Plasmacytoid dendritic cell-derived type I interferon is crucial for the adjuvant activity of Toll-like receptor 7 agonists

TLR agonists polarize interferon responses in conjunction with dendritic cell vaccination in malignant glioma: a randomized phase II Trial

In this randomized phase II clinical trial, we evaluated the effectiveness of adding the TLR agonists, poly-ICLC or resiquimod, to autologous tumor lysate-pulsed dendritic cell (ATL-DC) vaccination in patients with newly-diagnosed or recurrent WHO Grade III-IV malignant gliomas. The primary endpoints were to assess the most effective combination of vaccine and adjuvant in order to enhance the immune potency, along with safety. The combination of ATL-DC vaccination and TLR agonist was safe and found to enhance systemic immune responses, as indicated by increased interferon gene expression and changes in immune cell activation. Specifically, PD-1 expression increases on CD4+ T-cells, while CD38 and CD39 expression are reduced on CD8+ T cells, alongside an increase in monocytes. Poly-ICLC treatment amplifies the induction of interferon-induced genes in monocytes and T lymphocytes. Patients that exhibit higher interferon response gene expression demonstrate prolonged survival and delayed disease progression. These findings suggest that combining ATL-DC with poly-ICLC can induce a polarized interferon response in circulating monocytes and CD8+ T cells, which may represent an important blood biomarker for immunotherapy in this patient population.Trial Registration: ClinicalTrials.gov Identifier: NCT01204684.

Activated B-Cells enhance epitope spreading to support successful cancer immunotherapy

Immune checkpoint therapies (ICT) have transformed the treatment of cancer over the past decade. However, many patients do not respond or suffer relapses. Successful immunotherapy requires epitope spreading, but the slow or inefficient induction of functional antitumoral immunity delays the benefit to patients or causes resistances. Therefore, understanding the key mechanisms that support epitope spreading is essential to improve immunotherapy. In this review, we highlight the major role played by B-cells in breaking immune tolerance by epitope spreading. Activated B-cells are key Antigen-Presenting Cells (APC) that diversify the T-cell response against self-antigens, such as ribonucleoproteins, in autoimmunity but also during successful cancer immunotherapy. This has important implications for the design of future cancer vaccines.

Development of Long Asymmetric siRNA Structure for Target Gene Silencing and Immune Stimulation in Mammalian Cells

Post-transcriptional regulation of transcript abundances by RNA interference (RNAi) is a widely conserved regulatory mechanism to control cellular processes. We previously introduced an alternative siRNA structure called asymmetric siRNA (asiRNA), and showed that asiRNA exhibits comparable gene-silencing efficiency with reduced off-target effects compared with conventional siRNAs. However, to what extent the length of the guide strand affects the gene-silencing efficiency of asiRNAs is still elusive. In this study, we analyzed in detail the gene-silencing ability of asiRNAs along the guide strand length and immunostimulatory capacity of asiRNAs. We generated asiRNAs containing various guide strand lengths ranging from 25 to 29 nt, called long asiRNA (lasiRNA). We found that the gene-silencing activity of lasiRNAs decreased as the length of the guide strand increased. Nonetheless, the 3'-end overhangs that are complementary to the target gene have higher efficiency for gene silencing compared with mismatched overhangs. In addition, we found that the silencing efficiency of lasiRNAs correlates with their Ago2-binding affinity. Finally, replacing the mismatched overhang with a TLR7- or TLR9-associated immune response motif induced a toll-like receptor (TLR)-specific immune response and retained gene-silencing activity. Our findings demonstrate that lasiRNA structures can be tailored to function as bifunctional siRNA, which trigger a specific immune response combined with target gene silencing. Taken together, we anticipate that our findings provide a road map for the subsequent development of immune-stimulating lasiRNA, which bear the potential to be applied for therapeutic benefits.

Dendritic Cell Vaccination in Conjunction with a TLR Agonist Polarizes Interferon Immune Responses in Malignant Glioma Patients

Autologous tumor lysate-pulsed dendritic cell (ATL-DC) vaccination is a promising immunotherapy for patients with high grade gliomas, but responses have not been demonstrated in all patients. To determine the most effective combination of autologous tumor lysate-pulsed DC vaccination, with or without the adjuvant toll-like receptor (TLR) agonists poly-ICLC or resiquimod, we conducted a Phase 2 clinical trial in 23 patients with newly diagnosed or recurrent WHO Grade III-IV malignant gliomas. We then performed deep, high-dimensional immune profiling of these patients to better understand how TLR agonists may influence the systemic immune responses induced by ATL-DC vaccination. Bulk RNAseq data demonstrated highly significant upregulation of type 1 and type 2 interferon gene expression selectively in patients who received adjuvant a TLR agonist together with ATL-DC. CyTOF analysis of patient peripheral blood mononuclear cells (PBMCs) showed increased expression of PD-1 on CD4+ T-cells, decreases in CD38 and CD39 on CD8+ T cells and elevated proportion of monocytes after ATL-DC + TLR agonist administration. In addition, scRNA-seq demonstrated a higher expression fold change of IFN-induced genes with poly-ICLC treatment in both peripheral blood monocytes and T lymphocytes. Patients who had higher expression of interferon response genes lived significantly longer and had longer time to progression compared to those with lower expression. The results suggest that ATL-DC in conjunction with adjuvant poly-ICLC induces a polarized interferon response in circulating monocytes and specific activation of a CD8+ T cell population, which may represent an important blood biomarker for immunotherapy in this patient population.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01204684.

Preclinical characterization of the Toll-like receptor 7/8 antagonist MHV370 for lupus therapy

Genetic and in vivo evidence suggests that aberrant recognition of RNA-containing autoantigens by Toll-like receptors (TLRs) 7 and 8 drives autoimmune diseases. Here we report on the preclinical characterization of MHV370, a selective oral TLR7/8 inhibitor. In vitro, MHV370 inhibits TLR7/8-dependent production of cytokines in human and mouse cells, notably interferon-α, a clinically validated driver of autoimmune diseases. Moreover, MHV370 abrogates B cell, plasmacytoid dendritic cell, monocyte, and neutrophil responses downstream of TLR7/8. In vivo, prophylactic or therapeutic administration of MHV370 blocks secretion of TLR7 responses, including cytokine secretion, B cell activation, and gene expression of, e.g., interferon-stimulated genes. In the NZB/W F1 mouse model of lupus, MHV370 halts disease. Unlike hydroxychloroquine, MHV370 potently blocks interferon responses triggered by specific immune complexes from systemic lupus erythematosus patient sera, suggesting differentiation from clinical standard of care. These data support advancement of MHV370 to an ongoing phase 2 clinical trial.

