Purification of interferon from chick embryonic allantoic fluids and fibroblast tissue infected with influenza virus.

Chick interferon has been purified to varying extents by several groups of investigators. Burke's (1961) starting material was interferon produced in chorioallantoic membranes; this was purified about 2o-fold mainly by chromatography on DEAE and SM celluloses. Zemla & Vilcek (196I) precipitated interferon, produced in chick embryo fibroblasts, with acetone or ethanol at I O ° to 1 5 ° and claimed an 8o-fold purification. As their purification factor was however based on total and not protein nitrogen, most of their purification probably consisted in the removal of amino acids and other nitrogenous components of low molecular weight derived from the '199' culture medium. Lampson et al. (1963) purified allantoic fluid interferon about 18oo times (45oo times after electrophoresis) by precipitation of inactive protein with perchloric acid, adsorption of the active material on zinc hydroxide, removal of zinc ions by dialysis in acid solution, chromatography of the active material on CM cellulose and finally electrophoresis on Pevikon. Similar methods were later used by the same authors to purify tissue culture interferon (Lampson et al. 1965). Fantes, O'Neill & Mason (1964) and Fantes (I965), in preliminary communications, described processes that raised the specific activity of chick allantoic-fluid interferon several thousand times. Phillips & Wood (1964) prepared partially purified interferon by fractionation on Sephadex G ioo. Cantell et al. (1965) and Pokidova et al. (1965) both used methods similar to that of Lampson et al. (1963). Merigan (1964a, b) modified Lampson's method to purify allantoic fluid interferon; he substituted CM Sephadex C25 for CM cellulose and eluted the activity, by employing a pH gradient. An even higher purification (65oo-fold) than that achieved by Lampson et al. (1963) was obtained but such material was later shown by electrophoresis (Merigan, Winget & Dixon, 1965) to be still far from homogeneous. This communication describes the isolation of chick interferon of probably even higher specific activity.