Replication and Translation of Sperm-introduced Hepatitis B Virus Genesin Embryonic Cells

Objective: Given that hepatitis B virus (HBV) can infect human sperm cells and HBV genes introduced by sperm can be transcribed in developing embryos, we sought to confirm the presence of mature HBV antigens and to assess the mechanism of viral gene replication in embryonic cells. Methods: Human sperm were transfected with recombinant plasmids pIRES2-EGFP-HBs or pIRES2-EGFP-HBc and were then used to fertilize zona-free golden hamster ova. Two-celled embryos with and without green fluorescence were collected for detection of HBV DNA or protein by fluorescence in situ hybridization (FISH), immunofluorescence assay (IA), and enzyme-linked immunosorbent assay (ELISA). Results: 1. Positive FISH signals for HBs- and HBc-DNA were observed in the sperm nuclei and in the nuclei of the two-celled embryos in the test samples but were not detected in the controls. 2. Positive IA signals for HBsAg or HBcAg were detected within the cytoplasm of the two-celled embryos in the test samples but not in the controls. 3. Using ELISA, the level of HBsAg in a single two-celled embryo was 0.064 ng/ ml. Likewise, HBcAg was detected in the five-embryo experimental group. Conclusion: The sperm-introduced HBV S or C genes were able to replicate concomitantly host embryo genome via a semiconservative mode of DNA replication and were able to express viral proteins in the embryonic cells.