Specialization and complementarity in microbial molecule recognition by human myeloid and plasmacytoid dendritic cells

In vivo cancer vaccination: Which dendritic cells to target and how?

The field of cancer immunotherapy has been revolutionized with the use of immune checkpoint blockade antibodies such as anti-programmed cell death 1 protein (PD-1) and chimeric antigen receptor T cells. Significant clinical benefits are observed in different cancer types with these treatments. While considerable efforts are made in augmenting tumor-specific T cell responses with these therapies, other immunotherapies that actively stimulate endogenous anti-tumor T cells and generating long-term memory have received less attention. Given the high cost of cancer immunotherapies especially with chimeric antigen receptor T cells, not many patients will have access to such treatments. The next-generation of cancer immunotherapy could entail in vivo cancer vaccination to activate both the innate and adaptive anti-tumor responses. This could potentially be achieved via in vivo targeting of dendritic cells which are an indispensable link between the innate and adaptive immunities. Dendritic cells highly expressed toll-like receptors for recognizing and eliminating pathogens. Synthetic toll-like receptors agonists could be synthesized at a low cost and have shown promise in preclinical and clinical trials. As different subsets of human dendritic cells exist in the immune system, activation with different toll-like receptor agonists could exert profound effects on the quality and magnitude of anti-tumor T cell responses. Here, we reviewed the different subsets of human dendritic cells. Using published preclinical and clinical cancers studies available on PubMed, we discussed the use of clinically approved and emerging toll-like receptor agonists to activate dendritic cells in vivo for cancer immunotherapy. Finally, we searched www.clinicaltrials.gov and summarized the active cancer trials evaluating toll-like receptor agonists as an adjuvant.

E-cadherin expression on multiple myeloma cells activates tumor-promoting properties in plasmacytoid DCs

Plasmacytoid dendritic cells (pDCs) play a key role in antiviral responses by producing type-1 IFNs. However, recent studies showed that pDCs induce immune suppression and promote tumor growth in human ovarian cancer and myeloma. The molecular mechanisms underlying pDC acquisition of these properties are unknown. Here we show that human pDCs activated by CpG inhibited growth and induced apoptosis in myeloma cells via secreted IFN-α, but direct contact with myeloma cells converted pDCs into tumor-promoting cells by suppressing pDC IFN-α production. E-cadherin, expressed on both myeloma cells and pDCs, mediated these effects via a homophilic interaction - activation of E-cadherin signaling upregulated and activated TNFAIP3 to interact with TLR9, resulting in TLR9 ubiquitination and degradation, and inhibition of IFN-α production in pDCs. These findings were supported by an in vivo study in which pDC depletion induced tumor regression and better survival in the Vk*MYC myeloma mouse model. Furthermore, IFNAR1 expression level positively correlated to overall survival of patients with multiple myeloma (MM), and the IFN-α level in patient bone marrow was significantly lower than that in marrow of healthy individuals. This study reveals a novel mechanism underlying how MM tumors educate pDCs in their microenvironment and provides new targets for improving the treatment of MM.

Immunolocalization of Dendritic Cells and Pattern Recognition Receptors in Chronic Rhinosinusitis

Background

Dendritic cell (DC) activation and antigen presentation to T cells are critical to innate and adaptive immunity. Toll-like receptors (TLRs) are known to bind pathogen-associated molecular patterns in addition to sinonasally secreted surfactant proteins (SP) such as SP-A and SP-D. TLR binding is known to activate DCs. Based on these observations, we sought to establish the presence, in sinonasal mucosa, of DC and the pattern recognition receptors (PRRs), CD14, TLR2, and TLR4.

Methods

Sinonasal biopsy specimens were taken from patients with eosinophilic nonatopic nasal polyposis (n = 4), allergic fungal sinusitis (n = 1), and nondiseased patients undergoing cerebrospinal fluid leak repair or pituitary tumor resection (n = 2). Tissue samples were stained immunohistochemically for PRR (CD14, TLR2, and TLR4), mature DC marker (CD208), iDC marker (CD209), or isotype controls.

Results

Immature and mature DC were immunolocalized to the subepithelial stroma and ciliated epithelial surface, respectively. Diffuse staining of CD14 was observed throughout the stroma with additional staining in the ciliated epithelium. The TLR markers showed no staining in the ciliated epithelium. TLR2 primarily localized in stroma immediately deep to the ciliated epithelial surface. TLR4 immunolocalized to submucosal seromucinous gland ductal epithelium. Data from nondiseased patients were mixed, with one patient showing minimal staining of any of the tested cellular markers.

Conclusion

This study indicates progressive DC activation and emigration of mature antigen-presenting cells from the epithelial surfaces of sinonasal mucosa. The presence of TLR known to bind SP-A and SP-D suggests a link between SP expression and immune response in sinonasal mucosa.

Modulation of toll-like receptor signaling by antimicrobial peptides

Antimicrobial peptides (AMPs) are typically thought of as molecular hole punchers that directly kill pathogens by membrane permeation. However, recent work has shown that AMPs are pleiotropic, multifunctional molecules that can strongly modulate immune responses. In this review, we provide a historical overview of the immunomodulatory properties of natural and synthetic antimicrobial peptides, with a special focus on human cathelicidin and defensins. We also summarize the various mechanisms of AMP immune modulation and outline key structural rules underlying the recently-discovered phenomenon of AMP-mediated Toll-like receptor (TLR) signaling. In particular, we describe several complementary studies demonstrating how AMPs self-assemble with nucleic acids to form nanocrystalline complexes that amplify TLR-mediated inflammation. In a broader scope, we discuss how this new conceptual framework allows for the prediction of immunomodulatory behavior in AMPs, how the discovery of hidden antimicrobial activity in known immune signaling proteins can inform these predictions, and how these findings reshape our understanding of AMPs in normal host defense and autoimmune disease.

Scanning the Immunopathogenesis of Psoriasis

Psoriasis is a chronic inflammatory skin disease, the immunologic model of which has been profoundly revised following recent advances in the understanding of its pathophysiology. In the current model, a crosstalk between keratinocytes, neutrophils, mast cells, T cells, and dendritic cells is thought to create inflammatory and pro-proliferative circuits mediated by chemokines and cytokines. Various triggers, including recently identified autoantigens, Toll-like receptor agonists, chemerin, and thymic stromal lymphopoietin may activate the pathogenic cascade resulting in enhanced production of pro-inflammatory and proliferation-inducing mediators such as interleukin (IL)-17, tumor necrosis factor (TNF)-α, IL-23, IL-22, interferon (IFN)-α, and IFN-γ by immune cells. Among these key cytokines lie therapeutic targets for currently approved antipsoriatic therapies. This review aims to provide a comprehensive overview on the immune-mediated mechanisms characterizing the current pathogenic model of psoriasis.

Pathogenic mechanisms of IgE-mediated inflammation in self-destructive autoimmune responses

Autoantibodies of the IgG subclass are pathogenic in a number of autoimmune disorders such as systemic lupus erythomatosus. The presence of circulating IgE autoantibodies in autoimmune patients has also been known for almost 40 years. Despite their role in allergies, IgE autoantibodies are not associated with a higher rate of atopy in these patients. However, recently they have been recognized as active drivers of autoimmunity through mechanisms involving the secretion of Type I interferons by plasmacytoid dendritic cells (pDC), the recruitment of basophils to lymph nodes, and the activation of adaptive immune responses through B and T cells. Here, we will review the formation, prevalence, affinity, and roles of the IgE autoantibodies that have been described in autoimmunity. We also present novel evidence supporting that triggering of IgE receptors in pDC induces LC3-associated phagocytosis, a cellular process also known as LAP that is associated with interferon responses. The activation of pDC with immune complexes formed by DNA-specific IgE antibodies also induce potent B-cell differentiation and plasma cell formation, which further define IgE's role in autoimmune humoral responses.

