Tunisian Study on Anti-MCV in Psoriasis

2009/09/23 - News from medical groups

The increased serum levels of anti-mutated citrullinated vementin antibodies (anti-MCV) in psoriasis correlates with severity and disease duration.

S.Samoud1, 2, Y.Galai2, L.Lachheb3, C.Belajouza3, M.Denguezli3, R.Nouira3, J.Boukadida1

1. Laboratory of Immunology, Farhat Hached Hospital. Sousse, Tunisia
2. Laboratory of Immunology, Institut Pasteur de Tunis, Tunisia
3. Department of Dermatology, Farhat Hached Hospital. Sousse, Tunisia

Background Antibodies directed against citrullinated vimentin are members of the family of autoantibodies reactive with citrullinated proteins and are among the most specific serological markers for the diagnosis of rheumatoid arthritis (RA). There are recent finding of secernation and modification of vimentin by macrophages depending on pro-inflammatory signals. Psoriasis is at one and the same time a chronic inflammatory skin and autoimmune disease. Moreover, a part of patients with longstanding psoriasis will develop psoriatic arthritis (PsA) which seems to have some common characteristics with RA.

ObjectiveThe aim of this study was to assess the prevalence of anti-mutated citrullinated vementin antibodies (anti-MCV) in psoriasis and to compare it with this of healthy controls (HC).

Patients and Methods Serum anti-MCV was measured in 52 patients with psoriasis and 30 healthy controls (HC). Anti-MCV were detected by second-generation ELISA. Using the PASI score, the patients were composed of 25 subjects suffering from a severe psoriatic form (PASI score>20) and 27 from a common one. Statistical analysis was performed using the non parametric Mann-Whitney test. Significance was assigned to p values lower than 0.05.

Results Anti-MCV were detected in all psoriatic patients but only in two HC and with weak levels (p<10-3). Their title significantly correlated with the disease activity score (PASI) (p=0.05). Moreover, when we looked for disease duration, we observed that anti-MCV levels depending of this parameter. In fact, their strongly increase with a disease duration longer than ten years (n=10) as compared with a less of ten years one (n=42), (p=0.023).

Conclusion. This surprising high prevalence of anti-MCV could be explained, in one hand, by the less specificity of these antibodies compared with anti-cyclic citrullinated peptide antibodies (anti-CCP) in RA. In the other hand, they would be the reflection of general chronic inflammation rather than joint inflammation only. Finally, this result should push us to study the real role of macrophage, the producer of MCV, in psoriasis.

KEY-WORDS: Psoriasis, rheumatoid arthritis, anti-mutated citrullinated vementin antibodies (anti-MCV)

BACKGROUND

Antibodies directed against citrullinated vimentin (anti-MCV) are members of the family of autoantibodies reactive with citrullinated proteins and are among the most specific serological markers for the diagnosis of rheumatoid arthritis (RA) 1. There are recent findings of modification of vimentin by macrophages depending on pro-inflammatory signals2. Psoriasis is a chronic inflammatory skin disease with an autoimmune aetiology. Moreover, a part of patients with longstanding psoriasis will develop a psoriatic arthritis (PsA) which seems to have some common characteristics with RA. The aim of this study was to assess the prevalence of anti-mutated citrullinated vimentin antibodies (anti-MCV) in psoriasis patients and in healthy controls (HC).

MATERIAL AND METHODS

I-Materials

Patients and Controls

Serum samples from 52 patients with psoriasis were analysed. All patients were seen at the Department of Dermatology, Farhat Hached Hospital, Sousse, Tunisia. At the time of sampling, all the patients didn’t receive any specific treatment for their disease. The median age was 38 years [between 10-77 years]. Twenty-six patients were female and 26 male. Using the PASI score, the patients were composed of 25 subjects suffering from a severe psoriatic form (PASI score>20) and 27 from a common one. Patients were also divided in two groups depending on disease duration: less than 10 years (n= 42) and more than 10 years (n=10). Sera from 30 healthy controls (HC) volunteers’ age and sex matched were also included.

II-Methods

Anti-MCV ELISA

The screening of sera for anti-MCV antibodies was done by an Immunometric Enzyme Immunoassay kit (Orgentec Diagnostika GmbH, Mainz, DE) according to the manufacturer instructions. Briefly, standards and serum samples were added to microplate wells pre-coated with MCV. Next, Horseradish peroxidase (HRP) conjugated anti-human IgG immunologically detects the bound patient antibodies forming a conjugate/antibody/antigen complex. Washing of the microwells removes unbound conjugate. An enzyme substrate in the presence of bound conjugate hydrolyzes to form a blue color. The addition of an acid stops the reaction forming a yellow end-product. The intensity of this yellow color is measured photometrically at 450 nm. The amount of colour is directly proportional to the concentration of IgG antibodies present in the original sample. The concentration of unknowns may then be estimated from the calibration curve by interpolation. Sera with anti-MCV titer > 20 U/mL was considered positive.

