Presence of antibodies to sperm YLP(12) synthetic peptide in sera and seminal plasma of immunoinfertile men

Immune infertility in men

Male factors are implicated as the cause of roughly half of cases of infertility, and the presence of antisperm antibodies (ASA) may be responsible for some of these. Their presence is associated with a reduction in natural conception and live birth and impacts the success of assisted reproductive technologies. Interpretation of the data regarding ASAs and fertility is complicated by a lack of standardization in testing methodology and test thresholds and a lack of data on their prevalence in the healthy fertile population. Although their pathogenesis remains elusive, and many cases are idiopathic, a disruption in the immunologic blood-testis barrier (BTB) appears to contribute to the formation of ASA. As delineation of the specific antigen targets of ASA advances, it has been recognized that they may affect almost all aspects of sperm function, and ASA against different targets likely have specific mechanisms of impairing fertility. Intracytoplasmic sperm injection (ICSI) appears to be the most reliable method by which to overcome fertility impairment due to ASA, achieving similar outcomes to ASA-negative patients with regard to fertilization rates, embryonic development, clinical pregnancy rates, and live birth rates. The lack of consistency in testing for and reporting ASA remains a substantial barrier to achieving clarity in describing their role in infertility and the optimal management approach, and future research should use a unified approach to the detection and description of ASA. Determination of the specific antigens targeted by ASA, and their function and clinical relevance, would contribute to improving the understanding of ASA-mediated impacts on fertility and tailoring treatment appropriately to achieve the best outcomes for patients.

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.

Antibodies to prostate-specific antigen in immunoinfertile women and men

Immunoinfertility is caused by antisperm antibodies (ASA) present in the female or male partner of an infertile couple. PSA is a serine protease produced primarily by the prostate gland and is present in human semen. Although the modulation of PSA has been investigated in prostate abnormalities, its role and effect of its dysfunction on human fertility has not been examined. The present study was conducted to examine the presence and incidence of antibodies to PSA in sera of immunoinfertile women and men. The presence of iso- and autoantibodies in the sera of immunoinfertile patients was examined using the well-characterized purified human PSA and seminal plasma from normal fertile men in ELISA. Sera were collected from infertile women (n=25) and infertile men (n=19) who were positive for ASA. Sera from ASA-negative fertile women (n=24) and fertile men (n=19) served as controls. In women, sera from 40% of the immunoinfertile women showed positive reactivity with PSA, and 20% reacted positively with seminal plasma. None of the sera from fertile women reacted positively with PSA or seminal plasma. In men, sera from 16% of the immunoinfertile men showed positive reactivity with PSA, and none (0%) with seminal plasma. None of the sera from fertile men reacted positively with PSA or seminal plasma. This is the first study to examine the presence and incidence of PSA antibodies in immunoinfertile women and men. The findings may have clinical application in the specific diagnosis and treatment of immunoinfertility in humans.

Isolation of human single chain variable fragment antibodies against specific sperm antigens for immunocontraceptive development

BACKGROUND

Contraceptive vaccines can provide valuable alternatives to current methods of contraception. We describe here the development of sperm-reactive human single chain variable fragment (scFv) antibodies of defined sperm specificity for immunocontraception.

METHODS

Peripheral blood leukocytes (PBL) from antisperm antibody-positive immunoinfertile and vasectomized men were activated with human sperm antigens in vitro, and the complementary DNA prepared and PCR-amplified using primers based on all the variable regions of heavy and light chains of immunoglobulins. The scFv repertoire was cloned into pCANTAB5E vector to create a human scFv antibody library.

RESULTS

Panning of the library against specific sperm antigens yielded several clones, and the four strongest reactive were selected for further analysis. These clones had novel sequences with unique complementarity-determining regions. ScFv antibodies were expressed, purified and analyzed for human sperm reactivity and effect on human sperm function. AFA-1 and FAB-7 scFv antibodies both reacted with fertilization antigen-1 antigen, but against different epitopes. YLP20 antibody reacted with the expected human sperm protein of 48 +/- 5 kDa. The fourth antibody, AS16, reacted with an 18 kDa sperm protein and seems to be a human homologue of the mouse monoclonal recombinant antisperm antibody that causes sperm agglutination. All these antibodies inhibited human sperm function.

CONCLUSIONS

This is the first study to report the use of phage display technology to obtain antisperm scFv antibodies of defined antigen specificity. These antibodies will find clinical applications in the development of novel immunocontraceptives, and specific diagnostics for immunoinfertility.

