Characteristics of monoclonal antibodies reactive with human sperm and seminal plasma

The characteristics of monoclonal antibodies developed against human spermatozoa are described. Out of 10 monoclonal antibodies 9 did not react in ELISA with human RBC, WBC, platelets, Raji cells nor mouse sperm. Four monoclonal antibodies reacted with monkey sperm and all 10 reacted with human seminal plasma. Monoclonal antibodies showed differential reactivity with pre- and post-capacitated sperm. Four monoclonal antibodies were able to agglutinate sperm whereas none of these were positive in sperm-immobilization assay. Interestingly, two monoclonal antibodies (MA-46 and MA-50) were able to block the attachment of pre-capacitated sperm to zona denuded hamster oocytes. MA-46 and MA-50 recognized in immunoblot spermatozoa antigens having apparent molecular weights of 14 and 20 K Da and greater than 200 K Da respectively. The monoclonal antibodies reported in this study will be useful in further delineating the spermatozoa antigens involved in regulation of fertility.     

Sterility due to inhibition of sperm motility by oral administration of benzene chromatographic fraction of the chloroform extract of the seeds of Carica papaya in rats.

The contraceptive effects of benzene chromatographic fraction of the chloroform extract of the seeds of Carica papaya have been reported in male albino rats at the dose regimens 5 and 10 mg/animal/day; oral for 150 days. The body weight, weight of testis, epididymis, seminal vesicle and ventral prostate remained unaltered during the entire course of the investigation. Total suppression of cauda epididymal sperm motility coincided with a decrease in sperm count, viability and an increase in per cent abnormal spermatozoa during 60-150 days observation period. Minor changes in the germ cell proliferations in the testis and vacuolization and pyknotic nuclei in the few epithelial cells of the cauda epididymis were observed. Histology and biochemical composition of testis and accessory sex organs, haematology and serum clinical biochemistry and serum testosterone levels remained unchanged throughout the course of the investigation. Test for estrogenicity indicated mild estrogenicity. Monthly fertility test showed negative fertility. All the altered parameters returned to normal level following 60 days withdrawal of the treatment. The results suggest that the benzene chromatographic fraction of the chloroform extract of the seeds of Carica papaya exerts antifertility effects in rats without adverse toxicity and that the effects may be directly rendered on the spermatozoa.     

A novel approach to the generation of antibodies against phylogenetically preserved sperm antigens

Conventional methods for immunization of laboratory animals against human spermatozoa proved not to be efficient enough to identify phylogenetically conserved sperm-specific antigens. A combination of vasectomy and subcutaneous administration of autologous testis homogenates was tested in 5 New-Zealand rabbits, and in 7 Long-Evans and 8 Spraque-Dawley rats in an attempt to induce an autoimmune response against such antigens. This experimental procedure resulted in a generation of sperm autoantibodies cross-reactive with human, rabbit and rat spermatozoa, as demonstrated by sperm-agglutination, ELISA and flow cytometry (FCM). No specific binding to human seminal plasma was detected by ELISA, indicating that intrinsic sperm membrane antigens rather than sperm-coating antigens were involved in establishing cross-reactivity with human spermatozoa. This suggestion was confirmed by the finding that rabbit autoantisera reacted more strongly against epididymal than against ejaculated human spermatozoa as shown by FCM. Humoral antispermatozoal response correlated well with impaired spermatogenesis in rabbits. The autoimmunized rats revealed severe alterations in reproductive tissues, including testicular and epididymal sperm granulomas; however, they showed a lower incidence of circulating antibodies. The results indicate that the established experimental model in rabbits can be further used to identify and characterize evolutionary preserved intrinsic sperm membrane autoantigens, which are desirable candidates for contraceptive vaccine development.     

