Mammalian Toll-like receptors: to immunity and beyond

Probiotic therapy: immunomodulating approach toward urinary tract infection

Urinary tract infection (UTI) is an extremely common health problem, with an unpredictable history. Members of enterobacteriaceae family such as Escherichia coli, which are normal inhabitants of human intestines, account for the majority of these uncomplicated infections. Rarely, UTI can result from virus or fungus. There is a close correlation between loss of the normal genital microbiota, particularly Lactobacillus species, and an increased incidence of genital and bladder infections. Although antimicrobial agents are generally effective in eradicating these infections, there is a high incidence of recurrence. Use of Lactobacillus species to combat UTI is now giving modern concept of modern genitourinary vaccine with the facts that it not only maintains low pH of the genital area, produces hydrogen peroxide and hinders the growth of E. coli but also activates Toll-like receptor-2 (TLR2), which produces interleukin-10 (IL-10) and myeloid differentiation factor 88 (MyD88). E. coli activates TLR4, which is responsible for the activation of IL-12, extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK). This process downregulates inflammatory reactions caused due to pathogens. Current review covers the probiotics-based TLR therapy and shed some knowledge for the use of Lactobacillus species as probiotics.

Antigen-dependent and -independent mechanisms of T and B cell hyperactivation during chronic HIV-1 infection

Continuous loss of CD4(+) T lymphocytes and systemic immune activation are hallmarks of untreated chronic HIV-1 infection. Chronic immune activation during HIV-1 infection is characterized by increased expression of activation markers on T cells, elevated levels of proinflammatory cytokines, and B cell hyperactivation together with hypergammaglobulinemia. Importantly, hyperactivation of T cells is one of the best predictive markers for progression toward AIDS, and it is closely linked to CD4(+) T cell depletion and sustained viral replication. Aberrant activation of T cells is observed mainly for memory CD4(+) and CD8(+) T cells and is documented, in addition to increased expression of surface activation markers, by increased cell cycling and apoptosis. Notably, the majority of these activated T cells are neither HIV specific nor HIV infected, and the antigen specificities of hyperactivated T cells are largely unknown, as are the exact mechanisms driving their activation. B cells are also severely affected by HIV-1 infection, which is manifested by major changes in B cell subpopulations, B cell hyperactivation, and hypergammaglobulinemia. Similar to those of T cells, the mechanisms underlying this aberrant B cell activation remain largely unknown. In this review, we summarized current knowledge about proposed antigen-dependent and -independent mechanisms leading to lymphocyte hyperactivation in the context of HIV-1 infection.

Induction of toll-like receptor 2 positive antigen-presenting cells in spleen of pristane-induced arthritis in rats

Toll-like receptors (TLRs) have been found to contribute to the pathogenesis of rheumatoid arthritis (RA). The aim of this study is to investigate the regulation and potential role of TLR2 in spleen of pristane-induced arthritis (PIA) rat, which can be used to further understand the mechanisms of RA. Arthritis in DA rats was induced by pristane. TLR2 expression in spleen was detected by real-time quantitative PCR and western blotting, and TLR2 expression at both mRNA and protein levels was upregulated in PIA rats. Peptidoglycan (PGN) was systemically administrated to PIA rats, and arthritis severity was evaluated macroscopically and microscopically. Results showed that systemic administration of PGN to PIA rats obviously deteriorated arthritis severity. TLR2 expression on splenocytes and different types of immune cells was measured by flow cytometry. And it was found that TLR2 was mainly expressed on antigen-presenting cells (APCs) of spleen, and the proportion of TLR2(+) dendritic cells and macrophages in spleen of PIA rats was increased remarkably. Thus, we conclude that the induction of TLR2(+) APCs in spleen may participate in the maintenance of PIA.

Increased expression of toll-like receptors (TLR) 2, 4 and 5 in gastric dysplasia

TLRs are important innate immunity receptors. Even though TLR2, 4 and 5 appear to be important for Helicobacter pylori (HP) recognition, their role in the evolution of gastritis to more advanced lesions is still unknown. To compare the expression of TLR2, 4 and 5 in normal gastric mucosa, HP+ gastritis, intestinal metaplasia, dysplasia and adenocarcinoma. Immunohistochemistry for TLR2, 4 and 5 was performed with anti-TLR2-TLR4-TLR5 antibodies in 117 histological samples of normal gastric mucosa (n = 22), HP+ gastritis (n = 20), intestinal metaplasia (n = 33), dysplasia (mucosectomy specimens, n = 20) and intestinal type adenocarcinoma (surgery specimens,n = 22); quantification of expression was performed independently by two pathologists taking into account the percentage of positive epithelial cells and the degree of expression (zero to three score). A statistically significant trend for progressive increase of TLRs expression from normal mucosa to gastric dysplasia was found (mean expression: normal mucosa 0.1; gastritis 1.0; metaplasia 2.2; dysplasia 2.8, p < 0.01). All dysplasia samples presented more than 90% positive epithelial cells with strong expression (2.8;95%CI2.7-3). There was less TLRs expression in carcinomas (TLR2:1.0; TLR4:2.0 and TLR5:1.2, p < 0.05) when compared with dysplasia, with TLR4 being more expressed than TLR2 and 5 in these lesions (p = 0.03). A score of all markers' expression of eight leads to a low (4%) false positive rate in patients with precancerous conditions. Progression of gastric lesions associated with gastric carcinogenesis is associated with increased TLRs expression. Gastric dysplasia presents a high level of TLRs expression, suggesting that these receptors may play a role in adenocarcinoma development.

Genomics of the NF-κB signaling pathway: hypothesized role in ovarian cancer

OBJECTIVE

We sought to review evidence linking nuclear factor-kappa B (NF-κB) to ovarian cancer and to identify genetic variants involved in NF-κB signaling.

METHODS

PubMed was reviewed to inform on ovarian cancer biology and NF-κB signaling and to identify key genes. Public linkage disequilibrium (LD) data were analyzed to identify informative inherited variants (tagSNPs) using ldSelect.

RESULTS

We identified 319 key NF-κB genes including five NF-κB subunits, 167 activating genes, and 55 inhibiting genes. We found that the 1000 Genomes Project was the most informative LD source for most genes (92.8%), and we identified 13,027 LD bins (r (2) ≥ 0.9, minor allele frequency ≥ 0.05) and 1,018 putative-functional variants worthy of investigation. We also report that reliance on a commonly used genome-wide SNP array and genotype imputation with HapMap Phase II data provides data on only 74% of the common inherited NF-κB SNPs of interest.

CONCLUSIONS

Compelling evidence suggests that NF-κB plays a critical role in ovarian cancer, yet inherited variation in these genes has not been thoroughly assessed in relation to disease risk or outcome. We present a collection of variants in key genes and suggest creation of a custom genotyping array as an optimal approach.

