USE OF MANNOSE LIGANDS IN IVF SCREENS TO MIMIC ZONA-PELLUCIDA-INDUCEDACROSOME REACTIONS AND PREDICT FERTILIZATION SUCCESS

A predictive test for determining whether motile populations of human spermatozoa will fertilize eggs in vitro has been an elusive goal of c linical research. We have developed an assay for the ability of motile human spermatozoa to bind fluorescein isothiocyanate-labelled mannosy lated bovine serum albumin (Man-FITC-BSA) as a test for the presence o f sperm surface receptors (lectins) for mannose ligands. Mannosylated ligands are present on the human zona pellucida and are involved in th e species-specific binding of human spermatozoa to the zona pellucida. We now demonstrate in prospective blinded analysis that the fractiona l increase in acrosome loss following a mannose ligand challenge is hi ghly correlated with the rate of fertilization in vitro. Using an incr emental increase of acrosome exocytosis of >0.1 as a threshold to pred ict which specimens will yield normal fertilization, the assay has a s ensitivity of 97.8%, a specificity of 83.3%, a positive predictive val ue of 95.7% and a negative predictive value of 90.7%. These data indic ate that testing for a mannose-induced acrosome reaction may be useful in assessment of sperm function prior to in-vitro fertilization in or der to assign males to conventional insemination or intracytoplasmic s perm injection protocols.