Computer-predicted peptides that mimic discontinuous epitopes on the A2 domain of factor VIII.

Summary. Development of antibodies (Abs) againstfactor VIII (FVIII) is a severe complication ofhaemophilia A treatment. Recent publications suggestthat domain specificity of anti-FVIII antibodies,particularly during immune tolerance induction (ITI),might be related to the outcome of the treatment.Obtaining suitable tools for a fine mapping ofdiscontinuous epitopes could thus be helpful. Theaim of this study was to map discontinuous epitopeson FVIII A2 domain using a new epitope predictionfunctionality of the PEPOP bioinformatics tool and apeptide inhibition assay based on the Luminextechnology. We predicted, selected and synthesized40 peptides mimicking discontinuous epitopes on theA2 domain of FVIII. A new inhibition assays usingLuminex technology was performed to identifypeptides able to inhibit the binding of anti-A2Abs to A2 domain. We identified two peptides(IFKKLYHVWTKEVG and LYSRRLPKGVKHFD)able to block the binding of anti-A2 allo-antibodiesto this domain. The three-dimensional representationof these two peptides on the A2 domain revealedthat they are localized on a limited region of A2. Wealso confirmed that residues 484–508 of the A2domain define an antigenic site. We suggest thatdissection of the antibody response during ITI usingsynthetic peptide epitopes could provide importantinformation for the management of patients withinhibitors.Keywords: A2 domain, bioinformatic, discontinuousepitope, FVIII, haemophilia, inhibitors