Ribavirin improves the IFN-γ response of natural killer cells to IFN-based therapy of hepatitis C virus infection.

UNLABELLED: Ribavirin (RBV) is an important component of interferon (IFN)-based and direct antiviral treatment regimens for hepatitis C virus (HCV) infection. Immunomodulation, in particular improvement of the host IFN response, has been proposed as RBV's mechanism of action. Natural killer (NK) cells are sensitive biomarkers for IFN-α/ß receptor signaling, as NK cell cytotoxicity and IFN-γ production are regulated by signal transducer and activator of transcription (STAT)1- and STAT4-phosphorylation, respectively. Specifically, pSTAT1-dependent NK cell cytotoxicity increases and pSTAT4-dependent IFN-γ production decreases in response to endogenous, virus-induced IFN-α and during IFN-α-based therapy. To assess whether RBV has a direct effect on NK cells and/or improves the IFN-γ response of NK cells in the presence of IFN-α, we prospectively studied 22 HCV patients with and 32 patients without 4 weeks of RBV pretreatment, who all received subsequent pegylated (Peg)IFN/ribavirin combination therapy. During RBV pretreatment, both the frequency of CD56(dim) NK cells with cytotoxic effector functions and the frequency of CD56(bright) NK cells with the capacity to produce IFN-γ decreased (P = 0.049 and P = 0.001, respectively). In vitro or in vivo exposure of NK cells to RBV improved the pSTAT4 (P < 0.01) but not pSTAT1 response of NK cells to subsequent stimulation with IFN-α. This was associated with an increase in IFN-γ production but not cytotoxicity of NK cells during subsequent IFN-α-based therapy. The frequency of IFN-γ-producing NK cells was greater in fast second-phase virological responders than in slow responders. CONCLUSION: RBV enhances the pSTAT4 and IFN-γ response of NK cells to IFN-α-stimulation.

Effect of ribavirin on viral kinetics and liver gene expression in chronic hepatitis C.

OBJECTIVE: Ribavirin improves treatment response to pegylated-interferon (PEG-IFN) in chronic hepatitis C but the mechanism remains controversial. We studied correlates of response and mechanism of action of ribavirin in treatment of hepatitis C. DESIGN: 70 treatment-naive patients were randomised to 4 weeks of ribavirin (1000-1200 mg/d) or none, followed by PEG-IFNα-2a and ribavirin at standard doses and durations. Patients were also randomised to a liver biopsy 24 h before or 6 h after starting PEG-IFN. Hepatic gene expression was assessed by microarray and interferon-stimulated gene (ISG) expression quantified by nCounter platform. Temporal changes in ISG expression were assessed by qPCR in peripheral-blood mononuclear cells (PBMC) and by serum levels of IP-10. RESULTS: After 4 weeks of ribavirin monotherapy, hepatitis C virus (HCV) levels decreased by 0.5±0.5 log10 (p=0.009 vs controls) and ALT by 33% (p<0.001). Ribavirin pretreatment, while modestly augmenting ISG induction by PEG-IFN, did not modify the virological response to subsequent PEG-IFN and ribavirin treatment. However, biochemical, but not virological, response to ribavirin monotherapy predicted response to subsequent combination treatment (rapid virological response, 71% in biochemical responders vs 22% non-responders, p=0.01; early virological response, 100% vs 68%, p=0.03; sustained virological response 83% vs 41%, p=0.053). Ribavirin monotherapy lowered serum IP-10 levels but had no effect on ISG expression in PBMC. CONCLUSIONS: Ribavirin is a weak antiviral but its clinical effect seems to be mediated by a separate, indirect mechanism, which may act to reset IFN-responsiveness in HCV-infected liver.

Temperature rise after peginterferon alfa-2a injection in patients with chronic hepatitis C is associated with virological response and is modulated by IL28B genotype.

BACKGROUND & AIMS: Interferon treatment for chronic hepatitis C is associated with non-specific symptoms including fever. We aimed to determine the association of temperature changes with interferon antiviral activity. METHODS: 60 treatment-naïve patients with chronic hepatitis C (67% genotype 1/4/6, 33% genotype 2/3) were admitted to start peginterferon alfa-2a and ribavirin in a clinical trial. Temperature was measured at baseline and 3 times daily for the first 24h and the maximal increase from baseline during that time (ΔTmax) was determined. Serum HCV-RNA, interferon-gamma-inducible protein-10 (IP-10) and expression of interferon-stimulated genes (ISGs - CD274, ISG15, RSAD2, IRF7, CXCL10) in peripheral blood mononuclear cells (PBMCs) were measured at very early time points, and response kinetics calculated. The IL28B single nucleotide polymorphism, rs12979860, was genotyped. RESULTS: Temperatures rose by 1.2±0.8°C, peaking after 12.5h. ΔTmax was strongly associated with 1st phase virological decline (r=0.59, p<0.0001) and was independent of gender, cirrhosis, viral genotype or baseline HCV-RNA. The association with 1st phase decline was seen in patients with rs12979860CC genotype (r = 0.65, p <0.0001) but not in CT/TT (r = 0.13, p = 0.53) and patients with CC genotype had a higher DTmax (1.4 ± 0.8 C vs. 0.8 ± 0.6 +C, p = 0.001). DTmax was associated with 6- and 24-h induction of serum IP-10 and of PBMC ISG expression, but only in patients with rs12979860CC [corrected].ΔTmax weakly predicted early virological response (AUC=0.68, CI 0.49-0.88). CONCLUSIONS: Temperature rise following peginterferon injection is closely associated with virological response and is modulated by IL28B polymorphism, reflecting host interferon-responsiveness.

