Viral kinetics in hepatitis C or hepatitis C/human immunodeficiency virus-infected patients

Background & Aims: Kinetic modeling of hepatitis C virus (HCV) response to interferon (IFN)-based therapy provides insights into factors associated with treatment outcomes. HCV/human immunodeficiency virus (HIV)-co-infected patients show lower response rates vs. HCV-monoinfected patients. Reasons for this remain unclear. This study evaluated kinetic parameters and treatment responses in co-infected vs monoinfected patients. Methods. Co-infected patients were randomized within a US multicenter trial (ACTG 5071) to receive pegylated-interferon (PEG-IFN) alfa-2a + ribavirin vs. IFN alfa-2a + ribavirin. Monoinfected controls were matched prospectively for treatment, genotype, age, sex, race, and histology. Quantitative HCV-RNA testing was performed at hours 0, 6, :12, 24, 48, and 72; days 7, 10, 14, 28, and 56; and weeks 12, 24, 48, and 72. Results: Twelve HCV/HIV-co-infected and 15 HCV-monoinfected patients underwent viral kinetic sampling. Among HIV-positive patients the mean CD4+ count was 325 cells/mm(3). Seventy-five percent of patients were genotype 1. The HCV-RNA level was undetectable at 72 weeks in 25% and 40% of co-infected and monoinfected patients, respectively. Phase 1/2 declines, free virus clearance rate, and infected hepatocyte death rate were not affected by co-infection status but differed by treatment. Efficiency (epsilon) greater than or equal to 90% at 60 hours was associated with viral clearance (P = .02). Modeling with pooled parameters suggests baseline viral load is a key factor in time to response in this cohort. Predicted clearance time increased by 28% in co-infected patients. Conclusions: Co-infection status did not affect key kinetic parameters. Among kinetic parameters, efficiency was associated significantly with viral clearance. Co-infected patients may require longer treatment duration than monoinfected patients given their generally higher baseline viral loads.