The enigma of sclera-specific autoimmunity in scleritis

Scleritis is a severe and painful ophthalmic disorder, in which a pathogenic role for collagen-directed autoimmunity was repeatedly suggested. We evaluated the presence of sclera-specific antibodies in a large cohort of patients with non-infectious scleritis. Therefore, we prospectively collected serum samples from 121 patients with non-infectious scleritis in a multicenter cohort study in the Netherlands. In addition, healthy (n = 39) and uveitis controls (n = 48) were included. Serum samples were tested for anti-native human type II collagen antibodies using a validated enzyme-linked immunosorbent assay (ELISA). Further, sclera-specific antibodies were determined using indirect immunofluorescence (IIF) on primate retinal/scleral cryosections. Lastly, human leukocyte antigen (HLA) typing was performed in 111 patients with scleritis. Anti-type II collagen antibodies were found in 13% of scleritis patients, in 10% of healthy controls and in 11% of uveitis controls (p = 0.91). A specific reaction to scleral nerve tissue on IIF was observed in 33% of patients with scleritis, which was higher than in healthy controls (11%; p = 0.01), but similar to uveitis controls (25%; p = 0.36). Reactivity to the scleral nerve tissue was significantly associated with earlier onset of scleritis (48 versus 56 years; p < 0.001), bilateral involvement (65% versus 42%; p = 0.01), and less frequent development of scleral necrosis (5% versus 22%; p = 0.02). HLA-B27 was found to be twice as prevalent in patients with scleritis (15.3%) compared to a healthy population (7.2%). In conclusion, scleral nerve autoantibody reactivity was more common in scleritis and uveitis patients in contrast to healthy controls. Further research is needed to characterize these scleral-nerve directed antibodies and assess their clinical value.

Anti-histone and anti-nucleosome rather than anti-dsDNA antibodies associate with IFN-induced biomarkers in Sudanese and Swedish Systemic Lupus Erythematosus patients

OBJECTIVES

In SLE, anti-dsDNA can co-occur with autoantibodies against other chromatin components, like histones and nucleosomes. These antibodies induce type-1 interferon production, a hallmark of SLE. We measured antinuclear antibody (ANA) sub-specificities and investigated their associations to inflammatory biomarkers including interferon-regulated chemokines.

METHODS

We included 93 Sudanese and 480 Swedish SLE patients and matched controls (N = 104 + 192). Autoantibodies targeting ANA-subspecificites: dsDNA, Sm, Sm/U1RNPcomplex, U1RNP, SSA/Ro52, SSA/Ro60, SSB/La, ribosomal P, PCNA and histones were quantified in all subjects, anti-nucleosome only in the Swedish patients, with a bead-based multiplex immunoassay. Levels of 72 plasma biomarkers were determined with Proximity Extension Assay technique or ELISA.

RESULTS

Among Sudanese patients, the investigated antibodies significantly associated with 9/72 biomarkers. Anti-histone antibodies showed the strongest positive correlations with MCP-3 and S100A12 as well as with interferon I-inducible factors MCP-1 and CXCL10. Anti-dsDNA antibodies associated with CXCL10 and S100A12, but in multivariate analyses, unlike anti-histone, associations lost significance.Among Swedish patients, MCP-1, CXCL10, SA100A12 also demonstrated stronger associations to anti-histone and anti-nucleosome antibodies, compared with anti-dsDNA and other ANA sub-specificities. In multiple regression models, anti-histone/nucleosome retained the strongest associations. When excluding anti-histone or anti-nucleosome positive patients, the associations between MCP-1/CXCL10 and anti-dsDNA were lost. In contrast, when excluding anti-dsDNA positive patients, associations with anti-histone and anti-nucleosome remained significant.

CONCLUSION

In two cohorts of different ethnical origin, autoantibodies targeting chromatin correlate stronger with IFN-induced inflammatory biomarkers than anti-dsDNA or other ANA sub-specificities. Our results suggest that anti-histone/nucleosome autoantibodies may be main drivers of type-1 interferon activity in SLE.

In early rheumatoid arthritis, anticitrullinated peptide antibodies associate with low number of affected joints and rheumatoid factor associates with systemic inflammation

OBJECTIVES

To investigate how individual rheumatoid arthritis (RA) autoantibodies associate with individual signs and symptoms at the time of RA diagnosis.

METHODS

IgA, IgG, IgM rheumatoid factor (RF), antibodies against cyclic citrullinated peptide version 2 (anti-CCP2) and 16 individual antibodies against citrullinated protein (ACPA) reactivities were analysed centrally in baseline sera from 1600 patients with RA classified according to the 1987 American College of Rheumatology (ACR) criteria. These results were related to C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), number of swollen and tender joints (SJC and TJC), 28-joint disease activity scores (DAS28 and DAS28CRP), global disease activity evaluated by the patients and Health Assessment Questionnaire, all obtained at baseline.

