The enzyme-linked immunosorbent assay for detection of the antispermatozoal antibodies

Antisperm antibodies detection by flow cytometry is affected by aggregation of antigen-antibody complexes on the surface of spermatozoa

Flow cytometry (FCM) analysis of live antibody-coated spermatozoa subjected to immunofluorescence staining (FCM test) is considered an objective method for the quantitative detection of antisperm antibodies (ASA). But the cross-linking of cell surface antigen (Ag) with bivalent antibodies and/or antigen-antibody (Ag-Ab) complexes with second antibodies may induce the reorganization of surface components (patching and capping) and result in their shedding from the sperm surface. The present study estimates the relationship between aggregation of Ag-Ab complexes on the sperm surface and the results of indirect FCM test. Swim-up spermatozoa of normozoospermic men were incubated with ASA-positive sera from infertile patients and with second antibodies fluorescein isothiocyanate (FITC)-labelled goat anti-human IgG polyclonal antiserum under different conditions and then analysed by FCM and fluorescence microscopy. It was shown that low temperature, cytochalasin B, excess or lack of the primary and/or secondary antibodies and sperm fixation by paraformaldehyde may inhibit aggregation and shedding of Ag-Ab complexes and dramatically increase ASA quantity determined on the sperm surface. However, inhibition of aggregation on the live sperm surface was observed only in a minority of ASA-positive samples and was poorly reproducible using semen of different donors. A high probability of Ag-Ab complex shedding from the sperm surface during experimental manipulation limits the use of indirect FCM test for quantitative ASA determination.

Detection of antiendometrial antibodies in patients with endometriosis by cell ELISA

PROBLEM

To determine whether infertile patients with endometriosis have serum antiendometrial antibodies.

METHODS

Sera from 40 infertile patients with or without endometriosis were tested by cell enzyme-linked immunosorbent assay (ELISA), in which endometrial cancer cells were used as endometrial antigens, and uterine cervix cancer cells as control antigens. As a negative control, eight healthy adult males were included. The level greater than the mean +/- 2 standard deviations (SD) of the male control group was judged positive.

RESULTS

The mean value of antiendometrial antibody level was significantly higher in patients with endometriosis than in those without endometriosis (ANOVA, P < 0.01). The frequency of antiendometrial antibody-positive patients was also higher in the former than in the latter (chi 2 test, P < 0.05). However, when uterine cervix cancer cells were used as antigens, no difference was observed in the mean antibody levels or in the positive rates between the two groups.

CONCLUSIONS

Endometriosis seems to be associated with autoantibody production against the endometrium-related antigen(s).

Monoclonal antibody against a 52 K sperm surface protein inhibits sperm-zona pellucida interactions in the rat

A major regulatory site for species specificity of fertilization in mammals lies at the level of sperm binding to the zona pellucida. This implies a high degree of complementarity between gamete and receptor molecules. These molecules support species-specific interactions between sperm and oocyte that lead to gamete fusion (fertilization). We identified a rat sperm head surface antigen using an IgG1 monoclonal antibody (HD1) against rat sperm of epididymis cauda. By electron microscopy the antigen was shown to be present on the plasma membrane surface of the sperm dorsal head. One- and two-dimensional immunoblotting analysis of sperm proteins demonstrated that HD1 reacted only with a 52 K molecule with a pI ranging from 6.6 to 7.2. The 52 K protein was first detected in situ by indirect immunofluorescence and showed to be underlining few elongated spermatids in testis. However, when the sperm reached the epididymis caput, the antigen was seen to be expressed on the dorsal surface of spermatozoa head. A similar fluorescence reaction was detected on sperms in the epididymis corpus and cauda. The specific spermatozoa-zona pellucida interaction was inhibited in the presence of monoclonal antibody HD1 in a sperm binding assay of in vitro fertilization.