Antibody conjugates for targeted delivery of Toll-like receptor 9 agonist to the tumor tissue

Imiquimod, a Toll-like receptor 7 (TLR7) agonist is routinely used for topical administration in basal cell carcinoma and stage zero melanoma. Similarly, the TLR agonist Bacillus Calmette-Guérin is used for the local treatment of bladder cancer and clinical trials showed treatment efficacy of intratumoral injections with TLR9 agonists. However, when administered systemically, endosomal TLR agonists cause adverse responses due to broad immune activation. Hence, strategies for targeted delivery of TLR agonists to the tumor tissue are needed to enable the widespread use of endosomal TLR agonists in the context of tumor immunotherapy. One strategy for targeted delivery of TLR agonist is their conjugation to tumor antigen-specific therapeutic antibodies. Such antibody-TLR agonist conjugates act synergistically by inducing local TLR-mediated innate immune activation which complements the anti-tumor immune mechanisms induced by the therapeutic antibody. In this study, we explored different conjugation strategies for TLR9 agonists to immunoglobulin G (IgG). We evaluated biochemical conjugation of immunostimulatory CpG oligodesoxyribonucleotides (ODN) to the HER2-specific therapeutic antibody Trastuzumab with different cross-linkers comparing stochastic with site-specific conjugation. The physiochemical make-up and biological activities of the generated Trastuzumab-ODN conjugates were characterized in vitro and demonstrated that site-specific conjugation of CpG ODN is crucial for maintaining the antigen-binding capabilities of Trastuzumab. Furthermore, site-specific conjugate was effective in promoting anti-tumor immune responses in vivo in a pseudo-metastasis mouse model with engineered human HER2-transgenic tumor cells. In this in vivo model, co-delivery of Trastuzumab and CpG ODN in form of site-specific conjugates was superior to co-injection of unconjugated Trastuzumab, CpG ODN or stochastic conjugate in promoting T cell activation and expansion. Thereby, this study highlights that site-specific conjugation of CpG ODN to therapeutic antibodies targeting tumor markers is a feasible and more reliable approach for generation of conjugates which retain and combine the functional properties of the adjuvant and the antibody.

Myeloid-derived suppressor cells in head and neck squamous cell carcinoma

Myeloid-derived suppressor cells (MDSCs), which originated from hematopoietic stem cells, are heterogeneous population of cells that have different differentiation patterns and widely presented in tumor microenvironment. For tumor research, myeloid suppressor cells have received extensive attention since their discovery due to their specific immunosuppressive properties, and the mechanisms of immunosuppression and therapeutic approaches for MDSCs have been investigated in a variety of different types of malignancies. To improve the efficacy of treatment for head and neck squamous cell carcinoma (HNSCC), a disease with a high occurrence, immunotherapy has gradually emerged in after traditional surgery and subsequent radiotherapy and chemotherapy, and has made some progress. In this review, we introduced the mechanisms on the development, differentiation, and elimination of MDSCs and provided a detailed overview of the mechanisms behind the immunosuppressive properties of MDSCs. We summarized the recent researches on MDSCs in HNSCC, especially for targeting-MDSCs therapy and combination with other types of therapy such as immune checkpoint blockade (ICB). Furthermore, we looked at drug delivery patterns and collected the current diverse drug delivery systems for the improvement that contributed to therapy against MDSCs in HNSCC. Most importantly, we made possible outlooks for the future research priorities, which provide a basis for further study on the clinical significance and therapeutic value of MDSCs in HNSCC.

Systematic characterization of seed overlap microRNA cotargeting associated with lupus pathogenesis

BACKGROUND

Combinatorial gene regulation by multiple microRNAs (miRNAs) is widespread and closely spaced target sites often act cooperatively to achieve stronger repression ("neighborhood" miRNA cotargeting). While miRNA cotarget sites are suggested to be more conserved and implicated in developmental control, the pathological significance of miRNA cotargeting remains elusive.

RESULTS

Here, we report the pathogenic impacts of combinatorial miRNA regulation on inflammation in systemic lupus erythematosus (SLE). In the SLE mouse model, we identified the downregulation of two miRNAs, miR-128 and miR-148a, by TLR7 stimulation in plasmacytoid dendritic cells. Functional analyses using human cell lines demonstrated that miR-128 and miR-148a additively target KLF4 via extensively overlapping target sites ("seed overlap" miRNA cotargeting) and suppress the inflammatory responses. At the transcriptome level, "seed overlap" miRNA cotargeting increases susceptibility to downregulation by two miRNAs, consistent with additive but not cooperative recruitment of two miRNAs. Systematic characterization further revealed that extensive "seed overlap" is a prevalent feature among broadly conserved miRNAs. Highly conserved target sites of broadly conserved miRNAs are largely divided into two classes-those conserved among eutherian mammals and from human to Coelacanth, and the latter, including KLF4-cotargeting sites, has a stronger association with both "seed overlap" and "neighborhood" miRNA cotargeting. Furthermore, a deeply conserved miRNA target class has a higher probability of haplo-insufficient genes.

CONCLUSIONS

Our study collectively suggests the complexity of distinct modes of miRNA cotargeting and the importance of their perturbations in human diseases.

Ultrasound improved immune adjuvant delivery to induce DC maturation and T cell activation

Tumor immunotherapy has emerged as a promising approach to tumor treatment. Currently, immune adjuvant-based therapeutic modalities are rarely curative in solid tumors owing to challenges including the low permeability and extremely poor water solubility of these adjuvants, limiting their ability to effectively promote dendritic cell (DC) maturation. Herein, we employed ultrasound-mediated cavitation (UMC) to promote the delivery of Toll-like receptor agonist (R837)-loaded pH-responsive liposomes (PEOz-Lip@R837) to tumors. The tumor-associated antigens (TAAs) produced by UMC treatment exhibited vaccinal activity, particularly in the presence of immune adjuvants, together promoting the maturation of DC and inducing cytokine production. Importantly, UMC can down-regulate immune checkpoint molecules, like Cd274, Foxp3 and Ctla4, synergistically stimulating the activation and proliferation of T cells in the body to facilitate tumor treatment. This UMC-enhanced PEOz-Lip@R837 approach was able to induce a robust antitumor immune response capable of arresting primary and distant tumor growth, while also developing immunological memory, protecting against tumor rechallenge following initial tumor clearance. Overall, these results highlight a promising UMC- and pH-sensitive immune adjuvant delivery-based treatment for tumors with the potential for clinical application.

Synergistic Activation of Antitumor Immunity by a Particulate Therapeutic Vaccine

Success in anticancer immune therapy relies on stimulation of tumor antigen-specific T lymphocytes and effective infiltration of the T cells into tumor tissue. Here, a therapeutic vaccine that promotes proliferation and tumor infiltration of antigen-specific T cells in both inflamed and noninflamed tumor types is described. The vaccine consists of STING agonist 2'3'-cGAMP, TLR9 ligand CpG, and tumor antigen peptides that are loaded into nanoporous microparticles (μGCVax). μGCVax is effective in inhibiting lung metastatic melanoma, primary breast cancer, and subcutaneous colorectal cancer in their respective murine models, including functional cure of HER2-positive breast cancer. Mechanistically, μGCVax potently stimulates type I interferon expression in dendritic cells, and promotes CD8+ and CD103+ dendritic cell maturation and migration to lymph nodes and other lymphatic tissues. Antitumor responses are dependent on TLR9 and interferon α/β receptor signaling, and to a less extent on STING signaling. These results demonstrate a high potential for μGCVax in mediating antitumor immunity in personalized cancer therapy.

