The cleavage site of C5 from man and animals as a common target for neutralizing human monoclonal antibodies: in vitro and in vivo studies.
The isolation of an anti-C5 single-chain fragment variable (scFv) antibody, TS-A12/22, from a human phage display library, is described. This antibody inhibits the activation of C5 and the assembly of the terminal complement complex implicated in cell and tissue damage. Using antibody-sensitized sheep erythrocytes and rabbit red cells as target cells in hemolytic assays, we found that TS-A12/22 inhibited the activation of C5 by the convertases of both classical and alternative pathways. Western blot analysis and competition experiments with synthetic peptides showed that TS-A12/22 reacted with the alpha chain of C5 and recognized the cleavage site of this complement component by the C5 convertase. As a result, the antibody prevented splitting of C5 and inhibited the generation of C5a and of the terminal complement complex. The identification of the TS-A12/22 recognition site as a conserved sequence in man, mouse, rat and rabbit enabled the demonstration of in vitro inhibition of complement activity in these species. The scFv TS-A12/22 was tested in a rat model of antigen-induced arthritis and proved to be effective in preventing influx of polymorphonuclear cells into the knee joint and C9 deposition on synovial tissue.
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D001168:Arthritis / Q000517:prevention & control; D003182:Complement C5 / Q000276:immunology* / Q000378:metabolism; D005260:Female; D006801:Humans; D007128:Immunoglobulin Fragments / Q000276:immunology*; D051379:Mice; D008808:Mice, Inbred CBA; D019151:Peptide Library; D051381:Rats; D017208:Rats, Wistar
D000911:Antibodies, Monoclonal; D003182:Complement C5; D007128:Immunoglobulin Fragments; D019151:Peptide Library; C055966:immunoglobulin Fv