Innate transcriptional effects by adjuvants on the magnitude, quality, and durability of HIV envelope responses in NHPs

Adjuvants have a critical role for improving vaccine efficacy against many pathogens, including HIV. Here, using transcriptional RNA profiling and systems serology, we assessed how distinct innate pathways altered HIV-specific antibody responses in nonhuman primates (NHPs) using 8 clinically based adjuvants. NHPs were immunized with a glycoprotein 140 HIV envelope protein (Env) and insoluble aluminum salts (alum), MF59, or adjuvant nanoemulsion (ANE) coformulated with or without Toll-like receptor 4 (TLR4) and 7 agonists. These were compared with Env administered with polyinosinic-polycytidylic acid:poly-L-lysine, carboxymethylcellulose (pIC:LC) or immune-stimulating complexes. Addition of the TLR4 agonist to alum enhanced upregulation of a set of inflammatory genes, whereas the TLR7 agonist suppressed expression of alum-responsive inflammatory genes and enhanced upregulation of antiviral and interferon (IFN) genes. Moreover, coformulation of the TLR4 or 7 agonists with alum boosted Env-binding titers approximately threefold to 10-fold compared with alum alone, but remarkably did not alter gene expression or enhance antibody titers when formulated with ANE. The hierarchy of adjuvant potency was established after the second of 4 immunizations. In terms of antibody durability, antibody titers decreased ∼10-fold after the final immunization and then remained stable after 65 weeks for all adjuvants. Last, Env-specific Fc-domain glycan structures and a series of antibody effector functions were assessed by systems serology. Antiviral/IFN gene signatures correlated with Fc-receptor binding across all adjuvant groups. This study defines the potency and durability of 8 different clinically based adjuvants in NHPs and shows how specific innate pathways can alter qualitative aspects of Env antibody function.

Activation of innate immunity in primary human cells using a plant virus derived nanoparticle TLR7/8 agonist

Rod-shaped virus-like nanoparticles (VLNP) made of papaya mosaic virus (PapMV) coat proteins (CP) self-assembled around a single stranded RNA (ssRNA) were showed to be a TLR7 agonist. Their utilization as an immune modulator in cancer immunotherapy was shown to be promising. To establish a clinical relevance in human for PapMV VLNP, we showed that stimulation of human peripheral blood mononuclear cells (PBMC) with VLNP induces the secretion of interferon alpha (IFNα) and other pro-inflammatory cytokines and chemokines. Plasmacytoid dendritic cells (pDCs) were activated and secreted IFN-α upon VLNP exposure. Monocyte-derived dendritic cells upregulate maturation markers and produce IL-6 in response to PapMV VLNP stimulation, which suggests the activation of TLR8. Finally, when co-cultured with NK cells, PapMV induced pDCs promoted the NK cytolytic activity against cancer cells. These data obtained with primary human immune cells further strengthen the clinical relevance of PapMV VLNPs as a cancer immunotherapy agent.

Profiling dendritic cell subsets in the patients with active pulmonary tuberculosis

Dendritic cell (DC) plays an important role in the immune response against pulmonary tuberculosis. However, the phenotypic profile of DC subsets in peripheral blood in individuals with active pulmonary tuberculosis (APT) is still inconclusive. Here, we demonstrated that the absolute numbers of total DC (tDC), myeloid DC (mDC) and plasmacytoid DC (pDC) in individuals with APT were decreased compared to healthy controls (HCs). The decreased number of DCs, especially of pDC, seems to be a useful diagnostic marker of APT. Meanwhile, the number of DCs was associated with the prolonged/complicated TB, ATD treatment effect and lymphocyte immune reactions, as manifested that relapsed APT patients with a higher number of tDC and lower number of pDC compared to newly diagnosed patients. Interestingly, mDC from APT patients displayed high expressions of CD83 and CCR7, but pDC displayed low expressions of CD83 and CCR7. Moreover, DCs from APT patients expressed lower levels of HLA-DR and CD80, but expressed a higher level of CD86 than those from HCs. However, the antigen uptake capacity of DC subsets was not different between APT and HCs, despite the antigen uptake capacity of pDC was much lower than that of mDC in both APT patients and HCs. Our data represent a systematic profile of DC subsets in the blood of APT patients, and would represent a useful biomarker for APT.

Dendritic Cell Immune Responses in HIV-1 Controllers

PURPOSE OF REVIEW

Robust HIV-1-specific CD8 T cell responses are currently regarded as the main correlate of immune defense in rare individuals who achieve natural, drug-free control of HIV-1; however, the mechanisms that support evolution of such powerful immune responses are not well understood. Dendritic cells (DCs) are specialized innate immune cells critical for immune recognition, immune regulation, and immune induction, but their possible contribution to HIV-1 immune defense in controllers remains ill-defined.

RECENT FINDINGS

Recent studies suggest that myeloid DCs from controllers have improved abilities to recognize HIV-1 through cytoplasmic immune sensors, resulting in more potent, cell-intrinsic type I interferon secretion in response to viral infection. This innate immune response may facilitate DC-mediated induction of highly potent antiviral HIV-1-specific T cells. Moreover, protective HLA class I isotypes restricting HIV-1-specific CD8 T cells may influence DC function through specific interactions with innate myelomonocytic MHC class I receptors from the leukocyte immunoglobulin-like receptor family. Bi-directional interactions between dendritic cells and HIV-1-specific T cells may contribute to natural HIV-1 immune control, highlighting the importance of a fine-tuned interplay between innate and adaptive immune activities for effective antiviral immune defense.

Epstein Barr virus Latent Membrane Protein-1 enhances dendritic cell therapy lymph node migration, activation, and IL-12 secretion

Dendritic cells (DC) are a promising cell type for cancer vaccines due to their high immunostimulatory capacity. However, improper maturation of DC prior to treatment may account for the limited efficacy of DC vaccine clinical trials. Latent Membrane Protein-1 (LMP1) of Epstein-Barr virus was examined for its ability to mature and activate DC as a gene-based molecular adjuvant for DC vaccines. DC were transduced with an adenovirus 5 vector (Ad5) expressing LMP1 under the control of a Tet-inducible promoter. Ad5-LMP1 was found to mature and activate both human and mouse DC. LMP1 enhanced in vitro migration of DC toward CCL19, as well as in vivo migration of DC to the inguinal lymph nodes of mice following intradermal injection. LMP1-transduced DC increased T cell proliferation in a Pmel-1 adoptive transfer model and enhanced survival in B16-F10 melanoma models. LMP1-DC also enhanced protection in a vaccinia-Gag viral challenge assay. LMP1 induced high levels of IL-12p70 secretion in mouse DC when compared to standard maturation protocols. Importantly, LMP1-transduced human DC retained the capacity to secrete IL-12p70 and TNF in response to DC restimulation. In contrast, DC matured with Monocyte Conditioned Media-Mimic cocktail (Mimic) were impaired in IL-12p70 secretion following restimulation. Overall, LMP1 matured and activated DC, induced migration to the lymph node, and generated high levels of IL-12p70 in a murine model. We propose LMP1 as a promising molecular adjuvant for DC vaccines.

Δ9-Tetrahydrocannabinol Suppresses Secretion of IFNα by Plasmacytoid Dendritic Cells From Healthy and HIV-Infected Individuals

Plasmacytoid dendritic cells (pDCs) play a crucial role in host antiviral immune response through secretion of type I interferon. Interferon alpha (IFNα), a type I IFN, is critical for mounting the initial response to viral pathogens. A consequence of Human Immunodeficiency Virus-1 (HIV) infection is a decrease in both pDC number and function, but prolonged pDC activity has been linked with progression from HIV infection to the development of AIDS. Patients with HIV in the United States routinely use cannabinoid-based therapies to combat the side effects of HIV infection and antiretroviral therapy. However, cannabinoids, including Δ-tetrahydrocannabinol (THC), are well-characterized immunosuppressants. Here, we report that THC suppressed secretion of IFNα by pDC from both healthy and HIV+ donors through a mechanism involving impaired phosphorylation of interferon regulatory factor 7. These results suggest that THC can suppress pDC function during the early host antiviral response by dampening pDC activation.

