pDC biology, MN oncogenesis and immune response. This review provides a comprehensive overview about the biological aspects of pDCs, the description of pDC proliferation in MN, and an insight into putative therapies in pDC-AML regarding personalized medicine.

Recent advances in cancer immunotherapy: Modulation of tumor microenvironment by Toll-like receptor ligands

Immunotherapy is considered a promising approach for cancer treatment. An important strategy for cancer immunotherapy is the use of cancer vaccines, which have been widely used for cancer treatment. Despite the great potential of cancer vaccines for cancer treatment, their therapeutic effects in clinical settings have been limited. The main reason behind the lack of significant therapeutic outcomes for cancer vaccines is believed to be the immunosuppressive tumor microenvironment (TME). The TME counteracts the therapeutic effects of immunotherapy and provides a favorable environment for tumor growth and progression. Therefore, overcoming the immunosuppressive TME can potentially augment the therapeutic effects of cancer immunotherapy in general and therapeutic cancer vaccines in particular. Among the strategies developed for overcoming immunosuppression in TME, the use of toll-like receptor (TLR) agonists has been suggested as a promising approach to reverse immunosuppression. In this paper, we will review the application of the four most widely studied TLR agonists including agonists of TLR3, 4, 7, and 9 in cancer immunotherapy.

Tumor Necrosis Factor Receptor 2 (TNFR2): An Emerging Target in Cancer Therapy

Despite the great success of TNF blockers in the treatment of autoimmune diseases and the identification of TNF as a factor that influences the development of tumors in many ways, the role of TNFR2 in tumor biology and its potential suitability as a therapeutic target in cancer therapy have long been underestimated. This has been fundamentally changed with the identification of TNFR2 as a regulatory T-cell (Treg)-stimulating factor and the general clinical breakthrough of immunotherapeutic approaches. However, considering TNFR2 as a sole immunosuppressive factor in the tumor microenvironment does not go far enough. TNFR2 can also co-stimulate CD8⁺ T-cells, sensitize some immune and tumor cells to the cytotoxic effects of TNFR1 and/or acts as an oncogene. In view of the wide range of cancer-associated TNFR2 activities, it is not surprising that both antagonists and agonists of TNFR2 are considered for tumor therapy and have indeed shown overwhelming anti-tumor activity in preclinical studies. Based on a brief summary of TNFR2 signaling and the immunoregulatory functions of TNFR2, we discuss here the main preclinical findings and insights gained with TNFR2 agonists and antagonists. In particular, we address the question of which TNFR2-associated molecular and cellular mechanisms underlie the observed anti-tumoral activities of TNFR2 agonists and antagonists.

GM-CSF is key in the efficacy of vaccine-induced reduction of Helicobacter pylori infection

BACKGROUND

Helicobacter pylori (H. pylori) colonizes the human gastric mucosa with a high worldwide prevalence. Currently, H. pylori is eradicated by the use of antibiotics. However, elevated antibiotic resistance suggests new therapeutic strategies need to be envisioned: one approach being prophylactic vaccination. Pre-clinical and clinical data show that a urease-based vaccine is efficient in decreasing H. pylori infection through the mobilization of T helper (Th) cells, especially Th17 cells. Th17 cells produce interleukins such as IL-22 and IL-17, among others, and are key players in vaccine efficacy. Recently, granulocyte-macrophage colony-stimulating factor (GM-CSF)-producing Th17 cells have been identified.

AIM

This study explores the possibility that GM-CSF plays a role in the reduction of H. pylori infection following vaccination.

RESULTS

We demonstrate that GM-CSF⁺ IL-17⁺ Th17 cells accumulate in the stomach mucosa of H. pylori infected mice during the vaccine-induced reduction of H. pylori infection. Secondly, we provide evidence that vaccinated GM-CSF deficient mice only modestly reduce H. pylori infection. Conversely, we observe that an increase in GM-CSF availability reduces H. pylori burden in chronically infected mice. Thirdly, we show that GM-CSF, by acting on gastric epithelial cells, promotes the production of βdefensin3, which exhibits H. pylori bactericidal activities.

CONCLUSION

Taken together, we demonstrate a key role of GM-CSF, most probably originating from Th17 cells, in the vaccine-induced reduction of H. pylori infection.

Plasmacytoid Dendritic Cells and Cancer Immunotherapy

Despite largely disappointing clinical trials of dendritic cell (DC)-based vaccines, recent studies have shown that DC-mediated cross-priming plays a critical role in generating anti-tumor CD8 T cell immunity and regulating anti-tumor efficacy of immunotherapies. These new findings thus support further development and refinement of DC-based vaccines as mono-immunotherapy or combinational immunotherapies. One exciting development is recent clinical studies with naturally circulating DCs including plasmacytoid DCs (pDCs). pDC vaccines were particularly intriguing, as pDCs are generally presumed to play a negative role in regulating T cell responses in tumors. Similarly, DC-derived exosomes (DCexos) have been heralded as cell-free therapeutic cancer vaccines that are potentially superior to DC vaccines in overcoming tumor-mediated immunosuppression, although DCexo clinical trials have not led to expected clinical outcomes. Using a pDC-targeted vaccine model, we have recently reported that pDCs required type 1 conventional DCs (cDC1s) for optimal cross-priming by transferring antigens through pDC-derived exosomes (pDCexos), which also cross-prime CD8 T cells in a bystander cDC-dependent manner. Thus, pDCexos could combine the advantages of both cDC1s and pDCs as cancer vaccines to achieve better anti-tumor efficacy. In this review, we will focus on the pDC-based cancer vaccines and discuss potential clinical application of pDCexos in cancer immunotherapy.

