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Anna M Blom - One of the best experts on this subject based on the ideXlab platform.
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novel structure of the n terminal helical domain of biba a group b streptococcus immunogenic bacterial adhesin
2020Co-Authors: Kartik Manne, Anna M Blom, Debasish Chattopadhyay, Vaibhav Agarwal, Baldeep Khare, Srinivas Chakravarthy, Chungyu Chang, Hung Tonthat, Sthanam V L NarayanaAbstract:BibA, a group B streptococcus (GBS) surface Protein, has been shown to protect the pathogen from phagocytic killing by sequestering a complement inhibitor: C4b-Binding Protein (C4BP). Here, the X-ray crystallographic structure of a GBS BibA fragment (BibA126-398) and a low-resolution small-angle X-ray scattering (SAXS) structure of the full-length N-terminal domain (BibA34-400) are described. The BibA126-398 fragment crystal structure displayed a novel and predominantly helical structure. The tertiary arrangement of helices forms four antiparallel three-helix-bundle-motif repeats, with one long helix from a bundle extending into the next. Multiple mutations on recombinant BibA34-400 delayed the degradation of the Protein, and circular dichroism spectroscopy of BibA34-400 suggested a similar secondary-structure composition to that observed in the crystallized BibA126-398 fragment. A model was generated for the 92 N-terminal residues (BibA34-125) using structural similarity prediction programs, and a BibA34-400 model was generated by combining the coordinates of BibA34-126 and BibA126-398. The X-ray structure of BibA126-398 and the model of BibA34-400 fitted well into the calculated SAXS envelope. One possible binding site for the BibA N-terminal domain was localized to the N-terminal CCP (complement-control Protein) domains of the C4BP α-chain, as indicated by the decreased binding of BibA to a ΔCCP1 C4BP α-chain mutant. In summary, it is suggested that the GBS surface Protein BibA, which consists of three antiparallel α-helical-bundle motifs, is unique and belongs to a new class of Gram-positive surface adhesins.
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short leucine rich proteoglycans modulate complement activity and increase killing of the respiratory pathogen moraxella catarrhalis
2018Co-Authors: Maisem Laabei, Kristian Riesbeck, John D. Lambris, David Ermert, Guanghui Liu, Anna M BlomAbstract:The respiratory pathogen Moraxella catarrhalis is a human-specific commensal that frequently causes acute otitis media in children and stimulates acute exacerbations in chronic obstructive pulmonary disease patients. The exact molecular mechanisms defining host-pathogen interactions promoting pathogenesis are not clearly understood. Limited knowledge hampers vaccine and immunotherapeutic development required to treat this emerging pathogen. In this study, we reveal in detail a novel antibacterial role displayed by short leucine-rich proteoglycans (SLRPs) in concert with complement. We show that fibromodulin (FMOD), osteoadherin (OSAD), and biglycan (BGN) but not decorin (DCN) enhance serum killing of M. catarrhalis. Our results suggest that M. catarrhalis binding to SLRPs is a conserved feature, as the overwhelming majority of clinical and laboratory strains bound all four SLRPs. Furthermore, we resolve the binding mechanism responsible for this interaction and highlight the role of the ubiquitous surface Protein (Usp) A2/A2H in mediating binding to host SLRPs. A conserved immune evasive strategy used by M. catarrhalis and other pathogens is the surface acquisition of host complement inhibitors such as C4b-Binding Protein (C4BP). We observed that FMOD, OSAD, and BGN competitively inhibit binding of C4BP to the surface of M. catarrhalis, resulting in increased C3b/iC3b deposition, membrane attack complex (MAC) formation, and subsequently decreased bacterial survival. Furthermore, both OSAD and BGN promote enhanced neutrophil killing in vitro, both in a complement-dependent and independent fashion. In summary, our results illustrate that SLRPs, FMOD, OSAD, and BGN portray complement-modulating activity enhancing M. catarrhalis killing, defining a new antibacterial role supplied by SLRPs.
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prelp enhances host innate immunity against the respiratory tract pathogen moraxella catarrhalis
2017Co-Authors: Guanghui Liu, Kristian Riesbeck, David Ermert, Martin Johansson, Birendra Singh, Magnus Paulsson, Anna M BlomAbstract:Respiratory tract infections are one of the leading causes of mortality worldwide urging better understanding of interactions between pathogens causing these infections and the host. Here we report that an extracellular matrix component proline/arginine-rich end leucine-rich repeat Protein (PRELP) is a novel antibacterial component of innate immunity. We detected the presence of PRELP in human bronchoalveolar lavage fluid and showed that PRELP can be found in alveolar fluid, resident macrophages/monocytes, myofibroblasts, and the adventitia of blood vessels in lung tissue. PRELP specifically binds respiratory tract pathogens Moraxella catarrhalis , Haemophilus influenzae , and Streptococcus pneumoniae , but not other bacterial pathogens tested. We focused our study on M. catarrhalis and found that PRELP binds the majority of clinical isolates of M. catarrhalis ( n = 49) through interaction with the ubiquitous surface Protein A2/A2H. M. catarrhalis usually resists complement-mediated serum killing by recruiting to its surface a complement inhibitor C4b-Binding Protein, which is also a ligand for PRELP. We found that PRELP competitively inhibits binding of C4b-Binding Protein to bacteria, which enhances membrane attack complex formation on M. catarrhalis and thus leads to increased serum sensitivity. Furthermore, PRELP enhances phagocytic killing of serum-opsonized M. catarrhalis by human neutrophils in vitro. Moreover, PRELP reduces Moraxella adherence to and invasion of human lung epithelial A549 cells. Taken together, PRELP enhances host innate immunity against M. catarrhalis through increasing complement-mediated attack, improving phagocytic killing activity of neutrophils, and preventing bacterial adherence to lung epithelial cells.
