HLA shared epitope and ACPA: Just a marker or an active player?

Autoimmunity Reviews 12 (2013) 1182–1187

Contents lists available at ScienceDirect

Autoimmunity Reviews journal homepage: www.elsevier.com/locate/autrev

Review

HLA shared epitope and ACPA: Just a marker or an active player? Federico Pratesi a, Elisabeth Petit Teixeira b, John Sidney c, Laetitia Michou d, Ilaria Puxeddu a, Alessandro Sette c, Francois Cornelis b,e, Paola Migliorini a,⁎ a

Clinical Immunology and Allergy Unit, Department of Internal Medicine, University of Pisa, Pisa, Italy GenHotel-EA3886, Evry University, Paris 7 University Medical School, Evry, France Department of Vaccine Discovery, La Jolla Institute for Allergy and Immunology, San Diego, CA, USA d Department of Medicine, Laval University, CHUQ (CHUL) Research Centre and Division of Rheumatology, CHUQ (CHUL), Quebec City, QC, Canada e GenHotel-Auvergne, Clermont-Ferrand University Hospital, Auvergne University, France b c

a r t i c l e

i n f o

a b s t r a c t

Article history: Received 24 July 2013 Accepted 8 August 2013 Available online 16 August 2013

Autoantibody production is genetically controlled and anti-citrullinated protein/peptide antibodies (ACPA) are not an exception to the rule. ACPA are highly specific markers of rheumatoid arthritis (RA) and are also associated with a more severe disease course. The production of ACPA is almost invariably observed in HLA-shared epitope (SE) positive patients. The DRB1 alleles sharing SE are those conferring susceptibility to RA. SE alleles behave like immune response genes, controlling both the specificity and the amount of ACPA produced. These data suggest a role of SE in the presentation of citrullinated antigens. The ability of SE alleles to bind selectively to citrullinated sequences as compared to the native counterparts has been demonstrated in the case of peptides derived from several joint associated proteins (vimentin, fibrinogen and cartilage intermediate-layer protein). On the contrary, EBV-derived citrullinated peptides do not display a biologically relevant binding to SE alleles even if the immune response to VCPs is under the genetic control of these alleles (namely *0401 and *0404). Thus, the presentation of citrullinated epitopes does not represent the only molecular mechanisms underlying the HLA-DRB1 effect on ACPA production. © 2013 Published by Elsevier B.V.

Contents 1. 2. 3. 4. 5.

Introduction . . . . . . . . . . . ACPA and RA . . . . . . . . . . . HLA SE and ACPA+ . . . . . . . HLA SE new classification and ACPA HLA SE and antigen presentation . . 5.1. HLA SE and T cell response . 5.2. HLA SE and peptide binding Take home messages . . . . . . . . . References . . . . . . . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

1. Introduction Rheumatoid arthritis (RA) is a common, chronic and systemic inflammatory autoimmune disease primarily characterized by bilateral symmetrical polyarticular arthritis, which is often erosive. Although the etiology of RA remains unknown, it is widely accepted that multiple ⁎ Corresponding author at: Clinical Immunology and Allergy Unit, Department of Internal Medicine, University of Pisa, Via Roma 67, 56126 Pisa, Italy. Tel.: +39 50 558609; fax: +39 50 558630. E-mail address: [email protected] (P. Migliorini). 1568-9972/$ – see front matter © 2013 Published by Elsevier B.V. http://dx.doi.org/10.1016/j.autrev.2013.08.002

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

. . . . . . . . .

1182 1183 1183 1185 1185 1185 1185 1186 1186

cumulative/compounding genetic and environmental ‘hits’ are required between the initiation of self-peptide recognition, subsequent loss of tolerance, and the development of autoimmunity [1]. Evidence of familial clustering was the first indication of a genetic susceptibility to RA [2,3]. Twin studies have determined that the RA heritability (that is the relative contribution of genetic variation to the liability of developing RA) has been estimated to be about 60% based on the higher monozygotic twin concordance rates (12–15%) compared to dizygotic twins (2–4%) [4]. Familial aggregation for RA, measured by the sibling recurrent risk ratio, varies from 2 to 17 depending upon the disease prevalence in the population used as reference [5].

