Detection of Human Cytomegalovirus in Amniotic Fluid and Villous Tissues

Background/PurposeHuman cytomegalovirus (HCMV) is the most common cause of intrauterine infection. Endothelial and/or epithelial cells in uterine tissue are major sites of latent or persistent HCMV infection in women, and the uterus may play an important role in viral dissemination. To elucidate the pathomechanisms of intrauterine infection by HCMV, we examined the presence of the HCMV genome, antigen and infectious virion in amniotic fluid and villous tissues.MethodsThe isolation of infectious HCMV in amniotic fluid was detected using the MRC-5 human embryonic fibroblast cell line. The HCMV genome was detected by polymerase chain reaction. Expression and distribution of HCMV antigens and mRNA transcripts in villous tissues were examined by immunostaining using primary antibodies specific for an immediate early nuclear antigen and for a late cytoplasmic antigen of HCMV, and in situ hybridization using an antisense probe specific for the phosphoprotein 71 (pp71) region of HCMV, respectively.ResultsThe HCMV genome was detected in 46 (26%) out of 176 amniotic fluid specimens. Moreover, the infectious virus was isolated in nine of these specimens (5.1%), with viral immediate early and late antigens being detected in the cultured cells of amniotic fluid. In the villous tissues of all examined cases (7/7), viral mRNA and antigen were detected, and 48% of the pregnant women whose cervical smears were positive for the HCMV genome by polymerase chain reaction delivered babies with positive urinary samples.ConclusionThese results suggest that transplacental transmission of HCMV to the fetus occurs more frequently than has been previously reported. Further studies are necessary to precisely clarify the mechanisms of intrauterine HCMV infection.