Analysis of the contraceptive potential of antibodies against native and deglycosylated porcine ZP3 in vivo and in vitro

Zona pellucida glycoproteins: Relevance in fertility and development of contraceptive vaccines

Mammalian zona pellucida (ZP) is composed of three to four glycoproteins, which plays an important role during fertilization. Mutations in the genes encoding zona proteins are reported in women with empty follicle syndrome, degenerated oocytes and those with an abnormal or no ZP further emphasizing their relevance during fertility. Immunization with either native or recombinant ZP glycoproteins/proteins leads to curtailment of fertility in various animal species. Observed infertility is frequently associated with ovarian pathology characterized by follicular atresia and degenerative changes in ZP, which may be due to oophoritogenic T cell epitope(s) within ZP glycoproteins. To avoid ovarian dystrophy, B cell epitopes of ZP glycoproteins have been mapped by using bio-effective monoclonal antibodies. Immunization with the immunogens encompassing the mapped B cell epitopes by and large led to amelioration of follicular atresia. However, their use for human application will require more rigorous research to establish their safety and reversibility of the contraceptive effect. Nonetheless, to minimize human-animal conflicts, ZP-based contraceptive vaccines have been used successfully in the population management of free-ranging animal species such as feral horses, white-tailed deer and elephants. To control zoonotic diseases, attempts are also underway to control the population of other animal species including stray dogs, which acts as one of the major vectors for the rabies virus.

Enhanced contraception of canine zona pellucida 3 DNA vaccine via targeting DEC-205 in mice

Zona pellucida 3 (ZP3) is a potential antigen for the development of contraceptive vaccines to control animal population. In this study, we designed a canine ZP3 (CZP3) DNA vaccine through targeting DEC-205 (named as pcD-scFv-CZP3c) and investigated its contraceptive effect in mice. Female BALB/c mice were intramuscularly immunized 3 times at 2 weeks intervals. After immunization, humoral and cellular immune responses were detected by ELISA and flow cytometry. The results showed that pcD-CZP3 and pcD-scFv-CZP3c induced CZP3-specific antibody (Ab) responses both in serum and vaginal secretions compared to pcDNA3.1. Additionally, compared to pcD-CZP3, pcD-scFv-CZP3c increased the levels of CZP3-specific Abs after a third immunization. Abs induced by these two DNA vaccines could bind with mice and dogs oocytes. Moreover, pcD-scFv-CZP3c enhanced the activation of CD4⁺ T cells characterized by the increased frequencies of CD4⁺CD44⁺ T cells. Finally, the contraceptive effect was evaluated in the immunized mice. These two DNA vaccines significantly decreased a mean litter size of mice compared to pcDNA3.1, but pcD-scFv-CZP3c group showed the smallest mean litter size. The mean litter size of pcD-scFv-CZP3 were 3.2 ± 0.742 and 4.6 ± 1.118 in two mating tests, which were significantly lower than pcDNA3.1(P < 0.001 and P < 0.05). Our results suggest that the CZP3 DNA vaccine targeted with DEC-205 may be a potential strategy for developing a contraceptive DNA vaccine.

Immunocontraception for Animals: Current Status and Future Perspective

An alternative to surgical sterilization for fertility control of animals (wild, zoo, farm, and domestic) is needed to prevent problems related to overpopulation, including culling and relocation. A PubMed and Google Scholar database search was conducted using the keywords 'contraceptive vaccine animals,' 'immunocontraception animals,' 'non-surgical sterilization animals,' 'PZP vaccine,' and 'GnRH vaccine.' The searches from 1972 to 2015 yielded over 1500 publications. These articles were read, and 375 were selected for detailed analysis. Articles referenced in these publications were also thoroughly examined. PZP and GnRH contraceptive vaccines (CVs) have been extensively investigated for fertility control of wild, zoo, farm, and domestic animal populations. Both vaccines have shown tremendous success with PZP vaccines taking the lead. Novel technologies and targets are being developed to improve existing vaccines and generate second-generation CVs. Single-shot vaccines, which can be delivered remotely, will greatly advance the field of immunocontraception for animal use with potential human application.

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.

Transgenic mice expressing inhibin α-subunit promoter (inhα)/Simian Virus 40 T-antigen (Tag) transgene as a model for the therapy of granulosa cell-derived ovarian cancer

Granulosa cell tumors are rare, 3-7.6% of primary ovarian tumors, although with poor prognosis as the tumor-related mortality rate is 37.3%, with 80% of deaths occurring on recurrence. We have created a transgenic (TG) murine model for gonadal somatic cell tumors by expressing the powerful viral oncogene, Simian Virus 40 T-antigen (Tag), under the regulation of murine inhibin α-subunit 6 kb promoter (inhα/Tag). Gonadotropin dependent ovarian granulosa cell tumors were formed in females by the age of 5-6 months, with a 100% penetrance. We have successfully used the inhα/Tag model to test different treatment strategies for ovarian tumors. With a gene therapy trial in inhα/Tag mice crossbred with inhα/HSV-TK (herpes simplex virus thymidine kinase) mice (double TG), we proved the principle that targeted expression of HSV-TK gene in gonadal somatic cell tumors enabled tumor ablation by anti-herpes treatment. When we aimed at targeted destruction of luteinizing hormone/chorionic gonadotropin receptor (LHCGR) expressing inhα/Tag tumor cells in vivo by a lytic peptide Hecate-CGβ conjugate, we could successfully kill the tumor cells, sparing the normal cells. We recently found high zona pellucida glycoprotein 3 (ZP3) expression in inhα/Tag granulosa cell tumors, as well as in human granulosa cell tumors. We tested the concept of treating the ovarian tumors of inhα/Tag mice by vaccination against the ectopically expressed ZP3. Immunotherapy with recombinant human (rh) ZP3 was highly successful with no objective side effects in inhα/Tag females, suggesting rhZP3 immunization as a novel strategy for the immunotherapy of ovarian granulosa cell tumors.

Infertility and Immunocontraception based on zona pellucida

The zona pellucida (ZP) is an extracellular matrix surrounding ovarian oocytes, ovulated eggs and preimplantation embryos. It plays several important roles at different stages of reproduction. Its constituent glycoproteins are expressed specifically in the ovary. It is thus possible to produce autoantibodies to ZP proteins that interfere with reproductive functions including folliculogenesis, fertilization and implantation. First, this article describes the history of anti-ZP antibodies detected in women with idiopathic infertility. Second, the current relationship between anti-ZP antibodies and infertility is discussed in relation to assisted reproductive medicine. Third, we introduce the latest studies of animal experiments involving the ZP. Finally, immunocontraceptive vaccine development using various ZP antigens is reviewed.

Granulocyte-macrophage colony-stimulating factor enhances the humoral immune responses of mouse zona pellucida 3 vaccine strategy based on DNA and protein coadministration in BALB/c mice

We recently demonstrated that co-administration of mouse zona pellucida 3 (mZP3) DNA and protein vaccine enhanced the contraception of mice by increasing humoral immune responses. In this study, we try to use granulocyte-macrophage colony-stimulating factor (GM-CSF) to further improve the humoral immune responses induced by mZP3 DNA and protein co-administration. BALB/c mice were intranasally pre-injected with GM-CSF 4 days before co-administration. Compared to DNA and protein coadministration without GM-CSF, the combination of GM-CSF and coadministration significantly enhances humoral immune responses, especially the level of secretory immunoglobulin A (sIgA) in vaginal washes. The enhanced antibody responses are correlated with the upregulated level of interleukin 4 (IL-4) and enhanced maturation of dendritic cells (DCs). Thus, GM-CSF is a potential candidate adjuvant to be used for the development of a safe and effective contraceptive vaccine.

