Recent progress toward development of vaccines against conception

Abstract

Although there are several methods of contraception available, the population explosion and unintended pregnancies continue to cause major health issues and constrain resources worldwide. A better method of contraception that is acceptable in developed as well as developing countries is urgently needed. Contraceptive vaccines (CVs) can fulfil most of the properties of an ideal contraceptive. The development of CVs is an exciting proposition and has drawn significant attention lately. The purpose of this article is to review the present status and future perspectives of CVs for human use, and for control of farm, feral, stray and domestic animal populations.

Keywords::

• birth control
• contraception
• human chorionic gonadotropin (hCG)
• immunocontraception
• infertility
• leukemia inhibitory factor (LIF)
• sperm
• vaccines
• wildlife control
• zona pellucida

Financial & competing interests disclosure

The author has no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending or royalties.

No writing assistance was utilized in the production of this manuscript.

Key issues

• Population explosion and unintended pregnancies resulting in elective abortions are major concerns worldwide.

• Although several methods are available for contraception, there are limitations and side effects associated with each of these methods. A nonsteroidal, nonsurgical, nonbarrier, intercourse-independent, less expensive method, with a longer duration is urgently needed. Contraceptive vaccines (CVs) can fulfil most of the desirable attributes of a highly acceptable modality for contraception.

• Besides, CVs for human contraception, immunologic methods for control of feral populations of dogs, cats, horses, deer, elephants, zoo animals and domestic pets are required.

• Several targets are being explored for CV development including gonadotropin-releasing hormone, zona pellucida, sperm antigens, leukemia inhibitory factor and human chorionic gonadotropin (hCG).

• CVs based upon gonadotropin-releasing hormone and zona pellucida, especially porcine zona pellucida, have shown remarkable long-term contraceptive efficacy in controlling several species of wildlife, zoo animals and domestic pets. Many of these CVs are commercially available for contraceptive use in these animals.

• CVs based upon sperm antigens and leukemia inhibitory factor have shown excellent results in laboratory animals, especially the mouse model. They are at the experimental stage and are being explored for clinical trials in humans. CVs based upon sperm antigens can be used for both women and men.

• The vaccine based upon β-hCG has undergone Phases I and II clinical trials in sexually active women, with only one pregnancy reported in 1224 cycles with antibody titers ≥50 ng/ml. When the titers decreased to <30 ng/ml, there was a rapid regain of fertility. Vaccination did not cause any side effect, including no effect on menstrual cycle. Besides birth control, this vaccine also showed extremely promising results against prevention of several hCG-secreting cancers.

• Recently, recombinant β-hCG vaccine has been constructed that is highly immunogenic and more potent than the prototype original vaccine. Presently, this vaccine is undergoing toxicological testing before starting the clinical trials in women.

• In a recent WHO meeting on Contraception in Geneva, Switzerland, 13–14 November 2012, development of CVs was enlisted as one of the highest priorities. An International Task-Force has been set for CV development.

• Development of CV will be a major breakthrough in the field of contraception, with a high acceptability both in the developed and developing nations.

Notes