Abstract
To investigate the effect of murine cytomegalovirus (MCMV) infection on implantation stage embryos, mouse blastocysts were exposed to MCMV in vitro and then surgically transferred to foster mice. When denuded blastocysts were exposed to MCMV, only 1 mother out of 14 gave birth to two live babies. In contrast when intact blastocysts were exposed to MCMV, the percentage of live births occurring in all mothers was not significantly different from that of controls. MCMV was also isolated from uterine washings of five out of seven mice which had received denuded MCMV-exposed blastocysts. Serological and DNA restriction enzyme analyses showed that the stock MCMV and the virus isolates were identical. MCMV microinjected into uterine lumen of pregnant mice at the time of embryo implantation resulted in a fetal loss with occasional inflammation of uteri. Tissue extracts obtained from implantation sites of the mice shed MCMV when cocultivated with mouse embryo fibroblasts (MEF). In contrast, little fetal loss occurred in pregnant mice whose uteri were microinjected with heat-inactivated MCMV. Tissue extracts derived from implantation sites of these mice did not yield virus when cocultivated with MEF. Thus, MCMV has a detrimental effect on mouse implantation stage embryos and the presence of MCMV at the time of embryo implantation may result in fetal loss.
