Molecular mimicry and auto-immunity

The term "molecular mimicry" was coined by R. Damian in 1964, who was first to suggest that antigenic determinants of micro-organisms may resemble antigenic determinants of their host. Damian suggested that this similarity served as a defense mechanism of a microorganism from the host's immune system and prevented the development of immune response to the micro-organism, thereby protecting it from host defense. Years later, the term "molecular mimicry" was attributed a different meaning-namely, antigenic determinants of microorganisms might elicit an auto-immune response that harms the host. The concept of molecular mimicry is based on a structural similarity between a pathogen or metabolite and self-structures. The similarity could be expressed as shared amino acid sequences (linear or mimotope) or similar conformational structure between a pathogen and self-antigen. "Molecular mimicry" has become a very popular explanation for the frequent association of infection with auto-immune disease.

Epstein Barr Virus and Cytomegalovirus in Autoimmune Diseases: Are They Truly Notorious? A Preliminary Report

To date, it is believed that the origin of autoimmune diseases is one of a multifactorial background. A genetic predisposition, an immune system malfunction or even backfire, hormonal regulation, and environmental factors all play important roles in the pathogenesis of autoimmune diseases. Among these environmental factors, the role of infection is known to be a major one. Epstein-Barr virus (EBV) and cytomegalovirus (CMV) are considered to be notorious as they are consistently associated with multiple autoimmune diseases. A cohort of 1595 serum samples, of 23 different autoimmune disease groups, was screened for evidence of prior infection with EBV and CMV. All samples were screened for antibodies against EBV nuclear antigen-1 (IgG), EBV viral capsid antigen (IgG and IgM), EBV early antigen (IgG), EBV heterophile antibody, and CMV (IgG and IgM) antibodies using Bio-Rad's BioPlex 2200. A new association is proposed between EBV and polymyositis, as results show a significant increase in titers of various EBV target analytes when compared with healthy controls. Our results also support prior information suggesting the association between EBV and multiple autoimmune diseases, including SLE, antiphospholipid syndrome, rheumatoid arthritis, multiple sclerosis, pemphigus vulgaris, giant cell arthritis, Wegener's granulomatosis, and polyarteritis nodosa (PAN). Elevated CMV IgG titers were observed in sera of SLE patients. Our data support the theory that EBV is notoriously associated with many autoimmune diseases. CMV appears to be associated to autoimmune diseases as well, yet establishing this theory requires further investigation.

Reduced placental growth and hCG secretion in vitro induced by antiphospholipid antibodies but not by anti-Ro or anti-La: studies on sera from women with SLE/PAPS

Systemic lupus erythematosus (SLE) and primary anti-phospholipid syndrome (PAPS) are autoimmune diseases causing recurrent pregnancy loss. We hypothesized that anti-phospholipid antibodies (aPL), but not anti-Ro and anti-La antibodies, might have a role through direct placental damage. We cultured human placental explants in sera from women with SLE/PAPS with different antibodies. These sera were found to reduce placental growth and increase trophoblastic apoptosis. No effect was found on estradiol or progesterone secretion, but inhibition in betahCG secretion was detected. BetahCG was reduced in women with a history of recurrent pregnancy loss or thromboembolic events, and was also the most sensitive marker when examining the effects of specific antibodies. High titers of aPL were found to cause the largest reduction in betahCG. Anti-Ro and anti-La did not induce placental damage. A strong correlation was found between the rise in the number of different antibodies in the sera and the incidence of recurrent pregnancy loss, which was also accompanied by a decline in the betahCG levels. In conclusion, aPL, but not anti-Ro or anti-La, may cause placental damage in vitro. Thus betahCG levels might constitute a predictive marker for the risk of placental damage and pregnancy loss in women with SLE/PAPS.

Evaluation of the BioPlex 2200 ANA screen: analysis of 510 healthy subjects: incidence of natural/predictive autoantibodies

The BioPlex 2200 ANA Screen is a fully automated system that determines levels for 13 different autoimmune antibodies of established clinical significance. The objective of this study was to determine the specificity of the BioPlex 2200 ANA Screen assay and to analyze the antibody profile samples collected from healthy subjects against comparative ELISA and IIF screening methods. A total of 510 specimens were randomly selected from a cohort of apparently healthy blood bank donors. Samples were distributed to five age brackets. All samples were tested using Bio-Rad's ANA Screen kit. Specificity was compared to IIF and ELISA results. Most of the samples were found negative in all ANA screening systems (84.5% by IIF, 92.5% by BioPlex 2200 ANA Screen kit, and 94.5% by ELISA). The frequency of positive results was highest (15.5%) using IIF, in comparison to almost similar results (5.5% vs. 7.5%) achieved by ANA ELISA and BioPlex 2200 ANA Screen kits. The positive rate of autoantibodies was significantly reduced when analyzed by different combinations of ANA screen assays (from 2.35% using IIF + BioPlex ANA Screen tests to 0.98% by using all three tests). Using the BioPlex 2200 ANA Screen system, we were able to identify samples with high levels of individual antibodies: anti-dsDNA at 20-63 IU/mL, antichromatin at 4-8 AI, anti-SmRNP at 2-6 AI, and anti-RNPA at 2-4.5 AI. Importantly, from 7 IIF and ELISA positive sera, 5 of these were also BioPlex 2200 positive, suggesting that the BioPlex is seeing the samples that are of the greatest interest, using the established techniques. The specificity of the BioPlex 2200 ANA Screen analysis of 13 different analytes (dsDNA, centromere B, chromatin, Jo1, ribosomal P, RNP 68, RNP A, Scl-70, Sm, SmPNP, SS-A52, SS-A60, SS-B) is comparable (P < 0.252) to the ELISA ANA screening test. Like the ELISA, the BioPlex 2200 has a lower (P < 0.001) positive rate than IIF for the autoantibody screening.