Dendritic Cell-Targeted Therapies to Treat Neurological Disorders

Dendritic cells (DCs) are the immune system's highly specialized antigen-presenting cells. When DCs are sluggish and mature, self-antigen presentation results in tolerance; however, when pathogen-associated molecular patterns stimulate mature DCs, antigen presentation results in the development of antigen-specific immunity. DCs have been identified in various vital organs of mammals (e.g., the skin, heart, lungs, intestines, and spleen), but the brain has long been thought to be devoid of DCs in the absence of neuroinflammation. However, neuroinflammation is becoming more recognized as a factor in a variety of brain illnesses. DCs are present in the brain parenchyma in trace amounts under healthy circumstances, but their numbers rise during neuroinflammation. New therapeutics are being developed that can reduce dendritic cell immunogenicity by inhibiting pro-inflammatory cytokine production and T cell co-stimulatory pathways. Additionally, innovative ways of regulating dendritic cell growth and differentiation and harnessing their tolerogenic capability are being explored. Herein, we described the function of dendritic cells in neurological disorders and discussed the potential for future therapeutic techniques that target dendritic cells and dendritic cell-related targets in the treatment of neurological disorders.

Bone Marrow Soluble Immunological Mediators as Clinical Prognosis Biomarkers in B-Cell Acute Lymphoblastic Leukemia Patients Undergoing Induction Therapy

Different factors are used as predictors of unfavorable clinical outcomes in B-Cell Acute Lymphoblastic Leukemia (B-ALL) patients. However, new prognostic markers are needed in order to allow treatment to be more accurate, providing better results and an improved quality of life. In the present study, we have characterized the profile of bone marrow soluble mediators as possible biomarkers for risk group stratification and minimal residual disease (MRD) detection during induction therapy. The study featured 47 newly-diagnosed B-cell acute lymphoblastic leukemia (B-ALL) patients that were categorized into subgroups during induction therapy according to risk stratification at day 15 [Low Risk (LR), Low Risk increasing to High Risk (LR→HR) and High Risk (HR)] and the MRD detection on day 35 (MRD^(-) and MRD⁽⁺⁾). Soluble immunological mediators (CXCL8, CCL2, CXCL9, CCL5, CXCL10, IL-1β, IL-6, TNF, IFN-γ, IL-17A, IL-4, IL-5, IL-10 and IL-2) were quantified by cytometric bead array and ELISA. Our findings demonstrated that increased levels of CCL5, IFN-γ and IL-2 at baseline appeared as putative candidates of good prognosis in LR and MRD^(-) subgroups, while CCL2 was identified as a consistent late biomarker associated with poor prognosis, which was observed on D35 in HR and MRD⁽⁺⁾ subgroups. Furthermore, apparently controversial data regarding IL-17A and TNF did not allow the definition of these molecules as either positive or negative biomarkers. These results contribute to the search for novel prognostic indicators, and indicate the potential of bone marrow soluble mediators in prognosis and follow-up of B-ALL patients during induction therapy.

MHC Class II Antigen Presentation by Lymphatic Endothelial Cells in Tumors Promotes Intratumoral Regulatory T cell-Suppressive Functions

Several solid malignancies trigger lymphangiogenesis, facilitating metastasis. Tumor-associated lymphatic vessels significantly contribute to the generation of an immunosuppressive tumor microenvironment (TME). Here, we have investigated the ability of tumoral lymphatic endothelial cells (LEC) to function as MHC class II-restricted antigen-presenting cells in the regulation of antitumor immunity. Using murine models of lymphangiogenic tumors engrafted under the skin, we have shown that tumoral LECs upregulate MHC class II and the MHC class II antigen-processing machinery, and that they promote regulatory T-cell (Treg) expansion ex vivo. In mice with LEC-restricted lack of MHC class II expression, tumor growth was severely impaired, whereas tumor-infiltrating effector T cells were increased. Reduction of tumor growth and reinvigoration of tumor-specific T-cell responses both resulted from alterations of the tumor-infiltrating Treg transcriptome and phenotype. Treg-suppressive functions were profoundly altered in tumors lacking MHC class II in LECs. No difference in effector T-cell responses or Treg phenotype and functions was observed in tumor-draining lymph nodes, indicating that MHC class II-restricted antigen presentation by LECs was required locally in the TME to confer potent suppressive functions to Tregs. Altogether, our study suggests that MHC class II-restricted antigen-presenting tumoral LECs function as a local brake, dampening T cell-mediated antitumor immunity and promoting intratumoral Treg-suppressive functions.

Immunoadjunctive Therapy against Bacterial Infections Using Herbal Medicines Based on Th17 Cell-mediated Protective Immunity

One of the major health concerns in the world is the global increase in intractable bacterial infectious diseases due to the emergence of multi- and extensively drug-resistant bacterial pathogens as well as an increase in compromised hosts around the world. Particularly, in the case of mycobacteriosis, the high incidence of tuberculosis in developing countries, resurgence of tuberculosis in industrialized countries, and increase in the prevalence of Mycobacterium avium complex infections are important worldwide health concerns. However, the development of novel antimycobacterial drugs is currently making slow progress. Therefore, it is considered that devising improved administration protocols for clinical treatment against refractory mycobacteriosis using existing chemotherapeutics is more practical than awaiting the development of new antimycobacterial drugs. The regulation of host immune responses using immunoadjunctive agents may increase the efficacy of antimicrobial treatment against mycobacteriosis. The same situations also exist in cases of intractable infectious diseases due to common bacteria other than mycobacteria. The mild and long-term up-regulation of host immune reactions in hosts with intractable chronic bacterial infections, using herbal medicines and medicinal plants, may be beneficial for such immunoadjunctive therapy. This review describes the current status regarding basic and clinical studies on therapeutic regimens using herbal medicines, useful for the clinical treatment of patients with intractable bacterial infections. In particular, we focus on immunoadjunctive effects of herbal medicines on the establishment and manifestation of host antibacterial immunity related to the immunological roles of Th17 cell lineages.

