The Effects of Endosomal Toll-like Receptor Inhibitors in an EBV DNA-Exacerbated Inflammatory Bowel Disease Mouse Model.

Epstein-Barr virus (EBV), a Herpesviridae family member, is associated with an increased risk of autoimmune disease development in the host. We previously demonstrated that EBV DNA elevates levels of the pro-inflammatory cytokine IL-17A and that inhibiting Toll-like receptor (TLR) 3, 7, or 9 reduces its levels. Moreover, this DNA exacerbated colitis in a mouse model of inflammatory bowel disease (IBD). In the study at hand, we examined whether inhibition of TLR3, 7, or 9 alleviates this exacerbation. Mice were fed 1.5% dextran sulfate sodium (DSS) water and administered EBV DNA. Then, they were treated with a TLR3, 7, or 9 inhibitor or left untreated. We also assessed the additive impact of combined inhibition of all three receptors. Mice that received DSS, EBV DNA, and each inhibitor alone, or a combination of inhibitors, showed significant improvement. They also had a decrease in the numbers of the pathogenic colonic IL-17A+IFN-γ+ foci. Inhibition of all three endosomal TLR receptors offered no additive benefit over administering a single inhibitor. Therefore, inhibition of endosomal TLRs reduces EBV DNA exacerbation of mouse colitis, offering a potential approach for managing IBD patients infected with EBV.

Recent Advances on Small-Molecule Antagonists Targeting TLR7.

Toll-like receptor 7 (TLR7) is a class of pattern recognition receptors (PRRs) recognizing the pathogen-associated elements and damage and as such is a major player in the innate immune system. TLR7 triggers the release of pro-inflammatory cytokines or type-I interferons (IFN), which is essential for immunoregulation. Increasing reports also highlight that the abnormal activation of endosomal TLR7 is implicated in various immune-related diseases, carcinogenesis as well as the proliferation of human immunodeficiency virus (HIV). Hence, the design and development of potent and selective TLR7 antagonists based on small molecules or oligonucleotides may offer new tools for the prevention and management of such diseases. In this review, we offer an updated overview of the main structural features and therapeutic potential of small-molecule antagonists of TLR7. Various heterocyclic scaffolds targeting TLR7 binding sites are presented: pyrazoloquinoxaline, quinazoline, purine, imidazopyridine, pyridone, benzanilide, pyrazolopyrimidine/pyridine, benzoxazole, indazole, indole, and quinoline. Additionally, their structure-activity relationships (SAR) studies associated with biological activities and protein binding modes are introduced.

Toll-like receptor 7 and 8 imidazoquinoline-based agonist/antagonist pairs.

Toll-like receptors (TLRs) 7 and 8 are key targets in the development of immunomodulatory drugs for treating infectious disease, cancer, and autoimmune disorders. These receptors can adopt both agonist and antagonist binding conformations that switch the receptor signal on or off to the downstream production of cytokines. In this study, we examined the effect of simple isomeric substitutions to the C2-butyl group of two imidazoquinoline agonists and evaluated the activity of these analogs using both TLR7 and TLR8 reporter cells and cytokine induction assays. Results are presented showing the C2-isobutyl and C2-cyclopropylmethyl isomers are both mixed TLR7/8 competitive antagonists of the parent agonist [4-Amino-1-(4-(aminomethyl)benzyl)-2-butyl-7-methoxycarbonyl-1H-imidazo[4,5-c]quinoline], indicating the conformation of the dimeric receptor complex is highly sensitive to steric perturbations to the ligand binding pocket. This observation is consistent with prior work demonstrating TLR7 and TLR8 activity is directly correlated to C2-alkyl substitutions that project into a hydrophobic pocket at the dimer interface of the receptor. The close structural relationship of the agonist/antagonist pairs identified here highlights the importance of this pocket in tipping the balance between the agonist and antagonist binding states of the receptor which may have significant ramifications to the design of imidazoquinoline-based immunomodulatory agents.

TRAIL Mediates Neuronal Death in AUD: A Link between Neuroinflammation and Neurodegeneration.

