Construction of replication-deficient recombinant adenoviral vector carrying HBV S and C region gene by homologous recombination in bacteria and its expression in vitro

Improvement of HBsAg gene-modified dendritic cell-based vaccine efficacy by optimizing immunization method or the application of β-glucosylceramide

Hepatocellular carcinoma (HCC) in China is mostly Hepatitis B virus infection related. The antitumor efficacy of HBsAg gene-modified dendritic cells (DC) has been widely tested both in vitro and in vivo. In this study, we analyzed whether adenoviral vector mediated HBsAg expression would alter cell surface phenotype or autologous T cell stimulating function of mature DCs. Further, the anti-tumor efficacy of pAd-HBsAg-DC-based vaccine was evaluated in mice bearing HBsAg expressing HCC. We also tested whether β-glucosylceramide (β-GC) would enhance the anti-tumor activity of pAd-HBsAg-DC. Results revealed that pAd-HBsAg-DC expressed and secreted HBsAg, while maintaining phenotypic characteristics of mature DCs. Vaccination with pAd-HBsAg-DC conferred specific therapeutic antitumor immunity to animal model bearing HBsAg expressing HCC. The application of β-GC activated mice hepatic NKT cells and enhanced the antitumor activity of pAd-HBsAg-DC. Most importantly, in vivo results showed that the inhibiting effect of pAd-HBsAg-DC vaccination on tumor growth was more significant when applied before tumor inoculation, suggesting that genetically modified DC based therapeutic cancer vaccine may achieve the most optimized antitumor effect when applied before tumor onset, and β-GC may serve as a potent innate immune enhancer for augmenting the antitumor effect of pAd-HBsAg-DC vaccine.

Induction of specific cytotoxic T lymphocyte responses against hepatitis B virus by hepatitis B virus antigen gene-modified dendritic cells

AIM: To explore whether hepatitis B virus (HBV) antigen gene-modified dendritic cells (DCs) are able to induce a specific cytotoxic T lymphocyte (CTL) response.

METHODS: Three recombinant adenoviruses, Ad-HBs, Ad-HBe and Ad-HBc (carrying HBsAg, HBeAg and HBcAg genes respectively), were prepared and transfected into DCs generated from cord blood. The efficacy of transfection was observed through the expression of enhanced green fluorescent protein (EGFP) in DCs and the expression of HBV antigen were detected by enzyme-linked immunosorbent assay (ELISA). HBV antigen gene-modified DCs were co-cultured with T lymphocytes from cord blood and the proliferation of T cells were detected using mixed lymphocyte reaction (MLR). Lactate dehydrogenase (LDH) release assay was carried out to assess the killing ability of CTL cells against HepG₂22.1.5 cells.

RESULTS: HBV antigen genes were expressed in DCs with a high efficacy by recombinant adenoviral vector. EGFP were observed in 90% transfected DCs and DCs kept their typical forms after transfection. The titers (absorbance) of HBsAg and HBeAg were 0.919 and 0.328, respectively, in the culture supernatant 72 h after transfection. The result of MLR showed that HBV gene-modified DCs effectively stimulated naive T lymphocytes to proliferate. There was no significant difference among Ad-HBs, Ad-HBe, Ad-HBc transfection group and normal group (F = 1.194, P = 0.389). The specific CTL cells generated by HBV antigen gene-modified DCs had obvious cytotoxity against HepG₂22.1.5 cells, and the cytotoxity in Ad-HBs, Ad-HBe, Ad-HBc transfection group was significantly higher than that in normal group (all P < 0.001). The cytotoxity in Ad-HBc transfected group was the strongest.

CONCLUSION: HBV gene-modified DCs are able to effectively stimulate naive T lymphocytes to proliferate and enhance the specific CTL response at the same time, showing its promising future for developing anti-viral vaccine.