Human plasmacytoid dendritic cells at the crossroad of type I interferon-regulated B cell differentiation and antiviral response to tick-borne encephalitis virus

The Tick-borne encephalitis virus (TBEV) causes different disease symptoms varying from asymptomatic infection to severe encephalitis and meningitis suggesting a crucial role of the human host immune system in determining the fate of the infection. There is a need to understand the mechanisms underpinning TBEV-host interactions leading to protective immunity. To this aim, we studied the response of human peripheral blood mononuclear cells (PBMC) to the whole formaldehyde inactivated TBEV (I-TBEV), the drug substance of Encepur, one of the five commercially available vaccine. Immunophenotyping, transcriptome and cytokine profiling of PBMC revealed that I-TBEV generates differentiation of a sub-population of plasmacytoid dendritic cells (pDC) that is specialized in type I interferon (IFN) production. In contrast, likely due to the presence of aluminum hydroxide, Encepur vaccine was a poor pDC stimulus. We demonstrated I-TBEV-induced type I IFN together with Interleukin 6 and BAFF to be critical for B cell differentiation to plasmablasts as measured by immunophenotyping and immunoglobulin production. Robust type I IFN secretion was induced by pDC with the concerted action of both viral E glycoprotein and RNA mirroring previous data on dual stimulation of pDC by both S. aureus and influenza virus protein and nucleic acid that leads to a type I IFN-mediated sustained immune response. E glycoprotein neutralization or high temperature denaturation and inhibition of Toll-like receptor 7 signalling confirmed the importance of preserving the functional integrity of these key viral molecules during the inactivation procedure and manufacturing process to produce a vaccine able to stimulate strong immune responses.

Though vaccination is generally considered effective in reducing tick-borne encephalitis (TBE) incidence, several studies have shown that the antibody response to TBEV vaccination declines with age resulting in more frequent TBE cases among 50+ year-old vaccinees. These observations together with the lack of a specific antiviral drug impose to pinpoint novel host- and pathogen-directed therapies and to improve the control of vaccine efficacy. Thus, we interrogated in vitro human PBMC, whose response to TBEV may provide a picture closer to what occurs in vivo in humans after vaccination or natural infection compared to animal models. The role of E glycoprotein and viral RNA in promoting antiviral and B cell-mediated responses was investigated. Thus, these key viral molecules should be considered, in future, for novel subunit vaccine formulations than the current whole inactivated TBEV-based vaccines, which require laborious manipulation in biosafety level-3 laboratory and animal testing for manufacturing and batch release.

Niclosamide suppresses the expansion of follicular helper T cells and alleviates disease severity in two murine models of lupus via STAT3

Background

Autoantibody production against endogenous cellular components is pathogenic feature of systemic lupus erythematosus (SLE). Follicular helper T (T_FH) cells aid in B cell differentiation into autoantibody-producing plasma cells (PCs). The IL-6 and IL-21 cytokine-mediated STAT3 signaling are crucial for the differentiation to T_FH cells. Niclosamide is an anti-helminthic drug used to treat parasitic infections but also exhibits a therapeutic effect on autoimmune diseases due to its potential immune regulatory effects. In this study, we examined whether niclosamide treatment could relieve lupus-like autoimmunity by modulating the differentiation of T_FH cells in two murine models of lupus.

Methods

10-week-old MRL/lpr mice were orally administered with 100 mg/kg of niclosamide or with 0.5% methylcellulose (MC, vehicle) daily for 7 weeks. TLR7 agonist, resiquimod was topically applied to an ear of 8-week-old C57BL/6 mice 3 times a week for 5 weeks. And they were orally administered with 100 mg/kg of niclosamide or with 0.5% MC daily for 5 weeks. Every mouse was analyzed for lupus nephritis, proteinuria, autoantibodies, immune complex, immune cell subsets at the time of the euthanization.

Results

Niclosamide treatment greatly improved proteinuria, anti-dsDNA antibody levels, immunoglobulin subclass titers, histology of lupus nephritis, and C3 deposition in MRL/lpr and R848-induced mice. In addition, niclosamide inhibited the proportion of T_FH cells and PCs in the spleens of these animals, and effectively suppressed differentiation of T_FH-like cells and expression of associated genes in vitro.

Conclusions

Niclosamide exerted therapeutic effects on murine lupus models by suppressing T_FH cells and plasma cells through STAT3 inhibition.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-02760-2.

Systemic cancer immunotherapy with Toll-like receptor 7 agonists: Timing is everything

Toll-like receptor (TLR) 7 agonists represent a promising strategy for the immunotherapy of cancer. We have recently investigated the influence of TLR tolerance on the efficacy of systemic tumor treatment with TLR7 ligands. We propose that considering the kinetics of receptor sensitivity highly improves the outcome of cancer immunotherapy.

A TLR7/8 Agonist-Including DOEPC-Based Cationic Liposome Formulation Mediates Its Adjuvanticity Through the Sustained Recruitment of Highly Activated Monocytes in a Type I IFN-Independent but NF-κB-Dependent Manner

Novel adjuvants, such as Toll-like receptors (TLRs) agonists, are needed for the development of new formulations able to circumvent limitations of current vaccines. Among TLRs, TLR7/8 agonists represent promising candidates, as they are well described to enhance antigen-specific antibody responses and skew immunity toward T helper (T_H) 1 responses. We find here that the incorporation of the synthetic TLR7/8 ligand 3M-052 in a cationic DOEPC-based liposome formulation shifts immunity toward T_H1 responses and elicits strong and long-lasting germinal center and follicular T helper cell responses in adult mice. This reflects the prolonged recruitment of innate cells toward the site of immunization and homing of activated antigen-loaded monocytes and monocyte-derived dendritic cells toward draining lymph nodes. We further show that this adjuvanticity is independent of type I IFN but NF-κB-dependent. Overall, our data identify TLR7/8 agonists incorporated in liposomes as promising and effective adjuvants to enhance T_H1 and germinal center responses.

Immunogenicity and Toxicity of Different Adjuvants Can Be Characterized by Profiling Lung Biomarker Genes After Nasal Immunization

The efficacy of vaccine adjuvants depends on their ability to appropriately enhance the immunogenicity of vaccine antigens, which is often insufficient in non-adjuvanted vaccines. Genomic analyses of immune responses elicited by vaccine adjuvants provide information that is critical for the rational design of adjuvant vaccination strategies. In this study, biomarker genes from the genomic analyses of lungs after priming were used to predict the efficacy and toxicity of vaccine adjuvants. Based on the results, it was verified whether the efficacy and toxicity of the tested adjuvants could be predicted based on the biomarker gene profiles after priming. Various commercially available adjuvants were assessed by combining them with the split influenza vaccine and were subsequently administered in mice through nasal inoculation. The expression levels of lung biomarker genes within 24 h after priming were analyzed. Furthermore, we analyzed the antibody titer, cytotoxic T lymphocyte (CTL) induction, IgG1/IgG2a ratio, leukopenic toxicity, and cytotoxicity in mice vaccinated at similar doses. The association between the phenotypes and the changes in the expression levels of biomarker genes were analyzed. The ability of the adjuvants to induce the production of antigen-specific IgA could be assessed based on the levels of Timp1 expression. Furthermore, the expression of this gene partially correlated with the levels of other damage-associated molecular patterns in bronchoalveolar lavage fluid. Additionally, the changes in the expression of proteasome- and transporter-related genes involved in major histocompatibility complex class 1 antigen presentation could be monitored to effectively assess the expansion of CTL by adjuvants. The monitoring of certain genes is necessary for the assessment of leukopenic toxicity and cytotoxicity of the tested adjuvant. These results indicate that the efficacy and toxicity of various adjuvants can be characterized by profiling lung biomarker genes after the first instance of immunization. This approach could make a significant contribution to the development of optimal selection and exploratory screening strategies for novel adjuvants.