Although the cause of progressive neurodegeneration is often unclear, neuronal death can occur through several mechanisms. In conditions such as Alzheimer's or alcohol use disorder (AUD), Toll-like receptor (TLR) induction is observed with neurodegeneration. However, links between TLR activation and neurodegeneration are lacking. We report a role of apoptotic neuronal death in AUD through TLR7-mediated induction of death receptor signaling. In postmortem human cortex, a two-fold increase in apoptotic terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining in neurons was found in AUD versus controls. This occurred with the increased expression of TLR7 and tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) death receptors. Binge ethanol treatment in C57BL/6 mice increased TLR7 and induced neuronal apoptosis in cortical regions that was blocked by TLR7 antagonism. Mechanistic studies in primary organotypic brain slice culture (OBSC) found that the inhibition of TLR7 and its endogenous ligand let-7b blocked ethanol-induced neuronal cell death. Both IMQ and ethanol induced the expression of TRAIL and its death receptor. In addition, TRAIL-neutralizing monoclonal antibodies blocked both imiquimod (IMQ) and ethanol induced neuronal death. These findings implicate TRAIL as a mediator of neuronal apoptosis downstream of TLR7 activation. TLR7 and neuronal apoptosis are implicated in other neurodegenerative diseases, including Alzheimer's disease. Therefore, TRAIL may represent a therapeutic target to slow neurodegeneration in multiple diseases.

Carvacrol inhibits the excessive immune response induced by influenza virus A via suppressing viral replication and TLR/RLR pattern recognition.

ETHNOPHARMACOLOGICAL RELEVANCE: Carvacrol, a monoterpene phenol from Mosla chinensis Maxim, which is a commonly Chinese herbal medicine. The most important pharmacology of it is dispelling exogenous evils by increasing perspiration. And it is the gentleman medicine in the Chinese herbal compound prescription of Xin-Jia-Xiang-Ru-Yin, mainly for the treatment of summer colds with dampness including influenza virus A infection. AIM OF THE STUDY: Our preliminary study verified that the Xin-Jia-Xiang-Ru-Yin could inhibit acute lung injury of mice with influenza virus A infection. And there have been some reports implicating the high antimicrobial activity of carvacrol for a wide range of product preservation, but little research including the effects of it on viral infection. The aim of this study was to reveal the antiviral effects of carvacrol, the main constituent in Mosla chinensis Maxim. MATERIALS AND METHODS: Initially, C57BL/6 mice were grouped and intranasally administered FM1 virus to construct viral infection models. After treatment with ribavirin and carvacrol for 5 days, all mice were euthanized, and specimens were immediately obtained. Histology, flow cytometry and Meso Scale Discovery (MSD) analysis were used to analyze pathological changes in lung tissue, the expression levels of cytokines and the differentiation and proportion of CD4+ T cells subsets, while Western blot and qRT-PCR were used to detect the expression of related proteins and mRNA. RESULTS: Carvacrol attenuated lung tissue damage, the proportions of Th1, Th2, Th17 and Treg in CD4+ T cells and the relative proportions of Th1/Th2 and Th17/Treg cells. Carvacrol inhibited the expression of inflammation-associated cytokines including IFN-γ, IL-2, IL-4, IL-5, IL-12 and TNF-ɑ, IL-1, IL-10, IL-6. Decreased levels of TLR7, MyD88, IRAK4, TRAK6, NF-κB, RIG-I, IPS-I and IRF mRNA in carvacrol-treated mice were observed comparing to the mice in VC group. Further, the total expression of RIG-I, MyD88 and NF-κB proteins had increased significantly in the VC group but reduced obviously in the group treated with ribavirin or carvacrol. CONCLUSIONS: These results indicate that carvacrol is a potential alternative treatment for the excessive immune response induced by influenza virus A infection, the cold-fighting effect of Mosla chinensis Maxim may depend on the anti-virus of carvacrol.

Design, synthesis, and biological activity of TLR7-based compounds for chemotherapy-induced alopecia.

Hair loss is a common dermatosis symptom and side-effect in cancer chemotherapeutics. Imiquimod application at mid and late telogen activated the hair follicle stem cells leading to premature hair cycle entry. Based on quinoline structure, a newly synthesized compound 6b displayed proliferation activity in vitro and in vivo through branch chain replacement and triazole ring cyclization. Toll-like receptors (TLRs) are also critical mediators of the immune system, and their activation is linked to various diseases. The present study aimed to expand new agonists within co-crystallization of TLR7 (PDB code: 5GMH); however, biological assays of NF-κB activity and NO-inhibition indicated that five selected compounds were TLR7 antagonists. Molecular docking indicated the binding mode differences: antagonists binding TLR7 in a different direction and interacting with adjacent TLR7 with difficulty in forming dimers.