Plasmacytoid dendritic cells cross-prime naive CD8 T cells by transferring antigen to conventional dendritic cells through exosomes

Although plasmacytoid dendritic cells (pDCs) have been shown to play a critical role in generating viral immunity and promoting tolerance to suppress antitumor immunity, whether and how pDCs cross-prime CD8 T cells in vivo remain controversial. Using a pDC-targeted vaccine model to deliver antigens specifically to pDCs, we have demonstrated that pDC-targeted vaccination led to strong cross-priming and durable CD8 T cell immunity. Surprisingly, cross-presenting pDCs required conventional DCs (cDCs) to achieve cross-priming in vivo by transferring antigens to cDCs. Taking advantage of an in vitro system where only pDCs had access to antigens, we further demonstrated that cross-presenting pDCs were unable to efficiently prime CD8 T cells by themselves, but conferred antigen-naive cDCs the capability of cross-priming CD8 T cells by transferring antigens to cDCs. Although both cDC1s and cDC2s exhibited similar efficiency in acquiring antigens from pDCs, cDC1s but not cDC2s were required for cross-priming upon pDC-targeted vaccination, suggesting that cDC1s played a critical role in pDC-mediated cross-priming independent of their function in antigen presentation. Antigen transfer from pDCs to cDCs was mediated by previously unreported pDC-derived exosomes (pDCexos), that were also produced by pDCs under various conditions. Importantly, all these pDCexos primed naive antigen-specific CD8 T cells only in the presence of bystander cDCs, similarly to cross-presenting pDCs, thus identifying pDCexo-mediated antigen transfer to cDCs as a mechanism for pDCs to achieve cross-priming. In summary, our data suggest that pDCs employ a unique mechanism of pDCexo-mediated antigen transfer to cDCs for cross-priming.

Plasmacytoid dendritic cells in the eye

Plasmacytoid dendritic cells (pDCs) are a unique subpopulation of immune cells, distinct from classical dendritic cells. pDCs are generated in the bone marrow and following development, they typically home to secondary lymphoid tissues. While peripheral tissues are generally devoid of pDCs during steady state, few tissues, including the lung, kidney, vagina, and in particular ocular tissues harbor resident pDCs. pDCs were originally appreciated for their potential to produce large quantities of type I interferons in viral immunity. Subsequent studies have now unraveled their pivotal role in mediating immune responses, in particular in the induction of tolerance. In this review, we summarize our current knowledge on pDCs in ocular tissues in both mice and humans, in particular in the cornea, limbus, conjunctiva, choroid, retina, and lacrimal gland. Further, we will review our current understanding on the significance of pDCs in ameliorating inflammatory responses during herpes simplex virus keratitis, sterile inflammation, and corneal transplantation. Moreover, we describe their novel and pivotal neuroprotective role, their key function in preserving corneal angiogenic privilege, as well as their potential application as a cell-based therapy for ocular diseases.

Cytokine network analysis of immune responses before and after autologous dendritic cell and tumor cell vaccine immunotherapies in a randomized trial

Background

In a randomized phase II trial conducted in patients with metastatic melanoma, patient-specific autologous dendritic cell vaccines (DCV) were associated with longer survival than autologous tumor cell vaccines (TCV). Both vaccines presented antigens from cell-renewing autologous tumor cells. The current analysis was performed to better understand the immune responses induced by these vaccines, and their association with survival.

Methods

110 proteomic markers were measured at a week-0 baseline, 1 week before the first of 3 weekly vaccine injections, and at week-4, 1 week after the third injection. Data was presented as a deviation from normal controls. A two-component principal component (PC) statistical analysis and discriminant analysis were performed on this data set for all patients and for each treatment cohort.

Results

At baseline PC-1 contained 64.4% of the variance and included the majority of cytokines associated with Th1 and Th2 responses, which positively correlated with beta-2-microglobulin (B2M), programmed death protein-1 (PD-1) and transforming growth factor beta (TGFβ1). Results were similar at baseline for both treatment cohorts. After three injections, DCV-treated patients showed correlative grouping among Th1/Th17 cytokines on PC-1, with an inverse correlation with B2M, FAS, and IL-18, and correlations among immunoglobulins in PC-2. TCV-treated patients showed a positive correlation on PC-1 among most of the cytokines and tumor markers B2M and FAS receptor. There were also correlative changes of IL12p40 with both Th1 and Th2 cytokines and TGFβ1. Discriminant analysis provided additional evidence that DCV was associated with innate, Th1/Th17, and Th2 responses while TCV was only associated with innate and Th2 responses.

Conclusions

These analyses confirm that DCV induced a different immune response than that induced by TCV, and these immune responses were associated with improved survival.

