Hepatitis C virus NS5A protein inhibits interferon antiviral activity, but the effects do not correlate with clinical response.
OBJECTIVE
Patients with chronic hepatitis C virus infection are commonly treated with interferon alfa (IFN-alpha), but the long-term response rate is poor. A region of NS5A of hepatitis C virus genotype 1 (the ISDR) has been associated with treatment outcome in some patients. NS5A binds to and inhibits PKR in vitro and inhibits IFN-alpha in human cells. We examined the effects of the NS5A protein from patients who did or did not respond to IFN-alpha to determine whether NS5A from IFN-alpha nonresponders inhibited the effects of IFN-alpha in vitro.


METHODS
We cloned NS5A from patients who had well-characterized responses to IFN-alpha and expressed them in a human fibroblast cell line under the control of an inducible promoter. The NS5A expression levels were controlled, and the effects of different proteins on the protective actions of IFN-alpha against encephalomyocarditis virus were investigated.


RESULTS
NS5A expression blocked the antiviral effects of IFN-alpha in human cells. This inhibition was dependent on the level of NS5A expression. Although ISDR changes gave only small differences in IFN-alpha inhibition, clones derived from a patient who did not respond to IFN-alpha and one who did respond to treatment differed greatly: the clones from a patient with response to IFN-alpha were much more inhibitory than those derived from the patient with no response.


CONCLUSIONS
The inhibition of the antiviral effects of IFN-alpha by NS5A is not regulated exclusively by the ISDR, and the effects of NS5A in vitro do not correlate with treatment outcomes.
Paterson
M
M
Imperial College of Medicine at St. Mary's Campus, London, England.
Laxton
C D
CD
Thomas
H C
HC
Ackrill
A M
AM
Foster
G R
GR
D000998:Antiviral Agents / Q000037:antagonists & inhibitors* / Q000494:pharmacology / Q000627:therapeutic use; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D004351:Drug Resistance; D004686:Encephalomyocarditis virus / Q000187:drug effects; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism / Q000821:virology; D019698:Hepatitis C, Chronic / Q000097:blood; D006801:Humans; D016898:Interferon-alpha / Q000037:antagonists & inhibitors* / Q000494:pharmacology / Q000627:therapeutic use; D010446:Peptide Fragments / Q000378:metabolism / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D014162:Transfection; D017361:Viral Nonstructural Proteins / Q000097:blood / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D012324:RNA-Dependent RNA Polymerase
D000998:Antiviral Agents; D016898:Interferon-alpha; D010446:Peptide Fragments; D012333:RNA, Messenger; D017361:Viral Nonstructural Proteins; C087036:NS-5 protein, hepatitis C virus; D012324:RNA-Dependent RNA Polymerase