The effects of selective complement and CD14 inhibition on the E. coli-induced tissue factor mRNA upregulation, monocyte tissue factor expression, and tissue factor functional activity in human whole blood

Disseminated intravascular coagulation and its immune mechanisms

Disseminated intravascular coagulation (DIC) is a syndrome triggered by infectious and noninfectious pathologies characterized by excessive generation of thrombin within the vasculature and widespread proteolytic conversion of fibrinogen. Despite diverse clinical manifestations ranging from thrombo-occlusive damage to bleeding diathesis, DIC etiology commonly involves excessive activation of blood coagulation and overlapping dysregulation of anticoagulants and fibrinolysis. Initiation of blood coagulation follows intravascular expression of tissue factor or activation of the contact pathway in response to pathogen-associated or host-derived, damage-associated molecular patterns. The process is further amplified through inflammatory and immunothrombotic mechanisms. Consumption of anticoagulants and disruption of endothelial homeostasis lower the regulatory control and disseminate microvascular thrombosis. Clinical DIC development in patients is associated with worsening morbidities and increased mortality, regardless of the underlying pathology; therefore, timely recognition of DIC is critical for reducing the pathologic burden. Due to the diversity of triggers and pathogenic mechanisms leading to DIC, diagnosis is based on algorithms that quantify hemostatic imbalance, thrombocytopenia, and fibrinogen conversion. Because current diagnosis primarily assesses overt consumptive coagulopathies, there is a critical need for better recognition of nonovert DIC and/or pre-DIC states. Therapeutic strategies for patients with DIC involve resolution of the eliciting triggers and supportive care for the hemostatic imbalance. Despite medical care, mortality in patients with DIC remains high, and new strategies, tailored to the underlying pathologic mechanisms, are needed.

Oleanolic acid reshapes the gut microbiota and alters immune-related gene expression of intestinal epithelial cells

BACKGROUND

Oleanolic acid (OA) is a pentacyclic triterpenoid compound that is present at high levels in olive oil and has several promising pharmacological effects, such as liver protection and anti-inflammatory, antioxidant, and anticancer effects. The purpose of the present study was to assess whether OA treatment affects gut health compared to a control condition, including gut microbiota and intestinal epithelial immunity.

RESULTS

Illumina MiSeq sequencing (16S rRNA gene) was used to investigate the effect of OA on the microbial community of the intestinal tract, while Illumina HiSeq (RNA-seq) technology was used to investigate the regulatory effect of OA on gene expression in intestinal epithelial cells, which allowed for a comprehensive analysis of the effects of OA on intestinal health. The results showed that the consumption of OA initially controlled weight gain in mice and altered the composition of the gut microbiota. At the phylum level, OA significantly increased the relative abundances of cecum Firmicutes but decreased the abundance of Actinobacteria, and at the genus level it increased the relative abundance of potentially beneficial bacteria such as Oscillibacter and Ruminiclostridium 9. Oleanolic acid treatment also altered the expression of 12 genes involved in the Kyoto Encyclopedia of Genes and Genomes（KEGG）pathways of complement and coagulation cascades, hematopoietic cell lineage, and leukocyte transendothelial migration in intestinal epithelial cells to improve gut immunity.

CONCLUSION

Intake of OA can contribute beneficial effects by optimizing gut microbiota and altering the immune function of intestinal epithelial cells, potentially to improve intestinal health status. © 2021 Society of Chemical Industry.

Application of the C3 inhibitor compstatin in a human whole blood model designed for complement research - 20 years of experience and future perspectives

