Comparison of 125I-interferon-alpha binding to peripheral blood cells from African-Americans and Caucasians with hepatitis C

Optimizing the current therapy for chronic hepatitis C virus: peginterferon and ribavirin dosing and the utility of growth factors

Achieving a sustained virologic response depends on the patient achieving three sequential independent milestones: virologic response, maintaining this response throughout treatment, and not relapsing after treatment has been completed. The ability to achieve these milestones depends on the doses of interferon/peginterferon and ribavirin used and on whether treatment with these medications is adjusted, interrupted, or prematurely discontinued in response to adverse events. This review discusses strategies to optimize peginterferon and ribavirin dosing and the impact that growth factors may have on the ability to achieve a sustained virologic response.

Reduced expression of Jak-1 and Tyk-2 proteins leads to interferon resistance in hepatitis C virus replicon

BACKGROUND

Alpha interferon in combination with ribavirin is the standard therapy for hepatitis C virus infection. Unfortunately, a significant number of patients fail to eradicate their infection with this regimen. The mechanisms of IFN-resistance are unclear. The aim of this study was to determine the contribution of host cell factors to the mechanisms of interferon resistance using replicon cell lines.

RESULTS

HCV replicons with high and low activation of the IFN-promoter were cultured for a prolonged period of time in the presence of interferon-alpha (IFN-alpha2b). Stable replicon cell lines with resistant phenotype were isolated and characterized by their ability to continue viral replication in the presence of IFN-alpha. Interferon resistant cell colonies developed only in replicons having lower activation of the IFN promoter and no resistant colonies arose from replicons that exhibit higher activation of the IFN promoter. Individual cell clones were isolated and nine IFN resistant cell lines were established. HCV RNA and protein levels in these cells were not altered by IFN- alpha2b. Reduced signaling and IFN-resistant phenotype was found in all Huh-7 cell lines even after eliminating HCV, suggesting that cellular factors are involved. Resistant phenotype in the replicons is not due to lack of interferon receptor expression. All the cell lines show defect in the JAK-STAT signaling and phosphorylation of STAT 1 and STAT 2 proteins were strongly inhibited due to reduced expression of Tyk2 and Jak-1 protein.

CONCLUSION

This in vitro study provides evidence that altered expression of the Jak-Stat signaling proteins can cause IFN resistance using HCV replicon cell clones.

Treatment of chronic hepatitis C virus in African Americans with genotypes 2 and 3

Previous studies have documented that sustained virologic response (SVR) is significantly reduced in African Americans with chronic HCV genotype 1 following treatment with interferon and ribavirin when compared with Caucasians. The specific aim of the present retrospective study was to assess virologic response to interferon and ribavirin in African Americans with HCV genotypes 2 and 3. A review of our database identified 42 African Americans and 334 Caucasians with HCV genotypes 2 and 3. Patients coinfected with hepatitis B or human immunodeficiency virus, chronic renal failure, and recipients of an organ transplant were excluded. Thirty of the African Americans were treated with either standard interferon or peginterferon and ribavirin as initial treatment for chronic HCV. Ninety of the 334 Caucasians were matched to the African Americans with regards to genotype, cirrhosis, treatment regimen, sex, age, and body weight for comparison of virologic response. The proportion of patients with HCV genotype 2 was significantly greater (P < 0.001) in African Americans compared with Caucasians (81%vs 52%). End-of-treatment virologic response was observed in 94% of Caucasians compared with 80% in African Americans (P= 0.036). SVR was observed in 82% and 57% of Caucasians and African Americans, respectively (P= 0.012). Similar results were observed when patients who had been treated with only peginterferon and ribavirin were assessed. These results suggest that African Americans have a global defect in their ability to eradicate HCV infection following treatment with interferon and ribavirin which transcends across all genotypes.