Pharmacodynamic and safety considerations for influenza vaccine and adjuvant design

INTRODUCTION

A novel adjuvant evaluation system for safety and immunogenicity is needed. Vaccination is important for infection prevention, for example, from influenza viruses. Adjuvants are considered critical for improving the effectiveness of influenza vaccines. Adjuvant development is an important issue in influenza vaccine design.

AREAS COVERED

A conventional in vivo evaluation method for vaccine safety has been limited in analyzing phenotypic and pathological changes. Therefore, it is difficult to obtain information on the changes at the molecular level. This review aims to explain the recently developed genomics analysis-based vaccine adjuvant safety evaluation tools verified by AddaVax^TM and polyinosinic-polycytidylic acid (poly I:C) using 18 biomarker genes and whole-virion inactivated influenza vaccine as a toxicity control. Genomics analyzes would help provide safety and efficacy information regarding influenza vaccine design by facilitating appropriate adjuvant selection.

EXPERT OPINION

The efficacy and safety profiles of influenza vaccines and adjuvants using genomics technologies provide useful information regarding immunogenicity, which is related to safety and efficacy. This approach provides important information to select appropriate inoculation routes, combinations of vaccine antigens and adjuvants, and dosing amounts. The efficacy of vaccine adjuvant evaluation by genomics analysis should be verified by various studies using various vaccines in the future.

Lyophilizable and Multifaceted Toll-like Receptor 7/8 Agonist-Loaded Nanoemulsion for the Reprogramming of Tumor Microenvironments and Enhanced Cancer Immunotherapy

The low therapeutic efficacy of current cancer immunotherapy is related to nonimmunogenic and immunosuppressive tumor microenvironments (TMEs). To overcome these limitations, both the immune priming of antitumoral lymphocytes and the reprogramming of immunosuppressive factors in TMEs are essential. Here, we suggest a nanoemulsion (NE)-based immunotherapeutic platform that can not only modulate tumor-induced suppression but also induce an effective cell-mediated immune response for T cell proliferation. Multifunctional NEs can be fabricated by integrating the efficacy of NEs as delivery systems and the multifaceted immunomodulation characteristics (i.e., immunostimulation and reprogramming of immunosuppression) of small molecule-based Toll-like receptor 7/8 agonists. Local in situ vaccination of melanoma and cervical tumor models with tumor antigens (protein and peptide) adjuvanted with NE loaded with TLR7/8 agonists [NE (TLR7/8a)] induced the recruitment and activation of innate immune cells, infiltration of lymphocytes, and polarization of tumor-associated M2 macrophages, which resulted in inhibition of tumor growth and prolonged survival in both primary and rechallenged tumor models. Antibody-depletion experiments also suggested that macrophages, type I IFN (IFN-α and IFN-β), CD8⁺ T cells, and NK1.1⁺ cells contributed to the antitumor effect of NE (TLR7/8a). The combination of antitumoral lymphocytes and reprogramming of immunosuppressive TMEs induced by NE (TLR7/8a) treatment evoked a synergistic antitumor immune response with immune checkpoint blockade therapy (anti-PD-1 and anti-PD-L1).

pDC depletion induced by CD317 blockade drives the antitumor immune response in head and neck squamous cell carcinoma

OBJECTIVES

Dysregulation of immune cells in the tumor microenvironment is a hallmark of head and neck squamous cell carcinoma (HNSCC). Increased infiltration of pDCs has been reported in the microenvironment of HNSCC. However, the precise immunological role of pDC and the therapeutic effects of pDC depletion in HNSCC need to be further investigated.

MATERIALS AND METHODS

CD317 antibodies were applied for depleting pDCs in an immunocompetent transgenic HNSCC mouse model. Tumor volume was monitored. Flow cytometric analysis was conducted for studying the immune profile changes after pDC depletion. In addition, immunohistochemical staining was carried out in a human HNSCC tissue microarray for detecting the infiltration of pDCs. We also analyzed the survival implication of pDCs and its correlation with other immune related markers in human HNSCC.

RESULTS

pDC depletion in the transgenic HNSCC mouse model significantly delayed tumor growth. After pDCs were depleted, T cells were markedly revitalized, and the proportions of regulatory T cells (Tregs) and monocytic myeloid-derived suppressor cells (MDSCs) were decreased. In human HNSCC microenvironment, pDC infiltration was upregulated and its high infiltration conferred a poor prognosis. Moreover, pDC infiltration was closely correlated with the expression of Foxp-3, PD-1, TIM-3, and LAG-3.

CONCLUSION

Our findings demonstrated that pDCs play a negative immunomodulatory role in HNSCC and may present as a target for effective immunotherapy.

Immune Cell Composition in Human Non-small Cell Lung Cancer

Non-small cell lung cancer (NSCLC) is the leading cause of cancer-related death in the world. Immunological analysis of the tumor microenvironment (immunoscore) shows great promise for improved prognosis and prediction of response to immunotherapy. However, the exact immune cell composition in NSCLC remains unclear. Here, we used flow cytometry to characterize the immune infiltrate in NSCLC tumors, non-cancerous lung tissue, regional lymph node, and blood. The cellular identity of >95% of all CD45⁺ immune cells was determined. Thirteen distinct immune cell types were identified in NSCLC tumors. T cells dominated the lung cancer landscape (on average 47% of all CD45⁺ immune cells). CD4⁺ T cells were the most abundant T cell population (26%), closely followed by CD8⁺ T cells (22%). Double negative CD4⁻CD8⁻ T cells represented a small fraction (1.4%). CD19⁺ B cells were the second most common immune cell type in NSCLC tumors (16%), and four different B cell sub-populations were identified. Macrophages and natural killer (NK) cells composed 4.7 and 4.5% of the immune cell infiltrate, respectively. Three types of dendritic cells (DCs) were identified (plasmacytoid DCs, CD1c⁺ DCs, and CD141⁺ DCs) which together represented 2.1% of all immune cells. Among granulocytes, neutrophils were frequent (8.6%) with a high patient-to-patient variability, while mast cells (1.4%), basophils (0.4%), and eosinophils (0.3%) were less common. Across the cohort of patients, only B cells showed a significantly higher representation in NSCLC tumors compared to the distal lung. In contrast, the percentages of macrophages and NK cells were lower in tumors than in non-cancerous lung tissue. Furthermore, the fraction of macrophages with high HLA-DR expression levels was higher in NSCLC tumors relative to distal lung tissue. To make the method readily accessible, antibody panels and flow cytometry gating strategy used to identify the various immune cells are described in detail. This work should represent a useful resource for the immunomonitoring of patients with NSCLC.

