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Li Q, Li YX, Douthitt K, Stahl GL, Thurman JM, Tong HH. Role of the alternative and classical complement activation pathway in complement mediated killing against Streptococcus pneumoniae colony opacity variants during acute pneumococcal otitis media in mice. Microbes Infect 2012; 14:1308-18. [PMID: 22975410 PMCID: PMC3511655 DOI: 10.1016/j.micinf.2012.08.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2012] [Revised: 07/30/2012] [Accepted: 08/10/2012] [Indexed: 01/24/2023]
Abstract
There is considerable evidence that phase variation among transparent and opaque colony phenotypes of Streptococcus pneumoniae (Spn) plays an important role in the pneumococcal adherence and invasion. The current study was designed to investigate the interactions of the opacity phenotype variants of Spn with specific complement pathway activation in a mouse model of acute otitis media (AOM). Although the opaque colony phenotype was expected to be more resistant to complement mediated killing compared to the transparent Spn variant, we discovered that C3b deposition on the transparent Spn is, in large part, dependent on the alternative pathway activation. There were no significant differences in resistance to complement mediated opsonophagocytosis between the two variants in factor B deficient mice. In addition, an in vitro study demonstrated that significantly more C4b-binding protein (C4BP) (the classical pathway inhibitor) and factor H (FH) (the alternative pathway inhibitor) bound to the transparent strain compared with the opaque one. Our data suggest that the difference in the relative virulence of Spn opacity phenotypes is associated with its ability to evade complement-mediated opsonophagocytosis in a mouse model of pneumococcal AOM.
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Affiliation(s)
- Qian Li
- Department of Otolaryngology, College of Medicine and Public Health, The Ohio State University, Columbus, OH 43210, USA
- Department of Infectious Diseases, FuDan University affiliated Hua Shan Hospital, Shanghai, China
| | - Yong Xing Li
- Department of Otolaryngology, College of Medicine and Public Health, The Ohio State University, Columbus, OH 43210, USA
| | - Kelsey Douthitt
- Department of Otolaryngology, College of Medicine and Public Health, The Ohio State University, Columbus, OH 43210, USA
| | - Gregory L. Stahl
- Center for Experimental Therapeutics and Reperfusion Injury, Department of Anesthesiology, Perioperative and Pain Medicine, Harvard Institutes of Medicine,, Harvard Medical School, Boston, MA 02115, USA
| | - Joshua M. Thurman
- Department of Medicine, University of Colorado Denver, Aurora, CO 80045, USA
| | - Hua Hua Tong
- Department of Otolaryngology, College of Medicine and Public Health, The Ohio State University, Columbus, OH 43210, USA
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Terrasse R, Tacnet-Delorme P, Moriscot C, Pérard J, Schoehn G, Vernet T, Thielens NM, Di Guilmi AM, Frachet P. Human and pneumococcal cell surface glyceraldehyde-3-phosphate dehydrogenase (GAPDH) proteins are both ligands of human C1q protein. J Biol Chem 2012; 287:42620-33. [PMID: 23086952 DOI: 10.1074/jbc.m112.423731] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
C1q, a key component of the classical complement pathway, is a major player in the response to microbial infection and has been shown to detect noxious altered-self substances such as apoptotic cells. In this work, using complementary experimental approaches, we identified the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) as a C1q partner when exposed at the surface of human pathogenic bacteria Streptococcus pneumoniae and human apoptotic cells. The membrane-associated GAPDH on HeLa cells bound the globular regions of C1q as demonstrated by pulldown and cell surface co-localization experiments. Pneumococcal strains deficient in surface-exposed GAPDH harbored a decreased level of C1q recognition when compared with the wild-type strains. Both recombinant human and pneumococcal GAPDHs interacted avidly with C1q as measured by surface plasmon resonance experiments (K(D) = 0.34-2.17 nm). In addition, GAPDH-C1q complexes were observed by transmission electron microscopy after cross-linking. The purified pneumococcal GAPDH protein activated C1 in an in vitro assay unlike the human form. Deposition of C1q, C3b, and C4b from human serum at the surface of pneumococcal cells was dependent on the presence of surface-exposed GAPDH. This ability of C1q to sense both human and bacterial GAPDHs sheds new insights on the role of this important defense collagen molecule in modulating the immune response.