Toll-like receptor 7-adapter complex modulates interferon-α production in HIV-stimulated plasmacytoid dendritic cells.

Plasmacytoid dendritic cells (PDCs) and their production of interferon-alpha (IFN-α) are believed to play an important role in human immunodeficiency virus, type I (HIV-1) pathogenesis. PDCs produce IFN-α and other proinflammatory cytokines through stimulation of Toll-like receptor 7 (TLR7) and TLR9 present in endosomal compartments. TLR7 recognizes single-stranded viral RNA, while TLR9 recognizes unmethylated DNA. In this study, we examined the mechanisms that may underlie variations in IFN-α production in response to HIV, and the impact of these variations on HIV pathogenesis. In four distinct cohorts, we examined PDC production of IFN-α upon stimulation with inactivated HIV-1 particles and unmethylated DNA. The signaling cascade of TLR7 bifurcates at the myeloid differentiation protein 88 (MyD88) adaptor protein to induce expression of either IFN-α or TNF-α. To determine whether variations in IFN-α production are modulated at the level of the receptor complex or downstream of it, we correlated production of IFN-α and TNF-α following stimulation of TLR7 or TLR9 receptors. Flow cytometry detection of intracellular cytokines showed strong, direct correlations between IFN-α and TNF-α expression in all four cohorts, suggesting that variations in IFN-α production are not due to variations downstream of the receptor complex. We then investigated the events upstream of TLR binding by using lipid-like vesicles to deliver TLR ligands directly to the TLR receptors, bypassing the need for CD4 binding and endocytosis. Similar tight correlations were found in IFN-α and TNF-α production in response to the TLR ligands. Taken together, these results strongly suggest that differences in IFN-α production depend on the regulatory processes at the level of the TLR7 receptor complex. Additionally, we found no association between IFN-α production before HIV infection and disease progression.

Discovery of Novel Small Molecule Dual Inhibitors Targeting Toll-Like Receptors 7 and 8.

Endosomal toll-like receptors (TLRs) 7 and 8 recognize viral single-stranded RNAs, a class of imidazoquinoline compounds, 8-oxo-adenosines, 8-aminobenzodiazepines, pyrimidines, and guanosine analogues. Substantial evidence is present linking chronic inflammation mediated specifically by TLR7 to the progression of autoimmunity. We identified a new TLR7/8 dual inhibitor (1) and a TLR8-specific inhibitor (2) based on our previous screen targeting TLR8. Compound 1, bearing a benzanilide scaffold, was found to inhibit TLR7 and TLR8 at low micromolar concentrations. We envisioned making modifications on the benzanilide scaffold of 1 resulting in a class of highly specific TLR7 inhibitors. Our efforts led to the discovery of a new TLR8 inhibitor (CU-115) and identification of a TLR7/8 dual inhibitor (CU-72), bearing a distinct diphenyl ether skeleton, with potential for TLR7 selectivity optimization. Given the role of TLR8 in autoimmunity, we also optimized the potency of 2 and developed a new TLR8 inhibitor bearing a 1,3,4-oxadiazole motif.

Development of a Nanostructured RNA/DNA Assembly as an Adjuvant Targeting Toll-Like Receptor 7/8.

Adjuvants are essential for efficiently inducing an antigen-specific immune response in vaccine therapy. Single-stranded RNA (ssRNA) containing guanosine- and uridine-rich sequences is recognized by Toll-like receptor (TLR)7 and/or TLR8 and induces strong immune responses; thus, the application of ssRNA as an adjuvant is desirable. The development of a ssRNA-based adjuvant, however, requires the efficient delivery of ssRNA into the endosomes of antigen-presenting cells, where the TLRs exist. To achieve this, we developed a nanostructured RNA/DNA assembly using DNA nanotechnology, which can be efficiently recognized by antigen-presenting cells. The nanostructured RNA/DNA assembly, named tetrapodRD3, was designed using a 40-mer phosphorothioate-stabilized RNA and three 40-mer phosphodiester DNAs. TetrapodRD3 was more stable than ssRNA under serum conditions. The secreted alkaline phosphatase assay using HEK-Blue hTLR cells showed that tetrapodRD3 triggered human TLR8-specific responses. Fluorescently labeled tetrapodRD3 was efficiently taken up by murine dendritic DC2.4 cells and induced a high level of tumor necrosis factor-α release from the cells. Antigen presentation by the major histocompatibility complex class I on bone marrow-derived dendritic cells was significantly increased by the addition of an antigen along with tetrapodRD3. These results indicate that tetrapodRD3 constructed using DNA nanotechnology can be a useful adjuvant targeting human TLR8.

