Humanized recombinant vaccinia virus complement control protein (hrVCP) with three amino acid changes, H98Y, E102K, and E120K creating an additional putative heparin binding site, is 100-fold more active than rVCP in blocking both classical and alternative complement pathways

Ann N Y Acad Sci. 2005 Nov;1056:113-22. doi: 10.1196/annals.1352.024.


Vaccinia virus complement control protein (VCP) is able to modulate the host complement system by regulating both pathways of complement activation. Efficient downregulation of complement activation depends on the ability of the regulatory protein to effectively bind the activated third (C3b) and fourth (C4b) complement components. Based on native crystallographic structure, molecular modeling, and sequence alignment with other Orthopoxviral complement control proteins (CCPs) and their host homologs, putative sites have been found on VCP as contact points for C3b/C4b. Here, we report that using site-directed mutagenesis, modified proteins have been generated. In addition, we report that the generated modified proteins with postulated contact point substitutions have shown greater ability to regulate both the classical and the alternative pathways of complement activation than the recombinant Western Reserve VCP, with one modified protein showing nearly 100-fold more potency in regulating both complement activation pathways independently. The augmented in vitro inhibitory activity of the modified protein together with the newly created putative heparin binding site suggests its promising potential as a competent therapeutic agent in modulating various complement-mediated ailments, for example, traumatic brain injury, Alzheimer's disease, rheumatoid arthritis, multiple organ dysfunction syndrome, reperfusion injury, and xenorejection.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Amino Acid Substitution
  • Binding Sites
  • Cloning, Molecular
  • Complement Pathway, Alternative / drug effects*
  • Complement Pathway, Classical / drug effects*
  • Heparin / metabolism*
  • Humans
  • Kinetics
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / pharmacology
  • Viral Proteins / chemistry
  • Viral Proteins / pharmacology*


  • Recombinant Proteins
  • Viral Proteins
  • complement-control protein, Vaccinia virus
  • Heparin