Experimental Models of Septic Shock Therapy Affords Protection in TLR4/MD2 Monoclonal Antibody (original) (raw)
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Protection from lethal Gram-negative bacterial sepsis by targeting Toll-like receptor 4
Proceedings of the National Academy of Sciences, 2009
Toll-like receptor 4 (TLR4), the signal-transducing molecule of the LPS receptor complex, plays a fundamental role in the sensing of LPS from Gram-negative bacteria. Activation of TLR4 signaling pathways by LPS is a critical upstream event in the pathogenesis of Gram-negative sepsis, making TLR4 an attractive target for novel antisepsis therapy. To validate the concept of TLR4-targeted treatment strategies in Gram-negative sepsis, we first showed that TLR4 ؊/؊ and myeloid differentiation primary response gene 88 (MyD88) ؊/؊ mice were fully resistant to Escherichia coli-induced septic shock, whereas TLR2 ؊/؊ and wild-type mice rapidly died of fulminant sepsis. Neutralizing anti-TLR4 antibodies were then generated using a soluble chimeric fusion protein composed of the N-terminal domain of mouse TLR4 (amino acids 1-334) and the Fc portion of human IgG1. Anti-TLR4 antibodies inhibited intracellular signaling, markedly reduced cytokine production, and protected mice from lethal endotoxic shock and E. coli sepsis when administered in a prophylactic and therapeutic manner up to 13 h after the onset of bacterial sepsis. These experimental data provide strong support for the concept of TLR4-targeted therapy for Gram-negative sepsis. endotoxic shock ͉ Gram-negative bacteria ͉ lipopolysaccharide ͉ TLR4
TLR4/MD-2 Monoclonal Antibody Therapy Affords Protection in Experimental Models of Septic Shock
The Journal of Immunology, 2007
Overactivation of the immune system upon acute bacterial infection leads to septic shock. Specific bacterial products potently stimulate immune cells via toll-like receptors (TLRs). Gram-negative bacteria induce a predominantly TLR4-driven signal through LPS release. To neutralize LPS signaling in experimental models of sepsis, we generated mAbs toward the TLR4/myeloid differentiation protein-2 (MD-2) complex. The binding properties of an array of selected rat mAbs differed in respect to their specificity for TLR4/MD-2 complex. The specificity of one such mAb, 5E3, to murine TLR4 was confirmed by its recognition of an epitope within the second quarter of the ectodomain. 5E3 inhibited LPS-dependent cell activation in vitro and prevented proinflammatory cytokine production in vivo following LPS challenge in a dose-dependent manner. Furthermore, 5E3 protected mice from lethal shock-like syndrome when applied using both preventative and therapeutic protocols. Most notably, in the colon ascendens stent peritonitis model of polymicrobial abdominal sepsis, administration of a single dose of 5E3 (50 g) protected mice against mortality. These results demonstrate that neutralizing TLR4/MD-2 is highly efficacious in protecting against bacterial infection-induced toxemia and offers TLR4/MD-2 mAb treatment as a potential therapy for numerous clinical indications. The Journal of Immunology, 2007, 179: 6107-6114.
Signal transduction by the lipopolysaccharide receptor, Toll-like receptor-4
Immunology, 2004
An understanding of lipopolysaccharide (LPS) signal transduction is a key goal in the effort to provide a molecular basis for the lethal effect of LPS during septic shock and point the way to novel therapies. Rapid progress in this field during the last 6 years has resulted in the discovery of not only the receptor for LPS -Toll-like receptor 4 (TLR4) -but also in a better appreciation of the complexity of the signalling pathways activated by LPS. Soon after the discovery of TLR4, the formation of a receptor complex in response to LPS, consisting of dimerized TLR4 and MD-2, was described. Intracellular events following the formation of this receptor complex depend on different sets of adapters. An early response, which is dependent on MyD88 and MyD88-like adapter (Mal), leads to the activation of nuclear factor-jB (NF-jB). A later response to LPS makes use of TIR-domain-containing adapter-inducing interferon-b (TRIF) and TRIF-related adapter molecule (TRAM), and leads to the late activation of NF-jB and IRF3, and to the induction of cytokines, chemokines, and other transcription factors. As LPS signal transduction is an area of intense research and rapid progress, this review is intended to sum up our present understanding of the events following LPS binding to TLR4, and we also attempt to create a model of the signalling pathways activated by LPS.
