Immunocontraceptive effect of Izumo and enhancement by combination vaccination

Immunogenicity and contraceptive efficacy of plant-produced putative mouse-specific contraceptive peptides

Rodent population control through contraception requires species-specific oral contraceptive vaccines. Therefore, in this study, we produced putative mouse-specific contraceptive peptides, mZP2 (from oocyte) and mIzumo1 (from sperm), in plants using Agrobacterium-mediated transient expression. Peptides were produced separately in Nicotiana benthamiana using constructs encoding antigens containing three copies of each peptide. We also determined the immunogenicity and contraceptive effects of the plant-produced antigens in female BALB/c mice. Mice immunized subcutaneously with a relatively low amount of antigen (5 µg/dose of each peptide in a mixture) showed systemic immune responses against mZP2-3 and mIzumo1-3 antigens. Moreover, the mean litter size of mice treated with the plant-produced antigens was reduced by 39% compared to that of the control mice. Notably, there was a significant negative correlation between the number of pups born and individual antibody levels against both antigens. Immunofluorescence assays demonstrated the binding of induced antibodies to the oocytes of BALB/c and wild-type mice in vivo and in vitro, respectively. Our study demonstrate the feasibility of producing small contraceptive peptides in plants that can be further used to develop oral contraceptive vaccines against mouse populations.

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.

The Role of Sperm Proteins IZUMO1 and TMEM95 in Mammalian Fertilization: A Systematic Review

Gamete membrane fusion is a critical cellular event in sexual reproduction. In addition, the generation of knockout models has provided a powerful tool for testing the functional relevance of proteins thought to be involved in mammalian fertilization, suggesting IZUMO1 and TMEM95 (transmembrane protein 95) as essential proteins. However, the molecular mechanisms underlying the process remain largely unknown. Therefore, the aim of this study was to summarize the current knowledge about IZUMO1 and TMEM95 during mammalian fertilization. Hence, three distinct databases were consulted—PubMed, Scopus and Web of Science—using single keywords. As a result, a total of 429 articles were identified. Based on both inclusion and exclusion criteria, the final number of articles included in this study was 103. The results showed that IZUMO1 is mostly studied in rodents whereas TMEM95 is studied primarily in bovines. Despite the research, the topological localization of IZUMO1 remains controversial. IZUMO1 may be involved in organizing or stabilizing a multiprotein complex essential for the membrane fusion in which TMEM95 could act as a fusogen due to its possible interaction with IZUMO1. Overall, the expression of these two proteins is not sufficient for sperm–oocyte fusion; therefore, other molecules must be involved in the membrane fusion process.

Engineering sperm-binding IgG antibodies for the development of an effective nonhormonal female contraception

Many women risk unintended pregnancy because of medical contraindications or dissatisfaction with contraceptive methods, including real and perceived side effects associated with the use of exogenous hormones. We pursued direct vaginal delivery of sperm-binding monoclonal antibodies (mAbs) that can limit progressive sperm motility in the female reproductive tract as a strategy for effective nonhormonal contraception. Here, motivated by the greater agglutination potencies of polyvalent immunoglobulins but the bioprocessing ease and stability of immunoglobulin G (IgG), we engineered a panel of sperm-binding IgGs with 6 to 10 antigen-binding fragments (Fabs), isolated from a healthy immune-infertile woman against a unique surface antigen universally present on human sperm. These highly multivalent IgGs (HM-IgGs) were at least 10- to 16-fold more potent and faster at agglutinating sperm than the parent IgG while preserving the crystallizable fragment (Fc) of IgG that mediates trapping of individual spermatozoa in mucus. The increased potencies translated into effective (>99.9%) reduction of progressively motile sperm in the sheep vagina using as little as 33 μg of the 10-Fab HM-IgG. HM-IgGs were produced at comparable yields and had identical thermal stability to the parent IgG, with greater homogeneity. HM-IgGs represent not only promising biologics for nonhormonal contraception but also a promising platform for engineering potent multivalent mAbs for other biomedical applications.