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Affiliation(s)
- Rémi Terrasse
- Pneumococcus (PG), Université Joseph Fourier Grenoble, France
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Agarwal V, Hammerschmidt S, Malm S, Bergmann S, Riesbeck K, Blom AM. Enolase of Streptococcus pneumoniae binds human complement inhibitor C4b-binding protein and contributes to complement evasion. THE JOURNAL OF IMMUNOLOGY 2012; 189:3575-84. [PMID: 22925928 DOI: 10.4049/jimmunol.1102934] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Streptococcus pneumoniae (pneumococcus) is a pathogen that causes severe local and life-threatening invasive diseases, which are associated with high mortality rates. Pneumococci have evolved several strategies to evade the host immune system, including complement to disseminate and to survive in various host niches. Thus, pneumococci bind complement inhibitors such as C4b-binding protein (C4BP) and factor H via pneumococcal surface protein C, thereby inhibiting the classical and alternative complement pathways. In this study, we identified the pneumococcal glycolytic enzyme enolase, a nonclassical cell surface and plasminogen-binding protein, as an additional pneumococcal C4BP-binding protein. Furthermore, we demonstrated that human, but not mouse, C4BP bound pneumococci. Recombinant enolase bound in a dose-dependent manner C4BP purified from plasma, and the interaction was reduced by increasing ionic strength. Enolase recruited C4BP and plasminogen, but not factor H, from human serum. Moreover, C4BP and plasminogen bound to different domains of enolase as they did not compete for the interaction with enolase. In direct binding assays with recombinant C4BP mutants lacking individual domains, two binding sites for enolase were identified on the complement control protein (CCP) domain 1/CCP2 and CCP8 of the C4BP α-chains. C4BP bound to the enolase retained its cofactor activity as determined by C4b degradation. Furthermore, in the presence of exogenously added enolase, an increased C4BP binding to and subsequently decreased C3b deposition on pneumococci was observed. Taken together, pneumococci specifically interact with human C4BP via enolase, which represents an additional mechanism of human complement control by this versatile pathogen.
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Affiliation(s)
- Vaibhav Agarwal
- Medical Protein Chemistry, Department of Laboratory Medicine, Lund University, S-205 02 Malmö, Sweden
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Ali YM, Lynch NJ, Haleem KS, Fujita T, Endo Y, Hansen S, Holmskov U, Takahashi K, Stahl GL, Dudler T, Girija UV, Wallis R, Kadioglu A, Stover CM, Andrew PW, Schwaeble WJ. The lectin pathway of complement activation is a critical component of the innate immune response to pneumococcal infection. PLoS Pathog 2012; 8:e1002793. [PMID: 22792067 PMCID: PMC3390405 DOI: 10.1371/journal.ppat.1002793] [Citation(s) in RCA: 119] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2012] [Accepted: 05/23/2012] [Indexed: 01/19/2023] Open
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.
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Affiliation(s)
- Youssif M. Ali
- Department of Infection, Immunity and Inflammation, University of Leicester, Leicester, United Kingdom
- Faculty of Pharmacy, University of Mansoura, Mansoura, Egypt
| | - Nicholas J. Lynch
- Department of Infection, Immunity and Inflammation, University of Leicester, Leicester, United Kingdom
| | - Kashif S. Haleem
- Department of Infection, Immunity and Inflammation, University of Leicester, Leicester, United Kingdom
| | - Teizo Fujita
- Department of Immunology, Fukushima Medical University, Fukushima, Japan
| | - Yuichi Endo
- Department of Immunology, Fukushima Medical University, Fukushima, Japan
| | - Soren Hansen
- Institute of Molecular Medicine, University of Southern Denmark, Odense, Denmark
| | - Uffe Holmskov
- Institute of Molecular Medicine, University of Southern Denmark, Odense, Denmark
| | - Kazue Takahashi
- Department of Anesthesiology, Perioperative and Pain Medicine, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Gregory L. Stahl
- Department of Anesthesiology, Perioperative and Pain Medicine, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Thomas Dudler
- Omeros Corporation, Seattle, Washington, United States of America
| | - Umakhanth V. Girija
- Department of Infection, Immunity and Inflammation, University of Leicester, Leicester, United Kingdom
| | - Russell Wallis
- Department of Infection, Immunity and Inflammation, University of Leicester, Leicester, United Kingdom
| | - Aras Kadioglu
- Department of Infection, Immunity and Inflammation, University of Leicester, Leicester, United Kingdom
| | - Cordula M. Stover
- Department of Infection, Immunity and Inflammation, University of Leicester, Leicester, United Kingdom
| | - Peter W. Andrew
- Department of Infection, Immunity and Inflammation, University of Leicester, Leicester, United Kingdom
| | - Wilhelm J. Schwaeble
- Department of Infection, Immunity and Inflammation, University of Leicester, Leicester, United Kingdom
