Abstract: BACKGROUND ＆ AIM: To study whether hepatitis B virus DNA carried by oocyte can express and replicate in mouse embryo, then provide evidence for that HBV can transmit vertically via oocytes. MATERIAL AND METHODS: Ovaries of young adult female mice were injected with HBV DNA. These females were superovulated after an estrual cycle and serially mated to males. Two-cell embryos were collected for Fluorescence in situ hybridization (FISH) to detect the integration of HBV DNA into nuclei and its replication with cell division in embryonic development. Reverse transcriptase polymerase chain reaction(RT-PCR) and immunofluorescence assay were performed to observe the expression of the HBV gene in two-cell stage. RESULTS: FISH demonstrated that the each nucleus in some two-cell embryos presented positive signals for HBx DNA.RT-PCR showed the specific bands of cDNA of HBx DNA in some two-cell embryos. Immunofluoresence assay presented the positive signals for HBsAg in some two-cell embryos. CONCLUSION: HBV DNA integrated into oocyte genome can be brought into embryo by fertilization with normal spermatozoon. The replication and expression of HBV genes in embryo provide the direct evidence for that HBV DNA are able to transmit vertically to next generation via female germ line.

Key words: hepatitis B virus DNA, replication and expression, oocyte, mouse embryo