Publications (61)331.49 Total impact
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Article: Roles of Adipocytes and Fibroblasts in Activation of the Alternative Pathway of Complement in Inflammatory Arthritis in Mice.
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ABSTRACT: The complement system is involved in mediation of joint damage in rheumatoid arthritis, with evidence suggesting activation of both the classical and alternative pathway (AP). The AP is both necessary and sufficient to mediate collagen Ab-induced arthritis, an experimental animal model of immune complex-induced joint disease. The AP in mice is dependent on MASP-1/3 cleavage of pro-factor D (pro-FD) into mature factor D (FD). The objectives of the current study were to determine the cells synthesizing MASP-1/3 and pro-FD in synovial tissue. Collagen Ab-induced arthritis was studied in wild-type C57BL/6 mice, and the localization of mRNA and protein for FD and MASP-1/3 in synovial adipose tissue (SAT) and fibroblast-like synoviocytes (FLS) was determined using various techniques, including laser capture microdissection. SAT was the sole source of mRNA for pro-FD. Cultured differentiated 3T3 adipocytes, a surrogate for SAT, produced pro-FD but no mature FD. FLS were the main source of MASP-1/3 mRNA and protein. Using cartilage microparticles (CMPs) coated with anti-collagen mAb and serum from MASP-1/3(-/-) mice as a source of factor B, pro-FD in 3T3 supernatants was cleaved into mature FD by MASP-1/3 in FLS supernatants. The mature FD was eluted from the CMP, and was not present in the supernatants from the incubation with CMP, indicating that cleavage of pro-FD into mature FD by MASP-1 occurred on the CMP. These results demonstrate that pathogenic activation of the AP can occur in the joint through immune complexes adherent to cartilage and the local production of necessary AP proteins by adipocytes and FLS.The Journal of Immunology 05/2013; · 5.79 Impact Factor -
Article: Lectin-Dependent Enhancement of Ebola Virus Infection via Soluble and Transmembrane C-type Lectin Receptors.
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ABSTRACT: Mannose-binding lectin (MBL) is a key soluble effector of the innate immune system that recognizes pathogen-specific surface glycans. Surprisingly, low-producing MBL genetic variants that may predispose children and immunocompromised individuals to infectious diseases are more common than would be expected in human populations. Since certain immune defense molecules, such as immunoglobulins, can be exploited by invasive pathogens, we hypothesized that MBL might also enhance infections in some circumstances. Consequently, the low and intermediate MBL levels commonly found in human populations might be the result of balancing selection. Using model infection systems with pseudotyped and authentic glycosylated viruses, we demonstrated that MBL indeed enhances infection of Ebola, Hendra, Nipah and West Nile viruses in low complement conditions. Mechanistic studies with Ebola virus (EBOV) glycoprotein pseudotyped lentiviruses confirmed that MBL binds to N-linked glycan epitopes on viral surfaces in a specific manner via the MBL carbohydrate recognition domain, which is necessary for enhanced infection. MBL mediates lipid-raft-dependent macropinocytosis of EBOV via a pathway that appears to require less actin or early endosomal processing compared with the filovirus canonical endocytic pathway. Using a validated RNA interference screen, we identified C1QBP (gC1qR) as a candidate surface receptor that mediates MBL-dependent enhancement of EBOV infection. We also identified dectin-2 (CLEC6A) as a potentially novel candidate attachment factor for EBOV. Our findings support the concept of an innate immune haplotype that represents critical interactions between MBL and complement component C4 genes and that may modify susceptibility or resistance to certain glycosylated pathogens. Therefore, higher levels of native or exogenous MBL could be deleterious in the setting of relative hypocomplementemia which can occur genetically or because of immunodepletion during active infections. Our findings confirm our hypothesis that the pressure of infectious diseases may have contributed in part to evolutionary selection of MBL mutant haplotypes.PLoS ONE 01/2013; 8(4):e60838. · 4.09 Impact Factor -
Article: The alternative complement pathway propagates inflammation and injury in murine ischemic stroke.
