Natural and synthetic TLR7 ligands inhibit CpG-A- and CpG-C-oligodeoxynucleotide-induced IFN-alpha production

Placental TLR recognition of salivary and subgingival microbiota is associated with pregnancy complications

BACKGROUND

Pre-term birth, the leading cause of neonatal mortality, has been associated with maternal periodontal disease and the presence of oral pathogens in the placenta. However, the mechanisms that underpin this link are not known. This investigation aimed to identify the origins of placental microbiota and to interrogate the association between parturition complications and immune recognition of placental microbial motifs. Video Abstract METHODS: Saliva, plaque, serum, and placenta were collected during 130 full-term (FT), pre-term (PT), or pre-term complicated by pre-eclampsia (PTPE) deliveries and subjected to whole-genome shotgun sequencing. Real-time quantitative PCR was used to measure toll-like receptors (TLR) 1-10 expression in placental samples. Source tracking was employed to trace the origins of the placental microbiota.

RESULTS

We discovered 10,007 functionally annotated genes representing 420 taxa in the placenta that could not be attributed to contamination. Placental microbial composition was the biggest discriminator of pregnancy complications, outweighing hypertension, BMI, smoking, and maternal age. A machine-learning algorithm trained on this microbial dataset predicted PTPE and PT with error rates of 4.05% and 8.6% (taxonomy) and 6.21% and 7.38% (function). Logistic regression revealed 32% higher odds of parturition complication (95% CI 2.8%, 81%) for every IQR increase in the Shannon diversity index after adjusting for maternal smoking status, maternal age, and gravida. We also discovered distinct expression patterns of TLRs that detect RNA- and DNA-containing antigens in the three groups, with significant upregulation of TLR9, and concomitant downregulation of TLR7 in PTPE and PT groups, and dense correlation networks between microbial genes and these TLRs. 70-82% of placental microbiota were traced to serum and thence to the salivary and subgingival microbiomes. The oral and serum microbiomes of PTPE and PT groups displayed significant enrichment of genes encoding iron transport, exosome, adhesion, quorum sensing, lipopolysaccharide, biofilm, and steroid degradation.

CONCLUSIONS

Within the limits of cross-sectional analysis, we find evidence to suggest that oral bacteria might translocate to the placenta via serum and trigger immune signaling pathways capable of inducing placental vascular pathology. This might explain, in part, the higher incidence of obstetric syndromes in women with periodontal disease.

Sex differences in the percentage of IRF5 positive B cells are associated with higher production of TNF-α in women in response to TLR9 in humans

BACKGROUND

The clinical course and outcome of many diseases differ between women and men, with women experiencing a higher prevalence and more severe pathogenesis of autoimmune diseases. The precise mechanisms underlying these sex differences still remain to be fully understood. IRF5 is a master transcription factor that regulates TLR/MyD88-mediated responses to pathogen-associated molecular patterns (PAMPS) in DCs and B cells. B cells are central effector cells involved in autoimmune diseases via the production of antibodies and pro-inflammatory cytokines as well as mediating T cell help. Dysregulation of IRF5 expression has been reported in autoimmune diseases, including systemic lupus erythematosus, primary Sjögren syndrome, and rheumatoid arthritis.

METHODS

In the current study, we analyzed whether the percentage of IRF5 positive B cells differs between women and men and assessed the resulting consequences for the production of inflammatory cytokines after TLR7- or TLR9 stimulation.

RESULTS

The percentage of IRF5 positive B cells was significantly higher in B cells of women compared to men in both unstimulated and TLR7- or TLR9-stimulated B cells. B cells of women produced higher levels of TNF-α in response to TLR9 stimulation.

CONCLUSIONS

Taken together, our data contribute to the understanding of sex differences in immune responses and may identify IRF5 as a potential therapeutic target to reduce harmful B cell-mediated immune responses in women.

Type I Interferon Production of Plasmacytoid Dendritic Cells under Control

One of the most powerful and multifaceted cytokines produced by immune cells are type I interferons (IFNs), the basal secretion of which contributes to the maintenance of immune homeostasis, while their activation-induced production is essential to effective immune responses. Although, each cell is capable of producing type I IFNs, plasmacytoid dendritic cells (pDCs) possess a unique ability to rapidly produce large amounts of them. Importantly, type I IFNs have a prominent role in the pathomechanism of various pDC-associated diseases. Deficiency in type I IFN production increases the risk of more severe viral infections and the development of certain allergic reactions, and supports tumor resistance; nevertheless, its overproduction promotes autoimmune reactions. Therefore, the tight regulation of type I IFN responses of pDCs is essential to maintain an adequate level of immune response without causing adverse effects. Here, our goal was to summarize those endogenous factors that can influence the type I IFN responses of pDCs, and thus might serve as possible therapeutic targets in pDC-associated diseases. Furthermore, we briefly discuss the current therapeutic approaches targeting the pDC-type I IFN axis in viral infections, cancer, autoimmunity, and allergy, together with their limitations defined by the Janus-faced nature of pDC-derived type I IFNs.

Microvesicles in active lupus nephritis show Toll-like receptor 9-dependent co-expression of galectin-3 binding protein and double-stranded DNA

Circulating microvesicles (MVs) from patients with systemic lupus erythematosus (SLE) express the type 1 interferon (IFN)-inducible protein galectin-3 binding protein (G3BP), which may enhance their deposition in the glomerular basement membrane. The release of G3BP-expressing MVs from normal peripheral blood mononuclear cells (PBMCs) is induced by Toll-like receptor 9 (TLR-9) ligands, and these vesicles contain autoantibody-accessible double-stranded DNA (dsDNA). This study compares the release of MVs expressing G3BP and dsDNA from PBMCs derived from SLE patients with or without active lupus nephritis (LN) and from healthy donors, and taps further into the potential dependency on IFN-α for their generation and impacts of TLR-7/TLR-9 co-stimulation. PBMCs from 10 healthy donors and 12 SLE patients, six of whom had active LN at study inclusion, were stimulated in-vitro with recombinant human IFN-α and the TLR-9 agonists oligodeoxynucleotide (ODN)2216 or ODN2395 alone or in combination with the TLR-7 agonist gardiquimod. MVs in the supernatants were subsequently isolated by differential centrifugation and their expression of G3BP and dsDNA was quantified by flow cytometry. Stimulation with ODN2395 significantly increased the release of MVs co-expressing G3BP and dsDNA from PBMCs isolated from healthy donors and SLE patients. The expression of G3BP on individual MVs and the proportion of G3BP and dsDNA double-positive MVs released were increased in active LN patients. Neither co-stimulation with gardiquimod nor with the IFN-α inhibitor IN-1 had any effect on the MV release induced by ODN2395. In conclusion, the TLR-9-mediated inducibility of MVs co-expressing G3BP and dsDNA is increased in SLE patients with active LN.