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Malm S, Jusko M, Eick S, Potempa J, Riesbeck K, Blom AM. Acquisition of complement inhibitor serine protease factor I and its cofactors C4b-binding protein and factor H by Prevotella intermedia. PLoS One 2012; 7:e34852. [PMID: 22514678 PMCID: PMC3325944 DOI: 10.1371/journal.pone.0034852] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2011] [Accepted: 03/09/2012] [Indexed: 01/01/2023] Open
Abstract
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 125I-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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Affiliation(s)
- Sven Malm
- Section of Medical Protein Chemistry, Department of Laboratory Medicine, Skåne University Hospital, Lund University, Malmö, Sweden
| | - Monika Jusko
- Section of Medical Protein Chemistry, Department of Laboratory Medicine, Skåne University Hospital, Lund University, Malmö, Sweden
| | - Sigrun Eick
- Laboratory of Oral Microbiology, Department of Periodontology, University of Bern, Bern, Switzerland
| | - Jan Potempa
- Faculty of Biochemistry, Biophysics and Biotechnology, Department of Microbiology, Jagiellonian University, Krakow, Poland
- Center of Oral Health and Systemic Diseases, University of Louisville Dental School, Louisville, Kentucky, United States of America
| | - Kristian Riesbeck
- Medical Microbiology, Department of Laboratory Medicine, Skåne University Hospital, Lund University, Malmö, Sweden
| | - Anna M. Blom
- Section of Medical Protein Chemistry, Department of Laboratory Medicine, Skåne University Hospital, Lund University, Malmö, Sweden
- * E-mail:
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Cross-reactivity of antipneumococcal surface protein C (PspC) antibodies with different strains and evaluation of inhibition of human complement factor H and secretory IgA binding via PspC. CLINICAL AND VACCINE IMMUNOLOGY : CVI 2012; 19:499-507. [PMID: 22336290 DOI: 10.1128/cvi.05706-11] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Pneumococcal surface protein C (PspC) is an important candidate for a cost-effective vaccine with broad coverage against pneumococcal diseases. Previous studies have shown that Streptococcus pneumoniae is able to bind to both human factor H (FH), an inhibitor of complement alternative pathway, and human secretory IgA (sIgA) via PspC. PspC was classified into 11 groups based on variations of the gene. In this work, we used three PspC fragments from different groups (PspC3, PspC5, and PspC8) to immunize mice for the production of antibodies. Immunization with PspC3 induced antibodies that recognized the majority of the clinical isolates as analyzed by Western blotting of whole-cell extracts and flow cytometry of intact bacteria, while anti-PspC5 antibodies showed cross-reactivity with the paralogue pneumococcal surface protein A (PspA), and anti-PspC8 antibodies reacted only with the PspC8-expressing strain. Most of the isolates tested showed strong binding to FH and weaker interaction with sIgA. Preincubation with anti-PspC3 and anti-PspC5 IgG led to some inhibition of binding of FH, and preincubation with anti-PspC3 partially inhibited sIgA binding in Western blotting. The analysis of intact bacteria through flow cytometry showed only a small decrease in FH binding after incubation of strain D39 with anti-PspC3 IgG, and one clinical isolate showed inhibition of sIgA binding by anti-PspC3 IgG. We conclude that although anti-PspC3 antibodies were able to recognize PspC variants from the majority of the strains tested, partial inhibition of FH and sIgA binding through anti-PspC3 antibodies in vitro could be observed for only a restricted number of isolates.
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Complement regulator C4BP binds to Staphylococcus aureus and decreases opsonization. Mol Immunol 2012; 50:253-61. [PMID: 22333221 DOI: 10.1016/j.molimm.2012.01.010] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2011] [Revised: 01/24/2012] [Accepted: 01/26/2012] [Indexed: 11/21/2022]
Abstract
Staphylococcus aureus is the major cause of human skin and soft-tissue infections as well as invasive infections like post-operative wound infections, septic arthritis, and osteomyelitis. The complement system plays an important role in the immunological control of many bacteria, but can be inhibited by a variety of strategies including recruitment of complement regulatory proteins like C4b-binding protein (C4BP). These experiments demonstrate that S. aureus opsonization with C4b occurs rapidly in serum and is predominantly initiated by anti-staphylococcal antibodies. Much of the S. aureus-bound C4b is quickly cleaved to the inactive forms iC4b and C4d. Clinical S. aureus strains rapidly bind significant amounts of the complement regulator C4BP from serum. S. aureus also binds purified C4BP. S. aureus-bound C4BP functions as a cofactor for factor I-mediated C4b cleavage to iC4b and C4d. In the absence of factor I, C4BP decreases classical pathway-mediated deposition of C3b on the S. aureus surface by inhibiting the classical pathway C3-convertase. In summary, C4BP is recruited to the S. aureus surface where it functions to inhibit C4 complement effectors, suggesting a previously undescribed immune evasion strategy for this pathogen.