Early changes in interferon signaling define natural killer cell response and refractoriness to interferon-based therapy of hepatitis C patients.

UNLABELLED: Natural killer (NK) cells exhibit a polarized phenotype with increased cytotoxicity and decreased interferon gamma (IFN-γ) production in chronic hepatitis C virus (HCV) infection. Here, we asked whether this is caused by type I interferon (IFN)-induced expression and phosphorylation levels of signal transducer and activator of transcription (STAT) molecules in NK cells and whether it affects the response and refractoriness of NK cells to IFN-α-based therapy of HCV. STAT1 levels in NK cells were significantly higher in patients with chronic HCV infection than in uninfected controls. STAT1 levels and induction of phosphorylated STAT1 (pSTAT1) increased further during IFN-α-based therapy with preferential STAT1 over STAT4 phosphorylation. Induction of pSTAT1 correlated with increased NK cytotoxicity (tumor necrosis factor-apoptosis-inducing ligand [TRAIL] expression and degranulation) and decreased IFN-γ production. NK cells from patients with a greater than 2 log(10) first-phase HCV RNA decline to IFN-α-based therapy (>99% IFN effectiveness) displayed strong pSTAT1 induction in vivo and were refractory to further stimulation in vitro. In contrast, NK cells from patients with a less than 2 log(10) first-phase HCV RNA decline exhibited lower pSTAT1 induction in vivo (P = 0.024), but retained greater IFN-α responsiveness in vitro (P = 0.024). NK cells of all patients became refractory to in vivo and in vitro stimulation by IFN-α during the second-phase virological response. CONCLUSION: These data show that IFN-α-induced modulation of STAT1/4 phosphorylation underlies the polarization of NK cells toward increased cytotoxicity and decreased IFN-γ production in HCV infection, and that NK cell responsiveness and refractoriness correlate to the antiviral effectiveness of IFN-α-based therapy.

Early changes in natural killer cell function indicate virologic response to interferon therapy for hepatitis C.

BACKGROUND & AIMS: Mathematical modeling of hepatitis C virus (HCV) kinetics indicated that cellular immune responses contribute to interferon (IFN)-induced clearance of HCV. We investigated a potential role of natural killer (NK) cells in this process. METHODS: Phenotype and function of blood and liver NK cells were studied during the first 12 weeks of treatment with pegylated IFN-alfa and ribavirin, the time period used to define the early virological response. RESULTS: Within hours of treatment initiation, NK cells of patients that had an early virological response increased expression of activating receptors NKG2D, NKp30, and CD16 and decreased expression of NKG2C and 2B4, along with inhibitory receptors SIGLEC7 and NKG2A, resulting in NK cell activation. NK cell cytotoxicity, measured by degranulation and tumor necrosis factor-related apoptosis-inducing ligand production, peaked after 24 hours (P<.01), concomitant with an increase in alanine aminotransferase levels (P<.05), whereas IFN-γ production decreased within 6 hours and did not recover for more than 4 weeks (P<.05). NK cells from liver biopsies taken 6 hours after treatment initiation had increased numbers of cytotoxic CD16+NK cells (P<.05) and a trend toward increased production of tumor necrosis factor-related apoptosis-inducing ligand. Degranulation of peripheral blood NK cells correlated with treatment-induced, first-phase decreases in viral load (P<.05) and remained higher in early virological responders than in nonresponders for weeks. CONCLUSIONS: IFN activates NK cells early after treatment is initiated. Their cytotoxic function, in particular, is strongly induced, which correlates to virologic response. Therefore, NK cell activation indicates responsiveness to IFN-α-based treatment and suggests the involvement of the innate immune cells in viral clearance.

Editorial: Treatment of patients with HCV-related cirrhosis with peginterferon and ribavirin: Swinging the pendulum toward treatment.

Patients with hepatitis C virus-related cirrhosis are at increased risk for hepatic decompensation and hepatocellular carcinoma (HCC). They also responded less well to standard therapy compared with those without cirrhosis. Several recent studies have demonstrated that patients with cirrhosis can be safely treated and those who achieve a sustained virological response have better clinical outcomes compared with nonresponders. These results support treatment for patients with compensated cirrhosis. In addition, cirrhotic patients should be monitored after a sustained virological response is obtained, because some patients remain at risk for complications of liver disease, particularly HCC. Newer, more effective therapy is needed for patients with cirrhosis.

Pharmacokinetics and pharmacodynamics of peginterferon and ribavirin: implications for clinical efficacy in the treatment of chronic hepatitis C.

The pharmacokinetics and pharmacodynamics of standard interferon alfa-2a and interferon alfa-2b are substantially altered by pegylation. The size, geometry, and site of attachment of the PEG moiety affect the pharmacokinetics and pharmacodynamics as evidenced by the different absorption, volume of distribution, and clearance of the linear 12-kDa peginterferon alfa-2b and the branched 40-kDa peginterferon alfa-2a. Despite these differences, the clinical efficacy, safety, and tolerability of the 2 peginterferons are similar. However, evidence exists that peginterferon alfa-2 plus ribavirin is associated with small but significantly higher sustained virological response rates compared with peginterferon alfa-2b. This article discusses the pharmacokinetics and pharmacodynamics of the 2 peginterferons and their combination with ribavirin.