Acrosomal Protein SP-10 is a testis-specific differentiation antigen that is associated with acrosomal membranes and matrix of mature sperm. It has been detected in several species including humans. Acrosomal Protein SP-10 may be involved in sperm-zona binding or penetration as a potential contraceptive vaccine immunogen for humans. ACRV1 is also a intra-acrosomal protein that is considered to be a vaccine candidate for immunocontraception.