title: Functional and Structural Characterization of a Novel HLA-DRB1*04:01-Restricted α-Enolase T Cell Epitope in Rheumatoid Arthritis.
abstract: Antibodies to citrullinated proteins, common in rheumatoid arthritis (RA) patients, are strongly associated to a specific set of HLA-DR alleles including HLA-DRB1*04:01, *04:04, and *01:01. Here, we first demonstrate that autoantibody levels toward the dominant citrullinated B cell epitope from α-enolase are significantly elevated in HLA-DRB1*04:01-positive RA patients. Furthermore, we identified α-enolase-derived T cell epitopes and demonstrated that native and citrullinated versions of several peptides bind with different affinities to HLA-DRB1*04:01, *04:04, and *01:01. The citrulline residues in the eight identified peptides are distributed throughout the entire length of the presented epitopes and more specifically, localized at peptide positions p-2, p2, p4, p6, p7, p10, and p11. Importantly, in contrast to its native version peptide 26 (TSKGLFRAAVPSGAS), the HLA-DRB1*04:01-restricted citrullinated peptide Cit26 (TSKGLFCitAAVPSGAS) elicited significant functional T cell responses in primary cells from RA patients. Comparative analysis of the crystal structures of HLA-DRB1*04:01 in complex with peptide 26 or Cit26 demonstrated that the posttranslational modification did not alter the conformation of the peptide. And since citrullination is the only structural difference between the two complexes, this indicates that the neo-antigen Cit26 is recognized by T cells with high specificity to the citrulline residue.
authors.affiliation: Rheumatology Unit, Department of Medicine Solna, Center for Molecular Medicine, Karolinska Institutet, Karolinska University Hospital , Stockholm , Sweden.
authors.forename: Christina
authors.initials: C
authors.lastname: Gerstner
authors.affiliation: Neuroimmunology Unit, Department of Clinical Neurosciences, Center for Molecular Medicine, Karolinska Institutet, Stockholm, Sweden; Science for Life Laboratory, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Anatoly
authors.initials: A
authors.lastname: Dubnovitsky
authors.affiliation: Rheumatology Unit, Department of Medicine Solna, Center for Molecular Medicine, Karolinska Institutet, Karolinska University Hospital , Stockholm , Sweden.
authors.forename: Charlotta
authors.initials: C
authors.lastname: Sandin
authors.affiliation: Rheumatology Unit, Department of Medicine Solna, Center for Molecular Medicine, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden; Science for Life Laboratory, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Genadiy
authors.initials: G
authors.lastname: Kozhukh
authors.affiliation: Rheumatology Unit, Department of Medicine Solna, Center for Molecular Medicine, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden; Translational Research program, BRI at Virginia Mason, Seattle, WA, USA.
authors.forename: Hannes
authors.initials: H
authors.lastname: Uchtenhagen
authors.affiliation: Tetramer Core, BRI at Virginia Mason , Seattle, WA , USA.
authors.forename: Eddie A
authors.initials: EA
authors.lastname: James
authors.affiliation: Department of Immunology, Genetics and Pathology, Uppsala University , Uppsala , Sweden.
authors.forename: Johan
authors.initials: J
authors.lastname: Rönnelid
authors.affiliation: Rheumatology Unit, Department of Medicine Solna, Center for Molecular Medicine, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden; Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Anders Jimmy
authors.initials: AJ
authors.lastname: Ytterberg
authors.affiliation: Rheumatology Unit, Department of Medicine Solna, Center for Molecular Medicine, Karolinska Institutet, Karolinska University Hospital , Stockholm , Sweden.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Pieper
authors.affiliation: Rheumatology Unit, Department of Medicine Solna, Center for Molecular Medicine, Karolinska Institutet, Karolinska University Hospital , Stockholm , Sweden.
authors.forename: Evan
authors.initials: E
authors.lastname: Reed
authors.affiliation: Science for Life Laboratory, Department of Medical Sciences, Rheumatology, Uppsala University , Uppsala , Sweden.
authors.forename: Karolina
authors.initials: K
authors.lastname: Tandre
authors.affiliation: Translational Research program, BRI at Virginia Mason , Seattle, WA , USA.
authors.forename: Mary
authors.initials: M
authors.lastname: Rieck
authors.affiliation: Department of Medical Biochemistry and Biophysics, Karolinska Institutet , Stockholm , Sweden.
authors.forename: Roman A
authors.initials: RA
authors.lastname: Zubarev
authors.affiliation: Science for Life Laboratory, Department of Medical Sciences, Rheumatology, Uppsala University , Uppsala , Sweden.
authors.forename: Lars
authors.initials: L
authors.lastname: Rönnblom
authors.affiliation: Science for Life Laboratory, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden; Department of Infectious Diseases, Karolinska University Hospital Solna, Stockholm, Sweden.
authors.forename: Tatyana
authors.initials: T
authors.lastname: Sandalova
authors.affiliation: Translational Research program, BRI at Virginia Mason , Seattle, WA , USA.
authors.forename: Jane H
authors.initials: JH
authors.lastname: Buckner
authors.affiliation: Science for Life Laboratory, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden; Department of Infectious Diseases, Karolinska University Hospital Solna, Stockholm, Sweden.
authors.forename: Adnane
authors.initials: A
authors.lastname: Achour
authors.affiliation: Rheumatology Unit, Department of Medicine Solna, Center for Molecular Medicine, Karolinska Institutet, Karolinska University Hospital , Stockholm , Sweden.
authors.forename: Vivianne
authors.initials: V
authors.lastname: Malmström
keywords: CD4+ T cell; HLA-DR4/α-enolase; autoimmunity; crystal structures; cytokines; neo-antigen; rheumatoid arthritis