Journal of Endotoxin Research, 1999
An invading pathogen must be held in check by the innate immune system until a specific immune response can be mounted. In the case of Gram-negative bacteria, the principal stimulator is LPS, a component of the outer membrane of the bacteria. In vitro LPS is bound by LBP and transferred to the LPS receptor CD14 on the macrophage surface. Binding to CD14 triggers an inflammatory response which is crucial for keeping an infection under control. In vitro, LBP mediates a response not only to LPS but also to intact Gram-negative bacteria. We show that whole Escherichia coli bacteria are recognised by CD14 on human monocytes, and subsequently may become phagocytosed. Although neither LBP nor CD14 interact with the heat inactivated, intact Gram-positive bacterium Bacillus subtilis both proteins form stable complexes with lipoteichoic acid derived from the bacterial cell wall. A brief exposure of B. subtilis to serum or antibiotics converts them into a form which can be recognised by CD14 i...
Immunity, 2016
Receptor CD300b is implicated in regulating the immune response to bacterial infection by an unknown mechanism. Here, we identified CD300b as a lipopolysaccharide (LPS)-binding receptor and determined the mechanism underlying CD300b augmentation of septic shock. In vivo depletion and adoptive transfer studies identified CD300b-expressing macrophages as the key cell type augmenting sepsis. We showed that CD300b, and its adaptor DAP12, associated with Toll-like receptor 4 (TLR4) upon LPS binding, thereby enhancing TLR4-adaptor MyD88- and TRIF-dependent signaling that resulted in an elevated pro-inflammatory cytokine storm. LPS engagement of the CD300b-TLR4 complex led to the recruitment and activation of spleen tyrosine kinase (Syk) and phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K). This resulted in an inhibition of the ERK1/2 protein kinase- and NF-κB transcription factor-mediated signaling pathways, which subsequently led to a reduced interleukin-10 (IL-10) production. Colle...
TLR4 influences the humoral and cellular immune response during polymicrobial sepsis
Injury, 2010
Sepsis, systemic inflammatory response syndrome (SIRS) and associated multiple organ failure (MOF) as well as the multiple organ dysfunction syndrome (MODS) remain the most common causes for fatalities during the clinical course following trauma or major surgery. Both the innate and the adaptive immune systems are activated and contribute to a complex pathogenesis of sepsis. As part of the innate immune system, Toll-like receptors (TLRs) play a central role in the early immune response during sepsis. In contrast to the adaptive immune system, TLRs react rapidly on a wide range of pathogen-associated molecular patterns (PAMPs) 1 without prior exposure. They are activated not only by PAMPs but also by dangerassociated molecular patterns (DAMPs). 1,38 TLRs build the initial line of host defence in the human organism and the 13 TLRs identified to date 47 are expressed on many immune cells such as polymorpho-nuclear granulocytes (PMN), macrophages, dendritic cells and certain epithelial cells. These immune cells recruit further leucocytes through cytokine production to fight the invading micro-organism. The most famous member of the TLR-family, TLR4, is activated by lipopolysaccharide (LPS), a component of the membrane of Gram-negative bacteria. Once activated, production of proinflammatory cytokines such as tumour necrosis factor-a (TNFa), interleukin (IL)-1b or IL-6 40 is induced through an intracellular signalling cascade. 35 These pro-inflammatory mediators are released into the peripheral blood and lead to activation and extravasation of T-cells, macrophages and PMNs. The release of these inflammatory mediators correlates with the clinical entity of SIRS or septic shock. Lymphocyte sub-populations such as CD4 + , CD8 + and CD56 + natural killer (NK) cells show a strong influence on the course of sepsis. A decreased CD4 + /CD8 + ratio was associated with a lower incidence of MODS. 26 Furthermore, an increase of NK cells was associated with increased mortality after caecal ligation and puncture (CLP) in dehydroepiandrosterone (DHEA)-treated mice, 41 while depletion of NK cells showed a beneficial effect. 7 Injury, Int.
TLR4-induced IFN- production increases TLR2 sensitivity and drives Gram-negative sepsis in mice
Journal of Experimental Medicine, 2008
PBMCs released IFN-␥ in a TLR4-dependent manner, leading to enhanced surface TLR2 expression and sensitivity for TLR2 ligands. Our results implicate TLR2 as an important, TLR4-driven sensor of Gram-negative bacterial infection and provide a rationale for blockade of both TLRs, in addition to antibiotic therapy for the treatment of Gram-negative bacterial infection.