Molecular pathogenesis of endometriosis; Toll-like receptor-4 A896G (D299G) polymorphism: a novel explanation

BACKGROUND

Endometriosis is a distressing gynecological disorder. Toll-like receptor 4 (TLR4) is specific for recognition of the molecular pattern of gram-negative bacteria. TLR4 is present on the surface of endometrial cells. Their role in the molecular pathogenesis of endometriosis is postulated through a novel explanation.

OBJECTIVE

To study the TLR4 A896G polymorphism in cases of endometriosis and age- and sex-matched healthy controls and evaluate its role in the molecular pathogenesis of endometriosis.

DESIGN

Case-control study, involving patients from four gynecological centers from Hyderabad Samples: The study was carried out on 400 women who include 200 surgically confirmed cases of endometriosis and 200 healthy women volunteers in whom endometriosis was excluded by the standard diagnostic criteria.

RESULTS

An association of G allele, GG, and AG genotype of TLR4 A896G polymorphism was seen in cases of endometriosis. "G" allele was found to be significantly associated with endometriosis (odds ratio=4.4827; 95% confidence interval: 2.2829-8.8021; χ(2) p<0.0001). An eightfold increase of endometriosis risk was seen in women who carry GG genotype, whereas AA genotype can be considered as protective in our population.

CONCLUSION

TLR4 A896G polymorphism (rs4986790) is a functional polymorphism resulting in hypo-responsiveness of the receptor, thus resulting in peritoneal inflammation. The molecular microenvironment becomes favorable for the endometrial cells to adhere to the peritonium, thereby resulting in the initiation of endometriosis.

Propolis immunomodulatory action in vivo on Toll-like receptors 2 and 4 expression and on pro-inflammatory cytokines production in mice

Propolis is a bee product and its immunomodulatory action has been the subject of intense investigation lately. The recent discovery and characterization of the family of Toll-like receptors (TLR) have triggered a great deal of interest in the field of innate immunity due to their crucial role in microbial recognition and development of the adaptive immune response. This work aimed to evaluate propolis's effect on TLR-2 and TLR-4 expression and on the production of pro-inflammatory cytokines (IL-1beta and IL-6). Male BALB/c mice were treated with propolis (200 mg/kg) for three consecutive days, and TLR-2 and TLR-4 expression as well as IL-1beta and IL-6 production were assessed in peritoneal macrophages and spleen cells. Basal IL-1beta production and TLR-2 and TLR-4 expression were increased in peritoneal macrophages of propolis-treated mice. TLR-2 and TLR-4 expression and IL-1beta and IL-6 production were also upregulated in the spleen cells of propolis-treated mice. One may conclude that propolis activated the initial steps of the immune response by upregulating TLRs expression and the production of pro-inflammatory cytokines in mice, modulating the mechanisms of the innate immunity.

Alloimmune activation enhances innate tissue inflammation/injury in a mouse model of liver ischemia/reperfusion injury

The deleterious sensitization to donor MHC Ags represents one of the most challenging problems in clinical organ transplantation. Although the role of effector/memory T cells in the rejection cascade has been extensively studied, it remains unknown whether and how these 'Ag-specific' cells influence host innate immunity, such as tissue inflammation associated with ischemia and reperfusion injury (IRI). In this study, we analyzed how allogeneic skin transplant (Tx) affected the sequel of host's own liver damage induced by partial warm ischemia and reperfusion. Our data clearly showed that allo-Tx recipients had increased inflammatory response against IR insult in their native livers, as evidenced by significantly more severe hepatocelluar damage, compared with syngeneic Tx recipient controls, and determined by serum ALT levels, liver histology (Suzuki's score) and intrahepatic proinflammatory gene inductions (TNF-alpha, IL-1beta and CXCL10). The CD4 T cells, but neither CD8 nor NK cells, mediated the detrimental effect of allo-Ag sensitization in liver IRI. Furthermore, CD154, but not IFN-gamma, was the key mechanism in allo-Tx recipients to facilitate IR-triggered liver damage. These results provide new evidence that alloreactive CD4 T cells are capable of enhancing innate tissue inflammation and organ injury via an Ag-nonspecific CD154-dependent but IFN-gamma independent mechanism.

Differential induction of inflammatory cytokines by dendritic cells treated with novel TLR-agonist and cytokine based cocktails: targeting dendritic cells in autoimmunity

Background

Dendritic cells (DC) are main gate-keepers of the immune system, bridging the innate and adaptive immune system. DCs are able to mature into inflammatory DCs at sites of inflammation in both autoimmune and allergic disease, thereby sustaining a continuous activation of the adaptive immune system at sites of inflammation. This function of DCs makes them attractive target cells for therapeutic intervention in inflammatory diseases. We have designed a DC-based screening model by which drug candidates can be evaluated for their ability to suppress DC maturation into an inflammatory and disease promoting phenotype.

Methods

Human monocyte derived DCs were differentiated using IL-4 and GM-CSF to immature DCs (imDCs). The imDCs were treated with various combinations of TLR-agonists and pro-inflammatory cytokines to identify cocktails with ability to mature imDCs into inflammatory DCs. The effect of the cocktails on DC maturation was evaluated using ELISA and cytokine arrays to measure secreted cytokines and chemokines. FACS analysis was used to assess expression of maturation markers, and functional studies were carried out using naïve allogeneic T-cells to assay for a Th1-promoting DC phenotype.

Results

Nine cocktails were designed with potent ability to induce secretion of the Th1-promoting cytokines IL-12p70 and TNFα from imDCs, and three were able to induce the Th17-promoting cytokine IL-23. The cocktails were further characterized using cytokine arrays, showing induction of inflammation related cytokines and chemokines like CXCL10, CCL2, CCL4, CCL8, CCL15, CCL20 and IL-8, of which some are present in a range of autoimmune pathologies. Prostaglandin E2 secretion was identified from DCs treated with TLR agonists poly I:C and peptidoglycan, but not LPS. The cocktails were able to induce DC maturation markers like HLA-DR, CD40, CD80, CD83 and CD86, except the TLR7/8 agonist R848. Functional end-points made by co-culture of allogeneic CD4⁺ T cells with the cocktail treated DCs, showed that five cocktails in particular could induce a classical Th1-phenotype with ability to secrete high amounts of the hall-mark cytokine IFNγ. The model was validated using dexamethasone and two COX-inhibitors, which were able to suppress the cocktail driven pro-inflammatory DC maturation.

Conclusions

The identification of novel Th1-promoting cocktails allows screening of anti-inflammatory drug candidates by assessing the ability to suppress the activation and differentiation of imDCs into inflammatory DCs with a specific Th1-promoting phenotype. The model thus provides a screening tool, which can identify potential anti-inflammatory effects on the natural regulator of the immune response, the dendritic cell.

Toll-like receptors as therapeutic targets in gastrointestinal diseases

IMPORTANCE OF THE FIELD

Toll-like receptors (TLRs) are innate immunity receptors that recognize several different antigens, initiating immunological/inflammatory responses. Recent evidence associates numerous pathophysiological processes and diseases with dysregulated activation of these receptors, conferring a potential therapeutic value to their modulation.