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Abstract
Pneumococcal meningitis continues to be associated with high rates of mortality and long-term neurological sequelae. The most common route of infection starts by nasopharyngeal colonization by Streptococcus pneumoniae, which must avoid mucosal entrapment and evade the host immune system after local activation. During invasive disease, pneumococcal epithelial adhesion is followed by bloodstream invasion and activation of the complement and coagulation systems. The release of inflammatory mediators facilitates pneumococcal crossing of the blood-brain barrier into the brain, where the bacteria multiply freely and trigger activation of circulating antigen-presenting cells and resident microglial cells. The resulting massive inflammation leads to further neutrophil recruitment and inflammation, resulting in the well-known features of bacterial meningitis, including cerebrospinal fluid pleocytosis, cochlear damage, cerebral edema, hydrocephalus, and cerebrovascular complications. Experimental animal models continue to further our understanding of the pathophysiology of pneumococcal meningitis and provide the platform for the development of new adjuvant treatments and antimicrobial therapy. This review discusses the most recent views on the pathophysiology of pneumococcal meningitis, as well as potential targets for (adjunctive) therapy.
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Functional recruitment of human complement inhibitor C4B-binding protein to outer membrane protein Rck of Salmonella. PLoS One 2011; 6:e27546. [PMID: 22102907 PMCID: PMC3213152 DOI: 10.1371/journal.pone.0027546] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2011] [Accepted: 10/19/2011] [Indexed: 12/05/2022] Open
Abstract
Resistance to complement mediated killing, or serum resistance, is a common trait of pathogenic bacteria. Rck is a 17 kDa outer membrane protein encoded on the virulence plasmid of Salmonella enterica serovars Typhimurium and Enteritidis. When expressed in either E. coli or S. enterica Typhimurium, Rck confers LPS-independent serum resistance as well as the ability to bind to and invade mammalian cells. Having recently shown that Rck binds the inhibitor of the alternative pathway of complement, factor H (fH), we hypothesized that Rck can also bind the inhibitor of the classical and lectin pathways, C4b-binding protein (C4BP). Using flow cytometry and direct binding assays, we demonstrate that E. coli expressing Rck binds C4BP from heat-inactivated serum and by using the purified protein. No binding was detected in the absence of Rck expression. C4BP bound to Rck is functional, as we observed factor I-mediated cleavage of C4b in cofactor assays. In competition assays, binding of radiolabeled C4BP to Rck was reduced by increasing concentrations of unlabeled protein. No effect was observed by increasing heparin or salt concentrations, suggesting mainly non-ionic interactions. Reduced binding of C4BP mutants lacking complement control protein domains (CCPs) 7 or 8 was observed compared to wt C4BP, suggesting that these CCPs are involved in Rck binding. While these findings are restricted to Rck expression in E. coli, these data suggest that C4BP binding may be an additional mechanism of Rck-mediated complement resistance.
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Hyams C, Opel S, Hanage W, Yuste J, Bax K, Henriques-Normark B, Spratt BG, Brown JS. Effects of Streptococcus pneumoniae strain background on complement resistance. PLoS One 2011; 6:e24581. [PMID: 22022358 PMCID: PMC3192701 DOI: 10.1371/journal.pone.0024581] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2011] [Accepted: 08/15/2011] [Indexed: 01/04/2023] Open
Abstract
Background Immunity to infections caused by Streptococcus pneumoniae is dependent on complement. There are wide variations in sensitivity to complement between S. pneumoniae strains that could affect their ability to cause invasive infections. Although capsular serotype is one important factor causing differences in complement resistance between strains, there is also considerable other genetic variation between S. pneumoniae strains that may affect complement-mediated immunity. We have therefore investigated whether genetically distinct S. pneumoniae strains with the same capsular serotype vary in their sensitivity to complement mediated immunity. Methodology and Principal Findings C3b/iC3b deposition and neutrophil association were measured using flow cytometry assays for S. pneumoniae strains with different genetic backgrounds for each of eight capsular serotypes. For some capsular serotypes there was marked variation in C3b/iC3b deposition between different strains that was independent of capsule thickness and correlated closely to susceptibility to neutrophil association. C3b/iC3b deposition results also correlated weakly with the degree of IgG binding to each strain. However, the binding of C1q (the first component of the classical pathway) correlated more closely with C3b/iC3b deposition, and large differences remained in complement sensitivity between strains with the same capsular serotype in sera in which IgG had been cleaved with IdeS. Conclusions These data demonstrate that bacterial factors independent of the capsule and recognition by IgG have strong effects on the susceptibility of S. pneumoniae to complement, and could therefore potentially account for some of the differences in virulence between strains.
