-
Frontiers in Pharmacology 2022Despite the power of antibiotics, bacterial infections remain a major killer, due to antibiotic resistance and hosts with dysregulated immune systems. We and others have...
Despite the power of antibiotics, bacterial infections remain a major killer, due to antibiotic resistance and hosts with dysregulated immune systems. We and others have been developing drug-loaded nanoparticles that home to the sites of infection and inflammation via engineered tropism for neutrophils, the first-responder leukocytes in bacterial infections. Here, we examined how a member of a broad class of neutrophil-tropic nanoparticles affects neutrophil behavior, specifically questioning whether the nanoparticles attenuate an important function, bacterial phagocytosis. We found these nanoparticles actually phagocytosis of non-opsonized bacteria, increasing it by ∼50%. We showed this augmentation of phagocytosis is likely co-opting an evolved response, as opsonized bacteria also augment phagocytosis of non-opsonized bacteria. Enhancing phagocytosis of non-opsonized bacteria may prove particularly beneficial in two clinical situations: in hypocomplementemic patients (meaning low levels of the main bacterial opsonins, complement proteins, seen in conditions such as neonatal sepsis and liver failure) or for bacteria that are largely resistant to complement opsonization (e.g., ). Additionally, we observe that; 1) prior treatment with bacteria augments neutrophil uptake of neutrophil-tropic nanoparticles; 2) neutrophil-tropic nanoparticles colocalize with bacteria inside of neutrophils. The observation that neutrophil-tropic nanoparticles enhance neutrophil phagocytosis and localize with bacteria inside neutrophils suggests that these nanoparticles will serve as useful carriers for drugs to ameliorate bacterial diseases.
PubMed: 35860017
DOI: 10.3389/fphar.2022.923814 -
Virulence Dec 2022, a leading human pathogen, is responsible for a wide range of diseases, including skin and soft tissue infections and severe invasive diseases. produces a large...
, a leading human pathogen, is responsible for a wide range of diseases, including skin and soft tissue infections and severe invasive diseases. produces a large arsenal of virulence factors, including several immune evasion factors. We have identified an open reading frame () in the SF370 genome encoding a protein of unknown function. Using recombinant Spy0136 in a pull-down assay with human plasma and ELISA, we have identified four complement proteins (C1r, C1s, C3, and C5) as binding partners. Treatment of the complement proteins with PNGase F abrogated binding to C1s, C3, and C5, indicating glycan-dependent interactions. rSpy0136 inhibited complement-mediated hemolysis and interfered with all three complement pathways in a Wieslab complement assay. Furthermore, rSpy0136 inhibited deposition of the C3b opsonin and the membrane attack complex (MAC) on the surface of . We therefore named the previously unknown protein 'complement evasion factor' (CEF).An deletion mutant showed decreased virulence in an whole blood killing assay and a (wax moth) infection model. Furthermore, an gain-of-function mutant showed increased survival during growth in whole human blood. Analysis of serum samples from patients with invasive revealed Spy0136/CEF sero-conversion indicating expression during disease. In summary, we have identified a novel immune evasion factor that binds to several complement proteins to interfere with complement function. This is the first example of a virulence factor binding to several different target proteins via glycan-dependent interactions.
Topics: Bacterial Proteins; Complement System Proteins; Humans; Immune Evasion; Streptococcal Infections; Streptococcus pyogenes; Virulence Factors
PubMed: 35094646
DOI: 10.1080/21505594.2022.2027629 -
Proceedings of the National Academy of... Jul 2020Atherosclerosis is the process underlying heart attack and stroke. Despite decades of research, its pathogenesis remains unclear. Dogma suggests that atherosclerotic...
Atherosclerosis is the process underlying heart attack and stroke. Despite decades of research, its pathogenesis remains unclear. Dogma suggests that atherosclerotic plaques expand primarily via the accumulation of cholesterol and inflammatory cells. However, recent evidence suggests that a substantial portion of the plaque may arise from a subset of "dedifferentiated" vascular smooth muscle cells (SMCs) which proliferate in a clonal fashion. Herein we use multicolor lineage-tracing models to confirm that the mature SMC can give rise to a hyperproliferative cell which appears to promote inflammation via elaboration of complement-dependent anaphylatoxins. Despite being extensively opsonized with prophagocytic complement fragments, we find that this cell also escapes immune surveillance by neighboring macrophages, thereby exacerbating its relative survival advantage. Mechanistic studies indicate this phenomenon results from a generalized opsonin-sensing defect acquired by macrophages during polarization. This defect coincides with the noncanonical up-regulation of so-called don't eat me molecules on inflamed phagocytes, which reduces their capacity for programmed cell removal (PrCR). Knockdown or knockout of the key antiphagocytic molecule CD47 restores the ability of macrophages to sense and clear opsonized targets in vitro, allowing for potent and targeted suppression of clonal SMC expansion in the plaque in vivo. Because integrated clinical and genomic analyses indicate that similar pathways are active in humans with cardiovascular disease, these studies suggest that the clonally expanding SMC may represent a translational target for treating atherosclerosis.
