Altered Thymic Function during Interferon Therapy in HCV-Infected Patients

Interferon alpha (IFNα) therapy, despite good efficacy in curing HCV infection, leads to major side effects, in particular inducement of a strong peripheral T-cell lymphocytopenia. We here analyze the early consequences of IFNα therapy on both thymic function and peripheral T-cell homeostasis in patients in the acute or chronic phase of HCV-infection as well as in HIV/HCV co-infected patients. The evolution of T-cell subsets and T-cell homeostasis were estimated by flow cytometry while thymic function was measured through quantification of T-cell receptor excision circles (TREC) and estimation of intrathymic precursor T-cell proliferation during the first four months following the initiation of IFNα therapy. Beginning with the first month of therapy, a profound lymphocytopenia was observed for all T-cell subsets, including naïve T-cells and recent thymic emigrants (RTE), associated with inhibition of intrathymic precursor T-cell proliferation. Interleukin (IL)-7 plasma concentration rapidly dropped while lymphocytopenia progressed. This was neither a consequence of higher consumption of the cytokine nor due to its neutralization by soluble CD127. Decrease in IL-7 plasma concentration under IFNα therapy correlated with the decline in HCV viral load, thymic activity and RTE concentration in blood. These data demonstrate that IFNα-based therapy rapidly impacts on thymopoiesis and, consequently, perturbs T-cell homeostasis. Such a side effect might be detrimental for the continuation of IFNα therapy and may lead to an increased level of infectious risk, in particular in HIV/HCV co-infected patients. Altogether, this study suggests the therapeutic potential of IL-7 in the maintenance of peripheral T-cell homeostasis in IFNα-treated patients

IFNα therapy leads to naïve T-cell lymphocytopenia.

<p>(A) CD4⁺ (top panel) and CD8⁺ (bottom panel) naïve T-cell counts were quantified in peripheral blood cells from acutely HCV-infected (light grey symbols), chronically HCV-infected (black symbols) and HIV/HCV co-infected (white symbols) patients at study entry, as compared to healthy donors (HCV-, dark grey symbols). (B) Evolution of CD4⁺ (top panels) and CD8⁺ (bottom panels) naïve T-cell counts during the first 4 months of IFNα therapy in acutely HCV-infected (left panels), chronically HCV-infected (central panels) and HIV/HCV co-infected (right panels) patients. Each line represents data from an individual patient. Statistical significances of the differences to baseline values (time 0), calculated on the absolute naïve T-cell counts in each individual sample, (Wilcoxon matched-pairs signed-ranks test) are shown on top. The horizontal bars represent median values.</p

Variations in IL-7 plasma levels correlate with evolution of RTE

<p><b>production.</b> Correlations. between variations in IL-7 plasma levels (ΔIL-7) and either variations in (A) total (CD4⁺ + CD8⁺) naïve T-cell counts (Δnaïve T-cell counts), (B) RTE defined as CD31^hi naïve CD4⁺ T-cells (ΔRTE CD4 counts), (C) the sj/βTREC ratio (Δsj/βTREC ratio), (D) the frequency of Ki-67⁺ cells in the RTE CD4⁺ T-cell subset (Δ%Ki-67⁺ in CD4⁺ RTEs) or (E) the number of circulating Ki-67⁺CD4⁺ RTEs (ΔKi-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.</p

IFNα therapy leads to reduction in IL-7 plasma concentration.

<p>(A) IL-7 plasma levels were quantified in peripheral blood cells from acutely HCV-infected (light grey symbols), chronically HCV-infected (black symbols) and HIV/HCV co-infected (white symbols) patients at study entry, as compared to healthy donors (HCV-, dark grey symbols). **: p<0.001 for any HCV-infected patients group. (B) Evolution of plasma IL-7 levels over the first 4 months of IFNα therapy in acutely HCV-infected (left panels), chronically HCV-infected (central panels) and HIV/HCV co-infected (right panels) patients. Each line represents an individual patient. Statistical significances of the differences to baseline values (time 0), calculated on the absolute IL-7 plasma levels in each individual sample (Wilcoxon matched-pairs signed-ranks test) are shown on top. (C) Soluble CD127 was quantified in plasma from acutely HCV-infected (white symbols, top panel), chronically HCV-infected (black symbols, top panel) and HIV/HCV co-infected (bottom panel) patients at baseline (0) and M2. (D) CD127 expression was measured on circulating CD4⁺ (top panel) and CD8⁺ (bottom panel) and expressed as mean fluorescence intensity (left panels) and percentages of positive cells (right panels) over the 4 first months of IFNα therapy.</p

IFNα therapy leads to major impairment of thymic function.

<p>(A) The frequency of Ki-67 expressing cells in the CD4⁺ RTE subset (CD31^hi naïve T-cells) was measured in acutely HCV-infected (grey symbols, top panel), chronically HCV-infected (white symbols, top panel) and HIV/HCV co-infected (bottom panel) patients (central panels) and HIV/HCV co-infected (right panels) patients. Each line represents data from an individual patient. Statistical significances of the differences to baseline values (time 0), calculated on the absolute sj/βTREC ratio in each individual sample (Wilcoxon matched-pairs signed-ranks test) are shown on top. The horizontal bars represent median values.</p