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

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.

Lack of association between antisperm antibodies and language dysfunction in Alzheimer's disease

Alzheimer's disease (AD) is the single most common cause of primary dementia. Language-based frontotemporal dementia, another type of primary dementia, is known as primary progressive aphasia (PPA). Although the cardinal feature of AD is a progressive loss of memory, many patients with AD also present with language impairment. Moreover AD and PPA have partially shared pathophysiology. Recently, it was suggested that a history of vasectomy might be a risk factor for PPA, by immune responses to sperm or antisperm antibody (ASA), which has long been known to have antigenic property. As ASAs could develop naturally in both men and women, we studied the relation between the presence of ASAs and cognitive function in AD. A total of 86 elderly were selected (46 patient with AD, 20 with mild cognitive impairment, and 20 without cognitive dysfunction) and were assessed for the presence of ASAs with neuropsychological evaluation. However, there were no significant differences in the distribution of ASAs according to cognitive status or language function status. Thus, the current study does not support the association between the immune responses and language dysfunction in AD.

Serum sperm antibodies unrelated to mumps orchitis

In order to determine whether there is an association between mumps orchitis and serum sperm antibodies, we tested patients at the time orchitis was diagnosed (n = 7) and individuals who had had orchitis at least 1 month previously (n = 14). Data were compared with the results for a control group of blood donors (n = 20). Sperm antibodies were detected by the gelatin agglutination test of Kibrick, the tray agglutination test of Friberg and the ELISA. Clinically significant sperm antibody levels were not found in patients in the early stages of the disease. Four subjects tested post-disease were positive in the Friberg test and one was positive in the ELISA. One control serum was also positive in the latter test. Significant differences were not found between levels in patients in the early stages of the disease and levels in individuals post-disease, although the results of the Friberg test differed significantly between controls and former mumps orchitis cases. These data do not support the assumption of an involvement of humoral immunity against spermatozoa in mumps orchitis patients.

Monoclonal antibodies to epididymis-specific proteins using mice rendered immune tolerant to testicular proteins

Monoclonal antibodies (mabs) have been used as a powerful tool for identification of newer sperm proteins. However, conventional hybridoma technology rarely provides chance to obtain mabs to epididymal proteins. To increase this chance, we have used an alternate method of neonatal tolerization. In this protocol, animals were tolerized at birth using testicular proteins followed by immunization with cauda epididymal sperm protein (which is a cocktail of proteins both from testicular and epididymal origin). This protocol induced a specific immune response to epididymal sperm proteins. Spleen from one of these animals was then used for preparation of mabs. This fusion resulted in a number of mabs reacting specifically to epididymal proteins. Although mabs identified a protein of approximately similar molecular weight on 1-dimensional Western blot analysis, there were differences in regional localization on rat sperm as seen by indirect immunofluorescence. Immunohistochemical localization of these proteins in rat epididymis showed region specific synthesis. The synthesis of proteins was seen in the distal caput epididymis, and maximum expression was seen in supranuclear region of corpus epithelium. The proteins were localized on sperm from corpus and cauda region. Epididymis specific synthesis of the proteins and agglutinating nature of the mabs to these underlines the functional importance of these proteins in sperm maturation in epididymis. These antibodies could therefore, be used as tools for understanding the physiology of maturation of sperm in epididymis and role of the epididymal protein in fertilization.

The age-related changes in the incidence of 'natural' anti-sperm antibodies suggest they are not auto-/isoantibodies

PROBLEM

Establishing the age-dependent patterns of sperm antibody levels among normal humans.

METHODS OF STUDY

Sera samples from 498 healthy subjects aged 0-97 years - 246 males and 252 females - were tested by the gelatin agglutination test of Kibrick, tray agglutination test of Friberg, sperm immobilization test of Isojima and enzyme-linked immunosorbent assay (ELISA).

RESULTS

We found a significant increase in the level of sperm agglutinins after 40 years, which decreased after 88 years. The antibodies detected by ELISA were the highest among prepubertal subjects and also declined with aging. No age-dependent changes were established for the sperm immobilizins. With few exceptions, there were no significant differences between male and female sera, as well as between sera of newborn and their mothers.

CONCLUSIONS

These data are similar to those established for the age-dependent changes of antibodies towards exogenous antigens, suggesting that the 'naturally occurring' antibodies against human spermatozoa are not auto-/isoantibodies.

Sperm antigenicity shared in five vertebrate classes

The antigens of spermatozoa are of special interest because of their involvement in immunoinfertility and because they are candidate targets for immunocontraception. Conserved sperm epitopes from divergent species may present a suitable source and an animal model for the investigation of the above factors. We compared spermatozoa from six species of vertebrates belonging to five different classes, in order to demonstrate the existence of shared antigens. We used whole fixed male germ cells from trout, frog, turtle, rooster, rabbit and human in the enzyme-linked immunosorbent assay with rabbit polyclonal sperm-specific antisera. After absorption of the antisera with non-gametic (liver powder) and gametic tissue preparations, we established significant cross-reactions among the spermatozoa of all tested species. The antigenic similarities were the strongest between spermatozoa of trout and frog, trout and human, rabbit and turtle, rabbit and rooster. These data demonstrate the existence of highly conserved epitopes in spermatozoa from divergent vertebrate species belonging to different animal classes, in contrast to structures of the female gametes (zona pellucida) for which antigenicity was found to be limited to the animal class.

