Fully effective contraception in male and female guinea pigs immunized with the sperm protein PH-20

Epididymal SPAM1 and its impact on sperm function

The most widely conserved mammalian sperm antigen is sperm adhesion molecule 1, SPAM1/PH-20, which is also the major testicular hyaluronidase. This multifunctional glycosyl phosphatidylinositol (GPI)-linked protein plays several roles in fertilization and is encoded by a gene that resides among hyaluronidase family members in a cluster on human 7q31/mouse 6A2. In the human cluster, SPAM1 is the only functional hyaluronidase and of all six hyaluronidases in the genome it is the best characterized, both structurally and functionally. While SPAM1 transcripts are abundantly expressed only in the testis, specifically in spermatids, the RNA and protein are present in the male reproductive tract and accessory organs and in the female tract of mice. Our investigation of the post-testicular expression of SPAM1 shows that the protein is widely expressed in the epididymis. Like testicular SPAM1, epididymal SPAM1 (ES) has hyaluronidase activity and is conserved in at least five species (mouse, rat, bull, macaque, and human) all of which have putative androgen response elements in the gene promoters, consistent with androgen regulation. Testicular lumicrine factors have also been implicated in ES regulation. Based on regional expression, the protein is likely to play a role in both sperm maturation and storage. A minor secretory glycoprotein, ES is present in the epididymal luminal fluid in both a soluble and insoluble form (epididymosomes), with the latter having an intact lipid anchor. Genetic approaches have provided evidence for sperm uptake of ES in vivo, and in vitro uptake has been demonstrated with the use of Spam1 null mice. In vitro acquisition of ES on the sperm surface results in a pattern that mimics the wild-type distribution. More importantly it significantly increases the ability of null sperm to penetrate the cumulus of oocytes via hyaluronidase activity, directly relating ES uptake with fertilizing ability and indicating that ES is a marker of sperm maturation.

Immunisation of the male tammar wallaby (Macropus eugenii) with spermatozoa elicits epididymal antigen-specific antibody secretion and compromised fertilisation rate

Immunocontraception has been proposed as an effective and humane means of controlling overabundant kangaroo populations in Australia. We have examined the feasibility of using a sperm-based vaccine for this purpose using a model macropod species, the tammar wallaby (Macropus eugenii). This study has demonstrated immunocontraception in a marsupial species following immunisation of males with homologous spermatozoa. Serum anti-sperm IgG titres were associated with a significant reduction in fertilisation rates following mating with superovulated female wallabies. Antigen-specific IgG penetrated the reproductive tract at the rete testis and bound spermatozoa in vivo. IgG was detected bound to the acrosome and midpiece regions of both epididymal and ejaculated spermatozoa. The absence of adverse testicular pathology and sperm movement effects suggests that contraception may have been achieved by antibody-mediated blocking of sperm surface antigens essential for fertilisation. This study demonstrates that a contraceptive vaccine targeting sperm antigens has potential for fertility control in male macropods.

Effect of sperm DNA vaccine on fertility of female mice

Our laboratory has identified a sperm-specific dodecamer peptide sequence, designated as YLP(12), vaccination with which causes a long-term reversible immunocontraceptive effect in female mice. In the present study, the effects of YLP(12) DNA vaccine were examined. YLP(12) 36 bp cDNA was cloned into pVAX1 vector to prepare the DNA vaccine. Two additional vaccine constructs were made by in frame cloning of one and two CpG repeats in the YLP(12)-cDNA vaccine. Five groups of female mice were immunized intradermally by using gene gun with YLP(12)-cDNA, YLP(12)-cDNA-CpG, YLP(12)-cDNA-CpG-CpG, YLP(12)-cDNA mixed with exogenous synthetic CpG oligodeoxynucleotide (ODN), or vector DNA alone, respectively. Vaccination with all three constructs and the YLP(12) vaccine mixed with exogenous ODN raised antibody response both in the sera as well as locally in the vaginal tract. There was no antibody response in the mice injected with the vector alone. In sera, the highest titers were obtained for the IgG class for all constructs and formulation followed by IgA class. In vaginal washings the highest titers were obtained for the IgA class followed by IgG class. Within the IgG class, the titers for the IgG2a subclass were significantly greater than the IgG1 subclass. Immunization with all constructs and formulation caused a significant (P < 0.05 to <0.001) reduction (20-43%) in fertility of female mice. The highest reductions were seen in mice immunized with YLP(12)-cDNA-CpG-CpG (two repeats) (43% reduction) and with the YLP(12) vaccine administered with exogenous CpG ODN (42% reduction). T lymphocytes obtained from DNA-vaccinated mice showed clearly distinguished comparative RT-PCR analysis of cytokine mRNA expression for Th1 and Th2 immune responses compared to T lymphocytes obtained from control animals injected with vector DNA. Expression of both Th1 cytokines (IL-2 and IFN-gamma) and Th2 cytokines (IL-4 and IL-10) was enhanced after DNA vaccination as compared to controls, with a bias towards Th1 response. The immunocontraceptive effects were long-lasting observed up to 1.3 years of the observation period and increased with time. These novel findings indicate that the intradermal immunization with a sperm-specific DNA vaccine causes a long-term circulating and local immune response resulting in immunocontraceptive effects in female mice.

Contraceptive responses of female hamsters immunized with recombinant sperm protein P26h

BACKGROUND

A number of antigens have been characterized and proposed as potential candidates for immunocontraception. P26h, a 26-kDa hamster sperm protein located on the acrosomal cap, is known to be involved in sperm-zona pellucida interactions. Furthermore, in vivo fertilization can be blocked by active immunization of male hamsters against P26h or maltose-binding protein recombinant P26h (MBP-P26h).

OBJECTIVE

The aim of this study was to investigate the immune response and reproductive function of female hamsters immunized against MBP-P26h.

RESULTS

Active immunization against MBP-P26h resulted in anti-P26h circulating antibodies, with enzyme-linked immunosorbent assay (ELISA) titers showing interindividual variability. The antibodies produced by the animals immunized against MBP-P26h reacted with the native P26h protein in ELISA, in Western blot analysis and in immunostaining performed on cauda epididymal spermatozoa. Mating of immunized female hamsters resulted in a significant decrease in the number of viable fetuses only in females with high titers of anti-P26h circulating antibodies.

DISCUSSION

This result is in agreement with the sperm-zona pellucida binding assay's results. Indeed, sera collected from immunized animals, and not from control animals, significantly blocked sperm-zona pellucida binding in vitro. Histological studies showed that active immunization did not cause any pathology in the reproductive tissues.

CONCLUSION

These findings suggest that P26h is a potential candidate for the development of a contraceptive vaccine in both males and females.

Antisperm Vaccine for Contraception

PROBLEM

This study is a review of antisperm contraceptive vaccine (CV) development with the main focus on research going on in our laboratory.

METHOD OF STUDY

Various methods of proteomics and genomics, hybridoma technology, substractive libraries, differential display method, and phage display technology were used to obtain sperm-specific genes and proteins. The present study will primarily focus on the sequences obtained by using the phage display technology and their role in CV development and human immunoinfertility.

