Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 10 de 10
Filtrar
Más filtros










Base de datos
Intervalo de año de publicación
1.
Front Immunol ; 15: 1152000, 2024.
Artículo en Inglés | MEDLINE | ID: mdl-38361922

RESUMEN

Chagas disease, a chronic disabling disease caused by the protozoan Trypanosoma cruzi, has no standardized treatment or preventative vaccine. The infective trypomastigote form of T. cruzi is highly resistant to killing by the complement immune system. Factor H (FH), a negative regulator of the alternative pathway (AP) of complement on cell surfaces and in blood, contains 20 short consensus repeat domains. The four N-terminal domains of FH inactivate the AP, while the other domains interact with C3b/d and glycan markers on cell surfaces. Various pathogens bind FH to inactivate the AP. T. cruzi uses its trans-sialidase enzyme to transfer host sialic acids to its own surface, which could be one of the approaches it uses to bind FH. Previous studies have shown that FH binds to complement-opsonized T. cruzi and parasite desialylation increases complement-mediated lysis of trypomastigotes. However, the molecular basis of FH binding to T. cruzi remain unknown. Only trypomastigotes, but not epimastigotes (non-infective, complement susceptible) bound FH directly, independent of C3 deposition, in a dose-dependent manner. Domain mapping experiments using 3-5 FH domain fragments showed that domains 5-8 competitively inhibited FH binding to the trypomastigotes by ~35% but did not decrease survival in complement. FH-Fc or mutant FH-Fc fusion proteins (3-11 contiguous FH domains fused to the IgG Fc) also did not kill trypomastigotes. FH-related protein-5, whose domains bear significant sequence identity to all known polyanion-binding FH domains (6-7, 10-14, 19-20), fully inhibited FH binding to trypomastigotes and reduced trypomastigote survival to < 24% in the presence of serum. In conclusion, we have elucidated the role of FH in complement resistance of trypomastigotes.


Asunto(s)
Enfermedad de Chagas , Trypanosoma cruzi , Humanos , Factor H de Complemento , Enfermedad de Chagas/prevención & control
2.
Front Immunol ; 13: 975676, 2022.
Artículo en Inglés | MEDLINE | ID: mdl-36110842

RESUMEN

Novel therapeutics against the global threat of multidrug-resistant Neisseria gonorrhoeae are urgently needed. Gonococci evade killing by complement by binding factor H (FH), a key inhibitor of the alternative pathway. FH comprises 20 short consensus repeat (SCR) domains organized as a single chain. Gonococci bind FH through domains 6 and 7, and C-terminal domains 18 through 20. Previously, we showed that a chimeric protein comprising (from the N- to C-terminus) FH domains 18-20 (containing a point mutation in domain 19 to prevent lysis of host cells) fused to human IgG1 Fc (called FH*/Fc1) killed gonococci in a complement-dependent manner and reduced the duration and bacterial burden in the mouse vaginal colonization model of gonorrhea. Considering the N. gonorrhoeae-binding FH domains 18-20 are C-terminal in native FH, we reasoned that positioning Fc N-terminal to FH* (Fc1/FH*) would improve binding and bactericidal activity. Although both molecules bound gonococci similarly, Fc1/FH* displayed a 5-fold lower IC50 (the concentration required for 50% killing in complement-dependent bactericidal assays) than FH*/Fc1. To further increase complement activation, we replaced human IgG1 Fc in Fc1/FH* with Fc from human IgG3, the most potent complement-activating IgG subclass, to obtain Fc3/FH*. Bactericidal activity was further increased ~2.3-fold in Fc3/FH* compared to Fc1/FH*. Fc3/FH* killed (defined by <50% survival) 45/45 (100%) diverse PorB1B-expessing gonococci, but only 2/15 PorB1A-expressing isolates, in a complement-dependent manner. Decreased Fc3/FH* binding accounted for the limited activity against PorB1A strains. Fc3/FH* was efficacious against all four tested PorB1B gonococcal strains in the mouse vaginal colonization model when administered at a dose of 5 µg intravaginally, daily. Furthermore, Fc3/FH* retained bactericidal activity when reconstituted following lyophilization or spray-drying, suggesting feasibility for formulation into intravaginal rings. In conclusion, Fc3/FH* represents a promising prophylactic immunotherapeutic against multidrug-resistant gonococci.


