Characterization of human sperm antigens reacting with antisperm antibodies from autologous sera and seminal plasma: comparison among infertile subpopulations

Antisperm antibodies and fertility association

OBJECTIVE

To evaluate the relation between antisperm antibodies (ASA) and human fertility by reviewing the scientific literature of the last 45 years.

METHODS

We carried out a review of scientific literature about antisperm antibodies and infertility published in spanish or english in databases as Pubmed, Medline, Scielo, some books and another gray literature include information related to this review and that is published in the last 45 years.

SUMMARY OF EVIDENCE

Infertile couples suffer infertility by immunological mechanisms mainly by the presence of antisperm antibodies ASA in blood, semen or cervicovaginal secretions; the formation of ASA in men and women may be associated with disturbance in immunomodulatory mechanisms that result in functional impairment of sperm and thus its inability to fertilize the oocyte.

CONCLUSION

Immunological infertility caused by ASA is the result of interference of these antibodies in various stages of fertilization process, inhibiting the ability of interaction between sperm and oocyte.

Antisperm immunity and infertility

Immunoinfertility is one of several causes of infertility in humans. Although progress on antisperm immunity and infertility has advanced during the past three decades, the nature of a real antisperm antibody (ASA) is still poorly understood. Dozens of sperm antigens have been isolated and characterized in association with infertility. However, it is difficult to identify a single predominant target antigen that could interact with all the ASAs. There are some protective mechanisms preventing ASA production in males and females. As chronic infection, vasectomy and vasovasostomy, heavy metals, and testicular cancer and torsion may induce the production of ASAs, they may be responsible for decreased motility and sperm penetration of cervical mucus, and the blockage of the acrosome reaction and the sperm-egg interaction. Many ASA assay methods have been developed, each with advantages and disadvantages. Efforts for the treatment of ASA-mediated infertility have been attempted. However, current therapy for ASA-associated infertility is almost empiric and largely unproven.

In vitro and in vivo studies evaluating antisemen antibodies as a potential spermicidal agent in hamsters

OBJECTIVE

To determine the spermicidal activity of antisemen antibodies in the hamster model.

DESIGN

Prospective, controlled study.

SETTING

Advanced preclinical sciences center.

ANIMAL(S)

Subgroups of 10 and 14 golden hamsters.

INTERVENTION(S)

Ex vitro and in vivo treatment of sperm with antisemen antibodies or normal rabbit serum.

MAIN OUTCOME MEASURE(S)

The EC(50) value of antisemen antibodies, the time required for 50% motility loss of progressively motile spermatozoa exposed to antisemen antibodies, the average sperm mitochondrion fluorescence intensity, the rate of fertilization, and the scoring of histologic changes in the hamster vaginal tissue.

RESULT(S)

The EC(50) value of antisemen antibodies was found 70 microg/mL, and the time required for 50% motility loss of progressively motile spermatozoa exposed to antisemen antibodies (at 70 microg/mL) was 5 minutes; for the experimental and control groups, the average fluorescence intensities of sperm mitochondria were respectively 180.28 +/- 82.24 and 309.74 +/- 148.37, the fertilization rates in vitro were 0.09% and 45%, the rates of fertilization with intrauterine sperm injection were 0 and 15.0%. There was a significant difference between two groups. None of the four hamsters that received antisemen antibodies in gel-polyoxyl-40-stearate had epithelial disruption characteristic of inflammation.

CONCLUSION(S)

Antisemen antibodies possess appreciable spermicidal potential, which may be explored as an effective constituent of spermicide.

Human seminal plasma antibody-binding proteins

PROBLEM

The physiological role of antibody-binding proteins in human seminal plasma and the potential role of these proteins in infertility is relatively unknown.

METHOD OF STUDY

Literature on antibody-binding proteins.

RESULTS

Human seminal plasma has a diverse effect on immune function of the reproductive tracts. This review describes (1) the presence of receptors like proteins that can react with monoclonal antibodies against Fcgamma receptors III (Fcgamma RIII) but are distinctly different from Fcgamma RIII; (2) IgG binding factors (IgGBF), a group of low molecular weight proteins that are capable of binding human IgG; (3) other proteins that can bind antibodies, such as prolactin-inducible protein and three other novel proteins that we have discovered. These proteins potentially all have the ability to reduce the interactions between antisperm antibodies and effector components of the immune system, such as phagocytic cells.

CONCLUSIONS

Human seminal plasma contains proteins that can bind antibodies. However, to date our knowledge of these proteins especially, whether they have a physiological role in either the male and female reproductive tracts is limited.

