The immunogenicity of recombinant and dimeric gonadotrophin-releasing hormone vaccines incorporating a T-helper epitope and GnRH or repeated GnRH units

Plant-Produced Mouse-Specific Zona Pellucida 3 Peptide Induces Immune Responses in Mice

Contraceptive vaccines are designed to stimulate autoimmune responses to molecules involved in the reproductive process. A mouse-specific peptide from zona pellucida 3 (mZP3) has been proposed as a target epitope. Here, we employed a plant expression system for the production of glycosylated mZP3 and evaluated the immunogenicity of plant-produced mZP3-based antigens in a female BALB/c mouse model. In the mZP3-1 antigen, mZP3 fused with a T-cell epitope of tetanus toxoid, a histidine tag, and a SEKDEL sequence. A fusion antigen (GFP-mZP3-1) and a polypeptide antigen containing three repeats of mZP3 (mZP3-3) were also examined. Glycosylation of mZP3 should be achieved by targeting proteins to the endoplasmic reticulum. Agrobacterium-mediated transient expression of antigens resulted in successful production of mZP3 in Nicotiana benthamiana. Compared with mZP3-1, GFP-mZP3-1 and mZP3-3 increased the production of the mZP3 peptide by more than 20 and 25 times, respectively. The glycosylation of the proteins was indicated by their size and their binding to a carbohydrate-binding protein. Both plant-produced GFP-mZP3-1 and mZP3-3 antigens were immunogenic in mice; however, mZP3-3 generated significantly higher levels of serum antibodies against mZP3. Induced antibodies recognized native zona pellucida of wild mouse, and specific binding of antibodies to the oocytes was observed in immunohistochemical studies. Therefore, these preliminary results indicated that the plants can be an efficient system for the production of immunogenic mZP3 peptide, which may affect the fertility of wild mice.

Palmitic acid-modified GnRH-Th epitope peptide immunocastration vaccine (W/O/W adjuvant) can effectively ensure the castration and reduce the smelly smell in boars

Introduction

Recent studies have demonstrated the effectiveness of Gonadotropin-releasing hormone (GnRH) in inhibiting testicular growth and development in male animals to achieve castration while improving the meat quality of various livestock species, including cattle, sheep, goats, and pigs.

Methods

In this research, a GnRH-Th vaccine was synthesized using the Fmoc solid-phase synthesis technique, and the T helper (Th) antigen was modified with palmitic acid to improve its efficacy. The vaccine was then coated with a water-in-oil-in-water adjuvant to improve stability and safety. After passing safety and stability tests, the vaccine was administered to 13-week-old boars.

Results

The results showed that it was stable, safe, and effective for up to 15 months. Moreover, the vaccine did not negatively affect the growth rate and body weight of the pigs. The palmitic acid-modified "GnRH-Th epitope peptide immunocastration vaccine (Water-in-Oil-in-Water (W/O/W)) effectively reduced the testosterone concentration and achieved castration. The concentration of androstenone and skatole hormones significantly decreased, leading to improved meat quality in the boars. The boars were then slaughtered at 33 weeks of age, and the results showed that the meat quality of the vaccinated boars was superior to that of the non-vaccinated control group (p < 0.05).

Discussion

This study demonstrated that GnRH can safely and effectively achieve immune castration in boars after coupling T cell epitopes, palmitic acid modification and W-O-W coating. Provide a better method for the further development of GnRH and the realization of animal welfare.

Contraceptive efficacy of recombinant porcine zona proteins and fusion protein encompassing canine ZP3 fragment and GnRH in female beagle dogs

PROBLEM

To manage population of dogs (Canis familiaris), the efficacy of recombinant proteins-based contraceptive vaccines to inhibit fertility has been evaluated in female beagle dogs.

METHOD OF STUDY

Female beagle dogs (n = 4) were immunized with physical mixture of Escherichia coli-expressed recombinant porcine ZP3 with promiscuous T cell epitope of tetanus toxoid (TT-KK-pZP3) and porcine ZP4 with promiscuous T cell epitope of bovine RNase (bRNase-KK-pZP4), or with a fusion protein encompassing dog ZP3 fragment and two copies of GnRH with appropriate promiscuous T cell epitopes (dZP3-GnRH₂ ); control animals received only alum, the adjuvant. The immunized animals were followed-up for antibody titres by ELISA as well as for fertility status subsequent to mating with male dogs.

