Characterization and comparison of the polyclonal immune response to purified PLP and DM-20 in the Lewis rat: determination of a new antigenic determinant.

Lewis rat polyclonal antibodies raised against pure PLP and DM-20 were characterized by indirect and competitive ELISA assays. Anti-PLP antibodies showed a good cross-reactivity with DM-20 and vice versa, suggesting that the chief B-cell epitopes are the same on both proteolipids. Three antigenic determinants, PLP 57-70, PLP 200-218 and the carboxyl-terminal sequence PLP 262-276, were identified for both proteolipids. Peptide PLP 57-70 represents a new B-cell epitope. The major hydrophilic loop (PLP 116-150), deleted in DM-20, did not show any antigenic activity. The study of polyclonal immune response to PLP and DM-20 will be helpful in resolving their potential role in the development and course of experimental allergic encephalomyelitis (EAE) and multiple sclerosis (MS).