Cloning and sequencing of cDNAs coding for the human intra-acrosomal antigen SP-10

Immunocontraceptives: new approaches to fertility control

The rapidly increasing global population has bowed the attention of family planning and associated reproductive health programmes in the direction of providing a safe and reliable method which can be used to limit family size. The world population is estimated to exceed a phenomenal 10 billion by the year 2050 A.D., thus presenting a real jeopardy of overpopulation with severe implications for the future. Despite the availability of contraceptive methods, there are over one million elective abortions globally each year due to unintended pregnancies, having devastating impact on reproductive health of women worldwide. This highlights the need for the development of newer and improved contraceptive methods. A novel contraceptive approach that is gaining substantial attention is "immunocontraception" targeting gamete production, gamete outcome, or gamete function. Amongst these, use of sperm antigens (gamete function) seems to be an exciting and feasible approach. However, the variability of immune response and time lag to attain titer among vaccinated individuals after active immunization has highlighted the potential relevance of preformed antibodies in this league. This review is an attempt to analyze the current status and progress of immunocontraceptive approaches with respect to their establishment as a future fertility control agent.

Short toxin-like proteins attack the defense line of innate immunity

ClanTox (classifier of animal toxins) was developed for identifying toxin-like candidates from complete proteomes. Searching mammalian proteomes for short toxin-like proteins (coined TOLIPs) revealed a number of overlooked secreted short proteins with an abundance of cysteines throughout their sequences. We applied bioinformatics and data-mining methods to infer the function of several top predicted candidates. We focused on cysteine-rich peptides that adopt the fold of the three-finger proteins (TFPs). We identified a cluster of duplicated genes that share a structural similarity with elapid neurotoxins, such as α-bungarotoxin. In the murine proteome, there are about 60 such proteins that belong to the Ly6/uPAR family. These proteins are secreted or anchored to the cell membrane. Ly6/uPAR proteins are associated with a rich repertoire of functions, including binding to receptors and adhesion. Ly6/uPAR proteins modulate cell signaling in the context of brain functions and cells of the innate immune system. We postulate that TOLIPs, as modulators of cell signaling, may be associated with pathologies and cellular imbalance. We show that proteins of the Ly6/uPAR family are associated with cancer diagnosis and malfunction of the immune system.

Members of the murine Pate family are predominantly expressed in the epididymis in a segment-specific fashion and regulated by androgens and other testicular factors

BACKGROUND

Spermatozoa leaving the testis are not able to fertilize the egg in vivo. They must undergo further maturation in the epididymis. Proteins secreted to the epididymal lumen by the epithelial cells interact with the spermatozoa and enable these maturational changes, and are responsible for proper storage conditions before ejaculation. The present study was carried out in order to characterize the expression of a novel Pate (prostate and testis expression) gene family, coding for secreted cysteine-rich proteins, in the epididymis.

METHODS

Murine genome databases were searched and sequence comparisons were performed to identify members of the Pate gene family, and their expression profiles in several mouse tissues were characterized by RT-PCR. Alternate transcripts were identified by RT-PCR, sequencing and Northern hybridization. Also, to study the regulation of expression of Pate family genes by the testis, quantitative (q) RT-PCR analyses were performed to compare gene expression levels in the epididymides of intact mice, gonadectomized mice, and gonadectomized mice under testosterone replacement treatment.

RESULTS

A revised family tree of Pate genes is presented, including a previously uncharacterized Pate gene named Pate-X, and the data revealed that Acrv1 and Sslp1 should also be considered as members of the Pate family. Alternate splicing was observed for Pate-X, Pate-C and Pate-M. All the Pate genes studied are predominantly expressed in the epididymis, whereas expression in the testis and prostate is notably lower. Loss of androgens and/or testicular luminal factors was observed to affect the epididymal expression of several Pate genes.

CONCLUSIONS

We have characterized a gene cluster consisting of at least 14 expressed Pate gene members, including Acrv1, Sslp1 and a previously uncharacterized gene which we named Pate-X. The genes code for putatively secreted, cysteine-rich proteins with a TFP/Ly-6/uPAR domain. Members of the Pate gene cluster characterized are predominantly expressed in the murine epididymis, not in the testis or prostate, and are regulated by testicular factors. Similar proteins are present in venoms of several reptiles, and they are thought to mediate their effects by regulating certain ion channels, and are thus expected to have a clinical relevance in sperm maturation and epididymal infections.

Cloning and expression of SOLD1 in ovine and caprine placenta, and their expected roles during the development of placentomes

Background

The Ly-6 (Ly-6/uPAR) superfamily members share the Ly-6 domain defined by distinct disulfide bonding patterns between 8 or 10 cysteine residues. They comprise membrane- and secretory-type proteins. We recently reported the gene and protein characterization of the bovine secreted protein of Ly-6 domain 1 (SOLD1). Bovine SOLD1 is expressed in trophoblast mononucleate cells (TMCs) and is localized in the cotyledonary mesenchyme. Here, we compared the expression and functionality of SOLD1 among the ruminants. We examined mRNA expression by chorionic fibroblasts as a measure of one of the SOLD1 functions.

Results

Ovine and caprine SOLD1 mRNAs have 303 bp open reading frames and encode for deduced SOLD1 proteins with 100 amino acids, including a 22-aa-long signal peptide at the N-terminal. Both of the SOLD1 amino acid sequences have high similarities with the bovine sequence. Both SOLD1 mRNAs were also expressed in TMCs of cotyledons and intercotyledonary membranes. The mature SOLD1 proteins were localized in the mesenchymal villi of cotyledons after secretion. Bovine, ovine and caprine SOLD1 affected gene expression in mesenchymal fibroblasts in vitro; nucleoredoxin expression was upregulated and BCL2-like 13 was downregulated. Thus, we suggest that SOLD1 acts as a modulator of cell proliferation and apoptosis.

Conclusion

Expressing cells and protein localization of SOLD1 coincided among the three ruminants. SOLD1 participated in regulating nucleoredoxin and BCL2-like 13 expression in chorionic fibroblasts. SOLD1 is produced specifically in the cotyledons and intercotyledonary membranes in ruminants and appears to be involved in the construction of the ruminant placenta.

Characterization and expression analysis of SOLD1, a novel member of the retrotransposon-derived Ly-6 superfamily, in bovine placental villi

Background

Ly-6 superfamily members have a conserved Ly-6 domain that is defined by a distinct disulfide bonding pattern between eight or ten cysteine residues. These members are divided into membrane-type and secretory-type proteins. In the present study, we report the identification of a novel Ly-6 domain protein, secreted protein of Ly-6 domain 1 (SOLD1), from bovine placenta.

