The HSD-hCG vaccine prevents pregnancy in women: feasibility study of a reversible safe contraceptive vaccine

Oral immunocontraceptive vaccines: A novel approach for fertility control in wildlife

The overabundant populations of wildlife have caused many negative impacts, such as human-wildlife conflicts and ecological degradation. The existing approaches like injectable immunocontraceptive vaccines and lethal methods have limitations in many aspects, which has prompted the advancement of oral immunocontraceptive vaccine. There is growing interest in oral immunocontraceptive vaccines for reasons including high immunization coverage, easier administration, frequent boosting, the ability to induce systemic and mucosal immune responses, and cost-effectiveness. Delivery systems have been developed to protect oral antigens and enhance the immunogenicity, including live vectors, microparticles and nanoparticles, bacterial ghosts, and mucosal adjuvants. However, currently, no effective oral immunocontraceptive vaccine is available for field trials because of the enormous development challenges, including biological and physicochemical barriers of the gastrointestinal tract, mucosal tolerance, pre-existing immunity, antigen residence time in the small intestine, species specificity and other safety issues. To overcome these challenges, this article summarizes achievements in delivery systems and contraceptive antigens in oral immunocontraceptive vaccines and explores the potential barriers for future vaccine design and application.

Unconventional Actions of Glycoprotein Hormone Subunits: A Comprehensive Review

The glycoprotein hormones (GPH) are heterodimers composed of a common α subunit and a specific β subunit. They act by activating specific leucine-rich repeat G protein-coupled receptors. However, individual subunits have been shown to elicit responses in cells devoid of the receptor for the dimeric hormones. The α subunit is involved in prolactin production from different tissues. The human chorionic gonadotropin β subunit (βhCG) plays determinant roles in placentation and in cancer development and metastasis. A truncated form of the thyrotropin (TSH) β subunit is also reported to have biological effects. The GPH α- and β subunits are derived from precursor genes (gpa and gpb, respectively), which are expressed in most invertebrate species and are still represented in vertebrates as GPH subunit paralogs (gpa2 and gpb5, respectively). No specific receptor has been found for the vertebrate GPA2 and GPB5 even if their heterodimeric form is able to activate the TSH receptor in mammals. Interestingly, GPA and GPB are phylogenetically and structurally related to cysteine-knot growth factors (CKGF) and particularly to a group of antagonists that act independently on any receptor. This review article summarizes the observed actions of individual GPH subunits and presents the current hypotheses of how these actions might be induced. New approaches are also proposed in light of the evolutionary relatedness with antagonists of the CKGF family of proteins.

Latheef S, Sharun K, Khurana SK, K. A, Tiwari R, Bhatt P, K. V, Chaicumpa W. Role of Antisperm Antibodies in Infertility, Pregnancy, and Potential forContraceptive and Antifertility Vaccine Designs: Research Progress and Pioneering Vision

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.

Gonadotropins and their receptors: coevolution, genetic variants, receptor imaging, and functional antagonists

Gonadotropins belong to the family of dimeric glycoprotein hormones and regulate gonadal physiology mediated by G protein-coupled, seven-transmembrane receptors. These glycoprotein hormones are widely used in the clinic to promote ovarian follicle development and for treating some cases of male infertility. We traced the coevolution of dimeric gonadotropin hormones and their receptors, together with thyrotropin and its receptor. We updated recent findings on human genetic variants of these genes and their association with dizygotic twining, polycystic ovarian syndrome, primary ovarian insufficiency, male-limited precocious puberty, and infertility. In addition to the known physiological roles of gonadotropin-receptor signaling in gonadal tissues, we also discussed emerging understanding of extragonadal functions of gonadotropins in bones and adipose tissues, together with recent advances in in vivo imaging of gonadotropin receptors in live animals. Recent development of gonadotropin receptor agonists and antagonists were summarized with an emphasis on the development of functional antagonists for FSH receptors to alleviate osteoporosis and obesity associated with menopause.

Investigation of factors influencing the immunogenicity of hCG as a potential cancer vaccine

Human chorionic gonadotrophin (hCG) and its β-subunit (hCGβ) are tumour autocrine growth factors whose presence in the serum of cancer patients has been linked to poorer prognosis. Previous studies have shown that vaccines which target these molecules and/or the 37 amino acid C-terminal hCGβ peptide (hCGβCTP) induce antibody responses in a majority of human recipients. Here we explored whether the immunogenicity of vaccines containing an hCGβ mutant (hCGβR68E, designed to eliminate cross-reactivity with luteinizing hormone) or hCGβCTP could be enhanced by coupling the immunogen to different carriers [keyhole limpet haemocyanin (KLH) or heat shock protein 70 (Hsp70)] using different cross-linkers [1-ethyl-3(3-dimethylaminopropyl)carboiimide (EDC) or glutaraldehyde (GAD)] and formulated with different adjuvants (RIBI or Montanide ISA720). While there was little to choose between KLH and Hsp70 as carriers, their influence on the effectiveness of a vaccine containing the BAChCGβR68E mutant was less marked, presumably because, being a foreign species, this mutant protein itself might provide T helper epitopes. The mutant provided a significantly better vaccine than the hCGβCTP peptide irrespective of the carrier used, how it was cross-linked to the carrier or which adjuvant was used when hCG was the target. Nonetheless, for use in humans where hCG is a tolerated self-protein, the need for a carrier is of fundamental importance. Highest antibody titres were obtained by linking the BAChCGβR68E to Hsp70 as a carrier by GAD and using RIBI as the adjuvant, which also resulted in antibodies with significantly higher affinity than those elicited by hCGβCTP peptide vaccine. This makes this mutant vaccine a promising candidate for therapeutic studies in hCGβ-positive cancer patients.

Human Chorionic Gonadotropin as a Pivotal Endocrine Immune Regulator Initiating and Preserving Fetal Tolerance

The pregnancy hormone, human chorionic gonadotropin (hCG), is crucially involved in processes such as implantation and placentation, two milestones of pregnancy whose successful progress is a prerequisite for adequate fetal growth. Moreover, hCG determines fetal fate by regulating maternal innate and adaptive immune responses allowing the acceptance of the foreign fetal antigens. As one of the first signals provided by the embryo to its mother, hCG has the potential to regulate very early pregnancy-driven immune responses, allowing the establishment and preservation of fetal tolerance. This mini review focuses on how hCG modulates the adaptive arm of the immune system including dendritic cells as key regulators of adaptive immune responses.