AREAS COVERED IN THIS REVIEW

The aim of this systematic review that covers literature from the past 10 years is to address the role of TLRs in the pathophysiology of gastrointestinal (GI) diseases as well as the therapeutic potential of modulating TLRs' signaling pathways in GI pathology.

WHAT THE READER WILL GAIN

This review shows that TLRs play an important role in the pathophysiology of several GI diseases and that modulating TLRs signaling pathways may have an enormous therapeutic potential. Different methods for modulation of TLRs' activity in GI tract, with direct agonists/antagonists but also with non-specific substances, like antibiotics or probiotics, are presented.

TAKE HOME MESSAGE

Even though TLRs modulators have been used for therapy in some GI diseases, further research, particularly in humans, is needed in order to establish the precise role of the different TLRs in the diverse GI diseases and to motivate clinical trials that consider TLRs as therapeutic targets in GI pathology.

Non-healing is associated with persistent stimulation of the innate immune response in chronic venous leg ulcers

BACKGROUND

The molecular pathogenesis of chronic skin wounds is complex and not fully understood. Although these wounds are often characterized as being in a state of persistent inflammation, the impact and participation of the innate immune responses in sustaining this inflammation needs further investigation.

OBJECTIVE

We investigated the cytokine profiles, Toll-like receptor (TLR)-stimulating activities and the levels of the antibacterial peptide Lipocalin-2 (Lcn-2) in a series of healing and non-healing chronic venous leg ulcers (CVLUs) through a study time of 8 weeks.

METHODS

Wound fluids from healing and non-healing CVLUs were run on a Human Cytokine Antibody Array, and Lcn-2 levels measured with ELISA. HEK 293 cells transfected with TLR2 or TLR4 and their respective co-receptors, and human peripheral blood monocytes were then stimulated with the wound fluids from healing and non-healing venous leg ulcers.

RESULTS

Healing wounds were associated with decreasing levels of IL-1alpha, IL-1beta and MIP-1delta, whereas in non-healing wounds decreasing levels of IL-8 and MIP-1alpha were found. Accordingly, wound fluid from non-healing CVLUs contained persistent Lcn-2 levels and TLR2- and TLR4-stimulating activities, while, in healing wounds, the TLR-stimulating activities decreased over time with significantly diminished levels of Lcn-2 (p<0.005).

CONCLUSIONS

Innate immune responses contribute to the chronic inflammation in non-healing CVLUs through participation of Toll-like receptors. The levels of the antimicrobial peptide Lcn-2 in wound fluids from these ulcers are elevated as a reflection of this contribution.

Positive T cell co-stimulation by TLR7/8 ligands is dependent on the cellular environment

Toll-like receptors (TLRs) are mediators of innate immune responses detecting conserved pathogen-associated molecules. Whereas most TLRs are expressed on the cell surface, TLR3, 7, 8 and 9 are predominantly localized in endosomal compartments. Recent studies reported that TLRs are also expressed by T lymphocytes, resulting in direct co-stimulation of isolated CD4(+) T cells for example by Pam3CSK4 (TLR2 ligand) or flagellin (TLR5 ligand). We here describe enhanced IFN-γ production and T cell proliferation by anti-CD3 T cell receptor (TCR) or antigenic stimulation of purified human CD4(+) T cells upon co-culture with TLR7/8 specific single-stranded oligoribonucleotides or small molecule ligands. Surprisingly, TLR7/8 stimulation of CD4(+) T cells within a whole peripheral mononuclear cell (PBMC) environment did not result in enhanced T cell proliferation, but in a lack of proliferation that was cell-cell contact dependent. Immune cell depletion assays pointed towards a monocyte-mediated effect. Different TLR ligands influenced T cell proliferation differently. The effect of inhibition of T cell proliferation was most prominently seen for TLR7 ligands whereas the effects were minimal for TLR8 and TLR9 ligands indicating that the suppressive phenotype is unique only for certain TLRs. Our results strongly suggest that co-stimulation of T cell proliferation by TLR7/8 agonists is dependent on the specific cellular context.

Local interleukin-1-driven joint pathology is dependent on toll-like receptor 4 activation

Toll-like receptors (TLRs) may contribute to the pathogenesis of chronic inflammatory destructive diseases through the recognition of endogenous ligands produced on either inflammation or degeneration of the extracellular matrix. The presence of endogenous TLR agonists has been reported in rheumatoid joints. In the present study, we investigated the significance of TLR2 and TLR4 activation by locally- produced endogenous ligands in the severity of joint inflammation and destruction. Local joint pathology independent of systemic immune activation was induced by overexpression of interleukin (IL)-1 and TNF in naive joints using adenoviral gene transfer. Here, we report that at certain doses, IL-1-induced local joint inflammation, cartilage proteoglycan depletion, and bone erosion are dependent on TLR4 activation, whereas TLR2 activation is not significantly involved. In comparison, tumor necrosis factor alpha-driven joint pathology seemed to be less dependent on TLR2 and TLR4. The severity of IL-1-induced bone erosion and irreversible cartilage destruction was markedly reduced in TLR4(-/-) mice, even though the degree of inflammation was similar, suggesting uncoupled processes. Furthermore, the expression of cathepsin K, a marker for osteoclast activity, induced by IL-1beta was dependent on TLR4. Overexpression of IL-1beta in the joint as well as ex vivo IL-1 stimulation of patellae provoked the release of endogenous TLR4 agonists capable of inducing TLR4-mediated cytokine production. These data emphasize the potential relevance of TLR4 activation in rheumatoid arthritis, particularly with respect to IL-1-mediated joint pathology.

Toll-like receptors and their role in gastrointestinal disease

The innate immune response to invading pathogens is centred upon a family of non-clonal, germline-encoded pattern recognition receptors (PRRs), the Toll-like receptors (TLRs). These provide specificity for a vast range of microbial pathogens, and offer an immediate anti-microbial response system. Thirteen mammalian TLRs have been described; 10 are expressed in humans, each responsible for the recognition of distinct, invariant microbial structures originating from bacteria, viruses, fungi and protozoa. The two most thoroughly studied are TLR4 and TLR2, the PRRs for Gram-negative and Gram-positive bacterial products, respectively. TLR4 is also the major receptor recognising endogenous ligands released from damaged or dying cells. Activation of a TLR by its relevant ligand rapidly ignites a complex intracellular signaling cascade that ultimately results in upregulation of inflammatory genes and production of proinflammatory cytokines, interferons and recruitment of myeloid cells. It also stimulates expression, upon antigen presenting cells, of co-stimulatory molecules required to induce an adaptive immune response. Whilst a robust TLR response is critical for survival and defence against invading pathogens, inappropriate signaling in response to alterations in the local microflora environment can be detrimental. Such 'unhelpful TLR responses' could form the basis for a large number of gastrointestinal and liver disorders, including inflammatory bowel disease, viral hepatitis, autoimmune liver diseases and hepatic fibrosis. As our understanding of TLRs expands, the pathogenesis of a number of gastrointestinal disorders will be further elucidated, and this offers potential for specific therapies aimed directly at TLR signaling.