Principal Findings

SOLD1 mRNA was expressed in trophoblast mononucleate cells and the protein was secreted into and localized in the extracellular matrix of the mesenchyme in cotyledonary villi. SOLD1 bound mainly with type I collagen telopeptide. We confirmed secretion of SOLD1 from the basolateral surface of a bovine trophoblast cell line (BT-1). It may be related to the organization of the extra-cellular matrix in the mesenchyme of fetal villi. Since trophoblast mononucleate cells are epithelial cells, their polar organization is expected to have a crucial role in the SOLD1 secretion system. We established that SOLD1 is an intronless bovine gene containing the Alu retrotransposon, which was integrated via cytoplasmic reverse transcription.

Conclusion

We identified a novel retrotransposon-like Ly-6 domain protein in bovine placenta. SOLD1 is a crucial secreted protein that is involved in the organization of the mesenchyme of the cotyledonary villi. Furthermore, the gene encoding SOLD1 has an interesting genomic structure.

Sperm surface antigens and the prospects for contraceptive vaccine development

It has been estimated that 500 million couples world-wide have no access to contraception and that approximately 20% of births between 1995 and 2000 will be unwanted. Such statistics have important implications for the rate of world population growth and the possibility of maintaining a sustainable population. Although political change and the empowerment of women across the world will help address these issues, it will also be important to increase the availability of contraceptives; not only the modalities that are in current use, but also novel methods that will satisfy needs that are presently unfulfilled. One such alternative could be a vaccine targeting the human spermatozoon.

Spermatid-specific promoter of the SP-10 gene functions as an insulator in somatic cells

Spermatid differentiation markers such as the acrosomal protein SP-10 display remarkable testis- and germ cell-restricted gene expression. However, little is known about the mechanisms that prevent their expression in somatic tissues. We have previously noted that the -408/+28 or the -266/+28 promoter of SP-10 directed strictly spermatid-specific transcription in transgenic mice, Biol. Reprod. 61, 1256-1266). Lack of ectopic expression in these mouse lines implied that the SP-10 promoter might have protected the transgene from the influence of neighboring enhancers. The present study tested this directly by performing enhancer-blocking assays. In transiently transfected COS cells, the -408/-92 SP-10 promoter, but not stuffer DNA, blocked the transcriptional activity of a heterologous enhancer (CMV) in a position- and orientation-dependent manner. In transgenic mice, despite integration adjacent to the pan-active CMV enhancer, the -408/+28 promoter maintained spermatid-specificity and no ectopic expression of the transgene resulted. Enhancer blocking is a characteristic feature of insulators. Our results show that the SP-10 proximal promoter, which activates transcription in spermatids, functions as an insulator in somatic cells. Insulator activity mapped to the -186/-135 region and mutation of two ACACAC motifs compromised the insulator function. In conclusion, the evolutionarily conserved SP-10 insulator is novel and is the first one shown to regulate transcription of a germ cell differentiation marker.

Isolation and characterization of a human sperm antigen gene h-Sp-1

We isolated and characterized a human sperm antigen gene (h-Sp-1) from human testis complementary DNA using antiserum against the human sperm membrane. Northern blot analysis detected two transcripts (2.3 and 1.1 kb) of the h-Sp-1 gene. The 2.3-kb transcript is ubiquitous, whereas the 1.1-kb transcript is specific to the human testis with a high level of expression. Determination of the base sequence of h-Sp-1 showed a size of 2170 bp and 43.4% homology with human synaptophysin. The base sequence indicates a molecule consisting of 259 amino acids, with four hydrophilic and four hydrophobic regions. In order to further characterize the h-Sp-1 molecule, we synthesized the probable region of amino acids with high antigenicity based on the amino acid sequence (amino acid nos. 174-198) and immunized rabbits to prepare an antiserum. In our experimental model of fertilization between human sperm and zona pellucida-free hamster ova, partial inhibition of fertilization was observed. We were able to synthesize a large quantity of recombinant protein by inserting the h-Sp-1 gene into a baculovirus vector and infecting spodoptera frugiperda culture cells (sf9 insect cells). The synthesized protein had a molecular weight of 30 kDa. We then immunized Balb/c mice with this protein to prepare a monoclonal antibody (G3G9), which was used to localize the h-Sp-1 molecule in sperm and tissues (e.g. testis). The h-Sp-1 molecule was present in the cell membrane from the head to tail of human sperm. Staining of the testis and epididymis also showed h-Sp-1 to be present in spermatogonia, spermatocyte, sperm and epididymal duct epithelium. These findings suggest that the h-Sp-1 molecule is expressed in sperm and testes and plays a role in fertilization.

Identification of human sperm proteins involved in the interaction with homologous zona pellucida

OBJECTIVE

To identify human sperm proteins involved in homologous zona pellucida (ZP) interaction.

DESIGN

Prospective study.

SETTINGS

Basic research laboratory.

PATIENT(S)

Semen samples from normozoospermic donors, tissue sections from surgical pieces, and ZP from nonfertilized oocytes.

INTERVENTION(S)

Antibodies for sperm proteins (HSE; high salt extract) were developed (anti-HSE) and partially characterized. Participation of sperm proteins on ZP-interaction was tested with the hemizona assay (HZA). Antigens were immunolocalized in sperm and tissues.

MAIN OUTCOME MEASURE(S)

Sperm and tissue immunostaining; Western blotting; and number of sperm bound to the ZP.

RESULT(S)

Anti-HSE antibodies recognized several polypeptides in HSE (9 to 200 kd). Specific antibodies for 49 and 66 kd proteins (p49, p66) were obtained. Both (anti-p49 and anti-p66) stained the head of ejaculated and capacitated sperm. In the HZA, sperm preincubation with a mixture of anti-p49 and anti-p66 (100 micro g/mL) resulted in a decrease in the number of spermatozoa bound to the ZP. Presence of p66 (10 micro g/mL) inhibited sperm-ZP interaction. In contrast, p49 did not alter sperm binding to the ZP. Immunohistochemical analysis showed that p66 is present in the epididymis. No staining was observed in testicular sections.

CONCLUSION(S)

We found that p66 is an epididymal protein that participates in human sperm interaction with homologous ZP.

