Amino acid mutations in the interferon sensitivity determining region and serum virus load in hepatitis C virus carriers with long-term normal ALT levels.
The amino acid mutations in a part of the non-structural region 5A (NS5A) of the hepatitis C virus (HCV) genome, called the interferon sensitivity determining region (ISDR), can affect the response to interferon (IFN) treatment. We analyzed the serial changes of the amino acid substitutions in the ISDR during the natural course of patients with sustained long-term normal alanine aminotransferase (ALT) levels in relation to the changes in virus load, and assessed the clinical significance of ISDR in the natural course and IFN treatment. The subjects were nine patients infected with HCV (genotype 1b) who had been examined for serum ALT levels every month for more than 1 year and had well-sustained normal levels. The amino acid sequence of the ISDR was determined by the direct sequencing method, and the number of amino acid mutations was evaluated in comparison with the prototype (HCV-J). Quantitation of serum HCV RNA levels was conducted by the Amplicor-monitor method (Nihon Roche). On the initial analysis of the ISDR, six patients were determined to have no mutations, and three patients had one or two mutations. However, an increased number in amino acid mutations compared with the wild type during the follow-up period was confirmed in only one patient, and that increase was limited to within two amino acids. Virus load changed regardless of the changes in amino acid substitutions in the ISDR. The ISDR was therefore inferred to be a stable region unrelated to the virus load in patients with well-sustained normal ALT levels. Additional changes of amino acid sequence in this region were not a sensitive marker for determining whether IFN treatment is indicated.
Takatori
M
Department of Gastroenterology and Hepatology, St. Marianna University School of Medicine, 2-16-1 Sugao Miyamae-ku, Kawasaki, Japan
Sugata
F
Okuse
C
Suzuki
M
Iwabuchi
S
Iino
S