Why do antibodies react with cardiolipin

Conclusion We believe that with the continuous improvements in medicine and the rapid development of science and technology, the detection method of ACA will be more standardized. Conflicts of Interest The authors report no financial or commercial conflict of interest in this work. References K. Habe, H. Wada, T. Matsumoto et al. Giannakopoulos, F. Passam, S. Rahgozar, and S. Pierangeli and E. McDonnell, C. Wincup, I.

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Jy, L. Horstman, E. Ahn, M. Yaniz, and Y. Naess, S. Christiansen, S. Cannegieter, F. Rosendaal, and J. Pathologic levels of autoantibodies reflect loss of tolerance and increased production of antibodies. These autoantibodies are called phospholipid or cardiolipin antibodies when they are detected by immunoassays that employ anionic phospholipids as substrates.

The most commonly used phospholipid substrate is cardiolipin. The term phospholipid antibody is actually a misnomer. The autoantibodies react with epitopes of protein molecules that associate noncovalently with reagent phospholipids. The best characterized phospholipid-binding protein is beta-2 glycoprotein 1 beta-2 GP1 and most immunoassays for phospholipid antibodies employ a composite substrate consisting of cardiolipin plus beta-2 GP1.

Beta-2 GP1 is a amino acid polypeptide that contains 5 homologous domains of approximately 60 amino acids each. Most phospholipid antibodies bind to an epitope associated with domain 1 near the N-terminus.

Autoantibodies can also be detected by the use of functional, phospholipid-dependent coagulation assays. Phospholipid antibodies detected by functional assays are often called lupus anticoagulants because they produce prolongation of phospholipid-dependent clotting in vitro and are found in some patients with systemic lupus erythematosus.

Not all phospholipid antibodies possess lupus anticoagulant activity. It is hypothesized that complexes formed in vivo between bivalent, natural autoantibodies and beta-2 GP1 bind to translocated, anionic phospholipid on activated platelets at sites of endothelial injury.

This binding is believed to promote further platelet activation that may lead to thrombosis. Antiphospholipid syndrome APS is an autoimmune disorder characterized by thromboses, complications of pregnancy, and certain laboratory abnormalities. The diagnosis of APS requires at least 1 clinical criteria and 1 laboratory criteria be met.

Other clinical manifestations, including heart valve disease, livedo reticularis, thrombocytopenia, nephropathy and neurological symptoms, are often associated with APS but are not included in the diagnostic criteria. All antibodies must be demonstrated on 2 or more occasions separated by at least 12 weeks. Moreover, the treponemes had a mostly intact cell structure after inactivation. First, we explored the variation tendency of treponemal antibodies in rabbits immunized with inactivated treponemes, including the formalin- and heat-treated treponemes.

All the rabbits had positive serum TPPA, indicating that the inactivated treponemes had potent immunogenicity and could elicit the production of treponemal antibodies. The TPPA antibodies began to appear 3 weeks and 4 weeks after the initial injection of treponemes in the heat- and formalin-treated groups, respectively Table 1.

The TPPA test titers in these 2 inactivated treponeme groups increased over time. The highest TPPA titer in the heat-treated group was , which was similar to the titer achieved in the formalin-treated group. In contrast, the TPPA test titer in the active treponemal group showed positive results and a rapid increase at an earlier time point than that in the formalin- and heat-treated groups Table 1. All the rabbits in this group showed a positive TPPA result 1 week after the initial treponeme injection.

One rabbit that died 32 days after the initial treponeme injection in the heat-treated group was excluded from the experiment. Variation tendency in the postimmunization Treponema pallidum particle agglutination assay TPPA titer in the groups immunized with various treponemal antigens. Second, we analyzed the variation tendency of nontreponemal antibodies throughout the experimental phase.

One rabbit in the heat-treated group number 1 appeared to have a persistent VDRL titer of 9 weeks after the initial treponeme injection, and another rabbit in the formalin-treated group number 4 had a persistent titer at 2 weeks after the initial treponeme injection Table 2. Their titers did not increase over time.

In addition, several rabbits appeared to have weakly discontinuous VDRL reactivity. In contrast, positive VDRL results were observed in all the rabbits as early as 2 weeks after the initial injection, and the VDRL titer was notably increased in the active treponemal group. Consecutive and higher VDRL titers were observed in all the rabbits in the active treponemal group.

At 3 weeks following the initial treponeme injection, the VDRL test titer reached a peak at and then decreased. The results from the 2 inactivated groups indicated that T.