F. Pratesi et al. / Autoimmunity Reviews 12 (2013) 1182–1187

Several whole-genome scans for RA have been performed with multi-locus nonparametric linkage analysis to identify susceptibility loci. The HLA region has been the only one with significant evidence of linkage (LOD score N 3.6, P value b 3 × 10−5) across all the genome scans with an estimated contribution of about 30–35% [6]. Such a prominent contribution of the HLA region is a common finding in autoimmune disorders: type I diabetes [7] and multiple sclerosis [8] are similarly characterized by a strong influence of HLA genes on the susceptibility to the disease. An association between genes located in the HLA region and the likelihood of developing RA was first suspected in 1976 by Stastny, who found RA to be associated with the mixed leukocyte culture type Dw4 (HLA-DRB1*0401) [9]. In the late 1990s, after sequencing of the HLA-DRB1 locus, Gregersen et al. proposed the shared epitope (SE) hypothesis, according to which the association between HLA-DR and RA can be ascribed to susceptibility alleles encoding a homologous amino acid sequence in the third hypervariable region of the first domain of the HLA-DR beta chain [10]. This sequence, which extends from position 70 to position 74 (70QRRAA74 or 70KRRAA74 or 70 RRRAA 74 ), is encoded by the HLA-DR4 (DRB1*0401, *0404, and *0405), HLA-DR1 (DRB1*0101 and *0102), and HLA-DR10 (DRB1*1010) alleles and is associated with RA. The conserved motif ([Q/R]-[R/K]-RA-A) constitutes an α-helical domain forming one side of the antigen binding site, and thus likely to affect the antigen presentation (Table 1). HLA alleles with a negatively charged amino acid at any one of these positions are not associated with the disease. These alleles usually contain an aspartic acid (D) at residue 70 or the common motif 70DERAA74 (HLA-DRB1*0103, *0402, *1102, *1103, *1301, *1302, and *1304), and may protect against RA or favor a less erosive disease. In fact, in the middle of nineties, Zanelli et al. discovered that the DRB1 carrying 70DERAA74 (alleles DRB1*0103, *0402, *1102, *1103, *1301, *1302) are associated with protection from RA [11]. He also extended the haplotype contributing to RA predisposition to HLA-DQDR alleles more than to DR alleles alone [12]. While the HLA-DQ involvement in RA remained elusive, the association of DERAA positive HLA-DRB1 alleles with protection from RA (even in the presence of susceptibility alleles) has been confirmed by other studies [13]. Moreover, while HLA-DRB1 SE alleles have been found to be associated with a severe course of the disease (in terms of bone destruction), DERAA DRB1 alleles are protective against the development of bone destruction [14]. There is a general agreement on the role of SE alleles in the predisposition to the disease, although the contribution of individual alleles is still a matter of debate. Some SE alleles, such as HLA-DRB1*0401, appear to confer a higher risk than others; moreover, the presence of two SE alleles and in particular HLA-DRB1*0401/*0404 confers a high risk to develop the disease and has also an influence on disease severity. Different studies have proposed models to explain the role of SE in RA susceptibility, focusing on the aminoacids that surround the “classical” 72–74 SE motif. De Vries et al. suggested a role for isoleucine at position 67 in the protection from RA [15], whereas Mattey et al. brought into play a protective role of aspartic acid at position 70 [16]. Reviron et al. classified the SE-negative HLA-DRB1 alleles according to the electric charge of the P4 pocket and observed an association between negative or neutral charge and protection [17]. Recently, Tezenas du Montcel et al. proposed a new model of the SE component in RA [18]. They proposed that the risk for developing RA depends on the presence of the RAA sequence at positions 72–74 and also on amino acids at positions 71 and 70. For the RAA alleles, lysine (K) at position 71 conferred the highest risk, arginine (R) an intermediate risk, and alanine (A) or glutamic acid (E) the lowest risk. Glutamine (Q) or arginine (R) at position 70 conferred greater risk than aspartic acid (D). This resulted initially in five allele groups (S2, S3P, S3D, S1, and X), which were simplified to three allele groups (S2, S3P, and L) defining six genotypes with different

1183

RA risks. This study was the first to model the HLA component in RA taking into account both association and linkage data, resulting in a reshaped SE hypothesis. This new classification has been validated by different studies in different international populations [19,20]. A recent analysis by Morgan et al., using 3 different HLA-DRB1 classification systems in Caucasian RA and healthy subjects, confirms the association of S2 and S3P with RA and validates the hierarchy of risk proposed by this new classification [21]. 2. ACPA and RA It is widely accepted that among all the autoantibodies present in RA sera those specific for citrullinated peptides/proteins (ACPA) are endowed with the highest diagnostic and prognostic significance [22]. ACPA can be considered highly specific markers of RA, that allow the differential diagnosis with other chronic disorders affecting the joints: for this strict disease-specificity, ACPA have been recently included in the serological criteria for the classification of RA [23]. ACPA are produced early in the disease course [24] and may appear many years before onset of symptoms [25]. Epitope spreading towards more citrullinated epitopes [26] and avidity maturation [27] occurs before the onset of RA. B cells producing ACPA use a diverse set of heavy and light chain genes, that bear a high number of mutations with a bias towards replacement mutations. Thus, somatic hypermutation seems to play a role in the generation of ACPA, suggesting an affinity maturation possibly driven by T cells [28]. ACPA are associated with disease severity and the simultaneous presence of different isotypes in undifferentiated arthritis, indicate a more severe course and a high probability of progression towards RA. ACPA titers were found to increase in the very first stages after disease onset and then tend to persist in the majority of patients. On the contrary, the rate of seroconversion of ACPA negative early inflammatory arthritis (EIA) and/or RA to ACPA positive disease is very low, thus suggesting that repeated testing during follow up may not have an added value [29]. ACPA recognize citrullinated self or exogenous proteins, such as filaggrin, fibrinogen, vimentin, collagen II, enolase, histone H4 or EBNAderived peptides [30–33]. All these citrullinated proteins and peptides have been used to set up ELISA assays for ACPA detection, but the more frequently used test is the anti-cyclic citrullinated peptide (CCP) assay, originally based on cyclic citrullinated sequences derived from filaggrin [34]. Using these different citrullinated substrates in direct binding or inhibition assays, experimental proof for the existence of cross-reactive as well as non-cross-reactive ACPA has been obtained [35]. Studies of the immune response to citrullinated sequences indicated that epitope spreading occurs in patients affected by undifferentiated arthritis that develop RA [36]. Similarly, RA patients as compared with undifferentiated arthritis display a wider variety of ACPA in terms of isotype usage: not only IgG but also IgM, IgA and even IgE ACPA [37]. Evidences from a wide number of studies clearly suggest that ACPA positive RA represent a different subset of RA in terms of clinical phenotype and prognosis, with respect to the ACPA negative disease and the two subsets are also genetically different. 3. HLA SE and ACPA+ The discovery of ACPA has modified the hypothesis on the role of HLA SE as susceptibility factor in RA. In fact, linkage and association analysis demonstrated that the HLA SE alleles predispose not to RA as such, but rather to ACPA-positive disease, that accounts for approximately two-thirds of RA patients [38]. Moreover, while the estimated heritability of anti-CCP negative RA patients is similar to the heritability of anti-CCP positive RA (66% and 68%, respectively), the presence of HLA

