A comparison of the contraceptive potential of different immunologic presentations of a conjugated preparation of porcine zona pellucida in cow tule elk and domestic ewes

The contraceptive potential of a conjugated preparation of porcine zona pellucida (pZP) was investigated for use in free-ranging tule elk cows and domestic ewes. Native pZP was conjugated to the immunoenhancer keyhole limpet hemocyanin (KLH). To establish the role that presentation of pZP:KLH plays in the immunologic and anti-fertility responses in cow tule elk 4 different immunization groups were employed. During year 2000, calf production ranged from 0% to 50% in pZP:KLH-treated cows, while cows receiving only FIA had a 75% calf production rate. Cows immunized with pZP:KLH emulsified in S-TDCM and FIA, regardless of whether they received a booster inoculation, exhibited the highest anti-pZP antibody titer response and a 0% calving rate in year 2000. Cows from groups immunized with pZP:KLH incorporated into the time-release delivery gel showed absent or minimal anti-pZP antibody titers depending on whether pZP:KLH was presented with adjuvant. Normal ovarian follicular histopathology was present in all cows treated with pZP:KLH as well as in FIA-only immunized cows. Additionally, we examined the ability to generalize physiologic responses to pZP immunization between ungulate species. Ewes immunized with pZP/FCA produced a high anti-pZP antibody response, displayed anovulatory cycles following primary immunization and were infertile. Ewes immunized against pZP:KLH presented with adjuvant S-TDCM and FIA produced only minimal anti-pZP antibody responses, displayed normal estrous cycles and became pregnant. Ewes immunized with pZP:KLH presented in time-release gel or emulsified in mineral oil did not mount an immune response to pZP. Normal ovarian histopathology was present in all ewes treated with pZP:KLH as well as in FIA-only immunized ewes. Taken together, the combined results of research in tule elk and domestic ewes revealed that presentation of the same epitope(s) can elicit a humoral response associated with a reversible return to fertility or an irreversible response associated with destruction of the ovarian microenvironment depending on the species immunized. This research demonstrates clear differences between 2 species of ungulates in the specific mechanism of contraceptive action that results from pZP immunization and confirms previous conjecture that species specificity may be the most important variable in selecting and applying immunocontraceptives. (Abstract shortened by UMI.)...