Effects of sperm-reactive antibodies present in human infertile sera on fertility of female rabbits

Gene Expression Alteration of Sperm-Associated Antigens in Human Cryopreserved Sperm

Background: Sperm-associated antigens (SPAGs) are 18 types of proteins, some of which play important roles in various biological functions associated with assisted reproductive technology outcomes, and are consequently important to the success of fertility programs. Despite the favorable outcomes of fecundity rates among male patients with cancer using cryopreserved sperm, the detrimental impact of freezing on cells has been noted in many studies. Cryopreservation has been thought to have adverse effects on sperm quality through disruptions in the expressions of SPAG genes. This study aimed to evaluate the effects of cryopreservation on the expressions of SPAGs genes and their transcriptome alterations in human sperm. Materials and Methods: A total of 12 normal ejaculations were prepared using the density gradient centrifugation procedure, and the motile sperm fractions were divided into fresh and frozen groups. In the latter, sperm samples were mixed with SpermFreeze^® solution as the cryoprotectant. The cryovial of sperm suspension was first held just over nitrogen vapor and then dipped inside liquid nitrogen. After 3 days, the specimens were thawed in tap water and incubated for 2 hours for recovery. Then, RNA from sperm was extracted for SPAG gene expression analysis, using real-time polymerase chain reaction. Results: Our findings showed a decrease in expression of SPAG5 (p-value = 0.009), SPAG7 (p-value = 0.004), and SPAG12 (SNU13/NHP2L1; p-value = 0.039) genes during cryopreservation. Discussion: The results indicate that the freezing procedure could negatively affect gene expression and to some extent proteins in human spermatozoa. Conclusion: The alteration of SPAG expression could provide new information on the molecular correlation between cryopreservation and increased failure in intracytoplasmic sperm injection and in vitro fertilization.

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

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

Protamines and male infertility

Protamines are the major nuclear sperm proteins. The human sperm nucleus contains two types of protamine: protamine 1 (P1) encoded by a single-copy gene and the family of protamine 2 (P2) proteins (P2, P3 and P4), all also encoded by a single gene that is transcribed and translated into a precursor protein. The protamines were discovered more than a century ago, but their function is not yet fully understood. In fact, different hypotheses have been proposed: condensation of the sperm nucleus into a compact hydrodynamic shape, protection of the genetic message delivered by the spermatozoa, involvement in the processes maintaining the integrity and repair of DNA during or after the nucleohistone-nucleoprotamine transition and involvement in the epigenetic imprinting of the spermatozoa. Protamines are also one of the most variable proteins found in nature, with data supporting a positive Darwinian selection. Changes in the expression of P1 and P2 protamines have been found to be associated with infertility in man. Mutations in the protamine genes have also been found in some infertile patients. Transgenic mice defective in the expression of protamines also present several structural defects in the sperm nucleus and have variable degrees of infertility. There is also evidence that altered levels of protamines may result in an increased susceptibility to injury in the spermatozoan DNA causing infertility or poor outcomes in assisted reproduction. The present work reviews the articles published to date on the relationship between protamines and 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.

Antiidiotypic antibodies to sperm in sera of fertile women that neutralize antisperm antibodies

The presence of antiidiotypic antibodies (ab-2) to sperm was investigated in the sera of fertile, infertile, and virgin women using sperm-specific anti-FA-1 monoclonal antibody Fab'.ab-2 were detected in 71% (17/24) of sera from fertile women and in none (0/12) of the sera from virgin females by the enzyme-linked immunosorbent assay, Western blot procedure, and immunoprecipitation procedure. Sera from infertile women that had antisperm antibodies showed a minimal presence of ab-2, with only three sera (13%, 3/23) demonstrating the presence of low levels of ab-2. The ab-2 present in fertile women were capable of neutralizing the fertilization-inhibitory activity of anti-FA-1 antibody in a concentration-dependent manner in a human sperm penetration assay (SPA) of zona-free hamster oocytes. ab-2 were also capable of inhibiting the binding of antisperm antibodies to the sperm surface as determined by the immunobead binding technique. This is the first report demonstrating the presence of ab-2 in the sera of fertile women that are capable of neutralizing antisperm antibodies present in sera of infertile women. These findings suggest that the inability to detect antisperm antibody activity in the sera of fertile women may be due to higher levels of ab-2 present in these sera than levels found in sera of infertile women, although both groups may be producing antisperm antibody response after sexual exposure to sperm.