1184

F. Pratesi et al. / Autoimmunity Reviews 12 (2013) 1182–1187

Table 1 Classification of HLA-DRB1 alleles according to the third hypervariable region of the DRβ chain. HLA DRB1 alleles

HLA-DRB1 amino-acid position

HLA DRB1*0101 HLA DRB1*0102 HLA DRB1*0103 HLA DRB1*03 HLA DRB1*0401 HLA DRB1*0402 HLA DRB1*0403 HLA DRB1*0404 HLA DRB1*0405 HLA DRB1*0407 HLA DRB1*0408 HLA DRB1*0411 HLA DRB1*07 HLA DRB1*08 HLA DRB1*0901 HLA DRB1*1001 HLA DRB1*1101 HLA DRB1*1102 HLA DRB1*1103 HLA DRB1*1104 HLA DRB1*12 HLA DRB1*1301 HLA DRB1*1302 HLA DRB1*1303 HLA DRB1*1323 HLA DRB1*1401 HLA DRB1*1402 HLA DRB1*1404 HLA DRB1*15 HLA DRB1*16

67

…

70

71

72

73

74

…

85

86

L L I L L I L L L L L L I F F L F I F F I I I I I L L L L F

… … … … … … … … … … … … … … … … … … … … … … … … … … … … … …

Q Q D Q Q D Q Q Q Q Q Q D D R Q D D D D D D D D D R Q R Q D

R R E K K E R R R R R R R R R R R E E R R E E K E R R R A R

R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R

A A A G A A A A A A A A G A A A A A A A A A A A A A A A A A

A A A R A A E A A E A E Q L E A A A A A A A A A A E A E A A

… … … … … … … … … … … … … … … … … … … … … … … … … … … … … …

V A V V V V V V V V V V V V V V V V V V A V V V V V V V V V

G V G V G V V V G G G V G G G G G V V V V V G G G V G V V G

Predisposing

Gregersen (×)

Gao (×)

De Vries (×)

*0401 *0404 *0405 *0408

*0401 *0404 *0405 *0408

E3 E2 E1

*0101 *0102 *1402 *1001

*0101 *1402 *1001 *0102

E1 E1 E2

*1303 *1310 *1419 *1421

*1303 *1310 *1419 *1421

*0401 *0404 *0405 *0408

SE+

Reviron (×)

*0401 *0404 *0405 *0408

*0101 *0102

Neutral

*0403 *0406 *0407 *0901 *1107

*0403 *0406 *0407 *0901 *1107

*14

*14

*15 *16

*07 *08 *11 *12 *13

L67

*1001

Tezenas du Montcel (×)

*0401 *0404 *0405 *0408 SE

*0101 *0102 *1402 *1001

E×

N

*08 *09 *11 *14 *16

*03 *0403 *0406 *0407 *09 *14 *15

N D70-

*03 *0403 *0406 *0407

N

*0901 *1107 *14 *15 *16

RAP (DERAA)

S3P

*1101 *1104 *12 *1305 *1306 *1325 *1422 *16

S3D

*0103 *0402 *1102 *1103 *1301 *1302

*0901 *1401 *1404

E×

P

*07 *08 *11 *12 *13 *16

P

*07 *08 *11 *12 *13 P

*0103 *0402 *1102 *1103 *1301 *1302

*0101 *0102 *1402 *1001 *10

*03 *0403 *0407 *0411 *07 *08

*07 *08 *11 *12 *13 *15 *0103 *0402 *1102 *1103 *1301 *1302

S2

I67 E×

*0103 *0402

D70+ *0103 *0402

*0103 *0402

S1

*1304 *1323

*15 *16

*07 *08 *11 *12 *13

*0401 *1303 *1310 SE

*0101 *0102 *1402 *1001

E× *03 *0403 *0406 *0407

Protective

Mattey (×)

