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Two PKR inhibitor HCV proteins correlate with early but not sustained response to interferon
M Gerotto1, F Dal Pero, P Pontisso
1Department of Clinical and Experimental Medicine, University of Padua, Padua, Italy.
Background & Aims:
The NS5A and the E2 proteins of hepatitis C virus (HCV)-1b can bind and inhibit in vitro the interferon (IFN)-induced cellular kinase PKR. The role of such interaction in modulating the antiviral effect of IFN is still controversial. We have analyzed the E2 and the NS5A sequences in HCV-1b-infected patients treated with IFN to assess whether and how different combinations of wild-type and mutant proteins correlated with early and long-term virological response.
Methods:
In 30 patients, sequences of pretreatment and on-treatment E2-PePHD and NS5A-PKR binding domain (including the putative ISDR) were analyzed in parallel by sequencing cDNA-polymerase chain reaction products and up to 25 independent clones.
Results:
The E2-PePHD sequence was highly conserved with a homogeneous quasispecies and was identical in 29 of 30 cases with no association with the pattern of response and no evidence of evolution during therapy. Patients with a mutated NS5A-ISDR had a higher rate of early virological response (67%) than cases with wild-type ISDR (17%). This association was lost in long-term responders (33% vs. 17%).
Conclusions:
Although the highly conserved E2-PePHD motif might contribute to reduce IFN responsiveness, variations within this region do not seem to play a role in modulating IFN sensitivity. The NS5A-ISDR sequence influenced the early, but not the sustained response, to IFN, suggesting that other factors may be more important for the long-term outcome of therapy.
Insights
Hepatitis C virus (HCV) mutations in the NS5A protein’s ISDR region impact early treatment response to interferon (IFN). However, these NS5A variations do not affect long-term virological outcomes in HCV-1b patients.
Area of Science:
- Virology
- Immunology
- Hepatology
Background:
- Hepatitis C virus (HCV) proteins NS5A and E2 can inhibit the interferon (IFN)-induced kinase PKR.
- The precise role of this interaction in modulating IFN's antiviral efficacy remains debated.
- Understanding viral sequence variations in patients undergoing IFN therapy is crucial for predicting treatment outcomes.
Purpose of the Study:
- To analyze E2 and NS5A protein sequences in HCV-1b infected patients undergoing IFN treatment.
- To correlate wild-type and mutant protein combinations with early and long-term virological response.
- To investigate the role of specific viral regions (E2-PePHD, NS5A-ISDR) in IFN sensitivity.
Main Methods:
- Sequencing of E2-PePHD and NS5A-PKR binding domain (including ISDR) from 30 HCV-1b patients.
- Analysis of pretreatment and on-treatment viral sequences.
- Utilized cDNA-polymerase chain reaction products and sequencing of up to 25 independent clones per sample.
Main Results:
- The E2-PePHD sequence was highly conserved and showed no association with treatment response or evolution during therapy.
- Patients with mutated NS5A-ISDR exhibited a significantly higher rate of early virological response (67%) compared to wild-type (17%).
- This association between NS5A-ISDR mutation and response was not observed in long-term responders (33% vs. 17%).
Conclusions:
- While the conserved E2-PePHD motif may influence IFN responsiveness, its variations do not appear to modulate IFN sensitivity.
- NS5A-ISDR sequence variations impact early IFN response but not sustained virological response in HCV-1b infection.
- Other uncharacterized factors likely play a more significant role in achieving long-term therapeutic success.