Epitope-Specific Anti-hCG Vaccines on a Virus Like Particle Platform

The possibility of a contraceptive vaccine targeting human chorionic gonadotropin has long been recognized, but never fully realized. Here we describe an epitope-specific approach based on immunogenic display of hCG-derived peptides on virus-like particles of RNA bacteriophage. A number of recombinant VLPs were constructed, each displaying a different hCG-derived peptide. Some were taken from the disordered C-terminal tail of the hormone, another came from an internal loop, and yet another was an epitope mimic produced by affinity-selection on an hCG-neutralizing antibody target. Immunization of mice with some VLPs yielded antisera that bound the hormone and neutralized hCG biological activity.

Priming with DNA Enhances Considerably the Immunogenicity of hCG β-LTB Vaccine

PROBLEM

Necessity to elicit antibody response above the protective threshold titres by sexually active women immunized to prevent pregnancy.

METHOD OF STUDY

Recombinant hCGβ-LTB vaccine expressed as both DNA and protein. Balb C mice employed for testing immunogenicity.

RESULTS

Necessity to give three primary injections of the vaccine to elicit proper antibody response. Immunization twice with DNA form of the vaccine at fortnightly interval followed by the protein elicits a distinctly higher antibody response than proteinic vaccine alone. Antibodies generated are bio-effective against hCG.

CONCLUSION

Immunization with the DNA form of the recombinant hCGβ-LTB vaccine twice at fortnightly interval followed by the proteinic form of the vaccine induces distinctly higher antibody response.

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.

Immunocontraceptives: new approaches to fertility control

The rapidly increasing global population has bowed the attention of family planning and associated reproductive health programmes in the direction of providing a safe and reliable method which can be used to limit family size. The world population is estimated to exceed a phenomenal 10 billion by the year 2050 A.D., thus presenting a real jeopardy of overpopulation with severe implications for the future. Despite the availability of contraceptive methods, there are over one million elective abortions globally each year due to unintended pregnancies, having devastating impact on reproductive health of women worldwide. This highlights the need for the development of newer and improved contraceptive methods. A novel contraceptive approach that is gaining substantial attention is "immunocontraception" targeting gamete production, gamete outcome, or gamete function. Amongst these, use of sperm antigens (gamete function) seems to be an exciting and feasible approach. However, the variability of immune response and time lag to attain titer among vaccinated individuals after active immunization has highlighted the potential relevance of preformed antibodies in this league. This review is an attempt to analyze the current status and progress of immunocontraceptive approaches with respect to their establishment as a future fertility control agent.

Milestones in contraceptive vaccines development and hurdles in their application

Contraceptive vaccines have been proposed for controlling the growing human population and wildlife population management. Multiple targets such as gonadotropin releasing hormone (GnRH), luteinizing hormone, follicle stimulating hormone, gonadotropin receptors, sperm-specific proteins and zona pellucida glycoproteins have been exploited to develop contraceptive vaccine and their efficacy investigated and shown in various experimental animal models. Vaccines based on GnRH have found application in immuno-castration of male pigs for prevention of boar-taint. Vaccines based on zona pellucida glycoproteins have shown promising results for population management of wild horses and white-tailed deer. Phase II clinical trials in women with β-human chorionic gonadotropin (β-hCG)-based contraceptive vaccine established proof of principle that these can be developed for human application. Block in fertility by β-hCG contraceptive vaccine was reversible. Further research inputs are required to establish the safety of contraceptive vaccines, improve their immunogenicity and to develop novel vaccine delivery platforms for providing long lasting immunity.

Making of a vaccine preventing pregnancy without impairment of ovulation and derangement of menstrual regularity and bleeding profiles

The story of making a vaccine against human chorionic gonadotropin (hCG) for control of fertility is briefly reviewed. The choice of hCG was made on the consideration that it is not involved in the cascade of hormones leading to ovulation; hence, antibodies against hCG would neither disturb ovulation nor normal production of sex hormones by the female. It would not react with any other tissue of the body because no organ of a healthy noncancerous female expresses hCG. International Committee for Contraception Research played a historic role in testing its immunogenicity, safety and reversibility in women in Finland, Sweden, Chile and Brazil. The Population Council also conducted valuable long-term studies (5 years) in New York in 63 rhesus monkeys, which demonstrated the lack of pathological consequences of antibodies cross-reactive with species luteinizing hormone. The first-ever efficacy trials on a birth control vaccine established high efficacy (one pregnancy in 1224 cycles) of anti-hCG antibodies at and above 50 ng/mL titers. Fertility was regained in the immediate next cycle, at titers falling below 35 ng/mL. A recombinant vaccine, hCGβ-LTB, has been made, which is highly immunogenic in mice. It is due to undergo toxicology studies prior to resumption of clinical trials. An additional utility of this vaccine is likely in advanced-stage terminal cancers expressing hCG/subunits.

Phase I study utilizing a novel antigen-presenting cell-targeted vaccine with Toll-like receptor stimulation to induce immunity to self-antigens in cancer patients

PURPOSE

The use of tumor-derived proteins as cancer vaccines is complicated by tolerance to these self-antigens. Tolerance may be broken by immunization with activated, autologous, ex vivo generated and antigen-loaded, antigen-presenting cells (APC); however, targeting tumor antigen directly to APC in vivo would be a less complicated strategy. We wished to test whether targeted delivery of an otherwise poorly immunogenic, soluble antigen to APC through their mannose receptors (MR) would induce clinically relevant immunity.

EXPERIMENTAL DESIGN

Two phase I studies were conducted with CDX-1307, a vaccine composed of human chorionic gonadotropin beta-chain (hCG-β) fused to an MR-specific monoclonal antibody, administered either locally (intradermally) or systemically (intravenously) in patients with advanced epithelial malignancies. An initial dose escalation of single-agent CDX-1307 was followed by additional cohorts of CDX-1307 combined with granulocyte-macrophage colony-stimulating factor (GM-CSF) and the Toll-like receptor (TLR) 3 agonist polyinosinic-polycytidylic acid (poly-ICLC) and TLR7/8 agonist resiquimod to activate the APC.

