The sensitivity of syphilis assays in detecting different stages of early syphilis

Our aim was to determine the sensitivity of the Murex ICE enzyme immunoassay (EIA) as a screening test for early syphilis and to determine how many additional cases of infection were detected by performing additional tests when requested on clinical grounds.

This was an observational study on consecutive patients diagnosed with syphilis in the Department of Genitourinary Medicine, Edinburgh between January 1st 2004 and April 1st 2005. Additional tests were performed on sera that gave a positive or equivocal EIA on screening as well as by clinical request on sera from contacts of syphilis, and those with clinical signs of syphilis. Additional tests included a Venereal Diseases Research Laboratory (VDRL) carbon antigen test, a Treponema pallidum particle agglutination (TPPA) test, INNO-LIA line immunoblot assay, and an EIA specific for anti-treponemal IgM.

A total of 105 patients were diagnosed with syphilis: primary (50), secondary (26), early latent (8), and of unknown duration (21). The TPPA was the most sensitive test in primary syphilis and had a sensitivity of 96% (48/50), which was significantly higher ( P <0.05) than the sensitivity of 84% (42/50) for the screening EIA: seven of the EIA negatives were detected by EIA–IgM, six by TPPA, five by immunoblot, and two by VDRL. EIA–IgM was negative in six primaries; all were positive by TPPA and immunoblot.

We conclude that, in order to maximize the serological detection of primary syphilis a specific EIA–IgM test and a TPPA test should be performed whenever there is a clinical suspicion of primary infection. This is particularly important when an EIA such as Murex ICE is used as a single screening test as it is less sensitive than the TPPA in primary infection.

Absence of risk factors for false-positive test results in blood donors with a reactive test result in an automated treponemal test (PK-TP) for syphilis

BACKGROUND

Screening and confirmatory serologic tests for syphilis are known to generate false-positive results in low-risk populations, which include blood donors. This study assessed whether conditions previously reported to cause biological false-positive (BFP) test results for syphilis are relevant to contemporary syphilis testing of blood donors and the extent to which seropositive donors report a history of syphilis.

STUDY DESIGN AND METHODS

A history of conditions reported to be associated with BFP syphilis tests or a history of syphilis infection was assessed by a case-control study of donors with reactive and nonreactive automated treponemal test results, using an anonymous mail survey. Analysis of cases was stratified by fluorescent treponemal antibody absorption (FTA-ABS) result.

RESULTS

Adjusted ORs (95% CIs) for reported BFP-associated conditions were 1.3 (0.8-2.1) for FTA-ABS-positive cases and 0.8 (0.3-1.9) for FTA-ABS-negative cases. Among responding blood donors, syphilis history was reported in 78 (51%) of 153 FTA-ABS-positive cases, 0 of 142 FTA-ABS-negative cases, and 3 (0.4%) of 716 automated treponemal test (PK-TP)-negative controls.

CONCLUSION

Approximately half of donors with FTA-ABS-positive test results reported a syphilis history. There was no difference between reported BFP conditions for FTA-ABS-positive or FTA-ABS-negative cases and controls. This information may be useful when providing donors with better predonation or post-test counseling information about syphilis testing.

Treponema pallidum surface immunofluorescence assay for serologic diagnosis of syphilis

A surface immunofluorescence assay (SIFA) using live spirochetes was analyzed and compared with Western blot (WB), fluorescent treponemal antibody absorption (FTA-ABS), microhemagglutination (MHA-TP), and Treponema pallidum immobilization (TPI) assays for detecting serum antibodies to T. pallidum in patients with syphilis, in disease controls, and in healthy subjects. SIFA and WB were 99% sensitive (99 of 100 positive specimens) and specific (140 of 140 negative specimens); FTA-ABS showed a sensitivity and a specificity of 90 and 89% (90 of 100 positive and 125 of 140 negative specimens), respectively. MHA-TP showed a sensitivity of 84% (84 of 100 positive specimens) and a specificity of 98.5% (138 of 140 negative specimens). Finally, TPI had a sensitivity of 52% (52 of 100 positive specimens) and a specificity of 100% (140 of 140 negative specimens). The T. pallidum SIFA was therefore highly specific, showing no equivocal reactivities with control sera, and sensitive. The results suggest the possible use of SIFA as a confirmatory test in the serologic diagnosis of syphilis.

