The synergy in cytokine production through MyD88-TRIF pathways is co-ordinated with ERK phosphorylation in macrophages

Multimodal Identification by Transcriptomics and Multiscale Bioassays of Active Components in Xuanfeibaidu Formula to Suppress Macrophage-Mediated Immune Response

Xuanfeibaidu Formula (XFBD) is a Chinese medicine used in the clinical treatment of coronavirus disease 2019 (COVID-19) patients. Although XFBD has exhibited significant therapeutic efficacy in clinical practice, its underlying pharmacological mechanism remains unclear. Here, we combine a comprehensive research approach that includes network pharmacology, transcriptomics, and bioassays in multiple model systems to investigate the pharmacological mechanism of XFBD and its bioactive substances. High-resolution mass spectrometry was combined with molecular networking to profile the major active substances in XFBD. A total of 104 compounds were identified or tentatively characterized, including flavonoids, terpenes, carboxylic acids, and other types of constituents. Based on the chemical composition of XFBD, a network pharmacology-based analysis identified inflammation-related pathways as primary targets. Thus, we examined the anti-inflammation activity of XFBD in a lipopolysaccharide-induced acute inflammation mice model. XFBD significantly alleviated pulmonary inflammation and decreased the level of serum proinflammatory cytokines. Transcriptomic profiling suggested that genes related to macrophage function were differently expressed after XFBD treatment. Consequently, the effects of XFBD on macrophage activation and mobilization were investigated in a macrophage cell line and a zebrafish wounding model. XFBD exerts strong inhibitory effects on both macrophage activation and migration. Moreover, through multimodal screening, we further identified the major components and compounds from the different herbs of XFBD that mediate its anti-inflammation function. Active components from XFBD, including Polygoni cuspidati Rhizoma, Phragmitis Rhizoma, and Citri grandis Exocarpium rubrum, were then found to strongly downregulate macrophage activation, and polydatin, isoliquiritin, and acteoside were identified as active compounds. Components of Artemisiae annuae Herba and Ephedrae Herba were found to substantially inhibit endogenous macrophage migration, while the presence of ephedrine, atractylenolide I, and kaempferol was attributed to these effects. In summary, our study explores the pharmacological mechanism and effective components of XFBD in inflammation regulation via multimodal approaches, and thereby provides a biological illustration of the clinical efficacy of XFBD.

Epigenomics of conventional type-I dendritic cells depicted preferential control of TLR9 versus TLR3 response by NCoR1 through differential IRF3 activation

Tight control of gene regulation in dendritic cells (DCs) is important to mount pathogen specific immune responses. Apart from transcription factor binding, dynamic regulation of enhancer activity through global transcriptional repressors like Nuclear Receptor Co-repressor 1 (NCoR1) plays a major role in fine-tuning of DC responses. However, how NCoR1 regulates enhancer activity and gene expression in individual or multiple Toll-like receptor (TLR) activation in DCs is largely unknown. In this study, we did a comprehensive epigenomic analysis of murine conventional type-I DCs (cDC1) across different TLR ligation conditions. We profiled gene expression changes along with H3K27ac active enhancers and NCoR1 binding in the TLR9, TLR3 and combined TLR9 + TLR3 activated cDC1. We observed spatio-temporal activity of TLR9 and TLR3 specific enhancers regulating signal specific target genes. Interestingly, we found that NCoR1 differentially controls the TLR9 and TLR3-specific responses. NCoR1 depletion specifically enhanced TLR9 responses as evident from increased enhancer activity as well as TLR9-specific gene expression, whereas TLR3-mediated antiviral response genes were negatively regulated. We validated that NCoR1 KD cDC1 showed significantly decreased TLR3 specific antiviral responses through decreased IRF3 activation. In addition, decreased IRF3 binding was observed at selected ISGs leading to their decreased expression upon NCoR1 depletion. Consequently, the NCoR1 depleted cDC1 showed reduced Sendai Virus (SeV) clearance and cytotoxic potential of CD8+ T cells upon TLR3 activation. NCoR1 directly controls the majority of these TLR specific enhancer activity and the gene expression. Overall, for the first time, we revealed NCoR1 mediates transcriptional control towards TLR9 as compared to TLR3 in cDC1.

Babaodan controls excessive immune responses and may represent a cytokine-targeted agent suitable for COVID-19 treatment

It has become evident that the actions of pro-inflammatory cytokines and/or the development of a cytokine storm are responsible for the occurrence of severe COVID-19 during SARS-CoV-2 infection. Although immunomodulatory mechanisms vary among viruses, the activation of multiple TLRs that occurs primarily through the recruitment of adapter proteins such as MyD88 and TRIF contributes to the induction of a cytokine storm. Based on this, controlling the robust production of pro-inflammatory cytokines by macrophages may be applicable as a cellular approach to investigate potential cytokine-targeted therapies against COVID-19. In the current study, we utilized TLR2/MyD88 and TLR3/TRIF co-activated macrophages and evaluated the anti-cytokine storm effect of the traditional Chinese medicine (TCM) formula Babaodan (BBD). An RNA-seq-based transcriptomic approach was used to determine the molecular mode of action. Additionally, we evaluated the anti-inflammatory activity of BBD in vivo using a mouse model of post-viral bacterial infection-induced pneumonia and seven severely ill COVID-19 patients. Our study reveals the protective role of BBD against excessive immune responses in macrophages, where the underlying mechanisms involve the inhibition of the NF-κB and MAPK signaling pathways. In vivo, BBD significantly inhibited the release of IL-6, thus resulting in increased survival rates in mice. Based on limited data, we demonstrated that severely ill COVID-19 patients benefited from BBD treatment due to a reduction in the overproduction of IL-6. In conclusion, our study indicated that BBD controls excessive immune responses and may thus represent a cytokine-targeted agent that could be considered to treating COVID-19.

