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

Immune response of the tammar wallaby (Macropus eugenii) to sperm antigens

In the present study, male and female tammar wallabies were immunised with whole tammar wallaby sperm in adjuvant. An assay for sperm antibodies using a live sperm ELISA has been developed to detect sperm surface antigens and used to validate an assay using a 3-[(3-cholamidopropyl) dimethylammonio]-1 propanesulfonate (CHAPS) membrane extract of whole tammar wallaby sperm. The tests were used to monitor the immune response to whole sperm in both male and female tammar wallabies. Antisera with a limited array of specificities were generated, with those locating to the midpiece region of the sperm appearing the most likely candidates for targets for fertility perturbation based on immunofluorescence of fixed and non-fixed sperm. These systemically generated antibodies were demonstrated to have access to both the female and male tammar reproductive tracts and were found on ejaculated sperm and antibodies from female sera and follicular fluid-labelled fresh ejaculated sperm from non-immunised males. Preliminary sequencing of these proteins has identified some possibilities for further investigation.

A convenient mixed immunobeads screen for antisperm antibodies during routine semen analysis

OBJECTIVE

To determine if leftover unused IgG, IgA, and IgM immunobeads could be combined as a convenient screen for antisperm antibodies in unwashed sperm. For comparisons, the mixed antiglobulin reaction (SpermMar) and immunobead test were performed.

DESIGN

Prospective comparative study.

SETTING

Clinical and academic research environment.

SUBJECT(S)

Donor human sperm negative for antisperm antibodies.

INTERVENTION(S)

Sperm specimens (n = 9) were equally divided and sera with antisperm antibodies added to one portion (positive control).

MAIN OUTCOME MEASURE(S)

Assessment of antisperm antibodies in sperm.

RESULT(S)

The mixed immunobeads screen qualitative results were the same for both the SpermMar and immunobead tests. The mixed immunobeads screen (positive when > or =10% motile sperm was bound) had a sensitivity and specificity of 100%. The percentages of bound sperm for the mixed immunobeads screen correlated with the SpermMar but not the immunobead test. The mixed immunobeads screen intraassay and interassay coefficients of variation were 28.9% and 45.6%, respectively.

CONCLUSION(S)

Matching results between the mixed immunobeads screen and the SpermMar or immunobead test suggested that the screen could be used to detect antisperm antibodies in unwashed sperm. There was no advantage to washing the sperm, although the screen was flexible and applicable for both unwashed and washed sperm.

Quantitative determination of IgG and IgA on sperm from infertile patients with and without antisperm antibodies

Immunoglobulins on patients sperm were determined by an ELISA technique, modified from the RIA described by Haas and D'Cruz (Am J Reprod Immunol, 1989; 20:37-43), i.e., suspensions of washed sperm (40, 20, 10, and 5 mill/ml) were added to a dilution of peroxydase-labelled anti-IgG or anti IgA, and after incubation the supernatants were transferred to cups in microtrays, coated with IgG or IgA, respectively. After incubation and washing ELISA reaction was carried out. Known amounts of IgG and IgA were processed in the same way to obtain a standard curve, allowing the Ig on the sperm to be expressed in ng/mill sperm. Ejaculates with increased viscosity revealed high values, irrespective of MAR-results and in some cases the same was true for samples with large numbers of non-spermatozoal cells (NSC). However, among 48 samples from men from infertile couples with negative MAR, > 20 mill sperm/ml, normal viscosity, and a ratio between sperm and NSC > 5, the median for IgG was 0.2 ng/mill sperm, 90% had < or = 0.8 ng/mill sperm, and the highest value recorded was 1.9 ng/mill sperm. For IgA the median was 0.5 ng, 90% of the 47 samples contained < or = 1.9 ng, and the highest value was 3.1 ng/mill sperm. The values for sperm from patients with a positive MAR, but without free antibodies in seminal plasma, were generally within the normal range. In contrast, increased values were recorded for most of the patients with free antibodies in seminal plasma, up to 4.2 ng/mill sperm for IgG and up to 12.5 ng/mill sperm for IgA.

