Monoclonal antibody against human sperm acrosome inhibits sperm penetration of zona-free hamster eggs

The conserved fertility factor SPACA4/Bouncer has divergent modes of action in vertebrate fertilization

Fertilization is the fundamental process that initiates the development of a new individual in all sexually reproducing species. Despite its importance, our understanding of the molecular players that govern mammalian sperm-egg interaction is incomplete, partly because many of the essential factors found in nonmammalian species do not have obvious mammalian homologs. We have recently identified the lymphocyte antigen-6 (Ly6)/urokinase-type plasminogen activator receptor (uPAR) protein Bouncer as an essential fertilization factor in zebrafish [S. Herberg, K. R. Gert, A. Schleiffer, A. Pauli, Science 361, 1029-1033 (2018)]. Here, we show that Bouncer's homolog in mammals, Sperm Acrosome Associated 4 (SPACA4), is also required for efficient fertilization in mice. In contrast to fish, in which Bouncer is expressed specifically in the egg, SPACA4 is expressed exclusively in the sperm. Male knockout mice are severely subfertile, and sperm lacking SPACA4 fail to fertilize wild-type eggs in vitro. Interestingly, removal of the zona pellucida rescues the fertilization defect of Spaca4-deficient sperm in vitro, indicating that SPACA4 is not required for the interaction of sperm and the oolemma but rather of sperm and the zona pellucida. Our work identifies SPACA4 as an important sperm protein necessary for zona pellucida penetration during mammalian fertilization.

Characterization of monoclonal antibodies specific for human sperm: effect of CRL-10 on acrosome reaction

Monoclonal antibodies to human sperm were obtained from hyperimmunized BALB/c mouse spleen cells fused with myeloma NS-1 cells. Each antibody recognized definite regions in fresh unfixed sperm: equatorial region, acrosome, postacrosome, midpiece, tail. All the antibodies were specific for sperm. We selected CRL-10 monoclonal antibody, specific for acrosome, for a detailed study. The expression of the CRL-10 antibody-bound antigen was detected in other mammalian species. When CRL-10 antibody was added prior to sperm incubation in a capacitating medium, promotion of the acrosome reaction was observed.

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.

Inhibition by anti-sperm monoclonal antibodies of the penetration of zona-free hamster oocytes by human spermatozoa

Fourteen mAb specific for human sperm membrane antigens were selected to investigate their inhibitory effect on fertilization. The antigens were not expressed in other human somatic tissues but were present in sperm from other species. The antibodies were purified from ascites fluid produced in mice. The zona-free hamster egg penetration assay was used for the evaluation of the blocking ability of these antibodies. The inhibition rate was generally related to a decrease in the number of adherent sperm. Three groups of antibodies were distinguished: (i) four mAb that have high inhibition at any concentration; (ii) four mAb with an intermediate inhibitory effect, that is more dependent on the antibody concentration tested; and (iii) six mAb with little or no effect at any concentration. The presence of antibodies leads to a lower penetration index, or number of penetrating sperm per oocyte. MAb specific for head antigens promote high inhibition of fertilization; these antibodies show a patchy staining on the sperm head. The antibodies localized in the midpiece have an intermediate inhibitory effect. No inhibition is detected with the equatorial region binding pattern. Sperm agglutination does not play any role in the inhibition caused by the antibodies described here.

The fertilization antigen-1 does not have proteolytic/acrosin activity, but its monoclonal antibody inhibits sperm capacitation and acrosome reaction

OBJECTIVE

To determine if human sperm surface fertilization antigen exhibits proteolytic or acrosin activity and to investigate the mechanism(s) whereby monoclonal antibody (mAb) to fertilization antigen inhibits human sperm penetration of zona-free hamster ova.

DESIGN

Proteolytic and acrosin activities of human fertilization antigen were determined. Acrosomal status, acrosin activity, and motion characteristics were evaluated after incubation of human sperm with immunoaffinity-purified mAb to fertilization antigen.

SETTING

Academic research environment.

PARTICIPANTS

Fertile donors used as controls for infertile patients for fertility evaluation.

INTERVENTIONS

Human spermatozoa were treated with mAb to fertilization antigen and induced to undergo acrosome reaction using calcium ionophore A23187.

MAIN OUTCOME MEASURES

Proteolytic and acrosin activities of fertilization antigen. Sperm penetration assay, acrosomal status, and motion parameters.

RESULTS

Fertilization antigen does not exhibit proteolytic or acrosin activity; however, its mAb completely blocks human sperm penetration of zona-free hamster ova. The mAb to fertilization antigen inhibits ionophore-induced acrosome reaction and blocks development of the hyperactivated state of human sperm cells.

CONCLUSIONS

Monoclonal antibody to fertilization antigen blocks fertilization by inhibiting capacitation and acrosome reaction.

Antisperm antibody binding to human acrosin: a study of patients with unexplained infertility

OBJECTIVE

Antisperm antibody binding to acrosin was investigated by Western Blotting. The clinical significance of this binding specificity was assessed in a 2-year clinical follow-up.

DESIGN

Consecutive serum samples positive for antisperm antibodies by both enzyme-linked immunosorbent assay and immunobead testing were evaluated for acrosin-binding specificity.

SETTING

The patients were followed in an outpatient setting by private infertility specialists.

PATIENTS

Sixty-five consecutive infertile referral patients with positive antisperm antibody were evaluated. Clinical follow-up was obtained on 8 of 9 females with evidence of antibody binding to acrosin and 19 of 26 females with no specific binding to acrosin.

INTERVENTIONS

Prednisone therapy was given during six courses of intrauterine insemination with husband's sperm. All treatment decisions were made by private physicians independent of the acrosin-binding result.

MAIN OUTCOME MEASURES

Pregnancy status was obtained as part of a 2-year follow-up.

RESULTS

Acrosin-binding specificity was demonstrated in 10 (15%) of the 65 patients. Two of the 8 women (25%) with antibody binding to acrosin and 6 of the 19 women (32%) with antisperm antibodies but no specific binding to acrosin delivered normal children.

CONCLUSIONS

Although antibody-binding specificity to acrosin could be demonstrated, a 2-year clinical follow-up showed no difference in pregnancy rates when compared with women with antisperm antibodies showing no binding specificity to acrosin.

GDA-J/F7 monoclonal antibody: a new marker for sperm cell precursors in human semen

Germ cells isolated from semen of oligospermic human donors were found to react with GDA-J/F7 monoclonal antibody (MoAb). Their reactions with this antibody were demonstrated by using fluorescein activated cell sorter (FACS) analysis and indirect immunofluorescence (IIF) test. In the IIF test, the MoAb recognised an antigen on the surface of the sperm cell precursors (SpP) as well as on mature spermatozoa. The specificity of the antibody reaction with the SpP was further confirmed by immunoelectron microscopy. The MoAb did not react with peripheral blood lymphocytes or polymorphonuclear cells but did show cross-reactivity with monocytes. This antibody therefore provides the first marker for the SpP and could be used as a probe for their distinction from leucocytes. This could have clinical application in seminal analysis.