RESULTS

Individually, all autoantibodies except immunoglobulin G (IgG) RF associated with low SJC and TJC and with high ESR. In IgM RF-negative patients, ACPA associated strictly with low number of swollen and tender joints. This association persisted in multiple regression and stratified analyses where IgM and IgA RF instead associated with inflammation expressed as ESR. Among subjects without any ACPA peptide reactivity, there was no association between RF isotypes and ESR. The effect of RF on ESR increased with the number of ACPA reactivities, especially for IgM RF. In patients fulfilling the 1987 ACR criteria without taking RF into account, associations between IgM RF and high ESR, as well as between ACPA and low joint counts, remained.

CONCLUSION

Whereas ACPA associate with low counts of affected joints in early RA, RF associates with elevated measures of systemic inflammation in an ACPA-dependent manner. This latter finding corroborates in vitro models of ACPA and RF in immune complex-induced inflammation. These phenotypic associations are independent of classification criteria.

Serum calprotectin correlates more strongly with inflammation and disease activity in ACPA positive than ACPA negative rheumatoid arthritis

OBJECTIVES

The aim of the present study was to evaluate performance of serum and synovial fluid levels of the granulocyte protein calprotectin as inflammatory biomarker in rheumatoid arthritis (RA) patients with knee synovitis.

METHODS

76 RA patients with ongoing knee synovitis were included. Data on disease activity score with 28 joints and their subcomponents and radiological destruction of the affected knee were collected. White blood cell count, C-reactive protein, anti-citrullinated peptide antibodies (ACPA) against cyclic citrullinated peptide version 2 (anti-CCP2), IgM rheumatoid factor (RF) and calprotectin were analysed in parallel in circulation and in synovial fluid (SF). Counts of polynuclear and mononuclear cells were measured in SF.

RESULTS

Serum (S) calprotectin correlated stronger than SF-calprotectin with inflammatory markers and disease activity. Instead, SF-calprotectin showed a strong correlation to SF counts of white blood cells, and especially to polymorphonuclear cell counts (Spearman's rho = 0.72, p< 0.001). S-calprotectin showed markedly stronger correlation with inflammatory markers and disease activity in ACPA positive as compared with ACPA negative RA patients; a similar difference was observed for patients with and without IgM RF.

CONCLUSION

The particularly strong association between circulating calprotectin and inflammation in ACPA positive RA is a new argument for a specific role for polymorphonuclear granulocytes/neutrophils in this RA subset. Measurement of calprotectin in SF does not convey any additional benefit compared with measurement in the circulation in RA patients with knee synovitis.

Anti-Ro52 positivity is associated with progressive interstitial lung disease in systemic sclerosis-an exploratory study

BACKGROUND

Interstitial lung disease (ILD) is the most common cause of death in patients with systemic sclerosis (SSc). Prognostic biomarkers are needed to identify SSc-ILD patients at risk for progressive pulmonary fibrosis. This study investigates autoantibodies measured in bronchoalveolar lavage (BAL) fluid and in serum in reference to the clinical disease course of SSc-ILD.

METHODS

Fifteen patients with new onset SSc-ILD underwent bronchoscopy. Autoantibody levels were analyzed using addressable laser bead immunoassay from BAL fluid and the serum. In a separate longitudinal cohort of 43 patients with early SSc-ILD, autoantibodies in serum were measured at baseline and pulmonary function tests were performed at least 2 times over the course of at least 2 or more years. Linear mixed effect models were created to investigate the relationship between specific autoantibodies and progression of SSc-ILD. Finally, lung tissue from healthy controls and from subjects with SSc was analyzed for the presence of the Ro52 antigen using immunohistochemistry.

RESULTS

Among SSc-ILD patients who were positive for anti-Ro52 (N = 5), 3 (60%) had enrichment of anti-Ro52 in BAL fluid at a ratio exceeding 50x. In the longitudinal cohort, 10/43 patients (23%) were anti-Ro52 positive and 16/43 (37%) were anti-scl-70 positive. Presence of anti-Scl-70 was associated with a lower vital capacity (VC) at baseline (-12.6% predicted VC [%pVC]; 95%CI: -25.0, -0.29; p = 0.045), but was not significantly associated with loss of lung function over time (-1.07%pVC/year; 95%CI: -2.86, 0.71; p = 0.230). The presence of anti-Ro52 was significantly associated with the loss of lung function over time (-2.41%pVC/year; 95% CI: -4.28, -0.54; p = 0.013). Rate of loss of lung function increased linearly with increasing anti-Ro52 antibody levels (-0.03%pVC per arbitrary units/mL and year; 95%CI: -0.05, -0.02; p < 0.001). Immunohistochemical staining localized the Ro52 antigen to alveolar M2 macrophages in peripheral lung tissue both in subjects with and without SSc.

CONCLUSIONS

This study suggests that antibodies targeting Ro52 are enriched in the lungs of patients with new-onset SSc-ILD, linking Ro52 autoimmunity to the pulmonary pathology of SSc. Clinical and immunohistochemical data corroborates these findings and suggest that anti-Ro52 may serve as a potential biomarker of progressive SSc-ILD.

