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The purpose of this study was to evaluate the diagnostic performance of the LIAISON Borrelia Screen (Diasorin, Saluggia, Italy), a new automated immunoassay based on the chemiluminescent technology (chemiluminescence immunoassay). To assess whether a decrease in a negative value in the anti-VlsE immunoglobulin G (IgG) antibody titer was correlated with a positive response to treatment, a group of serially collected serum samples from 67 patients with culture-confirmed erythema migrans was retrospectively studied. All the patients had been treated with antibiotics and were free of disease within 3 to 6 months of follow-up. All the 15 patients who were found to be IgG positive at the time of enrollment and who were bled at least four times during the follow-up became IgG seronegative at 2 to 6 months posttreatment. These results indicate that a decline in the anti-VlsE antibody titer coincides with effective antimicrobial therapy in patients with early localized Lyme disease.

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. The diagnosis of syphilis depends on clinical findings, examination of lesions for treponemes, and/or serologic tests. Serologic tests are divided into nontreponemal and treponemal tests. Nontreponemal tests are useful for screening, while treponemal tests are used as confirmatory tests. In practice, two or three assays are performed in series for the serologic diagnosis of syphilis (22, 28). First, sera are screened in a microflocculation assay, such as the Venereal Disease Research Laboratory test (VDRL), using nontreponemal antigens (25). Reactive sera are then tested for antibodies specific for Treponema pallidum antigens by using the fluorescent treponemal antibody absorption assay (FTA-ABS) or the microhemagglutination assay (MHA-TP) (12, 22, 28). Since the mid-1980s, the Western blot assay (WB), set up with boiled sodium dodecyl sulfate extracts of T. pallidum, has been introduced as an alternative to the other confirmatory methods (5, 13, 15). In addition, among the treponemal tests, several enzyme immunoassays have been described and evaluated, showing sensitivities and specificities similar to those of FTA-ABS and MHA-TP (9, 11, 23, 37). Currently, the T. pallidum immobilization test (TPI), the first treponemal antibody test developed (by Nelson and Mayer in 1949 [26]), is limited to mostly research purposes, since it is complex and technically difficult. The test is based on the ability of the patient’s antibody to bind to the surface of T. pallidum (2) and to immobilize living spirochetes in the presence of complement, as observed by dark-field microscopy. TPI is accepted as a specific test for syphilis, though it is less sensitive than the newer treponemal tests (30). Previous observations from our laboratory showed the high specificity of surface immunofluorescence assay (SIFA) performed with live Borrelia burgdorferi spirochetes for the detection of serum-specific antibodies against surface antigens of the Lyme disease agent (7). In this study, we investigated the sensitivity and specificity of SIFA both for the detection of specific antibodies against T. pallidum and for the serologic diagnosis of syphilis.

The purpose of this study was to evaluate the diagnostic performance of LIAISON Treponema Screen (DiaSorin, Saluggia, Italy), a new automated chemiluminescence immunoassay (CLIA), in comparison with that of rapid plasma reagin (RPR) and the following currently used treponemal tests: hemagglutination test (TPHA), immunoenzymatic assay (EIA), and Western blot (WB). First, a retrospective study was performed with a panel of 2,494 blood donor sera, a panel of 131 clinical and serologically characterized syphilitic sera, and 96 samples obtained from subjects with potentially interfering diseases or conditions. A prospective study was also performed by testing 1,800 unselected samples submitted to the Microbiology Laboratory of the St. Orsola Hospital in Bologna, Italy, for routine screening for syphilis. As expected, RPR was the least specific method, especially when potentially cross-reacting sera were tested. On the contrary, all of the treponemal tests proved to be very specific (99.9%) and they performed with the following sensitivities: 100% (WB), 99.2% (CLIA), 95.4% (EIA), and 94.7% (TPHA).

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.