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.

Spondylarthritis in HLA–B27/human β2‐microglobulin–transgenic rats is not prevented by lack of CD8

“…For example, two peptides derived from B27 itself have been found to be natural ligands for B27, including peptides with homology to proteins from enteric bacteria (2) and Chlamydia trachomatis (3), which are known infectious triggers of B27-associated reactive arthritis. A chlamydial peptide homologous to one of these B27-derived peptides is generated in Chlamydia-infected human cells, binds to B27, and shares homology with a number of other human protein sequences (4). Another pair of peptides that share homology with each other, one from an Epstein-Barr virus epitope protein and the other from the human vasoactive intestinal peptide receptor 1, both bind to B27 and are recognized by cross-reactive T cells (5).…”

Genética, HLA-B27 y espondilitis anquilosante: 40 años

“…Se ha identificado un ligando de HLA-B27 perteneciente a su propia secuencia, que presenta similitud con una secuencia de la ADN-primasa de Chlamydia trachomatis 15 . Posteriormente, se expresó un fragmento proteico que incluía parte de la secuencia homóloga a B27 de esta ADN-primasa bacteriana en líneas celulares B27-positivas, probando que la construcción proteica era procesada y presentada "in vivo" por B*27:05 16 . Además, mediante inmunoproteómica comparada, se demostró que un péptido bacteriano homólogo al ligando propio de B*27 era procesado y presentado endógena-mente, demostrando la existencia de mimetismo molecular 17 .…”

Multiple, Non-conserved, Internal Viral Ligands Naturally Presented by HLA-B27 in Human Respiratory Syncytial Virus-infected Cells

“…HLA-peptide complexes were isolated by affinity chromatography of the soluble fraction with the W6/32 monoclonal Ab. HLAbound peptides were eluted at room temperature with 0.1% aqueous TFA and concentrated with a Centricon 3 column (Amicon, Beverly, MA) as described previously (30,31).…”