Adenoviral infection with hepatocyte-restricted antigen expression leads to virus persistence

Question:

Infections with the Hepatitis B virus (HBV) lead to self-limited infections in most cases. However, some affected persons develop chronic infection accounting for 240 million chronic hepatitis B patients worldwide. The decisive factors ruling between acute or chronic disease outcome are so far ill understood. Since HBV infection is restricted to humans and chimpanzees, experiments bear ethical and cost difficulties. Therefore, investigation of T cell effector function is limited by available in-vivo-models. We aimed to establish recombinant adenoviruses causing acute and chronic liver infection in mice to address the dynamics of altered CD8 T cell phenotype and function during virus persistence.

Methods:

We generated recombinant adenoviruses encoding for eGFP, luciferase and ovalbumin under the CMV promoter (Ad-CMV-GOL) causing acute infection, or under the Transthyretin (TTR) promoter (Ad-TTR-GOL) causing chronic liver infection. Mice were infected by these viruses and virus-specific OT-I x CD45.1 T cells were adoptively transferred to study CD8 T cells during acute vs. chronic liver infection. Viral infection was monitored by in-vivo bioluminescence imaging, serum ALT levels, histology and realtime PCR. CD8 T cells were analyzed by FACS and in-vitro-restimulation assay.

Results:

Ad-CMV-GOL infection was cleared within 18 days, whereas infection with Ad-TTR-GOL showed viral persistence detectable for more than 3 months. Mice clearing Ad-CMV-GOL featured expanded virus-specific CD8 T cells in-vivo and full anti-viral characteristics indicated by ex-vivo-restimulation resulting in IFNg and TNF production. Similarly, as seen in chronic hepatitis B patients, Ad-TTR-GOL infected mice showed little expansion of CD8 T cells and absent restimulation capacity. Furthermore, virus-specific CD8 T cells displayed up-regulated exhaustion markers PD-1, LAG-3 and Tim-3 and down-regulated effector marker KLRG-1.

Conclusion:

We established a novel model system to induce either acute or chronic viral hepatitis in mice using adenoviruses resulting in differential CD8 T cell activation and functionality referring to a HBV infection. With this model system the dynamics of CD8 T cell behavior and response in acute vs. chronic infection can be characterized in detail. Understanding the principles of T cell dynamics during chronic viral hepatitis will help to improve targeted immune therapy.