| 1. |
- Blom, Anna, et al.
(författare)
-
Complement evasion strategies of pathogens-Acquisition of inhibitors and beyond.
- 2009
-
Ingår i: Molecular Immunology. - : Elsevier BV. - 1872-9142 .- 0161-5890. ; 46, s. 2808-2817
-
Tidskriftsartikel (refereegranskat)abstract
- Activation of the complement system and resulting opsonisation with C3b are key events of the innate immune defense against infections. However, a wide variety of bacterial pathogens subvert complement attack by binding host complement inhibitors such as C4b-binding protein, factor H and vitronectin, which results in diminished opsonophagocytosis and killing of bacteria by lysis. Another widely used strategy is production of proteases, which can effectively degrade crucial complement components. Furthermore, bacterial pathogens such as Moraxella catarrhalis and Staphylococcus aureus capture and incapacitate the key complement component C3. The current review describes examples of these three strategies. Targeting binding sites for complement inhibitors on bacterial surfaces and complement-degrading proteases with vaccine-induced antibodies may be used to enhance a common vaccine design strategy that depends on the generation of complement-dependent bactericidal and opsonophagocytic antibody activities.
|
|
| 2. |
- Hallström, Teresia, et al.
(författare)
-
Haemophilus influenzae interacts with the human complement inhibitor factor H
- 2008
-
Ingår i: Journal of Immunology. - 1550-6606. ; 181:1, s. 537-545
-
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.
|
|
| 3. |
|
|
| 4. |
- Hallström, Teresia, et al.
(författare)
-
Interaction with C4b-binding protein contributes to nontypeable Haemophilus influenzae serum resistance.
- 2007
-
Ingår i: Journal of Immunology. - 1550-6606. ; 178:10, s. 6359-6366
-
Tidskriftsartikel (refereegranskat)abstract
- Complement evasion by various mechanisms is important for microbial virulence and survival in the host. One strategy used by some pathogenic bacteria is to bind the complement inhibitor of the classical pathway, C4b-binding protein (C4BP). In this study, we have identified a novel interaction between nontypeable Haemophilus influenzae (NTHi) and C4BP, whereas the majority of the typeable H. influenzae (a-f) tested showed no binding. One of the clinical isolates, NTHi 506, displayed a particularly high binding of C4BP and was used for detailed analysis of the interaction. Importantly, a low C4BP-binding isolate (NTHi 69) showed an increased deposition of C3b followed by reduced survival as compared with NTHi 506 when exposed to normal human serum. The main isoform of C4BP contains seven identical a-chains and one beta-chain linked together with disulfide bridges. Each a-chain is composed of eight complement control protein (CCP) modules and we have found that the NTHi 506 strain did not interact with rC4BP lacking CCP2 or CCP7 showing that these two CCPs are important for the binding. Importantly, C4BP bound to the surface of H. influenzae retained its cofactor activity as determined by analysis of C3b and C4b degradation. Taken together, NTHi interferes with the classical complement activation pathway by binding to C4BP.
|
|
| 5. |
- Hallström, Teresia, et al.
(författare)
-
Nontypeable Haemophilus influenzae Protein E Binds Vitronectin and Is Important for Serum Resistance
- 2009
-
Ingår i: Journal of Immunology. - : The American Association of Immunologists. - 1550-6606 .- 0022-1767. ; 183:4, s. 2593-2601
-
Tidskriftsartikel (refereegranskat)abstract
- Nontypeable Haemophilus influenzae (NTHi) commonly causes local disease in the upper and lower respiratory tract and has recently been shown to interfere with both the classical and alternative pathways of complement activation. The terminal pathway of the complement system is regulated by vitronectin that is a component of both plasma and the extracellular matrix. In this study, we identify protein E (PE; 16 kDa), which is a recently characterized ubiquitous outer membrane protein, as a vitronectin-binding protein of NTHi. A PE-deficient NTHi mutant had a markedly reduced survival in serum compared with the PE-expressing isogenic NTHi wild type. Moreover, the PE-deficient mutant showed a significantly decreased binding to both soluble and immobilized vitronectin. In parallel, PE-expressing Escherichia coli bound soluble vitronectin and adhered to immobilized vitronectin compared with controls. Surface plasmon resonance technology revealed a K-D of 0.4 mu M for the interaction between recombinant PE and immobilized vitronectin. Moreover, the PE-dependent vitronectin-binding site was located at the heparin-binding domains of vitronectin and the major vitronectin-binding domain was found in the central core of PE (aa 84-108). Importantly, vitronectin bound to the surface of NTHi 3655 reduced membrane attack complex-induced hemolysis. In contrast to incubation with normal human serum, NTHi 3655 showed a reduced survival in vitronectin-depleted human serum, thus demonstrating that vitronectin mediates a protective role at the bacteria] surface. Our findings show that PE, by binding vitronectin, may play an important role in NTHi pathogenesis. The Journal of Immunology, 2009, 183: 2593-2601.
