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Although reactivity in nontreponemal tests develops in patients with untreated syphilis, no immunologic function has been ascribed to these antibodies. This study demonstrates that rabbit antibodies induced by immunization with VDRL antigen and VDRL antibodies affinity-purified from syphilitic rabbit serum enhance phagocytosis of Treponema pallidum. The proportion of macrophages ingesting treponemes in the presence of these antisera was 45% +/- 5% and 27% +/- 4%, respectively, versus 14% +/- 3% for normal serum (P < .001 and P < .01). Both IgG and IgM fractions contained opsonic activity. Absorption of VDRL antibodies from syphilitic serum diminished but did not eliminate opsonization, suggesting at least two classes of target molecules. Despite opsonic capacity, VDRL antibodies fail to facilitate macrophage-mediated killing of T. pallidum. Nevertheless, VDRL-immunized rabbits are partially protected against T. pallidum infection, developing fewer lesions (delayed and smaller) than do unimmunized controls. These results suggest a heretofore unrecognized functional role for VDRL antibodies in syphilis infection.

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Serum pools were collected from rabbits bled at various times after intra-testicular infection with Treponema pallidum ssp. pallidum. These were tested for their ability to opsonize T. pallidum and promote killing of the organisms by macrophages. Compared to normal sera, significant opsonization was first seen on day 10 of infection as measured by both ingestion (P < 0.001) and macrophage-mediated killing (P = 0.006); significant levels of functional antibodies persisted through 300 days of infection. Although opsonic activity peaked early in infection, antibodies that promoted optimal macrophage-mediated killing developed much later, suggesting that these two functions may represent activities of antibodies with differing specificities or affinities. The initial development of antibodies that augment both phagocytosis and killing corresponds with the in vivo clearance of treponemes from the primary site of infection. These observations support the hypothesis that macrophages are the major effector mechanism for elimination of T. pallidum during early syphilis infection.

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Rabbit antisera to Leptospira interrogans, Borrelia hermsii, and Treponema phagedenis biotype Reiter, reactive to shared spirochetal antigens, failed to enhance phagocytosis of Treponema pallidum by macrophages, while immunoglobulin G to Treponema pallidum subsp. pertenue and Treponema paraluiscuniculi promoted phagocytosis. Opsonic antibodies are directed to pathogen-restricted, not shared spirochetal, antigens.

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While untreated syphilis infection is characterized by spontaneous resolution of early lesions, a few organisms evade the host immune response and persist for many years. Macrophages are generally recognized as the effector cell responsible for bacterial clearance, and phagocytosis is enhanced by immune serum. This study examined the susceptibility of Treponema pallidum isolated at various stages of lesion resolution to opsonization and phagocytosis by macrophages in vitro. Findings suggest that the population of organisms remaining after the majority of bacteria have been cleared in vivo is resistant to phagocytosis. This may provide a mechanism for the persistence of T. pallidum in the face of an otherwise active immune response.

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The ability of proteose peptone-induced normal rabbit peritoneal macrophages to kill Treponema pallidum subspecies pallidum in vitro is demonstrated. Treponemes and 10% heated immune or normal sera were incubated with macrophages at a ratio of 1:200. After 2-10 h of incubation, these mixtures were injected intradermally at duplicate sites on normal rabbits. Maximal killing (failure to develop lesions) was seen at 10 h of incubation with immune serum: Only 7% (1/14) of lesions developed compared with 90% (9/10) after incubation in the presence of normal serum (P less than .001). Maximal phagocytosis (detected by immunofluorescence) occurred by 8 h in the presence of immune serum, when 90% of macrophages had ingested treponemes. At this point, however, 70% of lesion sites from macrophages incubated with treponemes and immune serum still developed, suggesting that effective killing may require at least 2 h after phagocytosis.