Trial registration Clinical trials.gov NCT004936930 retrospectively registered 28 July 2009

A C-type CpG ODN accelerates wound healing via regulating fibroblasts and immune response

Abolished or delayed wound healing is a serious problem in clinical surgery, therefore, the new therapy for wound healing is needed. Synthetic oligodeoxynucleotides containing one or more CpG motifs (CpG ODN) has been reported to activate the immune system and improves skin wound healing. The aim of the present study was to evaluate the role of a new C-type CpG ODN in wound healing. We found that the CpG ODN promoted cell proliferation and collagen I production in human skin fibroblasts cells. Besides, we also investigated the effect of CpG ODN on the activation of immune cells. The macrophages and plasmacytoid dendritic cells (pDCs) were incubated with CpG ODN. CpG ODN activated macrophage and pDCs via regulating TLR9/MyD88/NF-κB pathway and TLR9/MyD88/IRF7 pathway, respectively. To further evaluate the effect of CpG ODN on wound healing in vivo a wound healing model was established in mice. The results showed that CpG ODN treatment accelerated wound healing in mice. CpG ODN increased cytokines secretion in wound skin and elevated the ratio of CD4 ⁺ and CD8 ⁺ T cells in the spleen. Our results showed that CpG ODN accelerated wound healing, which was partly due to the regulation of fibroblasts and immune response. The findings suggested that the CpG ODN might be a proper medicament for the treatment of wound healing.

pDC Activation by TLR7/8 Ligand CL097 Compared to TLR7 Ligand IMQ or TLR9 Ligand CpG

Plasmacytoid dendritic cells (pDCs) express high levels of the toll-like receptors (TLRs) TLR7 and TLR9. In response to TLR7 and TLR9 ligands, pDCs are primary producers of type I interferons. Our previous study demonstrated that pDCs activated by the TLR7 ligand imiquimod (IMQ) and the TLR9 ligand CpG A can kill breast cancer cells in vitro and inhibit tumor growth in vivo. Moreover, we observed a distinctive morphological, phenotypic change in pDCs after activation by IMQ and CpG A. However, the effect of other TLR7 and TLR9 ligands on pDCs remains less understood. In this study, we treat pDCs with the TLR7 ligand IMQ, TLR7/8 ligands (CL097 and CL075), and three TLR9 ligands (different types of CpGs). The size of pDCs increased significantly after activation by TLR7, or TLR7/8 ligands. TLR7, TLR7/8, and TLR9 ligands similarly modulated cytokine release, as well as protein expression of pDC markers, costimulatory molecules, and cytotoxic molecules. Interestingly, TLR7/8 ligands, especially CL097, induced stronger responses. These results are relevant to the further study of the role and mechanism of pDC-induced antitumor effects and may aid in the development of a new strategy for future tumor immunotherapy.

The role of T helper 17 and regulatory T cells in tumor microenvironment

T helper 17 (Th17) cells were first described as a novel T helper cell lineage independent from Th1 and Th2 subsets. Th17 cells play vital roles in inflammation and tumor immunity. It causes the dissipation of antitumor immunity and contribution to the survival of tumor cells, worsening tumor growth and metastasis. Tumor-infiltrating Th17 cells were seen innumerous cancers in mice and humans. There has been an association between intratumoral Th17 cell infiltration and both good and bad prognoses. Besides the protumoral roles defined for IL-17 andTh17 cells, several reports have shown that Th17 cells also drive antitumoral immunity. Various mechanisms by which Th17 cells control tumor growth are as following: recruitment of several immune cells including DCs, CD4⁺ T cells, and CD8⁺ T cells within tumors, activation of CD8⁺ T cells, and probably plasticity toward Th1 phenotype, related to IFN-γ and TNF-α production. Regulatory T cells (Tregs) have been exhibited to infiltrate human tumors and are believed to restrict antitumor immunity. The effect of Treg cells has been more controversial. Whereas some studies have proposed that a high density of Treg cells within the tumor associated with a poor clinical prognosis, other studies have presented a positive clinical prognosis, underlining the importance of elucidating the clinical significance of Treg cells further. Treg and Th17 cells play both positive and negative roles in regulating antitumor immune responses. In spite of the presence of these cells, yet some tumors develop and grow. These T cells by themselves are not adequate to efficiently mount antitumor immune responses.

The Role of Plasmacytoid Dendritic Cells in Gut Health

Plasmacytoid dendritic cells (pDCs) are a unique subset of cells with different functional characteristics compared to classical dendritic cells. The pDCs are critical for the production of type I IFN in response to microbial and self-nucleic acids. They have an important role for host defense against viral pathogen infections. In addition, pDCs have been well studied as a critical player for breaking tolerance to self-nucleic acids that induce autoimmune disorders such as systemic lupus erythematosus. However, pDCs have an immunoregulatory role in inducing the immune tolerance by generating Tregs and various regulatory mechanisms in mucosal tissues. Here, we summarize the recent studies of pDCs that focused on the functional characteristics of gut pDCs, including interactions with other immune cells in the gut. Furthermore, the dynamic role of gut pDCs will be investigated with respect to disease status including gut infection, inflammatory bowel disease, and cancers.

Extended Freeze-Dried BCG Instructed pDCs Induce Suppressive Tregs and Dampen EAE

Several clinical observations have shown that Bacillus Calmette-Guérin (BCG) vaccine has beneficial impact on patients suffering from different chronic inflammatory diseases. Here we evaluated whether BCG inactivated by Extended Freeze-Drying (EFD) which circumvents all the side effects linked to the live bacteria, could influence the development of experimental autoimmune encephalomyelitis (EAE), a mouse model for Multiple Sclerosis. EFD BCG strongly attenuates inflammation, both systemically and at the central nervous system (CNS) level, alleviating EAE. Mechanistically, EFD BCG directly impacts the phenotype of plasmacytoid dendritic cells (pDCs), and promotes their ability to induce suppressive IL-10 secreting regulatory T cells (Tregs) that inhibit encephalitogenic CD4⁺ T cells. When co-cultured with human allogenic naive CD4⁺ T cells, EFD BCG exposed human pDCs similarly induce the differentiation of IL-10 producing Tregs. Our study provides evidence that EFD BCG could be used as an immunomodulator of encephalitogenic T cells in multiple sclerosis patients.