×

F. Pratesi et al. / Autoimmunity Reviews 12 (2013) 1182–1187

SE alleles explained 18% of the genetic variance of ACPA-positive RA but only 2.4% of the genetic variance of ACPA-negative RA [39]. The HLA-DRB1 SE alleles are associated with anti-CCP-positive RA [36] and also influence the magnitude of the anti-CCP response [40]. Since rheumatoid factor (RF) and ACPA often are present together, it has been also suggested that the association between HLA SE and RF is secondary to the association between HLA and ACPA [40]. The ACPA family, however, encompasses antibodies that bind different citrullinated antigens such as fibrinogen, vimentin, enolase, collagen, Epstein Barr Virus proteins and derived citrullinated synthetic peptides [30–32]; some member of the family is mono-specific for a single citrullinated epitope, others are cross-reactive. Thus, it is of interest to analyze the association of SE alleles with the various members of the ACPA family. Recently a few studies have extensively compared different welldefined ACPA specificities in terms of association with HLA SE. The results showed that HLA SE is more strongly associated with antiCCP, anti-citrullinated enolase peptide-1 (CEP-1) and anti-modified citrullinated vimentin (MCV) than with anti-Collagen I and antiFibrinogen antibodies [41,42]. SE alleles confer also an increased risk to produce ACPA of different fine specificity. Besides controlling the production and the specificity of ACPA, SE alleles regulate the amount of antibodies produced. Under this respect, a gene-dose effect has clearly been demonstrated. Snir et al. reported that patients with RA carrying two SE alleles produce higher levels of anti-CCP antibodies, anti-citrullinated fibrinogen and anti-CEP-1 than patients carrying single allele or no SE alleles. Conversely, patients carrying one SE allele displayed higher, even if not statistically significant, antibody levels toward CCP, citrullinated fibrinogen and CEP-1 than patients who had no SE alleles [43]. Analyzing in more detail the contribution of individual SE alleles, HLA-DRB1*04 (and *0404 in particular) are associated with higher levels of ACPA than HLA-DRB1*01 group [43]. A gene-dose effect is observed also on the production of ACPA reactive with exogenous citrullinated antigens. One of the specificities recognized by ACPA is represented by viral citrullinated peptides [31]. VCP1 and VCP2 are citrullinated peptides derived from Epstein Barr virus nuclear proteins EBNA1 and EBNA2. Anti-VCP1 and anti-VCP2 antibodies are detected almost exclusively in RA and their levels are highly correlated with the levels of anti-CCP antibodies [32]. In a cohort of 172 French RA patients the presence of two copies of the HLA-SE alleles confers an increased risk to produce anti-CCP or anti-VCP2 antibodies with respect to one or no SE allele. As far as the effect of individual alleles is concerned, the *0401 allele confers an increased risk to produce anti-VCP2 and anti-CCP antibodies, while *0404 is associated with the production of anti-VCP1 and anti-VCP2 antibodies [44]. 4. HLA SE new classification and ACPA The new classification of HLA-DRB1 alleles proposed by Tezenas Du Montcel et al. gives the opportunity to distinguish predisposing and protective alleles for RA-specific antibody production [18,45]. The presence of an S2 or S3P allele has been correlated with RF, anti-CCP and anti-citrullinated fibrinogen antibody production, whereas the presence of S3D and S1 alleles appeared to be protective. S2 alleles are associated also with anti-VCP2 antibodies, but no other HLA SE subtype is correlated with anti VCP1 or anti VCP2 antibodies. Recently, Gyetvai et al. [46] examined the impact of S1, S2, S3P, S3D alleles on antibody production, using the SE negative genotypes as reference. The authors found that not only S2 and S3P but also S1 and S3D alleles predispose to the production of anti-CCP antibodies, with the hierarchy S2 + S3P N S1 + S3D N X/X. Anti-citrullinated fibrinogen antibodies display a different association pattern, being strongly correlated with S1 alleles. Finally, the authors found that a double dose of S2 and/or S3P alleles did not significantly increase the risk for