Enhancement of immune responses by co-stimulation of TLR3 - TLR7 agonists as a potential therapeutics against rabies in mouse model

Rabies is always fatal, when post-exposure prophylaxis is administered after the onset of clinical symptoms. To date, there is no effective treatment of rabies once clinical symptoms has initiated. Therefore, we aimed to provide evidences which indicate the promising effects of combination treatment with TLR agonists following rabies infection. Four groups of rabies infected-mice (10-mice/group) were treated with PolyI:C 50 μg (a TLR3 agonist), Imiquimod50 μg (a TLR7 agonist), (Poly + Imi)25 μg and (Poly + Imi)50 μg respectively. The immune responses in each experimental groups were investigated in the brain through evaluation of GFAP, MAP2, CD4, HSP70, TLR3, TLR7 and apoptotic cell expression as well as determination of IFN-γ, TNF-α and IL-4, levels. The treatment with combination of agonists (Poly + Imi)50 μg/mouse resulted a 75% decrease of mortality rate and better extended survival time following street rabies virus infection. Higher number of CD4⁺T cells, TLR3 and TLR7 expression in the brain parenchyma observed in the groups receiving both combined agonist therapies at the levels of 25 μg and 50 μg. In spite of decreased number of neuronal cell, significant higher number of astrocytes was shown in the group given (Poly + Imi)25 μg. The obtained results also pointed to the dramatic decrease of HSP70 expression in all groups of infected mice whereas higher number of apoptotic cells and Caspase 8 expression were recorded in (Poly + Imi)25 μg treated group. Furthermore, the cytokine profile consisting the increased levels of TNF-α, IFN-γ and IL-4 revealed that both humoral and cellular responses were highly modulated in combination therapy of 50 μg of Imiquimod and Poly I:C. Reduced viral load as quantified by real-time PCR of rabies N gene expression in the brain also correlated with the better survival of agonist-treated groups of mice. Based on obtained results, we have presented evidences of beneficial utilization of combined agonist therapy composed of TLR3/TLR7 ligands. This treatment regimen extended survival of infected mice and decreased significantly their mortality rate. We believe that the results of synergy-inducing protection of both TLR3/TLR7 agonists lead to the enhancement of innate immune responses cells residing in the CNS which warrant the studies to further understanding of crosstalk mechanisms in cellular immunity against rabies in the future.

Applications of Non-invasive Neuromodulation for the Management of Disorders Related to COVID-19

Background: Novel coronavirus disease (COVID-19) morbidity is not restricted to the respiratory system, but also affects the nervous system. Non-invasive neuromodulation may be useful in the treatment of the disorders associated with COVID-19. Objective: To describe the rationale and empirical basis of the use of non-invasive neuromodulation in the management of patients with COVID-10 and related disorders. Methods: We summarize COVID-19 pathophysiology with emphasis of direct neuroinvasiveness, neuroimmune response and inflammation, autonomic balance and neurological, musculoskeletal and neuropsychiatric sequela. This supports the development of a framework for advancing applications of non-invasive neuromodulation in the management COVID-19 and related disorders. Results: Non-invasive neuromodulation may manage disorders associated with COVID-19 through four pathways: (1) Direct infection mitigation through the stimulation of regions involved in the regulation of systemic anti-inflammatory responses and/or autonomic responses and prevention of neuroinflammation and recovery of respiration; (2) Amelioration of COVID-19 symptoms of musculoskeletal pain and systemic fatigue; (3) Augmenting cognitive and physical rehabilitation following critical illness; and (4) Treating outbreak-related mental distress including neurological and psychiatric disorders exacerbated by surrounding psychosocial stressors related to COVID-19. The selection of the appropriate techniques will depend on the identified target treatment pathway. Conclusion: COVID-19 infection results in a myriad of acute and chronic symptoms, both directly associated with respiratory distress (e.g., rehabilitation) or of yet-to-be-determined etiology (e.g., fatigue). Non-invasive neuromodulation is a toolbox of techniques that based on targeted pathways and empirical evidence (largely in non-COVID-19 patients) can be investigated in the management of patients with COVID-19.

RETRACTED ARTICLE: Selected TLR7/8 agonist and type I interferon (IFN-α) cooperatively redefine the microglia transcriptome

Background

Microglia, the primary immune cells of the central nervous system, exerts multiple functions to mediate many neurological diseases. Upon any detection of invading pathogen products (e.g., TLR agonists) or host-released signaling factors (e.g., interferon/IFN), these cells undergo an activation process to release large numbers of inflammatory substances that participate in inflammation and homeostasis. The profound effects of inflammation associated with TLR7/8 agonist Resiquimod (R848) and type 1 interferon (e.g., IFN-α)-induced macrophage and dendritic cell activation on biological outcomes have long been recognized. However, the underlying mechanisms are not well defined in microglial cells.

Methods

The present study investigated the molecular signatures of microglia and identified genes that are uniquely or synergistically expressed in R848-, IFN-α- or R848 with IFN-α-treated primary microglial (PM) cells. We used RNA-sequencing, quantitative real-time PCR, and bioinformatics approaches to derive regulatory networks that control the transcriptional response of PM to R848, IFN-α and R848 with IFN-α.

Results

Our approach revealed that the inflammatory response in R848 with IFN-α-treated PM is faster and more intense than that in R848 or IFN-α-treated PM in terms of the number of differentially expressed genes and the magnitude of induction/repression. In particular, our integrative analysis enabled us to suggest the regulatory functions of TFs, which allowed the construction of a network model that explains how TLR7/8 and IFN-α-sensing pathways achieve specificity.

Conclusion

In conclusion, the systematic approach presented herein could be important to the understanding microglial activation-mediated molecular signatures induced by inflammatory stimuli related to TLR7/8, IFN-α or co-signaling, and associated transcriptional machinery of microglial functions and neuroinflammatory mechanisms.

Electronic supplementary material

The online version of this article (10.1007/s10787-019-00610-8) contains supplementary material, which is available to authorized users.

Inter-relation analysis of signaling adaptors of porcine innate immune pathways

To study the interrelationship between the signaling adaptors of innate pattern recognition receptor (PRR) pathways including toll-like receptor (TLR), retinoic acid-inducible gene-1-like receptor (RLR), nucleotide-binding oligomerization domain-like receptor (NLR), and cytoplasmic DNA recognition receptors (CDR) pathways. The coding genes of porcine TRIF, MAVS, STING, MyD88, RIPK2, and ASC were isolated from PK15 cells. Phylogenetic analysis of the six adaptor proteins in pig, cattle, goat, horse, human, mouse, chicken, and duck performed by MEGA 5.05 showed that these adaptors have slightly different similarity across species. The expression of these proteins in transfected cells were detected by both Western blotting and confocal microscopy. All six adaptors were visualized in cytoplasm but with different distribution patterns. The activities of the six adaptors triggering NF-κB and ISRE signaling and downstream gene productions were examined by dual-luciferase reporter assay and real-time RT-PCR, respectively. The results showed that STING has an ability to activate ISRE signaling, MyD88, RIPK2 and ASC possess NF-κB signal activity, while TRIF and MAVS can activate both. Furthermore, the mutual signaling effects were assessed by NF-κB and ISRE dual-luciferase reporter assay in the co-expression experiments. STING was shown to enhance MAVS activated NF-κB signaling and MyD88 could heighten STING activated ISRE signaling. However, all other adaptors inhibited each other to varying degrees. The work provides a global insight of porcine innate immune signaling pathways and their interaction network.

