A new look at antifertility vaccines**The work described in this article, Publication No. 1253 of the Oregon Regional Primate Research Center, was supported by National Institutes of Health grants RR-00163 and CA-32132

Inhibition of mouse acrosome reaction and sperm-zona pellucida binding by anti-human sperm membrane protein 1 antibody

AIM

To investigate the possible functions of human sperm membrane protein (hSMP-1) in the process of fertilization.

METHODS

A 576-bp cDNA fragment of HSD-1 gene coding for the extracellular domain of hSMP-1 was cloned and expressed. The localization of this protein on human and mouse sperm was determined by indirect immunofluorescent staining by using anti-recombinant hSMP-1 (anti-rhSMP-1) antibodies. Sperm acrosome reaction and sperm-zona pellucida (ZP) binding assay were carried out in 10-week-old BALB/c mice.

RESULTS

Recombinant hSMP-1 was successfully cloned and expressed. The expression of the native protein was limited on the acrosome of human and mouse sperm. Treatment of anti-rhSMP-1 antibodies significantly decreased the average number of sperms bound to each egg. Meanwhile, the percentage of acrosome reaction was decreased in comparison to pre-immune control after treatment with anti-rhSMP-1 (P < 0.05).

CONCLUSION

The results suggest that anti-rhSMP-1 antibody inhibited mouse acrosome reaction and sperm-ZP binding.

Partial amino acid sequencing of 80-kDa human sperm antigen (80-kDa HSA)

An 80-kDa human sperm antigen (80-kDa HSA) has been identified as a sperm protein responsible for inducing immunoinfertility. Immunization with the purified protein induced infertility in male and female rats. Immunohistochemical and immunofluorescent studies have demonstrated that the antigen is specific to spermatozoa. The present study describes the partial amino acid sequencing of 80-kDa HSA. The homogeneous protein was electrophoretically transferred onto a PVDF membrane and the excised band of 80-kDa HSA was used to determine the partial N-terminal amino acid sequence. The protein was then subjected to enzymatic digestion with endoproteinase Lys-C and endoproteinase Glu-C. The partial amino acid sequence of the major peptides thus obtained was determined. The digestion with endoproteinase Lys-C generated 4 major peptides, two of which showed partial sequence homology with lactoferrin. Endoproteinase Glu-C digestion produced 3 major peptides. The sequences of the 2 peptides were determined for which no matches were found in the databank. These results confirmed earlier observations that 80-kDa HSA is a sperm-specific protein that is chemically distinct from any other protein involved in normal physiological process. Earlier studies have demonstrated that it is antigenic, efficacious, conserved, and could be a promising candidate for the development of an antifertility vaccine.

Fertility Control: An Option for Non-Lethal Control of Wild Carnivores?

Three types of fertility control, surgical sterilization, hormonal chemosterilization, and immunosterilization, are reviewed with regard to their potential for controlling problematic populations of carnivores. The fertility control agent and delivery protocol of choice may vary considerably according to: (i) the reason for control; (ii) the degree, urgency and duration of population reduction required; (iii) concerns about ethics and public opinion; and (iv) the status, population dynamics, social structure, mating system, size, behaviour and reproductive endocrinology of the target animals. Although they are often perceived and advocated as more preferable methods of population control than lethal approaches, it is important that wildlife managers as well as members of the public realize that the ethical acceptability of the various fertility control techniques may differ considerably - and that numerous questions regarding their effectiveness, humaneness and ecological safety remain unanswered.

