Evaluation of the acrosome reaction using monoclonal antibodies against different acrosomal antigens--comparison with the triple stain technique

Increased expression of secretory actin-binding protein on human spermatozoa is associated with poor semen quality

BACKGROUND

Antibodies to human sperm are useful diagnostic reagents for detection of changes in sperm protein expression and their relationship with sperm defects and male infertility. The specificity of Hs-16 monoclonal antibody (mAb) and the localization and frequency of the occurrence of Hs-16-recognized protein on human spermatozoa were investigated.

METHODS

Samples from 30 fertile men with normal spermiograms and 30 men with pathological spermiograms were studied. The specificity of Hs-16 mAb was analysed by the western blotting technique and matrix-assisted laser desorption/ionization mass spectrometry. Indirect immunofluorescence with Hs-16 antibody was used to test sperm ejaculates.

RESULTS

The Hs-16 antibody detected a human sperm and seminal plasma protein, which was determined to be secretory actin-binding protein (SABP). This specificity was also verified by co-localization of SABP and actin on spermatozoa with Hs-16 and anti-actin antibodies, and partial co-localization of these proteins was found. SABP was localized on the sperm tail, mainly in the midpiece of the tail. Other parts of spermatozoa were labelled with lower frequency. A significant difference was found in SABP labelling between men with normal spermiograms and donors with asthenozoospermia or oligoasthenoteratozoospermia (both P < 0.01), and asthenozoospermia versus oligoasthenoteratozoospermia (P < 0.05). Increased expression of SABP was observed in men with pathological spermiograms.

CONCLUSIONS

Hs-16 antibody reacts specifically with SABP. SABP can serve as a marker of defective sperm and may be associated with fertility failure.

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.

A novel method for evaluating the acrosomal status of mammalian spermatozoa

A novel method was developed to evaluate the acrosomal status of mammalian spermatozoa. The method is based on the ability of the lectin Pisum sativum agglutinin (PSA) to bind specifically to glycoproteins of the acrosomal matrix released during the acrosome reaction. The amount of released acrosomal content is proportional to the fraction of spermatozoa that underwent acrosome reaction. The released glycoproteins present in the supernatant separated from the cells were detected via an ELISA-like assay. The authors suggest that one of these glycoproteins might be the acrosin as identified by anti-acrosin antibodies, using Western blot analysis. The new method (demonstrated here with ram and bull spermatozoa) correlates well with the results obtained by conventional methods. Its advantages are simplicity, objectiveness, rapidity, and low cost. In addition, many samples can be processed in parallel. The method can be used in experimental as well as clinical applications.

Flow cytometric determination of binding of monoclonal antibodies to human spermatozoa

Although several monoclonal antibodies to sperm antigens are available, only few systematical reports on the appearance of distinct antibody binding structures in spermatozoa of infertile patients are available. We studied the binding frequency of six monoclonal antibodies (TUS-1, -2, -10, -17, -19, -20) by means of a flow cytometer in different semen samples and their possible relationship to other sperm parameters, in particular to the motility parameters as determined by computer-assisted semen analysis. The percentage of vital spermatozoa binding the different antibodies was 21.5% (TUS-2) to 52.1% (TUS-20). The percentage binding was higher in samples with normozoospermia than in those with oligo-asthenoteratozoospermia. A significant correlation occurred between sperm concentration and the percentage of spermatozoa stained by TUS-2 and TUS-17; between motile spermatozoa and those binding TUS-17 and TUS-20; the velocity average path and those binding TUS-17; an inverse correlation occurred between the morphologically-abnormal spermatozoa and those binding TUS-20; an inverse correlation between TUS-17 and acrosin. We conclude from our results that although the antigens of the antibodies concerned are not yet characterized, the determination of antibody binding will give additional information on the functional status during capacitation and acrosome reaction of spermatozoa.

Monoclonal antibodies as direct probes for human sperm acrosome reaction

PROBLEM

To develop simple and rapid assay procedures for determining human sperm acrosome reaction under various experimental conditions.

METHODS

Specific monoclonal antibodies against human sperm acrosome were generated and utilized as probes for acrosome reaction assays by direct labelling of antibodies with fluorescein-isothiocyanate (FITC).

RESULTS

Among the generated monoclonal antibodies, HS-63 was shown to react with antigens in the acrosome content of permeabilized acrosome-intact human sperm, but not with those of the live ones. HSA-10 was found to recognize antigens on the surface of sperm inner acrosome and to react with acrosome-reacted human sperm in suspension. Following a swim-up procedure, highly motile sperm were recovered and incubated in BWW medium at 37 degrees C for 18 h. The percentages of acrosome-reacted sperm were determined at various incubation times by using FITC-labeled HS-63 or HSA-10 as the indicators in 10 min direct immunofluorescent assay. With the FITC-labeled HS-63 probe, the percentage of positively stained human sperm fixed in methanol decreased significantly after 18 h of incubation from > 90 to 70-80%. In contrast, positively stained live human sperm by HSA-10 increased significantly from < 1% to 15-30%. A high correlation was obtained between the use of monoclonal antibodies and PSA (Pissum sativum agglutinin) for direct assessment of human sperm acrosome reaction.

