THE COMPLEMENT CONTROL PROTEIN HOMOLOG OF HERPESVIRUS SAIMIRI REGULATES SERUM COMPLEMENT BY INHIBITING C3 CONVERTASE ACTIVITY

The herpesvirus saimiri genome encodes a complement control protein ho molog (CCPH). Stable mammalian cell transfectants expressing a recombi nant transmembrane form of CCPH (mCCPH) or a 5'FLAG epitope-tagged mCC PH (5'FLAGmCCPH) conferred resistance to complement-mediated cell dama ge by inhibiting the lytic activity of human serum complement. The fun ction of CCPH was further defined by showing that the mCCPH and the 5' FLAGmCCPH transfectants inhibited, C3 convertase activity and effectiv ely reduced cell surface deposition of the activated complement compon ent, C3d.