title: Endogenous processing and presentation of T-cell epitopes from Chlamydia trachomatis with relevance in HLA-B27-associated reactive arthritis.
abstract: Chlamydia trachomatis triggers reactive arthritis, a spondyloarthropathy linked to the human major histocompatibility complex molecule HLA-B27, through an unknown mechanism that might involve molecular mimicry between chlamydial and self-derived HLA-B27 ligands. Chlamydia-specific CD8(+) T-cells are found in reactive arthritis patients, but the immunogenic epitopes are unknown. A previous screening of the chlamydial genome for putative HLA-B27 ligands predicted multiple peptides that were recognized in vitro by CD8(+) T-lymphocytes from patients. Here stable transfectants expressing bacterial fusion proteins in human cells were generated to investigate the endogenous processing and presentation by HLA-B27 of two such epitopes through comparative immunoproteomics of HLA-B27-bound peptide repertoires. A predicted T-cell epitope, from the CT610 gene product, was presented by HLA-B27. This is, to our knowledge, the first endogenously processed epitope involved in HLA-B27-restricted responses against C. trachomatis in reactive arthritis. A second predicted epitope, from the CT634 gene product, was not detected. Instead a non-predicted nonamer from the same protein was identified. Both bacterial peptides showed very high homology with human sequences containing the HLA-B27 binding motif. Thus, expression and intracellular processing of chlamydial proteins into human cells allowed us to identify two bacterial HLA-B27 ligands, including the first endogenous T-cell epitope from C. trachomatis involved in spondyloarthropathy. That human proteins contain sequences mimicking chlamydial T-cell epitopes suggests a basis for an autoimmune component of Chlamydia-induced HLA-B27-associated disease.
authors.affiliation: Centro de Biología Molecular Severo Ochoa (Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid), Universidad Autónoma, 28049 Madrid, Spain.
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Cragnolini
authors.forename: Noel
authors.initials: N
authors.lastname: García-Medel
authors.forename: José A López
authors.initials: JA
authors.lastname: de Castro
mesh_terms: D017951:Antigen Presentation; D016918:Arthritis, Reactive / Q000276:immunology / Q000473:pathology; D001426:Bacterial Proteins / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D002460:Cell Line; D002692:Chlamydia trachomatis / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D000939:Epitopes / Q000032:analysis / Q000276:immunology* / Q000378:metabolism; D005434:Flow Cytometry; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D015796:HLA-B27 Antigen / Q000276:immunology*; D006801:Humans; D040901:Proteomics / Q000379:methods; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D014162:Transfection
chemical_list: D001426:Bacterial Proteins; D000939:Epitopes; D015796:HLA-B27 Antigen; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins