The fertilization antigen (FA-1): applications in immunocontraception and infertility in humans

Expression of recombinant mouse sperm protein sp56 and assessment of its potential for use as an antigen in an immunocontraceptive vaccine

Recombinant mouse sp56 protein was produced for testing as an antigen in an immunocontraceptive vaccine. The coding sequence for the mature sp56 protein was cloned into the bacterial expression system pFLAG using a PCR-based method on mouse testis cDNA. Polyclonal antisera were raised in mice against affinity purified recombinant sp56 fusion protein (sp56FLAG) or an artificial sp56 peptide fused to a carrier protein (KLH) and shown to cross-react to a protein band of 75 kD in detergent extracts of mouse sperm by Western immunoblot analysis under reducing conditions. The antisera to sp56FLAG also immunolocalized over the entire acrosome of mouse sperm. Female BALB/c mice were immunized intraperitoneally with sp56FLAG in a fertility trial with 20 microg sp56FLAG in Freund's Complete Adjuvant and boosted three to five times with 20 microg sp56FLAG in Freund's Incomplete Adjuvant. Litter sizes of sp56FLAG-treated mice were significantly smaller than control-treated animals after five boosts.

Review: in vitro spermicidal tests

This review analyzes in vitro spermicidal tests that have been used to evaluate the spermicidal activity of contraceptive products. Special requirements and processes in numerous technologies were also reviewed. Nonoxynol-9 (N-9) was used as an example of a vaginally delivered spermicidal agent, and its spermicidal potency was compared by various spermicidal tests, such as Sander-Cramer, computer-assisted semen analysis, hypoosmotic swelling test, cervical mucus penetration test, and flow cytometry, and advantages and disadvantages of each test were specified. This provides an insight into the different aspects of sperm functionality on which each spermicidal agent exerts its activity. A rationale of the best combination of in vitro spermicidal tests, with particular emphasis on a simple and efficient strategy that targets the complete fertility control, was explained.

Immunization to regulate fertility: biological and cultural frameworks

Deliberate immunization to control fertility differs from that to control disease. Those differences can be discussed within various frameworks, e.g., intent, recipient population, biological bases, and immunological targets. Others include differing perspectives of developers, providers and users, and rights of the state to impose programs of control. Almost all of the differences are grounded in the social, economic, and gendered aspects of societies. The intent of providing a fertility-regulating vaccine is to prevent pregnancy. In theory, men as well as women could receive such vaccines; in reality, most are designed for women. Traditional vaccines are intended to prevent disease and are generally given to susceptible individuals whether male or female, child or adult. The biological bases of contraceptive vaccines are molecules specific to reproduction. The immune response generated by most anti-fertility vaccines is directed toward 'self', one's own cells and molecules. In contrast, the bases of traditional vaccines are materials derived from non-self, disease-causing microorganisms; the immunological targets are those microorganisms or their toxic products. From a developer perspective vaccines that regulate fertility differ little from those that control disease; both prevent a particular condition. Developers cite these advantages to contraceptive vaccines: non-invasive, no serious side-effects, easy to use, reduced patient failure, and long-lasting but naturally reversible. Because anti-fertility vaccines have been tested only in small-scale clinical trials, information on user reactions and experiences is limited. Not surprisingly, the perspectives of women's health advocates and of potential users (mostly women) often differ markedly from those of developers. Women cite as disadvantages the cryptic nature of immunity which leaves one without an obvious signal for the beginning of protection (against pregnancy) and its decline, and the inability to 'turn-off' an immune response. Further, long-acting contraception can complicate alleviation and side-effects, and it leaves women always vulnerable to sexual demands. Most women object to the lack of user control and are especially concerned about the enormous potential for misuse and coercion by population control programs should fertility-regulating vaccines become widely available. Many scholars and government officials subscribe to the following logic: the global environmental crisis is due to over-population which necessitates population control programs; thus pregnancy can be considered a disease subject to state control. But pregnancy is not a disease nor is over-population the single major cause of environmental degradation. However, as governments grapple with the economic, social, and ecological consequences of population growth, draconian measures to control fertility will be ever more tempting.(ABSTRACT TRUNCATED AT 400 WORDS)

Thymosin alpha-1 and FA-1 monoclonal antibody affect fertilizing capacity of human sperm by modulating protein phosphorylation pattern

