Review article
Anti-CCP antibodies, a highly specific marker for (early) rheumatoid arthritis

https://doi.org/10.1016/j.cair.2003.11.001Get rights and content

Abstract

Rheumatoid arthritis (RA) is a chronic, destructive autoimmune disease affecting the joints. With more sophisticated and effective therapies becoming available and with the understanding that early intervention is crucial in preventing irreversible joint damage, it is more and more important to diagnose RA at a very early stage in the disease. To facilitate diagnosis during the early stages of the disease, when often not all clinical symptoms are manifest, a good serological marker is needed. Antibodies directed to citrullinated proteins provide this ability. The most sensitive assay to detect these antibodies is the so-called anti-cyclic citrullinated peptide (CCP) enzyme-linked immunosorbent assay (ELISA) assay. In this review, the diagnostic and prognostic potential and the general utility in clinical practice of anti-CCP antibodies are discussed. Furthermore, we elaborate on the mechanisms involved in the generation of citrullinated autoantigens and the possible role of the anti-CCP antibodies and their antigens in the disease.

Introduction

Rheumatoid arthritis (RA) is a common, systemic autoimmune disease affecting 0.5–1% of the population [1], [2]. It is characterized by chronic inflammation of the synovial joints, which commonly leads to progressive joint destruction and consequent disability and reduction of quality of life [3]. Disease outcome may vary from mild symptoms to severe systemic disease when joint destruction is accompanied by extraarticular manifestations (i.e., rheumatoid nodules, vasculitis). Mortality in the latter group is significantly increased compared to the former group and the general population [4], [5].

With more sophisticated and effective therapies becoming available (reviewed in [6]) and with the understanding that early intervention is crucial in preventing irreversible joint damage [7], [8], [9], it is more and more important to diagnose RA at a very early stage in the disease. Although the 1987 American College of Rheumatology (ACR; formerly, American Rheumatism Association) classification criteria for RA [10] are often used in clinical practice as diagnostic tool for RA, they are not very well suited for the diagnosis of early RA [11], [12], [13]. The ACR criteria rely heavily on the expression of clinical symptoms of RA, but in early RA these clinical parameters are often not (yet) manifest. Therefore, a specific and sensitive (serological) marker, which is present very early in the disease, is needed. Rheumatologists need to be able to target the use of potentially toxic and expensive drugs to those patients where the benefits clearly outweigh the risks [13], [14]. Therefore a good marker should ideally be able to predict the erosive or nonerosive progression of the disease. Fortunately, the anti-CCP (cyclic citrullinated peptide) antibodies meet the demands for a good and useful marker for early RA and this will be the focus of this review.

Section snippets

RA-associated antibodies

The serum of RA patients contains a large repertoire of antibodies directed against self-proteins. Most of these autoantibodies, however, can also be detected in patients with other (autoimmune) conditions, and are therefore not specific for RA. Even the well known rheumatoid factor (RF) antibodies, directed against the Fc domain of IgG molecules (reviewed in [15]), which are part of the ACR criteria [10] have only moderate specificity for RA. They can be found in patients with other autoimmune

The original systems: APF and AKA

In 1964 the antiperinuclear factor (APF) was described for the first time [48]. These autoantibodies are specific for RA (reviewed in [49]) and can be detected by indirect immunofluorescence using human buccal mucosa cells as the antigenic substrate. Light and immunoelectron microscopy revealed that the perinuclear factor is localized in the keratohyalin granules [50], [51]. These granules are 0.5–4 μm amorphous structures of densely packed proteins located in the cytoplasm of epithelial cells.

The CCP1 and CCP2 systems

To increase the sensitivity of the citrulline-containing peptide ELISA [63], peptides were modified to adopt a structure in which the citrulline moiety is optimally exposed for antibody binding ([76] and our unpublished 3D-NMR observations). With a single cyclic citrullinated peptide (CCP), antibodies could be detected in 68% of RA sera with a very high specificity (98%) [76]. This filaggrin-derived cyclic peptide was used as the antigenic substrate in the CCP1 test (results described below).

