The Hepatitis B Virus Genotype Affects the Persistence of Viral Replication in Immunodeficient NOG Mice.

At least eight genotypes of Hepatitis B virus (HBV) have been identified. HBV genotype C is the most common genotype in Japan, although the incidence of HBV genotype A is increasing. The reason underlying the differences in viral multiplication of the HBV genotypes is unclear, especially in vivo. The purpose of this study was to elucidate the differences in HBV load and the persistence of viremia in vivo between genotypes A and C.Immunodeficient NOG mice were transfected by hydrodynamic injection with the HBV expression plasmids pHBA1.2 or pHBC1.2, which contain overlength (1.2-mer) copies of the genomes of HBV genotype A or C, respectively.One day after transfection, the number of HBcAg-positive hepatocytes and serum HBV DNA levels were similar between mice transfected with pHBA1.2 and pHBC1.2. Serum levels of HBV DNA, HBsAg and HBeAg in mice transfected with pHBA1.2 were maintained over 5 months. In contrast, those in mice with pHBC1.2 gradually decreased over time and reached undetectable levels within 3 months after transfection. HBcAg-stained hepatocytes were detected in mice transfected with pHBA1.2, but not pHBC1.2, 5 months post-transfection. Double-staining immunohistochemistry revealed that the number of cleaved caspase3-stained, HBcAg-positive hepatocytes in the pHBC1.2-transfected mice was higher than in the pHBA1.2-transfected mice 3 days post-transfection. Moreover, the plasmid DNA and covalently closed circular DNA levels were decreased in the livers of pHBC1.2-transfected mice. These results suggested that hepatocytes expressing HBV genotype C were eliminated by apoptosis in the absence of immune cells more often than in hepatocytes expressing HBV genotype A.Immunodeficient mice transfected with HBV genotype A develop persistent viremia, whereas those transfected with HBV genotype C exhibit transient viremia accompanied by apoptosis of HBV-expressing hepatocytes. This differences may affect the clinical courses of patients infected with HBV genotypes A and C

Huh7 cells were transfected with pHBA1.2 or pHBC1.2.

<p><b>(A-D)</b> Huh7 cells were transfected with pHBA1.2 or pHBC1.2 in combination with pCMV-SEAP (N = 3). The culture media were collected at days 4 and 7 after transfection. <b>(A)</b> HBV DNA levels, <b>(B)</b> HBsAg levels <b>(C)</b> HbeAg levels and <b>(D)</b> Caspase-3/7 activity were assessed in culture medium. <b>(E)</b> Huh7 cells were transfected with pHBA1.2 or pHBC1.2 in the absence or presence of Z-VAD-FMK. HBV DNA levels were assessed in culture medium (*, P < 0.05).</p

Type 1 interferon signaling in the livers of NOG mice transfected with pHBA1.2 or pHBC1.2.

<p>The expression levels of type 1 interferons and ISGs were examined in the livers of NOG mice 3 days <b>(A-C)</b> or 7 days <b>(D-F)</b> after receiving pHBA1.2 or pHBC1.2 by hydrodynamic injection. <b>(A, D)</b> The expression levels of IFN-α4, IFN-β1 and <b>(B, E)</b> ISGs (N = 7–8 for 3 days, N = 4 for 7 days). ANOVA was performed to detect any overall difference among the 3 groups. All p values are greater than 0.05. <b>(C, F)</b> Western blotting of interferon-signaling related proteins.</p

Hepatocyte apoptosis in the livers of NOG mice 3 days post-transfection with pHBA1.2 or pHBC1.2.

<p>Liver sections from NOG mice 3 days after transfection with pHBA1.2 or pHBC1.2 were subjected to immunohistochemical staining. <b>(A)</b> Representative images of immunohistochemical staining for TUNEL and cleaved caspase-3, and the number of positive cells (N = 4–5). <b>(B)</b> Representative images of pHBA1.2-transfected or pHBC1.2-transfected livers with double immunofluorescence staining for the HBc protein (green) and cleaved caspase-3 (red). The arrows indicate HBc and cleaved caspase-3 double-positive cells, while the arrowheads indicate HBc-positive and cleaved caspase-3-negative cells. <b>(C)</b> The ratio of cleaved caspase-3-positive cells in HBcAg-negative or -positive hepatocytes (right panel) (N = 4–5). pA: pHBA1.2, pC: pHBC1.2. *, P < 0.05.</p

HBV expression in NOG mice transfected with pHBA1.2 or pHBC1.2.

<p><b>(A-C)</b> NOG mice were transfected with pHBA1.2 or pHBC1.2 by hydrodynamic injection and analyzed 1 and 3 days after transfection. <b>(A)</b> Representative images of immunohistochemical staining for HBcAg in liver sections 1 day after hydrodynamic injection. The number of HBcAg-positive cells in liver sections and the plasmid levels in the livers (N = 9–10). <b>(B)</b> Serum HBV DNA levels, <b>(C)</b> HBsAg levels and HBeAg levels 1 day after injection (N = 9–10) and 3 days after injection (N = 4). <b>(D-E)</b> NOG mice were transfected with pHBA1.2 or pHBC1.2, and blood was collected at the indicated time points. Open squares stands for mice with pHBA1.2, while closed triangles stands for mice with pHBC1.2. <b>(D)</b> The serum levels of HBV DNA (N = 7–10). <b>(E)</b> The serum levels of HBsAg and HBeAg (N = 7–10). <b>(F-G)</b> NOG mice were transfected with pHBA1.2 or pHBC1.2 and analyzed at the indicated time points post-transfection. Gray bars stands for mice with pHBA1.2, and black bars stands for mice with pHBC1.2. <b>(F)</b> The number of HBcAg-positive cells in the liver sections was determined by immunohistochemical staining. They were subjected to the Mann–Whitney U-test. (N = 5–7). <b>(G)</b> CccDNA and plasmid DNA levels in livers at each time point (N = 4–7). *, P < 0.05.</p