Sanguinarine and Chelidonine Synergistically Induce Endosomal Toll-like Receptor and M1-Associated Mediators Expression

Natural compounds represent the great capability to stimulate several cell types. Macrophage plays an important role for an effective immune response for infection and inflammation. Isoquinoline alkaloid, sanguinarine, and chelidonine are active compounds that exhibit activity on various tumor cells and immune cells. However, the effect of these compounds on the endosomal toll-like receptor (enTLR) and type I interferon (IFN) are still unclear. The monocyte-derived macrophages (MDMs) were cultured and were determined their cell viability and phagocytic activity to Staphylococcus aureus DMST8840. The nitric oxide (NO) production and inducible nitric oxide synthase (iNOS) expression were also examined. The expression of enTLRs, type I IFN, and cytokines were determined by real-time PCR. Result shows that the compounds did not affect on MDM cell viability. Sanguinarine and chelidonine enhance phagocytic activity of MDM against Staphylococcus aureus DMST8840 by revealing a higher number of bacterial survival than the MDM treated by polyI:C, and the cell control after co-culture for 3 h. The production of NO has no difference amount but iNOS mRNA production was down-regulated in sanguinarine, chelidonine and their mixed treated MDM. The expressions of enTLRs and IFN-β1 mRNA were up-regulated in both compounds and their combination. Additionally, these compounds also enhance M1-liked cytokine by up-regulated IL-6 and down-regulated IL-10 and TGF-β1, respectively. Therefore, sanguinarine and chelidonine enhance enTLR and IFN-β1 expression and trend to stimulate the cell into M1-liked MDM.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Toll-like receptor 7 deficiency protects apolipoprotein E-deficient mice from diet-induced atherosclerosis

Toll-like receptor 7 (TLR7) mediates autoantigen and viral RNA-induced cytokine production. Increased TLR7 expression in human atherosclerotic lesions suggests its involvement in atherogenesis. Here we demonstrated TLR7 expression in macrophages, smooth muscle cells (SMCs), and endothelial cells from mouse atherosclerotic lesions. To test a direct participation of TLR7 in atherosclerosis, we crossbred TLR7-deficient (Tlr7 ^-/-) mice with apolipoprotein E-deficient (Apoe ^-/-) mice and produced Apoe ^-/- Tlr7 ^-/- and Apoe ^-/- Tlr7 ^+/+ littermates, followed by feeding them an atherogenic diet to produce atherosclerosis. Compared to Apoe ^-/- Tlr7 ^+/+ mice, Apoe ^-/- Tlr7 ^-/- mice showed reduced aortic arch and sinus lesion areas. Reduced atherosclerosis in Apoe ^-/- Tlr7 ^-/- mice did not affect lesion macrophage-positive area and CD4⁺ T-cell number per lesion area, but reduced lesion expression of inflammatory markers major histocompatibility complex-class II and IL6, lesion matrix-degrading proteases cathepsin S and matrix metalloproteinase-9, and systemic serum amyloid A levels. TLR7 deficiency also reduced aortic arch SMC loss and lesion intima and media cell apoptosis. However, TLR7 deficiency did not affect aortic wall elastin fragmentation and collagen contents, or plasma lipoproteins. Therefore, TLR7 contributes to atherogenesis in Apoe ^-/- mice by regulating lesion and systemic inflammation. A TLR7 antagonist may mitigate atherosclerosis.

Unique high and homogenous surface expression of the transferrin receptor CD71 on murine plasmacytoid dendritic cells in different tissues

Plasmacytoid dendritic cells (pDC) are of increasing interest in cancer vaccine development, but many functions of these highly specialized, multifaceted cells are poorly understood. The transferrin receptor CD71 has also been suggested to function as an antigen uptake receptor on professional antigen-presenting cells. In this study, we employed multiparameter flow cytometry to investigate CD71 expression on various leukocyte subsets, including DC subsets, granulocytes, macrophages, T and B lymphocytes, γδ T cells, and natural killer cells. Cells from various lymphoid and non-lymphoid murine tissues were analyzed using fluorochrome-conjugated monoclonal antibodies. High CD71 expression (90-100%) was observed, uniquely on pDC amongst the leukocyte populations examined, in both lymphoid and non-lymphoid tissues, including other DC subsets. In contrast, CD71 expression on non-tissue pDC, in the bone marrow and peripheral blood, was reduced. The cause and function of this high tissue pDC-selective CD71 expression remain to be examined.

The innate immune system in human systemic lupus erythematosus

Although the role of adaptive immune mechanisms, e.g. autoantibody formation and abnormal T-cell activation, has been long noted in the pathogenesis of human systemic lupus erythematosus (SLE), the role of innate immunity has been less well characterized. An intricate interplay between both innate and adaptive immune elements exists in protective anti-infective immunity as well as in detrimental autoimmunity. More recently, it has become clear that the innate immune system in this regard not only starts inflammation cascades in SLE leading to disease flares, but also continues to fuel adaptive immune responses throughout the course of the disease. This is why targeting the innate immune system offers an additional means of treating SLE. First trials assessing the efficacy of anti-type I interferon (IFN) therapy or modulators of pattern recognition receptor (PRR) signalling have been attempted. In this review, we summarize the available evidence on the role of several distinct innate immune elements, especially neutrophils and dendritic cells as well as the IFN system, as well as specific innate PRRs along with their signalling pathways. Finally, we highlight recent clinical trials in SLE addressing one or more of the aforementioned components of the innate immune system.