Distribution of endogenous and exogenous 5′-nucleotidase on bovine spermatozoa

A polyclonal rabbit antibody against 5-nucleotidase purified from bull seminal plasma was used to localize the antigen on bovine spermatozoa. Spermatozoa taken from the ampulla of the vas deferens showed strong immunofluorescence at the anterior rim of the head portion. Evaluation of spermatozoa prepared from different segments of the seminal pathway indicated the presence of the antigen already in rete testis and epididymal spermatozoa. On cryostat sections of testis tissue a positive immunoreaction was found in the anterior head portion of elongated spermatids, but not in earlier forms of sperm development. This distribution corresponded with the enzyme activity and results of Western blotting in extracts of testicular and epididymal spermatozoa. Immunoelectron microscopy of ampullary spermatozoa using antibody detection with gold-labelled anti-rabbit IgG showed a clear-cut labelling of the plasma membrane in the acrosome region. Treatment of ampullary spermatozoa with 0.1% Triton X-100 did not completely remove the immunoreactive material from the acrosome, showing a very stable linkage of the protein to the plasma membrane. Treatment with phospholipase C from Bacillus thuringiensis, however, removed immunoreactive material from the plasma membrane, indicating its binding by a phosphoinositol anchor. Our findings show that endogenous 5-nucleotidase is present on the plasma membrane covering the anterior head portion of bovine spermatozoa and indicate specialized functions during the acrosomal reaction. Soluble enzyme derived from seminal vesicle secretion covers the whole sperm surface during emission, but is not covalently bound. It provides generalized enzyme activity to the sperm surface in addition to the specialized area of the sperm head.     

Binding of a 15 kDa glycoprotein from spermatozoa of boars to surface of zona pellucida and cumulus oophorus cells.

A highly purified 15 kDa glycoprotein isolated from ejaculated spermatozoa was used to raise antisera in female rabbits. An indirect immunofluorescence technique was used to detect the antigen in the seminal vesicle tissue and on the acrosomes of ejaculated, native and capacitated, boar spermatozoa. No immunoreactivity was detected on cells of the seminiferous tubules (spermatogonia, spermatocytes, and spermatids), on spermatozoa in the ductus epididymis and in cells of the epididymal and testicular tissues. These observations support the view that the 15 kDa protein is produced in the seminal vesicle secretory epithelium, and is attached to the sperm plasma membrane during the exposure of spermatozoa to seminal vesicle compounds. The observations that the antigen remained on the acrosome of ejaculated spermatozoa after capacitation and blocked sperm-oocyte binding in vitro suggest that the antigen plays a role in sperm-egg interactions. The strong immunoreactivity exhibited by cumulus cells after incubation of antisera with the porcine egg surrounded by cumulus cells shows the possible importance of the 15 kDa glycoprotein for contact of spermatozoa with cells of the cumulus oophorus surrounding the egg.     

Effect of antibodies against seminal vesicle secretion on fertility in the rat.

Fertile female Wistar rats were immunised against rat and mouse seminal vesicle secretion (SVS) to test the production of allo-antibodies and the effect of the antibodies elicited on fertility. Twenty-six per cent of the rat and mouse SVS-immunised females were infertile after the treatment. The sera were titrated by ELISA and used in Western blots to detect the proteins recognised. Although neither the antibody titres nor the proteins recognised by the sera showed a close relation with the degree of fertility, in all females the highest antibody titre in the fluids from the genital tract was found in the oviductal fluid and during the night of oestrus. This fact suggested that the site of action of the antibody could be the oviduct. Similar results were obtained using mouse SVS as immunogen--a fact that can be related to the antigenic similarity between the SVS of the two species. The antibodies react with the spermatozoa but not with eggs or embryos. Analyses performed on embryos collected from sterile females showed that there was a delay in fertilisation and normal embryogenesis. Our results suggest that SVS proteins are antigenic and that these antigens are bound to the spermatozoa and could take part in early pre-fertilisation events such as capacitation or sperm transport.     

Purification and partial characterization of the 17 kDa sperm coating protein from boar seminal plasma.

Sperm coating proteins of 16, 17, and 19 kDa have been purified from boar seminal plasma. The 17 kDa protein has been identified as an antigen recognized by monoclonal antibody ACR.3 and is thus identical to low molecular mass zona pellucida binding protein from boar spermatozoa (Moos et al., 1990). The 17 and 19 kDa proteins are glycosylated and tend to form hetero-complexes. The 17 kDa ACR.3 antigen is sequentially released from the sperm cell surface during capacitation and, after induction of the acrosome reaction, the 16 kDa form was also observed. Immunocytochemical studies on boar reproductive tissues have suggested that the seminal vesicle epithelium may be the source of these proteins.     

