Deiminated proteins are the target of diagnostic anti-citrullinated peptide/protein autoantibodies (ACPA) in rheumatoid arthritis (RA). Deiminated histone H4 contained in the neutrophil extracellular traps reacts with ACPA, becoming an interesting diagnostic antigen for RA. The identification of the ACPA binding site in histone H4 was performed experimentally by mapping the complete sequence. The method describes the synthesis of an overlapping peptide library covering the entire deiminated sequence of H4 and its further evaluation in ELISA. A detailed description of an ELISA protocol to test RA patients' sera against the synthesized peptides and ACPA is provided.
Keywords: ACPA; ELISA; Epitope mapping; Histone H4; Peptide antigen; Rheumatoid arthritis.