1185

anti-CCP and anti-citrullinated vimentin as the majority of patients was positive even in the presence of single dose allele. At variance, some additive effect of susceptible alleles was observed in the case of anti citrullinated fibrinogen antibodies. 5. HLA SE and antigen presentation The strong association of SE alleles with ACPA-positive RA, and with the production of different members of the ACPA family, raises the question of the mechanisms underlying the genetic control of ACPA production and suggests a role of SE in the presentation of citrullinated antigens. 5.1. HLA SE and T cell response Several studies have addressed the issue of SE and antigen presentation studying T cell responses to citrullinated antigens in RA patients. Auger et al. [47] analyzed T cell proliferative responses to fibrinogen peptides in HLA-DRB1* subjects. The number of peptides inducing proliferation, and the amount of proliferative response, were much higher in RA patients than in healthy controls, without differences between native and citrullinated sequences. Thus, citrullination of fibrinogen does not affect antigen presentation by HLA-DRB1* alleles and T cell proliferative responses. Similarly, EBV-derived citrullinated peptides were unable to induce a T cell response, detected either by proliferation or cytokine secretion (Pratesi et al., unpublished data). On the contrary, a citrullinated aggrecan peptide induced T cell proliferation, and production of proinflammatory cytokines such as IL17 and IFN-γ, in RA patients but not in normal controls [48]. In HLADRB1*0401 RA patients, an antigen specific production of IFNγ was observed in memory T cells upon stimulation with a vimentin citrullinated peptide [49]. Noteworthy, SE alleles may confer the ability to respond to citrullinated sequences, but this response is not always associated with ACPA production, being detectable in ACPA negative RA patients as well as in ACPA negative normal subjects. In fact, cytokine secretion in response to citrullinated collagen II, to vimentin, to aggrecan and to fibrinogen peptides was observed in SE positive subjects, affected or not by RA [50]. RA patients, however, produced a more diverse array of cytokines, that included IFNγ and IL-10. SE transgenic mice allowed the exploration of more directly the immune response to citrullinated antigens, leading to the conclusion that citrulline-specific T cells can indeed be observed in this murine model. In HLA-DRB1*0401 transgenes, immunization with a candidate T cell epitope from human vimentin led to T cell proliferation that was specific for the citrulline-containing peptide [51]. Moreover, immunization with citrullinated fibrinogen induced a T cell response, production of ACPA and in one third of the animals an erosive arthritis [52]. In HLADRB1*0401 transgenes, two citrullinated vimentin peptides elicited an HLA-restricted and citrulline-specific T cell proliferation [49]. 5.2. HLA SE and peptide binding These functional data on T cell responses in the context of a SE background suggest the ability of SE alleles to bind selectively to citrullinated sequences as compared to the native counterparts. This issue was investigated by Hill et al. in 2003 [51]. The authors demonstrated that the conversion of one arginine to citrulline in a vimentin peptide strongly increased peptide affinity for HLA-DRB1*0101, *0401, *0404, but not for SE negative alleles. Citrulline, however, may also fit in other peptide-anchoring pockets of HLA class II and not only in pocket 4, that comprise the SE sequence. Studying the SE allele HLA-DRB*1001, James et al. [53] found that conversion of arginine to citrulline facilitates peptide binding to pocket 4, 7 and 9. In fact, citrulline containing peptides derived

1186

F. Pratesi et al. / Autoimmunity Reviews 12 (2013) 1182–1187

from several joint associated proteins (vimentin, fibrinogen and cartilage intermediate-layer protein) interacted with HLA-DRB*1001 while arginine disrupted peptide binding. The differential binding properties of HLA-DRB1* alleles for either arginine- or citrulline-containing sequences do not always explain the HLA control of the immune response to citrullinated epitopes. Auger et al. [47] screened fibrinogen peptides for direct binding to HLA-DRB1*alleles and found that both native and citrullinated sequences interacted to a similar extent with HLA molecules, while a hierarchy could be described for the alleles, HLA-DRB*0404 being the best binder. In the case of EBV-derived citrullinated peptides, competitive peptide binding assays were conducted to determine the affinity of VCP1 and VCP2 for purified MHC molecules (HLA-DRB1*0101, *0401, *0404, *0301, *0701, *0802, *1101, and *1302). Even if the immune response to VCPs is under the genetic control of the *0401 and *0404 alleles, biologically relevant binding was not detected with either peptide for any of the HLA class II molecules tested [44]. Thus, the presentation of citrullinated epitopes does not represent the only molecular mechanisms underlying the HLA-DRB1 effect on ACPA production. SE alleles might contribute to the genetic predisposition to RA causing an immune dysregulation or a premature immunosenescence. In fact, SE triggers innate immune signaling via cell surface calreticulin; citrullination of calreticulin enhances the signaling leading to a sustained Th17 expansion [54]. SE alleles are also associated with T cell telomere erosions, observed in lymphocytes and hematopoietic stem cells from RA patients and probably related to immunosenescence [55]. Take home messages • HLA SE is a susceptibility factor for ACPA positive RA, with allele-dose effect on antibody production. • Binding to SE molecules has been demonstrated for some citrullinated peptides and excluded for others. • HLA-SE restricted T cell responses to citrullinated antigens are detected in RA patients, but their role in ACPA production remains elusive.