The present investigation was conducted to investigate the modulation of phosphorylation pattern of human sperm membrane proteins during capacitation by thymosin alpha-1 (T alpha 1) (which enhanced sperm penetration index) and anti-FA-1 monoclonal antibody (anti-FA-1 mAb) (which completely blocked sperm penetration) using 32P metabolic labeling, in vitro kinase assay and Western immunoblot analysis. In 32P metabolic labeling experiments, T alpha 1 (0.25 and 0.5 microgram/100 microliters) enhanced phosphorylation of 7 proteins in four molecular regions namely one protein (190 kDa) in 200-kDa, two proteins (112 and 104 kDa) in 97-kDa, two proteins (48 and 42 kDa) in 43-kDa and two proteins (31 and 25 kDa) in 29-kDa molecular regions, respectively. Anti-FA-1 mAb (10 micrograms/100 microliters) resulted in a general decrease in the 32P labeling of these sperm proteins. In in vitro kinase assay using non-capacitated sperm extracts, T alpha 1 (0.5 microgram/100 microliters) enhanced autophosphorylation of 14 proteins in various molecular regions (122, 105, 95, 89, 73, 62, 48, 46, 40, 33, 30, 28, 25 and 22 kDa, respectively). The same concentration of T alpha 1 did not affect autophosphorylation of proteins in capacitated sperm extract. Anti-FA-1 mAb (10 micrograms/100 microliters) inhibited autophosphorylation of a subset of 8 proteins (122, 104, 95, 89, 73, 62, 48 and 46 kDa, respectively) in non-capacitated sperm membrane extracts, and 12 proteins (112, 104, 95, 89, 73, 62, 48, 46, 33, 30, 28 and 25 kDa, respectively) in capacitated sperm membrane extracts. In the Western immunoblot analysis, T alpha 1 resulted in a concentration-dependent increase in tyrosine phosphorylation of two proteins (95 and 51 kDa) during capacitation of human sperm, whereas anti-FA-1 mAb inhibited tyrosine phosphorylation of both proteins. These results indicate that T alpha 1 and anti-FA-1 mAb affect the fertilizing capacity of human sperm by modulating phosphorylation of proteins especially tyrosine phosphorylation of 95- and 51-kDa proteins during capacitation. These findings also suggest that there may be a signal transduction pathway(s) involved in phosphorylation of membrane proteins during capacitation and that an exogenous stimulus affecting a single membrane protein component can modulate phosphorylation of all the relevant proteins involved in capacitation/acrosome reaction of human sperm.

Semen alloantigens and lymphocytotoxic antibodies in AIDS and ICL

More than 90% of people with AIDS develop circulating immune complexes (CICs) and lymphocytotoxic antibodies (LCTAs). Animals infected with HIV, however, never display CICs or LCTAs, and remain healthy. Similarly, HIV-infected people who do not develop CICs or LCTAs also do not progress to AIDS. The appearance of CICs and LCTAs is, however, highly prognostic for AIDS and death. Since HIV infection does not, per se, lead to the development of CICs and LCTAs, other causes are likely. One such cause, for which both epidemiologic and experimental evidence exists, is semen. Semen components include sperm, seminal fluid, lymphocytes, and sometimes infectious agents, including HIV, mycoplasmas, and herpes and hepatitis viruses, all of which independently cause immune suppression. Extensive evidence demonstrates sperm (and various viruses) contains many proteins mimicking the CD4 protein of T-helper cells, while HIV, mycoplasmas, and seminal fluid mimic class II MHC proteins of other lymphocytes. We identify a large number of protein sequences that display such mimicry using computer homology searching, and demonstrate experimentally that sperm antibodies specifically precipitate antibodies against class II MHC mimics such as mycoplasmas, which in turn precipitate antibodies to lymphocyte antigens. These data prove that immunologic exposure to sperm and lymphocytes (as may occur in receptive anal intercourse, needle sharing, or blood transfusions) is theoretically capable of initiating lymphocytotoxic autoimmunity. Such autoimmunity may play a significant role in the pathogenesis of AIDS, and will need to be addressed clinically in high risk individuals regardless of HIV status and regardless of the success of anti-HIV prophylaxis and treatment.