RESULTS

CDX-1307 induced consistent humoral and T-cell responses to hCG-β when coadministered with TLR agonists. Greater immune responses and clinical benefit, including the longest duration of stable disease, were observed with immunization combined with local TLR agonists. Immune responses were induced equally efficiently in patients with elevated and nonelevated levels of serum hCG-β. Antibodies within the serum of vaccinated participants had tumor suppressive function in vitro. Toxicity consisted chiefly of mild injection site reactions.

CONCLUSIONS

APC targeting and activation induce adaptive immunity against poorly immunogenic self-antigens which has implications for enhancing the efficacy of cancer immunotherapy.

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.

Evaluation of the immunogenicity of a single chain chimeric peptide composed of hCGβ and oLHα for inhibition of the growth of hCGβ-expressing cancer cells

Human chorionic gonadotropin (hCG) is a membrane-associated protein highly expressed in several types of human cancer cells. The expression in the cancer cells indicates that hCG may be a potential target molecule for cancer immunotherapy. The objective of this study was to develop a novel immunogenic molecule, which can efficiently induce the neutralizing antibody against hCG and which is also suitable for mass production. The immunogenicity of the recombinant single chain chimeric protein of hCGβ-oLHα expressed by yeast was examined. Additionally, the inhibitory effects of the anti-hCGβ-oLHα antibody on the growth of hCG-positive cancer cells were determined. It was found that hCGβ-oLHα yielded high titers of anti-hCG rabbit antibody that could effectively neutralize the bioactivity of hCG. The rabbit anti-hCGβ-oLHα IgG inhibited the proliferation of hCG-expressing human colorectal cancer cells (LS-174, HCT-116, HCT-15 and KM-12) in a dose-dependent manner. Furthermore, an intact anti-tumor vaccine was prepared by conjugating hCGβ-oLHα with tetanus toxoid (TT) and this was used to immunize Balb/c mice bearing hCG-expressing SP2/0 tumor cells. The progression of tumors in these immunized mice was remarkably inhibited. These results suggest that hCGβ-oLHα is a new promising immunogenic molecule for the development of an anti-hCG-based cancer vaccine.

Kinetic analysis of a human chorionic gonadotropin-beta epitope-paratope interaction

Kinetics of protein-protein or ligand-ligate interaction has predominantly been studied by optical spectroscopy (particularly fluorescence) and surface plasmon resonance biosensors. Almost all such studies are based on association kinetics between ligand-ligate and suffer from certain methodological and interpretational limitations. Therefore, kinetic analyses of dissociation data of such interactions become indispensable. In the present investigation, the radiolabeled human chorionic gonadotropin-beta ((125)IhCGbeta) was employed as a probe and nitrocellulose (NC) as a solid support to immobilize monoclonal antibody (MAb) G(1)G(10).1. The NC-G(1)G(10).1-(125)IhCGbeta complex (NC(com)) was prepared and the dissociation of radiolabeled hCGbeta was carried out in the presence of excess unlabeled ligate. From the experimental dissociation data under varying ionic strength, dissociation constants (k(- 1)), association constants (k(+1)) and affinity constants (k(a)) were calculated. The values obtained were utilized in exploring the amino acid residues constituting an epitopic region of hCGbeta involved in interaction with the complementary paratope on MAb G(1)G(10).1. Kinetic data of the present study supported our recently published findings [using single step-solid phase radioimmunoassay (SS-SPRIA)] that the core region of hCGbeta epitope consists of Arg (94,95) and Asp (99) while a Lys (104) and a His (106) are in proximity to the core epitopic region. Based on the results of present investigation, we conclude that dissociation kinetics coupled with SS-SPRIA unequivocally provides considerable insight into the study of ligand-ligate interactions and epitope analysis.

Molecular adjuvant C3d3 improved the anti-hCGbeta humoral immune response in vaginal inoculation with live recombinant Lactobacillus expressing hCGbeta-C3d3 fusion protein

To enhance the contraceptive efficiency of human chorionic gonadotrophin (hCG)-beta contraceptive vaccine, we coupled hCG-beta gene with molecular adjuvant C3d3, and cloned into live Lactobacilli (Lb.) to express fusion protein hCGbeta-C3d3. The recombinant Lb. could survive in BALB/c murine vagina for at least 3 weeks. After inoculating BALB/c and C57BL/6 mice via vagina, we found that the antibody titer peaks induced by the Lb.hCGbeta-C3d3 inoculation were higher significantly than the Lb.hCGbeta. T and B cells in spleen and vagina were significantly increased, and anti-hCGbeta IgG and IgA antibody-secreting cells in uterus and vagina were significantly increased compared to the control in different strain mice. Our study shows that the C3d3 can display apparent adjuvant efficiency to induce more powerful humoral response to the hCGbeta antigen in vaginal mucosal immunization.

The quest for better contraception: future methods

With the highest rates of unintended pregnancy and abortion in the developed world, the United States has plenty of room for improving the distribution of existing contraceptive options and an imperative for developing new methods. This article surveys new and future contraceptive methods. It does not contain a comprehensive list but focuses on methods that are close to Food and Drug Administration approval or fulfill special needs across the globe.

