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ACS Nano Feb 2022For several decades, surface grafted polyethylene glycol (PEG) has been a go-to strategy for preserving the synthetic identity of liposomes in physiological milieu and...
For several decades, surface grafted polyethylene glycol (PEG) has been a go-to strategy for preserving the synthetic identity of liposomes in physiological milieu and preventing clearance by immune cells. However, the limited clinical translation of PEGylated liposomes is mainly due to the protein corona formation and the subsequent modification of liposomes' synthetic identity, which affects their interactions with immune cells and blood residency. Here we exploit the electric charge of DNA to generate unPEGylated liposome/DNA complexes that, upon exposure to human plasma, gets covered with an opsonin-deficient protein corona. The final product of the synthetic process is a biomimetic nanoparticle type covered by a proteonucleotidic corona, or "proteoDNAsome", which maintains its synthetic identity and is able to slip past the immune system more efficiently than PEGylated liposomes. Accumulation of proteoDNAsomes in the spleen and the liver was lower than that of PEGylated systems. Our work highlights the importance of generating stable biomolecular coronas in the development of stealth unPEGylated particles, thus providing a connection between the biological behavior of particles and their synthetic identity.
Topics: Humans; Liposomes; Opsonin Proteins; Polyethylene Glycols; Protein Corona
PubMed: 35040637
DOI: 10.1021/acsnano.1c07687 -
Frontiers in Immunology 2019Opsonins are soluble, extracellular proteins, released by activated immune cells, and when bound to a target cell, can induce phagocytes to phagocytose the target cell....
Opsonins are soluble, extracellular proteins, released by activated immune cells, and when bound to a target cell, can induce phagocytes to phagocytose the target cell. There are three known classes of opsonin: antibodies, complement factors and secreted pattern recognition receptors, but these have limited access to the brain. We identify here two novel opsonins of bacteria, calreticulin, and galectin-3 (both lectins that can bind lipopolysaccharide), which were released by microglia (brain-resident macrophages) when activated by bacterial lipopolysaccharide. Calreticulin and galectin-3 both bound to , and when bound increased phagocytosis of these bacteria by microglia. Furthermore, lipopolysaccharide-induced microglial phagocytosis of bacteria was partially inhibited by: sugars, an anti-calreticulin antibody, a blocker of the calreticulin phagocytic receptor LRP1, a blocker of the galectin-3 phagocytic receptor MerTK, or simply removing factors released from the microglia, indicating this phagocytosis is dependent on extracellular calreticulin and galectin-3. Thus, calreticulin and galectin-3 are opsonins, released by activated microglia to promote clearance of bacteria. This innate immune response of microglia may help clear bacterial infections of the brain.
Topics: Animals; Brain; Calreticulin; Escherichia coli; Escherichia coli Infections; Galectin 3; Immunity, Innate; Mice; Microglia; Opsonin Proteins; Phagocytosis; Rats
PubMed: 31781126
DOI: 10.3389/fimmu.2019.02647 -
Frontiers in Immunology 2020poly-γ-D-glutamic acid (PGA) capsule is an essential virulent factor that helps the bacterial pathogen to escape host immunity. Like other encapsulated bacterial...
poly-γ-D-glutamic acid (PGA) capsule is an essential virulent factor that helps the bacterial pathogen to escape host immunity. Like other encapsulated bacterial species, the capsule may also inhibit complement-mediated clearance and ensure bacterial survival in the host. Previous reports suggest that spore proteins inhibit complement activation. However, the mechanism through which the capsule imparts a survival advantage to the active bacteria has not been demonstrated till date. Thus, to evaluate the role of the PGA capsule in evading host immunity, we have undertaken the present head-to-head comparative study of the phagocytosis and complement activation of non-encapsulated and encapsulated strains. The encapsulated virulent strain exhibited resistance toward complement-dependent and complement-independent bacterial phagocytosis by human macrophages. The non-encapsulated Sterne strain was highly susceptible to phagocytosis by THP-1 macrophages, after incubation with normal human serum (NHS), heat-inactivated serum, and serum-free media, thus indicating that the capsule inhibited both complement-dependent and complement-independent opsonic phagocytosis. An increased binding of C3b and its subsequent activation to C3c and C3dg, which functionally act as potent opsonins, were observed with the non-encapsulated Sterne strain compared with the encapsulated strain. Other known mediators of complement fixation, IgG, C-reactive protein (CRP), and serum amyloid P component (SAP), also bound more prominently with the non-encapsulated Sterne strain. Studies with complement pathway-specific, component-deficient serum demonstrated that the classical pathway was primarily involved in mediating C3b binding on the non-encapsulated bacteria. Both strains equally bound the complement regulatory proteins C4BP and factor H. Importantly, we demonstrated that the negative charge of the PGA capsule was responsible for the differential binding of the complement proteins between the non-encapsulated and encapsulated strains. At lower pH closer to the isoelectric point of PGA, the neutralization of the negative charge was associated with an increased binding of C3b and IgG with the encapsulated strain. Overall, our data have demonstrated that the capsule inhibits complement fixation and opsonization resulting in reduced phagocytosis by macrophages, thus allowing the bacterial pathogen to evade host immunity.