Anti-phosphatidylserine/prothrombin antibodies and thrombosis associate positively with HLA-DRB1*13 and negatively with HLA-DRB1*03 in SLE

OBJECTIVES

Emerging evidence demonstrates that aPS-PT associate with thrombotic events. Genetic predisposition, including HLA-DRB1 alleles, is known to contribute to the occurrence of conventional aPL [anti-β2glycoprotein-I (anti-β2GPI) and aCL]. We investigated associations between aPS-PT and HLA-DRB1* alleles and thrombosis in SLE. Conventional aPL were included for comparison.

METHODS

We included 341 consecutive SLE patients, with information on general cardiovascular risk factors, including blood lipids, LA and thrombotic events. aPS/PT, anti-β2GPI and aCL of IgA/G/M isotypes and LA were quantified.

RESULTS

aPS/PT antibodies associated positively with HLA-DRB1*13 [odds ratio (OR) 2.7, P = 0.002], whereas anti-β2GPI and aCL antibodies associated primarily with HLA-DRB1*04 (OR 2.5, P = 0.0005). These associations remained after adjustment for age, gender and other HLA-DRB1* alleles. HLA-DRB1*13, but not DRB1*04, remained as an independent risk factor for thrombosis and APS after adjustment for aPL and cardiovascular risk factors. The association between DRB1*13 and thrombosis was mediated by aPS-PT positivity. HLA-DRB1*03, on the other hand, associated negatively with thrombotic events as well as all aPL using both uni- and multivariate analyses. HLA-DRB1*03 had a thrombo-protective effect in aPL-positive patients. Additionally, HLA-DRB1*03 was associated with a favourable lipid profile regarding high-density lipoprotein and triglycerides.

CONCLUSIONS

HLA-DRB1*13 confers risk for both aPS-PT and thrombotic events in lupus. The association between HLA-DRB1*13 and thrombosis is largely, but not totally, mediated through aPS-PT. HLA-DRB1*03 was negatively associated with aPL and positively with favourable lipid levels. Thus, HLA-DRB1*03 seems to identify a subgroup of SLE patients with reduced vascular risk.

The association between autoantibodies and risk for venous thromboembolic events among patients with rheumatoid arthritis

OBJECTIVES

To assess the association between venous thromboembolic (VTE) events and autoantibodies, following patients from rheumatoid arthritis (RA) diagnosis, measuring occurrence, levels and collective load of different autoantibodies against post-translational protein-modifications, in particular recognizing citrullination (e.g. citrullinated fibrinogen), and rheumatoid factor (RF), by isotype.

METHODS

A cohort of 2,814 patients with newly diagnosed RA were followed for incident VTE through register linkages. Sera from RA diagnosis were centrally analysed for antibodies to 2nd generation cyclic citrullinated peptides (anti-CCP2), 20 anti-citrullinated protein antibody (ACPA) fine-specificities, antibodies to additional protein-modifications (carbamylation and acetylation), and RF by isotype. Association between baseline serology status and future VTE was analysed using Cox regression adjusted for age, sex, calendar period of RA diagnosis, overall and stratified by anti-CCP2 and RF positivity.

RESULTS

During a median 16 years of follow-up, 213 first-ever VTE events were registered (5.0/1,000 person-years). IgG Anti-CCP2 (present in 65% of cohort) associated with VTE (HR = 1.33, 95%CI 1.00-1.78), in a dose-response manner. The risk of VTE increased with number of ACPA fine-specificities. IgM RF, but no other RF isotypes, associated with VTE (HR = 1.38 95%CI 1.04-1.82). The associations were independent from smoking and HLA-DRB1 shared epitope alleles. None of the carbamylated or acetylated antibody reactivities associated with VTE.

CONCLUSION

Anti-CCP2, load of ACPA fine-specificities, and IgM RF at RA diagnosis are associated with an increased risk of future VTE in RA. Antibodies to citrullinated fibrinogen did not differ substantially from other ACPA fine-specificities. Autoreactivity to other post-translational modifications were not associated with VTE risk.

[Myositis-related interstitial lung disease - a systemic autoimmune desease often overlooked]

Interstitial lung disease can be the first sign of systemic autoimmune disease. If associated with myositis, interstitial lung disease may be the only symptom, with no presence of muscular weakness or other extramuscular manifestations. ANA-testing performed with indirect immune fluorescence may be negative. Testing for myositis antibodies should be considered as a step in the diagnostic process when strong clinical suspicion of interstitial lung disease of unknown origin is present. If interstitial lung disease is suspected, the patients should be referred to a specialist clinic for further investigation and, if possible, for discussion within a multidisciplinary team. Early suspicion of systemic inflammatory disease, rapid diagnosis and early start of treatment are crucial for future prognosis, quality of life and survival.