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BACKGROUND: Spirochetes are commonly associated with periodontal disease, but it is not known whether these treponemes are pathogenic or merely opportunistic. We sought to determine whether spirochetes present in periodontal disease share antigens thought to be unique to spirochetes that are known pathogens. METHODS: We examined dental plaque from 24 healthy subjects, from ulcerative sites in 17 patients with ulcerative gingivitis, and from areas of involvement in 19 patients with chronic periodontitis, using an immunocyto-chemical technique with monoclonal antibodies against pathogen-specific determinants on 47-kd and 37-kd molecules from Treponema pallidum subspecies pallidum. Serum was tested against T. pallidum by immunoblotting and by serologic assays for syphilis. RESULTS: Spirochetes with a pathogen-specific epitope on a 47-kd molecule were not found in plaque samples from any of the 24 healthy subjects, but they were identified in plaque samples from 11 of 17 patients with ulcerative gingivitis (P less than 0.001) and from 10 of 19 patients with periodontitis (P less than 0.01). Monoclonal antibodies directed against a 37-kd molecule reacted with spirochetes in plaque samples from 1 of 14 controls, from all 11 patients with gingivitis from whom samples could be obtained (P less than 0.001), and from 14 of 19 patients with periodontitis (P less than 0.001). Five of 18 normal subjects had IgG against 47-kd and 37-kd molecules, but none had IgG against 14-kd or 12-kd molecules from T. pallidum subspecies pallidum. Among 19 patients with ulcerative gingivitis, IgG was identified against 47-kd molecules in 15, against 37-kd molecules in 12, against 14-kd molecules in 4, and against 12-kd molecules in 15. CONCLUSIONS: The spirochetes found in dental plaque from patients with ulcerative gingivitis or chronic periodontitis have antigens that are thought to be unique to pathogenic treponemes. This close antigenic relation suggests that T. pallidum or a closely related organism may be involved in the pathogenesis of periodontal disease.

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Although up to 40% of patients with early syphilis have evidence of central nervous system (CNS) invasion by Treponema pallidum, the pathogenesis of CNS syphilis is not understood. A rabbit model that mimics early CNS involvement in humans was developed and characterized. Mild cerebrospinal fluid pleocytosis was evident 2 weeks after intracisternal inoculation of T. pallidum and peaked at 9 weeks. The VDRL test in cerebrospinal fluid was reactive in 24% of animals, most commonly at 9 weeks after infection. T. pallidum could be isolated from the CNS of animals infected for 4, 6, or 9 weeks but not from animals infected for 12 or 20 weeks. Clinically, 6% of animals developed uveitis, similar to the frequency in patients with secondary syphilis. Thus, this model of meningeal and ocular syphilis seems to be analogous to the early CNS infection in humans and can be used for studies of pathogenesis and treatment.

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Azithromycin was shown to be as effective as standard benzathine penicillin and erythromycin in the therapy of active syphilis in the rabbit model. Following production of primary chancres by intradermal inoculation of 10(6) Treponema pallidum, groups of six rabbits were treated with benzathine penicillin (200,000 units im weekly for two weeks), erythromycin base (30 mg/kg/day orally four times daily for 15 days) or azithromycin (30 mg/kg/day given orally once or twice daily for 15 days); one group was untreated. Daily darkfield (DF) microscopic examinations of chancre aspirates were conducted to identify motile organisms. Although all treated animals became DF negative prior to completion of therapy, the median time to DF negativity was longer in animals given azithromycin once daily, compared with animals receiving benzathine penicillin (P less than 0.01); no difference was seen in comparison with animals receiving erythromycin. Untreated animals remained DF positive for greater than 15 days. The mean maximum lesion diameters for all treated animals were similar and were significantly smaller than in untreated rabbits; fewer lesions ulcerated in treated than in untreated animals. Subsequent dose-ranging studies indicated that administration of lower doses of azithromycin (15 mg/kg/day given orally either once or twice daily, or 7.5 mg/kg/day given once daily) was as effective as benzathine penicillin for therapy of active syphilis in this model, though the median time to darkfield negativity was significantly longer in the azithromycin-treated animals (P less than 0.01). Persistent infection was demonstrable in lymph nodes of untreated animals, but no evidence of virulent T. pallidum was found three months following transfer of tissue from any animal treated with penicillin, erythromycin, or azithromycin.