Transcriptional regulation of spermiogenesis: insights from the study of the gene encoding the acrosomal protein SP-10

Spermiogenesis is the terminal differentiation process of the male germ cell during which haploid spermatids acquire unique structures such as the acrosome and flagellum and undergo extensive cellular reorganization. Although well described morphologically, the molecular mechanisms underlying spermiogenesis are not well understood. The SP-10 gene, which codes for the acrosomal protein SP-10, has been well characterized in mice and men. This single copy gene is localized to syntenic regions of chromosomes 9 and 11 in mouse and human, respectively. The SP-10 gene is testis-specific, and is transcribed and translated in round spermatids. The differentiation marker SP-10 serves as a useful model to address questions regarding the regulation of round spermatid-specific gene transcription and acrosome biogenesis. This paper defines the temporal pattern of SP-10 gene expression during spermiogenesis and reviews the work done on analysis of the SP-10 promoter. Transgenic mice demonstrated that either the -408/+28 or the -266/+28 region of the SP-10 promoter could drive round spermatid-specific expression of a GFP reporter gene whereas the -91/+28 region lacked promoter activity. The transgene expression mimicked the spatial and temporal patterns of expression of the endogenous SP-10 gene. Surprisingly, none of the transgenic lines showed expression of GFP in tissues other than testis. Given the complexity of eukaryotic transcriptional regulation, the fact that a short 294-bp promoter is capable of conferring developmental stage- and cell type-specific transcription of a gene is intriguing and paradoxical.

A possible meiotic function of the peculiar patterns of gene expression in mammalian spermatogenic cells

This review focuses on the striking differences in the patterns of transcription and translation in somatic and spermatogenic cells in mammals. In early haploid cells, mRNA translation evidently functions to restrict the synthesis of certain proteins, notably protamines, to transcriptionally inert late haploid cells. However, this does not explain why a substantial proportion of virtually all mRNA species are sequestered in translationally inactive free-messenger ribonucleoprotein particles (free-mRNPs) in meiotic cells, since most mRNAs undergo little or no increase in translational activity in transcriptionally active early haploid cells. In addition, most mRNAs in meiotic cells appear to be overexpressed because they are never fully loaded on polysomes and the levels of the corresponding protein are often much lower than the mRNA and are sometimes undetectable. A large number of genes are expressed at grossly higher levels in meiotic and/or early haploid spermatogenic cells than in somatic cells, yet they too are translated inefficiently. Many genes utilize alternative promoters in somatic and spermatogenic cells. Some of the resulting spermatogenic cell-altered transcripts (SCATs) encode proteins with novel functions, while others contain features in their 5'-UTRs, secondary structure or upstream reading frames, that are predicted to inhibit translation. This review proposes that the transcriptional machinery is modified to provide access to specific DNA sequences during meiosis, which leads to mRNA overexpression and creates a need for translational fine-tuning to prevent deleterious consequences of overproducing proteins.

Molecular and immunological approaches to mammalian fertilization

By means of hybridoma technology, we obtained six hydriboma cell lines producing monoclonal antibody (mAb) to porcine zona pellucid (ZP), two of which recognizes the steric structure of common antigens between porcine ZP and humans. Furthermore, we have analyzed all or partial structures of N- and O-linked sugar chains of ZP glycprotein from porcine or murine oocytes. Then, we have clarified that beta-galactose and Le(X) residues on ZP played the binding roles to sperm cells in porcine and murine fertilization. We have also succeeded Sp38 cDNA cloning from cDNA library of porcine testis. We found that Sp38 protein bind to porcine ZP2 and expressed in murine and human sperm cells. Corresponding to the presence of major histocompatibility complex (MHC) class II on murine sperm, CD4 on the murine egg plasma membrane was clearly shown by indirect IIF and immunoprecipitation test. Furthermore, the transcriptional expression of CD4/p56(lck) in eggs was confirmed by RT-PCR method. In addition, the p56(lck) associated with CD4 underneath the plasma membrane of eggs was autophosphorylated after cross-linking of CD4 with anti CD4 mAb. The binding between eggs or Sf9-CD4 cells labeled with anti-CD4 mAb and sperm cells labeled with anti-monomorphic region of class II mAb was completely blocked. Considering these findings together with the fact that an interspecies' heterogeneity is present in CD4 amino acid sequence at the interactive site with class II, we elucidated that one of species' specific intercellular adhesions between two gametes at the fusion step in fertilization is definitely mediated by class II located on the posterior region of sperm head and CD4/p56(lck) complex on the plasma membrane of egg.

A monoclonal antibody to human SP-10 inhibits in vitro the binding of human sperm to hamster oolemma but not to human Zona pellucida

SP-10 is a sperm intra-acrosomal protein, specific to the testis, that is believed to play an important role in egg-sperm binding. While the molecular characterization of the SP-10 protein has been clarified, little is yet known of its functional role in fertilization. We therefore established a monoclonal antibody (mAb pep-SP10) against a peptide (pep-SP10) that included the most hydrophilic portion of human SP-10 between the 135th and 149th amino acids. Human SP-10 was found to be localized in the equatorial region of acrosome-reacted sperm by immunofluorescent staining using our mAb pep-SP10. Monoclonal Ab pep-SP10 inhibited sperm-oolemma binding in the zona-free hamster egg penetration test, but it did not inhibit sperm-zona binding in the hemizona assay. Furthermore, we demonstrated that the oolemmal ligands of human SP-10 did not include beta(1) integrins, the most promising candidates for oocyte ligands involved in sperm-oolemma binding, based on the findings of a human sperm-cultured cell binding assay using F9 mouse embryonal carcinoma cells and F9-transformed cells lacking beta(1) integrins. In conclusion, our present data suggest that human SP-10, expressed on the equatorial region of acrosome-reacted sperm, indeed mediates sperm-oolemma binding in a beta(1) integrin-independent manner, but not sperm-zona binding.

Round spermatid-specific transcription of the mouse SP-10 gene is mediated by a 294-base pair proximal promoter

Spermiogenesis is the terminal phase of male germ cell differentiation during which haploid spermatids engage in coordinate expression of a number of testis-specific genes, including those specifying acrosomal proteins. To begin to understand the transcriptional regulation during acrosomal biogenesis, we initiated promoter analysis of the gene encoding the acrosomal protein SP-10. SP-10 was previously shown to be transcribed within Golgi-phase round spermatids in the human. The present study characterizes SP-10 gene expression during spermiogenesis in the mouse and identifies regions of the mouse SP-10 (mSP-10) promoter that are capable of driving round spermatid-specific transcription in vivo. Expression of mSP-10 mRNA was initiated in early round spermatids coincident with acrosomal biogenesis and was terminated prior to nuclear elongation. The core promoter of mSP-10 lacked a TATA box but contained a canonical initiator (Inr) element surrounding the transcription start site. Using transgenic mice, we showed that the -408 to +28-base pair (bp) or the -266 to +28-bp mSP-10 5' flanking region is sufficient to direct round spermatid-specific expression of a green fluorescent protein reporter gene. On the other hand, the -91 to +28-bp mSP-10 gene fragment lacked promoter activity in vivo. This is the first functional characterization of a testis-specific gene promoter active in early round spermatids.