Evaluation of multi-epitope recombinant protein as a candidate for a contraceptive vaccine

Contraceptive vaccine (CV) is a valuable, non-invasive, and alternative method for purposeful contraception. Sperm antigens are useful targets for producing CVs due to their specialized expression in sperm. In this study, a recombinant protein containing three main sperm epitopes (IZUMO1, SACA3, and PH-20) was designed and evaluated as CV to control fertility in male mice. The chimeric recombinant protein was expressed and purified in E. coli. Male mice were immunized by 100 μg purified protein and sera were collected to assess IgG antibodies. Evaluating the reproductive performance, immunized male mice mated with normal-fertile female mice and mating rate and the number of newborns was studied. Immunized mice were sacrificed and necropsy and histopathology studies were conducted. The results revealed that the designed chimeric protein stimulated the immune system of the mice effectively. The level of IgG antibody was significantly higher in vaccinated mouse rather than control mouse. Eighty percent of the vaccinated mice became infertile and in the remaining ones, the number of children decreased to 4-6 offspring instead of 10-12 in normal mice. Histopathological studies showed that no organs including heart, brain, lung, liver, kidney and intestine were damaged. However, Normal spermatogenesis has been disrupted and necrotic spermatogonia cells were reported in Seminiferous tubules. We concluded that the designed chimeric protein containing IZUMO1, SACA3, and PH-20 epitopes can stimulate the immune system and cause male contraception without any side effects.

Perfect date-the review of current research into molecular bases of mammalian fertilization

Fertilization is a multistep process during which two terminally differentiated haploid cells, an egg and a sperm, combine to produce a totipotent diploid zygote. In the early 1950s, it became possible to fertilize mammalian eggs in vitro and study the sequence of cellular and molecular events leading to embryo development. Despite all the achievements of assisted reproduction in the last four decades, remarkably little is known about the molecular aspects of human conception. Current fertility research in animal models is casting more light on the complexity of the process all our lives start with. This review article provides an update on the investigation of mammalian fertilization and highlights the practical implications of scientific discoveries in the context of human reproduction and reproductive medicine.

Immunogenicity and contraceptive efficacy of recombinant fusion protein encompassing Sp17 spermatozoa-specific protein and GnRH: Relevance of adjuvants and microparticles based delivery to minimize number of injections

PROBLEM

Requirement of multiple injections of contraceptive vaccines to achieve infertility is one of the important impediments for their application. In the present study, attempts have been made to reduce the number of injections of contraceptive vaccine.

METHOD OF STUDY

Fusion protein encompassing C-terminus fragment of sperm protein Sp17 (aa residues 76-126) and two copies of gonadotropin-releasing hormone along with T-cell epitopes and dilysine linkers (abbreviated as Sp17_C -GnRH₂ ) was expressed in Escherichia coli. Its immunogenicity and contraceptive efficacy have been evaluated in female FVB/J mice using different adjuvants and delivery platforms.

RESULTS

Immunization of female mice with recombinant Sp17_C -GnRH₂ (25 μg/injection/mouse) emulsified with squalene-arlacel A following two injections schedule led to failure of 88.8% immunized animals to conceive, which was not significantly different from mice immunized with same protein along with alum following three injections schedule. To make single-dose vaccine, poly d,l-lactic acid-based microparticles (PLA-MPs) entrapping Sp17_C -GnRH₂ were prepared. Immunization of female mice with a combination of soluble Sp17_C -GnRH₂ (12.5 μg/injection/mouse) along with Sp17_C -GnRH₂ entrapped in PLA-MPs (12.5 μg/injection/mouse) in alum showed higher antibody titres and contraceptive efficacy as compared to mice immunized with Sp17_C -GnRH₂ entrapped in PLA-MPs alone in alum. Immunization with recombinant Sp17_C -GnRH₂ led to long-term infertility as second mating (150 days after immunization) of various groups of immunized mice showed similar infertility as observed during first mating.

CONCLUSION

Single-dose immunization with PLA-MPs entrapping Sp17_C -GnRH₂ along with soluble recombinant protein in alum generated long-lasting infertility in female mice.

