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Anti-chromatin (anti-nucleosome) antibodies: Diagnostic and clinical value
Autoimmunity Reviews 7 (2008) 606–611
Contents lists available at ScienceDirect
Autoimmunity Reviews j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / a u t r ev
Anti-chromatin (anti-nucleosome) antibodies: Diagnostic and clinical value José A. Gómez-Puerta a, Rufus W. Burlingame b, Ricard Cervera a,⁎ a b
Department of Autoimmune Diseases, Hospital Clínic, Barcelona, Catalonia, Spain INOVA Diagnostics, Inc., San Diego, CA 92131, USA
a r t i c l e
i n f o
Available online 9 July 2008 Keywords: Anti-chromatin antibodies Anti-nucleosome antibodies Systemic lupus erythematosus
a b s t r a c t Anti-chromatin (nucleosome) autoantibodies were one of the first autoantibodies ever detected since they make up the majority of antibodies causing LE Cell formation. The prevalence of anti-chromatin antibodies in systemic lupus erythematosus (SLE) varies from 50% to 100%, being similar to that of the classical positive LE cell. The presence of these antibodies can be used, in conjunction with clinical findings and other laboratory tests, to help in the diagnosis of SLE and drug-induced lupus. Anti-chromatin antibodies have also been found in a lesser percentage of other autoimmune disorders such as primary Sjögren's syndrome and primary antiphospholipid syndrome. The presence of anti-chromatin antibodies has also been linked to glomerulonephritis and disease activity in SLE patients. Recent studies demonstrated the induction of anti-chromatin (anti-nucleosome) antibodies after an anti-tumour necrosis factor (TNF)-alpha agent treatment. © 2008 Elsevier B.V. All rights reserved.
Contents 1. 2. 3. 4. 5.
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chromatin, nucleosomes and histones . . . . . . . . . . . . . . . . . Anti-chromatin antibodies in murine models . . . . . . . . . . . . . . Techniques to measure anti-chromatin antibodies . . . . . . . . . . . Clinical utility . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1. Anti-chromatin antibodies in SLE . . . . . . . . . . . . . . . . 5.2. Anti-chromatin antibodies in other autoimmune diseases . . . . 6. Anti-chromatin (anti-nucleosome) and anti-tumour necrosis factor agents 7. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Take-home messages . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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1. Introduction
Abbreviations: aCL, anticardiolipin;anti-ds-DNA, double-stranded-DNA antibodies;DNP, deoxyribonucleoprotein;DIL, drug-induced lupus;ELISA, enzyme-linked immunosorbent assay;RA, rheumatoid arthritis;SLE, systemic lupus erythematosus. ⁎ Corresponding author. Servei de Malalties Autoimmunes, Hospital Clínic, Villarroel, 170, 08036-Barcelona, Catalonia, Spain, Tel./fax: +34 93 227 5774. E-mail address: [email protected] (R. Cervera). 1568-9972/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.autrev.2008.06.005
Systemic lupus erythematosus (SLE) is the most diverse of the autoimmune diseases and it is characterized by the production of multiple autoantibodies [1]. The initial description of the LE cell test by Hargraves in 1948 was one of the first laboratory abnormalities associated with SLE [2]. Today, the spectrum of autoantibodies detected in SLE is wide and complex [3]. The prevalence of anti-chromatin (nucleosome) antibodies in SLE varies from 50% to 100% [4,5], being similar
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to that of positive LE cell [6]. The presence of these antibodies can be used, in conjunction with clinical findings and other laboratory tests, to help in the diagnosis of drug-induced lupus (DIL) and SLE. The presence of anti-chromatin antibodies has also been linked to glomerulonephritis in SLE patients [7]. 2. Chromatin, nucleosomes and histones Chromatin, the native complex of histones and DNA found in the cell nucleus of eukaryotes, is comprised of approximately 40% DNA, 40% histones and 20% non-histone proteins, RNA and other macromolecules. The fundamental subunit of chromatin is the nucleosome, which is composed of approximately 200 base pairs of DNA wrapped twice around the (H2A–H2B–H3–H4)2 histone octamer, with histone H1 bound on the outside (Fig. 1) [8,9]. The periodic arrangement of histones along the DNA gives chromatin a ‘beads-on-a string’ appearance in electron micrographs. The ‘beads’ can be isolated by digesting the linker DNA between them with micrococcal nuclease, yielding nucleosomes. Further digestion of nucleosomes and washing them in moderate ionic strength yields nucleosome core particles in which 146bp of helical DNA are wrapped around an octamer made up of two H2A–H2B dimers that surround an H3–H4 tetramer [8]. Histones are small proteins containing a high percentage of the positively charged amino acids, lysine and arginine. The mechanisms that underlie the induction of anti-histone antibodies are not clearly understood although a number of theories have been proposed to account for their origin. One of the strongest is that anti-histone antibodies are driven by endogenous nucleosomes that activate the immune system under certain circumstances such as in the presence of drug interactions or environmental agents, or during infection [7,10]. Antibodies reactive with histone epitopes that are present only in native chromatin and antibodies reactive with epitopes exposed only on denatured histones have both been reported as “anti-histone antibodies”. This makes the definition of anti-histone antibodies confusing. For clarity, only
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antibodies that react with structures found on the native histone–DNA complexes should be called “anti-chromatin antibodies” [11]. 3. Anti-chromatin antibodies in murine models A number of studies of lupus-like murine models have found genetic loci, such as SLE1, that are linked to the presence of anti-chromatin antibodies [12, reviewed in 7]. Li et al. [13] induced lupus-like syndrome in BALB/c mice after immunization with active chromatin. Mice developed antidouble-stranded-DNA antibodies (ds-DNA), anti-singlestranded-DNA (anti-ss-DNA) antibodies and anti-histone antibodies as well as a severe renal Ig deposition, mostly glomerular. Studies in knock-out mice (for C1q, serum amyloid P [SAP] and Dnase I) have demonstrated that impaired phagocytosis of apoptotic material may lead to an autoimmune response against chromatin and in some occasions glomerulonephritis (reviewed in [7,10]). SAP is another mediator related to the removal of apoptotic cells. SAP-deficient mice have high titer anti-chromatin antibodies, but no glomerulonephritis [14]. Further studies with knock-out mice models should target different alterations of apoptotic mechanisms and clarify their role as potential triggers of an anti-chromatin response with subsequent disease induction. 4. Techniques to measure anti-chromatin antibodies A number of techniques have been used to measure antichromatin antibodies, including the LE cell test, latex agglutination of chromatin-coated beads, immunoprecipitation, reconstitution of acid extracted tissue reactions and ELISA [11]. The most useful forms of chromatin to use as the antigen in ELISA are H1-stripped chromatin and nucleosome core particles. In both cases, the native chromatin is solubilized by digestion with micrococcal nuclease, and H1 and non-histone proteins are removed by extracting the chromatin with 0.5M NaCl at neutral pH. The nucleosome core particle consists of DNA wrapped around the native histone (H2A, H2B, H3, H4) octamer. Poly-nucleosome core particles, in which the linker DNA is not cut by the nuclease, is called H1-stripped chromatin. For ELISA, the cut-off between positive and negative should be determined by a nonparametric statistical technique such as rank order or area under the curve because the distribution of normal people and disease control groups is not shaped like a standard bell curve. Thus, statistical techniques such as average and standard deviation are inappropriate. 5. Clinical utility 5.1. Anti-chromatin antibodies in SLE
Fig. 1. The structure of chromatin and the production of nucleosome core particles. In chromatin, the DNA is wrapped around the core histone (H2A– H2B–H3–H4)2 octamer, and histone H1 and non-histones are bound to the DNA. After treatment with micrococcal nuclease and 0.5 M NaCl the linker DNA is digested and H1 and non-histones are removed, leaving the nucleosome core particle. H1-stripped chromatin is a polymer of nucleosome core particles in which some of the linker DNA is not digested.
