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Borrelia recurrentis employs a novel multifunctional surface protein with anti-complement, anti-opsonic and invasive potential to escape innate immunity.

Grosskinsky S, Schott M, Brenner C, Cutler SJ, Kraiczy P, Zipfel PF, Simon MM, Wallich R - PLoS ONE (2009)

Bottom Line: Moreover, ectopic expression of HcpA in a B. burgdorferi B313 strain, deficient in Factor H binding proteins, protected the transformed spirochetes from complement-mediated killing.Furthermore, HcpA-bound plasminogen/plasmin endows B. recurrentis with the potential to resist opsonization and to degrade extracellular matrix components.Together, the present study underscores the high virulence potential of B. recurrentis.

View Article: PubMed Central - PubMed

Affiliation: Infectious Immunology, Institute for Immunology, University of Heidelberg, Heidelberg, Germany.

ABSTRACT
Borrelia recurrentis, the etiologic agent of louse-borne relapsing fever in humans, has evolved strategies, including antigenic variation, to evade immune defence, thereby causing severe diseases with high mortality rates. Here we identify for the first time a multifunctional surface lipoprotein of B. recurrentis, termed HcpA, and demonstrate that it binds human complement regulators, Factor H, CFHR-1, and simultaneously, the host protease plasminogen. Cell surface bound factor H was found to retain its activity and to confer resistance to complement attack. Moreover, ectopic expression of HcpA in a B. burgdorferi B313 strain, deficient in Factor H binding proteins, protected the transformed spirochetes from complement-mediated killing. Furthermore, HcpA-bound plasminogen/plasmin endows B. recurrentis with the potential to resist opsonization and to degrade extracellular matrix components. Together, the present study underscores the high virulence potential of B. recurrentis. The elucidation of the molecular basis underlying the versatile strategies of B. recurrentis to escape innate immunity and to persist in human tissues, including the brain, may help to understand the pathological processes underlying louse-borne relapsing fever.

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Binding of CFH and CFHR-1 to the spirochetal surface.Binding of CFH to intact B. recurrentis cells was analyzed by flow cytometry and immunofluorescence microscopy. (A) Spirochetes were incubated with biotinylated purified human CFH (bold lines) or as a negative control with biotinylated BSA followed by PE-labeled streptavidin. B.hermsii HS1 and B. burgdorferi B313 were included as controls. (B) Cells were incubated with purified human CFH followed by the CFH-specific mAb JHD7 and a Cy3-conjugated anti-mouse IgG. Images were obtained employing epifluorescence microscopy. On the right panel the corresponding differential interference contrast image (DIC) is depicted. (C) Whole cell lysates of B. recurrentis strain A1 and A17 (B.r. A1 and B.r. A17) were separated by Tris/Tricine SDS-PAGE, transferred to nitrocellulose membrane and incubated with normal human serum. CFH binding was detected employing CFH specific mAb JHD7 and binding of CFHR-1 was analyzed using specific mAb JHD8. For control, cell lysates of B. hermsii HS1 (B.h HS1) and B. burgdorferi B313 (B.b B313) were included.
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pone-0004858-g001: Binding of CFH and CFHR-1 to the spirochetal surface.Binding of CFH to intact B. recurrentis cells was analyzed by flow cytometry and immunofluorescence microscopy. (A) Spirochetes were incubated with biotinylated purified human CFH (bold lines) or as a negative control with biotinylated BSA followed by PE-labeled streptavidin. B.hermsii HS1 and B. burgdorferi B313 were included as controls. (B) Cells were incubated with purified human CFH followed by the CFH-specific mAb JHD7 and a Cy3-conjugated anti-mouse IgG. Images were obtained employing epifluorescence microscopy. On the right panel the corresponding differential interference contrast image (DIC) is depicted. (C) Whole cell lysates of B. recurrentis strain A1 and A17 (B.r. A1 and B.r. A17) were separated by Tris/Tricine SDS-PAGE, transferred to nitrocellulose membrane and incubated with normal human serum. CFH binding was detected employing CFH specific mAb JHD7 and binding of CFHR-1 was analyzed using specific mAb JHD8. For control, cell lysates of B. hermsii HS1 (B.h HS1) and B. burgdorferi B313 (B.b B313) were included.

Mentions: In light of previous experience that B. hermsii and B. burgdorferi can specifically bind CFH via their outer surface lipoproteins [8], [11], [32], B. recurrentis spirochetes were incubated with biotinylated human CFH and analysed by flow cytometry. As seen in Figure 1A, both, B. recurrentis strains (A1 and A17) and B. hermsii HS1, but not B. burgdorferi B313, which lacks the CFH-binding lipoprotein, were able to bind CFH. In addition, biotinylated control protein, BSA, did not bind to any of the borrelial strains (Fig. 1A). Binding of CFH to intact and viable B. recurrentis spirochetes was confirmed by microscopy, using a CFH-specific mAb, JHD7 (Fig. 1B). By applying ligand affinity blot analysis for detection of CFH- and CFHR-1 binding molecules, a protein of approximately 17 kDa was detected in B. recurrentis but not in B. burgdorferi B313 (Fig. 1C), termed human complement regulator(s) and plasminogen binding protein A (HcpA) [8], [9].