Warming up the tumor microenvironment in order to enhance immunogenicity

We have recently demonstrated that intratumoral CpG-B vaccination enhances anti-tumor immunity and tumor regression in mice. We further show that the local delivery of TLR9 agonists converts the tolerogenic tumor microenvironment into an immunopermissive one, which may benefit current immunotherapeutic anticancer strategies by enhancing innate and adaptive tumor-associated immune cell responses.

Intratumoral CpG-B Promotes Antitumoral Neutrophil, cDC, and T-cell Cooperation without Reprograming Tolerogenic pDC

Cancer immunotherapies utilize distinct mechanisms to harness the power of the immune system to eradicate cancer cells. Therapeutic vaccines, aimed at inducing active immune responses against an existing cancer, are highly dependent on the immunological microenvironment, where many immune cell types display high levels of plasticity and, depending on the context, promote very different immunologic outcomes. Among them, plasmacytoid dendritic cells (pDC), known to be highly immunogenic upon inflammation, are maintained in a tolerogenic state by the tumor microenvironment. Here, we report that intratumoral (i.t.) injection of established solid tumors with CpG oligonucleotides-B (CpG-B) inhibits tumor growth. Interestingly, control of tumor growth was independent of tumor-associated pDC, which remained refractory to CpG-B stimulation and whose depletion did not alter the efficacy of the treatment. Instead, tumor growth inhibition subsequent to i.t. CpG-B injection depended on the recruitment of neutrophils into the milieu, resulting in the activation of conventional dendritic cells, subsequent increased antitumor T-cell priming in draining lymph nodes, and enhanced effector T-cell infiltration in the tumor microenvironment. These results reinforce the concept that i.t. delivery of TLR9 agonists alters the tumor microenvironment by improving the antitumor activity of both innate and adaptive immune cells.Significance: Intratumoral delivery of CpG-B disrupts the tolerogenic tumor microenvironment and inhibits tumor growth. Cancer Res; 78(12); 3280-92. ©2018 AACR.

Activation and selective IL-17 response of human Vγ9Vδ2 T lymphocytes by TLR-activated plasmacytoid dendritic cells

Vγ9Vδ2 T cells and plasmacytoid dendritic cells (pDCs) are two distinct cell types of innate immunity that participate in early phases of immune response. We investigated whether a close functional relationship exists between these two cell populations using an in vitro co-culture in a human system.

pDCs that had been activated by IL-3 and the TLR9 ligand CpG induced substantial activation of Vγ9Vδ2 T cells upon co-culture, which was cell-to-cell contact dependent, as demonstrated in transwell experiments, but that did not involve any of the costimulatory molecules potentially expressed by pDCs or Vγ9V2 T cells, such as ICOS-L, OX40 and CD40L. Activated pDCs selectively induced IL-17, but not IFN-γ, responses of Vγ9Vδ2T cells, which was dominant over the antigen-induced response, and this was associated with the expansion of memory (both central and effector memory) subsets of Vγ9Vδ2 T cells.

Overall, our results provide a further piece of information on the complex relationship between these two populations of cells with innate immunity features during inflammatory responses.

Immunization with HER2 extracellular subdomain proteins induces cellular response and tumor growth inhibition in mice

AIM

We investigated cellular and protective immune responses in mice vaccinated with recombinant HER2 extracellular subdomains.

MATERIALS & METHODS

Balb/C mice were immunized with recombinant full HER2 extracellular domain and subdomain proteins. Humoral and cellular immune response and antitumor effect was evaluated using a syngeneic mice tumor model.

RESULTS

All recombinant proteins induced secretion of IL-4 and particularly IFN-γ and IL-17 cytokines. Challenging of immunized mice with stable 4T1-HER2 transfected cells resulted in partial but significant tumor growth inhibition in all groups of mice particularly those immunized with fHER2-ECD together with CPG.

CONCLUSION

Our results suggest that the recombinant HER2-ECD subdomains induce mainly Th1 and Th17 responses, which seem to contribute to tumor growth inhibition in syngeneic mice.

Exosomes from heat-stressed tumour cells inhibit tumour growth by converting regulatory T cells to Th17 cells via IL-6

Exosomes derived from heat-stressed tumour cells (HS-TEXs), which contain abundant heat shock protein (HSP) 70, strongly induce antitumour immune responses. HSP70-induced interleukin (IL)-6 promotes IL-17 expression and causes rejection of established prostate tumours. However, it remains unclear whether HS-TEXs exhibit antitumour effects by converting regulatory T cells (T_regs ) into T helper type 17 (Th17) cells. In this study, we found that compared with TEXs, HS-TEXs were more potent in stimulating secretion of IL-6 from dendritic cells. In vitro, IL-6 blocked tumour cell-derived transforming growth factor beta 1-induced T_reg differentiation and promoted Th17 cell differentiation. HS-TEXs exerted strong antitumour effects, converting T_regs into Th17 cells with high efficiency, a process that was entirely dependent upon IL-6. Neutralization of IL-17 completely abolished the antitumour effect of TEXs, but only partially inhibited that of HS-TEXs. In addition, we found higher levels of IL-6 and IL-17 in serum from tumour patients treated with hyperthermia, and an increase in Th17 cells and a decrease in T_regs was detected in peripheral blood mononuclear cells isolated from these patients after hyperthermia. Therefore, our results demonstrate that HS-TEXs possess a powerful capacity to convert immunosuppressive T_regs into Th17 cells via IL-6, which contributes to their potent antitumour effect.

