Enhancing the potency of HBV DNA vaccines using fusion genes of HBV-specific antigens and the N-terminal fragment of gp96.
BACKGROUND
Many clinical trials show that DNA vaccine potency needs to be greatly enhanced. We have reported that the N-terminal fragment of glycoprotein 96 (gp96) is able to produce an adjuvant effect for production of cytotoxic T-lymphocytes (CTLs) with hepatitis B virus (HBV)-specific peptides. Here, we report a new strategy for HBV DNA vaccine design using a partial gp96 sequence.


METHODS
We linked the N-terminal 1-355aa (N355) of gp96 to HBV genes encoding for structural proteins, the major S and middle S2S envelope proteins and the truncated core HBcAg (1-149aa). ELISPOT, tetramer staining and intracellular IFN-gamma assay were performed to analyze the induced cellular immune responses of our DNA constructs in BALB/c mice and HLA-A2 transgenic mice. The relative humoral immune responses were analyzed in different IgG isotypes.


RESULTS
The fusion genes induced 2- to 6-fold higher HBV-specific CD8(+) T cells as compared to the antigens alone. There was an approximate 10-fold decrease in the humoral immune responses with fusion genes based on HBV envelope proteins. Interestingly, the decreased humoral immune responses were not observed when antigens and plasmid encoding N355 were co-delivered. However, an approximate 20-fold higher antibody level was induced when linking N355 to a truncated HBcAg. Immunization by intramuscular injection resulted in predominantly IgG2a antibodies, which indicated that these vaccines preferentially prime Th1 responses.


CONCLUSIONS
We constructed highly immunogenic fusions by linking the N-terminal fragment of gp96 to HBV antigens. Our results imply that the N-terminal fragment of gp96 may be used as a molecular adjuvant to enhance the potency of DNA vaccines.
Yan
Jiabin
J
Center for Molecular Virology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100080, P.R. China.
Liu
Xuqing
X
Wang
Yao
Y
Jiang
Xiaomo
X
Liu
Huayu
H
Wang
Mingying
M
Zhu
Xiaodong
X
Wu
Min
M
Tien
Po
P
D000818:Animals; D000951:Antigens, Neoplasm / Q000235:genetics* / Q000276:immunology; D005260:Female; D005434:Flow Cytometry; D006511:Hepatitis B Antigens / Q000235:genetics* / Q000276:immunology*; D017325:Hepatitis B Vaccines / Q000235:genetics* / Q000276:immunology*; D006515:Hepatitis B virus / Q000276:immunology; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D008822:Mice, Transgenic; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000276:immunology; D018417:Th1 Cells / Q000276:immunology; D019444:Vaccines, DNA / Q000235:genetics / Q000276:immunology
D000951:Antigens, Neoplasm; D006511:Hepatitis B Antigens; D017325:Hepatitis B Vaccines; D011993:Recombinant Fusion Proteins; D019444:Vaccines, DNA; C052646:sarcoma glycoprotein gp96 rejection antigens