Topics: Animals; Atherosclerosis; CD47 Antigen; Cell Lineage; Cell Proliferation; Cloning, Molecular; Complement Activation; Complement C3; Female; Humans; Inflammation; Macrophages; Male; Mice, Knockout, ApoE; Myocytes, Smooth Muscle; Phagocytosis; Plaque, Atherosclerotic; Sequence Analysis, RNA; Up-Regulation
PubMed: 32541024
DOI: 10.1073/pnas.2006348117 -
International Journal of Molecular... Dec 2021After stroke, there is a rapid necrosis of all cells in the infarct, followed by a delayed loss of neurons both in brain areas surrounding the infarct, known as... (Review)
Review
After stroke, there is a rapid necrosis of all cells in the infarct, followed by a delayed loss of neurons both in brain areas surrounding the infarct, known as 'selective neuronal loss', and in brain areas remote from, but connected to, the infarct, known as 'secondary neurodegeneration'. Here we review evidence indicating that this delayed loss of neurons after stroke is mediated by the microglial phagocytosis of stressed neurons. After a stroke, neurons are stressed by ongoing ischemia, excitotoxicity and/or inflammation and are known to: (i) release "find-me" signals such as ATP, (ii) expose "eat-me" signals such as phosphatidylserine, and (iii) bind to opsonins, such as complement components C1q and C3b, inducing microglia to phagocytose such neurons. Blocking these factors on neurons, or their phagocytic receptors on microglia, can prevent delayed neuronal loss and behavioral deficits in rodent models of ischemic stroke. Phagocytic receptors on microglia may be attractive treatment targets to prevent delayed neuronal loss after stroke due to the microglial phagocytosis of stressed neurons.
Topics: Animals; Brain; Humans; Inflammation; Microglia; Neurons; Phagocytosis; Stroke
PubMed: 34948237
DOI: 10.3390/ijms222413442 -
Biomedicine Hub 2016Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAVs) are a group of systemic autoimmune disorders characterized by necrotizing inflammation of... (Review)
Review
Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAVs) are a group of systemic autoimmune disorders characterized by necrotizing inflammation of medium-to-small vessels, a relative paucity of immune deposits, and an association with detectable circulating ANCAs. AAVs include granulomatosis with polyangiitis (renamed from Wegener's granulomatosis), microscopic polyangiitis, and eosinophilic granulomatosis with polyangiitis (Churg-Strauss syndrome). Until recently, AAVs have not been viewed as complement-mediated disorders. However, recent findings predominantly from animal studies demonstrated a crucial role of the complement system in the pathogenesis of AAVs. Complement activation or defects in its regulation have been described in an increasing number of acquired or genetically driven forms of thrombotic microangiopathy. Coinciding with this expanding spectrum of complement-mediated diseases, the question arises as to which AAV patients might benefit from a complement-targeted therapy. Therapies directed against the complement system point to the necessity of a genetic workup of genes of complement components and regulators in patients with AAV. Genetic testing together with pluripotent stem cells and bioinformatics tools may broaden our approach to the treatment of patients with aggressive forms of AAV.
PubMed: 31988889
DOI: 10.1159/000453106 -
Pharmaceutics Nov 2022Nanoparticles (NPs) are versatile candidates for nanomedical applications due to their unique physicochemical properties. However, their clinical applicability is... (Review)
Review
Nanoparticles (NPs) are versatile candidates for nanomedical applications due to their unique physicochemical properties. However, their clinical applicability is hindered by their undesirable recognition by the immune system and the consequent immunotoxicity, as well as their rapid clearance in vivo. After injection, NPs are usually covered with layers of proteins, called protein coronas (PCs), which alter their identity, biodistribution, half-life, and efficacy. Therefore, the characterization of the PC is for in predicting the fate of NPs in vivo. The aim of this review was to summarize the state of the art regarding the intrinsic factors closely related to the NP structure, and extrinsic factors that govern PC formation in vitro. In addition, well-known opsonins, including complement, immunoglobulins, fibrinogen, and dysopsonins, such as histidine-rich glycoprotein, apolipoproteins, and albumin, are described in relation to their role in NP detection by immune cells. Particular emphasis is placed on their role in mediating the interaction of NPs with innate and adaptive immune cells. Finally, strategies to reduce PC formation are discussed in detail.