IFIT1 Exerts Opposing Regulatory Effects on the Inflammatory and Interferon Gene Programs in LPS-Activated Human Macrophages

Activation of the TLR4 signaling pathway by lipopolysaccharide (LPS) leads to induction of both inflammatory and interferon-stimulated genes, but the mechanisms through which these coordinately activated transcriptional programs are balanced to promote an optimal innate immune response remain poorly understood. In a genome-wide small interfering RNA (siRNA) screen of the LPS-induced tumor necrosis factor α (TNF-α) response in macrophages, we identify the interferon-stimulated protein IFIT1 as a negative regulator of the inflammatory gene program. Transcriptional profiling further identifies a positive regulatory role for IFIT1 in type I interferon expression, implicating IFIT1 as a reciprocal modulator of LPS-induced gene classes. We demonstrate that these effects of IFIT1 are mediated through modulation of a Sin3A-HDAC2 transcriptional regulatory complex at LPS-induced gene loci. Beyond the well-studied role of cytosolic IFIT1 in restricting viral replication, our data demonstrate a function for nuclear IFIT1 in differential transcriptional regulation of separate branches of the LPS-induced gene program.

MEK1/2 Inhibitors Unlock the Constrained Interferon Response in Macrophages Through IRF1 Signaling

Macrophages are immune sentinels essential for pathogen recognition and immune defense. Nucleic acid-sensing toll-like receptors like TLR7 activate tailored proinflammatory and interferon responses in macrophages. Here we found that TLR7 activation constrained itself and other TLRs from inducing interferon response genes in macrophages through MAPK kinase 1/2 (MEK1/2)-dependent IRF1 inhibition. Downstream of the MEK1/2-ERK pathway, TLR7-activated macrophages induced interleukin-10 (IL-10), a signal transducer and activator of transcription 3 (STAT3) signaling axis, which constrained the expression of interferon response genes, immunomodulatory cytokines, and chemokines. Nevertheless, MEK1/2 inhibitors unlocked an IRF1-interferon signature response in an NF-κB-dependent manner. Deficiency in interferon regulatory factor 1 (Irf1) completely abrogated the interferon response and prevented the reprogramming of macrophages into an immunostimulatory phenotype. As a proof of concept, combination treatment with a TLR7 agonist and MEK1/2 inhibitor synergistically extended the survival of wild-type but not Irf1-deficient melanoma-bearing mice. In a retrospective study, higher expression of Irf1 and interferon response genes correlated with more favorable prognosis in patients with cutaneous melanoma. Our findings demonstrated how MEK1/2 inhibitor unlocks IRF1-mediated interferon signature response in macrophages, and the therapeutic potentials of combination therapy with MEK1/2 inhibitor and TLR7 agonist.

Effective chemoimmunotherapy by co-delivery of doxorubicin and immune adjuvants in biodegradable nanoparticles

Chemoimmunotherapy is an emerging combinatorial modality for the treatment of cancers resistant to common first-line therapies, such as chemotherapy and checkpoint blockade immunotherapy. We used biodegradable nanoparticles as delivery vehicles for local, slow and sustained release of doxorubicin, two immune adjuvants and one chemokine for the treatment of resistant solid tumors.

Methods: Bio-compatible poly(lactic-co-glycolic acid)-PEG nanoparticles were synthesized in an oil/water emulsion, using a solvent evaporation-extraction method. The nanoparticles were loaded with a NIR-dye for theranostic purposes, doxorubicin cytostatic agent, poly (I:C) and R848 immune adjuvants and CCL20 chemokine. After physicochemical and in vitro characterization the nanoparticles therapeutic efficacy were carried-out on established, highly aggressive and treatment resistant TC-1 lung carcinoma and MC-38 colon adenocarcinoma models in vivo.

Results: The yielded nanoparticles average size was 180 nm and -14 mV surface charge. The combined treatment with all compounds was significantly superior than separate compounds and the compounds nanoparticle encapsulation was required for effective tumor control in vivo. The mechanistic studies confirmed strong induction of circulating cancer specific T cells upon combined treatment in blood. Analysis of the tumor microenvironment revealed a significant increase of infiltrating leukocytes upon treatment.

Conclusion: The multi-drug loaded nanoparticles mediated delivery of chemoimmunotherapy exhibited excellent therapeutic efficacy gain on two treatment resistant cancer models and is a potent candidate strategy to improve cancer therapy of solid tumors resistant to first-line therapies.

Systematic Investigation of Multi-TLR Sensing Identifies Regulators of Sustained Gene Activation in Macrophages

A typical pathogen presents a combination of Toll-like receptor (TLR) ligands during infection. Although individual TLR pathways have been well characterized, the nature of this "combinatorial code" in pathogen sensing remains unclear. Here, we conducted a comprehensive transcriptomic analysis of primary macrophages stimulated with all possible pairwise combinations of four different TLR ligands to understand the requirements, kinetics, and outcome of combined pathway engagement. We find that signal integration between TLR pathways leads to non-additive responses for a subset of immune mediators with sustained expression (>6 hr) properties and T cell polarizing function. To identify the underlying regulators, we conducted a focused RNAi screen and identified four genes-Helz2, Phf11d, Sertad3, and Zscan12-which preferentially affect the late phase response of TLR-induced immune effector expression. This study reveals key molecular details of how contemporaneous signaling through multiple TLRs, as would often be the case with pathogen infection, produce biological outcomes distinct from the single ligands typically used to characterize TLR pathways.

NF-κB Signaling in Macrophages: Dynamics, Crosstalk, and Signal Integration

The nuclear factor-κB (NF-κB) signaling pathway is one of the best understood immune-related pathways thanks to almost four decades of intense research. NF-κB signaling is activated by numerous discrete stimuli and is a master regulator of the inflammatory response to pathogens and cancerous cells, as well as a key regulator of autoimmune diseases. In this regard, the role of NF-κB signaling in immunity is not unlike that of the macrophage. The dynamics by which NF-κB proteins shuttle between the cytoplasm and the nucleus to initiate transcription have been studied rigorously in fibroblasts and other non-hematopoietic cells, but many questions remain as to how current models of NF-κB signaling and dynamics can be translated to innate immune cells such as macrophages. In this review, we will present recent research on the dynamics of NF-κB signaling and focus especially on how these dynamics vary in different cell types, while discussing why these characteristics may be important. We will end by looking ahead to how new techniques and technologies should allow us to analyze these signaling processes with greater clarity, bringing us closer to a more complete understanding of inflammatory transcription factor dynamics and how different cellular contexts might allow for appropriate control of innate immune responses.

Neutrophil Activation During Septic Shock

In addition to their well-known role as the cellular mediators of immunity, key other roles have been identified for neutrophils during septic shock. Importantly, neutrophils indeed play a critical role in the recently described immunothrombosis concept and in septic shock-induced coagulopathy. Septic shock is one of the most severe forms of infection, characterized by an inadequate host response to the pathogenic organism. This host response involves numerous defense mechanisms with an intense cellular activation, including neutrophil activation. Neutrophils are key cells of innate immunity through complex interactions with vascular cells and their activation may participate in systemic tissue damages. Their activation also leads to the emission of neutrophil extracellular traps, which take part in both pathogen circumscription and phagocytosis, but also in coagulation activation. Neutrophils thus stand at the interface between hemostasis and immunity, called immunothrombosis.The present review will develop a cellular approach of septic shock pathophysiology focusing on neutrophils as key players of septic shock-induced vascular cell dysfunction and of the host response, associating immunity and hemostasis. We will therefore first develop the role of neutrophils in the interplay between innate and adaptive immunity, and will then highlight recent advances in our understanding of immunothrombosis septic shock-induced coagulopathy.

