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Linear Epitopes (linear + epitope)
Selected AbstractsNovel mechanism of antibodies to hepatitis B virus in blocking viral particle release from cells,HEPATOLOGY, Issue 3 2010Avidan U. Neumann Antibodies are thought to exert antiviral activities by blocking viral entry into cells and/or accelerating viral clearance from circulation. In particular, antibodies to hepatitis B virus (HBV) surface antigen (HBsAg) confer protection, by binding circulating virus. Here, we used mathematical modeling to gain information about viral dynamics during and after single or multiple infusions of a combination of two human monoclonal anti-HBs (HepeX-B) antibodies in patients with chronic hepatitis B. The antibody HBV-17 recognizes a conformational epitope, whereas antibody HBV-19 recognizes a linear epitope on the HBsAg. The kinetic profiles of the decline of serum HBV DNA and HBsAg revealed partial blocking of virion release from infected cells as a new antiviral mechanism, in addition to acceleration of HBV clearance from the circulation. We then replicated this approach in vitro, using cells secreting HBsAg, and compared the prediction of the mathematical modeling obtained from the in vivo kinetics. In vitro, HepeX-B treatment of HBsAg-producing cells showed cellular uptake of antibodies, resulting in intracellular accumulation of viral particles. Blocking of HBsAg secretion also continued after HepeX-B was removed from the cell culture supernatants. Conclusion: These results identify a novel antiviral mechanism of antibodies to HBsAg (anti-HBs) involving prolonged blocking of the HBV and HBsAg subviral particles release from infected cells. This may have implications in designing new therapies for patients with chronic HBV infection and may also be relevant in other viral infections. (HEPATOLOGY 2010;) [source] Post-translational modifications of the major linear epitope 169,190aa of Ro60 kDa autoantigen alter the autoantibody bindingCLINICAL & EXPERIMENTAL IMMUNOLOGY, Issue 1 2006A. G. Terzoglou Summary Ro60 kDa is a member of the Ro/LaRNP ribonucleoprotein complex and its major linear B cell epitope, corresponding to the region 169,190aa, has been found to be the initial target of the autoimmune response in patients with systemic lupus erythematosus. This sequence contains one serine and two arginine amino acid residues, which can potentially be modified post-translationally by phosphorylation or citrullination, respectively. The aim of this study was to develop an immunoassay for anti-Ro60 kDa epitope antibody detection and to investigate the changes in the antigenicity of the Ro60 kDa epitope when it is post-translationally modified, by either citrullination or phosphorylation. Peptide analogues corresponding to the unmodified form of the epitope, its phosphorylated form, and a form with both arginine residues citrullinated were synthesized. The peptide coating conditions were investigated and it was found that the use of highly hydrophilic surfaces increase the efficiency of the coating, as well as the sensitivity of the method for anti-peptide antibody detection. All peptides were tested by the optimized enzyme-linked immunosorbent assay (ELISA) against 119 sera from patients with primary Sjögren's syndrome, systemic lupus erythematosus and rheumatoid arthritis with anti-Ro/SSA reactivity, 20 sera from patients with systemic diseases without anti-Ro/SSA immune reactivity, as well as against 65 sera from normal individuals. A large proportion of the tested sera reacted against all three peptide analogues, although with a preference for the unmodified form of the epitope. In conclusion, post-translational modifications of the major Ro60 kDa B cell epitope can alter the autoantibody binding. [source] Mapping and characterization of B cell linear epitopes in the conservative regions of hepatitis C virus envelope glycoproteinsJOURNAL OF VIRAL HEPATITIS, Issue 3 2002L. V. Olenina Forty-eight overlapping octapeptides covering highly conservative regions of E1 and E2 hepatitis C virus (HCV) envelope proteins were synthesized and tested by ELISA against different groups of sera obtained from HCV-infected patients. All sera from patients with acute infection, except a single case of serum reactivity with the region HINRTALN, were nonreactive with any peptide. Sera obtained from chronic patients reacted with 12 peptides from five selected regions. Two immunodominant B epitopes were found, one being the precisely mapped antigenic site RMAWDM positioned inside the earlier shown immunodominant epitope from E1, and the second site, PALSTGLIH from E2, detected for the first time. New minor antigenic site was determined as PTDCFRKH from E2. We found only minor seroreactivity for one of the putative sites involved in CD81 binding, PYCWHYAP. [source] The epitope space of the human proteomePROTEIN SCIENCE, Issue 4 2008Lisa