Serum sperm antibodies are not elevated after mumps orchitis

OBJECTIVE

To assess the level of serum sperm antibodies after mumps orchitis.

DESIGN

Controlled descriptive study.

SETTING

Academic research environment.

PATIENT(S)

Seventy-four mumps orchitis patients.

INTERVENTION(S)

Sampling of serum at different intervals after the onset of orchitis symptoms: 1 to 7 days, 31 to 60 days, and 61 to 431 days.

MAIN OUTCOME MEASURE(S)

Level of serum sperm antibodies, using Kibrick's gelatin agglutination test, Friberg's tray agglutination test, Isojima's sperm immobilization test, and ELISA.

RESULT(S)

Clinically relevant sperm antibody values were detected by the Friberg method among patients tested from 1 to 7 days (10.5%) and 61 to 431 days (10.5%) after the onset of disease. The Isojima test revealed a statistically insignificant higher incidence among patients at 61 to 431 days (31.6%) as compared with those sampled at 1 to 7 days (10.5%). None of the orchitis sera tested positive by the Kibrick and ELISA techniques. The established incidences did not differ significantly from the results for negative controls (blood donors) and were lower than the values acquired from positive controls (males with unexplained infertility).

CONCLUSION(S)

Mumps orchitis does not cause enhanced humoral immunity to spermatozoa.

Common egg envelope antigens are limited to the animal class

The antigens of the egg envelope (zona pellucida) in mammals are of special interest because of their possible involvement in immunoinfertility and as candidate targets for immunocontraception. Conserved zona epitopes from divergent species may present a suitable source and an animal model for investigation of the above factors. We compared egg envelope antigens from 6 species of vertebrates belonging to 3 different classes in order to demonstrate the existence of shared antigens. Egg envelopes from the trout, carp, turtle, hen, duck and quail were isolated and heat-solubilized. They were tested with rabbit polyclonal antisera against carp, trout and duck egg envelopes by the enzyme-linked immunosorbent assay. The results showed significant cross-reactions among egg envelopes of fish and birds. The examined solubilized preparations did not show cross-reactivity with egg envelopes from any other class, suggesting that divergent species did not share common egg envelope antigens, and that their use may not be appropriate in the investigation of immunoinfertility and immunocontraception in humans.

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.

Anti-seminal plasma antibodies associated with infertility: II. Comparative investigation of human antibody binding to normo-, astheno-, and azoospermic seminal plasma antigens

PROBLEM

Sera from infertile patients with elevated reactivity against normozoospermic seminal plasma (NSP) have been selected to investigate human antibody binding to seminal fluid antigens present in abnormal ejaculates.

METHOD

Sera from 32 idiopathically infertile patients and 44 control sera from fertile individuals were examined by ELISA against: 1) pooled seminal plasma from asthenozoospermic ejaculates (AsthSP), 2) pooled seminal plasma from patients with aspermatogenic azoospermia (AzooSP), and 3) chromatographic fractions from NSP, AsthSP and AzooSP.

RESULTS

Of 32 patients positive for anti-NSP antibodies, only four exhibited increased reactivity to whole AsthSP and/or AzooSP, while 14 recognized antigens of different Mr and various distributions in the corresponding chromatographic fractions.

CONCLUSION

Targets of human anti-NSP antibodies might be lacking, less concentrated, and/or modified in AsthSP and AzooSP. These findings suggest their physiological importance and the possible relevance of the observed auto- and iso-immune responses to infertility.

A novel approach to the generation of antibodies against phylogenetically preserved sperm antigens

Conventional methods for immunization of laboratory animals against human spermatozoa proved not to be efficient enough to identify phylogenetically conserved sperm-specific antigens. A combination of vasectomy and subcutaneous administration of autologous testis homogenates was tested in 5 New-Zealand rabbits, and in 7 Long-Evans and 8 Spraque-Dawley rats in an attempt to induce an autoimmune response against such antigens. This experimental procedure resulted in a generation of sperm autoantibodies cross-reactive with human, rabbit and rat spermatozoa, as demonstrated by sperm-agglutination, ELISA and flow cytometry (FCM). No specific binding to human seminal plasma was detected by ELISA, indicating that intrinsic sperm membrane antigens rather than sperm-coating antigens were involved in establishing cross-reactivity with human spermatozoa. This suggestion was confirmed by the finding that rabbit autoantisera reacted more strongly against epididymal than against ejaculated human spermatozoa as shown by FCM. Humoral antispermatozoal response correlated well with impaired spermatogenesis in rabbits. The autoimmunized rats revealed severe alterations in reproductive tissues, including testicular and epididymal sperm granulomas; however, they showed a lower incidence of circulating antibodies. The results indicate that the established experimental model in rabbits can be further used to identify and characterize evolutionary preserved intrinsic sperm membrane autoantigens, which are desirable candidates for contraceptive vaccine development.

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.