TLR7 is expressed by support cells, but not sensory neurons, in ganglia.

BACKGROUND: Toll-like receptor 7 (TLR7) is an innate immune receptor that detects viral single-stranded RNA and triggers the production of proinflammatory cytokines and type 1 interferons in immune cells. TLR7 agonists also modulate sensory nerve function by increasing neuronal excitability, although studies are conflicting whether sensory neurons specifically express TLR7. This uncertainty has confounded the development of a mechanistic understanding of TLR7 function in nervous tissues. METHODS: TLR7 expression was tested using in situ hybridization with species-specific RNA probes in vagal and dorsal root sensory ganglia in wild-type and TLR7 knockout (KO) mice and in guinea pigs. Since TLR7 KO mice were generated by inserting an Escherichia coli lacZ gene in exon 3 of the mouse TLR7 gene, wild-type and TLR7 (KO) mouse vagal ganglia were also labeled for lacZ. In situ labeling was compared to immunohistochemistry using TLR7 antibody probes. The effects of influenza A infection on TLR7 expression in sensory ganglia and in the spleen were also assessed. RESULTS: In situ probes detected TLR7 in the spleen and in small support cells adjacent to sensory neurons in the dorsal root and vagal ganglia in wild-type mice and guinea pigs, but not in TLR7 KO mice. TLR7 was co-expressed with the macrophage marker Iba1 and the satellite glial cell marker GFAP, but not with the neuronal marker PGP9.5, indicating that TLR7 is not expressed by sensory nerves in either vagal or dorsal root ganglia in mice or guinea pigs. In contrast, TLR7 antibodies labeled small- and medium-sized neurons in wild-type and TLR7 KO mice in a TLR7-independent manner. Influenza A infection caused significant weight loss and upregulation of TLR7 in the spleens, but not in vagal ganglia, in mice. CONCLUSION: TLR7 is expressed by macrophages and satellite glial cells, but not neurons in sensory ganglia suggesting TLR7's neuromodulatory effects are mediated indirectly via activation of neuronally-associated support cells, not through activation of neurons directly. Our data also suggest TLR7's primary role in neuronal tissues is not related to antiviral immunity.

Copy number of the X-linked genes TLR7 and CD40L influences innate and adaptive immune responses.

The number of the X chromosome-linked genes has been previously suggested to influence immune responses and the development of autoimmune diseases. In the present study, we aimed at evaluating the level of expression of CD40L (an X-linked gene involved in adaptive immunity) and TLR7 (an X-linked gene involved in innate immunity) in a variety of different karyotypes. Those included males, females and patients with X chromosome aneuploidy. Healthy females (46, XX; n = 10) and healthy males (46, XY; n = 10) were compared to females with Turner syndrome (TS) (45, X; n = 11) and males with Klinefelter syndrome (KS) (47, XXY; n = 5). Stimulation of peripheral blood mononuclear cells (PBMCs) with PMA and ionomycin resulted in higher percentage of CD3 + CD40L+ T cells (P < 0.001) and higher level expression of CD40L in T cell (P < 0.001) in female and KS patients compared with male and TS patients. TLR7-mediated IFN-alpha production by HLADR + CD3- CD19- cells was significantly upregulated in healthy women compared with healthy males, TS and KS patients (P < 0.001). TLR7 agonist-stimulated PBMCs from healthy females and KS patients expressed significantly higher levels of TLR7 mRNA than those from male and TS patients (P < 0.05). The increased expression of the X-linked genes TLR7 and CD40L in healthy females and KS patients suggests that the presence of two X chromosomes plays a major role in enhancing both innate and adaptive immune responses. These results may contribute to the explanation of sex-based differences in immune biology and the sex bias in predisposition to autoimmune diseases.

Respiratory syncytial virus infection up-regulates TLR7 expression by inducing oxidative stress via the Nrf2/ARE pathway in A549 cells.