Sperm morphology of the neotropical harvestman Iporangaia pustulosa (Arachnida: Opiliones): comparative morphology and functional aspects

We describe herein the sperm morphology of the harvestman Iporangaia pustulosa. Adult males were dissected, the reproductive tract was schematized and the seminal vesicle was processed by light, transmission and scanning electron microscopy. The male reproductive tract is composed of a tubular testis, two deferent ducts, a seminal vesicle, a propulsive organ and a penis, similar to that observed in other Opiliones. The spermatozoa from the seminal vesicle are oval, aflagellate and immotile, presenting a nucleus surrounding an invagination of the cytoplasm, as well as a complex acrosome and projections on the cell surface. In the testis, spermatozoa are devoid of projections. In the seminal vesicle, they gradually acquire the projections with tufts adhering to it. Consequently, spermatozoa in various distinct stages of projection development can be found in the seminal vesicle. We believe that these projections (1) could help transport sperm along the male and perhaps female reproductive tracts; (2) are used to anchor the spermatozoa inside the female spermatheca in order to avoid mechanical displacement by the genitalia of other males and (3) may play a role in oocyte recognition. We propose that the evolution of aflagellarity in Opiliones is related to the unique morphology of the female reproductive tract. Since eggs are fertilized on the tip of the ovipositor just prior to being laid, there is no advantage favoring sperm mobility. Additionally, female sperm receptacles are small and males that produced small spermatozoa would have a higher chance of fertilizing more eggs.     

Purification and characterization of fertility‐associated antigen (FAA) in bovine seminal fluid

Heparin‐binding proteins (HBP) recognized by a monoclonal antibody (M1) are produced by male accessory sex glands and bind to distinct regions of ejaculated bull sperm. Immunoblots of sperm proteins probed with M1 identified HBP variants of approximately 31‐, 24‐, and 21.5‐kDa that were associated with increased fertility of bulls. The purpose of this study was to identify the 31‐kDa HBP known as fertility‐associated antigen (FAA). FAA was isolated by heparin‐affinity chromatography and reversed‐phase high performance liquid chromatography near homogeneity. Biochemical characterization indicated that FAA was an unglycosylated, basic protein. FAA protein was detected in seminal vesicle and prostate gland homogenates, and FAA extracted from sperm membranes by treatment with hypertonic media was identical biochemically to seminal fluid‐derived FAA. N‐terminal sequence analysis of purified FAA yielded a 26 amino acid sequence (L K I X S F N V R S F G E S K K A G F N A M R V I V) with 73% identity to a recently identified human deoxyribonuclease (DNase) I‐like protein. Two internal amino acid sequences generated from lys‐C digested FAA were 85% and 92% identical to the same DNase I‐like protein. In conclusion, we have identified a bovine seminal heparin‐binding protein that binds to sperm and is indicative of bull fertility as being similar to the family of DNase I‐like proteins. These data demonstrate the presence of a novel DNase I‐like protein in bull accessory sex glands and form the groundwork for the identification of a candidate genetic marker for fertility of bulls. Mol. Reprod. Dev. 54:145–153, 1999. © 1999 Wiley‐Liss, Inc.     

Antifertility effects in rats actively immunized with 80 kDa human semen glycoprotein.

A 80 kDa human sperm antigen has been identified using the serum of an infertile woman having circulating antisperm antibodies. The antigen was then purified to homogeneity by gel permeation chromatography using HPLC (protein PAK-125 column) system and on FPLC (superose-12 column) system. The antigen was found to be a glycoprotein. The antigen was mainly localized in the postacrosomal region of the human sperm, while it was localized in the head region of the rat sperm as demonstrated by immunofluorescent staining. The presence of this antigen was also demonstrated in the human prostate and endometrium and in the rat testis; epididymis and the prostate by immunocytochemical staining. The purified protein upon active immunization in female rats caused infertility in 100 percent animals. While in male rats it caused infertility in 90 percent animals. On morphometric analysis of testicular tissue it was observed that there was no significant change in spermatogonia and spermatocytes, but significant decrease in spermatids and sperm number as well as daily sperm production in the immunized male rats. The epididymal spermatozoa were markedly reduced in number and were largely found to be agglutinated. The results suggest that 80 kDa human sperm antigen appears to be a suitable candidate for immunocontraception both in male and female.     

Characterization of testicular mouse glucosamine 6-phosphate deaminase (GNPDA).

