Vaccinia virus encodes a secretory polypeptide structurally related to complement control proteins

Several polypeptides are secreted into the medium of cells infected with vaccinia virus, a cytoplasmic DNA virus belonging to the poxvirus family. One of these, a polypeptide of relative molecular mass 19,0001 is structurally related to epidermal growth factor2–4 and binds to epidermal growth factor receptor stimulating proliferation of uninfected cells in vitro6–7 and in vivo8. Here, we show that a second, and much more abundant secretory polypeptide, is also encoded by vaccinia virus and is structurally related to the superfamily of complement control proteins. Members of this family can block complement-mediated induction of the inflammatory response, and engulfment, killing and lysis of bacteria and viruses9,10.