Selective Toll-like receptor 7 agonists with novel chromeno[3,4-d]imidazol-4(1H)-one and 2-(trifluoromethyl)quinoline/ quinazoline-4-amine scaffolds.

Toll-like receptors (TLRs) are promising targets for treatment of viral infections, autoimmune diseases, and cancers. Here, two new series of selective small-molecule TLR7 agonists with novel scaffolds and good selectivity over TLR8 are described, some with potencies in the low micromolar range. 8-Hydroxy-1-isobutylchromeno[3,4-d]imidazol-4(1H)-one (26) from the first series was designed and synthesized on the basis of previously described TLR7 antagonist 2, and is shown to be a selective TLR7 agonist (EC50, 1.8 µM). The second series was based on 2-(trifluoromethyl)quinolin-4-amine and 2-(trifluoromethyl)quinazolin-4-amine scaffolds, which were defined according to our in-house ligand-based virtual screening protocol. Further synthesis of a focused library of analogs, biological evaluation, and docking studies provided systematic exploration of the structure-activity relationships, which indicate that a secondary or tertiary amine with smaller flexible alkyl substituents up to three carbon atoms in length, or bulkier rigid aliphatic rings is required at position 4 on 2-(trifluoromethyl)quinoline/quinazoline scaffold for potent TLR7 agonist activity. The influence of selected TLR7 agonists on cytokine production is also reported showing that N-cyclopropyl-2-(trifluoromethyl)quinazolin-4-amine (46) is able to induce increased levels of IL-6 and IL-8. These data demonstrate successful in-silico definition of novel TLR7 versus TLR8-selective compounds as promising chemical probes for further development of potent small-molecule immunomodulators.

TLR7 (Toll-Like Receptor 7) Facilitates Heme Scavenging Through the BTK (Bruton Tyrosine Kinase)-CRT (Calreticulin)-LRP1 (Low-Density Lipoprotein Receptor-Related Protein-1)-Hx (Hemopexin) Pathway in Murine Intracerebral Hemorrhage.

Background and Purpose- Heme and iron are considered to be key factors responsible for secondary insults after intracerebral hemorrhage (ICH). Our previous study showed that LRP1 (low-density lipoprotein receptor-related protein-1)-Hx (hemopexin) facilitates removal of heme. The TLR7 (Toll-like receptor 7)-BTK (Bruton tyrosine kinase)-CRT (calreticulin) pathway regulates the expression of LRP1-Hx. This study is designed to clarify whether TLR7 activation facilitates heme scavenging and to establish the potential role of the BTK-CRT-LRP1-Hx signaling pathway in the pathophysiology of ICH. Methods- ICH was induced by stereotactic, intrastriatal injection of type VII collagenase. Mice received TLR7 agonist (imiquimod) via intraperitoneal injection after ICH induction. TLR7 inhibitor (ODN2088), BTK inhibitor (LFM-A13), and CRT agonist (thapsigargin) were given in different groups to further evaluate the underlying pathway. Mice were randomly divided into sham, ICH+vehicle (normal saline), ICH+Imiquimod (2.5, 5, and 10 µg/g), ICH+ODN2088, ICH+LFM-A13, ICH+thapsigargin, and ICH+ODN2088+thapsigargin. Imiquimod was administered twice daily starting at 6 hours after ICH; ODN2088 was administered by intracerebroventricular injection at 30 minutes, and LFM-A13 or thapsigargin was administered by intraperitoneal injection at 3 hours after ICH induction. Neurological scores, cognitive abilities, as well as brain edema, blood-brain barrier permeability, hemoglobin level, brain expression of TLR7/BTK/CRT/LRP1/Hx were analyzed. Results- Low dosage imiquimod significantly attenuated hematoma volume, brain edema, BBB permeability, and neurological deficits after ICH. Imiquimod also increased protein expressions of TLR7, BTK, CRT, LRP1, and Hx; ODN2088 reduced TLR7, BTK, CRT, LRP1, and Hx expressions. Conclusions- TLR7 plays an important role in heme scavenging after ICH by modulating the BTK-CRT-LRP1-Hx pathway. TLR7 may offer protective effects by promoting heme resolution and reduction of brain edema after ICH.

