Abstract
The antiviral drug ribavirin (RBV) is widely used in combination with pegylated interferon (PegIFN) for the treatment of hepatitis C virus (HCV) infection. A major side effect of RBV is a reversible anemia. The mechanism underlying anemia in RBV treated patients remains speculative although hemolysis was suggested. To get further insights, we evaluated in vitro the effect of RBV and PegIFN on proliferation and erythroid differentiation of CD34 pheripheral blood cells. The mononuclear cells derived from pheripheral blood of healthy volunteers were enriched for CD34+ cells by positive selection using anti-CD34-tagged magnetic beads. CD34+ cells were cultured for 14 days with a specific medium containing erythropoietin to induce erythroid differentiation. RBV (0.5mM and 0.1mM) and PegIFN (100U and 1000U) were added alone or in combination at different days of culture: precisely at day 0 corresponding to CD34 stage and at day 7 corresponding to proerythroblast stage. Cells growth and viability were evaluated by tripan blue exclusion; erythroid differentiation was investigated by cytofluorimetric analysis of Glicophorin A (GPA) expression, by morphological analysis on benzidine-May-Grunwald-Giemsa stained smears and by erythroid specific (γ-globin and GATA2) gene expression analysis with real-time PCR. RBV added at day 0 of culture drastically inhibited cell growth and differentiation (RBV 0.1mM: 8.5-fold reduction in cells growth and 1.6-fold reduction in GPA+ cells vs untreated cells at day 14; RBV 0.5mM: 12-fold reduction in cells growth and 30-fold reduction in GPA+ cells vs untreated cells at day 14). Addition of RBV at day 7 of culture had a milder inhibitory effect (RBV 0.1mM: 2.4-fold reduction in cells growth and 0.7-fold reduction in GPA+ cells vs untreated cells at day 14; RBV 0.5mM: 3.6-fold reduction in cells growth and 2.3-fold reduction in GPA+ cells vs untreated cells at day 14). Addition of PegIFN both at day 0 and day 7 of culture delayed erythroid differentiation, with reduction of GPA+ cells, decrease of orthocromatic erythroblasts and increase of more undifferentiated polychromatophilic erythroblasts, and increased expression of primitive erythropoietic genes (tab 1). The combined addition of PegIFN and RBV both at day 0 and day 7 of culture affected cell growth and erythroid differentiation less than RBV alone, with increase of GPA+ cells, decrease of basophilic erythroblasts and increase of more differentiated orthocromatic erythroblasts, and decreased expression of γ-globin gene. However cells treated with the combination of PegIFN and RBV were more undifferentiated than cells treated with PegIFN alone. All these observations confirmed the inhibitory effect of PegIFN on erythroid differentiation and strongly suggested an inhibitory action of RBV on cell growth, particularly on undifferentiated stem cells. These observations provide a model for the pathophysiology of anemia observed with ribavirin treatment.Tab. 1% GPA+ cells% polychromatophilic e.% orthocromatic e.γ-geneGATA2 geneUntreated cells61175511PegIFN 100U5037561,751,16PegIFN 1000U4757232,391,7
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