Tumor microenvironmental plasmacytoid dendritic cells contribute to breast cancer lymph node metastasis via CXCR4/SDF-1 axis

PURPOSE

Plasmacytoid dendritic cells (PDCs) infiltration into breast cancer tissues is associated with poor prognosis. Also, CXCR4 shows compelling evidences to be exploited by cancer cells to migrate to distant sites. The present study investigated lymph node metastasis in the light of PDCs infiltration and the potential cross talk with CXCR4/SDF-1 chemokine axis.

METHODS

We assessed circulating PDCs proportions drained from the axillary tributaries, and the in situ expression of both CD303 and CXCR4 in breast cancer patients with positive lymph nodes (pLN) and negative lymph nodes (nLN) using immunohistochemistry and flow cytometry. We also analyzed the expression of SDF-1 in lymph nodes of pLN and nLN patients. We studied the effect of the secretome of PDCs of pLN and nLN patients on the expression of CXCR4 and activation of NF-κB in human breast cancer cell lines SKBR3 and MCF-7. TNF-α mRNA expression level in PDCs from both groups was determined by qPCR.

RESULTS

Our findings indicate increased infiltration of PDCs in breast cancer tissues of pLN patients than nLN patients, which correlates with CXCR4⁺ cells percentage. Interestingly, SDF-1 is highly immunostained in lymph nodes of pLN patients compared to nLN patients. Our in vitro experiments demonstrate an upregulation of NF-κB expression and CXCR4 cells upon stimulation with PDCs secretome of pLN patients than those of nLN patients. Also, PDCs isolated from pLN patients exhibited a higher TNF-α mRNA expression than nLN patients. Treatment of MCF-7 cell lines with TNF-α significantly upregulates CXCR4 expression.

CONCLUSIONS

Our findings suggest a potential role for microenvironmental PDCs in breast cancer lymph node metastasis via CXCR4/SDF-1 axis.

CD169+ Macrophages Capture and Dendritic Cells Instruct: The Interplay of the Gatekeeper and the General of the Immune System

Since the seminal discovery of dendritic cells (DCs) by Steinman and Cohn in 1973, there has been an ongoing debate to what extent macrophages and DCs are related and perform different functions. The current view is that macrophages and DCs originate from different lineages and that only DCs have the capacity to initiate adaptive immunity. Nevertheless, as we will discuss in this review, lymphoid tissue resident CD169⁺ macrophages have been shown to act in concert with DCs to promote or suppress adaptive immune responses for pathogens and self-antigens, respectively. Accordingly, we propose a functional alliance between CD169⁺ macrophages and DCs in which a division of tasks is established. CD169⁺ macrophages are responsible for the capture of pathogens and are frequently the first cell type infected and thereby provide a confined source of antigen. Subsequently, cross-presenting DCs interact with these antigen-containing CD169⁺ macrophages, pick up antigens and activate T cells. The cross-priming of T cells by DCs is enhanced by the localized production of type I interferons (IFN-I) derived from CD169⁺ macrophages and plasmacytoid DCs (pDCs) that induces DC maturation. The interaction between CD169⁺ macrophages and DCs appears not only to be essential for immune responses against pathogens, but also plays a role in the induction of self-tolerance and immune responses against cancer. In this review we will discuss the studies that demonstrate the collaboration between CD169⁺ macrophages and DCs in adaptive immunity.

A requirement for slc15a4 in imiquimod-induced systemic inflammation and psoriasiform inflammation in mice

There is competing evidence that plasmacytoid dendritic cells (pDC), the most potent source of IFN-I, may initiate psoriasis. We targeted pDC function using the slc15a4^feeble loss-of-function mouse whose pDC are unresponsive to TLR agonists. slc15a4^feeble treated with the topical TLR7-agonist imiquimod (IMQ) demonstrated decreased epidermal thickening 24 hours post-treatment which was more pronounced by day 5 as compared to wildtype mice. These findings were specific to the acute IMQ model and not the protracted IL23 model that drives inflammation downstream of TLR activation. Systemically, slc15a4 was required for IMQ-induced weight loss and cutaneous accumulation of CD4+ and Siglec H+, but not CD11b+ cells. Consistent with this phenotype and the function of slc15a4, induction of IFN-I was virtually absent systemically and via cutaneous gene expression. Induction of other inflammatory cytokines (cytokine storm) was modestly blunted in slc15a4^feeble except for inflammasome-associated genes consistent with slc15a4 being required for TLR7-mediated (but not inflammasome-mediated) inflammation downstream of IMQ. Surprisingly, only IFN-I gene expression was suppressed within IMQ-treated skin. Other genes including conserved psoriasiform trademark gene expression were augmented in slc15a4^feeble versus littermate controls. Taken together, we have identified a role for slc15a4 but not canonical psoriasiform genes in the imiquimod model of psoriasiform dermatitis.

Interferon priming is essential for human CD34+ cell-derived plasmacytoid dendritic cell maturation and function

Plasmacytoid dendritic cells (pDC) are essential for immune competence. Here we show that pDC precursor differentiated from human CD34+ hematopoietic stem and progenitor cells (HSPC) has low surface expression of pDC markers, and has limited induction of type I interferon (IFN) and IL-6 upon TLR7 and TLR9 agonists treatment; by contrast, cGAS or RIG-I agonists-mediated activation is not altered. Importantly, after priming with type I and II IFN, these precursor pDCs attain a phenotype and functional activity similar to that of peripheral blood-derived pDCs. Data from CRISPR/Cas9-mediated genome editing of HSPCs further show that HSPC-pDCs with genetic modifications can be obtained, and that expression of the IFN-α receptor is essential for the optimal function, but dispensable for the differentiation, of HSPC-pDC percursor. Our results thus demonstrate the biological effects of IFNs for regulating pDC function, and provide the means of generating of gene-modified human pDCs.

The inhibition of malignant melanoma cell invasion of bone by the TLR7 agonist R848 is dependent upon pro-inflammatory cytokines produced by bone marrow macrophages

Distant metastasis remarkably worsens the prognoses of malignant melanoma patients. Toll-like receptors (TLRs) recognize molecules derived from many types of pathogens and activate the innate intravital immune system. In this study, we examined the effects of R848, a TLR7 ligand, on bone invasion by malignant melanoma cells. Mice underwent transplantation with cells of a malignant melanoma cell line B16F10, and were also administered R848 every three days. Hindlimbs were obtained 13 days after transplantation and invasion of bone marrow by B16F10 cells was evaluated. ELISA was used to determine the concentrations of cytokines in mouse serum and in the culture medium from bone marrow macrophages (BMMs) in the presence or absence of R848. In addition, MTS assays were used to examine the effects of media from BMM cultures on the proliferation of B16F10 cells. The rate of infiltration by B16F10 cells and the area of invasion were significantly reduced with R848 administration. Furthermore, serum levels of IL-6, IL-12, and IFN-γ were significantly increased in mice administered R848, with the same trend observed in the culture medium of BMMs treated with R848. In addition, B16F10 cell proliferation was suppressed by the addition of medium from cultured BMMs treated with R848. Neutralization by antibodies against IL-6, IL-12, and IFN-γ abrogated the suppression of proliferation of B16F10 cells by culture medium from BMMs treated with R848. Our results suggest that R848 drives the production of IL-6, IL-12, and IFN-γ in BMMs, which reduces proliferation and bone invasion by B16F10 cells.