A comparison of enzyme-linked immunosorbent assay (ELISA) with sperm immobilization test (SIT) in detection of antisperm antibodies in sera of infertile women

In the present study, an enzyme-linked immunosorbent assay (ELISA) for antisperm antibodies was compared with a traditional standard sperm immobilization test (SIT) in sera from 158 infertile women in order to evaluate their clinical usefulness for various causes of infertility. Ten pregnant and unmarried women were used as the control group. There was a higher incidence rate by ELISA (13.9%) compared with that by SIT (10.1%) after examination of overall samples, although the difference was not statistically significant. The unexplained infertility group exhibited the highest incidence among the various causes of infertility in both of these two methods. Fifteen (93.8%) of 16 patients with positive SIT showed positive reaction in ELISA method, indicating that a close correlation exists between the two methods. The positive predictive value (54.5%) of ELISA was significantly (p < 0.05) lower than that (87.5%) of SIT, as evaluated with the results of postcoital test (PCT) performed at periovulatory phase. This suggests that the ELISA method for antisperm antibodies is less specific than SIT in view of the PCT results. Nevertheless, no fresh sperms are not required for the ELISA examination. Thus, it seems that the ELISA method may provide a convenient and practical means for mass screening in detecting antisperm antibodies in clinical practice.

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.

Risk factors for antisperm antibodies in infertile men

PROBLEM

The prevalence of anti-sperm antibodies (ASAs) in the general population is 0 to 2%; the prevalence in infertile men is much higher at 7 to 26%. However, the role of ASAs in male infertility remains controversial to date. Although several risk factors for ASA development have been defined (such as testicular torsion, varicocele, cryptorchidism, vasectomy, and genital tract infection), there are no specific indications for ASA testing.

METHOD

In order to examine if a single parameter exists identifying patients with elevated ASA titers, serum ASA testing was performed with an enzyme-linked immunosorbent assay (ELISA) in 226 consecutive male patients. The new assay, synchron ELISA (Synelisa) used in our study represents a new type of ELISA without fixation of the sperm surface antigens by formaldehyde or glutaraldehyde. Therefore, the quantitative assay is highly sensitive and reproducible since the structure of sperm surface antigens is not altered by the fixation process.

CONCLUSIONS

The prevalence of ASAs in this population was 14%, while the prevalence of the control group was 2.5%. Of all factors analyzed only a history of vasectomy, an acute epididymitis, and an abnormal result in the bovine mucus penetration test was associated with elevated ASA titers (P < .001). In addition, we could demonstrate a time related formation of ASAs in men after vasectomy.

Association of antisperm antibodies with chronic nonbacterial prostatitis

Antisperm antibodies are significant in male factor infertility. The prevalence of antisperm antibodies in the infertile population is approximately 10 percent, and it is not cost-effective to test for these antibodies in every male partner of an infertile marriage. Earlier studies have demonstrated a higher prevalence of antisperm antibodies among men with a history of bacterial prostatitis or urethritis. Because of this established association, we measured the prevalence of serum antisperm antibodies, using a gel agglutination assay, in 28 men with chronic nonbacterial prostatitis and in age-matched control group of 69 men without a history of prostatitis. The prevalence was 25 percent (test subjects) and 7.2 percent (controls) (p less than 0.05). This finding indicates that nonbacterial prostatitis is a risk factor for the presence of serum antisperm antibodies and that subfertile men with a history of nonbacterial prostatitis should be tested for these antibodies.

Enzyme-linked immunosorbent assay (ELISA) for detecting antisperm antibodies in mice with testicular autoimmunity

We developed an ELISA for measuring antisperm antibodies in the mouse by using serum samples obtained from mice immunized with murine testicular antigens in complete Freund's adjuvant (CFA) as well as from mice rendered vasectomized. Sperm antigens used were syngeneic epididymal spermatozoa and two types of soluble, murine testicular antigens prepared in our laboratory. This study deals with a) the sequential changes of antisperm antibody levels following immunization; b) determination of immunoglobulin classes of these antibodies; c) a correlation between the absorbance values and the endpoint titers of antisperm antibodies; and d) comparison of endpoint titers of antisperm antibodies detected by ELISA with those by immunoperoxidase staining method in immune and nonimmune sera. It is suggested that serum dilution as high as 1/800 or more is required for detecting antibody titers of immune sera, because nonimmune mouse sera reveal a definite, although low, level of absorbance value at a serum dilution of 1/400 or less.