Antiviral Functions of Human Immunodeficiency Virus Type 1 (HIV-1)-Specific IgG Antibodies: Effects of Antiretroviral Therapy and Implications for Therapeutic HIV-1 Vaccine Design

Contemporary antiretroviral therapy (ART) is effective and tolerable for long periods of time but cannot eradicate human immunodeficiency virus type 1 (HIV-1) infection by either elimination of viral reservoirs or enhancement of HIV-1-specific immune responses. Boosting "protective" HIV-1-specific immune responses by active or passive immunization will therefore be necessary to control or eradicate HIV-1 infection and is currently the topic of intense investigation. Recently reported studies conducted in HIV patients and non-human primate (NHP) models of HIV-1 infection suggest that HIV-1-specific IgG antibody responses may contribute to the control of HIV-1 infection. However, production of IgG antibodies with virus neutralizing activity by vaccination remains problematic and while vaccine-induced natural killer cell-activating IgG antibodies have been shown to prevent the acquisition of HIV-1 infection, they may not be sufficient to control or eradicate established HIV-1 infection. It is, therefore, important to consider other functional characteristics of IgG antibody responses. IgG antibodies to viruses also mediate opsonophagocytic antibody responses against virions and capsids that enhance the function of phagocytic cells playing critical roles in antiviral immune responses, particularly conventional dendritic cells and plasmacytoid dendritic cells. Emerging evidence suggests that these antibody functions might contribute to the control of HIV-1 infection. In addition, IgG antibodies contribute to the intracellular degradation of viruses via binding to the cytosolic fragment crystallizable (Fc) receptor tripartite motif containing-21 (TRIM21). The functional activity of an IgG antibody response is influenced by the IgG subclass content, which affects binding to antigens and to Fcγ receptors on phagocytic cells and to TRIM21. The IgG subclass content and avidity of IgG antibodies is determined by germinal center (GC) reactions in follicles of lymphoid tissue. As HIV-1 infects cells in GCs and induces GC dysfunction, which may persist during ART, strategies for boosting HIV-1-specific IgG antibody responses should include early commencement of ART and possibly the use of particular antiretroviral drugs to optimize drug levels in lymphoid follicles. Finally, enhancing particular functions of HIV-1-specific IgG antibody responses by using adjuvants or cytokines to modulate the IgG subclass content of the antibody response might be investigated in NHP models of HIV-1 infection and during trials of therapeutic vaccines in HIV patients.

Dendritic Cell Dysfunction in Patients with End-stage Renal Disease

End-stage renal disease (ESRD) with immune disorder involves complex interactions between the innate and adaptive immune responses. ESRD is associated with various alterations in immune function such as a reduction in polymorphonuclear leukocyte bactericidal activity, a suppression of lymphocyte proliferative response to stimuli, and a malfunction of cell-mediated immunity at the molecular level. ESRD also increases patients' propensity for infections and malignancies as well as causing a diminished response to vaccination. Several factors influence the immunodeficiency in patients with ESRD, including uremic toxins, malnutrition, chronic inflammation, and the therapeutic dialysis modality. The alteration of T-cell function in ESRD has been considered to be a major factor underlying the impaired adaptive cellular immunity in these patients. However, cumulative evidence has suggested that the immune defect in ESRD can be caused by an Ag-presenting dendritic cell (DC) dysfunction in addition to a T-cell defect. It has been reported that ESRD has a deleterious effect on DCs both in terms of their number and function, although the precise mechanism by which DC function becomes altered in these patients is unclear. In this review, we discuss the effects of ESRD on the number and function of DCs and propose a possible molecular mechanism for DC dysfunction. We also address therapeutic approaches to improve immune function by optimally activating DCs in patients with ESRD.

Enhanced stimulation of human tumor-specific T cells by dendritic cells matured in the presence of interferon-γ and multiple toll-like receptor agonists

Dendritic cell (DC) vaccines have been demonstrated to elicit immunological responses in numerous cancer immunotherapy trials. However, long-lasting clinical effects are infrequent. We therefore sought to establish a protocol to generate DC with greater immunostimulatory capacity. Immature DC were generated from healthy donor monocytes by culturing in the presence of IL-4 and GM-CSF and were further differentiated into mature DC by the addition of cocktails containing different cytokines and toll-like receptor (TLR) agonists. Overall, addition of IFNγ and the TLR7/8 agonist R848 during maturation was essential for the production of high levels of IL-12p70 which was further augmented by adding the TLR3 agonist poly I:C. In addition, the DC matured with IFNγ, R848, and poly I:C also induced upregulation of several other pro-inflammatory and Th1-skewing cytokines/chemokines, co-stimulatory receptors, and the chemokine receptor CCR7. For most cytokines and chemokines the production was even further potentiated by addition of the TLR4 agonist LPS. Concurrently, upregulation of the anti-inflammatory cytokine IL-10 was modest. Most importantly, DC matured with IFNγ, R848, and poly I:C had the ability to activate IFNγ production in allogeneic T cells and this was further enhanced by adding LPS to the cocktail. Furthermore, epitope-specific stimulation of TCR-transduced T cells by peptide- or whole tumor lysate-loaded DC was efficiently stimulated only by DC matured in the full maturation cocktail containing IFNγ and the three TLR ligands R848, poly I:C, and LPS. We suggest that this cocktail is used for future clinical trials of anti-cancer DC vaccines.

Biofilms and host response - helpful or harmful

Biofilm infections are one of the modern medical world's greatest challenges. Probably, all non-obligate intracellular bacteria and fungi can establish biofilms. In addition, there are numerous biofilm-related infections, both foreign body-related and non-foreign body-related. Although biofilm infections can present in numerous ways, one common feature is involvement of the host response with significant impact on the course. A special characteristic is the synergy of the innate and the acquired immune responses for the induced pathology. Here, we review the impact of the host response for the course of biofilm infections, with special focus on cystic fibrosis, chronic wounds and infective endocarditis.

Dual activation of Toll-like receptors 7 and 9 impairs the efficacy of antitumor vaccines in murine models of metastatic breast cancer

PURPOSE

Since combination of Toll-like receptor (TLR) ligands could boost antitumor immunity, we evaluated the efficacy of dendritic cell (DC) vaccines upon dual activation of TLR9 and TLR7 in breast cancer models.

METHODS

DCs were generated from mouse bone marrow or peripheral blood from healthy human donors and stimulated with CpG1826 (mouse TLR9 agonist), CpG2006 or IMT504 (human TLR9 agonists) and R848 (TLR7 agonist). Efficacy of antitumor vaccines was evaluated in BALB/c mice bearing metastatic mammary adenocarcinomas.

RESULTS

CpG-DCs improved the survival of tumor-bearing mice, reduced the development of lung metastases and generated immunological memory. However, dual activation of TLRs impaired the efficacy of DC vaccines. In vitro, we found that R848 inhibited CpG-mediated maturation of murine DCs. A positive feedback loop in TLR9 mRNA expression was observed upon CpG stimulation that was inhibited in the presence of R848. Impaired activation of NF-κB was detected when TLR9 and TLR7 were simultaneously activated. Blockade of nitric oxide synthase (NOS) and indoleamine-pyrrole-2,3-dioxygenase (IDO) improved the activation of CpG-DCs. When we evaluated the effect of combined activation of TLR9 and TLR7 in human DCs, we found that R848 induced robust DC activation that was inhibited by TLR9 agonists.

CONCLUSIONS

These observations provide insight in the biology of TLR9 and TLR7 crosstalk and suggest caution in the selection of agonists for multiple TLR stimulation. Blockade of NOS and IDO could improve the maturation of antitumor DC vaccines. R848 could prove a useful adjuvant for DC vaccines in human patients.

Interleukin-10 and prostaglandin E2 have complementary but distinct suppressive effects on Toll-like receptor-mediated dendritic cell activation in ovarian carcinoma

Dendritic cells (DC) have the potential to instigate a tumour-specific immune response, but their ability to prime naïve lymphocytes depends on their activation status. Thus, for tumour immunotherapy to be effective, the provision of appropriate DC activation stimuli such as Toll-like receptor (TLR) agonists is crucial in order to overcome immunosuppression associated with the tumour microenvironment. To address this, we investigated how ovarian carcinoma (OC)-associated ascites impedes activation of DC by TLR agonists. Our results show that ascites reduces the TLR-mediated up-regulation of CD86 and partially inhibits the production of the pro-inflammatory cytokines interleukin 6 (IL-6), IL-12 and tumour necrosis factor α (TNFα) in monocyte-derived DC from healthy controls. We further observe an impaired T cell stimulatory capacity of DC upon activation with TLR agonists in the presence of ascites, indicating that their functionality is affected by the immunosuppressive factors. We identify IL-10 and prostaglandin E2 (PGE₂) as the pivotal immunosuppressive components in OC-associated ascites compromising TLR-mediated DC activation. Interestingly, IL-10 is present in both ascites from patients with malignant OC and in peritoneal fluid from patients with benign ovarian conditions and both fluids have similar ability to reduce TLR-mediated DC activation. However, depletion of IL-10 from ascites revealed that the presence of paracrine IL-10 is not crucial for ascites-mediated suppression of DC activation in response to TLR activation. Unlike IL-10, PGE₂ is absent from peritoneal fluid of patients with benign conditions and selectively reduces TNFα induction in response to TLR-mediated activation in the presence of OC-associated ascites. Our study highlights PGE₂ as an immunosuppressive component of the malignant OC microenvironment rendering PGE₂ a potentially important target for immunotherapy in OC.