Asunto(s)
Gonorrea , Neisseria gonorrhoeae , Animales , Factor H de Complemento/metabolismo , Proteínas del Sistema Complemento/metabolismo , Modelos Animales de Enfermedad , Femenino , Gonorrea/tratamiento farmacológico , Humanos , Inmunoglobulina G/metabolismo , Ratones , Neisseria gonorrhoeae/genética , Proteínas Recombinantes de Fusión/genética , Proteínas Recombinantes de Fusión/metabolismo , Proteínas Recombinantes de Fusión/farmacología
3.
PLoS One ; 17(3): e0265774, 2022.
Artículo en Inglés | MEDLINE | ID: mdl-35324969

RESUMEN

Staphylococcus aureus employs a multitude of immune-evasive tactics to circumvent host defenses including the complement system, a component of innate immunity central to controlling bacterial infections. With antibiotic resistance becoming increasingly common, there is a dire need for novel therapies. Previously, we have shown that S. aureus binds the complement regulator factor H (FH) via surface protein SdrE to inhibit complement. To address the need for novel therapeutics and take advantage of the FH:SdrE interaction, we examined the effect of a fusion protein comprised of the SdrE-interacting domain of FH coupled with IgG Fc on complement-mediated opsonophagocytosis and bacterial killing of community associated methicillin-resistant S. aureus. S. aureus bound significantly more FH-Fc compared to Fc-control proteins and FH-Fc competed with serum FH for S. aureus binding. FH-Fc treatment increased C3-fragment opsonization of S. aureus for both C3b and iC3b, and boosted generation of the anaphylatoxin C5a. In 5 and 10% serum, FH-Fc treatment significantly increased S. aureus killing by polymorphonuclear cells. This anti-staphylococcal effect was evident in 75% (3/4) of clinical isolates tested. This study demonstrates that FH-Fc fusion proteins have the potential to mitigate the protective effects of bound serum FH rendering S. aureus more vulnerable to the host immune system. Thus, we report the promise of virulence-factor-targeted fusion-proteins as an avenue for prospective anti-staphylococcal therapeutic development.


Asunto(s)
Factor H de Complemento , Staphylococcus aureus Resistente a Meticilina , Complemento C3b/metabolismo , Proteínas del Sistema Complemento/metabolismo , Staphylococcus aureus Resistente a Meticilina/metabolismo , Opsonización , Unión Proteica , Staphylococcus aureus/metabolismo
4.
Sci Rep ; 12(1): 1464, 2022 01 27.
Artículo en Inglés | MEDLINE | ID: mdl-35087132

RESUMEN

Glioblastoma (GBM) is the most common primary brain tumor with a median survival under two years. Using in silico and in vitro techniques, we demonstrate heterogeneous expression of CD97, a leukocyte adhesion marker, in human GBM. Beyond its previous demonstrated role in tumor invasion, we show that CD97 is also associated with upregulation of the mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/Erk) and phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) pathways in GBM. While CD97 knockout decreased Akt activation, CD97 targeting did not alter MAPK/Erk activation, did not slow GBM cell proliferation in culture, and increased levels of glycolytic and oxidative phosphorylation metabolites. Treatment with a soluble CD97 inhibitor did not alter activation of the MAPK/Erk and PI3K/Akt pathways. Tumors with high CD97 expression were associated with immune microenvironment changes including increased naïve macrophages, regulatory T cells, and resting natural killer (NK) cells. These data suggest that, while CD97 expression is associated with conflicting effects on tumor cell proliferative and metabolic pathways that overall do not affect tumor cell proliferation, CD97 exerts pro-tumoral effects on the tumor immune microenvironment, which along with the pro-invasive effects of CD97 we previously demonstrated, provides impetus to continue exploring CD97 as a therapeutic target in GBM.


