Effect of ionophore challenge on hamster egg penetration and acrosome reaction of antibody-coated human sperm

Antisperm antibodies and conception

Sperm have been known to be antigenic for more than a century. There is a strong body of evidence that in humans and in other species at least some antibodies that bind to sperm antigens can cause infertility. Therefore, these antibodies are of interest today for two practical reasons. Firstly, the association of the antibodies with infertility means that they must be detected and then the couples treated appropriately. Secondly, because these antibodies can induce infertility they have the potential to be developed for contraceptive purposes in humans and also for the control of feral animal populations.

Localization of binding sites of naturally occurring antisperm antibodies on human spermatozoa by immunofluorescence

Antisperm antibodies (ASA) may affect sperm motility, acrosome reaction, sperm penetration of cervical mucus, binding to the zona pellucida, and sperm-egg fusion. We investigated the localization of ASA of infertile men or men after vasectomy bound on the sperm surface using an immunofluorescence method. Binding occurred in the acrosomal region, midpiece, and tail. Most of the ASA in both groups of patients bound to the midpiece alone or in combination with other regions of spermatozoa. Only few ASA samples showed binding to all the three sperm regions. A combination of binding to the acrosomal region and to the midpiece was never observed. In infertile patients with ASA, the binding site was compared with sperm parameters. ASA binding to the sperm head influenced the acrosome reaction. Binding of ASA on tail and/or midpiece was not associated with a significant alteration of viability and motility. Immunofluorescence appears to be a valuable tool in the diagnosis of immune infertility, in particular when impairment of the acrosome activity is suggested.

Clinical associations and mechanisms of action of antisperm antibodies

OBJECTIVE

To review and critique the current English literature describing the effects of antisperm antibodies (ASA) on mammalian fertility.

DESIGN

A comprehensive English language literature was searched using Medline and by hand-searching. Emphasis was placed on clinically relevant articles.

RESULT(S)

Results from the studies were extrapolated and the effects of ASA on fertility described.

CONCLUSION(S)

Antisperm antibodies may interfere with fertility. Not all ASA cause infertility. Current tests cannot differentiate the infertility-related ASA from those that do not interfere with infertility, because the antigenic specificities of these ASA are not known. The antigens which the infertility-related ASA must be characterized to allow an accurate detection and proper treatment for couples with ASA.

Characterization of spermatozoa surface antigens by antisperm antibodies and its influence on acrosomal exocytosis

PROBLEM

Antisperm antibodies (ASA) are the main cause of immunological infertility, they impair sperm functions by binding to the sperm membrane. The aim of this study was to characterize highly enriched sperm membrane proteins by 2-D-electrophoresis and to identify membrane antigens binding ASA and to evaluate the influence of ASA on the acrosome reaction (AR).

METHOD OF STUDY

Sperm membrane proteins were separated by 2-D-electrophoresis and antigens were identified by immunoblotting with ASA from seminal plasma samples of infertile men. The influence of ASA on the AR were observed and determined by means of flowcytometry.

RESULTS

A total of 18 antigens were identified by using ASA from seminal plasma. Six of the recognized proteins were analyzed by means of mass spectrometry and peptide matching: HSP70 and HSP70-2, disulfide-isomerase-ER60, caspase-3 and two subunits of the proteasome (component-C2 and zeta-chain). ASA from seminal plasma are able to enhance the AR in donor-spermatozoa.

CONCLUSION

The biochemical identification of these proteins will be helpful to understand the mechanism by which ASA impair sperm function and the fertilization process. Spermatozoa, in which the AR was prematurely induced by ASA, will not be able to fertilize anymore.

Influence of antisperm antibodies on the acrosome reaction as determined by flow cytometry

OBJECTIVE

To evaluate the influence of antisperm antibodies on the acrosome reaction (AR).

DESIGN

Clinical study.

SETTING

University of Marburg, Department of Andrology, Clinical Training Center of the European Academy of Andrology.

PATIENT(S)

Spermatozoa from a pool of healthy donors were incubated with 30 seminal plasma samples from infertile men containing antisperm antibodies; they were compared to a control group of 10 samples without antisperm antibodies and five samples with buffer only.