In order to better understand the early pathways of the pathogenesis of, and immune response to, RSV, herein, we explored the relationship between TLR7 expression and oxidative stress induction following RSV infection in A549 cells. We studied the intervening effects of the Nrf2/ARE pathway agonist butylated hydroxyanisole (BHA) and inhibitor trigonelline (TRI) on TLR7 modulation or oxidative stress induction. For comparison purposes, we set up seven treatment groups in this study, including RSV-treated cells, BHA + RSV-treated cells, TRI + RSV-treated cells, normal cell controls, inactivated RSV controls, BHA controls and TRI controls. We measured changes in TLR7, IL-6, TNF-α mRNA using RT-PCR and IL-6, TNF-α and IL-1ß protein using ELISA as well as TLR7, Nrf2 and HO-1 protein using Western blot in A549 cells from the different treatment groups. We also assessed changes in cell proliferation and measured changes in ·OH and NO in A549 cells from the different treatment groups. The results indicate that TLR7 up-regulation is related to RSV infection and the induction of oxidative stress and that TLR7 expression was mediated by the anti-inflammatory effects of Nrf2/ARE pathway inhibitors or agonists. Our experiments may help elucidate the underlying pathology of RSV infection and suggest potential therapeutic targets for drug development and the prevention of RSV-induced human diseases.

Toll-like receptor 5 and 7 expression may impact prognosis of HPV-positive oropharyngeal squamous cell carcinoma patients.

A large subset of oropharyngeal squamous cell carcinomas (OPSCCs) is associated with HPV infection and has better outcome than non-viral-related tumors. Various malignancies also carry a role for TLRs, key activators of inflammation and innate immunity. We examined the expression of TLRs in OPSCC, and their association with HPV status and treatment outcome. TLR 5, 7, 9, and p16 were studied by immunohistochemistry and HPV status was detected with in situ hybridization in 202 tumors of consecutively treated OPSCC patients using tissue microarray method. The relations between TLR expression and HPV status, p16 expression, clinicopathological factors, and survival were analyzed. TLR 5, 7, and 9 expression patterns differed between HPV-positive and -negative tumors, and they were statistically significantly associated with history of smoking, heavy drinking, tumor site, grade, size (T), metastasis (N), and stage. Moreover, in HPV-positive tumors the expression of TLR 5 and 7 correlated with tumor recurrence. After adjustment, among HPV-positive OPSCC patients, high TLR 5 and low TLR 7 expression were associated with poor disease-specific survival. Our results indicate that TLR 5 and 7 may have a role in the prognostication of HPV-positive OPSCC, however, further studies are needed to clarify the comprehensive role of these TLRs in OPSCC.

Toll-Like Receptor 7 Staining in Malignant Epithelial Tumors.

BACKGROUND: As important players of the innate immune system, Toll-like receptors (TLRs) and their role for tumorigenesis have been in the focus of research. In particular TLR7 is an interesting candidate, as TLR7 agonists are broadly used for the treatment of cutaneous tumors. However, data addressing the baseline expression of TLR7 in both basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) on the protein level are lacking, while on the genomic level significantly elevated expression of TLR7 in SCC but not in BCC has been demonstrated. AIM: Our aim was to characterize the immunohistochemical staining pattern of TLR7 in SCC and BCC. Besides, we aimed to clarify if, in case of different TLR7 expression between SCC and BCC, TLR7 expression would help to define basosquamous carcinoma (BSC), a tumor entity sharing characteristics of both SCC and BCC. METHODS: We examined histopathological samples from 23 BCC, 4 BSC, and 24 SCC and characterized the expression of TLR7 by immunohistochemistry and immunofluorescence. RESULTS: We found that TLR7 was not expressed by the tumor tissue of SCC, BCC, and BSC, but by inflammatory cells located within the tumoral and/or peritumoral tissue. Whereas the overall expression of TLR7 did not differ between BCC and SCC (30.4% vs. 45.8%, respectively), we found that within the group of SCC, the well-differentiated SCC showed strong tumoral and/or peritumoral immunocellular TLR7 reactivity in contrast to the poorly differentiated SCC (73.33% vs. 11.1%, respectively). Besides, immunofluorescence double staining revealed the expression of TLR7 in immune cells closely interacting with T cells and natural killer cells. CONCLUSIONS: In contrast to genomic data, we did not find a general difference between baseline TLR7 expression of SCC and BCC on the protein level. Nevertheless, the expression of TLR7 by the inflammatory infiltrate associated with SCC may correlate with the degree of differentiation of SCC possibly indicating better outcome.

Predictive value of TLR7 polymorphism for cetuximab-based chemotherapy in patients with metastatic colorectal cancer.