Mucosal inoculation of Lactobacillus expressing hCGβ induces an anti-hCGβ antibody response in mice of different strains

To show that an anti-human chorionic gonadotrophin-beta (hCGbeta) antibody response can be induced by inoculating Lb. expressing hCGbeta through different mucosal pathways in mice of two strains, female BALB/c and C57BL/6 mice were immunized via vaginal, oral or nasal routes with 10(8), 10(9), and 10(10)Lb.hCGbeta (a recombinant Lactobacillus expressing hCGbeta). The mice were immunized twice with a booster in study week 3. An indirect ELISA was used to determine anti-hCGbeta IgG and IgA antibodies in vaginal lavage and serum, obtained from the 2nd to 8th week after the primary immunization. Flow cytometry was used to analyze the lymphocyte proliferation from these tissues, 1 week after the primary immunization. The hCGbeta antigen-specific antibody-secreting cells of spleen, uterus, and vagina were evaluated by enzyme-linked immunospot assay (ELISpot), 2 weeks after the booster. The analysis showed that 10(9) and 10(10)Lb.hCGbeta inoculations induced similar anti-hCGbeta antibody responses, while the three mucosal pathways induced similar antibody responses. The antiserum obtained after boosters with 10(9) and 10(10)Lb. hCGbeta was able to neutralize more than 100 ng/ml hCG antigen, both in BALB/c and C57BL/6 mice. The highest antibody titer induced by vaginal mucosal immunization was stronger than that obtained via the other mucosal pathways. The B cells in the vagina appeared to proliferate after vaginal immunization (P<0.05). The numbers of anti-hCGbeta IgG and IgA antibody-secreting cells in the uterus and vagina were greater than in the spleen. Therefore, the vaginal mucosal route appears to be a better immunization pathway to induce higher anti-hCGbeta antibody levels in the reproductive tract.

Endometrial receptivity: Clinical assessment in relation to fertility, infertility, and antifertility

Fertility in humans and other mammalian species depends absolutely on synchronous events that render the developing blastocyst and the receiving uterus competent for implantation. Endometrial receptivity is defined as the period during which the endometrial epithelium acquires functional, but transient, ovarian steroid-dependent status supportive to blastocyst acceptance and implantation. Once inside the uterus, the blastocyst is surrounded by an intact luminal epithelium, which is considered to act as barrier to its attachment, except for this short period of high endometrial receptivity to blastocyst signal(s). Its transport and permeability properties, in conjunction with cellular action of the endometrium and the embryo, have been suggested to influence creation and maintenance of informational and nutritional status of uterine luminal milieu. This period, also termed as the 'window of implantation,' is limited to days 20-24 of menstrual cycle in humans. However, establishment of endometrial receptivity is still a biological mystery that remains unsolved despite marked advances in our understanding of endometrial physiology following extensive research associated with its development and function. This review deals with various structural, biochemical, and molecular events in the endometrium coordinated within the implantation window that constitute essential elements in the repertoire that signifies endometrial receptivity and is aimed to achieve a better understanding of its relationship to fertility, infertility, and for the development of targeted antifertility agents for human use and welfare.

Gene conjugation of molecular adjuvant C3d3 to hCGβ increased the anti-hCGβ Th2 and humoral immune response in DNA immunization

Human chorionic gonadotropin (hCG) has been used as an anti-fertility vaccine and as a target for cancer immunotherapy. We have explored the use of three copies of C3d in DNA vaccine as molecular adjuvant to improve the immunogenicity of this hormone in previous work and found that the immune response induced by pcDNA3-hCGbeta-C3d3 has been enhanced 243-fold compared with pcDNA3-hCGbeta following DNA immunization in BALB/c mice. In the present study, a new functionally active DNA vaccine of hCGbeta-C3d3 chimera based on pCMV4 vector has been described. We compared the expression efficiency of pCMV4 and pcDNA3 eukaryotic vectors for hCGbeta and hCGbeta-C3d3 fusion protein and the immune response of mice immunized with pcDNA3-hCGbeta, pCMV4-hCGbeta, pcDNA3-hCGbeta-C3d3 and pCMV4-hCGbeta-C3d3, respectively, at 25, 50 and 100 pmol dose, and further analyzed the levels of Th1 and Th2 cytokines produced by spleen lymphocytes of the immunized mice upon hCG restimulation in vitro. It was found that pCMV4 vector achieved 1.3-1.5-fold higher protein expression and raised 1.1-1.2 (primary) and 1.2-1.3 (booster) logs higher titer of anti-hCGbeta IgG than pcDNA3. Mice vaccinated with 50 pmol of hCGbeta-C3d3-DNAs elicited the highest titer of hCGbeta-specific antibody among the serial doses and the immune response induced by pCMV4-hCGbeta-C3d3 were, respectively, 1.3, 1.3 and 1.2 logs higher than that of pcDNA3-hCGbeta-C3d3 and 2.2, 2.9 and 2.4 logs higher than that of pCMV4-hCGbeta at week 2 following the booster immunization. Moreover, we observed that the production of IL-4 and IL-10 increased in mice vaccinated with hCGbeta-C3d3-DNAs and the ratio of IL-4/IFN-(gamma) showed a Th2 bias of immune response in the mice immunized with hCGbeta-C3d3-DNAs. These findings indicated that gene fusion of C3d3 to hCGbeta, as a means of harnessing the adjuvant potential of the innate immune system, may improve the antigen-specific Th2 humoral immune response of the hCGbeta DNA vaccine and the pCMV4 vector is a more ideal eukaryotic vector for DNA vaccine than pcDNA3.

Recent advances in contraceptive vaccine development: a mini-review

Contraceptive vaccines (CV) may provide viable and valuable alternatives to the presently available methods of contraception. The molecules that are being explored for CV development either target gamete production [luteinizing hormone-releasing hormone (LHRH)/GnRH, FSH], gamete function [sperm antigens and oocyte zona pellucida (ZP)], and gamete outcome (HCG). CV targeting gamete production have shown varied degrees of efficacy; however, they either affect sex steroids causing impotency and/or show only a partial rather than a complete effect in inhibiting gametogenesis. However, vaccines based on LHRH/GnRH are being developed by several pharmaceutical companies as substitutes for castration of domestic pets, farm and wild animals, and for therapeutic anticancer purposes such as in prostatic hypertrophy and carcinoma. These vaccines may also find applications in clinical situations that require the inhibition of increased secretions of sex steroids, such as in uterine fibroids, polycystic ovary syndrome, endometriosis and precocious puberty. CV targeting molecules involved in gamete function such as sperm antigens and ZP proteins are exciting choices. Sperm constitute the most promising and exciting target for CV. Several sperm-specific antigens have been delineated in several laboratories and are being actively explored for CV development. Studies are focused on delineating appropriate sperm-specific epitopes, and increasing the immunogenicity (specifically in the local genital tract) and efficacy on the vaccines. Anti-sperm antibody (ASA)-mediated immunoinfertility provides a naturally occurring model to indicate how a vaccine might work in humans. Vaccines based on ZP proteins are quite efficacious in producing contraceptive effects, but may induce oophoritis, affecting sex steroids. They are being successfully tested to control feral populations of dogs, deer, horses and elephants, and populations of several species of zoo animals. The current research for human applicability is focused on delineating infertility-related epitopes (B-cell epitopes) from oophoritis-inducing epitopes (T-cell epitopes). Vaccines targeting gamete outcome primarily focus on the HCG molecule. The HCG vaccine is the first vaccine to undergo Phase I and II clinical trials in humans. Both efficacy and lack of immunopathology have been reasonably well demonstrated for this vaccine. At the present time, studies are focused on increasing the immunogenicity and efficacy of the birth control vaccine, and examining its clinical applications in various HCG-producing cancers. The present article will focus on the current status of the anti-sperm, anti-ZP, anti-LHRH/GnRH and anti-HCG vaccines.