The two most important recurring observations concerning anti-chromatin antibodies are that this antibody is sensitive and specific for SLE and DIL, and the presence of anti-chromatin antibodies is often correlated with glomerulonephritis in patients with SLE. The findings that immune complexes comprising chromatin and anti-chromatin antibodies can deposit in the glomerular basement membrane of
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the kidney [10], and that anti-chromatin antibodies are a necessary component for the development of glomerulonephritis in one strain of mouse [12], provide theoretical evidence that anti-chromatin antibodies can have pathological properties in some patients with SLE. Anti-chromatin antibodies have been measured in several clinical studies with US, European, Asian, Latin American and South African SLE patients [4,5,15–25]. In most of them, a series of other autoimmune diseases were used as controls. Data of these series is collected in Table 1. According to these series, anti-chromatin antibodies have a sensitivity range between 48 and 100% and a specificity between 90 and 99%. Regarding clinical associations, anti-chromatin antibodies were related with renal involvement [4,15,16,18,20,23] and, in a less proportion, with hematological involvement [18,22], or arthritis, malar rash, pleuritis and oral ulcers [23]. Antichromatin antibodies were correlated with disease activity measured by SLEDAI in three different studies [17,20,23]. Anti-chromatin reactivity is detected in patients with active SLE at a frequency similar to that for anti-ds-DNA antibodies, while it is less in inactive SLE [15,28]. Anti-chromatin antibodies correlated positively with anti-ds-DNA antibody titers [16,18–20,22]. Interestingly, anti-chromatin antibodies were positive in some patients who were negative for anti-dsDNA antibodies. This particular situation was found by Burlingame et al. [4], Cervera et al. [16], Cairns et al. [18], Gómez-Puerta et al. [19], Min et al. [20] Braun et al. [24] and Su et al. [26] in 35%, 20%, 21%, 12%, 11%, 23% and 51% of cases, respectively. Ghillani-Dalbin et al. [29] studied a large population of 1696 patients with autoimmune diseases. The authors tested them for a series of antibodies, including anti-ds-DNA antibodies, antinuclear antibodies (ANA) and anti-nucleo-
some antibodies. A high proportion of SLE patients [240/307 (78%)] were positive for anti-nucleosome antibodies. Only a small percentage of patients with other autoimmune diseases were positive for anti-nucleosome antibodies. Interestingly enough, 43 patients in the SLE group were positive for anti-nucleosome antibodies and negative for anti-ds-DNA antibodies. Cortés-Hernández et al. [30] analyzed the presence of anti-nucleosome, anti-histone and anti-DNA antibodies by ELISA in a series of 199 patients with SLE, with special emphasis in those with or without renal involvement. IgG anti-nucleosome antibodies were higher in those patients with active disease, lupus nephritis and active proliferative lesions on renal biopsy (type II, III and IV vs type V nephropathy). When the authors analyzed the development of proliferative glomerulonephritis during follow-up, only those patients positive at baseline for anti-histone antibodies had a higher risk. Anti-nucleosome antibodies have also been measured in juvenile SLE patients. Campos et al. [27] analyzed the presence of anti-nucleosome antibodies in 74 Brazilian children and adolescents (mean age 14years) with SLE. Fifty-two percent of patients were positive for anti-nucleosome antibodies. Those antibodies were correlated with malar rash, hematological involvement, and decreased serum complement levels. Additionally, a significant association was found between anti-nucleosome antibodies and SLEDAI score. Only a moderate correlation was found between anti-nucleosome and anti-ds-DNA antibodies. There was no correlation with renal involvement. There is limited information about successive determination of anti-chromatin antibodies in SLE. Grootscholten et al. [31] evaluated in a prospective manner the presence of anti-
Table 1 Clinical studies of anti-chromatin (nucleosome) antibodies in patients with SLE Author (reference)
Population
SLE
Controls AD
Healthy
Amoura et al. [15]
France
120
376
406
Cervera et al. [16] Schett et al. [17] Cairns et al. [18]
Catalonia Austria Nother Ireland
100 73 95
140 348 48
100 27 95
Gómez-Puerta et al. [19] Min et al. [20]
Colombia Korea
90 129
45 –
– 50
Hmida et al. [21] Ghirardello et al. [22] Simon et al. [23]
Luxemburg Italy Mexico
32 101 73
52 85 261
– 100 130
Braun et al. [24]
Germany
78
141
–
Tikly et al. [25]
South Africa
86
57
30
Su et al. [26]
Chinese
220
31
Campos et al. [27]
Brasil
–
64
233 74
Clinical associations
Laboratory correlations
Anti-Chr + ve anti-ds-DNA − ve
Nephropathy a Disease activity b Nephropathy No Nephropathy Hematological No Nephropathy Disease activity b NR Hematological Nephropathy, AR MR, OU, Pleur Disease activity b Disease activity b
NR
NR
72
90
ds-DNA ds-DNA
20/100 (20%) NR 20/95 (21%)
69 48 64
92 95 99
ds-DNA ds-DNA
11/90 (12%) 15/129 (11%)
73 76
95 98
NR ds-DNA NR
NR NR NR
81 86 100
97 95 97
ds-DNA c C1q antibodies c ds-DNA IgG aCL Proteinuria Leukopenia ds-DNA Low complement
18/78 (23%)
64
99
NR
45
94
64/125 (51%)
61
97
9/74 (12%)
53
98
Skin involvement Disease activity MR, arthralgia Disease activity Hematological MR
Sensitivity (%)
Specificity (%)
aCL: anticardiolipin antibodies, AR: arthritis, AD: autoimmune diseases, ds-DNA: double-stranded-DNA antibodies, MR: malar rash, NR: not reported, OU: oral ulcers, Pleur: pleuritis. a Only for IgG3 isotype. b Disease activity measured by SLEDAI. c Only in patients with lupus nephritis.