Statistical analysis

Statistical analysis was performed using the non parametric Mann-Whitney-U test, statistical significance was assigned to p values lower than 0.05. Correlation between serum anti-MCV levels and disease activity was assessed by Spearman’s correlation coefficient.

RESULTS

Anti-MCV were detected in all psoriatic patients but only in one HC. The level of serum anti-MCV was significantly increased in patients with psoriasis compared to HC (p<10-3). In fact, the mean level in Ps sera including sPs and cPs was 95.98 +/- 55.79U/ml whereas in HC was 17.81+/-24.79 U/ml (Figs1).

More interestingly, the elevation in serum anti-MCV was associated with severity (P<0.05, Fig 2) and disease duration (P=0.023, Fig 3)

DISCUSSION

Biological tests could bring an invaluable help to pose precociously positive diagnosis. They could distinguish without ambiguity two affections sharing a lot of semiological similarity: RA and PsA. Anti- cyclic citrullinated peptide antibodies (anti-CCP) are highly specific of rheumatoid arthritis (RA). They are detected very early and have a predictive value on the clinical evolution of this disease1. Anti-MCV are members of the family of autoantibodies reactive with citrullinated proteins and are among the most specific serological markers for the diagnosis of rheumatoid arthritis (RA). However, anti-CCP would be higher than in RA3.

Thus, it was interesting to study the profile of anti-MCV, not yet established in PsA and cutaneous forms of psoriasis. The objectified positivity of all our patients for these antibodies was striking. Indeed, it was reported that their prevalence varied only between 23 and 62.5% among patients suffering from RA4. Moreover, we found that their rates are correlated with the severity of the disease. They would be associated, not only with the rheumatic form of the psoriasis, but also with its cutaneous forms and would be correlated with the activity of these forms. Vimentin has also been shown to be a target for an autoimmune reaction, not only in rheumatic diseases but also in bacterial, parasitic and viral infections5. It is increasingly allowed that psoriasis pathogenesis accuses microbial factors6. In addition, several autoantibodies directed against some target proteins are modified at the time of cellular death in particular at the time of the apoptosis7. These self modified proteins wouldn’t be any more recognized by the immune system and would be regarded as non self proteins8. Vimentin would probably undergo such modifications in psoriasis where apoptosis process is particularly active as well as the cytotoxic immune mechanism2.

Other studies already showed that unmasking of hidden antigens after cell injury during the inflammatory process of disease may lead to sensitization and antibody production. Then, the resulting antibody–antigen interaction with immune complex formation could have a significant role in the perpetuation of the disease processes, either by direct injury of fibroblasts, myofibroblasts, or via local macrophage activation2. Although the initiating events in autoantibody production remain unknown, there is increasing evidence that apoptotic cells may serve as reservoirs of these autoantigens9. In addition, human keratinocytes induced to undergo apoptosis demonstrate clustering of autoantigens at the cell surface membrane10. So, psoriasis, a chronic inflammatory skin disorder resulting from an abnormal interaction between T lymphocytes and keratinocytes could constitute a reservoir of such autoantigens, in particular anti-MCV ones, sitting on affected keratinocytes cell membrane.

Our results showed surprisingly that all our psoriasis patients had anti-MCV. This could be explained by the lower specificity of these antibodies compared to anti-CCP which are highly specific in RA. In the other hand, they would rather reflect a state of a chronic inflammation than a specific joint inflammation. Finally, this result will encourage us to study the role of macrophage (producer of MCV) in psoriasis.

REFERENCES

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6. Michelle A. Lowes, Anne M. Bowcock, James G. Krueger.Pathogenesis and therapy of psoriasis. NATURE 2007; 445: 866-874.
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8. Rodenburg RJ, Raats JM, Pruijn GJ, van Venrooij WJ: Cell death: a trigger of autoimmunity? Bioessays 2000, 22:627-636.
9. Mevorach D, Zhou J, Song X et al. Systemic exposure to irradiated apoptotic cells induces autoantibody production. J Exp Med 1998; 188:387–92.
10. Casciola-Rosen LA, Anhalt G, and Rosen A. Autoantigens targeted in systemic lupus erythramatosus are clustered in two populations of surface blebs on cultured keratinocytes. J Exp Med 1994; 179:1317–30.

Correspondence:

Samar Samoud-El Kissi, MD

Laboratory of Clinical Immunology, Institut Pasteur de Tunis,

University of Sousse School of Medicine

Laboratory of Immunology and Microbiology, Farhat Hached Hospital,

Email: samarsamoud@voila.fr

Tel:(216)96085513/(216)73221411

Fax: (216) 73226702