BACKGROUNDTo construct recombinant retroviral vector expressing HBcAg in eukaryotic cells.

METHODSThe HBV core gene fragment was amplified by using PCR from pADR which contains complement nucleotide sequence of HBV subtype adr and cloned into retroviral expression plasmid pLXSN, then transfected into packing cell (PT67) with lipofec AMINE. After 2-3 weeks selection with G418, large colonies were isolated and transferred to individual plates. Virus-containing medium was collected and used to infect NIH3T3, EL4 and mouse bone marrow derived dendritic cells(DC). DNA was extracted from infected cells and tested by PCR. Indirect immunofluorescence and FACS were used to detect the expression of HBcAg. Cell mediated immunity of immunized C57BL/6 mice with transduced DC was analyzed.

RESULTSThe insertion of HBV core gene fragment in the recombinant retroviral plasmid was confirmed by PCR as well as enzyme digestion with EcoR1 and BamH2. The viral titer reached 3 x 10(5) CFU/ml. The result of PCR showed that the HBV core gene had been integrated into the genome of infected NIH3T3 cells. Indirect immunofluorescence and FACS analysis showed that HBcAg had been expressed in these cells. HBcAg specific CTL responses could be generated in mice immunized with retrovirus transduced DC.

CONCLUSIONSHBV core gene had been integrated into eukaryotic cells with retroviral vector and target gene had been expressed efficiently. These results may have some impact on gene therapy of chronic hepatitis B.