Identification of adjuvants that enhance the therapeutic antibody response to host IgE

In the development of a novel vaccine against atopic allergies, we have screened for adjuvants that enhance the therapeutic antibody response against self immunoglobulin E (IgE). The response against self IgE is induced by administration of a vaccine antigen, which contains both self and non-self IgE regions, together with an adjuvant. We evaluated five commonly used adjuvants; Freund's, aluminium hydroxide, ISCOMs, Montanide ISA 51 and Montanide ISA 720, and found that the mineral oil-based adjuvants; Montanide ISA 51 and Freund's induced at least 5-10-fold higher anti-self IgE titers than any of the other candidates. However, with one exception, Alum, the immune responses against the carrier, i.e. the non-self regions, were similar for all adjuvants, indicating that the ability to induce responses against self and non-self antigens differ among adjuvants. The responses against non-self IgE were more than 50-fold higher than antibody responses against self IgE in both the Freund's and Montanide 51-administered animals, indicating that the response against self molecules is markedly inhibited by tolerance-inducing mechanisms. Co-administration of Montanide ISA 51 with immuno-stimulatory substances from bacteria; muramyldipeptide (MDP), monophosphoryl-lipid A (MPL) or a formyl-methionine-containing tripeptide (fMLP), did not elevate the anti-self IgE response. Hence, adjuvants based on pure mineral oil without additional immuno-stimulatory substances appear to be the best adjuvant candidates in therapeutic vaccines aimed at regulating the in vivo levels of self-proteins.

Engineering, cloning, and expression of genes encoding the multimeric luteinizing-hormone-releasing hormone linked to T cell determinants in Escherichia coli

Two synthetic genes were designed and engineered to encode for multimeric luteinizing-hormone-releasing hormone (LHRH) peptides linked to T cell determinants. These genes were cloned into the prokaryotic expression vectors under control of strong inducible promoters, to overexpress the multimeric LHRH peptides as recombinant proteins. Multimeric LHRH-T cell peptides were expressed as insoluble inclusion bodies in Escherichia coli cultures. Cell extracts containing the recombinant proteins showed immunoreactivity on Western blots with monoclonal antibody recognizing the native hormonal peptide. These gene constructs have potential applications in therapy of sex-steroid-hormone-dependent cancers.

How far from a hormone-based contraceptive vaccine?

Antibodies of appropriate specificity are able to block the action of hormones which are obligatory for successful reproduction. Thus, if immunisation using such hormones can provoke adequate titres of bioneutralizing antibodies in sexually mature individuals, the vaccinee becomes infertile ('immunocontraception') for as long as sufficient titres of the antibodies are maintained. In the case of hormones that are required for the development of sexual maturity in the male, immunisation of young animals can prevent sexual maturation ('immunocastration'). The hormones which have been targeted are gonadotropin-releasing hormone (GnRH) for both immunocastration and immunocontraception, and follicle-stimulating hormone (FSH) and human chorionic gonadotropin (hCG) for immunocontraception.

Efficacy of a Recombinant Chimeric Anti-hCG Antibody to Prevent Human Cytotrophoblasts Fusion and Block Progesterone Synthesis

PROBLEM

A recombinant chimeric antibody against hCG (cPIPP) has been engineered and expressed at high yield in plants. The purpose of this work was to enquire whether this antibody is competent to neutralize the bioactivity of hCG on human trophoblasts.

METHODS

Cytotrophoblast cells, isolated from term placentae were maintained in culture for 3 days in presence or absence of humanized chimeric anti-hCG antibodies. Progesterone secreted was quantitated by ELISA. Fusion and cyto-architecture of the cells was studied by light and electron microscopy. Modulation of E-cadherin was investigated using RT-PCR and immunocytochemistry.

RESULTS

Recombinant chimeric anti-hCG antibody blocked the synthesis of progesterone by trophoblasts. No fusion of cytotrophoblasts to form syncytium took place. E-cadherin, a vital cell adhesion molecule involved in cell-to-cell interaction did not show differentiation related decline in its expression in presence of the antibody.

CONCLUSION

Recombinant chimeric anti-hCG antibody (cPIPP) was effective to neutralize hCG induced bioactivities in the human derived trophoblast cells.

Gene fusion of molecular adjuvant C3d to hCGβ enhances the anti-hCGβ antibody response in DNA immunization

OBJECTIVE

To express the hCGbeta-C3d3 fusion protein in a CHO cell continual expression system to investigate further the adjuvant effects of C3d on contraceptive vaccination.

METHOD

We constructed a plasmid pcDNA3-hCGbeta-C3d3 which contains three copies of murine C3d cDNA and the hCGbeta gene by cloning the chimerical hCGbeta-C3d3 cDNA into the eukaryotic vector pcDNA3 downstream of the CMV promoter. The plasmid was transfected into a COS-7 cell transient expression system and a CHO cell continual expression system. RIA was used to detect hCGbeta in the culture supernatant. Western blot and Raji cell immunohistochemical assays were performed to evaluate the expressed protein. Then, 6-8-week-old female BALB/c mice were inoculated intramuscularly with pcDNA3-hCGbeta and pcDNA3-hCGbeta-C3d3, and ELISA was used to assess anti-hCGbeta IgG antibody in serum.

