Human cytomegalovirus infection of human placental explants in culture: histologic and immunohistochemical studies.

The induction of human cytomegalovirus infection in human first-trimester placentas was studied with a placental explant culture model. Replication and/or release of human cytomegalovirus in placental explant cultures did not occur at any time from 1 to 10 days after infection when examined by plaque assay and analyses of extracted deoxyribonucleic acids. In contrast, typical human cytomegalovirus-induced histopathologic lesions bearing human cytomegalovirus antigens were consistently localized in the trophoblastic cells covering placental villi. These data clearly demonstrate that placental cells are permissive of latent and/or abortive human cytomegalovirus infection in vitro. Our results support the hypothesis that during human cytomegalovirus infection of pregnant women, maternal viremia or intrauterine infection results in latent human cytomegalovirus infection of placental cells that may persist during the course of pregnancy.