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Cefmetazole, a cephamycin-type antibiotic, was shown to be as effective as standard benzathine penicillin for therapy of active syphilis in the rabbit model. Four groups of six adult male rabbits were inoculated intradermally with 10(6) Treponema pallidum per site, producing primary syphilitic lesions. One week following infection, groups of rabbits were treated with benzathine penicillin (200,000 U intramuscularly weekly for 2 weeks) or cefmetazole (20 or 40 mg/kg per day intramuscularly in four divided doses for 15 days); one group was untreated. Daily dark-field microscopic examination of lesion aspirates demonstrated that the mean times to dark-field negativity were the same for benzathine penicillin- and two cefmetazole-treated groups (1.0. 1.0, and 1.17 days, respectively), while all untreated animals remained dark-field positive for greater than 15 days. Mean maximum lesion diameters in cefmetazole-treated animals (8.7 +/- 1.3 and 8.1 +/- 1.3 mm) were equivalent to those in penicillin-treated animals (8.6 +/- 1.6 mm) and were smaller than observed in untreated animals (12.4 +/- 2.2 mm; P less than 0.01); fewer lesions ulcerated in penicillin- or cefmetazole-treated rabbits than in untreated rabbits (P less than 0.001). Persistent infection was documented in lymph nodes of untreated rabbits; no evidence of latent infection was found in penicillin- or cefmetazole-treated animals.

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STUDY OBJECTIVES: To determine the prevalence of Treponema pallidum in cerebrospinal fluid (CSF) of patients with syphilis, to determine the effect of concurrent HIV infection on central nervous system involvement by T. pallidum, and to examine the efficacy of conventional therapy for asymptomatic neurologic involvement. PATIENTS: Fifty-eight patients with untreated syphilis who consented to lumbar puncture, representing approximately 10% of new cases of syphilis during the study period. INTERVENTIONS: Lumbar puncture was done on all patients. Rabbit inoculation was used to test cerebrospinal fluid for viable T. pallidum. Patients with normal fluid received recommended benzathine penicillin therapy according to the stage of syphilis; patients with CSF abnormalities were offered 10-day therapy for neurosyphilis. RESULTS: Treponema pallidum was isolated from the CSF of 12 (30%) of 40 patients (95% CI, 17 to 46) with untreated primary and secondary syphilis; isolation of T. pallidum was significantly associated (P = 0.008) with the presence of two or more abnormal laboratory variables (among leukocyte count, protein concentration, and CSF-Venereal Disease Research Laboratory [VDRL] test). Two (67%) of 3 early latent (CI, 13 to 100) and 3 (20%) of 15 late latent syphilis patients (CI, 5 to 47) also had reactive CSF-VDRL tests and elevated cell and protein levels, although T. pallidum was not isolated. Concurrent infection with the human immunodeficiency virus (HIV) was not associated with isolation of T. pallidum, increased number of CSF abnormalities, or reactive CSF serologic tests for syphilis, although CSF pleocytosis was commoner in subjects infected with HIV. Treatment with conventional benzathine penicillin G (2.4 mIU) failed to cure 3 of 4 patients with secondary syphilis from whom T. pallidum was isolated before therapy; all 3 patients in whom treatment failed were HIV seropositive when treated or seroconverted during follow-up. CONCLUSIONS: Central nervous system invasion by T. pallidum is common in early syphilis, and is apparently independent of HIV infection. Examination of the CSF may be beneficial in patients with early syphilis, and therapy should be guided by knowledge of central nervous system involvement. Conventional benzathine penicillin G therapy may have reduced efficacy in patients with early syphilis who are also infected with HIV.

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The contribution of individual specific molecules of Treponema pallidum subspecies pallidum to cellular immunity in experimental syphilis was evaluated by combining the techniques of Ag identification and purification with the lymphocyte proliferation assay. Proliferative responses of splenic lymphocytes from syphilitic rabbits to complex treponemal Ag and Con A were vigorous throughout the course of intratesticular infection (6, 10, 17, 30, and 210 days). Normal rabbits did not respond to any treponemal preparations and all rabbits failed to respond to normal rabbit testicular Ag (NRT). Seven defined treponemal Ag (47 kDa, 37 kDa, 35, 33-kDa, 30-kDa, 14 kDa, and 12 kDa) stimulated lymphocytes from infected rabbits. Cellular responses to the 37-kDa and 30-kDa fractions were evident by day 6 of infection and responses to the 35, 33-kDa and 14-kDa Ag were first detected on day 10; responsiveness to these Ag continued throughout the observation period. Cellular responses to the 47-kDa molecule were detectable but lower when compared with other individual Ag. Responsiveness to the 12-kDa Ag was not evident until 7 mo postinfection. Specific immunoblot reactivity of serum from rabbits used in this study generally correlated with the development of cellular reactivity to individual Ag of T. pallidum.