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c4b binding Protein the good the bad and the deadly novel functions of an old friend
2016Co-Authors: David Ermert, Anna M BlomAbstract:C4b-Binding Protein (C4BP) is best known as a potent soluble inhibitor of the classical and lectin pathways of the complement system. This large 500 kDa multimeric plasma glycoProtein is expressed mainly in the liver but also in lung and pancreas. It consists of several identical 75 kDa α-chains and often also one 40 kDa β-chain, both of which are mainly composed of complement control Protein (CCP) domains. Structure-function studies revealed that one crucial binding site responsible for inhibition of complement is located to CCP1-3 of the α-chain. Binding of anticoagulant Protein S to the CCP1 of the β-chain provides C4BP with the ability to strongly bind apoptotic and necrotic cells in order to prevent inflammation arising from activation of complement by these cells. Further, C4BP interacts strongly with various types of amyloid and enhances fibrillation of islet amyloid polypeptide secreted from pancreatic beta cells, which may attenuate pro-inflammatory and cytotoxic effects of this amyloid. Full deficiency of C4BP has not been identified but non-synonymous alterations in its sequence have been found in haemolytic uremic syndrome and recurrent pregnancy loss. Furthermore, C4BP is bound by several bacterial pathogens, notably Streptococcus pyogenes, which due to inhibition of complement and enhancement of bacterial adhesion to endothelial cells provides these bacteria with a survival advantage in the host. Thus, depending on the context, C4BP has a protective or detrimental role in the organism.
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fine mapping of the interaction between c4b binding Protein and outer membrane Proteins liga and ligb of pathogenic leptospira interrogans
2015Co-Authors: Leandro Carvalho Dantas Breda, Anna M Blom, Angela S Barbosa, Chinglin Hsieh, Monica Marcela Castiblanco Valencia, Ludmila Bezerra Da Silva, Chang Yungfu, Lourdes IsaacAbstract:The complement system consists of more than 40 Proteins that participate in the inflammatory response and in pathogen killing. Complement inhibitors are necessary to avoid the excessive consumption and activation of this system on host cells. Leptospirosis is a worldwide zoonosis caused by spirochetes from the genus Leptospira. Pathogenic leptospires are able to escape from complement activation by binding to host complement inhibitors Factor H [FH] and C4b-Binding Protein (C4BP) while non-pathogenic leptospires are rapidly killed in the presence of fresh serum. In this study, we demonstrate that complement control Protein domains (CCP) 7 and 8 of C4BP α-chain interact with the outer membrane Proteins LcpA, LigA and LigB from the pathogenic leptospire L. interrogans. The interaction between C4BP and LcpA, LigA and LigB is sensitive to ionic strength and inhibited by heparin. We fine mapped the LigA and LigB domains involved in its binding to C4BP and heparin and found that both interactions are mediated through the bacterial immunoglobulin-like (Big) domains 7 and 8 (LigA7-8 and LigB7-8) of both LigA and LigB and also through LigB9-10. Therefore, C4BP and heparin may share the same binding sites on Lig Proteins.
Björn Dahlbäck - One of the best experts on this subject based on the ideXlab platform.
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Amino acid residues in the laminin G domains of Protein S involved in tissue factor pathway inhibitor interaction
2015Co-Authors: Sofia Somajo, Magdalena Gierula, Josefin Ahnstrom, Bruno O Villoutreix, Juan Fernández-recio, Björn DahlbäckAbstract:Protein S functions as a cofactor for tissue factor pathway inhibitor (TFPI) and activated Protein C (APC). The sex hormone binding globulin (SHBG)-like region of Protein S, consisting of two laminin G-like domains (LG1 and LG2), contains the binding site for C4b-Binding Protein (C4BP) and TFPI. Furthermore, the LG-domains are essential for the TFPI-cofactor function and for expression of full APC-cofactor function. The aim of the current study was to localise functionally important interaction sites in the Protein S LG-domains using amino acid substitutions. Four Protein S variants were created in which clusters of surface-exposed amino acid residues within the LG-domains were substituted. All variants bound normally to C4BP and were fully functional as cofactors for APC in plasma and in pure component assays. Two variants, SHBG2 (E612A, I614A, F265A, V393A, H453A), involving residues from both LG-domains, and SHBG3 (K317A, I330A, V336A, D365A) where residues in LG1 were substituted, showed 50–60 % reduction in enhancement of TFPI in FXa inhibition assays. For SHBG3 the decreased TFPI cofactor function was confirmed in plasma based thrombin generation assays. Both SHBG variants bound to TFPI with decreased affinity in surface plasmon resonance experiments. The TFPI Kunitz 3 domain is known to contain the interaction site for Protein S. Using in silico analysis and Protein docking exercises, preliminary models of the Protein S SHBG/TFPI Kunitz domain 3 complex were created. Based on a combination of experimental and in silico data we propose a binding site for TFPI on Protein S, involving both LGdomains.