RESULTS

In 72 h after COS-7 cells were transfected with the plasmid pcDNA3-hCGbeta-C3d3, 1.0x10(5) cells could secrete 152 ng of the recombinant protein (calculated by hCGbeta contained). The transfected CHO cells, which were then screened by G418, could continuously secrete the fusion protein at 660 ng/10(6) cells/48 h. The hCGbeta-C3d3 protein was purified by anti-hCGbeta immunoaffinity chromatography. Raji cell immunohistochemical assay demonstrated that both the hCGbeta and C3d3 were successfully fused. After DNA immunization intramuscularly, the anti-hCGbeta IgG antibody titer in the pcDNA3-hCGbeta-C3d3 immunized group was 243-fold higher than that of the pcDNA3-hCGbeta immunized group.

CONCLUSION

We have expressed the hCGbeta-C3d3 protein successfully, both in a transient expression system (COS-7 cells) and in a stable expression system (CHO cells). The C3d3 molecular adjuvant can enhance significantly the immunogenecity of hCGbeta antigen in DNA immunization.

The safety and immunogenicity of a CETP vaccine in healthy adults

A cholesterol ester transfer protein (CETP) vaccine (CETi-1) that induces auto-antibodies that specifically bind and inhibit activity of endogenous CETP has been demonstrated in rabbits to significantly increase HDL-C and reduce the development of atherosclerosis. In a Phase I human trial with CETi-1, one patient at the highest dose (250 mg) out of a total of 36 patients who received a single injection developed anti-CETP antibodies. In an extension study of 23 patients, 53% (8/15) who received a second injection of the active vaccine developed anti-CETP antibodies compared with 0% (0/8) in the placebo group. The vaccine was well tolerated and no significant laboratory abnormalities occurred. CETi-1 is a feasible therapy in humans to induce CETP auto-antibodies. Future research will determine if repeat inoculations will induce a sufficient anti-CETP antibody response to inhibit CETP and increase HDL levels.

Embryo-maternal signalling: how the embryo starts talking to its mother to accomplish implantation

The process of implantation and trophoblast invasion is currently considered as the most limiting factor for the establishment of pregnancy. Molecular interactions at the embryo-maternal interface during the time of adhesion and subsequent invasion are crucial to the process of embryonic implantation. Both partners, the mother as well as the embryo, play equal roles in the embryo-maternal dialogue, the embryonic part being the main topic in this study. Investigations of the proteins in the extra-embryonic matrices (i.e. zona pellucida) indicate that the embryo participates intensively in this early embryo-maternal signalling. One unique feature during implantation process of primate embryos is the release of chorionic gonadotrophin, which seems to influence endometrial activity by two different mechanisms: (i) luteotrophic activity with increasing progesterone release and (ii) a direct action on the endometrium. Furthermore, embryonic interleukin-1beta may be involved in embryo-maternal signalling. Other significant signals in this interaction are most likely leukaemia inhibitory factor (LIF) and colony-stimulating factor (CSF), which stimulate matrix metalloproteinase (MMP)/insulin-like growth factor binding protein-1 (IGFBP-1) activity and the insulin-like growth factor (IGF) system, which is modulated by embryonic IGFBP-3. Similar significances are discussed for uteroglobin and haptoglobin. Finally, the phenomenon of maternal immunological tolerance, triggered by the presence of the early embryo, is fundamental to the understanding of implantation and trophoblast invasion. A tightly regulated balance between activated and inactivated T cells at the implantation site may control the beginning of adequate trophoblast invasion and also limit this invasion to a tolerable extent for the maternal system, consequently ensuring a biologically healthy haemo-chorial placenta.

Elimination of luteinizing hormone cross-reactive epitopes from human chorionic gonadotropin

The beta-chain of human chorionic gonadotropin (hCG) has been shown to have efficacy in clinical trials when used as a contraceptive vaccine. This hormone is a heterodimer, the alpha-chain being shared with the other members of the glycoprotein hormone family but the beta-chain being unique to hCG. Nevertheless, there is sequence homology between the hCG beta-chain and the beta-chain of human luteinizing hormone (hLH) which results in cross-reactive antibodies being produced following immunization with wild-type hCGbeta. To reduce or eliminate such cross-reactions we generated a number of mutants of the hCGbeta-chain. One mutant (hCGbeta(R68E)), containing an arginine to glutamic acid replacement at position 68, has been expressed as a recombinant protein in High Five insect cells. The recombinant BAChCGbeta(R68E) form of this molecule was used to immunize rabbits and the antibody response compared to the response following immunization with the recombinant wild-type protein BAChCGbeta and with the native hCGalphabeta heterodimer isolated from pregnancy urine. The mutant elicited the production of antibodies which avidly recognize native hCG. Compared to immunization with wild-type hCG, the response showed very little cross reactivity with hLH. This is demonstrated to be due to a radically altered epitope usage in the response to the mutant, which now focuses mainly upon the C-terminal region of the beta-chain.

Infertility in mice induced by the rhesus monkey chorionic gonadotropin beta-subunit glycoprotein (rmCGbeta) using DNA immunization

The recombinant eukaryotic expression vector pCMV4-rmCGbeta, inserted full-length cDNA of the beta-subunit of rhesus monkey chorionic gonadotropin (rmCGbeta), as DNA immuno-contraceptive against CGbeta glycoprotein, has previously demonstrated the biological expression of rmCGbeta in vitro and in vivo. The plasmid DNA of pCMV4-rmCGbeta was inoculated into BALB/c mice at different doses and routes as DNA immuno-contraceptive to understand its antifertility effect. The results of immune responses indicated that the intradermal inoculation is the optimal pCMV4-rmCGbeta DNA delivery method for BALB/c mice, and the dose of 10 microg should be enough to elicit immune response. With different doses from 10-50 microg, marked reductions in the fertility of the female mice after two intramuscular inoculations of pCMV4-rmCGbeta DNA were seen, while the similar level of humoral immune responses were induced. With the dose of 20 microg of pCMV4-rmCGbeta DNA, the mice showed reduction in fertility from intraperitoneal, and intradermal to intramuscular inoculating method. The antifertility effect of antiserum from immunized mice confirmed that the antibodies elicited by pCMV4-rmCGbeta DNA could prevent pregnancy in female mice. At the same time, the full-length cDNA of beta-subunit of mouse chorionic gonadotropin (muCGbeta) was cloned from placenta and sequenced for the first time (GenBank Accession No. AF333067). Sequence analysis showed that muCGbeta shares 99.6% homology with rmCGbeta and 90.6% with hCGbeta respectively. The results indicated that the infertility of BALB/c mice induced by pCMV4-rmCGbeta contraceptive should be further studied as a CGbeta DNA contraceptive. (Mol Cell Biochem 231: 89-96, 2002)