Sperm IZUMO1-Dependent Gamete Fusion Influences Male Fertility in Mice

Sperm–egg fusion is accomplished through the interaction of a specific set of membrane proteins in each gamete: sperm IZUMO1 and oocyte JUNO. Recently, we found that alternative splicing of the Izumo1 gene generates a novel IZUMO1 isoform (IZUMO1_v2). Here, we obtained four mouse lines, having graded different levels of IZUMO1 protein by combining an original IZUMO1 (IZUMO1_v1) knockout with IZUMO1-null (both IZUMO1_v1 and _v2 disrupted) genetic background, in order to determine how the quantity of IZUMO1 influences male fertility. Subsequently, we clarified that the signal intensity from two quantitative assays, western blot and immunostaining analyses with a monoclonal antibody against mouse IZUMO1, were strongly correlated with average litter size. These results suggest that evaluating IZUMO1 protein levels is useful for predicting fecundity, and is a suitable test for male fertility.

Vaccination with an Epitope Peptide of IZUMO1 to Induce Contraception in Female Mice

PROBLEM

The development of a new and suitable contraceptive methods, as well as in-depth and systematic research into underlying contraceptive mechanisms, is crucial. IZUMO1 plays an important role in the fusion of the sperm and ovum during fertilization. Izumo(-/-) mice are infertile. Therefore, IZUMO1 may be a potential target for the development of a contraceptive vaccine.

METHOD OF STUDY

Linear B-cell epitopes (BCE) were identified in IZUMO using biosynthetic peptides and used to immunize female mice.

RESULTS

Five IZUMO BCE were identified: DLVLDCL177-183, YSFYRV196-201 (named BCE-2), YLT217-219, SMVGPED221-227, and DAGNY228-232. Active immunization with the BCE-2 vaccine sharply decreased the fertility rate in female mice in a safe and reversible manner. In vitro fertilization showed that the BCE-2 vaccine interferes with and blocks the fusion of the sperm and the ovum.

CONCLUSIONS

B-cell epitopes-2 may be a new candidate for the development of contraceptive vaccine due to its effectiveness, safety, and reversibility.

Prospects for immunocontraception in feral horse population control: exploring novel targets for an equine fertility vaccine

Feral horses populate vast land areas and often induce significant ecological and economic damage throughout the landscape. Non-lethal population control methods are considered favourable in light of animal welfare, social and ethical considerations; however, no single effective, safe and species-specific contraceptive agent is currently available for use in free-ranging wild and feral horses. This review explores aspects of equine reproductive physiology that may provide avenues for the development of specific and long-lasting immunocontraceptive vaccines and some of the novel strategies that may be employed to facilitate appropriate antigen discovery in future research. Potential antigen targets pertaining to spermatozoa, the ovary and oocyte, as well as the early conceptus and its associated factors, are reviewed in the context of their suitability for immunocontraceptive vaccine development.

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.

Investigation of the stallion sperm proteome by mass spectrometry

Stallion spermatozoa continue to present scientific and clinical challenges with regard to the biological mechanisms responsible for their survival and function. In particular, deeper understanding of sperm energy metabolism, defence against oxidative damage and cell–cell interactions should improve fertility assessment and the application of advanced reproductive technologies in the equine species. In this study, we used highly sensitive LC–MS/MS technology and sequence database analysis to identify and characterise the proteome of Percoll-isolated ejaculated equine spermatozoa, with the aim of furthering our understanding of this cell's complex biological machinery. We were able to identify 9883 peptides comprising 1030 proteins, which were subsequently attributed to 975 gene products. Gene ontology analysis for molecular and cellular processes revealed new information about the metabolism, antioxidant defences and receptors of stallion spermatozoa. Mitochondrial proteins and those involved in catabolic processes constituted dominant categories. Several enzymes specific to β-oxidation of fatty acids were identified, and further experiments were carried out to ascertain their functional significance. Inhibition of carnitine palmitoyl transferase 1, a rate-limiting enzyme of β-oxidation, reduced motility parameters, indicating that β-oxidation contributes to maintenance of motility in stallion spermatozoa.

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.