Clinical evaluation of the enzyme-linked immunosorbent assay (ELISA) kit for antisperm antibodies

A commercially available enzyme-linked immunosorbent assay (ELISA) kit for the detection of antisperm antibodies in serum was compared with standard sperm immobilization test (SIT) with the use of sera from 83 infertile women and 29 control individuals. For the ELISA, 24% of the infertile patients and 10% of the controls showed positive results, whereas 15% of the patients and none of the control were positive in the SIT. Parallel tests carried out on the same sera indicated that these methods detect a different, though often overlapping, spectrum of antibody activity. The presence and number of motile sperm in cervical mucus during postcoital tests were found to be related to the results of the SIT. On the other hand, the ELISA did not appear to be related to the quality of postcoital tests. These data indicate that care must be employed to interpret the results of this ELISA kit for the detection of antisperm antibodies.

Effect of therapy on infertile couples with antisperm antibodies

One hundred seventy-eight couples with positive antisperm antibody titers in serum and genital secretions were offered treatment with prednisone. Of 60 couples who received prednisone only, 43% conceived. Of 25 who had no therapy, 48% conceived. Fifty-four patients treated with prednisone received additional therapy and 31% conceived. Ten of 39 patients not treated with prednisone but receiving other therapies conceived. Cytotoxic antibodies were reduced in 30% to 42% of serum samples and in 24% to 33% of genital secretion samples. In those couples with decreased cytotoxic antibodies pregnancy rates were 40% to 60% compared with 0% to 23% in those with decreased hemagglutinating antibody titers. Our data suggest that prednisone did not improve overall pregnancy rates; pregnancy rates were comparable in both groups treated with other therapies; donor insemination was the most successful of the alternative therapies; reduction of cytotoxic antibody titers after prednisone treatment was associated with increased pregnancy rates.

A comparison of sperm agglutination and immobilization assays with a quantitative ELISA for anti-sperm antibody in serum

An enzyme-linked immunosorbent assay (ELISA) that quantitates antisperm antibody in serum was compared with standard sperm agglutination and immobilization assays with the use of sera from 40 normal and 292 subfertile individuals. Quantitation of the assay was accomplished by standardizing assay parameters, including the incorporation of a standard reference curve, the number of whole target sperm, the optimal dilution of serum, the selection of microtiter plate, and the time and temperatures involved in the adsorption and incubation phases. With this method, the level of antisperm antibody binding to target sperm in 40 normal fertile individuals was found to be 2.3 (+/- 1.1 standard deviation [SD]) fg immunoglobulin (Ig)/sperm. An increased mean level of 7.4 +/- 3.7 fg Ig/sperm was determined in 84 infertile patients with positive agglutination and/or immobilization tests. In 208 individuals with negative agglutination and immobilization tests the mean concentration of antisperm antibody was 2.5 +/- 1.3 fg Ig/sperm. Postvasectomy patients assayed by this method had a mean Ig binding value of 7.1 +/- 2.4 fg Ig/sperm. The infertile group with positive agglutination and/or immobilization tests had a significantly higher mean antisperm antibody level than the normal fertile group, according to the Student's t-test for independent samples (P less than 0.001). This indirect serum-based assay reproducibly quantitates antisperm antibody binding to whole target sperm, suggests the normal and abnormal levels of antisperm antibody, and correlates with standard functional assays.

