 For any clinical or industrial applications, it is important that SeV genomic and inserted foreign trans genes would be expressed in a stable way.Genetic stability enables performance of many serial passages in cell cultures or embryonated chicken eggs without viral genomic change.The SeV F protein is a type I membrane glycoprotein that is synthesized as an inactive precursor (F0) that must be activated by proteolytic cleavage at residue arginine-116.