Immunoprecipitation of Sperm and Somatic Antigens with Antibodies from Sera of Sperm-Sensitized and Anti-sperm Antibody- Free Individuals

PROBLEM

Immune infertility may result from the presence of anti-sperm antibodies (ASA) in sera of sensitized individuals or in their genito-urinary millieu. According to some authors, sera of pre-pubertal boys with genital disorders may contain ASA, too. When identified and characterized, sperm antigenic components can be employed for diagnostic and/or for immunocontraceptive purposes.

METHOD OF STUDY

Sperm auto- and isoimmune reactive surface antigens were identified by means of immunoprecipitation. Comparative immunoprecipitations of somatic antigens by using antibodies, contained in polyclonal sera of fertile and (immunologically) infertile adults as well as pre-pubertal boys with gonadal failures were performed.

RESULTS AND CONCLUSIONS

Antibodies contained in sera of the all studied populations reacted with a number of sperm as well as somatic antigens. However, we distinguished a panel of antigens localized exclusively on the surface of sperm cells, reacting with ASA positive sera (in the range of molecular weight between 15 and 115 kDa), some of them seem to present novel entities as can be judged by the molecular weight.

Differential extraction and enrichment of human sperm surface proteins in a proteome: identification of immunocontraceptive candidates

The objective of this study was to discover previously unknown human sperm surface proteins that may be candidate contraceptive vaccinogens. To this end, methods of concentrating human sperm proteins for microsequencing by mass spectrometry were used, which increased the likelihood of identifying surface proteins. Vectorial labeling, differential extraction and two-dimensional (2-D) gel electrophoresis were employed to identify and isolate proteins accessible at the cell surface. Percoll harvested or swim-up sperm were either solubilized directly or solubilized after surface labeling with sulfo-succinimidyl-6-(biotinamido)hexanoate (sulfo-NHS-LC-biotin). Comparisons were made of proteins extracted with four lysis buffers: (i) Celis buffer containing 9.8 M urea and 2% Igepal CA-630; (ii) 1% Triton X (TX)-100; (iii) 1.7% TX-114 followed by phase partitioning; or (iv) 1 M NaCl. Blots of proteins separated by high-resolution 2-D electrophoresis were probed with avidin and antibodies to known proteins specific for three domains: the sperm surface (SAGA-1), the acrosome (SP-10), and the cytoskeleton (alpha-tubulin). Celis buffer (45 min) extracted proteins from all three major compartments. However, a 20-s extraction in Celis buffer enriched for several proteins and enabled the identification of several novel peptides by mass spectrometry. Mild extraction with TX-100 or 1 M NaCl solubilized mainly membrane and acrosomal proteins, but not cytoskeletal proteins. Comparison of biotinylated proteins extracted by each method showed that the major vectorially labeled proteins solubilized by Celis buffer were also solubilized by TX-100, TX-114, and 1 M NaCl. Extraction with TX-114 followed by phase-partitioning significantly enriched hydrophobic surface proteins and aided resolution and isolation. Eight protein spots microsequenced following all these extraction methods proved to be novel sperm molecules.

Human leukocyte antigen II expression in sperm cells: comparison between fertile and infertile men

Human leukocyte antigens (HLA) class II transcripts in mature spermatozoa of healthy volunteers have recently been demonstrated using reverse transcription polymerase chain reaction (RT-PCR). HLA II expression was investigated on ejaculated sperm cells in fertile and infertile men by RT-PCR and flow cytometry. Among 22 fertile and 20 infertile men, 18 were selected for the study because they showed no contamination with non-sperm cells. HLA II mRNA transcripts were expressed in all but 1 of 8 infertile subjects and in only 2 of 10 fertile ones. The cytofluorometric analysis on three RT-PCR positive samples confirmed the presence of class II antigens on cell surfaces. These data clearly confirm the presence of both HLA II mRNA and surface molecules on human sperm cells. In addition, an interesting nonrandom distribution of positivity among fertile and infertile samples regarding HLA II expression (p < .025) suggests a possible correlation with infertility.

Sperm antigens recognized by antisperm antibodies present in sera of infertile adults and prepubertal boys with testicular failure

Immunoblotting of a repertoire of sperm antigens reacting with antisperm antibodies present in sera of infertile adults and prepubertal boys with testicular failure was performed. In the subgroups selected for this study, 55% of examined infertile women, 65% of infertile men and 64% of prepubertal boys with gonadal failure gave positive results by Western blotting with extracted sperm antigens. Sperm antigens with molecular weights of 57, 58, 62, 63 and 66 kDa were the most immunodominant entities recognized by antisperm antibodies from prepubertal boys. No positive reactions were detected by Western blotting in a control population of fertile adults, whereas in a group of prepubertal healthy boys only one sample revealed reactivity against sperm antigens of 58 and 70 kDa.