Treponema pallidum surface immunofluorescence assay for serologic diagnosis of syphilis

The Traditional or Reverse Algorithm for Diagnosis of Syphilis: Pros and Cons

We reviewed relevant syphilis diagnostic literature to address the question “What diagnostic considerations should be taken into account when screening for syphilis using the traditional or reverse algorithm?” Improved laboratory diagnosis of syphilis is an important element of the effort to reduce syphilis rates. Screening for syphilis is performed using either a nontreponemal or treponemal test (part of the traditional or reverse algorithm, respectively). Both syphilis algorithms are used by laboratories. However, there are limited data on the performance and cost-effectiveness of the algorithms. An expert panel generated “key questions” in the laboratory diagnosis of syphilis. This paper pertains to the key factors that should be considered when deciding whether to screen for syphilis using either the traditional or the reverse algorithm. A systematic literature review was performed, and tables of evidence were created to address this question.

Evaluation of three automated Treponema pallidum antibody assays for syphilis screening

The accuracy of the test is critical for the syphilis serology diagnosis. This study aims to evaluate the values of the Elecsys syphilis assay, the Architect syphilis assay, and the Mindray syphilis assay, as syphilis screening tests for pregnant women and patients with syphilis or other diseases. A reverse algorithm was used for the syphilis serology diagnosis. Serum samples (n = 584) were tested with three automated screening assays. All reactive sera by one, two, or three screening assays were further analyzed with the tolulized red unheated serum test (TRUST). Inconsistent results were confirmed by the Treponema pallidum particle agglutination assay (TPPA). The final patient diagnosis was made according to the results of syphilis serology, clinical evidence, and past medical history. The sensitivity, specificity, accuracy, and kappa value of each assay were as follows: for the Elecsys syphilis assay, 100.0%, 98.5%, 98.6%, and 0.927, respectively; for the Architect syphilis assay: 100.0%, 94.5%, 95.0%, and 0.770; and for the Mindray syphilis assay: 100.0%, 97.0%, 97.3%, and 0.862. The McNemar test showed that there were significant differences in the performance between the Elecsys syphilis assay and the Architect syphilis assay (P < 0.001), and between the Mindray syphilis assay and the Architect syphilis assay (P = 0.001). Our study demonstrated that three automated Treponema pallidum antibody assays generally showed high sensitivities and specificities, and so, they are suitable for use in screening for syphilis. The performances of the Elecsys syphilis assay and the Mindray syphilis assay are superior to Architect syphilis assay.

Contribution of a Comparative Western Blot Method to Early Postnatal Diagnosis of Congenital Syphilis

Serology has a pivotal role in the diagnosis of congenital syphilis (CS), but problems arise because of the passive transfer of IgG antibodies across the placenta. The aim of this study was to assess the diagnostic value of a comparative Western blot (WB) method finalized to match the IgG immunological profiles of mothers and their own babies at birth in order to differentiate between passively transmitted maternal antibodies and antibodies synthesized by the infants against Treponema pallidum Thirty infants born to mothers with unknown or inadequate treatment for syphilis were entered in a retrospective study, conducted at St. Orsola-Malpighi Hospital, Bologna, Italy. All of the infants underwent clinical, instrumental, and laboratory examinations, including IgM WB testing. For the retrospective study, an IgG WB assay was performed by blotting T. pallidum antigens onto nitrocellulose sheets and incubating the strips with serum specimens from mother-child pairs. CS was diagnosed in 11 out of the 30 enrolled infants; 9/11 cases received the definitive diagnosis within the first week of life, whereas the remaining two were diagnosed later because of increasing serological test titers. The use of the comparative IgG WB testing performed with serum samples from mother-child pairs allowed a correct CS diagnosis in 10/11 cases. The CS diagnosis was improved by a strategy combining comparative IgG WB results with IgM WB results, leading to a sensitivity of 100%. The comparative IgG WB test is thus a welcome addition to the conventional laboratory methods used for CS diagnosis, allowing identification and adequate treatment of infected infants and avoiding unnecessary therapy of uninfected newborns.

