Various Gradients of the Second Phase of the Viral Kinetics of Hepatitis C Virus Infection Drawn using the Rapid Equilibrium Model

Mathematical models of Hepatitis C Virus (HCV) infection during antiviral treatment have revealed the major mechanism of the function of Interferon (IFN) and the estimated clearance rates of HCV virions and HCV-infected cells. However, differences in the estimated clearance rates of infected cells have been observed between subjects who are and are not treated with Protease Inhibitor. In this study, the author demonstrated that various gradients in the second phase were difficult to obtain by regulating the efficacy of treatment in the predominately used basic model but were easily obtained by regulating the clearance rate of infected cells. The author considers that the estimated clearance rate of infected cells differs depending on the type of treatment because fitting the second phase in the basic model to viral load by regulating efficacy is difficult; however, fitting the second phase by regulating the clearance rate of infected cells is not difficult. Consequently, different infected-cell clearance rates were obtained for different types of treatments. Previously, the author proposed the Rapid Equilibrium (RE) model, which is capable of displaying viral kinetics without rebounds or oscillations under some conditions. In this study the author demonstrated the applicability of the RE model by displaying various gradients of the second phase with various efficacies of treatment.