| 1. |
- Hallstroem, Teresia, et al.
(författare)
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CspA from Borrelia burgdorferi Inhibits the Terminal Complement Pathway
- 2013
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Ingår i: mBio. - 2161-2129. ; 4:4, s. 13-00481
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Tidskriftsartikel (refereegranskat)abstract
- In order to survive and persist in an immunocompetent human host, Borrelia burgdorferi controls the human immune attack and blocks the damaging effects of the activated complement system. These Gram-negative spirochetes use CspA (CRASP-1) and four additional immune evasion proteins to bind combinations of human plasma regulators, including factor H, factor H-like protein 1 (FHL-1), complement factor H-related protein 1 (CFHR1), CFHR2, CFHR5, and plasminogen. As many microbial immune evasion proteins have multiple functions, we hypothesized that CspA has additional roles in complement or immune control. Here, we identify CspA as a terminal complement inhibitor. Borrelial CspA binds the human terminal complement components C7 and C9 and blocks assembly and membrane insertion of the terminal complement complex (TCC). CspA inhibits TCC assembly at the level of C7, as revealed by hemolytic assays, and inhibits polymerization of C9. CspA, when ectopically expressed on the surface of serum-sensitive Borrelia garinii, blocks TCC assembly on the level of C7 and induces serum resistance in the transformed bacteria. This CspA-mediated serum resistance and terminal complement pathway inhibition allow B. burgdorferi to survive in the hostile environment of human plasma. IMPORTANCE The present study defines a new mechanism by which the pathogenic bacterium Borrelia burgdorferi controls the terminal complement pathway of the human host to survive in human serum. The borrelial CspA binds to terminal pathway proteins C7 and C9 and inhibits the terminal complement pathway at the step of C7 and thereby inhibits terminal complement complex (TCC) assembly and membrane insertion. CspA blocks TCC assembly and insertion when expressed at the bacterial surface. CspA is the first TCC inhibitor cloned and functionally characterized from a Gram-negative bacterium. This identification of a bacterial TCC inhibitor of pathogen origin expands our knowledge of complement evasion of pathogenic bacteria and shows that pathogenic bacteria target the terminal pathway of complement. Thus, CspA as a central microbial virulence factor can represent an interesting biomarker and a target to develop new therapeutics and vaccines against borreliae.
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| 2. |
- Hallström, Teresia, et al.
(författare)
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Conserved Patterns of Microbial Immune Escape: Pathogenic Microbes of Diverse Origin Target the Human Terminal Complement Inhibitor Vitronectin via a Single Common Motif.
- 2016
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Pathogenicity of many microbes relies on their capacity to resist innate immunity, and to survive and persist in an immunocompetent human host microbes have developed highly efficient and sophisticated complement evasion strategies. Here we show that different human pathogens including Gram-negative and Gram-positive bacteria, as well as the fungal pathogen Candida albicans, acquire the human terminal complement regulator vitronectin to their surface. By using truncated vitronectin fragments we found that all analyzed microbial pathogens (n = 13) bound human vitronectin via the same C-terminal heparin-binding domain (amino acids 352-374). This specific interaction leaves the terminal complement complex (TCC) regulatory region of vitronectin accessible, allowing inhibition of C5b-7 membrane insertion and C9 polymerization. Vitronectin complexed with the various microbes and corresponding proteins was thus functionally active and inhibited complement-mediated C5b-9 deposition. Taken together, diverse microbial pathogens expressing different structurally unrelated vitronectin-binding molecules interact with host vitronectin via the same conserved region to allow versatile control of the host innate immune response.
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| 3. |
- Barthel, Diana, et al.