Topics: Anthrax; Antigens, Bacterial; Bacillus anthracis; Bacterial Capsules; Complement Activation; Complement C3b; Humans; Immune Evasion; Macrophages; Opsonin Proteins; Phagocytosis; Polyglutamic Acid; Protein Binding; THP-1 Cells; Virulence
PubMed: 32296419
DOI: 10.3389/fimmu.2020.00462 -
Journal of the Royal Society of Medicine Oct 1994
Topics: History, 19th Century; History, 20th Century; Humans; Immunity, Innate; Opsonin Proteins; Phagocytosis; United Kingdom
PubMed: 7966100
DOI: 10.1177/014107689408701002 -
Journal of Visualized Experiments : JoVE Apr 2019A key aspect of the immune response to bacterial colonization of the host is phagocytosis. An opsonophagocytic killing assay (OPKA) is an experimental procedure in which...
A key aspect of the immune response to bacterial colonization of the host is phagocytosis. An opsonophagocytic killing assay (OPKA) is an experimental procedure in which phagocytic cells are co-cultured with bacterial units. The immune cells will phagocytose and kill the bacterial cultures in a complement-dependent manner. The efficiency of the immune-mediated cell killing is dependent on a number of factors and can be used to determine how different bacterial cultures compare with regard to resistance to cell death. In this way, the efficacy of potential immune-based therapeutics can be assessed against specific bacterial strains and/or serotypes. In this protocol, we describe a simplified OPKA that utilizes basic culture conditions and cell counting to determine bacterial cell viability after co-culture with treatment conditions and HL-60 immune cells. This method has been successfully utilized with a number of different pneumococcal serotypes, capsular and acapsular strains, and other bacterial species. The advantages of this OPKA protocol are its simplicity, versatility (as this assay is not limited to antibody treatments as opsonins), and minimization of time and reagents to assess basic experimental groups.
Topics: Bacteria; Biological Assay; Cell Survival; HL-60 Cells; Humans; Opsonin Proteins; Phagocytosis
PubMed: 31009013
DOI: 10.3791/59400 -
Microbes and Infection 2016Two clinical tests - the erythrocyte sedimentation rate and the opsonic index - have long been known to non-specifically detect pathology based on their responsiveness... (Review)
Review
Two clinical tests - the erythrocyte sedimentation rate and the opsonic index - have long been known to non-specifically detect pathology based on their responsiveness to changes in serum proteins. In infections serum levels of specific antibodies increase. However, for healthy subjects Wright held that antibodies contributed minimally to opsonic activity (the complement-enhanced phagocytosis of microorganisms). The activity was present in newborn serum, was increased in the acute phase of an immune response prior to antibody increase, and was less specific. Furthermore, defective opsonization was associated with undue susceptibility to certain infections, for which a genetic basis was later found. With the demonstrations of complement-mediated lysis both of normal cells by foreign (plant) lectins, and of foreign cells (microorganisms) by animal lectins, it now appears that endogenous lectins correspond to the heat-stable component of Wright's serum opsonic activity. His work leads to the lectin pathway of complement activation with specificities limited to the recognition of relatively immutable surface sugars - predictable pathogen characters that contrast with the less predictable targets of the adaptive immune system.
Topics: Allergy and Immunology; Animals; Complement Pathway, Mannose-Binding Lectin; History, 20th Century; Humans; Immunity, Innate; Immunologic Factors; Lectins; Opsonin Proteins
PubMed: 27109231
DOI: 10.1016/j.micinf.2016.04.003 -
Virulence 2018
Topics: Cell Division; Cryptococcus neoformans; Fungal Capsules; Microscopy, Interference; Opsonin Proteins; Staining and Labeling
PubMed: 30165795
DOI: 10.1080/21505594.2018.1515610 -
The Journal of Biological Chemistry Sep 2022Carcinoembryonic antigen-related cell adhesion molecule 3 (CEACAM3) is a human granulocyte receptor mediating the efficient phagocytosis of a subset of human-restricted...
