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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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Mapping of the CFH domain interacting with HcpA.(A) Purified recombinant HcpA protein was separated by SDS-PAGE and transferred to nitrocellulose membranes. The membrane strips were incubated with either normal human serum (NHS), recombinant CFHL-1 (CFHSCR 1-7), several deletion constructs of CFH (CFHSCR8-20, CFHSCR15-20, CFHSCR15-19, CFHSCR19-20) or recombinant CFHR-1 (CFHR-1). Bound proteins were visualized using either polyclonal anti-CFH immune serum (α-CFH) or mAb specific for SCR19-20 (JHD7) or CFHR-1 protein (JHD8), respectively. (B) Binding of CFH and deletion mutants to HcpA as analyzed by surface plasmon resonance. Recombinant HcpA was immobilized to the surface of a sensor chip and CFH or various deletion mutants (CFHSCR15-20, CFHSCR19-20, CFHSCR15-19) were applied in the fluid phase. No binding was detectable for CFHSCR15-19 mutant. (C) Schematic representation of the CFH, CFHL-1 and CFHR-1 protein. Complement regulatory domains in SCR1-4 are shown in gray and the HcpA binding region in SCR20 of CFH and the corresponding SCR5 of CFHR-1 are highlighted in black with white fonts. SCR domains are aligned vertically according to their amino acid sequence similarities.
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pone-0004858-g004: Mapping of the CFH domain interacting with HcpA.(A) Purified recombinant HcpA protein was separated by SDS-PAGE and transferred to nitrocellulose membranes. The membrane strips were incubated with either normal human serum (NHS), recombinant CFHL-1 (CFHSCR 1-7), several deletion constructs of CFH (CFHSCR8-20, CFHSCR15-20, CFHSCR15-19, CFHSCR19-20) or recombinant CFHR-1 (CFHR-1). Bound proteins were visualized using either polyclonal anti-CFH immune serum (α-CFH) or mAb specific for SCR19-20 (JHD7) or CFHR-1 protein (JHD8), respectively. (B) Binding of CFH and deletion mutants to HcpA as analyzed by surface plasmon resonance. Recombinant HcpA was immobilized to the surface of a sensor chip and CFH or various deletion mutants (CFHSCR15-20, CFHSCR19-20, CFHSCR15-19) were applied in the fluid phase. No binding was detectable for CFHSCR15-19 mutant. (C) Schematic representation of the CFH, CFHL-1 and CFHR-1 protein. Complement regulatory domains in SCR1-4 are shown in gray and the HcpA binding region in SCR20 of CFH and the corresponding SCR5 of CFHR-1 are highlighted in black with white fonts. SCR domains are aligned vertically according to their amino acid sequence similarities.

Mentions: To map the binding domain of CFH that interacts with HcpA, recombinant deletion constructs of CFH representing SCRs 8-10, SCRs 15-10, SCRs 19-20, and SCRs 1-7/FHL-1 were employed. HcpA showed strong binding to CFH and deletion constructs CFHSCR8-20, CFHSCR15-20, CFHSCR19-20, as well as CFHR-1. Construct CFHL-1 (CFHSCR1-7) did not bind to HcpA, indicating that the most C-terminal domains (SCR19-20) of CFH are involved in binding (Fig. 4A). We next conducted surface plasmon resonance analyses, a more physiological assay system, to further define the CFH domain interacting with HcpA. CFH and deletion constructs CFHSCR8-20, CFHSCR15-20 and CFHSCR19-20 bound to immobilized HcpA with similar intensity (Fig. 4B). However, in the absence of SCR20, represented by the deletion construct CFHSCR15-19, binding to HcpA was completely abrogated (Fig. 4B). As indicated by the schematic representation, domain SCR20 of CFH displays 97% sequence similarity to the SCR5 of CFHR-1 (Fig. 4C) [7]. Therefore it is assumed that the binding region of CFHR-1 for HcpA is located in the C-terminus, accordingly.


