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Why is the interferon sensitivity-determining region (ISDR) system useful in Japan?
1Second Department of Internal Medicine, Nagoya University School of Medicine, Japan.
Journal of Hepatology
|July 16, 1999
Summary
Geographical differences in hepatitis C virus (HCV) genotype-1b isolates explain why the interferon sensitivity-determining region (ISDR) predicts interferon (IFN) treatment response in Japan but not Europe.
Area of Science:
- Hepatology
- Virology
- Genetics
Background:
- The interferon sensitivity-determining region (ISDR) sequence in hepatitis C virus (HCV) genotype-1b has been linked to interferon (IFN) treatment response by Japanese researchers.
- European studies have not replicated this finding, suggesting geographical variations in HCV-1b isolates.
Purpose of the Study:
- To investigate geographical differences in HCV genotype-1b nucleotide sequences.
- To determine if these differences explain the conflicting findings regarding ISDR and IFN responsiveness.
Main Methods:
- Comparative analysis of HCV-1b nucleotide sequences from Japanese and international isolates using envelope 1 sequences.
- Phylogenetic tree analysis to group isolates geographically.
Main Results:
- Phylogenetic analysis identified two main geographical groups: the NJ group (non-Japanese) and the J group (Japanese).
- Japanese isolates were further classified into the J group (40%) and W group (60%).
- A strong correlation between ISDR type and IFN response was observed in the J group but not the W group among Japanese patients.
Conclusions:
- The existence of a Japan-specific HCV-1b isolate group (J group) is a key factor explaining the utility of the ISDR system for predicting IFN response solely in Japan.