Blockade of TNFR2 signaling enhances the immunotherapeutic effect of CpG ODN in a mouse model of colon cancer

Through the tumor necrosis factor (TNF) receptor type II (TNFR2), TNF preferentially activates, expands, and promotes the phenotypic stability of CD4⁺Foxp3⁺ regulatory T (T_reg) cells. Those T_reg cells that have a high abundance of TNFR2 have the maximal immunosuppressive capacity. We investigated whether targeting TNFR2 could effectively suppress the activity of T_reg cells and consequently enhance the efficacy of cancer immunotherapy. We found that, relative to a suboptimal dose of the immunostimulatory Toll-like receptor 9 ligand CpG oligodeoxynucleotide (ODN), the combination of the suboptimal dose of CpG ODN with the TNFR2-blocking antibody M861 more markedly inhibited the growth of subcutaneously grafted mouse CT26 colon tumor cells. This resulted in markedly fewer TNFR2⁺ T_reg cells and more interferon-γ-positive (IFN-γ⁺) CD8⁺ cytotoxic T lymphocytes infiltrating the tumor and improved long-term tumor-free survival in the mouse cohort. Tumor-free mice were resistant to rechallenge by the same but not unrelated (4T1 breast cancer) cells. Treatment with the combination of TNFR2-blocking antibody and a CD25-targeted antibody also resulted in enhanced inhibition of tumor growth in a syngeneic 4T1 mouse model of breast cancer. Thus, the combination of a TNFR2 inhibitor and an immunotherapeutic stimulant may represent a more effective treatment strategy for various cancers.

Protective effects of CpG-ODN 2007 administration against Edwardsiella tarda infection in olive flounder (Paralichthys olivaceus)

In this study, we investigated the immunostimulatory and protective effects of CpG motif oligonucleotides (CpG-ODNs) against Edwardsiella tarda infection in olive flounder (Paralichthys olivaceus). Groups of fish injected with CpG-ODNs (1585, 1668, and 2007) or PBS (control) showed varying mortality rates in response to challenge with E. tarda. The survival rates of fish treated with CpG-ODN 1668 and 2007, which belonged to the same class type B, were 45% and 60%, respectively, with CpG-ODN 2007 showing the highest survival rate. Further analysis showed that the respiratory burst and bactericidal activities induced by CpG-ODN 2007 were higher than those in the control group (induced by non-CpG-ODNs) or in the group of fish induced by CpG-ODN 1585, which belonged to class type A. Additionally, the respiratory burst activity induced by CpG-ODN 2007 was higher than that induced by CpG-ODN 1668, despite similar bactericidal activity titers. In vivo experiments showed that CpG-ODN 2007 stimulation resulted in higher survival rates than CpG-ODN 1668 stimulation, possibly owing to differences in respiratory burst activity. In summary, we demonstrated that differences in CpG-motif or class type altered respiratory burst and bactericidal activities, resulting in differences in survival rates against E. tarda challenge in the olive flounder. Therefore, it is necessary to use CpG-ODNs optimized against E. tarda infection in olive flounder, because different CpG motifs belonging to the same class type have different effects.

TLR-activated plasmacytoid dendritic cells inhibit breast cancer cell growth in vitro and in vivo

Plasmacytoid dendritic cells (pDCs) are a unique subset of naturally occurring dendritic cells, which triggers the production of large amounts of type I interferons (IFNs) after viral infections through Toll-like receptor (TLR) 7 and TLR9. Recent studies have demonstrated that the activation of pDCs kills melanoma cells. However, the role of activated pDCs in breast cancer remains to be determined. In the present study, we generated mouse models of breast cancer and demonstrated that activated pDCs can directly kill breast tumor cells through TRAIL and Granzyme B. Furthermore, we established that pDCs initiate the sequential activation of NK cells and CD8⁺ T cells, and ultimately inhibit breast tumor growth. Understanding the role of activated pDCs in breast cancer may help to develop new strategies for manipulating the function of pDCs and induce anti-tumor immunity in breast cancer.

Regulatory Dendritic Cells

Dendritic cells (DCs) comprise heterogeneous subsets, functionally classified into conventional DCs (cDCs) and plasmacytoid DCs (pDCs). DCs are considered to be essential antigen (Ag)-presenting cells (APCs) that play crucial roles in activation and fine-tuning of innate and adaptive immunity under inflammatory conditions, as well as induction of immune tolerance to maintain immune homeostasis under steady-state conditions. Furthermore, DC functions can be modified and influenced by stimulation with various extrinsic factors, such as ligands for pattern-recognition receptors (PRRs) and cytokines. On the other hand, treatment of DCs with certain immunosuppressive drugs and molecules leads to the generation of tolerogenic DCs that show downregulation of both the major histocompatibility complex (MHC) and costimulatory molecules, and not only show defective T-cell activation, but also possess tolerogenic properties including the induction of anergic T-cells and regulatory T (T_reg) cells. To develop an effective strategy for Ag-specific intervention of T-cell-mediated immune disorders, we have previously established the modified DCs with moderately high levels of MHC molecules that are defective in the expression of costimulatory molecules that had a greater immunoregulatory property than classical tolerogenic DCs, which we therefore designated as regulatory DCs (DC_reg). Herein, we integrate the current understanding of the role of DCs in the control of immune responses, and further provide new information of the characteristics of tolerogenic DCs and DC_reg, as well as their regulation of immune responses and disorders.

IDO-orchestrated crosstalk between pDCs and Tregs inhibits autoimmunity

Plasmacytoid dendritic cells (pDCs) have been shown to both mediate and prevent autoimmunity, and the regulation of their immunogenic versus tolerogenic functions remains incompletely understood. Here we demonstrate that, compared to other cells, pDCs are the major expressors of Indoleamine-2,3-dioxygenase (IDO) in steady-state lymph nodes (LNs). IDO expression by LN pDCs was closely dependent on MHCII-mediated, antigen-dependent, interactions with Treg. We further established that IDO production by pDCs was necessary to confer suppressive function to Tregs. During EAE development, IDO expression by pDCs was required for the generation of Tregs capable of dampening the priming of encephalitogenic T cell and disease severity. Thus, we describe a novel crosstalk between pDCs and Tregs: Tregs shape tolerogenic functions of pDCs prior to inflammation, such that pDCs in turn, promote Treg suppressive functions during autoimmunity.