Antisperm antibodies and conception

Sperm have been known to be antigenic for more than a century. There is a strong body of evidence that in humans and in other species at least some antibodies that bind to sperm antigens can cause infertility. Therefore, these antibodies are of interest today for two practical reasons. Firstly, the association of the antibodies with infertility means that they must be detected and then the couples treated appropriately. Secondly, because these antibodies can induce infertility they have the potential to be developed for contraceptive purposes in humans and also for the control of feral animal populations.

Contraceptions masculines non déférentielles : revue de la littérature

OBJECTIVES

To review the state of progress of the various male contraceptive methods (with the exception of deferential methods).

MATERIAL AND METHODS

A review of the literature was performed by using the key words: male/contraception, limiting the search to original articles in English and French. Articles on vasectomy and the other deferential methods of contraception are not considered in the present review.

RESULTS

Three methods of male contraception are widely used at the present time: withdrawal, male condom and vasectomy, although other types of male contraception have been shown to be effective, including hormonal contraception, which appears to be the most promising technique and the subject of the majority of research. Other contraceptive methods (immunological, thermal...) could constitute possible alternatives.

CONCLUSION

Male contraception remains under-used, as only male condoms are commonly used (apart from withdrawal and vasectomy). Consequently, new research protocols in the field of male contraception must be strongly encouraged.

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.

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.

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.

Search for peptide sequences involved in human antisperm antibody-mediated male immunoinfertility by using phage display technology

The aim of the present study was to delineate peptide sequences against which antisperm antibodies (ASA) are raised in immunoinfertile men. Using the phage display technology, seven unique and novel dodecamer amino acid sequences were identified that reacted with the sera of immunoinfertile men. The peptides were synthesized based upon these amino acid sequences and examined for their immunoreactivity with sera from ASA-positive immunofertile men (n = 15) and ASA-negative fertile men (n = 18) for IgM, IgG, and IgA class of antibody in the enzyme-linked immunosorbent assay (ELISA). All the seven synthetic peptides showed a significantly (P < 0.001) higher mean absorbance values for IgG and/or IgA class of antibody with the immunoinfertile sera compared to fertile control sera. Three of the seven peptides demonstrated a stronger reaction (>2 SD units) with 27%-40% of immunoinfertile sera compared to fertile controls. These peptide sequences may find applications in the specific diagnosis and treatment of immunoinfertility and in contraceptive vaccine development. The phage display technique provides an exciting and novel technology to delineate sperm epitopes involved in immunoinfertility.

Modalities for treatment of antisperm antibody mediated infertility: novel perspectives

Immunoinfertility because of antisperm antibodies (ASA) is an important cause of infertility in humans. The incidence of ASA in infertile couples is 9-36% depending on the reporting center. Early claims regarding the incidence and involvement of ASA in involuntary infertility were probably overemphasized, which has resulted in subsequent confusion, doubt, and underestimation of their clinical significance. No immunoglobulin that binds to sperm should be called an antisperm antibody in a strict sense unless it is directed against a sperm antigen that plays a role in fertilization and fertility. ASA directed against the fertilization-related antigens are more relevant to infertility than the immunoglobulins that bind to sperm associated antigens. Several methods have been reported for treatment of immunoinfertility. These include: immunosuppressive therapies using corticosteroids or cyclosporine; assisted reproductive technologies such as intrauterine insemination, gamete intrafallopian transfer, in vitro fertilization, and intracytoplasmic sperm injection; laboratory techniques such as sperm washing, immunomagnetic sperm separation, proteolytic enzyme treatment, and use of immunobeads. Most of the available techniques have side effects, are invasive and expensive, have low efficacy, or provide conflicting results. Recent findings using defined sperm antigens that have a role in fertilization/fertility have provided animal models and innovative novel perspectives for studying the mechanism of immunoinfertility and possible modalities for treatment. The better understanding of local immunity and latest advances in hybridoma and recombinant technologies, proteomics and genomics leading to characterization of sperm antigens relevant to fertility will help to clarify the controversy and to establish the significance of ASA in infertility.

Identification of sperm immunoreactive antigens for immunocontraceptive purposes: a review

Antisperm antibodies (ASA) may be a reason of infertility in some individuals. They may affect pre- as well as post-fertilization stages of the reproductive process. There is ongoing progress in the identification of sperm antigens related to fertilization. The employed methods for this purpose include recombinant DNA technology and the most advanced proteomic analysis. This paper enlists the different approaches undertaken in order to identify and characterize the immunoreactive sperm antigens. We have mainly focused on those, which have been already studied in regard of their immunocontraceptive potential, although it has been impossible to include all published data concerning the topic in a single article. Few novel sperm auto- and isoantigens, discovered recently, have also been reviewed even if their role in fertilization has not been yet established.

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.

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.

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.