Expression of the human antigen SPAG2 in the testis and localization to the outer dense fibers in spermatozoa

ABSTRACT Antisperm antibodies (ASAs) have been implicated in some instances of infertility. To characterize sperm antigens relevant to immunologic and immunocontraceptive development, SPAG2 (sperm-associated antigen 2) was identified by screening a human testis cDNA library with human sera positive for ASAs. Subsequently, two isoforms, SPAG2-1 and SPAG2-2, were identified in testis and placenta libraries, respectively. In the current study, Southern analysis of human genomic DNA with a probe common to the two SPAG2 isoforms indicated a single SPAG2 gene; therefore, alternative splicing is a likely mechanism for production of variant mRNAs. In situ hybridization of human testis sections demonstrated the expression of SPAG2 in primary spermatocytes, with decreased or arrested expression in postmeiotic cells. Immunofluorescence of Triton X-100-extracted spermatozoa with an anti-SPAG2 peptide antiserum indicate that SPAG2 is an intracellular component of the sperm flagellum. Electron microscopy refined this localization to the outer dense fibers (ODFs), structural filaments associated with the mammalian sperm axoneme. The ODFs have been reported to be composed of keratin-like intermediate filament proteins. However, SPAG2 does not exhibit the molecular characteristics of such proteins, nor does SPAG2 demonstrate sequence homology with previously characterized ODF proteins. Therefore, SPAG2 represents a novel protein of human sperm ODFs. Characterization of SPAG2 will further our understanding of ODF function in normal sperm motility and of flagellar abnormalities that lead to male infertility.

The biologic significance of white blood cells in semen

OBJECTIVE

To analyze the data available on the biologic significance of white blood cells (WBC) in semen of infertility patients.

DATA RESOURCES

The relevant literature was reviewed.

RESULTS

It is not possible to identify reliably WBC by conventional sperm staining techniques. The peroxidase method is sufficient for quantification of granulocytes, but immunocytology is the gold standard for the detection of all WBC populations in semen. Granulocytes are the most prevalent WBC type in semen (50% to 60%), followed by macrophages (20% to 30%) and T-lymphocytes (2% to 5%). The prevalence of leukocytospermia (> 10(6) WBC/mL semen) among male infertility patients is approximately 10% to 20%. There is controversy on the significance of WBC in semen. Whereas some authors did not observe sperm damage in the presence of leukocytospermia, others have found evidence that WBC are significant cofactors of male infertility: [1] seminal WBC numbers were higher in infertility patients than among fertile men; [2] leukocytospermia was associated with decreased sperm numbers and impaired sperm motility; [3] WBC damaged sperm function and hamster ovum penetration in vitro and were important prognostic factors for IVF-ET failure. Because of absence of clinical symptoms, the origin of WBC is difficult to determine. Normally, most WBC appear to originate from the epididymis because vasectomized men show very few WBC in semen. On the other hand, leukocytospermic samples show low citric acid levels, pointing to asymptomatic prostatitis as a source of WBC in semen. Surprisingly, approximately 80% of leukocytospermic samples are microbiologically negative. In some cases Chlamydia trachomatis might have triggered a persistent inflammatory reaction leading to leukocytospermia. Sperm damage by WBC can be mediated by reactive oxygen species, proteases and cytokines. Furthermore, genital tract inflammation facilitates the formation of sperm antibodies. As seminal plasma has strong anti-inflammatory properties and because there is only short contact between sperm and WBC in prostatitis and seminal vesiculitis, inflammations of the epididymis and testis are likely to have the largest impact on sperm.

CONCLUSIONS

There is ample evidence that WBC can affect sperm function. Further studies are needed to define cofactors that increase or decrease the risk of sperm damage by WBC.

Anti-sperm and anti-ovum vaccines: the selection of candidate antigens and the outcome of preclinical studies

A clear conceptual basis for anti-sperm and other modes of immunological birth control exists in spite of the limited basic research done on surface antigens of sperm or egg. In the normal physiological condition, the immune system does not respond to sperm, egg or fetus. Compared with anti-egg or anti-fetus immunocontraception, an anti-sperm vaccine has two theoretical advantages. First it would work in both males and females; second, it would not raise problems of autoimmunity in the female if a sperm-specific protein is used. However, for the development of such contraceptive vaccines the following scientific questions need to be resolved: (1) what surface protein to use as an antigen; (2) what adjuvant to use in humans for an anti-fertility vaccine; (3) how to maintain a high titre; (4) how the contraceptive effect will be terminated; and (5) what are the potential side-effects.