The potential use of sperm antigens as targets for immunocontraception; past, present and future

Immunocontraception, and in particular the targeting of antibodies to gamete-specific antigens implicated in sperm egg binding and fertilisation, offers an attractive approach to the growing global problem of overpopulation. Such an idea is not new; indeed several immunocontraception trials, using animal model systems, have been reported in recent years and a number are reviewed here. However, the results of these studies have been largely disappointing. We believe that two fundamental flaws attribute to the poor success of most of these preliminary immunocontraceptive trials. Firstly, loss of fertility has invariably been used as the assay. This presupposes that immuno-neutralisation of a single, gamete-specific antigen will be sufficient to cause a significant reduction in fertility; however, recent data suggests that such a premise may not be well-founded for a number of reasons. Secondly, and arguably the most important flaw, is the almost universal, but largely inappropriate, use of systemic immunisation as the sole route of antigen delivery. Whilst systemic immunisation regimes may lead to high serum IgG levels, these levels do not correlate with specific antibody levels in the reproductive tract or with contraceptive efficacy. Hence, an alternative antigen delivery approach is required which will induce an effective local immune response in the reproductive tract. Here we discuss the ways in which this might be achieved.

Characterization of a potent sperm-agglutinating monoclonal antibody and its cognate antigens

OBJECTIVE

To identify sperm antigens that are capable of eliciting infertility-related sperm-agglutinating antibodies.

DESIGN

In vitro laboratory experiments.

SETTING

University research laboratory.

PATIENT(S)

Fertile semen donors.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Sperm agglutination, immunofluorescence localization, and flow cytometric analysis of surface expression of A36 antigens. Antigen analysis by Western immunoblotting.

RESULT(S)

Monoclonal antibody A36 induced intensive head-to-head, tail-to-tail, and head-to-tail agglutination of motile human spermatozoa. Antigens recognized by A36 were localized on the acrosomal cap and in the principal tail regions of motile, noncapacitated human sperm. Changes in subcellular levels and localization of the A36-recognized epitope occurred after capacitation and acrosomal loss. A36 reacted with a polymorphic series of proteins in Western blots of sperm extracts from humans and various other animal species, including mouse testis extracts. A common 53-kd antigen was recognized by the antibody in the different antigenic preparations.

CONCLUSION(S)

A mouse antibody to human sperm, monoclonal antibody A36, caused intensive agglutination of noncapacitated human spermatozoa and reacted with antigens on the acrosomal cap and in the principal tail regions. Of the multiple polypeptides that were reactive with the monoclonal antibody in sperm extracts from humans and other animal species, a common 53-kd antigen was recognized.

Molecular cloning of human testis mRNA specifically expressed in haploid germ cells, having structural homology with the A-kinase anchoring proteins

We have cloned a human testis specific gene (hi), which encodes for a protein having regional homologies to the domain of A-kinase anchoring proteins. Open reading frame encodes a protein of 860 amino acids. The predicted protein has a molecular weight 95.8 kD and contains 32 cysteine residues and 34 potential phosphorylation sites. The deduced protein analysis revealed an eukaryotic secretory signal with a potential cleavage site. Northern blot analysis detected a single transcript of approximately 3.0 kb in testis and not in any other somatic tissues. Expression of hi transcript was observed only in round spermatids indicating post meiotic haploid gene expression.

Cloning of a novel human testis mRNA specifically expressed in testicular haploid germ cells, having unique palindromic sequences and encoding a leucine zipper dimerization motif

A novel gene coding for a human sperm surface protein (HSS) has been cloned from a human testis cDNA library. The 2.5 kb cDNA (hss) contains five direct repeats, three mirror repeats, three possible stem loop structures and three unique palindromic motifs located at functionally relevant positions. Open reading frame encodes a protein of 766 amino acids. The deduced protein analysis revealed a NH2 terminus extracellular domain having a leucine zipper (LZ) motif, a transmembrane helical domain and a cytoplasmic domain at the COOH terminus. Tissue specific expression studies demonstrated the presence of hss transcript only in testis. Cell type expression of hss mRNA was observed only on the round spermatids suggesting haploid germ cell expression.

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.

Microvascular permeability to the F(ab')2 fragment of IgG in the male rat reproductive tract at puberty

Development of contraceptive vaccines has recently raised much interest following the cloning of the sperm and oocyte components involved in the sperm-oocyte interaction. The main difficulty of immunocontraception in the male is the poor access of antibodies to the luminal compartment. As recent literature suggests that many substances are transported to the testis by receptor-mediated or fluid-phase transcytosis, the dependence of the transport of IgG on the Fc receptor was studied in the present investigation by comparing the penetration of whole IgG and the F(ab')2 fragment of IgG to the testis and epididymis. The maximum volume of distribution (Veq) for the F(ab')2 fragment was significantly higher than that for whole IgG in the testis of 30-60-day old rats, in the caput and cauda of 30- and 45-day old rats and the corpus of 45-day old rats. The speeds at which equilibrium between tissue extracellular fluid and serum was reached (K) for the F(ab')2 fragment and whole IgG were significantly different in the testicular capsule of the 60-day old, in the caput and corpus of the 45- and 60-day old and in the cauda of the 45-day old rats. The microvascular permeabilities (PE) to the F(ab')2 fragment were more than 2-fold higher than those to whole IgG in the testis of the 20-, 45- and 60-day old, in the testicular capsule of the 20- and 45-day old, in the caput of 20-, 30- and 60-day old and in the corpus of 20-day old rats. The PE to whole IgG was more than 2-fold higher than that to the F(ab')2 fragment in the cauda of the 45-day-old rats. The PE to the F(ab')2 fragment increased steadily from 20 to 60 days of age in the testis and caput, but in the corpus there was a more abrupt increase between 30 and 45 days of age. In the cauda, PE remained in the same range of magnitude throughout pubertal development. These results suggest that the F(ab')2 fragment reaches the lumen of the reproductive tract more easily than whole IgG from 30 days of age onwards in the testis, whereas in the caput, corpus and cauda epididymidis the rate at which F(ab')2 fragment reaches the lumen increases only temporarily at the time of appearance of spermatozoa in the lumen. Transport of IgG to the male reproductive tract is thus unlikely to be mediated by Fc receptors.

