Identification of TLR2 Signalling Mechanisms Which Contribute to Barrett's and Oesophageal Adenocarcinoma Disease Progression.

Chronic inflammation plays an important role in the pathogenesis of oesophageal adenocarcinoma (EAC) and its only known precursor, Barrett's oesophagus (BE). Recent studies have shown that oesophageal TLR2 levels increase from normal epithelium towards EAC. TLR2 signalling is therefore likely to be important during EAC development and progression, which requires an inflammatory microenvironment. Here, we show that, in response to TLR2 stimulation, BE organoids and early-stage EAC cells secrete pro-inflammatory cytokines and chemokines which recruit macrophages to the tumour site. Factors secreted from TLR2-stimulated EAC cells are shown to subsequently activate TLR2 on naïve macrophages, priming them for inflammasome activation and inducing their differentiation to an M2/TAM-like phenotype. We identify the endogenous TLR2 ligand, HMGB1, as the factor secreted from EAC cells responsible for the observed TLR2-mediated effects on macrophages. Our results indicate that HMGB1 signalling between EAC cells and macrophages creates an inflammatory tumour microenvironment to facilitate EAC progression. In addition to identifying HMGB1 as a potential target for early-stage EAC treatment, our data suggest that blocking TLR2 signalling represents a mechanism to limit HMGB1 release, inflammatory cell infiltration and inflammation during EAC progression.

Inhibiting TLR2 activation attenuates amyloid accumulation and glial activation in a mouse model of Alzheimer's disease.

The effects of Toll-like receptor (TLR) activation in peripheral cells are well characterized but, although several TLRs are expressed on cells of the brain, the consequences of their activation on neuronal function remain to be fully investigated, particularly in the context of assessing their potential as therapeutic targets in neurodegenerative diseases. Several endogenous TLR ligands have been identified, many of which are soluble factors released from cells exposed to stressors. In addition, amyloid-ß (Aß) the main constituent of the amyloid plaques in Alzheimer's disease (AD), activates TLR2, although it has also been shown to bind to several other receptors. The objective of this study was to determine whether activation of TLR2 played a role in the developing inflammatory changes and Aß accumulation in a mouse model of AD. Wild type and transgenic mice that overexpress amyloid precursor protein and presenilin 1 (APP/PS1 mice) were treated with anti-TLR2 antibody for 7months from the age of 7-14months. We demonstrate that microglial and astroglial activation, as assessed by MHCII, CD68 and GFAP immunoreactivity was decreased in anti-TLR2 antibody-treated compared with control (IgG)-treated mice. This was associated with reduced Aß plaque burden and improved performance in spatial learning. The data suggest that continued TLR2 activation contributes to the developing neuroinflammation and pathology and may be provide a strategy for limiting the progression of AD.

Treatment with OPN-305, a humanized anti-Toll-Like receptor-2 antibody, reduces myocardial ischemia/reperfusion injury in pigs.

BACKGROUND: Toll-like receptor (TLR)-2 is an important mediator of innate immunity and ischemia/reperfusion-induced cardiac injury. We have previously shown that TLR2 inhibition reduces infarct size and improves cardiac function in mice. However, the therapeutic efficacy of a clinical grade humanized anti-TLR2 antibody, OPN-305, in a large-animal model remained to be addressed. METHODS AND RESULTS: Pigs (n=38) underwent 75 minutes ischemia followed by 24 hours of reperfusion. Saline or OPN-305 (12.5, 6.25, or 1.56 mg/kg) was infused intravenously 15 minutes before reperfusion. Cardiac function and geometry were assessed by echocardiography. Infarct size was calculated as the percentage of the area at risk and by serum Troponin-I levels. Flow cytometry analysis revealed specific binding of OPN-305 to porcine TLR2. In vivo, OPN-305 exhibited a secondary half-life of 8±2 days. Intravenous administration of OPN-305 before reperfusion significantly reduced infarct size (45% reduction, P=0.041) in a dose-dependent manner. In addition, pigs treated with OPN-305 exhibited a significant preservation of systolic performance in a dose-dependent fashion, whereas saline treatment completely diminished the contractile performance of the ischemic/reperfused myocardium. CONCLUSIONS: OPN-305 significantly reduces infarct size and preserves cardiac function in pigs after ischemia/reperfusion injury. Hence, OPN-305 is a promising adjunctive therapeutic for patients with acute myocardial infarction.