The TLR7 and TLR9 signalings are implicated in the regulation of the immune system through type-I interferon induction. Preclinical studies have demonstrated the immunomodulatory and antitumor effects of TLR7 and TLR9 agonists in combination with cetuximab. We tested the hypothesis that genetic variations in TLR7 and TLR9 and their downstream molecules IRF5 and IRF7 were associated with outcomes in metastatic colorectal cancer (mCRC) patients receiving cetuximab-based chemotherapy. Six single nucleotide polymorphisms (SNPs) in TLR7, TLR9, IRF5 and IRF7 were tested for the association with RR, PFS, and OS in KRAS-wild type mCRC patients. Patients treated with FOLFIRI + cetuximab or FOLFIRI + bevacizumab in the FIRE-3 trial served as a discovery set (FIRE3-Cet, n = 244) or a control set (FIRE3-Bev, n = 246), respectively. Patients treated with FOLFOX or SOX + cetuximab in the JACCRO-CC05/06 trial served as a validation set (JACCRO, n = 76). Genomic DNA isolated from tumor tissue samples was analyzed by PCR-based direct sequencing. In the discovery cohort, patients with the TLR7 rs3853839 G/G variant showed a trend toward longer PFS than those with any C variants (median 10.0 vs. 11.8 months, HR 1.39, p = 0.092). This preliminary association was confirmed in the validation cohort, and those with the G/G genotype showed a PFS benefit compared with others (univariate: 9.1 vs. 11.6 months, HR 2.04, p = 0.005, multivariate: HR 2.02, 95% CI: 1.14-3.55, p = 0.015). This association was not observed in the control cohort. Our findings suggest that TLR7 rs3853839 predicts the outcome of cetuximab-based chemotherapy in mCRC patients.

Toll-like receptor 5 and 7 expression in adenoid cystic carcinoma of major salivary glands.

Adenoid cystic carcinoma (ACC) of the salivary glands has a poor long-term prognosis and high metastatic rate. Toll-like receptors (TLRs) have been related to tumour progression but have also tumour growth-inhibiting responses. To the best of our knowledge, they have not been studied previously in ACC. We studied the immunoexpression of TLR 5 and 7 in ACC of the major salivary glands. From a cohort of 54 patients with ACC of the major salivary glands treated at the Department of Otorhinolaryngology-Head and Neck Surgery, Helsinki University Hospital, Helsinki, Finland in 1974-2009, there were 34 primary tumours and six metastases available for immunohistochemical analysis. Immunohistochemical expression of TLR 5 and 7 were correlated to clinicopathological findings and patient survival. Both TLR 5 and 7 were expressed in ACCs and their metastases, mostly on the cell membranes. The expression was heterogeneous in individual tumours. TLR 5 was expressed less in male samples, and TLR 7 had lower expression in ACCs with solid growth pattern. No correlation with survival was found. In the normal salivary gland, the TLR 5 and 7 expression was mainly negative. Both TLR 5 and 7 are expressed in salivary adenoid cystic carcinoma on the cell membranes as well as in cytoplasm.

[Preliminary study on the expression of Toll-like receptors 7 and 8 in bladder urothelial tumors]. / Studio preliminare sull'espressione dei Toll-like receptors 7 e 8 nel tumore uroteliale della vescica.

The aim of the study was to demonstrate the expression of Toll-like receptor (TLR)-8 and to confirm the expression of TLR-7 on bladder transitional cell carcinomas (TCCs) analyzing the changes in expression between low-grade (LG) and high-grade (HG) and between non-muscle invasive (NMIBC) and muscle-invasive (MIBC) bladder cancers. In our study, 25 patients who underwent transurethral resection (TURB) for bladder TCC have been selected. Thirteen of those had an LG form,while the other cases were classified as HG; the lesions were NMIBC in 18 patients and MIBC in the others seven. The analysis of TLRs expression has been performed by immuno histochemistry. TRL-8 expression seems to be higher in MIBC (85%) than in NMIBC (78%), but it is associated with a reduced percentage of immuno reactive cells and with a lower intensity. The expression had a large nuclear localization in NMIBC (80%), althoughit was mainly cytoplasmic in MIBC (72%). TLR-7 was expressed in all NMIBC samples (where the localization was mainly nucleo-cytoplasmic) and in the 71% of MIBC samples (mainly in the nucleus). A higher expression of TRL-8 in HG TCC had been observed, while TRL-7 seems to be more expressed in LG forms. Our study allowed to document the immunohistochemical expression of TLR-8 in TCCs, confirm the immunohistochemical expression of TLR-7, and suggest an increased expression of TLR-7 in LG TCC and NMIBC, and a prevalent expression of TLR-8 in HG TCC and MIBC.