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.

The Pseudorabies Virus Glycoprotein gE/gI Complex Suppresses Type I Interferon Production by Plasmacytoid Dendritic Cells

Plasmacytoid dendritic cells (pDC) play a central role in the antiviral immune response, both in the innate response and in shaping the adaptive response, mainly because of their ability to produce massive amounts of type I interferon (TI-IFN). Here, we report that cells infected with the live attenuated Bartha vaccine strain of porcine alphaherpesvirus pseudorabies virus (PRV) trigger a dramatically increased TI-IFN response by porcine primary pDC compared to cells infected with wild-type PRV strains (Becker and Kaplan). Since Bartha is one of the relatively few examples of a highly successful alphaherpesvirus vaccine, identification of factors that may contribute to its efficacy may provide insights for the rational design of other alphaherpesvirus vaccines. The Bartha vaccine genome displays several mutations compared to the genome of wild-type PRV strains, including a large deletion in the unique short (US) region, encompassing the glycoprotein E (gE), gI, US9, and US2 genes. Using recombinant PRV Becker strains harboring the entire Bartha US deletion or single mutations in the four affected US genes, we demonstrate that the absence of the viral gE/gI complex contributes to the observed increased IFN-α response. Furthermore, we show that the absence of gE leads to an enhanced extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation in pDC, which correlates with a higher TI-IFN production by pDC. In conclusion, the PRV Bartha vaccine strain triggers strongly increased TI-IFN production by porcine pDC. Our data further indicate that the gE/gI glycoprotein complex suppresses TI-IFN production by pDC, which represents the first alphaherpesvirus factor that suppresses pDC activity.IMPORTANCE Several alphaherpesviruses, including herpes simpex virus, still lack effective vaccines. However, the highly successful Bartha vaccine has contributed substantially to eradication of the porcine alphaherpesvirus pseudorabies virus (PRV) in several countries. The impact of Bartha on the immune response is still poorly understood. Type I interferon (TI-IFN)-producing plasmacytoid dendritic cells (pDC) may play an important role in vaccine development. Here, we show that Bartha elicits a dramatically increased type I interferon (TI-IFN) response in primary porcine pDC compared to wild-type strains. In addition, we found that the gE/gI complex, which is absent in Bartha, inhibits the pDC TI-IFN response. This is the first description of an immune cell type that is differentially affected by Bartha versus wild-type PRV and is the first report describing an alphaherpesvirus protein that inhibits the TI-IFN response by pDC. These data may therefore contribute to the rational design of other alphaherpesvirus vaccines.

The Novel Toll-Like Receptor 2 Agonist SUP3 Enhances Antigen Presentation and T Cell Activation by Dendritic Cells

Dendritic cells (DCs) are highly specialized antigen-presenting cells that play crucial roles in innate and adaptive immunity. Previous studies suggested that Toll-like receptor (TLR) agonists could be used as potential adjuvants, as activation of TLRs can boost DC-induced immune responses. TLR2 agonists have been shown to enhance DC-mediated immune responses. However, classical TLR2 agonists such as Pam3CSK4 are not stable enough in vivo, which limits their clinical applications. In this study, a novel structurally stable TLR2 agonist named SUP3 was designed. Functional analysis showed that SUP3 induced much stronger antitumor response than Pam3CSK4 by promoting cytotoxic T lymphocytes activation in vivo. This effect was achieved through the following mechanisms: SUP3 strongly enhanced the ability of antigen cross-presentation by DCs and subsequent T cell activation. SUP3 upregulated the expression of costimulatory molecules on DCs and increased antigen deposition in draining lymph nodes. More interestingly, SUP3 induced less amount of pro-inflammatory cytokine production in vivo compared to other TLR agonists such as lipopolysaccharide. Taken together, SUP3 could serve as a novel promising immune adjuvant in vaccine development and immune modulations.

Hematopoietic stem cell-derived myeloid and plasmacytoid DC-based vaccines are highly potent inducers of tumor-reactive T cell and NK cell responses ex vivo

Because of the potent graft-versus-tumor (GVT) effect, allogeneic stem cell transplantation (alloSCT) can be a curative therapy for hematological malignancies. However, relapse remains the most frequent cause of treatment failure, illustrating the necessity for development of adjuvant post-transplant therapies to boost GVT immunity. Dendritic cell (DC) vaccination is a promising strategy in this respect, in particular, where distinct biologic functions of naturally occurring DC subsets, i.e. myeloid DCs (mDCs) and plasmacytoid DCs (pDCs), are harnessed. However, it is challenging to obtain high enough numbers of primary DC subsets from blood for immunotherapy due to their low frequencies. Therefore, we present here an ex vivo GMP-compliant cell culture protocol for generating different DC subsets from CD34⁺ hematopoietic stem and progenitor cells (HSPCs) of alloSCT donor origin. High numbers of BDCA1⁺ mDCs and pDCs could be generated, sufficient for multiple vaccination cycles. These HSPC-derived DC subsets were highly potent in inducing antitumor immune responses in vitro. Notably, HSPC-derived BDCA1⁺ mDCs were superior in eliciting T cell responses. They efficiently primed naïve T cells and robustly expanded patient-derived minor histocompatibility antigen (MiHA)-specific T cells. Though the HSPC-pDCs also efficiently induced T cell responses, they exhibited superior capacity in activating NK cells. pDC-primed NK cells highly upregulated TRAIL and possessed strong cytolytic capacity against tumor cells. Collectively, these findings indicate that HSPC-derived DC vaccines, comprising both mDCs and pDCs, may possess superior potential to boost antitumor immunity post alloSCT, due to their exceptional T cell and NK cell stimulatory capacity.

Complement Component 3 Regulates IFN-α Production by Plasmacytoid Dendritic Cells following TLR7 Activation by a Plant Virus-like Nanoparticle

The increasing use of plant viruses for the development of new vaccines and immunotherapy approaches poses questions regarding the mechanism by which the mammalian immune system recognizes these viruses. For example, although natural Abs (NA) and complement are key components of the innate immune system involved in the opsonization, phagocytosis, and destruction of microorganisms infecting mammals, their implication in plant virus recognition and immunogenicity is not well defined. In this study, we address the involvement of NA and the complement system in the activation of innate immunity through engagement of TLR7 with papaya mosaic virus (PapMV)-like nanoparticles. We demonstrate that NA, although binding to PapMV, are not involved in its recognition by the immune system. On the other hand, C3 strongly binds to PapMV nanoparticles and its depletion significantly reduces PapMV's interaction with immune cells. Unexpectedly, however, we observed increased immune cell activation following administration of PapMV to complement-depleted mice. TLR7 activation by PapMV in the absence of C3 induced higher IFN-α production, resulting in superior immune cell activation and increased immunotherapeutic properties. In conclusion, in this study we established the involvement of the complement system in the recognition and the phagocytosis of PapMV nanoparticles and identified an unsuspected role for C3 in regulating the production of IFN-α following TLR7 activation.