Type-I Interferon Responses: From Friend to Foe in the Battle against Chronic Viral Infection

Type I interferons (IFN-I) have long been heralded as key contributors to effective antiviral responses. More widely understood in the context of acute viral infection, the role of this pleiotropic cytokine has been characterized as triggering antiviral states in cells and potentiating adaptive immune responses. Upon induction in the innate immune response, IFN-I triggers the expression of interferon-stimulated genes (ISGs), which upregulate the effector function of immune cells (e.g., dendritic cells, B cells, and T cells) toward successful resolution of infections. However, emerging lines of evidence reveal that viral persistence in the course of chronic infections could be driven by deleterious immunomodulatory effects upon sustained IFN-I expression. In this setting, elevation of IFN-I and ISGs is directly correlated to viral persistence and elevated viral loads. It is important to note that the correlation among IFN-I expression, ISGs, and viral persistence may be a cause or effect of chronic infection and this is an important distinction to make toward establishing the dichotomous nature of IFN-I responses. The aim of this mini review is to (i) summarize the interaction between IFN-I and downstream effector responses and therefore (ii) delineate the function of this cytokine on positive and negative immunoregulation in chronic infection. This is a significant consideration given the current therapeutic administration of IFN-I in chronic viral infections whose therapeutic significance is projected to continue despite emergence of increasingly efficacious antiviral regimens. Furthermore, elucidation of the interplay between virus and the antiviral response in the context of IFN-I will elucidate avenues toward more effective therapeutic and prophylactic measures against chronic viral infections.

Sex-dependent immune responses to infant vaccination: an individual participant data meta-analysis of antibody and memory B cells

BACKGROUND

Biological sex can be an important source of variation in infection and immunity and sex-dependent differences in immune response to vaccination have been reported in some studies.

METHODS

We conducted an individual participant data meta-analysis of vaccine trials from one research centre, in which vaccines were administered to children under three years of age and immunological parameters measured. Log-transformed antigen-specific antibody and memory B cell results were meta-analysed and differences between girls and boys reported as geometric mean ratios.

RESULTS

Antibody and memory B cell data were available from nine trials and 2378 children. Statistically significant differences between girls and boys were observed for diphtheria toxoid, capsular group A, W, and Y meningococcal, and pneumococcal vaccines. No sex-differences were observed for responses to Haemophilus influenzae type b, capsular group C meningococcal or tetanus toxoid vaccines.

CONCLUSIONS

In young children, immune responses to vaccines were consistently higher or equivalent in girls compared with boys. In no instance were responses in boys significantly higher than girls. While these data do not indicate differences in protection conferred by immunisation in boys and girls, they do support further consideration of biological sex in planning of clinical trials of vaccines.

CpG Oligonucleotides as Cancer Vaccine Adjuvants

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

The impact of single and pairwise Toll-like receptor activation on neuroinflammation and neurodegeneration

Background

Toll-like receptors (TLRs) enable innate immune cells to respond to pathogen- and host-derived molecules. The central nervous system (CNS) exhibits most of the TLRs identified with predominant expression in microglia, the major immune cells of the brain. Although individual TLRs have been shown to contribute to CNS disorders, the consequences of multiple activated TLRs on the brain are unclear. We therefore systematically investigated and compared the impact of sole and pairwise TLR activation on CNS inflammation and injury.

Methods

Selected TLRs expressed in microglia and neurons were stimulated with their specific TLR ligands in varying combinations. Cell cultures were then analyzed by immunocytochemistry, FlowCytomix, and ELISA. To determine neuronal injury and neuroinflammation in vivo, C57BL/6J mice were injected intrathecally with TLR agonists. Subsequently, brain sections were analyzed by quantitative real-time PCR and immunohistochemistry.

Results

Simultaneous stimulation of TLR4 plus TLR2, TLR4 plus TLR9, and TLR2 plus TLR9 in microglia by their respective specific ligands results in an increased inflammatory response compared to activation of the respective single TLR in vitro. In contrast, additional activation of TLR7 suppresses the inflammatory response mediated by the respective ligands for TLR2, TLR4, or TLR9 up to 24 h, indicating that specific combinations of activated TLRs individually modulate the inflammatory response. Accordingly, the composition of the inflammatory response pattern generated by microglia varies depending on the identity and combination of the activated TLRs engaged. Likewise, neuronal injury occurs in response to activation of only selected TLRs and TLR combinations in vitro. Activation of TLR2, TLR4, TLR7, and TLR9 in the brain by intrathecal injection of the respective TLR ligand into C57BL/6J mice leads to specific expression patterns of distinct TLR mRNAs in the brain and causes influx of leukocytes and inflammatory mediators into the cerebrospinal fluid to a variable extent. Also, the intensity of the inflammatory response and neurodegenerative effects differs according to the respective activated TLR and TLR combinations used in vivo.

Conclusions

Sole and pairwise activation of TLRs modifies the pattern and extent of inflammation and neurodegeneration in the CNS, thereby enabling innate immunity to take account of the CNS diseases’ diversity.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-014-0166-7) contains supplementary material, which is available to authorized users.

TLR ligands upregulate RIG-I expression in human plasmacytoid dendritic cells in a type I IFN-independent manner

Plasmacytoid dendritic cells (pDCs) are professional type I interferon (IFN)-producing cells that play an essential role in antiviral immunity. In many cell types, detection of intracellular pathogens is mostly dependent on endosomal Toll-like receptors (TLRs) and cytosolic sensors, such as retinoic acid-inducible gene I (RIG-I). However, the possible interplay between these two systems has not yet been elucidated. Here we aimed to study the collaboration of endosomal TLRs and RIG-I in primary human pDCs. We found that under steady-state conditions, pDCs express RIG-I at very low level, but the expression of this receptor is rapidly and dramatically upregulated upon stimulation by the TLR7 ligand imiquimod or the TLR9 ligand type A CpG. We also demonstrated that pDCs are able to sense and respond to 5'-triphosphate double-stranded RNA (5'-ppp-dsRNA) only following activation by endosomal TLRs. Experiments on primary pDCs with functionally blocked IFN-α/β receptor 1 (IFNAR1) and those on human pDC leukemia (pDC-L) cells defective in type I IFN secretion indicated that the upregulation of RIG-I expression in pDCs upon stimulation by endosomal TLR occurs in a type I IFN-independent manner. Selective phosphorylation of signal transducer and activator of transcription 1 (STAT1) on tyrosine 701 could be identified as an early signaling event in this process. Our results show that in contrast to many other cell types, where RIG-I expression is induced by type I IFN, in pDCs a disparate mechanism is responsible for the upregulation of RIG-I. Our findings also indicate that along with autophagy, an additional mechanism is operating in pDCs to promote the detection of replicating viruses.

