Abstract
Sperm of humans, non-human primates, and other mammalian subjects is considered to be antigenic. The effect of changes in autoimmunity on reproductive cells such as spermatozoa and oocytes play a critical but indistinct role in fertility. Antisperm antibodies (ASAs) are invariably present in both females and males. However, the degree of ASA occurrence may vary according to individual and gender. Although the extent of infertility due to ASAs alone is yet to be determined, it has been found in almost 9–12% of patients who are infertile due to different causes. Postcoital presence of spermatozoa in the reproductive tract of women is not a contributory factor in ASA generation. However, ASA generation may be induced by trauma to the vaginal mucosa, or by anal or oral sex resulting in the deposition of sperm inside the digestive tract. It is strongly believed that, in humans and other species, at least some antibodies may bind to sperm antigens, causing infertility. This form of infertility is termed as immunological infertility, which may be accompanied by impairment of fertility, even in individuals with normozoospermia. Researchers target ASAs for two major reasons: (i) to elucidate the association between ASAs and infertility, the reason ASAs causes infertility, and the mechanism underlying ASA-mediated infertility; and (ii) to assess the potential of ASAs as a contraceptive in humans in case ASAs influences infertility. Therefore, this review explores the potential application of ASAs in the development of anti-spermatozoa vaccines for contraceptive purposes. The usefulness of ASAs for diagnosing obstructive azoospermia, salpingitis, and oligoasthenoteratozoospermia has been reviewed extensively. Important patents pertaining to potential candidates for spermatozoa-derived vaccines that may be utilized as contraceptives are discussed in depth. Antifertility vaccines, as well as treatments for ASA-related infertility, are also highlighted. This review will address many unresolved issues regarding mechanisms involving ASAs in the diagnosis, as well as prognoses, of male infertility. More documented scientific reports are cited to support the mechanisms underlying the potential role of ASA in infertility. The usefulness of sperm antigens or ASAs (recombinant) in human and wild or captive animal contraceptive vaccines has been revealed through research but is yet to be validated via clinical testing.
Highlights
Sperm has been considered as being antigenic toward the female body for a long time [1]
Sub-meta-analysis was performed only for sperm counts and sperm motility in the random-effects model. This analysis indicated a significant difference between Antisperm antibodies (ASAs)-positive and ASA-negative groups, with lower levels in the ASA-positive group [7,98]. These results suggest that the presence of ASAs in semen significantly reduced the sperm concentration and sperm motility of the ASA-positive infertility males compared to the ASA-negative males [99,100,101,102,103,104,105,106]
Seminal ASA levels were found in infertile cases, and in fertile men and women. These findings reveal that a low concentration of ASAs is found even in fertile men
Summary
Sperm has been considered as being antigenic toward the female body for a long time [1]. Various sperm-associated proteins causing antigenicity have been identified and characterized, and their role in fertility disorders has been described. A disruption must occur in the blood–testis barrier (BTB) for ASAs to be generated, and in humans, ASAs have been associated with 2–50% of infertility incidences [2,3]. Changes in the masculine reproductive tract, which is substantially made up of smooth muscles and immune components, have been distinctly investigated, but not in the context of infertility and its associated problems. Recent studies pertaining to ASA-associated infertility conditions have unraveled the interaction between these two systems, suggesting a potent role of ASAs in the infliction of immunological infertility [4,5]
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