(författare)
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Haemophilus influenzae Uses the Surface Protein E To Acquire Human Plasminogen and To Evade Innate Immunity
- 2012
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Ingår i: Journal of Immunology. - : The American Association of Immunologists. - 1550-6606 .- 0022-1767. ; 188:1, s. 379-385
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Pathogenic microbes acquire the human plasma protein plasminogen to their surface. In this article, we characterize binding of this important coagulation regulator to the respiratory pathogen nontypeable Haemophilus influenzae and identify the Haemophilus surface protein E (PE) as a new plasminogen-binding protein. Plasminogen binds dose dependently to intact bacteria and to purified PE. The plasminogen-PE interaction is mediated by lysine residues and is also affected by ionic strength. The H. influenzae PE knockout strain (nontypeable H. influenzae 3655 Delta pe) bound plasminogen with similar to 65% lower intensity as compared with the wild-type, PE-expressing strain. In addition, PE expressed ectopically on the surface of Escherichia coli also bound plasminogen. Plasminogen, either attached to intact H. influenzae or bound to PE, was accessible for urokinase plasminogen activator. The converted active plasmin cleaved the synthetic substrate S-2251, and the natural substrates fibrinogen and C3b. Using synthetic peptides that cover the complete sequence of the PE protein, the major plasminogen-binding region was localized to a linear 28-aa-long N-terminal peptide, which represents aa 41-68. PE binds plasminogen and also vitronectin, and the two human plasma proteins compete for PE binding. Thus, PE is a major plasminogen-binding protein of the Gram-negative bacterium H. influenzae, and when converted to plasmin, PE-bound plasmin aids in immune evasion and contributes to bacterial virulence. The Journal of Immunology, 2012, 188: 379-385.
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| 4. |
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| 5. |
- Fleury, Christophe, et al.
(författare)
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Identification of a Haemophilus influenzae Factor H-Binding Lipoprotein Involved in Serum Resistance.
- 2014
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Ingår i: Journal of Immunology. - : The American Association of Immunologists. - 1550-6606 .- 0022-1767. ; 192:12, s. 5913-5923
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Tidskriftsartikel (refereegranskat)abstract
- Haemophilus influenzae is a Gram-negative human pathogen that resides in the upper respiratory tract. Encapsulated H. influenzae type b (Hib) and type f (Hif) are the most common serotypes associated with invasive disease. H. influenzae displays various strategies to circumvent the host innate immune response, including the bactericidal effect of the complement system. In this study, we identified an H. influenzae lipoprotein having the ability to bind factor H (FH), the major regulator of the alternative pathway of complement activation. This protein, named protein H (PH), was surface exposed and was found in all clinical Hib and Hif isolates tested. Deletion of the gene encoding for PH (lph) in Hib and Hif significantly reduced the interaction between bacteria and FH. When Hib and Hif PH variants were separately expressed in nontypeable (unencapsulated) H. influenzae, which did not bind FH, an increased FH affinity was observed. We recombinantly expressed the two PH variants in Escherichia coli, and despite sharing only 56% identical amino acids, both FH-binding Haemophilus proteins similarly interacted with the complement regulator FH short consensus repeats 7 and 18-20. Importantly, Hib and Hif resistance against the bactericidal effect of human serum was significantly reduced when bacterial mutants devoid of PH were tested. In conclusion, we have characterized a hitherto unknown bacterial protein that is crucial for mediating an interaction between the human pathogen H. influenzae and FH. This novel interaction is important for H. influenzae resistance against complement activation and will consequently promote bacterial pathogenesis.
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| 6. |
- Foltyn Zadura, Anna, et al.
(författare)
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Factor H autoantibodies and deletion of Complement Factor H-Related protein-1 in rheumatic diseases in comparison to atypical hemolytic uremic syndrome.
- 2012
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Ingår i: Arthritis research & therapy. - : Springer Science and Business Media LLC. - 1478-6362 .- 1478-6354. ; 14:4
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Tidskriftsartikel (refereegranskat)abstract
- ABSTRACT: INTRODUCTION: Complement activation is involved in rheumatoid arthritis (RA), systemic lupus erythematosus (SLE) and atypical hemolytic uremic syndrome (aHUS). Autoantibodies to complement inhibitor factor H (FH), particularly in association with deletions of the gene coding for FH-related protein 1 (CFHR1), are associated with aHUS. METHODS: Autoantibodies against FH, factor I (FI) and C4b-binding protein (C4BP) were measured by ELISA, while CFHR1 homozygous deletion was determined with Western blotting of sera. Epitopes for FH autoantibodies were mapped using recombinant fragments of FH. RESULTS: FH autoantibodies were detected in SLE (6.7%, n = 60, RA patients (16.5%, n = 97 in the Swedish cohort and 9.2%, n = 217 in the Dutch cohort) and thrombosis patients positive for the lupus anticoagulants (LA+) test (9.4%, n = 64) compared with aHUS patients (11.7%, n = 103). In the control groups (n = 354), an average of 4% of individuals were positive for FH autoantibodies. The frequencies observed in both RA cohorts and LA+ patients were statistically significantly higher than in controls. We also found that an average of 15.2% of the FH-autoantibody positive individuals in all studied disease groups had homozygous deficiency of CFHR1 compared with 3.8% of the FH autoantibody negative patients. The levels of FH autoantibodies varied in individual patients over time. FH autoantibodies found in LA+, SLE and RA were directed against several epitopes across FH in contrast to those found in aHUS, which bound mainly to the C-terminus. Autoantibodies against FI and C4BP were detected in some patients and controls but they were not associated with any of the diseases analyzed in this study. CONCLUSIONS: Autoantibodies against FH are not specific for aHUS but are present at a significant frequency in rheumatic diseases where they could be involved in pathophysiological mechanisms.
