Diagnosis and treatment of immunologically infertile women with sperm-immobilizing antibodies in their sera

Advancements in the detection and implications of sperm-immobilizing antibodies in female infertility

This review highlights over five decades of research on sperm-immobilizing antibodies (SI-Abs), which are crucial for understanding female infertility due to their effects on sperm motility and fertilization. Since the 1960s, Isojima et al. have made significant strides, notably with the Sperm Immobilization Test (SIT), which revolutionized the quantification of SI-Abs and their roles in infertility. Drawing from a comprehensive PubMed search on "the sperm immobilization test" and "sperm immobilizing antibody," our review underscores the critical insights gained into SI-Abs' impact on reproductive functions. SI-Abs result from the body's response to sperm antigens, potentially leading to infertility by affecting post-intercourse sperm function. However, the presence of anti-sperm antibodies does not guarantee infertility, indicating a complex relationship between these antibodies and reproductive outcomes. Isojima et al.'s pioneering studies paved the way for SIT and sperm immobilization titer (SI50), tools that have clarified the link between SI-Abs and infertility, focusing on disrupted sperm mobility and fertilization as key infertility mechanisms. Clinically, interventions such as in-vitro fertilization (IVF), which bypasses or eliminates SI-Abs, have improved pregnancy rates, whereas Freund's complete adjuvant therapy has deepened our understanding of infertility mechanisms. The SI50 value is crucial for predicting fertility treatment success and guiding therapeutic decisions based on antibody levels. In summary, the evolution of SI-Abs research has provided new hope for addressing infertility, significantly enriching the field of reproductive immunology, and highlighting the need for ongoing investigation.

SMA20/PMIS2 Is a Rapidly Evolving Sperm Membrane Alloantigen with Possible Species-Divergent Function in Fertilization

Immunodominant alloantigens in pig sperm membranes include 15 known gene products and a previously undiscovered Mr 20,000 sperm membrane-specific protein (SMA20). Here we characterize SMA20 and identify it as the unannotated pig ortholog of PMIS2. A composite SMA20 cDNA encoded a 126 amino acid polypeptide comprising two predicted transmembrane segments and an N-terminal alanine- and proline (AP)-rich region with no apparent signal peptide. The Northern blots showed that the composite SMA20 cDNA was derived from a 1.1 kb testis-specific transcript. A BLASTp search retrieved no SMA20 match from the pig genome, but it did retrieve a 99% match to the Pmis2 gene product in warthog. Sequence identity to predicted PMIS2 orthologs from other placental mammals ranged from no more than 80% overall in Cetartiodactyla to less than 60% in Primates, with the AP-rich region showing the highest divergence, including, in the extreme, its absence in most rodents, including the mouse. SMA20 immunoreactivity localized to the acrosome/apical head of methanol-fixed boar spermatozoa but not live, motile cells. Ultrastructurally, the SMA20 AP-rich domain immunolocalized to the inner leaflet of the plasma membrane, the outer acrosomal membrane, and the acrosomal contents of ejaculated spermatozoa. Gene name search failed to retrieve annotated Pmis2 from most mammalian genomes. Nevertheless, individual pairwise interrogation of loci spanning Atp4a-Haus5 identified Pmis2 in all placental mammals, but not in marsupials or monotremes. We conclude that the gene encoding sperm-specific SMA20/PMIS2 arose de novo in Eutheria after divergence from Metatheria, whereupon rapid molecular evolution likely drove the acquisition of a species-divergent function unique to fertilization in placental mammals.