Identification of human sperm antigens reacting with antisperm antibodies from sera and genital tract secretions

OBJECTIVE

To identify sperm antigens reacting with antisperm antibodies relevant in human infertility.

DESIGN

The reactions of separated sperm antigens with antibodies present in sera and genital tract secretions from infertile and fertile females and males were examined by immunoblotting techniques.

SETTING

The patients were followed in an outpatient setting of a hospital clinic.

PATIENTS

One hundred consecutive infertile males and females, referred for determinations of antisperm antibodies, comprised the study group. Fifty hospital and faculty employees with proven fertility served as a control group.

RESULTS

A high proportion of sera from fertile and infertile humans contained antibodies reacting with at least one sperm antigen. However, two discrete bands of antigenic proteins with molecular weights of 44 and 72 kd reacted significantly more frequently with serum antibodies from infertile females than from fertile females. No apparent correlation could be demonstrated between any particular antigen and serum antibodies from infertile males. Nevertheless, antigenic proteins of 62 kd were identified as the major sperm antigens reacting with antibodies present in seminal plasmas from infertile males.

CONCLUSIONS

The major sperm antigens reacting with systemic antibodies differ from the antigens recognized by local antisperm antibodies. Sperm antigens exhibiting relative molecular weights of 62 kd are major antigens reactive with local antisperm antibodies from infertile humans.

The fertilization antigen-1 does not have proteolytic/acrosin activity, but its monoclonal antibody inhibits sperm capacitation and acrosome reaction

OBJECTIVE

To determine if human sperm surface fertilization antigen exhibits proteolytic or acrosin activity and to investigate the mechanism(s) whereby monoclonal antibody (mAb) to fertilization antigen inhibits human sperm penetration of zona-free hamster ova.

DESIGN

Proteolytic and acrosin activities of human fertilization antigen were determined. Acrosomal status, acrosin activity, and motion characteristics were evaluated after incubation of human sperm with immunoaffinity-purified mAb to fertilization antigen.

SETTING

Academic research environment.

PARTICIPANTS

Fertile donors used as controls for infertile patients for fertility evaluation.

INTERVENTIONS

Human spermatozoa were treated with mAb to fertilization antigen and induced to undergo acrosome reaction using calcium ionophore A23187.

MAIN OUTCOME MEASURES

Proteolytic and acrosin activities of fertilization antigen. Sperm penetration assay, acrosomal status, and motion parameters.

RESULTS

Fertilization antigen does not exhibit proteolytic or acrosin activity; however, its mAb completely blocks human sperm penetration of zona-free hamster ova. The mAb to fertilization antigen inhibits ionophore-induced acrosome reaction and blocks development of the hyperactivated state of human sperm cells.

CONCLUSIONS

Monoclonal antibody to fertilization antigen blocks fertilization by inhibiting capacitation and acrosome reaction.

Human spermatozoal FA-1 binds with ZP3 of porcine zona pellucida

Experiments were carried out to study the binding of the major porcine zona pellucida glycoprotein ZP3 (Mr = 55,000) with human FA-1, a fertilization-related antigen isolated from human male germ cell plasma membranes and with GA-1, a germ cell antigen isolated from murine male germ cell plasma membranes. FA-1 showed a dose-dependent binding with ZP3 in an enzyme-linked immunosorbent assay (ELISA) and by the Western blot procedure. FA-1 also bioneutralized the sperm ligand activity of ZP3 in a boar sperm/porcine zona pellucida attachment assay. In contrast, GA-1 displayed no reactivity for ZP3 using any of these procedures. These results indicate that FA-1 but not GA-1 has zona pellucida binding activity in the porcine system.

Effects of sperm-reactive antibodies present in human infertile sera on fertility of female rabbits

Sera (n = 19) from immunoinfertile patients were analyzed for cross-reaction with lithium diiodosalicylate (LIS)-solubilized human sperm extract (HSE), protamine and fertilization antigen (FA-1) using an enzyme-linked immunosorbent assay (ELISA). Among the sera tested, 63% reacted with HSE, 58% with protamine and 63% with FA-1. None of the sera from male or female infertile patients was found to contain immune complexes, indicating the antibodies were present in free form. The seven sera that reacted strongest with HSE inhibited human sperm function in sperm penetration of zona-free hamster ova and were associated with fertilization failure in human in vitro fertilization (IVF) technique. The six of these sera that showed binding to rabbit sperm, especially in the head region, also inhibited fertility in female rabbits. Antibodies reactive with FA-1 and not those reactive with protamine reduced fertility in female rabbits. These results indicate that mammalian sperm have several fertilization-related antigens that are evolutionarily conserved. These data also indicate that the rabbit can provide an animal model for studying antibody-mediated human infertility.

