SYNTHETIC MIMOTOPES OF b2-GPI-SPECIFIC ANTI-CARDIOLIPIN ANTIBODIES.

Stephen M. Coutts, Paul A. Barstad, David S. Jones, David M. Marquis and Edward J. Victoria.

La Jolla Pharmaceutical Company, San Diego, CA 92121 USA

As a first step to define a drug to tolerize B cells specific for b2-GPI-dependent a-cardiolipin antibodies (ACA) affinity-purified ACA (adsorbed to cardiolipin-containing liposomes; aff-ACA) were probed with phage-displayed peptide libraries. Selection methods of increasing stringency were applied to yield immuno-specific sequences which translated into ELISA [+] synthetic peptides. Aff-ACA were screened with mixed libraries having a multiplicity of 109 sequences, containing 6 to 15 residue inserts, and flanked by either P or PC, or by just P on the C-terminus. A PC-flanked, 7 amino acid consensus motif was obtained for ACA#6501, peptide 5A12. This peptide, tethered to a bead via a PEG linker, gave a positive ELISA signal with 13 of 19 ACA sera. A Sepharose 4B-bound branched, tetravalent form of 5A12 removed over 80% of ACA#6501 activity, which could be recovered by pH elution. SAR studies showed that the N-terminal PC and C-terminal C residues were essential; substitution of a-Me-P for P in the center of the peptide increased its affinity. NMR measurements show that 5A12 has ordered structure. Conclusions: Phage epitope libraries can define mimotopes for ACA from patients with APS.

Presented at the
Australasian Society of Clinical Immunology and Allergy and Immunology Society Meeting
Oct. 30-Nov. 3, 1995
Sydney, Australia.