Autoantibodies Associated with Autoimmune Liver Diseases in a Healthy Population: Evaluation of a Commercial Immunoblot Test

Autoantibodies constitute important tools for diagnosing the autoimmune liver diseases (AILD) autoimmune hepatitis and primary biliary cholangitis. The EUROLINE immunoblot assay, detecting multiple specificities, is widely used, but the clinical importance of weakly positive findings is unclear. The manufacturer’s recommended cut-off was evaluated by investigating AILD-associated autoantibodies in 825 blood donors and 60 confirmed AILD cases. Positive findings were followed up with immunofluorescence microscopy on rat tissue, anti-M2-ELISA, alternative immunoblot assay, and liver function tests. Thirty-six (4.4%) blood donors were positive with EUROLINE. The most common specificities were LC-1 (1.6%), gp210 (1.3%), and AMA-M2 (1.1%). In general, the positive results were higher in patients than in blood donors, whereas anti-LC-1 was higher in blood donors. The liver function tests were slightly elevated in 2 of the 36 immunoblot positive blood donors. The majority of the positive EUROLINE findings could not be confirmed with the follow-up tests. The EUROLINE-Autoimmune Liver Diseases-(IgG) immunoblot detected autoantibodies in 4.4% of blood donors without signs of AILD. Our findings indicate that the recommended cut-off can be raised for most specificities without loss of diagnostic sensitivity. The prevalence of anti-LC-1 among blood donors indicates a problem with the antigen source.

Associations of C-reactive protein isoforms with systemic lupus erythematosus phenotypes and disease activity

Background

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by a large production of autoantibodies and deficient clearance of cellular waste. The disease typically oscillates between episodes of elevated disease activity and quiescent disease. C-reactive protein (CRP) is a pentameric acute-phase protein usually reflecting inflammation and tissue damage. However, despite increased inflammation and elevated interleukin-6, the levels of CRP typically remain low or only slightly raised in SLE. Under certain conditions, pentameric CRP (pCRP) can dissociate into its monomeric isoform (mCRP), which mainly has been ascribed pro-inflammatory properties. The present study aims to investigate the potential relationship between pCRP and mCRP, respectively, with disease activity and clinical features of SLE.

Methods

The levels of pCRP and mCRP were measured, by turbidimetry (high-sensitive) and sandwich enzyme-linked immunosorbent assay (ELISA) respectively, in serum samples from 160 patients with SLE and 30 patients with antineutrophil cytoplasmic antibody-associated vasculitis (AAV). Twenty-two of the SLE cases were selected for analysis at two time-points; quiescent disease and active disease. The two CRP isoforms were evaluated in relation to disease activity and clinical features in the two diseases.

Results

Levels of pCRP and mCRP were significantly lower in SLE than AAV (p < 0.001) and the ratio of mCRP/pCRP was higher in SLE compared to AAV. The mCRP/pCRP ratio was higher for patients in remission and able to significantly separate between active/quiescent disease in paired, but not in non-paired, samples from patients with SLE. Significant correlations were observed with SLICC/ACR damage index for pCRP levels as well as inversely with the mCRP/pCRP ratio. Lower mCRP levels associated with malar rash.

Conclusion

As the interrelationship between the two isoforms appear to (a) discriminate between quiescent and active SLE and (b) differ between SLE and AAV, our data indicates that the two CRP isoforms could exert contrasting immunological effects and/or reflect different milieus. Given the biological effects of mCRP, it is possible that altered levels may indicate increased opsonization of immune complexes and apoptotic debris, and thereby prevent their deposition outside the reticuloendothelial system and manifestations such as lupus nephritis and lupus-related skin disease.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-022-02831-9.

POS0515 THE ASSOCIATION BETWEEN AUTOANTIBODIES AND RISK FOR VENOUS THROMBOEMBOLIC EVENTS AMONG PATIENTS WITH RHEUMATOID ARTHRITIS

Background

Patients with rheumatoid arthritis (RA) have an increased risk for cardiovascular disease, including venous thromboembolic events (VTE)1. The reason behind the increased VTE risk is incompletely understood, but inherent features of RA, such as RA specific autoantibodies, could potentially play a role. For example, studies have linked occurrence and levels of rheumatoid factor (RF) in the general population to increased VTE risk2. We and others have demonstrated an association between ACPA and risk of later ischemic cardiovascular events3. There are also potential mechanistic links; citrullinated fibrinogen (cFib) has been associated to clot stability4.

Objectives

We aimed to examine the association between anti-modified protein antibodies (AMPAs) and risk of VTE in RA.

Methods

We included 2809 individuals newly diagnosed with RA and included in the Swedish EIRA study 1996-2009. Through linkage to nationwide health care registers we identified past and incident events of VTE based on validated ICD code algorithms. We centrally typed baseline sera for anti-CCP2, 20 different ACPA sub-specificities, RF isotypes, carbamylated antibodies and 10 additional post-translational modifications. We followed all individuals from RA diagnosis up until their first ever VTE event, migration, death or end of study (2020-12-31) whichever occurred first. We used a Cox regression to estimate hazard ratios (HR) with 95% confidence intervals (CI). Individuals with a history of a VTE event (n=27) at RA diagnosis were excluded.

Results

We included 2782 individuals; 72% were women, median age at RA diagnosis was 54 years (inter quartile range (IQR) 18 years) and median follow-up time was 15.5 (IQR 6.8) years. During follow-up 177 incident VTE events were observed corresponding to an incidence of 5.0 per 1,000 person years.

