Serum-resistant strains of Borrelia burgdorferi evade complement-mediated killing by expressing a CD59-like complement inhibitory molecule.
Borrelia burgdorferi, the etiological agent of Lyme disease, comprises three genospecies, Borrelia garinii, afzelii, and burgdorferi sensu strictu, that exhibit different pathogenicity and differ in the susceptibility to C-mediated killing. We examined C-sensitive and C-resistant strains of B. burgdorferi for deposition of C3 and late C components by fluorescence microscope and flow cytometry. Despite comparable deposition of C3 on the two strains, the resistant strain exhibited reduced staining for C6 and C7, barely detectable C9, and undetectable poly C9. Based on these findings, we searched for a protein that inhibits assembly of C membrane attack complex and documented an anti-human CD59-reactive molecule on the surface of C-resistant spirochetes by flow cytometry and electron microscopy. A molecule of 80 kDa recognized by polyclonal and monoclonal anti-CD59 Abs was identified in the membrane extract of C-resistant strains by SDS-PAGE and Western blot analysis. The molecule was released from the bacterial wall using deoxycholate and trypsin, suggesting its insertion into the bacterial membrane. The CD59-like molecule acts as C inhibitor on Borrelia because incubation with F(ab')(2) anti-CD59 renders the serum-resistant strain exquisitely susceptible to C-mediated killing and guinea pig erythrocytes bearing C5b-8, unlike the RBC coated with C5b-7, are protected from reactive lysis by the bacterial extract. Western blot analysis revealed preferential binding of the C inhibitory molecule to C9 and weak interaction with C8 beta.
Pausa
Mario
M
Department of Physiology and Pathology, University of Trieste, Trieste, Italy.
Pellis
Valentina
V
Cinco
Marina
M
Giulianini
Piero G
PG
Presani
Gianni
G
Perticarari
Sandra
S
Murgia
Rossella
R
Tedesco
Francesco
F
D019138:Antibodies, Blocking / Q000378:metabolism / Q000494:pharmacology; D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000276:immunology / Q000378:metabolism / Q000648:ultrastructure; D001666:Binding Sites, Antibody; D001770:Blood Bactericidal Activity / Q000276:immunology*; D025065:Borrelia burgdorferi / Q000254:growth & development* / Q000276:immunology* / Q000378:metabolism / Q000648:ultrastructure; D018957:CD59 Antigens / Q000096:biosynthesis* / Q000276:immunology / Q000378:metabolism / Q000648:ultrastructure; D002462:Cell Membrane / Q000276:immunology / Q000378:metabolism / Q000648:ultrastructure; D003176:Complement C3 / Q000378:metabolism; D003184:Complement C7 / Q000378:metabolism; D003185:Complement C8 / Q000378:metabolism; D003186:Complement C9 / Q000378:metabolism; D003169:Complement Inactivator Proteins / Q000096:biosynthesis* / Q000276:immunology / Q000378:metabolism / Q000648:ultrastructure; D015938:Complement Membrane Attack Complex / Q000037:antagonists & inhibitors; D003165:Complement System Proteins / Q000633:toxicity*; D003602:Cytotoxicity, Immunologic; D019085:Fluorescent Antibody Technique, Direct; D006801:Humans; D007113:Immunity, Innate; D013045:Species Specificity; D014357:Trypsin / Q000494:pharmacology
D019138:Antibodies, Blocking; D001426:Bacterial Proteins; D018957:CD59 Antigens; D003176:Complement C3; D003184:Complement C7; D003185:Complement C8; D003186:Complement C9; D003169:Complement Inactivator Proteins; D015938:Complement Membrane Attack Complex; D003165:Complement System Proteins; D014357:Trypsin