Effective antigen presentation by dendritic cells is NF-kappaB dependent: coordinate regulation of MHC, co-stimulatory molecules and cytokines

Pyrimethamine treatment in breast cancer lysate-loaded dendritic cells promotes autologous T cells' anti-tumor responses in vitro

BACKGROUND

Suppressing inhibitory molecules such as signal transducer and activator of transcription (STAT) 3 in dendritic cells (DCs) and eliciting an effective immune response via T cells against antigens (Ags) produced exclusively by malignant cells represents the major method in the process of DC-based vaccines. Pyrimethamine (Pyri), a potential STAT3 inhibitor, is an antimalarial drug that is employed for ameliorating various cancers, including breast cancer. The present study aimed to investigate T cell-mediated responses after DCs and T cells co-culturing using breast cancer lysate (BCL) and Pyri to inhibit STAT3 protein in the DCs for the first time.

METHOD

Employing the Magnetic Activated Cell Sorting (MACS) technique, monocytes were separated from peripheral blood mononuclear cells (PBMCs). After monocytes were differentiated into DCs, they were divided into two groups: mature dendritic cells (mDCs) (received lipopolysaccharide (LPS) and BCL) and Pyrimethamine-treated mature dendritic cells (Pyri-mDCs) (incubated with LPS, BCL, and Pyri). Flow cytometry was used to examine the surface markers related to DC phenotype in both groups of DCs. Consequently, RT-PCR was employed to investigate the expression of genes linked to inflammatory and anti-inflammatory cytokines in mDCs and Pyri-mDCs as well as related genes to T cell response after DC/T cell co-culturing.

RESULTS

Our outcomes revealed that Pyri-mediated STAT3 inhibition in DCs upregulates and downregulates the expression of inflammatory and anti-inflammatory cytokines' genes. Furthermore, co-culture of Pyri-mDCs with autologous T cells downregulated T helper (Th) 2 and regulatory T cell (Treg) responses and augmented Th1 activation compared to T cell cultured along with mDCs.

CONCLUSION

Overall, our research points to Pyri-mediated STAT3 suppression in DCs loaded with BCL as a potentially effective therapeutic method for inducing effective T cell responses; nevertheless, additional investigation is required to evaluate the effectiveness of this approach especially in pre-clinical settings.

Emulsion adjuvant-induced uric acid release modulates optimal immunogenicity by targeting dendritic cells and B cells

Squalene-based emulsion (SE) adjuvants like MF59 and AS03 are used in protein subunit vaccines against influenza virus (e.g., Fluad, Pandemrix, Arepanrix) and SARS-CoV-2 (e.g., Covifenz, SKYCovione). We demonstrate the critical role of uric acid (UA), a damage-associated molecular pattern (DAMP), in triggering immunogenicity by SE adjuvants. In mice, SE adjuvants elevated DAMP levels in draining lymph nodes. Strikingly, inhibition of UA synthesis reduced vaccine-induced innate immunity, subsequently impairing optimal antibody and T cell responses. In vivo treatment with UA crystals elicited partial adjuvant effects. In vitro stimulation with UA crystals augmented the activation of dendritic cells (DCs) and B cells and altered multiple pathways in these cells, including inflammation and antigen presentation in DCs and cell proliferation in B cells. In an influenza vaccine model, UA contributed to protection against influenza viral infection. These results demonstrate the importance of DAMPs, specifically the versatile role of UA in the immunogenicity of SE adjuvants, by regulating DCs and B cells.

WHOLE TRANSCRIPTION ANALYSIS IDENTIFIED THE REGULATION OF HYPOXIA-INDUCIBLE FACTORS IN MONOCYTES WITH IMMUNE SUPPRESSION: IMPLICATIONS FOR CLINICAL OUTCOMES

ABSTRACT

Aims: Sepsis progression is marked by a complex immune response, where the involvement of hypoxia-inducible factors (HIFs) plays an uncertain role. The study aims to elucidate the involvement of HIF-1α in monocyte function during sepsis and its potential as a prognostic indicator. Methods and Results: Transcriptomic data from healthy individuals and septic patients in datasets GSE54514, GSE167363, and GSE46955 were analyzed. Additionally, human monocytes were employed to elucidate how HIF regulates immune responses in the context of sepsis. Septic nonsurvivors exhibited sustained upregulation of HIF-1α expression alongside compromised inflammatory response and antigen presentation, with downregulation of NF-κB and HLADRB1 genes associated with poor sepsis prognosis. Conversely, septic survivors displayed an increased proportion of classical monocytes and enhanced inflammation and expression of antigen presentation-related genes. During the recovery phase of sepsis, monocytes continued to demonstrate elevated HIF-1α expression. In cultured THP1 cells and septic CD14 + monocytes, HIF hindered inflammatory responses and antigen presentation, while also suppressing the proportion of classical monocytes after LPS stimulation. Mechanistically, HIF significantly attenuated LPS-induced immune responses in monocytes by inhibiting the phosphorylation of IKK. Conclusions: HIF in monocytes acts as a suppressor of immune-inflammatory responses and antigen presentation, and may serve as a negative molecular marker for sepsis development.

NF-κB signaling pathway in tumor microenvironment

The genesis and progression of tumors are multifaceted processes influenced by genetic mutations within the tumor cells and the dynamic interplay with their surrounding milieu, which incessantly impacts the course of cancer. The tumor microenvironment (TME) is a complex and dynamic entity that encompasses not only the tumor cells but also an array of non-cancerous cells, signaling molecules, and the extracellular matrix. This intricate network is crucial in tumor progression, metastasis, and response to treatments. The TME is populated by diverse cell types, including immune cells, fibroblasts, endothelial cells, alongside cytokines and growth factors, all of which play roles in either suppressing or fostering tumor growth. Grasping the nuances of the interactions within the TME is vital for the advancement of targeted cancer therapies. Consequently, a thorough understanding of the alterations of TME and the identification of upstream regulatory targets have emerged as a research priority. NF-κB transcription factors, central to inflammation and innate immunity, are increasingly recognized for their significant role in cancer onset and progression. This review emphasizes the crucial influence of the NF-κB signaling pathway within the TME, underscoring its roles in the development and advancement of cancer. By examining the interactions between NF-κB and various components of the TME, targeting the NF-κB pathway appears as a promising cancer treatment approach.

Hypermigration of macrophages through the concerted action of GRA effectors on NF-κB/p38 signaling and host chromatin accessibility potentiates Toxoplasma dissemination

Mononuclear phagocytes facilitate the dissemination of the obligate intracellular parasite Toxoplasma gondii. Here, we report how a set of secreted parasite effector proteins from dense granule organelles (GRA) orchestrates dendritic cell-like chemotactic and pro-inflammatory activation of parasitized macrophages. These effects enabled efficient dissemination of the type II T. gondii lineage, a highly prevalent genotype in humans. We identify novel functions for effectors GRA15 and GRA24 in promoting CCR7-mediated macrophage chemotaxis by acting on NF-κB and p38 mitogen-activated protein kinase signaling pathways, respectively, with contributions by GRA16/18 and counter-regulation by effector TEEGR. Furthermore, GRA28 boosted chromatin accessibility and GRA15/24/NF-κB-dependent transcription at the Ccr7 gene locus in primary macrophages. In vivo, adoptively transferred macrophages infected with wild-type T. gondii outcompeted macrophages infected with a GRA15/24 double mutant in migrating to secondary organs in mice. The data show that T. gondii, rather than being passively shuttled, actively promotes its dissemination by inducing a finely regulated pro-migratory state in parasitized human and murine phagocytes via co-operating polymorphic GRA effectors.

IMPORTANCE

Intracellular pathogens can hijack the cellular functions of infected host cells to their advantage, for example, for intracellular survival and dissemination. However, how microbes orchestrate the hijacking of complex cellular processes, such as host cell migration, remains poorly understood. As such, the common parasite Toxoplasma gondii actively invades the immune cells of humans and other vertebrates and modifies their migratory properties. Here, we show that the concerted action of a number of secreted effector proteins from the parasite, principally GRA15 and GRA24, acts on host cell signaling pathways to activate chemotaxis. Furthermore, the protein effector GRA28 selectively acted on chromatin accessibility in the host cell nucleus to selectively boost host gene expression. The joint activities of GRA effectors culminated in pro-migratory signaling within the infected phagocyte. We provide a molecular framework delineating how T. gondii can orchestrate a complex biological phenotype, such as the migratory activation of phagocytes to boost dissemination.

