Magnetic resonance imaging of PLP-induced experimental allergic encephalomyelitis in Lewis rats

An in vivo magnetic resonance (MR) imaging study was performed on experimen tal allergic encephalomyelitis (EAE) induced in Lewis rats through proteoli pid protein (PLP). PLP was solubilized in water or in an aqueous solution o f 1% 10-tridecyl ether (TDE), a non-ionic detergent used in membrane protei n research. All 16 rats immunized with 500 mu g of TDE-solubilized PLP deve loped clinical signs and MR abnormalities fully comparable to those observe d in MBP-induced EAE. Total paraplegia was observed in 12.5% of rats, mild or moderate paraparesis in 68.8% of rats and tail paralysis in the remainin g 18.7% of rats. Whereas only 37.5% of the eight rats immunized with 500 mu g of water-solubilized PLP developed minor clinical signs (tail weakness o r paralysis). Our observations confirm that the difficulties encountered wh en trying to induce EAE by means of PLP arise from the highly hydrophobic n ature of this protein. Accordingly, if a reproducible model is to be develo ped, it seems more judicious to use non-ionic detergents in both the extrac tion and solubilization phases of PLP preparation, this would allow maximal solubilization of the protein while avoiding aggregates, which may otherwi se form during either of the PLP preparation. (C) 1998 Elsevier Science B.V . All rights reserved.