Allergic Encephalomyelitis

Tocopherol-mediated modulation of age-related changes in microglial cells: turnover of extracellular oxidized protein material

Proteins accumulate during aging and form insoluble protein aggregates. Microglia are responsible for their removal from the brain. During aging, changes within the microglia might play a crucial role in the malfunctioning of these cells. Therefore, we isolated primary microglial cells from adult rats and compared their activation status and their ability to degrade proteins to that of microglial cells isolated from newborn animals. The ability of adult microglial cells to degrade proteins is substantially decreased. However, the preincubation of microglial cells with vitamin E improves significantly the degradation of such modified proteins. The degradation of proteins from apoptotic vesicles is decreased in microglia isolated from adult rats. This might be the result of a suppression of the CD36 receptor due to vitamin E treatment. We concluded that microglial cells isolated from adult organisms have different metabolic properties and seem to be a more valuable model to study age-related diseases.

Molecular mimicry revisited: gut bacteria and multiple sclerosis

Molecular mimicry is a possible explanation for autoimmune side effects of microorganism infections. Protein sequences from a particular microorganism are compared to known autoimmune immunogens. For diseases such as multiple sclerosis (MS), where the infectious agent is unknown, guesses to its identity are made. Mimics are assumed to be rare. This study takes a radically different approach. Reported sequences from all known human bacterial and viral agents were searched for autoimmune immunogen mimics. Three encephalitogenic peptides, whose autoimmune requirements have been studied extensively, were selected for comparison. Mimics were seen in a wide variety of organisms. For each immunogen, the mimics were found predominantly in nonpathogenic gut bacteria. Since the three immunogens used in this study are related to MS, it is suggested that a microorganism responsible for autoimmune activity in MS could be a normally occurring gut bacterium. This would explain many of the peculiar MS epidemiological data and why no infective agent has been identified for MS and supports recently found MS gut metabolism abnormalities.

Antigen-specific therapies in multiple sclerosis: going beyond proteins and peptides

Multiple sclerosis (MS) is a complex immune-mediated disease resulting largely from an autoimmune attack against components of central nervous system myelin, including several proteins and lipids. Knowledge about the details of this anomalous immune response has come mostly from studies in the animal model experimental autoimmune encephalomyelitis (EAE). In this model, it has been possible to prevent and effectively treat established disease through several antigen-specific therapeutic strategies, which have included administration of whole myelin or myelin proteins by various routes, random copolymers consisting of the main major histocompatability complex (MHC) and T-cell receptor (TCR) contact amino acid residues, altered peptide ligands of dominant myelin epitopes in which one or more residues are selectively substituted, and lately DNA vaccination encoding self-myelin antigens. However, there have been difficulties in making successful transitions from animal models to human clinical trials, due either to lack of efficacy or unforeseen complications. Despite these problems, antigen-specific therapies have retained their attraction for clinicians and scientists alike, and hopefully the upcoming generation of agents--including altered peptide ligands and DNA vaccines--will benefit from the increasing knowledge about this disease and surmount existing difficulties to make an impact in the treatment of multiple sclerosis.

Degradation of oxidized extracellular proteins by microglia

In living organisms a permanent oxidation of protein oxidation occurs. The degradation of intracellular oxidized proteins is intensively studied, but knowledge about the fate of oxidatively modified extracellular proteins is still limited. We studied the fate of exogenously added oxidized proteins in microglial cells. Both primary microglial cells and RAW cells are able to remove added oxidized laminin and myelin basic protein from the extracellular environment. Moderately oxidized proteins are degraded most efficiently, whereas strongly oxidized proteins are taken up by the microglial cells without an efficient degradation. Activation of microglial cells enhances the selective recognition and degradation of moderately oxidized protein substrates by proteases. Inhibitor studies also revealed an involvement of the lysosomal and the proteasomal system in the degradation of extracellular proteins. These studies let us conclude that microglial cells are able to remove oxidized proteins from the extracellular environment in the brain.