NRF2 Plays a Crucial Role in the Tolerogenic Effect of Ethyl Pyruvate on Dendritic Cells

Ethyl pyruvate (EP) is a redox-active compound that has been previously shown to be effective in restraining immune hyperactivity in animal models of various autoimmune and chronic inflammatory diseases. Importantly, EP has also been proven to have a potent tolerogenic effect on dendritic cells (DCs). Here, the influence of EP on the signaling pathways in DCs relevant for their tolerogenicity, including anti-inflammatory NRF2 and pro-inflammatory NF-κB, was explored. Specifically, the effects of EP on DCs obtained by GM-CSF-directed differentiation of murine bone marrow precursor cells and matured under the influence of lipopolysaccharide (LPS) were examined via immunocytochemistry and RT-PCR. EP counteracted LPS-imposed morphological changes and down-regulated the LPS-induced expression of pro-inflammatory mediators in DCs. While it reduced the activation of NF-κB, EP potentiated NRF2 and downstream antioxidative molecules, thus implying the regulation of NRF2 signaling pathways as the major reason for the tolerizing effects of EP on DCs.

PCV2 Induced Endothelial Derived IL-8 Affects MoDCs Maturation Mainly via NF-κB Signaling Pathway

Porcine circovirus type 2 (PCV2) infection can cause immunosuppressive diseases in pigs. Vascular endothelial cells (VECs), as the target cells for PCV2, play an important role in the immune response and inflammatory regulation. Endothelial IL-8, which is produced by porcine hip artery endothelial cells (PIECs) infected with PCV2, can inhibit the maturation of monocyte-derived dendritic cells (MoDCs). Here, we established a co-culture system of MoDCs and different groups of PIECs to further investigate the PCV2-induced endothelial IL-8 signaling pathway that drives the inhibition of MoDC maturation. The differentially expressed genes related to MoDC maturation were mainly enriched in the NF-κB and JAK2-STAT3 signaling pathways. Both the NF-κB related factor RELA and JAK2-STAT3 signaling pathway related factors (IL2RA, JAK, STAT2, STAT5, IL23A, IL7, etc.) decreased significantly in the IL-8 up-regulated group, and increased significantly in the down-regulated group. The expression of NF-κB p65 in the IL-8 up-regulated group was reduced significantly, and the expression of IκBα was increased significantly. Nuclear translocation of NF-κB p65 was inhibited, while the nuclear translocation of p-STAT3 was increased in MoDCs in the PCV2-induced endothelial IL-8 group. The results of treatment with NF-κB signaling pathway inhibitors showed that the maturation of MoDCs was inhibited and the expression of IL-12 and GM-CSF at mRNA level were lower. Inhibition of the JAK2-STAT3 signaling pathway had no significant effect on maturation, and the expression of IL-12 and GM-CSF at mRNA level produced no significant change. In summary, the NF-κB signaling pathway is the main signaling pathway of MoDC maturation, and is inhibited by the PCV2-induced up-regulation of endothelial-derived IL-8.

Hypermigration of macrophages through the concerted action of GRA effectors on NF-κB/p38 signaling and host chromatin accessibility potentiates Toxoplasma dissemination

Mononuclear phagocytes facilitate the dissemination of the obligate intracellular parasite Toxoplasma gondii. Here, we report how a set of secreted parasite effector proteins from dense granule organelles (GRA) orchestrates dendritic cell-like chemotactic and pro-inflammatory activation of parasitized macrophages. These effects enabled efficient dissemination of the type II T. gondii lineage, a highly prevalent genotype in humans. We identify novel functions for effectors GRA15 and GRA24 in promoting CCR7-mediated macrophage chemotaxis by acting on NF-κB and p38 MAPK signaling pathways, respectively, with contributions of GRA16/18 and counter-regulation by effector TEEGR. Further, GRA28 boosted chromatin accessibility and GRA15/24/NF-κB-dependent transcription at the Ccr7 gene locus in primary macrophages. In vivo, adoptively transferred macrophages infected with wild-type T. gondii outcompeted macrophages infected with a GRA15/24 double mutant in migrating to secondary organs in mice. The data show that T. gondii, rather than being passively shuttled, actively promotes its dissemination by inducing a finely regulated pro-migratory state in parasitized human and murine phagocytes via co-operating polymorphic GRA effectors.

Ewing Sarcoma Single-cell Transcriptome Analysis Reveals Functionally Impaired Antigen-presenting Cells

Novel therapeutic strategies are urgently needed for patients with high-risk Ewing sarcoma and for the reduction of severe side effects for all patients. Immunotherapy may fill this need, but its successful application has been hampered by a lack of knowledge on the composition and function of the Ewing sarcoma immune microenvironment. Here, we explore the immune microenvironment of Ewing sarcoma, by single-cell RNA sequencing of 18 Ewing sarcoma primary tissue samples. Ewing sarcoma is infiltrated by natural killer, T, and B cells, dendritic cells, and immunosuppressive macrophages. Ewing sarcoma-associated T cells show various degrees of dysfunction. The antigen-presenting cells found in Ewing sarcoma lack costimulatory gene expression, implying functional impairment. Interaction analysis reveals a clear role for Ewing sarcoma tumor cells in turning the Ewing sarcoma immune microenvironment into an immunosuppressive niche. These results provide novel insights into the functional state of immune cells in the Ewing sarcoma tumor microenvironment and suggest mechanisms by which Ewing sarcoma tumor cells interact with, and shape, the immune microenvironment.

SIGNIFICANCE

This study is the first presenting a detailed analysis of the Ewing sarcoma microenvironment using single-cell RNA sequencing. We provide novel insight into the functional state of immune cells and suggests mechanisms by which Ewing tumor cells interact with, and shape, their immune microenvironment. These insights provide help in understanding the failures and successes of immunotherapy in Ewing sarcoma and may guide novel targeted (immuno) therapeutic approaches.

Developing a vaccine against velogenic sub-genotype seven of Newcastle disease virus based on virus-like particles

In the present study, for the first time, we released and assembled the particles of three major structural proteins of velogenic NDV (M, HN, and F glycoproteins) as a NDV-VLPs. The ElISA result of the cytokines of splenocyte suspension cells showed that IL2, IL10, TNF-α, and IFN- ˠ titers were significantly higher (p ≤ 0.05) in mice that were immunized only with NDV-VLPs three times with a 10-day interval, in comparison to those that were immunized with NDV-VLPs twice in a 10-day interval and received a B1 live vaccine boost on the third interval. Flow cytometry results showed that CD8 + titers in the group that only received NDV-VLP was higher than other group. However, serum ELISA results did not show a significantly (p ≥ 0.05) higher NDV antibody titer in NDV-VLPs immunized mice compared to the boosted group. Besides, HI results of SPF chickens vaccinated with NDV-VLPs and boosted with B1 live vaccine were significantly (p ≤ 0.05) higher than those that only received NDV-VLPs. Interestingly, after challenging with NDV sub-genotype VII, all the chickens that were solely vaccinated with NDV-VLPs remained alive (six out of six), whereas two out of six chickens that were vaccinated with NDV-VLPs and also received the B1 live vaccine boost died. In conclusion, our results strongly indicated that the T-cell immune response in an NDV host is more important than the B-cell response. Also, the results of the present study revealed that to completely protect chickens against velogenic NDV strains, a vaccine comprising specific epitopes of velogenic strain is needed.