Not so slowly progressive visual loss

A 51-year-old man presented with bilateral progressive visual loss during a 2-month period. Visual acuity was 20/60 in both eyes with bilateral constricted visual fields. Funduscopy revealed bilateral disk pallor and arteriolar attenuation. His vision declined rapidly during the next 2 weeks. Investigations showed a positive cerebrospinal fluid Venereal Disease Research Laboratory test (1:8). A diagnosis of neurosyphilis was made, and treatment was started with high-dose intravenous and intramuscular penicillin.

Immunization with Treponema pallidum outer membrane vesicles induces high-titer complement-dependent treponemicidal activity and aggregation of T. pallidum rare outer membrane proteins (TROMPs)

The purpose of this study was to determine whether immunization with purified outer membrane vesicles (OMV) from Treponema pallidum (T.p. ) could elicit Abs capable of killing this organism. It is well established that the immunization of rabbits or mice with killed T.p. or with recombinant T.p. Ags has failed to generate serum killing activity comparable with that of infection-derived immunity. Because of the small amount of T.p. OMV obtainable, a single mouse was immunized with purified OMV. The mouse anti-OMV serum and infection-derived immune rabbit serum (IRS) were compared by reactivities on two-dimensional T.p. immunoblots and by the T.p. immobilization test, a complement-dependent killing assay. Whereas IRS detected >40 Ags, the anti-OMV serum identified only 6 Ags corresponding to proteins identified previously in the outer membrane. T.p. immobilization testing showed that IRS had a 100% killing titer of 1:44 and a 50% killing titer of 1:662. By comparison, the mouse anti-OMV serum had a significantly greater 100% killing titer of 1:1,408 and a 50% killing titer of 1:16,896. Absorption of the anti-OMV serum to remove Ab against outer membrane-associated lipoproteins did not change the 100% killing titer. Freeze-fracture analysis of T.p. incubated in IRS or anti-OMV serum showed that T.p. rare membrane-spanning outer membrane proteins were aggregated. This is the first demonstration of high-titer killing Abs resulting from immunization with defined T.p. molecules; our study indicates that the targets for these Abs are T. p. rare outer membrane proteins.

Influence of cardiolipin antibodies on the binding of treponemal specific antibodies in the fluorescence treponemal antibody absorption test and the Treponema pallidum immobilisation test

The aim of the present study was to investigate the biological role of cardiolipin antibodies during Treponema pallidum infection. Inhibition of the binding of treponemal specific antibodies at the early and late stages of infection by cardiolipin antibodies was shown in the fluorescence treponemal antibody absorption (FTA-ABS) test and T. pallidum immobilisation (TPI) test. Incubation of treponemes with cardiolipin antibodies followed by a second incubation with treponemal specific antibodies resulted in a reduction of the titres of the FTA-ABS test and the TPI test. The findings suggest that cardiolipin antibody production should be considered as a virulence mechanism of pathogenic treponemes with the purpose of evading the host defence mechanisms.

Studies on the lysozyme independence of immune immobilisation of Treponema pallidum and the frequency of lysozyme autoantibodies in syphilitic sera

The role of lysozyme in the immune immobilisation of Treponema pallidum is not yet fully understood. The T. pallidum immobilisation assay was used to demonstrate that the immobilisation and lysis of T. pallidum in vitro by antibodies (serum, IgG fraction or IgM fraction) and complement proceed in a lysozyme-independent mode. In the presence of lysozyme the rate of immobilisation increased. In contrast with its effect on Escherichia coli, the effect of lysozyme on T. pallidum was governed exclusively by its enzymic activity rather than by the cationic protein nature of the molecule. Lysozyme, released from stimulated phagocytes, induced formation of lysozyme antibodies in 59.6% of syphilis patients as determined by lysozyme antibody ELISA. The highest frequency was found in patients with untreated secondary syphilis, whereas untreated primary syphilis was only rarely accompanied by the presence of lysozyme antibodies. Cross-reactivities between lysozyme and treponemal antigens were excluded by immunoblotting. The autoantibodies did not influence the lysozyme activity. It was concluded that the formation of lysozyme antibodies is only an epiphenomenon in the host defence against treponemal infection.