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Inhabitants of a remote Panamanian village were examined for clinical and serological evidence of pinta infection. Of 104 persons examined, 21 (20%) had clinical evidence of active or inactive pinta, and 54 (52%) were seropositive. Sera were evaluated for antibody to individual Treponema pallidum antigens. Sera from all four patients with active pinta contained antibody to the 47-48 kilodalton major antigen; the intensity of reactivity and the number of antigens recognized increased with age and, presumably, duration of infection. Sera from six children with inactive pinta reacted strongly with multiple T. pallidum antigens, whereas adults with inactive pinta had less intense reactivity against fewer molecules. Seronegative controls demonstrated only weak reactivity to fewer than five molecules. The development of antibody reactivity to the full spectrum of T. pallidum antigens during the course of infection demonstrates the high degree of antigenic relatedness of T. pallidum and Treponema carateum and is similar to the development of humoral responsiveness during syphilis infection.

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Roxithromycin (RU 965), a new macrolide antibiotic, was shown to be effective for therapy of active syphilis in rabbits. Dark-field-positive lesions were produced in adult male rabbits by intradermal inoculation of approximately 10(6) Treponema pallidum organisms at each of 11 sites. Beginning 7 days after infection, six animals per group were treated with benzathine penicillin G (200,000 U, intramuscularly, weekly for 2 weeks) or roxithromycin (15 mg/kg of body weight, orally, twice daily for 15 days); six animals were not treated. Chancres in untreated animals were dark-field positive throughout the 16-day observation period; all benzathine penicillin-treated rabbits were dark-field negative 1 day after the initiation of therapy. Five of six animals treated with roxithromycin were dark-field negative on day 3 following the initiation of therapy; the sixth animal was dark-field negative by day 6. Lesions in untreated animals reached a mean (+/- standard deviation) maximum diameter of 14.7 +/- 1.91 mm compared with 8.4 +/- 3.6 mm for benzathine penicillin-treated (P less than 0.005) and 10.4 +/- 1.2 mm for roxithromycin-treated (P less than 0.001) animals. Ulceration occurred at 62 of 66 lesions in untreated animals compared with 0 of 66 lesions in each treated group. At 3, 6, and 12 weeks postinfection, Venereal Disease Research Laboratory antibody titers were significantly higher (P less than 0.05) in untreated than in treated animals. Titers in penicillin-treated versus roxithromycin-treated animals were significantly different at 6 weeks postinfection but not at 3 and 12 weeks postinfection. Transfer of tissue from treated rabbits to seronegative recipient animals did not reveal any evidence of persistent infection in the benzathine penicillin- or roxithromycin-treated animals. These findings indicate that benzathine penicillin and roxithromycin, at the doses indicated above, are effective in treating active syphilis in rabbit model.

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The persistence or loss of IgG and IgM antibody specificities for individual polypeptides of Treponema pallidum after therapy for syphilis was examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and by the Western blot technique. Both IgG and IgM antibodies to as many as 12 treponemal antigens, including a major 47-kdalton molecule, were evident in plasma from patients with untreated primary syphilis. IgM reactivity declined rapidly and uniformly after therapy, whereas IgG persisted despite some diminution in intensity of staining. Faint-to-moderate IgM and strong IgG antibody reactivities to at least 22 treponemal antigens (12-85 kdaltons) were identified in plasma from patients with untreated secondary and early latent syphilis. Again, IgG antibody declined slightly in staining intensity after treatment but continued to show reactivity against all molecules detected initially. IgM antibody reactivity declined more rapidly and was lost entirely against some determinants, including the 14- and 12-kdalton molecules. Immunofluorescence titers of IgG and IgM antibodies to T. pallidum in sera from these patients generally correlated with results of Western blot analysis. Antibody to the 12-, 14-, and 47-kdalton molecules of T. pallidum may have potential diagnostic applications.