Intranasal co-delivery with the mouse zona pellucida 3 and GM-CSF expressing constructs enhances humoral immune responses and contraception in mice

Granulocyte-monocyte colony-stimulating factor (GM-CSF) regulates the function of antigen-presenting cells (APCs) and has been broadly used as the adjuvant. Here, we tested whether intranasal delivery of GM-CSF can improve the contraception of mouse zona pellucida 3 (mZP3) DNA vaccine. Our results showed that co-administration of GM-CSF and mZP3 DNA vaccine increased the levels of secretory IgA (sIgA) and IgG antibodies in vaginal washes and serum, respectively. Co-administration enhanced Th2 responses through improving the maturation of dendritic cells. Importantly, GM-CSF significantly reduced the fertility rate and mean litter size induced by mZP3 DNA vaccine alone without interfering the normal follicular development. These data suggest that GM-CSF could be used as adjuvant to develop immunocontraceptive vaccine.

Tolerogenic DNA vaccine for prevention of autoimmune ovarian disease

DNA vaccines have been widely used to induce immune responses against molecular targets. In this study, we explored the possibility of using DNA vaccine combined with the immunosuppressant FK506 (tacrolimus) to antigen-specifically suppress unwanted immune responses and prevent autoimmune ovarian disease. To that end, we immunized C57BL/6 mice with a DNA vaccine encoding mouse zona pellucida 3 (ZP3) together with FK506. The immunization induced ZP3-specific CD4(+)CD25(+)Foxp3(+) regulatory T cells (Treg), which suppressed the induction of ZP3-specific delayed-type hypersensitivity in the animals. Significantly, the immunization also protected the animals from experimentally induced autoimmune ovarian disease. These results suggest that DNA vaccination in the presence of FK506 may be used to induce Treg cells and prevent AOD.

Mapping of minimal motifs of B-cell epitopes on human zona pellucida glycoprotein-3

The human zona pellucida glycoprotein-3 (hZP3) by virtue of its critical role during fertilization has been proposed as a promising candidate antigen to develop a contraceptive vaccine. In this direction, it is imperative to map minimal motifs of the B cell epitopes (BCEs) so as to avoid ZP-specific oophoritogenic T cell epitopes (TCEs) in the ZP3-based immunogens. In this study, based on known results of mapping marmoset and bonnet monkey ZP3 (mstZP3 and bmZP3), two predictable epitopes^{23–30  and  301–320} on hZP3 were first confirmed and five minimal motifs within four epitopes on hZP3 were defined using serum to recombinant hZP3a^22–176 or hZP3b^177–348 as well as a biosynthetic peptide strategy. These defined minimal motifs were QPLWLL^23–28 for hZP3^23–30, MQVTDD^103–108 for hZP3^93–110, EENW^178–181 for hZP3^172–190, as well as SNSWF^306–310 and EGP^313–315 for hZP3^301–320, respectively. Furthermore, the antigenicity of two peptides for hZP3^172–187 and hZP3^301–315 and specificity of the antibody response to these peptides were also evaluated, which produced high-titer antibodies in immunized animals that were capable of reacting to ZP on human oocytes, r-hZP3b^177–348 protein, as well as r-hZP3^172–190, r-hZP3^303–310, and r-hZP3^313–320 epitope peptides fused with truncated GST188 protein.

A novel treatment strategy for ovarian cancer based on immunization against zona pellucida protein (ZP) 3

We tested the principle of treating malignant ovarian tumors by vaccination against their ectopically expressed protein, zona pellucida glycoprotein (ZP) 3, using as the experimental model the granulosa cell tumors that develop in transgenic mice expressing the simian virus 40 T-antigen under the inhibin-α promoter (inhα/Tag). We found high ZP3 expression in granulosa cell tumors of the transgenic mice, in human surface ovarian cancer and granulosa cell lines, and in human granulosa cell tumors and their metastases. Early preventive immunization (between 2 and 5.5 mo of age) of transgenic mice with recombinant human (rh) ZP3 prevented ovarian tumorigenesis, and delayed therapeutic immunization (between 4.5 and 7 mo) reduced weights of existing tumors by 86 and 75%, respectively (P<0.001), compared to vehicle-treated control mice. No objective side effects of the immunizations were observed. Liver metastases were found in nontreated/vehicle-treated controls (n=7/39), but none following active rhZP3 immunizations (n=0/36; P<0.05). Immunization with rhZP3 was highly effective, as demonstrated by the induction of anti-ZP3 antibodies, as well as proliferative responses to the ZP3 antigen. These results signal rhZP3 immunization as a novel strategy to be developed for the immunotherapy of ovarian granulosa cell tumors, as well as for that of other malignancies that may express ZP3.

Intranasal co-administration with the mouse zona pellucida 3 expressing construct and its coding protein induces contraception in mice

The zona pellucida 3 (ZP3), an autoantigen, once used to develop contraceptive vaccine has been faced a safety issue. Avoiding its pathogenic T cell activation, we intranasally co-delivered the mZP3 DNA- and protein-based vaccines in mice and observed that a higher level of sIgA and IgG antibodies in vaginal washes, bronchoalveolar lavages and serum and yielded a lower level of fertility and mean litter size. Importantly, histological analysis showed that normal follicular developments of the infertile mice were not disrupted in the co-delivered group. Thus, the intranasal co-delivery may present a safe strategy for the development of contraceptive vaccine.

Minimal motif mapping of a known epitope on human zona pellucida protein-4 using a peptide biosynthesis strategy

An important step in the development of a human zona pellucida (huZP) peptide vaccine is to define the minimal amino acid motif for a mapped B cell epitope peptide within huZP4. Identification of this minimal motif is necessary to remove an overlapping T cell epitope that induces a pathogenic T cell response. Here we describe motif (PLTLEL(314-319)) mapping of an 18mer B cell epitope peptide(308-325) on huZP4 protein (previously known as huZP1/ZPB protein), achieved using a set of 22 biosynthetic 8mer peptides fused with truncated glutathione S-transferase (GST) or truncated streptavidin protein, and detected using rabbit anti-porcine zona pellucida (pZP) IgG. The immunogenicity of the B cell epitope peptide was evaluated in rabbits using expressed B cell epitope peptide fused with truncated streptavidin as the antigen. This construct elicited high titer antibody to the 18mer B cell epitope peptide, with reactivity to native human ZP, the biosynthetic 18mer peptide and the 18mer peptide GST fusion protein.