TLR5 stimulation is sufficient to trigger reactivation of latent HIV-1 provirus in T lymphoid cells and activate virus gene expression in central memory CD4+ T cells

When effector CD4+ T cells carrying integrated HIV-1 proviruses revert back to a resting memory state, the virus can remain silent in those cells for years. Following re-exposure to the nominal antigen or in response to other stimuli (e.g. pro-inflammatory cytokines), these cells can begin to produce virus. Here we demonstrate that TLR5 stimulation induces activation of NF-kappaB and reactivate latent HIV-1 in CD4+ T lymphoid cells. Interestingly, we report also that TLR5 engagement leads to virus gene expression in quiescent central memory CD4+ T cells, a cell population recognized as a major reservoir in infected individuals. This study supports the hypothesis that translocation of microbes that can engage pathogen recognition receptors might play a dominant role in chronic immune activation seen in HIV-1-infected individuals and promote virus replication and dissemination.

TLR2 and TLR4 triggering exerts contrasting effects with regard to HIV-1 infection of human dendritic cells and subsequent virus transfer to CD4+ T cells

BACKGROUND

Recognition of microbial products through Toll-like receptors (TLRs) initiates inflammatory responses orchestrated by innate immune cells such as dendritic cells (DCs). As these cells are patrolling mucosal surfaces, a portal of entry for various pathogens including human immunodeficiency virus type-1 (HIV-1), we investigated the impact of TLR stimulation on productive HIV-1 infection of DCs and viral spreading to CD4+ T cells.

RESULTS

We report here that engagement of TLR2 on DCs increases HIV-1 transmission toward CD4+ T cells by primarily affecting de novo virus production by DCs. No noticeable and consistent effect was observed following engagement of TLR5, 7 and 9. Additional studies indicated that both HIV-1 infection of DCs and DC-mediated virus transmission to CD4+ T cells were reduced upon TLR4 triggering due to secretion of type-I interferons.

CONCLUSION

It can thus be proposed that exposure of DCs to TLR2-binding bacterial constituents derived, for example, from pathogens causing sexually transmissible infections, might influence the process of DC-mediated viral dissemination, a phenomenon that might contribute to a more rapid disease progression.

Host-pathogen interactions of Actinobacillus pleuropneumoniae with porcine lung and tracheal epithelial cells

Host-pathogen interactions are of great importance in understanding the pathogenesis of infectious microorganisms. We developed in vitro models to study the host-pathogen interactions of porcine respiratory tract pathogens using two immortalized epithelial cell lines, namely, the newborn pig trachea (NPTr) and St. Jude porcine lung (SJPL) cell lines. We first studied the interactions of Actinobacillus pleuropneumoniae, an important swine pathogen, using these models. Under conditions where cytotoxicity was absent or low, we showed that A. pleuropneumoniae adheres to both cell lines, stimulating the induction of NF-kappaB. The NPTr cells consequently secrete interleukin 8, while the SJPL cells do not, since they are deprived of the NF-kappaB p65 subunit. Cell death ultimately occurs by necrosis, not apoptosis. The transcriptomic profile of A. pleuropneumoniae was determined after contact with the porcine lung epithelial cells by using DNA microarrays. Genes such as tadB and rcpA, members of a putative adhesin locus, and a gene whose product has high homology to the Hsf autotransporter adhesin of Haemophilus influenzae were upregulated, as were the genes pgaBC, involved in biofilm biosynthesis, while capsular polysaccharide-associated genes were downregulated. The in vitro models also proved to be efficient with other swine pathogens, such as Actinobacillus suis, Haemophilus parasuis, and Pasteurella multocida. Our results demonstrate that interactions of A. pleuropneumoniae with host epithelial cells seem to involve complex cross talk which results in regulation of various bacterial genes, including some coding for putative adhesins. Furthermore, our data demonstrate the potential of these in vitro models in studying the host-pathogen interactions of other porcine respiratory tract pathogens.

Molecular and contextual markers of hepatitis C virus and drug abuse

The spread of hepatitis C virus (HCV) infection involves a complex interplay of social risks, and molecular factors of both virus and host. Injection drug abuse is the most powerful risk factor for HCV infection, followed by sexual transmission and additional non-injection drug abuse factors such as co-infection with other viruses and barriers to treatment. It is clearly important to understand the wider context in which the factors related to HCV infection occur. This understanding is required for a comprehensive approach leading to the successful prevention, diagnosis, and treatment of HCV. An additional consideration is that current treatments and advanced molecular methods are generally unavailable to socially disadvantaged patients. Thus, the recognition of behavioral/social, viral, and host factors as components of an integrated approach to HCV is important to help this vulnerable group. Equally important, this approach is key to the development of personalized patient treatment - a significant goal in global healthcare. In this review, we discuss recent findings concerning the impact of drug abuse, epidemiology, social behavior, virology, immunopathology, and genetics on HCV infection and the course of disease.

Toll-like receptors and their role in carcinogenesis and anti-tumor treatment

Toll-like receptors (TLRs) have been described as major components of the innate immune system, recognizing the conserved molecular structures found in the large groups of pathogens called pathogen-associated molecular patterns (PAMPs). TLR expression is ubiquitous, from epithelial to immunocompetent cells. TLR ligation triggers several adapter proteins and downstream kinases, leading to the induction of key pro-inflammatory mediators but also anti-inflammatory and anti-tumor cytokines. The result of this activation goes beyond innate immunity to shape the adaptive responses against pathogens and tumor cells, and maintains host homeostasis via cell debris utilization. TLRs have already become potent targets in infectious disease treatment and vaccine therapy and in neoplastic disease treatment, due to their ability to enhance antigen presentation. However, some studies show the dual effect of TLR stimulation on malignant cells: they can be proapoptotic or promote survival under different conditions. It is therefore crucial to design further studies assessing the biology of these receptors in normal and transformed cells. The established role of TLRs in human disease therapy is based on TLR7 and TLR4 agonists, respectively for the novel treatment of some types of skin cancer and for the anti-hepatitis B virus vaccine. Some clinical trials involving TLR agonists as potent enhancers of the anti-tumor response in solid tumors have begun.

Expression and functional analysis of toll-like receptors of peripheral blood cells in asthmatic patients: implication for immunopathological mechanism in asthma

BACKGROUND

We investigated the expression profile of toll-like receptors (TLRs) and TLR ligand-activated production profile of asthma-related inflammatory cytokines in asthmatic patients. The expression of TLR1-8 on monocytes, CD4+ T helper lymphocytes, CD8+ T cytotoxic lymphocytes, CD19+ B lymphocytes, and dendritic cells, and ex vivo production of cytokines from peripheral blood mononuclear cells activated by TLR ligands were measured by flow cytometry.