The expression of Toll-like receptors 2, 4, 5, 7 and 9 in Merkel cell carcinoma.

AIM: We sought to clarify whether the expression of toll-like receptors (TLR) in Merkel cell carcinoma (MCC) is linked to tumor and patient characteristics, especially the presence of Merkel cell polyoma virus (MCV). MATERIALS AND METHODS: The study comprised of 128 patients with data on Merkel cell polyomavirus (MCV) status and clinical features were included in the study. Immunohistochemistry for TLR expression was performed on tissue microarray (TMA) slides. RESULTS: TLR 2, 4, 5, 7 and 9 expression was noted in most of the tumor specimens. Decreased expression of TLR 9 correlated strongly with MCV positivity. Cytoplasmic TLR 2 expression correlated with small tumor size, while nuclear TLR 2 and TLR 5 expressions with larger tumors. Increased nuclear TLR 4 expression and decreased TLR 7 expression were associated with older age. CONCLUSION: TLR 2, 4, 5, 7 and 9 appear to reflect certain clinicopathological variables and prognostic markers of MCC tumors.

Distinct expression patterns of Toll-like receptor 7 in tumour cells and fibroblast-like cells in oral squamous cell carcinoma.

AIMS: Toll-like receptor (TLR)-7 agonists have been used in cancer immunotherapy, but tumour heterogeneity means that TLR-7 activity is variable in different components of the tumour microenvironment and the characteristics of TLR-7 in oral squamous cell carcinoma (OSCC) are unclear. METHODS AND RESULTS: Twenty healthy oral tissues, 50 oral leukoplakia tissues and 166 retrospective primary OSCC samples were collected for immunohistochemical staining of TLR-7 and showed up-regulated expression during carcinogenesis. Moreover, patients with high expression of TLR-7 in tumour cells (TCs) had poor differentiation and prognosis. Interestingly, patients with high expression of TLR-7 in stroma fibroblast-like cells (FLCs) had low tumour stage, no lymph node metastasis (LNM) and better prognosis. Furthermore, Ki-67, CD3, CD4, CD8 and forkhead box protein 3 (FoxP3)(+) tumour-infiltrated lymphocytes were assessed and we found that TLR-7(high) TCs were infiltrated by fewer CD3(+) CD4(+) but more FoxP3(+) lymphocytes. Importantly, patients with TLR-7(low) TCs and TLR-7(high) FLCs had less FoxP3(+) lymphocyte infiltration and longer survival time than those with TLR-7(high) TCs/TLR-7(low) FLCs, although TLR-7 was not an independent prognostic factor for OSCC. CONCLUSIONS: The low expression of TLR-7 in tumour and high expression of TLR-7 in stroma predict a good clinical outcome for OSCC patients, and stroma FLCs might be amenable to immunotherapy by a TLR-7 agonist.

Expression of microRNA-155 correlates positively with the expression of Toll-like receptor 7 and modulates hepatitis B virus via C/EBP-ß in hepatocytes.

Effective recognition of viral infection and successive activation of antiviral innate immune responses are vital for host antiviral defence, which largely depends on multiple regulators, including Toll-like receptors (TLRs) and microRNAs. Several early reports suggest that specific TLR-mediated immune responses can control hepatitis B virus (HBV) replication and express differentially with disease outcome. Considering the versatile function of miR-155 in the TLR-mediated innate immune response, we aimed to study the association between miR-155 and TLRs and their subsequent impact on HBV replication using both a HBV-replicating stable cell line (HepG2.2.15) and HBV-infected liver biopsy and serum samples. Our results showed that miR-155 was suppressed during HBV infection and a subsequent positive correlation of miR-155 with TLR7 activation was noted. Further, ectopic expression of miR-155 in vitro reduced HBV load as evidenced from reduced viral DNA, mRNA and subsequently reduced level of secreted viral antigens (HBsAg and HBeAg). Our results further suggested that CCAAT/enhancer-binding protein-ß (C/EBP-ß), a positive regulator of HBV transcription, was inhibited by miR-155. Taken together, our study established a correlation between miR-155 and TLR7 during HBV infection and also demonstrated in vitro that increased miR-155 level could help to reduce HBV viral load by targeting C/EBP-ß.

TLR9 is expressed in human papillomavirus-positive cervical cells and is overexpressed in persistent infections.