1797 (64.6%) patients were positive for IgG anti-CCP2 and the HR for VTE (vs. being negative for anti-CCP2) was 1.33 (95%CI 1.00-1.78). The risk of VTE increased with the level of anti-CCP2, with an HR of 1.49 (95%CI 0.99-2.22) for the group with extreme levels compared to those negative for anti-CCP2 (p-value for trend 0.048). For IgA anti-CCP2 the HR was 1.35 (95% CI 0.99-1.84) when comparing those expressing IgA anti-CCP2 against those who did not.

Of 20 ACPA fine-specificities studied, 18 occurred with a frequency > 10% in our sample. The median number of fine-specificities expressed was 6 (IQR 11). The risk of VTE increased with the number of ACPA fine-specificities expressed (p-value for trend 0.033). At the 0.05 significance level, two fine-specificities were each associated with VTE; cPept Z1 [HR=1.40 (95%CI 1.06-84)] and cPept-1 [HR=1.47 (95%CI 1.12-1.93)]. None of the six antibodies against cFib assessed were statistically significantly associated with VTE risk. No associations were observed for other AMPAs. Among the three RF isotypes, only IgM RF was statistically associated with VTE [HR=1.38 (95%CI 1.04-1.83)].

Conclusion

RA-related antibodies analysed in clinical practice (anti-CCP2 IgG, RF) are associated not only with risk of myocardial infarction, stroke and cardiovascular death as previously demonstrated but also with VTE. There were no clear specific signals with ACPA fine-specificities, other AMPAs, or IgA RA autoantibodies.

References

[1]Holmqvist ME,et al. Risk of venous thromboembolism in patients with rheumatoid arthritis and association with disease duration and hospitalization. JAMA. 2012;308(13):1350-6.

[2]Meyer-Olesen CL, et al. Increased rheumatoid factor and deep venous thrombosis: 2 cohort studies of 54628 individuals from the general population. Clin Chem. 2015;61(2):349-59.

[3]Westerlind H, et al. Anti-citrullinated protein antibody specificities, rheumatoid factor isotypes and incident cardiovascular events in patients with rheumatoid arthritis. Arthritis Rheumatol. 2020.

[4]Maners J, et al. A Mendelian randomization of gamma’ and total fibrinogen levels in relation to venous thromboembolism and ischemic stroke. Blood. 2020;136(26):3062-9.

Disclosure of Interests

Helga Westerlind: None declared, Alf Kastbom: None declared, Johan Rönnelid: None declared, Monika Hansson: None declared, Lars Alfredsson: None declared, Linda Mathsson-Alm Employee of: LMA an employee of Thermo Fisher Scientific producing the ACPA sub-specificity test, Guy Serre: None declared, Martin Cornillet: None declared, Rikard Holmdahl Consultant of: historically several. Currently paid advisor for Lipum AB and Cyxone AB, Per-Johan Jakobsson Consultant of: UCB – Nov 2021 to Feb 2022., Karl Skriner: None declared, Holger Bang Employee of: HB is an employee of Orgentec Diagnostica, an IVRc company, Lars Klareskog: None declared, Saedis Saevarsdottir Employee of: SS is a part-time employee of deCODE genetics Inc., Karin Lundberg: None declared, Caroline Grönwall: None declared, Johan Askling Grant/research support from: AbbVie, AstraZeneca, Bristol Myers Squibb, Eli Lilly, Janssen, Merck, Pfizer, Roche, Samsung Bioepis, Sanofi, and UCB.

POS0747 ANTI-PHOSPHATIDYLSERINE/PROTHROMBIN ANTIBODIES AND VASCULAR EVENTS ASSOCIATE POSITIVELY WITH HLA-DRB1*13 AND NEGATIVELY WITH HLA-DRB1*03 IN SLE

Background

Anti-phosphatidylserine/prothrombin antibodies (anti-PS/PT) associate with thrombotic events (1). HLA-DRB1 alleles contribute to the occurrence of conventional antiphospholipid antibodies (aPL), including anti-beta2glycoprotein-I (beta2GPI) and anti-cardiolipin (CL) (2).

Objectives

We investigated associations between anti-PS/PT and HLA-DRB1 alleles and thrombosis in patients with SLE. Conventional aPL were included for comparison.

Methods

We included 341 consecutive Swedish SLE patients, with information on general cardiovascular risk factors, including blood lipids, lupus anticoagulant (LAC) and thrombotic events. Anti-PS/PT, anti-beta2GPI and anti-CL of IgA/G/M isotypes were quantified in parallel using particle-based multi-analyte technology. The 99th percentiles among 162 age- and sex-matched populations controls were used as cutoffs. HLA-DRB1 typing was performed using sequence-specific primer PCR.