Effect of immunization with human SP-10 in male rodents

PROBLEM

Over the years immunocontraception has emerged as a promising modality. Theoretically it is possible to intercept fertility using a panel of antigens expressed along the entire pituitary, hypothalamus and gonadal axis. One such sperm antigen designated as SP-10 is in advanced stages of development. Its gene has been cloned by Wright et al. (Biol Reprod 1990; 42:693-701). It is envisaged that immunization with SP-10 would induce antisperm antibodies in females and hence interrupt fertility. However, the in vivo effect of SP-10 immunization has been assessed in male rodents with particular reference to spermatogenesis and effect of such immunization in various tissues. The SP-10 antigen was a generous gift from Dr. John Herr.

METHODS

A group of male Wistar rats and BALB/c mice were immunized with a total dose of 175 micrograms of SP-10 glutathione transferase fusion protein. Anti-SP-10 antibodies generated were detected by ELISA, immunofluorescence, flow cytometry and western blot assay. Histopathology of all the organs was conducted with particular reference to assess their effect on sperm maturation in testicular sections.

RESULTS

All the animals immunized with SP-10 depicted a significant antibody response. DNA analysis by flow cytometry did not reveal any arrest of spermatogenesis, which was confirmed by histological studies.

CONCLUSIONS

It is concluded that conventional immunization generating significant antibody titers does not induce arrest of spermatogenesis in male rodents.

Update on the Center for Recombinant Gamete Contraceptive Vaccinogens

The overall goal of the Center for Recombinant Gamete Contraceptive Vaccinogens is to develop a contraceptive vaccine which will induce antibodies in the female reproductive tract at sufficient levels to block fertilization. It is envisioned that antibodies developed by this vaccine will act to agglutinate, immobilize or coat either the egg or the sperm in the oviduct, uterus, cervix or vagina. Thus, the vaccine will exert its effects before the fertilization event, as a "prefertilization contraceptive." The Center has focused its activities over the past 4 years on four areas: 1) sperm antigens: the identification and characterization of novel sperm surface molecules which are attractive candidates for inclusion in a vaccine; 2) zona antigens: the identification of synthetic peptides derived from the zona pellucida which possess contraceptive potential without adverse pathology; 3) oral vaccine delivery: the development of live Salmonella vectors which deliver vaccine antigens through the oral route and which will stimulate secretory immunity in the female reproductive tract; and 4) animal testing: the testing of vaccine formulations in in vitro fertilization models, in small animals, in monkeys and in baboons. In addition, preparations for human testing are underway through preparation of an Investigational New Drug Application to begin Phase I human trials of a LDH-C4 peptide vaccine.

Isolation of a novel cDNA that encodes a protein localized to the pre-acrosome region of spermatids

We have identified a novel cDNA clone, named AZ1, obtained from a cDNA library of mRNA prepared from C3H10T1/2 cells that had been transiently exposed to 5-azacytidine, a potent demethylating reagent. The amount of transcript increased with 5-azacytidine treatment of C3H10T1/2 cells and the transcript was highly expressed in mouse testis. As the mutant mouse jsd/jsd, which has a defect in germ cell maturation, barely expressed the transcript, the message was expected to be expressed specifically in spermatocytes. The mRNA was detected at significant levels in the testes from mice aged 16 days after birth, suggesting that its expression started at the pachytene spermatocyte stage. The elucidated nucleotide sequence contained a 2841-nucleotide open reading frame, and the expected amino acid sequence had a molecular mass of 107,254 Da. Specific antibodies raised against the fusion protein including glutathione S-transferase revealed an approximately 130-kDa band of a translation product in testis and in cultured cells transfected with AZ1 cDNA in the expression vector on Western-blot analysis. The protein was localized to the pre-acrosome region of round and elongated spermatids. However, it was not detected at a more advanced stage of spermatids, i.e. just before their release from Sertoli cells. This protein may play an important role in spermatogenesis.

Characterization of alternatively spliced human SP-10 mRNAs

Alternatively spliced mRNAs encoding the human intraacrosomal protein SP-10 were sought by the reverse transcriptase polymerase chain reaction (RTPCR). Eleven RTPCR products were identified, characterized, and found to represent authentic alternatively spliced SP-10 mRNAs. The 11 alternatively spliced SP-10 mRNAs encoded proteins ranging from 81 to 265 amino acids. The 10 smaller variants all resulted from one or two in-frame deletions in exons 2 and/or 3 of the SP-10 genomic sequence. Quantitative competitive RTPCR showed that the four largest SP-10 mRNAs represented the majority (> 99%) of the SP-10 message in testes from each of four men. The relative abundance of each of the four SP-10 mRNAs varied between individuals, but the longest SP-10 mRNA, SP10-1, which encoded a 265 amino acid protein, was consistently the most abundant, comprising 53-72% of the total SP-10 message. This was followed by the second largest SP-10 mRNA, SP10-2, which encoded a protein of 246 amino acids and comprised 15-32%. The third and fourth largest SP-10 mRNAs, SP10-3 and SP10-4, encoded proteins of 210 and 195 amino acids and accounted for 3.4-8.3% and 8.7-12.5% of the total SP-10 messages, respectively. The remaining 7 SP-10 mRNAs combined accounted for < 1% of the total SP-10 message. Within the low abundance group of mRNAs were two that deleted the entire third exon of SP-10. The present study suggests that phenomena of cryptic splicing and exon skipping occur within the SP-10 mRNA. Along with proteolysis, alternative splicing also helps to explain the heterogeneous forms of SP-10 that have been observed on Western blots of human sperm extracts.

Cloning and partial characterization of the cDNA encoding the fox sperm protein FSA-Acr.1 with similarities to the SP-10 antigen

We have isolated and characterized a cDNA, cFSA-Acr.1, encoding a testis-specific fox sperm antigen. The antigen is located on the inner acrosomal compartment, and is expressed during spermatogenesis on the developing acrosome of round and elongating spermatids. Database searches with the deduced amino acid sequence of cFSA-Acr.1 revealed that the clone has high homology to both human and baboon sperm protein SP-10, and the mouse sperm protein, MSA-63. The region of highest homology is within the carboxyl terminus. In the middle of the open reading frame, the fox sequence shows unique sequences absent from both the human, baboon SP-10, and mouse MSA-63 sequences. In addition to cFSA-Acr.1, two other clones were also isolated from the same fox testis cDNA library, and sequence analysis shows that they may represent alternatively spliced mRNAs coding for other FSA-Acr proteins.