Mammalian glucosamine 6-phosphate deaminase (GNPDA) was first detected in hamster spermatozoa. To further elucidate its role, we have cloned mouse GNPDA and produced a polyclonal rabbit anti-GNPDA antibody. This antibody recognized a 33 kDa protein in soluble extracts from mouse brain, liver, kidney, muscle, ovary, testis and sperm. Immunofluorescent analysis of the localization of GNPDA in male reproductive tissue revealed its presence in spermatids and in spermatozoa. In spermatids, GNPDA localized close to the developing acrosome vesicle and in spermatozoa close to the acrosomal region. Following the induction of the acrosome reaction, GNPDA fluorescence in spermatozoa was either reduced or GNPDA was absent. These data suggest that GNPDA might play a role in the acrosome reaction.     

Intra-acrosomal 155,000 dalton protein increases the antigenicity during mouse sperm maturation in the epididymis: A study using a monoclonal antibody MC101

We found an intra-acrosomal antigen of about 155,000 daltons (155 kDa) in a survey using the monoclonal antibody MC101 raised against mouse cauda epididymal spermatozoa. Morphological studies by means of indirect immunofluorescence and immunogold electron microscopy localized the antigen to the cortex region of the anterior acrosome. Avidin biotin complex immunocytochemistry initially demonstrated a faint signal at the anterior acrosome in the testis spermatozoa that increased in intensity as the sperm moved toward the distal epididymis. This incremental immunoreactivity was also confirmed by immunoblotting following one-dimensional SDS-PAGE. The 155 kDa protein band was immunostained, and it was much more intense in the cauda epididymal than in the caput and corpus epididymal spermatozoa. Only a trace or no immunostain was evident in the caput or testis spermatozoa. The antigen localization did not change during passage through the epididymis, being confined at the cortex region of the anterior acrosome. The epididymal epithelial cells were not immunostained. These findings suggested that the 155 kDa protein is biochemically modified, further implying that the biochemical alteration of intra-acrosomal material is involved in sperm maturation in the epididymis. © 1995 wiley-Liss, Inc.     

Identification of a heparin-binding protein in bovine seminal fluid as tissue inhibitor of metalloproteinases-2

Presence or absence of three distinct bovine seminal heparin-binding proteins (21-31 kDa) recognized in sperm extracts by a monoclonal antibody, M1, is a diagnostic indicator of fertility differences among bulls producing normal semen. We recently identified a 31 kDa fertility-associated antigenin bovine seminal fluid as a unique DNase I-like protein. We now report purification and identification of a 24 kDa seminal heparin-binding protein (HBP-24) recognized by M1. N-terminal microsequence analysis of HBP-24 purified from seminal fluid yielded 20 amino acid residues that displayed 90% identity to the N-terminus of a bovine metalloproteinase inhibitor identified as tissue inhibitor of metalloproteinases-2 (TIMP-2). A single immunoreactive band migrating at 24 kDa was detected in Western blots of cauda epididymal sperm extracts following incubation with purified seminal heparin-binding proteins and subsequent washing in vitro, indicating TIMP-2 bound to sperm membranes. Expression of TIMP-2 mRNA was detected by RT-PCR in bovine bulbourethral gland, prostate, and seminal vesicles. Mobility of the 24 kDa heparin-binding protein increased under nonreducing SDS-PAGE to approximately 21 kDa, characteristic of the reported molecular mass of TIMP-2. To our knowledge, this is the first report of TIMP-2 binding to spermatozoa and of TIMP-2 mRNA expression in bovine accessory sex glands. These results corroborate previous reports regarding the site of production of heparin-binding proteins that are related to bull fertility, and suggest that TIMP-2 influences fertility of bulls, either through inhibition of metalloprotease activity in semen or via undefined activities independent of matrix metalloproteinase (MMP) inhibition.     