Increased Th17 cells and IL-17A exist in patients with B cell acute lymphoblastic leukemia and promote proliferation and resistance to daunorubicin through activation of Akt signaling

BACKGROUND

Immune regulation is crucial for the pathogenesis of B-cell acute lymphoblastic leukemia (B-ALL). It has been reported that Th17 cells as a newly identified subset of CD4(+) T cells are involved in the pathogenesis of several hematological disorders. However, the role of Th17 cells in the pathophysiology of B-ALL is still unclear.

METHODS

The frequencies of T cells were determined by flow cytometry in the peripheral blood and bone marrow of 44 newly diagnosed B-ALL patients and 25 age-matched healthy donors. The cell viability and apoptosis were determined by CCK-8 assay and Annexin V staining, respectively. Western blot was applied to identify the level of Akt and Stat3 phosphorylation.

RESULTS

We assessed and observed a significantly increased frequency of Th17 cells and a drastically decreased frequency of Th1 cells in peripheral blood mononuclear cells and bone marrow mononuclear cells from newly diagnosed B-ALL patients compared with healthy donors. Furthermore, increased levels of Th17-related cytokines including IL-17, IL-21, IL-23, IL-1β, and IL-6 were presented in between blood and marrow in B-ALL patients. Both IL-17A and IL-21, two Th17-secreted cytokines, induced the proliferation of B-ALL cell line Nalm-6 and patient B-ALL cells isolated from B-ALL patients, herein either cytokine led to the phosphorylation of Akt and Stat3. Additionally, IL-17A promoted resistance to daunorubicin via activation of Akt signaling and the PI3K/Akt inhibitor LY294002 or perifosine almost completely rescued daunorubicin-induced cell death in B-ALL cells.

CONCLUSIONS

Our findings suggest that elevated Th17 cells secrete IL-17A by which promotes the proliferation and resistance to daunorubicin in B-ALL cells through activation of Akt signaling. Th17 cells may represent a novel target to improve B-ALL immunotherapy.

Plasmacytoid dendritic cells orchestrate TLR7-mediated innate and adaptive immunity for the initiation of autoimmune inflammation

Endosomal toll-like receptor (TLR)-mediated detection of viral nucleic acids (NAs) and production of type I interferon (IFN-I) are key elements of antiviral defense, while inappropriate recognition of self NAs with the induction of IFN-I responses is linked to autoimmunity such as psoriasis and systemic lupus erythematosus. Plasmacytoid dendritic cells (pDCs) are cells specialized in robust IFN-I secretion by the engagement of endosomal TLRs, and predominantly express sialic acid-binding Ig-like lectin (Siglec)-H. However, how pDCs control endosomal TLR-mediated immune responses that cause autoimmunity remains unclear. Here we show a critical role of pDCs in TLR7-mediated autoimmunity using gene-modified mice with impaired expression of Siglec-H and selective ablation of pDCs. pDCs were shown to be indispensable for the induction of systemic inflammation and effector T-cell responses triggered by TLR7 ligand. pDCs aggravated psoriasiform dermatitis mediated through the hyperproliferation of keratinocytes and enhanced dermal infiltration of granulocytes and γδ T cells. Furthermore, pDCs promoted the production of anti-self NA antibodies and glomerulonephritis in lupus-like disease by activating inflammatory monocytes. On the other hand, Siglec-H regulated the TLR7-mediated activation of pDCs. Thus, our findings reveal that pDCs provide an essential link between TLR7-mediated innate and adaptive immunity for the initiation of IFN-I-associated autoimmune inflammation.

Th17 Cell Plasticity and Functions in Cancer Immunity

Th17 cells represent a particular subset of T helper lymphocytes characterized by high production of IL-17 and other inflammatory cytokines. Th17 cells participate in antimicrobial immunity at mucosal and epithelial barriers and particularly fight against extracellular bacteria and fungi. While a role for Th17 cells in promoting inflammation and autoimmune disorders has been extensively and elegantly demonstrated, it is still controversial whether and how Th17 cells influence tumor immunity. Although Th17 cells specifically accumulate in many different types of tumors compared to healthy tissues, the outcome might however differ from a tumor type to another. Th17 cells were consequently associated with both good and bad prognoses. The high plasticity of those cells toward cells exhibiting either anti-inflammatory or in contrast pathogenic functions might contribute to Th17 versatile functions in the tumor context. On one hand, Th17 cells promote tumor growth by inducing angiogenesis (via IL-17) and by exerting themselves immunosuppressive functions. On the other hand, Th17 cells drive antitumor immune responses by recruiting immune cells into tumors, activating effector CD8(+) T cells, or even directly by converting toward Th1 phenotype and producing IFN-γ. In this review, we are discussing the impact of the tumor microenvironment on Th17 cell plasticity and function and its implications in cancer immunity.

pDC therapy induces recovery from EAE by recruiting endogenous pDC to sites of CNS inflammation

Plasmacytoid dendritic cells (pDCs) exhibit both innate and adaptive functions. In particular they are the main source of type I IFNs and directly impact T cell responses through antigen presentation. We have previously demonstrated that during experimental autoimmune encephalomyelitis (EAE) initiation, myelin-antigen presentation by pDCs is associated with suppressive Treg development and results in attenuated EAE. Here, we show that pDCs transferred during acute disease phase confer recovery from EAE. Clinical improvement is associated with migration of injected pDCs into inflamed CNS and is dependent on the subsequent and selective chemerin-mediated recruitment of endogenous pDCs to the CNS. The protective effect requires pDC pre-loading with myelin antigen, and is associated with the modulation of CNS-infiltrating pDC phenotype and inhibition of CNS encephalitogenic T cells. This study may pave the way for novel pDC-based cell therapies in autoimmune diseases, aiming at specifically modulating pathogenic cells that induce and sustain autoimmune inflammation.