Asunto(s)
Antígenos CD/metabolismo , Neoplasias Encefálicas/inmunología , Glioblastoma/inmunología , Receptores Acoplados a Proteínas G/metabolismo , Microambiente Tumoral/inmunología , Activación Metabólica/inmunología , Antígenos CD/genética , Neoplasias Encefálicas/genética , Neoplasias Encefálicas/patología , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , Regulación Neoplásica de la Expresión Génica/inmunología , Técnicas de Silenciamiento del Gen , Técnicas de Inactivación de Genes , Glioblastoma/genética , Glioblastoma/patología , Humanos , Sistema de Señalización de MAP Quinasas/efectos de los fármacos , Sistema de Señalización de MAP Quinasas/inmunología , Metabolómica , Fosfatidilinositol 3-Quinasas/metabolismo , Proteínas Proto-Oncogénicas c-akt/metabolismo , Receptores Acoplados a Proteínas G/antagonistas & inhibidores , Receptores Acoplados a Proteínas G/genética , Microambiente Tumoral/efectos de los fármacos , Microambiente Tumoral/genética
5.
Front Immunol ; 11: 583305, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-33193396

RESUMEN

Novel therapeutics against the global threat of multidrug-resistant Neisseria gonorrhoeae are urgently needed. Gonococci possess several mechanisms to evade killing by human complement, including binding of factor H (FH), a key inhibitor of the alternative pathway. FH comprises 20 short consensus repeat (SCR) domains organized in a head-to-tail manner as a single chain. N. gonorrhoeae binds two regions in FH; domains 6 and 7 and domains 18 through 20. We designed a novel anti-infective immunotherapeutic molecule that fuses domains 18-20 of FH containing a D-to-G mutation in domain 19 at position 1119 (called FH*) with human IgG1 Fc. FH*/Fc retained binding to gonococci but did not lyse human erythrocytes. Expression of FH*/Fc in tobacco plants was undertaken as an alternative, economical production platform. FH*/Fc was expressed in high yields in tobacco plants (300-600 mg/kg biomass). The activities of plant- and CHO-cell produced FH*/Fc against gonococci were similar in vitro and in the mouse vaginal colonization model of gonorrhea. The addition of flexible linkers [e.g., (GGGGS)2 or (GGGGS)3] between FH* and Fc improved the bactericidal efficacy of FH*/Fc 2.7-fold. The linkers also improved PMN-mediated opsonophagocytosis about 11-fold. FH*/Fc with linker also effectively reduced the duration and burden of colonization of two gonococcal strains tested in mice. FH*/Fc lost efficacy: i) in C6-/- mice (no terminal complement) and ii) when Fc was mutated to abrogate complement activation, suggesting that an intact complement was necessary for FH*/Fc function in vivo. In summary, plant-produced FH*/Fc represent promising prophylactic or adjunctive immunotherapeutics against multidrug-resistant gonococci.


Asunto(s)
Resistencia a Múltiples Medicamentos/inmunología , Fragmentos Fc de Inmunoglobulinas/inmunología , Neisseria gonorrhoeae/inmunología , Nicotiana/genética , Plantas Modificadas Genéticamente , Animales , Antibacterianos/farmacología , Factor H de Complemento/genética , Factor H de Complemento/inmunología , Gonorrea , Humanos , Inmunoglobulina G , Inmunoterapia , Ratones , Plantas Modificadas Genéticamente/genética , Proteínas Recombinantes de Fusión/inmunología
7.
J Biol Chem ; 291(32): 16659-71, 2016 08 05.
Artículo en Inglés | MEDLINE | ID: mdl-27284008

