Pregnancy-blocking progesterone antibody targets specifically the uterus through its progesterone-binding sites

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.

Proto-oncogene erbA expression and increased abundance of progesterone receptors in the mouse uterus after passive immunisation against progesterone before implantation

Passive immunisation with a monoclonal anti-progesterone antibody (DB3) prevents pregnancy in the mouse, and antibody is localised in the endometrium before the onset of implantation. BALB/c female mice were injected intraperitoneally with 9 nmol of DB3 (a dose known to cause 100% infertility) 32 h post coitum, and the uterus was removed at various times after injection. Using a monoclonal anti-progesterone receptor antibody (PR6), expression of progesterone receptors was found to be abundant in uterine tissue of DB3-treated mice; this was associated with substantial progesterone receptor mRNA levels and with maximum localisation of DB3 antibody as detected by anti-idiotype antibody. Control animals treated with an equal amount of the mouse myeloma protein P3 showed very low levels of progesterone receptor in the uterus. DB3 treatment also affected uterine expression of the proto-oncogene erbA product (which shows primary sequence homology with the progesterone receptor) as revealed by specific antiserum to the ERBA protein and by in situ hybridisation with a cDNA probe to v-erbA. Time-course studies indicated that the erbA gene was expressed at a high level before progesterone receptor expression increased, that its expression was dependent on the presence of the embryo and that erbA expression persisted longer in DB3-treated females. The observations suggest that anti-progesterone immunisation has a direct effect within the uterus, involving persistence of proto-oncogene erbA expression (which itself may represent an early maternal response to pregnancy) and increased progesterone receptor levels resulting from an unopposed oestrogen effect derived from local ligand withdrawal.

Biotinylated anti-progesterone monoclonal antibodies specifically target the uterine epithelium and block implantation in the mouse

Post-coital administration of a mouse monoclonal antibody (mAb) against progesterone (DB3; IgG1) prevents pregnancy in several species. Our previous studies in mice have shown that passively transferred DB3 specifically targets the uterus before the expected time of implantation, probably through progesterone-binding sites. DB3 and two other anti-progesterone mAbs, i.e. 11/34 (IgG1) and 11/64 (IgM), were biotinylated and 9 nmol of each (a dose known to reduce pregnancy rate by greater than 80% with unconjugated mAbs) was injected into BALB/c female mice 32 h post coitum (p.c.). The biotin-mAb complexes were highly effective in blocking pregnancy (83-100%) compared with control animals that had received the biotinylated MOPC21 myeloma protein P3 (IgG1). Using the streptavidin-FITC (fluorescein isothiocyanate) reporter complex or second-stage anti-biotin-FITC antibodies, biotinylated conjugates of DB3, 11/34 and 11/64 were specifically localized on the uterine luminal epithelium at 68 h p.c. (i.e. 36 h after i.p. injection). Neither P3-biotin-treated pregnant mice nor biotinylated anti-progesterone mAb-treated pseudopregnant females showed a positive reaction. In addition, the localization of biotin-conjugated anti-progesterone mAbs could be blocked by absorption of the antibodies with free progesterone or progesterone conjugates prior to injection. These results show that localization to the uterine epithelium occurs with different anti-progesterone mAbs, and that this phenomenon is probably associated with progesterone-binding sites on the luminal epithelium.