As a prelude to characterization of the host and treponemal antigens present in purified immune complexes from the sera of rabbits with disseminated syphilis, autoradiographic and immunoenzymatic analyses of solubilized extracts of Treponema pallidum, Treponema phagedenis biotype Reiter, and Treponema refringens were performed on electroblots of polypeptides first separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Electroblots of purified immune complexes were developed with the same panel of antisera so that protein profiles could be compared. Eight treponemal antigens were consistently present in isolated complexes; four of these cross-reacted with antisera prepared against avirulent treponemes. The average molecular weights of these antigens were 87,000, 76,000, 66,000, and 45,000. Antibodies dissociated from isolated immune complexes, when used for the development of T. pallidum electroblots, reacted with four antigens of comparable molecular weight. Antibodies to those polypeptides were also present in the sera of animals immunized with immune complexes. The demonstration of treponemal antigens in purified immune complexes convincingly argues that their occurrence in experimental syphilis is not merely due to tissue destruction and responses to endogenous host antigens.
The in vivo activity of rosaramicin phosphate in disseminated and localized Treponema pallidum infections in rabbits was compared with that of penicillin G benzathine. Rabbits were injected either intradermally or intravenously to establish infection. Groups of four animals each then received either two weekly injections of 200,000 U of penicillin G benzathine, injections of 12.5 or 25 mg of rosaramicin per kg of body weight twice a day for 10 days, or no antibiotic therapy. Treatment of the intradermal and intravenous infections was initiated on days 7 and 14 postinfection, respectively. With both infection models, striking differences were noted between the untreated control rabbits and the three groups receiving treatment; no discernible differences, however, were detected among any of the treated groups. Rabbits that had been infected intravenously did not develop disseminated lesions or orchitis after treatment, and chancres produced by intradermal infection regressed and healed rapidly after the initiation of therapy. Continued increases in treponemal and nontreponemal antibody titers posttreatment did not occur in any of the treated rabbits. Infectivity studies also suggested that the lymph nodes and testes of treated animals were free from infectious organisms. Overall, at the dosage regimens employed, both rosaramicin and penicillin G benzathine appeared to effect complete control of the experimental disease.
The present study was designed to assess the in vivo activity of Sch 29482, a new penem antibiotic, against disseminated and localized Treponema pallidum infections in rabbits. Animals were inoculated either intravenously or intradermally. Randomized groups then received 25 or 50 mg of Sch 29482 per kilogram of body weight twice a day for 7 days, two weekly injections of 200,000 U of penicillin G benzathine for comparative purposes, or no antibiotic therapy. In both infection models, striking differences were noted between the untreated control rabbits and rabbits receiving penicillin G benzathine or high-dose Sch 29482.Intravenously infected rabbits did not develop disseminated lesions or orchitis, and chancres produced by intradermal infection regressed and healed rapidly after both treatment regimens. Infectivity studies also suggested that high-dose Sch 29482 and penicillin G benzathine were effective since the testes and lymph nodes of treated animals were free of infectious organisms. Treatment of animals with the lower dose of Sch 29482 represented borderline or suboptimal therapy, with a failure rate of one in four for each infection model.
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