Results

Anti-PS/PT antibodies associated positively with HLA-DRB1*13 (odds ratio [OR] 2.7, P=0.002), whereas anti-beta2GPI and anti-CL antibodies associated primarily with HLA-DRB1*04 (OR 2.5, P=0.0005; Table 1). These associations remained after adjustment for other significant HLA-DRB1 alleles identified in Table 1 (Figure 1a and b) also for LAC (Figure 1c), and also after adjustment for age and gender (not shown). HLA-DRB1*13, but not DRB1*04, remained as an independent risk factor for thrombosis after adjustment for significant HLA alleles (Figure 1d), and also after adjustment for cardiovascular risk factors in stepwise regression (not shown). Mediation analysis showed that 31.3% of the HLA-DRB1*13-related risk for thrombosis was mediated by anti-PS/PT positivity. HLA-DRB1*03, on the other hand, associated negatively with thrombotic events (Figure 1d) as well as with all aPL (Figure 1a-c). HLA-DRB1*03 had thrombo-protective effect in aPL positive patients (Figure 1d). Additionally, HLA-DRB1*03 positivity was associated with a favourable lipid profile regarding high-density lipoprotein (median 1.4 vs. 1.2 mmol/L, p=0.02) and triglycerides (median 0.9 vs 1.1 mmol/L, p=0.04); whereas no other HLA-DRB1 alleles showed any associations to lipid levels.

Table 1.

Frequency of individual HLA DRB1 and associations with antibody phenotypes. Odds ratios (OR) and confidence intervals (CI) for being antibody positive given a specific HLA allele and corresponding p values were calculated using Chi2 tests, with significant associations underlined.

HLA DRB1HLA-DRB1 n (%) total patientsAnti-PS/PT positive (any isotype) n=48OR (95%CI); PAnti-β2GPI or anti-CL positive (any isotype) n=96OR (95%CI); P*0141 (12.9%)4 (8.3%)0.6 (0.2-1.7); 0.311 (11.4%)0.8 (0.4-1.7); 0.6*03147 (46.5%)13 (27.1%)0.4 (0.2-0.7); 0.00433 (34.4%)0.5 (0.3-0.8); 0.006*0494 (29.7%)18 (37.5%)1.6 (0.8-2.9); 0.241 (42.7%)2.5 (1.5-4.1); 0.0005*0728 (8.9%)6 (12.5%)1.5 (0.6-4); 0.49 (9.4%)1 (0.4-2.4); 0.9*0828 (8.9%)6 (12.5%)1.6 (0.6-4.3); 0.39 (9.4%)1.2 (0.5-2.7); 0.7*099 (2.8%)1 (2.1%)0.7 (0.1-5.5); 0.72 (2.1%)0.6 (0.1-3.0); 0.5*107 (2.2%)0 (0)NA2 (2.1%)0.9 (0.2-4.6); 0.9*1127 (8.5%)6 (12.5%)1.6 (0.6-4.3); 0.38 (8.3%)0.9 (0.4-2.2); 0.8*127 (2.2%)0 (0)NA1 (1%)0.4 (0.05-3.7); 0.4*1379 (25%)21 (43.7%)2.7 (1.4-5.2); 0.00233 (34.3%)2 (1.2-3.4%); 0.01*146 (1.9%)2 (4.2%)3.7 (0.6-23); 0.12 (2.1%)1.4 (0.2-8.9); 0.8*15118 (37.3%)12 (48%)0.5 (0.2-0.9); 0.04527 (28.1%)0.5 (0.3-0.9); 0.01*168 (2.5%)1 (2.1%)0.8 (0.09-6.4); 0.84 (4.2%)2.2 (0.5-9.2); 0.2

Conclusion

HLA-DRB1*13 confers risk for both anti-PS/PT and thrombotic events in SLE. The association between HLA-DRB1*13 and thrombosis is largely, but not entirely, mediated through anti-PS/PT. Due to the negative association of HLA-DRB1*03 with aPL and the positive association with favourable lipid levels, HLA-DRB1*03 seems to identify a subgroup of SLE patients with reduced vascular risk.

References

[1]Elbagir S et al. Lupus 2021;30(8):1289.

[2]Lundström E et al. Ann Rheum Dis 2013;72:1018.

Disclosure of Interests

Sahwa Elbagir: None declared, Lina M. Diaz-Gallo: None declared, Giorgia Grosso: None declared, Agneta Zickert: None declared, Iva Gunnarsson: None declared, Michael Mahler Employee of: Dr Mahler is employee of Werfen., Elisabet Svenungsson Speakers bureau: Dr Svennungson has obtained speaker’s fees from Janssen., Grant/research support from: Dr Svennungson has obtained research grant from Merck., Johan Rönnelid Speakers bureau: Dr Rönnelid has given paid lectures for Thermo Fisher Scientific., Consultant of: Dr Rönnelid has been a member of the Scientific Advisory Board for Thermo Fisher Scientific.

OP0307 PULMONARY FIBROSIS IN EARLY RHEUMATOID ARTHRITIS IN RELATION TO GENETIC LOCI AND INDIVIDUAL ACPA SPECIFICITIES

Background

Pulmonary manifestations in rheumatoid arthritis (RA) are common comorbidities but the underlying mechanisms are largely unknown. We found in a previous study 3 SNPs associated with pulmonary fibrosis (PF); rs35705950 (MUC5B), rs111521887 (TOLLIP), and rs2609255 (FAM13A) besides age, rheumatoid factor positivity and methotrexate treatment.