PubMed: 36559099
DOI: 10.3390/pharmaceutics14122605 -
Nature Communications Mar 2020Expression of the matricellular protein CCN1 (CYR61) is associated with inflammation and is required for successful wound repair. Here, we show that CCN1 binds bacterial...
Expression of the matricellular protein CCN1 (CYR61) is associated with inflammation and is required for successful wound repair. Here, we show that CCN1 binds bacterial pathogen-associated molecular patterns including peptidoglycans of Gram-positive bacteria and lipopolysaccharides of Gram-negative bacteria. CCN1 opsonizes methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa and accelerates their removal by phagocytosis and increased production of bactericidal reactive oxygen species in macrophages through the engagement of integrin αβ. Mice with myeloid-specific Ccn1 deletion and knock-in mice expressing CCN1 unable to bind αβ are more susceptible to infection by S. aureus or P. aeruginosa, resulting in increased mortality and organ colonization. Furthermore, CCN1 binds directly to TLR2 and TLR4 to activate MyD88-dependent signaling, cytokine expression and neutrophil mobilization. CCN1 is therefore a pattern recognition receptor that opsonizes bacteria for clearance and functions as a damage-associated molecular pattern to activate inflammatory responses, activities that contribute to wound healing and tissue repair.
Topics: Animals; Cysteine-Rich Protein 61; Disease Models, Animal; Disease Susceptibility; Female; Gene Knock-In Techniques; Gene Knockdown Techniques; Humans; Integrin alphaVbeta3; Male; Methicillin-Resistant Staphylococcus aureus; Mice; Mice, Inbred C57BL; Mice, Transgenic; Opsonin Proteins; Pathogen-Associated Molecular Pattern Molecules; Phagocytosis; Pseudomonas Infections; Pseudomonas aeruginosa; Sf9 Cells; Signal Transduction; Staphylococcal Infections; Toll-Like Receptors
PubMed: 32144270
DOI: 10.1038/s41467-020-15075-5 -
Microbiology Spectrum Aug 2023Mycobacterium abscessus, an intracellular nontuberculous mycobacterium, is considered the most pathogenic species among the group of rapidly growing mycobacteria. The...
Mycobacterium abscessus, an intracellular nontuberculous mycobacterium, is considered the most pathogenic species among the group of rapidly growing mycobacteria. The resistance of M. abscessus to the host innate response contributes to its pathogenicity in addition to several virulence factors. We have recently shown in that antimicrobial peptides (AMPs), whose production is induced by M. abscessus, are unable to control mycobacterial infection. This could be due to their inability to kill mycobacteria and/or the hidden location of the pathogen in phagocytic cells. Here, we demonstrate that the rapid internalization of M. abscessus by macrophages allows it to escape the AMP-mediated humoral response. By depleting phagocytes in AMP-deficient flies, we found that several AMPs were required for the control of extracellular M. abscessus. This was confirmed in the Tep4 opsonin-deficient flies, which we show can better control M. abscessus growth and have increased survival through overproduction of some AMPs, including Defensin. Furthermore, Defensin alone was sufficient to kill extracellular M. abscessus both and and control its infection. Collectively, our data support that Tep4-mediated opsonization of M. abscessus allows its escape and resistance toward the Defensin bactericidal action in . Mycobacterium abscessus, an opportunistic pathogen in cystic fibrosis patients, is the most pathogenic species among the fast-growing mycobacteria. How M. abscessus resists the host innate response before establishing an infection remains unclear. Using , we have recently demonstrated that M. abscessus resists the host innate response by surviving the cytotoxic lysis of the infected phagocytes and the induced antimicrobial peptides (AMPs), including Defensin. In this work, we demonstrate that M. abscessus resists the latter response by being rapidly internalized by phagocytes. Indeed, by combining and approaches, we show that Defensin is able to control extracellular M. abscessus infection through a direct bactericidal action. In conclusion, we report that M. abscessus escapes the host AMP-mediated humoral response by taking advantage of its internalization by the phagocytes.