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chromatin antibodies in 87 patients with proliferative lupus nephritis treated with cyclophosphamide (CYC) pulses or azathioprine (AZA). At baseline, anti-chromatin antibodies were positive in 81% of patients. A significant correlation was found between anti-chromatin and anti-ds-DNA antibodies. No significant differences were found for serum creatinine levels or proteinuria and anti-chromatin antibody levels. Anti-chromatin reactivity declined over time. However, it remained above the cut-off in most patients. No differences between CYC and AZA were found on the course of autoantibody titers. The authors concluded that anti-chromatin antibodies are useful for diagnosis of lupus nephritis but not for monitoring disease course or treatment. Anti-chromatin antibodies are also useful to help diagnose DIL, especially in procainamide, quinidine and hydralazine induced lupus. A few other drugs rarely cause DIL, and these patients often have anti-chromatin antibody reactivity [11]. 5.2. Anti-chromatin antibodies in other autoimmune diseases Anti-chromatin antibodies have been found in other autoimmune diseases including systemic sclerosis (SSc), Sjögren's syndrome (SS) and mixed connective tissue disease (MCTD), but in a much smaller percentage than in SLE patients [15–17]. In some studies, anti-chromatin autoantibodies were not found in other connective tissue diseases [21,32]. When H1-stripped chromatin or nucleosome core particles are used as the antigen, and an appropriate cut-off between positive and negative is used, anti-chromatin antibodies are very specific for SLE, DIL and autoimmune hepatitis (AIH) type I [12]. In a recent study, Braun et al. [24] determined anti-chromatin antibodies and anti-C1q antibodies in 78 SLE patients and in 141 patients with other autoimmune disease (including small vessel vasculitis, SS and SSc). Anti-chromatin antibodies were much more specific for SLE than anti-C1q antibodies (specificity 99% vs 72%). Antichromatin was positive in only 1 patient with SS and was not found in patients with small vessel vasculitis or SSc. Anti-chromatin antibodies are found in 40%–50% of people with AIH type I [28,29]. Anti-chromatin antibodies were not found by Cacoub et al. [32] in any of 46 patients with hepatitis C infection with or without cryoglobulinemia, 22 patients with cryoglobulinemia but not hepatitis C, or 96 healthy controls. Li et al. [33] tested anti-chromatin antibodies in 36 Japanese patients with AIH type 1, 53 with primary biliary cirrhosis (PBC), 37 with chronic hepatitis C and 15 with chronic hepatitis B. The authors found a significantly higher frequency of anti-chromatin antibodies in patients with AIH, 19/36 (53%), in comparison with patients with PBC, chronic hepatitis C, and chronic hepatitis B (13%, 5.4% and 6.7%, respectively). They suggest that anti-chromatin antibodies cannot discriminate different subgroups of patients with AIH. This is in contrast with the findings of Czaja et al. [34] who found anti-chromatin more often in AIH patients with active disease who commonly relapsed after cessation of immunosuppressive therapy. Anti-chromatin antibodies have been measured in primary APS patients [16,35,36]. Cervera et al. [16] determined anti-chromatin antibodies in 30 patients with primary APS, and only 2 patients were positive. Abraham Simón et al. [35] analyzed the presence of anti-nucleosome antibodies in 18 patients with primary APS with a mean follow-up of 12years.
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Nine (50%) out of 18 patients were positive for antinucleosome antibodies. Of them, 6 developed clinical features of SLE after a mean primary APS duration of 9years. The presence of anti-nucleosome antibodies at the moment of primary APS diagnosis was related with the subsequent development of SLE. Recently, Andreoli et al. [36] analyzed the presence of anti-nucleosome antibodies (using H1-stripped chromatin as antigen) in a cohort of 105 Italian patients with primary APS. Samples were tested for IgG and IgM antinucleosome antibodies using a home-made ELISA. Forty-eight (45%) patients exhibited lupus-like features. Eighty-one (77%) out of 105 patients were positive for either IgG or IgM or both isotypes. Only medium and high titers of anti-nucleosome were weakly related to anti-ds-DNA antibodies. Forty-eight patients were tested for anti-nucleosome during the followup. The majority of patients displayed a stable course of antinucleosome. Only 10 of them became either negative or positive during the follow-up. Finally, the authors remarked that anti-nucleosome antibodies appear in early stages of the disease and could be a useful marker to identify those patients with primary APS and lupus-like features who will develop SLE in the future. 6. Anti-chromatin (anti-nucleosome) and anti-tumour necrosis factor agents Tumour necrosis factor (TNF)-α inhibitors (adalimumab, etanercept, infliximab) have proven to be highly effective in the treatment of several autoimmune diseases, mainly rheumatoid arthritis. They reduce disease activity and delay radiographic progression, with quite a good safety profile. Side effects of anti-TNF-α treatment include an increased risk for infection and induction of autoantibodies such as ANA, anti-ds-DNA, aCL and anti-chromatin antibodies. Eriksson et al. [37] analyzed the autoantibody formation in 59 RA patients treated with an anti-TNF-α agent (53 with infliximab and 6 with etanercept). Several autoantibodies were measured, including rheumatoid factor, ANA, antiextractable nuclear antigens antibodies, anti-nucleosome antibodies, anti-ds-DNA antibodies, aCL, anti-proteinase-3 and anti-myeloperoxidase antibodies. In patients treated with infliximab, anti-nucleosome antibodies were positive at baseline in 5/50 (10%) patients, while at 30 weeks in 13/50 (26%) and at 54 weeks in 10/40 (25%) patients. Additionally, the frequency of autoantibodies against ANA, anti-ds-DNA antibodies increased significantly during treatment with infliximab. No patients treated with etanercept developed any of the autoantibodies tested for in this study. Benucci et al. [38] analyzed the induction of antinucleosome, ANA and anti-ds-DNA in a series of 91 patients with RA that received an anti-TNF-α agent (19 infliximab, 43 etanercept and 29 adalimumab). Autoantibodies were measured at baseline and after 12 and 24 weeks of treatment. Anti-nucleosome positivity increased in the 3 groups, from 5% to 16% and 31% respectively in the infliximab group; from 5% to 7% and 25% respectively in the etanercept group; and from 7% to 10% and 14% respectively in the adalimumab group. In general terms, adalimumab showed a lower induction rate of autoantibodies. Information about anti-TNF-α treatment in SLE is limited. Aringer et al. [39] analyzed the autoantibody profile in 7 SLE