Anti-seminal plasma antibodies associated with infertility: I. Serum antibodies against normozoospermic seminal plasma in patients with unexplained infertility

PROBLEM

To determine whether patients whose infertility remains unexplained (by routine physical and laboratory investigations including sperm antibody testing) exhibits significantly elevated humoral anti-seminal plasma immune responses in comparison to fertile individuals.

METHOD

Sera from 72 infertile couples were examine by ELISA for the presence of antibodies against normozoospermic seminal plasma (NSP). A group of 36 fertile individuals was used to determine the level of physiological reactivity. Kibrick's and Friberg's sperm-agglutination tests were employed to distinguish patients routinely diagnosed as immunologically infertile.

RESULTS

Anti-NSP reactivity was elevated in 18% of male and 26% of female patients. In the female patients, the prevalence rate for elevated anti-NSP reactivity was significantly higher among partners of positive men. In only 4% the positive anti-NSP results coincided with sperm-agglutinating antibodies.

CONCLUSION

NSP constituents other than sperm-coating antigens might interfere with infertility related autoimmune imbalance. The identification of the corresponding NSP antigens might help to resolve more cases of unexplained infertility.

Detection of antibodies toward epididymal sperm antigens--an obligatory step in evaluation of human immunologic infertility?

PROBLEM

To test the relative impact of epididymal versus ejaculated sperm in immunologic infertility.

METHOD

Human antibody binding to epididymal and ejaculated spermatozoa was compared by flow cytometry (FCM) since it allows quantitative analysis of viable sperm while ignoring nonsperm cells. To select sera for FCM, GAT, TAT, and ELISA were applied on 145 sera from fertile men, idiopathically infertile and varicocele patients.

RESULTS

All GAT/TAT-positive infertile patients, a representative group of varicocele patients and the fertile control, were assessed by FCM. Higher reactivity toward epididymal sperm revealed 18/22 sera while only four out of them bound to ejaculated sperm stronger than the control. All varicocele sera were positive against epididymal while negative against ejaculated spermatozoa.

CONCLUSIONS

Epididymal sperm antigens may play a predominant role in some cases of immunologic infertility. Such patients might not be adequately diagnosed and respectively treated due to the limitations of diagnostic procedures applying only ejaculated spermatozoa.

Interlaboratory interprotocol comparison of indirect immunobead assay for sperm-associated antibodies in serum

This investigation was designed to study the effect of two different protocols on the indirect sperm-associated antibody test on serum performed using Bio-Rad immunobead (IBT) at two andrology laboratories. Aliquots of 31 serum samples from infertile couples were analyzed by both protocols. The IBT was negative by both protocols (100% concordance) for 18 serum samples. Seven of the 13 remaining samples were positive by both protocols (> or = 10% bead attachment by protocol A and > or = 20% bead attachment by protocol B), for a concordance of 54%. The remaining six samples were positive by one of the two protocols. The overall concordance for positive and negative results was 81% (25 of 31 samples). Protocol A detected a higher percentage of bead attachments for IgG and IgA, while protocol B detected a higher percentage of bead attachments for IgM. The discordance in the results of IgA attachment obtained by the two protocols was statistically significant (p < .05). A standardized, uniform protocol for the indirect IBT is needed.

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.

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.

The use of ELISA to evaluate human antibody binding to epididymal sperm from different species

PROBLEM

The impact of antibodies to epididymal sperm antigens in human infertility has been poorly understood. Cross-reactivity of human antibodies with animal epididymal sperm has been previously observed, however, only by means of qualitative methods. Moreover, it has been always compared to reactivity against human ejaculated rather than human epididymal sperm.

