Identification and medical applications of anti-citrullinated-protein antibodies in rheumatoid arthritis

A method of detecting anti-citrullinated antibodies in a sample from a rheumatoid arthritis patient, comprising the steps of:

• (i) contacting a plasma or serum sample obtained from the patient with a substrate comprising
• at least one in vitro citrullinated antigen selected from the group consisting of a Myelin Basic Protein (MBP) peptide fragment consisting of the sequence of SEQ ID NO. 1, and an MBP peptide fragment consisting of the sequence of SEQ ID NO. 2 and
• at least one additional in vitro citrullinated antigen selected from the group consisting of osteopontin (SPP1), flap endonuclease (FEN1), insulin like growth factor binding protein 6 (IGFBP6), insulin like growth factor I (IGF1), and stanniocalcin-2 (STC2) to form antibody-antigen complexes;
• wherein the at least one antigen and the at least one additional antigen are each linked to a haloalkane dehalogenase, wherein the substrate is coated with a ligand comprising a reactive chloroalkane capable of binding the haloalkane dehalogenase, thereby immobilizing the at least one antigen and the at least one additional antigen on the substrate;
• (ii) contacting the antibody-antigen complexes with a label;
• and
• (iii) detecting the antibody-antigen complexes, thereby detecting the anti-citrullinated antibodies in the sample by detecting the label.