Current status of fertility control methods in India

Approximately 48.2% of couples of 15 to 49 years of age practice family planning methods in India. Female sterilization accounts for 34.2%, with male sterilization declining from 3.4% in 1992-93 to 1.9% in 1998-99. Use of the condom increased to 3.1% from 2.4%. There is an urgent need for research to develop new contraceptive modalities especially for men and also for women and to make existing methods more safe, affordable and acceptable. Current efforts in India to develop a male contraceptive are mainly directed towards (i) development of antispermatogenic agents to suppress sperm production, (ii) prevention of sperm maturation, (iii) prevention of sperm transport through vas deferens or rendering these sperm infertile and (iv) prevention of sperm deposition. Research work in the field of prevention of sperm transport through vas deferens has made significant advances. Styrene maleic anhydride (SMA) disturbed the electrical charge of spermatozoa leading to acrosome rupture and consequent loss in fertilizing ability of sperm. A multicentre phase-III clinical trial using SMA is continuing and it is hoped that the SMA approach would be available in the near future as an indigenously developed injectable intra-vasal male contraceptive. The safety and efficacy of available oral contraceptives were evaluated. An indigenously developed oral contraceptive 'Centchorman', which is a nonsteroidal, weakly estrogenic but potently antiestrogenic, was found to be safe and effective and is now being marketed in India since 1991 as a 'once a week' pill. Cyclofem and Mesigyna have been recommended as injectable contraceptives with proper counselling and service delivery by Indian studies. It has been recommended that these injectable contraceptives be added to the existing range of contraceptive methods available in the National Family Planning Programme. Based on the Indian studies CuT 200 was also recommended. Studies have indicated the advantage of intrauterine devices (IUD); they are long acting, relatively easily removed and fertility returns rapidly after their removal. Recent studies have recommended CuT 200 for use up to 5 years. The combination of some plant products i.e. Embelia ribes, Borax and Piper longum has been found to be safe and effective as a female contraceptive and the results of phase-I clinical trials are encouraging. Research work is going on in the country in various areas with special reference to hormonal contraceptive - a three monthly injectable contraceptive, immuno-contraceptives, antiprogestins, etc.

Vaccines and passive immunological approaches for the control of fertility and hormone-dependent cancers

Reviewed here is the development of a vaccine against the human chorionic gonadotropin that prevents pregnancy in sexually active women without impairment of ovulation or derangement of menstrual regularity. Also reviewed are the vaccines inducing antibodies against the luteinizing hormone-releasing hormone, which have immunotherapeutic potential in prostatic hypertrophy and other sex hormone-dependent male and female cancers. The adoption of passive immunization using humanized recombinant antihormone antibodies is advocated for assured efficacy and safe, prompt therapeutic action.

The emerging role of immunoregulation of fibrinogen-related procoagulant Fgl2 in the success or spontaneous abortion of early pregnancy in mice and humans

PROBLEM

Abortion of chromosomally normal embryos in the CBA X DBA/2 mating combination is triggered by release of Th1 cytokines (tumor necrosis factor [TNF]-alpha, interferon [IFN]-gamma, and interleukin [IL]-1), which cause abortion via a novel prothrombinase, Fgl2, and polymorphonuclear leukocytes. The site of activation may be maternal vascular endothelium on arteries and veins nourishing the placenta. Activation of coagulation is also prominent in spontaneous abortion of chromosomally normal human embryos. We asked where is Fgl2 up-regulated in the uterus in murine abortions, and if similar Fgl2 expression occurs in human pregnancy failure.

METHODS

Control CBA X DBA/2 pregnant mice, or from mice injected with TNF-alpha + IFN-gamma on day 7.5 of gestation, were removed on day 8.5, fixed, sectioned, and subject to in situ hybridization for Fgl2. Sections were also stained for fibrin. Elective first trimester termination samples or biopsies taken early in the course of a recurrent miscarriage were similarly fixed, sectioned, and analyzed by in situ hybridization. Control and cytokine-treated mice were anticoagulated with heparin, an activator of antithrombin III, and/or the direct anti-thrombin inhibitor hirudin.

RESULTS

Low level Fgl2 expression localized to basal decidua remote from the embryo was noted in control mice; cytokine treatment, which causes greater than 80% of abortions, produced a striking up-regulation in this area as well as in a band at the junction of decidua and myometrium. Trophoblast also became strikingly positive. Fgl2 expression was associated with increased fibrin staining. Anticoagulation significantly protected against abortions, but doses were limited by the complication of retroplacental hemorrhage. In tissue from normal first trimester pregnancy, minimal Fgl2 positivity was seen in some villous syncytiotrophoblast, in villous stroma, cytotrophoblast, and in some cells in decidua. In spontaneous abortion of normal embryo, striking Fgl2 positivity was seen in syncytiotrophoblast and extravillous cytotrophoblast, in association with areas of thrombus formation.

CONCLUSIONS

Fgl2 appears to be physiologically expressed and may protect against the internal danger of maternal and/or fetal bleeding during pregnancy and at parturition; a role in inhibiting transplacental traffic is also possible. External dangers in the form of stress, endotoxin, and antigens eliciting Th1 cytokine responses upregulate Fgl2 prothrombinase in trophoblast as well as in decidua, which results in spontaneous abortion of immunogenetically "weaker" embryos.

Unconventional vaccine targets. Immunization for pregnancy, peptic ulcer, gastric cancer, cocaine abuse, and atherosclerosis

Vaccine technology can be applied to targets of intervention that currently have not been considered preventable by immunization. Targets include some diseases caused by, or related to, infectious agents, and other conditions clearly unassociated with disease pathogens. This article considers vaccines for pregnancy, peptic ulcer disease, gastric cancer, cocaine abuse and atherosclerosis.

