Species specificity in response to tryptophan modified encephalitogen

Sequence determinants of modified cobra venom neurotoxin which induce immune resistance to experimental allergic encephalomyelitis: molecular mechanisms for immunologic action

A nontoxic, iodoacetamide-modified cobratoxin derivative (CAM-NTX) induced resistance to experimental allergic encephalomyelitis (EAE) in guinea pigs. Resistance was retained after trypsin digestion and shown to reside in N-terminal and central peptides of CAM-NTX. A similarly modified protein cardiotoxin (CAM-CTX), representative of proteins homologous with cobratoxin, was not immunosuppressive. Depressed clinical symptoms in EAE-resistant animals correlated with reduced lymphocytic infiltration of the brain. Antibody to myelin basic protein (MBP) was reduced in immunosuppressed animals. The immunoinhibitory determinants in CAM-NTX may mimic immune response suppressor proteins (SIRS-alpha 7) and the EAE-resistance region of MBP.

Inhibition of experimental allergic encephalomyelitis by carrier administered prior to challenge with encephalitogenic peptide-carrier conjugate

Guinea pigs can be rendered unresponsive to experimental allergic encephalomyelitis (EAE) challenge by prior injections of myelin basic protein (BP) or peptides derived from BP. The synthesized tryptophan-containing peptide (TrpP, corresponding to residues 114-122) which is the primary encephalitogenic sequence in BP (for guinea pigs) had been conjugated to the non-central nervous system protein bovine serum albumin (BSA) and used for EAE challenge. It has been shown in this study that prechallenge treatment with the BSA carrier alone can significantly inhibit the induction of EAE by TrpP-BSA conjugate. That carrier treatment is immunologically specific was determined when prior treatment with cytochrome c did not protect animals from EAE challenge with TrpP conjugated to BSA. In addition, in disease induced with BP or TrpP, and while TrpP did protect guinea pigs challenged with TrpP, it did not protect those challenged with BP. This last finding raises the possibility of a second encephalitogenic sequence in BP or an important role for the carrier in the TrpP conjugate.

Myelin lipophilin-induced demyelinating disease of the central nervous system

Purified lipophilin, a hydrophobic lipoprotein of myelin, induces a cell-mediated demyelinating disease of the central nervous system similar to experimental allergic encephalomyelitis (EAE) induced by the myelin basic protein (MBP). Guinea pigs challenged with lipophilin (emulsified with CFA) developed clinical and histological signs of disease indistinguishable from those developed by animals similarly challenged with MBP. Both lipophilin and MBP induced and elicited delayed-type hypersensitivity in animals challenged with respective antigens. Tryptophan, an essential component of the MBP-determinant for disease in guinea pigs, is required for the encephalitogenicity of lipophilin.

Failure of myelin basic protein to prevent or suppress experimental allergic encephalomyelitis in guinea pigs

The encephalitogenic myelin basic protein (BP) was reported to be effective in preventing and suppressing the development of experimental allergic encephalomyelitis (EAE) when animals were treated before or after encephalitogenic challenge, respectively. In this report we show that pretreatment with 15 daily doses of 2.5 or 0.15 mg homologous BP (in IFA) failed to protect guinea pigs from subsequent challenge with encephalitogenic emulsion. Similarly, 15 daily injections of 1.0, 2.5, 5.0, or 10.0 mg guinea pig BP (in IFA) did not suppress development of or arrest ongoing EAE when the treatment was initiated on days 1, 4, 8, or 11 after an encephalitogenic challenge. The results show that over 50% of the treated animals developed hind leg paralysis (HLP), incontinence, or both, and the incidence of HLP was not altered significantly by a 10-fold increase in the amount of BP used for daily treatment. Further, all the treated and challenged animals developed histological lesions characteristic of disease. Treatment with BP delayed disease onset, prolonged the period of paralysis leading to recovery from HLP, and reduced both the prevelence of histological lesions as well as the incidence of death. It may be concluded that under these experimental conditions the administration of BP failed to protect from or suppress development of EAE.

Peptides and autoimmune disease

The use of derived and synthetic peptides has contributed greatly to our understanding of encephalitogenic determinants in the basic protein molecule. Peptides derived from BP by use of trypsin, pepsin, cathepsin D (brain and liver) and BNPS-skatole have proven most useful. Synthetic peptides have served to define the disease-inducing determinants with precision. A remarkable feature of these studies is that different antigenic determinants serve as encephalitogenic sites in different species. The encephalitogenic sites comprise short peptide domains of the BP polypeptide chain, only 8 residues (rat), 9 residues (guinea pig), and 10 residues (rabbit) in length. In view of the requirement for both haptenic and carrier specificity of an immunogenic molecule, it is impressive that these peptides themselves elicit the autoimmune disease, EAE. While less active than BP on a molar basis, they are nonetheless potent encephalitogens, producing clinical signs in rats and guinea pigs at less than 1 microgram dose. The data indicate that for most animal species (guinea pig, rat, monkey) there appears to be only one major encephalitogenic determinant, an unusual finding in view of the number of antigenic determinants for cell-mediated immunity existing in the BP molecule. Possibly a combination of genetic and anatomical factors may account for this phenomenon. A relationship may exist between multiple sclerosis and EAE as shown by peptide studies; lymphocytes are found in MS patients during exacerbation sensitized to the same region of BP active in the monkey. The major encephalitogenic sites are: Guinea Pig (9) Phe-Ser-Trp-Gly-Ala-Glu-Gly-Gln-Lys(Arg); Rabbit (10) Thr-Thr-His-Tyr-Gly-Ser-Leu-Pro-Gln-Lys; Rat (8) Ser-Gln-Arg-Ser-Gln-Asp-Glu-Asn; Monkey (14) Phe-Lys-Leu-Gly-Gly-Arg-Asp-Ser-Arg-Ser-Gly-Ser-Pro-Hser.

Molecular bases for the difference in the potency of myelin basic protein from different species in Lewis rats

The results of this study define the chemical bases for the difference in the encephalitogenic potency reported for the bovine and guinea pig myelin basic proteins. Studies with synthetic peptides showed that the sequence of peptide S53, H-Ser-Gln-Arg-Ser-Gln-Asp-Glu-Asn-OH, which is native to the guinea pig basic protein, is the minimum amino acid sequence necessary for inducing EAE in Lewis rats. The results of this study further showed that specific sequence modifications rendered the native bovine sequence highly encephalitogenic.

Autoimmune disease antigens

The first step towards understanding the cellular interaction which results in autoimmune disease is to determine what triggers the recognition between a specific autoimmune antigen determinant and the cellular receptor. In this review, we have focused on the antigen inducing experimental allergic encephalitis (EAE) because the antigen has been characterized and a relatively large body of information on its biological activities has been accumulated. Clearly, a specific allergic encephalitis-producing determinant is present and is represented on a relatively small portion of the molecule. The determinant induces a wide variety of biological reactivities, some of which are classed as cellular mediated. An attempt is made to dissect activities such as blast transformation (BT), migration inhibitory factor (MIF), in vivo delayed type hypersensitivity reaction (DTH) and EAE and to relate them to the structural requirements which the determinants possess. The complexities which arise indicate that subpopulations of cells with different receptor activities may respond selectively and that recognition of the receptor is produced by an EAE determinant consisting of three amino acids in a specific linear sequence. Furthermore, under experimental circumstances the EAE activity can be dissociated from the other activities (BT, MIF, DTH), indicating that while these tests are used generally to follow various human autoimmune disease activities, they may represent the reaction of a broad spectrum of cells.