Blockade of Toll-like receptor 2 prevents spontaneous cytokine release from rheumatoid arthritis ex vivo synovial explant cultures.

INTRODUCTION: The aim of this study was to examine the effect of blocking Toll-like receptor 2 (TLR2) in rheumatoid arthritis (RA) synovial cells. METHODS: RA synovial tissue biopsies, obtained under direct visualization at arthroscopy, were established as synovial explant cultures ex vivo or snap frozen for immunohistology. Mononuclear cell cultures were isolated from peripheral blood and synovial fluid of RA patients. Cultures were incubated with the TLR1/2 ligand, Pam3CSK4 (200 ng, 1 and 10 µg/ml), an anti-TLR2 antibody (OPN301, 1 µg/ml) or an immunoglobulin G (IgG) (1 µg/ml) matched control. The comparative effect of OPN301 and adalimumab (anti-tumour necrosis factor alpha) on spontaneous release of proinflammatory cytokines from RA synovial explants was determined using quantitative cytokine MSD multiplex assays or ELISA. OPN301 penetration into RA synovial tissue explants cultures was assessed by immunohistology. RESULTS: Pam3CSK4 significantly upregulated interleukin (IL)-6 and IL-8 in RA peripheral blood mononuclear cells (PBMCs), RA synovial fluid mononuclear cells (SFMCs) and RA synovial explant cultures (P < 0.05). OPN301 significantly decreased Pam3CSK4-induced cytokine production of tumour necrosis factor alpha (TNF-α), IL-1ß, IL-6, interferon (IFN)-γ and IL-8 compared to IgG control in RA PBMCs and SFMCs cultures (all P < 0.05). OPN301 penetration of RA synovial tissue cultures was detected in the lining layer and perivascular regions. OPN301 significantly decreased spontaneous cytokine production of TNF-α, IL-1ß, IFN-γ and IL-8 from RA synovial tissue explant cultures (all P < 0.05). Importantly, the inhibitory effect of OPN on spontaneous cytokine secretion was comparable to inhibition by anti-TNFα monoclonal antibody adalimumab. CONCLUSIONS: These findings further support targeting TLR2 as a potential therapeutic agent for the treatment of RA.

The role of regulatory T cells in respiratory infections and allergy and asthma.

The role of distinct CD4(+) T-cell populations in regulating the nature and strength of immune responses is well documented and in the past has principally focused on the cross-regulation of T-helper type 1 (Th1) and Th2 cells, which secrete interferon-gamma and interleukin-4, respectively. However, the identification of T cells capable of suppressing responses mediated by Th1 and Th2 cells, termed regulatory T cells (Treg cells), has prompted a paradigm shift in our understanding of the regulation of immune responses to infection and environmental antigens. This article focuses on the role of Treg cells in the lungs following infection with respiratory pathogens and discusses the targeting of Treg cells in the development of new therapies for immune-mediated respiratory diseases, such as allergy and asthma.

Myocardial ischemia/reperfusion injury is mediated by leukocytic toll-like receptor-2 and reduced by systemic administration of a novel anti-toll-like receptor-2 antibody.