IMMUNITY IN EXPERIMENTAL SYPHILIS. 3. ATTENUATION OF VIRULENT TREPONEMA PALLIDIUM BY GAMMA-IRRADIATION

Miller, James N. (University of California School of Medicine, Los Angeles). Immunity in experimental syphilis. III. Attenuation of virulent Treponema pallidum by gamma-irradiation. J. Bacteriol. 90:297-301. 1965.-Virulent, freshly isolated cells of Treponema pallidum strain Nichols suspended in a 50% rabbit serum-saline solution and exposed to a gamma-irradiation dosage of 652,800 r were rendered noninfectious without apparent loss of motility or change in observable morphological and staining characteristics. Although 5 x 10(7) gamma-irradiated organisms failed to elicit an immobilizing antibody response in rabbits, the same organisms retained their capacity to react with classical T. pallidum-immobilizing antibody.

A study of treponema pallidum haemagglutination positive blood donors in Singapore

The Treponema Pallidum Haemagglutination (TPHA) test has been used for screening of syphilis among blood donors in Singapore since September 1992. Among the 79 500 donations that were screened between September 1992 and December 1993, 191 were tested positive (incidence rate of 0.24%). Seventy-two donors (37.7%) were evaluated at the Department of Sexually Transmitted Disease Control clinic. Seventy-nine percent of these donors had high risk sexual exposure and 33.3% had a history of sexually transmitted diseases. Eighty-three percent of the donors were diagnosed to have late latent syphilis, 9.7% were diagnosed to have a serological scar and the remaining had secondary syphilis, early latent syphilis and a false positive reaction. At least 65.3% of these donors would have been missed if the reagin test was used alone as the screening test. Thus, the TPHA test is a good marker for screening those who have high risk sexual behaviour and it is a more sensitive test than the reagin test for screening blood donors.

Treponemicidal antibody measured by the "washed-killing" assay correlates with immunity in experimental rabbit syphilis

BACKGROUND AND OBJECTIVES

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.

GOAL OF THIS STUDY

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.

STUDY DESIGN

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.

CONCLUSION

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.

[Autoantibodies or immune defense against cholesterol?]

Serological study was made on the lues aspecific positive sera (BAP); The serum reactivity was demonstrated by Kolmer and rapid plasma reagin (RPR) tests. The specificity was verified by treponema immobilization est (TPIT), fluorescent treponemal antibody (FTA-ABS) and treponema haemagglutination (TPHA) tests. The BAP sera were studied by enzyme labelled immunoassay (ELISA) with the isolated antigen components of Kolmer and RPR tests. The previously supposed "cardio-BAP" appeared only about 50 per cent of the sera. Anti-cholesterol antibody was demonstrated in 38 sera of 112 (33.9%) and only one of 50 negative control sera (2%). To the author's knowledge anti-cholesterol antibodies have never been demonstrated before. The authors suppose it is an autoantibody and their new result will give new possibilities to understand and explain the role of cholesterol in the so called "cholesterol diseases". Additional research have to be made to specify the pathological importance and role in the disorders.

The importance of different components of normal human serum and lysozyme in the rapid immobilisation of purified Treponema pallidum, Nichols strain

OBJECTIVES

To study the role of different components in normal human serum and the role of lysozyme in rapid immobilisation of Percoll purified T pallidum (Nichols).

MATERIALS AND METHODS

The immobilisation of Percoll purified T pallidum was studied after pre-incubations with different serum fractions (Fr) of normal human serum (Fr 1, containing IgM; Fr 2, containing IgG and a low level of haemolytic complement, and Fr 1 (abs), depleted of IgG). A guinea-pig serum pool was used as a complement source in the immobilisation experiments. The influence was studied of removal of lysozyme from guinea-pig serum on the immobilisation reactions. Further experiments were performed, using a fluorescence technique, to detect C3b depositions on fixed treponemes and treponemes in suspension.