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)

Mapping of the CFH domain interacting with HcpA.(A) Purified recombinant HcpA protein was separated by SDS-PAGE and transferred to nitrocellulose membranes. The membrane strips were incubated with either normal human serum (NHS), recombinant CFHL-1 (CFHSCR 1-7), several deletion constructs of CFH (CFHSCR8-20, CFHSCR15-20, CFHSCR15-19, CFHSCR19-20) or recombinant CFHR-1 (CFHR-1). Bound proteins were visualized using either polyclonal anti-CFH immune serum (α-CFH) or mAb specific for SCR19-20 (JHD7) or CFHR-1 protein (JHD8), respectively. (B) Binding of CFH and deletion mutants to HcpA as analyzed by surface plasmon resonance. Recombinant HcpA was immobilized to the surface of a sensor chip and CFH or various deletion mutants (CFHSCR15-20, CFHSCR19-20, CFHSCR15-19) were applied in the fluid phase. No binding was detectable for CFHSCR15-19 mutant. (C) Schematic representation of the CFH, CFHL-1 and CFHR-1 protein. Complement regulatory domains in SCR1-4 are shown in gray and the HcpA binding region in SCR20 of CFH and the corresponding SCR5 of CFHR-1 are highlighted in black with white fonts. SCR domains are aligned vertically according to their amino acid sequence similarities.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2654920&req=5

pone-0004858-g004: Mapping of the CFH domain interacting with HcpA.(A) Purified recombinant HcpA protein was separated by SDS-PAGE and transferred to nitrocellulose membranes. The membrane strips were incubated with either normal human serum (NHS), recombinant CFHL-1 (CFHSCR 1-7), several deletion constructs of CFH (CFHSCR8-20, CFHSCR15-20, CFHSCR15-19, CFHSCR19-20) or recombinant CFHR-1 (CFHR-1). Bound proteins were visualized using either polyclonal anti-CFH immune serum (α-CFH) or mAb specific for SCR19-20 (JHD7) or CFHR-1 protein (JHD8), respectively. (B) Binding of CFH and deletion mutants to HcpA as analyzed by surface plasmon resonance. Recombinant HcpA was immobilized to the surface of a sensor chip and CFH or various deletion mutants (CFHSCR15-20, CFHSCR19-20, CFHSCR15-19) were applied in the fluid phase. No binding was detectable for CFHSCR15-19 mutant. (C) Schematic representation of the CFH, CFHL-1 and CFHR-1 protein. Complement regulatory domains in SCR1-4 are shown in gray and the HcpA binding region in SCR20 of CFH and the corresponding SCR5 of CFHR-1 are highlighted in black with white fonts. SCR domains are aligned vertically according to their amino acid sequence similarities.
Mentions: To map the binding domain of CFH that interacts with HcpA, recombinant deletion constructs of CFH representing SCRs 8-10, SCRs 15-10, SCRs 19-20, and SCRs 1-7/FHL-1 were employed. HcpA showed strong binding to CFH and deletion constructs CFHSCR8-20, CFHSCR15-20, CFHSCR19-20, as well as CFHR-1. Construct CFHL-1 (CFHSCR1-7) did not bind to HcpA, indicating that the most C-terminal domains (SCR19-20) of CFH are involved in binding (Fig. 4A). We next conducted surface plasmon resonance analyses, a more physiological assay system, to further define the CFH domain interacting with HcpA. CFH and deletion constructs CFHSCR8-20, CFHSCR15-20 and CFHSCR19-20 bound to immobilized HcpA with similar intensity (Fig. 4B). However, in the absence of SCR20, represented by the deletion construct CFHSCR15-19, binding to HcpA was completely abrogated (Fig. 4B). As indicated by the schematic representation, domain SCR20 of CFH displays 97% sequence similarity to the SCR5 of CFHR-1 (Fig. 4C) [7]. Therefore it is assumed that the binding region of CFHR-1 for HcpA is located in the C-terminus, accordingly.

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