RESULT

Four novel peptides, delineated by using the phage display technology, were found to be involved in human immunoinfertility. The vaccine based on one of these peptides, designated as YLP(12), caused a reversible contraception in female mice.

CONCLUSIONS

The vaccine targeting sperm is a feasible and exciting approach to contraception. The phage display technology is a powerful tool to delineate sperm-specific peptide sequences that can be used for the CV development and in the diagnosis and treatment of infertility mediated through antisperm antibodies.

Recent advances in contraceptive vaccine development: a mini-review

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

Contraceptive vaccines

The world's population is growing at a tremendous rate, affecting growth and development. Apart from this population growth, unintended pregnancies resulting in elective abortions continue to be a major public health issue. In over half of these unintended pregnancies, the women have used some type of contraception. Thus, there is an urgent need for a better method of contraception that is acceptable, effective and available. The contraceptive choices available to women at this time include steroid contraceptives, intrauterine devices, barrier methods, spermicides, natural family planning, male and female sterilisation, and recently available emergency contraceptives. Contraceptive vaccines (CVs) may provide viable and valuable alternatives that can fulfill most, if not all, properties of an ideal contraceptive. Since both the developed and most of the developing nations have an infrastructure for mass immunisation, the development of vaccines for contraception is an exciting proposition. The molecules that are being explored for CV development either target gamete production (gonadotropin releasing hormone, follicle-stimulating hormone and luteinising hormone), gamete function (zona pellucida [ZP] proteins and sperm antigens) or gamete outcome (human chorionic gonadotropin [hCG]). Disadvantages of CVs targeting gamete production are that they affect sex steroids and/or show only a partial effect in reducing fertility. CVs targeting gamete function are better choices. Vaccines based on ZP proteins are quite efficacious in producing contraceptive effects. However, they invariably induce oophoritis affecting sex steroids. Sperm antigens constitute the most promising and exciting targets for CVs. Several sperm-specific antigens have been delineated in several laboratories and are being actively explored for CV development. Antisperm antibody-mediated immunoinfertility provides a naturally occurring model to indicate how an antisperm vaccine will work in humans. Vaccines targeting gamete outcome primarily focus on the hCG molecule. The hCG vaccine is the first vaccine to undergo phase I and II clinical trials in humans. Both the efficacy and the lack of immunotoxicity have been reasonably well demonstrated for this vaccine. The present studies focus on increasing the immunogenicity and efficacy of this birth control vaccine.

Contraceptive vaccines targeting sperm

Overpopulation is a global problem of significant magnitude, with grave implications for the future. Development of new contraceptives is necessary, as existing forms of birth control are unavailable, impractical and/or too expensive for many individuals due to sociological, financial or educational limitations. Immunocontraception and, in particular, the targeting of antibodies to sperm-specific antigens implicated in sperm-egg binding and fertilisation offers an attractive approach to control fertility. Sperm-specific antibodies may impair fertility by inhibiting sperm motility, by reducing penetration of the cervical mucus by sperm, or by interfering in sperm capacitation or the acrosome reaction; alternatively, antisperm antibodies may invoke the complement cascade, resulting in sperm lysis. The antibodies raised against sperm-specific antigens have proved to be extremely effective at reducing sperm-egg interactions in vitro; fertility trials in subhuman primates will eventually be needed to prove the effectiveness of the sperm antigens in terms of contraceptive efficacy before trials in humans can be justified. In addition, existing and emerging strategies (such as sperm proteomics, the determination of molecular and structural details of sperm proteins, and the modelling of protein-ligand interactions using X-ray and/or NMR structures to name a few) are expected to provide the experimental foundation for the design of small molecule inhibitors with antifertility effects. The technology underpinning vaccine development is constantly being developed and the introduction of DNA/RNA vaccines is certain to impact upon the field of immunocontraception.

Identification of a New, Testis-Specific Sperm Antigen Localized on the Principal Piece of the Spermatozoa Tail in the Fox (Vulpes vulpes)1

Fox (Vulpes vulpes) sperm antigens were identified to assess them as a potential target for a contraceptive vaccine. We report here the cloning and sequencing of fSP13, a fox sperm protein of 97 kDa. The fSP13 protein was both auto- and iso-antigenic in foxes; it was recognized by sera of foxes immunized with fox sperm proteins and vasectomized foxes. The NH2-terminal sequence of fSP13 was determined, and a piece of cDNA was amplified from testicular RNA by reverse transcription polymerase chain reaction. This piece was used to screen a cDNA library from fox testis by Southern blot. A sequence of 1662 base pairs was obtained, including a major open reading frame coding for 498 amino acid. Mass spectrometry analysis confirmed the position of the open reading frame and the presence of posttranscriptional modifications. Analysis of the predicted amino acid sequence revealed no apparent transmembrane regions. Comparison of the protein sequence with the Prosite database demonstrated the presence of four potential N-linked glycosylation sites. The fSP13 bears the closest amino acid similarity to two human sperm proteins: fibrousheathin 2 and testis-specific calcium binding protein 86-VII. The deduced 80 N-terminal amino acid sequence also presents similarity with the RIIalpha domain. By using a serum against fSP13, this antigen was localized on the principal piece of the fox spermatozoa. Northern blot analysis showed that fSP13 is specifically expressed in testis. The fSP13 is one of the first fox sperm antigens to be cloned and sequenced.

Reversible immunocontraception in male monkeys immunized with eppin

Various forms of birth control have been developed for women; however, there are currently few options for men. The development of male contraceptives that are effective, safe, and reversible is desired for family planning throughout the world. We now report contraception of male nonhuman primates (Macaca radiata) immunized with Eppin, a testis/epididymis-specific protein. Seven out of nine males (78%) developed high titers to Eppin, and all of these high-titer monkeys were infertile. Five out of seven (71%) high-anti-Eppin titer males recovered fertility when immunization was stopped. This study demonstrates that effective and reversible male immunocontraception is an attainable goal. This method of immunocontraception may be extended to humans.

Molecular Cloning, Expression of Testicular Transcript Abundant in Germ Cells and Immunobiological Effects of the Recombinant Protein

PROBLEM

It has been well documented that antisperm antibodies can be causative factors for infertility. In this report we have identified a protein on human sperm referred as human sperm-associated protein (HSAP) using serum of an immunoinfertile woman; it is thus a sperm-specific protein--a candidate molecule for control of fertility.

METHOD OF STUDY

An immunoinfertile woman serum showing head-head sperm agglutination and acrosomal localization, reacted with human sperm protein of apparent molecular weight of 48 kDa on Western blot. Anti-48 kDa antiserum was raised in rabbit by eluting 48 kDa protein and was used to screen the human testis cDNA expression library. A putative positive hsap cDNA clone was obtained, sequenced and subjected to tissue specificities studies by Northern blotting. The cell type-specific expression was done using in situ RNA hybridization studies. To obtain recombinant HSAP (r-HSAP), hsap cDNA was cloned in pET 22b(+) expression vector. r-HSAP was expressed as polyhistidine fusion protein in Escherichia coli and purified. Rabbits were immunized with the purified r-HSAP, which led to generation of antibodies. In order to evaluate in vitro immunocontraceptive potential, the anti-r-HSAP antibodies were characterized by agglutination assay, zona-free hamster egg penetration assay, indirect immunofluorescence (IIF) assay, and by flow cytometry analysis.

