Lymphocyte proliferative response to fertilization antigen in patients with antisperm antibodies

Anti-sperm Antibodies as an Increasing Threat to Male Fertility: Immunological Insights, Diagnostic and Therapeutic Strategies

It is a fact that sperm possess antigenic properties. Substantial scientific research suggests that specific antibodies that attach to sperm antigens can induce infertility in both humans and other species. Antisperm antibodies (ASA) represent a significant etiology of infertility in humans, leading to immunoinfertility. The association between ASA and infertility is multifaceted. The observation of sperm agglutination, although not conclusive for the diagnosis of immunological infertility, may suggest the presence of ASA. Nevertheless, ASA may also manifest in the lack of any sperm agglutination. Managing ASA from an andrological perspective depends on the underlying cause and the specific approaches healthcare professionals adopt. The precise etiology of male infertility resulting from ASA remains unclear. Current research has examined the impact of ASA and its prevalence among infertile males to understand the relationship between ASA and changes in semen parameters. However, the findings have been inconclusive. Numerous techniques have been documented for the management of immunoinfertility. This review examines the importance of ASA in the context of infertility, encompassing the postulated mechanisms underlying the development of ASA, the various assays employed for detecting them, and the available treatments.

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.

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.

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.

Fertilization antigen-1: cDNA cloning, testis-specific expression, and immunocontraceptive effects

cDNA encoding for a sperm antigen, designated fertilization antigen (FA-1), was cloned and sequenced from murine testis cDNA-lambdagt11 expression library using FA-1 mAb. Computer-generated translation analysis of 649-bp cDNA yielded an ORF of 164 amino acids with the first ATG Met start codon at nucleotide 81 and the stop codon TAA at nucleotide 577 and a polyadenylylation tail following the stop codon. The translated protein has a calculated molecular mass of 18.2 kDa and a potential N-linked glycosylation site at amino acids 158-160, besides at least two O-linked glycosylation sites. The hydropathy plot generated from the deduced amino acid sequence indicated it to be a membrane-anchored peptide. Extensive computer search in the GenBank, National Biomedical Research Foundation, and Swiss sequence banks did not identify any known nucleotide/amino acid sequence having homology with FA-1 cDNA or deduced amino acids, indicating it to be a novel protein. Northern blot analysis and reverse transcription-PCR indicated testis-specific expression of FA-1 antigen. The FA-1 cDNA was subcloned into pGEX-2T vector and expressed in glutathione S-transferase gene fusion system to obtain the recombinant protein. The recombinant protein specifically reacted with ZP3 of oocyte zona pellucida and its affinity-purified antibodies completely blocked sperm-zona pellucida interaction in mice. These findings suggest that the sperm-specific recombinant FA-1 antigen is an attractive candidate for the development of a contraceptive vaccine.

Autoantigenicity of human sperm: molecular identities of sperm antigens recognized by sera of immunoinfertile men in the immunoprecipitation procedure

Autoantigenicity of human sperm as related to immunoinfertility was investigated using the immunoprecipitation procedure. Sera from immunoinfertile men specifically immunoprecipitated six specific bands of 135, 95, and 65 kD and double bands of 47, 41, and 23 kD that were not recognized by the sera from fertile men. Of these six specific bands, three bands of 65-, 47-, and 23-kD molecular identities were recognized by > 60% of immunoinfertile sera, and 47 and 23 kD may correspond to the dimeric and monomeric forms of FA-1 antigen, respectively. Seminal plasma from immunoinfertile men specifically recognized three specific bands of 95, 37, and 16 kD; only the 95-kD band was also recognized with the immunoinfertile sera. These specific antigens may find applications in immunocontraception and immunoinfertility in humans.

Levels of interferon-gamma and tumor necrosis factor-alpha in sera and cervical mucus of fertile and infertile women: implication in infertility

Concentrations of two immune cytokines, namely interferon-gamma (INF-gamma) and tumor necrosis factor-alpha (TNF-alpha), were determined in the sera and cervical mucus samples of fertile (n = 16), idiopathic infertile (n = 44), and immunoinfertile women (n = 45) to investigate their role, if any, in female infertility. Sera of idiopathic infertile women demonstrated significantly (P < 0.0001) higher levels of INF-gamma compared to those in fertile controls, whether expressed as pg/ml or pg/mg serum protein. Similarly, sera of immunoinfertile women demonstrated significantly (P = 0.0008) higher levels of INF-gamma compared to fertile controls and idiopathic infertile women. Cervical mucus of idiopathic infertile women also demonstrated significantly (P < 0.0001) higher concentrations of INF-gamma compared to those in fertile controls. Cervical mucus of immunoinfertile women demonstrated significantly (P < 0.0001) higher concentrations of INF-gamma compared to those in fertile controls and idiopathic infertile women. INF-gamma levels in serum did not significantly (P > 0.05) correlate (r = 0.12-0.43) with the concentrations in cervical mucus, when all the three groups were compared together. However, when the serum levels were compared with the cervical mucus concentrations by condition, only the idiopathic infertile group showed a significant (P = 0.005) correlation (r = 0.70). Serum levels of TNF-alpha did not differ significantly (P > 0.05) among three groups of women. Cervical mucus concentrations of TNF-alpha, however, varied among groups with levels being significantly (P = 0.04) higher-in idiopathic infertile women compared with fertile controls and in immunoinfertile women significantly (P = 0.0007) higher than in fertile controls as well as idiopathic infertile women. TNF-alpha levels in serum correlated (r = 0.65) significantly (P < 0.001) with the concentrations in cervical mucus when all the three groups were compared together or individually by infertility condition. These findings suggest the involvement of cytokines in infertility, and thus may have potential applications in diagnosis and treatment of female infertility.

