Role of placental tissues in the intrauterine transmission of hepatitis B virus

OBJECTIVE: The purpose of this study was to determine the mechanism of intr auterine transmission of hepatitis B virus. \STUDY DESIGN: Placental tissues from 158 pregnant women who tested positiv e for hepatitis B surface antigen were examined for hepatitis B virus marke rs, Fc gamma receptors, and hepatitis B surface antigen-anti-hepatitis B su rface antigen in different layers of cells. RESULTS: It was shown that the hepatitis B virus infection rate among diffe rent layers of placental cells gradually decreased from the maternal side t o the fetal side. Furthermore, the closer the infected cell layer was to th e fetal side, the higher the risk of intrauterine hepatitis B virus infecti on. Fe gamma receptors were found on cells of both hepatitis B surface anti gen positive and negative placentas; Fc, gamma receptors Ill were found on trophoblastic cells and villous mesenchymal cells, and Fc gamma receptors I I were found on only villous mesenchymal cells. Hepatitis B surface antigen -antibodies to hepatitis B surface antigen was detected in the cytoplasm an d on the membrane of trophoblastic cells and villous mesenchymal cells in 2 hepatitis B surface antigen-positive placentas. CONCLUSION: The results support the hypothesis that intrauterine hepatitis B virus transmission could be caused through "cellular transfer" in the pla centa. One of the means of cellular transfer could be through Fe gamma rece ptor III-mediated entry of hepatitis B surface antigen-antibodies to hepati tis B surface antigen into cells.