INTERVENTION(S)

The spontaneous acrosome reaction (SAR) and the induced acrosome reaction (IAR) by calcium ionophore A23187 were observed and determined by means of a flow cytometer. Flow cytometric double-staining estimates of acrosomal integrity were determined by using a monoclonal antibody (TUS 19), marked with a secondary fluorescein isothiocyanate-labeled antibody. Cell viability was determined by counterstaining with propidium iodide (PI).

MAIN OUTCOME MEASURE(S)

Number of acrosome reacted spermatozoa.

RESULT(S)

The spermatozoa treated with antisperm antibodies showed significantly higher SAR and IAR responses than the control group.

CONCLUSION(S)

Some of the antisperm antibodies from individual patients are able to enhance the acrosome reaction in donor sperm, but none of them appeared to inhibit acrosome reaction.

Interference of antisperm antibodies with the induction of the acrosome reaction by zona pellucida (ZP) and its relationship with the inhibition of ZP binding

OBJECTIVE

To determine whether antisperm antibodies can interfere with the induction of the acrosome reaction (AR) by the zona pellucida (ZP) and whether this interference also can occur in the absence of an inhibitory effect on ZP binding.

DESIGN

Prospective in vitro study.

SETTING

A tertiary care center, the Andrologic Clinic, University of L'Aquila.

PATIENT(S)

Sera from 12 infertile patients with high titers of circulating antibodies directed against the sperm head were studied.

INTERVENTION

None

MAIN OUTCOME MEASURE(S)

The effect of antisperm antibodies on ZP binding was evaluated by matching antibody-exposed and nonexposed donor sperm suspensions labeled with fluorescein or rhodamine, respectively, and incubated with the same salt-stored human ZPs. The effect of antibodies on ZP-induced AR was determined by challenging antibody-exposed and nonexposed donor sperm suspensions with human ZPs disaggregated with acidic NaH2PO4. Acrosomal status was evaluated using fluorescein-labeled Pisum sativum agglutinin and supravital stain Hoechst 33258. In some selected cases, the effect of antisperm antibodies on the acrosomal status of sperm bound to intact ZP also was evaluated using transmission electron microscopy.

RESULT(S)

Five of 12 sera exhibited an inhibitory effect on ZP binding. An inhibition of AR induction by disaggregated ZPs (ranging from 64% to 98%) was produced by all 5 sera with an inhibitory effect on ZP binding and by 2 of 7 sera without an inhibitory effect on ZP binding. The different effects of antisperm antibodies on AR induction by disaggregated ZP were confirmed by comparing with ultrastructural evaluations on the acrosomal status of sperm bound to intact ZP.

CONCLUSION(S)

Antisperm antibodies can interfere with the induction of AR by ZP. This inhibition can occur even in the absence of an inhibitory effect on ZP binding. Neither effect may occur.

Infertility due to antisperm antibodies

Immunoinfertility is an important problem, involving a significant number of infertile couples. Although the presence of antibodies on sperm has better prognostic value than those in serum or seminal plasma, it may not be the sole authentic evidence of immunoinfertility. Infertility from antisperm antibodies is likely only when they bind to a relevant sperm antigen involved in a specific fertility function. The variance in functional deficits seen in immunologic infertility is most likely related to antibodies directed at different sperm antigens or different class, subclass, or isotypes. Antibodies to FA-1 seem to be of significant importance in human immunoinfertility. In approaching couples with infertility, a high index of suspicion for antibodies is necessary to avoid misdiagnosis. In the optimal situation, all semen analyses should be screened for sperm-bound antibodies, but if this is impractical, testing should be performed on high-risk individuals (Table I). In couples in which the man has sperm-bound antibodies, and in whom there is no identifiable female factor, treatment should be instituted. Most treatments for immunoinfertility have been disappointing because of poor results, adverse effects, or high cost. Corticosteroid therapy has shown some promise in published reports (mostly poorly designed studies), but increase in pregnancy rate is modest and adverse effects may be significant. In our opinion, informed consent should be documented prior to institution of corticosteroid therapy, and subjects should be closely monitored. Advanced reproductive technologies offer a higher safety profile, and, with increasing technology, higher pregnancy rates. We recommend progressing from "low-tech" procedures, such as IUI and reserving the higher level procedures, such as IVF and ICSI, for those couples in whom pregnancy does not occur. The highest level reproductive technologies give the best current prospects for pregnancy in patients with this difficult problem but also are invasive and costly. It is hoped that further work in the laboratory will give rise to newer, safer, and less expensive effective treatments in the very near future.