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ABSTRACT: There is mounting evidence indicating an important role for complement in the pathogenesis of cerebral ischemia-reperfusion injury, or ischemic stroke. The role of the alternative complement pathway in ischemic stroke has not been investigated, and there is conflicting data on the role of the terminal pathway. In this study, we show that compared with wild-type mice, mice deficient in the alternative pathway protein factor B or mice treated with the alternative pathway inhibitor CR2-fH have improved outcomes after 60-min middle cerebral artery occlusion and 24-h reperfusion. Factor B-deficient or CR2-fH-treated mice were protected in terms of improved neurologic function and reduced cerebral infarct, demyelination, P-selectin expression, neutrophil infiltration, and microthrombi formation. Mice deficient in both the classical and lectin pathways (C1q/MBL deficient) were also protected from cerebral ischemia-reperfusion injury, and there was no detectable C3d deposition in the ipsilateral brain of these mice. These data demonstrate that the alternative pathway is not alone sufficient to initiate complement activation and indicate that the alternative pathway propagates cerebral injury via amplification of the cascade. Deficiency of C6, a component of the terminal cytolytic membrane attack complex, had no effect on outcome after ischemic stroke, indicating that the membrane attack complex is not involved in mediating injury in this model. We additionally show that the protective effect of factor B deficiency and CR2-fH treatment is sustained in the subacute stage of infarct development, adding to the clinical relevance of these findings.The Journal of Immunology 10/2012; 189(9):4640-7. · 5.79 Impact Factor -
Article: Human H-ficolin inhibits replication of seasonal and pandemic influenza a viruses.
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ABSTRACT: The collectins have been shown to have a role in host defense against influenza A virus (IAV) and other significant viral pathogens (e.g., HIV). The ficolins are a related group of innate immune proteins that are present at relatively high concentrations in serum, but also in respiratory secretions; however, there has been little study of the role of ficolins in viral infection. In this study, we demonstrate that purified recombinant human H-ficolin and H-ficolin in human serum and bronchoalveolar lavage fluid bind to IAV and inhibit viral infectivity and hemagglutination activity in vitro. Removal of ficolins from human serum or bronchoalveolar lavage fluid reduces their antiviral activity. Inhibition of IAV did not involve the calcium-dependent lectin activity of H-ficolin. We demonstrate that H-ficolin is sialylated and that removal of sialic acid abrogates IAV inhibition, while addition of the neuraminidase inhibitor oseltamivir potentiates neutralization, hemagglutinin inhibition, and viral aggregation caused by H-ficolin. Pandemic and mouse-adapted strains of IAV are generally not inhibited by the collectins surfactant protein D or mannose binding lectin because of a paucity of glycan attachments on the hemagglutinin of these strains. In contrast, H-ficolin inhibited both the mouse-adapted PR-8 H1N1 strain and a pandemic H1N1 strain from 2009. H-ficolin also fixed complement to a surface coated with IAV. These findings suggest that H-ficolin contributes to host defense against IAV.The Journal of Immunology 07/2012; 189(5):2478-87. · 5.79 Impact Factor -
Article: Micro-Autoradiographic Assessment of Cell Types Contributing to 2-Deoxy-2-[(18)F]Fluoro-D-: Glucose Uptake During Ventilator-Induced and Endotoxemic Lung Injury.
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ABSTRACT: PURPOSE: The aim of the study was to use micro-autoradiography to investigate the lung cell types responsible for 2-deoxy-2-[(18)F]fluoro-D-: glucose (FDG) uptake in murine models of acute lung injury (ALI). PROCEDURES: C57/BL6 mice were studied in three groups: controls, ventilator-induced lung injury (VILI), and endotoxin. VILI was produced by high tidal volumes and zero end-expiratory pressure and endotoxin ALI, by intranasal administration. Following FDG injection, the lungs were processed and exposed to autoradiographic emulsion. Grain density over cells was used to quantify FDG uptake. RESULTS: Neutrophils, macrophages, and type 2 epithelial cells presented higher grain densities during VILI and endotoxin ALI than controls. Remarkably, cell grain density in specific cell types was dependent on the injury mechanism. Whereas macrophages showed high grain densities during endotoxin ALI, similar to those exhibited by neutrophils, type 2 epithelial cells demonstrated the second highest grain density (with neutrophils as the highest) during VILI. CONCLUSIONS: In murine models of VILI and endotoxin ALI, FDG uptake occurs not only in neutrophils but also in macrophages and type 2 epithelial cells. FDG uptake by individual cell types depends on the mechanism underlying ALI.Molecular imaging and biology: MIB: the official publication of the Academy of Molecular Imaging 07/2012; · 2.47 Impact Factor -
Article: The lectin pathway of complement activation is a critical component of the innate immune response to pneumococcal infection.
