DNA
Immunization with Recombinant HCV E2 Expression Plasmids
ZHU Jun, WANG Chun-Lin, ZHU Li-Xin, KONG
Yu-Ying, WANG Yuan*, LI Guang-Di*
£¨ State Key Laboratory of Molecular Biology, Institute of Biochemistry
and Cell Biology, Shanghai Institutes for Biological Sciences, the Chinese
Academy of Sciences, Shanghai 200031, China
)
Abstract DNA-based
immunization, the delivery of plasmid DNA by direct inoculation, is a newly
developed method of vaccination. Besides of many advantages, DNA immunization
was demonstrated to generate weaker antibody and CTL responses than did protein
and live attenuated vaccines, respectively. To circumvent this shortage,
several methods were tested such as using different vector, changing injection
mode, and co-expressing cytokines, etc. The studies showed that many factors
could greatly affect the immune responses to DNA vaccine. The aim of this study
is to compare different vectors for the presentation of the HCV E2 to generate
immune responses by using DNA-based immunization. Four expression plasmids,
with different promoter types and with or without signal sequences were
constructed, which encode Cª²terminally truncated E2 (384¡ª660) with HBV preS1£¨21¡ª47£©tag fused to its N-termini.
Transient expression in HeLa cells showed that only recombinant plasmids with
signal sequence could be expressed and properly processed, and the product
could be secreted into medium. Protein expression level is slightly higher in
plasmids with CMV promoter than with EF1¦Á promoter. After
immunization of C57BL/6 mice, all the recombinant constructs could elicit both
anti-preS1 and anti-E2 antibodies. But only pCMV Sec-S1E2t660
with both CMV promoter and signal sequence could induce high-level and
long-lasting antibody, showing that it is a good vaccine candidate. Possible
reasons for the different immune responses to these constructs were discussed.
Key words HCV E2£» HBV preS1£» promoter£» signal sequence£» DNA vaccine
*Corresponding authors: Tel,
86-21-64374430-5326; Fax, 86-21-64338357;
e-mail£¬[email protected]