DNA vaccine encoding chimeric protein encompassing epitopes of human ZP3 and ZP4: immunogenicity and characterization of antibodies

Immunization with zona pellucida (ZP) glycoproteins leads to curtailment of fertility often associated with ovarian dysfunction. To avoid ovarian dysfunction, synthetic peptides corresponding to ZP glycoproteins have been proposed as candidate immunogens. In the present study, plasmid DNA encoding a human ZP glycoprotein-3 (ZP3) epitope corresponding to amino acid (aa) residues 334-343 and a human ZP glycoprotein-4 (ZP4) epitope corresponding to aa residues 251-273 separated by a triglycine spacer was constructed using the mammalian expression vector, VR1020. The plasmid DNA construct expressed both human ZP3 and ZP4 epitopes, as revealed by transient transfection of COS-1 (African green monkey, kidney) mammalian cells. Active immunization of female BALB/cJ mice with the DNA vaccine led to generation of antibodies reactive with baculovirus-expressed recombinant human ZP3, ZP4 and ZP3((334-343aa))-GGG-ZP4((251-273aa)) synthetic peptide in an ELISA as well as T cell responses. Antibodies generated by the DNA vaccine also recognized native ZP. The immune sera significantly inhibited (p<0.005) the binding of FITC-labeled ZP3 to capacitated human sperm, whereas no inhibition in the binding of FITC-labeled ZP4 was observed. However, a significant decrease in acrosomal exocytosis mediated by both recombinant human ZP3 (p<0.005) and ZP4 (p<0.005) was observed in presence of the immune sera. These studies demonstrate that a DNA vaccine can be designed to elicit antibodies against small epitopes of ZP glycoproteins.

Treatment of autoimmune ovarian disease by co-administration with mouse zona pellucida protein 3 and DNA vaccine through induction of adaptive regulatory T cells

BACKGROUND

Autoimmune ovarian disease (AOD) caused by auto-reactive T cells is considered a major reason for human premature ovarian failure, which affects 5% of women worldwide.

METHODS AND RESULTS

To develop an effective treatment for AOD, we showed that the co-administration of mouse zona pellucida protein 3 (mZP3) protein and DNA vaccine encoding the mZP3 was able to meliorate AOD in an AOD murine model induced by the mZP3. We observed that established AOD in mice reverted to a normal ovarian morphology without notable T-cell infiltration in the co-administrated group; whereas mice in the control groups developed severe AOD. The amelioration appears to be antigen specific because other co-administration combinations failed to reverse AOD and correlates with significant reductions of pathogenic T-cell responses and productions of tumor necrosis factor-alpha and interferon-gamma. Furthermore, the melioration is apparently associated with the induction of mZP3 specific regulatory T cells that exhibit a phenotypic CD4(+)CD25(-)FoxP3(+)IL-10(+) in the co-administrated group, which can be transferred to reverse AOD in vivo.

CONCLUSIONS

Thus, co-administration of mZP3 DNA and protein vaccines can be used to treat established AOD, and may provide a novel immunotherapy strategy to treat other autoimmune diseases.

Enhanced contraceptive response by co-immunization of DNA and protein vaccines encoding the mouse zona pellucida 3 with minimal oophoritis in mouse ovary

Zona pellucida 3 (ZP3) acts as the primary sperm receptor, induces autoantibody that can prevent oocyte fertilization and has been proposed as a vaccine candidate for contraception in humans. Due to the elicited autoreactive T cell inflammation that causes ovarian destruction, ZP3-based vaccine with removed T epitopes from the ZP3 is considered as a preferred approach. We present here a new strategy to eliminate the T cell inflammation while retaining a high level of antibody by co-immunization of mZP3 DNA and protein vaccines, which resulted in a higher reduction rate of fertility in this group. Histological analysis showed that there were normal follicular developments of infertile mice in the co-immunized group; while other vaccine groups of the most infertile mice lacked mature follicles. There was a significant correlation between normal follicular development and the inhibition of T cell response in co-immunized mice. At the same time, co-immunization reduced the production of inflammatory cytokine, IFN-gamma, and increased the productions of IL-10 and FoxP3 in CD4 T cells, suggesting the anti-inflammation may be via a T regulatory function. The results indicate that co-immunization of mZP3 DNA- and protein-based vaccines can reduce fertility without interfering with the normal follicular development and present a novel strategy to develop a contraceptive vaccine in humans.

Immunologic responses and adverse reactions to Freund's-adjuvanted porcine zona pellucida immunocontraceptives in domestic cats

A vaccine of native PZP with Freund's adjuvant has been widely used in zoo and wild ungulates, but safety in felids has not been evaluated. General health, immune response, and ovarian histology were assessed in five domestic cats vaccinated with PZP-Freund's and five cats given Freund's adjuvant alone. Peak antibody titers occurred 3 weeks after the third vaccination, and no ovarian lesions were present 6 months after vaccination. Seven cats developed extensive granulomatous reactions at injection sites, lymph nodes, and multiple visceral organs including lungs and brain. Persistent hypercalcemia and compromised renal function occurred in three cats with elevated serum calcitriol of probable macrophage origin. One cat died from an injection site sarcoma. Because of these severe adverse reactions, Freund's adjuvant is contraindicated in cats, and other adjuvants for PZP vaccines should be tested in cats for adverse reactions before use.

Experimental inoculation of European red foxes with recombinant vaccinia virus expressing zona pellucida C proteins

The antifertility potential of zona pellucida proteins was tested in European red foxes by immunizing females with recombinant vaccinia viruses that express zona pellucida subunit C proteins. The fox zona pellucida C (fZPC) protein was newly identified and isolated as a cDNA clone from fox ovary RNA. Eighteen European foxes were inoculated with the recombinant vaccinia viruses or with wildtype vaccinia virus (wtVV) and their clinical, virological and immune responses evaluated. Following intradermal inoculation with wtVV or recombinant vaccinia virus expressing fox zona pellucida C (rVV-fZPC), or after peroral administration with recombinant vaccinia virus expressing the porcine zona pellucida C protein (rVV-pZPC) clinical signs of disease were not observed. Five out of six foxes developed antibodies to wtVV proteins. However, none of 12 foxes (six inoculated intradermally with rVV-fZPC, six perorally with rVV-pZPC) reacted in immunoblots with the transgenic fZPC or pZPC, respectively. Infectious wtVV, rVV-fZPC or rVV-pZPC was not isolated from mucosal secretions of any of the foxes whereas viral DNA was present in oral swabs of 3/18 foxes as determined by PCR. Hematological parameters remained mostly unchanged. Histopathological changes were not observed in the ovaries of rVV-fZPC or wtVV inoculated foxes. The data indicate that inoculation of foxes with cell culture infectious wtVV, rVV-fZPC or rVV-pZPC did not result in production of infectious progeny virus in vivo. For this reason transgene expression may have been insufficient to induce adequate immune responses against the transgenic proteins.