References [1] Maini RN, Zvaifler NJ. Rheumathoid arthritis. In: Clipper JH, Dieppe PA, editors. Rheumatology. London: Mobsy; 1994. [2] Perricone C, Ceccarelli F, Valesini G. An overview on the genetic of rheumatoid arthritis: a never ending story. Autoimmun Rev 2011;10:599–608. [3] Dieude P, Cornelis F. Genetic basis of rheumatoid arthritis. Joint Bone Spine 2005;72: 520–6. [4] MacGregor AJ, Snieder H, Rigby AS, Koskenvuo M, Kaprio J, Aho K, et al. Characterizing the quantitative genetic contribution to rheumatoid arthritis using data from twins. Arthritis Rheum 2000;43:30–7. [5] Lin JP, Cash JM, Doyle SZ, Peden S, Kanik K, Amos CI, et al. Familial clustering of rheumatoid arthritis with other autoimmune diseases. Hum Genet 1998;103:475–82. [6] Deighton CM, Walker DJ, Griffiths ID, Roberts DF. The contribution of HLA to rheumatoid arthritis. Clin Genet 1989;36:178–82. [7] Gorodezky C, Alaez C, Murguia A, Rodriguez A, Balladares S, Vazquez M, et al. HLA and autoimmune diseases: type 1 diabetes (T1D) as an example. Autoimmun Rev 2006;5:187–94. [8] Zhang Q, Lin CY, Dong Q, Wang J, Wang W. Relationship between HLA-DRB1 polymorphism and susceptibility or resistance to multiple sclerosis in Caucasians: a meta-analysis of non-family-based studies. Autoimmun Rev 2011;10:474–81. [9] Stastny P. Mixed lymphocyte cultures in rheumatoid arthritis. J Clin Invest 1976;57: 1148–57. [10] Gregersen PK, Silver J, Winchester RJ. The shared epitope hypothesis. An approach to understanding the molecular genetics of susceptibility to rheumatoid arthritis. Arthritis Rheum 1987;30:1205–13. [11] Zanelli E, Gonzalez-Gay MA, David CS. Could HLA-DRB1 be the protective locus in rheumatoid arthritis? Immunol Today 1995;16:274–8. [12] Zanelli E, Huizinga TW, Guerne PA, Vischer TL, Tiercy JM, Verduyn W, et al. An extended HLA-DQ-DR haplotype rather than DRB1 alone contributes to RA predisposition. Immunogenetics 1998;48:394–401. [13] van der Helm-van Mil AHM, Huizinga TWJ, Schreuder GMT, Breedveld FC, de Vries RRP, Toes REM. An independent role of protective HLA class II alleles in rheumatoid arthritis severity and susceptibility. Arthritis Rheum 2005;9:2637–44.

[14] van Zeben D, Hazes JM, Zwinderman AH, Cats A, Schreuder GM, D'Amaro J, et al. Association of HLA-DR4 with a more progressive disease course in patients with rheumatoid arthritis. Results of a followup study. Arthritis Rheum 1991;34: 822–30. [15] de Vries N, Tijssen H, van Riel PL, van de Putte LB. Reshaping the shared epitope hypothesis: HLA-associated risk for rheumatoid arthritis is encoded by amino acid substitutions at positions 67–74 of the HLA-DRB1 molecule. Arthritis Rheum 2002;46:921–8. [16] Mattey DL, Dawes PT, Gonzalez-Gay MA, Garcia-Porrua C, Thomson W, Hajeer AH, et al. HLA-DRB1 alleles encoding an aspartic acid at position 70 protect against development of rheumatoid arthritis. J Rheumatol 2001;28:232–9. [17] Reviron D, Perdriger A, Toussirot E, Wendling D, Balandraud N, Guis S, et al. Influence of shared epitope-negative HLA-DRB1 alleles on genetic susceptibility to rheumatoid arthritis. Arthritis Rheum 2001;44:535–40. [18] Tezenas du Montcel S, Michou L, Petit-Teixeira E, Osorio J, Lemaire I, Lasbleiz S, et al. New classification of HLA-DRB1 alleles supports the shared epitope hypothesis of rheumatoid arthritis susceptibility. Arthritis Rheum 2005;52:1063–8. [19] Michou L, Croiseau P, Petit-Teixeira E, du Montcel ST, Lemaire I, Pierlot C, et al. European consortium on rheumatoid arthritis families. Validation of the reshaped shared epitope HLA-DRB1 classification in rheumatoid arthritis. Arthritis Res Ther 2006;8:R79. [20] Barnetche T, Constantin A, Cantagrel A, Cambon-Thomsen A, Gourraud PA. New classification of HLA-DRB1 alleles in rheumatoid arthritis susceptibility: a combined analysis of worldwide samples. Arthritis Res Ther 2008;10:R26. [21] Morgan AW, Haroon-Rashid L, Martin SG, Gooi HC, Worthington J, Thomson W, et al. The shared epitope hypothesis in rheumatoid arthritis: evaluation of alternative classification criteria in a large UK Caucasian cohort. Arthritis Rheum 2008;58: 1275–83. [22] Vander Cruyssen B, Peene I, Cantaert T, Hoffman IEA, De Rycke L, Veys EM, et al. Anti-citrullinated protein/peptide antibodies (ACPA) in rheumatoid arthritis: specificity and relation with rheumatoid factor. Autoimmun Rev 2005;4:468–74. [23] Aletaha D, Neogi T, Silman AJ, Funovits J, Felson DT, Bingham III CO, et al. 2010 rheumatoid arthritis classification criteria: an American College of Rheumatology/European League Against Rheumatism collaborative initiative. Arthritis Rheum 2010;62:2569–81. [24] Meyer O, Labarre C, Dougados M, Goupille P, Cantagrel A, Dubois A, et al. Anticitrullinated protein/peptide antibody assays in early rheumatoid arthritis for predicting five year radiographic damage. Ann Rheum Dis 2003;62(2): 120–6. [25] Nielen MM, van Schaardenburg D, Reesink HW, van de Stadt RJ, van der Horst-Bruinsma IE, de Koning MH, et al. Specific autoantibodies precede the symptoms of rheumatoid arthritis: a study of serial measurements in blood donors. Arthritis Rheum 2004;50:380–6. [26] van der Woude D, Rantapää-Dahlqvist S, Ioan-Facsinay A, Onnekink C, Schwarte CM, Verpoort KN, et al. Epitope spreading of the anti-citrullinated protein antibody response occurs before disease onset and is associated with the disease course of early arthritis. Ann Rheum Dis 2010;69:1554–61. [27] Suwannalai P, van de Stadt LA, Radner H, Steiner G, El-Gabalawy HS, Zijde CM, et al. Avidity maturation of anti-citrullinated protein antibodies in rheumatoid arthritis. Arthritis Rheum 2012;64:1323–8. [28] Amara K, Steen J, Murray F, Morbach H, Fernandez-Rodriguez BM, Joshua V, et al. Monoclonal IgG antibodies generated from joint-derived B cells of RA patients have a strong bias toward citrullinated autoantigen recognition. J Exp Med 2013;210:445–55. [29] Barra L, Pope J, Bessette L, Haraoui B, Bykerk V. Lack of seroconversion of rheumatoid factor and anti cyclic citrullinated peptide in patients with early inflammatory arthritis: a systematic literature review. Rheumatology 2011;50:311–6. [30] Uysal H, Nandakumar KS, Kessel C, Haag S, Carlsen S, Burkhardt H, et al. Antibodies to citrullinated proteins: molecular interactions and arthritogenicity. Immunol Rev 2010;233:9–33. [31] Pratesi F, Tommasi C, Anzilotti C, Chimenti D, Migliorini P. Deiminated Epstein–Barr virus nuclear antigen 1 is a target of anti-citrullinated protein antibodies in rheumatoid arthritis. Arthritis Rheum 2006;54:733–41. [32] Pratesi F, Tommasi C, Anzilotti C, Puxeddu I, Sardano E, Di Colo G, et al. Antibodies to a new viral citrullinated peptide, VCP2: fine specificity and correlation with anti-cyclic citrullinated peptide (CCP) and anti-VCP1 antibodies. Clin Exp Immunol 2011;164:337–45. [33] Pratesi F, Dioni I, Tommasi C, Alcaro MC, Paolini I, Barbetti F, et al. Antibodies from rheumatoid arthritis patients target citrullinated H4 contained in neutrophil extracellular traps. Ann Rheum Dis Jun. 1, 2013 [in press]. [34] van Boekel MA, Vossenaar ER, van den Hoogen FH, van Venrooij WJ. Autoantibody systems in rheumatoid arthritis: specificity, sensitivity and diagnostic value. Arthritis Res 2002;4:87–93. [35] Ioan-Facsinay A, el-Bannoudi H, Scherer HU, van der Woude D, Ménard HA, Lora M, et al. Anti-cyclic citrullinated peptide antibodies are a collection of anti-citrullinated protein antibodies and contain overlapping and non-overlapping reactivities. Ann Rheum Dis 2011;70:188–93. [36] van de Stadt LA, de Koning MH, van de Stadt RJ, Wolbink G, Dijkmans BA, Hamann D, et al. Development of the anti-citrullinated protein antibody repertoire prior to the onset of rheumatoid arthritis. Arthritis Rheum 2011;63:3226–33. [37] Verpoort KN, Jol-van der Zijde CM, Papendrecht-van der Voort EA, Ioan-Facsinay A, Drijfhout JW, van Tol MJ, et al. Isotype distribution of anti-cyclic citrullinated peptide antibodies in undifferentiated arthritis and rheumatoid arthritis reflects an ongoing immune response. Arthritis Rheum 2006;54:3799–808. [38] Huizinga TWJ, Amos CI, Van der Helm-Van Mil AHM, Chen W, Van Gaalen FA, Jawaeer D, et al. Refining the complex rheumatoid arthritis phenotype based on specificity of the HLA-DRB1 shared epitope for antibodies to citrullinated proteins. Arthritis Rheum 2005;52:3433–8.