Activity-guided development of potent and selective toll-like receptor 9 antagonists.

TLR9 is one of the major innate immune receptors expressed in the endosomes of pDCs and B cells in humans. Aberrant TLR9 activation is implicated in several autoimmune and metabolic disorders as well as in sepsis, making this receptor an important therapeutic target, though specific TLR9 antagonists are yet to be available for clinical use. Here we elucidate the importance of specific physiochemical properties through substitution patterns in quinazoline scaffold to achieve potent hTLR9 inhibition at < 50 nM as well as > 600 fold selectivity against hTLR7, another closely related TLR that shares downstream signaling with TLR9 but plays distinct roles in physiology and pathology. Assays were performed using hPBMC and reporter cell lines. Favorable in vitro ADME profile, pharmacokinetics as well as validation in a clinically relevant in vivo TLR9-inhibition efficacy model in mice establish these novel TLR9-antagonists as candidate therapeutic agents in relevant clinical contexts.

Acetalated Dextran Microparticles for Codelivery of STING and TLR7/8 Agonists.

Vaccines are the most effective tool for preventing infectious diseases; however, subunit vaccines, considered the safest type, suffer from poor immunogenicity and require adjuvants to create a strong and sustained immune response. As adjuvants, pathogen-associated molecular patterns (PAMPs) offer potent immunostimulatory properties and defined mechanisms of action through their cognate pattern recognition receptors (PRRs). Their activity can be further enhanced through combining two or more PAMPs, particularly those that activate multiple immune signaling pathways. However, the cytosolic localization of many PRRs requires intracellular delivery of PAMPs for optimal biological activity, which is particularly true of the stimulator of interferon genes (STING) PRR. Using acetalated dextran (Ace-DEX) microparticles (MPs) encapsulating STING agonist 3'3'-cyclic GMP-AMP (cGAMP) combined with soluble PAMPS, we screened the effect of codelivery of adjuvants using primary mouse bone marrow derived dendritic cells (BMDCs). We identified that codelivery of cGAMP MPs and soluble Toll-like receptor 7/8 (TLR7/8) agonist resiquimod (R848) elicited the broadest cytokine response. cGAMP and R848 were then coencapsulated within Ace-DEX MPs via electrospray. Using the model antigen ovalbumin, we observed that Ace-DEX MPs coencapsulating cGAMP and R848 (cGAMP/R848 Ace-DEX MPs) induced antigen-specific cellular immunity, and a balanced Th1/Th2 humoral response that was greater than cGAMP Ace-DEX MPs alone and PAMPs delivered in separate MPs. These data indicate that polymeric Ace-DEX MPs loaded with STING and TLR7/8 agonists represent a potent cellular and humoral vaccine adjuvant.

The TLR7/8/9 Antagonist IMO-8503 Inhibits Cancer-Induced Cachexia.

: Muscle wasting is a feature of the cachexia syndrome, which contributes significantly to the mortality of patients with cancer. We have previously demonstrated that miR-21 is secreted through extracellular vesicles (EV) by lung and pancreatic cancer cells and promotes JNK-dependent cell death through its binding to the TLR7 receptor in murine myoblasts. Here, we evaluate the ability of IMO-8503, a TLR7, 8, and 9 antagonist, to inhibit cancer-induced cachexia. Using EVs isolated from lung and pancreatic cancer cells and from patient plasma samples, we demonstrate that IMO-8503 inhibits cell death induced by circulating miRNAs with no significant toxicity. Intraperitoneal administration of the antagonist in a murine model for Lewis lung carcinoma (LLC-induced cachexia) strongly impaired several cachexia-related features, such as the expression of Pax7 as well as caspase-3 and PARP cleavage in skeletal muscles, and significantly prevented the loss of lean mass in tumor-bearing mice. IMO-8503 also impaired circulating miRNA-induced cell death in human primary myoblasts. Taken together, our findings strongly indicate that IMO-8503 serves as a potential therapy for the treatment of cancer cachexia. SIGNIFICANCE: Cancer-associated cachexia is a significant problem for patients with cancer that remain poorly understood, understudied, and inadequately treated; these findings report a potential new therapeutic for the treatment of TLR7-mediated cancer cachexia.