Characterization of a spontaneously occurring self-reactive antibody against sperm in mice

We previously established a spontaneously occurring monoclonal antibody, namely Ts3, that was reactive to sperm from an aged male mouse. The present study investigated the characteristic properties and reproductive functions of Ts3. Immunofluorescent staining revealed that Ts3 reacted to epididymal sperm, and the corresponding antigen was located in the midpiece and principal piece. Immunohistochemistry revealed positive reactions in the germ cells and Sertoli cells in the testis, the epithelial cells in the epididymis and vas deferens. Through western blotting with two-dimensional electrophoresis, we demonstrated that Ts3 reacted with four spots, which were around Mr ∼25,000-60,000 and pI 5-6. MALDI-TOF/TOF mass spectrometry identified outer dense fiber 2 (ODF2) as a candidate for Ts3. ODF2 is a cytoskeletal structural component located in the midpiece and principal piece of the flagella of mammalian sperm. This was validated with the result of immunofluorescent staining, suggesting that ODF2 was the main target antigen for Ts3. Sperm immobilization test showed that Ts3 possessed sperm immobilizing activity. Furthermore, Ts3 impaired early embryo development but not in vitro fertilization. These results suggest that ODF2 plays an important role in both sperm function and early embryonic development.

Sex difference in anti-sperm antibodies

Background

Some diseases have sex differences. There have been no reports on the relationship between anti‐sperm antibodies (ASA) and sex differences.

Methods

ASA are detected by sperm‐immobilization test using patients' sera in women. In men, the ASA testing is generally performed by direct‐immunobead test.

Main findings

Sperm‐immobilizing antibodies in women inhibit sperm migration in their genital tract and exert inhibitory effects on fertilization. ASA bound to sperm surface in men also show inhibitory effect on sperm passage through cervical mucus. The fertilization rate of IVF significantly decreased when sperm were coated with higher numbers of ASA. For women with the antibodies, it is important to assess individual patients' SI₅₀ titers. In patients with continuously high SI₅₀ titers, pregnancy can be obtained only by IVF. For men with abnormal fertilizing ability by ASA, it is necessary to select intracytoplasmic sperm injection. Production of sperm‐immobilizing antibodies is likely to occur in women with particular HLA after exposure to sperm. The risk factors for ASA production in men are still controversial.

Conclusion

Attention to sex differences in specimens, test methods and the diagnosis of ASA should be paid. For patients with ASA, treatment strategies have been established by considering sex difference for each.

Application of computer-aided sperm analysis (CASA) for detecting sperm-immobilizing antibody

PROBLEM

Since the 1970s, anti-sperm antibodies have been studied as a pathogenic factor contributing to infertility. The complement-dependent sperm-immobilization test (SIT) and quantitative SIT have been used as effective tools for detecting anti-sperm antibodies in clinical settings. These tests have been carried out traditionally by manually counting the number of motile sperm through eye estimation.

METHOD OF STUDY

In this study, we developed a novel method using computer-aided sperm analysis. The results were compared with those obtained by the traditional method.

RESULTS

The results were identical and 25 of 78 samples tested were positive and 53 samples were negative for sperm-immobilizing (SI) antibodies based on both methods. For SI-positive samples, the values of SI₅₀ obtained using the two methods correlated closely with high co-efficiency.

CONCLUSION

Using the novel method, manually counting the number of motile spermatozoa becomes unnecessary. The novel method presented here will increase the objectivity and convenience of using the SIT as a clinical indicator.

Intrauterine Insemination: Fundamentals Revisited

Intrauterine insemination (IUI) is an assisted conception technique that involves the deposition of a processed semen sample in the upper uterine cavity, overcoming natural barriers to sperm ascent in the female reproductive tract. It is a cost-effective, noninvasive first-line therapy for selected patients with functionally normal tubes, and infertility due to a cervical factor, anovulation, moderate male factor, unexplained factors, immunological factor, and ejaculatory disorders with clinical pregnancy rates per cycle ranging from 10 to 20%. It, however, has limited use in patients with endometriosis, severe male factor infertility, tubal factor infertility, and advanced maternal age ≥ 35 years. IUI may be performed with or without ovarian stimulation. Controlled ovarian stimulation, particularly with low-dose gonadotropins, with IUI offers significant benefit in terms of pregnancy outcomes compared with natural cycle or timed intercourse, while reducing associated COH complications such as multiple pregnancies and ovarian hyperstimulation syndrome. Important prognostic indicators of success with IUI include age of patient, duration of infertility, stimulation protocol, infertility etiology, number of cycles, timing of insemination, number of preovulatory follicles on the day of hCG, processed total motile sperm > 10 million, and insemination count > 1 × 106 with > 4% normal spermatozoa. Alternative insemination techniques, such as Fallopian tube sperm perfusion, intracervical insemination, and intratubal insemination, provide no additional benefit compared to IUI. A complete couple workup that includes patient history, physical examination, and clinical and laboratory investigations is mandatory to justify the choice in favor of IUI and guide alternative patient management, while individualizing the treatment protocol according to the patient characteristics with a strict cancelation policy to limit multi-follicular development may help optimize IUI pregnancy outcomes.