Differential recognition of sequences within the encephalitogenic region of myelin basic protein capable of eliciting cell-mediated immune responses in experimental autoimmune encephalomyelitis

The fine specificity of myelin basic protein (MBP) epitopes capable of eliciting in vivo delayed-type hypersensitivity responses in Lewis rats with experimental autoimmune encephalomyelitis (EAE) was compared to those eliciting in vitro antigen-specific T cell proliferation and augmentation of disease transfer. Utilizing a panel of synthetic peptides with sequences representing the 68-86 region of guinea pig (GP-) or bovine myelin basic protein (B-MBP), animals were primed with one species of peptide and subsequently challenged with either the same peptide or peptides with truncations or substitutions representative of the other species of MBP. In regard to minimal length sequences capable of eliciting delayed-type hypersensitivity (DTH), rats primed with GP-MBP and complete Freund's adjuvant (CFA) exhibited a hierarchical pattern of responsiveness to challenge with a series of truncated peptides, ranking as follows: GP-68-86 > GP-72-86 > GP-68-84 > > GP-75-86 = no activity. This response pattern corresponds to that previously reported for T cell proliferation and activation for disease transfer. Furthermore, a comparison of these T cell-mediated immune parameters, as elicited by the substituted peptides, revealed the response patterns of DTH reactivity to be similar to that previously described for in vitro T cell proliferation with significant DTH responses generated only by the peptide species for which the animal was primed. In contrast, a cross-reactive pattern of recognition was observed in cells mediating disease transfer, with all four 68-86 sequences capable of augmenting activation for adoptive transfer of disease, regardless of the peptide species for which the animal was primed.(ABSTRACT TRUNCATED AT 250 WORDS)

Myelin proteolipid protein: minimum sequence requirements for active induction of autoimmune encephalomyelitis in SWR/J and SJL/J mice

Proteolipid protein (PLP) is the major protein constituent of mammalian central nervous system myelin. We have previously identified two different PLP encephalitogenic T cell epitopes in two mouse strains. Murine PLP peptides 103-116 YKTTICGKGLSATV and 139-151 HCLGKWLGHPDKF are encephalitogenic determinants in SWR/J (H-2q) and SJL/J (H-2s) mice, respectively. The purpose of the present study was to determine the minimum sequence requirements for each of these PLP encephalitogens. In SWR/J mice, at least two distinct overlapping peptides can induce experimental autoimmune encephalomyelitis (EAE). The eleven residue sequences PLP 105-115 TTICGKGLSAT and PLP 106-116 TICGKGLSATV are encephalitogenic in SWR/J mice, but PLP 106-115 TICGKGLSAT, the decapeptide indigenous to both sequences, is non-encephalitogenic. In contrast, the shortest PLP sequence capable of inducing EAE in SJL/J mice is the nonapeptide 141-149 LGKWLGHPD. These data indicate that encephalitogenic determinants of PLP are short contiguous peptide sequences similar in length and diversity to those of MBP.

Antigen-specific inhibition of the adoptive transfer of experimental autoimmune enceophalomyelitis in Lewis rats

The efficacy of antigen-specific immunoregulation as a treatment for the efferent limb of an autoimmune disease was tested in a rat model of adoptive experimental autoimmune encephalomyelitis (EAE). Lewis rats receiving 4-5 x 10(7) guinea pig (GP) myelin basic protein (MBP)-activated lymph node T cell blasts from GPMBP/CFA sensitized donors routinely show clinical signs of disease 5-6 days post transfer. Intravenous injection of GPMBP coupled to syngeneic splenocytes using the chemical cross-linker carbodiimide was effective in completely abrogating the expression of clinical EAE in rats that received MBP-specific T cells 2 days previously. Partial inhibition was also observed in rats injected as early as day 0 (the same day as MBP-specific T cell transfer) and as late as 1 day prior to the onset of clinical signs (days 4-5 post transfer). Unresponsiveness was shown to be dose-dependent, dependent on the route of injection of the neuroantigen-coupled splenocytes, and was antigen-specific. Splenocytes coupled with GP or rat MBP (which are identical within the major encephalitogenic GP68-86 Lewis rat determinant with the exception of the residue at position 80) were equally efficient at eliminating disease expression in recipients of GPMBP-specific T cells. In contrast, splenocytes coupled with bovine or rabbit MBP (which differ significantly from GPMBP within the 68-86 region) had no inhibitory effect. The antigen specificity of the tolerance induction was also illustrated by the fact that splenocytes coupled with GP68-86, but not those coupled with the truncated GP68-84 peptide, induced profound unresponsiveness. Interestingly, de novo antigen processing by the antigen-coupled cells did not appear to be necessary as the inclusion of antigen processing inhibitors had no effect on inhibition of disease. However, the use of the carbodiimide coupling reagent was critical for the induction of unresponsiveness as essentially equivalent amounts of 125I-labelled MBP were bound in its presence or absence, but only splenocytes incubated in the presence of both MBP and carbodiimide inhibited clinical expression of disease. Antigen-specific tolerance is thus an effective means of inhibiting expression of clinical disease in the rat EAE model, and a powerful tool for determining the fine epitope specificity of encephalitogenic T cells.

