Title : Exploitation of sperm agglutination factor derived from Staphylococcus aureus as a putative candidate for vaginal contraception
Abstract:
Vaginal contraception is perhaps the oldest method of fertility regulation that has been practiced over the centuries. With minimal systemic involvement, it is also one of the safest methods of contraception. The use of vaginal contraceptives as local agents in a need-based manner makes them relatively much safer. They are also more advantageous against other contraceptives because of the following reasons: no loss of natural feeling when compared to condoms, no side effects when compared to oral pills, no bleeding or pain when compared to loop, no interference of a third party because it is do-it-yourself method and are inexpensive, reversible and relatively safe and easy to use. However, lack of interest and innovation in this important area of contraception made the available methods outdated, resulting in poor efficacy and acceptability. Thus, we are still away from the ideal vaginal contraceptive. The currently marketed vaginal contraceptive formulations contain a non-ionic surfactant as an active ingredient, the most common being nonoxynol-9 (N-9). A major drawback of N-9 and other surfactant spermicides is their detergent-like cytotoxicity to vaginal epithelial cells and Lactobacilli, disrupting normal microflora and increasing susceptibility to vaginal infections and STI/HIV transmission. Therefore, the development of vaginal contraceptives lacking membrane toxicity will offer a significant clinical advantage over the currently marketed detergent type spermicides. Notably, certain microorganisms are known to impair sperm function either by inducing sperm agglutination or by secreting extracellular products that immobilize spermatozoa, presenting a biologically relevant and non-invasive strategy for vaginal contraception. Motivated by this concept, a sperm-agglutinating bacterial strain was isolated from the cervix of a woman with unexplained infertility. Phenotypic and biochemical characterization identified the isolate as Staphylococcus aureus, which was confirmed by 16S rRNA gene sequencing (99% homology). In-vitro studies demonstrated that S. aureus induced sperm agglutination, sperm death and caused morphological alterations. These observations suggested that the presence of bacteria possessing sperm agglutination activity could compromise fertility in female mice and prompted further investigation into the underlying mediator, leading to the isolation and purification of the sperm-agglutinating factor (SAF). SAF showed a protein band of ~65 kDa on SDS-PAGE and depicted sequence homology to the hypothetical protein BACPEC_00178 of Bacteroides pectinophilus by MALDI-TOF analysis. In-vitro analysis revealed that SAF could induce complete agglutination, death, profound morphological alterations in human spermatozoa, significantly inhibited Mg²?-dependent ATPase activity, accelerated premature acrosome reaction, and triggered marked apoptotic responses. Intravaginal administration of SAF (10μg) in female BALB/c mice completely prevented conception, highlighting its contraceptive potential. However, safety is a critical prerequisite for the development of any vaginal contraceptive. Hence, when SAF was evaluated for safety, the results showed that SAF did not cause local inflammation or damage to the vaginal epithelium. No treatment related changes were observed in the reproductive performance of mice after cessation of treatment. Furthermore, SAF did not produce lethality in the mouse and was not toxic to other organs. Thus, SAF with all these properties has the potential to become an active ingredient of a vaginal contraceptive.
