Update on male contraception

Nanomaterial-dependent immunoregulation of dendritic cells and its effects on biological activities of contraceptive nanovaccines

Nanovehicles are promising delivery systems for various vaccines. Nevertheless, different biophysicochemical properties of nanoparticles (NPs), dominating their in vitro and in vivo performances for vaccination, remain unclear. We attempted to elucidate the effects of NPs and their pH-sensitivity on in vitro and in vivo efficacy of resulting prophylactic nanovaccines containing a contraceptive peptide (FSHR). To this end, pH-responsive and non-responsive nanovaccines were produced using acetalated β-cyclodextrin (Ac-bCD) and poly(lactic-co-glycolic acid) (PLGA), respectively. Meanwhile, FSHR derived from an epitope of the follicle-stimulating hormone receptor was used as the model antigen. FSHR-containing Ac-bCD and PLGA NPs were successfully prepared by a nanoemulsion technique, leading to well-shaped nanovaccines with high loading efficiency. The pH-sensitivity of Ac-bCD and PLGA nanovaccines was examined by in vitro hydrolysis and antigen release studies. Nanovaccines could be effectively engulfed by dendritic cells (DCs) via endocytosis in both dose and time dependent manners, and their intracellular trafficking was closely related to the pH-sensitivity of the carrier materials. Furthermore, nanovaccines could induce the secretion of inflammatory cytokines by DCs and T cells co-cultured with the stimulated DCs. In vivo evaluations demonstrated that nanovaccines were more potent than that based on the complete Freund's adjuvant, with respect to inducing anti-FSHR antibody, reducing the sperm count, inhibiting the sperm motility, and increasing the teratosperm rate. Immunization of male mice with nanovaccines notably decreased the parturition incidence of the mated females. Consequently, both in vitro and in vivo activities of FSHR could be considerably augmented by NPs. More importantly, our studies indicated that the pH-responsive nanovaccine was not superior over the non-responsive counterpart for the examined peptide antigen.

Immunocontraceptives: How far from reality?

Despite high expectations of safer, effective, economical, longer acting contraceptives, to date, there are no licensed contraceptive vaccines available in the market. Nevertheless, a role for vaccines undoubtedly exists as an aid to birth spacing and as a nonsurgical means of generating sterility. The research concerned in the area so far has been successful on the feline population, with room still for exhaustive studies on humans. The future of contraceptive vaccines holds great promise in terms of comfort, price, efficacy, rare complications, and possibly nonselective action on animal populations as well as on humans. This brief review deals with the basic aspects of immunocontraceptives along with the efforts done so far. There is a need for further research in aspects involving the rate of evolution of contraception resistance based on genetics, resistance phenotypes, or cross generation effects. Gonadotropin-releasing hormone and luteinizing-hormone have not been investigated in humans, as both reported impotency in animals; the follicle-stimulating hormone has been shown to cause oligospermia; zona pellucida has also not been studied in humans as it causes irreversible oophoritis, while the sperm has the potential for success in humans based on the data from immunoreproductive studies. Even as the position of the human chorionic gonadotropin vaccine looks hopeful, research on other possible targets continue with an eventual aim of discovering a vaccine that is more immunogenically effective.

Attitudes towards the male contraceptive pill: psychosocial and cultural explanations for delaying a marketable product

Even though years of research on the male contraceptive pill have been conducted, a marketable product is still absent from the arsenal of male and female products of contraception. In this paper, the following psychosocial and cultural factors have been elicited from the literature in order to reveal explanations for this delay: acceptability, trust, fear of side-effects, perceptions of contraceptive responsibility and fear of losing connotations of masculinity. Regardless of cultural variation, overall there seems to be a positive attitude towards the acceptability of male contraceptive for both males and females, especially males in stable relationships. Some indication shows that the media have played an important role in distorting the results of research regarding male and female trust. Ongoing and future researches into several projects on psychosocial and cultural factors are described.

Is there a role for immunocontraception?

The world's population is continuing to grow at an alarming rate and yet no novel methods of contraception have been introduced since 1960s. The paucity of our current contraceptive armoury is indicated by the 46 million abortions that are performed each year, largely in developing countries where population growth is greatest. Thus, whatever new forms of fertility control we develop for the next millennium, the particular needs of developing countries should be borne in mind. Contraceptive vaccines have the potential to provide safe, effective, prolonged, reversible protection against pregnancy in a form that can be easily administered in the Third World. In this review we consider the contraceptive targets that might be pursued, how vaccines might be engineered and the problems generated by inter-individual variations in antibody titre. We conclude that the specifications for a safe, effective, reversible vaccine are more likely to be met in animals than man.

The synthesis and antifertility evaluation of 3 analogs of pyrimethamine on male rat reproductive indices

Side effect assessment of medicaments on fertility indices may be used as a guide in the development of male contraceptive agents. In this study, 3 analogs of pyrimethamine were synthesized and evaluated for antifertility activity on reproductive indices of male rats. Test compounds were administered in a dosage of 50 mg/kg every other day till 60 days. On the 50th day, the fertility of rats was tested. On the 60th day, the gonadosomatic index and the serum testosterone content were determined. Iso-butyloxy and tertiary-butyloxy caused 40% and 11% reduction in sperm viability, respectively. They also significantly reduced fertility indices. Consequently, iso-butyloxy can be one of the best nominees in this class of compound and a suitable candidate for assessment of mechanism involved in future research activity. To synthesize a more effective agent, increasing the lipophilicity may play a major role in the development of more potent promising male contraceptive agents.