RESULTS

Active immunization of female dogs following a three injections schedule at 4-week intervals with a physical mixture of TT-KK-pZP3 + bRNase-KK-pZP4 as well as dZP3-GnRH₂ , led to generation of significant antibody titres against respective recombinant proteins. Active immunization with dZP3-GnRH₂ also led to generation of antibodies reactive with both dZP3 and GnRH. A booster dose on day 383 led to an increase in antibody titres and circulating antibodies against respective recombinant proteins could be observed on day 528. Antibodies in immune serum samples from dogs immunized with TT-KK-pZP3 + bRNase-KK-pZP4 or dZP3-GnRH₂ reacted with native canine ZP as assessed by an indirect immunofluorescence assay. Mating studies revealed a reduced number of pregnancies as well as a significant reduction in the number of pups born in the female dogs immunized with dZP3-GnRH₂ as compared to the adjuvanted control. Curtailment of pregnancy in dZP3-GnRH₂ immunized group was associated with antibody titres against dZP3-GnRH₂ . However, immunization with recombinant TT-KK-pZP3 + bRNase-KK-pZP4 did not significantly decrease the number of pups born as compared to the adjuvanted control.

CONCLUSION

These studies revealed the potential of recombinant dZP3-GnRH₂ -based contraceptive vaccine to curtail fertility in female dogs. Large scale studies to establish the efficacy and safety of this recombinant protein for the management of community dog population are thus warranted.

Contraceptive efficacy of recombinant fusion protein comprising zona pellucida glycoprotein-3 fragment and gonadotropin releasing hormone

Contraceptive vaccines have been used for the management of wildlife population. In the present study, we have examined the contraceptive potential of Escherichia coli-expressed recombinant fusion protein comprising of 'promiscuous' T cell epitope of tetanus toxoid [TT; amino acid (aa) residues 830-844] followed by dilysine linker (KK), dog ZP3 fragment (aa residues 307-346), triglycine spacer (GGG), T cell epitope of bovine RNase (bRNase; aa residues 94-104), GnRH, T cell epitope of circumsporozoite protein of Plasmodium falciparum (CSP; aa residues 362-383), and GnRH. SDS-PAGE analysis of the purified refolded protein revealed a dominant ∼12 kDa band, which in Western blot reacted with mouse polyclonal antibodies against dog ZP3 fragment and mouse monoclonal antibodies against GnRH. Immunization of female FvB/J mice following two booster schedule with the above recombinant protein supplemented with alum led to high antibody titres against the immunogen as well as ZP3 and GnRH as determined by ELISA. The immune sera reacted with zona pellucida of mouse oocyte and also inhibited in-vitro fertilization. The qRT-PCR studies showed decrease in the ovarian GnRH receptor in mice immunized with the recombinant fusion protein. Mating studies revealed high contraceptive efficacy of the recombinant protein as in two independent experiments, 90% of the immunized female mice failed to conceive. Following one booster immunization schedule, 50% of the immunized female mice failed to conceive. However, in adjuvanted controls, all the female mice became pregnant. To conclude, the recombinant protein described herein has a good potential to be developed as candidate contraceptive vaccine.

Inoculation of dogs with a recombinant ACTH vaccine

OBJECTIVE

To determine whether inoculation of healthy dogs with a recombinant peptide containing 3 copies of ACTH would result in the production of antibodies against ACTH and whether this would affect pituitary-adrenocortical function.

ANIMALS

8 healthy dogs.

PROCEDURES

A recombinant peptide consisting of 3 copies of ACTH fused to a T-helper cell epitope was produced in Escherichia coli. The protein was inoculated into 4 dogs at 4-week intervals (total of 3 inoculations/dog). Four control dogs received inoculations of PBS solution mixed with adjuvant. Blood samples were collected for determination of antibody titers against ACTH and for measurement of basal and ACTH-stimulated plasma cortisol concentrations.

RESULTS

Inoculation with the ACTH vaccine resulted in production of anti-ACTH antibodies in all 4 dogs. Titers were initially high but declined by 15 weeks after the initial inoculation. Basal cortisol concentrations were unaffected by inoculation with the ACTH vaccine. Plasma cortisol concentrations in response to ACTH stimulation were reduced at 12 weeks, but not at 15 weeks, after the first inoculation.

CONCLUSIONS AND CLINICAL RELEVANCE

Inoculation of dogs with a recombinant ACTH vaccine resulted in the production of antibodies against the hormone. Anti-ACTH titers were initially high but were not sustained. The only detectable endocrine effect in treated dogs was a reduction in cortisol concentration in response to ACTH stimulation in 2 of 4 dogs at 12 weeks after the first inoculation. The effect of vaccine administration on the pituitary-adrenal system was subtle and transient.

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.