The complex molecular and cellular biological systems that maintain host homeostasis undergo continuous crosstalk. Complement, a component of innate immunity, is one such system. Initially regarded as a system to protect the host from infection, complement has more recently been shown to have numerous other functions, including involvement in embryonic development, tissue modeling, and repair. Furthermore, the complement system plays a major role in the pathophysiology of many diseases. Through interactions with other plasma cascades, including hemostasis, complement activation leads to the broad host-protective response known as thromboinflammation. Most complement research has been limited to reductionistic models of purified components and cells and their interactions in vitro. However, to study the pathophysiology of complement-driven diseases, including the interaction between the complement system and other inflammatory systems, holistic models demonstrating only minimal interference with complement activity are needed. Here we describe two such models; whole blood anticoagulated with either the thrombin inhibitor lepirudin or the fibrin polymerization peptide blocker GPRP, both of which retain complement activity and preserve the ability of complement to be mutually reactive with other inflammatory systems. For instance, to examine the relative roles of C3 and C5 in complement activation, it is possible to compare the effects of the C3 inhibitor compstatin effects to those of inhibitors of C5 and C5aR1. We also discuss how complement is activated by both pathogen-associated molecular patterns, inducing infectious inflammation caused by organisms such as Gram-negative and Gram-positive bacteria, and by sterile damage-associated molecular patterns, including cholesterol crystals and artificial materials used in clinical medicine. When C3 is inhibited, it is important to determine the mechanism by which inflammation is attenuated, i.e., whether the attenuation derives directly from C3 activation products or via downstream activation of C5, since the mechanism involved may determine the appropriate choice of inhibitor under various conditions. With some exceptions, most inflammatory responses are dependent on C5 and C5aR1; one exception is venous air embolism, in which air bubbles enter the blood circulation and trigger a mainly C3-dependent thromboembolism, with the formation of an active C3 convertase, without a corresponding C5 activation. Under such conditions, an inhibitor of C3 is needed to attenuate the inflammation. Our holistic blood models will be useful for further studies of the inhibition of any complement target, not just C3 or C5. The focus here will be on targeting the critical complement component, activation product, or receptor that is important for the pathophysiology in a variety of disease conditions.

Complement Inhibition and COVID-19: The Story so Far

Acute respiratory distress syndrome (ARDS) is the most severe complication of COVID-19, a disease caused by severe acute respiratory syndrome coronavirus (SARS CoV) 2. The mechanisms underlying the progression from asymptomatic disease to pneumonia and ARDS are complex and by far unelucidated. As for bacterial sepsis, the release of damage associated molecular patterns and pathogen associated molecular patterns triggers activation of the complement cascade. Subsequently, overexpressed anaphylatoxins recruit inflammatory cells in the lung and other organs and contribute initiating and amplifying a vicious circle of thromboinflammation causing organs damage and eventually death. Preclinical and observational studies in patients with COVID-19 provided evidence that complement inhibition effectively may attenuate lung and systemic inflammation, restore the coagulation/fibrinolysis balance, improve organs function and eventually may save life. Ongoing Phase 2/3 trials should elucidate the benefit to risk profile of complement inhibitors and may clarify the optimal targets in the complement cascade.

Complement Component C5 and TLR Molecule CD14 Mediate Heme-Induced Thromboinflammation in Human Blood

Heme is a critical danger molecule liberated from hemeproteins in various conditions, including from hemoglobin in hemolytic diseases. Heme may cause thromboinflammatory damage by activating inflammatory and hemostatic pathways, such as complement, the TLRs, coagulation, and platelets. In this study, we explored the effect of single and dual inhibition of complement component C5 and TLR coreceptor CD14 on heme-induced thromboinflammation in an ex vivo human whole blood model. Heme induced a dose-dependent activation of complement via the alternative pathway. Single inhibition of C5 by eculizumab attenuated the release of IL-6, IL-8, TNF, MCP-1, MIP-1α, IFN-γ, LTB-4, MMP-8 and -9, and IL-1Ra with more than 60% (p < 0.05 for all) reduced the upregulation of CD11b on granulocytes and monocytes by 59 and 40%, respectively (p < 0.05), and attenuated monocytic tissue factor expression by 33% (p < 0.001). Blocking CD14 attenuated IL-6 and TNF by more than 50% (p < 0.05). In contrast to single inhibition, combined C5 and CD14 was required for a significantly attenuated prothrombin cleavage (72%, p < 0.05). Markers of thromboinflammation were also quantified in two patients admitted to the hospital with sickle cell disease (SCD) crisis. Both SCD patients had pronounced hemolysis and depleted plasma hemopexin and haptoglobin. Plasma heme and complement activation was markedly increased in one patient, a coinciding observation as demonstrated ex vivo. In conclusion, heme-induced thromboinflammation was largely attenuated by C5 inhibition alone, with a beneficial effect of adding a CD14 inhibitor to attenuate prothrombin activation. Targeting C5 has the potential to reduce thromboinflammation in SCD crisis patients.