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A 27-year-old man with documented hypersensitivity to penicillin was treated intramuscularly for asymptomatic neurosyphilis with ceftriaxone (1 g daily for 14 days). After treatment the serum titer in the VDRL (Venereal Disease Research Laboratory) test declined from 32 to four dilutions. Lumbar punctures at months 3, 6, 9, and 28 after treatment revealed normalization of the cell count in cerebrospinal fluid and a decline in the VDRL titer in cerebrospinal fluid from four to one dilution(s). Western blot analysis revealed the presence in serum of IgG antibodies to at least 17 treponemal antigens and in cerebrospinal fluid of antibodies to at least ten treponemal antigens. Following ceftriaxone therapy serum and cerebrospinal fluid IgG reactivity to all antigens steadily decreased in intensity. These results indicate that ceftriaxone may provide a useful alternative therapy for penicillin-allergic patients with neurosyphilis.

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The development of IgM and IgG antibody responses to antigenic molecules of Treponema pallidum was examined in intratesticularly and intradermally infected rabbits by use of immunofluorescence (IF) and Western blotting techniques. IgM antibody was first detectable on day 6 following intratesticular infection and reached maximal IF titers during the period of clinical orchitis (days 10-17). IgG reached peak IF titers in the resolution period following clearance of most organisms from the testes (after day 17). Initial IgM antibody responses on day 6 were directed against the 46-, 43-, and 37-kdalton molecules, with reactivity to the 14- and 12-kdalton molecules appearing on day 10. IgG antibody, which was first apparent in the Western blot on day 6, was directed against the 37-kdalton molecule. IgG antibody to the 46-kdalton molecule was first apparent on day 13, and the full spectrum of 22 molecules was recognized on day 31. Curative therapy of intradermally infected rabbits one week after infection resulted in lower IgG antibody titers but did not abrogate the development of humoral responses to all of the major antigens.

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Popliteal lymph nodes from eight New Zealand white rabbits with clinical or serological evidence of naturally acquired infection with Treponema paraluis-cuniculi were transferred to rabbits that had not been exposed to this infection. Lymph nodes from two rabbits successfully transmitted infection. The nodes from one of these rabbits transmitted infection during both the acute and chronic stages of infection. Recipients that were successfully infected showed concomitant antibody responses in the Venereal Disease Research Laboratory (VDRL), rapid plasma reagin (RPR), and fluorescent treponemal antibody-absorption (FTA-ABS) tests six to 10 weeks after inoculation; recipients of uninfected nodes showed no change in serological state. Antibody responses were followed by the development of dark field positive genital lesions 14 to 15 weeks after inoculation.

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IgG and IgM antibody specificities for antigens of Treponema pallidum Nichols strain were determined by using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and the western blot technique in sera from patients with untreated syphilis, normal persons, persons with biologic false-positive tests for syphilis, and sexual contacts of persons with infectious syphilis. IgG reactivities of sera from individuals with primary syphilis varied considerably but consistently exhibited strong reactivity to a 48-kilodalton band. Sera from patients with secondary and early latent syphilis uniformly demonstrated reactivity to 22 separate polypeptide antigens; decreased reactivity was seen in late latent syphilis. Normal and biologic false-positive sera showed weak IgG reactivity against none to 12 polypeptides. Sera from asymptomatic contacts of persons with infectious syphilis showed reactivity to a varying number of treponemal antigens, including some reactions not seen with normal sera. IgM reactivity was most prominent in secondary syphilis but was demonstrable at all stages of disease.

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Thirteen hybrid cell lines which produce mouse monoclonal antibodies to Treponema pallidum, the causative agent of syphilis, have been established. All of the monoclonal antibodies react with T. pallidum, Nichols strain, in ELISA and in immunofluorescence assays, but do not react with normal rabbit testicular tissue in the ELISA. Two of these antibodies were demonstrated to react with the nonpathogenic treponemes T. phagedenis, biotype Reiter, T. refringens (Noguchi strain), T. vincentii, and T. denticola (strains 11 and W), as well as with Borrelia recurrentis, Leptospira interrogans, serogroup Canicola, and the swine pathogen T. hyodysenteriae. The remaining 11 antibodies react with four recently isolated strains of T. pallidum, but with none of the related nonpathogens nor with Borrelia or Leptospira. Thus, our results to date indicate that these monoclonal antibodies may identify antigenic determinants that are specific either for T. pallidum alone or for those treponemes which are pathogenic for humans. The molecular specificities of six of the 13 antibodies were determined by Western blotting. We anticipate potential usefulness of these antibodies in the investigation of the antigenic structure of T. pallidum, the taxonomic study of the pathogenic and nonpathogenic treponemes, and in the diagnosis of syphilis.

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