Effect of sperm-associated antibodies on the dynamics of sperm movement and on the acrosome reaction of human spermatozoa

Germ cell-specific localization of immunoreactive riboflavin carrier protein in the male golden hamster: appearance during spermatogenesis and role in sperm function

Riboflavin carrier protein (RCP) is a phosphoglycoprotein (37 kDa) that is well studied in chicken. An immunologically cross-reacting protein was identified in mammals and active immunization of male rats and bonnet monkeys with chicken RCP lead to an approximately 80% reduction in fertility. However, the physiological mechanism responsible for inhibition of male fertility has not been investigated. Moreover, information on the cell type-specific localization and the origin of immunoreactive RCP during spermatogenesis is extremely limited. Hence, studies were carried out to determine the pattern of expression of immunoreactive RCP during spermatogenesis and its role in sperm function in the golden hamster. Immunoreactive RCP was germ cell-specific, found to be associated with the acrosome-organizing region of early spermatids and showed interesting patterns of immunolocalization during late stages of spermiogenesis. Mature spermatozoa exhibited acrosome-specific localization, mainly in the peri-acrosomal membrane. The immunoreactive protein was undetectable in (non)gonadal somatic cells tested. The protein had a molecular mass of 45-55 kDa and was biosynthesized by round spermatids. The acrosome-specific localization of immunoreactive RCP was unchanged during capacitation, but it was substantially lost during acrosome reaction. Functional studies indicated that treatment of spermatozoa with anti-RCP antibodies did not have any effect on either capacitation or acrosome reaction, but markedly reduced the rate of sperm penetration into zona-free hamster oocytes. These results show the existence of male germ cell-specific immunoreactive RCP, having a potential role in sperm-egg interaction in hamsters. Also the pattern of immunoreactive-RCP localization makes it an ideal marker to monitor development of acrosome in mammalian spermatozoa.

Sperm immobilizing antibodies in the sera of infertile women cause low fertilization rates and poor embryo quality in vitro

PROBLEM

The effects of sperm immobilizing antibodies in the sera of infertile women on fertilization and embryo quality in vitro were investigated.

METHOD OF STUDY

Before the introduction of sperm immobilization test (SIT) as a routine test for female infertility, 85 oocytes were collected in nine in vitro fertilization (IVF) cycles from four infertile women who were afterward found having had sperm immobilizing antibodies in their sera and the oocytes were inseminated with swim-up sperm in a medium containing the patient's serum. Fifty oocytes were collected in five IVF cycles from five infertile women possessing the antibodies in their sera and the oocytes were inseminated with swim-up sperm in a medium supplemented with human serum albumin (HSA).

RESULTS

In the former group, 41 of 85 oocytes were fertilized, giving a fertilization rate of 48.2%. In the latter group, 43 of 50 oocytes were fertilized, giving a fertilization rate of 86.0%. There was a significant difference of the fertilization rate between the groups (P < 0.0001). Embryo quality was assessed by the Veeck's classification. The grade 1 and grade 2 embryos were considered good quality. Using this classification, 16 (39.0%) of 41 embryos incubated in the medium containing the patient's serum were good quality, while 34 (79.1%) of 43 embryos incubated in the medium supplemented with HSA were good quality. There was also a significant difference between the groups (P = 0.0003).

CONCLUSIONS

These findings might indicate that sperm immobilizing antibodies in the sera of infertile women cause low fertilization rates and poor embryo quality in vitro. It is suggested that SIT in the sera of infertile women should be performed at least before proceeding IVF. The manipulation of gametes and embryos from patients having sperm immobilizing antibodies should be carefully carried out especially to avoid contaminating patient's serum and follicular fluid in the culture medium in order to have a better IVF result.

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.

Ultrasound, antisperm antibody, and hormone profiles after testicular Trucut biopsy

OBJECTIVE

To assess the effect of Trucut needle biopsy on the ultrasound appearances of the testis in obstructive and nonobstructive azoospermia to test serum samples for antisperm antibodies and gonadotropin and testosterone levels.

DESIGN

Prospective case analysis.

SETTING

IVF unit.

PATIENT(S)

Sixteen subjects with obstructive azoospermia had postbiopsy ultrasound scans, 18 had assessment of hormone profiles, and 20 had evaluation of antisperm antibodies.