Ex vivo modelling of the formation of inflammatory platelet-leucocyte aggregates and their adhesion on endothelial cells, an early event in sepsis

Septicaemia is an acute inflammatory reaction in the bloodstream to the presence of pathogen-associated molecular patterns. Whole blood stimulation assays capture endotoxin-induced formation of aggregates between platelets and leucocytes using flow cytometry. We wanted to assess extent of spontaneous aggregate formation in whole blood stimulation assays and compare the effects of endotoxin and heat-killed, clinically relevant, bacterial pathogens on aggregate formation and then on adhesion of aggregates to TNFα-stimulated endothelial cells. We found that endotoxin (from Escherichia coli or Salmonella enteritidis) was not a suitable stimulus to provoke platelet-leucocyte aggregates in vitro, as it did not further increase the extent of aggregates formed spontaneously in stasis of hirudin-anticoagulated blood. Specifically, whole blood samples stimulated with or without LPS produced aggregates with a mean surface area of 140.97 and 117.68 μm2, respectively. By contrast, incubation of whole blood with heat-killed Klebsiella pneumoniae or Staphylococcus aureus produced significantly enhanced and complex cellular aggregates (with a mean surface area of 470.61 and 518.39 μm2, respectively) which adhered more frequently to TNFα (and free fatty acid)-stimulated endothelial cells. These were reliably captured by scanning electron microscopy. Adhesion of cellular aggregates could be blocked by incubation of endothelial cells with a commercial P-selectin antibody and an angiopoietin-2 ligand trap. In conclusion, we have developed an in vitro method that models the acute inflammatory reaction in whole blood in the presence of sepsis-relevant bacterial pathogen surfaces.

Clinical promise of next-generation complement therapeutics

The complement system plays a key role in pathogen immunosurveillance and tissue homeostasis. However, subversion of its tight regulatory control can fuel a vicious cycle of inflammatory damage that exacerbates pathology. The clinical merit of targeting the complement system has been established for rare clinical disorders such as paroxysmal nocturnal haemoglobinuria and atypical haemolytic uraemic syndrome. Evidence from preclinical studies and human genome-wide analyses, supported by new molecular and structural insights, has revealed new pathomechanisms and unmet clinical needs that have thrust a new generation of complement inhibitors into clinical development for a variety of indications. This review critically discusses recent clinical milestones in complement drug discovery, providing an updated translational perspective that may guide optimal target selection and disease-tailored complement intervention.

Complement component 5 does not interfere with physiological hemostasis but is essential for Escherichia coli-induced coagulation accompanied by Toll-like receptor 4

There is a close cross-talk between complement, Toll-like receptors (TLRs) and coagulation. The role of the central complement component 5 (C5) in physiological and pathophysiological hemostasis has not, however, been fully elucidated. This study examined the effects of C5 in normal hemostasis and in Escherichia coli-induced coagulation and tissue factor (TF) up-regulation. Fresh whole blood obtained from six healthy donors and one C5-deficient individual (C5D) was anti-coagulated with the thrombin inhibitor lepirudin. Blood was incubated with or without E. coli in the presence of the C5 inhibitor eculizumab, a blocking anti-CD14 monoclonal antibody (anti-CD14) or the TLR-4 inhibitor eritoran. C5D blood was reconstituted with purified human C5. TF mRNA was measured by quantitative polymerase chain reaction (qPCR) and monocyte TF and CD11b surface expression by flow cytometry. Prothrombin fragment 1+2 (PTF1·2) in plasma and microparticles exposing TF (TF-MP) was measured by enzyme-linked immunosorbent assay (ELISA). Coagulation kinetics were analyzed by rotational thromboelastometry and platelet function by PFA-200. Normal blood with eculizumab as well as C5D blood with or without reconstitution with C5 displayed completely normal biochemical hemostatic patterns. In contrast, E. coli-induced TF mRNA and TF-MP were significantly reduced by C5 inhibition. C5 inhibition combined with anti-CD14 or eritoran completely inhibited the E. coli-induced monocyte TF, TF-MP and plasma PTF1·2. Addition of C5a alone did not induce TF expression on monocytes. In conclusion, C5 showed no impact on physiological hemostasis, but substantially contributed to E. coli-induced procoagulant events, which were abolished by the combined inhibition of C5 and CD14 or TLR-4.

