Enzyme-linked immunospot assay for the diagnosis of active Treponema pallidum infection during the various stages of syphilis

Origin of Nontreponemal Antibodies During Treponema pallidum Infection: Evidence From a Rabbit Model

The origin of nontreponemal antibodies during syphilis infection is hotly debated. Here, we analyzed the immune response in rabbits immunized with various antigens. Inactivated treponemes elicited the production of low-titer nontreponemal antibodies in some rabbits. Cardiolipin combined with bovine serum albumin also induced anticardiolipin antibody production. These findings indicate that Treponema pallidum contained a cardiolipin antigen with weak immunogenicity. However, active T. pallidum induced higher nontreponemal antibody production with strong immunogenicity at an earlier time point, and the antibody titer was consecutive, suggesting the high nontreponemal antibody titer resulted from the combined effects of both the T. pallidum cardiolipin antigen and the damaged host-cell cardiolipin antigen during syphilis infection, the latter of which plays a major role in the induction of nontreponemal antibody production. Our study provides direct animal evidence of the origin of nontreponemal antibodies during T. pallidum infection.

How Can Elispot Add Information to Improve Knowledge on Tropical Diseases?

Elispot has been used as an important tool for detecting immune cells' products and functions and has facilitated the understanding of host-pathogen interaction. Despite the incredible diversity of possibilities, two main approaches have been developed: the immunopathogenesis and diagnosis/prognosis of infectious diseases as well as cancer research. Much has been described on the topics of allergy, autoimmune diseases, and HIV-Aids, however, Elispot can also be applied to other infectious diseases, mainly leishmaniasis, malaria, some viruses, helminths and mycosis usually classified as tropical diseases. The comprehension of the function, concentration and diversity of the immune response in the infectious disease is pointed out as crucial to the development of infection or disease in humans and animals. In this review we will describe the knowledge already obtained using Elispot as a method for accessing the profile of immune response as well as the recent advances in information about host-pathogen interaction in order to better understand the clinical outcome of a group of tropical and neglected diseases.

Usefulness of IgM-specific enzyme immunoassays for serodiagnosis of syphilis: comparative evaluation of three different assays

OBJECTIVES

IgM antibodies are usually the first to be produced during treponemal infection. Three commercially available enzyme immunoassays (EIA) for detection of IgM antibodies against Treponema pallidum were evaluated.

METHODS

Results of the Anti-Treponema-pallidum-ELISA (IgM; Euroimmun), Pathozyme Syphilis M Capture (Omega Diagnostics) and recomWell Treponema IgM (Mikrogen) were compared with those of the T. pallidum particle agglutination (TPPA) and the Venereal Disease Research Laboratory (VDRL) tests for 307 serum samples.

RESULTS

The overall sensitivity (95% confidence interval [CI]) of the TPPA was 100% (97.7-100%) compared to 83.3% (76.5-88.8%) of the VDRL, 88.5% (82.4-93.0%) of the Pathozyme, 84.6% (78.0-89.9) of the Euroimmun, and 73.6% (66.1-80.4%) of a modified recomWell test procedure. Specificities were in the range of 91.4-100%. In primary syphilis, sensitivities of the Pathozyme (89.8%; 95% CI, 79.2-96.2%) and Euroimmun tests (81.4%; 95% CI, 69.1-90.3%) were significantly higher (p < 0.05) than the sensitivity of the VDRL test (61%; 95% CI, 47.4-73.5%). IgM EIAs even were positive in some cases of suspected very early infection where the VDRL was non-reactive and the TPPA was indeterminate.

CONCLUSIONS

In cases of suspected early infection specific IgM EIAs should be used in addition to other screening tests. The VDRL is not recommended for screening.

Evolutionary-developmental perspectives on immune system interactions among the pregnant woman, placenta, and fetus, and responses to sexually transmitted infectious agents

A balance has evolved over deep time between the various immune systems of the "triad" that is linked together for a short period: the pregnant woman, the fetus, and the placenta. This balance is affected by, and helps to determine, the immune responses to maternal infectious agents that may be transmitted to the fetus/infant transplacentally, intrapartum, or via breast milk. This review identifies newer evolutionary concepts and processes related particularly to the human placenta, innate and adaptive immune systems involved in tolerance, and in responses to sexually transmitted infectious (STI) agents that may be pathogenic to the fetus/infant at different gestational periods and in the first year of life. An evolutionary-developmental (EVO-DEVO) perspective has been applied to the complexities within, and among, the different actors and their beneficial or deleterious outcomes. Such a phylogenetic and ontogenic approach has helped to stimulate several basic questions and suggested possible explanations and novel practical interventions.

Sensitive and specific ELISA coated by TpN15-TpN17-TpN47 fusion protein for detection of antibodies to Treponema pallidum

BACKGROUND

We constructed an artificial fusion gene tpN15-17-47 and then used the prokaryotic expression fusion protein rTpN15-17-47 as the coated antigen to establish a new enzyme-linked immunosorbent assay (ELISA) for serological diagnosis of syphilis.

METHODS

tpN15, tpN17, and tpN47 genes were amplified separately by polymerase chain reaction (PCR) and then assembled into a fusion gene coding a trigeminy protein antigen by primer linking PCR. The target recombinant protein antigens rTpN15, rTpN17, rTpN-47, and rTpN15-17-47 were expressed and then purified antigens were immobilized on the surface of microplate wells for detecting Treponema pallidum-specific antibodies by ELISAs.

RESULTS

The relative positive rate of rTpN15-17-47-ELISA in 965 serum specimens of syphilis patients was 99.5%, which was higher than that of the T. pallidum hemagglutination assay (TPHA) (98.3%) (p<0.05) and much higher than that of the rTpN15-ELISA (83.1%), the rTpN17-ELISA (84.4%), the rTpN47-ELISA (82.1%), and the toluidine red unheated serum test (TRUST) (72.2%) (p<0.01). All the ELISAs and the TPHA in detecting serum specimens from 62 cases with systemic lupus erythematosus (SLE), 86 cases with rheumatic arthritis (RA), and 250 healthy cases were negative, but the TRUST was positive in five cases with SLE, seven cases with RA, and two healthy cases.

CONCLUSIONS

The rTpN15-17-47-ELISA is a sensitive and specific serological screening or a diagnostic method for syphilis in the clinical setting.