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Journal of Virology, September 1999, p. 7241-7247, Vol. 73, No. 9
Department of Clinical and Experimental
Medicine, University of Padua, Padua,
Italy,1 and Departments of Laboratory
Medicine2 and
Medicine,3 University of Washington,
Seattle, Washington
Received 4 February 1999/Accepted 27 May 1999
Alpha interferon (IFN-
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Effect of Retreatment with Interferon Alone or
Interferon plus Ribavirin on Hepatitis C Virus Quasispecies
Diversification in Nonresponder Patients with Chronic Hepatitis
C
) treatment is effective on a long-term
basis in only 15 to 25% of patients with chronic hepatitis C. The
results of recent trials indicate that response rates can be
significantly increased when IFN-
is given in combination with
ribavirin. However, a large number of patients do not respond even to
combination therapy. Nonresponsiveness to IFN is characterized by
evolution of the hepatitis C virus (HCV) quasispecies. Little is known
about the changes occurring within the HCV genomes when nonresponder
patients are retreated with IFN or with IFN plus ribavirin. In the
present study we have examined the genetic divergence of HCV
quasispecies during unsuccessful retreatment with IFN or IFN plus
ribavirin. Fifteen nonresponder patients with HCV-1 (4 patients with
HCV-1a and 11 patients with HCV-1b) infection were studied while being
retreated for 2 months (phase 1) with IFN-
(6 MU given three times a
week), followed by IFN plus ribavirin or IFN alone for an additional 6 months (phase 2). HCV quasispecies diversification in the E2
hypervariable region-1 (HVR1) and in the putative NS5A IFN sensitivity
determining region (ISDR) were analyzed for phase 1 and phase 2 by
using the heteroduplex tracking assay and clonal frequency analysis
techniques. A major finding of this study was the relatively rapid
evolution of the HCV quasispecies observed in both treatment groups
during the early phase 1 compared to the late phase 2 of treatment. The
rate of quasispecies diversification in HVR1 was significantly higher
during phase 1 versus phase 2 both in patients who received IFN plus
ribavirin (P = 0.017) and in patients who received IFN
alone (P = 0.05). A trend toward higher rates of
quasispecies evolution in the ISDR was also observed during phase 1 in
both groups, although the results did not reach statistical
significance. However, the NS5A quasispecies appeared to be rather
homogeneous and stable in most nonresponder patients, suggesting the
presence of a single well-fit major variant, resistant to antiviral
treatment, in agreement with published data which have identified an
IFN sensitivity determinant region within the NS5A. During the entire 8 months of retreatment, there was no difference in the rate of fixation
of mutation between patients who received combination therapy and
patients who were treated with IFN alone, suggesting that ribavirin had
no major effects on the evolution of the HCV quasispecies after the
initial 2 months of IFN therapy.
*
Corresponding author. Mailing address: Department of
Clinical and Experimental Medicine, University of Padua, Via
Giustiniani 2, Padua 35128, Italy. Phone: 390-49-8212294. Fax:
390-49-8211826. E-mail: labepvir{at}ux1.unipd.it.
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