Alginate microbeads are coagulation compatible, while alginate microcapsules activate coagulation secondary to complement or directly through FXII

Alginate microspheres are presently under evaluation for future cell-based therapy. Their ability to induce harmful host reactions needs to be identified for developing the most suitable devices and efficient prevention strategies. We used a lepirudin based human whole blood model to investigate the coagulation potentials of alginate-based microspheres: alginate microbeads (Ca/Ba Beads), alginate poly-l-lysine microcapsules (APA and AP microcapsules) and sodium alginate-sodium cellulose sulfate-poly(methylene-co-cyanoguanidine) microcapsules (PMCG microcapsules). Coagulation activation measured by prothrombin fragments 1+2 (PTF1.2) was rapidly and markedly induced by the PMCG microcapsules, delayed and lower induced by the APA and AP microcapsules, and not induced by the Ca/Ba Beads. Monocytes tissue factor (TF) expression was similarly activated by the microcapsules, whereas not by the Ca/Ba Beads. PMCG microcapsules-induced PTF1.2 was abolished by FXII inhibition (corn trypsin inhibitor), thus pointing to activation through the contact pathway. PTF1.2 induced by the AP and APA microcapsules was inhibited by anti-TF antibody, pointing to a TF driven coagulation. The TF induced coagulation was inhibited by the complement inhibitors compstatin (C3 inhibition) and eculizumab (C5 inhibition), revealing a complement-coagulation cross-talk. This is the first study on the coagulation potentials of alginate microspheres, and identifies differences in activation potential, pathways and possible intervention points.

STATEMENT OF SIGNIFICANCE

Alginate microcapsules are prospective candidate materials for cell encapsulation therapy. The material surface must be free of host cell adhesion to ensure free diffusion of nutrition and oxygen to the encapsulated cells. Coagulation activation is one gateway to cellular overgrowth through deposition of fibrin. Herein we used a physiologically relevant whole blood model to investigate the coagulation potential of alginate microcapsules and microbeads. The coagulation potentials and the pathways of activation were depending on the surface properties of the materials. Activation of the complement system could also be involved, thus emphasizing a complement-coagulation cross-talk. Our findings points to complement and coagulation inhibition as intervention point for preventing host reactions, and enhance functional cell-encapsulation devices.

Cell-specific deletion of C1qa identifies microglia as the dominant source of C1q in mouse brain

BACKGROUND

The complement cascade not only provides protection from infection but can also mediate destructive inflammation. Complement is also involved in elimination of neuronal synapses which is essential for proper development, but can be detrimental during aging and disease. C1q, required for several of these complement-mediated activities, is present in the neuropil, microglia, and a subset of interneurons in the brain.

METHODS

To identify the source(s) of C1q in the brain, the C1qa gene was selectively inactivated in the microglia or Thy-1⁺ neurons in both wild type mice and a mouse model of Alzheimer's disease (AD), and C1q synthesis assessed by immunohistochemistry, QPCR, and western blot analysis.

RESULTS

While C1q expression in the brain was unaffected after inactivation of C1qa in Thy-1⁺ neurons, the brains of C1qa ^FL/FL :Cx3cr1 ^CreERT2 mice in which C1qa was ablated in microglia were devoid of C1q with the exception of limited C1q in subsets of interneurons. Surprisingly, this loss of C1q occurred even in the absence of tamoxifen by 1 month of age, demonstrating that Cre activity is tamoxifen-independent in microglia in Cx3cr1 ^{CreERT2/WganJ} mice. C1q expression in C1qa ^FL/FL : Cx3cr1 ^{CreERT2/WganJ} mice continued to decline and remained almost completely absent through aging and in AD model mice. No difference in C1q was detected in the liver or kidney from C1qa ^FL/FL : Cx3cr1 ^{CreERT2/WganJ} mice relative to controls, and C1qa ^FL/FL : Cx3cr1 ^{CreERT2/WganJ} mice had minimal, if any, reduction in plasma C1q.

CONCLUSIONS

Thus, microglia, but not neurons or peripheral sources, are the dominant source of C1q in the brain. While demonstrating that the Cx3cr1 ^{CreERT2/WganJ} deleter cannot be used for adult-induced deletion of genes in microglia, the model described here enables further investigation of physiological roles of C1q in the brain and identification of therapeutic targets for the selective control of complement-mediated activities contributing to neurodegenerative disorders.