Preparation of chitosan-plasmid DNA nanoparticles encoding zona pellucida glycoprotein-3alpha and its expression in mouse

In the present study, the porcine zona pellucida (ZP)-3alpha eukaryotic expression vector pVAX1-pZP3alpha was constructed by genetic recombinant technology, then the recombinant plasmid was encapsulated in nanoparticles with chitosan, and the imaging of chitosan/pVAX1-pZP3alpha nanoparticles by Atomic Force Microscope (AFM) was processed. Feeding mouse with those microencapsulation by gastric larvae, and after 5 days, detecting its expression in mouse intestine by RT-PCR and indirect immunofluorescence (IIF). Results show that the porcine ZP-3alpha eukaryotic expression vector pVAX1-pZP3alpha had been constructed correctly, and the chitosan-DNA expressing ZP microencapsulation was prepared successfully. After 5 days of feeding mouse, the transcription and expression of those DNA vaccines were found in mouse alvine chorion. The preparation of chitosan/pVAX1-pZP3alpha plasmid DNA nanoparticles and its expression in mice will help to investigate the feasibility of ZP DNA vaccine to induce oviduct local mucosal immunity against ZP to block the fertilization without causing ovarian dysfunction, which will provide new ideas and ways for research and exploiting more effective, more convenient oral contraceptive vaccines.

Status of immunodiagnosis and immunocontraceptive vaccines in India

The article focuses on the Indian initiative of making kits for diagnosis of various infectious and non-infectious diseases as well as reproductive hormones and hormones in various other endocrine disorders. Indigenous diagnostic kits for the detection of various infections such as filariasis, typhoid, amebiasis, Japanese encephalitis, hepatitis, HIV, dengue, leishmaniasis, malaria, rabies, toxoplasmosis, rotavirus, and group A streptococci have been developed. Agreements to transfer the know-how of some of these leads to industries have been signed. The know-how of enzyme-linked immunosorbent assay (ELISA) for detection of hepatitis C has been successfully transferred to industry and is being commercially produced. For detection of HIV-1 and HIV-2, indigenous diagnostic kits based on three different formats, namely ELISA, Western blot and rapid test have been developed and are being commercially produced by Indian industries. The factors influencing the successful transfer of laboratory-scale diagnostic assays from academia to industry and their commercial exploitation have been discussed. Indian scientists have made seminal contributions in exploring the possibility to develop an effective and safe contraceptive vaccine to control the increasing human population of India. Achieving contraception by means of vaccine is a novel approach, which entails generation of a specific antibody response against antigens critically involved in the process of mammalian reproduction. In India, three major programs on contraceptive vaccines based on the beta-subunit of human chorionic gonadotrophin ((beta)hCG) for women, ovine follicle stimulating hormone (oFSH) for men, and riboflavin carrier protein for both males and females have been initiated. The work at the National Institute of Immunology, New Delhi on contraceptive vaccine for women, based on (beta)hCG, has demonstrated, for the first time, that it is feasible to regulate fertility by such an approach. Basic research being carried out to achieve immunocontraception by interfering at sperm-oocyte interaction level has been briefly discussed. These developments are still at the research stage. In addition to advances in the area of contraceptive vaccines, a non-steroidal contraceptive oral pill has been developed by Central Drug Research Institute, Lucknow, commercially produced by two Indian pharmaceutical companies and has been incorporated in the National Family Welfare Program. Another interesting approach for fertility regulation in male has been developed in India, which involves vas occlusion with styrene maleic anhydride (SMA) and is currently undergoing clinical trials in human subjects.

[Interests and limits of immunocontraception]

Recent studies from WHO indicated that a large proportion of human contraceptive needs cannot be covered by the already existing means for different reasons (medical, economical, political, and cultural). Therefore, development of new effective methods targeting birth control methods affordable by under-privileged populations turns out to be necessary. Over the last 20 years, a large number of strategies have been used for contraceptive vaccines and thus multiple antigens have been identified as potential targets for immunocontraception. Nowadays, the most acute researches are based on suppression of the secretion and the activity of gonadotropic hormones (GnRH, LH/hCG, FSH) or the targeting of antibodies specific to sperm surface (RSA-1, SP10, SP17, TCLe-1, PH-20) and oocyte antigens (ZP1, ZP2, ZP3). We developed a contraceptive vaccine against FSH receptor. Adult male monkeys (Macaca radiata) were immunized with filamentous phages displaying at their surface N-terminal peptides of the FSH receptor. Long term male contraception has been achieved without any alteration of circulating testosterone levels, sexual behaviour or of any other discernable metabolic changes. Interruption of vaccination resulted in full recovery of sperm production and male fertility. Contraceptive vaccines are aimed to block an essential step in the reproductive process. From this point of view, efforts have to be focused on the challenge to raise is to ally our knowledge on reproductive physiology and protein biochemistry for a better understanding of the target antigen's function.

Contraceptive vaccines

The control of human fertility would be revolutionised by the development of a safe, effective, long-acting contraceptive vaccine. The pursuit of this objective has involved the selection of appropriate targets within the reproductive process that are amenable to interference with antibodies. To date, three major targets have been researched. The zona pellucida (ZP) plays key roles in folliculogenesis, fertilisation and early development, and is comprised of powerful cell-specific antigens. The induction of infertility requires high ZP antibody titres that are difficult to maintain without inducing ovarian pathology characterised by a premature loss of primordial follicles. As a premature menopause would be a high price to pay for long-term contraception, this approach to a vaccine cannot progress until the cause of the ovarian pathology has been resolved. Sperm surface antigens represent another promising approach to contraceptive vaccine development. While there is some clinical data to support the likely efficacy of this strategy, none of the gamete-specific molecules characterised to date have fulfilled this promise. Anti-human chorionic gonadotropin (hCG) vaccines terminate pregnancy by preventing the maternal recognition of pregnancy. This vaccine has reached the stage of clinical trials, and preliminary indications are that the approach is safe and potentially effective. However, reliability may be an issue, given the observed inter-individual variability in antibody generation. The future of contraceptive vaccine development will clearly involve a continuation of the intense search for suitable targets and the development of improved immunisation procedures that exploit the latest innovations in vaccine technology.

Cloning and expression of cynomolgus monkey and baboon zona pellucida proteins

Partial clones for the three cynomolgus monkey (Macaca fasicularis) zona pellucida genes (cmZPA, cmZPB, and cmZPC) have previously been isolated. These partial clones contained the sequences for the C-terminal portion of each rcmZP protein. To obtain full-length clones for each cmZP, a fresh cynomolgus monkey ovarian cDNA library was constructed. PCR methodology was employed to speed the isolation of full-length clones for each cmZP cDNA. The 3' primers were designed based on sequence information from the previously identified clones; the 5' primers were designed using the human ZP sequences. The PCR technique yielded full-length clones of cmZPA and cmZPC, but not of cmZPB. Therefore, a genomic clone of cmZPB was isolated and the sequence determined. The exon/intron structure is nearly identical to the human ZPB exon/intron structure. New PCR primers were designed based on the cynomolgus monkey ZPB genomic sequence, and a full-length cmZPB cDNA was obtained. The same primers that were used to generate the cmZPB were also used to generate a baboon (Papio cynocephalus) ZPB (bZPB) cDNA. As was done previously for the human zona pellucida (hZP) cDNAs, the cmZP, and bZPB cDNAs were transferred to shuttle vectors for transfection into Chinese Hamster Ovary (CHO) cells. Stable cell lines for producing each ZP protein were isolated. Each cell line secreted the desired recombinant zona pellucida (rZP) protein into the culture medium, and each protein was purified using an established protocol. In terms of size and purity, the purified recombinant cmZP (rcmZP) and rbZPB proteins resemble the rhZP proteins.