RESULTS

Rapid immobilisation of Percoll-purified treponemes by the NHS serum fractions occurred only after preincubation with Fr 1 and Fr 2 simultaneously. This was largely dependent on the presence of a small amount of haemolytic C in Fr 2. Removal of lysozyme reduced this rapid rate of immobilisation. In fluorescence experiments it was demonstrated that C3b deposition on fixed (that is damaged) treponemes occurred upon their incubation with Fr 2 or the combination of Fr 1 and 2. However, on treponemes in suspension C3b deposition occurred only after incubation with the combination of Fr 1 and 2.

CONCLUSION

The rapid immobilisation of Percoll purified treponemes by serum fractions from normal human serum requires antibodies of the IgM and IgG class, together with complement and lysozyme. Omission of one of these reactants slows immobilisation. Our experiments suggest that the reactants act in sequence: the loss of integrity of the outer membrane by an attack by IgM and C offers the opportunity for lysozyme to hydrolyse the peptidoglycan layer surrounding the cytoplasmic membrane of the treponemes, which then is accessible for attack by antibodies and C.

Syphilis serology in men attending the Andrology Clinic at Ga-Rankuwa Hospital

The worldwide resurgence of syphilis may have serious implications on neonatal morbidity. The aim of this study was to evaluate the seroprevalence of syphilis in men attending an infertility clinic. Blood samples from 782 males were screened using the titrated RPR and TPHA tests. If either of these tests was positive, FTA-ABs IgG was performed. The RPR was positive in 63 (8%) cases. In 24 (3%) patients the titer was 1:8 with positive TPHA and FTA-Abs IgG tests and these were regarded as current infections. Thirty-nine (4.9%) cases had RPR titers 1:8 with positive specific tests. These were probably patients either treated inadequately or in the early stage of primary syphilis. In addition, 92 (12%) patients were RPR negative but TPHA and FTA positive. This was evidence of previous exposure to syphilis. The overall seropositivity in this group was 20% (155 cases). Six hundred and twenty-seven (80%) tested negative with RPR and TPHA. Syphilis may still have a major impact on health in Southern Africa. Since syphilis is significantly associated with HIV seropositivity, efforts to prevent and control syphilis may also be important in limiting the spread of HIV.

HIV-1 infection among New York City inmates

A blinded seroprevalence survey for HIV-1 infection was conducted among individuals entering New York City (NYC) prisons in 1989. Data collected included age group, race/ethnicity, syphilis serologic results and self-admitted drug use. Remnant serum specimens were tested for HIV-1 antibody by enzyme-linked immunosorbent assay and confirmed by Western blot. Of 2236 inmates surveyed, 413 (18.5%) were HIV-1 positive. Rates varied by subgroup, and were higher for women than men (25.8 versus 16.1%; odds ratio 1.8; P less than 0.01), for drug users than inmates who denied drug use (25 versus 14%; odds ratio 2.3; P less than 0.01), for intravenous heroin users (43 versus 15% in drug users not using heroin), and for inmates with positive rapid plasma reagin test (RPR) results (34.5 versus 16.1% in RPR-negative inmates). Use of intravenous heroin was most strongly related, by logistic regression, to HIV-1 seropositivity. The results are among the highest found in US inmates, and suggest that there were 12,500 seropositive individuals incarcerated in 1989. This represents approximately 10% of the estimated number of seropositive individuals in NYC. The NYC Correctional System should be viewed as a front-line institution in the fight against AIDS through provision of HIV-related prevention services and clinical care, and drug treatment.