Double-stranded RNA released from damaged articular chondrocytes promotes cartilage degeneration via Toll-like receptor 3-interleukin-33 pathway.

Pattern recognition receptors (PRRs), including Toll-like receptor 3 (TLR3), are involved in arthritic responses; however, whether interleukin-33 (IL-33) is involved in TLR3-mediated cartilage degeneration is unknown. Here, we found that IL-33 was abundantly increased in chondrocytes of osteoarthritis, especially the chondrocytes of weight-bearing cartilage. Furthermore, double-stranded RNA (dsRNA) released from damaged articular chondrocytes induced by mechanical stretching upregulated IL-33 expression to a greater degree than IL-1ß and tumor necrosis factor-α. dsRNA induced IL-33 expression via the TLR3-p38 mitogen-activated protein kinase-nuclear factor-κB (NF-κB) pathway. In addition, formation of the p65 and peroxisome proliferator-activated receptor-γ transcriptional complex was required for dsRNA-induced IL-33 expression. IL-33, in turn, acted on chondrocytes to induce matrix metalloproteinase-1/13 and inhibit type II collagen expression. These findings reveal that dsRNA released from damaged articular chondrocytes promotes cartilage degeneration via the TLR3-IL-33 pathway.

A pH-sensitive Macromolecular Prodrug as TLR7/8 Targeting Immune Response Modifier.

The chemical synthesis and biological activity of novel functionalized imidazoquinoline derivatives (ImQ) to generate Toll-like receptor (TLR) 7/8 specific prodrugs are presented. In vivo activity of ImQs to induce inflammation was confirmed in zebrafish larvae. After covalent ligation to fully biodegradable polyphosphazenes (ImQ-polymer), the macromolecular prodrugs were designed to undergo intracellular pH-sensitive release of ImQs to induce inflammation through binding to endosomal TLR7/8 (danger signal). We showed ImQ dissociation from prodrugs at a pH 5 pointing towards endosomal prodrug degradability. ImQ-polymers strongly activated ovalbumin-specific T cells in murine splenocytes as shown by increased proliferation and expression of the IL-2 receptor (CD25) on CD8+ T cells accompanied by strong IFN-γ release. ImQ prodrugs presented here are suggested to form the basis of novel nanovaccines, for example, for intravenous or intratumoral cancer immunotherapeutic applications to trigger physiological antitumor immune responses.

Combined immunotherapy: CTLA-4 blockade potentiates anti-tumor response induced by transcutaneous immunization.

BACKGROUND: The epidermal application of the Toll Like Receptor 7 agonist imiquimod and a T-cell peptide epitope (transcutaneous immunization, TCI) mediates systemic peptide-specific cytotoxic T-cell (CTL) responses and leads to tumor protection in a prophylactic tumor setting. However, it does not accomplish memory formation or permanent defiance of tumors in a therapeutic set-up. As a distinct immunologic approach, CTLA-4 blockade augments systemic immune responses and has shown long-lasting effects in preclinical experiments as well as in clinical trials. OBJECTIVE: The study investigates the vaccination capacity of TCI in combination with the checkpoint inhibitor CTLA-4 in matters of primary response, memory formation and tumor protection and characterizes the role of regulatory T cells (Tregs). METHODS: After performing TCI with IMI-Sol (containing 5% Imiquimod) and the model epitope SIINFEKL, 6-8 week old C57BL/6 mice received anti-CTLA-4 antibody either s.c or i.p. The CTL responses and frequency of peptide specific CD8+ T-cells were then evaluated on day 8. To determine anti-tumor effects, a therapeutic tumor challenge with B16 OVA melanoma was performed. RESULTS: The combination of s.c. anti-CTLA-4 antibody and TCI leads to an enhanced systemic cytotoxic response, to memory formation and allows significantly improved survival in a tumor setting with B16 OVA melanoma. Towards the mechanism, we show that in this vaccination protocol the CTLA-4 antibody acts mainly Treg-independent. CONCLUSION: We demonstrate that the combination of TCI with IMI-Sol and anti-CTLA-4 can confer potent immune responses and tumor-protection. These results might contribute to the development of advanced vaccination approaches targeting tumors or persistent infectious diseases.

