Laboratory evidence for impaired cellular immunity in different stages of syphilis

Abundant evidence suggests that Treponema pallidum (T.p.) escapes humoral immune defence despite the host produces antibodies early in the infection. Since the serologic responses in syphilis have been studied in detail this paper focuses on the cellular immune mechanisms. For this purpose the leukocyte migration inhibition was investigated in 17 patients in different stages of syphilis. Leukocyte migration inhibition assay was performed before, and 7 days, 3 weeks, 2 mo. and 1 yr after start of treatment. Ultrasonicated T.p. were used as antigen corresponding to 5 X 10(6) to 2 X 10(7) Treponema pallida per ml. Controls without antigen, with addition of Concanavalin. A instead of T.p. and using cells of normal volunteers were run. There was no leukocyte migration inhibition before treatment, suggesting nonexistent or depressed cellular immunity in the untreated syphilitic patient. Significant leukocyte migration inhibition, however, was observed as early as 2 days after start of treatment, being most pronounced after 1 week. Hypothetical circulating blocking factors for cellular immune reactions might be present in the untreated syphilitic patient, which become abolished after therapy. Since stimulation with Con A of syphilitic leukocytes gave normal results even before treatment in the syphilitic patient, there might be a specific block of leukocyte migration inhibition against T.p.

[The SPHA technic (solid phase hemadsorption) in syphilis serology. A year's experience in routine laboratory procedure]

The first results in routine syphilis serology with the new solid-phase hemadsorption assay (SPHA) are presented. Sera (63019) were screened by the VDRL test and by the automated hemagglutination assay with Treponema pallidum antigen (AMHA-TP). Samples reactive to one or both of these tests were further examined by the FTA-ABS test, the IgM-FTA-ABS test, the 19S IgM-FTA-ABS test (IgM-FTA-ABS test performed with the 19S fraction of the serum after gelfiltration) and the IgM-SPHA test. IgM-SPHA reactive sera derived from patients who were in the early stage or in the phase of latency (of undefinable duration), further from patients with active neurosyphilis and from 26 patients after reinfection. Erroneous results in the IgM-FTA-ABS test caused by a competitive inhibition of IgM by IgG can be eliminated by the IgM-SPHA method. The agreement between 19S IgM-FTA-ABS test and IgM-SPHA test is above 96.3%. As compared to the fluorescence test, the IgM-SPHA test is simpler to perform and can be easily automated.

[Serological diagnosis of syphilis by the SPHA test (author's transl)]

Despite the availability of a broad spectrum of specific and non-specific tests for the serodiagnosis of syphilis, the interpretation of the results may be difficult and may frequently not provide sufficient information for a precise decision on the needs for antisyphilitic treatment. The present paper reports on the serological IgM tests (IgM-FTA-ABS; 19S-IgM-FTA-ABS) and, in particular, on the newly-developed SPHA test (solid phase hemadsorption). Present experience indicates that for the first time in syphilis serology this test unifies the advantages of high specificity, high sensitivity, low costs and extraordinary clinical value for the decision whether or not the patient needs antisyphilitic treatment.

Diagnosis of neurosyphilis by examination of the cerebrospinal fluid

Thirty-six patients with reactive results in the cerebrospinal fluid to the Treponema pallidum haemagglutination assay (CSF-TPHA) were investigated by further serological tests for confirmation of active neurosyphilis. The results of the TPHA and fluorescent treponemal antibody tests were reactive in all CSF samples from patients with acute untreated neurosyphilis and from most patients with late latent syphilis but no signs of involvement of the central nervous system. The demonstration of 19S-IgM antibodies against Treponema pallidum in the CSF was a better indication of activity of the disease than the Venereal Disease Research Laboratory test. Ten of 11 patients with untreated acute neurosyphilis had reactive results in the solid-phase haemadsorption test for CSF-IgM (CSF-IgM-SPHA test). The TPHA index, which relates the CSF-TPHA titre to the albumin quotient and thus excludes errors from disturbed function of the blood-brain barrier, was above 100 in all but one of the patients with acute neurosyphilis but below 100 after treatment. Patients with late latent syphilis and without CNS signs had TPHA indices below 5. Thus a nonreactive CSF-TPHA test result excludes neurosyphilis but reactive CSF-IgM-SPHA results and TPHA indices above 100 strongly indicative active disease.

Cerebrospinal fluid immunoglobulins in neurosyphilis

Using the fluorescent treponemal antibody-absorption (FTA-ABS) test and the solid phase haemadsorption assay (SPHA) Treponema pallidum-specific IgA was found in the cerebrospinal fluid (CSF) of patients with neurosyphilis but not in those with late latent syphilis. The presence of T pallidum-specific IgA in the CSF may inhibit the antitreponemal activity of IgG and thus play some part in the pathogenesis of neurosyphilis.

Specificity of the Treponema pallidum haemagglutination test. Analysis of results

The automated haemagglutination assay using Treponema pallidum antigen (AMHA-TP) and the Venereal Disease Research Laboratory (VDRL) test were used to examine 330 163 sera. Reactive results were checked by the fluorescent treponemal antibody-absorption (FTA-ABS) test. When isolated reactivity or non-reactivity in the AMHA-TP test was investigated an estimated margin of error of 0.7% probably wrongly non-reactive and 0.008% presumably false non-reactive results were found. These figures were confirmed by randomised FTA-ABS tests on 504 sera with repeat AMHA-TP tests. The latter is therefore still the most reliable and practicable method for mass screening for syphilis.

Solid-hase hemadsorption: a method for rapid detection of Treponema pallidum-specific IgM

A solid-phase hemadsorption (SPHA) technique for the rapid detection of Treponema pallidum-specific IgM antibodies is described. The demonstration of these immunoglobulins permits differentiation between a recent and a long-lasting infection and facilitates the decision as to whether or not a patient should receive therapy for syphilis. Errors that occur in the fluorescent treponemal antibody-absorbed test with IgM conjugate (IgM-FTA-Abs test) because of high titers of T. pallidum-specific IgG (competitive inhibition), rheumatoid factors, or 7S IgM do not occur with the SPHA technique. This test is easy to perform; it requires only microtiter plates coated with antisera to human IgM in addition to the standard T. pallidum hemagglutination reagents. As compared with the Veneral Disease Research Laboratory (vdrl) test, SPHA test has the advantage of being specific for T. pallidum; furthermore, IgM antibodies can be demonstrated earlier after infection and disappear sooner after adequate treatment of syphilis.