Vaccine for human contraception targeting sperm Izumo protein and YLP12 dodecamer peptide

There is an urgent need to develop a better method of contraception which is non-steroidal and reversible to control world population explosion and unintended pregnancies. Contraceptive vaccines (CV), especially targeting sperm-specific proteins, can provide an ideal contraceptive modality. Sperm-specific proteins can induce an immune response in women as well as men, thus can be used for CV development in both sexes. In this article, we will review two sperm-specific proteins, namely Izumo protein and YLP12 dodecamer peptide. Gene-knockout studies indicate that Izumo protein is essential for sperm-egg membrane fusion. Vaccination with Izumo protein or its cDNA causes a significant reduction in fertility of female mice. The antibodies to human Izumo inhibit human sperm penetration assay. Recently, our laboratory found that a significant percentage of infertile women have antibodies to Izumo protein. The second sperm-specific protein is YLP12 , a peptide mimetic sequence present on human sperm involved in recognition and binding to the human oocyte zona pellucida. Vaccination with YLP12 or its cDNA causes long-term, reversible contraception, without side effects, in female mice. Infertile, but not fertile, men and women have antibodies to YLP12 peptide. Our laboratory has isolated, cloned, and sequenced cDNA encoding human single chain variable fragment (scFv) antibody from infertile men which reacts with YLP12 peptide. The human YLP12 scFv antibody may provide a novel passive immunocontraceptive, the first of its kind. In conclusion, sperm-specific Izumo protein and YLP12 peptide can provide exciting candidates for antisperm CV development.

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.

Preparation, characterization, and determination of immunological activities of transfer factor specific to human sperm antigen

OBJECTIVE. The objective of this study was to prepare, characterize, and determine immunological activities of specific transfer factor (STF) specific to human sperm antigen (HSA) for the preparation of antisperm contraceptive vaccine that can be used as an immunocontraceptive. METHODS. HSA-STF was prepared using the spleens of rabbits vaccinated with HSA. The specific immunological activities were examined by lymphocyte proliferation test (LPT), leukocyte adhesion inhibition test (LAIT), and by determining the concentrations of IL-4, γ -IFN, and IL-21. HSA-STF was a helveolous substance, having a pH value of 7.0 ± 0.4 and UV absorption maxima at 258 ± 6 nm. It contained seventeen amino acids; glycine and glutamic acids were the highest in terms of concentrations (38.8 μ g/mL and 36.3 μ g/mL, resp.). RESULTS. The concentration of polypeptide was 2.34 ± 0.31 mg/mL, and ribose was 0.717 ± 0.043 mg/mL. The stimulation index for lymphocyte proliferation test was 1.84, and the leukocyte adhesion inhibition rate was 37.7%. There was a statistically significant difference between the cultural lymphocytes with HSA-STF and non-HSA-STF for γ -IFN and IL-21 (P < 0.05), but there was no statistical significance for IL-4 (P > 0.05). CONCLUSION. HSA-STF was prepared and characterized successfully. It had immunological activity which could transfer the immune response specific to HSA and prove to be a potential candidate for the development of male immunocontraceptive agents.

Birth control vaccine targeting leukemia inhibitory factor

The population explosion and unintended pregnancies resulting in elective abortions continue to impose major public health issues. This calls for a better method of contraception. Immunocontraception has been proposed as a valuable alternative that can fulfill most, if not all, of the properties of an ideal contraceptive. There are several targets that are being explored for contraceptive vaccine development. Leukemia inhibitory factor (LIF), a member of interleukin-6 family, is required for embryo development and successful blastocyst implantation in several mammalian species. The present study was conducted to examine if LIF can be a target for the development of a birth control vaccine. Three sequences from LIF and two sequences from LIF-receptor (LIF-R) that span the regions involved in ligand-receptor binding were delineated, and peptides were synthesized based upon these sequences. Antibodies raised against these five peptides reduced LIF bioactivity in an in vitro culture assay using BA/F3 mLIF-R-mpg130 cells. Vaccines were prepared by conjugating these peptides to various carrier proteins. Immunization of female mice with these peptide vaccines induced a long-lasting, circulating as well as local antibody response in various parts of the genital tract, and resulted in a significant (P ≤ 0.05) inhibition in fertility in all the three trials; the LIF-R peptide vaccines proved to be a better vaccine target. The data indicate that LIF/LIF-R is an excellent target for the development of a birth control vaccine. This is the first study, to our knowledge, that examined LIF/LIF-R as a target for immunocontraception. The findings of this study can be easily translated to humans since LIF/LIF-R is also important for implantation and pregnancy in women.