Activated NK cells kill hepatic stellate cells via p38/PI3K signaling in a TRAIL-involved degranulation manner

NK cells are important in regulating hepatic fibrosis via their cytotoxic killing of hepatic stellate cells (HSCs). NK cells are activated by both cytokines such as IL-12 and IL-18, and innate immune stimuli such as ligation of TLRs. The secretion of IL-18 depends upon activation of the inflammasome, whereas TLRs are stimulated by microbial products. In the case of NK cells, IL-18 acts synergistically with stimulation of TLR3 to cause cell activation and cytotoxic function. In the present study, we activated NK cells to kill HSCs via IL-18 and TLR3 ligand stimulation, and dissected the signaling pathways or molecules critical for such activation or killing. We find that such activation depends on signaling via the p38/PI3K/AKT pathway, and that the activated NK cells mediate HSC death in a TRAIL-involved mechanism. As liver fibrosis is a major global health problem with no good solution, these results emphasize that the p38/PI3K/AKT pathway in NK cells may be a novel drug target to promote fibrosis regression.

Selective autophagy of the adaptor TRIF regulates innate inflammatory signaling

Defective autophagy is linked to diseases such as rheumatoid arthritis, lupus and inflammatory bowel disease (IBD). However, the mechanisms by which autophagy limits inflammation remain poorly understood. Here we found that loss of the autophagy-related gene Atg16l1 promoted accumulation of the adaptor TRIF and downstream signaling in macrophages. Multiplex proteomic profiling identified SQSTM1 and Tax1BP1 as selective autophagy-related receptors that mediated the turnover of TRIF. Knockdown of Tax1bp1 increased production of the cytokines IFN-β and IL-1β. Mice lacking Atg16l1 in myeloid cells succumbed to lipopolysaccharide-mediated sepsis but enhanced their clearance of intestinal Salmonella typhimurium in an interferon receptor-dependent manner. Human macrophages with the Crohn's disease-associated Atg16l1 variant T300A exhibited more production of IFN-β and IL-1β. An elevated interferon-response gene signature was observed in patients with IBD who were resistant to treatment with an antibody to the cytokine TNF. These findings identify selective autophagy as a key regulator of signaling via the innate immune system.

The toll-like receptor ligands Hiltonol® (polyICLC) and imiquimod effectively activate antigen-specific immune responses in Tasmanian devils (Sarcophilus harrisii)

Devil facial tumour disease (DFTD) describes two genetically distinct transmissible tumours that pose a significant threat to the survival of the Tasmanian devil. A prophylactic vaccine could protect devils from DFTD transmission. For this vaccine to be effective, potent immune adjuvants will be required. Toll-like receptors (TLRs) promote robust immune responses in human cancer studies and are highly conserved across mammalian species. In this study, we investigated the proficiency of TLR ligands for immune activation in the Tasmanian devil using in vitro mononuclear cell stimulations and in vivo immunisation trials with a model antigen. We identified two such TLR ligands, polyICLC (Hiltonol^®) (TLR3) and imiquimod (TLR7), that in combination induced significant IFNγ production from Tasmanian devil lymphocytes in vitro. Immunisation with these ligands and the model antigen keyhole limpet haemocyanin activated robust antigen-specific primary, secondary and long-term memory IgG responses. Our results support the conserved nature of TLR signaling across mammalian species. PolyICLC and imiquimod will be trialed as immune adjuvants in future DFTD vaccine formulations.

Transcriptome profiling of antiviral immune and dietary fatty acid dependent responses of Atlantic salmon macrophage-like cells

BACKGROUND

Due to the limited availability and high cost of fish oil in the face of increasing aquaculture production, there is a need to reduce usage of fish oil in aquafeeds without compromising farm fish health. Therefore, the present study was conducted to determine if different levels of vegetable and fish oils can alter antiviral responses of salmon macrophage-like cells (MLCs). Atlantic salmon (Salmo salar) were fed diets containing 7.4% (FO7) or 5.1% (FO5) fish oil. These diets were designed to be relatively low in EPA + DHA (i.e. FO7: 1.41% and FO5: 1%), but near the requirement level, and resulting in comparable growth. Vegetable oil (i.e. rapeseed oil) was used to balance fish oil in experimental diets. After a 16-week feeding trial, MLCs isolated from fish in these dietary groups were stimulated by a viral mimic (dsRNA: pIC) for 6 h (qPCR assay) and 24 h (microarray and qPCR assays).

RESULTS

The fatty acid composition of head kidney leukocytes varied between the two dietary groups (e.g. higher 20:5n-3 in the FO7 group). Following microarray assays using a 44K salmonid platform, Rank Products (RP) analysis showed 14 and 54 differentially expressed probes (DEP) (PFP < 0.05) between the two diets in control and pIC groups (FO5 vs. FO7), respectively. Nonetheless, Significance Analysis of Microarrays (SAM, FDR < 0.05) identified only one DEP between pIC groups of the two diets. Moreover, we identified a large number (i.e. 890 DEP in FO7 and 1128 DEP in FO5 overlapping between SAM and RP) of pIC-responsive transcripts, and several of them were involved in TLR-/RLR-dependent and cytokine-mediated pathways. The microarray results were validated as significantly differentially expressed by qPCR assays for 2 out of 9 diet-responsive transcripts and for all of the 35 selected pIC-responsive transcripts.

CONCLUSION

Fatty acid-binding protein adipocyte (fabp4) and proteasome subunit beta type-8 (psmb8) were significantly up- and down-regulated, respectively, in the MLCs of fish fed the diet with a lower level of fish oil, suggesting that they are important diet-responsive, immune-related biomarkers for future studies. Although the different levels of dietary fish and vegetable oils involved in this study affected the expression of some transcripts, the immune-related pathways and functions activated by the antiviral response of salmon MLCs in both groups were comparable overall. Moreover, the qPCR revealed transcripts responding early to pIC (e.g. lgp2, map3k8, socs1, dusp5 and cflar) and time-responsive transcripts (e.g. scarb1-a, csf1r, traf5a, cd80 and ctsf) in salmon MLCs. The present study provides a comprehensive picture of the putative molecular pathways (e.g. RLR-, TLR-, MAPK- and IFN-associated pathways) activated by the antiviral response of salmon MLCs.