METHOD

Following a screening study of 940 infertility patients, sperm agglutinating and immobilizing sera as well as sperm antibody negative controls were used to standardize an ELISA employing human ejaculated sperm. Nine sera positive in ELISA were further tested against epididymal human, guinea pig, rat, and hamster sperm. Differences among groups were evaluated by factorial analysis of variance (ANOVA).

RESULTS

The specificity and sensitivity of ELISA were shown to be 85.1% and 61.18%, respectively. Eight out of nine antisperm antibody-positive sera from infertile subjects reacted relatively stronger with epididymal than with ejaculated human sperm. All tested infertility sera showed strong although variable cross-reactivity with sperm from guinea pig, hamster, and rat.

CONCLUSION

ELISA has definite potential in sperm antibody research, allowing quantitative assessment of the results and immotile sperm employment. The suggested predominant role of epididymal sperm antigens in immune responses related to fertility needs further investigation. Some of these antigens are obviously phylogenetically preserved, and possibly in a quantitative aspect present differently on epididymal spermatozoa from various mammalian species.

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.

Radio-immuno binding test for anti-sperm antibody detection: analysis and critical revision of various methodological steps

The authors report the results of a methodological study to optimize a radioimmunoassay to detect anti-sperm antibodies. They describe here the definitive methodology with all the data relating to the laboratory trials conducted at each step of the technique. Results seem to demonstrate that this radioimmunological method is sufficiently simple, specific, sensitive and reliable for use in a highly specialized laboratory of reproductive immunology. Furthermore, this type of analytical approach, whilst indicating once more the difficulty of the technical study of anti-sperm autoimmunity, confirms (with concrete data) the necessity of being extremely "prudent" in evaluating the results of this kind of anti-sperm antibody test.

Binding of sperm-reactive antibodies in human sera to surface-associated antigens on human sperm compared by indirect immunobead, immunofluorescence, and immunogold assays

Human sera were identified as positive or negative for sperm-reactive antibodies in a solid-phase enzyme-linked immunosorbent assay (ELISA). Of these, 28 positive and 22 negative sera were blind-coded and used as first antibody to compare three immunoassays, a modified liquid-phase indirect immunobead assay (IBA); a liquid-phase indirect immunofluorescence assay (IFA); and a solid-phase indirect immunogold assay (IGA). These three immunoassays perform both as sperm-reactive antibody detection assays and as sperm-associated antigen localization assays. As antibody detection assays, the IBA, IFA, and IGA gave 37, 27, and 28 positives and 13, 23, and 22 negatives, respectively. The usefulness of the IBA as an antigen localization assay was limited by the size of the marker, while the smaller IFA and IGA markers enabled increased resolution of binding patterns of sperm-reactive antibodies to surface-associated sperm antigens. Although the antigen-antibody binding patterns were almost identical for IFA and IGA, suggesting the same sperm-associated antigens were detected by both assays, the IGA reaction product was stable, higher in resolution, and visible by light microscopy.

A comparison of sperm antibody assays

Cytotoxicity and Immunobead-binding immunoglobulin G assays agreed in 81% of sera from infertile men (n = 173), 74% of sera from their wives, 75% of seminal plasma, and 82% of cervical mucous samples (p less than 0.001; chi 2 analysis of positive and negative results) when tested against sperm from the same donors. Cytotoxic and immunofluorescent IgG antibody results agreed in 79% of sera from men and women, 76% of seminal plasma, and 76% of cervical mucus (p less than 0.001; chi 2 analysis of positive and negative results). Titers or percent binding of sperm by cytotoxicity, hemagglutination, and IgG Immunobead-binding or immunofluorescence assays in serum and secretions of husbands and wives correlated (p less than 0.001). A significantly increased number of positive results was observed in cytotoxic and Immunobead-binding IgG assays when the husbands' and donors' sperm were used rather than donors' sperm alone. On the basis of this study we conclude: (1) that cytotoxicity, Immunobead-binding IgG, and immunofluorescent IgG sperm antibody assays correlate when sperm from the same source are used, (2) that women's isoimmunity to husbands' sperm is associated with their husbands' autoimmunity to sperm irrespective of the assay, and (3) that it is desirable to use sperm from the husbands and nonautoimmune fertile men in these assays.

