PURIFICATION OF AN ATYPICAL BOVINE INTERFERON-INDUCED IN RESPONSE TO HEAT-SHOCK IN BOVINE CULTURED-CELLS - CHARACTERIZATION IN COMPARISON WITH THE CLASSICAL ALPHA-INTERFERON, BETA-INTERFERON AND GAMMA-INTERFERON

Heat-shock induced factor (HSIF) was excreted by bovine MDBK cells dur ing their recovery period after a heat shock. This factor has the capa city to induce 2',5' oligoadenylate synthetase activity, an enzyme gen erally induced by interferon treatment (J Biol Chem (1987) 262, 4806-4 811). We have observed that an antiviral state was also produced in re sponse to heat shock. HSIF was purified 10 000-fold and different tech niques showed a copurification of both activities. Certain properties of HSIF were established, such as its molecular mass (45 kDa) and isoe lectric point (6.8). This cytokine was acid-sensitive as IFN gamma (ty pe II) and temperature labile contrarily to alpha, beta and gamma bovi ne IFN. Immunoprecipitation and comparative chromatography on lectines or polynucleotides established that HSIF was structurally different f rom the three classes of bovine IFN. Moreover, two-dimensional electro phoresis and comparative analysis of [S-35] methionine-labeled protein s induced by HSIF, alpha, beta or gamma bovine IFN showed that HSIF in duces a specific set of proteins. Taken together, all these results st rongly suggest that HSIF is a new atypical bovine interferon induced i n response to heat shock.