Enhanced Effect of DNA Immunization plus In Vivo Electroporation with a Combination of Hepatitis B Virus Core-PreS1 and S-PreS1 Plasmids

Abstract

Hepatitis B virus (HBV) causes acute and chronic hepatitis and is associated with cirrhosis and liver cancer. Although the hepatitis B vaccine has been in use for over 20 years, HBV is still one of the most widespread pathogens (14). The most widely used HBV vaccine is a subunit vaccine containing the full-length S particle that is expressed by yeast or CHO cells (34). The HBV vaccine is very effective for mass immunization; however, 5% to 10% of the population do not produce protective anti-HBV surface (HBs) antigen antibodies, and in recent years, the S variant strains have increased in prevalence (5). The drugs that are currently used for the clinical treatment of hepatitis B include interferon and nucleoside analogues, such as lamivudine (5). Due to the limited effect of this drug treatment and the adverse reactions to their long-term application, new treatments for HBV, such as therapeutic HBV vaccines, are clearly needed (5).The direct injection of HBV DNA immunogens stimulates strong, long-lasting humoral and cellular immune responses in small-animal and chimpanzee models (11,18,22,25,27) and has become the focus of research on therapeutic HBV vaccines in recent years. However, applying these results to a larger population does not work well for small-animal models, and a large amount of DNA is needed to stimulate an effective immune response (17). Therefore, scientists are exploring ways to enhance the immunogenicity of DNA vaccines (1,16,30,32). Currently, electroporation is the most effective method for DNA vaccine delivery (16,30,32). Electroporation increases antigen (Ag) expression in muscle and skin 10-to 100-fold more than a direct injection, which leads to increased immunogenicity, a more durable response, and a reduced efficient dose in sheep, pigs, and other large animals.Another strategy for boosting the immunogenicity of DNA vaccines is to fuse exogenous B or T cell epitopes to virus-like particle (VLP) vectors to increase exposure after expression (26). After expression, a number of viral structural proteins automatically assemble into virus-like particles and can carry modified foreign epitopes without altering the particle's structure. For example, the widely used HBV and human papillomavirus (HPV) vaccines are virus-like particle immunogens. HBs antigen (29) and HBV core (HBc) antigen (10) were two of the first VLP antigens that were used to carry foreign epitopes (8,9,13,15,20,23,28,31,33).Previous data have shown that the HBCS1 that is expressed in Escherichia coli, containing core (amino acids [aa] 1 to 144) and PreS1 (aa 1 to 42), can form virus-like particles (33). Moreover, the HBSS1 that is expressed in CHO cells, containing S (aa 1 to 223) and PreS1 (aa 21 to 47), form stable, secreted virus-like particles with an equivalent molar ratio of PreS1 to S antigens (28). The two novel virus-like particle protein antigens can stimulate fast, effective humoral immune responses in animal models. Protein vaccines have a long life cycle and a complicated purification process and are expensiv...

Priming with two DNA vaccines expressing hepatitis C virus NS3 protein targeting dendritic cells elicits superior heterologous protective potential in mice

“…Previous studies by our group have shown that intradermal injection of a DNA vaccine combined with electroporation was more effective than other injection procedures (including intramuscular injection with electroporation or intramuscular injection alone) [31,32], and we therefore used intradermal injection with electroporation in the present study. Our data show that a conventional pVRC-based DNA vaccine induced higher levels of target protein expression after transfection and antigen-specific antibodies after priming when compared with suicidal pSC-based DNA.…”

“…Mice were immunized twice with pVRC-DEC-NS3 and pSC-DEC-NS3 administered by intradermal injection combined with electroporation [31,32], and subsequently boosted by intramuscular injection with rAd5-C44P at 3-week intervals (Fig. 2).…”

Protective efficacy and hepatitis B virus clearance in mice enhanced by cell‐mediated immunity with novel prime‐boost regimens

“…12,13 Our previous data suggested that the vaccine protein HBSS1, expressed in CHO cells containing S (1-223 aa) and preS1 (21-47 aa) combined with DNA or a viral vector-based vaccine, could elicit specific anti-HBV humoral and cell-mediated immunity (CMI) in mice. 12,14,15 However, the correlation between anti-HBV immunity and clearance of HBV infection is unknown. Thus, further studies in an HBV infection model are required to evaluate the protective efficacy of the vaccine and interpret the underlying immunological mechanisms.…”

“…Furthermore, preS1‐specific antibodies were produced earlier than S‐specific antibodies; preS1‐specific cell‐mediated immune responses may help confer HBV protection in nonresponders . Our previous data suggested that the vaccine protein HBSS1, expressed in CHO cells containing S (1‐223 aa) and preS1 (21‐47 aa) combined with DNA or a viral vector‐based vaccine, could elicit specific anti‐HBV humoral and cell‐mediated immunity (CMI) in mice . However, the correlation between anti‐HBV immunity and clearance of HBV infection is unknown.…”

N-Linked Glycosylation at an Appropriate Position in the Pre-S2 Domain Is Critical for Cellular and Humoral Immunity against Middle HBV Surface Antigen

“…Therefore, DNA vaccines, which are efficacious but inexpensive, may be a promising means for the control of HBV infections. Moreover, DNAmediated immunization has been shown to break immune tolerance in an HBV transgenic mouse model, indicating that DNA vaccines may also be beneficial for immunotherapy of chronic HBV infections (Chen et al 2011).…”