  Hepatitis B virus is a global health threat, and its elimination by 2030 has
been prioritised by the World Health Organisation. Here we present an
age-structured model for the immune response to an HBV infection, which takes
into account contributions from both cell-mediated and humoral immunity. The
model has been validated using published patient data recorded during acute
infection. It has been adapted to the scenarios of chronic infection, clearance
of infection, and flare-ups via variation of the immune response parameters.
The impacts of immune response exhaustion and non-infectious subviral particles
on the immune response dynamics are analysed. A comparison of different
treatment options in the context of this model reveals that drugs targeting
aspects of the viral life cycle are more effective than exhaustion therapy, a
form of therapy mitigating immune response exhaustion. Our results suggest that
antiviral treatment is best started when viral load is declining rather than in
a flare-up. The model suggests that a fast antibody production rate always lead
to viral clearance, highlighting the promise of antibody therapies currently in
clinical trials.