Covalent Conjugation of Small-Molecule Adjuvants to Nanoparticles Induces Robust Cytotoxic T Cell Responses via DC Activation

Specific recognitions of pathogen associated molecular patterns by Toll-like receptors (TLRs) initiate dendritic cell (DC) activation, which is critical for coordinating innate and adaptive immune responses. Imidazoquinolines as small-molecule TLR7 agonists often suffer from prompt dissemination and short half-life in the bloodstream, preventing their localization to the corresponding receptors and effective DC activation. We postulated that covalent incorporation of imidazoquinoline moieties onto the surface of biocompatible nanoparticles (∼30 nm size) would enhance their chemical stability, cellular uptake efficiency, and adjuvanticity. The fully synthetic adjuvant-nanocomplexes led to successful DC activation at lower nanomolar doses compared with free small-molecule agonists. Once a model antigen such as ovalbumin was used for immunization, we found that the nanocomplexes promoted an unusually strong cytotoxic T lymphocyte response, revealing their unique immunostimulatory capacity benefiting from multivalency and efficient transport to endosomal TLR7.

The genetic background influences the cellular and humoral immune responses to vaccines

The assessment of Toll-like receptor (TLR) agonists as candidate adjuvants for induction of effective T helper type 1 (Th1) immunity continues to rely on the use of mice. However, the genetic variation among inbred mice may influence the efficacy of adjuvants and bias a study's conclusions. Here, we evaluated the differences in cellular and humoral responses of genetically non-identical mouse strains immunized with ovalbumin (OVA) plus alum, TLR-3, TLR-4, TLR-7/8 or TLR-9 agonists. We found that all the tested TLR agonists recruited dendritic cells (DCs) and natural killer (NK) cells significantly into the lymph nodes, promoted DC-NK cross-talk and enhanced the cellular responses in B6 strain. In contrast, TLR-3 and TLR-7/8 were the only two agonists that showed the cellular adjuvanticity in the BALB/c strain. Compared with other TLR agonists, TLR-3 and TLR-7/8 were demonstrated to be the most effective adjuvants to generate interferon (IFN)-γ-producing effector NK, CD4, and CD8 T cells in B6 and BALB/c strains, respectively. We also found that compared with alum, all adjuvants induced the recruitment of B cells and production of OVA-specific immunoglobulin (Ig)G2a more effectively in both strains. In addition, the B6 strain recruited more B cells, but surprisingly produced significantly lower amounts of OVA-specific IgG2a in response to all adjuvants. However, consistent with the frequency of IFN-γ-producing effector cells observed in individual strains following immunizations, we detected more OVA-specific IgG2a in serum of B6 and BALB/c strains in response to TLR-3 and TLR-7/8, respectively. Our data suggest that genetic background should be taken into consideration when evaluating the activities of TLR agonists for the development of prophylactic and therapeutic vaccines.

MicroRNA-155 Mediates Augmented CD40 Expression in Bone Marrow Derived Plasmacytoid Dendritic Cells in Symptomatic Lupus-Prone NZB/W F1 Mice

Systemic lupus erythematosus (SLE) is a chronic multi-organ autoimmune disease characterized by hyperactivated immune responses to self-antigens and persistent systemic inflammation. Previously, we reported abnormalities in circulating and bone marrow (BM)-derived plasmacytoid dendritic cells (pDCs) from SLE patients. Here, we aim to seek for potential regulators that mediate functional aberrations of pDCs in SLE. BM-derived pDCs from NZB/W F1 mice before and after the disease onset were compared for toll-like receptor (TLR) induced responses and microRNA profile changes. While pDCs derived from symptomatic mice were phenotypically comparable to pre-symptomatic ones, functionally they exhibited hypersensitivity to TLR7 but not TLR9 stimulation, as represented by the elevated upregulation of CD40, CD86 and MHC class II molecules upon R837 stimulation. Upregulated induction of miR-155 in symptomatic pDCs following TLR7 stimulation was observed. Transfection of miR-155 mimics in pre-symptomatic pDCs induced an augmented expression of Cd40, which is consistent with the increased CD40 expression in symptomatic pDCs. Overall, our results provide evidence for miR-155-mediated regulation in pDC functional abnormalities in SLE. Findings from this study contribute to a better understanding of SLE pathogenesis and ignite future interests in evaluating the molecular regulation in autoimmunity.

Direct Delivery of Antigens to Dendritic Cells via Antibodies Specific for Endocytic Receptors as a Promising Strategy for Future Therapies

Dendritic cells (DCs) are the most potent professional antigen presenting cells and are therefore indispensable for the control of immunity. The technique of antibody mediated antigen targeting to DC subsets has been the basis of intense research for more than a decade. Many murine studies have utilized this approach of antigen delivery to various kinds of endocytic receptors of DCs both in vitro and in vivo. Today, it is widely accepted that different DC subsets are important for the induction of select immune responses. Nevertheless, many questions still remain to be answered, such as the actual influence of the targeted receptor on the initiation of the immune response to the delivered antigen. Further efforts to better understand the induction of antigen-specific immune responses will support the transfer of this knowledge into novel treatment strategies for human diseases. In this review, we will discuss the state-of-the-art aspects of the basic principles of antibody mediated antigen targeting approaches. A table will also provide a broad overview of the latest studies using antigen targeting including addressed DC subset, targeted receptors, outcome, and applied coupling techniques.

Expression of TLR-7, MyD88, NF-kB, and INF-α in B Lymphocytes of Mayan Women with Systemic Lupus Erythematosus in Mexico

Background

Systemic lupus erythematosus (SLE) is a chronic inflammatory autoimmune disease involving multiple organs. It is currently accepted that several genetic, environmental, and hormonal factors are contributing to its development. Innate immunity may have a great influence in autoimmunity through Toll-like receptors. TLR-7 recognizing single-strand RNA has been involved in SLE. Its activation induces intracellular signal with attraction of MyD88 and NF-kBp65, leading to IFN-α synthesis which correlate with disease activity.

Objective

To assess the expression of TLR-7, MyD88, and NF-kBp65 in B lymphocytes of Mayan women with SLE.

Methods

One hundred patients with SLE and 100 healthy controls, all of them Mayan women, were included. TLR-7 was analyzed on B and T lymphocytes, and MyD88 and NF-kB only in B lymphocytes. Serum INF-α level was evaluated by ELISA.

Results

Significant expression (p < 0.0001) of TLR-7 in B and T lymphocytes and serum IFN-α increased (p = 0.034) was observed in patients. MyD88 and NF-kBp65 were also increased in B lymphocytes of patients. TLR-7 and NF-kBp65 expression correlated, but no correlation with INF-α and disease activity was detected.

Conclusion

Data support the role of TLR-7 and signal proteins in the pathogenesis of SLE in the Mayan population of Yucatán.

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.