Efficacy of antibodies against Escherichia coli expressed chimeric recombinant protein encompassing multiple epitopes of zona pellucida glycoproteins to inhibit in vitro human sperm-egg binding

To minimize ovarian dysfunction subsequent to immunization with zona pellucida (ZP) glycoproteins, synthetic peptides encompassing the antigenic B cell epitopes as immunogens have been proposed. In this study, attempts have been made to clone and express a recombinant chimeric protein encompassing the epitopes corresponding to bonnet monkey (Macaca radiata) ZP glycoprotein-1 (bmZP1, amino acid residues 132-147), ZP glycoprotein-2 (bmZP2, amino acid residues 86-113), and ZP glycoprotein-3 (bmZP3, amino acid residues 324-347). The above chimeric recombinant protein (r-bmZP123) was expressed as a polyhistidine fusion protein in Escherichia coli. Immunoblot with murine monoclonal antibody, MA-813, generated against recombinant bmZP1 revealed a major band of approximately 10 kDa. The r-bmZP123 was purified on nickel-nitrilotriacetic acid resin under denaturing conditions. The female rabbits immunized with purified r-bmZP123 conjugated to diphtheria toxoid (DT) generated antibodies that reacted with r-bmZP123 and DT in an ELISA. In addition, the immune sera also reacted with E. coli expressed recombinant bmZP1, bmZP2, and bmZP3. In an indirect immunofluorescence assay, the antibodies against r-bmZP123 recognized native ZP of bonnet monkey as well as human. The immune sera also inhibited, in vitro, the binding of human spermatozoa to the human zona in the hemizona assay (HZA). These studies, for the first time, demonstrate the feasibility of assembling multiple epitopes of different ZP glycoproteins as a recombinant protein that elicit antibodies which are reactive with native zona and also inhibit, in vitro, human sperm-oocyte binding.

Construction of the plasmid pCMV4-rZPC' DNA vaccine and analysis of its contraceptive potential

Zona pellucida C (ZPC) is a major glycoprotein of the zona pellucida that possesses the sperm receptor function. ZPC induces autoantibody that can block sperm/oocyte interaction. We selected the partial sequence of rabbit ZPC (amino acid 263-415, rZPC') as the target and constructed the pCMV4-rZPC' gene vaccine by using DNA recombinant techniques. The total RNA was extracted from the ovaries of the sexually healthy female rabbit, and the rZPC' cDNA, which was amplified by reverse transcription-polymerase chain reaction, was directly inserted into the cloning vector PCR2.1 to construct the PCR2.1-rZPC'. This insertion fragment was subcloned into the pCMV4 vector to form the pCMV4-rZPC' prototype DNA vaccine. All experimental BALB/C mice and New Zealand rabbits received i.m. injection of pCMV4-rZPC' vaccine three times. The results show that 1) the pCMV4-rZPC' construct expresses rZPC' cDNA in mice muscle cells, 2) 60% of the immunized female mice were infertile at 6 wk after the immunization, 3) the mice immunized with pCMV4-rZPC' DNA vaccine developed anti-rZPC antibodies that bound to the ovarian ZP in situ, and 4) antibodies against rZPC' were also bound to normal animal ovarian ZP in vitro. The results indicate that anti-rZPC antibodies developed from pCMV4-rZPC' DNA vaccine can prevent the fertility course and do not interfere with normal follicular development. The pCMV4-rZPC' DNA vaccine may be possible to develop as a contraceptive vaccine.

Immunocontraceptive potential of recombinant bonnet monkey (Macaca radiata) zona pellucida glycoprotein-C expressed in Escherichia coli and its corresponding synthetic peptide

Zona pellucida (ZP) glycoproteins have been proposed as candidate antigens for development of immunocontraceptive vaccines. In this study, the efficacy to block fertility by immunization with recombinant bonnet monkey (Macaca radiata) zona pellucida glycoprotein-C (r-bmZPC) expressed in Escherichia coli and its synthetic peptide (P(4): KGDCGTPSHSRRQPHVVSQWSRSA, aa residues 324-347) conjugated to diphtheria toxoid (DT) has been evaluated in a homologous system. Female bonnet monkeys, immunized with P(4)-DT conjugate showed better immunocontraceptive potential as compared to an r-bmZPC-DT immunized group. In spite of high anti-P(4) antibody titres, animals continued to have ovulatory cycles and showed no disturbance in cyclicity (except summer amenorrhoea). No ovarian pathology was observed in the P(4) immunized group. These results suggest that immunization with the P(4) may lead to block in fertility without obvious ovarian dysfunction. However, further inputs are required to identify additional ZP based B-cell epitopes to enhance the contraceptive efficacy.

Evaluation of the immunocontraceptive potential of Escherichia coli expressed recombinant non-human primate zona pellucida glycoproteins in homologous animal model

In order to evaluate the immunocontraceptive potential of zona pellucida (ZP) glycoproteins, recombinant bonnet monkey (Macaca radiata) zona pellucida glycoprotein-1 (r-bmZP1) and -2 (r-bmZP2) were expressed as polyhistidine fusion proteins in Escherichia coli. Female bonnet monkeys were immunized with the purified r-bmZP1 (n=5) and r-bmZP2 (n=4) conjugated to diphtheria toxoid (DT). Immunization led to generation of antibodies against r-bmZP1, r-bmZP2 and DT as determined by enzyme linked immunosorbent assay. The immunized animals exhibited normal menstrual cyclicity and progesterone profile, except during the summer amenorrhoea. Immunized animals, when mated with males of proven fertility, showed protection from conceiving for cumulative 45 ovulatory cycles in r-bmZP1-DT immunized group and 32 ovulatory cycles in r-bmZP2-DT immunized group. Ovarian histopathology of both the immunized groups revealed the presence of atretic follicles with degenerated oocytes, which may have been the principle cause for the failure of immunized animals to conceive in spite of the decline in either anti-r-bmZP1 or anti-r-bmZP2 antibody titres to background levels. These studies demonstrate, for the first time, that the block of fertility subsequent to immunization with r-bmZP1 and r-bmZP2, in a homologous non-human primate model, may be mediated due to ovarian dysfunction.

Immunocontraceptive vaccines for human use

The development of safe, effective, reversible contraceptive vaccines for the regulation of human fertility would be a significant addition to our contraceptive armamentarium. However, because we are such an out-bred species, immunological responsiveness to any given vaccine is certain to exhibit a high level of inter-individual variation that will impact upon the efficacy, reversibility and feasibility of the approach. Nevertheless a role for vaccines undoubtedly exists as an aid to birth spacing, particularly in developing countries, and as a non-surgical means of inducing sterility in men. Currently vaccines are being researched that target one of two strategic points in the reproductive process, fertilization and the maternal recognition of pregnancy. Our ability to engineer vaccines that target fertilization is hampered by deficiencies in our knowledge of the molecular mechanisms that regulate this process. However, anti-hCG vaccines have advanced to the stage of clinical trials and appear promising.