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ABSTRACT: The complement system plays a key role in host defense against pneumococcal infection. Three different pathways, the classical, alternative and lectin pathways, mediate complement activation. While there is limited information available on the roles of the classical and the alternative activation pathways of complement in fighting streptococcal infection, little is known about the role of the lectin pathway, mainly due to the lack of appropriate experimental models of lectin pathway deficiency. We have recently established a mouse strain deficient of the lectin pathway effector enzyme mannan-binding lectin associated serine protease-2 (MASP-2) and shown that this mouse strain is unable to form the lectin pathway specific C3 and C5 convertases. Here we report that MASP-2 deficient mice (which can still activate complement via the classical pathway and the alternative pathway) are highly susceptible to pneumococcal infection and fail to opsonize Streptococcus pneumoniae in the none-immune host. This defect in complement opsonisation severely compromises pathogen clearance in the lectin pathway deficient host. Using sera from mice and humans with defined complement deficiencies, we demonstrate that mouse ficolin A, human L-ficolin, and collectin 11 in both species, but not mannan-binding lectin (MBL), are the pattern recognition molecules that drive lectin pathway activation on the surface of S. pneumoniae. We further show that pneumococcal opsonisation via the lectin pathway can proceed in the absence of C4. This study corroborates the essential function of MASP-2 in the lectin pathway and highlights the importance of MBL-independent lectin pathway activation in the host defense against pneumococci.PLoS Pathogens 07/2012; 8(7):e1002793. · 9.13 Impact Factor -
Article: 4-[18F]-tetraphenylphosphonium as a PET tracer for myocardial mitochondrial membrane potential.
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ABSTRACT: This study tested the hypothesis that 4-[(18)F]fluorophenyltriphenylphosphonium ((18)F-TPP) is useful for in vivo positron emission tomography (PET) measurement of mitochondrial membrane potential (ΔΨm). Its utility as a blood flow tracer also was evaluated. Tetraphenylphosphonium is useful for in vitro measurement of ΔΨm. In vivo measurement of ΔΨm has potential value in the assessment of heart failure pathophysiology and therapy as well as assessment of myocardial viability and so may be a very useful clinical tool. Anesthetized swine (N = 6) with a balloon catheter in the left anterior descending coronary artery were studied. Microsphere measurements of myocardial blood flow (MBF) were made after balloon inflation (baseline) and ∼10 min after intravenous administration of adenosine and phenylephrine after which ∼10 mCi (18)F-TPP was injected intravenously and dynamic PET data acquisition obtained for 30 min. After the swine were killed, the hearts were sectioned for microsphere measurement of MBF and (18)F-TPP measured by well counter in these same samples. PET images provided whole blood and myocardial (18)F-TPP concentration for determination of ΔΨm by the Nernst equation, corrected for nonspecific (18)F-TPP binding. Microsphere MBF, absolute (ml/min/g) and relative, was compared with PET data (standard uptake value and K1). Nonspecific binding of (18)F-TPP overestimated ΔΨm measured by -37 ± 4 mV (mean ± SD). Normal zone ΔΨm of ex vivo samples (-91 ± 11 mV; N = 52; sample weight, 1.07 ± 0.18 g) correlated strongly (R(2)= 0.93) with normal zone by PET (-81 ± 13 mV). Both ex vivo and PET normal zone ΔΨm, although somewhat lower, compared well with that reported for tritium labeled triphenylphosphonium in normal working Langendorff rat heart (-100 mV). Although the relative MBF by (18)F-TPP correlated strongly with relative microsphere MBF (R(2)= 0.83), there was no correlation between absolute MBF by (18)F-TPP and microsphere MBF. (18)F-TPP is a promising tracer for noninvasive PET measurement of ΔΨm in living subjects. It is useful as well for assessment of relative but not absolute MBF.JACC. Cardiovascular imaging 03/2012; 5(3):285-92. · 14.29 Impact Factor -
Article: Mannose-binding lectin binds to amyloid β protein and modulates inflammation.