Objectives

To evaluate for the added value of a multiplex of anti-citrullinated peptide antibodies (ACPA) for the development of pulmonary fibrosis (PF) in an inception cohort of RA patients.

Methods

A total of 1184 patients with early RA were consecutively included and followed prospectively from the date of diagnosis (index date) until death or until 31 December 2016. The diagnosis of PF was based on high resolution tomography. The presence of 21 ACPA fine specificities were analysed in plasma sampled at index date, using a custom-made microarray chip (Thermo Fisher Scientific, Uppsala, Sweden). Data on both ACPA and genetic data was available for 841 RA patients, of whom 50 developed PF. Associations were analysed using logistic regression analysis and presented as the odds ratio (OR) with the 95% confidence interval (CI). Models were adjusted for sex, age, DAS28 and presence of RF at RA diagnosis, smoking ever, and HLA-SE and in a second step for the three SNPs (.rs35705950, rs111521887 and rs2609255), respectively.

Results

In unadjusted analyses eight ACPA reactivities were found associated with PF development (p< 0.05-0.001). The number of ACPA reactivities was related to PF development, both in crude and adjusted models (p<0.05 for both). In models concomitantly adjusted for the three SNPs (rs35705950, rs111521887 and rs2609255) respectively, in addition to mentioned adjustments the number of ACPA reactivities (p<0.05 for all three nmodels), Vim60-75 (p<0.05, in all three models), Fibβ62–78 (72) (p<0.001-p<0.05) and F4-CIT-R (p<0.01-p<0.05) were all found significantly associated to PF development irrespective of the SNPs.

Conclusion

The development of PF in an inception cohort of RA patients was associated both with risk genes and, independently of the risk genes, the presence of certain ACPA, and the number of ACPA reactivities.

References

[1]Jönsson E, et al. Pulmonary fibrosis in relation to genetic loci in an inception cohort of patients with early rheumatoid arthritis from northern Sweden. Rheumatology (Oxford). 2021 May 16:keab441. doi: 10.1093/rheumatology/keab441.

Acknowledgements

I have no acknowledgements to declare. The staff and patients at the departments of rheumatology in northern Sweden.

Disclosure of Interests

None declared

ELISA, protein immunoprecipitation and line blot assays for anti-TIF1-gamma autoantibody detection in cancer-associated dermatomyositis

OBJECTIVES

Anti-TIF1-gamma autoantibodies can be detected with immunoprecipitation (IP), line blot (LB) and ELISA. We compared assay performance in patients with DM and the potential of these assays to detect anti-TIF1-gamma positive cancer-associated DM (CADM).

METHODS

We included sera from 131 patients with DM followed at Karolinska University Hospital, Stockholm, Sweden and 82 healthy controls. Serum samples taken at DM diagnosis were tested for anti-TIF1-gamma autoantibodies with IP, two ELISAs (in-house and commercial) and LB. Cancer diagnosis and dates were obtained from the Swedish national cancer register. CADM was defined as a malignancy that developed within 3 years of DM diagnosis.

RESULTS

Anti-TIF1-gamma autoantibodies were detected in 19/101 (18.8%), 15/113 (13.2%), 34/131 (26%) and 45/131 (34.4%) of the patients with IP, LB, in-house and commercial ELISA, respectively. The anti-TIF1-gamma results from the in-house ELISA were confirmed with IP in 93 of 101 (92%) cases, κ = 0.76, with a commercial ELISA in 110 of 131 (84%) cases, κ = 0.63, and with LB in 101 of 113 (89.3%) cases, κ = 0.67. Anti-TIF1-gamma results with IP were confirmed with LB in 85 of 92 (92.4%) cases, κ = 0.73. For detecting CADM, the anti-TIF1-gamma in-house ELISA had a sensitivity of 58% and specificity of 86%, the commercial ELISA had a sensitivity of 63% and specificity of 82%, IP had a sensitivity of 52% and specificity of 92%, LB had a sensitivity of 40% and specificity of 96%.

CONCLUSION

The two anti-TIF1-gamma ELISA assays had advantages both for autoantibody detection and to identify anti-TIF1-gamma-positive CADM.

Antibodies to a Citrullinated Porphyromonas gingivalis Epitope Are Increased in Early Rheumatoid Arthritis, and Can Be Produced by Gingival Tissue B Cells: Implications for a Bacterial Origin in RA Etiology

