Proteomics characterization of CENP-B epitope in Moroccan scleroderma patients with anti-centromere autoantibodies
Introduction
Scleroderma, or Systemic sclerosis (SSc), is a rare and severe autoimmune disease of the connective tissue characterized by microvascular lesions and excessive fibrosis of the skin and internal organs [1]. It affects mainly women and its etiology remains unknown so far. There are two forms of the disease; limited and diffused SSc [2]. Several abnormal immune reactions, including the production of auto-antibodies, suggest a disease autoimmune pathogenesis [3]. Antinuclear autoantibodies (ANA) are found in more than 95 % of scleroderma patients [4]. Anticentromere antibodies (ACA) are considered as important diagnostic markers of SSc (20–40 %) [5] and more frequently of the limited cutaneous form of the disease (lcSSc) [6]. Although their role in the pathogenesis of scleroderma is not yet established, ACA can also be detected in patients with other connective tissue diseases [7]. They have been described in 9 to –60% of sera from patients with Primary Biliary Cirrhosis (PBC) [8]. There are three major centromere proteins detected by ACA in the sera of patients suffered from scleroderma; CENP-A, CENP-B and CENP-C [9]. CENP-B is the major centromere auto-antigen recognized by more than 95 % of SSc patients with ACA positive [10]. Studies have demonstrated a high prevalence of CENP-B protein in the sera of patients with PBC [8].
PBC is a rare and chronic cholestatic liver autoimmune disease [11]. Anti-mitochondrial auto-antibodies (AMA) are considered as a hallmark of the disease and usually occurred in 80–95 % of PBC patients [3]. However, they are also reported in 25 % of patients with SSc [12].The coexistence of SSc and PBC has been reported by several studies [[12], [13], [14], [15]]. The prevalence of negative PBC-AMA is relatively high when combined with SSc or other autoimmune diseases [16]. However, there is no cross-reaction between ACA and AMA since no evidence of antigenic targets shared between these both auto-antibodies has been reported [17].
To the best of our knowledge, studies about scleroderma in the North African population and especially in Moroccan patients are scarce [[18], [19], [20], [21]]. Only one retrospective report about the prevalence of anti-centromere auto-antibodies in Moroccan scleroderma patients has been published [22]. The current work aims to study, for the first time in Morocco, the immune response against the centromeric protein CENP-B in order to identify the major epitope involved in the immune response of patients with SSc.
Section snippets
Patients and serum collection
This study includes 80 patients diagnosed with SSc and SLE in the Internal Medicine Department at the University Hospital Center Ibn Sina (Rabat, Morocco) during the period from December 2011 to December 2013. The diagnosis was reached based on clinical and serological features of both diseases according to the classification criteria of ACR [23], by an internist doctor, after elimination of differential diagnoses. These criteria included skin thickening, Raynaud’s phenomenon and SSc-related
Antinuclear auto-antibodies analysis
The presence of ANA was determined in all sera using IFA in Hep2 cells. Among 80 patients 73 had positive ANA and 11 sera were found ACA positive (Fig. 1). Regarding PBC-related antibodies, one patient had an aspect of anti-gp210/nuclear pore complex antibodies and another had aspect of anti-sp100 antibodies (data not presented). In order to verify these results, sera of these 11 scleroderma patients with positive ACA were examined for PBC-associated antibodies AMA-M2 on rat tissue section.
Discussion
The current work includes 80 Moroccan patients diagnosed with SSc and SLE in the University Hospital Center Ibn Sina, Rabat. We performed Western blot analysis in order to test for anti-CENPB autoimmune response in these patients. The CENP-B protein is a major target for SSc patients with positive ACA. Earnshaw et al. have shown that there are at least five independent epitopes on CENP-B recognized by ACA [25]. The 147-carboxyl-terminalamino acids of CENP-B contain at least two epitopes, and
Conclusion
Our study is the first conducted in Morocco and the findings showed that the Nt-CENPB auto-antigen was the dominant auto-epitope in our series. The identification of the centromere antigenic targets may contribute to better understanding the ANA response in SSc patients and could be beneficial for the diagnosis and monitoring of these patients. However, our data provide preliminary findings that need more investigations with extra samples from SSc patients from multicenter to validate and
Declaration of Competing Interest
The authors have declared no conflict of interest.
Acknowledgment
The authors would like to acknowledge Professor Manuel M. VALDIVIA Professor of Biochemistry and Molecular Biology at the Department of Biomedicine, Biotechnology and Public Health, Faculty of Sciences, Cadiz –Spain, for providing them the Nt-CENPB and Ct-CENPB antigens as well as anti-human antibodies.
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Clinical and serological correlation of systemic sclerosis in Moroccan patients
2023, Rheumatology Advances in Practice
- 1
These authors are both supervisors of this work.