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ABSTRACT: Mannose-binding lectin (MBL), a soluble factor of the innate immune system, is a pattern recognition molecule with a number of known ligands, including viruses, bacteria, and molecules from abnormal self tissues. In addition to its role in immunity, MBL also functions in the maintenance of tissue homeostasis. We present evidence here that MBL binds to amyloid β peptides. MBL binding to other known carbohydrate ligands is calcium-dependent and has been attributed to the carbohydrate-recognition domain, a common feature of other C-type lectins. In contrast, we find that the features of MBL binding to Aβ are more similar to the reported binding characteristics of the cysteine-rich domain of the unrelated mannose receptor and therefore may involve the MBL cysteine-rich domain. Differences in MBL ligand binding may contribute to modulation of inflammatory response and may correlate with the function of MBL in processes such as coagulation and tissue homeostasis.Journal of Biomedicine and Biotechnology 01/2012; 2012:929803. · 2.44 Impact Factor -
Article: Role of C3a receptors, C5a receptors, and complement protein C6 deficiency in collagen antibody-induced arthritis in mice.
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ABSTRACT: The complement system, especially the alternative pathway, plays essential roles in the induction of injury in collagen Ab-induced arthritis (CAIA) in mice. The goal of the current study was to directly compare the roles of receptors for C3a and C5a, as well as the membrane attack complex, as effector mechanisms in the pathogenesis of CAIA. Clinical disease activity in C3aR(-/-), C5aR(-/-), and C6-deficient (C6-def) mice was decreased by 52, 94, and 65%, respectively, as compared with wild-type mice. Decreases in histopathologic injury as well as in IgG and C3 deposition paralleled the clinical disease activity. A decrease in the percentage of synovial neutrophils was observed in C3aR(-/-), C5aR(-/-), and C6-def mice, and a decrease in macrophages was observed in C3aR(-/-) and C5aR(-/-), but not in C6-def, mice. Synovial mRNA obtained by laser capture microdissection exhibited a decrease in TNF-α in C5aR(-/-) mice and in IL-1β in both C5aR(-/-) and C6-def mice, whereas C3aR(-/-) mice demonstrated no change in either cytokine. Our findings show that absent C3aR-, C5aR-, or membrane attack complex-initiated effector mechanisms each decrease susceptibility to CAIA, with clinical effects most pronounced in C5aR-deficient mice. Although the absence of C3aR, C5aR, or C6 led to differential deficiencies in effector mechanisms, decreased proximal joint IgG and C3 deposition was common to all three genotypes in comparison with wild-type mice. These data suggest the existence of positive-feedback amplification pathways downstream of all three effectors that promote additional IgG deposition and C3 activation in the joint.The Journal of Immunology 12/2011; 188(3):1469-78. · 5.79 Impact Factor -
Article: Mannose-binding lectin-associated serine protease-1 is a significant contributor to coagulation in a murine model of occlusive thrombosis.
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ABSTRACT: Bleeding disorders and thrombotic complications constitute a major cause of death and disability worldwide. Although it is known that the complement and coagulation systems interact, no studies have investigated the specific role or mechanisms of lectin-mediated coagulation in vivo. FeCl(3) treatment resulted in intra-arterial occlusive thrombogenesis within 10 min in wild-type (WT) and C2/factor B-null mice. In contrast, mannose-binding lectin (MBL)-null and MBL-associated serine protease (MASP)-1/-3 knockout (KO) mice had significantly decreased FeCl(3)-induced thrombogenesis. Reconstitution with recombinant human (rh) MBL restored FeCl(3)-induced thrombogenesis in MBL-null mice to levels comparable to WT mice, suggesting a significant role of the MBL/MASP complex for in vivo coagulation. Additionally, whole blood aggregation demonstrated increased MBL/MASP complex-dependent platelet aggregation. In vitro, MBL/MASP complexes were captured on mannan-coated plates, and cleavage of a chromogenic thrombin substrate (S2238) was measured. We observed no significant differences in S2238 cleavage between WT, C2/factor B-null, MBL-A(-/-), or MBL-C(-/-) sera; however, MBL-null or MASP-1/-3 KO mouse sera demonstrated significantly decreased S2238 cleavage. rhMBL alone failed to cleave S2238, but cleavage was restored when rMASP-1 was added to either MASP-1/-3 KO sera or rhMBL. Taken together, these findings indicate that MBL/MASP complexes, and specifically MASP-1, play a key role in thrombus formation in vitro and in vivo.The Journal of Immunology 12/2011; 188(2):885-91. · 5.79 Impact Factor -
Article: Mannose-binding lectin and the balance between immune protection and complication.