Epitopes of human chorionic gonadotropin and their relationship to immunogenicity and cross-reactivity of beta-chain mutants

PROBLEM

Human chrionic gonadotropin (hCG) is a placental glycoprotein hormone, a heterodimeric molecule, consisting of alpha and beta chains. It induces the synthesis of progesterone, which is essential for the maintenance of the fertilized egg. Antibodies directed against hCG can, therefore, prevent pregnancy and serve as a vaccine. hCG belongs to the glycoprotein hormone family and shares the alpha chain with the other members. The beta chain is a hormone-specific subunit that is unique to hCG, but still possesses 85% amino acid homology with the beta chain of luteinizing hormone (LH), which means that prolonged immunization with hCG produces antibodies that cross-react with LH.

METHOD OF STUDY

We have taken an approach involving the mutation of beta hCG to eliminate cross-reactive epitopes without affecting the natural folding of the polypeptide chain and thus the unique beta hCG-specific epitopes.

RESULTS

Several mutants have been constructed that have maintained the binding to hCG-specific monoclonal antibodies (mAbs) but have lost the ability to bind to a panel of LH cross-reactive mAbs. To investigate the immunogenicity of selected mutants, mice were immunized with expression plasmid DNA, containing the gene for wild-type beta hCG and two mutants: mutant 3, with four amino acid substitutions (68 Arg-->Glu; 74 Arg-->Ser; 75 Gly-->His; 79 Val-->His), and mutant 7, with a single amino acid substitution (68 Arg-->Glu).

CONCLUSIONS

Although both mutants were able to elicit antibody responses in at least some animals, the levels were less than those seen with the wild-type beta hCG DNA, and there seems still to be a residual cross-reactivity with LH. Attempts to improve the immunogenicity of the mutants and to further modify the sequence to remove the cross-reactivity are currently underway.

Identification of novel transmembrane gene sequence and its use for cell-surface targeting of beta subunit of human chorionic gonadotropin

We identified a 685-nucleotide gene fragment that codes for the transmembrane and cytoplasmic domains of glycoprotein of the LEP strain rabies virus and carried out experiments designed to express a novel fusion protein on the cell surface. The cDNA encoding the membrane anchor sequence was fused in the correct reading frame to the 3' end of the cDNA encoding the beta subunit of human chorionic gonadotropin (beta(h)CG), a secretory glycoprotein that is used as an antigen for a contraceptive vaccine being developed in our laboratory. The fusion gene cassette was placed under the control of a vaccinia virus early promoter and cloned in a host-restricted fowlpox viral vector. The recombinants, when used to infect mammalian cells that do not allow the replication of fowlpox virus, expressed the N-terminal 135 amino acid residues of beta(h)CG anchored in the cell membrane by the 75-amino acid C-terminal sequence derived from rabies virus glycoprotein. This hybrid protein is correctly processed post-translationally and transported efficiently to the plasma membrane of non-permissive cells such that the anchored beta(h)CG molecule retains the correctly folded native antigenic epitope(s).

Preliminary studies with recombinant chorionic gonadotropin beta-subunit produced in Escherichia coli for use as an antigen in a birth control vaccine

PROBLEM

Prototype human chorionic gonadotropin (hCG) vaccines based on natural sources are unsuitable for widespread applications due to their complex manufacturing procedures, cost, and carrier-mediated immune suppression.

METHOD OF STUDY

Wistar rats were immunized with alum-adsorbed CG beta (recombinant), CG beta-TT, and nCG beta (native CG beta)-TT, whereas Bonnet monkeys were immunized with only CG beta. The anti-hCG antibody titre in the sera obtained at different time points were quantified by radioimmunoassay. The sera of Wistar rats were characterized in terms of their affinity to hCG, bioneutralization capacity (by inhibition of hCG-induced testosterone production in Leydig cells), and cross-reactivity with human luteinizing hormone, human follicle-stimulating hormone, and human thyroid-stimulating hormone (by direct binding assays).

RESULTS

Antigen-binding capacities of sera obtained upon immunization with CG beta were 3,080 +/- 943 ng/ml (n = 6) and 3,993 +/- 1,292 ng/ml (n = 4), respectively, in rats and monkeys. The analysis of data revealed that immunization of rats with CG beta produced antibodies comparable to that of CG beta-TT and nCG beta-TT.

CONCLUSION

The study opens up the possibility of producing pure and highly immunogenic CG beta by a recombinant DNA route, as a consistent source of antigen for birth control vaccine.

Molecular medicine and population control

As we uncover the physiological and molecular mechanisms behind human reproduction, we gain the potential to exert more control over our reproductive capabilities. In the past two decades, the prospects for 'infertile' women to bear children, or 'sterile' men to father them, have improved dramatically; recently, women have given birth in their sixties, well beyond their natural menopause. Thanks to developments in contraception, couples can now enjoy an active sex-life without a significant risk of pregnancy, and more accurately control the size and timing of their families. But these new freedoms have a price: they also have the potential to cause demographic distortions, medical harm to individuals and abuse of human rights.

Vaccines for control of fertility and hormone-dependent cancers

This article traces and reviews the development of vaccines against two reproductive hormones, luteinizing hormone release hormone (LHRH) and human chorionic gonadotrophin (hCG). The heterospecies dimer (HSD)-dehydrogenase hCG vaccine is the first to have completed phase II clinical trials providing evidence for the prevention of pregnancy in humans by immunization with this vaccine. The vaccine acts without blocking ovulation or disturbance of menstrual bleeding. Its effect is fully reversible and fertility is regained with decline of the antibodies. The antibody response in humans is directed against immunodominant epitopes located in the core part of beta hCG, distinct from the C-terminal region. However, problems arising from carrier-conjugated vaccines against 'self' hormones such as carrier-induced immuno-suppression on repeated immunization are evoked and solutions discussed. The LHRH vaccine, a model semi-synthetic vaccine, can be used in both sexes and has applications in regulation of fertility of animals. It has therapeutic applications as a cost-effective approach in clinical conditions where LHRH agonists and antagonists have therapeutic action. The vaccine has undergone phase I and II clinical trials in advanced-stage carcinoma of prostate patients with encouraging results.