Basic Research
Copyright ©The Author(s) 2005. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Aug 28, 2005; 11(32): 4967-4973
Published online Aug 28, 2005. doi: 10.3748/wjg.v11.i32.4967
IFN-γ increases efficiency of DNA vaccine in protecting ducks against infection
Jian-Er Long, Li-Na Huang, Zhi-Qiang Qin, Wen-Yi Wang, Di Qu
Jian-Er Long, Li-Na Huang, Zhi-Qiang Qin, Wen-Yi Wang, Di Qu, Department of Molecular Virology, Shanghai Medical College, Fudan University, Shanghai 200032, China
Jian-Er Long, Shanghai Institute of Medical Genetics, Shanghai Children’s Hospital, Shanghai Jiaotong University, Shanghai 200040, China
Author contributions: All authors contributed equally to the work.
Supported by the Major State Basic Research Development Program of China, 973 Program, No. G2002CB512803; the National Natural Science Foundation of China, No. 30070693; the Science and Technology Foundation of Shanghai, No. 02DJ14002
Correspondence to: Dr. Di Qu, Department of Molecular Virology, Shanghai Medical College, Fudan University, 138 Fenglin R. Shanghai 200032, China. dqu@shmu.edu.cn
Telephone: +86-21-54237524
Received: November 15, 2004
Revised: January 23, 2005
Accepted: January 26, 2005
Published online: August 28, 2005
Abstract

AIM: To detect the effects of DNA vaccines in combination with duck IFN-γ gene on the protection of ducks against duck hepatitis B virus (DHBV) infection.

METHODS: DuIFN-γ cDNA was cloned and expressed in COS-7 cells, and the antiviral activity of DuIFN-γ was detected and neutralized by specific antibodies. Ducks were vaccinated with DHBpreS/S DNA alone or co-immunized with plasmid expressing DuIFN-γ. DuIFN-γ mRNA in peripheral blood mononuclear cells (PBMCs) from immunized ducks was detected by semi-quantitative competitive RT-PCR. Anti-DHBpreS was titrated by enzyme-linked immunosorbent assay (ELISA). DHBV DNA in sera and liver was detected by Southern blot hybridization, after ducks were challenged with high doses of DHBV.

RESULTS: DuIFN-γ expressed by COS-7 was able to protect duck fibroblasts against vesicular stomatitis virus (VSV) infection in a dose-dependent fashion, and anti-DuIFN-γ antibodies neutralized the antiviral effects. DuIFN-γ in the supernatant also inhibited the release of DHBV DNA from LMH-D2 cells. When ducks were co-immunized with DNA vaccine expressing DHBpreS/S and DuIFN-γ gene as an adjuvant, the level of DuIFN-γ mRNA in PBMCs was higher than that in ducks vaccinated with DHBpreS/S DNA alone. However, the titer of anti-DHBpreS elicited by DHBpreS/S DNA alone was higher than that co-immunized with DuIFN-γ gene and DHBpreS/S DNA. After being challenged with DHBV at high doses, the load of DHBV in sera dropped faster, and the amount of total DNA and cccDNA in the liver decreased more significantly in the group of ducks co-immunized with DuIFN-γ gene and DHBpreS/S DNA than in other groups.

CONCLUSION: DHBV preS/S DNA vaccine can protect ducks against DHBV infection, DuIFN-γ gene as an immune adjuvant enhances its efficacy.

Keywords: Duck IFN-γ, DHBV, DNA vaccine, Immune adjuvant