Potentiation and tolerance of toll-like receptor priming in human endothelial cells

Repeated challenge of lipopolysaccharide (LPS) alters the response to subsequent LPS exposures via modulation of toll-like receptor 4 (TLR4). Whether activation of other TLRs can modulate TLR4 responses, and vice versa, remains unclear. Specifically with regards to endothelial cells, a key component of innate immunity, the impact of TLR cross-modulation is unknown. We postulated that TLR2 priming (via Pam3Csk4) would inhibit TLR4-mediated responses while TLR3 priming (via Poly I:C) would enhance subsequent TLR4-inflammatory signaling. We studied human umbilical vein endothelial cells (HUVECs) and neonatal human dermal microvascular endothelial cells (HMVECs). Cells were primed with a combination of Poly I:C (10 μg/ml), Pam3Csk4 (10 μg/ml), or LPS (100 ng/ml), then washed and allowed to rest. They were then rechallenged with either Poly I:C, Pam3Csk4 or LPS. Endothelial cells showed significant tolerance to repeated LPS challenge. Priming with Pam3Csk4 also reduced the response to secondary LPS challenge in both cell types, despite a reduced proinflammatory response to Pam3Csk4 in HMVECs compared to HUVECs. Poly I:C priming enhanced inflammatory and interferon producing signals upon Poly I:C or LPS rechallenge, respectively. Poly I:C priming induced interferon regulatory factor 7, leading to enhancement of interferon production. Finally, both Poly I:C and LPS priming induced significant changes in receptor-interacting serine/threonine-protein kinase 1 activity. Pharmacological inhibition of receptor-interacting serine/threonine-protein kinase 1 or interferon regulatory factor 7 reduced the potentiated phenotype of TLR3 priming on TLR4 rechallenge. These results demonstrate that in human endothelial cells, prior activation of TLRs can have a significant impact on subsequent exposures and may contribute to the severity of the host response.

Genome-Wide Immune Modulation of TLR3-Mediated Inflammation in Intestinal Epithelial Cells Differs between Single and Multi-Strain Probiotic Combination

Genome-wide transcriptional analysis in intestinal epithelial cells (IEC) can aid in elucidating the impact of single versus multi-strain probiotic combinations on immunological and cellular mechanisms of action. In this study we used human expression microarray chips in an in vitro intestinal epithelial cell model to investigate the impact of three probiotic bacteria, Lactobacillus helveticus R0052 (Lh-R0052), Bifidobacterium longum subsp. infantis R0033 (Bl-R0033) and Bifidobacterium bifidum R0071 (Bb-R0071) individually and in combination, and of a surface-layer protein (SLP) purified from Lh-R0052, on HT-29 cells' transcriptional profile to poly(I:C)-induced inflammation. Hierarchical heat map clustering, Set Distiller and String analyses revealed that the effects of Lh-R0052 and Bb-R0071 diverged from those of Bl-R0033 and Lh-R0052-SLP. It was evident from the global analyses with respect to the immune, cellular and homeostasis related pathways that the co-challenge with probiotic combination (PC) vastly differed in its effect from the single strains and Lh-R0052-SLP treatments. The multi-strain PC resulted in a greater reduction of modulated genes, found through functional connections between immune and cellular pathways. Cytokine and chemokine analyses based on specific outcomes from the TNF-α and NF-κB signaling pathways revealed single, multi-strain and Lh-R0052-SLP specific attenuation of the majority of proteins measured (TNF-α, IL-8, CXCL1, CXCL2 and CXCL10), indicating potentially different mechanisms. These findings indicate a synergistic effect of the bacterial combinations relative to the single strain and Lh-R0052-SLP treatments in resolving toll-like receptor 3 (TLR3)-induced inflammation in IEC and maintaining cellular homeostasis, reinforcing the rationale for using multi-strain formulations as a probiotic.

Innate immunity based cancer immunotherapy: B16-F10 murine melanoma model

Background

Using killed microorganisms or their parts to stimulate immunity for cancer treatment dates back to the end of 19^th century. Since then, it undergone considerable development. Our novel approach binds ligands to the tumor cell surface, which stimulates tumor phagocytosis. The therapeutic effect is further amplified by simultaneous application of agonists of Toll-like receptors. We searched for ligands that induce both a strong therapeutic effect and are safe for humans.

Methods

B16-F10 murine melanoma model was used. For the stimulation of phagocytosis, mannan or N-formyl-methionyl-leucyl-phenylalanine, was covalently bound to tumor cells or attached using hydrophobic anchor. The following agonists of Toll-like receptors were studied: monophosphoryl lipid A (MPLA), imiquimod (R-837), resiquimod (R-848), poly(I:C), and heat killed Listeria monocytogenes.

Results

R-848 proved to be the most suitable Toll-like receptor agonist for our novel immunotherapeutic approach. In combination with covalently bound mannan, R-848 significantly reduced tumor growth. Adding poly(I:C) and L. monocytogenes resulted in complete recovery in 83% of mice and in their protection from the re-transplantation of melanoma cells.

Conclusion

An efficient cancer treatment results from the combination of Toll-like receptor agonists and phagocytosis stimulating ligands bound to the tumor cells.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2982-x) contains supplementary material, which is available to authorized users.

Layer-by-layer nanocoating of live Bacille-Calmette-Guérin mycobacteria with poly(I:C) and chitosan enhances pro-inflammatory activation and bactericidal capacity in murine macrophages

Tuberculosis (TB) is a major disease burden globally causing more than 1.5 million deaths per year. The attenuated live vaccine strain Bacille Calmette-Guérin (BCG), although providing protection against childhood TB, is largely ineffective against adult pulmonary TB. A major aim therefore is to increase the potency of the BCG vaccine to generate stronger and more sustained immunity against TB. Here, we investigated the use of layer-by-layer (LbL) nanocoating of the surface of live BCG with several layers of polyinosinic-polycytidylic acid (poly(I:C)), a strong inducer of cell-mediated immunity, and the biodegradable polysaccharide chitosan to enhance BCG immunogenicity. Nanocoating of live BCG did not affect bacterial viability or growth in vitro but induced killing of the BCG in infected mouse bone marrow-derived macrophages and enhanced macrophage production of pro-inflammatory cytokines and expression of surface co-stimulatory molecules relative to uncoated BCG. In addition, poly(I:C) surface-coated BCG, but not BCG alone or together with soluble poly(I:C), induced high production of nitric oxide (NO) and IL-12. These results argue that BCG and surface absorbed poly(I:C) act in a synergistic manner to elicit pro-inflammatory macrophage activation. In conclusion, nanocoating of live BCG with the immunostimulatory agent poly(I:C) may be an appropriate strategy to enhance and modulate host responses to the BCG vaccine.

