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Wild-type Peptide (wild-type + peptide)
Selected AbstractsMechanism of modulation of T cell responses by N-palmitoylated peptidesEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 12 2004Clara Bueno Abstract Small structural changes in the antigenic peptides recognized by TCR can alter the biological properties of those peptides and convert them into weak agonists, partial agonists, or antagonists of these receptors. These altered peptide ligands (APL) are usually generated by conservative amino acid substitutions at TCR contact residues. Here, we show that APL with therapeutic properties can also be generated by attachment of palmitic acid at the N terminus of the peptide without the need to modify the peptide's primary sequence. Using N-palmitoylated pigeon cytochrome-c peptide 81,104 (PALPCC81,104), we were able to induce T cell hyporesponsiveness to the wild-type peptide in vitro. More importantly, administration of the PALPCC81,104 to mice reduced the responsiveness to the native peptide when tested ex vivo. Biochemical and functional experiments indicated that the action of N-palmitoylated peptides was due to the conversion of the native peptide into a weak agonist that could then induce T cell anergy. Our results demonstrate that N-palmitoylation of antigenic peptides is a feasible strategy to generate APL, as it avoids the need to screen multiple amino acid variants of each specific antigen to identify those with therapeutic properties. [source] Sequence flexibility of the immunodominant HLA A*0201 restricted ppUL83 CD8 T-cell epitope of human cytomegalovirusJOURNAL OF MEDICAL VIROLOGY, Issue 1 2010Jakub Kopycinski Abstract The cytomegalovirus ppUL83 protein contains an immunodominant A*0201 restricted epitope between residues 495 and 503. We investigated the tolerance of this epitope to sequence variation in the context of peptide binding to HLA A*0201 and the ability to induce an Interferon gamma (IFN,) response through engagement with the T-cell receptor (TCR). The majority of mutations investigated resulted in a decrease in the production of IFN, indicating that if such variants occurred in vivo they would not be recognized by CD8 T-cell clones specific for the wild-type epitope. The mechanistic basis for the majority of the mutant peptides was their failure to bind and stabilize class I HLA cell surface expression. However, one peptide with a mutation at the P5 position (methionine to cysteine) resulted in a significant enhanced binding to HLA A*0201 and also an increase in cell surface expression over the wild-type peptide but was unable to engage with the CD8 TCR and trigger IFN, production. This peptide acted as a competitive inhibitor of the wild-type peptide but could not fully inhibit IFN, production by the latter. We subsequently investigated whether mutations of the HLA A*0201 epitope were evident in immunocompromized patients experiencing either rapid exponential or persistent cytomegalovirus replication. J. Med. Virol. 82:94,103, 2010. © 2009 Wiley-Liss, Inc. [source] A new amyloid , variant favoring oligomerization in Alzheimer's-type dementiaANNALS OF NEUROLOGY, Issue 3 2008Takami Tomiyama PhD Objective Soluble oligomers of amyloid , (A,), rather than amyloid fibrils, have been proposed to initiate synaptic and cognitive dysfunction in Alzheimer's disease (AD). However, there is no direct evidence in humans that this mechanism can cause AD. Here, we report a novel amyloid precursor protein (APP) mutation that may provide evidence to address this question. Methods A Japanese pedigree showing Alzheimer's-type dementia was examined for mutations in APP, PSEN1, and PSEN2. In addition, 5,310 Japanese people, including 2,121 patients with AD, were screened for the novel APP mutation. The pathogenic effects of this mutation on A, production, degradation, aggregation, and synaptotoxicity were also investigated. Results We identified a novel APP mutation (E693,) producing variant A, lacking gulutamate-22 (E22,) in Japanese pedigrees showing Alzheimer's-type dementia and AD. Although the secretion of total A, was markedly reduced by this mutation, the variant A, was more resistant to proteolytic degradation. The mutant peptides showed the unique aggregation property of enhanced oligomerization but no fibrillization, and inhibited hippocampal long-term potentiation more potently than wild-type peptide in rats in vivo. Consistent with the nonfibrillogenic