The relationship of circulating antisperm antibodies to sperm surface antibodies in infertile men

Integrated transcriptomics and proteomics assay identifies the role of FCGR1A in maintaining sperm fertilization capacity during semen cryopreservation in sheep

Semen cryopreservation is a promising technology employed in preserving high-quality varieties in animal husbandry and is also widely applied in the human sperm bank. However, the compromised qualities, such as decreased sperm motility, damaged membrane structure, and reduced fertilization competency, have significantly hampered the efficient application of this technique. Therefore, it is imperative to depict various molecular changes found in cryopreserved sperm and identify the regulatory network in response to the cryopreservation stress. In this study, semen was collected from three Chinese Merino rams and divided into untreated (fresh semen, FS) and programmed freezing (programmed freezing semen, PS) groups. After measuring different quality parameters, the ultra-low RNA-seq and tandem mass tag-based (TMT) proteome were conducted in both the groups. The results indicated that the motility (82.63% ± 3.55% vs. 34.10% ± 2.90%, p < 0.05) and viability (89.46% ± 2.53% vs. 44.78% ± 2.29%, p < 0.05) of the sperm in the FS group were significantly higher compared to those in the PS group. In addition, 45 upregulated and 291 downregulated genes, as well as 30 upregulated and 48 downregulated proteins, were found in transcriptomics and proteomics data separately. Moreover, three integrated methods, namely, functional annotation and enrichment analysis, Pearson's correlation analysis, and two-way orthogonal partial least squares (O2PLS) analysis, were used for further analysis. The results suggested that various differentially expressed genes and proteins (DEGs and DEPs) were mainly enriched in leishmaniasis and hematopoietic cell lineage, and Fc gamma receptor Ia (FCGR1A) was significantly downregulated in cryopreserved sperm both at mRNA and protein levels in comparison with the fresh counterpart. In addition, top five genes (FCGR1A, HCK, SLX4, ITGA3, and BET1) and 22 proteins could form a distinct network in which genes and proteins were significantly correlated (p < 0.05). Interestingly, FCGR1A also appeared in the top 25 correlation list based on O2PLS analysis. Hence, FCGR1A was selected as the most potential differentially expressed candidate for screening by the three integrated multi-omics analysis methods. In addition, Pearson's correlation analysis indicated that the expression level of FCGR1A was positively correlated with sperm motility and viability. A subsequent experiment was conducted to identify the biological role of FCGR1A in sperm function. The results showed that both the sperm viability (fresh group: 87.65% ± 4.17% vs. 75.8% ± 1.15%, cryopreserved group: 48.15% ± 0.63% vs. 42.45% ± 2.61%, p < 0.05) and motility (fresh group: 83.27% ± 4.15% vs. 70.41% ± 1.07%, cryopreserved group: 45.31% ± 3.28% vs. 35.13% ± 2.82%, p < 0.05) were significantly reduced in fresh and frozen sperm when FCGR1A was blocked. Moreover, the cleavage rate of embryos fertilized by FCGR1A-blocked sperm was noted to be significantly lower in both fresh (95.28% ± 1.16% vs. 90.44% ± 1.56%, p < 0.05) and frozen groups (89.8% ± 1.50% vs. 82.53% ± 1.53%, p < 0.05). In conclusion, our results revealed that the downregulated membrane protein FCGR1A can potentially contribute to the reduced sperm fertility competency in the cryopreserved sheep sperm.

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.

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.

Varicocele-related infertility is not associated with increased sperm-bound antibody

Immunological factors have been implicated as a cause of unexplained infertility. Previous studies have demonstrated increased levels of sperm-bound antibody in infertile men with varicoceles and have postulated their role in varicocele-related infertility. However, these studies were performed using an enzyme-linked immunosorbent assay. We evaluated retrospectively 111 male patients referred for infertility using a direct immunobead assay. Of the patients 29 had grade II or III varicoceles (that is palpable or easily visualized) and 82 were without varicocele. Four patients who had undergone vasovasostomy were included as controls for the assay. A direct immunobead assay was performed for isotype IgG and IgA sperm-bound antibody using a standard protocol. A computerized semen analysis was also performed. Greater than 20% binding, excluding tail tip activity, was considered significant. Of 29 patients with and 82 without a varicocele significant binding was identified in 5 (17%) and 9 (11%), respectively. Chi-square statistical analysis did not reveal this difference to be significant (p < 0.05). All 4 vasovasostomy patients demonstrated significant binding. We conclude from this study that infertile men with varicoceles do not demonstrate significantly increased levels of sperm-bound antibody compared to infertile controls and, therefore, sperm-bound antibody does not appear to have a significant role in varicocele-related infertility.

