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Journal of Virology, January 2000, p. 661-668, Vol. 74, No. 2
Laboratoire de
Virologie,1 Service
d'Hépato-Gastro-Entérologie,2 and
Service de Medecine Interne,3
Hôpital Purpan, CHU Toulouse, 31059 Toulouse Cédex, France
Received 11 June 1999/Accepted 14 October 1999
Hepatitis C virus (HCV) populations persist in vivo as a mixture of
heterogeneous viruses called quasispecies. The relationship between the
genetic heterogeneity of these variants and their responses to
antiviral treatment remains to be elucidated. We have studied 26 virus
strains to determine the influence of hypervariable region 1 (HVR-1) of
the HCV genome on the effectiveness of alpha interferon (IFN-
0022-538X/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Genetic Heterogeneity of Hypervariable Region 1 of
the Hepatitis C Virus (HCV) Genome and Sensitivity of HCV to Alpha
Interferon Therapy
)
therapy. Following PCR amplification, we cloned and sequenced HVR-1.
Pretreatment serum samples from 13 individuals with chronic hepatitis C
whose virus was subsequently eradicated by treatment were compared with
samples from 13 nonresponders matched according to the major factors
known to influence the response, i.e., sex, genotype, and pretreatment
serum HCV RNA concentration. The degree of virus variation was assessed
by analyzing 20 clones per sample and by calculating nucleotide
sequence entropy (complexity) and genetic distances (diversity). Types
of mutational changes were also determined by calculating nonsynonymous
substitutions per nonsynonymous site (Ka) and
synonymous substitutions per synonymous site
(Ks). The paired-comparison analysis of the
nucleotide sequence entropy and genetic distance showed no statistical
differences between responders and nonresponders. By contrast,
nonsynonymous substitutions were more frequent than synonymous
substitutions (P
0.05) in responders, but there was
no significant difference in nonresponders. Nonsynonymous substitutions
tended to be more frequent than synonymous substitutions in women
(P = 0.06) but not in men. Nucleotide entropy and
genetic distances were significantly related to serum RNA concentration
(P
0.01). Our findings suggest that after
controlling for the major determinants of interferon response, neither
complexity nor diversity of the HVR-1 region is associated per se with
virus eradication. Because a higher proportion of nonsynonymous
substitutions than synonymous substitutions was found only in
responders, host anti-HCV-specific immune response rather than viral
factors may be playing an important role in the interferon response.
*
Corresponding author. Mailing address: Laboratoire de
Virologie, CHU Toulouse, 31059 Toulouse Cédex, France. Phone:
(33) 5 61 77 24 63. Fax: (33) 5 61 77 25 42. E-mail:
izopet{at}cict.fr.
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