Localization and characterization of glutathione peroxidase (GPx) in boar accessory sex glands, seminal plasma, and spermatozoa and activity of GPx in boar semen

Boar ejaculate owes its characteristic large volume mainly to accessory sex gland (ASG) secretions. These are main contributors to the protective functions of seminal plasma, especially against oxidative damage. Numerous antioxidants have been detected in ASG secretions, and, respectively, in seminal plasma. However, as regards one key antioxidant protector -- the Se-dependent enzyme glutathione peroxidase (GPx) -- there is no agreement yet among researchers as to its presence in boar seminal plasma. Nevertheless, the beneficial effect of dietary Se supplementation on male fertility has been widely recognized. The aim of the present study was to investigate the localization and characterization of GPx in boar ASGs, seminal plasma, and spermatozoa, as well as to evaluate GPx activity in boar semen. Immunohistochemical assays demonstrated GPx presence in the epithelial cells, vacuole membranes, and vascular endothelium of boar seminal vesicle, prostate and bulbourethral glands. Western blot analysis demonstrated the presence of a monomer form of GPx with MW 20 kDa in lysates from seminal vesicle, prostate, bulbourethral glands, and spermatozoa, but not in seminal plasma. Surprisingly, peroxidase activity detected in seminal plasma from normal ejaculates was nearly three times as high as in spermatozoa. Our findings confirmed the presence of immunoreactive GPx in the boar reproductive tract, while further investigation is still warranted to uncover the exact protein forms involved and their function.     

Molecular cloning of an acrosomal sperm antigen gene and the production of its recombinant protein for immunocontraceptive vaccine

A monoclonal antibody, HS-63, which reacts specifically with a highly conserved sperm acrosome antigen, was shown to inhibit in vitro fertilization of mouse and human. The corresponding sperm antigen designated as MSA-63 was purified to homogeneity from mouse testes and used as an immunogen to generate polyclonal antisera in rabbits. The cDNA fragments of MSA-63 gene were cloned from mouse testis cDNA library by an immunoscreening method using polyclonal antisera specific for MSA-63. Using the established cDNA clone as a probe, the gene encoding for MSA-63 protein was found to be conserved among different mammalian species. Only one specific mRNA 1.5 kb in size was identified from the adult mouse testis among different mouse tissues. The recombinant fusion protein containing MSA-63 protein fragment was produced in Escherichia coli and used to immunize female mice. Similar to the original HS-63 monoclonal antibody, the antisera thus produced reacted only with the sperm acrosome and revealed significant inhibition to the in vitro fertilization of mouse oocytes. The results of this preliminary study suggest that it is feasible to mass produce sperm-specific antigens or their antigenic fragments by recombinant DNA technology for the development of sperm antigen-based immunocontraceptive vaccines.     

A novel asparaginase-like protein is a sperm autoantigen in rats

A novel asparaginase-like protein (ALP) of spermatozoa was cloned from rat and human testis cDNA libraries on the basis of reactivity with antibodies produced after vasectomy. Although obstruction of the male reproductive tract is known to cause an immunologic response, few of the sperm antigens responsible for the generation of autoantibodies have been characterized. We are identifying proteins of interest by coring autoantigenic protein spots from two-dimensional (2-D) gels of rat sperm extracts and microsequencing them by mass spectrometry. The peptide sequences from ALP, a 28 kDa, pI 5.7 protein, matched to a single partial length rat EST. These peptide sequences were used to clone a cDNA encoding a novel 333 amino acid open reading frame. The new protein had a similarity to portions of L-asparaginases of plants (43%) and to glycosylasparaginases in animal cells (32%). Human ALP cDNA was subsequently cloned. It showed 77% identity to the rat ALP sequence and the gene, ASRGL1 (asparaginase-like 1), mapped to chromosome locus 11q12.3. Purified recombinant rat ALP (rALP), expressed in E. coli, was used to raise polyclonal antiserum in guinea pigs. Two observations verified that the correct protein had been cloned: 1) the anti-rALP antibody reacted with both rALP and rat sperm; and 2) post-vasectomy sera bound rALP. Anti-rALP antibody stained the midpiece of rat and human sperm coincident with staining by MitoTracker Green FM, suggesting that ALP is associated with the mitochondria. Northern analysis revealed that rat ALP message was abundantly expressed in the testis but was also present in heart, brain, liver, skeletal muscle, and kidney.     

