Abstract
It is well known that viral load of the hepatitis C virus (HCV) is related to the efficacy of interferon therapy. The complex biological parameters that impact on viral load are essentially unknown. The current knowledge of the hepatitis C virus does not provide a mathematical model for viral load dynamics within untreated patients. We car-ried out an empirical modelling to investigate whether different fluctuation patterns exist and how these patterns (if exist) are related to host-specific factors. Data was prospectively col-lected from 147 untreated patients chronically infected with hepatitis C, each contributing be-tween 2 to 10 years of measurements. We pro-pose to use a three parameter logistic model to describe the overall pattern of viral load fluctua-tion based on an exploratory analysis of the data. To incorporate the correlation feature of longitu-dinal data and patient to patient variation, we introduced random effects components into the model. On the basis of this nonlinear mixed ef-fects modelling, we investigated effects of host-specific factors on viral load fluctuation by in-corporating covariates into the model. The pro-posed model provided a good fit for describing fluctuations of viral load measured with varying frequency over different time intervals. The aver-age viral load growth time was significantly dif-ferent between infection sources. There was a large patient to patient variation in viral load as-ymptote.
Highlights
3% of the world population is infected by the hepatitis C virus (HCV)
We propose to use a three parameter logistic model to describe the overall pattern of viral load fluctuation based on an exploratory analysis of the data
On the basis of this nonlinear mixed effects modelling, we investigated effects of hostspecific factors on viral load fluctuation by incorporating covariates into the model
Summary
3% of the world population is infected by the hepatitis C virus (HCV). This virus is a single stranded positive sense RNA virus and does not exist as a single clonotype. Replicative homeostasis results dynamic equilibrium controlled by the specificity of the interactions between mutant or wild type envelope proteins and the replicas, the RNA dependant RNA polymerase (RDRP). Biomedical Science and Engineering 1 (2008) 85-90 fidelity of replication yielding a high intracellular concentration of mutant type envelope proteins This mutant population competes with wild type forms, resulting in a progressive increase in fidelity and a shift in the dynamic equilibrium which results in the generation of a dominant viral quasispecies and which may be reflected in a change in the absolute magnitude of the viral load. These models were developed to describe viral dynamics during antiviral treatment They cannot be used for long term investigations of viral load progression in untreated patients.
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