Sixteen HCV-infected patients (C-1 to C-16) and ten HIV/ HCV co-infected patients (I-1 to I-10) naïve to IFNa therapy were enrolled in this study. A summary of the virological and immunological status of patients at baseline is shown in table 1. All the HIV/HCV co-infected patients but one were under HAART with undetectable viremia (,40 HIV copies/mL). Chronically infected patients (C-9 to C-16 and I-1 to I-10) initiated pegylated IFNa/ribavirin treatment (IFNa-2a: Pegasys, 180 mg weekly, Ribavirin: Copegus, 800 mg to 1000 mg daily) and were followed over a 4 months period. Patients included in the acute phase of HCV infection (C-1 to C-8) were treated with pegylated IFNa (IFNa-2a: Pegasys, Roche, 180 mg weekly) [51, 52] . Blood samples were taken monthly on EDTA. Two milliliters of total blood were 2-fold diluted in FCS/20%DMSO frozen at 280uC and conserved in liquid nitrogen. These total blood samples were subsequently used for flow cytometry analyses. Plasma was separated from the remaining eight milliliters and mononuclear cells were purified on Ficoll Hypaque (Eurobio, Courtaboeuf, France) and frozen for further analyses. Patients from the HCV mono-infection group were followed at the Centre de Recherche du CHUM, Hôpital Saint Luc, Montreal, QC, Canada and its collaborators as previously described [9, 53] . Patients from the HIV-HCV groups were followed at the Hôpital Henri Mondor, Creteil, France. Clinical protocols conformed to Figure 5 . Variations in IL-7 plasma levels correlate with evolution of RTE production. Correlations. between variations in IL-7 plasma levels (DIL-7) and either variations in (A) total (CD4 + + CD8 + ) naïve T-cell counts (Dnaïve T-cell counts), (B) RTE defined as CD31 hi naïve CD4 + T-cells (DRTE CD4 counts), (C) the sj/bTREC ratio (Dsj/bTREC ratio), (D) the frequency of Ki-67 + cells in the RTE CD4 + T-cell subset (D%Ki-67 + in CD4 + RTEs) or (E) the number of circulating Ki-67 + CD4 + RTEs (DKi-67 + RTE counts) between study entry and month 1 of therapy were calculated for acutely (black symbols) and chronically (white symbols) HCV-infected patients (left panels) and HIV/HCV co-infected patients (right panels). Correlation coefficients (Spearman's r) and the associated probabilities (p) are shown. doi:10.1371/journal.pone.0034326.g005 ethical guidelines of the authors' institutions and the US Department of Health and Human Services' human experimentation guidelines. This study was approved by both the Ethical committee of Centre Hospitalier de l'Université de Montreal (CHUM) and the ethical committee of Hôpital Henri Mondor, Créteil, France. Samples were obtained with the written subjects' informed consent.