Toll-Like Receptor 7 Agonist GS-9620 Induces HIV Expression and HIV-Specific Immunity in Cells from HIV-Infected Individuals on Suppressive Antiretroviral Therapy

Antiretroviral therapy can suppress HIV replication to undetectable levels but does not eliminate latent HIV, thus necessitating lifelong therapy. Recent efforts to target this persistent reservoir have focused on inducing the expression of latent HIV so that infected cells may be recognized and eliminated by the immune system. Toll-like receptor (TLR) activation stimulates antiviral immunity and has been shown to induce HIV from latently infected cells. Activation of TLR7 leads to the production of several stimulatory cytokines, including type I interferons (IFNs). In this study, we show that the selective TLR7 agonist GS-9620 induced HIV in peripheral blood mononuclear cells (PBMCs) from HIV-infected individuals on suppressive antiretroviral therapy. GS-9620 increased extracellular HIV RNA 1.5- to 2-fold through a mechanism that required type I IFN signaling. GS-9620 also activated HIV-specific T cells and enhanced antibody-mediated clearance of HIV-infected cells. Activation by GS-9620 in combination with HIV peptide stimulation increased CD8 T cell degranulation, production of intracellular cytokines, and cytolytic activity. T cell activation was again dependent on type I IFNs produced by plasmacytoid dendritic cells. GS-9620 induced phagocytic cell maturation and improved effector-mediated killing of HIV-infected CD4 T cells by the HIV envelope-specific broadly neutralizing antibody PGT121. Collectively, these data show that GS-9620 can activate HIV production and improve the effector functions that target latently infected cells. GS-9620 may effectively complement orthogonal therapies designed to stimulate antiviral immunity, such as therapeutic vaccines or broadly neutralizing antibodies. Clinical studies are under way to determine if GS-9620 can target HIV reservoirs.

IMPORTANCE Though antiretroviral therapies effectively suppress viral replication, they do not eliminate integrated proviral DNA. This stable intermediate of viral infection is persistently maintained in reservoirs of latently infected cells. Consequently, lifelong therapy is required to maintain viral suppression. Ultimately, new therapies that specifically target and eliminate the latent HIV reservoir are needed. Toll-like receptor agonists are potent enhancers of innate antiviral immunity that can also improve the adaptive immune response. Here, we show that a highly selective TLR7 agonist, GS-9620, activated HIV from peripheral blood mononuclear cells isolated from HIV-infected individuals with suppressed infection. GS-9620 also improved immune effector functions that specifically targeted HIV-infected cells. Previously published studies on the compound in other chronic viral infections show that it can effectively induce immune activation at safe and tolerable clinical doses. Together, the results of these studies suggest that GS-9620 may be useful for treating HIV-infected individuals on suppressive antiretroviral therapy.

Excessive activation of the TLR9/TGF-β1/PDGF-B pathway in the peripheral blood of patients with systemic lupus erythematosus

Background

Our aim is to study the existence of the TLR9/TGF-β1/PDGF-B pathway in healthy humans and patients with systemic lupus erythematosus (SLE), and to explore its possible involvement in the pathogenesis of lupus nephritis (LN).

Methods

Protein levels of the cytokines were detected by ELISA. mRNA levels of the cytokines were analyzed by real-time PCR. MTT assay was used to test the proliferation of mesangial cells under different treatments.

Results

Compared to healthy controls (N_Control = 56), levels of Toll-like receptor (TLR)9, transforming growth factor (TGF)-β1, and platelet-derived growth factor B (PDGF-B) were increased significantly in the peripheral blood of SLE patients (N_SLE = 112). Significant correlations between the levels of TLR9, TGF-β1, and PDGF-B were observed in both healthy controls and SLE patients. The levels of TGF-β1 and PDGF-B were greatly enhanced by TLR9 activation in primary cell cultures. The proliferation of mesangial cells induced by the plasma of SLE patients was significantly higher than that induced by healthy controls; PDGF-B was involved in this process. The protein levels of PDGF-B homodimer correlated with the levels of urine protein in SLE patients with LN (N_LN =38).

Conclusions

The TLR9/TGF-β1/PDGF-B pathway exists in humans and can be excessively activated in SLE patients. High levels of PDGF-B may result in overproliferation of mesangial cells in the kidney that are involved in the development of glomerulonephritis and LN. Further studies are necessary to identify TLR9, TGF-β1, and PDGF-B as new therapeutic targets to prevent the development of glomerulonephritis and LN.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-017-1238-8) contains supplementary material, which is available to authorized users.

Differentially expressed immune-related genes in hemocytes of the pearl oyster Pinctada fucata against allograft identified by transcriptome analysis

The pearl oyster Pinctada fucata is commonly cultured for marine pearls in China. To culture pearls, a mantle piece from a donor pearl oyster is grafted with a nucleus into a receptor. This transplanted mantle piece may be rejected by the immune system of the recipient oyster, thus reducing the success of transplantation. However, there have been limited studies about the oyster's immune defense against allograft. In this study, hemocyte transcriptome analysis was performed to detect the immune responses to allograft in P. fucata at 0 h and 48 h after a transplant. The sequencing reaction produced 92.5 million reads that were mapped against the reference genome sequences of P. fucata. The Gene Ontology (GO) annotation and the Kyoto Encyclopedia of Genes and Genomes (KEGG) were used to identify all immune-related differentially expressed genes (DEGs). Compared with patterns at 0 h, a total of 798 DEGs were identified, including 410 up-regulated and 388 down-regulated genes at 48 h. The expression levels of interleukin receptor and toll-like receptor in hemocytes were increased significantly 48 h post-transplant, indicating that the oyster immune response was induced. Finally, altered levels of 18 randomly selected immune-related DEGs were confirmed by quantitative real-time PCR (qRT-PCR). Our results provide the basis for further analysis of the immune rejection of allotransplantation.

Natural amines inhibit activation of human plasmacytoid dendritic cells through CXCR4 engagement

Plasmacytoid dendritic cells (pDC) are specialized in secretion of type I interferon in response to pathogens. Here we show that natural monoamines and synthetic amines inhibit pDC activation by RNA viruses. Furthermore, a synthetic analogue of histamine reduces type I interferon production in a mouse model of influenza infection. We identify CXC chemokine receptor 4 (CXCR4) as a receptor used by amines to inhibit pDC. Our study establishes a functional link between natural amines and the innate immune system and identifies CXCR4 as a potential ‘on-off' switch of pDC activity with therapeutic potential.

Plasmacytoid dendritic cells produce type I interferons in response to viral sensing. Here the authors show that amines inhibit these plasmacytoid dendritic cell responses through CXCR4 engagement.

Antibody-mediated depletion of immunosuppressive factors from ovarian carcinoma-associated ascites for investigation of paracrine versus autocrine effects

Many studies seek to explore the impact of extrinsic soluble factors present in serum, interstitial fluids or cell-conditioned media on cells in vitro. A convenient approach to elucidate the effects of a particular factor is its selective neutralization. However, intrinsic production of soluble factors such as cytokines by the cultured cells is common and can have an impact via autocrine mechanisms. The addition of cytokine-specific neutralizing antibodies leads to neutralization of the targeted factors irrespective of their source and affects paracrine and autocrine effects alike. Thus, neutralization assays are not suitable to irrevocably demonstrate that the examined factors exert their effect via a paracrine mechanism. We were interested in investigating the impact of immunosuppressive factors present in ovarian carcinoma-associated ascites by dissecting paracrine versus autocrine effects of interleukin 10 (IL-10) and prostaglandin E2 (PGE₂) on the activation of monocyte-derived dendritic cells (DC). We explored several methods of depletion based on introduction of the neutralizing antibodies bound to beads. Here we describe the pitfalls of the investigated depletion approaches and show the importance of monitoring the presence of residual neutralizing antibodies in the sample upon depletion, which impacts on the suitability of the approach to distinguish paracrine from autocrine effects. Only one of three investigated approaches showed no dislocation of neutralizing antibody from the beads into the sample. This method, which is based on covalently linking antibody to magnetic beads harbouring a reactive group allowed for the complete removal of the investigated factors from ascites and represents an elegant tool to elucidate immunoregulatory or -stimulatory cytokine networks in considerably more depth than the use of neutralizing antibodies in cell cultures alone can contribute.

