Immunobiology of Early Pregnancy - A Model of Virus-induced Abortion

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The lack of 'self' molecule expression on the trophoblast cells of the placenta which interface directly with the mother's circulation, as well as the local suppression of the mother's immune response at this interface, may be important factors in the successful implantation of the embryo. This immunological 'silence' allows the embryo, whose paternal genetic contribution makes it immunologically foreign to the mother, to escape the rejection reaction normally associated with foreign graft transplantation. Infection with flaviviruses increases the concentrations of cell surface self and adhesion molecules in vertebrate cells, including the trophoblast cells of the placenta. As a result, these molecules can then be recognised by the maternal immune system and the embryo targeted for destruction. We hypothesise that the induction of these molecules by this and other viruses may break the immunological silence of the early embryo and reverse the local suppression of the maternal immune response. This would result in maternal immune rejection of the embryo and abortion. This initial sensitisation of the mother by the virus might be one of the reasons that some women suffer recurrent abortions. We will use a novel viral mouse model where we implant virus-infected embryos into receptive animals to enable us to dissect out the unusual requirements for induction of maternal anti-viral immunity during pregnancy. This model was developed in our laboratory to directly test our hypotheses. It does not cause systemic illness in the mother which itself can lead to non-specific abortion. This model therefore can for the first time elucidate the specific mechanisms associated with the delicate balance between eradicating virus and maintaining pregnancy. Results from this project will inform rational design of treatment of recurrent abortions in the community.