Therefore, we immunized 10 rabbits with whole-treponemal-cell lysates. Generally, cardiolipin is considered the most important antigenic substance in the nontreponemal test.

We immunized 4 rabbits per group with the cardiolipin antigen and the cardiolipin-BSA antigen. The optical density of the anticardiolipin antibody was measured weekly Figure 3. The ELISA showed that rabbits immunized with cardiolipin did not produce an anticardiolipin antibody. However, the anticardiolipin antibody test was positive at 4 weeks after the initial cardiolipin-BSA immunization and slowly increased over time.

Variation tendency in the anticardiolipin antibody titer postimmunization with the cardiolipin and cardiolipin—bovine serum albumin BSA antigens. The variation in anticardiolipin antibody titers among 4 rabbits in the cardiolipin-BSA group is shown in the dashed box. The nontreponemal antibody was the first recognized serological response to infection with T. In the last century, there has been a heated debate concerning the production of nontreponemal antibodies during T.

Some studies have shown that nontreponemal antibodies are actually elicited by T. A previous article supporting this finding showed that T. Therefore, T. In this study, we showed direct evidence of the origin of nontreponemal antibodies during syphilis infection using an animal model.

First, we applied different methods to inactivate the treponemes, including formalin, heat, and ultrasonication treatments, prior to the immunization of rabbits.

The results from these immunizations were similar to those of previous studies [ 30 , 31 ]. The results showed that inactivation of the treponemes stimulated the rabbits to produce nontreponemal antibodies.

Because the inactivated treponemes are unable to damage host tissue cells and thus may not induce the release of cardiolipin from host tissue cells, the rabbits immunized with the rabbit cellar debris did not show a positive nontreponemal antibody result data not shown.

The antigen that causes nontreponemal antibody reactions may originate from T. Our results indirectly demonstrate that T. Why did all the rabbits show a positive VDRL test, and why were the nontreponemal antibody titers low or weakly reactive in our inactivated treponemal experiment?

One reason may be that the cardiolipin antigen in T. Cardiolipin is the only phospholipid with antigenicity [ 28 ] and theoretically can elicit antibody production [ 24 ].

In our study, we immunized rabbits with cardiolipin from bovine hearts or cardiolipin-BSA and evaluated the immunogenicity of cardiolipin in the treponemes. The results indicated that pure cardiolipin could not elicit anticardiolipin antibody production in rabbits. However, cardiolipin elicited anticardiolipin antibody production with strong immunogenicity when it was combined with BSA. Therefore, the weak immunogenicity of cardiolipin in T. In addition, a previous study showed that the organisms could be labeled with VDRL antibodies when the T.

This possibility may be another reason for the weak immunogenicity of the cardiolipin antigen in T. In addition to the treponemal origin theory, which explains the origins of nontreponemal antibodies, another possibility is that cardiolipin complexes are liberated from damaged cells at the site of infection and that these complexes provoke an autoimmune reaction [ 10 , 11 , 33 ].

In our study, active T. Nontreponemal antibody production occurred earlier and reached higher titers in the active T. The treponemal antibody titer in the active treponemal group also increased more rapidly and was higher than that in the inactivated groups. Unlike inactivated T. Consequently, the high titer of nontreponemal antibodies is a result of the combined effect of both the T. We can assume that the host—cell cardiolipin antigen plays a major role in this process. Some articles reported that the fatty acid composition of T.

Our study showed the origin of nontreponemal antibodies in an animal model. However, our study has some limitations. The statistical power in this study was small due to the limited sample size and the outbred nature of the rabbit animal model. In addition, this study conducted experiments using antibody tests and lacked direct pathological evidence.

For this reason, additional studies are required to show that T. Which specific T. Furthermore, the biological function of nontreponemal antibodies is unclear—they may be protective, harmful, or simply a reflection of an immunological response in the host. These questions need to be answered in subsequent studies.

In conclusion, our results show that T. High titers of nontreponemal antibody are a result of the combined effect of both the T. Host—cell cardiolipin antigens play a major role in inducing nontreponemal antibody production. Supplementary materials are available at The Journal of Infectious Diseases online.

Consisting of data provided by the authors to benefit the reader, the posted materials are not copyedited and are the sole responsibility of the authors, so questions or comments should be addressed to the corresponding author.

The funders played no role in the study design, data collection or analysis, the decision to publish, or manuscript preparation. Financial support. Potential conflicts of interest. All authors: No reported conflicts of interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed. Analysis of 3 algorithms for syphilis serodiagnosis and implications for clinical management. Clin Infect Dis ; 58 : — Google Scholar.

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