Improving syphilis screening in deceased organ donors

BACKGROUND

Current U.S. policy requires screening of all deceased organ donors for syphilis infection. To date, information on syphilis test performance in this population is limited.

METHODS

All donors with a positive rapid plasma reagin (RPR) and matched donors with negative RPR who were evaluated by one organ procurement organization from January 1, 2000, to September 30, 2012, were retrospectively tested, using retained, residual serum, with two alternate RPR tests and four treponemal-specific tests: A fluorescent treponemal antibody absorption test, a microhemagglutination test, a chemiluminescence immunoassay (CLIA), and a Treponema pallidum particle agglutination (TP-PA) test.

RESULTS

Thirty-two of 3,555 (0.9%) potential deceased organ donors screened during the study period showed a positive RPR; 61 RPR-negative matched donor samples were studied as well. Thirteen (40.6%) of the RPR-positive donors were found to be false-positive based on confirmatory TP-PA. As compared to TP-PA, the sensitivity of the fluorescent treponemal antibody absorption, microhemagglutination, and CLIA was 87.5%, 91.7% and 100%, respectively. The CLIA and TP-PA results were 100% concordant. Only 17 (53.1%) of the RPR-positive donors had a total of 46 organs recovered for transplantation.

CONCLUSION

Current screening of deceased organ donors by RPR yields a significant number of false-positive results. Use of alternative tests or the routine use of confirmatory tests may reduce the frequency of false-positive results in deceased organ donors.

Performance Evaluation of CLIA for Treponema Pallidum Specific Antibodies Detection in Comparison with ELISA

OBJECTIVES

In this study we aimed to evaluate the performance effects of chemiluminescence assay (CLIA) for Treponema pallidum specific antibodies detection, and to compare T. pallidum specific antibodies detection accuracy between CLIA and ELISA with TPPA (T. pallidum particle agglutination assay) as a confirmatory test.

METHODS

A total of 865 samples from suspected syphilis patients and preoperative patients were included, in which T. pallidum specific antibodies were simultaneously detected by CLIA and ELISA. Among them, 457 samples were determined by TPPA.

RESULTS

All coefficients of variation (CVs) of ELISA in high-, median-, and low-level samples were more than 5% and the maximum CV was 54.39% in the low-level sample. CVs of CLIA in different-level samples were all below 5%. Among the three assays the Spearman correlation and Kappa coefficients were 0.771 (P ≤ 0.001) and 0.854 (P ≤ 0.001, CLIA vs. ELISA), 0.806 (P ≤ 0.001) and 0.897 (P ≤ 0.001, ELISA vs. TPPA), 0.937 (P ≤ 0.001) and 0.967 (P ≤ 0.001, CLIA vs. TPPA), respectively. The area under the receiver operating characteristic curve (AUC) of CLIA was higher than that of ELISA (0.994 vs. 0.989) with TPPA as the confirmatory test. In 18 discrepant samples the consistency rate between CLIA and TPPA was elevated compared with that between ELISA and TPPA (72.22% vs. 27.78%, P = 0.008). In gray zone, the consistency rate of CLIA with TPPA was higher than that of ELISA with TPPA (90.91% vs. 41.67%, P = 0.027).

CONCLUSIONS

Compared with ELISA, CLIA is more reliable, sensitive and accurate to detect serum T. pallidum specific antibodies. In the future it may be an alternative test with higher sensitivity to ELISA.

Syphilis in the United States: an update for clinicians with an emphasis on HIV coinfection

Diagnosis and treatment of syphilis are challenging because of its variable clinical presentation and course and the lack of definitive tests of cure after treatment. This review of the most recent literature on the epidemiology, clinical manifestations, current diagnosis, and treatment of syphilis is focused toward clinicians who treat patients with this disease. Syphilis coinfection with human immunodeficiency virus is emphasized because it is increasingly common in the United States and affects the initial presentation, disease course, diagnosis, and treatment of syphilis. Of particular consequence is the effect of human immunodeficiency virus on the clinical diagnosis, prevalence, and course of neurosyphilis, one of the most serious consequences of syphilis infection.

