Apoptosis of Hepatitis B Virus-Infected Hepatocytes Prevents Release of Infectious Virus▿

Apoptosis of infected cells is critically involved in antiviral defense. Apoptosis, however, may also support the release and spread of viruses. Although the elimination of infected hepatocytes is required to combat hepatitis B virus (HBV) infection, it is still unknown which consequences hepatocyte apoptosis has for the virus and whether or not it is advantageous to the virus. To study this, we designed a cell culture model consisting of both HBV-producing cell lines and primary human hepatocytes serving as an infection model. We showed that the release of mature, enveloped virions was 80% to 90% reduced 24 h after the induction of apoptosis in HBV-replicating hepatoma cells or HBV-infected hepatocytes. Importantly, HBV particles released from apoptotic hepatocytes were immature and nonenveloped and proved not to be infectious. We found an inverse correlation between the strength of an apoptotic stimulus and the infectivity of the virus particles released: the more potent the apoptotic stimulus, the higher the ratio of nonenveloped capsids to virions and the lower their infectivity. Furthermore, we demonstrated that HBV replication and, particularly, the expression of the HBx protein transcribed from the viral genome during replication do not sensitize cells to apoptosis. Our data clearly reject the hypothesis that the apoptosis of infected hepatocytes facilitates the propagation of HBV. Rather, these data indicate that HBV needs to prevent the apoptosis of its host hepatocyte to ensure the release of infectious progeny and, thus, virus spread in the liver

Hepatitis B virus X protein is essential to initiate and maintain virus replication after infection

The molecular biology of hepatitis B virus (HBV) has been extensively studied but the exact role of the hepatitis B X protein (HBx) in the context of natural HBV infections remains unknown

T cells expressing a chimeric antigen receptor that binds hepatitis B virus envelope proteins control virus replication in mice.

BACKGROUND & AIMS: Antiviral agents suppress hepatitis B virus (HBV) replication but do not clear the infection. A strong effector T-cell response is required to eradicate HBV, but this does not occur in patients with chronic infection. T cells might be directed toward virus-infected cells by expressing HBV-specific receptors, and thereby clear HBV and help to prevent development of liver cancer. In mice, we studied whether redirected T cells can engraft following adoptive transfer, without prior T-cell depletion, and whether the large amounts of circulating viral antigens inactivate the transferred T cells or lead to uncontrolled, immune-mediated damage. METHODS: CD8(+) T cells were isolated from mice and stimulated using an optimized protocol. Chimeric antigen receptors (CARs) that bind HBV envelope proteins (S-CAR) and activate T cells were expressed on the surface of cells using retroviral vectors. S-CAR-expressing CD8(+) T cells, which carried the marker CD45.1, were injected into CD45.2(+) HBV transgenic mice. We compared these mice with mice that received CD8(+) T cells induced by vaccination, cells that express a CAR without a proper signaling domain, or cells that express a CAR that does not bind HBV proteins (controls). RESULTS: CD8(+) T cells that expressed HBV-specific CARs recognized different HBV subtypes and were able to engraft and expand in immune-competent HBV transgenic mice. Following adoptive transfer, the S-CAR-expressing T cells localized to and functioned in the liver; they rapidly and efficiently controlled HBV replication, compared with controls, causing only transient liver damage. The large amount of circulating viral antigen did not impair or over-activate the S-CAR grafted T cells. CONCLUSION: T cells with a CAR specific for HBV envelop proteins localize to the livers of mice to reduce HBV replication, causing only transient liver damage. This immune-cell therapy might be developed for patients with chronic hepatitis B, regardless of their HLA-type