INTERVENTION(S)

Trucut needle testicular biopsies under local anesthetic.

MAIN OUTCOME MEASURE(S)

Postbiopsy testicular ultrasound, the presence of serum antisperm antibodies, and follicle stimulating and luteinizing hormone and testosterone levels.

RESULT(S)

There were no postbiopsy hematomas or scars, antisperm antibodies did not develop, and pituitary gonadotropins did not rise nor testosterone levels fall.

CONCLUSION(S)

Trucut needle testicular biopsy in men with obstructive azoospermia is not associated with defects of parenchymal structure or function.

Isolation and characterisation of two sperm membrane proteins recognised by sperm-associated antibodies in infertile men

Antisperm antibodies eluted from the surface of spermatozoa obtained from infertile men recognised several common epitopes. We tested whether these epitopes were relevant to fertility by isolating the immunodominant 37/36 and 19/18 protein zones. These protein zones were cut out of preparative slab gels and electro-eluted. The isolated proteins, P36 and P18, were used for biochemical characterisation and to produce specific antibodies in rabbits. The specific reactivity of P36 and P18 with WGA and AAL lectins, respectively, indicated the presence of lactosaminyl structures with sialic acid termini in P36 and of fucosylated residues in P18. Isoelectric focusing showed that the two proteins consist of several polypeptides. Some of these polypeptides were recognised by both human and rabbit antibodies: the pl of these epitopes was around 5.5 for P36 and 8.3-10.3 for P18. Rabbit antibodies detected the corresponding proteins on the sperm heads of methanol-fixed and of live acrosome-reacted spermatozoa. Anti-P36 antibodies bound mainly to the equatorial segment. They reduced the binding and, consequently, the penetration of zona-free hamster oocytes by human spermatozoa. Anti-P18 antibodies gave more diffuse staining of the acrosomal and post-acrosomal regions and reduced sperm-oocyte penetration without a significant effect on sperm binding. These results suggest that P36 and P18 antigens located in different compartments of the sperm head may participate in the sperm-oolemma interaction. We are currently investigating the physiological role of these antigens by sequencing the proteins isolated from the gels.

Fertilization antigen-1 removes antisperm autoantibodies from spermatozoa of infertile men and results in increased rates of acrosome reaction

OBJECTIVE

To determine if fertilization antigen (FA)-1 will remove autoantibodies from the surface of sperm cells of immunoinfertile men by immune adsorption and permit an increased acrosome reaction (AR).

DESIGN

Prospective analytic study.

SETTING

University medical center.

PATIENT(S)

Men from 18 infertile couples with autoantibodies present on their spermatozoa.

INTERVENTION(S)

Sperm samples after processing were examined for antibody binding and AR before and after adsorption with control medium or FA-1.

MAIN OUTCOME MEASURE(S)

Sperm-bound antibody was assessed by the immunobead assay (immunoglobulin [Ig] A and IgG) and the AR by induction with ionophore A23187.

RESULT(S)

Adsorption with FA-1 compared with control medium increased immunobead-free swimming sperm an average of 50% and 76% for IgA and IgG antisperm antibodies, respectively, with 78% and 100% of the 18 semen specimens increasing significantly. The AR rate increased an average of 10.3% compared with control medium and showed improvement in 78% of the sperm samples after FA-1 adsorption.

CONCLUSION(S)

The FA-1 sperm antigen appears to significantly free sperm cells coated with autoantibodies in the semen of most infertile men examined. Reducing sperm-bound antibodies that inhibited the AR allowed the sperm cells to undergo successful AR induction by calcium ionophore.

Male immunologic infertility: sperm performance on in vitro fertilization

OBJECTIVE

To analyze sperm performance in a group of patients with male immunologic infertility treated with IVF-ET.

DESIGN

Retrospective clinical study.

SETTING

Patients attending a private IVF clinic.

PATIENT(S)

The study group comprised seven men with significant levels of surface-bound antisperm antibodies treated in nine IVF cycles. The control group comprised nine couples with female tubal infertility and no indication of male factor infertility treated on the same cycle.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Fertilization rate, early embryonic development, implantation, and clinical pregnancy rate (PR).