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Affiliation(s)
- Catherine Hyams
- Centre for Respiratory Research, Department of Medicine, University College Medical School, Rayne Institute, London, United Kingdom
| | - Sophia Opel
- Centre for Respiratory Research, Department of Medicine, University College Medical School, Rayne Institute, London, United Kingdom
| | - William Hanage
- Department of Epidemiology, Harvard School of Public Health, Boston, Massachusetts, United States of America
| | - Jose Yuste
- Spanish Pneumococcal Reference Laboratory, Centro Nacional de Microbiologia, Instituto de Salud Carlos III, Majadahonda, Madrid, Spain
| | - Katie Bax
- Department of Anatomy, University College London, London, United Kingdom
| | - Birgitta Henriques-Normark
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet and the Swedish Institute for Infectious Disease Control, Stockholm, Sweden
| | - Brian G. Spratt
- Department of Infectious Disease Epidemiology, St. Mary's Hospital Campus, Imperial College London, London, United Kingdom
| | - Jeremy S. Brown
- Centre for Respiratory Research, Department of Medicine, University College Medical School, Rayne Institute, London, United Kingdom
- * E-mail:
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Ricci S, Janulczyk R, Gerlini A, Braione V, Colomba L, Iannelli F, Chiavolini D, Oggioni MR, Björck L, Pozzi G. The factor H-binding fragment of PspC as a vaccine antigen for the induction of protective humoral immunity against experimental pneumococcal sepsis. Vaccine 2011; 29:8241-9. [PMID: 21911026 DOI: 10.1016/j.vaccine.2011.08.119] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2011] [Revised: 08/13/2011] [Accepted: 08/30/2011] [Indexed: 01/12/2023]
Abstract
Pneumococcal surface protein C (PspC) is a major virulence factor of Streptococcus pneumoniae and interferes with complement activity by binding complement factor H (fH). In this study, protection against experimental sepsis caused by pneumococci carrying different PspC variants was evaluated by immunisation with the fH-binding fragment of PspC. The mechanisms of protection mediated by antibodies to PspC were also studied. Mice were immunised with a PspC fragment (PspC(39-261)) from the type 3 strain HB565 and infected intravenously with either strain HB565 (homologous challenge), or strains D39 and TIGR4 (heterologous challenge). Immunisation with PspC(39-261) elicited high titers (>300,000) of PspC-specific serum IgG and conferred protection from challenge with HB565. In contrast, cross-protection was either limited or absent in vaccinated animals infected with D39 and TIGR4, respectively. To correlate protection with reactivity and function of PspC antibodies, pooled sera from vaccinated mice were tested in IgG binding and complement deposition experiments. IgG antibodies efficiently bound to HB565, while binding was lower with D39 and absent with TIGR4. In the presence of mouse post-immune sera, C3 deposition was increased onto HB565, while no effect was observed with D39 and TIGR4. Antibody cross-reactivity and complement deposition progressively declined with reduced amino acid identity between PspC variants. Antibodies to PspC were also found to interfere with fH binding to HB565. Finally, in vitro and ex vivo phagocytosis assays demonstrated that PspC-specific antibodies promoted opsonophagocytic killing of bacteria.
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Affiliation(s)
- Susanna Ricci
- Department of Biotechnology, University of Siena, Italy.