Platelet-TLR7 mediates host survival and platelet count during viral infection in the absence of platelet-dependent thrombosis

Viral infections have been associated with reduced platelet counts, the biological significance of which has remained elusive. Here, we show that infection with encephalomyocarditis virus (EMCV) rapidly reduces platelet count, and this response is attributed to platelet Toll-like receptor 7 (TLR7). Platelet-TLR7 stimulation mediates formation of large platelet-neutrophil aggregates, both in mouse and human blood. Intriguingly, this process results in internalization of platelet CD41-fragments by neutrophils, as assessed biochemically and visualized by microscopy, with no influence on platelet prothrombotic properties. The mechanism includes TLR7-mediated platelet granule release, translocation of P-selectin to the cell surface, and a consequent increase in platelet-neutrophil adhesion. Viral infection of platelet-depleted mice also led to increased mortality. Transfusion of wild-type, TLR7-expressing platelets into TLR7-deficient mice caused a drop in platelet count and increased survival post EMCV infection. Thus, this study identifies a new link between platelets and their response to single-stranded RNA viruses that involves activation of TLR7. Finally, platelet-TLR7 stimulation is independent of thrombosis and has implications to the host immune response and survival.

Association of TLR7 and TSHR copy number variation with Graves' disease and Graves' ophthalmopathy in Chinese population in Taiwan

BACKGROUND

Graves' disease (GD) and Graves' ophthalmopathy (GO) are autoimmune disorders, which might be influenced by genetic factors. Copy number variation (CNV) is an important source of genomic diversity in humans, and influences disease susceptibility. This study investigated the association between CNV in the TSHR and TLR7 genes and the development of GD and GO in a Chinese population in Taiwan.

METHODS

For this case-control study, sample from 196 healthy controls and 484 GD patients, including 203 patients with GO were studied. CNV was detected by real-time polymerase chain reaction (PCR) using TaqMan™ probes and the relative copy number (CN) was estimated by using the comparative Ct method.

RESULTS

The differences in the distribution of TSHR CNV in healthy controls and GD patients were statistically significant (p value = 0.01). However, the difference in the distribution of TSHR CNV in the control group and the GO group was not statistically significant (p value = 0.06). For TLR7 CNV, the results were not significantly different when we compared the distribution in healthy controls and GD patients and in healthy controls and GO patients (p values for Fisher's exact test were 0.13 and 0.09, respectively). However, a lower than normal CNV for TLR7 (CNV < 2 for female and CNV < 1 for male) was found to have a protective effect against the development of GD (odds ratio (OR) = 0.24; 95% confidence interval (CI), 0.07-0.75) after adjusting for age and gender.

CONCLUSIONS

These results suggested that TSHR and TLR7 CNV might be associated with susceptibility to GD.

Assessment of the effect of TLR7/8, TLR9 agonists and CD40 ligand on the transformation efficiency of Epstein-Barr virus in human B lymphocytes by limiting dilution assay

Infection of human B cells with Epstein-Barr virus (EBV) induces polyclonal activation in almost all infected cells, but a small proportion of infected cells are transformed to immortalized lymphoblastoid cell lines. Since B cells are activated also by CD40 ligand (CD40L) and Toll-like receptor (TLR) agonists via a similar signaling pathway, it is likely that costimulation through these molecules could result in synergistic enhancement of the transformation efficiency of EBV. In this study, the stimulatory effect of TLR7/8 (R848), TLR9 (CpG) agonists and/or CD40L on transformation efficiency of EBV in normal human B cells was assessed using the limiting dilution assay. Costimulation of peripheral blood mononuclear cells (PBMCs) with CpG and R848, but not CD40L, increased significantly the frequency of EBV transformed B cells (p < 0.001). Neither synergistic nor additive effects were observed between TLR agonists and CD40L and also TLR7/8 and TLR9 agonists. Costimulation with R848, CpG and CD40L enhanced the proliferative response of B cells infected with EBV. This effect was more evident when enriched B cells were employed, compared to PBMCs. The promoting effect of TLR agonists stimulation, implies that EBV may take advantage of the genes induced by the TLR stimulation pathway for viral latency and oncogenesis.

The two-component adjuvant IC31® boosts type i interferon production of human monocyte-derived dendritic cells via ligation of endosomal TLRs

The aim of this study was to characterize and identify the mode of action of IC31®, a two-component vaccine adjuvant. We found that IC31® was accumulated in human peripheral blood monocytes, MHC class II positive cells and monocyte-derived DCs (moDCs) but not in plasmacytoid DCs (pDCs). In the presence of IC31® the differentiation of inflammatory CD1a⁺ moDCs and the secretion of chemokines, TNF-α and IL-6 cytokines was inhibited but the production of IFNβ was increased. Sustained addition of IC31® to differentiating moDCs interfered with IκBα phosphorylation, while the level of phospho-IRF3 increased. We also showed that both IC31® and its KLK component exhibited a booster effect on type I IFN responses induced by the specific ligands of TLR3 or TLR7/8, whereas TLR9 ligand induces type I IFN production only in the presence of IC31® or ODN1. Furthermore, long term incubation of moDCs with IC31® caused significantly higher expression of IRF and IFN genes than a single 24 hr treatment. The adjuvant activity of IC31® on the IFN response was shown to be exerted through TLRs residing in the vesicular compartment of moDCs. Based on these results IC31® was identified as a moDC modulatory adjuvant that sets the balance of the NF-κB and IRF3 mediated signaling pathways to the production of IFNβ. Thus IC31® is emerging as a potent adjuvant to increase immune responses against intracellular pathogens and cancer in future vaccination strategies.

Skin TLR7 triggering promotes accumulation of respiratory dendritic cells and natural killer cells

The TLR7 agonist imiquimod has been used successfully as adjuvant for skin treatment of virus-associated warts and basal cell carcinoma. The effects of skin TLR7 triggering on respiratory leukocyte populations are unknown. In a placebo-controlled experimental animal study we have used multicolour flow cytometry to systematically analyze the modulation of respiratory leukocyte subsets after skin administration of imiquimod. Compared to placebo, skin administration of imiquimod significantly increased respiratory dendritic cells (DC) and natural killer cells, whereas total respiratory leukocyte, alveolar macrophages, classical CD4+ T helper and CD8+ T killer cell numbers were not or only moderately affected. DC subpopulation analyses revealed that elevation of respiratory DC was caused by an increase of respiratory monocytic DC and CD11b^hi DC subsets. Lymphocyte subpopulation analyses indicated a marked elevation of respiratory natural killer cells and a significant reduction of B lymphocytes. Analysis of cytokine responses of respiratory leukocytes after stimulation with Klebsiella pneumonia indicated reduced IFN-γ and TNF-α expression and increased IL-10 and IL-12p70 production after 7 day low dose skin TLR7 triggering. Additionally, respiratory NK cytotoxic activity was increased after 7d skin TLR7 triggering. In contrast, lung histology and bronchoalveolar cell counts were not affected suggesting that skin TLR7 stimulation modulated respiratory leukocyte composition without inducing overt pulmonary inflammation. These data suggest the possibility to modulate respiratory leukocyte composition and respiratory cytokine responses against pathogens like Klebsiella pneumonia through skin administration of a clinically approved TLR7 ligand. Skin administration of synthetic TLR7 ligands may represent a novel, noninvasive means to modulate respiratory immunity.