Immunization with a recombinant GnRH vaccine fused to heat shock protein 65 inhibits mammary tumor growth in vivo

Gonadotrophin-releasing hormone (GnRH) is the prime decapeptide hormone in the regulation of mammalian reproduction. Active immunization against GnRH has been a good treatment option to fight against hormone-dependent disease such as breast cancer. We designed and purified a novel protein vaccine Hsp65-GnRH(6) containing heat shock protein 65 (Hsp65) and six copies of GnRH in linear alignment. Immunization with Hsp65-GnRH(6) evoked strong humoral response in female mice. The generation of specific anti-GnRH antibodies was detected by ELISA and verified by western blot. In addition, anti-GnRH antibodies effectively neutralized endogenous GnRH activity in vivo, as demonstrated by the degeneration of the ovaries and uteri in the vaccinated mice. Moreover, the growth of EMT-6 mammary tumor allografts was inhibited by anti-GnRH antibodies. Histological examinations have shown that there was increased focal necrosis in tumors. Taken together, our results showed that immunization with Hsp65-GnRH(6) elicited high titer of specific anti-GnRH antibodies and further led to atrophy of reproductive organs. The specific antibodies could inhibit the growth of EMT-6 murine mammary tumor probably via an indirect mechanism that includes the depletion of estrogen. In view of these results, the protein vaccine Hsp65-GnRH(6) appears to be a promising candidate vaccine for hormone-dependent cancer therapy.

The hinge region fragment of immunoglobulin G improves immunogenicity of recombinant gonadotrophin-releasing hormone conjugated to the T-helper epitope in designing peptide vaccines

In our previous study, the hinge fragment (225-232/225'-232') of human immunoglobulin G1 (IgG1) was used as a space peptide linker for synthesizing the GnRH3-hinge-MVP chimeric peptide, whereby three repeated gonadotrophin-releasing hormone (GnRH) units and a T-cell epitope from measles virus fusion protein (MVP) were amide-bond-linked at the N and C terminus, respectively, to the hinge peptide for producing anti-GnRH antibody responses. To investigate whether or not the hinge region fragment can improve the immunogenicity of GnRH, we further synthesized and purified GnRH3-hinge-MVP, GnRH3-hinge and GnRH3-MVP using recombinant DNA technology. Under high pH conditions, GnRH3-hinge-MVP was capable of forming double-chain structures. Immunization of male mice with the immunogens of GnRH3-hinge-MVP resulted in the generation of high-titre antibodies specific for GnRH. The synthetic GnRH3-hinge and GnRH3-MVP induced a lower titre of anti-GnRH antibody than GnRH3-hinge-MVP. This was followed by a decrease in serum testosterone levels, which resulted in a low level of expression of the relaxin-like factor gene in the testis. Our data suggest that peptide and T-cell epitopes oriented at the N-terminus or C-terminus of hinge peptides simplify the antigenic peptide conjugates and may be considered as potential synthetic immunogens.

A novel virus-like particle based on hepatitis B core antigen and substrate-binding domain of bacterial molecular chaperone DnaK

Hepatitis B virus core (HBc) protein has been proved to be an attractive carrier for foreign epitopes, and can display green fluorescent protein (GFP) on its surface. The structure of substrate-binding domain of DnaK [DnaK (394-504 aa), DnaK SBD] is similar to GFP, we therefore reasoned that DnaK SBD might also be tolerated. Electron microscopic observations suggested that the chimeric proteins containing the truncated HBc (HBcDelta) and DnaK SBD could self-assemble into virus-like particle (VLP). Then the accessibility of DnaK SBD and the adjuvanticity of VLP HBcDelta-SBD were demonstrated by two recombinant peptide vaccines against gonadotropin-releasing hormone (GnRH), GhM and GhMNR. The latter carries in addition the peptide motif NRLLLTG which is known to bind to DnaK and DnaK SBD. The combination of VLP HBcDelta-SBD and GhMNR elicited stronger humoral responses and caused further testicular atrophy than the combinations of VLP HBcDelta and GhMNR or VLP HBcDelta-SBD and GhM in Balb/c mice. These findings indicate VLP HBcDelta-SBD might serve as an excellent carrier for GhMNR and some other peptide vaccines.

