Antigenic homology between mouse spermatozoa and Vibrio cholerae: in-silico, in-vitro, and in-vivo evidence for immune-mediated infertility.

Molecular mimicry, a key concept in the field of autoimmune diseases and diagnosis, is increasingly being explored in the context of human infertility. A significant hypothesis in infertility research is the presence of anti-sperm antibodies (ASAs), which are found in males, females, prepubescent boys, and virgin girls. The mechanisms triggering ASA production in both sexes are varied, but the origin of these antibodies in children and adolescents remains unclear. Some studies have investigated the possibility of molecular mimicry between bacterial and spermatozoal antigens due to the substantial homology between these exogenous bacterial antigens and spermatozoal proteins. This study aimed to investigate the potential molecular mimicry between the Vibrio cholerae analog of the sperm receptor and a shared ligand. Specifically, the study utilized a strain of Staphylococcus aureus to isolate the sperm immobilization factor, which successfully immobilized 100% of mouse spermatozoa and demonstrated sequence homology with the cysteine-tRNA ligase of Mycoplasma penetrans (strain HF-2). An in-silico study using protein-protein docking revealed 87% similarity between V. cholerae's DnaK and mouse sperm Heat shock-related 70 kDa protein 2, as shown by BLASTp analysis. Both proteins, along with cysteine-tRNA ligase, were modeled using I-TASSER, and binding sites were identified. Multiple sequence alignment showed conserved motifs between DnaK and the mouse protein. Interaction analysis using ClusPro 2.0 indicated strong binding between the receptors and the ligand (cysteine-tRNA ligase), suggesting molecular mimicry. Further validation was conducted through in-vitro and in-vivo experiments, which confirmed antigenic similarities between the two receptors.