The detection of IRF-1 promoter polymorphisms and their possible contribution to T helper 1 response in chronic hepatitis C

We described the interferon (IFN) regulatory factor-1 (IRF-1) promoter single nucleotide polymorphisms (SNPs), and the clinical and immunologic implications of these SNPs have been investigated. We successfully determined the mutation at -300 of the IRF-1 promoter by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), and this mutation linked with other mutations in the promoter region. In our Japanese population, the frequency of the type -300*A/A was 11.9%, type A/G was 54.2%, and type G/G was 33.9%. We found no significant difference without IFN stimulation in the production levels of IFN-γ and interleukin-10 (IL-10) from peripheral blood mononuclear cells (PBMC) between subjects with -300*A/A and those with other types. IFN-α stimulation, however, increased the levels of IFN-γ significantly and decreased the IL-10 production level significantly only in the subject with -300*A/A type. Flow cytometric analysis showed that the Th1-type CD4⁺ cell population was significantly increased by IFN-β administration only in the patient with chronic hepatitis C with -300*A/A type. These results suggest that the IRF-1 promoter SNP types are positively involved in Th1-type response and, consequently, the -300*A/A type may be beneficial for viral elimination in chronic hepatitis C and IFN therapy.