Berglund Abstract In the post-genome era, there is a great need for protein-specific affinity reagents to explore the human proteome. Antibodies are suitable as reagents, but generation of antibodies with low cross-reactivity to other human proteins requires careful selection of antigens. Here we show the results from a proteome-wide effort to map linear epitopes based on uniqueness relative to the entire human proteome. The analysis was based on a sliding window sequence similarity search using short windows (8, 10, and 12 amino acid residues). A comparison of exact string matching (Hamming distance) and a heuristic method (BLAST) was performed, showing that the heuristic method combined with a grid strategy allows for whole proteome analysis with high accuracy and feasible run times. The analysis shows that it is possible to find unique antigens for a majority of the human proteins, with relatively strict rules involving low sequence identity of the possible linear epitopes. The implications for human antibody-based proteomics efforts are discussed. [source] Peptide microarrays for the characterization of antigenic regions of human chromogranin,APROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 14 2005Marcella Chiari Abstract Microarraying peptides is a powerful proteomics technique for studying molecular recognition events. Since peptides have small molecular mass, they are not easily accessible when adsorbed onto solid supports. Moreover, peptides can lack a well-defined three-dimensional structure, and therefore a correct orientation is essential to promote the interaction with their target. In this work, we investigated the suitability as a peptide array substrate of a glass slide coated with a copolymer of N,N -dimethylacrylamide, N,N -acryloyloxysuccinimide, and [3-(methacryloyl-oxy)propyl]trimethoxysilyl. This polymeric surface was used as substrate for peptides in the characterization of linear antigenic sites of human chromogranin,A, a useful tissue and serum marker for neuroendocrine tumors and a precursor of many biologically active peptides. The microarray support provided sufficient accessibility of the ligand, with no need for a spacer, as the polymer chains prevent interaction of immobilized peptides with substrate. In addition, the polymeric surface constitutes an aqueous micro-environment in which linear epitopes are freely exposed despite peptide random orientation. The results reported in this article are in accordance with those obtained in conventional ELISA assays using biotinylated and non-biotinylated peptides. [source] Analysis of the autoimmune epitopes on human testicular NASP using recombinant and synthetic peptidesCLINICAL & EXPERIMENTAL IMMUNOLOGY, Issue 2 2000I. N. Batova The human nuclear autoantigenic sperm protein, NASP, is a testicular histone-binding protein of 787 amino acids to which most vasectomized men develop autoantibodies. In this study to define the boundaries of antigenic regions and epitope recognition pattern, recombinant deletion mutants spanning the entire protein coding sequence and a human NASP cDNA sublibrary were screened with vasectomy patients' sera. Employing panel sera from 21 vasectomy patients with anti-sperm antibodies, a heterogeneous pattern of autoantibody binding to the recombinant polypeptides was detected in ELISA and immunoblotting. The majority of sera (20/21) had antibodies to one or more of the NASP fusion proteins. Antigenic sites preferentially recognized by the individual patients' sera were located within aa 32,352 and aa 572,787. Using a patient's serum selected for its reactivity to the whole recombinant protein in Western blots, cDNA clones positive for the C-terminal domain of the molecule were identified. The number and location of linear epitopes in this region were determined by synthetic peptide mapping and inhibition studies. The epitope-containing segment was delimited to the sequence aa 619,692 and analysis of a series of 74 concurrent overlapping 9mer synthetic peptides encompassing this region revealed four linear epitopes: amino acid residues IREKIEDAK (aa 648,656), KESQRSGNV (aa 656,664), AELALKATL (aa 665,673) and GFTPGGGGS (aa 680,688). All individual patients' sera reacted with epitopes within the sequence IRE,.GGS (aa 648,688). The strongest reactivity was displayed by peptides corresponding to the sequence AELALKATL (aa 665,673). Thus, multiple continuous autoimmune epitopes in NASP involving sequences in the conserved C-terminal domain as well as in the less conserved testis-specific N-terminal region comprising the histone-binding sites, as predicted for an antigen-driven immune response, may be a target of autoantibodies in vasectomized men and may provide a relevant laboratory variable to describe more accurately the spectrum of autoantibody specificities associated with the clinical manifestation of vasectomy. [source] | |||||||||||||