Negative regulation of the type I interferon signaling pathway by synthetic Toll-like receptor 7 ligands

Ten Toll-like receptor (TLR) family members have been reported in humans. Here, the endoplasmatic receptors TLR9, TLR8, TLR7, and TLR3 respond to nucleic acids and derivatives or to small molecules (TLR7 and 8). Another cytoplasmic RNA receptor, retinoic acid inducible gene I (RIG-I), is stimulated by 5' triphosphate double-stranded RNA. We discovered that TLR7 small-molecule agonists inhibit nucleic acid-mediated TLR3, TLR7, TLR9, or RIG-I-dependent interferon-α (IFN-α) immune response. Other cytokines and chemokines stimulated by nucleic acid agonists remained unaffected. The observed blockage of TLR3, TLR7, TLR9, and RIG-I-mediated IFN-α response appears to be driven by a competitive mechanism at the type I IFN pathway. Besides type I IFN, IFN response genes such as IFIT-1, Mx1, OAS1, or IRF7 were affected, which indicates that the key element driving the inhibition is located in the type I IFN pathway. Indeed, the heterotrimeric complex formation of phosphor-signal transducer and activator of transcription factor 1 (STAT1), phosphor-STAT2, and IRF9 (called ISGF3, IFN-stimulated gene factor 3) is inhibited through the TLR7 small-molecule agonists by phosphor-STAT2 blockage. These findings provide novel insights into the use of synthetic TLR7 or TLR7/8 small molecules as ligands for immune activation and suppression.

Differential regulation of toll-like receptor pathways in acute and chronic HIV-1 infection

OBJECTIVE AND DESIGN

The objective of this study was to determine changes in toll-like receptor (TLR) responses of monocytes, myeloid dendritic cells and plasmacytoid dendritic cells during primary and chronic HIV-1 infection. TLRs serve as important innate receptors to sense pathogens, and have been implicated in mediating immune activation in HIV-1 infection. Studies assessing the consequences of HIV-1 infection on the ability of innate immune cells to respond to TLR stimulation have come to varying conclusions.

METHODS

Using intracellular flow cytometry, cytokine production by cryopreserved peripheral blood mononuclear cells from healthy controls and HIV-1-infected individuals were examined after TLR stimulation.

RESULTS

We observed that the effect of HIV-1 infection on TLR responses not only depended on the stage of HIV-1 infection, but was also dependent on the individual receptor and cell type examined. Monocyte and myeloid dendritic cell responses to TLR8 stimulation were associated with HIV-1 viral load and CD4 T-cell count, whereas plasmacytoid dendritic cell responses to TLR7 stimulation were not. Responses to TLR2 stimulation were not affected by HIV-1 infection, whereas responses to TLR9 stimulation were universally decreased in all HIV-1-infected individuals examined regardless of treatment or clinical parameters.

CONCLUSION

Responsiveness to TLR7/8 stimulation, which have been shown to recognize HIV-1 ssRNA, did not decrease in chronic infection, and may represent a contributing factor to ongoing T-cell immune activation in the setting of chronic viremic HIV-1 infection.

Toll-like receptor stimulation differentially regulates vasoactive intestinal peptide type 2 receptor in macrophages

Vasoactive intestinal peptide (VIP) was originally isolated as a vasodilator intestinal peptide, then as a neuropeptide. In the immune system, VIP is described as an endogenous macrophage-deactivating factor. VIP exerts its immunological actions in a paracrine and/or autocrine manner, through specific receptors. However, very little is known about the molecular regulation of VIP type 2 receptor (VPAC(2)) in the immune system. We now report that different toll-like receptor (TLR) ligands selectively regulate the VPAC(2) receptor gene and show a gene repression system controlled by key protein kinase signalling cascades in macrophages. VPAC(2) gene expression is regulated by gram-positive (TLR2 ligands) and gram-negative bacteria wall constituents (TLR4 ligands). Moreover, VPAC(2) is tightly regulated: TLR2- or TLR2/6- but not TLR2/1-mediated mechanisms are responsible for the induction of VPAC(2). TLR stimulation by viral or bacterial nucleic acids did not modify the VPAC(2) mRNA levels. Remarkably, imiquimod--a synthetic TLR7 ligand--led to a potent up-regulation of VPAC(2) gene expression. TLR5 stimulation by flagellin present in gram-positive and gram-negative bacteria did not affect VPAC(2) mRNA. The p38 mitogen-activated protein kinase (MAPK) activity accounted for the TLR4-mediated induction of VPAC(2) gene expression. Surprisingly, our data strongly suggest for the first time a tightly repressed control of VPAC(2) mRNA induction by elements downstream of MAPK kinase 1/2, PI3K/Akt, and particularly Jun-NH(2)-terminal kinase signalling pathways.

Mechanism of endosomal TLR inhibition by antimalarial drugs and imidazoquinolines

Endosomal TLRs play an important role in innate immune response as well as in autoimmune processes. In the therapy of systemic lupus erythematosus, antimalarial drugs chloroquine, hydroxychloroquine, and quinacrine have been used for a long time. Their suppression of endosomal TLR activation has been attributed to the inhibition of endosomal acidification, which is a prerequisite for the activation of these receptors. We discovered that chloroquine inhibits only activation of endosomal TLRs by nucleic acids, whereas it augments activation of TLR8 by a small synthetic compound, R848. We detected direct binding of antimalarials to nucleic acids by spectroscopic experiments and determined their cellular colocalization. Further analysis revealed that other nucleic acid-binding compounds, such as propidium iodide, also inhibited activation of endosomal TLRs and colocalized with nucleic acids to endosomes. We found that imidazoquinolines, which are TLR7/8 agonists, inhibit TLR9 and TLR3 even in the absence of TLR7 or TLR8, and their mechanism of inhibition is similar to the antimalarials. In contrast to bafilomycin, none of the tested antimalarials and imidazoquinolines inhibited endosomal proteolysis or increased the endosomal pH, confirming that inhibition of pH acidification is not the underlying cause of inhibition. We conclude that the direct binding of inhibitors to nucleic acids mask their TLR-binding epitope and may explain the efficiency of those compounds in the treatment of autoimmune diseases.