Antisperm antibodies: invaluable tools toward the identification of sperm proteins involved in fertilization

The identification of sperm proteins involved in fertilization has been the subject of numerous investigations. Much interest has been dedicated to naturally occurring antisperm antibodies (ASA) and their impact in fertility. Their presence in men and women has been associated with 2-50% of infertility cases. ASA may impair pre- and post-fertilization steps. Experimental models have been developed using sperm proteins as immunogens to evaluate their involvement in sperm function. Our team has pursued investigations to assess ASA presence in biological fluids from patients consulting for infertility and their effect on fertilization. We found ASA in follicular fluids with ability of inducing the acrosome reaction and blocking sperm-zona pellucida interaction and used them to identify sperm entities involved in these events. We generated and utilized antibodies against proacrosin/acrosin to characterize the sperm protease system. We implemented an ELISA to detect proacrosin/acrosin antibodies in human sera and evaluated their impact upon fertility by developing in vitro assays and a gene immunization model. This review presents a summary of ASA history, etiology, current approaches for detection and effects upon fertility. ASA (naturally occurring, generated by animal immunization and/or of commercial origin) are invaluable tools to understand the molecular basis of fertilization, better diagnose/treat immunoinfertility and develop immunocontraceptive methods.

Methods for direct and indirect antisperm antibody testing

Antisperm antibodies (ASA) are one well-known cause of refractory infertility in both males and females. In females, a sperm immobilization test, which detects sperm-immobilizing antibodies indirectly in the patient's serum, requires complement for the reaction and thus seems to be a more specific immunological reaction. In males, an immunobead test or a mixed antiglobulin reaction test, which detects ASA directly on the sperm surface, is a screening test because of the nonspecific reaction.

Incidence of sperm-immobilizing antibodies in infertile women with past Chlamydia trachomatis infection

PROBLEM

Among the risk factors for antisperm antibody production, inflammatory diseases of the genital tract are believed to play an important role. Chlamydia trachomatis infection is one of the most common sexually transmitted diseases. There are some reports suggesting that human sperm have antigens that cross-react immunologically with certain microbial antigens, such as C. trachomatis. However, this is still controversial. We performed a retrospective study to investigate the correlation between anti-chlamydial antibodies and sperm-immobilizing antibodies in infertile women.

METHOD OF STUDY

Between January 2007 and March 2009, the presence of sperm-immobilizing antibodies was examined by the sperm immobilization test using sera from 273 infertile women. Anti-chlamydial antibodies (IgG and IgA) were examined to prove past C. trachomatis infection by ELISA using the same sera from infertile women.

RESULTS

The overall incidence of sperm-immobilizing antibodies was 2.9% (8/273) in infertile women. The incidences of sperm-immobilizing antibodies were 6.4% (5/78) in cases with past C. trachomatis infection and 1.5% (3/195) in cases without past C. trachomatis infection. There was a significant difference between the two groups (P = 0.031).

CONCLUSION

A significantly higher incidence of sperm-immobilizing antibodies was noted in infertile women with past C. trachomatis infection compared with that of those without past C. trachomatis infection. This is the first demonstration that C. trachomatis infection could play a role in the production of sperm-immobilizing antibodies in infertile women.