RESULTS

We have cloned a human testis gene encoding a protein (HSAP) of 328 amino acids. Antibodies against the purified recombinant protein specifically recognized approximately 40 kDa r-HSAP, and a cognate 48 kDa protein band in human sperm extract in Western blot procedure. The anti-r-HSAP antibodies localized acrosomal compartment, inhibited sperm binding/attachment in zona-free hamster penetration assay and revealed surface binding with human live sperm by flow cytometry. The cDNA sequence has been submitted to EMBL and has been given the accession number Y16676.

CONCLUSION

This study has put in evidence that novel sperm-specific r-HSAP has role in sperm function and may have application in the development of a contraceptive vaccine. The availability of the recombinant protein will facilitate studies on the assessment of its potential as a contraceptive immunogen.

Sperm specific proteins-potential candidate molecules for fertility control

The increase in population growth rate warrants the development of additional contraceptive methods that are widely acceptable, free from side effects and less expensive. Immunocontraception, and in particular the targeting of antibodies to gamete-specific antigens implicated in sperm egg binding and fertilization, offers an attractive approach to control fertility. The development of a contraceptive vaccine based on sperm antigen represents a promising approach to contraception. In mammals, fertilization is completed by the direct interaction of sperm and egg, a process mediated primarily by sperm surface proteins. Sperm have proteins that are unique, cell specific, immunogenic and accessible to antibodies. A few of the sperm specific proteins have been isolated and characterized. The antibodies raised against the sperm specific antigens have proved to be extremely effective at reducing sperm-egg interaction in vitro; fertility trials in sub-human primates would eventually prove the effectiveness of the sperm antigens in terms of contraceptive efficacy.

Assessment of contraceptive vaccines based on recombinant mouse sperm protein PH20

Mouse PH20 (mPH20), the mouse homologue to guinea pig hyaluronidase protein PH20 (gpPH20), was used to produce contraceptive vaccines that target both sexes of mice. Previously, immunization with a female gamete antigen (the zona pellucida subunit 3 protein) delivered in a recombinant murine cytomegalovirus (MCMV), or as a purified recombinant protein, has been shown to induce infertility in female mice. There is evidence, however, that sperm protein antigens could provide broader contraceptive coverage by affecting both males and females, and the most promising has been gpPH20 when tested in a guinea pig model. Mice were therefore either inoculated with a recombinant MCMV expressing mPH20 or immunized directly with purified recombinant mPH20 protein fused to maltose-binding protein. Mice treated with either vaccine formulation developed serum antibodies that cross-reacted to a protein band of 55 kDa corresponding to mPH20 in Western blots of mouse sperm. However, there was no significant reduction in the fertility of males or females compared with control animals with either formulation. We conclude from our data that recombinant mPH20 is not a useful antigen for inclusion in immunocontraceptive vaccines that target mice.

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.

Immunocontraception for population control: will resistance evolve?

The prospect for successful biocontrol using immunocontraception is threatened if there is adaptation to the vaccine through natural selection of individuals that are genetically resistant to the contraceptive agent. To assess this possibility we examined the literature and found that little relevant data are available for any species on the appropriate trait, fertility variation among immunized individuals, or about appropriate population and genetic parameters influencing the likelihood of a selection response. Some data are available on variation in antibody response to immunocontraceptives, but the relationship between antibody response and fertility levels is poorly documented. The antibody response data indicate low heritability for this trait suggesting that fertility levels of contraceptive-resistant individuals will also have a low heritability. Slow evolution of contraception resistance might therefore be anticipated. The absence of information about relevant parameters makes the construction of quantitative models premature. We discuss factors in particular need of investigation if predictions about resistance evolution are to be made. These include: 1. the genetic basis of fertility retention, 2. the proportion of the population resistant to the contraceptive agent and how this is affected by gene flow from refuge populations, 3. the genetically-based fitness tradeoffs of resistant individuals that often accompany selection, 4. cross-generation effects that can thwart the effects of selection, and 5. the efficiency of delivery of the contraceptive agent. An understanding of the above for particular species, and the development of appropriate divergently acting multiple vaccines that can be used in temporal rotation or in mixtures, should facilitate the development of management options to minimize resistance evolution.

Identification of a novel GPI-anchored CRISP glycoprotein, MAK248, located on the posterior head and equatorial segment of cynomolgus macaque sperm

To identify a sperm-surface component that is highly antigenic, we immunized female cynomolgus macaques with glycosylphosphatidylinositol (GPI)-anchored sperm surface proteins that were released following treatment with phosphatidylinositol-specific phospholipase C (PI-PLC). Five different adjuvants were used in combination with the PI-PLC-released proteins, and three of these proteins (24, 48, and 53 kDa) were shown to be potent antigens for immunization of female monkeys. The 53 kDa protein was found to be a surface coating protein and not a GPI-anchored protein. Polyclonal antibodies to the 24 kDa protein and the 48 kDa protein were produced in rabbits. The two antibodies recognized both proteins on Western blots. The same rabbit antibodies recognized 28, 18, and 10 kDa bands on a Western blot of chemically reduced PI-PLC-released proteins, suggesting that the 48 kDa protein is a dimer of the 24 kDa protein, which we refer to as MAK248. Rabbit polyclonal antibodies developed to reduced fragments of the 24 kDa protein showed that the 18 and 10 kDa bands are proteolytic peptide fragments of the 24 kDa protein. Screening of tissues from male macaques showed that MAK248 is expressed only in the epididymis. Microsequencing of two proteolytic fragments of the 18 kDa component showed 100% amino acid homology to a 233 deduced amino acid sequence previously identified in human testes genome. Antibodies to MAK248 recognized a 24 kDa protein released from human sperm exposed to PI-PLC. Antibodies to MAK248 recognized the equatorial segment and posterior head regions of capacitated cynomolgus macaque sperm. Structural analysis suggests that MAK248 is a novel CRISP protein and a member of the CAP (CRISP, Ag 5, PR-1) family of proteins. Based on amino acid sequence homology, it is possible that MAK248 functions as a protease inhibitor.

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.