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pDC therapy ameliorates established EAE.

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CNS inflammation is locally modulated after pDC transfer.

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Upon pDC transfer, resting endogenous pDCs are selectively recruited to the CNS via chemerin/CMKLR1 axis.

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Therapeutic pDC injection promotes a tolerogenic environment and inhibits encephalitogenic T cells in the CNS.

Targeting C-Type Lectin Receptors for Cancer Immunity

C-type lectin receptors (CLRs) are a large family of soluble and trans-membrane pattern recognition receptors that are widely and primarily expressed on myeloid cells. CLRs are important for cell-cell communication and host defense against pathogens through the recognition of specific carbohydrate structures. Similar to a family of Toll-like receptors, CLRs signaling are involved in the various steps for initiation of innate immune responses and promote secretion of soluble factors such as cytokines and interferons. Moreover, CLRs contribute to endocytosis and antigen presentation, thereby fine-tune adaptive immune responses. In addition, there may also be a direct activation of acquired immunity. On the other hand, glycans, such as mannose structures, Lewis-type antigens, or GalNAc are components of tumor antigens and ligate CLRs, leading to immunoregulation. Therefore, agonists or antagonists of CLRs signaling are potential therapeutic reagents for cancer immunotherapy. We aim to overview the current knowledge of CLRs signaling and the application of their ligands on tumor-associating immune response.

Harnessing the Therapeutic Potential of Th17 Cells

Th17 cells provide protective immunity to infections by fungi and extracellular bacteria as well as cancer but are also involved in chronic inflammation. The cells were first identified by their ability to produce interleukin 17A (IL-17A) and, subsequently, associated with chronic inflammation and autoimmunity. Th17 cells have some gene profile similarity with stem cells and can remain dormant in mucosal tissues for long periods. Indeed, recent studies suggest that functionally distinct subsets of pro- and anti-inflammatory Th17 cells can interchange phenotype and functions. For development, Th17 cells require activation of the transcription factors STAT3 and RORγt while RUNX1, c-Maf, and Aiolos are involved in changes of phenotype/functions. Attempts to harness Th17 cells against pathogens and cancer using vaccination strategies are being explored. The cells gain protective abilities when induced to produce interferon γ (IFNγ). In addition, treatment with antibodies to IL-17 is effective in treating patients with psoriasis, psoriatic arthritis, and refectory rheumatoid arthritis. Moreover, since RORγt is a nuclear receptor, it is likely to be a potential future drug target for modulating Th17 functions. This review explores pathways through which Th17 subsets are induced, the molecular basis of their plasticity, and potential therapeutic strategies for their modulation in diseases.

Dendritic cell-based vaccination in cancer: therapeutic implications emerging from murine models

Dendritic cells (DCs) play a pivotal role in the orchestration of immune responses, and are thus key targets in cancer vaccine design. Since the 2010 FDA approval of the first cancer DC-based vaccine (Sipuleucel-T), there has been a surge of interest in exploiting these cells as a therapeutic option for the treatment of tumors of diverse origin. In spite of the encouraging results obtained in the clinic, many elements of DC-based vaccination strategies need to be optimized. In this context, the use of experimental cancer models can help direct efforts toward an effective vaccine design. This paper reviews recent findings in murine models regarding the antitumoral mechanisms of DC-based vaccination, covering issues related to antigen sources, the use of adjuvants and maturing agents, and the role of DC subsets and their interaction in the initiation of antitumoral immune responses. The summary of such diverse aspects will highlight advantages and drawbacks in the use of murine models, and contribute to the design of successful DC-based translational approaches for cancer treatment.

CpG Oligonucleotides as Cancer Vaccine Adjuvants

Adjuvants improve host responsiveness to co-delivered vaccines through a variety of mechanisms. Agents that trigger cells expressing Toll-like receptors (TLR) activate an innate immune response that enhances the induction of vaccine-specific immunity. When administered in combination with vaccines designed to prevent or slow tumor growth, TLR agonists have significantly improved the generation of cytotoxic T lymphocytes. Unfortunately, vaccines containing TLR agonists have rarely been able to eliminate large established tumors when administered systemically. To improve efficacy, attention has focused on delivering TLR agonists intra-tumorally with the intent of altering the tumor microenvironment. Agonists targeting TLRs 7/8 or 9 can reduce the frequency of Tregs while causing immunosuppressive MDSC in the tumor bed to differentiate into tumoricidal macrophages thereby enhancing tumor elimination. This work reviews pre-clinical and clinical studies concerning the utility of TLR 7/8/9 agonists as adjuvants for tumor vaccines.

New role for antigen-presenting activated pDCs in promoting Th17 cells and impacting antitumor immunity

Plasmacytoid dendritic cells (pDCs) are not only potent inflammatory cytokine producers but also function as antigen-presenting cells (APCs). We have shown that vaccination using CpG-B activated tumor antigen (Ag) presenting pDCs induce Th17 cells that promote intratumoral immune cell recruitment, including antitumor cytotoxic T lymphocytes CTLs. Therefore, strategies targeting both innate and adaptive pDC functions may improve antitumor T-cell immunity.