The effect of experimental infection of mouse preimplantation embryos with paramyxovirus Sendai.

Zona-intact and zona-free mouse embryos at the morula stage were exposed to Sendai virus in vitro, and then transferred to the uteri of recipient foster mothers. Both embryos developed into expanded blastocyst stage after 48 hr of culture. Zona-intact embryos were resistant to infection and subsequent transfer resulted in the development of fetuses, indicating that the zona pellucida plays a role of a barrier to virus infection. On the other hand, zona-free embryos were susceptible to infection and only one fetus out of 64 transfers developed to term. Implantation sites were scarcely observed in the uteri of the foster mothers that received zona-free embryos, suggesting that most of the embryos did not develop after embryo transfer. Sendai virus was shed in the culture fluid of the zona-free embryos indicating viral replication in the embryonic cells. By immunofluorescence assay, viral antigens were detected in the embryos, tissues of the fetus and implantation site derived from the zona-free embryos. These findings indicate that replication of Sendai virus in the embryonic cells interfere with early embryonic development and fetal growth of the embryo.