Analysis of a human sperm CD52 glycoform in primates: identification of an animal model for immunocontraceptive vaccine development

Sperm agglutination antigen-1 (SAGA-1) is a human male reproductive tract glycoform of CD52. Unique modification of CD52 N-linked oligosaccharide chains in the epididymis and vas deferens results in the appearance of a carbohydrate epitope that is localized over the entire surface of human spermatozoa. SAGA-1 was characterized by the sperm-inhibitory murine monoclonal antibody (mAb) S19, and it is the target antigen of a human mAb (H6-3C4) associated with antibody-mediated infertility. Collectively, sperm surface localization, antibody inhibition of sperm function, and potential reproductive-tissue specificity identify SAGA-1 as an attractive candidate contraceptive immunogen. To establish an animal model for the study of SAGA-1 in immunologic infertility and immunocontraceptive development, we investigated the appearance of the S19 carbohydrate epitope in nonhuman primates. The S19 mAb demonstrated little to no immunoreactivity by Western blot analysis with protein extracts of spermatozoa from the baboon, marmoset, bonnet, cynomolgus, and pigtailed macaques. Immunohistochemical analysis identified CD52 in the bonnet monkey epididymis; however, the N-linked carbohydrate moiety recognized by the S19 mAb, and unique to SAGA-1, was absent. In contrast, the S19 carbohydrate epitope was identified in chimpanzee sperm extracts by Western blot analysis and in chimpanzee epididymal tissue sections by immunohistochemical analysis, indicating that it is conserved in this close relative of the human. Chimpanzee testis, seminal vesicle, and prostate do not express the S19 epitope. Although anti-CD52 immunoreactivity was identified in the spleen, the carbohydrate moiety recognized by the S19 mAb was absent, corroborating data in the human that demonstrated tissue-specific glycosylation of sperm CD52. Immunofluorescent analysis indicated that the chimpanzee homologue of sperm CD52 was present over the entire spermatozoon. In addition, the S19 mAb agglutinated chimpanzee spermatozoa in a manner similar to the effect observed on human spermatozoa. These data indicate that the distinctive carbohydrate moiety of human sperm CD52 is present in the chimpanzee, and they identify the chimpanzee as the most appropriate primate model to study the potential of this unique CD52 glycoform as a contraceptive immunogen.     

Comparative studies of the antigens recognized by sperm-immobilizing monoclonal antibodies.

Characteristic properties of the antigens recognized by sperm-immobilizing monoclonal antibodies (SI-mAbs) from different sources were compared by ELISA competitive inhibition assay, Western blot analysis, chromatographic analysis, and enzymatic digestion studies. Among 9 SI-mAbs, human mAb H6-3C4 and three mouse mAbs--2C6, 2B6, and 2E5--also possessed strong sperm-agglutinating activity. Binding of human mAb H6-3C4 to sperm was strongly inhibited by the three mouse mAbs (2C6, 2B6, and 2E5), but not by the rat or the other four mouse mAbs. SDS-PAGE revealed that mAb H6-3C4 and three mouse mAbs recognized the same antigen molecules of 15-25 kDa present in both sperm extracts and seminal plasma. Chemical treatments with trifluoromethanesulfonic acid and sodium metaperiodate destroyed the antigen determinants recognized by the above four mAbs, as detected by both ELISA and antibody absorption tests. Western blot analysis revealed that the antigens were susceptible to treatments with papain, proteinase K, and N-glycanase, but resistant to trypsin, V8 protease, and thermolysin. These results indicate that one of the major antigens recognized by mAbs with sperm-immobilizing action may be a sperm membrane-associated glycoprotein of 15-25 kDa and the epitope may involve N-linked oligosaccharides.     

Immunocytochemical localization of uteroglobin in the genital tract of male rabbits

Summary Using the immunoperoxidase technique and specific goat antiserum to uteroglobin, selective immunochemical staining products are localized in the epididymal epithelium of the caput and proximal corpus region, at the adluminal border of the cauda epididymidis and, as well known, in epithelial cells of the endometrium of pregnant and progesterone-treated rabbits. Specific staining is also seen on spermatozoa. A uteroglobin-like antigen has been similarly localized in alveolar and bronchial epithelial cells of the lung. Testis, prostate, seminal vesicle and ductus deferens do not seem to contain in their tissues immunoreactive uteroglobin-like antigens. Similarly, the uterus and ductus epididymidis of immature rabbits are devoid of immunoreactivity. The presence of uteroglobin-like antigens in tissues other than the endometrium, particularly the ductus epididymidis, stimulates new discussions on the function of this protein in reproductive physiology and fertility research.