Antibodies generated in response to plasmid DNA encoding zona pellucida glycoprotein-B inhibit in vitro human sperm-egg binding

To investigate the immunogenicity of plasmid DNA encoding bonnet monkey (Macaca radiata) zona pellucida (ZP) glycoprotein-B (bmZPB), the cDNA corresponding to bmZPB, excluding the N-terminal signal sequence and C-terminus transmembrane-like domain, was cloned in mammalian expression vector VR1020 downstream of tissue plasminogen activator signal sequence under cytomegalovirus promoter (VRbmZPB). In vitro transfection of COS-1, COS-7, CHO, HEK-293, and UM-449 mammalian cells with VRbmZPB plasmid DNA led to the expression of bmZPB. Expression of bmZPB in transfected cells was cytosolic. Flow cytometry analysis of COS-1 cells transfected with VRbmZPB revealed that approximately 15% cells expressed bmZPB. The expressed bmZPB has an apparent molecular weight of 57 kDa. Immunization of male BALB/cJ mice with VRbmZPB plasmid DNA in saline as compared to VR1020 immunized group, elicited significant antibodies against E. coli expressed recombinant bmZPB as evaluated in ELISA. The antibodies generated by VRbmZPB plasmid DNA recognized bonnet monkey as well as human ZP. The immune sera obtained from mice immunized with VRbmZPB plasmid DNA also inhibited, in vitro, the binding of spermatozoa to the ZP in the hemizona assay. These studies, for the first time, demonstrate the feasibility of DNA vaccine to generate antibodies against ZP that recognize native protein and inhibit human sperm-oocyte binding.

Prospect for immunocontraception using the NH2-terminal recombinant peptide of human zona pellucida protein (hZPA)

PROBLEM

The zona pellucida is a feasible candidate for contraceptive vaccine. Our previous study showed that a human zona pellucida (ZPA) recombinant protein produced antiserum that inhibited human in vitro fertilization in rabbits. The objective of this study is to examine whether the human recombinant protein produce fertilization-blocking antiserum in a non-human primate.

METHOD OF STUDY

The amino terminal regions consisting of pig (198 amino acids) and human (206 amino acids) zona pellucida proteins were prepared by Escherichia coli to produce antisera in bonnet monkeys (Macaca radiata). Antibody production was assessed by immunofluorescent staining and enzyme-linked immunosorbent assay (ELISA). Fertilization-blocking test was carried out using human oocytes that had failed in intracytoplasmic sperm injection (ICSI) treatment under patient's informed consent.

RESULTS

Both antisera against pig and human recombinant proteins recognized native human zona pellucida by immunofluorescent staining. However, anti-recombinant human ZPA reacted to native pig zona protein more strongly than pig zona pellucida by ELISA. When human oocytes were treated with antisera before insemination, anti-human ZPA antiserum inhibited human sperm binding to human zona pellucida, but anti-pig ZPA antiserum did not.

CONCLUSIONS

Bonnet monkey produced fertilization-blocking antibody by immunization with human recombinant ZPA. The homologous or highly similar sequence is effective for developing a contraceptive vaccine when using recombinant peptides.

The contraceptive potential of ZP3 and ZP3 peptides in a primate model

It has been known for some time that antibodies raised against ZP3, the major component of the glycoprotein shell that surrounds all mammalian oocytes, can successfully inhibit sperm-egg interaction in vitro. In our own studies using the non-human primate Callithrix jacchus, active immunisation was successfully achieved when homologous or heterologous ZP3 was used as an immunogen. However this long-term suppression of fertility was at the expense of ovarian function. An ovarian pathology was observed which was characterised by a disruption of folliculogenesis and depletion of the primordial follicle pool. Adverse auto-immune reactions have also been observed in mice following induction of immunity to mouse ZP3. Following careful selection of B-cell epitopes on mouse ZP3, peptide vaccines were formulated which could circumvent these adverse side effects and induce reversible infertility in actively immunised mice. To identify similar epitopes on primate ZP3, epitope mapping studies were performed and several candidate regions of the molecule were identified. These were incorporated into chimeric peptide vaccines and administered as single or triple peptide vaccines. Active immunisation successfully induced antibodies that bound exclusively to the zona pellucida of marmoset and human ovarian sections. These antibodies were able to suppress human sperm-egg binding by up to 60% in vitro. Encouragingly, no adverse side effects on ovarian function were observed following long-term immunisation however, no loss of fertility was consistently observed in vivo. Thus considerable research is still required to identify a combination of ZP epitopes that will induce reversible infertility in the absence of any ovarian dysfunction.

Induction and immunohistology of autoimmune ovarian disease in cynomolgus macaques (Macaca fascicularis)

Autoimmune ovarian disease (AOD) is a probable cause of human premature ovarian failure, and a potential complication of contraceptive vaccines based on ovarian antigens. The diagnosis depends on detection of noninfectious ovarian inflammation (oophoritis) and serum antibody to ovarian and placental antigens. Mechanisms underlying AOD have been investigated in mice but not in primates. Herein, we report induction of AOD in primates, and compare the immunopathology between monkey and murine AOD. Four cynomolgus macaques immunized with monkey or human zona pellucida 3 peptide (pZP3) in adjuvant, developed T-cell responses to the immunizing peptide and produced antibody that bound to native zona pellucida in vivo. Immunostaining of ovaries from pZP3-immunized macaques showed numerous clusters of T cells co-localized with major histocompatibility complex II-positive macrophages in the ovarian interstitium. Such foci were not detected in untreated or adjuvant-treated control monkeys. This finding is comparable to murine pZP3-induced AOD. However, unlike murine AOD in which numerous granulomatous lesions are detected, severe granulomatous inflammation was detected in only one of three monkeys with abnormal immunohistology. Similar to mice with pZP3-induced AOD, the immunized monkeys retained normal ovarian function. The results are discussed in the context of complications of ZP-based human immunocontraceptive vaccines and case reports of human autoimmune oophoritis.

Pregnancy following fertilization of zona-free, coronal cell intact human ova: Case Report

A pregnancy by intracytoplasmic sperm injection (ICSI) of a couple whose oocytes were recovered without a zona pellucida is reported. Previous IVF/ICSI cycles indicated all oocytes had either very thin or no zona pellucida at the time of cumulus removal prior to ICSI. As a result, many ova were very fragile and lysed upon handling. In the latest attempt, six ova were recovered. After coronal cell dissection of two ova where both lacked a zona pellucida and one lysed, it was elected to attempt to inject the remaining four ova without removal of their coronal cells. The zona pellucida was not visible through the cell layer and the position of the polar body in three ova was speculative. Two embryos possessed normal pronuclei on day 1, and displayed six blastomeres prior to transfer on day 3. During preparation for transfer, sufficient coronal cells fell away to confirm both embryos lacked a zona pellucida. Pregnancy was confirmed by ultrasound observation of a fetal heart 4 weeks later. This report documents that where the zona pellucida is absent, the coronal cells provide sufficient support to maintain blastomere interaction and embryo viability and the zona pellucida is not essential for early embryo development and pregnancy.