Analysis of antibodies against mouse spermatozoa using an enzyme-linked immunosorbent assay (ELISA)

Conventional techniques used for the analysis of antisperm antibodies are not suited to the mouse model because of their requirements for relatively large amounts of serum and their inability to handle large numbers of samples. This has inhibited use of the mouse as an experimental model in areas involving antisperm immunity. As the ELISA technique has been successfully applied to analysis of antisperm antibody in human sera, we investigated its use as an assay for screening antisperm antibody in mouse serum. This report describes a simplified version of the ELISA technique that we have found to be successful for this purpose. The assay described can assess levels and classes of antisperm antibody in mouse serum and can also be used as a screening assay for monoclonal antibodies to mouse sperm. It should facilitate use of the mouse in experimental work in areas involving assessment of immunity to sperm.

Antibodies to spermatozoa and seminal plasma antigens detected by various enzyme-linked immunosorbent (ELISA) assays

Various ELISA methods have been applied by different research centers to test the efficiency of this approach for the diagnosis of sperm-immune infertility cases. The antigens used were either whole spermatozoa or solubilized spermatozoal membrane preparations and were immobilized on microtiter plates, except in one case where plastic beads were employed. Polyvalent second antibodies or protein-A labelled with enzymes served as tracers. A high frequency of positive sera was found in all groups including fertile controls with tests using whole spermatozoa as antigen. The methods using solubilized antigen preparations showed fewer positives on the whole and correlated better with the various clinical categories of the WHO sera. Whilst there was some agreement in the results between the various laboratories on a few sera, most of the positive sera found by one laboratory were reported as negative by others. More investigative work is needed to improve reproducibility between different laboratories and to reduce non-specific reactions with normal controls. A more precise definition of the proper cut-off levels for positives and negatives is also needed. Despite these short-comings, the development of an ELISA for the diagnosis of sperm-immune infertility cases seems to be justified in the long term.

Sperm antibodies and infertility in patients with testicular cancer

The level of antisperm antibodies using the enzyme-linked immunosorbent assay (ELISA) in the serum of 48 patients with testicular cancer before and after therapy is reviewed. This is not a linear study of each patient, but some conclusions can be drawn: In a high percentage of testicular cancer patients serum antisperm antibodies can be detected: 73.3 per cent before orchiectomy and 43.7 per cent overall. The percentage of patients with antibodies decreases with adequate therapy. In patients with advanced disease there is a higher percentage of positivity (50%) for serum antisperm antibodies than in patients with low-stage disease (30%). The higher percentage of antibodies-positive patients among those with infertility patterns could be an important argument that supports the hypothesis that autoimmune pathology can play a role in oligo/azoospermia in testicular cancer patients.

An enzyme immunoassay for the detection of antisperm antibodies

A simple and reliable enzyme-linked immunosorbent assay (ELISA) for the detection of antisperm antibodies has been developed in our laboratory. The antigen for the solid phase was produced by sperm sonication while antihuman globulin conjugated to alkaline phosphatase was used as the developing reagent. The conditions and reagents of the assay were chosen to give a mild treatment of the antigen, simple manipulation during washing steps, and nontoxic and readily available reagents. The results were compared to a conventional microscopical method routinely used in our laboratory that detects agglutinating antibodies to human spermatozoa. In 96% of all cases antibodies detected by the microscopical method were also detected by ELISA. Moreover there were some cases where no antisperm antibodies could be demonstrated by microscopy, but gave a positive reaction with ELISA. These were usually cases of unexplained oligospermia, agglutinates in the ejaculate, and bad motility or low viability of the sperms. These results, and also titration experiments of positive samples demonstrate the higher sensitivity of the ELISA by comparison with microscopical methods.

Detection of anti-sperm activities of monoclonal antibodies to human sperm

The anti-sperm activities of a series of monoclonal antibodies to human sperm have been compared using agglutination, immunofluorescence, ELISA and 'panning' assays. The antibodies fell into two categories, those that could be detected by agglutination but not immunofluorescence assays and those that could be detected by immunofluorescence but not agglutination. Antibodies positive in the agglutination assays were also positive in the 'panning' assay. None of the antibodies tested was positive in the ELISA assays. These results, and others, are discussed in relation to the problems associated with the detection of anti-sperm antibodies in sub-fertile human populations.