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patients treated with infliximab at baseline and after 12, 24 and 36 weeks. Infliximab treatment increased anti-chromatin antibodies in 6 out of 7 patients, peaking between 4 and 10 weeks after the last infliximab infusion, but falling to baseline levels or lower thereafter. These transient increases were without pathological consequences. 7. Conclusions Most studies have found that anti-chromatin antibodies are very sensitive and specific markers of SLE. In patients with SLE there is a statistically significant correlation between antichromatin antibodies and renal involvement. Anti-chromatin reactivity is a useful marker to help in the diagnosis of people who are anti-ds-DNA negative but have SLE. Additionally, anti-chromatin antibodies are helpful in diagnosing DIL, as well as possibly identifying patients with autoimmune hepatitis who commonly relapse after immunosuppressive drugs are removed. Recent studies suggest a correlation between disease activity measured by SLEDAI and the presence of anti-chromatin antibodies. Anti-chromatin antibodies are useful for diagnosis but its role in monitoring of the disease is still limited. Patients exposed to anti-TNF-α agents induce the formation of anti-chromatin antibodies, though these seem to have no clinical relevance. Take-home messages • Anti-chromatin antibodies are a very helpful marker in supporting the diagnosis of SLE in a patient with an unclear systemic autoimmune disorder. • These antibodies have a high sensitivity (50–100%) and a very high specificity (90–99%) for SLE diagnosis. • Anti-chromatin antibodies are helpful in diagnosing DIL as well as possibly identifying patients with autoimmune hepatitis. • These antibodies are clinically correlated with kidney and disease activity in SLE patients. • Anti-TNF-α agents may induce anti-chromatin antibodies. These increases seem to have no clinical relevance. References [1] Cervera R, Khamashta MA, Font J, et al. Systemic lupus erythematosus: clinical and immunological patterns of disease expression in a cohort of 1000 patients. Medicine (Baltimore) 1993;72:113–24. [2] Hargraves MM, Richmond H, Morton R. Presentation of two bone marrow elements: the “Tart” cell and the “LE” cell. Proc Mayo Clin 1948;23:25–8. [3] Sherer Y, Gorstein A, Fritzler MJ, Shoenfeld Y. Autoantibody explosion in systemic lupus erythematosus: more than 100 different antibodies found in SLE patients. Semin Arthritis Rheum 2004;34:501–37. [4] Burlingame RW, Boey ML, Starkebaum G, et al. The central role of chromatin in the autoimmune responses to histones and DNA in systemic lupus erythematosus. J Clin Invest 1994;94:184–92. [5] Chabre H, Amoura Z, Piette JC, Godeau P, Bach JF, Koutouzov S. Presence of nucleosome restricted antibodies in patients with systemic lupus erythematosus. Arthritis Rheum 1995;38:1485–91. [6] Tan EM, Cohen AS, Fries JF, et al. The 1982 revised criteria for the classification of systemic lupus erythematosus. Arthritis Rheum 1982;25:1271–7. [7] Gómez-Puerta JA, Burlingame RW, Cervera R. Anti-chromatin (antinucleosome) antibodies. Lupus 2006;15:408–11. [8] Luger K, Mader AW, Richmond RK, Sargent DF, Richmond TJ. Crystal structure of the nucleosome core particle at 2.8 A resolution. Nature 1997;389:251–60.
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[33]
[34]
[35]
[36]
in hepatitis C virus infection and mixed cryoglobulinemia. Multivirc Group J Rheumatol 1997;24:2139–44. Li L, Nishioka M, Huang DY, Nishioka M. Frequency and significance of antibodies to chromatin in autoimmune hepatitis type 1. J Gastroenterol Hepatol 2000;15:1176–82. Czaja AJ, Shums Z, Binder WL, Lewis SL, Nelson VJ, Norman GL. Frequency and significance of antibodies to chromatin in autoimmune hepatitis. Dig Dis Sci 2003;48:1658–64. Abraham Simón J, Rojas-Serrano J, Cabiedes J, Alcocer-Varela J. Antinucleosome antibodies may help predict development of systemic lupus erythematosus in patients with primary antiphospholipid syndrome. Lupus 2004;13:177–81. Andreoli L, Pregnolato F, Burlingame RW, Allegri F, Rizzini S, Fanelli V, et al. Antinucleosome antibodies in primary antiphospholipid syndrome: a hint at systemic autoimmunity? J Autoimmun 2008;30:51–7.
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[37] Eriksson C, Engstrand S, Sundqvist KG, Rantapää-Dahlqvist S. Autoantibody formation in patients with rheumatoid arthritis treated with antiTNF alpha. Ann Rheum Dis 2005;64:403–7. [38] Benucci M, Saviola G, Baiardi P, Cammelli E, Manfredi M. Antinucleosome antibodies as prediction factor of development of autoantibodies during therapy with three different TNF alpha blocking agents in rheumatoid arthritis. Clin Rheumatol 2008;27:91–5. [39] Aringer M, Steiner G, Graninger WB, Höfler E, Steiner CW, Smolen JS. Effects of short-term infliximab therapy on autoantibodies in systemic lupus erythematosus. Arthritis Rheum 2007;56:274–9.
Autoantibodies against receptor tyrosine kinase in Chagas’ disease Trypanosoma cruzi, the etiologic agent of Chagas’ disease, induces survival and differentiation of neurons via activation of nerve growth factor receptor tyrosine kinase. Lu et al. (J Immunol 2008;67:603-9) have studied sera from chronic Chagas’ disease patients and observed that some sera recognized receptor tyrosisne kinase of the type A, and family members of this receptor (B and C). The authors have confirmed this specificity using five other growth factor receptors, nerve growth factor, neurotrophins, and Trypanosoma cruzi as antigens. In fact, no reactions was observed with these antigens. This study suggests that patients with Chagas´ disease produce autoantibodies against receptor tyrosine kinase, and it might inhibit cell apoptosis of the host and consequently to promote cell invasion.