Expression of cDNA fragment encoding sperm membrane peptide in E. coli

A secretory high-level expression cloning vector designated as pSBC-20 was constructed by inserting a DNA fragment encoding the signal peptide of ompA protein into pBV 220 vector. Any foreign DNA fragment can be inserted into the polylinker cloning sites located after the secretion signal sequence. The cloned foreign gene is under the control of the PR-PL promoter while the expression of the gene is regulated by the cI-gene product. The products are secreted into the periplasmic space of bacteria or into the medium. A recombinant plasmid (pRSD-220) was constructed by inserting the 210 bp from RSD-2, a cDNA encoding a peptide fragment of human sperm protein, into the EcoRI site of pSBC-20. The E. coli cells transformed with pRSD-220 were propagated at 30 degrees C, then incubated at 42 degrees C for several hrs. The cloned gene product was secreted into the culture medium at a high rate. The yield was about 60 mg of gene product per liter of cultured medium.

Molecular identities of human sperm proteins that bind human zona pellucida: nature of sperm-zona interaction, tyrosine kinase activity, and involvement of FA-1

The present study was conducted to investigate the molecular identities, nature of interaction, and tyrosine phosphorylation activity of the sperm-zona pellucida binding proteins in humans. Sperm proteins belonging to four major molecular regions, namely 95, 63, 51, and 14-18 kDa, reacted with zona pellucida proteins in the Western blot and immunoprecipitation procedures. In these procedures, zona pellucida protein that reacted strongest with the sperm proteins belonged to the molecular region of 55 kDa (ZP3), besides weakly reacting proteins in the 110-kDa (ZP1/ZP2) and 14-18-kDa molecular regions. The major forces involved in the sperm-zona protein interactions were of hydrophobic and ionic in nature. Three (95, 51, and 14-18 kDa) of the four molecular regions of sperm proteins that bound to the zona pellucida proteins also seem to involve o-phospho-L-tyrosine residues in their interaction, and these proteins demonstrated the presence of phosphotyrosine residues, and the 51-kDa protein also showed autophosphorylating activity in the in vitro kinase assay. The sperm binding zona protein of 55 kDa also demonstrated autophosphorylating activity. Using specific monoclonal antibody to the well characterized sperm-specific glycoprotein, designated FA-1, and the competitive inhibition in the immunoprecipitation procedure, it was found that the 51 kDa protein is indeed FA-1 antigen. Besides elucidating the molecular nature of the sperm-zona interaction, these antigens will find application in the development of a multivalent contraceptive vaccine, and may also help in specific diagnosis and treatment of infertility mediated through defective gamete (sperm or oocyte) function.

Antibodies to sperm-specific human FA-1 inhibit in vitro fertilization in rhesus monkeys: development of a simian model for testing of anti-FA-1 contraceptive vaccine

The feasibility of using the rhesus monkey as a non-human primate model for testing the efficacy of a contraceptive vaccine based on FA-1 antigen was evaluated. Affinity-purified anti-FA-1 polyclonal antibodies (Fab' fragments) and anti-FA-1 monoclonal antibody were used as probes in these studies. Anti-FA-1 antibodies (polyclonal Fab' as well as monoclonal IgG) predominantly reacted with the postacrosomal, mid-piece and tail regions of rhesus monkey sperm, as with human sperm, by an indirect immunofluorescence technique (IFT). These antibodies also specifically recognized a single protein band of 51 +/- 2 kDa, corresponding to the dimeric form of FA-1 antigen, on a Western blot of lithium diiodosalicylate (LIS)-solubilized monkey sperm. Anti-FA-1 antibodies, when present in the insemination mixture, inhibited the in vitro fertilization (IVF) of monkey oocytes. These results indicate that FA-1 antigen in rhesus monkey sperm is similar in subcellular localization, molecular identity and function to that in human sperm, and that the rhesus monkey represents a permissible non-human primate model in which the efficacy of a contraceptive vaccine based on FA-1 antigen can be tested.

Production in Escherichia coli, purification and immunogenicity of acrosomal protein SP-10, a candidate contraceptive vaccine

The testis-specific human sperm antigen, SP-10, has been designated a 'primary vaccine candidate' by the World Health Organization Taskforce on Contraceptive Vaccines. Molecular cloning and sequencing of the cDNAs coding for human (h) and baboon (b) SP-10 have been reported. To produce large amounts of pure antigen for ongoing studies of the immunogenicity and anti-fertility effects of SP-10, we used an efficient Escherichia coli expression system. The full-length open reading frames for hSP-10 and bSP-10 were placed under the inducible T7 bacteriophage RNA polymerase/promoter system. An in-frame fusion was made such that a His6 stretch was produced at the C terminus of SP-10. Upon induction of gene expression, large amounts of hSP-10 or bSP-10 were synthesized and the recombinant (re-) protein segregated into an insoluble fraction. The protein was then solubilized in 6 M guanidine.HCl and purified by immobilized metal affinity chromatography (IMAC). The yield of purified bSP-10 preparation was approx. 20 micrograms/ml of culture. Immunoreactivity of the purified re-SP-10 with MHS-10, a monoclonal antibody specific to SP-10, and rabbit polyclonal sera raised against SP-10, indicated that the synthesized antigen was suitable for immunization studies. Four female baboons were then immunized with the re-bSP-10 antigen. Immunoblots using pre-immune and immune sera from these animals indicated that all four baboons produced antibodies that reacted with native SP-10 extracted from human sperm in a manner identical to that of MHS-10, the positive control. Immune sera also stained the acrosome region of human and baboon sperm heads by immunofluorescence.(ABSTRACT TRUNCATED AT 250 WORDS)

Sequence homology among sperm antigens involved in mammalian fertilization: search for a common epitope for immunocontraception

Sequence homology was searched among the nine cDNAs/deduced amino acid sequences encoding for the eight fertilization-related sperm antigens: namely, lactate dehydrogenase (LDH-C4), galactosyltransferase (GT), SP-10, rabbit sperm autoantigen (RSA), guinea pig (g)PH-20, cleavage signal protein (CS-1), HSA-63, human (h)PH-20, and AgX-1, respectively. Most significant identity (> 50%) was found between HSA-63 and SP-10 (59.8%), and between gPH-20 and hPH-20 (61.1%); followed by identity between SP-10 and GT (34.7%); and then between AgX-1 and hPH-20 (39.4%). All others had identity < 25%. The significance of these sequence homologies among the sperm antigens in the development of an antisperm contraceptive vaccine is discussed.