Control of human papillomavirus (HPV) infection involves the activation of Toll-like receptors (TLRs), key components of the mucosal antiviral response. Available studies on TLR expression in HPV-positive cervical cells are limited and reported conflicting results. This study quantified TLR 2, 3, 4, 7 and 9 transcripts in low-risk (LR) and high-risk (HR) HPV-positive and HPV-negative cervical samples from 154 women attending a gynaecological clinic. Expression levels of TLR 2, 3, 4 and 7 did not differ among samples, whereas TLR9 levels were quite significantly higher in LR and marginally significant in HR HPV-positive samples, with respect to the HPV-negative samples. Interestingly, in a subgroup of women with documented previous HPV-infection, TLR9 levels were extremely higher in patients persistently positive to the same HPV genotype for more than 1 year, with respect to women who cleared HPV infection and to those re-infected with a different genotype. These findings implicate TLR9 in the response to LR and HR HPVs, including HPV 16 known to interfere with TLR9 transcription in cell lines. Elevated TLR9 levels without HPV clearance in persistently infected women could drive inflammation thereby contributing to cervical cancer risk.

Modulation of TLR 3, 7 and 8 expressions in HCV genotype 3 infected individuals: potential correlations of pathogenesis and spontaneous clearance.

BACKGROUND: Hepatitis C virus is the major cause of chronic hepatitis worldwide which finally leads to the development of hepatocellular carcinoma. Toll like receptors (TLRs) play an important role in the course of many viral infections, but the role of TLRs in HCV pathogenesis has not been well elucidated so far. OBJECTIVE: The aim of this study was to analyse the mRNA expression of TLRs 3, 7, and 8 in different stages of HCV infection including chronic, cirrhosis, interferon treated resolved, and relapsed cases. METHODOLOGY: Total RNA from whole blood was extracted and mRNA expression of TLRs 3, 7, and 8 genes was analyzed by quantitative real-time RT-PCR using ß-Actin gene as an internal control. RESULTS: This study consisted of 100 HCV infected individuals and twenty healthy controls. TLR 3 expression was found to be significantly elevated in individuals who had spontaneously cleared the virus (p < 0.001), whereas TLR 7 was found to be 3.26 times more elevated in patients with cirrhosis of liver. In IFN induced individuals, TLR 8 expression levels were found to be 2.28-fold elevated as compared to control population. CONCLUSION: TLRs 3, 7, and 8 are prime biomarker candidates for HCV infection mRNA expression analysis which might improve current therapeutic approaches.

Tamoxifen downregulates MxA expression by suppressing TLR7 expression in PBMCs of males infected with HCV.

Gender discrepancies in immune response to HCV infections and during HCV therapy exist and previous findings including those from this research team indicate the female sex hormone, 17ß-estradiol (E2), to be one probable cause of such inconsistencies. Also, it was recently demonstrated that estrogen receptor modulator Tamoxifen (TAM) exerts an upmodulating/enhancing effect on the TLR7 and JAK-STAT pathways in PBMCs of premenopausal females infected with HCV. Pursuing this work, a discrepancy was noticed in the results from male patients, therefore this study aimed to determine whether the effects of TAM previously observed in the PBMCs of women would hold true in PBMCs from males infected with HCV. Isolated PBMCs were pooled and relative expression of the TLR7 was quantified using RTqPCR. Sets of PBMCs were treated with exogenous interferon alpha (IFNα) or the TLR7 ligand, Imiquimod; these stimulations were performed with and without E2 and TAM pretreatment and the relative gene expressions of TLR7 and MxA were measured. Pretreatment with E2 and IFNα downregulated TLR7 (**P = 0.0080) and TAM further decreased this expression significantly (*P = 0.0284). TAM pretreatment also caused a significant downregulation in MxA expression in Imiquimod-stimulated PBMCs (*P = 0.0218). In conclusion, TAM displays several paradoxical effects in PBMCs of males infected with HCV compared to those of females. Contrary to the previous study involving premenopausal females, in PBMCs of infected males TAM may decrease IFNα release as indicated by reduced MxA expression possibly via the suppression of TLR7 expression.

Cutting edge: Type I IFN drives emergency myelopoiesis and peripheral myeloid expansion during chronic TLR7 signaling.