CCP for the clinician

A good serological marker should be:

  • 1.

    Sensitive and highly specific for the disease

  • 2.

    Detectable very early in the disease

  • 3.

    Able to prognose disease outcome

Local presence of citrullinated autoantigens at the site of inflammation in RA

The anti-CCP antibodies are probably produced locally in the synovium as they constitute a higher proportion of IgG in synovial fluid and synovial tissue compared to serum (1.4 and 7.5-fold, respectively) [66], [67]. Furthermore anti-CCP producing plasma cells have been isolated from the synovium of RA patients [66], [68]. This local antibody production requires the existence of citrullinated antigens in the inflamed synovium and consequently also the presence of PAD enzymes. Five isotypes of

For the researcher: possible pathoimmunological role in RA

Many animal models are being used to study the mechanisms of inflammation in RA (for an overview see [138]). We recently showed that synovial proteins are citrullinated during inflammation in both an acute (streptococcal cell wall arthritis) and a chronic destructive (collagen-induced arthritis) mouse model for arthritis [139]. One of the citrullinated proteins in the inflamed mouse synovium could be identified as fibrin. However, in contrast with the human disease, the mice did not produce

The future of CCP

The current second generation CCP system meets many of the requirements of a useful serological marker for RA. It is highly specific for the disease, can be detected early in the disease and because of its prognostic potential, it may provide an indication for aggressive treatment. With regard to the sensitivity of anti-CCP, there still is some room for improvement. The ideal marker would have a sensitivity of 100%, but because RA is such a complex and diverse condition, absolute sensitivity is

Conclusion

Anti-CCP antibodies meet all the requirements of a good serological marker for RA. Their high specificity and prognostic value make them a valuable diagnostic tool. Furthermore, all the available experimental data is compatible with a possible role in the disease process.

Currently, the revised 1987 ACR criteria are considered the gold standard for the classification of RA. Incorporation of anti-CCP positivity as an extra criterion would improve the accuracy of the ACR criteria [99], [107].

Acknowledgements

The authors wish to thank Dr. Han Zendman (Nijmegen, The Netherlands), Dr. Floris van Gaalen (Leiden, The Netherlands), Dr. Roberto Manetti (Florence, Italy), Dr. Anil Vasishta (Dundee, Scotland), Dr. Mark Nielen (Amsterdam, The Netherlands), Dr. Olivier Meyer (Paris, France), Dr. Solbritt Rantapää-Dahlqvist (Umea, Sweden), Dr. Guido Valesini (Rome, Italy), and Dr. Leen De Rycke (Ghent, Belgium) for providing valuable information and critical reading of the manuscript.

References (168)

  • E. Tarcsa et al.

    Protein unfolding by peptidylarginine deiminase. Substrate specificity and structural relationships of the natural substrates trichohyalin and filaggrin

    J Biol Chem

    (1996)
  • H.S. de Koster et al.

    The use of dedicated peptide libraries permits the discovery of high affinity binding peptides

    J Immunol Methods

    (1995)
  • I. Olivieri et al.

    Hepatitis C virus and arthritis

    Rheum Dis Clin North Am

    (2003)
  • A.J. Silman et al.

    Epidemiology and genetics of rheumatoid arthritis

    Arthritis Res

    (2002)
  • T.K. Kvien

    Epidemiology of disability in rheumatoid arthritis

    Rheumatology (Oxford)

    (2002)
  • C. Turesson et al.

    Extra-articular rheumatoid arthritis: prevalence and mortality

    Rheumatology (Oxford)

    (1999)
  • C. Turesson et al.

    Occurrence of extraarticular disease manifestations is associated with excess mortality in a community based cohort of patients with rheumatoid arthritis

    J Rheumatol

    (2002)
  • J.S. Smolen et al.

    Therapeutic strategies for rheumatoid arthritis

    Nat Rev Drug Discov

    (2003)
  • M.A. Bukhari et al.