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c4b binding Protein and factor h compensate for the loss of membrane bound complement inhibitors to protect apoptotic cells against excessive complement attack
2007Co-Authors: Leendert A Trouw, Björn Dahlbäck, Anders A Bengtsson, Kyra A Gelderman, Gunnar Sturfelt, Anna M BlomAbstract:Apoptotic cells have been reported to down-regulate membrane-bound complement regulatory Proteins (m-C-Reg) and to activate complement. Nonetheless, most apoptotic cells do not undergo complement-mediated lysis. Therefore, we hypothesized that fluid phase complement inhibitors would bind to apoptotic cells and compensate functionally for the loss of m-C-Reg. We observed that m-C-Reg are down-regulated rapidly upon apoptosis but that complement activation follows only after a gap of several hours. Coinciding with, but independent from, complement activation, fluid phase complement inhibitors C4b-Binding Protein (C4BP) and factor H (fH) bind to the cells. C4BP and fH do not entirely prevent complement activation but strongly limit C3 and C9 deposition. Late apoptotic cells, present in blood of healthy controls and systemic lupus erythematosus patients, are also positive for C4BP and fH. Upon culture, the percentage of late apoptotic cells increases, paralleled by increased C4BP binding. C4BP binds to dead cells mainly via phosphatidylserine, whereas fH binds via multiple interactions with CRP playing no major role for binding of C4BP or fH. In conclusion, during late apoptosis, cells acquire fluid phase complement inhibitors that compensate for the down-regulation of m-C-Reg and protect against excessive complement activation and lysis.
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complement inhibitor c4b binding Protein friend or foe in the innate immune system
2004Co-Authors: Anna M Blom, Bruno O Villoutreix, Björn DahlbäckAbstract:The complement system constitutes an important component of the defence against foreign organisms, functioning both in innate and adaptive immune systems. It is potentially harmful also to the own organism and is therefore tightly regulated by a number of membrane-bound and soluble factors. C4b-Binding Protein (C4BP) is a potent circulating soluble inhibitor of the classical and lectin pathways of complement. In recent years, the relationships between the structure of C4BP and its functions have been elucidated using a combination of computer-based molecular analysis and recombinant DNA technologies. Moreover, two novel functions have recently been ascribed to C4BP. One is the ability of C4BP to localize complement regulatory activity to the surface of apoptotic cells via its interaction with the membrane-binding vitamin K-dependent Protein S. The other is the ability of C4BP to act as a survival factor for B cells due to an interaction with CD40. The complement regulatory activity of C4BP is not only beneficial because it is also explored by pathogens such as Neisseria gonorrhoeae, Bordetella pertussis, Streptococcus pyogenes, Escherichia coli K1, and Candida albicans, that bind C4BP to their surfaces. This contributes to the serum resistance and the pathogenicity of these bacteria. In this review, the structural requirements and functional importance of the interactions between C4BP and its various ligands are discussed.
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ccp1 4 of the c4b binding Protein alpha chain are required for factor i mediated cleavage of complement factor c3b
2003Co-Authors: Anna M Blom, Lena Kask, Björn DahlbäckAbstract:C4b-Binding Protein (C4BP) is a potent regulator of the complement system because it strongly inhibits the classical pathway of complement. Furthermore, C4BP serves as a cofactor to factor I (FI) in the cleavage of fluid phase C3b and can, therefore, influence the alternative pathway of complement. The major form of C4BP in plasma consists of seven identical α-chains and one β-chain. Both types of subunits are composed of complement control Protein (CCP) domains, eight such domains make up one α-chain. To elucidate the structural requirements for the interaction between C3b and the α-chain, nineteen recombinant C4BP variants were used: six truncated monomeric variants, nine polymeric variants in which individual CCPs were deleted, and finally four variants in which double alanine residues were introduced between CCPs. We found that C4BP requires all four N-terminal CCPs of the α-chain, with CCP2 and 3 being the most important, to act as a cofactor in the cleavage of C3b. Also, a cluster of positively charged amino acids on the interface between CCP1 and 2 is involved in the binding. Compared to the interaction with C4b, we conclude that binding of C3b to C4BP requires larger molecular surface on C4BP. We found that C4BP was able to act as cofactor in degradation of surface bound C3b and to accelerate decay of alternative C3-convertase. However, in both cases 1000-fold molar excess of C4BP over factor H (FH), well known inhibitor of the alternative pathway, was required to obtain the same effect.
