Identification of a Linear Epitope Recognized by a Monoclonal Antibody Directed to the Heterogeneous Nucleoriboprotein A2

Author(s): Julie Tronstrøm, Anette Holck Draborg, Paul Robert Hansen, Gunnar Houen, Nicole Hartwig Trier.

Journal Name: Protein & Peptide Letters

Volume 21 , Issue 1 , 2014

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Abstract:

Rheumatoid arthritis (RA) is a chronic autoimmune disorder, characterized by progressive joint destruction and disability. Classical autoantibodies of RA are rheumatoid factors and citrulline antibodies. Patients positive for these autoantibodies are usually associated with a progressive disease course. A subgroup of RA patients does not express citrulline antibodies, instead are approximately 35% of these anti-citrulline-negative patients reported to express autoantibodies to the heterogeneous nucleoriboprotein A2, a ribonucleoprotein involved in RNA transport and processing also referred to as RA33. In the absence of citrulline antibodies, RA33 antibodies have been suggested to be associated with a milder disease course.

In this study we screened the reactivity of a monoclonal antibody to RA33-derived peptides by modified enzyme-linked immunosorbent assays (ELISA). Terminally truncated resin-bound peptides were applied for determination of the functional epitope necessary for antibody recognition. In addition, screening of substituted peptides by modified ELISA identified amino acids necessary for antibody reactivity.

A potential epitope was identified in the region 71-79 (PHSIDGRVV), where the amino acids Ser, Ile and Asp were found to be essential for antibody reactivity. These amino acids were found to contribute to the antibody-antigen interface through side-chain interactions, possibly in combination with a positively charged amino acid in position 77. Moreover, the amino acids in the N-terminal end (Pro and His) were found to contribute to the interface through backbone contributions. No notable reactivity was found with RA-positive patient sera, thus screening of RA33 antibodies does not seem to be a supplementary for the diagnosis of RA.

Keywords: Enzyme-linked immunosorbent assay, epitope mapping, heterogeneous nucleoriboprotein A2/B1, monoclonal antibody, RA33, synthetic resin-bound peptides.

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Article Details

VOLUME: 21
ISSUE: 1
Year: 2014
Page: [25 - 31]
Pages: 7
DOI: 10.2174/09298665113209990085

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