Neurosyphilis in human immunodeficiency virus type 1-seropositive individuals. A prospective study

The prevalence of neurosyphilis in human immunodeficiency virus type 1 (HIV-1)-seropositive (HIV+) persons was assessed during the course of a study of the neurological complications of HIV-1 infection. One hundred sixty-six asymptomatic HIV+ subjects, 63 neurologically symptomatic HIV+ subjects, and six at-risk HIV-1-seronegative (HIV-) control subjects underwent cerebrospinal fluid (CSF) analysis on entry into this longitudinal study. Three (1.8%) of the asymptomatic HIV+ subjects had both a reactive CSF VDRL test and a reactive CSF fluorescent treponemal antibody-absorption (FTA-ABS) test. Two of these three subjects had a history of appropriately treated early syphilis, and all had a reactive serum rapid plasma reagin test. Of the 63 neurologically symptomatic HIV+ subjects, one patient with dementia had both a reactive CSF VDRL test and a fluorescent treponemal antibody-absorption test. Subjective improvement in cognitive skills followed high-dose, intravenous penicillin therapy. Another subject had a penicillin-responsive myelopathy accompanied by a reactive CSF fluorescent treponemal antibody-absorption test result, but a nonreactive CSF VDRL. Unsuspected neurosyphilis is relatively common in our population of asymptomatic HIV+ subjects and may be responsible for neurological disease in a significant minority of neurologically symptomatic HIV+ persons. Cerebrospinal fluid examination should be performed in all HIV+ persons with a history of syphilis or serological evidence of syphilis, regardless of prior treatment. Additionally, neurosyphilis should be considered in the differential diagnosis of neurological disease in any HIV+ person.

Treponema pallidum-immobilizing antibodies in guinea pig experimental syphilis

Treponema pallidum-immobilizing (TPI) antibodies were examined in intradermally infected inbred strain 13 and adoptively immune inbred strain 2 guinea pigs. Both strains of animals produced TPI antibodies at or after 90 days of infection. TPI antibodies were not associated with the protective mechanism(s) operative after challenge in adoptively immune animals.

Juxta-articular bone lesions in tertiary yaws

A case of tertiary yaws in an immigrant from the Solomon Islands is presented. The report highlights the atypical features and diagnostic difficulties of late-stage treponemal infection.

In vitro and in vivo activities of sedecamycin against Treponema hyodysenteriae

Sedecamycin (lankacidin A), one of the lankacidin-group antibiotics, showed potent activity against Treponema hyodysenteriae. The MICs of sedecamycin against 79 field isolates of T. hyodysenteriae ranged from 0.78 to 12.5 micrograms/ml, the MIC for 90% of the strains tested (MIC90) being 3.13 micrograms/ml. The protective and therapeutic effects of sedecamycin were compared with those of carbadox, tiamulin, and lincomycin against experimental infection with T. hyodysenteriae in mice. The protective effect of sedecamycin was similar to that of carbadox, two times more potent than that of tiamulin, and three times greater than that of lincomycin. In the therapeutic test, sedecamycin showed activity similar to that of carbadox and was two times more active than both tiamulin and lincomycin. At doses of 10 mg or more of sedecamycin per kg, the recurrence of shedding of T. hyodysenteriae into the feces of mice was not detected for at least 8 weeks postmedication.

[Transient biological false-positive specific syphilis serology in a blood donor]

This paper reports the case of a 25 year-old blood donor with transient false positive specific syphilis serology and, furthermore, some transient immunological features similar to the findings in systemic lupus erythematosus.

Treponemal serology and blood groups on Bali island, Indonesia

As part of a multidisciplinary study of the population of Bali, Indonesia, 2452 blood samples from people of both sexes were tested for treponemal infection and blood groups. Analysis of blood groups of the 81 patients reactive to the Treponema pallidum immobilisation (TPI) test, who were considered to have latent or inactive yaws, compared with a control group of 552 healthy Balinese, showed that the ratio of MM to MN and NN phenotypes was 2.25 times higher in the patients than in the controls (chi 2(1) = 10.2, p less than 0.005). A speculative hypothesis is that yews infection gives people with the MM phenotype a lower selective fitness. This hypothesis could explain the low prevalence of the M gene in the Australo-Melanesian populations.