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Essential role of factor B of the alternative complement pathway in complement activation and opsonophagocytosis during acute pneumococcal otitis media in mice. Infect Immun 2011; 79:2578-85. [PMID: 21502587 DOI: 10.1128/iai.00168-11] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
We recently reported that the complement system plays a pivotal role in innate immune defense against Streptococcus pneumoniae during acute otitis media (OM) in mice. The current study was designed to determine which of the complement pathways are activated during acute pneumococcal OM and whether components of complement are expressed in the middle ear epithelium. Gene expression was determined by quantitative PCR, enzyme-linked immunosorbent assay (ELISA), and immunofluorescence staining. We found that S. pneumoniae induced increased gene expression of factor B of the alternative complement pathway and C3 in mouse middle ear epithelium. Activation of factor B and C3 in the middle ear lavage fluids was significantly greater than in simultaneously obtained serum samples as determined by Western blotting. Using mice deficient in complement C1qa, factor B, and factor B/C2, we found that complement C3 activation and opsonophagocytosis of S. pneumoniae were greatly attenuated in factor B- and factor B/C2-deficient mice. These findings support the concept that local complement activation is an important host innate immune response and that activation of the alternative complement pathway represents one of the innate immune defense mechanisms against pneumococcal infection during the early stage of acute OM.
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Hallström T, Nordström T, Tan TT, Manolov T, Lambris JD, Isenman DE, Zipfel PF, Blom AM, Riesbeck K. Immune evasion of Moraxella catarrhalis involves ubiquitous surface protein A-dependent C3d binding. THE JOURNAL OF IMMUNOLOGY 2011; 186:3120-9. [PMID: 21270401 DOI: 10.4049/jimmunol.1002621] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The complement system plays an important role in eliminating invading pathogens. Activation of complement results in C3b deposition (opsonization), phagocytosis, anaphylatoxin (C3a, C5a) release, and consequently cell lysis. Moraxella catarrhalis is a human respiratory pathogen commonly found in children with otitis media and in adults with chronic obstructive pulmonary disease. The species has evolved multiple complement evasion strategies, which among others involves the ubiquitous surface protein (Usp) family consisting of UspA1, A2, and A2 hybrid. In the present study, we found that the ability of M. catarrhalis to bind C3 correlated with UspA expression and that C3 binding contributed to serum resistance in a large number of clinical isolates. Recombinantly expressed UspA1 and A2 inhibit both the alternative and classical pathways, C3b deposition, and C3a generation when bound to the C3 molecule. We also revealed that the M. catarrhalis UspA-binding domain on C3b was located to C3d and that the major bacterial C3d-binding domains were within UspA1(299-452) and UspA2(165-318). The interaction with C3 was not species specific since UspA-expressing M. catarrhalis also bound mouse C3 that resulted in inhibition of the alternative pathway of mouse complement. Taken together, the binding of C3 to UspAs is an efficient strategy of Moraxella to block the activation of complement and to inhibit C3a-mediated inflammation.
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Affiliation(s)
- Teresia Hallström
- Department of Laboratory Medicine Malmö, Lund University, Skåne University Hospital, Malmö, Sweden
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Luo S, Blom AM, Rupp S, Hipler UC, Hube B, Skerka C, Zipfel PF. The pH-regulated antigen 1 of Candida albicans binds the human complement inhibitor C4b-binding protein and mediates fungal complement evasion. J Biol Chem 2011; 286:8021-8029. [PMID: 21212281 DOI: 10.1074/jbc.m110.130138] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Candida albicans binds and utilizes human complement inhibitors, such as C4b-binding protein (C4BP), Factor H, and FHL-1 for immune evasion. Here, we identify Candida pH-regulated antigen 1 (Pra1) as the first fungal C4BP-binding protein. Recombinant Pra1 binds C4BP, as shown by ELISA and isothermal titration calorimetry, and the Pra1-C4BP interaction is ionic in nature. The Pra1 binding domains within C4BP were localized to the complement control protein domain 4 (CCP4), CCP7, and CCP8. C4BP bound to Pra1 maintains complement-inhibitory activity. C4BP and Factor H bind simultaneously to Candida Pra1 and do not compete for binding at physiological levels. A Pra1-overexpressing C. albicans strain, which had about 2-fold Pra1 levels at the surface acquired also about 2-fold C4BP to the surface, compared with the wild type strain CAI4. A Pra1 knock-out strain showed ∼22% reduced C4BP binding. C4BP captured by C. albicans from human serum inhibits C4b and C3b surface deposition and also maintains cofactor activity. In summary, Candida Pra1 represents the first fungal C4BP-binding surface protein. Pra1, via binding to C4BP, mediates human complement control, thereby favoring the immune and complement evasion of C. albicans.