LM23 is a novel member of the Speedy/Ringo family at the crossroads of life and death of spermatogenic cell

LM23 is a gene specifically expressed in the testis of Rattus norvegicus, as previously reported by our laboratory. The aim of the study is to further investigate the biological function of LM23. Several bioinformatic tools were utilized, including PROSITE and BLAST. To determine the subcellullar localization of LM23, a polyclonal antibody specific for LM23 was generated via the immunization of rabbits. The LM23 gene was cloned from rat testis tissue, and LM23 protein was expressed in Escherichia coli. The biological function of LM23 was analyzed with microarray analysis and immunohistochemistry, using a rat model of LM23 gene knockdown. The results suggested that LM23 belongs to the Speedy/Ringo family. LM23 regulated the G₁/S and G₂/M transitions of the cell cycle during spermatogenesis. Downregulation of the LM23 gene during spermatogenesis could lead to the activation of both the Fas-FasL pathway and the mitochondrial pathway. These novel findings indicate that LM23 has a diverse array of functions that are important in both the life and death of the spermatogenic cell.

Antisperm contraceptive vaccines: where we are and where we are going?

This is a review of current status and future perspectives on the development of antisperm contraceptive vaccines (CV) and immunocontraceptives. The development of antisperm CV is an exciting proposition. There is a strong rationale and recent data indicating that this proposition can translate into reality. The search for novel sperm-specific antigens/genes, that can be used for CV, continues using various recent developing technologies. Various approaches of proteomics, genomics, reproductive biology, mucosal immunity and vaccinology and several novel technologies such as gene knockout technology, phage display technology, antibody engineering, differential display technique, subtractive hybridization, and hybridoma technology are being used to delineate sperm-specific antigens and construct CV. Various sperm antigens/genes have been delineated, cloned, and sequenced from various laboratories. Vaccination with these sperm antigens (recombinant/synthetic peptide/DNA) causes a reversible contraceptive effect in females and males of various animal species, by inducing a systemic and local antisperm antibody response. The efficacy is enhanced by combination vaccination, including peptides based on various sperm antigens. Several human novel scFv antibodies with unique complementarity-determining regions (CDRs), that react with specific well-defined fertility-related sperm antigens, have been synthesized. These human infertility-related antibodies may find application in the development of novel immunocontraceptives. Besides finding the novel sperm antigens, the present and future focus is on enhancing the immunogenicity, bioefficacy, and on obliterating the inter-individual variability of the immune response, and proceeding for primate and human clinical trials. Multi-epitope vaccines combining sperm proteins involved in various steps of fertilization cascade have been found to enhance the immunogenicity and bioefficacy of the contraceptive effect. The in vitro synthesis of infertility-related human scFv antibodies may provide unique once-a-month immunocontraceptives, the first of its kind, for human use. The multi-epitope CV and preformed engineered human antibodies of defined specificity may obliterate the concern related to inter-individual variability of the immune response.

Antifertility characteristics of the N-terminal region of mouse equatorial segment protein

To investigate antifertility characteristics of the equatorial segment protein (ESP) and its potential immunocontraceptive effect, three partially overlapping cDNA fragments P1/P2/P3, together covering the entire mouse ESP, were cloned, expressed, and purified. The roles of P1/P2/P3 in fertility were investigated through in vitro fertilization and mouse mating test. Antibodies against P1/P2 significantly reduced the rates of fertilization in vitro in the zona-intact experiments. Coincubation of zona-free mouse oocytes with capacitated mouse spermatozoa in the presence of antibodies against P1/P2 also inhibited sperm-oolemma binding and fusion, while anti-P3 antibody virtually had no effect on in vitro fertilization at the same concentration. Immunization of female BALB/c mice with N-terminal of mouse ESP (recombinant P1 and P2) resulted in a significant decrease in the fertility rate as well as the litter size. Double immunofluorescence staining showed that mouse ESP protein was localized to the equatorial segment of acrosome of mouse sperm, and was exposed and surface-accessible after acrosome reaction. Mouse ESP was also demonstrated to have complementary binding sites on the mouse egg plasma membrane by indirect immunofluorescence assay. These findings suggest that the N-terminal of mouse ESP could play an important role in fertility and might be a vaccine candidate for contraception.