Targeting different signaling pathways for food allergy regulation and potential therapy: a review

The rising incidence rate of food allergy is attracting more intention. The pathogenesis of food allergy is complex and its definite regulatory mechanism is not utterly understood. Exploring the molecular mechanism of food allergy to help find effective methods that can prevent or treat food allergy is widely necessary. Recently, targeting cellular signaling pathways have been employed as novel approaches to discover food allergy therapy. Supplementing probiotics and bioactive compounds with anti-allergic property are believed feasible approaches for food allergy therapy. These probiotics or bioactive compounds affect food allergy by regulating cellular signaling pathways, and ultimately alleviate food allergy. This review aims to report systematic information about the knowledge of signaling pathways participated in food allergy, the alterations of these signaling pathways during food allergy that treated with probiotics and bioactive compounds are discussed as well. Further studies on the mechanism of signaling pathway network regulating food allergy and the precise action mechanism of probiotics and bioactive compounds are in the urgent need to help develop efficient treatment or complete prevention. We hope to help scientists understand food allergy systematically.

The T Cell Journey: A Tour de Force

T cells act as the puppeteers in the adaptive immune response, and their dysfunction leads to the initiation and progression of pathological conditions. During their lifetime, T cells experience myriad forces that modulate their effector functions. These forces are imposed by interacting cells, surrounding tissues, and shear forces from fluid movement. In this review, a journey with T cells is made, from their development to their unique characteristics, including the early studies that uncovered their mechanosensitivity. Then the studies pertaining to the responses of T cell activation to changes in antigen-presenting cells' physical properties, to their immediate surrounding extracellular matrix microenvironment, and flow conditions are highlighted. In addition, it is explored how pathological conditions like the tumor microenvironment can hinder T cells and allow cancer cells to escape elimination.

Cellular inhibitor of apoptosis 2 (cIAP2) restricts neuroinflammation during experimental autoimmune encephalomyelitis

Background

Immune activation, neuroinflammation, and cell death are the hallmarks of multiple sclerosis (MS), which is an autoimmune demyelinating disease of the central nervous system (CNS). It is well-documented that the cellular inhibitor of apoptosis 2 (cIAP2) is induced by inflammatory stimuli and regulates adaptive and innate immune responses, cell death, and the production of inflammatory mediators. However, the impact of cIAP2 on neuroinflammation associated with MS and disease severity remains unknown.

Methods

We used experimental autoimmune encephalomyelitis (EAE), a widely used mouse model of MS, to assess the effect of cIAP2 deletion on disease outcomes. We performed a detailed analysis on the histological, cellular, and molecular levels. We generated and examined bone-marrow chimeras to identify the cIAP2-deficient cells that are critical to the disease outcomes.

Results

cIAP2^−/− mice exhibited increased EAE severity, increased CD4⁺ T cell infiltration, enhanced proinflammatory cytokine/chemokine expression, and augmented demyelination. This phenotype was driven by cIAP2-deficient non-hematopoietic cells. cIAP2 protected oligodendrocytes from cell death during EAE by limiting proliferation and activation of brain microglia. This protective role was likely exerted by cIAP2-mediated inhibition of the non-canonical NLRP3/caspase-8-dependent myeloid cell activation during EAE.

Conclusions

Our findings suggest that cIAP2 is needed to modulate neuroinflammation, cell death, and survival during EAE. Significantly, our data demonstrate the critical role of cIAP2 in limiting the activation of microglia during EAE, which could be explored for developing MS therapeutics in the future.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02527-6.

The Influence of Microenvironment on Survival of Intraportal Transplanted Islets

Clinical islet transplantation has the potential to cure type 1 diabetes. Despite recent therapeutic success, it is still uncommon because transplanted islets are damaged by multiple challenges, including instant blood mediated inflammatory reaction (IBMIR), inflammatory cytokines, hypoxia/reperfusion injury, and immune rejection. The transplantation microenvironment plays a vital role especially in intraportal islet transplantation. The identification and targeting of pathways that function as "master regulators" during deleterious inflammatory events after transplantation, and the induction of immune tolerance, are necessary to improve the survival of transplanted islets. In this article, we attempt to provide an overview of the influence of microenvironment on the survival of transplanted islets, as well as possible therapeutic targets.

Systemic Lupus Erythematosus Patients With Related Organic Damage Are at High Risk of Hypothyroidism

PURPOSE

The aim of this study included determining the prevalence of hypothyroidism in patients with systemic lupus erythematosus (SLE), clarifying the clinical characteristics of SLE patients with hypothyroidism, and identifying the relationship between hypothyroidism and SLE-related organic damage. Another purpose was to analyze the relationship between SLE and thyroid autoantibody. We also intended to discuss the pathogenesis of hypothyroidism in SLE patients, which would provide clues for further investigation.

METHODS

This study recruited 856 SLE patients and 856 age- and sex-matched healthy population and compared the prevalence of hypothyroidism between the cases and controls. Univariate and multivariate logistic analyses were applied to identify risk factors for hypothyroidism in SLE patients.

RESULTS

SLE patients had higher prevalence of clinical hypothyroidism (9.10%) and TgAb+TPOAb- (10.40%) than controls. The prevalence of hypothyroidism was the highest in SLE patients aged 16-26 years (18.9%) and decreased with age. The prevalence of autoimmune hypothyroidism in SLE group was higher than that in the control group (64.4% vs. 51.5%, P=0.042), which was mainly due to TgAb; the prevalence of non-autoimmune hypothyroidism in SLE group was also significantly higher than that in the control group (67.3% vs. 47.8%, P<0.001). Based on multivariate analysis, the use of glucocorticoids/immunosuppressants, liver abnormality, lupus nephritis (LN), and cardiac insufficiency were independently associated with hypothyroidism in SLE patients.

CONCLUSION

The prevalence of hypothyroidism in SLE patients was higher than that in controls and decreased with age. The results suggested that young SLE patients combined with LN, liver abnormality and cardiac insufficiency were at higher risk of hypothyroidism. According to the results of this study, we speculated that SLE might have impact on thyroid, and SLE might be one of the causes of hypothyroidism.

Impact of intrarectal chromofungin treatment on dendritic cells-related markers in different immune compartments in colonic inflammatory conditions

BACKGROUND

Chromofungin (CHR: chromogranin-A 47-66) is a chromogranin-A derived peptide with anti-inflammatory and anti-microbial properties. Ulcerative colitis (UC) is characterized by a colonic decrease of CHR and a dysregulation of dendritic CD11c⁺ cells.

AIM

To investigate the association between CHR treatment and dendritic cells (DCs)-related markers in different immune compartments in colitis.

METHODS

A model of acute UC-like colitis using dextran sulphate sodium (DSS) was used in addition to biopsies collected from UC patients.

RESULTS

Intrarectal CHR treatment reduced the severity of DSS-induced colitis and was associated with a significant decrease in the expression of CD11c, CD40, CD80, CD86 and interleukin (IL)-12p40 in the inflamed colonic mucosa and CD11c, CD80, CD86 IL-6 and IL-12p40 within the mesenteric lymph nodes and the spleen. Furthermore, CHR treatment decreased CD80 and CD86 expression markers of splenic CD11c⁺ cells and decreased NF-κB expression in the colon and of splenic CD11c⁺ cells. In vitro, CHR decreased CD40, CD80, CD86 IL-6 and IL-12p40 expression in naïve bone marrow-derived CD11c⁺ DCs stimulated with lipopolysaccharide. Pharmacological studies demonstrated an impact of CHR on the NF-κB pathway. In patients with active UC, CHR level was reduced and showed a negative linear relationship with CD11c and CD86.

CONCLUSION

CHR has protective properties against intestinal inflammation via the regulation of DC-related markers and CD11c⁺ cells. CHR could be a potential therapy of UC.