DISCUSSION

Ex vivo productions of TNF-alpha, IL-10, and IL-1beta by TLR4 and TLR5 ligand LPS and flagellin were significantly lower in asthmatic patients (all P < 0.05). Expression of TLR4 and TLR5 was also found to be significantly lower in asthmatic patients when compared to that of control subjects (all P < 0.05). Therefore, the decreased activation of TLR4 and TLR5 in asthmatic patients might contribute to the immunopathological mechanisms of asthma by reducing the release of Th1 and anti-inflammatory cytokines.

Effect of Lactobacillus acidophilus strain L-55 on the development of atopic dermatitis-like skin lesions in NC/Nga mice

In this study, we examined whether Lactobacillus acidophilus strain L-55 (strain L-55) suppresses the development of atopic dermatitis (AD)-like skin lesions induced by repeated application of 2,4,6-trinitrochlorobenzene (TNCB) in sensitized NC/Nga mice. The effect of strain L-55 was assessed by measuring clinical symptoms, ear swelling, scratching behavior and serum levels of total IgE. Strain L-55 was administered orally once a day: Strain L-55 at doses of 1 and 10 mg cells/mouse inhibited the development of AD-like skin lesions in dermatitis scores for the back. The increase of dermatitis score and ear swelling was also inhibited by strain L-55. In addition, strain L-55 also caused an inhibition of histological changes induced by repeated application of TNCB. Scratching behavior observed in the back and ear was inhibited by strain L-55. Furthermore elevated serum IgE levels observed by TNCB were also decreased by strain L-55. These results indicate that the inhibition of strain L-55 on AD-like lesions induced by repeated application of TNCB in sensitized NC/Nga mice occurred via a decrease in the serum total IgE level.

Evidence for the pivotal role of endogenous toll-like receptor 4 ligands in liver ischemia and reperfusion injury

BACKGROUND

Although toll-like receptor 4 (TLR4) activation has been demonstrated to play a key role in the induction of intrahepatic inflammation, leading to hepatocellular damage in liver ischemia/reperfusion injury (IRI), the nature of TLR4 ligands generated during tissue injury remains to be elucidated. We hypothesized that endogenous TLR4 ligands, rather than endotoxin (lipopolysaccharide [LPS]), are instrumental in the activation of liver TLR4 leading to local inflammation response that culminates in ultimate organ IRI.

METHODS AND RESULTS

By using the LPS-neutralizing agent, recombinant bactericidal/permeability-increasing protein, we showed that the endotoxin blockade failed to protect mouse livers from warm IRI, as assessed by serum alanine aminotransferase levels, intrahepatic inflammatory gene induction profile, and liver pathology. The recombinant bactericidal/permeability-increasing protein did not cause any hepatocytoxicity by itself if injected into normal naive mice. Furthermore, we demonstrated that liver perfusates, generated by isolated liver perfusion system, contained LPS-independent, heat-sensitive protein molecules that activated macrophages to produce tumor necrosis factor (TNF)-alpha through TLR4 but not TLR2 pathway.

CONCLUSION

This study provides a definitive evidence that endogenous TLR4 ligands are critical in the pathogenesis of liver IRI.

Molecular mediators of liver ischemia and reperfusion injury: a brief review

Ischemia and reperfusion injury is a dynamic process that involves multiple organ systems in various clinical states including transplantation, trauma, and surgery. Research into this field has identified key molecular and signaling players that mediate, modulate, or augment cellular, tissue, and organ injury during this disease process. Further elucidation of the molecular mechanisms should provide the rationale to identify much-needed novel therapeutic options to prevent or ameliorate organ damage due to ischemia and reperfusion in clinics.

The role of epithelial integrin receptors in recognition of pulmonary pathogens

Integrins are a large family of heterodimeric transmembrane cell adhesion receptors. During the last decade, it has become clear that integrins significantly participate in various host-pathogen interactions involving pathogenic bacteria, fungi, and viruses. Many bacteria possess adhesins that can bind either directly or indirectly to integrins. However, there appears to be an emerging role for integrins beyond simply adhesion molecules. Given the conserved nature of integrin structure and function, and the diversity of the pathogens which use integrins, it appears that they may act as pattern recognition receptors important for the innate immune response. Several clinically significant bacterial pathogens target lung epithelial integrins, and this review will focus on exploring various structures and mechanisms involved in these interactions.

Increased surface toll-like receptor 2 expression in superantigen shock

OBJECTIVE

Examination of the interaction between gram-positive bacterial superantigens and toll-like receptor 2 (TLR2) in health and critical illness.

DESIGN

Laboratory ex vivo model and prospective clinical, cohort study.

SETTING

Two research laboratories in university hospitals and two intensive care units.

SUBJECTS/PATIENTS

Laboratory study was performed in transfected HeLa cells and primary human monocytes from healthy volunteers. Clinical study used cells from 20 healthy controls and 45 critically ill patients with circulatory shock.

INTERVENTIONS

HeLa cells and purified monocytes were exposed to purified superantigens or isogenic bacterial supernatants and readout obtained by cytokine enzyme-linked immunosorbent assay, flow cytometry, and quantitative real-time polymerase chain reaction. Peripheral blood mononuclear cells from patients with circulatory shock were compared with controls using flow cytometry and measurement of cytokines after ligand exposure.

MEASUREMENTS AND MAIN RESULTS

Superantigens were unable to signal through ligation by TLR2. However, TLR2 was up-regulated on the surface of primary human monocytes, without detectable TLR2 messenger RNA neosynthesis, by a range of superantigens and superantigen-containing Streptococcus pyogenes supernatants, although not by isogenic superantigen-negative strains. Superantigen mutant constructs with disrupted major histocompatibility complex class II-binding sites did not support TLR2 up-regulation. TLR2 up-regulation was associated with an increase in the proinflammatory response to TLR2 ligands only at high ligand concentrations. TLR2 was up-regulated in a small subset of patients with severe S. pyogenes sepsis but not in patients with any other category of septic or circulatory shock; responses to TLR2 ligands were reduced in all categories of critically ill patient, however.

CONCLUSIONS

Superantigens up-regulate monocyte surface TLR2 expression through major histocompatibility complex class II signaling. Enhanced surface TLR2 expression may be a specific feature of patients with S. pyogenes-induced shock. Importantly, intensity of TLR2 signaling is not necessarily coupled to TLR2 expression when ligand concentrations are low or after onset of critical illness.

The immunology of sepsis

Sepsis, the systemic inflammatory response to infection, is considered the major cause of death among critically ill patients in the developed world. While there is a general view that this reflects contributions from both the pathogen and the host with respect to an inappropriate inflammatory response, there is a lack of agreement as to the key immune mechanisms. This has been reflected in the diverse range of immunotherapies tested in clinical trials, often with rather marginal effects. The case has been made for a pathogenic role of excessive immunity, the so-called 'cytokine storm', and for a role of too little immunity through immune paralysis. Apoptosis is implicated as a key mechanism in both this immune paralysis and the multi-organ failure that is a feature of severe sepsis. A number of polymorphisms have been implicated in susceptibility to sepsis, including cytokine genes, HLA class II and caspase-12. In this review we focus in particular on the role of group A streptococci in severe sepsis. Here the effect of bacterial superantigens appears to be a correlate of inflammatory activation, although the precise evolutionary role of the superantigens remains unclear.