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Affiliation(s)
| | - Anna M Blom
- the Department of Laboratory Medicine, Section of Medical Protein Chemistry, University of Lund, 20502 Malmö, Sweden
| | - Steffen Rupp
- the Fraunhofer Institute for Interfacial Engineering, Nobelstrasse 12, 70569 Stuttgart, Germany, and
| | - Uta-Christina Hipler
- the Clinic of Dermatology and Allergology, Friedrich-Schiller-University, 07743 Jena, Germany
| | - Bernhard Hube
- the Department of Microbial Pathogenicity Mechanisms, Leibniz-Institute for Natural Product Research and Infection Biology, Hans-Knöll-Institute, 07745 Jena, Germany
| | | | - Peter F Zipfel
- From the Department of Infection Biology and; the Department of Infection Biology and.
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The capsular serotype of Streptococcus pneumoniae is more important than the genetic background for resistance to complement. Infect Immun 2010; 78:5262-70. [PMID: 20855513 DOI: 10.1128/iai.00740-10] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The polysaccharide capsule of Streptococcus pneumoniae inhibits phagocytic killing by innate immune mechanisms. Certain serotypes are associated with invasive disease while others with a nasopharyngeal carriage. The invasiveness of serotypes may partly be explained by ability to resist deposition of complement (C3) on the bacterial surface and consequent opsonophagocytic killing. In our previous studies, we observed that clinical isolates of serotypes 1 and 5, which are rarely detected in asymptomatic carriage, were resistant to complement deposition and opsonophagocytosis, whereas serotypes 6B and 23F, both common in carriage, were more sensitive to deposition of C3 and opsonophagocytic killing. However, presence of significant variation in C3 deposition between isolates of the same serotype indicated that factors other than the capsule also affect complement resistance. To distinguish the relative effect of the capsular serotype and other virulence factors on C3 deposition, we compared capsule-switched mutants prepared in genetic backgrounds of pneumococcal strains TIGR4, 603, and 618. Clinical isolates which had the same multilocus sequence type but expressed different serotypes were also compared. We found that the serotype had a significant impact on complement resistance and that the more resistant the strain was to complement, the higher was the concentration of polysaccharide-specific antibodies required for opsonophagocytic killing. Comparison of strains expressing the same capsular polysaccharides in the different genetic backgrounds and various capsular mutants of the same strain suggests that while the genotype affects complement resistance, the serotype is the most important determinant. Differences between serotypes were more significant than the differences between strains.
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Abstract
Despite the development of vaccines and antibiotics, Streptococcus pneumoniae (the pneumococcus) continues to be a major cause of human morbidity and mortality throughout the world. In recent years our understanding of how the host innate immune system recognizes and responds to pneumococcal infection has advanced significantly. Herein, we highlight some of the key features of the innate response to the pneumococcus.
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Affiliation(s)
- Gavin K Paterson
- Department of Microbiology and Immunology, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78229-3900, USA
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67
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Agarwal V, Asmat TM, Luo S, Jensch I, Zipfel PF, Hammerschmidt S. Complement regulator Factor H mediates a two-step uptake of Streptococcus pneumoniae by human cells. J Biol Chem 2010; 285:23486-95. [PMID: 20504767 DOI: 10.1074/jbc.m110.142703] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Streptococcus pneumoniae, a human pathogen, recruits complement regulator factor H to its bacterial cell surface. The bacterial PspC protein binds Factor H via short consensus repeats (SCR) 8-11 and SCR19-20. In this study, we define how bacterially bound Factor H promotes pneumococcal adherence to and uptake by epithelial cells or human polymorphonuclear leukocytes (PMNs) via a two-step process. First, pneumococcal adherence to epithelial cells was significantly reduced by heparin and dermatan sulfate. However, none of the glycosaminoglycans affected binding of Factor H to pneumococci. Adherence of pneumococci to human epithelial cells was inhibited by monoclonal antibodies recognizing SCR19-20 of Factor H suggesting that the C-terminal glycosaminoglycan-binding region of Factor H mediates the contact between pneumococci and human cells. Blocking of the integrin CR3 receptor, i.e. CD11b and CD18, of PMNs or CR3-expressing epithelial cells reduced significantly the interaction of pneumococci with both cell types. Similarly, an additional CR3 ligand, Pra1, derived from Candida albicans, blocked the interaction of pneumococci with PMNs. Strikingly, Pra1 inhibited also pneumococcal uptake by lung epithelial cells but not adherence. In addition, invasion of Factor H-coated pneumococci required the dynamics of host-cell actin microfilaments and was affected by inhibitors of protein-tyrosine kinases and phosphatidylinositol 3-kinase. In conclusion, pneumococcal entry into host cells via Factor H is based on a two-step mechanism. The first and initial contact of Factor H-coated pneumococci is mediated by glycosaminoglycans expressed on the surface of human cells, and the second step, pneumococcal uptake, is integrin-mediated and depends on host signaling molecules such as phosphatidylinositol 3-kinase.