Immune immobilization of Treponema pallidum: antibody and complement interactions revisited

The Treponema pallidum immobilization test was designed for serodiagnosis of syphilis and is dependent upon specific antibody and a heat labile component of normal serum. Investigators have shown the component to be dependent upon divalent cations and it is presumed to be complement. Experiments were performed to reevaluate the interactions of antibody and complement and the mechanism of immobilization. The loss of treponemal motility was correlated to the loss of complement activity in the reaction mixture. When motility of treponemes incubated with immune serum IgG and complement had dropped to 50% (3.4 h), 72% of the available complement had been consumed. At the same time, treponemes incubated with normal serum IgG and complement were 82% motile and only 51% of the complement had been consumed. C6 deficient rabbit serum and C4 deficient guinea pig serum were used in conjunction with immune serum IgG to determine which components of the complement cascade were necessary for immobilization. Treponemes were not immobilized by either sera. Results suggest that the heat labile factor in normal sera is complement, that both early and late components of the complement cascade are necessary, and that the reaction proceeds via the classical complement pathway. Although T. pallidum is susceptible to the actions of antibody and complement, the organisms must interact with these components for at least 2 h before immobilization will result.

Immobilization and neutralization of Treponema pallidum attached to cultured mammalian cells

The in vitro effects of antibodies, complement, and (or) macrophages on Treponema pallidum have been previously characterized using relatively simple systems of organisms incubated with the immune components. In vivo, the more complex environment may alter immune reactivity. Experiments were performed to determine whether immobilizing and neutralizing antibodies retained their effectiveness in a more complex environment involving cultured mammalian cells. Two different protocols were used. In protocol A treponemes and normal or immune serum were mixed and added immediately to the cultured cells. In protocol B treponemes were preincubated for 18 h with cultured cells to maximize treponemal attachment; then normal or immune serum was added. With both protocols, attachment of organisms resulted in less efficient immobilization and neutralization. In further experiments, cultured cells were disrupted with Triton X, leaving cytoskeletal remnants on the vessel surface. Identical immobilization and neutralization experiments were performed in the presence of these remnants. In contrast to the findings with viable cultured cells, treponemal attachment to these nonviable remnants did not effect either antibody reaction. Attached organisms were immobilized or neutralized just as efficiently as unattached organisms. Results are discussed in terms of the altered immune reactivity in more complex in vitro environments.

Neurosyphilis

Syphilis and its consequent central nervous system sequelae remain clinical problems, especially when presenting in the unfamiliar acute meningeal forms of syphilitic meningitis and meningovascular syphilis. The diagnosis of neurosyphilis of all types depends on evaluation of spinal fluid reactivity as evidenced by pleocytosis and increased protein content with reactive serology. The cerebrospinal fluid is always abnormal in active disease, and only active disease responds to treatment. Penicillin remains the drug of choice for all forms of neurosyphilis, but disease progression has been frequently reported following the use of penicillin G benzathine. Documentation of cerebrospinal fluid resolution over the months following penicillin therapy is required to confirm curative treatment.

Prospects for improved laboratory diagnoses of treponemal infections and species differentiation

The serologic diagnosis of treponemal infections has depended in the past on a variety of tests in which specificity was defined on an epidemiologic rather than on an immunologic basis. The lipoidal antigen tests possess no immunologic specificity. Tests based on whole treponemal antigens, although they do have some immunologic specificity, react with antibodies other then those generated in the course of syphilis and yaws infections. Recent developments in biotechnology now permit the identification of immunologically specific antigens in Treponema pallidum, and cloning of appropriate genetic information in Escherichia coli has led to the production of pure specific reagents. These developments will finally place the serologic diagnosis of treponemal infections on a sound immunologic basis.

Binding of glycosaminoglycans to the surface of Treponema pallidum and subsequent effects on complement interactions between antigen and antibody

Acidified bovine serum albumin (acid BSA) reacts with glycosaminoglycans to form a precipitate. This reaction was adapted to Treponema pallidum to show glycosaminoglycans associated with the surface of the micro-organism. As testicular infection progressed from days 4 to 18, treponemes showed increasing amounts of these surface components. High speed centrifuging effectively removed the glycosaminoglycans, thus indicating that they were loosely bound. The subsequent addition of commercial preparations of hyaluronic acid or chondroitin sulphate resulted in their immediate adherence to the surface of the pathogens T pallidum and T pertenue, but not to the non-pathogens T vincenti, T denticola, or T phagedenis. The amount adhering to the treponemal surface varied depending on the concentration added. Intradermal inoculation showed that the virulence of T pallidum was not altered by the glycosaminoglycans associated with its surface. The coating of treponemes with hyaluronic acid or chondroitin sulphate did not interfere with neutralising antibodies or antibodies found by radioimmunoassay using whole organisms. In contrast, hyaluronic acid or chondroitin sulphate on the treponemal surface did interfere with immobilising antibodies. Results are discussed in terms of the potential role of the treponemal glycosaminoglycans in the infectious process.