Regulation of the activity of an adeno-associated virus vector cancer vaccine administered with synthetic Toll-like receptor agonists

Recombinant adeno-associated virus (rAAV) is being tested as a vaccine vector, but the cellular immune responses elicited in animal tumor models have not been completely protective. The adjuvant effects of the TLR7 agonist, imiquimod, and the TLR9 agonist, ODN1826, were tested with rAAV expressing the melanoma antigen, Trp2. Mice immunized with rAAV-TRP2 and either TLR agonist alone generated T-helper-1 antitumor immune responses. Antitumor activity in all experiments was still incomplete. Furthermore, antitumor activity was not achieved when the combination of ODN1826 and imiquimod was used as adjuvant. In vitro, the combination increased IL-10 production by dendritic cells. In vivo, the combination reduced T-helper-1 response and dendritic cell activation and increased myeloid suppressor cells; regulatory T cells were not significantly modulated. Depletion of myeloid derived suppressor cells enhanced the antitumor activity of immunization with rAAV-TRP2 and the imiquimod-ODN1826 combination; depletion of regulatory T cells did not. TLR7 and TLR9 agonists can be used to enhance the immune response to rAAV immunogens, but antagonism can be observed when combined. Suppressor mechanisms, including those mediated by myeloid cells, may negatively regulate the antitumor immune response.

Migration of dendritic cells from murine skeletal muscle

To better understand the role of dendritic cells (DCs) in skeletal muscle, we investigated the migration of DCs from murine skeletal muscle and compared that to previously studied footpad (FP) DC trafficking. We adoptively transferred carboxyfluorescein diacetate succinimidyl ester (CFSE)-labeled mature DCs to syngeneic mice and followed them in various lymphatic tissues at different time points. Injection of DCs into the tibialis anterior muscle resulted in the peak number of CFSE(+) DCs recovered in spleen at 12h, not at 24h, when the largest number of these cells appeared in the draining lymph nodes. Interestingly, this result for adoptive transfer of DCs to skeletal muscle differs with what is previously reported for adoptive transfer to the FP, a result that we also confirmed in parallel studies. These findings could have a significant impact on (1) understanding muscle diseases with immunological complications such as muscular dystrophies and (2) the immunologic effects of treatments for muscle diseases.

Interactions between TLR7 and TLR9 agonists and receptors regulate innate immune responses by astrocytes and microglia

Toll-like receptors 7 (TLR7) and 9 (TLR9) are important mediators of innate immune responses. Both receptors are located in endosomal compartments, recognize nucleic acids, and signal via Myeloid differentiation factor 88 (MyD88). In the current study, we analyzed TLR7 and TLR9 induced activation of astrocytes and microglia, two cell types that contribute to innate immune responses in the CNS. TLR7 and TLR9 agonists induced similar cytokine profiles within each cell type. However, there were notable differences in the cytokine profile between astrocytes and microglia, including the production of the anti-inflammatory cytokine IL-10 and antiapoptotic cytokines G-CSF and IL-9 by microglia but not astrocytes. Costimulation studies demonstrated that the TLR7 agonist, imiquimod, could inhibit TLR9 agonist-induced innate immune responses, in both cell types, in a concentration-dependent manner. Surprisingly, this inhibition was not mediated by TLR7, as deficiency in TLR7 did not alter suppression of the TLR9 agonist-induced responses. The suppression of innate immune responses was also not due to an inhibition of TLR9 agonist uptake. This suggested that imiquimod suppression may be a direct effect, possibly by blocking CpG-ODN binding and/or signaling with TLR9, thus limiting cell activation. An antagonistic relationship was also observed between the two receptors in microglia, with TLR7 deficiency resulting in enhanced cytokine responses to CpG-ODN stimulation. Thus, both TLR7 and its agonist can have inhibitory effects on TLR9-induced cytokine responses in glial cells.

Effective melanoma immunotherapy in mice by the skin-depigmenting agent monobenzone and the adjuvants imiquimod and CpG

BACKGROUND

Presently melanoma still lacks adequate treatment options for metastatic disease. While melanoma is exceptionally challenging to standard regimens, it is suited for treatment with immunotherapy based on its immunogenicity. Since treatment-related skin depigmentation is considered a favourable prognostic sign during melanoma intervention, we here aimed at the reverse approach of directly inducing vitiligo as a shortcut to effective anti-melanoma immunity.

METHODOLOGY AND PRINCIPAL FINDINGS

We developed an effective and simple to use form of immunotherapy by combining the topical skin-bleaching agent monobenzone with immune-stimulatory imiquimod cream and cytosine-guanine oligodeoxynucleotides (CpG) injections (MIC therapy). This powerful new approach promptly induced a melanoma antigen-specific immune response, which abolished subcutaneous B16.F10 melanoma growth in up to 85% of C57BL/6 mice. Importantly, this regimen induced over 100 days of tumor-free survival in up to 60% of the mice, and forcefully suppressed tumor growth upon re-challenge either 65- or 165 days after MIC treatment cessation.

CONCLUSIONS

MIC therapy is effective in eradicating melanoma, by vigilantly incorporating NK-, B- and T cells in its therapeutic effect. Based on these results, the MIC regimen presents a high-yield, low-cost and simple therapy, readily applicable in the clinic.