Mice overexpressing TLR7 (TLR7.1 mice) are a model of systemic lupus erythematosus pathogenesis and exhibit peripheral myeloid expansion. We show that TLR7.1 mice have a dramatic expansion of splenic cells that derive from granulocyte/macrophage progenitors (GMP) compared with wild-type mice. In the bone marrow, TLR7.1 mice exhibited hallmarks of emergency myelopoiesis and contained a discrete population of Sca-1(+) GMP, termed emergency GMP, which are more proliferative and superior myeloid precursors than classical Sca-1(-) GMP. The emergency myelopoiesis and peripheral myeloid expansion in TLR7.1 mice was dependent on type I IFN signaling. TLR7 agonist administration to nontransgenic mice also drove type I IFN-dependent emergency myelopoiesis. TLR7.1 plasmacytoid dendritic cells were cell-intrinsically activated by TLR7 overexpression and constitutively produced type I IFN mRNA. This study shows that type I IFN can act upon myeloid progenitors to promote the development of emergency GMP, which leads to an expansion of their progeny in the periphery.

Ligation of TLR7 by rheumatoid arthritis synovial fluid single strand RNA induces transcription of TNFα in monocytes.

OBJECTIVE: The aim of the study was to characterise the expression, regulation and pathogenic role of toll-like receptor 7 (TLR7) and TLR8 in rheumatoid arthritis (RA). METHODS: Expression of TLR7 and TLR8 was demonstrated in RA, osteoarthritis (OA) and normal (NL) synovial tissues (STs) employing immunohistochemistry. The authors next examined the mechanism by which TLR7 and TLR8 ligation mediates proinflammatory response by Western blot analysis and ELISA. Expression of TLR7 and TLR8 in RA monocytes was correlated to disease activity score (DAS28) and tumour necrosis factor α (TNFα) levels. Further, the effect of TLR7 ligation in RA monocytes was determined on synovial fluid (SF)-mediated TNFα transcription. RESULTS: TLR7/8 are predominately expressed in RA ST lining and sublining macrophages. The authors show that NF-κB and/or PI3K pathways are essential for TLR7/8 induction of proinflammatory factors in RA peripheral blood (PB)-differentiated macrophages. Expression of TLR7 in RA monocytes shows a strong correlation with DAS28 and TNFα levels. By contrast, expression of TLR8 in these cells does not correlate with DAS28, TLR7 or TNFα levels. The authors further demonstrate that RNA from RA SF, but not RA or NL plasma, could modulate TNFα transcription from RA monocytes that can be downregulated by antagonising TLR7 ligation or degradation of single stand (ss) RNA. Thus, ssRNA present in RA SF may function as a potential endogenous ligand for TLR7. CONCLUSIONS: These results suggest that expression of TLR7, but not TLR8, may be a predictor for RA disease activity and anti-TNFα responsiveness, and targeting TLR7 may suppress chronic progression of RA.

B cell TLR7 expression drives anti-RNA autoantibody production and exacerbates disease in systemic lupus erythematosus-prone mice.

Systemic lupus erythematosus (SLE) is a chronic systemic autoimmune disease characterized by the production of antinuclear autoantibodies. Antinuclear autoantibody development is recognized as one of the initial stages of disease that often results in systemic inflammation, kidney disease, and death. The etiology is complex, but it is clear that innate pathways may play an important role in disease progression. Recent data have highlighted an important role for the TLR family, particularly TLR7, in both human disease and murine models. In this study, we have presented a low copy conditional TLR7 transgenic (Tg7) mouse strain that does not develop spontaneous autoimmunity. When we combine Tg7 with the Sle1 lupus susceptibility locus, the mice develop severe disease. Using the CD19(Cre) recombinase system, we normalized expression of TLR7 solely within the B cells. Using this method we demonstrated that overexpression of TLR7 within the B cell compartment reduces the marginal zone B cell compartment and increases B and T cell activation but not T follicular helper cell development. Moreover, this enhanced B cell TLR7 expression permits the specific development of Abs to RNA/protein complexes and exacerbates SLE disease.

Imiquimod suppresses propagation of herpes simplex virus 1 by upregulation of cystatin A via the adenosine receptor A1 pathway.