Autoantibodies to survivin in chronic hepatitis and hepatocellular carcinoma Previous studies have demonstrated the presence of autoantibodies against tumor-associated antigens, including surviving, in sera from patients with hepatocellular carcinoma. To examine the presence of these antibodies in sera from chronic hepatitis patients, Yagihashi et al. (Autoimmunity 2005;38:445-8), using a recombinant surviving protein in ELISA, have included 57 individuals with chronic hepatitis, 29 with hepatocellular carcinoma and healthy controls. This study demonstrated that 10/57 (17.5%) of chronic hepatitis and 7/29 (24.1%) of liver carcinoma patients had these antibodies. Moreover, the authors have shown that titers of anti-survivin antibodies were higher in patients with hepatocellular carcinoma associated with hepatitis C virus than controls and individuals with this cancer associated with hepatitis B virus infection. On the other hand, no differences were observed regarding anti-survivin in patients with chronic hepatitis caused by C virus and liver carcinoma induced by this virus. This study showed the presence of anti-survivin antibodies in patients with chronic hepatitis and they do not seem to correlate with the progression to hepatocellular carcinoma.
Contents lists available at ScienceDirect
Autoimmunity Reviews j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / a u t r ev
Anti-chromatin (anti-nucleosome) antibodies: Diagnostic and clinical value José A. Gómez-Puerta a, Rufus W. Burlingame b, Ricard Cervera a,⁎ a b
Department of Autoimmune Diseases, Hospital Clínic, Barcelona, Catalonia, Spain INOVA Diagnostics, Inc., San Diego, CA 92131, USA
a r t i c l e
i n f o
Available online 9 July 2008 Keywords: Anti-chromatin antibodies Anti-nucleosome antibodies Systemic lupus erythematosus
a b s t r a c t Anti-chromatin (nucleosome) autoantibodies were one of the first autoantibodies ever detected since they make up the majority of antibodies causing LE Cell formation. The prevalence of anti-chromatin antibodies in systemic lupus erythematosus (SLE) varies from 50% to 100%, being similar to that of the classical positive LE cell. The presence of these antibodies can be used, in conjunction with clinical findings and other laboratory tests, to help in the diagnosis of SLE and drug-induced lupus. Anti-chromatin antibodies have also been found in a lesser percentage of other autoimmune disorders such as primary Sjögren's syndrome and primary antiphospholipid syndrome. The presence of anti-chromatin antibodies has also been linked to glomerulonephritis and disease activity in SLE patients. Recent studies demonstrated the induction of anti-chromatin (anti-nucleosome) antibodies after an anti-tumour necrosis factor (TNF)-alpha agent treatment. © 2008 Elsevier B.V. All rights reserved.
Contents 1. 2. 3. 4. 5.
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chromatin, nucleosomes and histones . . . . . . . . . . . . . . . . . Anti-chromatin antibodies in murine models . . . . . . . . . . . . . . Techniques to measure anti-chromatin antibodies . . . . . . . . . . . Clinical utility . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1. Anti-chromatin antibodies in SLE . . . . . . . . . . . . . . . . 5.2. Anti-chromatin antibodies in other autoimmune diseases . . . . 6. Anti-chromatin (anti-nucleosome) and anti-tumour necrosis factor agents 7. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Take-home messages . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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1. Introduction
Abbreviations: aCL, anticardiolipin;anti-ds-DNA, double-stranded-DNA antibodies;DNP, deoxyribonucleoprotein;DIL, drug-induced lupus;ELISA, enzyme-linked immunosorbent assay;RA, rheumatoid arthritis;SLE, systemic lupus erythematosus. ⁎ Corresponding author. Servei de Malalties Autoimmunes, Hospital Clínic, Villarroel, 170, 08036-Barcelona, Catalonia, Spain, Tel./fax: +34 93 227 5774. E-mail address: [email protected] (R. Cervera). 1568-9972/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.autrev.2008.06.005
Systemic lupus erythematosus (SLE) is the most diverse of the autoimmune diseases and it is characterized by the production of multiple autoantibodies [1]. The initial description of the LE cell test by Hargraves in 1948 was one of the first laboratory abnormalities associated with SLE [2]. Today, the spectrum of autoantibodies detected in SLE is wide and complex [3]. The prevalence of anti-chromatin (nucleosome) antibodies in SLE varies from 50% to 100% [4,5], being similar
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to that of positive LE cell [6]. The presence of these antibodies can be used, in conjunction with clinical findings and other laboratory tests, to help in the diagnosis of drug-induced lupus (DIL) and SLE. The presence of anti-chromatin antibodies has also been linked to glomerulonephritis in SLE patients [7]. 2. Chromatin, nucleosomes and histones Chromatin, the native complex of histones and DNA found in the cell nucleus of eukaryotes, is comprised of approximately 40% DNA, 40% histones and 20% non-histone proteins, RNA and other macromolecules. The fundamental subunit of chromatin is the nucleosome, which is composed of approximately 200 base pairs of DNA wrapped twice around the (H2A–H2B–H3–H4)2 histone octamer, with histone H1 bound on the outside (Fig. 1) [8,9]. The periodic arrangement of histones along the DNA gives chromatin a ‘beads-on-a string’ appearance in electron micrographs. The ‘beads’ can be isolated by digesting the linker DNA between them with micrococcal nuclease, yielding nucleosomes. Further digestion of nucleosomes and washing them in moderate ionic strength yields nucleosome core particles in which 146bp of helical DNA are wrapped around an octamer made up of two H2A–H2B dimers that surround an H3–H4 tetramer [8]. Histones are small proteins containing a high percentage of the positively charged amino acids, lysine and arginine. The mechanisms that underlie the induction of anti-histone antibodies are not clearly understood although a number of theories have been proposed to account for their origin. One of the strongest is that anti-histone antibodies are driven by endogenous nucleosomes that activate the immune system under certain circumstances such as in the presence of drug interactions or environmental agents, or during infection [7,10]. Antibodies reactive with histone epitopes that are present only in native chromatin and antibodies reactive with epitopes exposed only on denatured histones have both been reported as “anti-histone antibodies”. This makes the definition of anti-histone antibodies confusing. For clarity, only