CpG oligodeoxynucleotide nanomedicines for the prophylaxis or treatment of cancers, infectious diseases, and allergies

Unmethylated cytosine-guanine dinucleotide-containing oligodeoxynucleotides (CpG ODNs), which are synthetic agonists of Toll-like receptor 9 (TLR9), activate humoral and cellular immunity and are being developed as vaccine adjuvants to prevent or treat cancers, infectious diseases, and allergies. Free CpG ODNs have been used in many clinical trials implemented to verify their effects. However, recent research has reported that self-assembled CpG ODNs, protein/peptide–CpG ODN conjugates, and nanomaterial–CpG ODN complexes demonstrate higher adjuvant effects than free CpG ODNs, owing to their improved uptake efficiency into cells expressing TLR9. Moreover, protein/peptide–CpG ODN conjugates and nanomaterial–CpG ODN complexes are able to deliver CpG ODNs and antigens (or allergens) to the same types of cells, which enables a higher degree of prophylaxis or therapeutic effect. In this review, the author describes recent trends in the research and development of CpG ODN nanomedicines containing self-assembled CpG ODNs, protein/peptide–CpG ODN conjugates, and nanomaterial–CpG ODN complexes, focusing mainly on the results of preclinical and clinical studies.

Evaluation of TLR9 expression on PBMCs and CpG ODN-TLR9 ligation on IFN-α production in SLE patients

CONTEXT

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease characterized by autoreactive antibodies. Recent findings revealed the importance of innate immune responses, especially Toll-like receptors (TLRs) in the pathogenesis of SLE.

OBJECTIVE

In this study, the level of TLR9 expression on peripheral blood mononuclear cells (PBMCs) was analyzed. The levels of produced IFN-α were also measured in supernatant of PBMCs from SLE patients and healthy controls after stimulation with CpG ODN2216 which is a plasmocytoid dendritic cell (pDC)-specific TLR9 ligand.

MATERIALS AND METHODS

TLR9 expression was analyzed by real-time polymerase chain reaction (PCR) and flow cytometry in 35 SLE patients and 38 healthy controls and IFN-α concentration was measured in supernatants using enzyme-linked immunosorbent assay (ELISA).

RESULTS

The results showed that the TLR9 expression in the mRNA and the protein level was significantly higher in PBMCs from SLE patients. However, IFN-α concentration in patients and controls significantly increased in response to CpG stimulation but this increase was significantly higher in healthy controls compared with SLE patients. Our results do not show any association between taking hydroxychloroquine and reduction in IFN-α production in SLE patients.

DISCUSSION AND CONCLUSIONS

Regarding the findings of the study, there is the possibility that TLR9 has played a role in SLE pathogenesis, and consequently it implies that TLRs can be considered to be the therapeutic targets for systemic autoimmunity. We may conclude that PBMCs in patients are functionally impaired in response to TLR ligation via innate response stimulating pathogen-associated molecular patterns (PAMPs).

Generation of Immunostimulating 130 nm Protamine-RNA nanoparticles

Nanoparticles of defined size can be easily obtained by simply mixing Protamine, a pharmaceutical drug that is used to neutralize heparin after surgery, and RNA in the form of oligonucleotides or messenger RNA. Depending on the concentrations of the two reagents and their salt contents, homogenous nanoparticles with a mean diameter of 50 to more than 1000 nm can spontaneously be generated. RNA is a danger signal because it is an agonist of for example TLR-3, -7, and -8; therefore, Protamine-RNA nanoparticles are immunostimulating. We and others have shown in vitro that nanoparticle size and interferon-alpha production by human peripheral blood mononuclear cells (PBMCs) are inversely correlated. Conversely, nanoparticle size and TNF-alpha production by PBMCs are positively correlated (Rettig et al., Blood 115:4533-4541, 2010). Particles of less than 450 nm are most frequently used for research and clinical applications because they are very stable, remain polydispersed and induce interferon-alpha proteins, which are a natural antiviral and anticancer protein family with 12 members in humans. Herein, we describe a method to generate 130 nm nanoparticles as well as some of their physical and biological characteristics.

Oncolytic measles virus induces tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-mediated cytotoxicity by human myeloid and plasmacytoid dendritic cells

Attenuated measles virus (MV) is currently being evaluated in clinical trials as an oncolytic therapeutic agent. Originally used for its lytic activity against tumor cells, it is now admitted that the effectiveness of MV also lies in its ability to initiate antitumor immune responses through the activation of dendritic cells (DCs). In this study, we investigated the capacity of oncolytic MV to convert human blood myeloid CD1c⁺ DCs and plasmacytoid DCs (pDCs) into cytotoxic effectors. We found that MV induces the expression of the cytotoxic protein TNF-related apoptosis-inducing ligand (TRAIL) on the surface of DCs. We demonstrate that the secretion of interferon-α (IFN-α) by DCs in response to MV is responsible for this TRAIL expression. Several types of PRRs (pattern recognition receptors) have been implicated in MV genome recognition, including RLRs (RIG-I-like receptors) and TLRs (Toll-like receptors). We showed that CD1c⁺ DCs secrete modest amounts of IFN-α and express TRAIL in an RLR-dependent manner upon exposure to MV. In pDCs, MV is recognized by RLRs and also by TLR7, leading to the secretion of high amounts of IFN-α and TRAIL expression. Finally, we showed that MV-stimulated DCs induce TRAIL-mediated cell death of Jurkat cells, confirming their acquisition of cytotoxic functions. Our results demonstrate that MV can activate cytotoxic myeloid CD1c⁺ DCs and pDCs, which may participate to the antitumor immune response.

Thermoresponsive Polymer Nanoparticles Co-deliver RSV F Trimers with a TLR-7/8 Adjuvant

Structure-based vaccine design has been used to develop immunogens that display conserved neutralization sites on pathogens such as HIV-1, respiratory syncytial virus (RSV), and influenza. Improving the immunogenicity of these designed immunogens with adjuvants will require formulations that do not alter protein antigenicity. Here, we show that nanoparticle-forming thermoresponsive polymers (TRP) allow for co-delivery of RSV fusion (F) protein trimers with Toll-like receptor 7 and 8 agonists (TLR-7/8a) to enhance protective immunity. Although primary amine conjugation of TLR-7/8a to F trimers severely disrupted the recognition of critical neutralizing epitopes, F trimers site-selectively coupled to TRP nanoparticles retained appropriate antigenicity and elicited high titers of prefusion-specific, TH1 isotype anti-RSV F antibodies following vaccination. Moreover, coupling F trimers to TRP delivering TLR-7/8a resulted in ∼3-fold higher binding and neutralizing antibody titers than soluble F trimers admixed with TLR-7/8a and conferred protection from intranasal RSV challenge. Overall, these data show that TRP nanoparticles may provide a broadly applicable platform for eliciting neutralizing antibodies to structure-dependent epitopes on RSV, influenza, HIV-1, or other pathogens.

Human blood myeloid and plasmacytoid dendritic cells cross activate each other and synergize in inducing NK cell cytotoxicity

Human blood dendritic cells (DCs) hold great potential for use in anticancer immunotherapies. CD1c⁺ myeloid DCs and plasmacytoid DCs (pDCs) have been successfully utilized in clinical vaccination trials against melanoma. We hypothesize that combining both DC subsets in a single vaccine can further improve vaccine efficacy. Here, we have determined the potential synergy between the two subsets in vitro on the level of maturation, cytokine expression, and effector cell induction. Toll-like receptor (TLR) stimulation of CD1c⁺ DCs induced cross-activation of immature pDCs and vice versa. When both subsets were stimulated together using TLR agonists, CD86 expression on pDCs was increased and higher levels of interferon (IFN)-α were produced by DC co-cultures. Although the two subsets did not display any synergistic effect on naive CD4⁺ and CD8⁺ T cell polarization, CD1c⁺ DCs and pDCs were able to complement each other's induction of other immune effector cells. The mere presence of pDCs in DC co-cultures promoted plasma cell differentiation from activated autologous B cells. Similarly, CD1c⁺ DCs, alone or in co-cultures, induced high levels of IFN-γ from allogeneic peripheral blood lymphocytes or activated autologous natural killer (NK) cells. Both CD1c⁺ DCs and pDCs could enhance NK cell cytotoxicity, and interestingly DC co-cultures further enhanced NK cell-mediated killing of an NK-resistant tumor cell line. These results indicate that co-application of human blood DC subsets could render DC-based anticancer vaccines more efficacious.

