A reverse (antibody capture) enzyme-linked immunosorbent assay for detection of antisperm antibodies in sera and genital tract secretions

Characterization of a potent sperm-agglutinating monoclonal antibody and its cognate antigens

OBJECTIVE

To identify sperm antigens that are capable of eliciting infertility-related sperm-agglutinating antibodies.

DESIGN

In vitro laboratory experiments.

SETTING

University research laboratory.

PATIENT(S)

Fertile semen donors.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Sperm agglutination, immunofluorescence localization, and flow cytometric analysis of surface expression of A36 antigens. Antigen analysis by Western immunoblotting.

RESULT(S)

Monoclonal antibody A36 induced intensive head-to-head, tail-to-tail, and head-to-tail agglutination of motile human spermatozoa. Antigens recognized by A36 were localized on the acrosomal cap and in the principal tail regions of motile, noncapacitated human sperm. Changes in subcellular levels and localization of the A36-recognized epitope occurred after capacitation and acrosomal loss. A36 reacted with a polymorphic series of proteins in Western blots of sperm extracts from humans and various other animal species, including mouse testis extracts. A common 53-kd antigen was recognized by the antibody in the different antigenic preparations.

CONCLUSION(S)

A mouse antibody to human sperm, monoclonal antibody A36, caused intensive agglutination of noncapacitated human spermatozoa and reacted with antigens on the acrosomal cap and in the principal tail regions. Of the multiple polypeptides that were reactive with the monoclonal antibody in sperm extracts from humans and other animal species, a common 53-kd antigen was recognized.

The role of antisperm antibodies in infertility

OBJECTIVE

To discuss the role of antisperm antibodies (Ab) in infertility, including proposed mechanisms of antisperm Ab formation, assays for their detection, and treatments for immune-mediated infertility.

DESIGN

Major studies in the published literature and data from The University of Texas Southwestern Medical Center, Division of Reproductive Endocrinology. Reports were reviewed that investigated the development and impact of alloimmunity and autoimmunity to spermatozoa in men and alloimmunity in women and the current methods of treatment for resultant subfertility.

RESULTS

The exposure of spermatozoal antigens to the mucosal and systemic immune systems results in development of immunity to a multiplicity of spermatozoal epitopes. The evaluation of studies that examine the role of antisperm Ab in infertility is complicated by the lack of standardization of antisperm Ab assays and the difficulty in identifying those epitopes for antisperm Ab binding that are responsible for subfertility. Sperm-associated antisperm Ab and antisperm Ab in cervical mucus (CM) reduce sperm mobility and may also impair sperm-ovum interaction. The clinical significance of serum antisperm Ab in both men and women, however, is controversial. Current therapy for antisperm Ab associated infertility is empiric and largely unproven.

CONCLUSIONS

Antisperm Ab on the sperm surface and in CM are implicated in the pathogenesis of a subset of patients with infertility. Further studies that determine the clinically relevant sites of antisperm Ab interaction will aid in directing the treatment of subfertility mediated by antisperm Ab.

Sperm antigens and reactivity of antisperm monoclonal antibodies in ELISA

Several types of sperm antigenic suspensions as well as the whole sperm, either methanol-fixed or air-dried, were checked for intensity of binding to monoclonal antisperm antibodies with known characteristics of reactivity to sperm. The activity of sperm antigen--antibody binding was measured by ELISA (enzyme-linked immunosorbent assay) and compared in several variations (parallely run) of the assay where different types of sperm antigen preparations were applied. The obtained results were then evaluated for statistical significance in Wilcox test. It was shown that antibody reactivity was markedly higher in experiments where the whole sperm was coated in a solid-phase in comparison to results obtained with adhered different sperm antigenic suspensions. However, one exception was noted, where the results from ELISA, run with sperm organic extract, were (statistically) insignificantly lower than those obtained with the whole sperm. Therefore, organic sperm extracts (containing mostly glycolipids) can be a valuable alternative to screening for antisperm antibody activity and/or infertility background.

