Inhibition of hyperacute transplant rejection by soluble proteins with the functional domains of CD46 and FcgammaRII.
BACKGROUND
Recombinant soluble forms of complement regulatory molecules, including the human complement regulatory protein CD46 (rsCD46), have been shown to inhibit hyperacute transplant rejection (HAR) and protect against complement-mediated inflammatory tissue damage. Similarly, recombinant soluble forms of the immunoglobulin receptor FcgammaRII (rsFcgammaRII) can attenuate antibody-mediated inflammatory responses. We have produced and tested the function of novel recombinant chimeric proteins that incorporate the functional domains of both CD46 (membrane cofactor protein, MCP) and the low affinity human IgG receptor FcgammaRII (CD32).


METHODS
Two recombinant soluble chimeric proteins (CD46:FcR and FcR:CD46) were designed and produced using a human cell expression system. Their ability to protect cells against complement-mediated lysis (through the CD46 domain) and bind human IgG (through the Fc receptor domain) was assessed in vitro. They were also tested in vivo in the rat reverse passive Arthus reaction and a murine model of hyperacute cardiac transplant rejection.


RESULTS
In vitro, the functional domains of the chimeric proteins each retained their activity. In vivo, the serum half-life of the recombinant chimeric proteins in mice was more than either rsCD46 or rsFcgammaRII. In the rat reverse passive Arthus reaction, intradermal injection of each recombinant protein substantially reduced inflammatory skin edema (>50%) and polymorphonuclear neutrophil infiltration (>90%). In the hyperacute rejection model, i.v. treatment with FcR:CD46 prevented complement-mediated rejection, macroscopic bruising, edema, and thrombosis more effectively than rsCD46.


CONCLUSIONS
CD46/FcgammaRII bifunctional proteins have an improved ability to control complement-mediated hyperacute graft rejection and have therapeutic potential in other conditions involving antibody-mediated inflammation.
Lanteri
M B
MB
The Austin Research Institute, Heidelberg, Victoria, Australia.
Powell
M S
MS
Christiansen
D
D
Li
Y Q
YQ
Hogarth
M
M
Sandrin
M S
MS
Mckenzie
I F
IF
Loveland
B E
BE
D000818:Animals; D015703:Antigens, CD / Q000235:genetics / Q000627:therapeutic use*; D003169:Complement Inactivator Proteins / Q000235:genetics / Q000627:therapeutic use*; D004591:Electrophoresis, Polyacrylamide Gel; D006084:Graft Rejection / Q000517:prevention & control*; D006801:Humans; D016056:Immunodominant Epitopes / Q000235:genetics; D051916:Membrane Cofactor Protein; D008562:Membrane Glycoproteins / Q000235:genetics / Q000627:therapeutic use*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D017434:Protein Structure, Tertiary / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017452:Receptors, IgG / Q000627:therapeutic use*; D011993:Recombinant Fusion Proteins / Q000276:immunology; D011994:Recombinant Proteins / Q000235:genetics / Q000627:therapeutic use; D012967:Sodium Dodecyl Sulfate; D012995:Solubility
D015703:Antigens, CD; C497857:CD46 protein, human; C497860:Cd46 protein, rat; D003169:Complement Inactivator Proteins; D016056:Immunodominant Epitopes; C497859:Mcp protein, mouse; D051916:Membrane Cofactor Protein; D008562:Membrane Glycoproteins; D017452:Receptors, IgG; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D012967:Sodium Dodecyl Sulfate