Characterization of the Western blotting IgG reactivity patterns in the clinical phases of acquired syphilis

We standardized the Western blotting (WB) method for detecting Treponema pallidum IgG (Tp-IgG) antibodies in sera samples of patients with syphilis and correlated the reactivity profile of bands with the clinical phases of the disease. The WB Tp-IgG has 100% sensitivity and 99.5% specificity. The clinical phases of the disease were associated with the reactive bands from TpN15 to TpN47. Quantitative Venereal Disease Research Laboratories was used to assist the WB Tp-IgG analysis. In primary syphilis, the reaction intensity for the antigenic band TpN47 was usually more intense when compared with other clinical phase. In secondary and sometimes in early latent syphilis, antibodies reacted with high numbers of antigenic proteins of T. pallidum. In late latent syphilis, various bands became negative, but the TpN15 and TpN47 were reactive. In tertiary syphilis, we observed reactivity with the TpN15 band and low reactivity with the TpN47. We concluded that WB Tp-IgG could be used to confirm serologic tests and characterize clinical phases of syphilis.

Current Controversies in the Management of Adult Syphilis

Clinical management of patients with syphilis is controversial. This article summarizes recent research on syphilis treatment efficacy and outcomes and is based on a comprehensive systematic review of published literature, relevant abstracts, conference proceedings, technical reports, and guidelines. Penicillin remains the drug of choice for the treatment of syphilis. Although several studies have suggested that azithromycin may have clinical efficacy, macrolide resistance has been widely documented among strains of Treponema pallidum, and treatment failures have been reported. Ceftriaxone is effective for the treatment of syphilis when used in multiple-dose regimens. Lumbar puncture should be performed for human immunodeficiency virus-infected patients with syphilis of >1 year's duration and a serum nontreponemal test titer > or =1 : 32, as well for other patients for whom the clinical suspicion of neurosyphilis is high. Newer laboratory tests for syphilis are undergoing extensive evaluation and may prove to be useful for future clinical care. American and European approaches to syphilis treatment are similar, but they vary across several parameters.

A multianalyte Dot-ELISA for simultaneous detection of malaria, Chagas disease, and syphilis-specific IgG antibodies

A multianalyte Dot-enzyme-linked immunosorbent assay (Dot-ELISA-Multi) with Trypanosoma cruzi epimastigote alkaline extract (EAE), trypomastigote excreted-secreted antigen (TESA), recombinant protein derived from 19-kDa C-terminal region of the Plasmodium vivax merozoite surface protein 1 (PvMSP1(19)), Plasmodium falciparum Zwittergent extract (Pf-Zw), and Treponema pallidum Zwittergent extract (Tp-Zw) was standardized and evaluated as a method for surveying IgG-specific antibodies in Chagas disease, malaria, and syphilis in a single test. The study was carried out on serum samples from 52 patients with chronic Chagas disease, 103 individuals with current (parasitemic) or past malaria (aparasitemic), 43 patients with syphilis, 21 individuals with heterologous antibodies, and 100 blood donors. Dot-ELISA-Multi yielded 99% specificity for Chagas disease and 100% for malaria and syphilis. The test sensitivity was 100% for chronic Chagas disease, 88% for syphilis, 90% for P. vivax, and 47% for P. falciparum. In past malaria individuals, positivity was 92%. Therefore, Dot-ELISA-Multi can be useful under field conditions where laboratory facilities and resources are scarce, for small-scale epidemiologic studies.

