title: Identification of endogenously presented peptides from Chlamydia trachomatis with high homology to human proteins and to a natural self-ligand of HLA-B27.
abstract: A strategy for the stable expression of proteins, or large protein fragments, from Chlamydia trachomatis into human cells was designed to identify bacterial epitopes endogenously processed and presented by HLA-B27. Fusion protein constructs in which the green fluorescent protein gene was placed at the 5'-end of the bacterial DNA primase gene or some of its fragments were transfected into B*2705-C1R cells. One of these constructs, including residues 90-450 of the bacterial protein, was stably and efficiently expressed. Mass spectrometry-based comparative analysis of HLA-B27-bound peptide pools led to identification of three HLA-B27 ligands differentially presented in the transfectant cells. Sequencing of these peptides confirmed that they were derived from the bacterial DNA primase. One of them, spanning residues 211-221, showed 55% sequence identity with a known self-ligand of HLA-B27 derived from its own molecule. The other two bacterial ligands, P-(112-121) and P-(112-122), were derived from the same region and differed in length by one residue at the C terminus. Both peptides showed >50% identity with multiple human protein sequences that possessed the optimal peptide motifs for HLA-B27 binding. Thus, expression of proteins from arthritogenic bacteria in HLA-B27-positive human cells allows identifying bacterial peptides that are endogenously processed and presented by HLA-B27 and show molecular mimicry with known self-ligands of this molecule and human proteins.
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: José A López
authors.initials: JA
authors.lastname: de Castro
mesh_terms: D000595:Amino Acid Sequence; D017951:Antigen Presentation; D000942:Antigens, Bacterial / Q000032:analysis* / Q000737:chemistry*; D002460:Cell Line; D002692:Chlamydia trachomatis / Q000737:chemistry* / Q000201:enzymology; D019915:DNA Primase / Q000737:chemistry / Q000378:metabolism; D015796:HLA-B27 Antigen / Q000737:chemistry*; D006801:Humans; D008024:Ligands; D008969:Molecular Sequence Data; D010455:Peptides / Q000032:analysis* / Q000737:chemistry*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D020539:Sequence Analysis, Protein; D017386:Sequence Homology, Amino Acid; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014162:Transfection
chemical_list: D000942:Antigens, Bacterial; D015796:HLA-B27 Antigen; D008024:Ligands; D010455:Peptides; D011993:Recombinant Fusion Proteins; D019915:DNA Primase; D046988:Proteasome Endopeptidase Complex