Sinomenine in Cardio-Cerebrovascular Diseases: Potential Therapeutic Effects and Pharmacological Evidences

Cardio-cerebrovascular diseases, as a major cause of health loss all over the world, contribute to an important part of the global burden of disease. A large number of traditional Chinese medicines have been proved effective both clinically and in pharmacological investigations, with the acceleration of the modernization of Chinese medicine. Sinomenine is the main active constituent of sinomenium acutum and has been generally used in therapies of rheumatoid arthritis and neuralgia. Varieties of pharmacological effects of sinomenine in cardio-cerebrovascular system have been discovered recently, suggesting an inspiring application prospect of sinomenine in cardio-cerebrovascular diseases. Sinomenine may retard the progression of atherosclerosis by attenuating endothelial inflammation, regulating immune cells function, and inhibiting the proliferation of vascular smooth muscle cells. Sinomenine also alleviates chronic cardiac allograft rejection relying on its anti-inflammatory and anti-hyperplastic activities and suppresses autoimmune myocarditis by immunosuppression. Prevention of myocardial or cerebral ischemia-reperfusion injury by sinomenine is associated with its modulation of cardiomyocyte death, inflammation, calcium overload, and oxidative stress. The regulatory effects on vasodilation and electrophysiology make sinomenine a promising drug to treat hypertension and arrhythmia. Here, in this review, we will illustrate the pharmacological activities of sinomenine in cardio-cerebrovascular system and elaborate the underlying mechanisms, as well as give an overview of the potential therapeutic roles of sinomenine in cardio-cerebrovascular diseases, trying to provide clues and bases for its clinical usage.

The clinical landscape of chronic graft-versus-host disease management in 2021

Chronic graft-versus-host disease (cGVHD) is an important systemic complication of allogeneic haematopoietic stem cell transplantation with heterogeneous, multi-organ involvement that can lead to increased morbidity and mortality. Despite significant advances in understanding the complex pathophysiology driving the disease, curative treatment options remain suboptimal. The past decade, however, has seen much growth in collaborative research efforts and standardization of criteria for clinical trials that have led to discovery of several new second-line therapies in cGVHD. The key to successful cGVHD control and management includes a comprehensive and sustained multidisciplinary effort with emphasis on ancillary and supportive care for these patients. The focus of this review is to summarize the new developments in systemic, organ-specific, and topical treatments in the management of cGVHD that emerged since the 2014 NIH consensus conference.

The deubiquitinase OTUB1 augments NF-κB-dependent immune responses in dendritic cells in infection and inflammation by stabilizing UBC13

Dendritic cells (DCs) are indispensable for defense against pathogens but may also contribute to immunopathology. Activation of DCs upon the sensing of pathogens by Toll-like receptors (TLRs) is largely mediated by pattern recognition receptor/nuclear factor-κB (NF-κB) signaling and depends on the appropriate ubiquitination of the respective signaling molecules. However, the ubiquitinating and deubiquitinating enzymes involved and their interactions are only incompletely understood. Here, we reveal that the deubiquitinase OTU domain, ubiquitin aldehyde binding 1 (OTUB1) is upregulated in DCs upon murine Toxoplasma gondii infection and lipopolysaccharide challenge. Stimulation of DCs with the TLR11/12 ligand T. gondii profilin and the TLR4 ligand lipopolysaccharide induced an increase in NF-κB activation in OTUB1-competent cells, resulting in elevated interleukin-6 (IL-6), IL-12, and tumor necrosis factor (TNF) production, which was also observed upon the specific stimulation of TLR2, TLR3, TLR7, and TLR9. Mechanistically, OTUB1 promoted NF-κB activity in DCs by K48-linked deubiquitination and stabilization of the E2-conjugating enzyme UBC13, resulting in increased K63-linked ubiquitination of IRAK1 (IL-1 receptor-associated kinase 1) and TRAF6 (TNF receptor-associated factor 6). Consequently, DC-specific deletion of OTUB1 impaired the production of cytokines, in particular IL-12, by DCs over the first 2 days of T. gondii infection, resulting in the diminished production of protective interferon-γ (IFN-γ) by natural killer cells, impaired control of parasite replication, and, finally, death from chronic T. encephalitis, all of which could be prevented by low-dose IL-12 treatment in the first 3 days of infection. In contrast, impaired OTUB1-deficient DC activation and cytokine production by OTUB1-deficient DCs protected mice from lipopolysaccharide-induced immunopathology. Collectively, these findings identify OTUB1 as a potent novel regulator of DCs during infectious and inflammatory diseases.

Linking membrane fluidity with defective antigen presentation in leishmaniasis

Hampering-surface presentation of immunogenic peptides by class I/II MHCs is a key strategy opted by several intracellular protozoan pathogens including Leishmania to escape CD8/CD4 mediated host-protective T-cell response. Although Leishmania parasites (LP) primarily hijack/inhibit host lysosomal/proteasomal pathways to hamper antigen-processing/presentation machinery, recent pieces of evidence have linked host-membrane fluidity as a major cause of defective antigen presentation in leishmaniasis. Increased membrane fluidity severely compromised peptide-MHC stability in the lipid raft regions, thereby abrogating T-cell mediated-signalling in the infected host. LP primarily achieves this by quenching host cholesterol, which acts as cementing material in maintaining the membrane fluidity. In this review, we have particularly focused on several strategies opted by LP to hijack-host cholesterol resulting in lipid droplets accumulation around leishmania-containing parasitophorous vacuole favouring intracellular survival of LP. In fact, LP infection can result in altered cholesterol and lipid metabolism in the infected host, thereby favouring the establishment and progression of the infection. From our analysis of two genome-wide transcriptomics data sets of LP infected host, we propose a possible molecular network that connects these interrelated events of altered lipid metabolism with eventual compromised antigen presentation, still existing as a gap in our current understanding of Leishmania infection.

C-Reactive Protein Suppresses the Th17 Response Indirectly by Attenuating the Antigen Presentation Ability of Monocyte Derived Dendritic Cells in Experimental Autoimmune Encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is a classical murine model for Multiple Sclerosis (MS), a human autoimmune disease characterized by Th1 and Th17 responses. Numerous studies have reported that C-reactive protein (CRP) mitigates EAE severity, but studies on the relevant pathologic mechanisms are insufficient. Our previous study found that CRP suppresses Th1 response directly by receptor binding on naïve T cells; however, we did not observe the effect on Th17 response at that time; thus it remains unclear whether CRP could regulate Th17 response. In this study, we verified the downregulation of Th17 response by a single-dose CRP injection in MOG-immunized EAE mice in vivo while the direct and indirect effects of CRP on Th17 response were differentiated by comparing its actions on isolated CD4⁺ T cells and splenocytes in vitro, respectively. Moreover, the immune cell composition was examined in the blood and CNS (Central Nervous System), and a blood (monocytes) to CNS (dendritic cells) infiltration pathway is established in the course of EAE development. The infiltrated monocyte derived DCs (moDCs) were proved to be the only candidate antigen presenting cells to execute CRP’s function. Conversely, the decrease of Th17 responses caused by CRP disappeared in the above in vivo and in vitro studies with FcγR2B^−/− mice, indicating that FcγR2B expressed on moDCs mediates CRP function. Furthermore, peripheral blood monocytes were isolated and induced to establish moDCs, which were used to demonstrate that the antigen presenting ability of moDCs was attenuated by CRP through FcγR2B, and then NF-κB and ERK signaling pathways were manifested to be involved in this regulation. Ultimately, we perfected and enriched the mechanism studies of CRP in EAE remission, so we are more convinced that CRP plays a key role in protecting against EAE development, which may be a potential therapeutic target for the treatment of MS in human.

Mechanisms of allergen-specific immunotherapy and allergen tolerance

Allergen-specific immunotherapy (AIT) is the mainstay treatment for the cure of allergic disorders, with depicted efficacy and safety by several trials and meta-analysis. AIT impressively contributes to the management of allergic rhinitis, asthma and venom allergies. Food allergy is a new arena for AIT with promising results, especially via novel administration routes. Cell subsets with regulatory capacities are induced during AIT. IL-10 and transforming growth factor (TGF)-β are the main suppressor cytokines, in addition to surface molecules such as cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) and programmed cell death protein-1 (PD-1) within the micro milieu. Modified T- and B-cell responses and antibody isotypes, increased activity thresholds for eosinophils, basophils and mast cells and consequent limitation of inflammatory cascades altogether induce and maintain a state of sustained allergen-specific unresponsiveness. Established tolerance is reflected into the clinical perspectives as improvement of allergy symptoms together with reduced medication requirements and evolved disease severity. Long treatment durations, costs, reduced patient compliance and risk of severe, even life-threatening adverse reactions during treatment stand as major limiting factors for AIT. By development of purified non-allergenic, highly-immunogenic modified allergen extracts, and combinational usage of them with novel adjuvant molecules via new routes may shorten treatment durations and possibly reduce these drawbacks. AIT is the best model for custom-tailored therapy of allergic disorders. Better characterization of disease endotypes, definition of specific biomarkers for diagnosis and therapy follow-up, as well as precision medicine approaches may further contribute to success of AIT in management of allergic disorders.