Analysis of B cell epitopes of a glycoprotein porcine zona pellucida (pZP1)

The zona pellucida (ZP) of mammalian oocytes forms an extracellular matrix composed of three major glycoproteins and plays an important role in sperm-zona interactions. As ZP had a strong organ-specific but species-cross-reactive antigenicity and passive or active immunization with ZP antigens could impair fertilization, the possibility of developing a immunocontraceptive vaccine has been extensively studied. Studies on active immunization with porcine ZP (pZP) that contain B cell epitopes and T cell epitopes demonstrated that a temporary infertility could be induced along with the elevation of antibody titers, but it was always associated with ovarian failure. This could be due to the oophoritis by activation of pathogenic T cell immunity. It is the general consideration that any adverse effects by vaccination should be avoided for an immunocontraception. From this point of view, the analysis of B cell epitopes of pZP protein would be helpful for construction of a safe immunocontraceptive vaccine with zona antigens. We determined the amino acid sequence of the B epitope in the pZP1 protein by using a monoclonal antibody (MAb-5H4) that possesses a fertilization blocking ability. In addition, antiserum raised to the epitope sequence was revealed to block in vitro fertilization of homologous animal species.

Failure of female baboons (Papio anubis) to conceive following immunization with recombinant non-human primate zona pellucida glycoprotein-B expressed in Escherichia coli

Progress in the development of an immunocontraceptive vaccine based on zona pellucida glycoproteins has been hampered due to observed ovarian dysfunction associated with immunization using these as immunogens. In this study four female baboons (Papio anubis) were immunized with recombinant bonnet monkey (Macaca radiata) zona pellucida glycoprotein-B (r-bmZPB) expressed in Escherichia coli and conjugated to diphtheria toxoid (DT) using Arlacel-A and Squalene as adjuvants. All the immunized animals elicited a good antibody response against r-bmZPB, continued to have ovulatory cycles and showed no disturbance in the cyclicity. In presence of high titres of circulating anti-bmZPB antibodies (>2x10(3) antibody units), the immunized animals failed to conceive following mating with males of proven fertility. Pregnancy was observed in the immunized animals subsequent to the decline in anti-r-bmZPB antibody titres. These results, though preliminary, suggest that immunization with ZPB may be used for immunocontraception without obvious ovarian dysfunction.

Delineation of a conserved B cell epitope on bonnet monkey (Macaca radiata) and human zona pellucida glycoprotein-B by monoclonal antibodies demonstrating inhibition of sperm-egg binding

To circumvent autoimmune oophoritis after immunization with zona pellucida (ZP) glycoproteins, synthetic peptides encompassing B cell epitope(s) and devoid of oophoritogenic T cell epitopes as immunogens have been proposed. In this study, bonnet monkey (Macaca radiata) ZP glycoprotein-B (bmZPB) was expressed as polyhistidine fusion protein in Escherichia coli. Rabbit polyclonal antibodies against recombinant bmZPB (r-bmZPB) significantly inhibited human sperm-oocyte binding. To map B cell epitopes on ZPB, a panel of 7 murine monoclonal antibodies (mAbs) was generated against r-bmZPB. All 7 mAbs, when tested in an indirect immunofluorescence assay, reacted with bonnet monkey ZP, and only 6 recognized human zonae. Monoclonal antibodies MA-809, -811, -813, and -825 showed significant inhibition in the binding of human spermatozoa to human ZP in a hemizona assay. Epitope-mapping studies using multipin peptide synthesis strategy revealed that these 4 mAbs recognized a common epitope corresponding to amino acids (aa) 136-147 (DAPDTDWCDSIP). Competitive binding studies revealed that the synthetic peptide corresponding to the identified epitope (aa 136-147) inhibited the binding of MA-809, -811, -813, and -825 to r-bmZPB in an ELISA and to bonnet monkey ZP in an indirect immunofluorescence assay. The epitopic domain corresponding to aa 136-147 of bmZPB was completely conserved in human ZPB. These studies will further help in designing ZP-based synthetic peptide immunogens incorporating relevant B cell epitope for fertility regulation in humans.

Mapping of dominant B-cell epitopes of a human zona pellucida protein (ZP1)

Zona pellucida (ZP) glycoproteins contain numerous antigenic determinants including carbohydrate, protein, and conformational epitopes; and the immunogenicity of these complex glycoproteins varies in different mammalian hosts. Studies have now shown that antibodies from primates immunized with a cDNA-expressed recombinant rabbit ZP protein (the homologue of the human ZP1 [hZP1]) inhibit sperm binding to the ZP without altering ovarian function, unlike immunization with ZP3 and ZP2 protein families. The ZP1 protein or peptides derived from it (recombinant or synthetic) are therefore primary candidates for use in designing safe and reversible human and animal contraceptive vaccines. In order to define peptide epitope(s) that may be critical for eliciting an immune response sufficient to effect immunological contraception without causing any adverse effects on ovarian physiology, studies have been carried out to identify immunodominant B-cell epitopes of the ZP1 protein. The amino acid sequence of the hZP1 was used to design a set of 94 (15-mer) biotinylated peptides having an overlap of 9 amino acids. Using these peptides in a modified enzyme-linked immunoassay, antibodies in sera from rabbits or baboons immunized with native porcine ZP protein were screened for ZP1 peptide recognition. These studies demonstrate that there are a limited number of peptides recognized by primate antibodies but that the overlapping peptides sharing the sequence GPLTLELQI are recognized by both rabbit and baboon antibodies regardless of the adjuvant system used to induce the immune response. This peptide is 100% conserved in amino acid sequence between the human and pig, although the rabbit protein has two conserved amino acid substitutions (100% similar, 77% identical). Because this peptide is immunogenic as well as antigenic in primates, it could play a major role in the development of human contraceptive vaccines.

Autoimmune ovarian inflammation triggered by proinflammatory (Th1) T cells is compatible with normal ovarian function in mice

The detection of noninfectious ovarian inflammation (oophoritis) and serum ovarian autoantibodies in a patient with premature ovarian failure is indicative of an autoimmune etiology. The mechanisms of autoimmune ovarian injury leading to loss of function are currently unknown. In this study we investigated the impact of oophoritis on ovarian function based on two murine autoimmune ovarian disease (AOD) models. AOD can be induced by thymectomy at Day 3 after birth (d3tx). D3tx mice develop ovarian inflammation and atrophy with loss of oocytes. In these mice, ovarian atrophy and not oophoritis correlated with abnormal estrous cyclicity. The second AOD model is induced by active immunization of adult mice with a murine ZP3 peptide (pZP3) in adjuvant. After active immunization, the zona pellucida antibody titer, not oophoritis, correlated with reduced fertility. To investigate the effect of oophoritis in the absence of antibody response or ovarian atrophy, pZP3-specific T cells were passively transferred into naive syngeneic mice. This recruited cytokine-producing cells into the ovaries so that elevated cytokine production and its effect on ovarian function could be examined. Recipients of pZP3-specific T cells developed severe granulomatous oophoritis, and the diseased ovaries had elevated ovarian mRNA levels of interferon-gamma, interleukin-1beta, and tumor necrosis factor alpha. Despite these changes, fertility rates and gonadotropin-induced follicular development remained essentially normal. Therefore, normal ovarian function is compatible with severe ovarian inflammation mediated by autoreactive T cells.