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antibodies that react with structures found on the native histone–DNA complexes should be called “anti-chromatin antibodies” [11]. 3. Anti-chromatin antibodies in murine models A number of studies of lupus-like murine models have found genetic loci, such as SLE1, that are linked to the presence of anti-chromatin antibodies [12, reviewed in 7]. Li et al. [13] induced lupus-like syndrome in BALB/c mice after immunization with active chromatin. Mice developed antidouble-stranded-DNA antibodies (ds-DNA), anti-singlestranded-DNA (anti-ss-DNA) antibodies and anti-histone antibodies as well as a severe renal Ig deposition, mostly glomerular. Studies in knock-out mice (for C1q, serum amyloid P [SAP] and Dnase I) have demonstrated that impaired phagocytosis of apoptotic material may lead to an autoimmune response against chromatin and in some occasions glomerulonephritis (reviewed in [7,10]). SAP is another mediator related to the removal of apoptotic cells. SAP-deficient mice have high titer anti-chromatin antibodies, but no glomerulonephritis [14]. Further studies with knock-out mice models should target different alterations of apoptotic mechanisms and clarify their role as potential triggers of an anti-chromatin response with subsequent disease induction. 4. Techniques to measure anti-chromatin antibodies A number of techniques have been used to measure antichromatin antibodies, including the LE cell test, latex agglutination of chromatin-coated beads, immunoprecipitation, reconstitution of acid extracted tissue reactions and ELISA [11]. The most useful forms of chromatin to use as the antigen in ELISA are H1-stripped chromatin and nucleosome core particles. In both cases, the native chromatin is solubilized by digestion with micrococcal nuclease, and H1 and non-histone proteins are removed by extracting the chromatin with 0.5M NaCl at neutral pH. The nucleosome core particle consists of DNA wrapped around the native histone (H2A, H2B, H3, H4) octamer. Poly-nucleosome core particles, in which the linker DNA is not cut by the nuclease, is called H1-stripped chromatin. For ELISA, the cut-off between positive and negative should be determined by a nonparametric statistical technique such as rank order or area under the curve because the distribution of normal people and disease control groups is not shaped like a standard bell curve. Thus, statistical techniques such as average and standard deviation are inappropriate. 5. Clinical utility 5.1. Anti-chromatin antibodies in SLE
Fig. 1. The structure of chromatin and the production of nucleosome core particles. In chromatin, the DNA is wrapped around the core histone (H2A– H2B–H3–H4)2 octamer, and histone H1 and non-histones are bound to the DNA. After treatment with micrococcal nuclease and 0.5 M NaCl the linker DNA is digested and H1 and non-histones are removed, leaving the nucleosome core particle. H1-stripped chromatin is a polymer of nucleosome core particles in which some of the linker DNA is not digested.
The two most important recurring observations concerning anti-chromatin antibodies are that this antibody is sensitive and specific for SLE and DIL, and the presence of anti-chromatin antibodies is often correlated with glomerulonephritis in patients with SLE. The findings that immune complexes comprising chromatin and anti-chromatin antibodies can deposit in the glomerular basement membrane of
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the kidney [10], and that anti-chromatin antibodies are a necessary component for the development of glomerulonephritis in one strain of mouse [12], provide theoretical evidence that anti-chromatin antibodies can have pathological properties in some patients with SLE. Anti-chromatin antibodies have been measured in several clinical studies with US, European, Asian, Latin American and South African SLE patients [4,5,15–25]. In most of them, a series of other autoimmune diseases were used as controls. Data of these series is collected in Table 1. According to these series, anti-chromatin antibodies have a sensitivity range between 48 and 100% and a specificity between 90 and 99%. Regarding clinical associations, anti-chromatin antibodies were related with renal involvement [4,15,16,18,20,23] and, in a less proportion, with hematological involvement [18,22], or arthritis, malar rash, pleuritis and oral ulcers [23]. Antichromatin antibodies were correlated with disease activity measured by SLEDAI in three different studies [17,20,23]. Anti-chromatin reactivity is detected in patients with active SLE at a frequency similar to that for anti-ds-DNA antibodies, while it is less in inactive SLE [15,28]. Anti-chromatin antibodies correlated positively with anti-ds-DNA antibody titers [16,18–20,22]. Interestingly, anti-chromatin antibodies were positive in some patients who were negative for anti-dsDNA antibodies. This particular situation was found by Burlingame et al. [4], Cervera et al. [16], Cairns et al. [18], Gómez-Puerta et al. [19], Min et al. [20] Braun et al. [24] and Su et al. [26] in 35%, 20%, 21%, 12%, 11%, 23% and 51% of cases, respectively. Ghillani-Dalbin et al. [29] studied a large population of 1696 patients with autoimmune diseases. The authors tested them for a series of antibodies, including anti-ds-DNA antibodies, antinuclear antibodies (ANA) and anti-nucleo-
some antibodies. A high proportion of SLE patients [240/307 (78%)] were positive for anti-nucleosome antibodies. Only a small percentage of patients with other autoimmune diseases were positive for anti-nucleosome antibodies. Interestingly enough, 43 patients in the SLE group were positive for anti-nucleosome antibodies and negative for anti-ds-DNA antibodies. Cortés-Hernández et al. [30] analyzed the presence of anti-nucleosome, anti-histone and anti-DNA antibodies by ELISA in a series of 199 patients with SLE, with special emphasis in those with or without renal involvement. IgG anti-nucleosome antibodies were higher in those patients with active disease, lupus nephritis and active proliferative lesions on renal biopsy (type II, III and IV vs type V nephropathy). When the authors analyzed the development of proliferative glomerulonephritis during follow-up, only those patients positive at baseline for anti-histone antibodies had a higher risk. Anti-nucleosome antibodies have also been measured in juvenile SLE patients. Campos et al. [27] analyzed the presence of anti-nucleosome antibodies in 74 Brazilian children and adolescents (mean age 14years) with SLE. Fifty-two percent of patients were positive for anti-nucleosome antibodies. Those antibodies were correlated with malar rash, hematological involvement, and decreased serum complement levels. Additionally, a significant association was found between anti-nucleosome antibodies and SLEDAI score. Only a moderate correlation was found between anti-nucleosome and anti-ds-DNA antibodies. There was no correlation with renal involvement. There is limited information about successive determination of anti-chromatin antibodies in SLE. Grootscholten et al. [31] evaluated in a prospective manner the presence of anti-
Table 1 Clinical studies of anti-chromatin (nucleosome) antibodies in patients with SLE Author (reference)
Population
SLE
Controls AD
Healthy
Amoura et al. [15]
France
120
376
406
Cervera et al. [16] Schett et al. [17] Cairns et al. [18]
Catalonia Austria Nother Ireland
100 73 95
140 348 48
100 27 95
Gómez-Puerta et al. [19] Min et al. [20]
Colombia Korea
90 129
45 –
– 50
Hmida et al. [21] Ghirardello et al. [22] Simon et al. [23]
Luxemburg Italy Mexico
32 101 73
52 85 261
– 100 130
Braun et al. [24]
Germany
78
141
–
Tikly et al. [25]
South Africa
86
57
30
Su et al. [26]
Chinese
220
31
Campos et al. [27]
Brasil
–
64
233 74
Clinical associations
Laboratory correlations
Anti-Chr + ve anti-ds-DNA − ve
Nephropathy a Disease activity b Nephropathy No Nephropathy Hematological No Nephropathy Disease activity b NR Hematological Nephropathy, AR MR, OU, Pleur Disease activity b Disease activity b
NR
NR
72
90
ds-DNA ds-DNA
20/100 (20%) NR 20/95 (21%)
69 48 64
92 95 99
ds-DNA ds-DNA
11/90 (12%) 15/129 (11%)
73 76
95 98
NR ds-DNA NR
NR NR NR
81 86 100
97 95 97
ds-DNA c C1q antibodies c ds-DNA IgG aCL Proteinuria Leukopenia ds-DNA Low complement
18/78 (23%)
64
99
NR
45
94
64/125 (51%)
61
97
9/74 (12%)
53
98
Skin involvement Disease activity MR, arthralgia Disease activity Hematological MR
Sensitivity (%)
Specificity (%)
aCL: anticardiolipin antibodies, AR: arthritis, AD: autoimmune diseases, ds-DNA: double-stranded-DNA antibodies, MR: malar rash, NR: not reported, OU: oral ulcers, Pleur: pleuritis. a Only for IgG3 isotype. b Disease activity measured by SLEDAI. c Only in patients with lupus nephritis.