The key roles of complement and tissue factor in Escherichia coli-induced coagulation in human whole blood

The complement system and the Toll-like (TLR) co-receptor CD14 play important roles in innate immunity and sepsis. Tissue factor (TF) is a key initiating component in intravascular coagulation in sepsis, and long pentraxin 3 (PTX3) enhances the lipopolysaccharide (LPS)-induced transcription of TF. The aim of this study was to study the mechanism by which complement and CD14 affects LPS- and Escherichia coli (E. coli)-induced coagulation in human blood. Fresh whole blood was anti-coagulated with lepirudin, and incubated with ultra-purified LPS (100 ng/ml) or with E. coli (1 × 10(7) /ml). Inhibitors and controls included the C3 blocking peptide compstatin, an anti-CD14 F(ab')2 antibody and a control F(ab')2 . TF mRNA was measured using quantitative polymerase chain reaction (qPCR) and monocyte TF surface expression by flow cytometry. TF functional activity in plasma microparticles was measured using an amidolytic assay. Prothrombin fragment F 1+2 (PTF1.2) and PTX3 were measured by enzyme-linked immunosorbent assay (ELISA). The effect of TF was examined using an anti-TF blocking antibody. E. coli increased plasma PTF1.2 and PTX3 levels markedly. This increase was reduced by 84->99% with compstatin, 55-97% with anti-CD14 and > 99% with combined inhibition (P < 0·05 for all). The combined inhibition was significantly (P < 0·05) more efficient than compstatin and anti-CD14 alone. The LPS- and E. coli-induced TF mRNA levels, monocyte TF surface expression and TF functional activity were reduced by > 99% (P < 0·05) with combined C3 and CD14 inhibition. LPS- and E. coli-induced PTF1.2 was reduced by 76-81% (P < 0·05) with anti-TF antibody. LPS and E. coli activated the coagulation system by a complement- and CD14-dependent up-regulation of TF, leading subsequently to prothrombin activation.

Organ inflammation in porcine Escherichia coli sepsis is markedly attenuated by combined inhibition of C5 and CD14

Sepsis is an infection-induced systemic inflammatory syndrome, potentially causing organ failure. We previously showed attenuating effects on inflammation, thrombogenicity and haemodynamics by inhibiting the Toll-like receptor co-factor CD14 and complement factor C5 in a porcine Escherichia coli-induced sepsis model. The present study explored the effect on organ inflammation in these pigs. Tissue samples were examined from the combined treatment group (n = 8), the positive (n = 8) and negative (n = 6) control groups after 4h of sepsis. Inflammatory biomarkers were measured using ELISA, multiplex and qPCR analysis. Combined inhibition of C5 and CD14 markedly attenuated IL-1β by 31-66% (P < 0.05) and IL-6 by 54-96% (P < 0.01) in liver, kidney, lung and spleen; IL-8 by 65-100% in kidney, lung, spleen, and heart (P < 0.05) and MCP-1 by 46-69% in liver, kidney, spleen and heart (P < 0.05). Combined inhibition significantly attenuated tissue factor mRNA upregulation in spleen (P < 0.05) and IP-10 mRNA upregulation in four out of five organs. Finally, C5aR mRNA downregulation was prevented in heart and kidney (P < 0.05). Combined inhibition of C5 and CD14 thus markedly attenuated inflammatory responses in all organs examined. The anti-inflammatory effects observed in lung and heart may explain the delayed haemodynamic disturbances observed in septic pigs receiving combined inhibition of C5 and CD14.

Compstatin: a C3-targeted complement inhibitor reaching its prime for bedside intervention