Borrelia recurrentis employs a novel multifunctional surface protein with anti-complement, anti-opsonic and invasive potential to escape innate immunity.

Grosskinsky S, Schott M, Brenner C, Cutler SJ, Kraiczy P, Zipfel PF, Simon MM, Wallich R - PLoS ONE (2009)

Binding of CFH and CFHR-1 to the spirochetal surface.Binding of CFH to intact B. recurrentis cells was analyzed by flow cytometry and immunofluorescence microscopy. (A) Spirochetes were incubated with biotinylated purified human CFH (bold lines) or as a negative control with biotinylated BSA followed by PE-labeled streptavidin. B.hermsii HS1 and B. burgdorferi B313 were included as controls. (B) Cells were incubated with purified human CFH followed by the CFH-specific mAb JHD7 and a Cy3-conjugated anti-mouse IgG. Images were obtained employing epifluorescence microscopy. On the right panel the corresponding differential interference contrast image (DIC) is depicted. (C) Whole cell lysates of B. recurrentis strain A1 and A17 (B.r. A1 and B.r. A17) were separated by Tris/Tricine SDS-PAGE, transferred to nitrocellulose membrane and incubated with normal human serum. CFH binding was detected employing CFH specific mAb JHD7 and binding of CFHR-1 was analyzed using specific mAb JHD8. For control, cell lysates of B. hermsii HS1 (B.h HS1) and B. burgdorferi B313 (B.b B313) were included.
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Related In: Results  -  Collection

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pone-0004858-g001: Binding of CFH and CFHR-1 to the spirochetal surface.Binding of CFH to intact B. recurrentis cells was analyzed by flow cytometry and immunofluorescence microscopy. (A) Spirochetes were incubated with biotinylated purified human CFH (bold lines) or as a negative control with biotinylated BSA followed by PE-labeled streptavidin. B.hermsii HS1 and B. burgdorferi B313 were included as controls. (B) Cells were incubated with purified human CFH followed by the CFH-specific mAb JHD7 and a Cy3-conjugated anti-mouse IgG. Images were obtained employing epifluorescence microscopy. On the right panel the corresponding differential interference contrast image (DIC) is depicted. (C) Whole cell lysates of B. recurrentis strain A1 and A17 (B.r. A1 and B.r. A17) were separated by Tris/Tricine SDS-PAGE, transferred to nitrocellulose membrane and incubated with normal human serum. CFH binding was detected employing CFH specific mAb JHD7 and binding of CFHR-1 was analyzed using specific mAb JHD8. For control, cell lysates of B. hermsii HS1 (B.h HS1) and B. burgdorferi B313 (B.b B313) were included.
Mentions: In light of previous experience that B. hermsii and B. burgdorferi can specifically bind CFH via their outer surface lipoproteins [8], [11], [32], B. recurrentis spirochetes were incubated with biotinylated human CFH and analysed by flow cytometry. As seen in Figure 1A, both, B. recurrentis strains (A1 and A17) and B. hermsii HS1, but not B. burgdorferi B313, which lacks the CFH-binding lipoprotein, were able to bind CFH. In addition, biotinylated control protein, BSA, did not bind to any of the borrelial strains (Fig. 1A). Binding of CFH to intact and viable B. recurrentis spirochetes was confirmed by microscopy, using a CFH-specific mAb, JHD7 (Fig. 1B). By applying ligand affinity blot analysis for detection of CFH- and CFHR-1 binding molecules, a protein of approximately 17 kDa was detected in B. recurrentis but not in B. burgdorferi B313 (Fig. 1C), termed human complement regulator(s) and plasminogen binding protein A (HcpA) [8], [9].

Bottom Line: Moreover, ectopic expression of HcpA in a B. burgdorferi B313 strain, deficient in Factor H binding proteins, protected the transformed spirochetes from complement-mediated killing.Furthermore, HcpA-bound plasminogen/plasmin endows B. recurrentis with the potential to resist opsonization and to degrade extracellular matrix components.Together, the present study underscores the high virulence potential of B. recurrentis.

View Article: PubMed Central - PubMed

Affiliation: Infectious Immunology, Institute for Immunology, University of Heidelberg, Heidelberg, Germany.

ABSTRACT
Borrelia recurrentis, the etiologic agent of louse-borne relapsing fever in humans, has evolved strategies, including antigenic variation, to evade immune defence, thereby causing severe diseases with high mortality rates. Here we identify for the first time a multifunctional surface lipoprotein of B. recurrentis, termed HcpA, and demonstrate that it binds human complement regulators, Factor H, CFHR-1, and simultaneously, the host protease plasminogen. Cell surface bound factor H was found to retain its activity and to confer resistance to complement attack. Moreover, ectopic expression of HcpA in a B. burgdorferi B313 strain, deficient in Factor H binding proteins, protected the transformed spirochetes from complement-mediated killing. Furthermore, HcpA-bound plasminogen/plasmin endows B. recurrentis with the potential to resist opsonization and to degrade extracellular matrix components. Together, the present study underscores the high virulence potential of B. recurrentis. The elucidation of the molecular basis underlying the versatile strategies of B. recurrentis to escape innate immunity and to persist in human tissues, including the brain, may help to understand the pathological processes underlying louse-borne relapsing fever.

Show MeSH
Related in: MedlinePlus