Synthetic peptide specificity of anti-myelin basic protein from multiple sclerosis cerebrospinal fluid

Human myelin basic protein (h-MBP) purified from central nervous system (CNS) myelin has a molecular mass of 18.5 kDa and 170 residues. Eighteen synthetic peptides ranging from 8 to 25 residues and covering the length of h-MBP were prepared by the Fmoc method. Antibodies to h-MBP (anti-MBP) were isolated and purified from cerebrospinal fluid (CSF) of patients with multiple sclerosis (MS) by two-step affinity chromatography. Purified anti-MBP was reacted with increasing amounts of h-MBP as well as each of the 18 synthetic peptides in an initial liquid phase assay, and then titers of free anti-MBP in the resulting mixtures were determined by a solid phase radioimmunoassay. Purified anti-MBP was neutralized by h-MBP and 6 of the 18 synthetic peptides used in this study. The antibody was completely neutralized by peptides No. 12 (residues: 80-97), No. 15 (residues: 91-106) and No. 56 (residues: 75-95) and was partially neutralized by peptides No. 27 (residues: 61-75), No. 16 (residues: 64-78) and No. 21 (residues: 69-83). The 12 remaining synthetic peptides covering both the amino (residues 1-63) and carboxyl (residues 117-162) terminals of h-MBP did not neutralize purified anti-MBP. These results suggest that anti-MBP purified from CSF of patients with MS have affinity for discontinuous epitopes located between residues 61 and 106 on the h-MBP molecule. Alternatively anti-MBP may be polyspecific recognizing different amino acid sequences.