Antisperm antibodies in women: variability in antibody levels in serum, mucus, and peritoneal fluid

OBJECTIVE

To look for patterns of antisperm antibody expression in women by exploring the levels of antisperm antibodies in different body fluids. This was achieved by studying sequential serum samples from individual patients and by comparing the levels of antisperm antibodies in serum from a number of patients with the levels of antisperm antibodies in cervical mucus or peritoneal fluid (PF).

DESIGN

Prospective studies were performed on sequential serum samples within a menstrual cycle. Retrospective studies were done to compare antisperm antibodies in serum and mucus or PF. The immunobead assay was used to measure antisperm antibodies in these fluids.

SETTING

Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire.

PATIENTS

A random sample of patients undergoing evaluation for infertility.

RESULTS

The levels of antisperm antibodies in sera drawn from patients at different points in a menstrual cycle stimulated by the presence of exogenous hormones did not change during the follicular phase of the menstrual cycle. Also, in many samples, the antisperm antibody level in serum did not correlate with the antisperm antibody levels in mucus or PF.

CONCLUSIONS

The data suggest that measurement of antisperm antibodies at a single point in time or from a single fluid is not sufficient when evaluating a woman for immunological infertility. The data also suggest that numerous and complex factors contribute to the expression of antisperm antibodies in women.

Identification of human sperm antigens reacting with antisperm antibodies from sera and genital tract secretions

OBJECTIVE

To identify sperm antigens reacting with antisperm antibodies relevant in human infertility.

DESIGN

The reactions of separated sperm antigens with antibodies present in sera and genital tract secretions from infertile and fertile females and males were examined by immunoblotting techniques.

SETTING

The patients were followed in an outpatient setting of a hospital clinic.

PATIENTS

One hundred consecutive infertile males and females, referred for determinations of antisperm antibodies, comprised the study group. Fifty hospital and faculty employees with proven fertility served as a control group.

RESULTS

A high proportion of sera from fertile and infertile humans contained antibodies reacting with at least one sperm antigen. However, two discrete bands of antigenic proteins with molecular weights of 44 and 72 kd reacted significantly more frequently with serum antibodies from infertile females than from fertile females. No apparent correlation could be demonstrated between any particular antigen and serum antibodies from infertile males. Nevertheless, antigenic proteins of 62 kd were identified as the major sperm antigens reacting with antibodies present in seminal plasmas from infertile males.

CONCLUSIONS

The major sperm antigens reacting with systemic antibodies differ from the antigens recognized by local antisperm antibodies. Sperm antigens exhibiting relative molecular weights of 62 kd are major antigens reactive with local antisperm antibodies from infertile humans.

A study of the detection of sperm antibody in cervical mucus with a modified immunobead method

OBJECTIVE

To develop a new immunobead binding test (IBT) procedure that will detect sperm antibody in cervical mucus (CM), especially in very small samples of mucus.

DESIGN

After the interaction of donor sperm with bromelin-dissolved CM, the motile sperm cells were separated from other cells and debris and then tested with a standard immunobead method.

SETTING

The CM and serum samples were obtained from a sequence of referred patients who were sent to this testing laboratory.

PATIENTS

There were 60 women who provided 64 samples of CM and 41 samples of blood serum. They were partners in infertile couples.

INTERVENTIONS

None.

MAIN OUTCOME MEASURE

A useful distinction was made between positive and negative results for the mucus samples by this CM-IBT procedure. The usable samples of mucus could be as little as 0.05 g (wet weight).

RESULTS

From the 60 women, seven mucus samples were positive; in the repeated testing, the same results were obtained with five of the six positive samples and seven of seven negative samples.

CONCLUSION

This method (CM-IBT) can be clinically useful for detecting sperm antibody in CM, especially because it is effective for tiny samples. In this method, the motile sperm cells are better separated from the debris after the incubation step. When the IBT was applied to the serum samples from the same women, there was no correlation between serum-IBT and CM-IBT, showing that both materials must be tested.