BACKGROUND: Reperfusion therapy for myocardial infarction is hampered by detrimental inflammatory responses partly via Toll-like receptor (TLR) activation. Targeting TLR signaling may optimize reperfusion therapy and enhance cell survival and heart function after myocardial infarction. Here, we evaluated the role of TLR2 as a therapeutic target using a novel monoclonal anti-TLR2 antibody. METHOD AND RESULTS: Mice underwent 30 minutes of ischemia followed by reperfusion. Compounds were administered 5 minutes before reperfusion. Cardiac function and dimensions were assessed at baseline and 28 days after infarction with 9.4-T mouse magnetic resonance imaging. Saline and IgG isotype treatment resulted in 34.5 + or - 3.3% and 31.4 + or - 2.7% infarction, respectively. Bone marrow transplantation experiments between wild-type and TLR2-null mice revealed that final infarct size is determined by circulating TLR2 expression. A single intravenous bolus injection of anti-TLR2 antibody reduced infarct size to 18.9 + or - 2.2% (P=0.001). Compared with saline-treated mice, anti-TLR2-treated mice exhibited less expansive remodeling (end-diastolic volume 68.2 + or - 2.5 versus 76.8 + or - 3.5 microL; P=0.046) and preserved systolic performance (ejection fraction 51.0 + or - 2.1% versus 39.9 + or - 2.2%, P=0.009; systolic wall thickening 3.3 + or - 6.0% versus 22.0 + or - 4.4%, P=0.038). Anti-TLR2 treatment significantly reduced neutrophil, macrophage, and T-lymphocyte infiltration. Furthermore, tumor necrosis factor-alpha, interleukin-1alpha, granulocyte macrophage colony-stimulating factor, and interleukin-10 were significantly reduced, as were phosphorylated c-jun N-terminal kinase, phosphorylated p38 mitogen-activated protein kinase, and caspase 3/7 activity levels. CONCLUSIONS: Circulating TLR2 expression mediates myocardial ischemia/reperfusion injury. Antagonizing TLR2 just 5 minutes before reperfusion reduces infarct size and preserves cardiac function and geometry. Anti-TLR2 therapy exerts its action by reducing leukocyte influx, cytokine production, and proapoptotic signaling. Hence, monoclonal anti-TLR2 antibody is a potential candidate as an adjunctive for reperfusion therapy in patients with myocardial infarction.

Prevention of experimental colitis by parenteral administration of a pathogen-derived immunomodulatory molecule.

BACKGROUND: Filamentous haemagglutinin (FHA) of Bordetella pertussis subverts host immune responses by inhibiting interleukin (IL)12 and enhancing IL10 production by macrophages and dendritic cells, and promoting the induction of regulatory T cells. HYPOTHESIS: Injection of FHA would ameliorate disease in a T cell-dependent model of colitis via the induction of anti-inflammatory cytokines and regulatory T cells. METHODS: Colitis was induced by injection of CD4CD45RB(high) naive T cells into severe combined immunodeficient (SCID) mice. Mice were treated with four subcutaneous injections of FHA or buffer alone. RESULTS: Parenteral injection of FHA stimulated IL10 and/or transforming growth factor beta production in local and mesenteric lymph nodes and Peyer's patches of mice 2-6 h after administration. Compared with phosphate-buffered saline-treated mice, FHA-treated SCID mice had significantly (p<0.01) less weight loss, lower colon weight, less colon shrinkage and reduced inflammatory lesions. The therapeutic effect of FHA was associated with enhanced IL10 and reduced type 1 and type 2 T helper cytokine production by spleen cells. Finally, FHA also attenuated the symptoms of colitis in SCID mice transferred with CD4CD45RB(high) T cells from IL10-deficient mice. CONCLUSIONS: Our finding shows that FHA suppresses type 1 T helper and pro-inflammatory cytokines, and ameliorates disease activity in a chronic T cell-dependent model of colitis, an effect that was not dependent on IL10 production by T cells, but was associated with induction of anti-inflammatory cytokines in vivo. Having already been used as a pertussis vaccine component in children, FHA is a promising candidate for clinical testing in patients with Crohn's disease.

Mechanisms of disease: the hygiene hypothesis revisited.