Evaluation of specific antibodies for early diagnosis and management of syphilis

For many years, tests for cardiolipin antibodies Tp15, Tp17, Tp45, Tp47, and other specific Treponema pallidum antibodies, have been used to diagnose syphilis, but the timing and rates of antibody detection differ in primary and secondary syphilis. Our objective was to determine the value of the rapid plasma reagin (RPR) test, T. pallidum passive particle agglutination (TPPA) assay and Western blotting (WB) in the diagnosis of early syphilis, by studying 67 patients (20 with primary and 47 with secondary syphilis) over a recent 5-year period. All patients were tested before and 21/67 were tested after treatment. Western blotting showed that while there was a difference within the study group in terms of the number of bands detected, all patients with primary syphilis demonstrated the 47-kDa antibody, but RPR and TPPA were negative in some patients. Eighteen to 24 months after treatment, 21/67 patients were tested by WB and TPPA; antibodies to T. pallidum became undetectable within 24 months after treatment in 29% of patients. By RPR, 29% patients had negative titers within 6 months of treatment, and 86% returned to normal within 24 months. We conclude that detection of specific 47-kDa T. pallidum antibodies can be used to diagnose primary syphilis. By RPR, antibodies disappear in 6-24 months after treatment in many patients, suggesting that a change in titer may be an indicator of treatment success.

Immunological evaluation and cellular location analysis of the TprI antigen of Treponema pallidum subsp. pallidum

The TprI antigen of Treponema pallidum subsp. pallidum is a putative virulence factor predicted to be located in the outer membrane of the syphilis spirochete. In this study, we analyzed the immune response against TprI and its subunits in sera collected both from rabbits experimentally infected with the Nichols strain and from patients with syphilis, showing a different pattern of reactivity toward the antigen in these two groups of samples. The protective ability of recombinant TprI and its hypothetical outer membrane location were also investigated. Although no rabbit was protected after challenge, immunoelectron microscopy results, to be further investigated, were compatible with the outer membrane location of the antigen.

Phagocytosis of Treponema pallidum and reactive oxygen species production by isolated rat Kupffer cells

The in vitro phagocytosis of viable Treponema pallidum subsp. pallidum by isolated rat Kupffer cells, studied by immunofluorescence staining of Kupffer cells-associated bacteria, showed that ingestion of live, unopsonized treponemes was slow: in fact, Kupffer cells started to be positive 1 h after infection, when only 4% of the cells presented small round fluorescent inclusion-like bodies. Thereafter, the number of positive cells progressively increased with time: 7%, 17%, 36%, and 69% of Kupffer cells were positive, respectively, 2, 4, 6 and 8 h after infection. Opsonization of T. pallidum with human immune serum did not substantially modify the percentage (8%) of Kupffer cells ingesting T. pallidum 1 h after infection, whereas opsonization significantly ( P<0.01) increased phagocytosis after 2, 4 and 6 h of incubation, when 44%, 58%, and 68% of Kupffer cells were positive, respectively. At 8 h after infection of Kupffer cells by opsonized T. pallidum, 75% of the cells were positive by immunofluorescence. Heat-inactivation of T. pallidum slightly enhanced phagocytosis. In contrast, opsonization of heat-inactivated spirochetes with specific antibodies significantly ( P<0.01) increased the phagocytosis of bacteria by Kupffer cells, beginning as early as 30 min after infection, when 65% of the cells were positive by immunofluorescence. The reactive oxygen species (ROS) production by Kupffer cells following incubation with spirochetes was also determined by chemiluminescence. Treponemes induced an oxidative burst in Kupffer cells in a dose-dependent manner and the generation of ROS was already detectable 20 min after the exposure of the Kupffer cells to treponemes and peaked at 35 min of incubation. Live, as well as live and opsonized, and heat-inactivated treponemes, induced an O(2)(-) production lower than that induced by heat-inactivated and opsonized spirochetes.

