title: Treponemicidal antibody measured by the "washed-killing" assay correlates with immunity in experimental rabbit syphilis.
abstract: OBJECTIVE
  The authors have previously shown that complement-dependent treponemicidal antibody measured by the "washed-killing" assay is directed exclusively against surface-exposed targets on Treponema pallidum, presumably the Treponema pallidum rare outer membrane proteins detected by freeze-fracture electron microscopy.
  
  
  OBJECTIVE
  Because immune mechanisms against Treponema pallidum rare outer membrane proteins are likely to be central to a protective host response, it was examined whether a relationship could be established between treponemicidal levels as measured by the "washed-killing" assay and host immunity in experimental syphilis.
  
  
  METHODS
  Three groups of Treponema pallidum-infected rabbits were treated curatively with penicillin at 9 days, 30 days, and 6 months post-infection to generate animals with varying degrees of immunity to challenge re-infection. The level of complement-dependent treponemicidal activity in sera obtained before infection (basal) and before intradermal challenge was determined by the "washed-killing" assay and compared with that detected using conventional in vitro immobilization.
  
  
  RESULTS
  Using the "washed-killing" assay, a close quantitative correlation as measured by a treponemal immobilizing endpoint titer was demonstrable between prechallenge treponemicidal antibody and the status of immunity to re-infection. Sera from rabbits completely susceptible to symptomatic and disseminated asymptomatic re-infection lacked treponemicidal antibody. Sera from challenged rabbits with a relatively low degree of immunity to symptomatic disease showed endpoints of < or = 4. Rabbits with a relatively high degree of immunity to symptomatic reinfection and resistant to disseminated disease had endpoints that ranged from 6 to 96. Rabbits completely resistant to challenge exhibited endpoints ranging from 96 to 128.
  
  
  CONCLUSIONS
  Treponemicidal antibody measured by the "washed-killing" assay correlated closely with the status of immunity in experimental rabbit syphilis. Thus, antibody measured by this assay may be directed against key protective Treponema pallidum surface immunogens.
authors.affiliation: Department of Microbiology and Immunology, University of California School of Medicine, Los Angeles 90024.
authors.forename: M A
authors.initials: MA
authors.lastname: Lewinski
authors.forename: J N
authors.initials: JN
authors.lastname: Miller
authors.forename: C I
authors.initials: CI
authors.lastname: Champion
authors.forename: E M
authors.initials: EM
authors.lastname: Walker
authors.forename: L A
authors.initials: LA
authors.lastname: Borenstein
authors.forename: R J
authors.initials: RJ
authors.lastname: Gayek
authors.forename: M A
authors.initials: MA
authors.lastname: Lovett
authors.forename: D R
authors.initials: DR
authors.lastname: Blanco
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood*; D001425:Bacterial Outer Membrane Proteins / Q000276:immunology*; D003168:Complement Fixation Tests / Q000379:methods; D004195:Disease Models, Animal; D008297:Male; D010406:Penicillins / Q000627:therapeutic use; D011817:Rabbits; D012008:Recurrence; D013587:Syphilis / Q000097:blood / Q000188:drug therapy / Q000276:immunology*; D014209:Treponema Immobilization Test; D014210:Treponema pallidum / Q000276:immunology*
chemical_list: D000907:Antibodies, Bacterial; D001425:Bacterial Outer Membrane Proteins; D010406:Penicillins