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Affiliation(s)
- Vaibhav Agarwal
- Department of Genetics of Microorganisms, Institute for Genetics and Functional Genomics, Ernst Moritz Arndt University of Greifswald, Friedrich-Ludwig-Jahn-Strasse 15a, D-17487 Greifswald, Germany
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69
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Functional characterization of LcpA, a surface-exposed protein of Leptospira spp. that binds the human complement regulator C4BP. Infect Immun 2010; 78:3207-16. [PMID: 20404075 DOI: 10.1128/iai.00279-10] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We have previously shown that pathogenic leptospiral strains are able to bind C4b binding protein (C4BP). Surface-bound C4BP retains its cofactor activity, indicating that acquisition of this complement regulator may contribute to leptospiral serum resistance. In the present study, the abilities of seven recombinant putative leptospiral outer membrane proteins to interact with C4BP were evaluated. The protein encoded by LIC11947 interacted with this human complement regulator in a dose-dependent manner. The cofactor activity of C4BP bound to immobilized recombinant LIC11947 (rLIC11947) was confirmed by detecting factor I-mediated cleavage of C4b. rLIC11947 was therefore named LcpA (for leptospiral complement regulator-acquiring protein A). LcpA was shown to be an outer membrane protein by using immunoelectron microscopy, cell surface proteolysis, and Triton X-114 fractionation. The gene coding for LcpA is conserved among pathogenic leptospiral strains. This is the first characterization of a Leptospira surface protein that binds to the human complement regulator C4BP in a manner that allows this important regulator to control complement system activation mediated either by the classical pathway or by the lectin pathway. This newly identified protein may play a role in immune evasion by Leptospira spp. and may therefore represent a target for the development of a human vaccine against leptospirosis.
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70
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Henriques-Normark B, Normark S. Commensal pathogens, with a focus on Streptococcus pneumoniae, and interactions with the human host. Exp Cell Res 2010; 316:1408-14. [PMID: 20227406 DOI: 10.1016/j.yexcr.2010.03.003] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2010] [Accepted: 03/05/2010] [Indexed: 01/29/2023]
Abstract
Many important pathogens have humans as their normal ecological niche where healthy carriage dominates over disease. The ability of these commensal pathogens, such as Streptococcus pneumoniae, to cause disease depends on a series of microbial factors as well as of genetic and environmental factors in the human host affecting the clearing capacity mediated by the innate and adaptive immune system. This delicate interplay between microbe and host affects not only the likelihood for a commensal pathogen to cause disease, but also disease type and disease severity.
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Abstract
The pneumococcal histidine triad (Pht) proteins PhtA, PhtB, PhtD, and PhtE form a group of conserved pneumococcal surface proteins. Humans produce antibodies to Pht proteins upon exposure to pneumococcus, and immunization of mice has provided protective immunity against sepsis and pneumonia and reduced nasopharyngeal colonization. Pht proteins are candidates for inclusion in multicomponent pneumococcal protein vaccines. Their biological function in pneumococcal infections is not clear, but a role in complement inhibition has been suggested. We measured complement deposition on wild-type and Pht mutant strains in four genetic backgrounds: Streptococcus pneumoniae D39 (serotype 2) and R36A (unencapsulated derivative of D39) and strains of serotypes 3, 4, and 19F. PspA and PspC single and double mutants were compared to the wild-type and Pht-deficient D39 strains. Factor H binding was measured to bacterial cells, lysates, and protein antigens. Deletion of all four Pht proteins (Pht(-)) resulted in increased C3 deposition on the serotype 4 strain but not on the other strains. Pht antigens did not bind factor H, and deletion of Pht proteins did not affect factor H binding by bacterial lysates. The Pht(-) mutant serotype 4 strain bound slightly less factor H than the wild-type strain when binding was measured by flow cytometry. Pht proteins may play a role in immune evasion, but the mechanism of function is unlikely to be mediated by factor H binding. The relative contribution of Pht proteins to the inhibition of complement deposition is likely to be affected by the presence of other pneumococcal proteins and to depend on the genetic background.
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