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deficient apc cofactor activity of Protein s heerlen in degradation of factor va leiden a possible mechanism of synergism between thrombophilic risk factors
2000Co-Authors: Tusar Kanti Giri, Björn Dahlbäck, Tomio Yamazaki, Nuria Sala, Pablo Garcia De FrutosAbstract:In Protein S Heerlen, an S-to-P (single-letter amino acid codes) mutation at position 460 results in the loss of glycosylation of N458. This polymorphism has been found to be slightly more prevalent in thrombophilic populations than in normal controls, particularly in cohorts of patients having free Protein S deficiency. This suggests that carriers of the Heerlen allele may have an increased risk of thrombosis. We have now characterized the expression in cell cultures of recombinant Protein S Heerlen and investigated the anticoagulant functions of the purified recombinant Protein in vitro. Protein S Heerlen was synthesized and secreted equally well as wild-type Protein S by transiently transfected COS-1 cells. The recombinant Protein S Heerlen interacted with conformation-dependent monoclonal antibodies and bound C4b-Binding Protein to the same extent as wild-type Protein S. Protein S Heerlen displayed reduced anticoagulant activity as cofactor to activated Protein C (APC) in plasma-based assays, as well as in a factor VIIIa–degradation system. In contrast, Protein S Heerlen functioned equally well as an APC cofactor in the degradation of factor Va as wild-type Protein S did. However, when recombinant activated factor V Leiden (FVa:Q506) was used as APC substrate, Protein S Heerlen was found to be a poor APC cofactor as compared with wild-type Protein S. These in vitro results suggest a possible mechanism of synergy between Protein S Heerlen and factor V Leiden that might be involved in the pathogenesis of thrombosis in individuals carrying both genetic traits.
Kristian Riesbeck - One of the best experts on this subject based on the ideXlab platform.
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short leucine rich proteoglycans modulate complement activity and increase killing of the respiratory pathogen moraxella catarrhalis
2018Co-Authors: Maisem Laabei, Kristian Riesbeck, John D. Lambris, David Ermert, Guanghui Liu, Anna M BlomAbstract:The respiratory pathogen Moraxella catarrhalis is a human-specific commensal that frequently causes acute otitis media in children and stimulates acute exacerbations in chronic obstructive pulmonary disease patients. The exact molecular mechanisms defining host-pathogen interactions promoting pathogenesis are not clearly understood. Limited knowledge hampers vaccine and immunotherapeutic development required to treat this emerging pathogen. In this study, we reveal in detail a novel antibacterial role displayed by short leucine-rich proteoglycans (SLRPs) in concert with complement. We show that fibromodulin (FMOD), osteoadherin (OSAD), and biglycan (BGN) but not decorin (DCN) enhance serum killing of M. catarrhalis. Our results suggest that M. catarrhalis binding to SLRPs is a conserved feature, as the overwhelming majority of clinical and laboratory strains bound all four SLRPs. Furthermore, we resolve the binding mechanism responsible for this interaction and highlight the role of the ubiquitous surface Protein (Usp) A2/A2H in mediating binding to host SLRPs. A conserved immune evasive strategy used by M. catarrhalis and other pathogens is the surface acquisition of host complement inhibitors such as C4b-Binding Protein (C4BP). We observed that FMOD, OSAD, and BGN competitively inhibit binding of C4BP to the surface of M. catarrhalis, resulting in increased C3b/iC3b deposition, membrane attack complex (MAC) formation, and subsequently decreased bacterial survival. Furthermore, both OSAD and BGN promote enhanced neutrophil killing in vitro, both in a complement-dependent and independent fashion. In summary, our results illustrate that SLRPs, FMOD, OSAD, and BGN portray complement-modulating activity enhancing M. catarrhalis killing, defining a new antibacterial role supplied by SLRPs.
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prelp enhances host innate immunity against the respiratory tract pathogen moraxella catarrhalis
2017Co-Authors: Guanghui Liu, Kristian Riesbeck, David Ermert, Martin Johansson, Birendra Singh, Magnus Paulsson, Anna M BlomAbstract:Respiratory tract infections are one of the leading causes of mortality worldwide urging better understanding of interactions between pathogens causing these infections and the host. Here we report that an extracellular matrix component proline/arginine-rich end leucine-rich repeat Protein (PRELP) is a novel antibacterial component of innate immunity. We detected the presence of PRELP in human bronchoalveolar lavage fluid and showed that PRELP can be found in alveolar fluid, resident macrophages/monocytes, myofibroblasts, and the adventitia of blood vessels in lung tissue. PRELP specifically binds respiratory tract pathogens Moraxella catarrhalis , Haemophilus influenzae , and Streptococcus pneumoniae , but not other bacterial pathogens tested. We focused our study on M. catarrhalis and found that PRELP binds the majority of clinical isolates of M. catarrhalis ( n = 49) through interaction with the ubiquitous surface Protein A2/A2H. M. catarrhalis usually resists complement-mediated serum killing by recruiting to its surface a complement inhibitor C4b-Binding Protein, which is also a ligand for PRELP. We found that PRELP competitively inhibits binding of C4b-Binding Protein to bacteria, which enhances membrane attack complex formation on M. catarrhalis and thus leads to increased serum sensitivity. Furthermore, PRELP enhances phagocytic killing of serum-opsonized M. catarrhalis by human neutrophils in vitro. Moreover, PRELP reduces Moraxella adherence to and invasion of human lung epithelial A549 cells. Taken together, PRELP enhances host innate immunity against M. catarrhalis through increasing complement-mediated attack, improving phagocytic killing activity of neutrophils, and preventing bacterial adherence to lung epithelial cells.
