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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: Cell surface bound factor H was found to retain its activity and to confer resistance to complement attack.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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Activation and proteolytic activity of HcpA- and B. recurrentis-bound plasmin(ogen).Intact B. recurrentis organisms (A) or recombinant HcpA (B) were incubated with PLG. Bound PLG was converted into plasmin by uPA addition and plasmin activity was measured using the chromogenic substrate D-Val-Leu-Lys 4-nitroanilide dihydrochloride (S-2251). uPA mediated PLG activation was inhibited by tranexamic acid (TA). Substrate cleaving was monitored by measurement of the absorbance at 405 nm for up to 6 hrs. Mean of triplicates ± SEM is shown. (C) Degradation of fibrinogen by HcpA-bound plasmin. HcpA coated microtiter plates were incubated with PLG, subsequently fibrinogen and uPA were added. The reaction mixtures were separated by SDS-PAGE, transferred to nitrocellulose and probed with rabbit anti-fibrinogen followed by peroxidase-conjugated IgG for detection of α, β and γ chains (67, 57 and 47 kDa) and the small-size degradation products of fibrinogen.
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pone-0004858-g007: Activation and proteolytic activity of HcpA- and B. recurrentis-bound plasmin(ogen).Intact B. recurrentis organisms (A) or recombinant HcpA (B) were incubated with PLG. Bound PLG was converted into plasmin by uPA addition and plasmin activity was measured using the chromogenic substrate D-Val-Leu-Lys 4-nitroanilide dihydrochloride (S-2251). uPA mediated PLG activation was inhibited by tranexamic acid (TA). Substrate cleaving was monitored by measurement of the absorbance at 405 nm for up to 6 hrs. Mean of triplicates ± SEM is shown. (C) Degradation of fibrinogen by HcpA-bound plasmin. HcpA coated microtiter plates were incubated with PLG, subsequently fibrinogen and uPA were added. The reaction mixtures were separated by SDS-PAGE, transferred to nitrocellulose and probed with rabbit anti-fibrinogen followed by peroxidase-conjugated IgG for detection of α, β and γ chains (67, 57 and 47 kDa) and the small-size degradation products of fibrinogen.

Mentions: To assess whether B. recurrentis-attached PLG can be processed to active plasmin, spirochetes were pre-treated with PLG and subsequently incubated with the exogenous human plasminogen activator uPA. As shown in Figure 7A, B. recurrentis-attached PLG was readily processed by exogenous uPA. In contrast, only marginal plasmin activity was observed in the presence of tranexamic acid, a competitive inhibitor of the lysine-binding site of PLG. These data demonstrate that spirochetal surface-bound PLG is accessible for uPA, and that processed plasmin retains its proteolytic activity. No plasmin was generated from surface-bound PLG in the absence of uPA, indicating that spirochetes do not express endogenous plasminogen activators. Similar findings were observed when recombinant HcpA was coated onto microtiter plates supporting the notion that HcpA-bound PLG can be processed to stable functional active plasmin (Fig. 7B).


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)

Activation and proteolytic activity of HcpA- and B. recurrentis-bound plasmin(ogen).Intact B. recurrentis organisms (A) or recombinant HcpA (B) were incubated with PLG. Bound PLG was converted into plasmin by uPA addition and plasmin activity was measured using the chromogenic substrate D-Val-Leu-Lys 4-nitroanilide dihydrochloride (S-2251). uPA mediated PLG activation was inhibited by tranexamic acid (TA). Substrate cleaving was monitored by measurement of the absorbance at 405 nm for up to 6 hrs. Mean of triplicates ± SEM is shown. (C) Degradation of fibrinogen by HcpA-bound plasmin. HcpA coated microtiter plates were incubated with PLG, subsequently fibrinogen and uPA were added. The reaction mixtures were separated by SDS-PAGE, transferred to nitrocellulose and probed with rabbit anti-fibrinogen followed by peroxidase-conjugated IgG for detection of α, β and γ chains (67, 57 and 47 kDa) and the small-size degradation products of fibrinogen.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2654920&req=5

pone-0004858-g007: Activation and proteolytic activity of HcpA- and B. recurrentis-bound plasmin(ogen).Intact B. recurrentis organisms (A) or recombinant HcpA (B) were incubated with PLG. Bound PLG was converted into plasmin by uPA addition and plasmin activity was measured using the chromogenic substrate D-Val-Leu-Lys 4-nitroanilide dihydrochloride (S-2251). uPA mediated PLG activation was inhibited by tranexamic acid (TA). Substrate cleaving was monitored by measurement of the absorbance at 405 nm for up to 6 hrs. Mean of triplicates ± SEM is shown. (C) Degradation of fibrinogen by HcpA-bound plasmin. HcpA coated microtiter plates were incubated with PLG, subsequently fibrinogen and uPA were added. The reaction mixtures were separated by SDS-PAGE, transferred to nitrocellulose and probed with rabbit anti-fibrinogen followed by peroxidase-conjugated IgG for detection of α, β and γ chains (67, 57 and 47 kDa) and the small-size degradation products of fibrinogen.
Mentions: To assess whether B. recurrentis-attached PLG can be processed to active plasmin, spirochetes were pre-treated with PLG and subsequently incubated with the exogenous human plasminogen activator uPA. As shown in Figure 7A, B. recurrentis-attached PLG was readily processed by exogenous uPA. In contrast, only marginal plasmin activity was observed in the presence of tranexamic acid, a competitive inhibitor of the lysine-binding site of PLG. These data demonstrate that spirochetal surface-bound PLG is accessible for uPA, and that processed plasmin retains its proteolytic activity. No plasmin was generated from surface-bound PLG in the absence of uPA, indicating that spirochetes do not express endogenous plasminogen activators. Similar findings were observed when recombinant HcpA was coated onto microtiter plates supporting the notion that HcpA-bound PLG can be processed to stable functional active plasmin (Fig. 7B).

Bottom Line: Cell surface bound factor H was found to retain its activity and to confer resistance to complement attack.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