RESUMEN

Single domain antibodies (sdAbs) correspond to the antigen-binding domains of camelid antibodies. They have the same antigen-binding properties and specificity as monoclonal antibodies (mAbs) but are easier and cheaper to produce. We report here the development of sdAbs targeting human PCSK9 (proprotein convertase subtilisin/kexin type 9) as an alternative to anti-PCSK9 mAbs. After immunizing a llama with human PCSK9, we selected four sdAbs that bind PCSK9 with a high affinity and produced them as fusion proteins with a mouse Fc. All four sdAb-Fcs recognize the C-terminal Cys-His-rich domain of PCSK9. We performed multiple cellular assays and demonstrated that the selected sdAbs efficiently blocked PCSK9-mediated low density lipoprotein receptor (LDLR) degradation in cell lines, in human hepatocytes, and in mouse primary hepatocytes. We further showed that the sdAb-Fcs do not affect binding of PCSK9 to the LDLR but rather block its induced cellular LDLR degradation. Pcsk9 knock-out mice expressing a human bacterial artificial chromosome (BAC) transgene were generated, resulting in plasma levels of ∼300 ng/ml human PCSK9. Mice were singly or doubly injected with the best sdAb-Fc and analyzed at day 4 or 11, respectively. After 4 days, mice exhibited a 32 and 44% decrease in the levels of total cholesterol and apolipoprotein B and ∼1.8-fold higher liver LDLR protein levels. At 11 days, the equivalent values were 24 and 46% and ∼2.3-fold higher LDLR proteins. These data constitute a proof-of-principle for the future usage of sdAbs as PCSK9-targeting drugs that can efficiently reduce LDL-cholesterol, and as tools to study the Cys-His-rich domain-dependent sorting the PCSK9-LDLR complex to lysosomes.


Asunto(s)
LDL-Colesterol/metabolismo , Proproteína Convertasa 9/metabolismo , Proteolisis/efectos de los fármacos , Receptores de LDL/metabolismo , Anticuerpos de Dominio Único/farmacología , Animales , LDL-Colesterol/genética , Células HEK293 , Humanos , Ratones , Ratones Noqueados , Inhibidores de PCSK9 , Proproteína Convertasa 9/genética , Receptores de LDL/genética
8.
Plant Biotechnol J ; 13(8): 1078-93, 2015 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-26242703

RESUMEN

Immunoadhesins are recombinant proteins that combine the ligand-binding region of a receptor or adhesion molecule with immunoglobulin constant domains. All FDA-approved immunoadhesins are designed to modulate the interaction of a human receptor with its normal ligand, such as Etanercept (Enbrel(®) ), which interferes with the binding of tumour necrosis factor (TNF) to the TNF-alpha receptor and is used to treat inflammatory diseases such as rheumatoid arthritis. Like antibodies, immunoadhesins have long circulating half-lives, are readily purified by affinity-based methods and have the avidity advantages conferred by bivalency. Immunoadhesins that incorporate normal cellular receptors for viruses or bacterial toxins hold great, but as yet unrealized, potential for treating infectious disease. As decoy receptors, immunoadhesins have potential advantages over pathogen-targeted monoclonal antibodies. Planet Biotechnology has specialized in developing anti-infective immunoadhesins using plant expression systems. An immunoadhesin incorporating the cellular receptor for anthrax toxin, CMG2, potently blocks toxin activity in vitro and protects animals against inhalational anthrax. An immunoadhesin based on the receptor for human rhinovirus, ICAM-1, potently blocks infection of human cells by one of the major causes of the common cold. An immunoadhesin targeting the MERS coronavirus is in an early stage of development. We describe here the unique challenges involved in designing and developing immunoadhesins targeting infectious diseases in the hope of inspiring further research into this promising class of drugs.