F. Pratesi et al. / Autoimmunity Reviews 12 (2013) 1182–1187 [39] van der Woude D, Houwing-Duistermaat JJ, Toes RE, Huizinga TW, Thomson W, Worthington J, et al. Quantitative heritability of anti-citrullinated protein antibodypositive and anti-citrullinated protein antibody-negative rheumatoid arthritis. Arthritis Rheum 2009;60:916–23. [40] van der Helm-van Mil AH, Verpoort KN, Breedveld FC, Huizinga TW, Toes RE, de Vries RR. The HLA-DRB1 shared epitope alleles are primarily a risk factor for anti-cyclic citrullinated peptide antibodies and are not an independent risk factor for development of rheumatoid arthritis. Arthritis Rheum 2006;54:1117–21. [41] Lundberg K, Bengtsson C, Kharlamova N, Reed E, Jiang X, Kallberg H, et al. Genetic and environmental determinants for disease risk in subsets of rheumatoid arthritis defined by the anticitrullinated protein/peptide antibody fine specificity profile. Ann Rheum Dis 2013;72:652–8. [42] Verpoort KN, Papendrecht-van der Voort EA, van der Helm-van Mil AH, Jol-van der Zijde CM, van Tol MJ, Drijfhout JW, et al. Association of smoking with the constitution of the anti-cyclic citrullinated peptide response in the absence of HLA-DRB1 shared epitope alleles. Arthritis Rheum 2007;56:2913–8. [43] Snir O, Widhe M, von Spee C, Lindberg J, Padyukov L, Lundberg K, et al. Multiple antibody reactivities to citrullinated antigens in sera from patients with rheumatoid arthritis: association with HLA-DRB1 alleles. Ann Rheum Dis 2009;68:736–43. [44] Pratesi F, Petit-Teixeira E, Sidney J, Teixeira VH, Puxeddu I, Sette A, et al. Effect of rheumatoid arthritis (RA) susceptibility genes on the immune response to viral citrullinated peptides in RA. J Rheumatol 2012;39:1490–3. [45] Gourraud PA, Dieudé P, Boyer JF, Nogueira L, Cambon-Thomsen A, Mazières B, et al. A new classification of HLA-DRB1 alleles differentiates predisposing and protective alleles for autoantibody production in rheumatoid arthritis. Arthritis Res Ther 2007;9:R27. [46] Gyetvai A, Szekanecz Z, Soós L, Szabó Z, Fekete A, Kapitány A, et al. New classification of the shared epitope in rheumatoid arthritis: impact on the production of various anti-citrullinated protein antibodies. Rheumatology 2010;49:25–33.