Antisperm antibodies: origin, regulation, and sperm reactivity in human infertility

OBJECTIVE

To follow-up and expand discussion on the action mechanisms of antisperm antibodies in human infertility, the etiology and control of antisperm antibody induction, sperm antigens involved in immunoinfertility, and strategies for therapy.

DESIGN

A review of the recent literature with an emphasis on female immunoinfertility.

RESULTS

The role of antisperm antibodies in clinical infertility continues to be defined. Through assisted reproductive technologies, antisperm antibodies were shown to exert detrimental effects on different prefertilization and possibly postfertilization events. The female reproductive tract is part of the common mucosal immune system and is able to mount effective immune responses against infectious agents, foreign antigens, and, occasionally, sperm cells. Sperm membranes and constituents contain numerous antigenic components foreign to the human body, and yet antisperm antibodies become problematic in few women exposed to semen. Semen and sperm cells contain immunosuppressive factors capable of inhibiting different immune cells. Fertile women apparently produce antisperm antibodies but also possess neutralizing serum anti-idiotypic antibodies that are lacking in virgin and immunoinfertile women.

CONCLUSIONS

Antisperm antibodies can affect adversely human fertility but normally may be controlled by anti-idiotypic antibodies, which along with immunosuppressor factors in semen prevent their induction to a significant degree. This balance between detrimental and "beneficial" immune response to sperm may be shifted toward an antisperm antibody response by stimulatory factors such as infection. Therapies may be devised to stimulate the anti-idiotypic antibody system, to induce immune tolerance to sperm antigens, and to use antigens to adsorb antisperm antibodies from spermatozoa.

Significance of antibodies against human sperm FA-1 antigen in immunoinfertility

A fertilization antigen (FA-1) has been identified on human sperm cells that is involved in human fertilization. To better explain the participation of FA-1 in human infertility, the relationship of anti-FA-1 antibodies with the presence of general antisperm antibodies and with sperm function was examined in the sera of 30 men and women. None of the sera from fertile men and women (n = 10) reacted with FA-1. In contrast, 55% of the immunoinfertile sera (n = 20) that were positive for antisperm antibodies detected by OPTI-BEAD (immune-labeled microsphere) tested positive with FA-1 (p < .05). In these sera, penetration of hamster oocytes was reduced and was inversely related to monospecific anti-FA-1 absorbance values determined by an ELISA and with heterospecific general antisperm antibody binding to sperm in the OPTI-BEAD test (p < .05). Anti-FA-1 activity approached significance with antisperm antibody binding to the sperm head (p = .052). It is concluded that immunoinfertile sera have antibodies reacting with the FA-1 sperm antigen and their presence is significantly related to results of other functional tests, such as the SPA and the OPTI-BEAD test. The association of anti-FA-1 antibodies with antibody binding site (sperm head) may be relevant to the diagnosis and treatment of immunoinfertility.

Immunoglobulin (Ig) G, IgA, and IgA subclass antibodies against fertilization antigen-1 in cervical secretions and sera of women of infertile couples

OBJECTIVES

To assess the occurrence of immunoglobulin (Ig) G, IgA, and IgA subclass antibodies against human sperm fertilization antigen-1 (FA-1) in cervical mucus (CM) and serum of women of infertile couples.

DESIGN

Enzyme-linked immunosorbent assay methodology was used to detect anti-FA-1 antibodies. Antisperm antibodies were detected by agglutinating, immobilizing, and indirect immunobead (IB) methods. Control samples for the ELISA were from 10 women negative in the antisperm antibody assays.

PARTICIPANTS

Samples were from women of 32 infertile couples undergoing antisperm antibody analysis.

RESULTS

One of 10 control CM samples was slightly positive for IgG anti-FA-1 and none for IgA. Of the 22 CM samples from antisperm antibody-positive women, 9 were positive for IgG antibodies, 9 for IgA, 7 for IgA1, and 6 for IgA2. Cervical mucus samples from eight women were positive for both IgA and IgG antibodies. Assay of 19 serum samples, including 8 controls, by ELISA, indicated 9 of 11 from antisperm antibody-positive women and none from controls were positive for IgA and IgG (7 of 9 identical women). In addition, of the nine IgA-positive sera, seven were of the A1 subclass and five were of the A2 subclass. Positive IB assays occurred more frequently in CM and serum samples positive for anti-FA-1 antibodies than in negative samples.

CONCLUSION

The results suggest that cervical secretions and sera of antisperm antibody-positive women contain IgA and IgG antibodies against sperm antigen FA-1 that may be involved in antifertility effects.