TLR Signalling Pathways Diverge in Their Ability to Induce PGE2

PGE₂ is a lipid mediator abundantly produced in inflamed tissues that exerts relevant immunoregulatory functions. Dendritic cells (DCs) are key players in the onset and shaping of the inflammatory and immune responses and, as such, are well known PGE₂ targets. By contrast, the precise role of human DCs in the production of PGE₂ is poorly characterized. Here, we asked whether different ligands of Toll-like receptors (TLRs), a relevant family of pathogen-sensing receptors, could induce PGE₂ in human DCs. The only active ligands were LPS (TLR4 ligand) and R848 (TLR7-8 ligand) although all TLRs, but TLR9, were expressed and functional. While investigating the molecular mechanisms hindering the release of PGE₂, our experiments highlighted so far oversight differences in TLR signalling pathways in terms of MAPK and NF-κB activation. In addition, we identified that the PGE₂-limiting checkpoint downstream TLR3, TLR5, and TLR7 was a defect in COX2 induction, while TLR1/2 and TLR2/6 failed to mobilize arachidonic acid, the substrate for the COX2 enzyme. Finally, we demonstrated the in vivo expression of PGE₂ by myeloid CD11c⁺ cells, documenting a role for DCs in the production of PGE₂ in human inflamed tissues.

An efficient method for gene silencing in human primary plasmacytoid dendritic cells: silencing of the TLR7/IRF-7 pathway as a proof of concept

Plasmacytoid dendritic cells (pDC) are specialized immune cells that produce massive levels of type I interferon in response to pathogens. Unfortunately, pDC are fragile and extremely rare, rendering their functional study a tough challenge. However, because of their central role in numerous pathologies, there is a considerable need for an efficient and reproducible protocol for gene silencing in these cells. In this report, we tested six different methods for siRNA delivery into primary human pDC including viral-based, lipid-based, electroporation, and poly-ethylenimine (PEI) technologies. We show that lipid-based reagent DOTAP was extremely efficient for siRNA delivery into pDC, and did not induce cell death or pDC activation. We successfully silenced Toll-Like Receptor 7 (TLR7), CXCR4 and IFN regulatory factor 7 (IRF-7) gene expression in pDC as assessed by RT-qPCR or cytometry. Finally, we showed that TLR7 or IRF-7 silencing in pDC specifically suppressed IFN-α production upon stimulation, providing a functional validation of our transfection protocol.

Activation of myeloid dendritic cells, effector cells and regulatory T cells in lichen planus

Background

Lichen planus (LP) is a chronic mucocutaneous inflammatory disease. Evaluating the balance between regulatory T cells and effector T cells could be useful for monitoring the proinflammatory profile of LP. Therefore, this study aimed to assess populations of dendritic cells (DCs) and regulatory and effector T cells in peripheral blood samples collected from patients with LP to evaluate the polyfunctionality of T cells upon toll-like receptor (TLR) activation.

Methods

Peripheral blood mononuclear cells collected from 18 patients with LP and 22 healthy control subjects were stimulated with agonists of TLR4, TLR7, TLR7/TLR8 or TLR9. Frequencies of circulating IFN-α⁺ plasmacytoid DCs (pDCs); TNF-α⁺ myeloid DCs (mDCs); regulatory T cells (Tregs); and IL-17-, IL-10-, IL-22-, TNF-, and IFN-γ-secreting T cells were assessed via flow cytometry.

Results

The frequencies of regulatory CD4⁺ and CD8⁺CD25⁺Foxp3⁺CD127^low/− T cells and TNF-α⁺ mDCs were induced following activation with TLR4, TLR7 and TLR8 agonists in the LP group. Moreover, increased baseline frequencies of CD4⁺IL-10⁺ T cells and CD8⁺IL-22⁺ or IFN-γ⁺T cells were found. In the LP group, TLR4 activation induced an increased frequency of CD4⁺IFN-γ⁺ T cells, while TLR7/8 and staphylococcal enterotoxin B (SEB) activation induced an increased frequency of CD8⁺ IL-22⁺ T cells. An increased frequency of polyfunctional CD4⁺ T cells that simultaneously secreted 3 of the evaluated cytokines (not including IL-10) was verified upon TLR7/8/9 activation, while polyfunctional CD8⁺ T cells were already detectable at baseline.

Conclusions

TLR-mediated activation of the innate immune response induced the production of proinflammatory mDCs, Tregs and polyfunctional T cells in patients with LP. Therefore, TLR activation has an adjuvant role in inducing both innate and adaptive immune responses.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-016-0938-1) contains supplementary material, which is available to authorized users.

Impact of Exercise on Innate Immunity in Multiple Sclerosis Progression and Symptomatology

Multiple Sclerosis (MS), an idiopathic progressive immune-mediated neurological disorder of the central nervous system (CNS), is characterized by recurrent episodes of inflammatory demyelination and consequent axonal deterioration. It accounts for functional deterioration and lasting disability among young adults. A body of literature demonstrates that physical activity counteracts fatigue and depression and may improve overall quality of life in MS patients. Furthermore, much data indicates that exercise ameliorates chronic neuroinflammation and its related pathologies by tipping cytokine profiles toward an anti-inflammatory signature. Recent data has focused on the direct impact of exercise training on the innate immune system by targeting toll-like receptors (TLRs), signaling pattern recognition receptors that govern the innate immune response, shedding light on the physiological role of TLRs in health and disease. Indeed, TLRs continue to emerge as players in the neuroinflammatory processes underpinning MS. This review will highlight evidence that physical activity and exercise are potential immunomodulatory therapies, targeting innate signaling mechanism(s) to modulate MS symptom development and progression.

Dendritic Cells Expressing Triggering Receptor Expressed on Myeloid Cells-1 Correlate with Plaque Stability in Symptomatic and Asymptomatic Patients with Carotid Stenosis

Atherosclerosis is a chronic inflammatory disease with atherosclerotic plaques containing inflammatory cells, including T-lymphocytes, dendritic cells (DCs) and macrophages that are responsible for progression and destabilization of atherosclerotic plaques. Stressed cells undergoing necrosis release molecules that act as endogenous danger signals to alert and activate innate immune cells. In atherosclerotic tissue the number of DCs increases with the progression of the lesion and produce several inflammatory cytokines and growth factors. Triggering receptor expressed on myeloid cells (TREM)-1 plays a crucial role in inflammation. However, relationship of DCs and the role of TREM-1 with the stability of atherosclerotic plaques have not been examined. In this study, we investigated the heterogeneity of the plaque DCs, myeloid (mDC1 and mDC2) and plasmacytoid (pDCs), and examined the expression of TREM-1 and their co-localization with DCs in the plaques from symptomatic (S) and asymptomatic (AS) patients with carotid stenosis. We found increased expression of HLA-DR, fascin, and TREM-1 and decreased expression of TREM-2 and α-smooth muscle actin in S compared to AS atherosclerotic carotid plaques. Both TREM-1 and fascin were co-localized suggesting increased expression of TREM-1 in plaque DCs of S compared to AS patients. These data were supported by increased mRNA transcripts of TREM-1 and decreased mRNA transcripts of TREM-2 in carotid plaques of S compared to AS patients. There was higher density of both CD1c+ mDC₁ and CD141+ mDC₂ in the carotid plaques from AS compared to S patients, where as the density of CD303+ pDCs were higher in the carotid plaques of S compared to AS patients. These findings suggest a potential role of pDCs and TREM-1 in atherosclerotic plaque vulnerability. Thus, newer therapies could be developed to selectively block TREM-1 for stabilizing atherosclerotic plaques.

