Potential Contraceptive Use of Epididymal Proteins: Immunization of Male Rats with Epididymal Protein DE Inhibits Sperm Fusion Ability1

Abstract

Rat epididymal protein DE associates with the sperm surface during maturation and participates in sperm-egg fusion. Immunization of male rats with DE raised specific antibodies and produced a significant reduction in the animals' fertility. The present study focused on determining the in vivo mechanism involved in fertility inhibition. Wistar males were injected with DE, and antibody levels and animal fertility were evaluated. Results revealed an association between the two parameters, since animals with absorbance values lower than 0.5 in ELISA presented high fertility rates (66%, 100%) while those with absorbance values higher than 0.5 exhibited the lowest fertility rates (0%, 33%). Histological studies showed no evidence of orchitis, epididymitis, or vasitis in DE-immunized animals. ELISA results revealed the presence of anti-DE antibodies in epididymal and vas deferential fluids. Indirect immunofluorescence and ELISA experiments indicated that these antibodies would not interfere with the synthesis or secretion of DE or with its association with the sperm surface. Finally, while epididymal sperm recovered from DE-immunized animals presented no changes in motility, viability, or ability to undergo capacitation and acrosome reaction, they exhibited a significant decrease in their ability to fuse with zona-free eggs, with no effect on their ability to bind to the oolemma. Together these results indicate that immunization of male rats with epididymal protein DE specifically interferes with the sperm fertilizing ability, supporting the use of epididymal proteins for contraceptive vaccine development.

The Epididymis: Embryology, Structure, Function And Its Role In Fertilization And Infertility

“…The production and secretion of at least half of the epididymal proteins, including those later incorporated by the spermatozoa in transit, are under androgenic control. Androgenic control may act positively or negatively, depending on the varying levels of sensitivity (Tezon et al, 1985;Ellerman et al, 1998;Robaire et al, 2000, Dachuex et al 2005Robaire & Henderson, 2006).…”

“…These molecules interact sequentially with the surface of the spermatozoa or the acrosome, and alter their molecular function (Orgebin-Crist, 1967;Robaire et al, 2000Gatti et al, 2004;Dacheux et al, 2005;Sullivan et al, 2005) (Figure 7). In this process, some proteins bind to the sperm and presumably affect sperm function directly (Ellerman et al, 1998;Von Horsten et al, 2007). Some proteins will later bind to the zona pellucida (Ellerman et al, 1998) or the plasma membrane of the oocyte (Cohen et al, 1996;Flesch & Gadella, 2000).…”

“…In this process, some proteins bind to the sperm and presumably affect sperm function directly (Ellerman et al, 1998;Von Horsten et al, 2007). Some proteins will later bind to the zona pellucida (Ellerman et al, 1998) or the plasma membrane of the oocyte (Cohen et al, 1996;Flesch & Gadella, 2000). Other proteins remain in the lumen throughout the length of the tubule (Dacheux et al, 2005;Fouchécourt et al, 2002).…”

“…CRISPs (Cysteine-Rich Secretory Proteins, originally named DE) are epididymal proteins in rats and mice that do not require stable or long-term bounds with the sperm to perform their functions. CRISPs adhere to the sperm surface as epididymosomes during epididymal maturation and are subsequently lost during epididymal transit (Ellerman et al, 1998;Cohen et al, 2011).…”

The role of cysteine-rich secretory proteins in male fertility

“…Not surprisingly, therefore, the CRISP genes have been nominated as infertility candidate genes and proposed as targets for contraceptive action. [5][6][7] This article will review current literature on the role of CRISPs in male fertility; it will draw upon the function of related non-mammalian CRISPs and other related proteins to infer function and finally will summarize the actual evidence for the role of CRISPs in mammalian male fertility.…”