Production and characterization of poly(I):poly(C)-induced rat interferons in vitro

The synthetic polyribonucleotide polyinosinate:polycytidylate [poly(I):poly(C)] was used to induce interferon (IFN) production in a rat leiomyosarcoma cell line. Three separate IFN species were distinguished by antiviral activity on homologous and heterologous cells, interaction with Blue Sepharose CL-6B chromatography matrix, and antibody neutralization studies. Two IFN species, one with a weakly ionic and the other with a hydrophobic interaction with Blue Sepharose, exhibited heterologous antiviral activity, and were acid- and heat-labile. Both had a molecular weight of 30,000 daltons by HPLC-based molecular exclusion chromatography. The weakly ionic species was neutralized only by antiserum to L-cell IFN, whereas the hydrophobic species was neutralized by antiserum to L-cell IFN and antiserum to human leukocyte IFN. The remaining IFN species, with a weakly ionic interaction with Blue Sepharose, was acid- and heat-stable, exhibited no heterologous cell antiviral activity, and was not neutralized by any antisera to IFN. This species had a molecular weight of 39,000 daltons by HPLC-based molecular exclusion chromatography and 34,000 daltons by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. These rat fibroblast IFNs possess greater heterogeneity than that reported or observed for murine or human fibroblast IFNs. These IFNs could thus be classified as follows: one species of rat IFN-beta and two different species of unique acid-labile rat IFNs.