INHIBITION OF EXPERIMENTAL AUTOIMMUNE ENCEPHALOMYELITIS IN LEWIS RATSBY NASAL ADMINISTRATION OF ENCEPHALITOGENIC MBP PEPTIDES - SYNERGISTIC EFFECTS OF MBP-68-86 AND MBP-87-99

induction of mucosal tolerance by inhalation of soluble peptides with defined T cell epitopes is receiving much attention as a means of spec ifically down-regulating pathogenic T cell reactivities in autoimmune and allergic disorders. Experimental autoimmune encephalomyelitis (EAE ) induced in the Lewis rat by immunization with myelin basic protein ( MBP) and Freund's adjuvant (CFA) is mediated by CD4(+) T cells specifi c for the MBP amino acid sequences 68-86 and 87-99. To further define the principles of nasal tolerance induction, we generated three differ ent MBP peptides (MBP 68-86, 87-99 and the non-encephalitogenic peptid e 110-128), and evaluated whether their nasal administration on day -1 1, -10, -9, -8 and -7 prior to immunization with guinea pig MBP (gp-MB P) + CFA confers protection to Lewis rat EAE. Protection was achieved with the encephalitogenic peptides MBP 68-86 and 87-99, MBP 68-86 bein g more potent, but not with MBP 110-128. Neither MBP 68-86 nor 87-99 a t doses used conferred complete protection to gp-MBP-induced EAE. In c ontrast, nasal administration of a mixture of MBP 68-86 and 87-99 comp letely blocked gp-MBP-induced EAE even at lower dosage compared to tha t being used for individual peptides. Rats tolerized with MBP 68-86 87-99 nasally showed decreased T cell responses to MBP reflected by ly mphocyte proliferation and IFN-gamma ELISPOT assays. Rats tolerized wi th MBP 68-86 + 87-99 also had abrogated MBP-reactive IFN-gamma and tum or necrosis factor-alpha mRNA expression in lymph node cells compared to rats receiving MBP 110-128 nasally, while similar low levels of MBP -reactive transforming growth factor-beta and IL-4 mRNA expressing cel ls were observed in the two groups. Nasal administration of Map 68-86 + 87-99 only slightly inhibited guinea pig spinal cord homogenate-indu ced EAE, and passive transfer of spleen mononuclear cells from MBP 68- 86 + 87-99-tolerized rats did not protect naive rats from EAE. Finally , we show that nasal administration of MBP 68-86 + 87-99 can reverse o ngoing EAE induced with gp-MBP although higher doses are required comp ared to the dosage needed for prevention. In conclusion, nasal adminis tration of encephalitogenic Map peptides can induce antigen-specific T cell tolerance and confer incomplete protection to gp-MBP-induced EAE , and MBP 68-86 and 87-99 have synergistic effects. Nonregulatory mech anisms are proposed to be responsible for tolerance development after nasal peptide administration.