1024©2007 CPS and SIMM
Acta Pharmacol Sin 2007 Jul; 28 (7): 1024–1030
Non-cytolytic antigen clearance in DNA-vaccinated mice with electro-
Jin-liang PENG2,5, Yong-gang ZHAO2,5, Jun-hua MAI2, Wen-ka PANG2, Wei GUO2, Guang-ming CHEN4, Guo-yu MO4, Gui-
rong RAO4, Yu-hong XU2,3,6
Schools of 2Life Sciences and Technology and 3Pharmacy, Shanghai Jiao Tong University, Shanghai 200240, China; 4People’s Liberation
Army’s Liver Disease Research Center, 458 Hospital of People's Liberation Army. Guangzhou 510400, China
Hepatitis B virus (HBV) infection remains a serious world-
wide health problem. Approximately 5%–15% of infected
adults and 90%–95% of infected newborns fail to clear infec-
tion and become chronic carriers who would face greater risk
of developing cirrhosis and hepatocellular carcinoma later in
life. Although prophylactic vaccination using the recom-
binant HBV surface antigen was introduced more than 20
years ago and has been a great success, existing carriers still
account for up to 20% of the population in certain Asian and
African countries. Therefore, there is an urgent need for
new and effective therapeutic approaches to treat these
patients. The success of prophylactic vaccine brought high
hopes towards the development of immunotherapy ap-
proaches against existing viral infection to complement the
current interferon treatment and antiviral chemotherapy.
Agents such as the hepatitis B (HB) subunit vaccine, cyto-
toxic T lymphocyte (CTL) epitope vaccine, Hepatitis B vac-
cine and anti-HBs complex all have been under investigation
for such purposes[4–6].
Among all the approaches, DNA-based vaccination
agents seem most promising for their ability to elicit both
strong humoral and cellular immunities[7,8]. Further formula-
tion and delivery methods are being developed to augment
the immunogenicity, such as using viral vectors, micros-
pheres, gene gun, or electroporation (EP)[12,13]. We
adopted the EP-mediated delivery approach and showed that
the EP-mediated HBV surface antigen (HBsAg) encoding
DNA vaccination resulted in much higher antibody titers
and stronger CTL responses in healthy animals and non-
To evaluate the therapeutic potential of such a vaccina-
tion approach, it would be more important to demonstrate
viral clearance resulting from the treatment. Several earlier
studies used a transgenic mouse model containing the HBV
Aim: To explore the potential of electroporation (EP)-mediated hepatitis B virus
(HBV) DNA vaccination for the treatment of chronic HBV infection. Methods:
BALB/c mice were vaccinated with HBV DNA vaccine encoding for the HBV
preS2-S antigen, combined with or without EP. HBV surface antigen expression
plasmid was administered into mice liver via a hydrodynamic injection to mimic
HBV infection. The clearance of antigen in the serum and liver was detected by
ELISA assay and immunohistochemical staining. The histopathology of the liver
tissues was examined by HE staining and serum alanine aminotransferase assay.
Results: The immunogenicity of HBV DNA vaccine encoding for the HBV preS2-
S antigen can be improved by EP-mediated vaccine delivery. The elicited immune
responses can indeed reduce the expression of HBV surface antigen (HBsAg) in
hepatocytes of the mouse model that was transfected to express HBsAg using the
hydrodynamic injection method. The antigen clearance process did not cause
significant toxicity to liver tissue, suggesting a non-cytolytic mechanism.
Conclusion: The EP-aided DNA vaccination may have potential in mediating viral
clearance in chronic hepatitis B patients.
DNA vaccine; hepatitis B virus; electro-
poration; antigen clearance
1 Project supported by grants from the National
Natural Science Foundation of China (No
30571721) and the Fok Ying Tong Education
Foundation (No 91035).
5 These authors contributed equally to this
6 Correspondence to Prof Yu-hong XU.
Acta Pharmacologica Sinica ISSN 1671-4083Peng JL et al
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