Immunoneutralization of gonadotropin-releasing hormone and subsequent treatment with testosterone Silastic implants in rats: an approach toward developing a male contraceptive

STUDY OBJECTIVE

To determine the extent to which increasing doses of exogenous testosterone (T) administered via Silastic implants can restore spermatogenesis and fertility to rats made azoospermic by active immunization against gonadotropin-releasing hormone (GnRH).

DESIGN

Male rats were made azoospermic by active immunization against GnRH. Increasing doses of exogenously administered T (via Silastic implants) were administered for 8 weeks, and testicular sperm concentration and ability to impregnate female rats were evaluated.

SETTING

Reproductive Endocrinology Laboratory, Department of Obstetrics and Gynecology, University of Colorado Health Sciences Center, Denver, Colorado.

ANIMALS

Sexually mature male Sprague Dawley rats (SASCO, Omaha, NE).

RESULTS

Suppression of gonadotropins and azoospermia was achieved by actively immunizing rats against GnRH. Testosterone was capable of restoring quantitatively complete spermatogenesis and fertility in GnRH-immunized azoospermic rats. This relationship was dose-dependent, as evidenced by the partial restoration of spermatogenesis and fertility observed in animals replaced with smaller T Silastic implants.

CONCLUSION

Gonadotropin-releasing hormone immunization and T-filled Silastic implants may provide a model to study isolated gonadotropin deficiency and for the development of a reversible male contraceptive.

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.

Adoptive transfer of murine autoimmune orchitis with sperm-specific T lymphoblasts

A protocol was successfully developed for reproducibly transferring experimental autoimmune orchitis (EAO) to naive recipient mice with sperm-specific T lymphoblasts. Cell donors were Balb/c mice immunized about 12 days earlier with homologous epididymal sperm capacitated in vitro with complete Freund's adjuvant. Draining lymph node cells were collected and subjected to a second challenge with the same sperm antigen in vitro. Sperm-specific T lymphoblasts were isolated on Percoll density gradients and propagated in the presence of interleukin-2 for 3 days and then were transferred intraperitoneally to naive recipients. As few as 3 x 10(6) sperm-specific T lymphoblasts were able to transfer EAO, which began on day 7 as infiltration of lymphocytes and macrophages and on days 14 to 21 developed to degenerative changes of spermatids and exfoliation of germinal epithelium. These pathologic alterations resemble a delayed type of hypersensitivity. The results show that sensitized T lymphoblasts can mediate an antigen-specific, mononuclear cell-invasive lesion in autoimmune orchitis.

Phase I clinical trial of monoclonal anti-human chorionic gonadotropin antibody in women with an ectopic pregnancy

A phase-I clinical trial of a mouse monoclonal anti-human chorionic gonadotropin (hCG) antibody designated as HT13 was conducted in three patients treated for ectopic pregnancy. Doses of 5 and 25 mg of purified antibody were injected into patients. Monoclonal antibody serum levels dropped to 0 within 1 to 5 days. Human antibodies directed against mouse immunoglobulins were not detected at up to 41 days after injection. In one patient, the tubal pregnancy resolved, as confirmed by hCG levels of less than 10 mUl/mL and by tubal patency at hysterosalpingography. The time of resolution was 30 days. In two patients, salpingectomy was performed because of persistence of elevated hCG levels, whereas HT13 had a striking effect on progesterone (P) and estradiol (E2) serum levels. The injection of anti-hCG antibody did not appear to interfere with the subsequent fertility of patients, and two out of three patients later developed a successful pregnancy. While the precise role of antibody injection in the interruption of ectopic pregnancy remains speculative, the injection of monoclonal anti-hCG antibody appears to induce a dramatic decrease in the production of both P and E2.

The mucosa of the male genital tract; part of the common mucosal secretory immune system?

