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D C Wraith

Publications and source records attributed to D C Wraith.

At least 55 records · Page 3Linked to original sources
PubMed1993

Immunotherapy of autoimmune disease.

T-cell recognition of autoantigens stands as the primary target for immune intervention in autoimmune disease. Experiments in animal models, in combination with a number of clinical trials completed in the last year, have helped to clarify the pathogenesis of various autoimmune diseases and indicate future strategies for immunotherapy.

Animals↗
PubMed1993

An autoantigenic T cell epitope forms unstable complexes with class II MHC: a novel route for escape from tolerance induction.

The peptide rAc1-11 represents the dominant T cell epitope of rat myelin basic protein (MBP) in mice of the H-2u haplotype. Residue 4 has been shown previously to govern binding of the peptide to the class II molecule, I-Au. We have constructed peptide analogues bearing amino acid substitutions at position 4 and have assessed their ability to stimulate an antigen-specific T cell hybridoma when presented by viable antigen presenting cells (APC). Complexes between I-Au and one such analogue, rAc1-11[4A], were rapidly lost from the surface of live APC displaying a half-life (t 1/2) of approximately 10 min. Neither shedding of intact complexes from the cell surface, nor their internalization and recycling through an acidic intracellular compartment were found to account for their loss. The possible dissociation of rAc1-11[4A] from the peptide binding cleft was therefore addressed by comparing the t 1/2 of complexes between I-Au and peptide analogues of higher affinity. The tyrosine-substituted analogue, rAc1-11[4Y], remained stably bound to I-Au for at least 4 h, thereby displaying a t 1/2 far in excess of that evident for rAc1-11[4A]. Significantly, the wild type peptide, rAc1-11, bound so transiently that functional complexes could not be detected on the surface of peptide-pulsed APC. The physiological relevance of these findings was confirmed by extending our studies to an analysis of the homologous epitope of murine MBP; evidence that this epitope likewise displays minimal affinity for I-Au suggests a novel strategy for the escape from tolerance induction by encephalitogenic T cells.

Amino Acid Sequence↗
PubMed1993

Inhibition of experimental autoimmune encephalomyelitis by inhalation but not oral administration of the encephalitogenic peptide: influence of MHC binding affinity.

This study explores antigen administration via mucosal surfaces as a potential means of inducing antigen-specific non-responsiveness in experimental autoimmune encephalomyelitis (EAE). In the H-2u mouse model of EAE, the acetylated N-terminal peptide of myelin basic protein represents a dominant T cell epitope which on its own is sufficient to induce disease. Oral administration of the encephalitogenic peptide over a wide range of doses failed to induce oral tolerance to EAE. In marked contrast, a single intranasal dose of this peptide (Ac1-9 or Ac1-11) profoundly inhibited EAE when administered prior to disease induction. We investigated this phenomenon further by using two analogues of Ac1-11 with alanine or tyrosine at position 4 which display higher affinity binding to the I-Au molecule than the original peptide with lysine at this position. There was a positive correlation between the degree of protection from EAE and the affinity of individual peptides for class II MHC. Peptide inhalation inhibited not only EAE induced by subcutaneous injection of the encephalitogenic peptide but also disease induced by a complex mixture of potential auto-antigens such as spinal cord homogenate. Thus, in contrast to oral tolerance, nonresponsiveness by peptide inhalation is inducible with the encephalitogenic peptide in the absence of additional regulatory epitopes. The finding that a single epitope may protect against EAE induced with whole spinal cord homogenate implies, however, that regulatory mechanisms affecting additional potential self-epitopes may play a significant role.

Administration, Inhalation↗
PubMed1992

Cross-reactive antigen recognition by an encephalitogenic T cell receptor. Implications for T cell biology and autoimmunity.