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ABSTRACT: The innate immune system is evolutionarily ancient and biologically primitive. Historically, it was first identified as an element of the immune system that provides the first-line response to pathogens, and increasingly it is recognized for its central housekeeping role and its essential functions in tissue homeostasis, including coagulation and inflammation, among others. A pivotal link between the innate immune system and other functions is mannose-binding lectin (MBL), a pattern recognition molecule. Multiple studies have demonstrated that MBL deficiency increases susceptibility to infection, and the mechanisms associated with this susceptibility to infection include reduced opsonophagocytic killing and reduced activation of the lectin complement pathway. Results from our laboratory have demonstrated that MBL and MBL-associated serine protease (MASP)-1/3 together mediate coagulation factor-like activities, including thrombin-like activity. MBL and/or MASP-1/3-deficient hosts demonstrate in vivo evidence that MBL and MASP-1/3 are involved with hemostasis following injury. Staphylococcus aureus-infected MBL null mice developed disseminated intravascular coagulation, which was associated with elevated blood IL-6 levels (but not TNF-α) and systemic inflammatory responses. Infected MBL null mice also develop liver injury. These findings suggest that MBL deficiency may manifest as disseminated intravascular coagulation and organ failure with infection. Beginning from these observations, this review focuses on the interaction of innate immunity and other homeostatic systems, the derangement of which may lead to complications in infection and other inflammatory states.Expert Review of Anticancer Therapy 12/2011; 9(12):1179-90. · 3.28 Impact Factor -
Article: Complement 3 is involved with ventilator-induced lung injury.
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ABSTRACT: Humoral molecules can trigger injury on mechanically stressed and damaged tissue. We have studied the role of complement 3 (C3) in a mouse model of ventilator-induced lung injury (VILI). Compared with sham-treated wild type (WT) mice, ventilated WT mice have reduced total bronchoalveolar lavage (BAL) cells; and elevated activities of thrombin and matrix metalloproteinases (MMPs), such as gelatinase/collagenase in the BAL fluid. In contrast, these parameters in ventilated C3 null mice are not significantly different from sham-treated WT and C3 null mice. In mechanically ventilated mice, thrombin activity and MMPs are lower in C3 null mice than in WT mice and are inversely correlated with total single BAL cells. C3 activation is associated with MMP activation in vitro. Pretreatment of WT mice with humanized cobra venom factor, which inactivates C3, reduces C3 deposition in the lung and increases total BAL cells in VILI. We propose that C3 is involved with VILI and inhibition of complement activation may be a potential therapeutic strategy.International immunopharmacology 12/2011; 11(12):2138-43. · 2.21 Impact Factor -
Article: Mechanisms of mannose-binding lectin-associated serine proteases-1/3 activation of the alternative pathway of complement.
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ABSTRACT: Mannose-binding lectin-associated serine proteases-1/3 (MASP-1/3) are essential in activating the alternative pathway (AP) of complement through cleaving pro-factor D (pro-Df) into mature Df. MASP are believed to require binding to mannose binding lectins (MBL) or ficolins (FCN) to carry out their biological activities. Murine sera have been reported to contain MBL-A, MBL-C, and FCN-A, but not FCN-B that exists endogenously in monocytes and is thought not to bind MASP-1. We examined some possible mechanisms whereby MASP-1/3 might activate the AP. Collagen antibody-induced arthritis, a murine model of inflammatory arthritis dependent on the AP, was unchanged in mice lacking MBL-A, MBL-C, and FCN-A (MBL(-/-)/FCN A(-/-) mice) in comparison to wild-type mice. The in vitro induction of the AP by adherent mAb to collagen II was intact using sera from MBL(-/-)/FCN A(-/-) mice. Furthermore, sera from MBL(-/-)/FCN A(-/-) mice lacked pro-Df and possessed only mature Df. Gel filtration of sera from MBL(-/-)/FCN A(-/-) mice showed the presence of MASP-1 protein in fractions containing proteins smaller than the migration of MBL-A and MBL-C in sera from C4(-/-) mice, suggesting possible binding of MASP-1 to an unknown protein. Lastly, we show that FCN-B was present in the sera of MBL(-/-)/FCN A(-/-) mice and that it was bound to MASP-1. We conclude that MASP-1 does not require binding to MBL-A, MBL-C, or FCN-A to activate the AP. MASP-1 may cleave pro-Df into mature Df through binding to FCN-B or to an unknown protein, or may function as an unbound soluble protein.Molecular Immunology 09/2011; 49(1-2):281-9. · 2.90 Impact Factor -
Article: Identification of a cytochrome P4502E1/Bid/C1q-dependent axis mediating inflammation in adipose tissue after chronic ethanol feeding to mice.