    Influence of disease-modifying therapy on radiographic outcome in inflammatory polyarthritis at five years: results from a large observational inception study

    Arthritis Rheum

    (2003)
  • R.B. Landewe

    The benefits of early treatment in rheumatoid arthritis: confounding by indication, and the issue of timing

    Arthritis Rheum

    (2003)
  • F.C. Arnett et al.

    The American Rheumatism Association 1987 revised criteria for the classification of rheumatoid arthritis

    Arthritis Rheum

    (1988)
  • K. Kaarela et al.

    The value of the ACR 1987 criteria in very early rheumatoid arthritis

    Scand J Rheumatol

    (1995)
  • A. Saraux et al.

    Ability of the American College of Rheumatology 1987 criteria to predict rheumatoid arthritis in patients with early arthritis and classification of these patients two years later

    Arthritis Rheum

    (2001)
  • W.J. van Venrooij et al.

    Anticitrullinated protein/peptide antibody and its role in the diagnosis and prognosis of early rheumatoid arthritis

    Neth J Med

    (2002)
  • J.R. Kirwan et al.

    Prognostic criteria in rheumatoid arthritis: can we predict which patients will require specific anti-rheumatoid treatment?

    Clin Exp Rheumatol

    (1997)
  • R.A. Mageed

    The RF antigen

  • J.R. Lisse

    Does rheumatoid factor always mean arthritis?

    Postgrad Med

    (1993)
  • T. Palosuo et al.

    Filaggrin related antibodies among the aged

    Ann Rheum Dis

    (2003)
  • M.A. van Boekel et al.

    Autoantibody systems in rheumatoid arthritis: specificity, sensitivity and diagnostic value

    Arthritis Res

    (2002)
  • W. Hassfeld et al.

    Demonstration of a new antinuclear antibody (anti-RA33) that is highly specific for rheumatoid arthritis

    Arthritis Rheum

    (1989)
  • G. Steiner et al.

    Purification and partial sequencing of the nuclear autoantigen RA33 shows that it is indistinguishable from the A2 protein of the heterogeneous nuclear ribonucleoprotein complex

    J Clin Invest

    (1992)
  • G. Steiner et al.

    Clinical and immunological aspects of autoantibodies to RA33/hnRNP-A/B proteins–a link between RA, SLE and MCTD

    Mol Biol Rep

    (1996)
  • T. Mimori et al.

    Autoantibodies to calpastatin (an endogenous inhibitor for calcium-dependent neutral protease, calpain) in systemic rheumatic diseases

    Proc Natl Acad Sci USA

    (1995)
  • A.H. Mulder et al.

    Antineutrophil cytoplasmic antibodies in rheumatoid arthritis. Characterization and clinical correlations

    Arthritis Rheum

    (1993)
  • A. Schnabel et al.

    Anti-neutrophil cytoplasmic antibodies in generalized autoimmune diseases

    Int Arch Allergy Immunol

    (1996)
  • R.S. Warlow

    Antibodies to extractable nuclear antigens (ENA) in rheumatoid arthritis assayed by ELISA. A clinicopathological correlation

    Scand J Rheumatol

    (1986)
  • J. Ronnelid et al.

    Local anti-type II collagen antibody production in rheumatoid arthritis synovial fluid. Evidence for an HLA-DR4-restricted IgG response

    Arthritis Rheum

    (1994)
  • M.C. Boissier et al.

    Pattern of humoral reactivity to type II collagen in rheumatoid arthritis

    Clin Exp Immunol

    (1989)
  • M.S. Atta et al.

    Investigation of the prevalence and clinical associations of antibodies to human fibronectin in systemic lupus erythematosus

    Ann Rheum Dis

    (1995)
  • M. Schaller et al.

    Autoantibodies to GPI in rheumatoid arthritis: linkage between an animal model and human disease

    Nat Immunol

    (2001)
  • I. Matsumoto et al.

    Low prevalence of antibodies to glucose-6-phosphate isomerase in patients with rheumatoid arthritis and a spectrum of other chronic autoimmune disorders

    Arthritis Rheum

    (2003)
  • S. Bläss et al.