The dominant immune response to rat myelin basic protein in H-2u mice is directed against the acetylated, N-terminal peptide Ac1-11 (AcASQKR-PSQRHG). This peptide causes encephalomyelitis on injection into mice of the H-2u haplotype. Only two residues of the peptide are required for ligation of the TCR from an Ac1-11-specific T cell hybridoma. Proline at position 6 could not be substituted by any other L-amino acid, whereas glutamine at position 3 could be replaced by phenylalanine, histidine, methionine, or tyrosine. Cross-reactive recognition of these residues appears to be specific, because increasing the affinity of each analogue for its MHC restriction element, by replacing lysine with tyrosine at position 4, did not alter the pattern of cross-reactivity. For the majority of substitutions at this position, a lack of stimulation could not be explained by failure to bind to I-Au. However, competition binding studies showed that introduction of proline at position 3 reduced the efficacy of binding to I-Au. Cross-reactive analogues of Ac1-11 were injected into H-2u mice to test the extent to which cross-reactive T cell activation might lead to autoimmune disease in this model. An analogue containing methionine at position 3 caused clinical experimental autoimmune encephalomyelitis in a small percentage of H-2u mice.

Amino Acid Sequence↗
PubMed1992

MHC-binding peptides for immunotherapy of experimental autoimmune disease.

It is now well accepted that T helper cells play a central role in the induction and maintenance of autoimmune disease. Many experimental models have emphasized this fact and have illustrated the efficacy of therapeutic strategies aimed at disrupting T cell recognition of autoantigens. Antibodies directed at either class II proteins of the major histocompatibility complex (MHC) or CD4 accessory molecules have been universally successful. However, the potential use of antibodies for therapy in humans is complicated by host anti-globulin and anti-idiotype responses. An alternative approach to anti-MHC blockade with antibodies is peptide blockade of MHC molecules. In addition, peptides may be used as agonists of autoantigens in order to modulate the autoimmune response. The use of synthetic peptides for therapy is an innovative yet relatively unexplored approach and will be the subject for discussion in this article.

Amino Acid Sequence↗
PubMed1992

Peptide-MHC interaction in autoimmunity.

Our increased understanding of the molecular basis of autoimmunity owes much to an appreciation of general principles governing peptide-MHC interactions. Such understanding may help resolve long-standing questions concerning autoimmune diseases and aid development of improved therapeutic strategies for their treatment.

Animals↗
PubMed1991

A single amino acid change in a myelin basic protein peptide confers the capacity to prevent rather than induce experimental autoimmune encephalomyelitis.

Experimental autoimmune encephalomyelitis (EAE) is an experimental demyelinating disease of rodents. In (PL/J x SJL) F1 mice, it is induced by immunization with the myelin basic protein peptide Ac1-11. Ac1-11 [4A], a myelin basic protein peptide analog with a single amino acid substitution, (i) binds to class II major histocompatibility complex molecules and stimulates encephalitogenic T cells in vitro better than Ac1-11, (ii) is nonimmunogenic and nonencephalitogenic in vivo in (PL/J x SJL)F1 mice, (iii) prevents EAE when administered before or at the time of immunization with Ac1-11, and (iv) prevents EAE when administered later, near the time of disease onset. Initial studies suggest that Ac1-11 [4A] does not prevent EAE by competitive inhibition or by activation of regulatory cells. Thus, substitution of a single amino acid in a myelin basic protein peptide confers the capacity to prevent rather than induce EAE, even after peptide-specific encephalitogenic T cells have been activated.

Amino Acid Sequence↗
PubMed1990

T cell recognition in experimental autoimmune encephalomyelitis: prospects for immune intervention with synthetic peptides.

Peptide binding and lymph node T cell activation studies have been used to characterize T cell recognition of an encephalitogenic T cell autoantigen from myelin basic protein in mice of the H-2u haplotype. An important role for MHC class II molecules in "determinant selection" is revealed. Amino acids which determine interactions with either the restriction element of the major histocompatibility complex (MHC) or the encephalitogenic T cell receptor are defined. This information enables the design of peptides which bind MHC yet do not crossreact with the autoantigen. Two such peptides compete with the autoantigen for binding to the disease associated class II molecule and inhibit induction of experimental autoimmune encephalomyelitis in H-2u mice. Prospects for peptide mediated therapy are discussed.

Amino Acid Sequence↗
PubMed1990

Influenza peptide-induced self-lysis and down-regulation of cloned cytotoxic T cells.

