Van Voorhis, and S

Van Voorhis, and S. of 7.65 103 copies, while no DNA could be detected in the M131 group. At approximately the mean time to lesion appearance in the IRS and M131 groups (17 and 20 days, respectively), the numbers of DNA copies were still 5- and 30-fold less, respectively, than those in the control AVE5688 group at these times. By 30 days postchallenge, the DNA copy numbers were similar in all three groups. These findings indicate that this delays in appearance of syphilitic lesions conferred by IRS and M131 corresponded to a marked decrease in treponemal numbers during the course of lesion development. subsp. is the etiologic agent of venereal syphilis. While infection-derived immunity is usually a hallmark of experimental syphilis in the rabbit model, the molecular basis of this acquired protective immunity has not been elucidated. The outer membrane of has a remarkably low content of membrane-spanning protein (27, 33) and lacks lipopolysaccharide (3, 17, 18). Certain treponemal proteins have been advanced as outer membrane protein candidates based upon properties such as channel-forming activity (6), the induction of antibodies that result in opsonophagocytosis of (10, 12), or their representation in a paralogous gene family believed to represent antigenic variants (12-14, 17). None of these proteins has been definitively localized to the surface by physical means (1, 19, 28). Recently, using a monoclonal antibody termed M131, we identified a bone fide surface antigen of that is usually a target of bactericidal antibody and partial protective immunity (5, 7). The surface antigen bound by M131 was found to be membranous phosphorylcholine-containing lipid, not a protein (5). M131 administered to rabbits by passive immunization caused a significant delay AVE5688 in lesion appearance compared to controls (5). The rabbit model of experimental syphilis has been used for many decades to assess protective immunity (32). Lesion delays following challenge of animals passively immunized with immune rabbit serum (IRS) have been interpreted to represent partial protection (4, 26, 29, 31). This is based upon studies demonstrating that a 10-fold difference in challenge inoculum size results in a 3- to 4-day delay in time to lesion appearance (21, 31, 32). Over the past 20 years, numerous active immunization studies in rabbits, using native and recombinant proteins, have been conducted in an effort to identify targets of protective immunity (8-12, 15, 23). Lesion delays were not observed in any of these studies but rather in all cases, lesions AVE5688 Rabbit Polyclonal to KAPCB developed either in the same time frame as that in controls or in an accelerated time frame. These lesions were judged to be atypical in terms of being smaller, less erythematous, less prone to ulcerate, and made up of fewer treponemes, based upon dark-field microscopy examination of lesion aspirates. However, the accuracy of dark-field microscopy for enumerating treponemes in dermal lesions has never been established. Nonetheless, in some studies the development of atypical lesions has been interpreted to represent partial protection (9, 10, 12, 23). Whether such atypical lesions represent actual protective immunity has been controversial because bone fide quantitative microbiology has not been provided. In contrast to the study of other spirochetal pathogens, including and DNA copy number and address whether delays in lesion appearance reflect a reduction in the numbers of at dermal injection sites. We found that delays in the time to lesion appearance, conferred by IRS and in particular M131, corresponded to marked differences in DNA copy numbers. The use of real-time PCR provides an accurate assessment of protective immunity as it relates to lesion development in experimental syphilis. MATERIALS AND METHODS Source of subsp. was extracted from infected rabbit testes, as described above, and resuspended into heat-inactivated (56C, 30 min) NRS (H-NRS) or H-IRS to a concentration of 1 AVE5688 1 104 organisms/ml. To.