Molecular cloning and sequencing of cDNA encoding for human FA-1 antigen

The cDNA encoding for the human FA-1 sperm antigen was cloned and sequenced from the in-house constructed subtractive human testis cDNA expression library in lambda Ziplox using the FA-1 monoclonal antibody (mAb). The full--length sequence was obtained by using the 5' rapid amplification of 5'-cDNA end (5'-RACE) procedure. It is 1,576-bp long, and has an open reading frame (ORF) of 283 amino acids (aa) with the first ATG Met start codon at nucleotide (nt) 57 and the stop codon TAG at nt 906. It has two termination codons at the 5' end before the ATG start codon. The translated protein has a calculated molecular weight of 32.1 kDa and estimated isoelectric point (pI) of 11.59. It has one potential N-linked glycosylation site and one tyrosine phosphorylation site, besides several O-linked glycosylation and serine and threonine phosphorylation sites. Hydrophilicity analysis of the deduced aa sequence showed it to be a membrane-anchored protein. Extensive computer search in the database did not identify any known nt/aa sequence having homology with FA-1 cDNA or deduced aa, indicating it to be a novel gene. The Northern blot and reverse transcription-polymerase chain reaction (RT-PCR)-Southern blot analyses indicated the testis-specific expression of FA-1 antigen at the mRNA level. The ORF of the FA-1 was subcloned into pGEX- 1lambda T for expression. The expressed FA-1 recombinant protein had a molecular size of approximately 40 kDa, and was recognized by the FA-1 mAb, and not by the myeloma control Ig. The rabbit antibodies (Ab) raised against the recombinant (r) FA-1 antigen recognized the rFA-1 antigen as well as the native (n) FA-1 antigen. The rFA-1 Ab specifically recognized a protein band of approximately 50 kDa in human testis extract in the Western blot involving 11 types of human tissue extracts, indicating the testis-specific expression of FA-1 at the protein level. The Ab showed binding with live and methanol-fixed human sperm at the post-acrosomal, mid-piece, and tail regions. The Ab caused a significant (P < 0.001) and concentration-dependent inhibition of human sperm capacitation/acrosome reaction by blocking tyrosine phosphorylation of the FA-1 antigen. The sperm-specific human FA-1 recombinant antigen may find applications in immunocontraception, and diagnosis and treatment of immunoinfertility in humans.

The development of contraceptive vaccines

The use of vaccination as a means of controlling fertility was established during the last decade with the publication of a successful Phase II trial demonstrating the efficacy of this approach to family planning. However, only this one Phase II trial has been completed despite a plethora of hormonal and gamete antigens that have been proposed as candidate vaccines. Improvements in the design and formulation of contraceptive vaccines are underway and will be a necessary prelude to further clinical trials.

Human sperm-specific peptide vaccine that causes long-term reversible contraception

A novel dodecamer peptide sequence, YLP(12), was identified on human sperm that is involved in oocyte binding. We investigated its immunocontraceptive effects in a murine model. A vaccine was prepared by conjugating the synthetic YLP(12) peptide with the binding subunit of recombinant cholera toxin. Vaccination of female mice by i.m. or intranasal routes without any additional adjuvant induced a sperm-specific immune response in serum and the vaginal tract that caused a long-term contraceptive state. Fertility was fully regained when antibody reactivity diminished at 305-322 days. The contraceptive effect was also completely reversed voluntarily by intravaginal administration of the peptide. Antibodies affected fertility at the prefertilization stage by inhibiting sperm capacitation and the acrosome reaction, and sperm-oocyte binding. The peptide sequence is an epitope of a 50 +/- 5-kDa membrane protein localized on the acrosome and tail of spermatozoa. Thus, the sperm-specific YLP(12) is an attractive candidate for contraceptive vaccine.

Characterization of the porcine sperm adhesion molecule gene SPAM1- expression analysis, genomic structure, and chromosomal mapping

Sequence analysis of cDNA products, derived from adult porcine testis mRNA, gave overlapping nucleotide sequence correlating to 1952 bp of the sperm adhesion molecule 1 (SPAM1) gene. This sequence was shown to be homologous to SPAM1 genes known in other mammalian species and contained an open reading frame encoding a 493-amino acid protein. Fluorescence in situ hybridization (FISH), using a bacterial artificial chromosome (BAC) clone from the PigE BAC library, was used to map SPAM1 to chromosome 18 of the pig. This finding is consistent with comparative mapping experiments performed between pig and human chromosomes. Polymerase chain reaction (PCR) analysis of genomic DNA has shown that the 1952 bp of cDNA sequence spans approximately 9 kb of genomic DNA and comprises of at least four exons, with its size and structure being relatively conserved between mouse, human and pig. Reverse transcriptase (RT)-PCR analysis of mRNA from nine porcine tissues has also suggested that expression of SPAM1 is limited to the testis.

Monoclonal antibody against human sperm-specific YLP12 peptide sequence involved in oocyte binding

The monoclonalantibody (mAb) against YLP12 peptide was raised and its immunobiological properties were examined. In the Western blot procedure, the YLP12 mAb recognized a specific protein band of approximately 50 +/- 5 kD in human sperm extract and approximately 72 +/- 5 kD in human testis extract. The myeloma Ig control did not recognize these specific protein bands. In the immunofluorescence studies, the YLP12 mAb, and not the myeloma Ig, predominantly reacted with the acrosome regions of methanol-fixed human sperm. In the acrosome reaction assay, the YLP12 mAb showed a significant (p < .001) and a concentration-dependent inhibition of acrosome reaction. The myeloma Ig did not affect the acrosome reaction. There was no apparent effect of antibodies on sperm motility. Thus, the monoclonal antibody, if humanized by genetic engineering technology, may provide a useful immunocontraceptive agent.

Immunological response of female macaques to the PH-20 sperm protein following injection of recombinant proteins or synthesized peptides

Because of its location on the sperm surface and its multiple functions during fertilization, the PH-20 protein is a potential target for contraceptive vaccines. Cynomolgus macaques were immunized using four different adjuvants together with synthesized peptides or recombinant proteins representing selected regions of macaque PH-20. The synthesized peptide (amino acids 387-412, designated Peptide 4) was used as a linear molecule in a 1:1 ratio with a peptide sequence of tetanus toxoid, as well as a multiple antigenic peptide (MAP) matrix held together by scaffolding lysine residues. In the MAP construct, the ratio of Peptide 4 to tetanus peptide was 4:1. To circumvent the poor production of recombinant PH-20 in bacterial cells, two truncated forms of the molecule were expressed in Escherichia coli, G18 (encoding amino acids 143-510) and E10 (encoding amino acids 291-510). The adjuvants were Montanide ISA 51, Titermax Gold, Syntex adjuvant formulation (SAF), and QS-21. All of the antigen/adjuvant combinations produced significant immune responses as measured by ELISA. The circulating antibodies from immunized animals recognized macaque sperm surface PH-20 on Western blots and were shown by indirect immunofluorescence to bind to the surface of macaque sperm. Montanide and Titermax were associated with higher titers of anti-PH-20 antibodies than QS-21 and SAF adjuvants. Immunization with Titermax, however, resulted in sterile abscesses in 4 of 8 animals injected. We conclude that antigens derived from synthesized peptides and recombinant proteins representing selected regions of the PH-20 molecule can be used as vaccine components in combination with the adjuvant Montanide to elicit a significant sperm-directed antibody response in immunized macaques.

Restricted entry of IgG into male and female rabbit reproductive ducts following immunization with recombinant rabbit PH-20

PROBLEM

Successful immunocontraception using sperm antigens is dependent on achieving sufficient sperm-specific antibody in the reproductive ducts to prevent fertilization. The blood: luminal barrier of the male and female reproductive ducts must be overcome for this to occur. We have, therefore, investigated the relative titers of antigen-specific immunoglobulin G (IgG) in luminal fluids collected from male and female rabbit reproductive ducts following immunization with recombinant rabbit PH-20 (rPH-20).

METHOD OF STUDY

Male and female rabbits were immunized subcutaneously with rPH-20 in Freund's adjuvant. Reproductive tract fluids and plasma were collected and assayed for specific IgG by enzyme-linked immunoabsorbent assay (ELISA). Plasma anti-rPH-20 antibodies were tested for their ability to inhibit in vitro fertilization.