Co-stimulation with TLR7/8 and TLR9 agonists induce down-regulation of innate immune responses in sheep blood mononuclear and B cells

Toll-like receptors (TLRs) play an important role in the activation of innate and adaptive immune responses. Stimulation with multiple TLR agonists may result in synergistic, complimentary or inhibitory effects on innate immune responses. In this study, we investigated the effects of co-stimulation of sheep peripheral blood mononuclear cells (PBMC) and B cells with agonists for TLR3, 4, 7/8 and 9. Sheep PBMC stimulated with either CpG (TLR9 agonist) or RNA oligoribonucleotides ([ORNs], TLR7/8 agonist) exhibited significant IL-12 production, but only CpG induced IFNalpha, IgM and proliferative responses. In contrast, poly(I:C) (TLR3 agonist) and LPS (TLR4 agonist) did not induce any of these responses. Interestingly, we observed that co-stimulation of PBMC with CpG+ORN or CpG+imiquimod (another TLR7/8 agonist) resulted in significant reduction in CpG-induced IFNalpha production, B cell proliferation and IgM responses. Pre-incubation of cells with CpG prior to exposure of the cells to imiquimod resulted in similar inhibitory responses indicating that the down-regulatory mechanisms are not associated with competition for cellular uptake or for receptors of the two agonists. Sheep B cells constitutively expressed TLR7, TLR8 and TLR9 mRNA transcripts, suggesting a possible role of TLR cross-talk in the down-regulatory mechanisms. Down-regulation of responses by co-stimulation with closely related TLRs may be a regulatory mechanism by which the host prevents overstimulation of innate immune responses.

Antigen receptor signals rescue B cells from TLR tolerance

Interactions between innate and adaptive immune receptors are critical for an optimal immune response, but the role played by Ag receptors in modulating innate receptor functions is less clear. TLRs are a family of pattern recognition receptors that play crucial roles in detecting microbial pathogens and subsequent development of immune responses. However, chronic stimulation through TLRs renders immune cells hyporesponsive to subsequent stimulation with TLR ligands, a phenomenon known as TLR tolerance, well characterized in myeloid cells. However, it has not been studied in detail in B lymphocytes. In addition to the BCR, B cells express almost all known TLRs and respond robustly to many TLR ligands. Thus, B cells may receive signals through both TLRs and BCR during an infection and may respond differently to TLR stimulation than myeloid cells. We tested this possibility by stimulating repeatedly through either TLR alone or both TLR and BCR. Prestimulation through TLR7 resulted in reduced B cell proliferation, cytokine production, and IgM secretion upon subsequent TLR7 restimulation. The hyporesponsiveness to TLR7 restimulation was associated with reduced NF-kappaB and MAPK activation and defective c-Jun phosphorylation. However, simultaneous BCR signaling prevented or reversed TLR7 tolerance in both mouse and human B cells. Importantly, BCR signaling also rescued B cells from TLR7-mediated TLR9 tolerance. Additionally, the reversal of TLR7-mediated JNK activation was dependent on PI3K activation. Together these results present a novel mechanism to prevent and reverse TLR tolerance in B cells.

A class C CpG toll-like receptor 9 agonist successfully induces robust interferon-alpha production by plasmacytoid dendritic cells from patients chronically infected with hepatitis C

Immunomodulators that induce local endogenous interferon-alpha (IFN-alpha) production by plasmacytoid dendritic cells (pDCs) may offer new strategies for the treatment of patients chronically infected with the hepatitis C virus (HCV). However, such an approach may be compromised if reports are true that IFN-alpha production by pDCs from patients with chronic HCV (cHCV) is profoundly impaired. To address the question of pDC dysfunction in cHCV more definitively, in the present study a panel of four prototypic synthetic agonists of toll-like receptor 7 (TLR7) or TLR9 were administered in vitro to pDCs purified from cHCV patients and from normal uninfected donors and their responses compared in terms of not only IFN-alpha production but also the global expression of other cytokines and phenotypic maturation. Plasmacytoid DCs from uninfected donors produced substantial levels of IFN-alpha in response to three of the four agonists and yet only one TLR9 agonist, a class C CpG oligodeoxynucleotide (ODN), induced robust IFN-alpha production by pDCs from cHCV patients. Proinflammatory cytokine production and phenotypic maturation in response to all four agonists was equivalent in infected and uninfected pDCs. These data point to a profound but selective defect in IFN-alpha production by pDCs from cHCV donors. Nonetheless, a class C CpG ODN successfully induced robust IFN-alpha production, suggesting that this class of TLR9 agonist may have utility as a future immunotherapeutic for the treatment of chronic HCV infection.

Approaches to enhancing immune responses stimulated by CpG oligodeoxynucleotides

CpG oligodeoxynucleotides (ODN) activate the immune system and are promising immunotherapeutic agents against infectious diseases, allergy/asthma and cancer. It has become apparent that while CpG ODN are potent immune activators in mice, their immune stimulatory effects are often less dramatic in humans and large animals. This disparity between rodents and mammals has been attributed to the differences in TLR9 expression in different species. This along with the sometimes transient activity of ODN may limit its potential immunotherapeutic applications. Several approaches to enhance the activity of CpG ODN have been explored including formulation of ODN in depot-forming adjuvants, and more recently, coadministration with polyphosphazenes, inhibitors of cytokines that downregulate TLR9 activation, and simultaneous activation with multiple TLR agonists. We will discuss these approaches and the mechanisms involved, with emphasis on what we have learned from large animal models.

Reduced IgG anti-small nuclear ribonucleoprotein autoantibody production in systemic lupus erythematosus patients with positive IgM anti-cytomegalovirus antibodies

Introduction

Systemic lupus erythematosus is characterized by production of autoantibodies to RNA or DNA–protein complexes such as small nuclear ribonucleoproteins (snRNPs). A role of Epstein–Barr virus in the pathogenesis has been suggested. Similar to Epstein–Barr virus, cytomegalovirus (CMV) infects the majority of individuals at a young age and establishes latency with a potential for reactivation. Homology of CMV glycoprotein B (UL55) with the U1snRNP-70 kDa protein (U1–70 k) has been described; however, the role of CMV infection in production of anti-snRNPs is controversial. We investigated the association of CMV serology and autoantibodies in systemic lupus erythematosus.

Methods

Sixty-one Mexican patients with systemic lupus erythematosus were tested for CMV and Epstein–Barr virus serology (viral capsid antigen, IgG, IgM) and autoantibodies by immunoprecipitation and ELISA (IgG and IgM class, U1RNP/Sm, U1–70 k, P peptide, rheumatoid factor, dsDNA, β₂-glycoprotein I).