Comparative analysis of the small RNA transcriptomes of miiuy croaker revealed microRNA-mediated regulation of TLR signaling pathway response to Vibrio anguillarum infection

MicroRNAs (miRNAs) are an abundant class of endogenous noncoding small RNAs (sRNAs) that are partially complementary to their target messenger RNA (mRNA), which post-transcriptionally regulate various biological processes by repressing mRNA translation or inducing mRNA degradation. MiRNAs have been demonstrated to play crucial roles in the host response to infection by diverse pathogens. As an important bacterial pathogen, Vibrio anguillarum has been caused great economic losses in miiuy croaker aquaculture. To identify immune-related miRNAs of miiuy croaker in response to V. anguillarum infection, we constructed two sRNA libraries with or without bacterial infection. High-throughput deep sequencing and subsequent bioinformatic analysis identified 241 conserved and 137 novel miRNA precursors in miiuy croaker based on its whole genome sequences, encoding 293 and 124 mature miRNAs, respectively. Then we compared the expression patterns of miRNAs in the two libraries. There were significant differences in the expression of 12 miRNAs between the infection group (IG) and control group (CG). Further, the expressions of six miRNAs were validated by real-time quantitative PCR. The target gene prediction and function analysis were conducted for the 12 differential miRNAs. This analysis revealed that these miRNAs participated in the regulation multiple immune-related signaling pathways. Transcription factors in TLR signaling, such as AP-1, IRF5, NF-κB and IRF3, were activated by these miRNAs via post-transcriptionally regulating the expression of TLRs and TLR-associated signaling proteins, inducing effective host immune response to eradicate infectious pathogens. This is the first study of the identification and characterization of miiuy croaker miRNAs in response to V. anguillarum infection. The comprehensive analysis of the expression of miRNAs and the target gene and function prediction of differently expressed miRNAs may help to understand the regulatory mechanisms of miRNA in fish during the interaction between host and bacterial pathogens.

Effective Clinical Responses in Metastatic Melanoma Patients after Vaccination with Primary Myeloid Dendritic Cells

PURPOSE

Thus far, dendritic cell (DC)-based immunotherapy of cancer was primarily based on in vitro-generated monocyte-derived DCs, which require extensive in vitro manipulation. Here, we report on a clinical study exploiting primary CD1c(+) myeloid DCs, naturally circulating in the blood.

EXPERIMENTAL DESIGN

Fourteen stage IV melanoma patients, without previous systemic treatment for metastatic disease, received autologous CD1c(+) myeloid DCs, activated by only brief (16 hours) ex vivo culture and loaded with tumor-associated antigens of tyrosinase and gp100.

RESULTS

Our results show that therapeutic vaccination against melanoma with small amounts (3-10 × 10(6)) of myeloid DCs is feasible and without substantial toxicity. Four of 14 patients showed long-term progression-free survival (12-35 months), which directly correlated with the development of multifunctional CD8(+) T-cell responses in three of these patients. In particular, high CD107a expression, indicative for cytolytic activity, and IFNγ as well as TNFα and CCL4 production was observed. Apparently, these T-cell responses are essential to induce tumor regression and promote long-term survival by stalling tumor growth.

CONCLUSIONS

We show that vaccination of metastatic melanoma patients with primary myeloid DCs is feasible and safe and results in induction of effective antitumor immune responses that coincide with improved progression-free survival. Clin Cancer Res; 22(9); 2155-66. ©2015 AACR.

Molecular Determinants of GS-9620-Dependent TLR7 Activation

GS-9620 is an orally administered agonist of Toll-like receptor (TLR)7 currently being evaluated in clinical studies for the treatment of chronic HBV and HIV patients. GS-9620 has shown antiviral efficacy in preclinical models of chronic hepadnavirus infection in woodchuck as well as chimpanzee. However, the molecular determinants of GS-9620-dependent activation of TLR7 are not well defined. The studies presented here elucidate GS-9620 subcellular distribution and characterize its molecular interactions with human TLR7 using structure-guided mutational analysis. Based on our results we present a molecular model of TLR7 bound to GS-9620. We also determine that several coding SNPs had no effect on GS-9620-dependent TLR7 activation. In addition, our studies provide evidence that TLR7 exists in a ligand-independent oligomeric state and that, TLR7 activation by GS-9620 is likely associated with compound-induced conformational changes. Finally, we demonstrate that activation of NF-κB and Akt pathways in primary plasmacytoid dendritic cells occur as immediate downstream cellular responses to GS-9620 stimulation. The data presented here further our understanding of the molecular parameters governing TLR7 activation by GS-9620, and more generally by nucleos/tide-related ligands.

IRF5 and IRF8 modulate the CAL-1 human plasmacytoid dendritic cell line response following TLR9 ligation

Synthetic oligonucleotides (ODNs) containing CpG motifs stimulate human plasmacytoid dendritic cells (pDCs) to produce type-1 interferons (IFNs) and proinflammatory cytokines. Previous studies demonstrated that interferon regulatory factors (IRFs) play a central role in mediating CpG-induced pDC activation. This work explores the inverse effects of IRF5 and IRF8 (also known as IFN consensus sequence-binding protein) on CpG-dependent gene expression in the human CAL-1 pDC cell line. This cell line shares many of the phenotypic and functional properties of freshly isolated human pDCs. Results from RNA interference and microarray studies indicate that IRF5 upregulates TLR9-driven gene expression whereas IRF8 downregulates the same genes. Several findings support the conclusion that IRF8 inhibits TLR9-dependent gene expression by directly blocking the activity of IRF5. First, the inhibitory activity of IRF8 is only observed when IRF5 is present. Second, proximity ligation analysis shows that IRF8 and IRF5 colocalize within the cytoplasm of resting human pDCs and cotranslocate to the nucleus after CpG stimulation. Taken together, these findings suggest that IRF5 and IRF8, two transcription factors with opposing functions, control TLR9 signaling in human pDCs.

The role of BST-2/Tetherin in host protection and disease manifestation

Host cells respond to viral infections by activating immune response genes that are not only involved in inflammation, but may also predispose cells to cancerous transformation. One such gene is BST‐2, a type II transmembrane protein with a unique topology that endows it tethering and signaling potential. Through this ability to tether and signal, BST‐2 regulates host response to viral infection either by inhibiting release of nascent viral particles or in some models inhibiting viral dissemination. However, despite its antiviral functions, BST‐2 is involved in disease manifestation, a function linked to the ability of BST‐2 to promote cell‐to‐cell interaction. Therefore, modulating BST‐2 expression and/or activity has the potential to influence course of disease.

Synergistic Stimulation with Different TLR7 Ligands Modulates Gene Expression Patterns in the Human Plasmacytoid Dendritic Cell Line CAL-1

Objective. TLR7 ligation in plasmacytoid dendritic cells is promising for the treatment of cancer, allergy, and infectious diseases; however, high doses of ligands are required. We hypothesized that the combination of structurally different TLR7 ligands exponentiates the resulting immune response. Methods. CAL-1 (human pDC line) cells were incubated with the TLR7-specific adenine analog CL264 and single-stranded 9.2s RNA. Protein secretion was measured by ELISA. Microarray technique was used to detect modified gene expression patterns upon synergistic stimulation, revealing underlying functional groups and networks. Cell surface binding properties were studied using FACS analysis. Results. CL264 in combination with 9.2s RNA significantly enhanced cytokine and interferon secretion to supra-additive levels. This effect was due to a stronger stimulation of already regulated genes (by monostimulation) as well as to recruitment of thus far unregulated genes. Top scoring canonical pathways referred to immune-related processes. Network analysis revealed IL-1β, IL-6, TNF, and IFN-β as major regulatory nodes, while several minor regulatory nodes were also identified. Binding of CL264 to the cell surface was enhanced by 9.2s RNA. Conclusion. Structurally different TLR7 ligands act synergistically on gene expression patterns and on the resulting inflammatory response. These data could impact future strategies optimizing TLR7-targeted drug design.

Primary Human Blood Dendritic Cells for Cancer Immunotherapy-Tailoring the Immune Response by Dendritic Cell Maturation

Dendritic cell (DC)-based cancer vaccines hold the great promise of tipping the balance from tolerance of the tumor to rejection. In the last two decades, we have gained tremendous knowledge about DC-based cancer vaccines. The maturation of DCs has proven indispensable to induce immunogenic T cell responses. We review the insights gained from the development of maturation cocktails in monocyte derived DC-based trials. More recently, we have also gained insights into the functional specialization of primary human blood DC subsets. In peripheral human blood, we can distinguish at least three primary DC subsets, namely CD1c⁺ and CD141⁺ myeloid DCs and plasmacytoid DCs. We reflect the current knowledge on maturation and T helper polarization by these blood DC subsets in the context of DC-based cancer vaccines. The maturation stimulus in combination with the DC subset will determine the type of T cell response that is induced. First trials with these natural DCs underline their excellent in vivo functioning and mark them as promising tools for future vaccination strategies.