FAK-mediated activation of ERK for eosinophil migration: a novel mechanism for infection-induced allergic inflammation

Bacterial and viral infections often induce the exacerbation of allergic diseases. In this study, we investigated the activation of human eosinophils by different microbial products via Toll-like receptors (TLRs). The underlying intracellular mechanism involving activation of extracellular signal-regulated kinase (ERK) and focal adhesion kinase (FAK), an integrin-associated focal adhesion molecule, was also examined. Seven TLR ligands were studied for their abilities in promoting survival, modulating the expression of adhesion molecules and facilitating chemotactic migration of eosinophils. While peptidoglycan (PGN) (TLR2 ligand) showed the most prominent effects, flagellin (TLR5 ligand) and imiquimod R837 (TLR7 ligand) were also effective in activating eosinophils. However, little or no effect was observed for double-stranded polyinosinic-polycytidylic acid (TLR3 ligand), ultra-purified LPS (TLR4 ligand), single-stranded RNA (ssRNA) (TLR8 ligand) and CpG-DNA (TLR9 ligand). Further investigation confirmed that PGN, flagellin and R837 commonly transmitted signals through ERK activation that required prior phosphorylation of tyrosine 925, but not tyrosine 577, on FAK. Moreover, the inhibition of ERK activation by selective inhibitor PD98059 and FAK expression by FAK-specific RNA interference could significantly abolish the stimulatory effects induced by PGN, flagellin and R837. Taken together, our findings indicate the involvement of FAK-dependent activation of ERK1 in TLR-mediated eosinophil stimulation. A potential role of eosinophils was also suggested in exacerbating allergic inflammation in response to microbial infections.

Identification of cDNA encoding Toll receptor, MjToll gene from kuruma shrimp, Marsupenaeus japonicus

Toll receptors are cell-surface receptors acting as pattern recognition receptors (PRRs) that are involved in the signaling pathway for innate immunity activation and are genetically conserved from insects to mammals. Tolls from penaeid shrimp are found in white leg shrimp Litopenaeus vannamei (lToll) and black tiger shrimp Penaeus monodon (PmToll). However, the molecular ligand-recognition patterns and identification of these penaeid Toll classes remain unknown. Here, we report cDNA cloning of a new type of Toll receptor gene (MjToll) from kuruma shrimp, Marsupenaeus japonicus, and the modulation of expression by immunostimulation. The full length cDNA of MjToll gene has 3095 nucleotides coding for a putative protein of 1009 amino acids. The MjToll gene is constitutively expressed in the gill, gut, lymphoid organ, heart, hematopoietic organ, hemocyte, ventral abdominal nerve cord, eyestalk neural ganglia and brain tissues. The MjToll gene expression was significantly increased (76-fold) as compared to a control in lymphoid organ stimulated with peptidoglycan at 12h, in vitro. lToll gene showed high similarity to PmToll gene with 96.9% identity; however, MjToll gene exhibited a percentage identity of 59% with that of penaeid Toll homologues. Therefore, this suggests that the identified MjToll gene belongs to the other class of Toll receptors in shrimp.

Toll-like receptors in inflammation, infection and cancer

Members of the Toll-like receptor (TLR) family play key roles in both innate and adaptive immune responses. TLR proteins enable host to recognize a large number of pathogen-associated molecular patterns such as bacterial lipopolysaccharides, viral RNA, CPG-containing DNA, and flagellin, among others. TLRs are also apparently able to mediate responses to host molecules, including one defensin, ROS, HMGB1 (high-mobility group box protein 1), surfactant protein A, fibrinogen, breakdown products of tissue matrix, heat shock proteins (hsp) and eosinophil-derived neurotoxin (EDN). Thus, TLR are involved in the development of many pathological conditions including infectious diseases, tissue damage, autoimmune and neurodegenerative diseases and cancer. In this review, the contribution of TLRs to diseases of the central nervous system (CNS), lung, gastrointestinal tract, kidney and skin as well as cancer is evaluated. We hope to provide new insight into the pathogenesis and progression of diseases and more importantly, into the potential for TLRs as targets of therapeutics.

TLR2 Signaling Renders Quiescent Naive and Memory CD4+T Cells More Susceptible to Productive Infection with X4 and R5 HIV-Type 1

It has been recently demonstrated that circulating microbial products are responsible for a systemic immune activation in individuals infected with HIV-type 1. Bacterial products carry structural conserved motifs recognized by TLRs. Some TLR members are expressed in primary human CD4+ T cells but the precise functional role played by these pattern recognition receptors is still imprecise. In this study, we report that engagement of TLR2 in quiescent naive and memory CD4+ T cells leads to the acquisition of an effector-like phenotype. Interestingly, engagement of TLR2 renders both cell subsets more susceptible to productive infection with X4 virions and a higher virus production was seen with R5 viruses. It can be proposed that exposure of resting CD4+ T cells to pathogen-derived products that can engage TLR2 induces the acquisition of an effector-like phenotype in naive and memory CD4+ T lymphocytes, a phenomenon that might result in an acceleration of virus replication, immune dysregulation, and HIV-type 1-mediated disease progression.

Effect of growth conditions of Lactobacillus gasseri OLL2809 on the immunostimulatory activity for production of interleukin-12 (p70) by murine splenocytes

Lactobacillus gasseri OLL2809, a probiotic lactic acid bacterium, strongly stimulates interleukin (IL)-12 (p70) production by murine splenocytes; therefore, it is expected to ameliorate allergic diseases. Although many studies have investigated characteristics of the immunostimulatory activity of probiotics, little is known about how bacterial growth conditions affect the activity. In this study, we investigated the effects of the growth conditions of L. gasseri OLL2809 on the stimulation of IL-12 (p70) production. L. gasseri OLL2809 was grown under various culture conditions including different cultivation periods, media, and culture pH, and IL-12 (p70) production by murine splenocytes stimulated with these bacterial cells was determined. The results revealed that IL-12 (p70) production (i) increased with the growth of the bacterial cells and was higher in stationary-phase cells than in logarithmic-phase cells; (ii) it was higher in the cells grown in acidic pH; and (iii) it decreased when the cells were incubated in a buffer at neutral pH prior to heat treatment. These observations indicated that stimulation of IL-12 (p70) production is affected by culture medium pH. In addition, the observations of a difference in the stimulation of IL-12 (p70) production by L. gasseri OLL2809 grown under various conditions are consistent with the characteristics of autolysis. Therefore, it was deduced that the integrity of the bacterial cells is necessary for the stimulatory effect on IL-12 (p70) production and that acidic pH and heat treatment contributed to the stimulation by inhibiting the activity of autolysins indigenous to the bacteria. Our result suggests that cultivation until the stationary phase under acidic pH is required for the effective production of probiotics with immunostimulatory activity.

