INDUCTION AND CROSS-SPECIES ACTIVITY OF RAT FIBROBLAST-DERIVED INTERFERON

Abstract

Interferon (IFN) derived from rat fibroblasts (RFA-1) was pH 2 stable and heat labile. Denaturants such as sodium dodecyl sulfate and urea inactivated this interferon but .beta.-mercaptoethanol alone did not. IFN yield after Newcastle disease virus induction was multiplicity of infection (moi) dependent. Optimal induction was obtained with an moi of 10. RFA-1 cells produced small amounts of IFN (.ltoreq. 101.5 U/ml) when exposed to varying amounts of poly(rI):poly(rC). Addition of DEAE-dextran and/or pretreatment with IFN did not change this response. Pretreatment resulted in increased IFN production (priming), but on the average it was only about a 2-fold increase. The kinetics of IFN production were altered by pretreatment with IFN whether there was an increase in production or not. Both IFN synthesis and production peaks were detected 2-4 h earlier in IFN-pretreated RFA-1 cells. Rat IFN exhibited a great deal of cross-species activity. It was 100-300% cross-reactive on mouse (L929B and 3T3) cells and 5-10% active on guinea pig fibroblasts, human fibroblast (GM 2767) and bovine kidney (MDBK) cells. These cells were more sensitive to rat IFN than Jensen sarcoma cells (a rat tumor cell line). Neither chicken embryo fibroblasts nor African green monkey kidney (Vero) cells developed an antiviral state when exposed to rat IFN.