Some viruses seem to be capable of suppressing interferon (IFN)-induced 2',5'-oligoadenylate synthetase (2-5AS) induction. Cells infected with human T-lymphotropic virus type-I (HTLV-I) show different natures for the constitutive production of IFN-gamma or sensitivity to IFN. Poor induction of 2-5AS was found in IFN-gamma producer cells carrying HTLV-I (MT-1, MT-2 and SMT-1). On the other hand, in non- or low-producing cell lines of IFN-gamma such as HUT102 and OKM-2, significant activity of 2-5AS was induced by treatment with IFN-alpha. A satisfactory level of IFN receptor was detectable in SMT-1 cells in spite of the poor induction of 2-5AS. There were no differences in either the interferon regulatory factor-2 (IRF-2) mRNA transcript or the level of STAT-1 alpha between SMT-1 and HUT102 cells. However, the transcription of IRF-1 mRNA was slightly reduced in SMT-1 cells as compared with that of HUT102 cells.
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