Modes of action of TLR7 agonists in cancer therapy

From the numerous Toll-like receptor agonists, only TLR7 agonists have been approved for cancer treatment, although they are current restricted to topical application. The main target cells of TLR7 agonists are plasmacytoid dendritic cells, producing IFN-α and thus acting on other immune cells. Thereby dendritic cells acquire enhanced costimulatory and antigen-presenting capacity, priming an adaptive immune response. Besides NK cells, antigen-specific T cells are the main terminal effectors of TLR7 agonists in tumor therapy. This qualifies TLR7 agonists as vaccine adjuvants, which is currently being tested in clinical trials. However, the systemic application of TLR7 agonists shows insufficient efficacy, most likely owing to toxicity-limited dosing. The use of TLR7 agonists in combinational therapy holds the promise of synergistic activity and lower required doses.

Synergy between rapamycin and FLT3 ligand enhances plasmacytoid dendritic cell-dependent induction of CD4+CD25+FoxP3+ Treg

CD4(+)CD25(+)FoxP3(+) regulatory T cells (Treg) are critical elements for maintaining immune tolerance, for instance to exogenous antigens that are introduced during therapeutic interventions such as cell/organ transplant or gene/protein replacement therapy. Coadministration of antigen with rapamycin simultaneously promotes deletion of conventional CD4(+) T cells and induction of Treg. Here, we report that the cytokine FMS-like receptor tyrosine kinase ligand (Flt3L) enhances the in vivo effect of rapamycin. This occurs via selective expansion of plasmacytoid dendritic cells (pDCs), which further augments the number of Treg. Whereas in conventional DCs, rapamycin effectively blocks mammalian target of rapamycin (mTOR) 1 signaling induced by Flt3L, increased mTOR1 activity renders pDCs more resistant to inhibition by rapamycin. Consequently, Flt3L and rapamycin synergistically promote induction of antigen-specific Treg via selective expansion of pDCs. This concept is supported by the finding that Treg induction is abrogated upon pDC depletion. The combination with pDCs and rapamycin is requisite for Flt3L/antigen-induced Treg induction because Flt3L/antigen by itself fails to induce Treg. As co-administering Flt3L, rapamycin, and antigen blocked CD8(+) T-cell and antibody responses in models of gene and protein therapy, we conclude that the differential effect of rapamycin on DC subsets can be exploited for improved tolerance induction.

A single naturally occurring 2'-O-methylation converts a TLR7- and TLR8-activating RNA into a TLR8-specific ligand

TLR7 and TLR8 recognize RNA from pathogens and lead to subsequent immune stimulation. Here we demonstrate that a single naturally occurring 2’-O-methylation within a synthetic 18s rRNA derived RNA sequence prevents IFN-α production, however secretion of proinflammatory cytokines such as IL-6 is not impaired. By analysing TLR-deficient plasmacytoid dendritic cells and performing HEK293 genetic complementation assays we could demonstrate that the single 2’-O-methylation containing RNA still activated TLR8 but not TLR7. Therefore this specific 2’-O-ribose methylation in rRNA converts a TLR7 / TLR8 ligand to an exclusively TLR8-specific ligand. Interestingly, other modifications at this position such as 2’-O-deoxy or 2’-fluoro had no strong modulating effect on TLR7 or TLR8 activation suggesting an important role of 2’-O-methylation for shaping differential TLR7 or TLR8 activation.

Plant virus particles carrying tumour antigen activate TLR7 and Induce high levels of protective antibody

Induction of potent antibody is the goal of many vaccines targeted against infections or cancer. Modern vaccine designs that use virus-like particles (VLP) have shown efficacy for prophylactic vaccination against virus-associated cancer in the clinic. Here we used plant viral particles (PVP), which are structurally analogous to VLP, coupled to a weak idiotypic (Id) tumour antigen, as a conjugate vaccine to induce antibody against a murine B-cell malignancy. The Id-PVP vaccine incorporates a natural adjuvant, the viral ssRNA, which acts via TLR7. It induced potent protective anti-Id antibody responses in an in vivo mouse model, superior to the "gold standard" Id vaccine, with prevalence of the IgG2a isotype. Combination with alum further increased antibody levels and maintained the IgG2a bias. Engagement of TLR7 in vivo was followed by secretion of IFN-α by plasmacytoid dendritic cells and by activation of splenic CD11chi conventional dendritic cells. The latter was apparent from up-regulation of co-stimulatory molecules and from secretion of a wide range of inflammatory cytokines and chemokines including the Th1-governing cytokine IL-12, in keeping with the IgG2a antibody isotype distribution. PVP conjugates are a novel cancer vaccine design, offering an attractive molecular form, similar to VLP, and providing T-cell help. In contrast to VLP, they also incorporate a safe "in-built" ssRNA adjuvant.

Intraperitoneal and subcutaneous injections of the TLR9 agonist ODN 1668 in rats: brain inflammatory responses are related to peripheral IL-6 rather than interferons

Subcutaneous or intraperitoneal administration of Toll-like receptor (TLR)-9 agonist, ODN 1668 caused moderate fever and anorexia. In comparison to stimulation of other intracellular TLRs, activation of TLR9 did not result in pronounced peripheral induction of interferons, but rather induced interleukin-6. Expression of cytokines (TNFα, IL-1β) and inducible forms of enzymes for prostaglandin E2 synthesis occurred in the brain, in conjunction with a moderate activation of the transcription factors STAT3 and NF-IL6 in brain endothelial cells. The lack of a septic-like state in ODN 1668-treated rats reinforces the therapeutic value of this drug.

Toll-like receptor 7 agonist imiquimod in combination with influenza vaccine expedites and augments humoral immune responses against influenza A(H1N1)pdm09 virus infection in BALB/c mice

Toll-like receptors (TLRs) of the innate immune system are known targets for enhancing vaccine efficacy. We investigated whether imiquimod, a synthetic TLR7 agonist, can expedite the immune response against influenza virus infection when combined with influenza vaccine. BALB/c mice were immunized intraperitoneally with monovalent A(H1N1)pdm09 vaccine combined with imiquimod (VCI) prior to intranasal inoculation with a lethal dose of mouse-adapted A(H1N1)pdm09 virus. For mice immunized 3 days before infection, the survival rates were significantly higher in the VCI group (60%, mean survival time[MST], 11 days) than in the vaccine-alone (30%; MST, 8.8 days), imiquimod-alone (5%; MST, 8.4 days), and phosphate-buffered saline (PBS) (0%; MST, 6.2 days) groups (P < 0.01). In the VCI group, 45 and 35% of the mice survived even when they were infected 2 days or 1 day after immunization. Virus-specific serum IgM, IgG, and neutralizing antibodies appeared earlier with higher geometric mean titers in the VCI group than in the control groups. The pulmonary viral load was significantly lower at all time points postinfection in the VCI, vaccine-alone, and imiquimod-alone groups than in the PBS control group (P < 0.05). The protection induced by VCI was specific for A(H1N1)pdm09 virus but not for A(H5N1) virus. Since imiquimod combined with RNase-treated vaccine is as protective as imiquimod combined with untreated vaccine, mechanisms other than TLR7 may operate in expediting and augmenting immune protection. Moreover, increased gamma interferon mRNA expression and IgG isotype switching, which are markers of the Th1 response induced by imiquimod, were not apparent in our mouse model. The mechanisms of imiquimod-induced immune protection deserve further study.