A novel human parathyroid hormone (1-34) analog for the treatment of osteoporosis

The more effective bioactive peptides which can be efficiently prepared with low cost and high yield are in great demand for the development of therapeutic peptides. In this study, Pro-Pro-[Arg(11)]hPTH(1-34)-Pro-Pro-Asp (hPTH'), an analog of human parathyroid hormone (1-34) [hPTH(1-34)], was prepared by an efficiently cost-effective preparation strategy. It was repeated eight times on the gene level and expressed in the form of inclusion bodies in Escherichia coli. Following some primary purifications, the inclusion bodies of octapeptide repeats were hydrolyzed into hPTH' monomers by hydrochloric acid. After further purified by a CM52 chromatographic column, hPTH' reached a yield of 16.9% and output of 61 mg/l medium. Furthermore, we compared anabolic effects between hPTH' and hPTH(1-34) on ovariectomized rats. The results indicated that hPTH' led to more significant increments in bone material density (BMD), trabecular width and bone formation marker as well as less loss in marrow space area than what hPTH(1-34) did. In addition, the active form of hPTH' was introduced by the excision with dipeptidyl peptidase IV in vivo. These results suggest that hPTH' is more effective than hPTH(1-34) in stimulating bone formation and improving skeletal microarchitecture. We can conclude that hPTH' is potentially a more effective therapeutical agent on osteoporosis.

Immunisation with a plasmid DNA vaccine encoding gonadotrophin releasing hormone (GnRH-I) and T-helper epitopes in saline suppresses rodent fertility

Research into active immunisation against gonadotrophin releasing hormone (GnRH-I) has gained widespread acceptance as a means of controlling reproduction and behaviour of farm, companion and wild animals. Many studies describe the use of multiple copies of the self-peptide in linear alignment and conjugation with a large carrier protein to increase the immune response to the peptide. However, problems resulting from carrier protein epitope suppression have seen a diversion of interest into the use of genetic materials to elicit an optimum immune response. In this study, a 533-bp long DNA vaccine was constructed in pcDNAV5-HisB coding for 18.871 kDa GnRH-I-T-helper-V5 epitopes fusion protein. COS1 cells transfected with the vaccine construct were found to release fusion protein into culture supernatant. The vaccine construct (100 microg/mice) in saline solution administered into the anterior quadriceps muscle of ICR male and female mice stimulated antigen-specific IgG antibody responses. Testosterone levels in the vaccinated male mice were significantly (p = 0.021) reduced. A significant reduction in uterine implants were noted following mating between immunised males and control females (p = 0.028), as well as between immunised females and control males (p = 0.004). Histological examination of both the male and female gonads in study week 13 showed atrophy of the seminiferous epithelium and suppression of folliculogenesis.

Immunisation of male mice with a plasmid DNA vaccine encoding gonadotrophin releasing hormone (GnRH-I) and T-helper epitopes suppresses fertility in vivo

Immunisation against mammalian gonadotrophin releasing hormone (GnRH-I) linked to large carrier proteins has been shown to disrupt fertility. However, various studies have shown that the carrier protein causes epitope suppression of the hapten response, resulting in short-lived immunoneutralisation, followed by a return of fertility. A range of strategies has been used to resolve this, with limited success. The aim of this study was to construct a plasmid DNA vaccine encoding GnRH-I and T-helper epitopes. A 498 bp long vaccine construct in pcDNA3.1+ was administered to male mice in conjunction with a Hemagglutinating Virus of Japanese Envelop (HVJ-E) vector or in saline solution. The vaccine efficacy was evaluated in terms of GnRH-I specific IgG antibody response, serum testosterone levels, testicular spermatogenesis and the ability to produce offspring. The vaccine appeared to induce higher anti-GnRH-I IgG antibody response and insult the fertility axis, which was characterised by a drop of epididymal sperm counts, reduction of serum testosterone levels, suppressed testicular spermatogenesis and a significant decrease in litter numbers compared to control animals. The end-point vaccine efficacy was much higher in the HVJ-E vector mediated immunisation, than in saline alone.

Long-lasting specific antibodies against P277 induced by mucosal administration of P277 repeat sequences carried by Hsp65 in the absence of adjuvants

To improve the weak immunogenicity of peptide P277, the recombinant expression plasmid pET28-Hsp65-6 x P277 was constructed by inserting 5 x P277 which was amplified by PCR into the vector pET28-Hsp65-P277. It was transformed into Escherichia coli BL21 (DE3) and the fusion protein (Hsp65-6 x P277) was expressed effectively as soluble protein after inducing by lactose. The fusion protein was purified by means of cell disruption, ammonium sulfate precipitation, double-distilled H2O dialysis, DEAE52-cellulose column chromatography, and then used to immunize female NOD mice with three i.n. inoculations in the absence of adjuvants. Serum samples from the immunized mice were collected at 3 weeks interval. Antibodies against P277 and HSP65 were detected in immunized mice sera by enzyme-linked immunosorbent assay (ELISA) and Western blot. Specific antibodies were successfully induced and lasted for more than 20 weeks in animals immunized with the fusion protein via intranasal route even in the absence of adjuvants.

