Numerous members of the herpesvirus and poxvirus families express secreted proteins related to the super-family of complement regulators as defined by the presence of multiple short consensus repeats (SCRs) and which act by binding and inhibiting key elements of the classical and alternative complement cascades. In the case of poxviruses, the two most extensively studied members are from vaccinia virus and cowpox virus. The vaccinia version, also called vaccinia control protein (VCP), and the cowpox protein are both secreted from infected cells as 35kDa glycoproteins that exhibit anticomplenient activity in vitro and in vivo.