In industrialized countries the incidence of diseases caused by immune dysregulation has risen. Epidemiologic studies initially suggested this was connected to a reduction in the incidence of infectious diseases; however, an association with defects in immunoregulation is now being recognized. Effector T(H)1 and T(H)2 cells are controlled by specialized subsets of regulatory T cells. Some pathogens can induce regulatory cells to evade immune elimination, but regulatory pathways are homeostatic and mainly triggered by harmless microorganisms. Helminths, saprophytic mycobacteria, bifidobacteria and lactobacilli, which induce immunoregulatory mechanisms in the host, ameliorate aberrant immune responses in the setting of allergy and inflammatory bowel disease. These organisms cause little, if any, harm, and have been part of human microecology for millennia; however, they are now less frequent or even absent in the human environment of westernized societies. Deficient exposure to these 'old friends' might explain the increase in immunodysregulatory disorders. The use of probiotics, prebiotics, helminths or microbe-derived immunoregulatory vaccines might, therefore, become a valuable approach to disease prevention.

Regulatory cells and the control of respiratory infection.

The role of distinct CD4+ T-cell populations in regulating the nature and strength of immune responses is well documented, and has in the past principally focused on the mutual antagonism between Th1 and Th2 cells, which secrete interferon (IFN)-gamma and interleukin (IL)-4, respectively. However, the recent identification of T cells that secrete high levels of IL-10 and/or transforming growth factor-b, but not IFN-g or IL-4, called regulatory T (Tr) cells has prompted a paradigm shift in our understanding of the regulation of immune responses following infection. In this review, we focus on the role of antigen-specific Tr cells in the lungs following infection with various respiratory pathogens and discuss the targeting of Tr in the development of new therapies for immune-mediated diseases, such as allergy.

Depletion of NK cells results in disseminating lethal infection with Bordetella pertussis associated with a reduction of antigen-specific Th1 and enhancement of Th2, but not Tr1 cells.

IFN-gamma plays a critical role in protection against Bordetella pertussis, but Th1 cells are only detectable after the infection has started to resolve, suggesting a protective role for innate IFN-gamma early in infection. Here, we demonstrate significant recruitment of NK cells and NKT cells into the lungs following respiratory challenge with B. pertussis. Furthermore, NK cells are the primary source of IFN-gamma in the lungs during the acute stage of infection. Stimulation of IFN-gamma production by NK cells was indirect through B. pertussis-activated IL-12 or IL-23 production by dendritic cells. Depletion of NK cells with anti-asialo ganglio-N-tetraosylceramide antibody resulted in a lethal infection, with enhancement of bacterial load in the lungs and dissemination of the bacteria to the liver via the blood. NK cell-depleted mice had significantly reduced B. pertussis-specific IFN-gamma and enhanced IgG1 and IL-5, but not IL-10 production, suggesting that regulatory T cells are induced simultaneously with Th1 cells, but the absence of NK cells resulted in enhancement of Th2-type responses. These findings suggest that NK cells confer resistance to B. pertussis by activating IL-12-mediated production of IFN-gamma, which enhances the anti-bacterial activity of macrophages, but also promotes the differentiation of Th1 cells.

Antigen-specific regulatory T cells--their induction and role in infection.

In addition to the well-established role of natural CD4(+)CD25(+) regulatory T (Tr) cells in the maintenance of tolerance to self-antigens, there is accumulating evidence for distinct populations of Tr cells induced in the periphery after encounter with pathogens and foreign antigens. These antigen-specific T cells, termed Tr1 or Th3 cells, secrete IL-10 and or TGF-beta, but no IL-4 and little or no IFN-gamma, and are induced by semi-mature dendritic cells under the influence of regulatory cytokines, including IL-10, TGF-beta and IL-4. Tr1 or Th3 cells are capable of suppressing Th1 and Th2 responses and function in infection to limit pathogen-induced immunopathology, but can also be exploited in therapies for immune-mediated diseases.

Molecules of infectious agents as immunomodulatory drugs.

Microbes produce a wide range of molecules that can modulate eukaryotic immune responses. These include factors that subvert protective mechanisms in order to facilitate pathogen colonization and persistence. Viral, bacterial and parasite-derived molecules have been identified that can inhibit inflammatory responses. However, in addition to the plethora of microbial factors that suppress immune responses, the most potent immune activators are also of microbial origin. These include the bacterial enterotoxins, parasite-derived excretory-secretory products and viral nucleic acids. In fact, there are examples of immune modulators that can exert either stimulatory or suppressive effects depending on the mode of delivery, dose and experimental model. There is presently great interest in the therapeutic exploitation of these factors, for example as a means to stimulate enhanced immune responses to a new generation of subunit vaccines or to inhibit deleterious immune mediated diseases. This short review, describes representative microbial immunomodulators, their modes of action and the potential for therapeutic application.