    Novel 68 kDa autoantigen detected by rheumatoid arthritis specific antibodies

    Ann Rheum Dis

    (1995)
  • S. Bläss et al.

    The stress protein BiP is overexpressed and is a major B and T cell target in rheumatoid arthritis

    Arthritis Rheum

    (2001)
  • S. Bläss et al.

    The p68 autoantigen characteristic of rheumatoid arthritis is reactive with carbohydrate epitope specific autoantibodies

    Ann Rheum Dis

    (1998)
  • S. Bläss et al.

    Rheumatoid arthritis: autoreactive T cells recognising a novel 68k autoantigen

    Ann Rheum Dis

    (1997)
  • M.D. Bodman-Smith et al.

    BiP, a putative autoantigen in rheumatoid arthritis, stimulates IL-10-producing CD8-positive T cells from normal individuals

    Rheumatology (Oxford)

    (2003)
  • V.M. Corrigall et al.

    The human endoplasmic reticulum molecular chaperone BiP is an autoantigen for rheumatoid arthritis and prevents the induction of experimental arthritis

    J Immunol

    (2001)
  • N. Despres et al.

    The Sa system: a novel antigen-antibody system specific for rheumatoid arthritis

    J Rheumatol

    (1994)
  • G. Hayem et al.

    Anti-Sa antibody is an accurate diagnostic and prognostic marker in adult rheumatoid arthritis

    J Rheumatol

    (1999)
  • W. Hueber et al.

    Sensitivity and specificity of anti-Sa autoantibodies for rheumatoid arthritis

    Rheumatology (Oxford)

    (1999)
  • Cited by (109)

    • Anti -citrullinated peptide antibodies profiling in established rheumatoid arthritis

      2018, Joint Bone Spine
      Citation Excerpt :

      The method currently more often employed for ACPA detection, the CCP2 assay, is endowed with high sensitivity, comprised between 70 and 80%, with a specificity of 95%. Such sensitivity is probably explained by the assay format, employing several citrullinated epitopes, at least in part derived from the screening of a citrullinated peptide library [15]. Every assay based on a single citrullinated epitope displays in fact a lower sensitivity and the clinical utility of dissecting the ACPA repertoire by the use of multiplex assays has been questioned.

    • Structure-based design of peptide inhibitors for protein arginine deiminase type iv (PAD4)

      2018, Encyclopedia of Bioinformatics and Computational Biology: ABC of Bioinformatics
    • HLA-DRB1 alleles in Egyptian rheumatoid arthritis patients: Relations to anti-cyclic citrullinated peptide antibodies, disease activity and severity

      2016, Egyptian Rheumatologist
      Citation Excerpt :

      Best well known are the rheumatoid factors (RFs), which are antibodies against the Fc part of the immunoglobulin (IgG) molecules. They are not specific for RA; however, the detection of RF (IgM) is used in RA diagnosis [8]. Yet, anti-cyclic citrullinated peptide (anti-CCP) antibodies are highly specific markers for diagnosis of RA [9], preceding the appearance of the disease [10] and are reported to be good predictors for the development of RA [9].

    • Birds, babies and blood

      2013, Molecular Immunology
      Citation Excerpt :

      One of several anti-neutrophil cytoplasmic antibodies, that recognising proteinase 3, shows high sensitivity and specificity for the granulomatous small vessel necrotizing vasculitis (formerly called Wegener's granulomatosis), and correlates well with disease activity and response to treatment (Bosch et al., 2006; Kallenberg, 2008). Most recently, it has been found that the recent ELISA methods for detecting antibodies to cyclic citrullinated peptides are just as sensitive but much more specific for rheumatoid arthritis as rheumatoid factor and therefore represent an important diagnostic advance (Kudo-Tanaka et al., 2007; Vossenaar and van Venrooij, 2004). It is also interesting that autoantibodies to mannan-binding lectin may be a more sensitive and specific diagnostic aid than rheumatoid factors (Gupta et al., 2006, 2008).

    View all citing articles on Scopus
    View full text