Targeted delivery of miR-99b reprograms tumor-associated macrophage phenotype leading to tumor regression

Background

Accumulating evidence has shown that tumor-associated macrophages (TAMs) play a critical role in tumor progression. Targeting TAMs is a potential strategy for tumor immunotherapy. However, the mechanism underlying the TAM phenotype and function needs to be resolved. Our previous studies have demonstrated that miR-125a can reverse the TAM phenotype toward antitumor. Meanwhile, we have found that miR-125a and miR-99b cluster in the first intron of the same host gene, and are transcribed simultaneously in bone marrow-derived macrophages (BMDMs) following LPS+IFNγ stimulation. However, it remains unclear whether miR-99b by itself can exert an antitumor effect by regulating macrophage phenotype.

Methods

miR-99b and/or miR-125a were delivered into TAMs of orthotopic hepatocellular carcinoma (HCC) or subcutaneous Lewis lung cancer (LLC) mice. The effect of treatment was evaluated by live imaging, TUNEL staining and survival tests. The phenotype of the immune cells was determined by qRT-PCR, ELISA, western blot and FACS. The capability of miR-99b-mediated macrophage phagocytosis and antigen presentation was detected by FACS and immunofluorescence staining. The underlying molecular mechanism was examined by qRT-PCR, reporter assay and western blot, and further verified in the tumor model. The expression of miR-99b and its target genes was determined in TAMs sorted from tumor and adjacent tissues in patients with liver cancer.

Results

Targeted delivery of miR-99b and/or miR-125a into TAMs significantly impeded the growth of HCC and LLC, especially after miR-99b delivery. More importantly, the delivery of miR-99b re-educated TAM toward antitumor phenotype with enhanced immune surveillance. Further investigation of mechanisms showed that macrophage-specific overexpression of miR-99b promoted M1 while suppressing M2 macrophage polarization by targeting κB-Ras2 and/or mTOR, respectively. miR-99b-overexpressed M1 macrophage was characterized by stronger capability of phagocytosis and antigen presentation. Additionally, delivery of simTOR or siκB-Ras2 into TAMs inhibited miR-99b antagomir-triggered tumor growth. Finally, miR-99b expression was lower in TAMs of patients with liver cancer than that in adjacent tissues, while the expression of κB-Ras2 and mTOR was reversed.

Conclusions

Our results reveal the mechanism of miR-99b-mediated TAM phenotype, indicating that TAM-targeted delivery of miR-99b is a potential strategy for cancer immunotherapy.

Interleukin-dependent modulation of the expression of MHC class I and MHC class II genes in chicken HD11 cells

Interleukins (ILs) regulate cell surface antigens known as activation markers, which have distinct functional roles. However, the regulation of major histocompatibility complex (MHC) class I, MHC class II, and related genes by cytokines in chickens is not well understood. In the present study, we evaluated the influence of certain recently discovered chicken interleukins-i.e., IL-11, IL-12B, IL-17A, IL-17B, IL-26, and IL-34-on the expression and regulation of genes related to MHC class I, MHC class II, and the associated proteins in an HD11 chicken macrophage cell line. We used quantitative reverse transcription polymerase chain reaction (qRT-PCR), immunocytochemical, and flow cytometric analyses to assess dose- and time-dependent expression in the HD11 cell line and found that the ILs induced MHC class I, MHC class II, and associated protein. As NF-κB is actively involved in cell activation and is constitutively activated in many immune cells, we also determined whether NF-κB regulates MHC class I, MHC class II, and related gene expression in the HD11 cell line. The NF-κB inhibitor sulfasalazine (Sz) dose-dependently inhibited MHC class I and MHC class II in the HD11 cell line. Sz also downregulated the expression of MHC class I, MHC class II, and the associated proteins in the IL-induced HD11 cell line. The expression of MHC class I, MHC class II, and associated genes was accompanied by the Sz-sensitive degradation of the p65 (RelA) and p50 subunits of NF-κB and IκBα. Our results indicate that the different effects of each IL on the expression of genes related to MHC class I, MHC class II, and the associated proteins are involved with the regulation of the dose and duration of antigenic peptide presentation and, thus, also influence Th1, Th2, and Th17 production.

Blockade of RANKL/RANK and NF-ĸB signalling pathways as novel therapeutic strategies for allergic asthma: A comparative study in a mouse model of allergic airway inflammation

The main aims of this study were: (1) to investigate whether a blockade of the interaction between the receptor activator of nuclear factor-κB (NF-ĸB) ligand (RANKL) and its receptor RANK may have potential as a novel therapeutic strategy for allergic asthma; (2) to compare the efficacies of the blockade of RANKL/RANK interaction as well as the blockade of NF-κB inhibitor kinase (IKK) and of NF-κB translocation to the nucleus, also in comparison with glucocorticosteroid treatment, in terms of the development of a mouse model of allergic airway inflammation (AAI) and accompanying immune response. The blockade of each of the targets fully prevented the development of AAI. All the tested therapeutic strategies seemed to have a certain advantage over glucocorticosteroids with regard to counteracting the development of AAI. Prevention of the activation and clonal expansion of CD4⁺ effector T (Teff) cells in the mediastinal lymph nodes (MLNs) constitutes a fundamental event underlying the anti-asthmatic effect induced by the blockade of IKK, NF-κB translocation or of RANKL/RANK interaction. The results indicate that attenuation of the CD11b⁺CD103^-CD11c^high dendritic cell response in the MLNs is an initial but not the main mechanism responsible for this effect. In turn, the direct anti-proliferative action on CD4⁺ Teff cells seems to constitute the chief mechanism responsible for the anti-asthmatic effect of all the tested therapeutic strategies. A clinical implication is that local inhibition of RANKL/RANK interaction achieved via inhalatory administration of a RANKL antagonist can be considered as a novel therapeutic strategy in treatment of allergic asthma.

Transcriptome profiling of tolerogenic dendritic cells conditioned with dual mTOR kinase inhibitor, AZD8055

Dendritic cells (DCs) can initiate and regulate adaptive immunity depending on their maturation status. Many pharmacological and genetic means have been used in the generation of immature/tolerogenic DCs. However, the key factors controlling DCs tolerogenicity remain obscure. In this work, we demonstrated that AZD8055, an ATP-competitive inhibitor of mammalian target of rapamycin (mTOR), could also lead to a tolerogenic DC phenotype from several lines of evidence, such as suppression of T cell proliferation, promoting the generation of Tregs, and inducing allogeneic T cell apoptosis. Further studies using RNA-seq method identified 430, 1172 and 1436 differentially expressed genes (DEGs) between AZD-DCs vs. Control-DCs, LPS-DCs vs. Control-DCs, and AZD-DCs vs. LPS-DCs, respectively. The 5 most differentially expressed transcripts identified by RNA-seq expression profiles were validated by quantitative RT-PCR assays. NF-κB, p38MAPK, the ribosome and PPAR signaling pathways may be involved in the induction of tolerogenic DCs by AZD8055. Functional annotation showed some genes like MGL2, Cadherin-1, 4-1BB, RhoB and Pdpn, were quite different between AZD-DCs and Control-DCs/LPS-DCs, which might be related to the tolerogenic properties of AZD-DCs. Our work provided the potential underlying molecular mechanisms involved in the generation of tolerogenic DCs. Further functional characterization of individual target gene in DC tolerogenicity will help to develop novel therapeutic modalities in circumstances like transplant tolerance induction and autoimmunity.