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acquisition of complement inhibitor serine protease factor i and its cofactors c4b binding Protein and factor h by prevotella intermedia
2012Co-Authors: Sven Malm, Monika Jusko, Sigrun Eick, Jan Potempa, Kristian Riesbeck, Anna M BlomAbstract:Infection with the Gram-negative pathogen Prevotella intermedia gives rise to periodontitis and a growing number of studies implies an association of P. intermedia with rheumatoid arthritis. The serine protease Factor I (FI) is the central inhibitor of complement degrading complement components C3b and C4b in the presence of cofactors such as C4b-Binding Protein (C4BP) and Factor H (FH). Yet, the significance of complement inhibitor acquisition in P. intermedia infection and FI binding by Gram-negative pathogens has not been addressed. Here we show that P. intermedia isolates bound purified FI as well as FI directly from heat-inactivated human serum. FI bound to bacteria retained its serine protease activity as shown in degradation experiments with (125)I-labeled C4b. Since FI requires cofactors for its activity we also investigated the binding of purified cofactors C4BP and FH and found acquisition of both Proteins, which retained their activity in FI mediated degradation of C3b and C4b. We propose that FI binding by P. intermedia represents a new mechanism contributing to complement evasion by a Gram-negative bacterial pathogen associated with chronic diseases.
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vitronectin binds to the head region of moraxella catarrhalis ubiquitous surface Protein a2 and confers complement inhibitory activity
2010Co-Authors: Birendra Singh, Anna M Blom, Can Unal, Bo Nilson, Matthias Morgelin, Kristian RiesbeckAbstract:Summary The serum resistance of the common respiratory pathogen Moraxella catarrhalis is mainly dependent on ubiquitous surface Proteins (Usp) A1 and A2 that interact with complement factor 3 (C3) and complement inhibitor C4b binding Protein (C4BP) preventing the alternative and classical pathways of the complement system respectively. UspA2 also has the capacity to attract vitronectin that in turn binds C9 and hereby inhibits membrane attack complex (MAC) formation. We found UspA2 as a major vitronectin binding Protein and hence the UspA2/vitronectin interaction was studied in detail. The affinity constant (K(D)) for vitronectin binding to UspA2 was 2.3 x 10(-8) M, and the N-terminal region encompassing residues UspA2 30-170 bound vitronectin with a K(D) of 7.9 x 10(-8) M. Electron microscopy verified that the active binding domain (UspA2(30-177)) was located at the head region of UspA2. Experiments with recombinantly expressed vitronectin also revealed that UspA2(30-177) bound to the C-terminal region of vitronectin residues 312-396. Finally, when human serum was pre-incubated with UspA2, bacteria showed significantly less serum resistance. Our study directly reveals the binding mode between the N-terminal domain of UspA2 and the C-terminal part of vitronectin and thus sheds light upon the mechanism of M. catarrhalis-dependent serum resistance.
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ionic binding of c3 to the human pathogen moraxella catarrhalis is a unique mechanism for combating innate immunity
2005Co-Authors: Therese Nordstrom, Anna M Blom, Arne Forsgren, Thuan Tong Tan, Kristian RiesbeckAbstract:Moraxella catarrhalis ubiquitous surface Proteins A1 and A2 (UspA1/A2) interfere with the classical pathway of the complement system by binding C4b-Binding Protein. In this study we demonstrate that M. catarrhalis UspA1 and A2 noncovalently and in a dose-dependent manner bind both the third component of complement (C3) from EDTA-treated serum and methylamine-treated C3. In contrast, related Moraxella subspecies (n = 13) or other human pathogenic bacteria (n = 13) do not bind C3 or methylamine-treated C3. Experiments with recombinant Proteins and M. catarrhalis mutants devoid of UspA1/A2 revealed that UspA1/A2 exert their actions by absorbing and neutralizing C3 from serum and restrain complement activation. UspA2 was responsible for most of the effect, and the Moraxella mutant lacking UspA2 was more sensitive to the lytic effect of human serum compared with the wild type. Interestingly, among the large number of bacteria analyzed, only M. catarrhalis has this unique ability to interfere with the innate immune system of complement by binding C3.
