A candidate DNA vaccine elicits HCV specific humoral and cellular immune responses.
OBJECTIVE
To investigate the immunogenicity of candidate DNA vaccine against hepatitis C virus (HCV) delivered by two plasmids expressing HCV envelope protein 1 (E1) and envelope protein 2 (E2) antigens respectively and to study the effect of CpG adjuvant on this candidate vaccine.


METHODS
Recombinant plasmids expressing HCV E1 and E2 antigens respectively were used to simultaneously inoculate mice with or without CpG adjuvant. Antisera were then collected and titers of anti-HCV antibodies were analyzed by ELISA. One month after the last injection, animals were sacrificed to prepare single-cell suspension of splenocytes. These cells were subjected to HCV antigen specific proliferation assays and cytokine secretion assays to evaluate the cellular immune responses of the vaccinated animals.


RESULTS
Antibody responses to HCV E1 and E2 antigens were detected in vaccinated animals. Animals receiving CpG adjuvant had slightly lower titers of anti-HCV antibodies in the sera, while the splenocytes from these animals showed higher HCV-antigen specific proliferation. Analysis of cytokine secretion from the splenocytes was consistent with the above results. While no antigen-specific IL-4 secretion was detected for all vaccinated animals, HCV antigen-specific INF-gamma secretion was detected for the splenocytes of vaccinated animals. CpG adjuvant enhanced the secretion of INF-gamma but did not change the profile of IL-4 secretion.


CONCLUSIONS
Vaccination of mice with plasmids encoding HCV E1 and E2 antigens induces humoral and cellular immune responses. CpG adjuvant significantly enhances the cellular immune response.
State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Yue-Yang Road 320, Shanghai 200031, China.
Li-Xin
LX
Zhu
Jing
J
Liu
Ye
Y
Ye
You-Hua
YH
Xie
Yu-Ying
YY
Kong
Guang-Di
GD
Li
Yuan
Y
Wang
D000276:Adjuvants, Immunologic / Q000235:genetics / Q000494:pharmacology; D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D000917:Antibody Formation; D002455:Cell Division / Q000276:immunology; D002460:Cell Line; D018899:CpG Islands / Q000276:immunology; D006224:Cricetinae; D016207:Cytokines / Q000378:metabolism; D005260:Female; D006526:Hepatitis C / Q000276:immunology / Q000517:prevention & control*; D018936:Hepatitis C Antigens / Q000235:genetics / Q000276:immunology*; D007111:Immunity, Cellular; D007668:Kidney / Q000166:cytology; D051379:Mice; D008807:Mice, Inbred BALB C; D009838:Oligodeoxyribonucleotides / Q000276:immunology / Q000494:pharmacology; D010957:Plasmids; D013154:Spleen / Q000166:cytology / Q000276:immunology; D019444:Vaccines, DNA / Q000276:immunology / Q000494:pharmacology*; D014759:Viral Envelope Proteins / Q000235:genetics / Q000276:immunology; D014761:Viral Hepatitis Vaccines / Q000276:immunology / Q000494:pharmacology*
D000276:Adjuvants, Immunologic; D000914:Antibodies, Viral; D016207:Cytokines; C087035:E1 protein, Hepatitis C virus; D018936:Hepatitis C Antigens; D009838:Oligodeoxyribonucleotides; D019444:Vaccines, DNA; D014759:Viral Envelope Proteins; D014761:Viral Hepatitis Vaccines; C091015:glycoprotein E2, Hepatitis C virus