Detection and functional characterization of early appearing antibodies in rabbits with experimental syphilis

Following testicular infection of rabbits with Treponema pallidum, different antibodies become detectable initially at the time of healing. Experiments were performed to determine a functional role for these antibodies. Rabbits were sacrificed after 4-8 days. Treponemal numbers steadily increased for 10-12 days. Thereafter, host defenses were sufficiently stimulated to begin clearing the organisms. Antibodies in serum and antibodies localized at the site of infection were quantitated using radioimmunoassay and enzyme-linked immunosorbent assay (ELISA) techniques. Anti-treponemal IgG was detected as early as day 4. Quantities of antibody correspondingly increased with time following infection. Treponema pallidum was harvested 7 and 14 days postinfection and tested for surface antibodies. With increasing days postinfection, more antibody was found on the organisms. Two functional properties of these antibodies were shown. Sera from 24 of 45 rabbits infected for 14 days immobilized T. pallidum in the presence of complement and 14-day sera blocked the attachment of T. pallidum to tissue culture cells. We suggest that antibody-mediated, complement-dependent immobilization of T. pallidum and blockage of attachment are at least partially responsible for healing of testicular lesions.

Monoclonal antibody with hemagglutination, immobilization, and neutralization activities defines an immunodominant, 47,000 mol wt, surface-exposed immunogen of Treponema pallidum (Nichols)

Radioimmunoprecipitation (RIP) analyses performed on 125I-surface-labeled Treponema pallidum cells using various immune sera revealed the presence of six major surface antigens (immunogens) with apparent molecular weights of 47 K, 36 K, 34 K, 32 K, 29 K, and 13 K. Among these, the 47 K surface antigen was most abundant. Radioimmunoprecipitation assays using 125I-labeled T. phagedenis biotype Reiter or immunoblot analyses using the same strain, failed to reveal the presence of the 47 K mol wt antigen in the representative nonpathogenic treponeme. Preabsorption of anti-T. pallidum immune rabbit serum (IRS) with the Reiter organism did not remove anti-T. pallidum antibodies from immune serum that reacted with the 47 K mol wt immunogen or other immunogens of T. pallidum present in the characteristic antigenic profile. Monoclonal antibodies (mAb) directed specifically against the 47 K mol wt immunogen of T. pallidum also failed to react with an analogous 47 K mol wt component in Treponema phagedenis biotype Reiter, further suggesting the unique presence of this antigen in pathogenic treponemes. The presence of the 47 K mol wt surface immunogen in pathogenic treponemes other than T. pallidum subspecies pallidum was also observed (43). Anti-47 K immunogen mAb was nonreactive against rabbit IgG or IgM. mAb directed specifically against the 47 K mol wt immunogen of T. pallidum was examined for strategic functional activities. It was found to be reactive in the microhemagglutination assay for T. pallidum antibodies, the T. pallidum immobilization test, and was found to be capable of significant blockage of attachment of virulent T. pallidum to host cells in tissue culture. Additional significant biological activity for the anti-47 K mol wt immunogen mAb was revealed through results of the in vitro-in vivo neutralization test of Bishop and Miller, in which a 99% or 100% neutralizing activity was demonstrated. The combined data of this study suggest that the 47 K mol wt immunogen of T. pallidum represents an abundant, immunodominant, surface-exposed immunogen possessing potential biological importance in the pathogenesis and immunology of T. pallidum infection. These studies serve to establish the first functionally defined immunogen for T. pallidum, which may represent the major immunogen of the organism.