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chromatin antibodies in 87 patients with proliferative lupus nephritis treated with cyclophosphamide (CYC) pulses or azathioprine (AZA). At baseline, anti-chromatin antibodies were positive in 81% of patients. A significant correlation was found between anti-chromatin and anti-ds-DNA antibodies. No significant differences were found for serum creatinine levels or proteinuria and anti-chromatin antibody levels. Anti-chromatin reactivity declined over time. However, it remained above the cut-off in most patients. No differences between CYC and AZA were found on the course of autoantibody titers. The authors concluded that anti-chromatin antibodies are useful for diagnosis of lupus nephritis but not for monitoring disease course or treatment. Anti-chromatin antibodies are also useful to help diagnose DIL, especially in procainamide, quinidine and hydralazine induced lupus. A few other drugs rarely cause DIL, and these patients often have anti-chromatin antibody reactivity [11]. 5.2. Anti-chromatin antibodies in other autoimmune diseases Anti-chromatin antibodies have been found in other autoimmune diseases including systemic sclerosis (SSc), Sjögren's syndrome (SS) and mixed connective tissue disease (MCTD), but in a much smaller percentage than in SLE patients [15–17]. In some studies, anti-chromatin autoantibodies were not found in other connective tissue diseases [21,32]. When H1-stripped chromatin or nucleosome core particles are used as the antigen, and an appropriate cut-off between positive and negative is used, anti-chromatin antibodies are very specific for SLE, DIL and autoimmune hepatitis (AIH) type I [12]. In a recent study, Braun et al. [24] determined anti-chromatin antibodies and anti-C1q antibodies in 78 SLE patients and in 141 patients with other autoimmune disease (including small vessel vasculitis, SS and SSc). Anti-chromatin antibodies were much more specific for SLE than anti-C1q antibodies (specificity 99% vs 72%). Antichromatin was positive in only 1 patient with SS and was not found in patients with small vessel vasculitis or SSc. Anti-chromatin antibodies are found in 40%–50% of people with AIH type I [28,29]. Anti-chromatin antibodies were not found by Cacoub et al. [32] in any of 46 patients with hepatitis C infection with or without cryoglobulinemia, 22 patients with cryoglobulinemia but not hepatitis C, or 96 healthy controls. Li et al. [33] tested anti-chromatin antibodies in 36 Japanese patients with AIH type 1, 53 with primary biliary cirrhosis (PBC), 37 with chronic hepatitis C and 15 with chronic hepatitis B. The authors found a significantly higher frequency of anti-chromatin antibodies in patients with AIH, 19/36 (53%), in comparison with patients with PBC, chronic hepatitis C, and chronic hepatitis B (13%, 5.4% and 6.7%, respectively). They suggest that anti-chromatin antibodies cannot discriminate different subgroups of patients with AIH. This is in contrast with the findings of Czaja et al. [34] who found anti-chromatin more often in AIH patients with active disease who commonly relapsed after cessation of immunosuppressive therapy. Anti-chromatin antibodies have been measured in primary APS patients [16,35,36]. Cervera et al. [16] determined anti-chromatin antibodies in 30 patients with primary APS, and only 2 patients were positive. Abraham Simón et al. [35] analyzed the presence of anti-nucleosome antibodies in 18 patients with primary APS with a mean follow-up of 12years.
