Reduction of fertility in female rabbits and mice actively immunized with a germ cell antigen (GA-1) from the rabbit

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.

Immunoregulation of mammalian fertility

Fertility management is a global issue of agricultural, medical, economic, and social consequence. Although many methods have been devised to both inhibit and assist reproduction, more acceptable alternatives are needed. Regulation by immune intervention is a promising technology as applied to livestock, pets, wildlife, and human beings. Outcome is dictated by site within the reproductive axis that is targeted. Fertility is suppressed by immunization against gonadotropin-releasing hormone, gonadotropins, prostaglandin F2 alpha, oxytocin, gonadotropin receptors, and gamete/embryonic antigens. It also is possible to lyse gonadal cells with ligand-antibody hybrid molecules. Ovulation rates are enhanced by vaccination with inhibin. Antibodies to sex steroid hormones have yielded mixed results. Perhaps recombinant viral vectors can be used to deliver reproductive immunogens. A new and simple technique to generate sustained autoimmune reactions to hormones and cellular antigens entails direct gene transfer into somatic cells. Evolving advances in reproductive immunology and biotechnology should furnish us with novel nonsurgical contraceptives and profertility agents that can be efficiently and safely implemented.

Effects of antibodies to sperm surface fertilization antigen-1 on human sperm-zona pellucida interaction

OBJECTIVE

To investigate the effects of antibodies to well-defined sperm surface antigens (the fertilization antigen [FA-1] and germ-cell antigen [GA-1]) and nuclear antigen (protamine) on human sperm-zona interaction.

DESIGN

Number of total and acrosome-reacted human sperm bound to the human zona pellucida and the sperm movement characteristics assessed by computer-aided sperm analysis were evaluated after incubation of sperm with the antibodies.

SETTING

Academic research environment approved by the Institute Review Board.

PATIENTS

Human oocytes were obtained from ovaries removed at surgery. Semen from fertile donors was used in all assays.

INTERVENTIONS

Human oocytes were stored in salt solution at -80 degrees C until used. Spermatozoa were treated with the antibodies to various sperm antigens.

MAIN OUTCOME MEASURES

Total and acrosome-reacted sperm bound to zona pellucida and sperm movement characteristics were evaluated after 3 to 5 hours of incubation of the antibodies with human sperm.

RESULTS

Anti-FA-1 antibodies significantly reduced human sperm fusion with zona-free hamster oocytes and sperm binding to the human zona pellucida but did not affect binding of acrosome-reacted sperm and sperm movement characteristics. Anti-GA-1 and antiprotamine antibodies did not affect sperm-oocyte interaction, acrosomal reaction, or sperm motility.

CONCLUSIONS

Antibodies to FA-1 but not to GA-1 and protamine inhibit human sperm-zona interaction.

Localization of post-vasectomy sperm autoantigens in the Lewis rat

Major rat sperm autoantigens of 86, 63, 43, 28 and 20 kDa are recognized by post-vasectomy and hyperimmunization antisera from the Lewis rat (Handley et al., Biol. Reprod. 39 (1988) 1239-1250). In the present study, affinity purified monospecific isoantibodies to each autoantigen were produced by elution from antigens which had been separated by SDS-PAGE and transferred to nitrocellulose. Western blot analysis confirmed a singular specificity for the 63, 28 and 20 kDa antisera and demonstrated some cross reactivity between the 86 kDa and the 43 kDa antisera. The polyclonal antiserum from which the monospecific antisera were produced stained the entire spermatozoon, while monospecific antibodies bound only to the sperm tail, staining the proximal portion (43 and 28 kDa), a distal domain (63 kDa), or the entire tail (86 kDa). Immunohistochemically stained sections of normal rat testes revealed that the 63, 43 and 28 kDa autoantigens were synchronously expressed in the cytoplasm of spermatids in the apical portions of seminiferous tubules during stages II-VIII in the cycle of the seminiferous epithelium. The 86 kDa autoantigen showed little or no staining in testis sections, implying that this autoantigen appeared on mature sperm following spermiation. These and other data suggest that a highly polymeric structure, possibly within the outer dense fibers of the tail, is a dominant sperm autoimmunogen following vasectomy of the Lewis rat.

Vasectomy-induced autoimmunity: monoclonal antibodies affect sperm function and in vitro fertilization

A panel of sperm-reacted monoclonal auto-antibodies developed from spleen cells of vasectomized mice (BDF1) were characterized. Immunogenic antigens were mainly located on the acrosome, midpiece and principal piece. All of the monoclonals were IgM; three demonstrated a multispecific reaction with testis and/or epididymis antigen extracts by immunoblotting. Immunobead studies indicated that most of the antibodies were to surface molecules, a finding supported by the observation that five of the seven antibodies caused complement-mediated immobilization (although not sperm agglutination) of mouse sperm. In vitro fertilization was significantly impaired when antibodies (Vx5, 8 and 10) were added to the sperm prior to exposure to the eggs. Furthermore, passive immunization with Vx5 antibody reduced in vivo fertilization. Our findings indicate that vasectomy-generated antibodies can reduce sperm function in vitro and in vivo.

The fertilization antigen (FA-1) causes a reduction of fertility in actively immunized female rabbits

Female rabbits were actively immunized against the fertilization antigen (FA-1) isolated from lithium diiodosalicylate (LIS)-solubilized murine testis. Three trials were performed in order to check the effect of immunization on fertility. In all of these trials, there was a significant (P less than 0.001) reduction of fertility as determined by the percentage of 9-day implants/corpora lutea ratio (FA-1, 0-26.3%; adjuvant control, 79.4-100%). A complete block was observed in animals which received intravenous booster immunization with the antigen. Antisera collected from FA-1-immunized rabbits were negative in the agglutination and the immobilization techniques, and demonstrated modal titers of greater than or equal to 1:2560 in the enzyme linked immunosorbent assay (ELISA) using FA-1. Antisera were tissue-specific and showed binding to the specific protein bands of 47,000 and 23,000 Mr, dimeric and monomeric forms of FA-1, respectively, in the Western blot procedure. Ova collected from rabbits inseminated with sperm which had been treated with antiserum from immunized rabbits showed reduced fertilization rates (anti-FA-1, 3.9-27.7%; control rabbit serum, 87.8%). There was again a reduction in percentage of the 9-day implants/corpora lutea ratio in the rabbits inseminated with treated sperm (anti-FA-1, 10.7%; control rabbit serum, 72.7%). It is concluded that active immunization with FA-1 resulted in a tissue-specific immune response which caused a reduction of fertility in rabbits, by a mechanism(s) involving an inhibition of the fertilization process.