Vaccines for immunological control of fertility

Vaccines have been proposed as one of the strategies for population control. Immunocontraceptive vaccines can be designed to inhibit: (1) production of gametes (sperm and egg); (2) functions of gametes, leading to blocking of fertilization; and (3) gamete outcome (pregnancy). Immunization with gonadotropin-releasing hormone coupled to different carriers has shown curtailment in the production of sperm with concomitant infertility in various species. Immunization of nonhuman primates and men with ovine follicle stimulating hormone has also resulted in reduced sperm output. Various spermatozoa-specific proteins such as FA1, PH-20, LDH-C₄, SP-10, SP-17, sp56, SPAG9, and Izumo have been proposed as candidate antigens to develop contraceptive vaccines, which have shown efficacy in inhibiting fertility in different animal models. Immunization with zona pellucida glycoproteins-based immunogens also results in curtailment of fertility in a variety of species. However, ways to overcome the observed oophoritis associated with zona proteins immunization have yet to be discovered, a necessary step before their proposal for control of human population. Nonetheless, this is a very promising approach to control wildlife animal population. Phase II clinical trials of β-human chorionic gonadotropin-based vaccine in women have established the proof of principle that it is possible to inhibit fertility without any untoward side-effects by vaccination. Further scientific inputs are required to increase the efficacy of contraceptive vaccines and establish their safety beyond doubt, before they can become applicable for control of fertility in humans.

Development of genetically engineered human sperm immunocontraceptives

Contraceptive vaccines targeting sperm are an exciting proposition. This review is focused on anti-sperm contraceptive vaccines and genetically engineered human antibodies that can be used as immunocontraceptives. Various methods of vaccinology and antibody engineering have been used to obtain multi-epitope contraceptive vaccines and human single chain variable fragment (scFv) antibodies from immunoinfertile and vasectomized men. Contraceptive vaccines comprised of various sperm antigens, peptide epitopes or DNA have shown various degrees of reversible contraceptive effect in the mouse model and their efficacy is enhanced with the multi-epitope combination vaccine. Failure to achieve a complete fertility block is probably due to variability in the host immune response. Using phage display technology, our laboratory has synthesized in vitro at least four novel scFv antibodies with unique complementarity determining regions (CDRs) that react with specific fertility-related sperm antigens employing cDNA from immunoinfertile and vasectomized men. These antibodies inhibit human sperm function in vitro, and their immunocontraceptive effect in vivo is being investigated. If these human scFv antibodies block fertility in vivo they may provide unique and novel immunocontraceptives, a first-in-kind for human use. The multi-epitope contraceptive vaccines and preformed engineered antibodies of defined specificity may eliminate concern related to inter-individual variability of the immune response.

Sperm–egg adhesion and fusion in mammals

Fertilisation is an orchestrated, stepwise process during which the participating male and female gametes undergo irreversible changes, losing some of their structural components while contributing others to the resultant zygote. Following sperm penetration through the egg coat, the sperm plasma membrane fuses with its oocyte counterpart, the oolemma. At least two plasma membrane proteins essential for sperm–oolemma fusion – IZUMO and CD9 on the male and female gametes, respectively – have been identified recently by classical cell biology approaches and confirmed by gene deletion. Oolemma-associated tetraspanin CD81, closely related to CD9, also appears to have an essential role in fusion. Additional proteins that may have nonessential yet still facilitating roles in sperm–oolemma adhesion and fusion include oolemma-anchored integrins and oocyte-expressed retroviral envelope proteins, sperm disintegrins, and sperm-borne proteins of epididymal origin such as CRISP1 and CRISP2. This review discusses these components of the gamete fusion mechanism within the framework of gamete structure, membrane biology, cell signalling and cytoskeletal dynamics, and revisits the topic of antipolyspermy defence at the oolemma level. Harnessing the mechanisms of sperm–egg fusion is of importance to animal biotechnology and to human assisted fertilisation, wherein male patients with reduced sperm fusibility have been identified.

