The position of the LysN(epsilon)H(2)-grafted antigens along the sequential oligopeptide carrier, Ac-(Aib-Lys-Aib-Gly)(n) (SOCn-II), influences the antibody recognition: Application to the Sm main autoimmune epitope

A sequential oligopeptide carrier of antigenic peptides is presented, incor porating two Aib residues in each repetitive moiety: Ac-(Aib-Lys-Aib-Gly)(n ), (SOCn-II; n = 2-4). The conformational study, by H-1-nmr, CD, and Fourie r transform ir spectroscopy; indicated that the SOCn-II carrier displays a pronounced 3(10)-helix, compared to the Ac-(Lys-Aib-Gly)(n) (SOCn-I) carrie r of the same approximately backbone length, previously reported One of the dominant autoimmune epitopes of the Sm and U1RNP cellular components, the PPGMRPP sequence, was coupled to the Lys-(NH2)-H-epsilon groups of the SOCn -II carrier and used as antigenic substrate for detecting anti-Sm/ U1RNP au toantibodies in ELISA assays. Anti-Sm antibodies are highly specific for sy stemic lupus erythematosus, while anti-U1RNP are specific for mixed connect ive tissue disease. The anti-(PPGMRPP)(5)-SOCn-II ELISA was compared with t he anti-(PPGMRPP)(n)-SOCn-I ELISA, provided that both antigenic substrates possess the same amount of the epitope replicates. The significance of the lysine positions along the oligopeptide backbone of the carrier for a favor able antibody recognition of the anchored antigens is also examined. (C) 20 00 John Wiley & Sons, Inc. Biopoly 54: 1-10, 2000.