Lipid-free versus lipid-bound P2 protein-induced experimental allergic neuritis: Clinicopathological, neurophysiological, and immunological study

The P2 protein of the peripheral nervous system myelin is a neuritogenic pr otein capable of inducing experimental allergic neuritis (EAN) in the Lewis rat. It has been suggested that the addition of some lipids to the protein isolated in the lipid-free form might enhance its immunogenicity. In this study, we compared lipid-free P2 (the EAN factor) and the corresponding lip id-bound form of the protein regarding their ability to induce EAN. Lipid-b ound P2, copurified with all the myelin lipids, shows a conformation differ ent from that of LF-P2. The timing of disease and the clinical scores of li pid-bound P2-induced EAN animals (n = 23) did not differ statistically from those injected with lipid-free P2 (n = 23), with only a tendency to higher clinical severity in the former group. Tail nerve conduction velocities di d not differ in the two groups and in both were significantly lower in comp arison to Freund adjuvant controls (n = 8), Inflammation and demyelination predominated in the spinal roots and were less evident in the sciatic nerve for both groups of animals. The ELISA determination of antibodies to lipid -free and lipid-bound P2 revealed the development of antibodies recognizing the lipid-free form of the protein in both groups of animals. Our results stand in contrast to results of previous studies performed after addition o f exogenous lipids to the P2 purified in the lipid-free form and indicate t hat lipid-bound P2 is not significantly more immunogenic than lipid-deplete d P2. J, Neurosci, Res. 62:709-716, 2000. (C) 2000 Wiley-Liss, Inc.