Inhibition of mouse in vitro fertilization by an antibody against a unique 18-amino acid domain in the polysulfate-binding domain of proacrosin/acrosin.

<bold>Objective: </bold>To determine the contribution of the polysulfate-binding domain (PSBD) of acrosin during sperm penetration.<bold>Design: </bold>To inhibit the in vitro fertilization of mouse zona-intact oocytes by using a polyclonal antibody raised against an 18-amino acid peptide of proacrosin (anti-PSBD).<bold>Setting: </bold>Unit of Reproduction and Development, Faculty of Biological Sciences, Pontifical Catholic University of Chile.<bold>Patient(s): </bold>None.<bold>Intervention(s): </bold>A polyclonal antibody against the 43IFMYHNNRRYHTCGGILL(60) peptide was raised in New Zealand female rabbits. The specificity of the antibody was evaluated by an ELISA. Zona-intact mouse oocytes were coincubated with capacitated spermatozoa for 3 hours in the presence of 0.63 mg/mL of the antibody or preimmune serum. As a control, we used zona-free mouse oocytes under the same experimental conditions.<bold>Main Outcome Measure(s): </bold>We evaluated the fertilization rate of zona-intact and zona-free mouse oocytes by phase-contrast microscopy. An oocyte was considered fertilized when at least one decondensed sperm head was found within the egg cytoplasm. We evaluated 50-60 mouse oocytes in each group in three independent experiments.<bold>Result(s): </bold>The anti-PSBD antibody inhibited the fertilization of zona-intact, but not zona-free, mouse oocytes, by capacitated spermatozoa. In addition, the binding of the anti-PSBD to proacrosin/acrosin in a solid-phase assay was inhibited in the presence of polysulfates (fucoidan).<bold>Conclusion(s): </bold>The anti-PSBD directed against the PSBD of proacrosin/acrosin inhibited the penetration of capacitated mouse spermatozoa through the zona pellucida. This antibody may be a useful tool to define the roles of the different domains of proacrosin/acrosin during gamete interaction. [ABSTRACT FROM AUTHOR]