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Nine (50%) out of 18 patients were positive for antinucleosome antibodies. Of them, 6 developed clinical features of SLE after a mean primary APS duration of 9years. The presence of anti-nucleosome antibodies at the moment of primary APS diagnosis was related with the subsequent development of SLE. Recently, Andreoli et al. [36] analyzed the presence of anti-nucleosome antibodies (using H1-stripped chromatin as antigen) in a cohort of 105 Italian patients with primary APS. Samples were tested for IgG and IgM antinucleosome antibodies using a home-made ELISA. Forty-eight (45%) patients exhibited lupus-like features. Eighty-one (77%) out of 105 patients were positive for either IgG or IgM or both isotypes. Only medium and high titers of anti-nucleosome were weakly related to anti-ds-DNA antibodies. Forty-eight patients were tested for anti-nucleosome during the followup. The majority of patients displayed a stable course of antinucleosome. Only 10 of them became either negative or positive during the follow-up. Finally, the authors remarked that anti-nucleosome antibodies appear in early stages of the disease and could be a useful marker to identify those patients with primary APS and lupus-like features who will develop SLE in the future. 6. Anti-chromatin (anti-nucleosome) and anti-tumour necrosis factor agents Tumour necrosis factor (TNF)-α inhibitors (adalimumab, etanercept, infliximab) have proven to be highly effective in the treatment of several autoimmune diseases, mainly rheumatoid arthritis. They reduce disease activity and delay radiographic progression, with quite a good safety profile. Side effects of anti-TNF-α treatment include an increased risk for infection and induction of autoantibodies such as ANA, anti-ds-DNA, aCL and anti-chromatin antibodies. Eriksson et al. [37] analyzed the autoantibody formation in 59 RA patients treated with an anti-TNF-α agent (53 with infliximab and 6 with etanercept). Several autoantibodies were measured, including rheumatoid factor, ANA, antiextractable nuclear antigens antibodies, anti-nucleosome antibodies, anti-ds-DNA antibodies, aCL, anti-proteinase-3 and anti-myeloperoxidase antibodies. In patients treated with infliximab, anti-nucleosome antibodies were positive at baseline in 5/50 (10%) patients, while at 30 weeks in 13/50 (26%) and at 54 weeks in 10/40 (25%) patients. Additionally, the frequency of autoantibodies against ANA, anti-ds-DNA antibodies increased significantly during treatment with infliximab. No patients treated with etanercept developed any of the autoantibodies tested for in this study. Benucci et al. [38] analyzed the induction of antinucleosome, ANA and anti-ds-DNA in a series of 91 patients with RA that received an anti-TNF-α agent (19 infliximab, 43 etanercept and 29 adalimumab). Autoantibodies were measured at baseline and after 12 and 24 weeks of treatment. Anti-nucleosome positivity increased in the 3 groups, from 5% to 16% and 31% respectively in the infliximab group; from 5% to 7% and 25% respectively in the etanercept group; and from 7% to 10% and 14% respectively in the adalimumab group. In general terms, adalimumab showed a lower induction rate of autoantibodies. Information about anti-TNF-α treatment in SLE is limited. Aringer et al. [39] analyzed the autoantibody profile in 7 SLE
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patients treated with infliximab at baseline and after 12, 24 and 36 weeks. Infliximab treatment increased anti-chromatin antibodies in 6 out of 7 patients, peaking between 4 and 10 weeks after the last infliximab infusion, but falling to baseline levels or lower thereafter. These transient increases were without pathological consequences. 7. Conclusions Most studies have found that anti-chromatin antibodies are very sensitive and specific markers of SLE. In patients with SLE there is a statistically significant correlation between antichromatin antibodies and renal involvement. Anti-chromatin reactivity is a useful marker to help in the diagnosis of people who are anti-ds-DNA negative but have SLE. Additionally, anti-chromatin antibodies are helpful in diagnosing DIL, as well as possibly identifying patients with autoimmune hepatitis who commonly relapse after immunosuppressive drugs are removed. Recent studies suggest a correlation between disease activity measured by SLEDAI and the presence of anti-chromatin antibodies. Anti-chromatin antibodies are useful for diagnosis but its role in monitoring of the disease is still limited. Patients exposed to anti-TNF-α agents induce the formation of anti-chromatin antibodies, though these seem to have no clinical relevance. Take-home messages • Anti-chromatin antibodies are a very helpful marker in supporting the diagnosis of SLE in a patient with an unclear systemic autoimmune disorder. • These antibodies have a high sensitivity (50–100%) and a very high specificity (90–99%) for SLE diagnosis. • Anti-chromatin antibodies are helpful in diagnosing DIL as well as possibly identifying patients with autoimmune hepatitis. • These antibodies are clinically correlated with kidney and disease activity in SLE patients. • Anti-TNF-α agents may induce anti-chromatin antibodies. These increases seem to have no clinical relevance. References [1] Cervera R, Khamashta MA, Font J, et al. Systemic lupus erythematosus: clinical and immunological patterns of disease expression in a cohort of 1000 patients. Medicine (Baltimore) 1993;72:113–24. [2] Hargraves MM, Richmond H, Morton R. Presentation of two bone marrow elements: the “Tart” cell and the “LE” cell. Proc Mayo Clin 1948;23:25–8. [3] Sherer Y, Gorstein A, Fritzler MJ, Shoenfeld Y. Autoantibody explosion in systemic lupus erythematosus: more than 100 different antibodies found in SLE patients. Semin Arthritis Rheum 2004;34:501–37. [4] Burlingame RW, Boey ML, Starkebaum G, et al. The central role of chromatin in the autoimmune responses to histones and DNA in systemic lupus erythematosus. J Clin Invest 1994;94:184–92. [5] Chabre H, Amoura Z, Piette JC, Godeau P, Bach JF, Koutouzov S. Presence of nucleosome restricted antibodies in patients with systemic lupus erythematosus. Arthritis Rheum 1995;38:1485–91. [6] Tan EM, Cohen AS, Fries JF, et al. The 1982 revised criteria for the classification of systemic lupus erythematosus. Arthritis Rheum 1982;25:1271–7. [7] Gómez-Puerta JA, Burlingame RW, Cervera R. Anti-chromatin (antinucleosome) antibodies. Lupus 2006;15:408–11. [8] Luger K, Mader AW, Richmond RK, Sargent DF, Richmond TJ. Crystal structure of the nucleosome core particle at 2.8 A resolution. Nature 1997;389:251–60.
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Autoantibodies against receptor tyrosine kinase in Chagas’ disease Trypanosoma cruzi, the etiologic agent of Chagas’ disease, induces survival and differentiation of neurons via activation of nerve growth factor receptor tyrosine kinase. Lu et al. (J Immunol 2008;67:603-9) have studied sera from chronic Chagas’ disease patients and observed that some sera recognized receptor tyrosisne kinase of the type A, and family members of this receptor (B and C). The authors have confirmed this specificity using five other growth factor receptors, nerve growth factor, neurotrophins, and Trypanosoma cruzi as antigens. In fact, no reactions was observed with these antigens. This study suggests that patients with Chagas´ disease produce autoantibodies against receptor tyrosine kinase, and it might inhibit cell apoptosis of the host and consequently to promote cell invasion.
Autoantibodies to survivin in chronic hepatitis and hepatocellular carcinoma Previous studies have demonstrated the presence of autoantibodies against tumor-associated antigens, including surviving, in sera from patients with hepatocellular carcinoma. To examine the presence of these antibodies in sera from chronic hepatitis patients, Yagihashi et al. (Autoimmunity 2005;38:445-8), using a recombinant surviving protein in ELISA, have included 57 individuals with chronic hepatitis, 29 with hepatocellular carcinoma and healthy controls. This study demonstrated that 10/57 (17.5%) of chronic hepatitis and 7/29 (24.1%) of liver carcinoma patients had these antibodies. Moreover, the authors have shown that titers of anti-survivin antibodies were higher in patients with hepatocellular carcinoma associated with hepatitis C virus than controls and individuals with this cancer associated with hepatitis B virus infection. On the other hand, no differences were observed regarding anti-survivin in patients with chronic hepatitis caused by C virus and liver carcinoma induced by this virus. This study showed the presence of anti-survivin antibodies in patients with chronic hepatitis and they do not seem to correlate with the progression to hepatocellular carcinoma.