AIM:Cytotoxic T lymphocytes (CTLs) play an important rolein resolving HBV infection.In the present study,weattempted to evaluate the efficiency of bone marrow-deriveddendritic cells (DCs) transduced with recombinant retroviralvector bearing hepatitis B virus (HBV) core gene and thecapability of generating CTLs against HBcAg by geneticallymodified DCs in vivo.METHODS:A retroviral vector containing HBV core genewas constructed.Replicating DC progenitor of C57BL/6 micewas transduced by retroviral vector and continually culturedin the presence of recombinant mouse granulocyte-macrophage colony-stimulating factor (rmGM-CSF) andinterleukin-4(IL-4) for 6 days.LPS was added and culturedfor additional two days.The efficiency of gene transfer wasdetermined by PCR,Western blot and FACS.Transduced DCsimmunized C57BL/6 mice subcutaneously 2 times at an one-week interval.Intracellular IFN-γ,and IL-4 of immunized micelymphocytes were analyzed.Generation of CTLs in lymphocytesstimulated with mitomycin C-treated EL4-C cell which stablyexpresses HBcAg was determined by LDH release assays.RESULTS:Recombinant retroviral expression vector(pLCSN) was positively detected by PCR as well as enzymedigestion with EcoRI and BamH I.Retroviruses weregenerated by pLCSN transfection packing cell and the virustiter was 3×10~5 CFU/ml.Indirect immunofluorescence andFACS showed that HBV core gene was expressed in murinefibroblasts.Transduced bone marrow cells had capability ofdifferentiating into DCs in vitro in the presence of rmGM-CSF and rmIL-4.The result of PCR showed that HBV coregene was integrated into the genome of transduced DCs.Western blot analysis showed that HBV core gene wasexpressed in DCs.The transduction rate was 28% determinedby FACS.Retroviral transduction had no influence on DCsexpressions of CDS0 and MHC class Ⅱ.HBcAg specific CTLsand Thl type immune responses could be generated inthe mice by using transduced DCs as antigen presentingcells (APCs).CONCLUSION:Retroviral transduction of myeloid DCs progenitors expresses efficiently HBcAg,and geneticallymodified DCs evoke a higher CTLs response than HBcAgin vivo. AIM: Cytotoxic T lymphocytes (CTLs) play an important rolein resolving HBV infection. In the present study, weattempted to evaluate the efficiency of bone marrow-derived dendritic cells (DCs) transduced with recombinant retroviral vector bearing hepatitis B virus (HBV) core gene and thecapability of generating CTLs against HBcAg by genetically modified DCs in vivo. METHODS: A retroviral vector containing HBV core genewas constructed. Replicating DC progenitor of C57BL / 6 micewas transduced by retroviral vector and continually cultured in the presence of recombinant mouse granulocyte-macrophage colony-stimulating factor ( rmGM-CSF) and interleukin-4 (IL-4) for 6 days. LPS was added and cultured for additional two days. The efficiency of gene transfer was determined by PCR, Western blot and FACS. Transduced DCsimmunized C57BL / 6 mice subcutaneously 2 times at an one-week interval. Intracellular IFN-γ, and IL-4 of immunized mice lymphocytes were analyzed. Generation of CTLs in lymphocytesstimulated with mitomyci nC-treated EL4-C cell which stablyexpresses HBcAg was determined by LDH release assays .RESULTS: Recombinant retroviral expression vector (pLCSN) was positively detected by PCR as well as enzymedigestion with EcoRI and BamH I.Retroviruses weregenerated by pLCSN transfection packing cell and the virustiter was 3 × 10 ~ 5 CFU / ml. Indirect immunofluorescence and FACS showed that HBV core gene was expressed in murine fibroblasts. Transduced bone marrow cells had capability of differentiating into DCs in vitro in presence of rmGM-CSF and rmIL-4.The result of PCR showed that HBV core gene was integrated into the genome of transduced DCs. Western blot analysis showed that HBV core gene wasexpressed in DCs. The transduction rate was 28% determined by FACS. Retroviral transduction had no influence on DCsexpressions of CDS0 and MHC class II. HBcAg specific CTLs and Thl type immune responses could be generated inthe mice by using transduced DCs as antigen presenting cells (APCs) .CONCLUSION: Retroviral transduc tion of myeloid DCs progenitors expressesfficient HBcAg, and genetically modified DCs evoke a higher CTLs response than HBcAgin vivo.