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

A reverse (antibody capture) enzyme-linked immunosorbent assay (ELISA) for detection of antisperm antibodies has been developed. The assay enables detection of immunoglobulin (Ig) M, IgG, IgA, or IgM, IgG, and IgA--antisperm antibodies in serum, cervical mucus, and seminal plasma samples. The reverse ELISA is more specific and sensitive than conventional ELISA in detecting human antisperm antibodies of different isotypes. Using this assay, statistically significant differences in levels of antibodies between infertile and fertile individuals were demonstrated in sera and in genital tract secretions. Studies with 143 infertile couples revealed that the presence of antibodies in sera was not necessarily reflected in individual's genital tract secretion and vice versa. These data emphasize the importance of detecting antisperm antibodies in sera as well as in genital tract secretions for correct evaluation of sperm immunity.

Anti-sperm antibodies in homosexual men: prevalence and correlation with sexual behaviour

The sera of 60 homosexual males were examined for the presence of antibodies to sperm using an indirect immunobead test (IBT). Six of 60 (10%) had antibodies of IgG isotype; in addition two of the six had antibodies of IgA isotype. The presence of antibodies was associated with the practice of unprotected receptive anal intercourse in the previous six months. Antibodies were not found in homosexual men who were celibate, or who practised only oral intercourse during the same period. There was no correlation between the presence of anti-sperm antibodies and antibodies to human immunodeficiency virus (HIV), or numbers of T lymphocytes. These preliminary results lend support to the hypothesis that antigen presentation in the lower gut may be a source of sensitisation against sperm. The possibility that anti-sperm antibodies may be a marker of receptive anal intercourse merits further investigation.

Antibodies to sperm basic nuclear proteins detected in infertile patients by dot-immunobinding assay and by enzyme-linked immunosorbent assay

The auto-antibody response in infertile men was investigated by means of immunoenzymatic methods, dot-immunobinding assay (DIBA), and ELISA, using, as antigens, human sperm basic nuclear proteins. Comparison was made, for the same patients, with antibody response to membrane antigens, detected by tray agglutination test (TAT), spermotoxic test (STT), and immunobead binding test (IBT). A very good agreement was observed between the two kinds of antibody responses. Thus, an ELISA or a dot-immunobinding test with sperm nuclear proteins may be considered as a simple and sensitive method for detection of auto-antibodies in infertile men. The reactivity in ELISA of various synthetic peptides corresponding to sequences of human protamines HP1 and HP2 was also studied: all the sera containing anti-nuclear antibodies do not react with synthetic peptides. This observation suggests that antibodies to sperm nuclear proteins recognize conformational epitopes that are not present on small synthetic peptides.

Lack of correlation between the immunobead test and the enzyme-linked immunosorbent assay for sperm antibody detection

A total of 41 sera submitted for routine sperm antibody screening were tested by both the indirect immunobead test (IBT) against viable sperm as antigen, and an enzyme-linked immunosorbent assay (ELISA) using the supernatant fraction from washed, sonicated sperm as antigen. Sixteen sera were positive by either IBT or ELISA, but none were positive by both tests. It was concluded that the tests may be detecting antibodies reacting with distinct antigen subgroups, possibly because the ELISA may be detecting antibodies directed against internal antigens or non-sperm-specific antigens such as HLA.