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ABSTRACT: Chronic, heavy alcohol exposure results in inflammation in adipose tissue, insulin resistance, and liver injury. Here we have identified a CYP2E1/Bid/C1q-dependent pathway that is activated in response to chronic ethanol and is required for the development of inflammation in adipose tissue. Ethanol feeding for 25 days to wild-type (C57BL/6J) mice increased expression of multiple markers of adipose tissue inflammation relative to pair-fed controls independent of increased body weight or adipocyte size. Ethanol feeding increased the expression of CYP2E1 in adipocytes, but not stromal vascular cells, in adipose tissue and Cyp2e1(-/-) mice were protected from adipose tissue inflammation in response to ethanol. Ethanol feeding also increased the number of TUNEL-positive nuclei in adipose tissue of wild-type mice but not in Cyp2e1(-/-) or Bid (-/-) mice. Apoptosis contributed to adipose inflammation, as the expression of multiple inflammatory markers was decreased in mice lacking the Bid-dependent apoptotic pathway. The complement protein C1q binds to apoptotic cells, facilitating their clearance and activating complement. Making use of C1q-deficient mice, we found that activation of complement via C1q provided the critical link between CYP2E1/Bid-dependent apoptosis and onset of adipose tissue inflammation in response to chronic ethanol. In summary, chronic ethanol increases CYP2E1 activity in adipose, leading to Bid-mediated apoptosis and activation of complement via C1q, finally resulting in adipose tissue inflammation. Taken together, these data identify a novel mechanism for the development of adipose tissue inflammation that likely contributes to the pathophysiological effects of ethanol.Journal of Biological Chemistry 08/2011; 286(41):35989-97. · 4.77 Impact Factor -
Article: The alternative pathway is required, but not alone sufficient, for retinal pathology in mouse laser-induced choroidal neovascularization.
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ABSTRACT: Human genetic studies have demonstrated that polymorphisms in different complement proteins can increase the risk for developing AMD. There are three pathways of complement activation, classical (CP), alternative (AP), and lectin (LP), which all activate a final common pathway. Proteins encoded by the AMD risk genes participate in the AP (CFB), CP/LP (C2), or in the AP and final common pathway (C3). Here we tested which pathway is essential in mouse laser-induced CNV. CNV was analyzed using single complement pathway knockouts (i.e., eliminating one complement pathway at a time), followed by a double knockout in which only the AP is present, and the CP and LP are disabled, using molecular, histological and electrophysiological outcomes. First, single-gene knockouts were analyzed and compared to wild type mice; C1q(-/-) (no CP), MBL(-/-) (no LP), and CFB(-/-) (no AP). Six days after the laser-induced lesion, mice without a functional AP had reduced CNV progression (P<0.001) and preserved ERG amplitudes, whereas those without a functional CP or LP were indistinguishable from the wild type controls (P>0.3). Second, AP-only mice (C1q(-/-)MBL(-/-)) were as protected from developing CNV as the CFB(-/-) mice. The degree of pathology in each strain correlated with protein levels of the angiogenic and anti-angiogenic protein VEGF and PEDF, respectively, as well as levels of terminal pathway activation product C5a, and C9. The analysis of complement activation pathways in mouse laser-induced CNV allows for the following conclusions. Comparing the single pathway knockouts with those having only a functional AP showed: (1) that AP activation is necessary, but not alone sufficient for injury; and (2) that initial complement activation proceeds via both the LP and CP. Thus, these data indicate an important role for the AP in the generation of complement-dependent injury in the RPE and choroid via amplification of CP- and LP-initiated complement activation. Improving our understanding of the local regulation of this pathway in the eye is essential for developing improved treatment approaches for AMD.Molecular Immunology 03/2011; 48(6-7):e1-8. · 2.90 Impact Factor -
Article: High-dose mannose-binding lectin therapy for Ebola virus infection.
