Immunochemical characterization of antibodies to the myelin proteolipid protein (PLP)

The immunochemical specificity of antibodies raised against the bovine myelin proteolipid protein (PLP) and a series of PLP synthetic peptides was examined by enzyme-linked immunosorbent assay (ELISA) and immunoblot analyses. Polyclonal rabbit anti-bovine PLP antibodies were cross-reactive with PLP isolated from rat, monkey, and human CNS white matter, as well as with PLP incorporated into rat myelin vesicles. Immunochemical analyses of 11 anti-peptide antisera revealed a more restrictive cross-reactivity pattern with only five of the 11 antisera, against peptides encompassing residues 48-59, 97-105, 183-193, 192-200 and 264-276, cross-reacting with bovine PLP by ELISA. Immunoblot analyses with the anti-peptide antisera demonstrated a similar recognition with four of the 11 antisera against peptides 48-59, 97-105, 192-200 and 264-276 recognizing the myelin PLP. These data suggest that, despite its strong phylogenetic conservation, multiple antigenic sites exist within the PLP molecule, and some of these determinants can be mimicked by synthetic peptides. However, the restrictive cross-reactivities of the anti-peptide antisera suggest that humoral recognition of the myelin PLP is conformationally dependent. The availability of anti-peptide antibodies of predetermined specificity, capable of recognizing the intact protein, should permit detailed examination of PLP topography in various experimental systems.