The fertilization antigen-1 does not have proteolytic/acrosin activity, but its monoclonal antibody inhibits sperm capacitation and acrosome reaction.

OBJECTIVE

To determine if human sperm surface fertilization antigen exhibits proteolytic or acrosin activity and to investigate the mechanism(s) whereby monoclonal antibody (mAb) to fertilization antigen inhibits human sperm penetration of zona-free hamster ova.

DESIGN

Proteolytic and acrosin activities of human fertilization antigen were determined. Acrosomal status, acrosin activity, and motion characteristics were evaluated after incubation of human sperm with immunoaffinity-purified mAb to fertilization antigen.

SETTING

Academic research environment.

PARTICIPANTS

Fertile donors used as controls for infertile patients for fertility evaluation.

INTERVENTIONS

Human spermatozoa were treated with mAb to fertilization antigen and induced to undergo acrosome reaction using calcium ionophore A23187.

MAIN OUTCOME MEASURES

Proteolytic and acrosin activities of fertilization antigen. Sperm penetration assay, acrosomal status, and motion parameters.

RESULTS

Fertilization antigen does not exhibit proteolytic or acrosin activity; however, its mAb completely blocks human sperm penetration of zona-free hamster ova. The mAb to fertilization antigen inhibits ionophore-induced acrosome reaction and blocks development of the hyperactivated state of human sperm cells.

CONCLUSIONS

Monoclonal antibody to fertilization antigen blocks fertilization by inhibiting capacitation and acrosome reaction.