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ABSTRACT: Mannose-binding lectin (MBL) targets diverse microorganisms for phagocytosis and complement-mediated lysis by binding specific surface glycans. Although recombinant human MBL (rhMBL) trials have focused on reconstitution therapy, safety studies have identified no barriers to its use at higher levels. Ebola viruses cause fatal hemorrhagic fevers for which no treatment exists and that are feared as potential biothreat agents. We found that mice whose rhMBL serum concentrations were increased ≥7-fold above average human levels survived otherwise fatal Ebola virus infections and became immune to virus rechallenge. Because Ebola glycoproteins potentially model other glycosylated viruses, rhMBL may offer a novel broad-spectrum antiviral approach.The Journal of Infectious Diseases 01/2011; 203(2):175-9. · 6.41 Impact Factor -
Article: Essential role of complement mannose-binding lectin-associated serine proteases-1/3 in the murine collagen antibody-induced model of inflammatory arthritis.
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ABSTRACT: Gene-targeted mice deficient in the complement mannose-binding lectin-associated serine protease-1 and -3 (MASP1/3(-/-)) express only the zymogen of factor D (pro-factor D [pro-Df]), a necessary component of the alternative pathway (AP). We used the murine collagen Ab-induced arthritis (CAIA) model, in which the AP is unique among complement pathways in being both necessary and sufficient for disease induction, to determine whether MASP-1/3 are required in vivo for the development of tissue injury. Disease activity scores, complement C3 tissue deposition in the joint, and histopathologic injury scores were markedly decreased in MASP1/3(-/-) as compared with wild-type (WT) mice. MASP-1 protein was immunochemically localized to synovial cells of knees of WT mice with arthritis. Pro-Df was present in both synovial cells and chondrocytes of knees of WT and MASP1/3(-/-) mice without arthritis, with increased amounts present in synovial cells of WT mice with CAIA. No conversion of pro-Df to mature Df was detectable in the serum of MASP1/3(-/-) mice during the evolution of CAIA. C3 activation and deposition as well as C5a generation induced in vitro by adherent anti-type II collagen mAbs were absent using sera from MASP1/3(-/-) mice under conditions in which only the AP was active. The addition of human Df fully reconstituted in vitro C3 activation and C5a generation using sera from MASP1/3(-/-) mice. Our studies demonstrate for the first time, to our knowledge, the absolute requirement for the activity of MASP-1 protein in autoimmune-associated inflammatory tissue injury in vivo through activation of the AP of complement by cleavage of pro-Df to mature Df.The Journal of Immunology 11/2010; 185(9):5598-606. · 5.79 Impact Factor -
Article: Recombinant chimeric lectins consisting of mannose-binding lectin and L-ficolin are potent inhibitors of influenza A virus compared with mannose-binding lectin.
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ABSTRACT: MBL structurally contains a type II-like collagenous domain and a carbohydrate recognition domain (CRD). We have recently generated three novel recombinant chimeric lectins (RCL), in which varying length of collagenous domain of mannose-binding lectin (MBL) is replaced with that of L-ficolin (L-FCN). CRD of MBL is used for target recognition because it has a broad spectrum in pathogen recognition compared with L-FCN. Results of our study demonstrate that these RCLs are potent inhibitors of influenza A virus (IAV). RCLs, against IAV, show dose-dependent activation of the lectin complement pathway, which is significantly higher than that of recombinant human MBL (rMBL). This activity is observed even without MBL-associated serine proteases (MASPs, provided by MBL deficient mouse sera), which have been thought to mediate complement activation. These observations suggest that RCLs are more efficient in associating with MASP-2, which predominantly mediates the activity. Yet, additional serum further increases the activity while RCL-mediated coagulation-like enzyme activities are diminished compared with rMBL, suggesting reduced association with MASP-1, which has been shown to mediate coagulation-like activity. These data suggest that RCLs may interfere less with host coagulation, which is advantageous to be a therapeutic drug. Importantly, these RCLs have surpassed rMBL for anti-viral activities, such as viral aggregation, reduction of viral hemagglutination (HA) and inhibition of virus-mediated HA and neuraminidase (NA) activities. These results are encouraging that novel RCLs could be used as anti-IAV agents with less side effect and that RCLs would be suitable candidates in developing a new anti-IAV therapy.Biochemical pharmacology 10/2010; 81(3):388-95. · 4.25 Impact Factor -
Article: B cell subsets contribute to renal injury and renal protection after ischemia/reperfusion.