Antigenic differences in human sperm samples related to various morphological abnormalities

Sperm samples were collected from male partners of fertile and infertile couples having unexplained and male factor infertility and analyzed for morphological abnormalities. After a staining procedure, sperm samples of these infertile men showed a variety of abnormalities. The sperm samples were also studied for their binding with the Abs directed against protamine (the nuclear protein), fertilization antigen (FA-1, sperm surface antigen), and the lithium diiodosalicylate- (LIS-) solubilized sperm preparation, and the binding was correlated with the percentage of morphologically abnormal sperm in the sample. Abs used in the present study were raised in female rabbits and had high titers (ELISA titers, 1:4096 to 1:8196), and recognized no band (anti-protamine), one 49,000- +/- 2000-dalton band (anti-FA-1), and at least 8 bands of various molecular identities in the 14,000- to 92,000-dalton range (anti-LIS sperm) on the Western blot of LIS-solubilized human sperm. The affinity-purified Fab' antibodies were iodinated and used in a radioimmunobindingassay for testing their binding with the sperm cells. Anti-protamine Fab's showed minimal binding and the binding activity (cpm bound/10 x 10(6) sperm cells) did not correlate (head defect, r = .12; midpiece defect, r = .07; tail defect, r = .11) significantly with percentage of abnormal cells in the sample. The binding of the anti-FA-1 Fab's also did not show a significant correlation (head defect, r = .29; midpiece defect, r = .48; tail defect, r = .23), though a positive trend (p = .05) was observed with the midpiece defect. In contrast, the binding of anti-LIS sperm Fab's demonstrated a significant correlation with the percentage of abnormal sperm cells in the sample (head defect, r = .51, p = .04; midpiece defect, r = .80, p less than .0001; tail defect, r = .23, p = .039). With an increased percentage of abnormal sperm cells, especially those with midpiece defect, there was an increased binding of anti-LIS sperm Fab's. These results suggest that with an increase in percentage of abnormal sperm, there is a change in antigenicity of the sperm cells. An increase in structural abnormality may enhance antibody binding to an abnormal sperm cell, thus causing a further decrease in its fertilizing capacity.

Effects of antibodies to sperm surface fertilization antigen-1 on human sperm-zona pellucida interaction

OBJECTIVE

To investigate the effects of antibodies to well-defined sperm surface antigens (the fertilization antigen [FA-1] and germ-cell antigen [GA-1]) and nuclear antigen (protamine) on human sperm-zona interaction.

DESIGN

Number of total and acrosome-reacted human sperm bound to the human zona pellucida and the sperm movement characteristics assessed by computer-aided sperm analysis were evaluated after incubation of sperm with the antibodies.

SETTING

Academic research environment approved by the Institute Review Board.

PATIENTS

Human oocytes were obtained from ovaries removed at surgery. Semen from fertile donors was used in all assays.

INTERVENTIONS

Human oocytes were stored in salt solution at -80 degrees C until used. Spermatozoa were treated with the antibodies to various sperm antigens.

MAIN OUTCOME MEASURES

Total and acrosome-reacted sperm bound to zona pellucida and sperm movement characteristics were evaluated after 3 to 5 hours of incubation of the antibodies with human sperm.

RESULTS

Anti-FA-1 antibodies significantly reduced human sperm fusion with zona-free hamster oocytes and sperm binding to the human zona pellucida but did not affect binding of acrosome-reacted sperm and sperm movement characteristics. Anti-GA-1 and antiprotamine antibodies did not affect sperm-oocyte interaction, acrosomal reaction, or sperm motility.

CONCLUSIONS

Antibodies to FA-1 but not to GA-1 and protamine inhibit human sperm-zona interaction.