RESULTS

Plasma rPH-20-specific IgG titers of > 21 x 106 were induced in bucks. Antibody levels in the rete testis and cauda epididymidis fluids were only 0.026 and 0.168% of plasma levels, respectively. Plasma IgG titers were > 30 x 10(6) in does, but antibody levels in free flow vaginal fluid, free flow uterine fluid and free flow oviduct fluid were only 0.016, 0.078 and 0.072% of plasma levels, respectively. Induction of ovulation by administration of human chorionic gonadotrophin (hCG) significantly increased rPH-20-specific IgG only in free flow vaginal fluids. Plasma antibody from immunized rabbits inhibited in vitro fertilization but conception rates following mating of rPH-20 immunized male to untreated female rabbits were not affected.

CONCLUSIONS

The IgG antibody entry into the reproductive ducts of both male and female rabbits is restricted to less than 0.2% of levels induced in plasma following subcutaneous immunization. This finding raises doubts about the suitability of rPH-20 to induce immunocontraception in rabbits using strategies optimized for induction of a serum antibody response. Whether mucosal immunization strategies can achieve this remains to be tested.

Shedding light on sheddases: role in growth and development

The extracellular domains of several integral membrane proteins are released from the cell surface by a group of enzymes known as "sheddases" through a process called "ectodomain shedding". Because many transmembrane growth and differentiation factors, including members of the epidermal growth factor (EGF) family that play a crucial role in development, require ectodomain shedding for proper action in vivo, proteolysis is now viewed as a regulatory mechanism in the developing embryos. Two recent reports by Zhao et al. provide evidence for the role of cell surface proteolysis by an ADAM (a disintegrin and metalloprotease) in the development of murine lung. Inhibition of tumor necrosis factor-alpha converting enzyme (TACE, ADAM17) by the hydroxamic acid-based metalloprotease inhibitor (TAPI), or a targeted mutation in Zn(2+)-binding domain of TACE, disrupts two essential epithelial functions in lung development: branching morphogenesis and cytodifferentiation. Evidence for the role of ADAMs as sheddases in development and growth factor signaling is discussed.

Testis-specific antigen (TSA-1) is expressed in murine sperm and its antibodies inhibit fertilization

PROBLEM

We recently cloned and sequenced a sperm-specific antigen, designated as testis-specific antigen-1 (TSA-1), from human testis. The present study was conducted to examine its expression and function in murine sperm, in order to find out whether or not the mouse can provide a suitable model for examining its immunocontraceptive effects.

METHOD OF STUDY

The antibodies (Ab) were raised against purified human rTSA-1 in virgin female rabbits. The rTSA-1 was run in sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and the gel containing the approximately 18 kDa band was cut, minced and used for immunization to obtain the specific Ab. The immunoglobulins from preimmune bleed and from animals injected with adjuvant alone served as control. These Ab were analysed in enzyme-linked immunosorbent assay (ELISA), Western blot procedure, immunoprecipitation procedure, immunocytochemical technique (ICT), immunobead binding technique (IBT), acrosome reaction and sperm-zona binding assay.

RESULTS

Active immunization of female rabbits with purified rTSA-1 protein of 18 kDa, produced high titer Ab against the recombinant antigen. These Ab to rTSA-1 were used in the present study. In Western blot procedure, rTSA-1 Ab recognized a specific protein band of approximately 24 +/- 3 kDa in murine sperm extract, the band similar to found in human sperm extract. In the immunoprecipitation procedure, rTSA-1 Ab immunoprecipitated the protein band of similar size from extracts of murine sperm and murine testis. The ICT and the IBT studies revealed the subcellular localization of TSA-1 on the surface of acrosome and tail regions of the non-capacitated and capacitated murine sperm cells. In functional bioassays, rTSA-1 Ab inhibited the acrosome reaction and sperm-egg binding in vitro.

CONCLUSIONS

These data indicate that the TSA-1 is expressed in murine sperm and may have a biological role in sperm function and sperm-egg binding. In vitro inhibition of capacitation/acrosome reaction and sperm-zona binding suggests that the mouse can provide a suitable model to examine the immunocontraceptive effects of TSA-1 in actively immunized animals.

Molecular and immunological characteristics of sperm antigens involved in egg binding

Development of a vaccine(s) based on sperm antigens represents a promising approach to contraception. The utility of an antigen in immunocontraception is contingent upon sperm/testis-specificity and its involvement in the fertilization process. Since, the sperm-zona pellucida (ZP) recognition and binding constitutes the most important event in the fertilization process, molecules involved at this site are attractive candidates for immunocontraception. Using hybridoma technology, subtractive hybridization, and differential display technology, our laboratory has delineated several sperm antigens. These antigens have testis-specific expression and have a role in the fertilization process. The cDNAs encoding for the antigens have been cloned and sequenced. Among these, the fertilization antigen (FA-1) is particularly interesting, because it is involved in immuno-infertility in humans. Using the phage peptide display technique, a novel dodecamer sequence of a approximately 72+/-5 kD antigen, designated as YLP(12), that is testis-specific and involved in human sperm-ZP recognition/binding, was identified. A synthetic 12-mer peptide was generated based on this sequence. In the hemizona assay, YLP(12) peptide and its monovalent Fab' antibodies specifically and significantly inhibited human sperm-ZP binding. Furthermore, the presence of specific antibodies reactive with YLP(12) peptide, were identified in the serum and seminal plasma of immuno-infertile men. Thus, FA-1 and YLP(12) are promising target antigens for the development of contraceptive vaccines as well as for specific diagnosis and treatment of male infertility.

Effect of antibodies to sperm-specific recombinant contraceptive vaccinogen (rCV) on murine fertilization: search for an animal model to examine its contraceptive potential

Recently, we cloned and sequenced a sperm-specific antigen, designated as Contraceptive Vaccinogen (rCV), from human testis (Naz et al., 2001). The present study was conducted to examine its proteomic homologue and function in murine sperm, in order to find out whether or not the mouse can provide a suitable model for examining its immunocontraceptive effects. This was examined by using purified antibodies (Ab) raised against the recombinant (r) human CV antigen of approximately 44 kD. In the Western blot procedure, rCV antibodies recognized a specific protein band of approximately 64 +/- 5 kD in murine testis and murine sperm extracts, the band similar to that found in human testis and human sperm. In the immunoprecipitation procedure, rCV Ab immunoprecipitated a protein band of similar size from murine sperm and murine testis extracts. The immunocytochemical (ICT), immunoscanning electronmicroscopic (ISEM) and the immunobead binding technique (IBT) revealed the subcellular localization of CV antigen on the surface of acrosome and tail regions of the noncapacitated and capacitated murine sperm cell. In functional bioassays, rCV Ab inhibited the acrosome reaction as well as sperm-egg binding in vitro. These data indicate that the CV antigen is expressed in murine sperm and has a biological role in sperm function and sperm-egg binding. In vitro inhibition of capacitation/acrosome reaction and sperm-zona binding suggest that the mouse can provide a suitable model to examine the immunocontraceptive effects of CV antigen in actively-immunized animals.

