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  • Title: Anti-trophectoderm vaccines: rationale and methods used for antigen identification and selection.
    Author: Bambra CS.
    Journal: Scand J Immunol Suppl; 1992; 11():131-6. PubMed ID: 1514028.
    Abstract:
    Trophoblast, forming a continuous interface at the maternal-fetal junction, is of considerable interest to biologists. An area of recent research is the search for trophoblast-specific antigens. It is believed that identification and characterization of these antigens may have many practical applications such as in development of contragestational vaccines. To be acceptable for humans such a vaccine will need to be effective before the completion of implantation and appearance of the primitive streak about 14 days after fertilization. This will not alter the menstrual cycle or the time of menses. Vaccines having a later effect resulting in termination of pregnancy after this time would be considered abortifacients. Although logistical and ethical considerations necessitated the use of post-implantation human trophoblast in WHO Birth Control Vaccine studies, the antigens isolated from such tissues would need to be expressed and be detectable on the surface of pre-implantation trophectoderm if they are to represent appropriate candidates for vaccine development. The criteria for identification and selection of these antigens will be reviewed. Monoclonal or polyclonal antibodies to trophoblast components can be used to identify specific antigens. Such a vaccine will need to be effective before the completion of implantation and the appearance of the primitive streak about 14 days after fertilization. Monoclonal antibodies were evaluated at the Institute of Primate Research from WHO Panels and ones produced locally. Based on the results of placental reactivity, 12 antibodies were selected for further study and screened against selected baboon tissues. Monoclonal antibody T75 had the best specificity. A laparoscopic-guided uterine flush system was developed to replace the existing non surgical flush method in an effort to improve on the embryo recovery rate. Female baboons were introduced into the male cage for 5 hours/day for 6.3 +or- 3.4 days at stage 2, 3, or 4. 30 baboons were used in this study, but the animals were not flushed when bilateral adhesions were evident and the cervix or uterus could not be cannulated. Successful uterine flushed with immediate and complete return of the cultural medium were don in 20 animals. Superovulation of the baboons was tried to raise more embryos available for screening monoclonal antibodies. 4 animals were injected with human M gonadotropin (hMG) to stimulate follicular growth followed by human chorionic gonadotropin (hCG) to induce ovulation. Animals were mated following injection of hCG and laparoscopy was performed on day 6 of estimated pregnancy. Although follicular growth was evident, ovulation was not successful. Only 1 embryo was recovered from the 4 animals flushed. The recovered embryos were used for developing a cryosectioning technique to provide sections for screening monoclonal antibodies against pre implantation trophectoderm. Of the 8 baboon antibodies screened only 3 E7 showed reactivity against pre implantation baboon embryos.
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