1187

[47] Auger I, Sebbag M, Vincent C, Balandraud N, Guis S, Nogueira L, et al. Influence of HLA-DR genes on the production of rheumatoid arthritis-specific autoantibodies to citrullinated fibrinogen. 2005;52:3424–32. [48] von Delwig A, Locke J, Robinson JH, Ng WF. Response of Th17 cells to a citrullinated arthritogenic aggrecan peptide in patients with rheumatoid arthritis. Arthritis Rheum 2010;62:143–9. [49] Feitsma AL, van der Voort EI, Franken KL, el Bannoudi H, Elferink BG, Drijfhout JW, et al. Identification of citrullinated vimentin peptides as T cell epitopes in HLADR4-positive patients with rheumatoid arthritis. Arthritis Rheum 2010;62:117–25. [50] Law SC, Street S, Yu CH, Capini C, Ramnoruth S, Nel HJ, et al. T-cell autoreactivity to citrullinated autoantigenic peptides in rheumatoid arthritis patients carrying HLA-DRB1 shared epitope alleles. Arthritis Res Ther 2012;14:R118. [51] Hill JA, Southwood S, Sette A, Jevnikar AM, Bell DA, Cairns E. Cutting edge: the conversion of arginine to citrulline allows for a high-affinity peptide interaction with the rheumatoid arthritis-associated HLA-DRB1*0401 MHC class II molecule. J Immunol 2003;171:538–41. [52] Hill JA, Bell DA, Brintnell W, Yue D, Wehrli B, Jevnikar AM, et al. Arthritis induced by posttranslationally modified (citrullinated) fibrinogen in DR4-IE transgenic mice. J Exp Med 2008;205:967–79. [53] James EA, Moustakas AK, Bui J, Papadopoulos GK, Bondinas G, Buckner JH, et al. HLA-DRB*1001 presents “altered self” peptides derived from joint associated proteins by accepting citrulline in three of its binding pockets. Arthritis Rheum 2010;62: 2909–18. [54] Ling S, Cline EN, Haug TS, Fox DA, Holoshitz J. Citrullinated calreticulin potentiates rheumatoid arthritis shared epitope signaling. Arthritis Rheum 2013;65(3): 618–26. [55] Costenbader KH, Prescott J, Zee RY, De Vivo I. Immunosenescence and rheumatoid arthritis: does telomere shortening predict impending disease? Autoimmun Rev 2011;10(9):569–73.

Myeloperoxidase (MPO)-specific CD4+ T cells contribute to MPO-anti-neutrophil cytoplasmic antibody (ANCA) associated glomerulonephritis Autoimmunity to the neutrophil enzyme myeloperoxidase (MPO) is an important cause of rapidly progressive glomerulonephritis, but the relative roles of MPO-specific anti-neutrophil cytoplasmic antibodies (MPO-ANCA) and autoreactive effector MPO-specific CD4 (+) T cells are unclear. Gan P.Y. et al. (Cell Immunol. 2013; 282(1): 21-7) confirmed that passive transfer of murine MPO-ANCA to agammaglobulinemic μMT mice immunized with OVA induces glomerular injury with capillary wall thickening, fibrinoid necrosis, mesangial cell proliferation, and periglomerular cell infiltration. Preimmunization of μMT mice with MPO induced MPO-specific CD4(+) T cells and significantly enhanced renal injury after MPO-ANCA transfer. CD4(+) T cell depletion prevented this augmentation of injury, confirming the importance of effector T cells in the development of MPO-ANCA associated glomerulonephritis. Therefore, MPO-ANCA can induce glomerulonephritis through both direct humoral mechanisms (recruitment of neutrophils and deposition of MPO) and indirectly by initiating MPO deposition in glomeruli, thereby directing effector CD4(+) T cell mediated injury. To confirm and support this data, they transferred T cells from MPO-immunized Mpo(-/-)μMT mice into Rag1(-/-) mice (control mice received ovalbumin specific T cells) and triggered injury by passive MPO-ANCA. Renal injury was significantly greater in mice transferred with T cells from MPO-immunized mice. These current studies demonstrate that MPO-ANCA induces injury via both humoral and cell mediated immune mechanisms.