Human testis vitamin D binding protein involved in infertility

Immunoglobulin G (IgG) fraction was prepared from a serum obtained from an infertile woman containing antisperm antibodies that induced head-to-head agglutination of human sperm. The antibodies in the IgG fraction interacted with a 60-kD protein found in human testes determined by Western blot. The 60-kD protein was purified from human testis by isoelectric focusing (IEF), affinity chromatography on blue sepharose column, and preparative electrophoresis with electroelution. The purified 60-kD protein migrated as a single homogeneous band when analyzed by SDS-PAGE. The amino acid sequence of the N-terminus was determined. The initial 10 amino acid residues were identical to the human serum vitamin D binding protein (VDBP). Polyclonal antibodies were raised against the 60-kD protein. The polyclonal anti-60-kD antibodies and the anti-VDBP antibodies obtained from a commercial source immobilized human sperm in vitro. The interacting antigens were located on the postacrosomal region and midpiece of human sperm, as determined by an immunofluorescence method. The IgG fraction prepared from the serum of an infertile woman interacted with the human testis 60-kD protein but failed to stain serum VDBP. The results suggest that the 60-kD and VDBP are related proteins but not identical entities and that the 60-kD protein contains a unique structural group lacking in serum VDBP. Production of antibodies against the unique structure of the 60-kD protein may be the cause of the infertility.

Antisperm antibodies: origin, regulation, and sperm reactivity in human infertility

OBJECTIVE

To follow-up and expand discussion on the action mechanisms of antisperm antibodies in human infertility, the etiology and control of antisperm antibody induction, sperm antigens involved in immunoinfertility, and strategies for therapy.

DESIGN

A review of the recent literature with an emphasis on female immunoinfertility.

RESULTS

The role of antisperm antibodies in clinical infertility continues to be defined. Through assisted reproductive technologies, antisperm antibodies were shown to exert detrimental effects on different prefertilization and possibly postfertilization events. The female reproductive tract is part of the common mucosal immune system and is able to mount effective immune responses against infectious agents, foreign antigens, and, occasionally, sperm cells. Sperm membranes and constituents contain numerous antigenic components foreign to the human body, and yet antisperm antibodies become problematic in few women exposed to semen. Semen and sperm cells contain immunosuppressive factors capable of inhibiting different immune cells. Fertile women apparently produce antisperm antibodies but also possess neutralizing serum anti-idiotypic antibodies that are lacking in virgin and immunoinfertile women.

CONCLUSIONS

Antisperm antibodies can affect adversely human fertility but normally may be controlled by anti-idiotypic antibodies, which along with immunosuppressor factors in semen prevent their induction to a significant degree. This balance between detrimental and "beneficial" immune response to sperm may be shifted toward an antisperm antibody response by stimulatory factors such as infection. Therapies may be devised to stimulate the anti-idiotypic antibody system, to induce immune tolerance to sperm antigens, and to use antigens to adsorb antisperm antibodies from spermatozoa.

Fertility studies with antisperm antibodies

Serum obtained from an infertile subject possessed antibodies that interacted with a human sperm glycoprotein with an estimated M(r) of 17,550 and pI of 5.65 containing 17.7% neutral hexoses and designated as the BS-17 component. Polyclonal antibodies raised against the BS-17 antigen blocked the capacity of human sperm to fertilize zona-free hamster ova in vitro; however, the antibodies did not influence the binding of human sperm to zone-free ova or alter the motility of human sperm. The antibodies inhibited the capacity of mouse sperm to fertilize ova upon in vivo insemination. The BS-17 antigen was detected in human, rat, mouse, rabbit, and hamster sperm by an immunocytochemical method, using polyclonal anti-BS-17 antibodies. Intense staining occurred over the surface of the acrosomal region of all mammalian sperm. The results suggest that the production of anti-BS-17 antibodies contribute to infertility by preventing the capacitation of sperm and/or by blocking the ability of capacitated sperm to fertilize the egg.

Identification and characterization of a 27 kDa acrosome protein of human sperm defined by a monoclonal antibody with fertilization-blocking effect

A monoclonal antibody, MAb 1G1, possessing a strong fertilization-blocking activity was prepared by immunizing a BALB/c mouse with capacitated human sperm in order to study the molecular nature of sperm antigens relevant to fertilization. MAb 1G1 inhibited human sperm penetration into zona-free hamster eggs. It reacted to the apical portion of acrosome-reacted human sperm, but did not react to live sperm before the acrosome reaction as demonstrated by immunofluorescence staining. In paraffin-embedded testis sections, the round spermatids, spermatocytes and spermatozoa were stained with MAb 1G1, but the spermatogonia were not stained. Neither Sertoli cells, Leydig cells nor other somatic tissues were stained. The sperm of Japanese monkey, bull, boar, hamster and mouse were not stained. Therefore, the staining of sperm was species specific. The antigen corresponding to MAb 1G1 showed a band at 27 kDa by immunoblotting. The reactivity of the antigenic component was not destroyed by periodic acid treatment. From the results obtained, it was postulated that the antigenic molecule might be a polypeptide. These results indicated that this MAb might be a useful tool for studying the mechanism of human sperm-egg fertilization and the development of a contraceptive vaccine.

Stage-specific detection of mRNA for the sperm antigen SP-10 in human testes

SP-10 is a sperm-specific, intra-acrosomal protein that is considered to be a vaccine candidate for immunocontraception. In the present study, in situ hybridization with biotin and 35S labeled riboprobes was used to determine the pattern of SP-10 mRNA expression in human testes. Both methods demonstrated SP-10 mRNA primarily in round spermatids found in stages I, II, and III of the seminiferous cycle. Morphometric analysis of silver grains with the 35S-labeled probe showed less SP-10 mRNA in spermatids at stages IV, V, and VI than in previous stages, and rarely was label found in spermatogonia or spermatocytes. The expression of SP-10 mRNA first appeared at stage I coincident with the appearance of the protein, which was shown previously to persist in the acrosomal matrix throughout spermiogenesis. The decrease in SP-10 mRNA occurred when spermatids underwent polarization, nuclear condensation, and elongation. The appearance of SP-10 mRNA in round spermatids suggests that increases in SP-10 transcription or SP-10 mRNA stability or both occur as spermatids develop from the Golgi phase to the cap phase. The subsequent decline of SP-10 mRNA, despite the persistence of the SP-10 protein in all spermatids, suggests that a decrease in SP-10 transcription or an increase in mRNA degradation occurs when spermatids elongate.

