gp 58/68, a parasite component that contributes to the escape of the trypomastigote form of T. cruzi from damage by the human alternative complement pathway.
A glycoprotein of apparent molecular weight 58,000 (unreduced)/68,000 (in its reduced form) (gp 58/68), which is one of the fibronectin/collagen receptors of Trypanosoma cruzi, was purified to homogeneity from the trypomastigote forms of the Tehuantepec and Y strains of the parasite. Purified gp 58/68 inhibited formation of cell-bound and fluid-phase alternative pathway C3 convertase in a dose-dependent fashion, as assessed using purified human complement components. Gp 58/68 differed from the human regulatory proteins H, DAF, MCP and CR1 and from previously reported regulatory proteins on the parasite membrane in that it was unable to enhance decay-dissociation of preformed alternative pathway C3 convertase sites, did not serve as a co-factor for I-mediated cleavage of C3b and had no inhibitory activity on the classical pathway convertases. The inhibitory effect of gp 58/68 was most likely dependent on an interaction of the protein with factor B rather than with C3b. Gp 58/68 provides trypomastigotes with an additional potential mechanism for escaping complement lysis by the human alternative pathway.
Fischer
E
E
INSERM U28, Hôpital Broussais, Paris, France.
Ouaissi
M A
MA
Velge
P
P
Cornette
J
J
Kazatchkine
M D
MD
D000818:Animals; D003166:Complement Activating Enzymes / Q000276:immunology*; D003167:Complement Activation; D050577:Complement C3-C5 Convertases / Q000276:immunology*; D003179:Complement C3b / Q000276:immunology; D003180:Complement C3b Inactivator Proteins / Q000276:immunology; D017244:Complement Factor I; D003170:Complement Pathway, Alternative; D008562:Membrane Glycoproteins / Q000276:immunology*; D012697:Serine Endopeptidases / Q000276:immunology; D014349:Trypanosoma cruzi / Q000276:immunology*
D003180:Complement C3b Inactivator Proteins; D008562:Membrane Glycoproteins; D003179:Complement C3b; D003166:Complement Activating Enzymes; D050577:Complement C3-C5 Convertases; D012697:Serine Endopeptidases; D017244:Complement Factor I