Cases of human infertility are associated with the absence of P34H an epididymal sperm antigen.

The interaction of spermatozoa with the zona pellucida is a critical step of fertilization. Specific sperm surface proteins involved in this process can be added or modified during epididymal transit. We have previously described a 34-kDa human epididymal sperm protein (P34H) that we proposed to be involved in sperm-zona pellucida interaction. In this study, Western blot analysis were performed to determine the level of P34H protein present on the spermatozoa of 16 men with idiopathic infertility. These levels were compared with the amount of P34H protein found in men of proven fertility. In addition, a sperm-zona pellucida binding assay was performed with spermatozoa from fertile and infertile men. Spermatozoa obtained from different semen samples from a given individual had similar P34H levels. However, the amount of P34H varied from one man to another. Nine of 16 infertile men had a P34H level that was less than 30% of the normal value based on a population of fertile men, while the remaining 7 males were in the normal range. Sperm from infertile subjects with a normal P43H determination bound to zonae pellucidae as efficiently as those from controls. However, spermatozoa from subjects with a low amount of P34H exhibited a dramatic diminution in their ability to interact with zonae pellucidae. Our results show that the quantity of the epididymal protein P34H varied from one male to another and that low levels of this epididymal sperm protein are associated with certain cases of idiopathic infertility. Results are discussed with regard to the function of human epididymis in sperm maturation.