Carcinoembryonic antigen-related cell adhesion molecule 3 (CEACAM3) is a human granulocyte receptor mediating the efficient phagocytosis of a subset of human-restricted bacterial pathogens. Its function depends on phosphorylation of a tyrosine-based sequence motif, but the enzyme(s) responsible for reversing this modification are unclear. Here, we identify the receptor-type protein tyrosine phosphatase PTPRJ as a negative regulator of CEACAM3-mediated phagocytosis. We show depletion of PTPRJ results in a gain-of-function phenotype, while overexpression of a constitutively active PTPRJ phosphatase strongly reduces bacterial uptake via CEACAM3. We also determined that recombinant PTPRJ directly dephosphorylates the cytoplasmic tyrosine residues of purified full-length CEACAM3 and recognizes synthetic CEACAM3-derived phosphopeptides as substrates. Dephosphorylation of CEACAM3 by PTPRJ is also observed in intact cells, thereby limiting receptor-initiated cytoskeletal re-arrangements, lamellipodia formation, and bacterial uptake. Finally, we show that human phagocytes deficient for PTPRJ exhibit exaggerated lamellipodia formation and enhanced opsonin-independent phagocytosis of CEACAM3-binding bacteria. Taken together, our results highlight PTPRJ as a bona fide negative regulator of CEACAM3-initiated phagocyte functions, revealing a potential molecular target to limit CEACAM3-driven inflammatory responses.
Topics: Carcinoembryonic Antigen; Granulocytes; Humans; Opsonin Proteins; Phagocytosis; Phosphopeptides; Receptor-Like Protein Tyrosine Phosphatases, Class 3
PubMed: 35850306
DOI: 10.1016/j.jbc.2022.102269 -
Clinical and Vaccine Immunology : CVI Feb 2017Plasmodium falciparum malaria remains the deadliest parasitic disease worldwide. Vaccines targeting the preerythrocytic sporozoite and liver stages have the potential to...
Plasmodium falciparum malaria remains the deadliest parasitic disease worldwide. Vaccines targeting the preerythrocytic sporozoite and liver stages have the potential to entirely prevent blood-stage infection and disease, as well as onward transmission. Sporozoite surface and secreted proteins are leading candidates for inclusion in a preerythrocytic stage-specific, antibody-based vaccine. Preclinical functional assays to identify humoral correlates of protection in vitro and to validate novel sporozoite protein targets for inclusion in multisubunit vaccines currently do not consider the interaction of sporozoite-targeting antibodies with other components of the immune system. Here, we describe the development of a simple flow cytometric assay to quantitatively assess the ability of antibodies directed against P. falciparum sporozoites to facilitate their phagocytosis. We demonstrate that this sporozoite opsonic phagocytosis assay (SOPA) is compatible with both monoclonal antibodies and human immune serum and can be performed using cryopreserved P. falciparum sporozoites. This simple, accessible assay will aid with the assessment of antibody responses to vaccination with Plasmodium antigens and their interaction with phagocytic cells of the immune system.
Topics: Antibodies, Protozoan; Flow Cytometry; Humans; Immunoassay; Opsonin Proteins; Phagocytosis; Plasmodium falciparum; Sporozoites
PubMed: 27881488
DOI: 10.1128/CVI.00445-16 -
Developmental and Comparative Immunology Dec 2011Protein-carbohydrate interactions mediated by lectins have been recognized as key components of innate immunity in vertebrates and invertebrates, not only for... (Review)
Review
Protein-carbohydrate interactions mediated by lectins have been recognized as key components of innate immunity in vertebrates and invertebrates, not only for recognition of potential pathogens, but also for participating in downstream effector functions, such as their agglutination, immobilization, and complement-mediated opsonization and killing. More recently, lectins have been identified as critical regulators of mammalian adaptive immune responses. Fish are endowed with virtually all components of the mammalian adaptive immunity, and are equipped with a complex lectin repertoire. In this review, we discuss evidence suggesting that: (a) lectin repertoires in teleost fish are highly diversified, and include not only representatives of the lectin families described in mammals, but also members of lectin families described for the first time in fish species; (b) the tissue-specific expression and localization of the diverse lectin repertoires and their molecular partners is consistent with their distinct biological roles in innate and adaptive immunity; (c) although some lectins may bind endogenous ligands, others bind sugars on the surface of potential pathogens; (d) in addition to pathogen recognition and opsonization, some lectins display additional effector roles, such as complement activation and regulation of immune functions; (e) some lectins that recognize exogenous ligands mediate processes unrelated to immunity: they may act as anti-freeze proteins or prevent polyspermia during fertilization.
Topics: Adaptive Immunity; Animals; Antifreeze Proteins; Antigens, Bacterial; Antigens, Viral; Bacteria; Complement Activation; Complement System Proteins; Fish Proteins; Fishes; Gene Expression Regulation; Immunity, Innate; Invertebrates; Lectins; Models, Molecular; Opsonin Proteins; Organ Specificity; Phagocytosis; Protein Structure, Quaternary; Protein Structure, Tertiary; Vertebrates; Viruses
PubMed: 21896283
DOI: 10.1016/j.dci.2011.08.011