Lymphocyte proliferative response to fertilization antigen in patients with antisperm antibodies

The fertilization antigen, immunopurified from human testes, activated lymphocytes from three of the six men and women with antisperm antibodies. Lymphocytes from none of the six men and women without antibodies were activated with fertilization antigen. Another sperm surface antigen, the germ cell antigen, immunopurified from murine testes, did not activate lymphocytes from any of the individuals with or without antisperm antibodies. These results indicate that the men and women with antisperm antibodies are sensitized against fertilization antigen and not germ cell antigen. These results reinforce our previous findings on the involvement of fertilization antigen in immunoinfertility in humans.

Antibodies to sperm surface fertilization antigen (FA-1): their specificities and site of interaction with sperm in male genital tract

The fertilization antigen (FA-1) isolated from murine testes demonstrated its dimeric form of 49,000 +/- 2,000 molecular weight (M.W.) or a monomer of 23,000 M.W. on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The FA-1 was immunogenic in all three female rabbits tested and raised a high-titer antisera [enzyme-linked immunosorbent assay (ELISA) titers; 1:1,024 to 1:4,096]. The rabbit anti-FA-1 antisera predominantly recognized the dimeric form of 49,000 +/- 2,000 M.W. on the Western blot of lithium diiodosalicylate (LIS)-solubilized murine testes. None of the antisera reacted with any somatic tissue, indicating germ-cell specificity of FA-1. To determine the cellular localization of the immunoreactive FA-1, a novel ultrasensitive immunogold-silver staining (IGSS) procedure was developed. The anti-FA-1-IgG showed intense staining in the luminal region of the seminiferous tubules containing spermatids and spermatozoa. No reaction was observed in the peripheral area of the tubules containing Sertoli cells, spermatogonia, leptotene, and zygotene spermatocytes. The biodistribution studies of 125I-labeled anti-FA-1 IgG in mice revealed that the antibodies do not bind to somatic tissues such as blood cell, liver, heart, kidney, muscle, and gastrointestinal tissue and do not transudate into testes and seminal vesicle. However, the antibodies preferentially transudate into epididymis (especially corpus or cauda regions) and vas deferens to bind to sperm cells. In conclusion, our data indicate that FA-1 can induce an immune response that is germ cell-specific, directed against later stages of spermatogenesis. The antibodies to FA-1 interact with sperm after penetration through epididymis (especially corpus and cauda regions) and vas deferens rather than through testes and seminal vesicles.

Sperm antibodies after intraperitoneal insemination of sperm: a preliminary report

To test the hypothesis that intraperitoneal insemination of sperm induces the expression of anti-sperm antibodies a prospective study was designed. Fifteen women undergoing intraperitoneal insemination (with or without oocyte transfer) were studied with 11 women having evaluation of anti-sperm antibodies. Sperm antibodies were detected by the immunobead test prior to intraperitoneal insemination and after each treatment cycle. Two criteria were used to assess positivity: the first based upon negative controls and the second based upon the evaluation of 20 fertile control couples. Using the first criteria, of 11 of the women undergoing IPI for the first time, 7 were initially negative and 4 were initially positive for at least 1 isotype. After treatment, 3 additional patients were positive (for a total of 7) and 4 patients remained negative. This alteration in sperm antibody frequency was not different (P = .4) as determined by the Fisher's Exact Test. Four of the 11 patients underwent a second cycle of IPI. All 4 patients were negative prior to the first treatment and 3 were negative prior to the second treatment. Subsequent to the second exposure, all 4 of these women were positive for at least 1 isotype. This shift in frequency distribution after 2 cycles was significant (P = .01). The frequency of antisperm antibodies for the same 11 patients was evaluated by using fertile control values as the basis of positivity. Two patients (18%) were positive for anti-sperm antibodies prior to intraperitoneal insemination. There was no change in the frequency of positivity after 1 cycle of IPI.(ABSTRACT TRUNCATED AT 250 WORDS)