Topics: Animals; Mycobacterium abscessus; Drosophila; Opsonization; Mycobacterium; Antimicrobial Peptides; Defensins; Mycobacterium Infections, Nontuberculous; Anti-Bacterial Agents
PubMed: 37260399
DOI: 10.1128/spectrum.00777-23 -
IUBMB Life Jan 2018Lacking protein synthesis machinery and organelles necessary for autophagy or apoptosis, aged red blood cells (RBCs) are marked by circulating auto-antibodies for... (Review)
Review
Lacking protein synthesis machinery and organelles necessary for autophagy or apoptosis, aged red blood cells (RBCs) are marked by circulating auto-antibodies for macrophage-mediated clearance. The antigen recognized by these auto-antibodies is the major protein of the RBC membrane, Band 3. To ensure regulation and specificity in clearance, the molecular "clock" must mark senescent cells in a way that differentiates them from younger cells, to prevent premature clearance. Predominant models of Band 3 senescence signaling are reviewed, and merits are discussed in light of the recently published crystal structure of the Band 3 membrane domain. © 2017 IUBMB Life, 70(1):32-40, 2018.
Topics: Anion Exchange Protein 1, Erythrocyte; Autoantibodies; Autoantigens; Binding Sites, Antibody; Cellular Senescence; Epitopes; Erythrocytes; Humans; Ion Transport; Macrophages; Opsonin Proteins; Phagocytosis; Protein Interaction Domains and Motifs; Protein Structure, Secondary; Signal Transduction; Time Factors
PubMed: 29240292
DOI: 10.1002/iub.1703 -
Exercise Immunology Review 2022The complement system is comprised of the classical, lectin and alternative pathways that result in the formation of: pro-inflammatory anaphylatoxins; opsonins that...
BACKGROUND
The complement system is comprised of the classical, lectin and alternative pathways that result in the formation of: pro-inflammatory anaphylatoxins; opsonins that label cells for phagocytic removal; and, a membrane attack complex that directly lyses target cells. Complement-dependent cytotoxicity (CDC) - cell lysis triggered by complement protein C1q binding to the Fc region of antibodies bound to target cells - is another effector function of complement and a key mechanism-of-action of several monoclonal antibody therapies. At present, it is not well established how exercise affects complement system proteins in humans.
METHODS
A systematic search was conducted to identify studies that included original data and investigated the association between soluble complement proteins in the blood of healthy humans, and: 1) an acute bout of exercise; 2) exercise training interventions; or, 3) measurements of habitual physical activity and fitness.
RESULTS
77 studies were eligible for inclusion in this review, which included a total of 10,236 participants, and 40 complement proteins and constituent fragments. Higher levels of exercise training and cardiorespiratory fitness were commonly associated with reduced C3 in blood. Additionally, muscle strength was negatively associated with C1q. Elevated C3a-des-Arg, C4a-des-Arg and C5a, lower C1-inhibitor, and unchanged C3 and C4 were reported immediately post-laboratory based exercise, compared to baseline. Whereas, ultra-endurance running and resistance training increased markers of the alternative (factor B and H), classical (C1s), and leptin (mannose binding lectin) pathways, as well as C3 and C6 family proteins, up to 72-h following exercise. Heterogeneity among studies may be due to discrepancies in blood sampling/handling procedures, analytical techniques, exercise interventions/measurements and fitness of included populations.
CONCLUSIONS
Increased anaphylatoxins were observed immediately following an acute bout of exercise in a laboratory setting, whereas field-based exercise interventions of a longer duration (e.g. ultra-endurance running) or designed to elicit muscle damage (e.g. resistance training) increased complement proteins for up to 72-h. C3 in blood was mostly reduced by exercise training and associated with increased cardiorespiratory fitness, whereas C1q appeared to be negatively associated to muscle strength. Thus, both acute bouts of exercise and exercise training appear to modulate complement system proteins. Future research is needed to assess the clinical implications of these changes, for example on the efficacy of monoclonal antibody therapies dependent on CDC.
Topics: Anaphylatoxins; Antibodies, Monoclonal; Complement C1q; Complement System Proteins; Exercise; Humans
PubMed: 35452398
DOI: No ID Found