Soluble galactoside-binding vertebrate lectins: a protein family with common properties

1. Soluble galactoside-binding lectins could play a key role in vertebrates by specifical binding to complementary glycoconjugates. 2. Their expression and localization are developmentally regulated. 3. They constitute a large family of structurally related proteins which contain a series of conserved aminoacids. 4. Their functional role could vary from an organ to another, and the same lectin may probably mediate several biological activities.

Experimental allergic encephalomyelitis in rabbits. A major encephalitogenic determinant within residues 1-44 of myelin basic protein

Experimental allergic encephalomyelitis could be induced in rabbits by injection in Freund's complete adjuvant of either peptide 1-44 or peptide 45-87 of rabbit myelin basic protein. In order to localize the encephalitogenic determinant present in peptide 1-44, several smaller derivative peptides were prepared and examined. Peptic peptide 15-44 and thrombic peptide 1-31 were as active as peptide 1-44, whereas peptic peptides 1-14 and 18-38 and BrCN peptide 22-44 were virtually inactive. Weak activity was shown by BrCN peptide 1-21. These results provide evidence that a major encephalitogenic determinant present in peptide 1-44 lies within sequence 15-31. The encephalitogenic activity of peptide 15-44 was essentially destroyed by oxidation of methionine-21 to methionine sulfoxide; methylation of Met-21, on the other hand, appeared to be relatively ineffective in eliminating the encephalitogenicity of peptide 1-44.

Simple and rapid identification of phosphorylated peptides from bovine brain myelin basic protein by reversed-phase high-performance liquid chromatography

The phosphorylation sites of the myelin basic protein from bovine brain were determined after phosphorylation with a cyclic 3':5'-phosphate-dependent protein kinase from the same source. Three phosphorylated peptides were selectively and rapidly separated, before and after dephosphorylation, by reversed-phase high-performance liquid chromatography on a styrene 250 column under alkaline conditions. Partial sequencing of the peptides by automated Edman degradation revealed that the serine-115 residue located in the main encephalitogenic determinant of the protein was a phosphorylation site, in addition to the two phosphorylation sites established (threonine-34 and serine-55).

Computed tomography in experimental allergic encephalomyelitis--preliminary results

Four dogs were immunized with a mixture of spinal cord homogenate and complete Freund's adjuvant. One of these dogs developed hyperacute allergic encephalomyelitis. Cranial computed tomography in this animal demonstrated a low absorption area in the internal capsule that corresponded to the pathologic lesion. Computed tomography scanning may be a useful tool in monitoring experimental allergic encephalomyelitis.

Cleavage of rabbit myelin basic protein by pepsin

Rapid cleavage of bovine and guinea pig myelin basic proteins by pepsin at pH 6.0 is limited to the Phe-Phe bond in the middle of the molecule. In the rabbit protein, however, rapid cleavages occur elsewhere in addition to the Phe87-Phe88 bond in regions in which there are amino acid substitutions. Rapid cleavage occurs at the Leu151-Phe152 bond, at which Ile-151 has been replaced by Leu, the residue that actually contributes the scissile bond. Rapid cleavages occur at the Phe44-Phe45 and Leu109-Ser110 bonds, which in the bovine and guinea pig proteins are relatively resistant under the experimental conditions (pH 6.0). The increased susceptibility of these bonds in the rabbit protein appears to be related to the replacement of Gly-46 by Ser and the change in the sequence immediately NH2-terminal to Leu-109, from Leu-Ser to Thr-Val. These cleavages of the rabbit protein at the four very susceptible bonds have permitted us to isolate peptides (1-44), (45-87), (88-109), (110-151), and (152-168) in high yield. We have also isolated peptides (88-151), (1-14), and (15-44) in low yield; the latter two result from limited cleavage at the relatively resistant Tyr14-Leu15 bond. Peptide (88-109) has been chromatographically resolved into species differing in the degree of methylation of Arg-105; this resolution is thought to result from differences in hydrogen bonding ability of the guanidinium groups.