CONCLUSION

In view of the simplicity in assay procedures and evaluations, these FITC-labeled monoclonal antibodies are reliable probes for direct assessment of acrosomal status of human sperm.

Effect of oocyte-sperm co-incubation on acrosome reaction in the goat

The induction of acrosome reaction of goat spermatozoa was investigated. The acrosomal status of spermatozoa was determined by a triple-staining technique. The effect of the presence of goat oocytes on the proportion of acrosome-reacted spermatozoa was also determined. Ovulated oocytes were obtained from superstimulated adult goats. Other sources of oocytes were adult and prepubertal goats; oocytes from both sources were maturated in vitro. There was an increase in the percentage of acrosome-reacted spermatozoa from 4% +/- 0.98 to 9% +/- 1.41 when oocytes from adult females were used. Similar induction rates were measured with prepubertal and adult oocytes maturated in vitro (10.4% +/- 2.06 and 8.75% +/- 1.06, respectively). The influence of several qualities of cumulus oophorus as well as the presence of zona pellucida was also investigated. No significant differences were obtained with any cumulus oophorus or zona pellucida oocyte complexes. Although oocyte quality is important for high fertilization rates, it does not seem to be crucial for the induction of acrosome reaction.

Acrobeads test using monoclonal antibody-coated immunobeads: clinical application

Acrosome-reacted sperm was examined in infertile and fertile males using the Acrobeads test. The Acrobeads score was significantly higher in fertile males than in infertile males with normal or abnormal seminal findings (p < .005 and p < .001, respectively). The Acrobeads score was 2 or more in all the fertile males, but 62% of the infertile males with abnormal seminal findings (p < .02). Therefore, a disturbance in the acrosome reaction is suggested to be one of the causes of decreased fertility potential. A high correlation was found between Acrobeads score and sperm motility (r = .46, p < .001) or motile sperm concentration (r = .51, p < .0001). The Acrobeads test, the results of which reflect the acrosome condition of the sperm, is useful in the assessment of sperm function related to fertility.

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.

Comparison of a fluoresceinated lectin stain with triple staining for evaluating acrosome reactions of dog sperm

In this study a technique which utilized a fluoresceinated lectin and a fluorescent supravital stain was compared with the conventional triple stain technique for evaluating the viability and acrosomal status of dog sperm. Ten semen samples obtained from 6 normal beagle dogs were evaluated after incubation in vitro with canine capacitation medium. Sperm viability and acrosomal status were assessed at 0, 4, and 7 hours of incubation. Both staining techniques were capable of detecting the increase in spontaneous acrosome reactions which occurs during in vitro capacitation of dog sperm. High positive correlations were observed between the fluorescent stain and the triple stain in the mean values for the percentage of viable sperm and for the percentage of acrosome-reacted sperm among the viable sperm (r = 0.91, r = 0.97, respectively). However, the fluorescent staining techniques could be carried out much more rapidly than the triple stain technique, and the slides prepared with fluorescent stain were more easily scored because of the higher intensity and greater consistency of staining. These characteristics make the fluoresceinated lectin and the fluorescent supravital stain superior for evaluating acrosome reactions and viability of dog sperm.

Acrosome-reacted sperm in infertile and fertile men using the triple-stain technique

By means of a triple-stain technique, the acrosome reaction in infertile and fertile males was investigated. The highest correlations with the percentage of acrosome-reacted sperm were found for motile sperm concentration (r = .60, p < .01) and percent motility (r = .58, p < .05). Significant correlations were also demonstrated between acrosome reactivity and both sperm concentration (r = .50, p < .05) and velocity (r = .40, p < .05). There was only a weak correlation between the percentage of acrosome-reacted sperm and that of swollen sperm. The ratio of acrosome-reacted sperm demonstrated in oligoasthenozoospermic patients was significantly lower than that observed in normozoospermic or fertile males (both, p < .05). There was no significant difference in the ratio of acrosome-reacted sperm between normozoospermic and fertile males. However, all the cases in the latter group had 15% or more acrosome-reacted sperm, whereas the parameter was widely distributed in the former group and some in this group had a decreased ratio. It would appear that a disturbance of the acrosome reaction is one of the causes of reduced fertility potential in normozoospermic males.