RESULT(S)

Forty-six (44.2%) of 104 inseminated oocytes were fertilized in the study group compared with 65 (84.4%) of 77 in the control group, which was a significant difference. Surface-bound antisperm antibodies significantly inhibited early embryonic cleavage in the study group (13 [28.3%] of 46 embryos with at least 3 blastomeres) compared with the control group (41 [63.1%] of 65 embryos, with at least 3 blastomeres). The percentage of good-quality embryos (grades 1 and 2) was similar in the study and control groups (71.7% and 78.5%, respectively). The percentage of poor-quality embryos (grade 4 and two pronuclei) was higher in the study group compared with the control group (13.9% versus 9.2%, respectively); however, the difference was not significant. The implantation rate and clinical PR were lower in the study group (3% and 11%, respectively) compared with the control group (9.5% and 44%, respectively), but the difference was not statistically significant.

CONCLUSION(S)

The fertilization rate and early embryonic cleavage of human embryos was found to be reduced significantly in patients with high levels of surface-bound antisperm antibodies. Moreover, embryonic quality and the PR may be compromised by the presence of significant levels of surface-bound antisperm antibodies.

Sperm-associated and circulating IgA and IgG classes of antibodies recognise different antigens on the human sperm plasma membrane

IgA and IgG antibodies eluted from the surface of spermatozoa obtained from 11 infertile men were used to analyse the antigens defined by each class of sperm-associated antibodies. An enhanced chemiluminescent Western blot technique was developed to detect the low concentrations of immunoglobulins present in the eluted samples. The same analysis was performed with the sperm membrane-specific antibodies isolated from the sera of 8 of the patients included in the study. Sperm-eluted antibodies reacted with a total of 18 protein bands migrating with molecular masses of between 110 and 18 kDa. Individual antibody-binding patterns differed. Furthermore, IgA and IgG antibodies from any one patient recognised different sets of antigens. In spite of the apparent heterogeneity of the antigens defined by sperm-associated antibodies, the majority of these antibodies reacted with three protein zones of 68/64, 37/36 and 20/18 kDa. The antigens defined by the sperm surface-specific antibodies obtained from the sera of eight infertile patients differed from one patient to another and, in the majority of the patients, differed from those defined by the corresponding sperm-associated antibodies. Nevertheless, two protein zones of 68/64 and 20/18 kDa were recognised by both local and systemic antibodies in 6 and 4 patients, respectively.

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.

The effect of the antisperm auto-antibody-bound sperm on in vitro fertilization outcome

To evaluate the effects of antisperm auto-antibody-bound sperm on the outcome of in vitro fertilization-embryo transfer (IVF-ET), 160 infertile couples undergoing treatment by in vitro fertilization were recruited in this study. In the study group (11 couples, 15 cycles), the male partners were positive for antisperm autoantibodies determined by immunobead test (IBT). In the control group (149 couples, 152 cycles), the men had no such antibodies. The percentages of fertilization rate, cleavage rate and pregnancy rate of the study group and control group wer 75.0 +/- 5.2% vs. 69.3 +/- 2.4%; 82.8% +/- 3.7% and 6.7% +/- 11.8%, respectively. There were no significant differences in in vitro region, type and/or percentage of sperm-bound antibodies also had no effect on the in vitro fertilization outcome. In conclusion, in vitro fertilization-embryo transfer is not significantly affected by antisperm autoantibody-bound sperm determined by immunobead test.

Co-expression of mannose-ligand and non-nuclear progesterone receptors on motile human sperm identifies an acrosome-reaction inducible subpopulation

PROBLEM

To determine whether surface expression of receptors for progesterone and mannose can be used to identify spermatozoa likely to undergo an acrosome reaction after zona binding and to compare the reactivity of these receptors with naturally occurring sperm head-directed anti-sperm antibodies (ASAs).

METHOD

Progesterone binding sites on the surface of fresh and capacitated motile human sperm in relation to acrosome status were visualized using a cell-impermeant progesterone. Free progesterone and/or mannose ligands were compared for percent sperm binding and ability to induce an acrosome reaction. Western blots of sperm proteins localized to the plasma membrane and surface proteins precipitated following passive transfer of serum ASAs were probed with progesterone-horseradish peroxidase. The effects of the same ASAs on ligand binding and on the induced acrosome reaction were examined.