High dose inhibition of the tryptophan peptide induced encephalitogenicity

In a previous publication (Immunol. Comm. 3:219, 1974) a hypothesis was proposed that the high dose inhibition of encephalitogenicity in giunea pigs seen with the tryptophan peptide, phe ser trp gly ala glu gly gln arg, and not observed with the whole myelin basic protein which contains this sequence, was the result of competitive inhibition by non-encephalitogenic fragments of the tryptophan peptide produced in vivo possibly by exopeptidases. I present data which disagrees with this hypothesis.

Multiple sclerosis: sensitization of a myelin basic protein fragment (peptide T) encephalitogenic to primates. A preliminary report

Myelin basic A1 protein is the sole antigen of the central nervous system capable of inducing experimental allergic encephalitis (EAE), but sensitization with peptide fragments of the molecule may also induce disease. Using the macrophage migration inhibition factor (MIF) assay we have compared sensitization to portions of the molecule active in inducing EAE in monkeys with results obtained concomitantly using the intact protein. Cellular sensitization to human myelin A1 protein, peptide L (residues 1-116), peptide T (residues 117-170), and petide Y (residues 154-170) was studied using the Thor-Rocklin MIF assay system. Lymphocytes of 10 normal subjects, 10 multiple sclerosis patients 0-3 weeks after onset, 10 4 weeks to 3 months after and 10 6 months or longer after onset of an acute exacerbation were assayed. Results of the investigation reveal evidence of cellular sensitization to myelin basic protein encephalitogenic peptide T occurring during attacks of multiple sclerosis. Peptide L, relatively nonencephalitogenic to primates, failed to induce a significant lymphocyte response, whereas peptide Y which is encephalitogenic gave irregular results.

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.

Hyperacute allergic encephalomyelitis: a single determinant

HEAE cannot be induced in either guinea pigs using 10(10) or 20x10(10) organisms of B. pertussis or in rabbits using 4x10(10) organisms of B. pertussis and basic protein from the following species: guinea pig, Lewis rat, human, bovine, porcine, monkey and rabbit. The only encephalitogenic region for Lewis rats which also produces HEAE in Lewis rats is not encephalitogenic in either rabbits or guinea pigs. Therefore it seems highly probably that there is only one HEAE determinant for all species which are able to express HEAE.

Purification and partial characterization of two basic proteins from human peripheral nerve

Two basic proteins, denoted P1 and P2 protein, were purified from human sciatic nerve. The isolation was achieved by the following steps: delipidation with chloroform/methanol mixtures, dry acetone and dry ether; acid extraction at pH 2; ion exchange chromatography on QAE-Sephadex A-25 and gel filtration on Sephadex G-100. P1, P2 proteins and the basic protein of the central nervous system have been shown to have different electrophoretic mobility, and each of the two peripheral basic proteins was shown to be homogeneous by disc electrophoresis. The molecular weight of P1 protein is around 14 100 and that of P2 protein is around 12 200, as determined by ultracentrifugal analysis. There was some difference in the amino acid composition of human P1 and P2 protein, and a marked difference between their composition and the composition of central basic protein and bovine peripheral P1 and P2 proteins which were described previously. When injected to animals, P1 protein induced only experimental allergic neuritis while P2 protein induced both mild experimental allergic neuritis and experimental allergic encephalomyelitis. Thus, the human P1 protein is similar to the bovine P1 protein and human P2 protein is similar to bovine P2 protein, concerning their electrophoretic mobilities, molecular weights and biological properties.

Induction of allergic encephalomyelitis using hydrosoluble adjuvant and the tryptophan region of myelin basic protein

Experimental allergic encephalomyelitis has been induced in guinea pigs using the encephalitogenic tryptophan peptide as antigen and a hydrosoluble adjuvant extracted from Mycobacterium tuberculosis, var. hominis, strain H37Ra. The maximum response was observed using 100mug of adjuvant per animal. This is a quantity of adjuvant substantially higher than was necessary to induce disease utilizing the whole myelin basic protein as antigen.