Complement regulator-acquiring surface protein 1 imparts resistance to human serum in Borrelia burgdorferi.
Factor H and factor H-like protein 1 (FH/FHL-1) are soluble serum proteins that negatively regulate the alternative pathway of complement. It is now well recognized that many pathogenic bacteria, including Borrelia burgdorferi, bind FH/FHL-1 on their cell surface to evade complement-mediated destruction during infection. Recently, it was suggested that B. burgdorferi open reading frame bbA68, known as complement regulator-acquiring surface protein 1 (CRASP-1), encodes the major FH/FHL-1-binding protein of B. burgdorferi. However, because several other proteins have been identified on the surface of B. burgdorferi that also can bind FH/FHL-1, it is presently unclear what role CRASP-1 plays in serum resistance. To examine the contribution of CRASP-1 in serum resistance, we generated a B. burgdorferi mutant that does not express CRASP-1. The B. burgdorferi CRASP-1 mutant, designated B31cF-CRASP-1, was found to be as susceptible to human serum as a wild-type strain of Borrelia garinii 50 known to be sensitive to human serum. To further examine the role of CRASP-1 in serum resistance, we also created a shuttle vector that expresses CRASP-1 from the native B. burgdorferi gene, which was designated pKFSS-1::CRASP-1. When the pKFSS-1::CRASP-1 construct was transformed into the B. burgdorferi B31cF-CRASP-1 mutant, wild-type levels of serum resistance were restored. Additionally, when pKFSS-1::CRASP-1 was transformed into the serum-sensitive B. garinii 50 isolate, human serum resistance was imparted on this strain to a level indistinguishable from wild-type B. burgdorferi. The combined data led us to conclude that CRASP-1 expression is necessary for B. burgdorferi to resist killing by human serum.
Brooks
Chad S
CS
Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA.
Vuppala
Santosh R
SR
Jett
Amy M
AM
Alitalo
Antti
A
Meri
Seppo
S
Akins
Darrin R
DR
D001426:Bacterial Proteins / Q000502:physiology*; D001770:Blood Bactericidal Activity; D001798:Blood Proteins / Q000378:metabolism; D025065:Borrelia burgdorferi / Q000276:immunology*; D003180:Complement C3b Inactivator Proteins; D017242:Complement Factor H / Q000378:metabolism; D006801:Humans; D008565:Membrane Proteins / Q000502:physiology*; D021381:Protein Transport
D001426:Bacterial Proteins; D001798:Blood Proteins; C493495:CFH protein, human; C517621:CFHR1 protein, human; D003180:Complement C3b Inactivator Proteins; D008565:Membrane Proteins; C440651:complement regulator-acquiring surface proteins, Borrelia burgdorferi; D017242:Complement Factor H