RESULTS

The two receptors are located in close proximity on a subset of capacitated motile sperm and are coordinately cleared from the plasma membrane overlying the acrosomal cap prior to exocytosis. The surface appearance of functional binding sites for each ligand, however, is regulated by different mechanisms and the progesterone receptor alone is specifically precipitated by ASAs. Passive transfer of ASAs to capacitated sperm selectively inhibits the progesterone-stimulated acrosome reaction but not the ionomycin-induced acrosome reaction or the ability of sperm to bind mannose ligands.

CONCLUSIONS

Sperm from fertile donors incubated under capacitating conditions in vitro can be subdivided into acrosome reaction inducible and noninducible subpopulations on the basis of the co-expression or total absence of these receptors. The combined data indicate that reaction of sperm surface progesterone receptors with ASAs contributes to the acrosome reaction insufficiency observed in anti-sperm immune infertility.

The effect of pentoxifylline on in-vitro fertilization in the presence of anti-sperm antibodies

In cases of severe immunological male-factor infertility, impairment of spermatozoal motility and of acrosome reaction resulting in reduced fertilization capacity have been described by several authors. The present study investigated the use of pentoxifylline in enhancing in-vitro fertilization (IVF) in the presence of anti-sperm antibodies. Thirty-seven IVF cycles were conducted in 28 different couples suffering from immunological male-factor infertility with at least 50% antibody-coated spermatozoa. Sibling oocytes were inseminated at random with spermatozoa incubated with or without 3.6 mM pentoxifylline after selection by a Percoll gradient. No difference in motility of the final sperm preparations was observed prior to insemination. Fertilization rate, cleavage rate and embryo quality were similar in both treatment and control groups. Nine out of ten pregnancies were achieved after the replacement of embryos both from the treatment and control group. Although pentoxifylline is known to enhance motility in-vitro and to promote induced acrosomal loss, its indiscriminate use failed to improve IVF performance in patients with anti-sperm antibodies. Further research may be necessary in order to elucidate whether a given subpopulation of these patients may benefit from a selective application of pentoxifylline.

Fertilization efficiency of morphologically abnormal spermatozoa in assisted reproduction is further impaired by antisperm antibodies on the male partner's sperm

OBJECTIVE

To investigate the influence of antisperm antibodies on the sperm surface on the outcome of IVF and GIFT.

DESIGN

Matched controlled retrospective review of two large series.

SETTING

Reproductive endocrine divisions of two level-three academic centers.

PATIENTS

Twenty-nine male factor patients (38 IVF cycles) showing positive antisperm antibodies on the sperm by immunobead test treated by IVF at the Norfolk program and 56 similar patients (57 cycles) treated by GIFT at the Tygerberg program. Twenty-nine male factor patients (29 IVF cycles) with negative antisperm antibodies screening matched by wife's stimulation protocol and baseline semen analysis characteristics were used as controls in Norfolk; 56 GIFT patients (56 GIFT cycles) matched similarly were the Tygerberg controls. Study and control groups were divided according to sperm morphology pattern in normal, good, and poor prognosis subgroups for comparison.

MAIN OUTCOME MEASURES

Fertilization rate of preovulatory oocytes used in IVF in Norfolk and of GIFT supernumerary preovulatory oocytes in Tygerberg; total and term pregnancy rates (PRs) and abortion rates.

RESULTS

Fertilization rate was significantly lower in the IVF (41.9% +/- 2.8%) as well as in the GIFT (26.8% +/- 3.8%) (mean +/- SE) study groups than in the respective control groups (73.1% +/- 3.9% and 61.8% +/- 3.9%). Total and term PRs in IVF per cycle (21.1% +/- 6.6%; 13.2% +/- 5.5%) and per transfer (23.5% +/- 7.4%; 14.7% +/- 6.1%), and in GIFT (25.0% +/- 5.8%; 19.6% +/- 5.3%) in the study groups were also lower when compared with their control counterparts (IVF per cycle: 62.1% +/- 6.2% and 41.4% +/- 6.0%; IVF per transfer: 41.9% +/- 2.0% and 27.9% +/- 1.9%; GIFT: 31.6% +/- 6.2% and 28.1% +/- 6.0%), but the difference did not reach statistical significance. Abortion rates were similar in the IVF study group (37.5% +/- 17.1%) and its control groups (39.9% +/- 11.5%). The abortion rate in the GIFT study group was 14.3% +/- 9.4%, and no abortions were recorded in the control group (not significant).