property of the variant A,, a very low amyloid signal was observed in the patient's brain on positron emission tomography using Pittsburgh compound-B. Interpretation The E693, mutation has been suggested as a cause of dementia because of enhanced formation of synaptotoxic A, oligomers. Our findings may provide genetic validation in humans for the emerging hypothesis that the synaptic and cognitive impairment in AD is primarily caused by soluble A, oligomers. Ann Neurol 2008 [source] Peptide-induced suppression of collagen-induced arthritis in HLA,DR1 transgenic miceARTHRITIS & RHEUMATISM, Issue 12 2002Linda K. Myers Objective To identify peptides capable of altering the immune response to type II collagen (CII) in the context of HLA,DR. Methods Immunizing mice transgenic for the human HLA,DRB1*0101 immune response gene with CII elicits an arthritis (collagen-induced arthritis [CIA]) that resembles rheumatoid arthritis. We have previously identified an immunodominant determinant of CII, CII (263,270), recognized by T cells in the context of DR1. To produce synthetic peptides with the potential of disrupting the DR1-restricted immune response, synthetic analog peptides were developed that contain site-directed substitutions in critical positions. These peptides were used to treat CIA in DR1 transgenic mice. Results An analog peptide, CII (256,276, N263, D266), that inhibited T cell responses in vitro, was identified. When DR1 mice were coimmunized with CII and CII (256,276, N263, D266), the incidence and severity of arthritis were greatly reduced, as was the antibody response to CII. Moreover, CII (256,276, N263, D266) was effective in down-regulating the immune responses to CII and arthritis, even when administered 2 weeks following immunization with CII. Spleen and lymph node cells from CII-immunized mice cultured with CII (256,276, N263, D266) in vitro produced increased amounts of interleukin-4 (IL-4) compared with cells cultured with the wild-type peptide, CII (256,276). Furthermore, CII (256,276, N263, D266) was incapable of preventing arthritis in DR1 IL-4,/, mice (genetically deficient in IL-4). Conclusion These data establish that CII (256,276, N263, D266) is a potent suppressor of the DR-mediated immune response to CII. Its effect is mediated, at least in part, by IL-4. These experiments represent the first description of an analog peptide of CII recognized by T cells in the context of a human major histocompatibility complex molecule that can suppress autoimmune arthritis. [source] Merozoite surface protein 2 of Plasmodium falciparum: Expression, structure, dynamics, and fibril formation of the conserved N-terminal domainBIOPOLYMERS, Issue 1 2007Andrew Low Abstract Merozoite surface protein 2 (MSP2) is a GPI-anchored protein on the surface of the merozoite stage of the malaria parasite Plasmodium falciparum. It is largely disordered in solution, but has a propensity to form amyloid-like fibrils under physiological conditions. The N-terminal conserved region (MSP21,25) is part of the protease-resistant core of these fibrils. To investigate the structure and dynamics of this region, its ability to form fibrils, and the role of individual residues in these properties, we have developed a bacterial expression system that yields ,10 mg of unlabeled or 15N-labeled peptide per litre of culture. Two recombinant versions of MSP21,25, wild-type and a Y7A/Y16A mutant, have been produced. Detailed conformational analysis of the wild-type peptide and backbone 15N relaxation data indicated that it contains ,-turn and nascent helical structures in the central and C-terminal regions. Residues 6,21 represent the most ordered region of the structure, although there is some flexibility around residues 8 and 9. The 10-residue sequence (MSP27,16) (with two Tyr residues) was predicted to have a higher propensity for ,-aggregation than the 8-mer sequence (MSP28,15), but there was no significant difference in conformation between MSP21,25 and [Y7A,Y16A]MSP21,25 and the rate of fibril formation was only slightly slower in the mutant. The peptide expression system described here will facilitate further mutational analyses to define the roles of individual residues in transient structural elements and fibril formation, and thus contribute to the further development of MSP2 as a malaria vaccine candidate. © 2007 Wiley Periodicals, Inc. Biopolymers 87: 12,22, 2007. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] | ||||||||||