Targets of anti-trophoblast antibodies

Background: Our former study demonstrated that anti-trophoblast antibodies (ATAB) are more prevalent in the sera of patients with unexplained recurrent miscarriages (uRM), and the detection of ATAB is restricted to binding to JEG-3 cells and the quantification by flow cytometry. We further proved that the ATAB-positive sera decrease the production of β-hCG and progesterone in the same cell model. The specific antigenic epitopes of ATAB are still unclear, therefore our aim was to identify one specific target of ATAB in uRM patients. Methods: The possible targets of ATAB were identified by western blots and mass spectrometry, and α-Enolase (ENO1) was further confirmed by a competition assay. The level of anti-ENO1 antibodies in the sera and the production of β-hCG and progesterone were evaluated with enzyme-linked immunosorbent assay (ELISA). Additionally, the expression of ENO1 in the first trimester placenta was analyzed with immunohistochemistry and triple fluorescence staining in uRM patients and healthy controls. Findings: ENO1 was identified to be a prominent target of ATAB and anti-ENO1 antibodies can decrease the secretion of β-hCG and progesterone. The titer of anti-ENO1 antibodies was increased in the sera of ATAB-positive patients compared to ATAB-negative patients. Overexpression of ENO1 and co-expression of ENO1 and β-arrestin was found in the extra villous trophoblasts of uRM patients in the first trimester placenta. Interpretation: Anti-ENO1 antibody in the sera may be a novel autoimmune biomarker of uRM. Decreasing anti-ENO1 antibodies or inhibiting ENO1 expression might be a potential therapeutic treatment for uRM patients.