In vitro and in vivo studies evaluating recombinant plasmid pCXN2-mIzumo as a potential immunocontraceptive antigen

PROBLEMS

Study on feasibility of pCXN2-mIzumo as a potential immunocontraceptive antigen.

METHOD OF STUDY

Two groups of mice received 100 microg/mouse plasmids of pCXN2-mIzumo and pCXN2 respectively. RT-PCR Immunofluorescence assay and ELISA were performed to observe pCXN2-mIzumo expression and antibody response in the inoculated mice. Sperm penetration assay and animal mating were employed to detect differences of in vitro fertilization (IVF) rate and mean litter size between the experimental and control groups.

RESULTS

Izumo cDNA positive bands were detected in sample from mice immunized with pCXN2-mIzumo. IgG response started to rise at 2 weeks after first boost and reached the highest antibody titers at 2 weeks after third boost of immunization with pCXN2-mIzumo in the experimental mice. In vitro fertilization rate in the experimental group (11.57%) was significantly lower than that in control (36.60%). Significant difference of mean litter size between female experimental and control groups was observed, and there was significant negative correlation between individual anti-serum titers and litter size (r = -0.308, P < 0.05).

CONCLUSION

pCXN2-mIzumo plasmid possesses appreciable anti-fertility potential.

Status of contraceptive vaccines

PROBLEM

This is a review of anti-sperm contraceptive vaccines (CV), and synthesis of human scFv antibodies that can be used as immunocontraceptives.

METHOD OF STUDY

Various methods of proteomics and genomics, peptide synthesis, phage display technology, and antibody engineering were used to obtain multi-epitope vaccines and human scFv antibodies from immunoinfertile and vasectomized men. The present review primarily focuses on the effect of multi-epitope vaccines and Izumo on fertility, and synthesis and characterization of sperm specific human scFv antibodies.

RESULTS

The immunization with Izumo peptides causes a contraceptive effect in female mice. The efficacy is enhanced by combination vaccination, including peptides based on other sperm antigens. Using phage display technology, we were able to synthesize at least four novel scFv antibodies with unique complementarity determining regions (CDRs) that reacted with specific fertility-related sperm antigens. These antibodies inhibited human sperm function in vitro, and their immunocontraceptive effect in vivo by these antibodies is currently being investigated.

CONCLUSION

The multi-epitope vaccines may provide an efficacious and viable approach to contraception. The human scFv antibodies, if they block fertility in vivo, may provide unique and novel immunocontraceptives, the first of its kind for human use. The multi-epitope CV and preformed engineered antibodies of defined specificity may obliterate the concern related to inter-individual variability of the immune response.

Experimental immunological infertility effect of anti-GAPDH-2 antibodies on the fertility of female mice

OBJECTIVE

To examine the relationship between an antibody against GAPDH-2, a sperm-specific protein, and infertility of female mice.

DESIGN

Basic research.

SETTING

National Research Institute for Family Planning Beijing, World Health Organization Collaboration Center of Human Reproduction.

ANIMAL(S)

New Zealand rabbit, NIH and ICR mice.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Enzyme-linked immunoabsorbent assay, Western blot and indirect immunostaining assays, standard fertility assay, and sperm agglutination assay.

RESULT(S)

Antibodies against the full-length GAPDH-2 were raised. Its specificity was assessed by immunoblotting and indirect immunostaining assays. The antibody immunoreacted with human sperm GAPDH-2 and the mouse homolog GAPDS but did not cross-react with GAPDH. Treatment of female mice with IP injection of anti-GAPDH-2 serum significantly reduced their fertility. Anti-GAPDH-2 serum caused the agglutination of normal mice sperm in vitro. The anti-GAPDH-2 antibody was detectable in the sera and uterine fluid of the mice immunized with GAPDH-2.

CONCLUSION(S)

These results show that GAPDH-2 should be further evaluated as a promising candidate in the development of an antifertility immunogen. Detecting anti-GAPDH-2 antibodies in the bodily fluid of subjects afflicted with indeterminate infertility may be a new diagnostic index.