Uncovering candidate protein(s) in murine vaginal lavage fluid linked to sperm-agglutinating Escherichia coli-induced infertility menace: a discovery phase analysis.

Despite advances in reproductive medicine, the role of microbes in infertility remains underexplored. Our earlier research demonstrated an Escherichia coli strain, capable of causing 100% sperm immobilization via agglutination in-vitro, and infertility in-vivo. Also, sperm agglutination factor (SAF), extracted and purified from bacterial culture, depicted similar results and, showed homology to glutamate decarboxylase. However, it remained unclear whether such bacterial protein signatures are produced within the vaginal milieu post-colonization of E. coli in host environment. Addressing this, discovery-phase proteomics approach was used to investigate vaginal lavage fluid (VLf) of female mice following intravaginal administration of E. coli. VLf from E. coli-administered and PBS-treated groups revealed distinct protein banding patterns (SDS-PAGE) and chromatographic profiles (RP-HPLC). Proteomic-profiling of pooled VLf using nano-LC-MS/MS depicted a ~ 20-kDa bacterial protein, annotated as Uncharacterized protein YfgI, only in test group. Gel-filtration chromatography of VLf revealed a purified protein of ~ 20-kDa that aligned with the proteomic analysis and hence, designated as VLf-protein. Functionally, VLf-protein impaired sperm motility, viability, induced ultrastructural abnormalities, demonstrated binding to sperm surface, and infertility in-vivo. Structural modeling and comparative analysis revealed only suggestive similarity between VLf-protein and SAF.