Use of the skin protection assay in experimental syphilis to assess protective immunity against a specific Treponema pallidum surface epitope.

We have recently shown that a monoclonal antibody, designated M131, that binds a surface phosphorylcholine epitope on Treponema pallidum possesses complement-dependent killing activity and confers partial protection in rabbits following passive immunization (Blanco et al., 2005, Infect. Immun. 73:3083-3095). In this study, the protective potential of M131 was further tested using the rabbit skin protection assay of Titus and Weiser. Both M131 and infection-derived immune rabbit serum resulted in significant lesion delays corresponding to at least a 90% reduction of the treponemal challenge inoculum. The skin protection assay provides a way to assess the protective potential of specific immunogens while using far less antibody than in passive immunization protocols.