The TLR7 agonist induces tumor regression both by promoting CD4⁺T cells proliferation and by reversing T regulatory cell-mediated suppression via dendritic cells

Treg-induced immunosuppression is now recognized as a key element in enabling tumors to escape immune-mediated destruction. Although topical TLR7 therapies such as imiquimod have been proved successful in the treatment of dermatological malignancy and a number of conditions beyond the FDA-approved indications, the mechanism behind the effect of TLR7 on effector T cell and Treg cell function in cancer immunosurveillance is still not well understood. Here, we found that Loxoribin, one of the TLR7 ligands, could inhibit tumor growth in xenograft models of colon cancer and lung cancer, and these anti-tumor effects of Loxoribin were mediated by promoting CD4⁺T cell proliferation and reversing Treg-mediated suppression via dendritic cells (DCs). However, deprivation of IL-6 using a neutralizing antibody abrogated the ability of Loxoribin-treated DCs, which reversed the Treg cell-mediated suppression. Furthermore, adoptive transfer of Loxoribin-treated DCs inhibited the tumor growth in vivo. Thus, this study links TLR7 signaling to the functional control of effector T cells and Treg cells and identifies Loxoribin as a new therapeutic strategy in cancer treatment, which may offer new opportunities to improve the outcome of cancer immunotherapy.

Expression and regulation of Schlafen (SLFN) family members in primary human monocytes, monocyte-derived dendritic cells and T cells

Schlafen (SLFN/Slfn) family members have been investigated for their involvement in fundamental cellular processes including growth regulation, differentiation and control of viral replication. However, most research has been focused on the characterization of Slfns within the murine system or in human cell lines. Since little is known about SLFNs in primary human immune cells, we set out to analyze the expression and regulation of the six human SLFN genes in monocytes, monocyte-derived dendritic cells (moDCs) and T cells. Comparison of SLFN gene expression across these three cell types showed high mRNA expression of SLFN11 in monocytes and moDCs and high SLFN5 expression in T cells, indicating functional importance within these cell types. Differentiation of monocytes to moDCs leads to the gradual upregulation of SLFN12L and SLFN13 while SLFN12 levels were decreased by differentiation stimuli. Stimulation of moDCs via human rhinovirus, lipopolysaccharide, or IFN-α lead to strong upregulation of SLFN gene expression, while peptidoglycan poorly stimulated regulation of both SLFNs and the classical interferon-stimulated gene MxA. T cell activation was found to downregulate the expression of SLFN5, SLFN12 and SLFN12L, which was reversible upon addition of exogenous IFN-α. In conclusion, we demonstrate, that SLFN gene upregulation is mainly dependent on autocrine type I interferon signaling in primary human immune cells. Rapid decrease of SLFN expression levels following T cell receptor stimulation indicates a role of SLFNs in the regulation of human T cell quiescence.

Inflammatory and immune pathways in the pathogenesis of periodontal disease

The pathogenesis of periodontitis involves a complex immune/inflammatory cascade that is initiated by the bacteria of the oral biofilm that forms naturally on the teeth. The susceptibility to periodontitis appears to be determined by the host response; specifically, the magnitude of the inflammatory response and the differential activation of immune pathways. The purpose of this review was to delineate our current knowledge of the host response in periodontitis. The role of innate immunity, the failure of acute inflammation to resolve (thus becoming chronic), the cytokine pathways that regulate the activation of acquired immunity and the cells and products of the immune system are considered. New information relating to regulation of both inflammation and the immune response will be reviewed in the context of susceptibility to, and perhaps control of, periodontitis.

Immunity to Pathogens Taught by Specialized Human Dendritic Cell Subsets

Dendritic cells (DCs) are specialized antigen-presenting cells (APCs) that have a key role in immune responses because they bridge the innate and adaptive arms of the immune system. They mature upon recognition of pathogens and upregulate MHC molecules and costimulatory receptors to activate antigen-specific CD4⁺ and CD8⁺ T cells. It is now well established that DCs are not a homogeneous population but are composed of different subsets with specialized functions in immune responses to specific pathogens. Upon viral infections, plasmacytoid DCs (pDCs) rapidly produce large amounts of IFN-α, which has potent antiviral functions and activates several other immune cells. However, pDCs are not particularly potent APCs and induce the tolerogenic cytokine IL-10 in CD4⁺ T cells. In contrast, myeloid DCs (mDCs) are very potent APCs and possess the unique capacity to prime naive T cells and consequently to initiate a primary adaptive immune response. Different subsets of mDCs with specialized functions have been identified. In mice, CD8α⁺ mDCs capture antigenic material from necrotic cells, secrete high levels of IL-12, and prime Th1 and cytotoxic T-cell responses to control intracellular pathogens. Conversely, CD8α⁻ mDCs preferentially prime CD4⁺ T cells and promote Th2 or Th17 differentiation. BDCA-3⁺ mDC2 are the human homologue of CD8α⁺ mDCs, since they share the expression of several key molecules, the capacity to cross-present antigens to CD8⁺ T-cells and to produce IFN-λ. However, although several features of the DC network are conserved between humans and mice, the expression of several toll-like receptors as well as the production of cytokines that regulate T-cell differentiation are different. Intriguingly, recent data suggest specific roles for human DC subsets in immune responses against individual pathogens. The biology of human DC subsets holds the promise to be exploitable in translational medicine, in particular for the development of vaccines against persistent infections or cancer.

Contribution of dendritic cells to the autoimmune pathology of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a heterogeneous disease in which excessive inflammation, autoantibodies and complement activation lead to multisystem tissue damage. The contribution of the individual genetic composition has been extensively studied, and several susceptibility genes related to immune pathways that participate in SLE pathogenesis have been identified. It has been proposed that SLE takes place when susceptibility factors interact with environmental stimuli leading to a deregulated immune response. Experimental evidence suggests that such events are related to the failure of T-cell and B-cell suppression mediated by defects in cell signalling, immune tolerance and apoptotic mechanism promoting autoimmunity. In addition, it has been reported that dendritic cells (DCs) from SLE patients, which are crucial in the modulation of peripheral tolerance to self-antigens, show an increased ratio of activating/inhibitory receptors on their surfaces. This phenotype and an augmented expression of co-stimulatory molecules is thought to be critical for disease pathogenesis. Accordingly, tolerogenic DCs can be a potential strategy for developing antigen-specific therapies to reduce detrimental inflammation without causing systemic immunosuppression. In this review article we discuss the most relevant data relative to the contribution of DCs to the triggering of SLE.

Fms-like tyrosine kinase 3 ligand is required for thymic dendritic cell generation from bone marrow-derived CD117⁺ hematopoietic progenitor cells

Thymic dendritic cells (TDCs) are a type of dendritic cell (DC) in the thymus, which can enhance the proliferation of thymic T lymphocytes, regulate negative selection and induce central tolerance through autoantigen presentation. However, further investigations using TDCs has been restricted due to insufficient numbers. Therefore, an effective expansion method for TDCs in vitro is urgently required to further examine their biological characteristics. In the present study, a novel system was established using fetal thymus organ culture (FTOC) and a hanging drop culture system in the presence of fms‑like tyrosine kinase 3 ligand (Flt3L), termed the Flt3L/FTOC system. TDCs were successfully generated and expanded from CD117+ bone marrow hematopoietic progenitor cells. Conventional DCs (cDCs; CD11c+B220‑ DCs) and plasmacytoid DCs (pDCs; CD11c+B220+ DCs) were found in the TDCs generated using the Flt3L/FTOC system. These cells exhibited the specific morphological features of DCs, which were confirmed using Giemsa staining. Furthermore, the cytokine and surface marker profiles were also analyzed. Higher expression levels of interferon‑α and interleukin‑12 were observed in the pDCs, compared with the cDCs, and higher expression levels of toll‑like receptor (TLR)7 and TLR9 were found in the pDCs than in the cDCs. In addition, the Flt3L/FTOC‑derived TDCs also exhibited the ability to stimulate the allogenic T cell response. In conclusion, a novel in vitro culture system of thymic cDCs and pDCs using Flt3L was established, and this may provide a methodological basis for understanding the properties of TDCs.