Seppo Meri - One of the best experts on this subject based on the ideXlab platform.
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interactions of the humoral pattern recognition molecule ptx3 with the complement system
2012Co-Authors: Andrea Doni, Peter Garred, Seppo Meri, Cecilia Garlanda, Barbara Bottazzi, Alberto MantovaniAbstract:Abstract The innate immune system comprises a cellular and a humoral arm. The long pentraxin PTX3 is a fluid phase pattern recognition molecule, which acts as an essential component of the humoral arm of innate immunity. PTX3 has antibody-like properties including interactions with complement components. PTX3 interacts with C1q, ficolin-1 and ficolin-2 as well as mannose-binding lectin, recognition molecules in the classical and lectin complement pathways. The formation of these heterocomplexes results in cooperative pathogen recognition and complement activation. Interactions with C4b binding Protein and factor H, the principal regulators of the classical, lectin and alternative complement pathways, show that PTX3 also may have a major influence on the regulation of the complement system. The complex interaction of PTX3 with the complement system at different levels has broad implications for host defence and regulation of inflammation.
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functional recruitment of the human complement inhibitor c4bp to yersinia pseudotuberculosis outer membrane Protein ail
2012Co-Authors: Rauna Riva, Anna M Blom, Seppo Meri, Vesa Kirjavainen, Hanna Jarva, Erica Ginstrom, Mikael SkurnikAbstract:Ail is a 17-kDa chromosomally encoded outer membrane Protein that mediates serum resistance (complement resistance) in the pathogenic Yersiniae (Yersinia pestis, Y. enterocolitica, and Y. pseudotuberculosis). In this article, we demonstrate that Y. pseudotuberculosis Ail from strains PB1, 2812/79, and YPIII/pIB1 (serotypes O:1a, O:1b, and O:3, respectively) can bind the inhibitor of the classical and lectin pathways of complement, C4b-Binding Protein (C4BP). Binding was observed irrespective of serotype tested and independently of YadA, which is the primary C4BP receptor of Y. enterocolitica. Disruption of the ail gene in Y. pseudotuberculosis resulted in loss of C4BP binding. Cofactor assays revealed that bound C4BP is functional, because bound C4BP in the presence of factor I cleaved C4b. In the absence of YadA, Ail conferred serum resistance to strains PB1 and YPIII, whereas serum resistance was observed in strain 2812/79 in the absence of both YadA and Ail, suggesting additional serum resistance factors. Ail from strain YPIII/pIB1 alone can mediate serum resistance and C4BP binding, because its expression in a serum-sensitive laboratory strain of Escherichia coli conferred both of these phenotypes. Using a panel of C4BP mutants, each deficient in a single complement control Protein domain, we observed that complement control Protein domains 6–8 are important for binding to Ail. Binding of C4BP was unaffected by increasing heparin or salt concentrations, suggesting primarily nonionic interactions. These results indicate that Y. pseudotuberculosis Ail recruits C4BP in a functional manner, facilitating resistance to attack from complement.
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complement regulation in human atherosclerotic coronary lesions immunohistochemical evidence that c4b binding Protein negatively regulates the classical complement pathway and that c5b 9 is formed via the alternative complement pathway
2007Co-Authors: Riina Oksjoki, Anna M Blom, Petri T Kovanen, Mikko I Mayranpaa, Petri Laine, Seppo Meri, Markku O PentikainenAbstract:Objective: The complement system is activated in human atherosclerotic lesions and may hence aggravate local inflammation. We studied the presence and localization of C4b-Binding Protein (C4bp), the major inhibitor of the classical complement pathway, in human atherosclerotic lesions in relation to complement activation products and Protein S, which circulates in complex with C4bp. Methods and results: Immunohistochemistry, of human coronary arteries showed C4bp to be virtually absent in normal arteries but present in early and advanced atherosclerotic lesions. In the lesions, C4bp is associated with proteoglycans, and affinity chromatography showed that C4bp interacts with human arterial proteoglycans. Areas containing C4bp also contained IgM and C4 suggesting that C4bp is involved in the regulation of the classical complement pathway. However, C5b-9 was virtually absent in these areas but, instead, colocalized with properdin deeper in the intima, suggesting that C5b-9 is formed by the alternative complement pathway. A fraction of C4bp was associated with Protein S and apoptotic cells. Conclusions: The results indicate that C4bp regulates the classical complement pathway in human atherosclerotic lesions. Thus, unlike the alternative pathway, the classical complement pathway does not generate C5b-9, but is likely to be involved in the clean-up of apoptotic cells and cell debris in the arterial intima. (c) 2006 Elsevier Ireland Ltd. All rights reserved.