RNA and a cell wall component of Enterococcus faecalis IC-1 are required for phagocytosis and interleukin 12 production by the mouse macrophage cell line J774.1.

Enterococcus faecalis is a resident lactic acid bacterium in the human intestine. Its immunostimulatory action was reported to be enhanced by heat sterilization. To investigate its beneficial actions, we evaluated the ability of 10 E. faecalis strains to induce interleukin-12 (IL-12) production in a mouse macrophage cell line, J774.1 and found that the strain, E. faecalis IC-1, had a potent IL-12-inducing ability. Furthermore, we investigated the underlying mechanism by treating IC-1 cells with RNase or lysozyme. Its activity almost disappeared and an antagonist of Toll-like receptor (TLR) 7 inhibited this activity. Moreover, lysozyme-treated IC-1 bacteria were not phagocytized by J774.1 cells, and did not induce IL-12 production. Based on our results, we propose that macrophages recognize the cell wall components of IC-1, leading to phagocytosis. The IC-1 RNA is then recognized by TLR7, which induces the production of IL-12.

Increased number of mast cells in the dermis in actinic keratosis lesions effectively treated with imiquimod.

Actinic keratosis (AK) is a cutaneous cancer in situ which develops as a result of excessive exposure to ultraviolet (UV). Toll-like receptor (TLR)7 agonist imiquimod is a topical immune response modifier and is effective for the treatment of non-melanoma skin cancers. Recently, the diagnostic role of the dermatoscope has been reported in the course of treatment of AK. In addition, mast cells are now considered to contribute to both the innate and adaptive immune systems in topical imiquimod therapy. We assessed the effect of imiquimod treatment by dermatoscopic and immunohistochemical findings in 14 patients with a total of 21 AK lesions. With the dermatoscope, though the mean erythema score was not significantly different between the cured lesions and the unresponsive lesions, the erythema/red pseudo-network ("strawberry") pattern was decreased significantly in the cured lesions. By immunohistochemistry, the number of Ki-67-positive proliferative cells in the epidermis was decreased and that of CD117-positive mast cells in the dermis was increased in the responding lesions. To the best of our knowledge, this is the first study demonstrating that the number of mast cells in the dermis was increased in AK lesions effectively treated with imiquimod. Our present result suggests that mast cells may contribute an antitumor effect in human skin treated with topical imiquimod.

TLR7 Agonist GS-9620 Is a Potent Inhibitor of Acute HIV-1 Infection in Human Peripheral Blood Mononuclear Cells.

GS-9620 is a potent and selective oral Toll-like receptor 7 (TLR7) agonist that directly activates plasmacytoid dendritic cells (pDCs). GS-9620 suppressed hepatitis B virus (HBV) in animal models of chronic infection and transiently activated HIV expression ex vivo in latently infected peripheral blood mononuclear cells (PBMCs) from virally suppressed patients. Currently, GS-9620 is under clinical evaluation for treating chronic HBV infection and for reducing latent reservoirs in virally suppressed HIV-infected patients. Here, we investigated the in vitro anti-HIV-1 activity of GS-9620. GS-9620 potently inhibited viral replication in PBMCs, particularly when it was added 24 to 48 h prior to HIV infection (50% effective concentration = 27 nM). Depletion of pDCs but not other immune cell subsets from PBMC cultures suppressed GS-9620 antiviral activity. Although GS-9620 was inactive against HIV in purified CD4+ T cells and macrophages, HIV replication was potently inhibited by conditioned medium derived from GS-9620-treated pDC cultures when added to CD4+ T cells prior to infection. This suggests that GS-9620-mediated stimulation of PBMCs induced the production of a soluble factor(s) inhibiting HIV replication in trans GS-9620-treated PBMCs primarily showed increased production of interferon alpha (IFN-α), and cotreatment with IFN-α-blocking antibodies reversed the HIV-1-inhibitory effect of GS-9620. Additional studies demonstrated that GS-9620 inhibited a postentry event in HIV replication at a step coincident with or prior to reverse transcription. The simultaneous activation of HIV-1 expression and inhibition of HIV-1 replication are important considerations for the clinical evaluation of GS-9620 since these antiviral effects may help restrict potential local HIV spread upon in vivo latency reversal.