Particles from the Echinococcus granulosus Laminated Layer Inhibit CD40 Upregulation in Dendritic Cells by Interfering with Akt Activation

The larval stage of the cestode Echinococcus granulosus causes cystic echinococcosis in humans and livestock. This larva is protected by the millimeter-thick, mucin-based laminated layer (LL), from which materials have to be shed to allow parasite growth. We previously reported that dendritic cells (DCs) respond to microscopic pieces of the mucin gel of the LL (pLL) with unconventional maturation phenotypes, in the absence or presence of Toll-like receptor (TLR) agonists, including lipopolysaccharide (LPS).

The larval stage of the cestode Echinococcus granulosus causes cystic echinococcosis in humans and livestock. This larva is protected by the millimeter-thick, mucin-based laminated layer (LL), from which materials have to be shed to allow parasite growth. We previously reported that dendritic cells (DCs) respond to microscopic pieces of the mucin gel of the LL (pLL) with unconventional maturation phenotypes, in the absence or presence of Toll-like receptor (TLR) agonists, including lipopolysaccharide (LPS). We also reported that the presence of pLL inhibited the activating phosphorylation of the phosphatidylinositol 3-kinase (PI3K) effector Akt induced by granulocyte-macrophage colony-stimulating factor or interleukin-4. We now show that the inhibitory effect of pLL extends to LPS as a PI3K activator, and results in diminished phosphorylation of GSK3 downstream from Akt. Functionally, the inhibition of Akt and GSK3 phosphorylation are linked to the blunted upregulation of CD40, a major feature of the unconventional maturation phenotype. Paradoxically, all aspects of unconventional maturation induced by pLL depend on PI3K class I. Additional components of the phagocytic machinery are needed, but phagocytosis of pLL particles is not required. These observations hint at a DC response mechanism related to receptor-independent mechanisms proposed for certain crystalline and synthetic polymer-based particles; this would fit the previously reported lack of detection of molecular-level motifs necessary of the effects of pLL on DCs. Finally, we report that DCs exposed to pLL are able to condition DCs not exposed to the material so that these cannot upregulate CD40 in full in response to LPS.

Role of dendritic cells in the host response to biomaterials and their signaling pathways

Strategies to enhance, inhibit, or qualitatively modulate immune responses are important for diverse biomedical applications such as vaccine adjuvant, drug delivery, immunotherapy, cell transplant, tissue engineering, and regenerative medicine. However, the clinical efficiency of these biomaterial systems is affected by the limited understanding of their interaction with complex host microenvironments, for example, excessive foreign body reaction and immunotoxicity. Biomaterials and biomedical devices implanted in the body may induce a highly complicated and orchestrated series of host responses. As macrophages are among the first cells to infiltrate and respond to implanted biomaterials, the macrophage-mediated host response to biomaterials has been well studied. Dendritic cells (DCs) are the most potent antigen-presenting cells that activate naive T cells and bridge innate and adaptive immunity. The potential interaction of DCs with biomaterials appears to be critical for exerting the function of biomaterials and has become an important, developing area of investigation. Herein, we summarize the effects of the physicochemical properties of biomaterials on the immune function of DCs together with their receptors and signaling pathways. This review might provide a complete understanding of the interaction of DCs with biomaterials and serve as a reference for the design and selection of biomaterials with particular effects on targeted cells. STATEMENT OF SIGNIFICANCE: Biomaterials implanted in the body are increasingly applied in clinical practice. The performance of these implanted biomaterials is largely dependent on their interaction with the host immune system. As antigen-presenting cells, dendritic cells (DCs) directly interact with biomaterials through pattern recognition receptors (PRRs) recognizing "biomaterial-associated molecular patterns" and generate a battery of immune responses. In this review, the physicochemical properties of biomaterials that regulate the immune function of DCs together with their receptors and signaling pathways of biomaterial-DC interactions are summarized and discussed. We believe that knowledge of the interplay of DC and biomaterials may spur clinical translation by guiding the design and selection of biomaterials with particular effects on targeted cell for tissue engineering, vaccine delivery, and cancer therapy.

The Deubiquitinase Inhibitor b-AP15 and Its Effect on Phenotype and Function of Monocyte-Derived Dendritic Cells

The ubiquitin-proteasome system is elementary for cellular protein degradation and gained rising attention as a new target for cancer therapy due to promising clinical trials with bortezomib, the first-in class proteasome inhibitor meanwhile approved for multiple myeloma and mantle cell lymphoma. Both bortezomib and next-generation proteasome inhibitors mediate their effects by targeting the 20S core particle of the 26S proteasome. The novel small molecule inhibitor b-AP15 affects upstream elements of the ubiquitin-proteasome cascade by suppressing the deubiquitinase activity of both proteasomal regulatory 19S subunits and showed promising anticancer activity in preclinical models. Nonetheless, effects of inhibitors on the ubiquitin-proteasome system are not exclusively restricted to malignant cells: alteration of natural killer cell-mediated immune responses had already been described for drugs targeting either 19S or 20S proteasomal subunits. Moreover, it has been shown that bortezomib impairs dendritic cell (DC) phenotype and function at different levels. In the present study, we comparatively analyzed effects of bortezomib and b-AP15 on monocyte-derived DCs. In line with previous results, bortezomib exposure impaired maturation, antigen uptake, migration, cytokine secretion and immunostimulation, whereas treatment with b-AP15 had no compromising effects on these DC features. Our findings warrant the further investigation of b-AP15 as an alternative to clinically approved proteasome inhibitors in the therapy of malignancies, especially in the context of combinatorial treatment with DC-based immunotherapies.

A versatile supramolecular nanoadjuvant that activates NF-κB for cancer immunotherapy

Although powerful adjuvants hold promise of vaccines for cancer immunotherapy, cumbersome preparation processes, elusive mechanisms and failure to induce T cell responses have largely limited their clinical translation. Due to their ease of synthesis, good biocompatibility and designable bioactivity, peptide derivatives-based supramolecular nanomaterials have attracted increasing interest in improving the immunogenicity of cancer vaccines. Methods: Herein, we synthesized an NF-κB-activating supramolecular nanoadjuvant (3DSNA) that is prepared by pH-triggering self-assembly of a positively charged D-configurational peptide derivative. The immunostimulatory activity of 3DNSA was explored in vitro and in vivo. Results: 3DSNA can strongly absorb the model antigen (ovalbumin, OVA) through electrostatic interaction. Then, 3DSNA promotes ingestion and cross-presentation of OVA, upregulation of costimulatory factors (CD80 and CD86) and secretion of proinflammatory cytokines (IL-6 and IL-12) by dendritic cells (DCs), accompanied by activation of the innate immune response (NF-κB signaling), resulting in long-term antigen-specific memory and effector CD8+ T cells response. When compared with conventional aluminum hydroxide adjuvant and the corresponding L-configurational supramolecular nanoadjuvant (3LSNA), 3DSNA-adjuvanted OVA (3DSNA+OVA) significantly prevents oncogenesis in naïve mice with a complete response rate of 60 %, restrains the tumor growth and prolongs the survival of melanoma-bearing mice. Conclusion: These findings demonstrate that 3DSNA is a promising neo-adjuvant that enables various vaccines to be therapeutic for many important diseases including cancer.

Anti-glioma effect of intracranial vaccination with tumor cell lysate plus flagellin in mice

The adjuvant effects of flagellin on regulation of immune response have been proved; whether flagellin could assist tumor cell lysate (TCL) to enhance anti-glioma immunity remains to be investigated. This study tests a hypothesis that therapeuticly intracranial administration with flagellin plus TCL enhances the effects of specific immunotherapy on glioma in mice. In this study, GL261 cells were transferred into C57BL/6 mice and the GL261-bearing mice were subcutaneously or intracranially inoculated with flagellin plus TCL, flagellin, TCL or saline. Our results showed that prophylacticly subcutaneous administration with TCL and flagellin could induce potent cytotoxic T lymphocyte (CTL) and prolong the survival of GL261-bearing mice significantly, but therapeuticly subcutaneous administration failed to. However, therapeuticly intracranial administration of TCL plus flagellin could prolong the survival. Moreover, intracranial administration of flagellin could recruit CD4⁺ T cells and CD8⁺ T cells to brain tissues, induce proliferation of natural killer (NK) cells, CD4⁺ T cells and CD8⁺ T cells in peripheral blood mononuclear cells and induce to splenomegaly. The results suggested that flagellin could be acted as an efficient adjuvant for TCL based vaccine.

