Constitutive interferon expression from retroviral vector.

A genomic fragment with the human beta-interferon gene was cloned into a pL3-4, a defective Moloney murine leukemia virus (M-MuLV) vector. Here we show that clones selected after viral infection of mouse NIH 3T3 cells constitutively produced 128 IU/ml of human beta-interferon. Constitutive synthesis of retroviral RNA was confirmed by dot blot hybridization of RNA isolated from two of the selected clones. Poly(I) x poly(C) and cycloheximide induction resulted in an increased RNA level, but this was not reflected in an increased production of biologically active interferon.