Asunto(s)
Enfermedades Transmisibles/tratamiento farmacológico , Fragmentos Fc de Inmunoglobulinas/uso terapéutico , Plantas/metabolismo , Animales , Humanos
9.
Viruses ; 6(3): 1091-111, 2014 Mar 10.
Artículo en Inglés | MEDLINE | ID: mdl-24618810

RESUMEN

Decay accelerating factor (DAF/CD55) is targeted by many pathogens for cell entry. It has been implicated as a co-receptor for hantaviruses. To examine the binding of hantaviruses to DAF, we describe the use of Protein G beads for binding human IgG Fc domain-functionalized DAF ((DAF)2-Fc). When mixed with Protein G beads the resulting DAF beads can be used as a generalizable platform for measuring kinetic and equilibrium binding constants of DAF binding targets. The hantavirus interaction has high affinity (24-30 nM; k(on) ~ 105 M⁻¹ s⁻¹, k(off) ~ 0.0045 s⁻¹). The bivalent (DAF)2-Fc/SNV data agree with hantavirus binding to DAF expressed on Tanoue B cells (K(d) = 14.0 nM). Monovalent affinity interaction between SNV and recombinant DAF of 58.0 nM is determined from competition binding. This study serves a dual purpose of presenting a convenient and quantitative approach of measuring binding affinities between DAF and the many cognate viral and bacterial ligands and providing new data on the binding constant of DAF and Sin Nombre hantavirus. Knowledge of the equilibrium binding constant allows for the determination of the relative fractions of bound and free virus particles in cell entry assays. This is important for drug discovery assays for cell entry inhibitors.


Asunto(s)
Antígenos CD55/metabolismo , Receptores Virales/metabolismo , Virus Sin Nombre/fisiología , Acoplamiento Viral , Humanos , Microesferas
10.
Antimicrob Agents Chemother ; 55(1): 132-9, 2011 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-20956592

RESUMEN

Inhalational anthrax, a zoonotic disease caused by the inhalation of Bacillus anthracis spores, has a ∼50% fatality rate even when treated with antibiotics. Pathogenesis is dependent on the activity of two toxic noncovalent complexes: edema toxin (EdTx) and lethal toxin (LeTx). Protective antigen (PA), an essential component of both complexes, binds with high affinity to the major receptor mediating the lethality of anthrax toxin in vivo, capillary morphogenesis protein 2 (CMG2). Certain antibodies against PA have been shown to protect against anthrax in vivo. As an alternative to anti-PA antibodies, we produced a fusion of the extracellular domain of human CMG2 and human IgG Fc, using both transient and stable tobacco plant expression systems. Optimized expression led to the CMG2-Fc fusion protein being produced at high levels: 730 mg/kg fresh leaf weight in Nicotiana benthamiana and 65 mg/kg in N. tabacum. CMG2-Fc, purified from tobacco plants, fully protected rabbits against a lethal challenge with B. anthracis spores at a dose of 2 mg/kg body weight administered at the time of challenge. Treatment with CMG2-Fc did not interfere with the development of the animals' own immunity to anthrax, as treated animals that survived an initial challenge also survived a rechallenge 30 days later. The glycosylation of the Fc (or lack thereof) had no significant effect on the protective potency of CMG2-Fc in rabbits or on its serum half-life, which was about 5 days. Significantly, CMG2-Fc effectively neutralized, in vitro, LeTx-containing mutant forms of PA that were not neutralized by anti-PA monoclonal antibodies.


Asunto(s)
Carbunco/inmunología , Fragmentos Fc de Inmunoglobulinas/inmunología , Fragmentos Fc de Inmunoglobulinas/metabolismo , Nicotiana/metabolismo , Receptores de Péptidos/inmunología , Receptores de Péptidos/metabolismo , Proteínas Recombinantes de Fusión/inmunología , Proteínas Recombinantes de Fusión/metabolismo , Animales , Humanos , Fragmentos Fc de Inmunoglobulinas/genética , Conejos , Receptores de Péptidos/genética , Proteínas Recombinantes de Fusión/genética , Nicotiana/genética
SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA
...