Plasmodium falciparum infection causes proinflammatory priming of human TLR responses

TLRs are a major group of pattern recognition receptors that are crucial in initiating innate immune responses and are capable of recognizing Plasmodium ligands. We have investigated TLR responses during acute experimental P. falciparum (P.f.) infection in 15 malaria-naive volunteers. TLR-4 responses in whole blood ex vivo stimulations were characterized by significantly (p < 0.01) up-regulated proinflammatory cytokine production during infection compared with baseline, whereas TLR-2/TLR-1 responses demonstrated increases in both proinflammatory and anti-inflammatory cytokine production. Responses through other TLRs were less obviously modified by malaria infection. The degree to which proinflammatory TLR responses were boosted early in infection was partially prognostic of clinical inflammatory parameters during the subsequent clinical course. Although simultaneous costimulation of human PBMC with P.f. lysate and specific TLR stimuli in vitro did not induce synergistic effects on cytokine synthesis, PBMC started to respond to subsequent TLR-4 and TLR-2 stimulation with significantly (p < 0.05) increased TNF-alpha and reduced IL-10 production following increasing periods of preincubation with P.f. Ag. In contrast, preincubation with preparations derived from other parasitic, bacterial, and fungal pathogens strongly suppressed subsequent TLR responses. Taken together, P.f. primes human TLR responses toward a more proinflammatory cytokine profile both in vitro and in vivo, a characteristic exceptional among microorganisms.

Linkage between Toll-like receptor (TLR) 2 promotor and intron polymorphisms: functional effects and relevance to sarcoidosis

The intracellular pathogens Propionibacterium acnes and Mycobacterium tuberculosis have been leading suspects as the cause of sarcoidosis, a systemic disorder characterized by the formation of non-caseating granulomas. Toll-like receptor (TLR) 2 is important in the innate immune response against both pathogens, and is therefore of interest in sarcoidosis research. In the present study, three single nucleotide polymorphisms and one dinucleotide repeat polymorphism in the TLR-2 gene were genotyped in 419 sarcoidosis patients, divided into a study cohort and a validation cohort, and 196 healthy controls. In the study cohort we found a significant increase in prevalence of the AA-genotype at promotor location -16934 in patients with chronic disease compared to patients with acute/self-remitting sarcoidosis (34.5% versus 15.9%, respectively, P = 0.006, P(c) = 0.019). These results could not be confirmed in our validation cohort, implicating a possible role for TLR-2 genetics in only a small percentage of sarcoidosis patients. Furthermore, linkage was found between the promotor polymorphism -16934 A/T and the number of GT repeats in intron 1 (P < 0.0001). After in vitro stimulation of peripheral blood mononuclear cells (PMBCs) with different TLR-2 agonists, a correlation between induction of TNF-alpha (P = 0.008), interleukin (IL)-12 (P = 0.008) as well as IL-6 (P = 0.02), and the number of GT repeats was observed. In conclusion, the data show that polymorphisms in TLR-2 might be important in a small group of sarcoidosis patients and that their functional consequences explain partly some of the variance in cytokine pattern observed in different clinical phenotypes of this disease.

The effect of 17beta-estradiol on IL-6 secretion and NF-kappaB DNA-binding activity in human retinal pigment epithelial cells

Toll-like receptors (TLRs) and inflammatory cascades participate in the pathology of age-related macular degeneration (AMD). The effect of estrogens on the development of AMD is poorly understood, although many studies indicate that these compounds can modulate inflammatory responses. In this study, we investigated the regulatory role of TLR agonists and 17beta-estradiol (E(2)) on IL-6 expression and NF-kappaB DNA-binding activity in human retinal pigment epithelial cells (ARPE-19). The inflammatory response of ARPE-19 cells to various TLR agonists, e.g. Pam, zymosan, flagellin, SLTA and lipopolysaccharide (LPS) exposures were examined via the secretion of IL-6 cytokine as analyzed by ELISA. In addition, the IL-6 responses to the estrogen-receptor agonist, E(2), and to the estrogen-receptor antagonist ICI 182.780 as well as to the NF-kappaB inhibitor helenalin were compared. The DNA-binding activity of NF-kappaB transcription factor of nuclear cell extracts was analyzed by the gel mobility shift assay (EMSA). TLR4 gene expression was studied by quantitave PCR. The TLR4 agonist, LPS, caused a clear IL-6 response that was attenuated by E(2) in ARPE-19-cells. The anti-inflammatory properties of E(2) were mediated through estrogen receptors and were associated with decreased NF-kappaB DNA-binding activity. The level of TLR4 gene expression was not affected by LPS exposure. Our results indicate that IL-6 expression is regulated through NF-kappaB transcription factor and stereoid-receptor signalling pathways in ARPE-19 cells.

Intracellular signaling mechanisms regulating toll-like receptor-mediated activation of eosinophils

Activation of eosinophils by microbe-derived molecules via Toll-like receptors (TLR) potentially provides the link between microbe-induced innate immune responses and the exacerbation of allergic inflammation. We investigated the expression of TLRs and the effect of their ligands on human eosinophils. Expression of TLR1-9 was detected by Western blot and flow cytometry. Adhesion molecules, cytokines, superoxides, and eosinophlilic cationic protein (ECP) were assessed by flow cytometry, enzyme-linked immunosorbent assay, chemiluminescent method, and fluorescence immunoassay, respectively. Human eosinophils differentially expressed TLR1, -2, -4, -5, -6, -7, and -9. Peptidoglycan (PGN) (TLR2 ligand), flagellin (TLR5 ligand), and Imiquimod R837 (TLR7 ligand) could significantly upregulate cell surface expression of intercellular adhesion molecule (ICAM)-1 and CD18, and induce the release of IL-1beta, IL-6, IL-8, growth-related oncogene (GRO)-alpha, and superoxides of eosinophils. Only PGN could induce the degranulation for ECP release. However, ds poly I-C (TLR3 ligand), LPS (TLR4 ligand), ssRNA (TLR8 ligand), and CpG-DNA (TLR9 ligand) were much less effective or inactive. PGN, flagellin, and R837 could activate both nuclear factor (NF)-kappaB and extracellular signal-regulated protein kinase (ERK). PGN could activate phosphatidylinositol 3-kinase (PI3K)-Akt, and R837 both PI3K-Akt and p38 mitogen-activated protein kinase (MAPK). The induction of the release of IL-1beta, IL-6, IL-8, GRO-alpha, superoxides, and ECP by PGN, flagellin, and R837 was found to be differentially regulated by NF-kappaB, ERK, PI3K-Akt, and p38 MAPK. The above results therefore support that microbial infection may lead to the exacerbation of allergic inflammation.