Stability of plasmid and expression of a recombinant gonadotropin-releasing hormone (GnRH) vaccine in Escherichia coli

In our previous studies, the recombinant gonadotropin-releasing hormone (GnRH) peptide was constructed into a T7 RNA polymerase-based expression system. The recombinant gene encoding GnRH3-hinge-MVP, which contained three repeated GnRH units, a fragment of hinge region (225-232/225'-232'), and a T cell epitope of measles virus protein, was cloned into Escherichia coli BL21 harboring pED-GnRH3. The high activity of T7 RNA polymerase could make the expression system very powerful for high-level expression of the recombinant protein. However, during the large-scale production of recombinant protein, the productivity of the fermentation process was directly affected by many factors, such as plasmid stability, protein production, and culture conditions. In this study, we studied the effects of various culture conditions on the plasmid stability and the target protein yield including selective pressure, the time of induction by lactose, and the number of successive cultures. The results indicate that the plasmid instability may be caused by a loss of plasmid rather than structural change. However, to go down to future generations, engineered bacteria have the stability of plasmid and protein yield to a large extent. The amount of the fusion protein was also up to 40% of the total cell protein after the 50th generation. These data would be useful for the industrial production of the recombinant GnRH vaccine.

Cloning, expression, and purification of a highly immunogenic recombinant gonadotropin-releasing hormone (GnRH) chimeric peptide

To design an anti-gonadotropin-releasing hormone (GnRH) vaccine capable of eliciting strong immunogenicity, a gene fragment encoding a chimeric peptide was constructed using polymerase chain reaction and ligated into a novel expression vector for recombinant expression in a T7 RNA polymerase-based expression system. The chimeric peptide called GnRH3-hinge-MVP contained three linear repeats of GnRH (GnRH3), a fragment of the human IgG1 hinge region, and a T-cell epitope of measles virus protein (MVP). The expression plasmid contained the GnRH3-hinge-MVP construct ligated to its fusion partner (AnsB-C) via an unique acid labile Asp-Pro linker. The recombinant fusion protein was expressed in an inclusion body in Escherichia coli under IPTG or lactose induction and the target peptide was easily purified using washing of urea and ethanol precipitation. The target chimeric peptide was isolated from the fusion partner following acid hydrolysis and purified using DEAE-Sephacel chromatography. The purified GnRH3-hinge-MVP was determined to be highly homogeneous by IEF analysis and the N-terminal sequencing. Further, immunization of female mice with the recombinant chimeric peptide resulted in generation of high-titer antibodies specific for GnRH. The results showed that GnRH3-hinge-MVP could be considered as a candidate anti-GnRH vaccine.

A synthetic gonadotropin-releasing hormone (GnRH) vaccine for control of fertility and hormone dependent diseases without any adjuvant

Active immunization against self-peptides have gained widespread acceptance inspite of their low immunogenicity. Recent applications involving multiple copies of self-peptides in linear alignment and conjugation with carrier proteins appear to increase the immune response against self-peptides. As with most vaccines, however, immunogens require supplementation with adjuvants to elicit an optimum immune response. In the present study, we prepared a double-chain mini-protein with each chain containing three linear repeats of the self-peptide gonadotropin-releasing hormone (GnRH3), the hinge region of human IgG1 (hinge), and a T-helper epitope from the measles virus protein (MVP). The GnRH3-hinge-MVP mini-protein was conjugated to purified recombinant heat shock protein 65 (Hsp 65) of Mycobacterium bovis and used to immunize rats primed with subcutaneous injections of Bacillus Calmette-Guerin (BCG) in the absence of adjuvants. The GnRH3-hinge-MVP-Hsp 65 stimulated the production of specific anti-GnRH antibodies in the absence of adjuvants and the antibody titer was comparable to that produced in rats immunized with the dimeric mini-protein in the presence of Freund's adjuvant. Moreover, immunization with the adjuvant-free GnRH3-hinge-MVP-Hsp 65 induced degeneration of the reproductive organs in both male and female rats unlike those immunized in the absence of Hsp 65 or in control animals inoculated with the vehicle only. Histological examination of the affected organs showed atrophy of the seminiferous tubules with diminished spermatogenesis in the testes of male rats. In female rats, the uteri were much smaller in size and the ovaries exhibited reduced follicular development. These findings demonstrated that GnRH3-hinge-MVP-Hsp 65 mounted a strong immune response in the absence of conventional adjuvants, and could prove useful in control of fertility and the treatment of conditions/diseases where GnRH ablation is required.

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.