Novel human testis-specific cDNA: molecular cloning, expression and immunobiological effects of the recombinant protein

A differential display-polymerase chain reaction was employed to obtain a testis-specific cDNA fragment. On screening the human testis-(lambda)gt10-cDNA library with testis-specific cDNA fragment, a novel cDNA encoding for a sperm antigen, designated TSA-1, was obtained. It has a novel open reading frame (ORF) of 471 base pairs encoding for 156 amino acids. The computer generated translated protein has a calculated molecular mass of 17.4 kDa and contains a potential N-glycosylation site at amino acids 122-124. The hydrophilicity analysis of the amino acid sequence suggested that this protein is a membrane-anchored peptide. Extensive analysis for tissue-specificity by Northern blots and RT-PCR-Southern blot procedures using various human tissues indicated that TSA-1 was specifically expressed only in the human testis. Based on the results of in vitro transcription and translation experiments, the TSA-1 (ORF) was subcloned into pGEX-6P-3 vector and expressed using the glutathione S-transferase gene fusion system. Antibodies (Ab) against the purified recombinant protein specifically recognized the approximately 17 kDa recombinant TSA-1, and a approximately 24 kDa band in human sperm extract in the Western blot procedure. The recombinant TSA-1 Ab recognized the acrosomal, equatorial, mid-piece, and tail regions of human sperm cell in indirect immunofluorescence, bound to live human sperm in the immunobeads binding technique (IBT) and caused a significant concentration-dependent inhibition of human sperm acrosome reaction. These findings indicate that the novel sperm-specific recombinant TSA-1 has a role in sperm function and may have applications in the development of a contraceptive vaccine, and in the specific diagnosis and treatment of male infertility.

Molecular cloning and sequencing of a novel cDNA encoding for a protein involved in human sperm function

A cDNA encoding for an antigen, designated as NZ-3, was cloned and sequenced from human testis. The 1481-bp NZ-3 cDNA yielded an open reading frame (ORF) of 231 amino acids (aa) with the first ATG, Met start codon at nucleotide (nt) 104 and the stop codon TGA at nt 797. Extensive computer search indicated it to be a novel cDNA/protein. The ORF of NZ-3 cDNA was subcloned into pGEX-1lambdaT vector and expressed in glutathione S-transferase gene fusion system. The expressed recombinant protein had a molecular size of approximately 25 kDa, and the rabbit antibodies (Ab) against the recombinant antigen recognized a specific protein band of 63 +/- 3 kDa in the human testis extract. The NZ-3 antigen was located on the acrosomal and tail regions of human sperm cell and the NZ-3 Ab significantly (P < 0.001) inhibited human sperm capacitation and/or acrosome reaction. The novel recombinant NZ-3 antigen may find applications in immunocontraception and in specific diagnosis of human infertility.

Systematic characterization of sperm-specific membrane proteins in swine

To establish a systematic strategy for characterizing fertilization proteins of sperm cells, we prepared alloantisera by immunizing gilts with salt-washed membranes from boar spermatozoa. The antisera recognized a unique subset of sperm membrane proteins that migrated with M(r) 7500-66,000 in SDS-PAGE under nonreducing conditions. The antisera did not recognize proteins of erythrocyte membranes, and tissue absorption experiments further confirmed that the alloantigens were sperm-specific proteins. Each of these sperm-specific membrane proteins (SSMPs) possessed one or more disulfide bonds that were essential for its interaction with alloantibody. Enzymatic deglycosylation revealed that most of the SSMPs were glycoproteins, and their alloantigenicity was not dependent on the presence of N-linked oligosaccharides. The presence of disulfide bonds and glycosylation indicated that the SSMPs identified each comprise at least one extracellular domain. Two-dimensional electrophoresis resolved at least 14 distinct SSMPs, 13 of which possessed acidic pIs (range 4.2-4.8). By indirect immunofluorescence, the SSMPs localized to the cell surface overlying all major regions of the sperm cell. We conclude that the repertoire of immunodominant SSMPs in the pig is relatively small, which makes feasible the systematic elucidation of their functions in fertilization.

Crystal structure of hyaluronidase, a major allergen of bee venom

BACKGROUND

Hyaluronic acid (HA) is the most abundant glycosaminoglycan of vertebrate extracellular spaces and is specifically degraded by a beta-1,4 glycosidase. Bee venom hyaluronidase (Hya) shares 30% sequence identity with human hyaluronidases, which are involved in fertilization and the turnover of HA. On the basis of sequence similarity, mammalian enzymes and Hya are assigned to glycosidase family 56 for which no structure has been reported yet.

RESULTS

The crystal structure of recombinant (Baculovirus) Hya was determined at 1.6 A resolution. The overall topology resembles a classical (beta/alpha)(8) TIM barrel except that the barrel is composed of only seven strands. A long substrate binding groove extends across the C-terminal end of the barrel. Cocrystallization with a substrate analog revealed the presence of a HA tetramer bound to subsites -4 to -1 and distortion of the -1 sugar.

CONCLUSIONS

The structure of the complex strongly suggest an acid-base catalytic mechanism, in which Glu113 acts as the proton donor and the N-acetyl group of the substrate is the nucleophile. The location of the catalytic residues shows striking similarity to bacterial chitinase which also operates via a substrate-assisted mechanism.

Rat sperm 2B1 glycoprotein (PH20) contains a C-terminal sequence motif for attachment of a glycosyl phosphatidylinositol anchor. Effects of endoproteolytic cleavage on hyaluronidase activity

Rat sperm 2B1 antigen (the orthologue of guinea pig sperm PH20) is a plasma membrane-bound glycoprotein that is endoproteolytically cleaved during passage through the epididymis and subsequently migrates from the tail to the acrosomal domain during capacitation. Unlike guinea pig PH20, however, sperm surface 2B1 is insensitive to phosphatidylinositol phospholipase C, nor is it known how endoproteolytic cleavage affects its hyaluronidase activity. In this investigation we have expressed 2B1 cDNA in Chinese hamster ovary cells; we have shown that it contains an internal sequence motif for attachment of a glycosyl phosphatidylinositol (GPI) anchor and that cleavage from a single- into a two-chain molecule causes a significant shift in the optimum pH for hyaluronidase activity. Functionally, these results suggest that 1) 2B1 glycoprotein on rat spermatozoa is attached to the plasma membrane via a GPI anchor and that this is an important factor in its ability to migrate from the tail to the acrosomal domain during capacitation; and 2) endoproteolytic cleavage of 2B1 serves to optimize its hyaluronidase activity immediately before fertilization, thereby facilitating penetration of spermatozoa through the cumulus oophorus.

