Monoclonal Antibody That Conveys In Vitro Killing and Partial Protection in Experimental Syphilis Binds a Phosphorylcholine Surface Epitope of Treponema pallidum

• Published in: Infection and Immunity 2005-05, Vol.73 (5), p.3083-3095
• Main Authors: Blanco, David R, Champion, Cheryl I, Dooley, Alek, Cox, David L, Whitelegge, Julian P, Faull, Kym, Lovett, Michael A
• Format: Article
• Language: English
• Subjects: Animals; Antibodies, Monoclonal - administration & dosage; Antibodies, Monoclonal - immunology; Antibodies, Monoclonal - metabolism; Antibodies, Monoclonal - therapeutic use; Antibody Specificity; Antigens, Surface - immunology; Antigens, Surface - metabolism; Applied microbiology; Bacterial diseases; Bacterial diseases of the genital system; Bacteriology; Biological and medical sciences; Epitopes - immunology; Fundamental and applied biological sciences. Psychology; Human bacterial diseases; Humans; Immunization, Passive; Infectious diseases; Medical sciences; Mice; Mice, Inbred BALB C; Microbial Immunity and Vaccines; Microbiology; Miscellaneous; Phosphorylcholine - immunology; Phosphorylcholine - metabolism; Polymerase Chain Reaction; Rabbits; Syphilis - immunology; Syphilis - microbiology; Syphilis - prevention & control; Treponema pallidum; Treponema pallidum - genetics; Treponema pallidum - immunology; Vaccines, antisera, therapeutical immunoglobulins and monoclonal antibodies (general aspects)
• ISSN: 0019-9567; 1098-5522
• DOI: 10.1128/IAI.73.5.3083-3095.2005

Immunization with purified Treponema pallidum outer membrane vesicles (OMV) has previously resulted in high-titer complement-dependent serum bactericidal activity. In this study, OMV immunization resulted in the isolation of a monoclonal antibody, M131, with complement-dependent killing activity. Passive immunization of rabbits with M131 administered intravenously conferred significant immunity demonstrated by the failure of syphilitic lesions to appear at 29% of intradermal challenge sites (7/24) and a mean delay of approximately 8 days to lesion appearance at the remaining sites (17/24). M131 not only bound to OMV and to the surfaces of intact motile T. pallidum cells but also bound to organisms whose outer membranes were removed, indicating both surface and subsurface locations for the killing target. This target was determined to be a T. pallidum lipid. Lipid extracted from T. pallidum and made into liposomes bound M131. Reverse-phase high-pressure liquid chromatography separation and fraction collection mass spectrometry (LC-MS+) of T. pallidum lipid showed that the target of M131 was phosphorylcholine. M131 binding required both liposome formation and a critical concentration of phospholipid containing phosphorylcholine, suggesting that the epitope has both a conformational and a compositional requirement. M131 did not react with red blood cells, which have phosphorylcholine-containing lipids in their exterior membrane leaflets, or with Venereal Disease Research Laboratory antigen that also contains phosphorylcholine, further indicating the specificity of M131. This is the first physical demonstration of an antigen on the T. pallidum surface and indication that such a surface antigen can be a target of immunity.