Toll-like receptor 4-mediated innate IL-10 activates antigen-specific regulatory T cells and confers resistance to Bordetella pertussis by inhibiting inflammatory pathology.

Signaling through Toll-like receptors (TLR) activates dendritic cell (DC) maturation and IL-12 production, which directs the induction of Th1 cells. We found that the production of IL-10, in addition to inflammatory cytokines and chemokines, was significantly reduced in DCs from TLR4-defective C3H/HeJ mice in response to Bordetella pertussis. TLR4 was also required for B. pertussis LPS-induced maturation of DCs, but other B. pertussis components stimulated DC maturation independently of TLR4. The course of B. pertussis infection was more severe in C3H/HeJ than in C3H/HeN mice. Surprisingly, Ab- and Ag-specific IFN-gamma responses were enhanced at the peak of infection, whereas Ag-specific IL-10-producing T cells were significantly reduced in C3H/HeJ mice. This was associated with enhanced inflammatory cytokine production, cellular infiltration, and severe pathological changes in the lungs of TLR4-defective mice. Our findings suggest that TLR-4 signaling activates innate IL-10 production in response to B. pertussis, which both directly, and by promoting the induction of IL-10-secreting type 1 regulatory T cells, may inhibit Th1 responses and limit inflammatory pathology in the lungs during infection with B. pertussis.

Pathogen-specific regulatory T cells provoke a shift in the Th1/Th2 paradigm in immunity to infectious diseases.

Current dogma suggests that immunity to infection is controlled by distinct type 1 (Th1) and type 2 (Th2) subpopulations of T cells discriminated on the basis of cytokine secretion and function. However, a further subtype of T cells, with immunosuppressive function and cytokine profiles distinct from either Th1 or Th2 T cells, termed regulatory T (Tr) cells has been described. Although considered to have a role in the maintenance of self-tolerance, recent studies suggest that Tr cells can be induced against bacterial, viral and parasite antigens in vivo and might prevent infection-induced immunopathology or prolong pathogen persistence by suppressing protective Th1 responses. These observations have significant implications for our understanding of the role of T cells in immunity to infectious diseases and for the development of new therapies for immune-mediated disorders.

Pathogen-specific T regulatory 1 cells induced in the respiratory tract by a bacterial molecule that stimulates interleukin 10 production by dendritic cells: a novel strategy for evasion of protective T helper type 1 responses by Bordetella pertussis.

Antigen-specific T helper type 1 (Th1) cells mediate protective immunity against a range of infectious diseases, including that caused by Bordetella pertussis. Distinct T cell subtypes that secrete interleukin (IL)-10 or tumor growth factor (TGF)-beta are considered to play a role in the maintenance of self-tolerance. However, the antigens recognized by these regulatory T cells in vivo have not been defined. Here we provide the first demonstration of pathogen-specific T regulatory type 1 (Tr1) cells at the clonal level and demonstrate that these cells are induced at a mucosal surface during an infection where local Th1 responses are suppressed. Tr1 clones specific for filamentous hemagglutinin (FHA) and pertactin were generated from the lungs of mice during acute infection with B. pertussis. The Tr1 clones expressed T1/ST2 and CC chemokine receptor 5, secreted high levels of IL-10, but not IL-4 or interferon (IFN)-gamma, and suppressed Th1 responses against B. pertussis or an unrelated pathogen. Furthermore, FHA inhibited IL-12 and stimulated IL-10 production by dendritic cells (DCs), and these DCs directed naive T cells into the regulatory subtype. The induction of Tr1 cells after interaction of a pathogen-derived molecule with cells of the innate immune system represents a novel strategy exploited by an infectious pathogen to subvert protective immune responses in vivo.