Western immunoblotting with five Treponema pallidum recombinant antigens for serologic diagnosis of syphilis

Five immunodominant Treponema pallidum recombinant polypeptides (rTpN47, rTmpA, rTpN37, rTpN17, and rTpN15) were blotted onto strips, and 450 sera (200 from blood donors, 200 from syphilis patients, and 50 potentially cross-reactive) were tested to evaluate the diagnostic performance of recombinant Western blotting (recWB) in comparison with in-house whole-cell lysate antigen-based immunoblotting (wclWB) and T. pallidum hemagglutination (MHA-TP) for the laboratory diagnosis of syphilis. None of the serum specimens from blood donors or from potential cross-reactors gave a positive result when evaluated by recWB, wclWB, or MHA-TP. The evaluation of the immunoglobulin G immune response by recWB in sera from patients with different stages of syphilis showed that rTmpA was the most frequently identified antigen (95%), whereas only 41% of the specimens were reactive to rTpN37. The remaining recombinant polypeptides were recognized as follows: rTpN47, 92.5%; rTpN17, 89.5%; and rTpN15, 67.5%. The agreement between recWB and MHA-TP was 95.0% (100% with sera from patients with latent and late disease), and the concordance between wclWB and MHA-TP was 92.0%. The overall concordance between recWB and wclWB was 97.5% (100% with sera from patients with secondary and late syphilis and 94.6 and 98.6% with sera from patients with primary and latent syphilis, respectively). The overall sensitivity of recWB was 98.8% and the specificity was 97.1% with MHA-TP as the reference method. These values for sensitivity and specificity were slightly superior to those calculated for wclWB (sensitivity, 97.1%, and specificity, 96.1%). With wclWB as the standard test, the sensitivity and specificity of recWB were 98.9 and 99.3%, respectively. These findings suggest that the five recombinant polypeptides used in this study could be used as substitutes for the whole-cell lysate T. pallidum antigens and that this newly developed recWB test is a good, easy-to-use confirmatory method for the detection of syphilis antibodies in serum.

Evaluation of recomWell Treponema, a novel recombinant antigen-based enzyme-linked immunosorbent assay for the diagnosis of syphilis

OBJECTIVE

To evaluate the diagnostic performance of an enzyme immunosorbent assay (recomWell Treponema) for the diagnosis of syphilis. The novel recombinant antigens Tpn47, TpN17 and TpN15 were utilized.

METHODS

A total of 782 human serum specimens, belonging to four different categories (blood donors, n = 200; routine laboratory screening for syphilis, n = 400; syphilis patients, n = 122; potential cross-reactors, n = 60), were evaluated to compare the sensitivity and specificity of the recomWell Treponema kit with a standard whole Treponema pallidum cell lysate antigen-based ELISA (Syphilis Screening) and with micro-haemagglutination (MHA-TP).

RESULTS

The overall specificity and sensitivity of the recomWell Treponema IgG was 98.9% and 98.3%, respectively. The specificity and sensitivity of Syphilis Screening ELISA was 98.7% and 98.3%, respectively. The agreement between recomWell Treponema and Syphilis Screening was 100%, 97.8%, 95.9% and 95% among the blood donor specimens, screening samples, syphilis specimens and the potential cross-reactors, respectively. Values of concordance varying from 96.7% to 98.3% were found in the different groups of sera between recomWell Treponema and MHA-TP. In addition, recomWell Treponema demonstrated a good diagnostic performance when used to detect the IgM to T. pallidum. No false-positive sera were identified and, in 17/19 samples from primary infection, an IgM immune response was found.

CONCLUSIONS

recomWell Treponema was shown to be a highly specific and sensitive method in all stages of syphilis screening and it can be considered as alternative to other ELISA tests based on native antigen preparations.

New tests for bacterial sexually transmitted diseases

Recent advances in diagnostic tests for sexually transmitted diseases include the development of a synthetic Venereal Disease Research Laboratory reagent that will improve the sensitivity and stability of nontreponemal serologic tests for syphilis. A second generation user friendly and high throughput nucleic acid amplification test for Chlamydia trachomatis and Neisseria gonorrhoeae has also been developed.