Preliminary evidence for high anti-PLAC1 antibody levels in infertile patients with repeated unexplained implantation failure

Objective: Placenta-specific1 (PLAC1) is a trophoblast-specific gene encoding for a protein that is highly expressed in human placenta, on the surface of the syncytiotrophoblast. PLAC1 was found to elicit spontaneous antibody responses in cancer patients. We aimed to determine the levels of anti-PLAC1 antibodies in infertile women with a history of unexplained repeated implantation failure after IVF cy- cles as compared to fertile women. Study design: An observational caseecontrol clinical study. Main outcome measure(s): Two groups of patients were analysed in two different experimental settings: 21 infertile women and 81 control patients were enrolled in the first group, 16 infertile women and 67 fertile controls in the second group. Anti-PLAC1 antibody levels and ranking were analysed by ELISA test. Results: In both groups of infertile patients enrolled, optical densities (OD) from ELISA test ranked sig- nificantly higher than those of controls (0.27 ` 0.2 vs. 0.13 ` 0.1 respectively; p 1⁄4 0.0009 in the first group), (0.62 ` 0.38 vs. 0.39 ` 0.35 respectively; p 1⁄4 0.0044 in the second experiment). In the first group about one case in four (29%) had OD levels above the 95thpercentile (0.337) for healthy controls (p 1⁄4 0.005). In the second experiment 4 out of 16 cases (25%) had OD levels above the 95th percentile (0.878) for healthy controls (p 1⁄4 0.023). Conclusions: Anti-PLAC1 antibodies could represent a biomarker associated with infertility and with high probability of repeated implantation failure after ovarian stimulation and IVF-ET, greatly improving the diagnostic work up of infertile couples.