There is a growing awareness that complement plays an integral role in human physiology and disease, transcending its traditional perception as an accessory system for pathogen clearance and opsonic cell killing. As the list of pathologies linked to dysregulated complement activation grows longer, it has become clear that targeted modulation of this innate immune system opens new windows of therapeutic opportunity for anti-inflammatory drug design. Indeed, the introduction of the first complement-targeting drugs has reignited a vibrant interest in the clinical translation of complement-based inhibitors. Compstatin was discovered as a cyclic peptide that inhibits complement activation by binding C3 and interfering with convertase formation and C3 cleavage. As the convergence point of all activation pathways and a molecular hub for crosstalk with multiple pathogenic pathways, C3 represents an attractive target for therapeutic modulation of the complement cascade. A multidisciplinary drug optimization effort encompassing rational 'wet' and in silico synthetic approaches and an array of biophysical, structural and analytical tools has culminated in an impressive structure-function refinement of compstatin, yielding a series of analogues that show promise for a wide spectrum of clinical applications. These new derivatives have improved inhibitory potency and pharmacokinetic profiles and show efficacy in clinically relevant primate models of disease. This review provides an up-to-date survey of the drug design effort placed on the compstatin family of C3 inhibitors, highlighting the most promising drug candidates. It also discusses translational challenges in complement drug discovery and peptide drug development and reviews concerns related to systemic C3 interception.

Microparticle-associated tissue factor activity is reduced by inhibition of the complement protein 5 in Neisseria meningitidis-exposed whole blood

Neisseria meningitidis causes fulminant meningococcal sepsis with a massive activation of the coagulation and complement cascades. Bacterial cell envelope molecules from N. meningitidis, particularly lipopolysaccharide (LPS), induce tissue factor (TF) expression. In meningococcal sepsis, TF can be detected on circulating monocytes and microparticles (MPs) within the bloodstream. During infection, Nm activates C5 and C5a, which also is able to induce TF. We evaluated the effect of eculizumab, a C5-blocking monoclonal antibodies (mAb), on cell- and MP-associated TF. Using a lepirudin-anticoagulated whole blood model, we activated the coagulation and complement cascades by N. meningitidis, and investigated the interaction between the cascade systems with special focus on cell-associated TF-expression (mRNA and protein) and MP-associated TF-dependent thrombin and fibrin generation in platelet-free plasma. We also examined the ability of TF-positive MPs to support clot formation in whole blood. In addition, the effect of corn trypsin inhibitor and time-dependent changes on MP-associated functional TF activity was examined. Inhibition of C5 reduced cell-associated TF expression at both gene and protein level, and reduced MP-associated TF-dependent thrombin and fibrin generation in platelet-poor plasma, MP-induced TF-dependent clot formation in whole blood, implying that the complement and coagulation cascades are interplayers in N. meningitidis-mediated activation of these cascades.

Advances in biocompatibility and physico-chemical characterization of microspheres for cell encapsulation

Cell encapsulation has already shown its high potential and holds the promise for future cell therapies to enter the clinics as a large scale treatment option for various types of diseases. The advancement in cell biology towards this goal has to be complemented with functional biomaterials suitable for cell encapsulation. This cannot be achieved without understanding the close correlation between cell performance and properties of microspheres. The ongoing challenges in the field of cell encapsulation require a critical view on techniques and approaches currently utilized to characterize microspheres. This review deals with both principal subjects of microspheres characterization in the cell encapsulation field: physico-chemical characterization and biocompatibility. The up-to-day knowledge is summarized and discussed with the focus to identify missing knowledge and uncertainties, and to propose the mandatory next steps in characterization of microspheres for cell encapsulation. The primary conclusion of this review is that further success in development of microspheres for cell therapies cannot be accomplished without careful selection of characterization techniques, which are employed in conjunction with biological tests.

Chimeric anti-CD14 IGG2/4 Hybrid antibodies for therapeutic intervention in pig and human models of inflammation

CD14 is a key recognition molecule of innate immune responses, interacting with several TLRs. TLR signaling cross-talks extensively with the complement system, and combined CD14 and complement inhibition has been proved effective in attenuating inflammatory responses. Pig models of human diseases have emerged as valuable tools to study therapeutic intervention, but suitable neutralizing Abs are rare. Undesired Fc-mediated functions, such as platelet activation and IL-8 release induced by the porcine CD14-specific clone Mil2, limit further studies. Therefore, an inert human IgG2/IgG4 hybrid C region was chosen for an rMil2. As revealed in ex vivo and in vivo pig experiments, rMil2 inhibited the CD14-mediated proinflammatory cytokine response similar to the original clone, but lacked the undesired Fc-effects, and inflammation was attenuated further by simultaneous complement inhibition. Moreover, rMil2 bound porcine FcRn, a regulator of t1/2 and biodistribution. Thus, rMil2, particularly combined with complement inhibitors, should be well suited for in vivo studies using porcine models of diseases, such as sepsis and ischemia-reperfusion injury. Similarly, the recombinant anti-human CD14 IgG2/4 Ab, r18D11, was generated with greatly reduced Fc-mediated effects and preserved inhibitory function ex vivo. Such Abs might be drug candidates for the treatment of innate immunity-mediated human diseases.