An improved indirect enzyme-linked immunosorbent assay (ELISA) for the detection of antisperm antibodies

An indirect enzyme-linked immunosorbent assay (ELISA) was used for the detection of antisperm antibodies which provides a sensitivity and ease of quantitation that is not available with conventional bioassay systems. A standardized protocol was developed in which washed whole sperm were coated onto polystyrene microelisa plates at a density of 1 X 10(5) sperm per well using a commercially available spray fixative. Urease was employed in the enzyme-antiimmunoglobulin conjugate to minimize nonspecific background reactions. Diluted positive and negative human sera were incubated at 37 degrees C and the results were read on an ELISA auto reader. Using mouse antihuman sperm antisera and sera from selected infertile patients, it was found that the ELISA method was significantly more sensitive than the sperm microimmobilization test and the microtray agglutination test. The results also confirmed that the ELISA detected a different spectrum of sperm antibodies compared with the other two techniques.

Immunological screening of a male population with infertile marriages

Four hundred not preselected male partners of infertile marriages were screened for the presence of anti-sperm antibodies. Serum and seminal plasma specimens from each patient were tested by the modified slide agglutination test (MSAT) and by the sperm-immobilization test. In addition, the IgG MAR test was performed on fresh ejaculates. Thirteen per cent of patients showed sperm agglutinating activity in serum and 5.7% also in seminal plasma. Sperm-immobilizing activity was found in 4.7% of serum and 1% of seminal plasma specimens, always associated with a high titre of sperm agglutinating activity. A highly significant linear correlation was found between the results of the MAR test and serum sperm-agglutinating activity; the presence of sperm-agglutinating activity in seminal plasma was always associated with MAR test positivity greater than 50%. The incidence of anti-sperm antibodies was not significantly different in patients with normo-, oligo- and azoospermia. The effectiveness and the easiness of both the MAR test and the MSAT do not justify, in our opinion, the utilization of more complex and expensive techniques for the detection of anti-sperm antibodies.

A simplified method using enzyme-linked immunosorbent assay for titration of antisperm antibodies

We selected sera from 44 patients (36 males and 8 females) that were positive for antisperm antibodies using ELISA (titer ranged from 1:32 to 1:512) for the evaluation of a simplified method for determination of antisperm antibodies. This method uses a correlation between a single absorbant value and the endpoint titer of the same serum. This simplified procedure increases the number of the sera that can be tested on each plate, resulting in considerable saving of time, reagent costs, and materials. A standard curve allows the direct determination of endpoint titer using the absorbance value found at a single dilution. This modification improves the utility of the assay for the epidemiological screening of antisperm antibodies in patients who may have an immunological cause of infertility.

An immunosorption assay for antibodies to spermatozoa: comparison with agglutination and immobilization tests

We have developed an enzyme-linked immunosorption assay (ELISA) with an antigen extract made by treatment of freeze-thawed sperm pools with 0.3 M lithium 3,5-diiodosalicylate (LIS). This procedure is quick, safe, and simple to perform in a clinical laboratory. When the LIS antigen preparation was compared by ELISA with whole sperm and several other antigen extracts, it was found to be superior in detecting human antisperm antibodies related to infertility; it gave less variability, better precision, and fewer false-positive reactions than whole sperm fixed to the wells as antigen. The antigen was stable when stored at -20 degrees C. In one experimental series, serum samples from 18 normal control subjects and 159 infertility patients with positive sperm-immobilizing titers, positive sperm-agglutinating titers, or both, were tested by ELISA with LIS antigen; the correlation yielded a P less than or equal to 0.0001. Based on another series of 156 samples from patients with positive antibody titers by the sperm agglutination test and 30 sera from normal humans, the predictive value of the test was 96%. In a third series of 162 serum samples obtained from 82 women and 80 men, we found no difference in the test results based on sex. The assay is specific for the antibody binding portion of the immunoglobulin. Absorption of positive sera with sperm but not red blood cells markedly reduces the response. In addition to being more efficient and precise than standard methods, the ELISA eliminates the need for fresh sperm and provides data that can be objectively interpreted.