Polysaccharide isolated from seeds of Plantago asiatica L. induces maturation of dendritic cells through MAPK and NF-κB pathway

Plantago species are used as traditional medicine in Asian and Europe. Polysaccharide isolated from the seeds of Plantago asiatica L. could stimulate maturation transformation of bone-marrow derived dendritic cells (DCs). We found that blocking p38, ERK1/2 and JNK MAPK signal transduction could significantly decreased the PLP-2 induced expression of MHC II, CD86 surface molecules on DCs. Blocking p38 and JNK signal also significantly inhibited the cytokine secretion of TNF-α and IL-12p70 as well, while blocking ERK1/2 signal only decreased the secretion of TNF-α. Meanwhile, DCs in the three MAPK signal-blocking groups showed dramatically attenuated effects on stimulating proliferation of T lymphocytes. Similarly, blocking signal transduction of NF-κB pathway also significantly impaired the phenotypic and functional maturation development of DCs induced by PLP-2. These data suggest that MAPK and NF-κB pathway mediates the PLP-induced maturation on DCs. Especially, among the three MAPK pathways, activation of JNK signal transduction is the most important for DCs development after PLP-2 incubation. And PLP-2 may activate the MAPK and NF-κB pathway by triggering toll-like receptor 4 on DCs.

Nrf2-mediated metabolic reprogramming of tolerogenic dendritic cells is protective against aplastic anemia

Aplastic anemia (AA) is a rare disease characterized by immune-mediated suppression of bone marrow (BM) function resulting in progressive pancytopenia. Stem cell transplant and immunosuppressive therapies remain the major treatment choices for AA patients with limited benefit and undesired side effects. Here, we report for the first time the therapeutic utility of Nrf2-induced metabolically reprogrammed tolerogenic dendritic cells (TolDCs) in the suppression of AA in mice. CDDO-DFPA-induced Nrf2 activation resulted in a TolDC phenotype as evidenced by induction of IL-4, IL-10, and TGF-β and suppression of TNFα, IFN-γ, and IL-12 levels in Nrf2^+/+ but not Nrf2^-/- DCs. Cellular metabolism holds the key to determining DC immunogenic or tolerogenic cell fate. Although immature and LPS-induced (mature) Nrf2^+/+ and Nrf2^-/- DCs exhibited similar patterns of oxidative phosphorylation (OXPHOS) and glycolysis, only Nrf2^+/+ DCs partially restored OXPHOS and reduced glycolysis during CDDO-DFPA-induced Nrf2 activation. These results were further confirmed by altered glucose uptake and lactate production. We observed significantly enhanced HO-1 and reduced iNOS/NO production in Nrf2^+/+ compared to Nrf2^-/- DCs, suggesting Nrf2-dependent TolDC induction is linked to suppression of the inhibitory effect of NO on OXPHOS. Furthermore, Nrf2^-/- DCs demonstrated higher antigen-specific T cell proliferation. Lastly, TolDC administration improved hematopoiesis and survival in AA murine model, with decreased Th17 and increased Treg cells. Concomitantly, immunohistochemical analysis of AA patient BM biopsies displayed higher DCs, T cells, and iNOS expression accompanied with lower Nrf2 and HO-1 expression when compared to normal subjects. These results provide new insight into the therapeutic utility of metabolically reprogrammed TolDCs by CDDO-DFPA induced Nrf2 signaling in the treatment of AA.

Mycobacterium tuberculosis protein Rv2220 induces maturation and activation of dendritic cells

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

Increased surface expression of HIV-1 envelope is associated with improved antibody response in vaccinia prime/protein boost immunization

HIV-1 envelope (Env)-based vaccines have so far largely failed to induce antibodies that prevent HIV-1 infection. One factor proposed to limit the immunogenicity of cell-associated Env is its low level of expression on the cell surface, restricting accessibility to antibodies. Using a vaccinia prime/protein boost protocol in mice, we explored the immunologic effects of mutations in the Env cytoplasmic tail (CT) that increased surface expression, including partial truncation and ablation of a tyrosine-dependent endocytosis motif. After vaccinia primes, CT-modified Envs induced up to 7-fold higher gp120-specific IgG, and after gp120 protein boosts, they elicited up to 16-fold greater Tier-1 HIV-1 neutralizing antibody titers, although results were variable between isolates. These data indicate that the immunogenicity of HIV-1 Env in a prime/boost vaccine can be enhanced in a strain-dependent manner by CT mutations that increase Env surface expression, thus highlighting the importance of the prime in this vaccine format.

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Novel HIV Env cytoplasmic tail (CT) modifications increase surface expression.

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Vaccinia vector vaccination with CT-modified Envs induces high gp120-specific IgG.

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gp120 boosts in mice primed with CT-modified Envs induce high Tier-1 Nabs.

Cathepsin S inhibition suppresses autoimmune-triggered inflammatory responses in macrophages

In several types of antigen-presenting cells (APCs), Cathepsin S (CatS) plays a crucial role in the regulation of MHC class II surface expression and consequently influences antigen (Ag) presentation of APCs to CD4⁺ T cells. During the assembly of MHC class II-Ag peptide complexes, CatS cleaves the invariant chain p10 (Lip10) - a fragment of the MHC class II-associated invariant chain peptide. In this report, we used a selective, high-affinity CatS inhibitor to suppress the proteolytic activity of CatS in lymphoid and myeloid cells. CatS inhibition resulted in a concentration-dependent Lip10 accumulation in B cells from both healthy donors and patients with systemic lupus erythematosus (SLE). Furthermore, CatS inhibition led to a decreased MHC class II expression on B cells, monocytes, and proinflammatory macrophages. In SLE patient-derived peripheral blood mononuclear cells, CatS inhibition led to a suppressed secretion of IL-6, TNFα, and IL-10. In a second step, we tested the effect of CatS inhibition on macrophages being exposed to patient-derived autoantibodies against C1q (anti-C1q) that are known to be associated with severe lupus nephritis. As shown previously, those SLE patient-derived high-affinity anti-C1q bound to immobilized C1q induce a proinflammatory phenotype in macrophages. Using this human in vitro model of autoimmunity, we found that CatS inhibition reduces the inflammatory responses of macrophages as demonstrated by a decreased secretion of proinflammatory cytokines, the downregulation of MHC class II and CD80. In summary, we can show that the used CatS inhibitor is able to block Lip10 degradation in healthy donor- and SLE patient-derived B cells and inhibits the induction of proinflammatory macrophages. Thus, CatS inhibition seems to be a promising future treatment of SLE.

Distinct Roles of Vaccinia Virus NF-κB Inhibitor Proteins A52, B15, and K7 in the Immune Response

Poxviruses use a complex strategy to escape immune control, by expressing immunomodulatory proteins that could limit their use as vaccine vectors. To test the role of poxvirus NF-κB pathway inhibitors A52, B15, and K7 in immunity, we deleted their genes in an NYVAC (New York vaccinia virus) strain that expresses HIV-1 clade C antigens. After infection of mice, ablation of the A52R, B15R, and K7R genes increased dendritic cell, natural killer cell, and neutrophil migration as well as chemokine/cytokine expression. Revertant viruses with these genes confirmed their role in inhibiting the innate immune system. To different extents, enhanced innate immune responses correlated with increased HIV Pol- and Gag-specific polyfunctional CD8 T cell and HIV Env-specific IgG responses induced by single-, double-, and triple-deletion mutants. These poxvirus proteins thus influence innate and adaptive cell-mediated and humoral immunity, and their ablation offers alternatives for design of vaccine vectors that regulate immune responses distinctly.IMPORTANCE Poxvirus vectors are used in clinical trials as candidate vaccines for several pathogens, yet how these vectors influence the immune system is unknown. We developed distinct poxvirus vectors that express heterologous antigens but lack different inhibitors of the central host-cell signaling pathway. Using mice, we studied the capacity of these viruses to induce innate and adaptive immune responses and showed that these vectors can distinctly regulate the magnitude and quality of these responses. These findings provide important insights into the mechanism of poxvirus-induced immune response and alternative strategies for vaccine vector design.