Simple radioimmunobinding assay for quantitation of sperm antibodies of IgG immunoglobulin class

The immunobead test (IBT) is an excellent test for initial sperm antibody screening and evaluation but is impractical when used to quantitate antibody levels using a twofold dilution series. The aim of this study, therefore, was to develop a relatively simple radioimmunobinding assay that would allow quantitation of sperm antibodies of IgG immunoglobulin class, which predominate in male sera. [125I]-Protein G was chosen as the radioligand because it binds to all IgG subclasses, but not to IgA or IgM. The results of the investigation indicate that the [125I]-protein G assay (PGA) allows efficient quantitation of sperm antibodies, as evidenced by a highly significant (P less than .0001) correlation (Spearman's, Rs = 0.94) between the PGA results and IgG-IBT titres.

Sperm and seminal plasma antibodies in acquired immune deficiency (AIDS) and other associated syndromes

Although HIV has been established as the etiologic agent in AIDS, other contributory cofactors may be responsible for selective clinical manifestations of the syndrome. While the pathogenesis remains unclear, the development of immunologic abnormalities observed in some homosexual males with AIDS and AIDS-related complex may be attributed to repeated exposure to allogeneic sperm and seminal plasma components. Accordingly, antibody levels to semen fractions were measured in sera from 338 individuals (295 AIDS, 36 ARC, 16 randomly selected homosexuals, 29 patients with infectious hepatitis, 12 hemophiliacs, 20 rheumatic disease patients, and 24 healthy heterosexual adults). The methods were (i) passive hemagglutination for antibodies to human seminal plasma (HuSePl), and (ii) indirect immunofluorescence (IF) assay on methanol-fixed human sperm noting staining of acrosomal, equatorial, postnuclear, and tail main-piece regions. HuSePl was positive in 31% AIDS sera, while 39% were positive by IF. ARC sera were 30% positive for HuSePl and 38% positive IF. No control sera were positive. Results reveal a significant incidence of antibody to sperm and seminal plasma components in ARC and AIDS patients. Because of the known immunomodulating properties of both, it is possible that these responses may indicate risk factors for disease progression and severity.

How should sperm antibody tests be used clinically?

Immunoglobulin-specific assays are currently available for detection of patients with antibody-mediated infertility. Care must be taken in insuring that the correct immunoglobulin class is assayed, the assay is directed to the possible interaction of antibodies and sperm in the male or female genital tract, and the antigen employed will not detect antibodies against antigens not found on the plasma membrane of living sperm.

Antibody binding specificity to donor sperm in sera from infertile patients

Indirect testing for elevated sera levels of antisperm antibody assumes that all relevant antigens are present on the target sperm utilized. In the present study, the heterogeneity of reactivity of positive sera with sperm from different donors was addressed. When 68 sera that previously tested positive by either sperm immobilization test (SIT) or ELISA or both were tested for antisperm antibody levels by a quantitative ELISA using nine different sperm donors, the frequency of positive reactions was 51% for men and 81% for women. A 50% correlation of SIT- and ELISA-positive results could be improved to 85% using the same sperm specimen. This would improve the overall correlation of functional and ELISA test results from 95% to 99% in the infertile population studied. The data suggest that individual sperm may vary in their antigenic expression and that comparison of methods between laboratories could be improved if equivalent target sperm were used.

Antisperm antibodies detected by ZER enzyme-linked immunosorbent assay kit are not those detected by tray agglutination test

Antisperm antibodies may play a role in the pathogenesis of infertility, particularly in the male. One of the standardized methods for detecting antisperm antibodies is the tray agglutination test (TAT). Unfortunately, this assay requires fresh motile spermatozoa. Tests for binding of antibody to fixed sperm or sperm extracts have been developed as enzyme-linked immunosorbent assays (ELISA), and we compared the results of using one such ELISA method with the TAT to detect antisperm antibodies in a panel of known positive and negative sera from infertile and control patients. With respect to the TAT assay, the ELISA gave a 75% false-positive test rate and a 63% false-negative rate. It is important to validate new assays such as the ELISA before widespread application to patient screening particularly since patients judged to have antisperm antibodies may be treated with high-dose corticosteroid drugs that are not without significant side effects.