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relapsing fever spirochetes borrelia recurrentis and b duttonii acquire complement regulators c4b binding Protein and factor h
2006Co-Authors: Taru Meri, Anna M Blom, Seppo Meri, Sally J Cutler, T S JokirantaAbstract:Relapsing fever is a rapidly progressive and severe septic disease caused by certain Borrelia spirochetes. The disease is divided into two forms, i.e., epidemic relapsing fever, caused by Borrelia recurrentis and transmitted by lice, and the endemic form, caused by several Borrelia species, such as B. duttonii, and transmitted by soft-bodied ticks. The spirochetes enter the bloodstream by the vector bite and live persistently in plasma even after the development of specific antibodies. This leads to fever relapses and high mortality and clearly indicates that the Borrelia organisms utilize effective immune evasion strategies. In this study, we show that the epidemic relapsing fever pathogen B. recurrentis and an endemic relapsing fever pathogen, B. duttonii, are serum resistant, i.e., resistant to complement in vitro. They acquire the host alternative complement pathway regulator factor H on their surfaces in a similar way to that of the less serum-resistant Lyme disease pathogen, B. burgdorferi sensu stricto. More importantly, the relapsing fever spirochetes specifically bind host C4b-Binding Protein, a major regulator of the antibody-mediated classical complement pathway. Both complement regulators retained their functional activities when bound to the surfaces of the spirochetes. In conclusion, this is the first report of complement evasion by Borrelia recurrentis and B. duttonii and the first report showing capture of C4b-Binding Protein by spirochetes.
Sanjay Ram - One of the best experts on this subject based on the ideXlab platform.
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yersinia pestis uses the ail outer membrane Protein to recruit vitronectin
2015Co-Authors: Sara Schesser Bartra, Sanjay Ram, Yi Ding, Miya L Fujimoto, Joshua G Ring, Vishal Jain, Francesca M Marassi, Gregory V PlanoAbstract:Yersinia pestis, the agent of plague, requires the Ail (attachment invasion locus) outer membrane Protein to survive in the blood and tissues of its mammalian hosts. Ail is important for both attachment to host cells and for resistance to complement-dependent bacteriolysis. Previous studies have shown that Ail interacts with components of the extracellular matrix, including fibronectin, laminin and heparan sulfate proteoglycans, and with the complement inhibitor C4b-Binding Protein. Here, we demonstrate that Ail-expressing Y. pestis strains bind vitronectin – a host Protein with functions in cell attachment, fibrinolysis and inhibition of the complement system. The Ail-dependent recruitment of vitronectin resulted in efficient cleavage of vitronectin by the outer membrane Pla (plasminogen activator protease). Escherichia coli DH5α expressing Y. pestis Ail bound vitronectin, but not heat-treated vitronectin. The ability of Ail to directly bind vitronectin was demonstrated by ELISA using purified refolded Ail in nanodiscs.
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phosphoethanolamine residues on the lipid a moiety of neisseria gonorrhoeae lipooligosaccharide modulate binding of complement inhibitors and resistance to complement killing
2013Co-Authors: Lisa A Lewis, Sanjay Ram, William M Shafer, Tathagat Dutta Ray, Peter A RiceAbstract:Loss of phosphoethanolamine (PEA) from the lipid A of gonococcal strain FA19 results in increased sensitivity to killing by the classical pathway of complement. Here we demonstrate that loss of PEA from lipid A diminishes binding of the complement regulatory Protein C4b binding Protein (C4BP) to the FA19 porin B (PorB), providing a molecular basis to explain the susceptibility of an lptA null strain of FA19 to killing by normal human serum (NHS). Loss of PEA from lipid A in three additional gonococcal strains that expressed diverse PorB molecules also resulted in decreased C4BP binding, increased deposition of C4b, and increased susceptibility to killing by NHS. Complementation of lptA null strains with lptA restored C4BP binding, decreased C4b deposition, and increased resistance to killing by NHS. These effects of lipid A PEA on C4BP binding to gonococcal PorB and serum resistance were simulated when gonococcal PorB was expressed in a meningococcal background. Loss of PEA from lipid A also affected binding of the alternative pathway regulator factor H (fH) to PorB of some strains. For instance, PorB molecules of lptA null mutants of strains 252 and 1291 bound less fH than those of their parent strains when lipooligosaccharide (LOS) was sialylated, whereas PorB molecules of lptA null mutants of strains FA1090 and 273 retained the ability to bind fH when LOS was sialylated. These data indicate that replacement of lipid A with PEA alters binding of C4BP and fH to PorB and contributes to the ability of gonococci to resist complement-mediated killing.