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ABSTRACT: Ischemia/reperfusion (I/R) triggers a robust inflammatory response within the kidney. Numerous components of the immune system contribute to the resultant renal injury, including the complement system. We sought to identify whether natural Abs bind to the postischemic kidney and contribute to complement activation after I/R. We depleted peritoneal B cells in mice by hypotonic shock. Depletion of the peritoneal B cells prevented the deposition of IgM within the glomeruli after renal I/R and attenuated renal injury after I/R. We found that glomerular IgM activates the classical pathway of complement, but it does not cause substantial deposition of C3 within the kidney. Furthermore, mice deficient in classical pathway proteins were not protected from injury, indicating that glomerular IgM does not cause injury through activation of the classical pathway. We also subjected mice deficient in all mature B cells (μMT mice) to renal I/R and found that they sustained worse renal injury than wild-type controls. Serum IL-10 levels were lower in the μMT mice. Taken together, these results indicate that natural Ab produced by peritoneal B cells binds within the glomerulus after renal I/R and contributes to functional renal injury. However, nonperitoneal B cells attenuate renal injury after I/R, possibly through the production of IL-10.The Journal of Immunology 10/2010; 185(7):4393-400. · 5.79 Impact Factor -
Article: A novel L-ficolin/mannose-binding lectin chimeric molecule with enhanced activity against Ebola virus.
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ABSTRACT: Ebola viruses constitute a newly emerging public threat because they cause rapidly fatal hemorrhagic fevers for which no treatment exists, and they can be manipulated as bioweapons. We targeted conserved N-glycosylated carbohydrate ligands on viral envelope surfaces using novel immune therapies. Mannose-binding lectin (MBL) and L-ficolin (L-FCN) were selected because they function as opsonins and activate complement. Given that MBL has a complex quaternary structure unsuitable for large scale cost-effective production, we sought to develop a less complex chimeric fusion protein with similar ligand recognition and enhanced effector functions. We tested recombinant human MBL and three L-FCN/MBL variants that contained the MBL carbohydrate recognition domain and varying lengths of the L-FCN collagenous domain. Non-reduced chimeric proteins formed predominantly nona- and dodecameric oligomers, whereas recombinant human MBL formed octadecameric and larger oligomers. Surface plasmon resonance revealed that L-FCN/MBL76 had the highest binding affinities for N-acetylglucosamine-bovine serum albumin and mannan. The same chimeric protein displayed superior complement C4 cleavage and binding to calreticulin (cC1qR), a putative receptor for MBL. L-FCN/MBL76 reduced infection by wild type Ebola virus Zaire significantly greater than the other molecules. Tapping mode atomic force microscopy revealed that L-FCN/MBL76 was significantly less tall than the other molecules despite similar polypeptide lengths. We propose that alterations in the quaternary structure of L-FCN/MBL76 resulted in greater flexibility in the collagenous or neck region. Similarly, a more pliable molecule might enhance cooperativity between the carbohydrate recognition domains and their cognate ligands, complement activation, and calreticulin binding dynamics. L-FCN/MBL chimeric proteins should be considered as potential novel therapeutics.Journal of Biological Chemistry 08/2010; 285(32):24729-39. · 4.77 Impact Factor
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Institutions
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2002–2012
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Massachusetts General Hospital
- • Department of Radiology
- • MassGeneral Hospital for Children
Boston, MA, USA
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2011
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Medical University of South Carolina
- Department of Ophthalmology
Charleston, SC, USA
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2010–2011
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University of Colorado Hospital
Aurora, CO, USA
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2005–2011
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Harvard University
- Department of Medicine Brigham and Women's Hospital
Boston, MA, USA
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2007–2009
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University of Colorado Denver
- Department of Medicine
Denver, CO, USA
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