The selective migration of mucosal-derived lymphoid blasts to other mucosal organs is taken to be an essential part of the common secretory immune system. In rats, proliferating lymphoid cells from mesenteric lymph nodes (mLN) and peripheral lymph nodes (pLN) were labeled in vitro using two different techniques, in order to test the hypothesis that the mucosa of the male genital tract is a preferential site for mLN lymphoid blasts to home to. A low but significant migration to male genital organs was found, but with no difference between blasts from pLN and mLN. Thus there is no evidence to include the male genital tract in the common mucosal secretory immune system. Recirculating lymphocytes from the thoracic duct entered the male genital organs with a similar distribution to the pattern of lymphoid blasts. There is probably an exchange between these immigrating lymphocytes and the different subsets, which are localized in the epithelium (T suppressor) and interstitial tissue (T helper) in male genital organs. The lymphoid cells in the male genital tract might play an important role in the immune function of seminal fluid and in sexually transmissible diseases.

Immunocytochemistry of male reproductive organs

Immunological techniques have enabled us to see that mammalian sperm undergo complex surface changes during maturation in the male reproductive tract. Binding affinity and sperm surface binding domains have been demonstrated using immunocytochemical technique. Recent studies using monoclonal antibodies suggest that these highly specific probes are useful for detecting changes in the sperm surface during epididymal transit and in defining the role of these complex changes in sperm maturation and the process of fertilization. Studies involving immunological mapping of the sperm surface, in parallel with immunohistological and functional inhibition test, have provided important information concerning the role of individual sperm antigens in fertility. A better understanding of local antibody production and cell-mediated immune responses in the male reproductive tract has also led to the understanding of immunological infertility. Sperm membrane is comprised of multiple domains each of which is sharply demarcated, with a unique composition and physiological role.

Fully effective contraception in male and female guinea pigs immunized with the sperm protein PH-20

Immunization of male and female animals with extracts of whole sperm cells is known to cause infertility. Also, men and women who spontaneously produce antisperm antibodies are infertile but otherwise healthy. Although the critical sperm antigens are unknown, these observations have led to the proposal that sperm proteins might be useful in the development of a contraceptive vaccine. The guinea pig sperm surface protein PH-20 is essential in sperm adhesion to the extracellular coat (zona pellucida) of the egg, a necessary initial step in fertilization. Here, we report that 100% effective contraception was obtained in male and female guinea pigs immunized with PH-20. Antisera from immunized females had high titres, specifically recognized PH-20 in sperm extracts, and blocked sperm adhesion to the egg zona pellucida in vitro. The contraceptive effect was long-lasting and reversible: immunized females, mated at intervals of six to fifteen months after immunization, progressively regained fertility.

Pathways to immunocontraception: biochemical and immunological properties of glycoprotein antigens of the porcine zona pellucida

The zona pellucida (ZP) is an extracellular coat which surrounds the mammalian oocyte and whose macromolecular composition is unique for each species. Two-dimensional gel electrophoresis of porcine ZP under reducing conditions resolves four major acidic, charge-heterogeneous glycoproteins with apparent molecular weights of 82,000 (ZP1), 61,000 (ZP2), 55,000 (ZP3) and 21,000 (ZP4). Fractionation of heat-solubilized porcine ZP under nondissociative, nonreducing conditions resulted in a preparation, termed purified pig zona antigen (PPZA), substantially enriched in ZP3 and lacking ZP1 and ZP2. PPZA was highly immunogenic in both rabbit and squirrel monkey. Anti-PPZA sera exhibited contraceptive potential as assessed by in vitro inhibition of homologous sperm-zona binding following antibody treatment of human, pig and squirrel monkey oocytes. Alternatively, fractionation of sodium dodecyl sulfate (SDS)-dissociated porcine ZP under nonreducing conditions resulted in isolation of two electrophoretically homogeneous antigens with apparent molecular weights of 82,000 (82K antigen) and 55,000 (55K antigen) as judged by nonreducing SDS-polyacrylamide gel electrophoresis. The 82K antigen exhibited an estimated molecular weight of 345,000 by gel filtration chromatography in nondissociative solvent and was comprised of ZP1 and disulfide-linked heterodimers of ZP2+ZP4 and ZP3+ZP4. The 55K antigen was comprised of ZP3 which was highly aggregated in nondissociative solvent. Each antigen had a characteristic carbohydrate composition and proved to be immunogenic in the rabbit. The effects of active heteroimmunization of squirrel monkeys with 55K antigen on fertility are under investigation.