Local pulmonary immune stimulation by the Toll-like receptor 2 and 6 ligand MALP-2 in rats is age dependent

Recent studies indicate that the pulmonary immune response in humans and experimental animals is different in newborn, adult and elderly age groups. The aim of this study was to investigate the influence of age on the leukocyte composition in different lung compartments and peripheral blood of weaned and adult rats. A mycoplasma-like inflammatory response was mimicked by intratracheal application of the synthetic macrophage-activating lipopeptide-2 (MALP-2) which activates macrophages and other cells via the Toll-like receptor (TLR) 2 and 6. TLR 2 and 6 mRNA expressions were investigated by semiquantitative RT-PCR in cells of the bronchoalveolar lavage (BAL) and lung interstitium. Weaned Lewis rats (3-4 weeks old) and adults (12-14 months old) were treated with vehicle control or MALP-2. Cytokines and cell infiltration were measured in the BAL and lung interstitium. In control rats, no differences in TLR 2 and 6 mRNA expression level were found between the age groups. After MALP-2 treatment, the maximum of MCP-1 concentration in the BAL fluid was reached in weaned rats after 4h and in adults after 2h. The TNF-alpha maximum was measured after 2h in both age groups. Three days after MALP-2 the numbers of different leukocyte subsets were significantly increased in the BAL of both groups. In contrast, in the lung interstitium MALP-2 induced a leukocyte increase in adult rats but not in weaned rats. In conclusion, data on pulmonary immune responses from one age group and one lung compartment should not be generalized or extrapolated to other groups.

Expression and function of Toll-like receptors in T lymphocytes

Toll-like receptors (TLRs) are widely expressed in the innate immune system. They recognize conserved microbial ligands such as bacterial lipopolysaccharide, lipopeptides or viral and bacterial RNA and DNA. TLRs play an essential role in innate immune responses and in the initiation of adaptive immune responses. However, certain TLRs are also expressed in T lymphocytes, and the respective ligands can directly modulate T cell function. TLR2, TLR3, TLR5 and TLR9 act as co-stimulatory receptors to enhance proliferation and/or cytokine production of T-cell receptor-stimulated T lymphocytes. In addition, TLR2, TLR5 and TLR8 modulate the suppressive activity of naturally occurring CD25(+)CD4(+) regulatory T cells. The direct responsiveness of T lymphocytes to TLR ligands offers new perspectives for the immunotherapeutic manipulation of T cell responses.

Molecular cloning and characterisation of the griffon vulture (Gyps fulvus) toll-like receptor 1

The toll-like receptor (TLR) family is an ancient pattern recognition receptor family, conserved from insects to mammals. Members of the TLR family are vital to immune function through the sensing of pathogenic agents and initiation of an appropriate immune response. In this study, we cloned a cDNA encoding for a griffon vulture (Gyps fulvus) orthologue of mammalian TLR1 (CD281). The predicted 650 amino acid sequence comprised an extracellular domain with five leucine-rich repeats (LRR) and an LRR-C-terminal (LRR-CT) motif, followed by a 23 amino acid transmembrane segment, and a 190 amino acid intracytoplasmic region containing the Toll/IL-1R (TIR) domain. Vulture TLR1 and TIR domain showed 64% and 86% amino acid sequence similarity with chicken sequences. The tissue and cell expression pattern of vulture TLR1 were analysed by real time-PCR (RT-PCR) and correlated with the ability to respond to various pathogenic challenges. Despite the similarities in the overall structure and expression pattern of vulture TLR1 with other vertebrate TLRs, the length of the vulture TLR ectodomain, number and position of LRRs and N-glycosylation sites suggest structural differences that may have functional implications.

Impaired interferon-gamma production in response to live bacteria and Toll-like receptor agonists in patients with ataxia telangiectasia

Ataxia telangiectasia (AT) is a pleiotropic autosomal recessive neurodegenerative disorder with associated immunodeficiency and cancer predisposition, caused by mutational inactivation of the ATM gene. Early death usually results from lymphoreticular malignancy or recurrent, chronic respiratory infections. Immune deficiency of AT patients is heterogeneous and involves both humoral and cellular responses. Reports on the number and integrity of immunocompetent cells in AT are conflicting. In the early phase of infection, the interleukin (IL)-12/interferon (IFN)-gamma axis plays a crucial role in first-line defence against pathogens. In a whole blood assay we studied the IL-12/IFN-gamma axis in the immune response of AT cells to the Toll-like receptor agonists lipopolysaccharide and heat-killed Staphylococcus aureus, as well as whole live M. bovis bacille Calmette-Guérin (BCG). The function of AT antigen-presenting cells was normal in terms of IL-12 production, while IFN-gamma production by T and natural killer (NK) cells was severely impaired, even in the presence of adequate co-stimulation by exogenous IL-12.

EMERGING PARADIGM

The systemic inflammatory response syndrome initiated by infection shares many features in common with the trauma-induced systemic response. The toll-like receptors (TLRs) stand at the interface of innate immune activation in the settings of both infection and sterile injury by responding to a variety of microbial and endogenous ligands alike. Recently, a body of literature has evolved describing a key role for TLRs in acute injury using rodent models of hemorrhagic shock, ischemia and reperfusion, tissue trauma and wound repair, and various toxic exposures. This review will detail the observations implicating a TLR family member, TLR4, as a key component of the initial injury response.

Involvement of innate immunity in the pathogenesis of chronic hepatitis C in children

The aim of the study was to assess the role of selected elements of innate immunity in the pathogenesis of chronic hepatitis C in children. The study comprised 20 children with chronic hepatitis C (group 1), nine healthy hepatitis C virus (HCV) seropositive children (group 2) and 18 healthy children (control group). We evaluated the expression of Toll-like receptor (TLR)2 and TLR4 on peripheral blood neutrophils, and generation of interleukin (IL)-8, IL-10, IL-12 and reactive oxygen species (ROS) by neutrophils. The performed tests demonstrated higher expression of TLR2 and TLR4 on stimulated neutrophils and of TLR4 on non-stimulated neutrophils in group 1 in comparison to HCV seropositive children and controls. In group 1, the expression of TLR2 after granulocyte colony-stimulating factor (GCSF) stimulation showed positive correlation with alanine aminotransferase and asparate aminotransferase activities, while the expression of TLR2 without stimulation and of TLR4 after GCSF stimulation also correlated with necrosis. IL-12 generation by lipopolysachcharide-stimulated neutrophils was higher in group 1 versus controls. In group 1, maximum chemiluminescence (CL) without pre-activation, both spontaneous and after formyl-methionyl-leucyl-phenylanine and phorbol-myristate-acetate (PMA) stimulation, was significantly lower than in the controls. CL after tumour necrosis factor-alpha pre-activation and PMA stimulation was still lower than in the controls, however, after opsonized zymosane stimulation it was significantly higher than in the controls. Our studies suggest the involvement of neutrophils in the pathogenesis of chronic hepatitis C in children. Neutrophils demonstrate increased expression of TLR2 and TLR4 (correlating with the features of hepatocytic damage and intensification of necrosis), inhibition of oxygen metabolism, and after TNF-alpha pre-activation higher ability to produce ROS.