Identification of human sperm peptide sequence involved in egg binding for immunocontraception

Development of a vaccine based on sperm antigens represents a promising approach to contraception. The sperm-zona pellucida (ZP) interaction constitutes the most important event in the fertilization process, and the molecular sequences involved at this site may provide the most attractive candidates for immunocontraception. In the present study, using the phase peptide display technique, a novel dodecamer sequence, designated as YLP(12), was identified that is involved in sperm-ZP recognition/binding. The synthetic 12-mer peptide based on this sequence and its monovalent Fab' antibodies specifically and significantly (P < 0.05) inhibited human sperm-ZP binding. In Western blot and immunoprecipitation procedures, the YLP(12) peptide recognized the ZP3 component of solubilized human ZP proteins. In the Western blot procedure involving 10 different human tissue extracts, the anti-YLP(12) Fab' antibodies recognized a protein band of approximately 72 +/- 2 kDa only in the testis lane. The peptide sequence was localized on the acrosomal region of the human sperm cell. These findings indicate that the novel testis-specific 12-mer YLP(12) that is present in the acrosomal region and is involved in human sperm-ZP interaction may find applications in contraceptive vaccine development, as well as in diagnosis and treatment of male infertility mediated through sperm dysfunction.

FSP95, a testis-specific 95-kilodalton fibrous sheath antigen that undergoes tyrosine phosphorylation in capacitated human spermatozoa

Protein tyrosine phosphorylation has been associated with both capacitation and motility of mammalian sperm. During capacitation, human spermatozoa undergo tyrosine phosphorylation of a characteristic set of proteins, only one of which has thus far been cloned and localized. We report here the sequence of a fibrous sheath protein of 95 kDa (FSP95) that undergoes tyrosine phosphorylation during capacitation of human spermatozoa and has similarity to sperm A-kinase anchor proteins (AKAPs). FSP95 is both auto- and iso-antigenic in humans as it is recognized by sera containing antisperm antibodies from infertile men and women. The 853-residue protein has a calculated molecular weight of 94.6 kDa and an isoelectric point (pI) of 6.0, and it contains multiple potential phosphorylation sites for protein kinase C and casein kinase II as well as one potential tyrosine kinase phosphorylation site at amino acid 435. The sequence has amino acid homology to mouse sperm fibrous sheath AKAP82 (pro-mAKAP82, 34% identity) and to human sperm fibrous sheath AKAP82 (pro-hAKAP82, 32% identity). The gene encoding FSP95 has 5 exons separated by 4 introns and is located on chromosome 12 at locus p13.3. Northern analysis detected a single transcript of approximately 3.0 kilobases, and Northern dot blot analysis of 50 human tissues revealed FSP95 mRNA expression only in testis. By employing sperm immobilization, indirect immunofluorescence, and immunoelectron microscopy with antisera to purified recombinant FSP95, the protein was localized to the ribs of the fibrous sheath in the principal piece of the sperm tail. FSP95 is the second fibrous sheath protein to be cloned, sequenced and localized in human spermatozoa.

Vaccine for contraception targeting sperm

Development of a vaccine(s) based on sperm antigens represents a promising approach to contraception. The utility of a sperm antigen in immunocontraception is contingent upon its tissue specificity, involvement in fertility and on raising high antibody titer, especially locally in the genital tract, that is capable of inducing reversible infertility. Several sperm antigens, such as lactate dehydrogenase C4, PH-20, sperm protein (SP)-10, fertilization antigen (FA)-1, FA-2, cleavage signal (CS)-1, NZ-1, and NZ-2 have been proposed as potential candidates for the vaccine development. Spermzona pellucida (ZP) binding is a pivotal tissue- and mostly species-specific event in the fertilization process, and the molecules involved in this site constitute the most exciting candidates for immuno-contraception. FA-1 is a sperm-specific glycoprotein having receptor activity for ZP recognition and binding. Complementary DNA encoding for FA-1 antigen has been cloned and sequenced. Active immunization of animals with recombinant FA-1 antigen causes a long-lasting reversible inhibition in fertility by raising a sperm-specific immune response. This antigen is also involved in human immunoinfertility. The exciting findings from the recent trial in immunoinfertile couples indicate that the FA-1 antigen may have clinical application in the treatment of male infertility. A vaccine having most appropriate tissue-specific and effective recombinant and/or synthetic epitopes of various sperm antigens, such as the FA-1 antigen, in a single formulation may provide a highly immunogenic and efficacious antisperm vaccine for contraception. The advances made during the last 5 years suggest that it may be a realistic proposition.

Vaccines for fertility regulation of wild and domestic species

The application of fertility control technologies for the management of animal populations is still a relatively new concept and remains to be proven on a large scale. While there have been demonstrations of its utility using crude antigenic preparations of porcine zona pellucida, refined, cheap and easily delivered vaccines are still in the early phases of development, especially those required for remote delivery to free-ranging wild animal populations. The relative slow emergence of such technologies for practical application clearly reflects the complexity of the science and the requirement for a multidisciplinary research approach when attempting to develop such technologies for wild animal management. In many cases, one of the areas where further information is required is the immunobiology of such target species. Effective immunocontraceptive vaccines will also be critically dependent upon the design of the delivery systems. These will be unique to each species under study. A major challenge for free-ranging species will be to ensure that the vaccine can induce a long-lasting immune response to a high percentage of the target population, thus reducing the frequency and, hence, the cost of vaccine application. Many of the delivery systems being considered will utilise recombinant organisms. Hence, considerations on the use of such organisms needs to take into account the political, ethical and safety constraints prior to any environmental release. Also of prime importance is the issue of species specificity. In some instances, this will be a major challenge and careful thought will need to be given to ensure that specificity can be built into the vaccine at several levels. These might include the target antigen or epitopes, the microbial or other delivery vector, and, where applicable, the bait matrix and any target-specific attractive properties it may require. If these caveats can be satisfied and the public is able to accept the use of such vaccines, the potential for their application to manage animal populations and their impact is most certainly assured.

PH-20 but not acrosin is involved in sperm penetration of the macaque zona pellucida

In this study, we investigated the functions of PH-20 and acrosin during the interaction of macaque sperm with the zona pellucida. Both of these sperm enzymes have been reported to be present on the inner acrosomal membrane of acrosome reacted sperm, and have been suggested to play a role during secondary sperm-zona binding in other species. Anti-macaque PH-20 IgG, anti-pig acrosin IgG and soybean trypsin inhibitor (SBTI) were used as probes for immunolocalization of the two proteins at the ultrastructural level, and as reagents for blocking sperm penetration of the macaque zona pellucida in vitro. As a control, we performed similar studies with antibodies to CD-46, which is also located on the inner acrosomal membrane, but has no known function in sperm-zona pellucida interaction. After labeling with anti-acrosin IgG, gold label was not present on the sperm surface before the acrosome reaction, but was detected over the entire head of sperm that were induced to acrosome react with calcium ionophore A23187. In contrast, when sperm were induced to acrosome react by binding to intact zona pellucida, acrosin was present in the acrosomal shroud but not on the inner acrosomal membrane. Similar results were obtained when SBTI was used as a probe for enzyme localization. PH-20 and CD-46 were demonstrated on the inner acrosomal membrane of sperm induced to acrosome react by ionophore treatment and by zona binding. Neither anti-acrosin IgG nor anti-CD-46 IgG affected sperm penetration of the zona at concentrations up to 300 microg/ml, but zona penetration was blocked completely when anti-PH-20 IgG (100 microg/ml) was present during sperm-oocyte interaction. Ultrastructural observations of oocytes incubated with anti-PH-20 IgG showed that acrosomal shrouds were present on the zona surface but no sperm had begun to penetrate into the zona substance. We conclude that anti-PH-20 IgG prevented sperm penetration of the macaque zona pellucida by interference with secondary sperm-zona binding, rather than primary sperm-zona binding or the zona-induced acrosome reaction. Acrosin was not detected on the inner acrosomal membrane of sperm that are induced to acrosome react after zona binding, and acrosin does not appear to be critical for sperm penetration of the macaque zona pellucida.