A contraceptive peptide vaccine targeting sulfated glycoprotein ZP2 of the mouse zona pellucida

In this study, we have mapped and characterized a B cell epitope of sulfated glycoprotein ZP2 (ZP2) as a step toward the development of a multi-epitope zona pellucida (ZP) vaccine. Recombinant polypeptides expressed by random deoxyribonuclease-digested fragments of ZP2 cDNA were screened for binding to IE-3, a monoclonal antibody to murine ZP2. Positive clones contained cDNA inserts encoding polypeptide corresponding to ZP2(103-134). When normal or ovariectomized female mice were immunized with three overlapping peptides that span this region of ZP2 (101-120, 111-130, 121-140), only ZP2(121-140) elicited IgG antibodies that reacted with mouse ovarian ZP, indicative of the presence of native B epitope and helper T cell epitope in ZP2(121-140). To more finely map the ZP2 B cell epitope, a random peptide display library was screened with the IE-3 antibody, and a consensus tetramer sequence VxYK that matched the ZP2(123-126) sequence VRYK was located. Competitive immunofluorescence analysis with single alanine-substituted VxYK peptides ranked the relative contribution of the three critical B cell epitope residues as Y > V > K. A chimeric peptide was constructed that contained the YRYK motif of ZP2 and a bovine RNase T cell epitope. Although (C57BL/6xA/J) F1 (B6AF1) female mice immunized with the chimeric peptide developed ZP antibody response, this peptide elicited antibody only in mice of the histocompatibility complex (MHC) H-2(k or b) haplotype. In contrast, ZP2(121-140) peptide elicited antibody in inbred mice with three additional mouse MHC haplotypes. Moreover, although ZP2(121-140) contained a T cell epitope, no oophoritis was observed after immunization of B6AF1 mice with ZP2(121-140) in complete Freund's adjuvant (CFA). In a preliminary trial, female B6AF1 mice immunized with ZP2(121-140) in CFA had reduced litter sizes as compared with mice injected with CFA alone.

Molecular basis of sperm-egg interaction and the prospects for immunocontraception

As the molecular basis of sperm-egg interaction is resolved, so new opportunities are created for the development of immunological approaches to disrupt the process of conception. Thus, realisation that the zona glycoprotein, ZP3, serves as a specific receptor for spermatozoa, has prompted a detailed examination of its contraceptive potential. In primate models, recombinant ZP3 has been shown to suppress fertility very efficiently, however this efficacy is tempered by the appearance of adverse side-effects involving accelerated primordial follicle depletion and a lymphocytic infiltration of the ovarian stroma. Synthetic peptides encoding B-cell epitopes have been found to circumvent the lymphocyte response although the effectiveness of such reagents in preventing the loss of primordial follicles has not yet been determined. The induction of active immunity against sperm-specific antigens has also been shown to generate long term infertility in both males and females. Molecular and immunological techniques are now being used to produce a rapidly expanding list of unique sperm antigens which are currently being evaluated to determine their potential contribution to the development of safe, effective, contraceptive vaccines.

Evaluation of the contraceptive potential of recombinant human ZP3 and human ZP3 peptides in a primate model: their safety and efficacy

PROBLEM

The unique recognition events that result in the avid binding of mammalian spermatozoa to the surface of the zona pellucida (ZP) are being exploited in the development of contraceptive vaccines. In this study, the safety and efficacy of a vaccination strategy based on the induction of active immunity against purified, glycosylated, recombinant human ZP3 (rhZP3) has been evaluated in a primate model, Callithrix jacchus.

METHOD OF STUDY

Long-term infertility was established after immunization with rhZP3 and the resulting immune sera reacted with rhZP3 on an enzyme-linked immunosorbent assay (ELISA) and immunolocalized exclusively to the outer surface of native ZP on marmoset ovarian sections. However, this contraceptive effect was inevitably associated with the eventual appearance of an ovarian pathology characterized by a depletion of primordial follicles. In an attempt to circumvent this side effect, human ZP3 (hZP3) was epitope mapped and four continuous, immunodominant B-cell epitopes (hZP3(45-64), hZP3(93-110), hZP3(172-190) and hZP3(341-360) were evaluated for contraceptive efficacy in vivo. Using peptide-tetanus toxoid (TT) conjugates to enhance immunogenicity, antipeptide antibodies were raised against these immunogens, which also cross-reacted with rhZP3 on ELISA. In addition, antibodies against hZP3(45-64) and hZP3(172-190) recognized native ZP on marmoset ovarian sections when a microwave technique was used to enhance epitope presentation.

RESULTS

No ovarian pathology was observed after the long-term administration of these peptide immunogens, and fertility was suppressed when compared with TT controls but could not be correlated to the antibody titer.

CONCLUSION

Clearly, further research is required to identify optimal B-cell epitopes that will reliably induce infertility, free from any ovarian pathology.

Localization of the zona glycoproteins ZPB (ZP3 alpha) and ZPC (ZP3 beta) in the bovine ovary during pre- and postnatal development

The purpose of this study was to investigate the expression of two zona pellucida gene families ZPB (ZP3 alpha) and ZPC (ZP3 beta). Sections of ovaries from bovine fetuses, calves and cows were labelled with polyclonal antibodies. Immunopositive labelling was found in both the follicle cells and the oocyte. Labelling was dependent on the stage of development. The specific sequence of immunopositive reactions suggests that in the bovine fetus both the ovary and the follicle cells contribute to the production of the zona pellucida during pre- and postnatal development.

Identification of epitopes of monoclonal antibodies to porcine zona pellucida 3 beta glycoprotein, a homologue of the mouse/human sperm receptor

PROBLEM

Immunization with zona pellucida (ZP) glycoproteins leads to a block in fertility with a variable degree of ovarian dysfunction. To avoid autoimmune oophoritis, synthetic peptides corresponding to B cell epitope(s) and devoid of oophoritogenic T cell epitopes as immunogens have been proposed. The main objective of the present study is to define the epitopes recognized by monoclonal antibodies (mAbs) generated against porcine ZP3 beta, a homologue of the designated primary sperm receptor in mice and humans.

METHODS

A multipin synthetic peptides approach has been used to map the epitopes recognized by mAbs. Dodecapeptides with an overlap of 6 amino acids corresponding to a precursor pZP3 beta-deduced amino acid sequence (excluding the signal sequence) were synthesized on polypropylene pins and were tested for their reactivity with mAbs by enzyme-linked immunoadsorbent assay (ELISA). The ability of synthetic peptides corresponding to the identified epitopes to inhibit the binding of mAbs to pZP3 beta in a competitive inhibition ELISA was investigated to confirm the above findings.

RESULTS

Reactivity of the mAbs with the pin-bound peptides in ELISA-identified epitopes for mAb-451 to EEKLVF (166-171) and mAb-462/470 to FKAPRP (250-255) amino acid residues. mAb-30 recognized QPVWQDEGQRLR (23-34) and VICRCC (316-321) amino acid residues. Competitive inhibition with synthetic peptides encompassing the motifs corresponding to 23-34 and 316-321 for binding of mAb-30 to pZP3 beta revealed the epitopic domain to be 23-34 amino acids. Synthesis of overlapping octapeptides further identified WQDE as the minimum motif for binding of mAb-30, and the replacement of one amino acid at a time with glycine revealed tryptophan as the critical residue.

CONCLUSIONS

Collectively, these results describe peptide epitopes that will help in the design of an immunocontraceptive vaccine based on synthetic peptides corresponding to pZP3 beta or its homologues in other species.