Imiquimod is recognized as an agonist for Toll-like receptor 7 (TLR7) in immunocompetent cells. TLR7, as well as TLR3 and TLR8, triggers the immune responses, such as the production of type I interferons (IFNs) and proinflammatory cytokines via recognition of viral nucleic acids in the infected cells. In this study, we proposed that imiquimod has an IFN-independent antiviral effect in nonimmune cells. Imiquimod, but not resiquimod, suppressed replication of human herpes simplex virus 1 (HSV-1) in FL cells. We analyzed alternation of gene expression by treatment with imiquimod using microarray analysis. Neither type I IFNs, nor TLRs, nor IFN-inducible antiviral genes were induced in imiquimod-treated FL cells. Cystatin A, a host cysteine protease inhibitor, was strongly upregulated by imiquimod and took a major part in the anti-HSV-1 activity deduced by the suppression experiment using its small interfering RNA. Upregulation of cystatin A was suggested to be mediated by antagonizing adenosine receptor A(1) and activating the protein kinase A pathway. Imiquimod, but not resiquimod, was shown to interact with adenosine receptor A(1). Imiquimod-induced anti-HSV-1 activity was observed in other cells, such as HeLa, SiHa, and CaSki cells, in a manner consistent with the cystatin A induction by imiquimod. These results indicated that imiquimod acted as an antagonist for adenosine receptor A(1) and induced a host antiviral protein, cystatin A. The process occurred independently of TLR7 and type I IFNs.

Induction and activation of antiviral enzyme 2',5'-oligoadenylate synthetase by in vitro transcribed insulin mRNA and other cellular RNAs.

Double-stranded RNA (dsRNA) can induce antiviral enzyme 2',5'-oligoadenylate synthetase (2'5'AS) expression and activate latent 2'5'AS. Our previous data have shown pancreatic ß cells are sensitive to dsRNA-induced 2'5'AS expression, and constitutive high basal 2'5'AS expression is associated with susceptibility to developing type 1 diabetes (T1D), a disease due to pancreatic ß cell loss. Here we report that in vitro transcribed human insulin mRNA induces the activation of human OAS gene promoter sequences, and specifically and dose-dependently induces 2'5'AS expression in murine pancreatic ßTC3 cells. Over-expression of dsRNA receptor retinoic acid-inducible gene-1 enhances insulin mRNA-induced 2'5'AS expression. In vitro transcribed insulin and other mRNAs, as well as total cellular RNAs, activate latent 2'5'AS in vitro with activation ability likely associated with the sequence and length of individual mRNAs or the sample source of total cellular RNA. Insulin mRNA does not show any specificity to activate 2'5'AS, but total cellular RNA from ßTC3 cells has high activation ability. Constitutive 2'5'AS expression in ßTC3 cells leads to cell proliferation inhibition and apoptosis. Our study suggests the possibility of cellular RNA-regulated 2'5'AS expression and activation, and the potential risk of high insulin gene transcription in pancreatic ß cells, and may help explain genetic predisposition to T1D associated with INS VNTR class I alleles.

R-848 triggers the expression of TLR7/8 and suppresses HIV replication in monocytes.

BACKGROUND: Toll-like receptors (TLR) 7 and 8 are important in single-stranded viral RNA recognition and may play a role in HIV infection and disease progression. We analyzed TLR7/8 expression and signaling in monocytes from HIV-infected and uninfected subjects to investigate a pathway with new potential for the suppression of HIV replication. METHODS: Eighty-one HIV-infected and uninfected subjects from Liaoning and Henan provinces in China participated in this study. Monocytes were isolated from subjects' peripheral blood mononuclear cells by magnetic bead selection. TLR7 and TLR8 mRNA was measured using quantitative real-time reverse transcriptase PCR. R-848 (resiquimod) was used as a ligand for TLR7 and TLR8 in order to 1) assess TLR7/8-mediated monocyte responsiveness as indicated by IL-12 p40 and TNF-α secretion and 2) to examine HIV replication in cultured monocytes in the presence of R-848. RESULTS: We found that expression of TLR7/8 mRNA in peripheral blood monocytes decreased with disease progression. TLR7 expression was decreased with stimulation with the TLR7/8 agonist, R-848, in vitro, whereas TLR8 expression was unaffected. Following R-848 stimulation, monocytes from HIV-infected subjects produced significantly less TNF-α than those from uninfected subjects, but trended towards greater production of IL-12 than stimulated monocytes from uninfected subjects. R-848 stimulation also suppressed HIV replication in cultured monocytes. CONCLUSIONS: Our study provides evidence that the TLR7 and TLR8 triggering can suppress HIV replication in monocytes and lead to postpone HIV disease progression, thereby offering novel targets for immunomodulatory therapy.