Hepatitis B virus precore protein augments genetic immunizations of the truncated hepatitis C virus core in BALB/c mice

Abstract

DNA immunization has been used to induce either humoral or cellular immune responses against many antigens, including hepatitis C virus (HCV). In addition, DNA immunizations can be enhanced or modulated at the nucleotide level. Genetic immunizations were examined in BALB/c mice through the use of plasmids and chimeric DNA constructs encoding HCV core proteins and hepatitis B virus (HBV) precore (preC) regions. Plasmids encoding the truncated HCV core induced potent humoral and cellular responses to HCV; pcDNA3.0A-C154 produced a stronger antibody response than pcDNA3.0A-C191 (P < 0.01) and pcDNA3.0A-C69 (P < 0.05). HBV preC enhanced the humoral and cellular immune responses of BALB/c mice to HCV; however, pcDNA3.0A-C69preC resulted in a weak cytotoxic T lymphocyte (CTL) response. In addition, the humoral and cellular immune responses to HCV of groups immunized with pcDNA3.0A-C154preC and pcDNA3.0A-C191preC plasmids were higher than those of groups immunized with pcDNA3.0A-C154 and pcDNA3.0A-C191. In vivo CTL responses verified that mice immunized with preC core fused DNAs showed significantly high specific lysis compared with mice immunized with HCV cores only (P < 0.01). In our study, pcDNA3.0A-C154preC led to the highest immune response among all DNA constructs. Conclusion: DNA that encodes truncated HCV core proteins may lead to increased immune responses in vivo, and these responses may be enhanced by HBV preC. (HEPATOLOGY 2008;47:25-34.)

The Wild-Type Hepatitis C Virus Core Inhibits Initiation of Antigen-Specific T- and B-Cell Immune Responses in BALB/c Mice

“…Truncating the HCV core protein could improve its immunogenicity and evoke stronger immune responses in DNA-vaccinated mice. These findings are largely consistent with those of previous studies (27). We demonstrated that DNA immunization using the truncated HCV core protein induced specific T-and B-cell responses in a dose-dependent manner, while no significant improvement of immune responses could be reached by administration of increased doses of plasmids expressing the full-length HCV core protein.…”

“…Previous studies indicated that DNA vaccination with plasmids encoding the fulllength HCV core protein led to low levels of B-and Th-cell responses (18,27). Enhancement of the expression of the HCV core gene does not enhance core-specific immune responses in DNA immunization (2).…”

“…Current data demonstrated that HCV core proteins that are truncated at the carboxy termini are able to evoke stronger immune responses than the full-length HCV core protein (9,18,27). Therefore, we systematically investigated whether amino-and carboxy-terminal truncations could enhance the ability of the HCV core protein to induce specific immune responses.…”

“…The ELISPOT assay was carried out using a mouse gamma IFN (IFN-␥)-secreting cell kit (U-CyTech), according to the manufacturer's instructions. In brief, 2 ϫ 10 5 mouse splenocytes plus 2 g of HBsAg CTL peptide (IPQSLDSWWTSL) (Shanghai Sangon, China) (15), 2 g of HCV core-specific CTL peptide (RRGPRLGVRA) (Shanghai Sangon, China) (27), or 5 g of concanavalin A was added to each well of 96-well plates coated with anti-IFN-␥ monoclonal antibody (MAb) and incubated for 18 h at 37°C in 5% CO 2 . Biotinylated anti-IFN-␥ antibody, ␥-aminobutyric acid (GABA) solution, and activator I/II solution were added one by one.…”

“…Truncated HCV core proteins were able to trigger stronger immune responses in DNA vaccination than the full-length HCV core protein. Some researchers have attributed this observation to that fact that carboxy-terminally truncated HCV core proteins can enter the nucleus (27). However, other explanations were possible.…”