Newcastle disease virus-like particles induce DC maturation through TLR4/NF-κB pathway and facilitate DC migration by CCR7-CCL19/CCL21 axis

Newcastle disease virus-like particles (NDV VLPs) are a potential candidate vaccine, as shown by eliciting specific immune response against NDV in mice and chickens. Activation of dendritic cells (DCs) is critical to initiate immune response. However, the mechanism of how NDV VLPs induce DC maturation and migration remains elusive. In this study, we found that NDV VLPs are efficient in DC activation by up-regulating surface MHC II and costimulatory molecules, and proinflammatory cytokines through the TLR4/NF-κB pathway. Furthermore, NDV VLPs elevated CCR7 expression on DCs, resulting in DC migration towards CCL19/CCL21 both in vitro and ex vivo. As a consequence of DC maturation and migration, CD4+ T cells were also activated in vivo, demonstrating increased intracellular IFN-γ and IL-4 levels. Together, these results present new insights for NDV VLPs induced DC maturation and migration, providing a better understanding of VLP-triggered innate immune responses.

PPAR-γ agonist pioglitazone regulates dendritic cells immunogenicity mediated by DC-SIGN via the MAPK and NF-κB pathways

Dendritic cell-specific ICAM-3 grabbing non-integrin (DC-SIGN) is a dendritic cell-specific lectin which participates in dendritic cell (DC) trafficking, antigen uptake and DC-T cell interactions at the initiation of immune responses. This study investigated whether peroxisome proliferator-activated receptor-gamma (PPAR-γ) activation in human DCs regulates the immunogenicity of DCs mediated by DC-SIGN and exploited the possible molecular mechanisms, especially focused on the signaling pathways of mitogen-activated protein kinases (MAPK) and nuclear factor-κB (NF-κB). Here, we show that the PPAR-γ agonist pioglitazone decreased DC adhesion and transmigration, and DC stimulation of T cell proliferation mediated by DC-SIGN dependent on activation of PPAR-γ, although it increased DC endocytosis independent of PPAR-γ activation. Furthermore, PPAR-γ activation by pioglitazone in DCs down-regulated the expression of DC-SIGN, which was mediated by modulating the balance of the signaling pathways of extracellular signal-regulated kinase, c-Jun N-terminal kinase and NF-κB, but not p38 MAPK. Therefore, we conclude that PPAR-γ activation in human DCs regulates the immunogenicity of DCs mediated by DC-SIGN via the pathways of MAPK and NF-κB. These findings may support the important role of these mediators in the regulation of DC-mediated inflammatory and immunologic processes.

Impact of in vitro treatments of physiological levels of estradiol and progesterone observed in pregnancy on bovine monocyte-derived dendritic cell differentiation and maturation

The specific factors which regulate differentiation and maturation of dendritic cells in bovine pregnancy remain unclear. We evaluated the influence of physiologically relevant in vitro treatments of progesterone (PG) and estradiol (E2) observed in late pregnancy on the differentiation and maturation of CD14+ monocyte-derived dendritic cell (moDC) from non-pregnant, lactating dairy cows (n=7). We found that moDC differentiated in the presence of both E2 and PG had impaired E. coli-induced phenotypic maturation, specifically a significant reduction in CD80 and MHC II expression. Contrary to our previous work characterizing moDC from late gestating dairy cattle, we did not observe an increase in CD14 expression relative to the untreated control; this increase was only observed in the current data in the dexamethasone-treated moDC. The moDC treated with a combination of both E2 and PG had significantly greater upregulation of anti-inflammatory cytokine IL-10 relative to the untreated control, but TNFα production was not suppressed; only dexamethasone-treated moDC showed abrogated TNFα production. These data suggest moDC may be regulated by E2 and PG to hinder phenotypic maturation and regulate inflammatory responses. Pregnancy-associated hormone profiles appear to be involved in the generation of maternal immune tolerance in pregnancy. These hormone-facilitated changes to moDC in pregnancy may also impede optimal immune responses to both invading pathogens and routine vaccinations administered in late gestation through limited antigen presentation and increased anti-inflammatory cytokine production. These results provide insight into maternal immune modulation and elucidate potential immune changes necessary to facilitate bovine pregnancy.

Differential maturation of murine bone-marrow derived dendritic cells with lipopolysaccharide and tumor necrosis factor-α

Dendritic cells (DCs) play a key role in the interface between the innate and acquired immune systems. In response to both exogenous as well as endogenous signals, DCs undergo a programmed maturation to become an efficient, antigen-presenting cell. Yet little is known regarding the differential responses by endogenous versus exogenous stimuli on DC maturation. In the present report, we have compared the phenotypic, functional, and genome-wide expression responses associated with maturation by bone marrow derived DCs to either an endogenous danger signal, tumor necrosis factor-α (TNF-α), or a microbial product, bacterial lipopolysaccharide (LPS). Examination of the cell surface expression of DCs as well as cytokine production demonstrated that patterns of DC maturation varied dramatically depending upon the stimulus. Whereas LPS was highly effective in terms of inducing phenotypic and functional maturation, TNF-α exposure produced a phenotypically distinct DC. Gene expression patterns in DCs 6 and 24 h after LPS and TNF-α exposure revealed that these activation signals produce fundamentally different genomic responses. Supervised analysis revealed that the expression of 929 probe sets discriminated among the treatment groups, and the patterns of gene expression in TNF-α stimulated DCs were more similar to unstimulated cells at both 6 and 24 h post-stimulation than to LPS-stimulated cells at the same time points. These findings reveal that DCs are capable of a varying phenotypic response to different antigens and endogenous signals.

LPS, dsRNA and the interferon bridge to adaptive immune responses: Trif, Tram, and other TIR adaptor proteins

Toll-like receptors (TLRs) expressed on antigen-presenting cells (APCs), form a critical link between innate and the adaptive immune responses. Activation of TLRs by LPS and dsRNA results in up-regulation of co-stimulatory molecules (UCM) essential for the generation of robust T-cell responses. It is now evident that type I interferons (IFNs) play an important role in UCM and in the subsequent maturation of APCs. The recently identified adaptor molecules Trif and Tram, unlike their counterparts MyD88 and MAL/Tirap, induce type I IFN via the TLR4 signaling pathway, whereas Trif appears to be the sole adaptor molecule involved in TLR3 signaling, resulting in subsequent production of type I IFN. Here, we discuss how Trif and type I IFN are involved in the optimization of APC-T cell interaction in response not only to viral but also bacterial stimuli.

Stimulatory versus suppressive effects of GM-CSF on tumor progression in multiple cancer types

Granulocyte-macrophage colony-stimulating factor (GM-CSF, also called CSF-2) is best known for its critical role in immune modulation and hematopoiesis. A large body of experimental evidence indicates that GM-CSF, which is frequently upregulated in multiple types of human cancers, effectively marks cancer cells with a ‘danger flag' for the immune system. In this context, most studies have focused on its function as an immunomodulator, namely its ability to stimulate dendritic cell (DC) maturation and monocyte/macrophage activity. However, recent studies have suggested that GM-CSF also promotes immune-independent tumor progression by supporting tumor microenvironments and stimulating tumor growth and metastasis. Although some studies have suggested that GM-CSF has inhibitory effects on tumor growth and metastasis, an even greater number of studies show that GM-CSF exerts stimulatory effects on tumor progression. In this review, we summarize a number of findings to provide the currently available information regarding the anticancer immune response of GM-CSG. We then discuss the potential roles of GM-CSF in the progression of multiple types of cancer to provide insights into some of the complexities of its clinical applications.