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.

Male infertility: current concepts

The purpose of the article is to review the current concepts regarding the etiology and treatment of male-factor infertility. The following general conclusions can be drawn: (a) conventional parameters for sperm quality and male fertility are inadequate and any assessment should involve several different tests of sperm cell function to increase the fertility prognosis; (b) the causes of disturbed sperm quality are still poorly understood; (c) the role of the varicocele is still controversial but some of the discrepancies reported in the literature may be explained by the negative influence of other factors such as smoking, epididymal pathology or glandular infections operating either in conjunction or independent of the varicocele; (d) the role of chronic inflammatory processes in the reproductive organs, in particular the involvement of chronic chlamydial infections, has been underestimated, largely because it is often asymptomatic and difficult to demonstrate objectively; (e) partial androgen insensitivity may account for a significant number of cases of severe oligozoospermia; (f) no major advances have been made in the medical treatment of poor sperm quality; (g) assisted fertilization techniques such as IVF and GIFT offer encouraging possibilities for the treatment of male-factor infertility; and (h) recent advances in microsurgical techniques are increasing the treatment possibilities for certain forms of obstructive azoospermia and severe oligozoospermia.

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

Anti-sperm antibodies were eluted from the sperm cell fraction of autoimmune human ejaculates and transferred onto normal motile spermatozoa. The movement and the acrosomal status of these antibody-coated spermatozoa were evaluated after incubation in a capacitating medium. The amplitude of lateral head displacement (ALH) and the straight line velocity (VSL) were analyzed using an HTM automated motility analyser. Acrosomal loss was monitored by an FITC-conjugated lectin binding technique. During the 6-h incubation in BWW-BSA medium, antibody-free and antibody-coated spermatozoa exhibited significant changes of ALH and VSL distribution that evolved differently in the two populations. The dynamics of sperm movement in control spermatozoa were apparently modified by the presence of antibodies on the sperm membrane. The low percentage of spontaneous acrosomal loss obtained in control populations, even after 20 h of incubation, was not modified by the presence of antibodies on spermatozoa. However, the same antibodies decreased the acrosomal loss induced by a calcium ionophore after 3 h of incubation in capacitating conditions. These results suggest that sperm capacitation and acrosome reaction, considered as essential for successful fertilization, can be altered by antisperm antibodies present on human ejaculated spermatozoa.

A comparison of the usefulness of SpermMar and immunobead tests for the detection of antisperm antibodies

We compared two testing protocols designed to detect immunoglobulin (Ig) G antibodies on sperm surfaces: (1) SpermMar (Ortho, Raritan, NJ) and (2) Immunobead Testing (Biorad, Richmond, CA). The standard SpermMar (SPMAR) protocol (direct test of unwashed semen) was performed with 47 ejaculates and found to be more sensitive than Immunobead Testing (IBT) on washed sperm, detecting five samples with greater than or equal to 30% bead binding, all of which by IBT had less than 20% bead binding. In contrast, when SPMAR was performed on washed sperm or with an indirect antibody transfer from serum or seminal plasma, SPMAR results gave mostly low values for bead binding in comparison with IBT. Our data suggest that SPMAR be used only in direct assays employing unwashed ejaculates, that it can be easily incorporated into routine semen analysis as a screening test, and that positive results should be confirmed by IBT (IgG and IgA).

Immunological status of patients before and after vasovasostomy as determined by the immunobead antisperm antibody test

With the immunobead antisperm antibody test a prospective study was conducted to evaluate the immune status of 55 men before and after vasectomy reversal. A third of the vasectomy patients (19 of 55) had significant serum-sperm antibodies (20 per cent binding or more) detected by the indirect immunobead antisperm antibody test. Of 31 vasovasostomy patients 12 (38 per cent) had significant sperm-surface antibodies (20 per cent binding or more) by the direct immunobead antisperm antibody test. Preoperative serum assays correctly classified the antibody status of 69 per cent of the vasectomy patients. The immunological impact of spermatic granuloma formation, duration of vasal obstruction, patient age and presence of sperm in the vasal fluid at operation also were assessed. An inverse relationship between the proportion of antibody-bound sperm and the percentage of motile sperm in the ejaculate of vas reversal patients was found with videomicrographic semen analysis. The percentage motility was significantly lower among patients with greater quantities of sperm-surface antibodies. No other parameter of semen analysis showed this difference when compared for positive or negative immunobead antisperm antibody test results.