Studies of a sperm/placenta cross-reacting antigen, STX-10

Molecular nature of a sperm acrosomal antigen recognized by HS-13 monoclonal antibody

Among the numerous monoclonal antibodies generated against human sperm antigens, HS-13 monoclonal antibody was shown to react with an intra-acrosomal antigen from human, mouse and rat. In this study, HS-13 was used as the affinity ligand for the purification of the cognate antigen from human sperm by immunoaffinity chromatography. The purified cognate antigen from human sperm, designated as HSAg-13, was found to be a protein with a molecular weight of approximately 80 kDa on SDS-PAGE in the presence of reducing reagents. This monoclonal antibody was used as the probe to study the tissue distributions and developmental expression of the cognate antigen from human, mouse and rat by immunohistochemical assays. It was concluded that the antigen recognized by HS-13 antibody is highly sperm specific and found only in sperm and mature testis, but not in any other somatic tissues examined in human and mouse. The antigen was shown to be expressed at the postmeiotic stages of spermatogenesis in mouse and rat. By using indirect immunofluorescent staining assay, HS-13 was shown to react only with the methanol-fixed acrosome-intact sperm but not with the live sperm. Following calcium ionophore A23187 treatment, acrosome-reacted sperm showed either negative staining or residual staining in the equatorial region, suggesting the intra-acrosomal location of HSAg-13. The spontaneous acrosome reaction following overnight incubation in BWW medium resulted in a statistically significant decrease of antibody-stained human sperm. In view of excellent correlations for the scoring of acrosome-intact sperm with that of fluorescence-labeled Pisum sativum agglutinin (PSA) probe, HS-13 monoclonal antibody can be routinely used for monitoring sperm capacitation and acrosome reaction.

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.

Immune interferon gamma inhibits translational mobility of a plasma membrane protein in preimplantation stage mouse embryos: a T-helper 1 mechanism for immunologic reproductive failure

OBJECTIVE

Immune interferon gamma adversely affects mouse embryo development and has been proposed as a mediator of reproductive failure involving T-helper 1 immunity. We hypothesized that one mechanism by which interferon gamma could exert an adverse effect on embryos was by altering plasma membrane organization and transmembrane protein mobility.

STUDY DESIGN

The fluorescence photobleaching recovery technique was used to measure the effect of the T-helper 1 cytokine interferon gamma on the translational mobility of a specific embryonic surface glycoprotein recognized by the monoclonal antibody S75.

RESULTS

Compared with controls interferon gamma significantly decreased the fractional mobility of fluorescein isothiocyanate S75 in one- and two-cell mouse embryos.

CONCLUSION

Interferon gamma may alter plasma membrane domains or cytoskeletal organization in early-stage embryos. By restricting plasma membrane protein mobility interferon gamma could effect T-helper 1-mediated reproductive failure.

Epitope analysis of a sperm acrosomal antigen defined by HSA-5 monoclonal antibody

Among the monoclonal antibodies recommended by the WHO Sperm Antigen Workshop for immunocontraceptive vaccine development, HSA-5 showed a high degree of sperm specificity and significantly inhibited in vitro fertilization in both humans and mice. Using a Western blot assay, HSA-5 was found to recognize a sperm antigen designated as HSAg-5 (human) or MSAg-5 (mouse) which ranged in molecular weight from 18 to 100 kDa. This monoclonal antibody was used as the probe for the immunoscreening of mouse testis cDNA libraries constructed in the lambda gt-11 expression vector. One of the positive cDNA clones was shown to have a cDNA insert of approximately 1 kb and to encode a recombinant fusion protein containing 77 amino acid residues in the C-terminal region of MSAg-5. This 1 kb cDNA insert was engineered in a pGEX vector to express a recombinant glutathione S-transferase fusion protein (GST-5). Using an enzyme-linked immunosorbent assay (ELISA) and Western blot analysis, both anti-GST-5 sera and the monoclonal antibody were shown to react with GST-5. The Northern blot of a mouse testis RNA preparation revealed that the isolated cDNA probe hybridized with a 4.0 kb mRNA. Several oligopeptides were synthesized based on the predicted C-terminal hydrophilic regions of the recombinant fusion protein. Using ELISA and a dot blot assay, peptide regions containing the immunogenic epitopes recognized by HSA-5 monoclonal antibody were identified.

Purification and characterization of a sperm antigen recognized by HSA-5 monoclonal antibody

Among the monoclonal antibodies generated against acrosome-reacted human sperm, HSA-5 was shown to react with a sperm antigen localized predominantly to the equatorial region of the acrosome of human sperm and to the head and tail of mouse sperm. This antibody reacted with the methanol-fixed sperm, but not with fresh live sperm. When purified by immunoaffinity column, a major protein band with a molecular mass of approximately 100 kDa on SDS gel was isolated from fresh human sperm extract. The immunospecificity of isolated human sperm protein to this monoclonal antibody was verified by enzyme-linked immunosorbent assay and Western blot analysis. This antigen, designated as HSA-5, was susceptible to proteolytic degradation and revealed multiple immunoreactive bands in Western blot analyses of some preparations. Mouse sperm homogenates showed a similar polymorphic pattern to that of human samples. The tissue specificity of this antigen was examined immunohistochemically using various mouse and human tissues. HSA-5 did not cross-react with any other tissues except for sperm in adult testes and epididymis. This antibody also showed no binding activity to testicular tissue sections from mice of 13 and 21 days of age. The results of our study suggest that the sperm antigen recognized by HSA-5 monoclonal antibody is a differentiation antigen, which is expressed postmeiotically in testicular sperm but not in any somatic tissues.

Generation and characterization of monoclonal antibodies specific to surface antigens of human trophoblast cells

PROBLEM

To generate and utilize specific monoclonal antibodies for routine fetal cell isolation from the maternal circulation.

METHODS

Monoclonal antibodies specific to human trophoblast cell surface antigens were generated and characterized. After cell fusion, antibodies secreted by hybridomas were screened by enzyme-linked immunosorbent assay and immunohistochemical assays.

RESULTS

By using cultured BeWo choriocarcinoma cells or the membrane fraction of human placenta as the immunogen, seven (BW-108, 110, 123, 124, HP-15, 16 and 17) antibodies specific to the surface antigens of trophoblast were produced. They were shown to have little cross-reactivity to other human tissues. Among the antibodies raised against human sperm, HSA-10 was also found to cross-react with human trophoblast, but not detected in other tissues. When immobilized to magnetic beads, these antibodies were shown to react only with BeWo cells in suspension, but not blood cells and ovarian carcinoma cell line, OC-3-VGH.

CONCLUSION

Therefore, these antibodies may have potential application in fetal trophoblast cell isolation from the maternal circulation for prenatal genetic diagnosis.