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phenotypic and genotypic analyses of neisseria gonorrhoeae isolates that express frequently recovered porb pia variable region types suggest that certain p1a porin sequences confer a selective advantage for urogenital tract infection
2008Co-Authors: Lotisha E Garvin, Sanjay Ram, Margaret C Bash, Christine E Keys, Douglas M Warner, William M Shafer, Ann E JerseAbstract:Typing of the porB variable region (VR) is an epidemiological tool that classifies gonococcal strains based on sequence differences in regions of the porB gene that encode surface-exposed loops. The frequent isolation of certain porB VR types suggests that some porin sequences confer a selective advantage during infection and/or transmission. Alternatively, certain porin types may be markers of strains that are successful due to factors unrelated to porin. In support of the first hypothesis, here we show urogenital tract isolates representing the most common PIA VR types identified in an urban clinic in Baltimore, MD, over a 10-year period belonged to several different clonal types, as determined by pulsed-field gel electrophoresis (PFGE). Serum resistance, which was confirmed by factor H and C4b-Binding Protein binding studies, was more often associated with gonococcal the most common VR types. In contrast, three porin-independent phenotypes, namely, lactoferrin utilization, β-lactamase production, and multiple transferable resistance (Mtr), were segregated with the PFGE cluster and not with the VR type. Data combined with another PIA strain collection showed a strong correlation between serum resistance and the most common VR types. A comparison of VR typing hybridization patterns and nucleotide sequences of 12 porB1a genes suggests that certain porin loop 1, 3, 6, and/or 7 sequences may play a role in the serum resistance phenotype. We conclude that some PorB PIA sequences confer a survival or transmission advantage in the urogenital tract, perhaps via increased resistance to complement-mediated killing. The capacity of some porin types to evade a porin-specific adaptive immune response must also be considered.
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heptose i glycan substitutions on neisseria gonorrhoeae lipooligosaccharide influence c4b binding Protein binding and serum resistance
2007Co-Authors: Sanjay Ram, Anna M Blom, Sunita Gulati, Jutamas Ngampasutadol, Andrew D Cox, Lisa A Lewis, Frank St Michael, Jacek Stupak, Peter A RiceAbstract:Lipooligosaccharide (LOS) heptose (Hep) glycan substitutions influence gonococcal serum resistance. Several gonococcal strains bind the classical complement pathway inhibitor, C4b-Binding Protein (C4BP), via their porin (Por) molecule to escape complement-dependent killing by normal human serum (NHS). We show that the proximal glucose (Glc) on HepI is required for C4BP binding to Por1B-bearing gonococcal strains MS11 and 1291 but not to FA19 (Por1A). The presence of only the proximal Glc on HepI (lgtE mutant) permitted maximal C4BP binding to MS11 but not to 1291. Replacing 1291 lgtE Por with MS11 Por increased C4BP binding to levels that paralleled MS11 lgtE, suggesting that replacement of the Por1B molecule dictated the effects of HepI glycans on C4BP binding. The remainder of the strain background did not affect C4BP binding; replacing the Por of strain F62 with MS11 Por (F62 PorMS11) and truncating HepI mirrored the findings in the MS11 background. C4BP binding correlated with resistance to killing by NHS in most instances. F62 PorMS11 and its lgtE mutant were sensitive to NHS despite binding C4BP, secondary to kinetically overwhelming classical pathway activation and possibly increased alternative pathway activation (measured by factor Bb binding) by the F62 background. FA19 lgtF (HepI unsubstituted) resisted killing by only 10% NHS, not 50% NHS, despite binding levels of C4BP similar to those of FA19 and FA19 lgtE (both resistant to 50% serum), suggesting a role for the proximal Glc in serum resistance independently of C4BP binding. This study provides mechanistic insights into how HepI LOS substitutions affect the serum resistance of N. gonorrhoeae.
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binding of vitronectin by the moraxella catarrhalis uspa2 Protein interferes with late stages of the complement cascade
2006Co-Authors: Ahmed S Attia, Sanjay Ram, Peter A Rice, Eric J HansenAbstract:Many Moraxella catarrhalis strains are resistant to the bactericidal activity of normal human serum (NHS). The UspA2 Protein of the serum-resistant strain O35E has previously been shown to be directly involved in conferring serum resistance on this strain. Testing of 11 additional serum-resistant M. catarrhalis wild-type isolates and their uspA1 and uspA2 mutants showed that the uspA1 mutants of all 11 strains were consistently serum resistant and that the uspA2 mutants of these same 11 strains were always serum sensitive. Analysis of complement deposition on four different serum-resistant M. catarrhalis strains and their serum-sensitive uspA2 mutants showed that, for three of these four strain sets, the wild-type and mutant strains bound similar amounts of early complement components. In contrast, there was a significant reduction in the amount of the polymerized C9 on the wild-type strains relative to that on the uspA2 mutants. These same three wild-type strains bound more vitronectin than did their uspA2 mutants. UspA2 Proteins from these three strains, when expressed in Haemophilus influenzae, bound vitronectin and conferred serum resistance on this organism. Furthermore, vitronectin-depleted NHS exhibited bactericidal activity against these same three serum-resistant wild-type strains; addition of purified vitronectin to this serum restored serum resistance. In contrast, binding of the complement regulator C4b-Binding Protein by the M. catarrhalis strains used in this study was found to be highly variable and did not appear to correlate with the serum-resistant phenotype. These results indicate that binding of vitronectin by UspA2 is involved in the serum resistance of M. catarrhalis; this represents the first example of vitronectin-mediated serum resistance on a microbe.