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| 7. |
- Hallstroem, Teresia, et al.
(författare)
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Dihydrolipoamide Dehydrogenase of Pseudomonas aeruginosa Is a Surface-Exposed Immune Evasion Protein That Binds Three Members of the Factor H Family and Plasminogen
- 2012
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Ingår i: Journal of Immunology. - : The American Association of Immunologists. - 1550-6606 .- 0022-1767. ; 189:10, s. 4939-4950
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Tidskriftsartikel (refereegranskat)abstract
- The opportunistic human pathogen Pseudomonas aeruginosa causes a wide range of diseases. To cross host innate immune barriers, P. aeruginosa has developed efficient strategies to escape host complement attack. In this study, we identify the 57-kDa dihydrolipoamide dehydrogenase (Lpd) as a surface-exposed protein of P. aeruginosa that binds the four human plasma proteins, Factor H, Factor H-like protein-1 (FHL-1), complement Factor H-related protein 1 (CFHR1), and plasminogen. Factor H contacts Lpd via short consensus repeats 7 and 18-20. Factor H, FHL-1, and plasminogen when bound to Lpd were functionally active. Factor H and FHL-1 displayed complement-regulatory activity, and bound plasminogen, when converted to the active protease plasmin, cleaved the chromogenic substrate S-2251 and the natural substrate fibrinogen. The lpd of P. aeruginosa is a rather conserved gene; a total of 22 synonymous and 3 nonsynonymous mutations was identified in the lpd gene of the 5 laboratory strains and 13 clinical isolates. Lpd is surface exposed and contributes to survival of P. aeruginosa in human serum. Bacterial survival was reduced when Lpd was blocked on the surface prior to challenge with human serum. Similarly, bacterial survival was reduced up to 84% when the bacteria was challenged with complement active serum depleted of Factor H, FHL-1, and CFHR1, demonstrating a protective role of the attached human regulators from complement attack. In summary, Lpd is a novel surface-exposed virulence factor of P. aeruginosa that binds Factor H, FHL-1, CFHR1, and plasminogen, and the Lpd-attached regulators are relevant for innate immune escape and most likely contribute to tissue invasion. The Journal of Immunology, 2012, 189: 4939-4950.
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| 8. |
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| 9. |
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| 10. |
- Hallström, Teresia, et al.
(författare)
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Haemophilus influenzae interacts with the human complement inhibitor factor H
- 2008
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Ingår i: Journal of Immunology. - 1550-6606. ; 181:1, s. 537-545
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Tidskriftsartikel (refereegranskat)abstract
- Pathogenic microbes acquire human complement inhibitors to circumvent the innate immune system. In this study, we identify two novel host-pathogen interactions, factor H (FH) and factor H-like protein 1 (FHL-1), the inhibitors of the alternative pathway that binds to Hib. A collection of clinical Haemophilus influenzae isolates was tested and the majority of encapsulated and unencapsulated bound FH. The isolate Hib 541 with a particularly high FH-binding was selected for detailed analysis. An increased survival in normal human serum was observed with Hib 541 as compared with the low FH-binding Hib 568. Interestingly, two binding domains were identified within FH; one binding site common to both FH and FHL-1 was located in the N-terminal short consensus repeat domains 6-7, whereas the other, specific for FH, was located in the C-terminal short consensus repeat domains 18-20. Importantly, both FH and FHL-1, when bound to the surface of Hib 541, retained cofactor activity as determined by analysis of C3b degradation. Two H. influenzae outer membrane proteins of similar to 32 and 40 kDa were detected with radiolabeled FH in Far Western blot. Taken together, in addition to interactions with the classical, lectin, and terminal pathways, H. influenzae interferes with the alternative complement activation pathway by binding FH and FHL-1, and thereby reducing the complement-mediated bactericidal activity resulting in an increased survival. In contrast to incubation with active complement, H. influenzae had a reduced survival in FH-depleted human serum, thus demonstrating that FH mediates a protective role at the bacterial surface.
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