Characterization of TLR-induced inflammatory responses in COPD and control lung tissue explants

PURPOSE

Viruses are a common cause of exacerbations in chronic obstructive pulmonary disease (COPD). They activate toll-like receptors (TLRs) 3, 7, and 8, leading to a pro-inflammatory response. We have characterized the responses of TLR3 and TLR7/8 in lung tissue explants from COPD patients and control smokers.

METHODS

We prepared lung whole tissue explants (WTEs) from patients undergoing surgery for confirmed or suspected lung cancer. In order to mimic the conditions of viral infection, we used poly(I:C) for TLR3 stimulation and R848 for TLR7/8 stimulation. These TLR ligands were used alone and in combination. The effects of tumor necrosis factor α (TNFα) neutralization and dexamethasone on TLR responses were examined. Inflammatory cytokine release was measured by enzyme-linked immunosorbent assay and gene expression by quantitative real-time polymerase chain reaction.

RESULTS

WTEs from COPD patients released higher levels of pro-inflammatory cytokines compared with WTEs from smokers. Activation of multiple TLRs led to a greater than additive release of TNFα and CCL5. TNFα neutralization and dexamethasone treatment decreased cytokine release.

CONCLUSION

This WTE model shows an enhanced response of COPD compared with controls, suggesting an increased response to viral infection. There was amplification of innate immune responses with multiple TLR stimulation.

Innate immune memory and homeostasis may be conferred through crosstalk between the TLR3 and TLR7 pathways

Toll-like receptors (TLRs) recognize pathogen-associated molecular patterns (PAMPs) and stimulate the innate immune response through the production of cytokines. The innate immune response depends on the timing of encountering PAMPs, suggesting a short-term "memory." In particular, activation of TLR3 appears to prime macrophages for the subsequent activation of TLR7, which leads to synergistically increased production of cytokines. By developing a calibrated mathematical model for the kinetics of TLR3 and TLR7 pathway crosstalk and providing experimental validation, we demonstrated the involvement of the Janus-activated kinase (JAK)-signal transducer and activator of transcription (STAT) pathway in controlling the synergistic production of cytokines. Signaling through this pathway played a dual role: It mediated the synergistic production of cytokines, thus boosting the immune response, and it also maintained homeostasis to avoid an excessive inflammatory response. Thus, we propose that the JAK-STAT pathway provides a cytokine rheostat mechanism, which enables macrophages to fine-tune their responses to multiple, temporally separated infection events involving the TLR3 and TLR7 pathways.

Investigating the Role of TNF-α and IFN-γ Activation on the Dynamics of iNOS Gene Expression in LPS Stimulated Macrophages

Macrophage produced inducible nitric oxide synthase (iNOS) is known to play a critical role in the proinflammatory response against intracellular pathogens by promoting the generation of bactericidal reactive nitrogen species. Robust and timely production of nitric oxide (NO) by iNOS and analogous production of reactive oxygen species are critical components of an effective immune response. In addition to pathogen associated lipopolysaccharides (LPS), iNOS gene expression is dependent on numerous proinflammatory cytokines in the cellular microenvironment of the macrophage, two of which include interferon gamma (IFN-γ) and tumor necrosis factor alpha (TNF-α). To understand the synergistic effect of IFN-γ and TNF-α activation, and LPS stimulation on iNOS expression dynamics and NO production, we developed a systems biology based mathematical model. Using our model, we investigated the impact of pre-infection cytokine exposure, or priming, on the system. We explored the essentiality of IFN-γ priming to the robustness of initial proinflammatory response with respect to the ability of macrophages to produce reactive species needed for pathogen clearance. Results from our theoretical studies indicated that IFN-γ and subsequent activation of IRF1 are essential in consequential production of iNOS upon LPS stimulation. We showed that IFN-γ priming at low concentrations greatly increases the effector response of macrophages against intracellular pathogens. Ultimately the model demonstrated that although TNF-α contributed towards a more rapid response time, measured as time to reach maximum iNOS production, IFN-γ stimulation was significantly more significant in terms of the maximum expression of iNOS and the concentration of NO produced.

The molecular mechanisms of TLR-signaling cooperation in cytokine regulation

Innate immune cells recognize pathogens through pattern recognition receptors (PRRs), and activation of PRRs induces downstream signaling pathways to mount appropriate immune responses. Pathogens usually carry multiple ligands, which can simultaneously activate multiple PRRs. The cooperation of multiple PRRs and consequential crosstalk between their downstream pathways could enhance cytokine expression, which is required for effective immune responses. On the other hand, immune over-activation could also harm the host if immune homeostasis is not restored. Therefore, it is important to understand the mechanisms of PRR cooperation during an infection. As the best characterized PRRs, Toll-like receptors (TLRs) have an important role in pathogen recognition, and crosstalk among TLRs is common. In this review, we provide an update on the recent findings on the mechanisms of TLR cooperation. We summarize the known mechanisms and provide a future perspective on TLR crosstalk study, with a caution against the use of multiple TLR ligands as adjuvants in therapeutic strategies.

Integration of Innate Immune Signaling

The last decades of research in innate immunology have revealed a multitude of sensing receptors that evaluate the presence of microorganisms or cellular damage in tissues. In the context of a complex tissue, many such sensing events occur simultaneously. Thus, the downstream pathways need to be integrated to launch an appropriate cellular response, to tailor the magnitude of the reaction to the inciting event, and to terminate it in a manner that avoids immunopathology. Here, we provide a conceptual overview of the crosstalk between innate immune receptors in the initiation of a concerted immune reaction to microbial and endogenous triggers. We classify the known interactions into categories of communication and provide examples of their importance in pathogenic infection.

Modulation of Innate Immune Responses via Covalently Linked TLR Agonists

We present the synthesis of novel adjuvants for vaccine development using multivalent scaffolds and bioconjugation chemistry to spatially manipulate Toll-like receptor (TLR) agonists. TLRs are primary receptors for activation of the innate immune system during vaccination. Vaccines that contain a combination of small and macromolecule TLR agonists elicit more directed immune responses and prolong responses against foreign pathogens. In addition, immune activation is enhanced upon stimulation of two distinct TLRs. Here, we synthesized combinations of TLR agonists as spatially defined tri- and di-agonists to understand how specific TLR agonist combinations contribute to the overall immune response. We covalently conjugated three TLR agonists (TLR4, 7, and 9) to a small molecule core to probe the spatial arrangement of the agonists. Treating immune cells with the linked agonists increased activation of the transcription factor NF-κB and enhanced and directed immune related cytokine production and gene expression beyond cells treated with an unconjugated mixture of the same three agonists. The use of TLR signaling inhibitors and knockout studies confirmed that the tri-agonist molecule activated multiple signaling pathways leading to the observed higher activity. To validate that the TLR4, 7, and 9 agonist combination would activate the immune response to a greater extent, we performed in vivo studies using a vaccinia vaccination model. Mice vaccinated with the linked TLR agonists showed an increase in antibody depth and breadth compared to mice vaccinated with the unconjugated mixture. These studies demonstrate how activation of multiple TLRs through chemically and spatially defined organization assists in guiding immune responses, providing the potential to use chemical tools to design and develop more effective vaccines.

