[HBsAg uptake into human trophoblasts cultured in vitro]

To detect the entry of HBsAg into human trophoblasts cultured in vitro, to provide some clues for the mechanism responsible for HBV intrauterine transmission.

Digestion with both trypsin (0.25%) and Dnase I(0.15 U/ml) followed by repeated purification was performed to obtain a homogeneous population of trophoblast cells. The well-developed cells during longitudinal phase were randomly divided in 6 groups, which were co-incubated respectively with HBsAg-anti-HBs complex (I), co-culture of heat-inactivated sera positive for HBsAg, HBeAg, and anti-HBc and sera with high titer anti-HBs(II), heat-inactivated sera positive for HBsAg, HBeAg, and anti-HBc(III), HBsAg (IV), heat-inactivated normal sera (V), and normal medium(VI). The coverglasses mounted with confluent cells were harvested for anti-HBs immunohistochemical staining.

The isolated cells comprised a highly purified villous trophoblast population and could meet the demands of further experiments. After co-incubation of the cells with different agents, HBsAg test yielded positive results in the cells co-incubated with the HBsAg-anti-HBs complex and in the co-cultures of heat-inactivated sera positive for HBsAg, HBeAg and anti-HBc with sera containing high-titer anti-HBs. HBsAg test was negative in all other cell groups.

Human trophoblast cells could take in HBsAg in the form of HBsAg-anti-HBs complex instead of single HBsAg molecule.