|
|
| 6. |
- Hallström, Teresia
(författare)
-
Survival strategies of the human respiratory tract pathogen Haemophilus influenzae
- 2007
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Haemophilus influenzae is an important respiratory tract pathogen responsible for a variety of infections in humans. Encapsulated H. influenzae belongs to one of six serotypes (a-f), of which type b is the most virulent one causing serious and sometimes life-threatening diseases (e.g., epiglottitis, septicaemia and meningitis). In contrast, non-typeable H. influenzae (NTHi) accounts for the majority of local and upper and lower respiratory tract infections. The pathogenesis of many microorganisms relies on the capacity of pathogens to avoid, resist or neutralise the host defence including the complement system. We demonstrate that H. influenzae interferes with both the classical/lectin and alternative pathways of the complement system. NTHi binds C4BP, the inhibitor of the classical pathway, and the majority of the H. influenzae tested bound factor H, the inhibitor of the alternative pathway. Importantly, the capacity to bind C4BP and factor H appears to render the bacteria more resistant to serum mediated killing. Furthermore, both C4BP and factor H bound to the surface of H. influenzae retains its cofactor activity as determined by analysis of C4b and/or C3b degradation. In addition to interacting with the classical/lectin and alternative pathways, we demonstrate that Haemophilus surface fibrils (Hsf), which is expressed by encapsulated H. influenzae, binds vitronectin, a regulator of the terminal pathway of the complement system. Mapping of the membrane bound Hsf with gold-labelled specific antibodies in transmission electron microscopy (TEM) revealed a double-folded 100 nm long fibrillar structure. Using a series of mutants, we showed that when the C-terminal translocator domain was inactivated, Hsf was not translocated to the bacterial surface. Interestingly, we also show that outer membrane vesicles (OMV) secreted by the bacteria carry Hsf, and that Hsf is secreted into the extracellular milieu. IgD-binding is another important feature of encapsulated H. influenzae type b. By using a series of different IgD chimeric proteins, the site on the IgD molecule responsible for the interaction with H. influenzae was characterised. The binding site was localised to the CH1 region of IgD. In summary, H. influenzae binds C4BP, factor H and vitronectin, which are regulators of the complement system. The interaction between H. influenzae and these regulators protects the bacteria and makes them more resistant to the bactericidal activity of human serum. Finally, H. influenzae type b binds human IgD.
|
|
| 7. |
- Hallström, Teresia, et al.
(författare)
-
The Moraxella IgD-binding protein MID/Hag is an oligomeric autotransporter.
- 2008
-
Ingår i: Microbes and Infection. - : Elsevier BV. - 1769-714X .- 1286-4579. ; 10:4, s. 374-381
-
Tidskriftsartikel (refereegranskat)abstract
- The immunoglobulin D (IgD)-binding protein MID/Hag of the human respiratory pathogen Moraxella catarrhalis is an outer membrane protein of approximately 200kDa belonging to the autotransporter family. MID also functions as an adhesin and hemagglutinin. In the present paper, the ultrastructure of MID was mapped. Using a series of Escherichia coli transformants, the last 210 aa of the C-terminal region were shown to translocate protein MID through the outer membrane suggesting that MID has a beta-barrel structure comprising of 10 transmembrane beta-sheets. Electron microscopy mapping with gold-labelled specific antibodies, and partial unravelling using guanidine hydrochloride showed that the rest of the MID protein forms an approximately 120nm long, fibrillar structure in which the individual monomers fold back on themselves to expose a globular distal domain at their tips comprising both the IgD-binding (MID962-1200) and adhesive (MID764-913) regions. This positions their N-termini close to the C-terminal membrane spanning domains. Mass measurements by scanning transmission electron microscopy (STEM) verified that the MID molecule is an oligomer.
|
|
| 8. |
- Samuelsson, Martin, et al.
(författare)
-
Characterization of the IgD binding site of encapsulated Haemophilus influenzae serotype b.
- 2007
-
Ingår i: Journal of Immunology. - 1550-6606. ; 178:10, s. 6316-6319
-
Tidskriftsartikel (refereegranskat)abstract
- Encapsulated Haemophilus influenzae is a causative agent of invasive disease, such as meningitis and septicemia. Several interactions exist between H. influenzae and the human host. H. influenzae has been reported to bind IgD in a nonimmune manner, but the responsible protein has not yet been identified. To define the binding site on IgD for H. influenzae, full-length IgD and four chimeric IgDs with interspersed TgG sequences and Ag specificity for dansyl chloride were expressed in stably transfected Chinese hamster ovary cells. The binding of recombinant IgD to a panel of encapsulated H. influenzae serotype b (Hib) and nontypeable strains were investigated using a whole cell ELISA and flow cytometry. IgD binding was detected in 50% of the encapsulated Hib strains examined, whereas nontypeable H. influenzae did not interact with IgD. Finally, mapping experiments using the chimeric IgD/IgG indicated that IgD C(H)1 aa 198-224 were involved in the interaction between IgD and H. influenzae. Thus, by using recombinant IgD and chimeras with defined Ag specificity, we have confirmed that Hib specifically binds IgD, and that this binding involves the IgD CHI region.
|
|