Identification of linear surface epitopes on the guinea pig sperm membrane protein PH-20

The sperm plasma membrane protein PH-20 has previously been shown to be an effective immunogen for protection against fertilization in guinea pigs. To identify immunodominant regions on gpPH-20 that may be related to this contraceptive effect, we used several high-titer immune sera obtained from animals rendered infertile by gpPH-20 injections to screen a set of overlapping peptides that cover the entire 494-residue sequence. Multiple clusters of peptide sequences exhibited specific reactivity. Some of these sequences were then constructed as octameric synthetic peptides and tested for immunogenicity in female guinea pigs. Our results indicated two regions (res. 94-119 and res. 424-444) to be highly immunogenic and both are surface accessible when native gpPH-20 is in solution or anchored on sperm surface. Both anti-peptide antibodies are specific for gpPH-20 and one of them inhibited hyaluronidase activity partially. These monospecific antibodies should be useful probes for further molecular definition of gpPH-20 structure-function relationships.

The potential use of sperm antigens as targets for immunocontraception; past, present and future

Immunocontraception, and in particular the targeting of antibodies to gamete-specific antigens implicated in sperm egg binding and fertilisation, offers an attractive approach to the growing global problem of overpopulation. Such an idea is not new; indeed several immunocontraception trials, using animal model systems, have been reported in recent years and a number are reviewed here. However, the results of these studies have been largely disappointing. We believe that two fundamental flaws attribute to the poor success of most of these preliminary immunocontraceptive trials. Firstly, loss of fertility has invariably been used as the assay. This presupposes that immuno-neutralisation of a single, gamete-specific antigen will be sufficient to cause a significant reduction in fertility; however, recent data suggests that such a premise may not be well-founded for a number of reasons. Secondly, and arguably the most important flaw, is the almost universal, but largely inappropriate, use of systemic immunisation as the sole route of antigen delivery. Whilst systemic immunisation regimes may lead to high serum IgG levels, these levels do not correlate with specific antibody levels in the reproductive tract or with contraceptive efficacy. Hence, an alternative antigen delivery approach is required which will induce an effective local immune response in the reproductive tract. Here we discuss the ways in which this might be achieved.

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

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

Expression of recombinant mouse sperm protein sp56 and assessment of its potential for use as an antigen in an immunocontraceptive vaccine

Recombinant mouse sp56 protein was produced for testing as an antigen in an immunocontraceptive vaccine. The coding sequence for the mature sp56 protein was cloned into the bacterial expression system pFLAG using a PCR-based method on mouse testis cDNA. Polyclonal antisera were raised in mice against affinity purified recombinant sp56 fusion protein (sp56FLAG) or an artificial sp56 peptide fused to a carrier protein (KLH) and shown to cross-react to a protein band of 75 kD in detergent extracts of mouse sperm by Western immunoblot analysis under reducing conditions. The antisera to sp56FLAG also immunolocalized over the entire acrosome of mouse sperm. Female BALB/c mice were immunized intraperitoneally with sp56FLAG in a fertility trial with 20 microg sp56FLAG in Freund's Complete Adjuvant and boosted three to five times with 20 microg sp56FLAG in Freund's Incomplete Adjuvant. Litter sizes of sp56FLAG-treated mice were significantly smaller than control-treated animals after five boosts.

Recombinant fertilization antigen-1 causes a contraceptive effect in actively immunized mice

Recombinant (r) fertilization antigen (FA)-1 was investigated for its immunocontraceptive effect using the mouse as a model. Active immunization with the murine rFA-1 antigen raised high antibody titers in all the immunized mice (n = 16 in two trials); these titers were long lasting and reached preimmunization levels by the 255th day. There was a significant (p < 0.0001) effect (64% reduction in trial I and 70% reduction in trial II) in fertility of immunized animals compared to PBS-control animals (n = 22 in two trials). The effect on fertility was reversible. When the antibody titers declined to control levels, all the animals conceived and delivered healthy babies without a significant (p > 0.05) effect on the litter size compared to that of controls. There was a significant (p = 0.025) correlation (r = 0.76) between the reduction in fertility and the circulating rFA-1 antibody titers. Anti-rFA-1 antibodies from immunized mice, and not the immunoglobulins from the PBS-control mice, significantly (p < 0.001) blocked murine sperm binding to zona pellucida and in vitro fertilization of murine oocytes. In a Western blot procedure, the anti-rFA-1 antibodies specifically recognized the protein band of approximately 47 kDa (dimeric form of cognate FA-1 antigen) only in the protein extract of testes and not in the extracts of somatic tissues tested, namely kidney, liver, intestine, spleen, muscle, heart, lung, brain, and ovary. In conclusion, our data indicate that active immunization with rFA-1 antigen induces a strong and sperm/testis-specific antibody response that causes a reversible inhibition of fertility by affecting sperm-zona binding and the fertilization process. These findings suggest that rFA-1 antigen is an exciting candidate for the development of a contraceptive vaccine.

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.

Fertility Control: An Option for Non-Lethal Control of Wild Carnivores?

Three types of fertility control, surgical sterilization, hormonal chemosterilization, and immunosterilization, are reviewed with regard to their potential for controlling problematic populations of carnivores. The fertility control agent and delivery protocol of choice may vary considerably according to: (i) the reason for control; (ii) the degree, urgency and duration of population reduction required; (iii) concerns about ethics and public opinion; and (iv) the status, population dynamics, social structure, mating system, size, behaviour and reproductive endocrinology of the target animals. Although they are often perceived and advocated as more preferable methods of population control than lethal approaches, it is important that wildlife managers as well as members of the public realize that the ethical acceptability of the various fertility control techniques may differ considerably - and that numerous questions regarding their effectiveness, humaneness and ecological safety remain unanswered.

Manipulation of the fertility of marsupials for conservation of endangered species and control of over-abundant populations

Marsupials present a dichotomy in population management; the numbers of many Australian marsupial species have declined due to loss of habitat, competition from introduced herbivores and predation by introduced carnivores, but other species have become locally overabundant in Australia or are introduced pests in New Zealand. The manipulation of reproduction offers the means to increase or decrease productivity; however, considerable fundamental research is required before reproductive technologies can be applied to marsupials. Marsupials differ from eutherian mammals in several aspects of their reproduction including sex differentiation, gamete function and endocrinology, as well as in the relative lengths of gestation and lactation. Although these differences present unique problems in the application of reproductive technologies to marsupials, they also present unique opportunities for marsupial-specific fertility control. This paper summarises the assisted breeding technologies currently being applied to marsupials including superovulation, artificial insemination, in vitro fertilization and gene banking; unique marsupial targets for contraceptive intervention including gamete production, sperm capacitation, gamete surface antigens and embryonic development; and some options for the delivery of contraceptive vaccines to marsupial populations.