TLR and RLR Signaling Are Reprogrammed in Opposite Directions after Detection of Viral Infection

Innate immune recognition of RNA is key for the initiation of immunity in response to viral infection. Although the factors controlling the detection of viral RNA by innate immune receptors in host cells are increasingly well understood, little is known about the dynamic changes in signaling after the initial triggering of these receptors. In this study, we report that preconditioning with the synthetic dsRNA polyinosinic-polycytidylic acid [poly(I:C)], a mimetic of viral RNA, rapidly reprograms murine APCs by simultaneously augmenting sensitivity of endosomal TLRs and inhibiting activation of RIG-I-like receptors (RLRs) in an IFN-β-dependent manner. These changes in receptor sensitivity were also seen in vivo after treatment of mice with poly(I:C). Mechanistically, the increased sensitivity of the TLR pathway was associated with elevated MAPK and NF-κB activity. The RLR response was inhibited downstream of TANK-binding kinase-1, resulting in decreased IFN regulatory factor 3 phosphorylation. Reprogramming of pattern-recognition receptor signaling also occurred after viral infection, because infection of host cells with Sendai virus or their exposure to supernatant from virus-infected cells induced the same changes in TLR and RLR sensitivity as poly(I:C). Thus, innate recognition of viral infection critically modifies responses to pattern-recognition receptor stimulation. These dynamic adaptations to infection may reinforce antiviral immunity and at the same time serve to limit pathological inflammation.

Cutting Edge: Synchronization of IRF1, JunB, and C/EBPβ Activities during TLR3-TLR7 Cross-Talk Orchestrates Timely Cytokine Synergy in the Proinflammatory Response

Multiple pathogen-associated molecular pattern-induced TLR pathway cross-talk provokes proinflammatory cytokine synergy in macrophages, which is important for pathogen resistance and immune homeostasis. However, the detailed mechanisms are unclear. In this article, we demonstrate viral RNA analog-induced transcription synergy of Il6 and Il12b via IFN regulatory factor (IRF)1 (TLR3-TIR domain-containing adaptor inducing IFN-β [TRIF] responsive), C/EBPβ (TLR7-MyD88 responsive), and JunB (all responsive). Coactivation of the TLR3 and TLR7 pathways synchronizes the interaction of IRF1, JunB, and C/EBPβ with the Il6 and Il12b promoters, facilitating maximal gene expression. MyD88 pathway activation suppresses TRIF-induced IRF1 in a delayed manner, controlling the magnitude and timing of cytokine expression. Our findings provide novel mechanisms of cooperation of different TLR pathways to achieve optimal immune responses, with the potential for immunomodulatory strategies.

Electrophysiological characterization of the first Tityus serrulatus alpha-like toxin, Ts5: Evidence of a pro-inflammatory toxin on macrophages

Tityus serrulatus (Ts) venom is composed of mainly neurotoxins specific for voltage-gated K(+) and Na(+) channels, which are expressed in many cells such as macrophages. Macrophages are the first line of defense invasion and they participate in the inflammatory response of Ts envenoming. However, little is known about the effect of Ts toxins on macrophage activation. This study investigated the effect of Ts5 toxin on different sodium channels as well as its role on the macrophage immunomodulation. The electrophysiological assays showed that Ts5 inhibits the rapid inactivation of the mammalian sodium channels Nav1.2, Nav1.3, Nav1.4, Nav1.5, Nav1.6 and Nav1.7. Interestingly, Ts5 also inhibits the inactivation of the insect Drosophila melanogaster sodium channel (DmNav1), and it is therefore classified as the first Ts α-like toxin. The immunological experiments on macrophages reveal that Ts5 is a pro-inflammatory toxin inducing the cytokine production of tumor necrosis factor (TNF)-α and interleukin (IL)-6. On the basis of recent literature, our study also stresses a possible mechanism responsible for venom-associated molecular patterns (VAMPs) internalization and macrophage activation and moreover we suggest two main pathways of VAMPs signaling: direct and indirect. This work provides useful insights for a better understanding of the involvement of VAMPs in macrophage modulation.

A temporal gate for viral enhancers to co-opt Toll-like-receptor transcriptional activation pathways upon acute infection

Viral engagement with macrophages activates Toll-Like-Receptors (TLRs) and viruses must contend with the ensuing inflammatory responses to successfully complete their replication cycle. To date, known counter-strategies involve the use of viral-encoded proteins that often employ mimicry mechanisms to block or redirect the host response to benefit the virus. Whether viral regulatory DNA sequences provide an opportunistic strategy by which viral enhancer elements functionally mimic innate immune enhancers is unknown. Here we find that host innate immune genes and the prototypical viral enhancer of cytomegalovirus (CMV) have comparable expression kinetics, and positively respond to common TLR agonists. In macrophages but not fibroblasts we show that activation of NFκB at immediate-early times of infection is independent of virion-associated protein, M45. We find upon virus infection or transfection of viral genomic DNA the TLR-agonist treatment results in significant enhancement of the virus transcription-replication cycle. In macrophage time-course infection experiments we demonstrate that TLR-agonist stimulation of the viral enhancer and replication cycle is strictly delimited by a temporal gate with a determined half-maximal time for enhancer-activation of 6 h; after which TLR-activation blocks the viral transcription-replication cycle. By performing a systematic siRNA screen of 149 innate immune regulatory factors we identify not only anticipated anti-viral and pro-viral contributions but also new factors involved in the CMV transcription-replication cycle. We identify a central convergent NFκB-SP1-RXR-IRF axis downstream of TLR-signalling. Activation of the RXR component potentiated direct and indirect TLR-induced activation of CMV transcription-replication cycle; whereas chromatin binding experiments using wild-type and enhancer-deletion virus revealed IRF3 and 5 as new pro-viral host transcription factor interactions with the CMV enhancer in macrophages. In a series of pharmacologic, siRNA and genetic loss-of-function experiments we determined that signalling mediated by the TLR-adaptor protein MyD88 plays a vital role for governing the inflammatory activation of the CMV enhancer in macrophages. Downstream TLR-regulated transcription factor binding motif disruption for NFκB, AP1 and CREB/ATF in the CMV enhancer demonstrated the requirement of these inflammatory signal-regulated elements in driving viral gene expression and growth in cells as well as in primary infection of neonatal mice. Thus, this study shows that the prototypical CMV enhancer, in a restricted time-gated manner, co-opts through DNA regulatory mimicry elements, innate-immune transcription factors to drive viral expression and replication in the face of on-going pro-inflammatory antiviral responses in vitro and in vivo and; suggests an unexpected role for inflammation in promoting acute infection and has important future implications for regulating latency.