Results

IgG anti-CMV and IgM anti-CMV were positive in 95% (58/61) and 33% (20/61), respectively, and two cases were negative for both. Clinical manifestation and autoantibodies in the IgM anti-CMV(+) group (n = 20) versus the IgM anti-CMV(-)IgG (+) (n = 39) group were compared. Most (19/20) of the IgM anti-CMV(+) cases were IgG anti-CMV(+), consistent with reactivation or reinfection. IgM anti-CMV was unrelated to rheumatoid factor or IgM class autoantibodies and none was positive for IgM anti-Epstein–Barr virus–viral capsid antigen, indicating that this is not simply due to false positive results caused by rheumatoid factor or nonspecific binding by certain IgM. The IgM anti-CMV(+) group has significantly lower levels of IgG anti-U1RNP/Sm and IgG anti-U1–70 k (P = 0.0004 and P = 0.0046, respectively). This finding was also confirmed by immunoprecipitation. Among the IgM anti-CMV(-) subset, anti-Su was associated with anti-U1RNP and anti-Ro (P < 0.05). High levels of IgG anti-CMV were associated with production of lupus-related autoantibodies to RNA or DNA–protein complex (P = 0.0077).

Conclusions

Our findings suggest a potential role of CMV in regulation of autoantibodies to snRNPs and may provide a unique insight to understand the pathogenesis.

Visualization of IFNbeta production by plasmacytoid versus conventional dendritic cells under specific stimulation conditions in vivo

Type I interferons, a protein family of multiple IFNalphas and a single IFNbeta, initially identified on the basis of their antiviral activities have recently been attributed important roles in bacterial and parasitic infections. To assess the cellular sources of IFNbeta, the IFN produced first in most situations, we created an IFNbeta reporter-knockin mouse, in which yellow fluorescent protein (YFP) is expressed from a bicistronic mRNA linked by an internal ribosomal entry site to the endogenous IFNbeta mRNA. This YFP expression allows spatiotemporal tracking of the initiation of the type I IFN response on a single-cell level. In vitro bone marrow-derived macrophages (BMMPhis) and bone marrow-derived dendritic cells (BMDCs) show IFNbeta production from distinct cell subpopulations in response to defined pathogen compounds. A subpopulation of GMCSF-derived BMDCs produced IFNbeta after poly(I:C), 3'5'-cytidylylguanosine (CpG), or LPS treatment, whereas Flt3-L-cultured plasmacytoid DCs (pDCs) responded mainly to CpG. After poly(I:C) injection in vivo, IFNbeta-producing cells localize to the splenic marginal zone and the lymph node subcapsular sinus. Infection with murine cytomegalovirus (MCMV) induces IFNbeta/YFP expression exclusively in few activated pDCs at the T cell/B cell interface of the splenic white pulp. This IFNbeta/YFP reporter mouse represents a reliable tool for the visualization and characterization of IFNbeta-producing cells in vitro and in vivo.

Influence of the Toll-like receptor 9 1635A/G polymorphism on the CD4 count, HIV viral load, and clinical progression

OBJECTIVE

: To analyze the influence of single-nucleotide polymorphisms (SNPs) in TLR2 (1892A/C and 2258G/A), TLR4 (896A/G and 1196C/T), and TLR9 (1635A/G) genes on CD4 count, HIV viral load, and clinical progression in a cohort of naive HIV-infected patients.

METHODS

: TLR2, TLR4, and TLR9 SNPs were analyzed in 369 naive HIV-infected patients by real-time polymerase chain reaction and melting curve technology. TLR2 1892C/A and TLR9 1635A/G SNPs were also analyzed in a non-HIV-infected population. Multivariate multiple regression analysis and Cox regression analyses were performed to assess the potential association between the SNPs and the end points.

RESULTS

: TLR2 and TLR4 SNPs were not associated with the end points of the study. Regarding TLR9 1635A/G SNP, patients with the AA genotype showed statistically lower CD4 count (P = 0.003) and higher HIV viral load (P = 0.0018) compared with AG+GG genotypes at cohort entry. The multivariate analysis showed a significant association between the 1635AA genotype and both end points. Cox regression analysis showed that HIV clinical progression to clinical stage C and death due to AIDS-related events under antiretroviral therapy was earlier in patients with the 1635AA genotype (P = 0.035, P = 0.017, respectively).

CONCLUSIONS

: TLR9 1635A/G SNP might have a role in HIV clinical disease progression.

The clathrin-mediated endocytic pathway participates in dsRNA-induced IFN-beta production

TLR3 and cytoplasmic RIG-I-like receptor (RLR) recognize virus-derived dsRNA and induce type I IFN production in a distinct manner. Human TLR3 localizes to the endosomal compartments in myeloid dendritic cells (mDCs), while it localizes to both the cell surface and interior in fibroblasts and epithelial cells. TLR3 signaling arises in the intracellular compartment in both cell types and requires endosomal maturation. The mechanisms by which extracellular dsRNA is delivered to the TLR3-containing organelle remain largely unknown. Among various synthetic dsRNAs, poly(I:C) is preferentially internalized and activates TLR3 in mDCs. In vitro transcribed dsRNAs hardly induce IFN-beta production in mDCs. In this study, we demonstrate that the clathrin-dependent endocytic pathway mediates cell entry of poly(I:C) to induce IFN-beta gene transcription. Furthermore, poly(I:C)-induced IFN-beta production is inhibited by pretreatment of cells with B- and C-type oligodeoxynucleotides (ODNs) but not with TLR7/8 ligands. The binding and internalization of B-type ODNs by mDCs was reduced in the presence of poly(I:C), suggesting that poly(I:C) shares the uptake receptor with B- and C-type ODNs. Hence, foreign dsRNA is recognized by differently categorized receptors, cytoplasmic RIG-I-like receptor, membrane-bound TLR3 and cell-surface RNA capture. The endocytic pathway is critical for dsRNA-induced TLR3-mediated cell activation.

Broad-spectrum drugs against viral agents

Development of antivirals has focused primarily on vaccines and on treatments for specific viral agents. Although effective, these approaches may be limited in situations where the etiologic agent is unknown or when the target virus has undergone mutation, recombination or reassortment. Augmentation of the innate immune response may be an effective alternative for disease amelioration. Nonspecific, broad-spectrum immune responses can be induced by double-stranded (ds)RNAs such as poly (ICLC), or oligonucleotides (ODNs) containing unmethylated deocycytidyl-deoxyguanosinyl (CpG) motifs. These may offer protection against various bacterial and viral pathogens regardless of their genetic makeup, zoonotic origin or drug resistance.