Combined inhibition of complement C5 and CD14 markedly attenuates inflammation, thrombogenicity, and hemodynamic changes in porcine sepsis

Complement and the TLR family constitute two important branches of innate immunity. We previously showed attenuating effects on inflammation and thromogenicity by inhibiting the TLR coreceptor CD14 in porcine sepsis. In the present study, we explored the effect of the C5 and leukotriene B4 inhibitor Ornithodoros moubata complement inhibitor (OmCI; also known as coversin) alone and combined with anti-CD14 on the early inflammatory, hemostatic, and hemodynamic responses in porcine Escherichia coli-induced sepsis. Pigs were randomly allocated to negative controls (n = 6), positive controls (n = 8), intervention with OmCI (n = 8), or with OmCI and anti-CD14 (n = 8). OmCI ablated C5 activation and formation of the terminal complement complex and significantly decreased leukotriene B4 levels in septic pigs. Granulocyte tissue factor expression, formation of thrombin-antithrombin complexes (p < 0.001), and formation of TNF-α and IL-6 (p < 0.05) were efficiently inhibited by OmCI alone and abolished or strongly attenuated by the combination of OmCI and anti-CD14 (p < 0.001 for all). Additionally, the combined therapy attenuated the formation of plasminogen activator inhibitor-1 (p < 0.05), IL-1β, and IL-8, increased the formation of IL-10, and abolished the expression of wCD11R3 (CD11b) and the fall in neutrophil cell count (p < 0.001 for all). Finally, OmCI combined with anti-CD14 delayed increases in heart rate by 60 min (p < 0.05) and mean pulmonary artery pressure by 30 min (p < 0.01). Ex vivo studies confirmed the additional effect of combining anti-CD14 with OmCI. In conclusion, upstream inhibition of the key innate immunity molecules, C5 and CD14, is a potential broad-acting treatment regimen in sepsis as it efficiently attenuated inflammation and thrombogenicity and delayed hemodynamic changes.

Complement in immune and inflammatory disorders: therapeutic interventions

With the awareness that immune-inflammatory cross-talk is at the heart of many disorders, the desire for novel immunomodulatory strategies in the therapy of such diseases has grown dramatically. As a prime initiator and important modulator of immunological and inflammatory processes, the complement system has emerged as an attractive target for early and upstream intervention in inflammatory diseases and has moved into the spotlight of drug discovery. Although prevalent conditions such as age-related macular degeneration have attracted the most attention, the diverse array of complement-mediated pathologies, with distinct underlying mechanisms, demands a multifaceted arsenal of therapeutic strategies. Fortunately, efforts in recent years have not only introduced the first complement inhibitors to the clinic but also filled the pipelines with promising candidates. With a focus on immunomodulatory strategies, in this review we discuss complement-directed therapeutic concepts and highlight promising candidate molecules.

Bride and groom in systemic inflammation--the bells ring for complement and Toll in cooperation

Attenuating the sepsis-induced systemic inflammatory response, with subsequent homeostatic imbalance, has for years been one of the main tasks in sepsis related research. Complement and the TLR family constitute two important upstream sensor and effector-systems of innate immunity. Although they act as partly independent branches of pattern recognition, recent evidence indicate a considerable cross-talk implying that they can either compensate, synergize or antagonize each other. Combined inhibition of these pathways is therefore a particularly interesting approach with a profound anti-inflammatory potential. In previous preclinical studies, we demonstrated that targeting the key molecules C3 or C5 of complement and CD14 of the TLR family had a vast anti-inflammatory effect on Gram-negative bacteria-induced inflammation and sepsis. In this review, we elucidate the significance of these key molecules as important targets for intervention in sepsis and systemic inflammatory response syndrome. Finally, we argue that a combined inhibition of complement and CD14 represent a potential general treatment regimen, beyond the limit of sepsis, including non-infectious systemic inflammation and ischemia reperfusion injury.