Here we discover how inflammatory signalling may unintentionally promote infection, as a result of viruses evolving DNA sequences, known as enhancers, which act as a bait to prey on the infected cell transcription factors induced by inflammation. The major inflammatory transcription factors activated are part of the TLR-signalling pathway. We find the prototypical viral enhancer of cytomegalovirus can be paradoxically boosted by activation of inflammatory “anti-viral” TLR-signalling independent of viral structural proteins. This leads to an increase in viral gene expression and replication in cell-culture and upon infection of mice. We identify an axis of inflammatory transcription factors, acting downstream of TLR-signalling but upstream of interferon inhibition. Mechanistically, the central TLR-adapter protein MyD88 is shown to play a critical role in promoting viral enhancer activity in the first 6h of infection. The co-option of TLR-signalling exceeds the usage of NFκB, and we identify IRF3 and 5 as newly found viral-enhancer interacting inflammatory transcription factors. Taken together this study reveals how virus enhancers, employ a path of least resistance by directly harnessing within a short temporal window, the activation of anti-viral signalling in macrophages to drive viral gene expression and replication to an extent that has not been recognised before.

Synthetic Toll-like receptor 4 (TLR4) and TLR7 ligands as influenza virus vaccine adjuvants induce rapid, sustained, and broadly protective responses

Current vaccines against influenza virus infection rely on the induction of neutralizing antibodies targeting the globular head of the viral hemagglutinin (HA). Protection against seasonal antigenic drift or sporadic pandemic outbreaks requires further vaccine development to induce cross-protective humoral responses, potentially to the more conserved HA stalk region. Here, we present a novel viral vaccine adjuvant comprised of two synthetic ligands for Toll-like receptor 4 (TLR4) and TLR7. 1Z105 is a substituted pyrimido[5,4-b]indole specific for the TLR4-MD2 complex, and 1V270 is a phospholipid-conjugated TLR7 agonist. Separately, 1Z105 induces rapid Th2-associated IgG1 responses, and 1V270 potently generates Th1 cellular immunity. 1Z105 and 1V270 in combination with recombinant HA from the A/Puerto Rico/8/1934 strain (rPR/8 HA) effectively induces rapid and sustained humoral immunity that is protective against lethal challenge with a homologous virus. More importantly, immunization with the combined adjuvant and rPR/8 HA, a commercially available split vaccine, or chimeric rHA antigens significantly improves protection against both heterologous and heterosubtypic challenge viruses. Heterosubtypic protection is associated with broadly reactive antibodies to HA stalk epitopes. Histological examination and cytokine profiling reveal that intramuscular (i.m.) administration of 1Z105 and 1V270 is less reactogenic than a squalene-based adjuvant, AddaVax. In summary, the combination of 1Z105 and 1V270 with a recombinant HA induces rapid, long-lasting, and balanced Th1- and Th2-type immunity; demonstrates efficacy in a variety of murine influenza virus vaccine models assaying homologous, heterologous, and heterosubtypic challenge viruses; and has an excellent safety profile.

IMPORTANCE

Novel adjuvants are needed to enhance immunogenicity and increase the protective breadth of influenza virus vaccines to reduce the seasonal disease burden and ensure pandemic preparedness. We show here that the combination of synthetic Toll-like receptor 4 (TLR4) and TLR7 ligands is a potent adjuvant for recombinant influenza virus hemagglutinin, inducing rapid and sustained immunity that is protective against influenza viruses in homologous, heterologous, and heterosubtypic challenge models. Combining TLR4 and TLR7 ligands balances Th1- and Th2-type immune responses for long-lived cellular and neutralizing humoral immunity against the viral hemagglutinin. The combined adjuvant has an attractive safety profile and the potential to augment seasonal-vaccine breadth, contribute to a broadly neutralizing universal vaccine formulation, and improve response time in an emerging pandemic.

TLR cross-talk confers specificity to innate immunity

Cross-talk within the innate immune pathways is highly complex and contains many unknowns. Here, we discuss the different combinations of PAMPs, together with the sequence, order, and dosage of consecutive PAMP challenges, which determine the nature of the immune response by macrophages. The engagement of different Toll-like receptor (TLR) ligands leads to quantitatively and qualitatively unique cytokine production, showing that TLR pathway crosstalk enables the innate immune system to orchestrate immediate local and global responses. It is likely that multiple pathways are involved in the regulation of cytokine synergy, including many that have yet to be discovered.

Human bladder uroepithelial cells synergize with monocytes to promote IL-10 synthesis and other cytokine responses to uropathogenic Escherichia coli

Urinary tract infections are a major source of morbidity for women and the elderly, with Uropathogenic Escherichia coli (UPEC) being the most prevalent causative pathogen. Studies in recent years have defined a key anti-inflammatory role for Interleukin-10 (IL-10) in urinary tract infection mediated by UPEC and other uropathogens. We investigated the nature of the IL-10-producing interactions between UPEC and host cells by utilising a novel co-culture model that incorporated lymphocytes, mononuclear and uroepithelial cells in histotypic proportions. This co-culture model demonstrated synergistic IL-10 production effects between monocytes and uroepithelial cells following infection with UPEC. Membrane inserts were used to separate the monocyte and uroepithelial cell types during infection and revealed two synergistic IL-10 production effects based on contact-dependent and soluble interactions. Analysis of a comprehensive set of immunologically relevant biomarkers in monocyte-uroepithelial cell co-cultures highlighted that multiple cytokine, chemokine and signalling factors were also produced in a synergistic or antagonistic fashion. These results demonstrate that IL-10 responses to UPEC occur via multiple interactions between several cells types, implying a complex role for infection-related IL-10 during UTI. Development and application of the co-culture model described in this study is thus useful to define the degree of contact dependency of biomarker production to UPEC, and highlights the relevance of histotypic co-cultures in studying complex host-pathogen interactions.

Cytokine production and signaling pathways in respiratory virus infection

It has been confirmed that respiratory virus infections can induce abberant cytokine production in the host. These cytokines may be associated with both elimination of the virus and complications in the host, such as virus-induced asthma. Representative host defense mechanisms against pathogens, including bacteria and viruses, are mediated by the innate immune system. Cells of the innate immune system express essential molecules, namely pattern recognition receptors (PRRs), such as Toll-like receptors, nucleotide-binding oligomerization domain-like receptors, and retinoic acid-inducible gene-I-like receptors. These PRRs can recognize components of pathogens such as bacterial lipopolysaccharide, viral antigens, and their genomes (DNA and RNA). Furthermore, PRRs activate various signaling pathways resulting in cytokine production against pathogen infection. However, the exact mechanisms remain unknown. In this review, we mainly focus on the representative mechanisms of cytokine production through PRRs and signaling pathways due to virus infections, including respiratory virus infections. In addition, we describe the relationships between respiratory infections and virus-induced asthma.