Molecular identity of a sperm acrosome antigen recognized by HS-63 monoclonal antibody

The molecular identity of mouse sperm acrosome antigen recognized by HS-63 monoclonal antibody was analyzed by various biochemical, immunological and molecular biological methods. When its cognate antigen, MSA-63 was isolated from mouse testis by immunoaffinity chromatography, a group of protein spots with wide range of molecular sizes and isoelectric points were identified. Through previous studies, it was established that most of these protein spots were actin-like molecules co-purified with MSA-63 protein from mouse testis. To analyze the molecular size heterogeneity of the isolated MSA-63 proteins, rabbit antisera against a computer-predicted antigenic synthetic peptide (amino acid residue No. 160-171) and a recombinant glutathione S-transferase (GST) fusion protein (GST-63) were raised. These two antisera and those raised against the isolated MSA-63 protein were used as the probes in comparative Western blot assay, indirect immunofluorescent assay and enzyme-linked immunosorbent assay (ELISA). Using ELISA, antisera against GST-63 and computer-predicted antigenic synthetic peptides were shown to cross-react with affinity-isolated MSA-63 protein coated on microwells. However, little immunological cross-reactivity was observed between GST-63 fusion protein and the synthetic peptide. By using a Western blot assay, two major protein bands of 22 and 32 kDa, respectively were commonly detected on mouse testis homogenate strips by both anti-MSA-63 and anti-GST-63. In addition, anti-MSA-63 also recognized several protein bands with molecular masses greater than 35 kDa. The results of this study suggested that the molecular heterogeneity of MSA-63 protein isolated from mouse testis and sperm, is due to a series of post-translational modifications on a single gene product. These modifications may include glycosylations, proteolytic digestions and tight non-covalent associations with other testicular cytoskeletal proteins, such as actins.

Assay for recombinant and native human intraacrosomal antigen SP-10

PROBLEM

To develop a method to measure a recombinant sperm protein, SP-10, during scale up and purification for a contraceptive vaccine formulation.

METHOD

A quantitative assay method for the human intraacrosomal protein SP-10 was developed utilizing the format of indirect capture enzyme-linked immunosorbent assay (ELISA). A SP-10 specific monoclonal antibody mAb, MHS-10, was used as the capture antibody. Two recognition reagents, a rabbit polyclonal anti-SP-10 antisera (pAb) and a biotin-labeled mAb, MHS-10, were used as the recognition antibodies, respectively. A SP-10 recombinant fusion protein consisting of 125 SP-10 amino acids linked to glutathione transferase was used as a working SP-10 standard. The coefficient of variance for the assay system using the rabbit pAb was in the range of 0.099 to 0.157, and for the assay system using the biotinylated mAb MHS-10 was in the range of 0.081 to 0.084.

RESULTS

Employing biotinylated MHS-10 as the recognition antibody, it was found that the native SP-10 molecule had more than one MHS-10 epitope. The concentration of SP-10 in a pool of human sperm extracts was found to be approximately 1% of the total proteins, assayed by both of the recognition antibody systems.

CONCLUSIONS

The assay system described is useful to monitor the yield of recombinant SP-10 during scale-up production of the SP-10 vaccine.

Cloning and sequencing of baboon and cynomolgus monkey intra-acrosomal protein SP-10: homology with human SP-10 and a mouse sperm antigen (MSA-63)

In this study, cDNAs encoding the intraacrosomal protein SP-10 were cloned and sequenced from baboon (Papio papio) and macaque (Macaca fascicularis) testis libraries and the sequence compared to that of human SP-10. Two alternatively spliced SP-10 cDNAs were obtained from both baboon and macaque testis libraries. The two cDNAs in each species contained open reading frames encoding proteins of exactly 285 and 251 amino acids. A 98% homology between baboon and macaque SP-10 was found at the protein and DNA levels. An 85% and 89% homology between baboon and macaque SP-10 and human SP-10 was present at the protein and DNA level, respectively. A mouse intraacrosomal protein, MSA-63, considered to be an SP-10 homologue, exhibited an overall 53% homology to nonhuman primate SP-10 and a 60% homology to human SP-10 at the protein level. Polymerase chain reaction analysis of testis mRNA confirmed the existence of two alternatively spliced SP-10 mRNAs in both nonhuman primates. Primer extension analysis indicated a common major transcriptional start site in baboon, macaque, and human SP-10 67 nucleotides 5' to the ATG codon. The amino acid sequence data for nonhuman primate SP-10s suggest that antibodies generated by vaccinating baboons and macaques with human SP-10 will likely recognize nonhuman primate SP-10, supporting the testing of an SP-10 contraceptive vaccine based on human SP-10 in these nonhuman primate models.

Human sperm proteins from testicular and epididymal origin that participate in fertilization: modulation of sperm binding to zona-free hamster oocytes, using monoclonal antibodies

In order to identify human sperm surface proteins involved in the gamete recognition process, mouse monoclonal antibodies were directed against human spermatozoa and screened with live spermatozoa by enzyme-linked immunosorbent assay (ELISA). Immunoperoxidase staining of human testis showed the early presence of four corresponding proteins on germinal cells, while six were detected primarily in testis fluid. The presence of 17 proteins was evidenced in the epididymis. Eight were detected with a decreasing gradient from the beginning to the end of the organ, including vasa efferentia for three of them. The other nine were observed in only one defined segment, usually the caput epididymis, which was found to be the most active region. Comparison of spermatozoa patterns from testis, vasa efferentia, and the three regions of epididymis pointed out a progressive coating. By contrast, three antibodies displayed a migration of spermatozoa surface domains in the course of epididymal transit. Six antibodies were found to inhibit human spermatozoa adherence to zona-free hamster oocytes, while nine promoted it. Molecular weights of antigens corresponding to nine of the antibodies ranged from 11 to 215 kDa. No correlation could be established with previously described human proteins. These observations emphasize the role of epididymis in human sperm maturation.

Vaccines against fertility

The first evidence for the efficacy of a birth control vaccine in humans is now available from the Phase II trials on the human chorionic gonadotrophin vaccine in India. Several sperm antigens have been identified as potential contraceptive immunogens and zona pellucida antigens have been reported that reversibly control fertility.