CONCLUSIONS

The presence of antisperm antibodies on the sperm surface per se impairs the outcome of assisted reproduction, mainly in terms of fertilization rate of preovulatory oocytes, and possibly in terms of total and term PRs. This holds true regardless of the impact of other semen parameters, particularly the morphology of the sperm within the semen sample.

Effect of sperm-associated antibodies on human sperm ability to bind to zona pellucida and to penetrate zona-free hamster oocytes

Antibodies directed against sperm membrane antigens located mainly over the sperm heads were eluted from the sperm cell fraction of autoimmune ejaculates and transferred to antibody-negative spermatozoa of fertile donors. The ability of these antibody-coated spermatozoa to bind to the human zona pellucida and to penetrate zona-free hamster oocytes was evaluated in vitro. The majority of the sperm-eluted samples contained both IgA and IgG antibodies. In order to evaluate the effect of each class of antibody on the analyzed sperm functions, each isotype was specifically absorbed before transfer. Sperm-binding to salt-stored zona pellucida, as assayed by FITC and TRITC labeling of antibody-free and antibody-coated spermatozoa incubated with the same zona, was consistently reduced by 60-85% by the five eluted samples tested. Removal of either IgA or IgG antibodies from the eluted samples did not change the overall effect. Sperm penetration of zona-free hamster eggs was variously affected by sperm-associated antibodies. Of the 8 samples of sperm-eluted antibodies tested, only 4 had a significant effect on sperm penetration. Three of them decreased the penetration by 67-78%, while the fourth exhibited a modest increasing effect of 39%. These four samples contained antibodies of the two isotypes. In the samples with a decreasing effect, the elimination of one or another of the two isotypes restored the ability of the sperm to penetrate the hamster oocytes. These results suggest that sperm-associated antibodies may have different effects on zona-binding and gametic fusion events that lead to fertilization. Whereas IgA and IgG antibodies taken together or separately decreased sperm binding to the human zona pellucida, the two classes of antibodies must be associated in order to impair sperm penetration into zona-free hamster oocytes.

Localization of antibodies on spermatozoa and sperm movement characteristics are good predictors of in vitro fertilization success in cases of male autoimmune infertility

OBJECTIVE

To define sperm factors related to in vitro fertilization (IVF) failure in cases of antisperm autoimmunity.

DESIGN

A detailed analysis of sperm morphology, movement characteristics, acrosomal function, and antibody binding was performed on the sperm population selected on a discontinuous two-layer Percoll gradient and used for IVF. The results were compared retrospectively between fertilizing (n = 13) and nonfertilizing (n = 11) sperm populations.

PATIENTS

Twenty-one infertile couples undergoing 24 cycles of IVF treatment because of antisperm autoimmunity were included in this study.

RESULTS

Fertilizing and nonfertilizing sperm populations were not different with respect to the percentage of motility, the normal morphology, the multiple anomalies index, the acrosome abnormalities, and the spontaneous or induced acrosome reaction. If the proportion of spermatozoa coated with either immunoglobulin (Ig)A or IgG antibodies was similar in the two groups, their localization was often different: antibodies were mainly on the sperm heads in the cases of fertilization failure. There were significant differences between fertilizing and nonfertilizing sperm samples in several movement parameters. Among them, the amplitude of lateral head displacement (ALH) was the most significantly correlated with fertilization success. Finally, spermatozoa were poorly bound to the zona pellucida (ZP) when fertilization failed, whereas high numbers of spermatozoa were attached to the ZP when fertilization occurred.

CONCLUSION

Fertilization failure in patients with antisperm antibodies may be the result of several factors in which the impact of the antibodies on the membrane function play a critical role. Movement parameters, particularly the ALH and the localization of antibodies on migrated spermatozoa could predict the IVF failure or success more accurately than the proportion of antibody-coated spermatozoa in the inseminated populations. The fertilization failure was associated with an incapacity of spermatozoa to bind to ZP.