Hepatitis B virus core antigen determines viral persistence in a C57BL/6 mouse model

Abstract

We recently developed a mouse model of hepatitis B virus (HBV) persistence, in which a single i.v. hydrodynamic injection of HBV DNA to C57BL/6 mice allows HBV replication and induces a partial immune response, so that about 20-30% of the mice carry HBV for more than 6 months. The model was used to identify the viral antigen crucial for HBV persistence. We knocked out individual HBV genes by introducing a premature termination codon to the HBV core, HBeAg, HBx, and polymerase ORFs. The specific-genedeficient HBV mutants were hydrodynamically injected into mice and the HBV profiles of the mice were monitored. About 90% of the mice that received the HBcAg-mutated HBV plasmid exhibited high levels of hepatitis B surface antigenemia and maintained HBsAg expression for more than 6 months after injection. To map the region of HBcAg essential for viral clearance, we constructed a set of serial HBcAg deletion mutants for hydrodynamic injection. We localized the essential region of HBcAg to the carboxyl terminus, specifically to the 10 terminal amino acids (HBcAg176-185). The majority of mice receiving this HBV mutant DNA did not elicit a proper HBcAg-specific IFN-γ response and expressed HBV virions for 6 months. These results indicate that the immune response triggered in mice by HBcAg during exposure to HBV is important in determining HBV persistence.hepatitis B surface antigenemia | hydrodynamic injection P ersistent hepatitis B virus (HBV) infections affect about 350 million people worldwide and are a major health problem. Factors directing the infection toward chronicity have been studied extensively. The exposure of neonates or young children to a high HBV viral load, together with hepatitis B e antigen (HBeAg), predicts a high rate of persistent HBV infection. A recent genomewide association study identified HLA-DP polymorphisms as another factor in the persistence of HBV infections (1). Nevertheless, the immune mechanisms that lead to HBV persistence have not been resolved. To address this issue, a commonly used mouse model, such as the HBV transgenic mouse, has been used to study the possible mechanisms. However, the main drawback of HBV transgenic mouse models is that they are immunologically tolerant of viral antigens. Therefore, to explore the issue of HBV persistence, the adoptive transfer of HBV-primed immune cells or other manipulations must be used to overcome this tolerance. Another alternative is to introduce the HBV genome into the mouse liver by hydrodynamic injection through the tail vein. With this approach, HBV was shown to replicate in the mouse liver, and the immune responses against HBV proteins to clear the HBV infection could be documented in 1-2 weeks after the injection (2). Recently, we improved this approach by modifying the HBV DNA plasmid and injecting the plasmid into C57BL/6 mice and succeeded in delaying the mouse immune clearance of HBV (3). Clearance could be postponed for 6-8 weeks and about 10-30% of the injected mice maintained HBV persistence even up to 6 months after injection...

Liver type I regulatory T cells suppress germinal center formation in HBV-tolerant mice

“…To explore the mechanism involved in the liver-induced systemic tolerance, we established an HBV-carrier mouse model by hydrodynamic injection of pAAV/HBV1.2 plasmid into C57BL/6 mice (17), which has been extensively used (18,19). In contrast to control (pAAV/Control-injected) mice, HBV-carrier (pAAV/ HBV1.2-injected) mice did not secrete anti-HBs antibodies after peripheral immunization with HBsAg (20); indicating the tolerance toward HBsAg was developed in HBV-carrier mice.…”

Hepatitis B Virus Core Protein Sensitizes Hepatocytes to Tumor Necrosis Factor-Induced Apoptosis by Suppression of the Phosphorylation of Mitogen-Activated Protein Kinase Kinase 7

“…HBc therefore could be a pathogen-associated molecular pattern that sensitizes hepatocytes to TNF-␣-induced apoptosis. Supporting this possibility, Lin et al (31,44) recently showed that HBc is a major viral factor for HBV clearance in a hydrodynamics-based mouse model. This effect depends on the self-assembly of HBc into capsid particles, which, however, is not obligatory for the proapoptotic activity of HBc described here.…”

Hepatitis B Virus X Protein Induces Hepatic Steatosis by Enhancing the Expression of Liver Fatty Acid Binding Protein

“…pRep-HBV (harboring 1.2 unit lengths of the HBV genome) and control plasmid pRep-Sal were described previously (6). The pRep-HBV-X(-) mutation plasmid, which contains an stop codon at HBx codon 8 (CAA to UAA), was generated by site-specific mutagenesis as described previously (22). DNA transfection was carried out using Lipofectamine 2000 (Invitrogen), and siRNA transfections were performed by use of Lipofectamine RNAiMAX (Invitrogen).…”