Virus-specific cytotoxic T-cell (Tc) clones can lyse target cells in vitro in the presence of their specific peptide epitopes. The lytic potency of murine influenza nucleoprotein (NP)-specific Tc clones was investigated after observing that target cell killing was reduced in the presence of high (greater than 0.2 microM) concentrations of specific NP peptide antigen. Following incubation of Tc for 16 hr in the presence of a range of peptide concentrations, two effects were observed; (i) a peptide dose-dependent mortality of Tc, which has been attributed to self-lysis by clonal Tc in the presence of specific peptide; (ii) and a reduced ability to specifically lyse NP-expressing target cells whilst retaining lectin-dependent lytic activity in the surviving Tc. This functional down-regulation was reversible after 24 hr incubation in the absence of peptide. Toxic effects were excluded, since inhibition of specific target lysis by Tc was mediated only be pretreatment with specifically recognized peptide.

Animals↗
PubMed1989

Antigen recognition in autoimmune encephalomyelitis and the potential for peptide-mediated immunotherapy.

Peptide binding and lymph node T cell activation studies have been used to characterize T cell recognition of an encephalitogenic T cell autoantigen from myelin basic protein in (PL/J x SJL)F1 mice. Amino acids that determine interactions with either the restriction element of the major histocompatibility complex (MHC) or the encephalitogenic T cell receptor are defined. This information enables the design of peptides that bind MHC yet do not cross-react with the autoantigen. A peptide analog of the encephalitogenic epitope is shown to be "heteroclitic" for MHC binding and activation of encephalitogenic T cells in vitro. This analog is not immunogenic for encephalitogenic T cells in vivo and is shown to inhibit disease that is induced by the autoantigen itself.

Amino Acid Sequence↗
PubMed1989

Polymorphic residues on the I-A beta chain modulate the stimulation of T cell clones specific for the N-terminal peptide of the autoantigen myelin basic protein.

The effect of polymorphic residues on the A alpha A beta molecule on T cell recognition of the N-terminal nonapeptide of myelin basic protein (R1-9) was determined. Ak-restricted T cell clones recognizing R1-9 were isolated. The peptide-Ia specificities of these clones were determined by testing the response to 1) a panel of peptide analogs of R1-11, 2) splenic APC from mice expressing MHC molecules from serologically distinct haplotypes, and 3) L cell transfectants expressing mutant/recombinant A beta cDNA containing combinations of polymorphic nucleotide sequences from the k and u alleles. Comparisons were made between the Ak-restricted clones and a previously characterized panel of Au-restricted clones. Certain Ak-restricted clones were able to recognize MBP peptide analogs that were not recognized by any of the Au-restricted clones. The Au-restricted T cell clones did not cross-react with R1-9 presented in the context of Ak, whereas the majority of the Ak-restricted clones responded to R1-9 presented in the context of Au. This nonreciprocal cross-reactivity was also reflected in the relative responses of the two sets of T cell clones to the interchange of u- and k-derived residues in the A beta chain. Residues in regions corresponding both the alpha-helical or beta-sheet portions of the hypothetical Ia three-dimensional structure were involved. The results suggest that overall specificity of the T cell clones is the summation of numerous distinct subspecificities for different regions of the peptide-Ia ligand. These results indicate that there can be striking differences in T cell specificity for an autoantigenic epitope, even in the context of A alpha A beta molecules from very closely related haplotypes.

Amino Acid Sequence↗
PubMed1989

The role of polymorphic I-Ak beta chain residues in presentation of a peptide from myelin basic protein.

Proteins encoded by genes in the MHC are highly polymorphic. For class II proteins the highest level of polymorphism is found in distinct regions of variability, notably in the membrane-distal domains. To investigate the role of such residues in antigen presentation, we have tested cells transfected with wild-type or mutant I-Ak beta chains for their ability to present the NH2-terminal peptide of myelin basic protein to a panel of T cell clones. We were unable to detect a gross effect on peptide binding, in that all of the mutant cell lines presented antigen to at least one of the cloned T cells. However, the results imply that the more NH2-terminal residues, particularly 12 and 14, are involved in peptide interactions. Mutations at these residues presented antigen only at high antigen concentrations. Furthermore, residues of the more COOH-terminal regions appear to determine TCR interactions. Mutations in the predicted alpha-helical regions of the beta chain affected antigen presentation without abolishing peptide binding.

Amino Acids↗