Cell-produced viral inhibitor: possible mechanism of action and chemical composition

A newly recognized cell-produced viral inhibitor appeared to be spontaneously released from most cells in tissue culture. It strongly inhibited the replication of a variety of viruses but did not exhibit species specificity as does interferon. These studies on the inhibitor's mechanism of action indicated that it inhibited attachment and penetration of virus by a readily reversible reaction requiring the presence of both virus and cells. Studies of inactivation by specific enzymes or chemicals indicated that for activity the inhibitor required intact protein but not lipid, carbohydrate, deoxyribonucleic acid, or ribonucleic acid.