Based on the epidemiological link between periodontitis and rheumatoid arthritis (RA), and the unique feature of the periodontal bacterium Porphyromonas gingivalis to citrullinate proteins, it has been suggested that production of anti-citrullinated protein antibodies (ACPA), which are present in a majority of RA patients, may be triggered in the gum mucosa. To address this hypothesis, we investigated the antibody response to a citrullinated P. gingivalis peptide in relation to the autoimmune ACPA response in early RA, and examined citrulline-reactivity in monoclonal antibodies derived from human gingival B cells. Antibodies to a citrullinated peptide derived from P. gingivalis (denoted CPP3) and human citrullinated peptides were analyzed by multiplex array in 2,807 RA patients and 372 controls; associations with RA risk factors and clinical features were examined. B cells from inflamed gingival tissue were single-cell sorted, and immunoglobulin (Ig) genes were amplified, sequenced, cloned and expressed (n=63) as recombinant monoclonal antibodies, and assayed for citrulline-reactivities by enzyme-linked immunosorbent assay. Additionally, affinity-purified polyclonal anti-cyclic-citrullinated peptide (CCP2) IgG, and monoclonal antibodies derived from RA blood and synovial fluid B cells (n=175), were screened for CPP3-reactivity. Elevated anti-CPP3 antibody levels were detected in RA (11%), mainly CCP2+ RA, compared to controls (2%), p<0.0001, with a significant association to HLA-DRB1 shared epitope alleles, smoking and baseline pain, but with low correlation to autoimmune ACPA fine-specificities. Monoclonal antibodies derived from gingival B cells showed cross-reactivity between P. gingivalis CPP3 and human citrullinated peptides, and a CPP3+/CCP2+ clone, derived from an RA blood memory B cell, was identified. Our data support the possibility that immunity to P. gingivalis derived citrullinated antigens, triggered in the inflamed gum mucosa, may contribute to the presence of ACPA in RA patients, through mechanisms of molecular mimicry.

Anti-citrullinated protein antibody specificities and pulmonary fibrosis in relation to genetic loci in early rheumatoid arthritis

OBJECTIVES

Pulmonary manifestations in RA are common comorbidities, but the underlying mechanisms are largely unknown. The added value of a multiplex of ACPA and genetic risk markers was evaluated for the development of pulmonary fibrosis (PF) in an inception cohort.

METHODS

A total of 1184 patients with early RA were consecutively included and followed prospectively from the index date until death or 31 December 2016. The presence of 21 ACPA fine specificities was analysed using a custom-made microarray chip (Thermo Fisher Scientific, Uppsala, Sweden). Three SNPs, previously found related to PF were evaluated, rs2609255 (FAM13A), rs111521887 (TOLLIP) and rs35705950 (MUC5B). ACPA and genetic data were available for 841 RA patients, of whom 50 developed radiologically defined PF.

RESULTS

In unadjusted analyses, 11 ACPA specificities were associated with PF development. In multiple variable analyses, six ACPA specificities were associated with increased risk of PF: vimentin (Vim)60-75, fibrinogen (Fib)β62-78 (72), Fibα621-635, Bla26, collagen (C)II359-369 and F4-CIT-R (P < 0.01 to P < 0.05). The number of ACPA specificities was also related to PF development (P < 0.05 crude and adjusted models). In multiple variable models respectively adjusted for each of the SNPs, the number of ACPA specificities (P < 0.05 in all models), anti-Vim60-75 (P < 0.05, in all models), anti-Fibβ62-78 (72) (P < 0.001 to P < 0.05), anti-CII359-369 (P < 0.05 in all models) and anti-F4-CIT-R AQ4 (P < 0.01 to P < 0.05), anti-Fibα621-635 (P < 0.05 in one) and anti-Bla26 (P < 0.05 in two) were significantly associated with PF development.

CONCLUSION

The development of PF in an inception cohort of RA patients was associated with both presence of certain ACPA and the number of ACPA specificities and risk genes.

Extramucosal Formation and Prognostic Value of Secretory Antibodies in Rheumatoid Arthritis

OBJECTIVE

To investigate levels and possible extramucosal formation of secretory Ig, including anti-citrullinated protein antibodies (ACPAs), in rheumatoid arthritis (RA).

METHODS

Three patient groups were studied: 1) ACPA-positive patients with musculoskeletal pain without clinical arthritis, 2) patients with recent-onset RA, and 3) patients with established RA. In baseline serum samples (groups 1 and 2) and paired synovial fluid samples (group 3), we analyzed total secretory IgA, total secretory IgM, free secretory component (SC), and SC-containing ACPA. Extramucosal formation of SC-containing ACPA was investigated by preincubating RA sera and affinity-purified ACPA with recombinant free SC.

RESULTS

Compared to healthy controls, serum levels of total secretory IgA and total secretory IgM were increased both in patients with early RA and at-risk patients (P < 0.05). Patients with early RA with elevated total secretory Ig had significantly higher disease activity during the 3-year follow-up period compared to those without increased levels. At-risk patients who developed arthritis during follow-up (39 of 82) had higher baseline total secretory IgA levels compared to those who did not (P = 0.041). In established RA, total secretory IgA and total secretory IgM levels were higher in serum than in synovial fluid (P < 0.0001), but SC-containing ACPAs adjusted for total secretory Ig concentration were higher in synovial fluid (P < 0.0001). Preincubation with recombinant free SC yielded increased SC-containing ACPA reactivity in sera as well as in affinity-purified IgA and IgM ACPA preparations.

CONCLUSION

Circulating secretory Ig are elevated before and at RA onset. In the presence of free SC, secretory Ig may form outside the mucosa, and SC-containing ACPAs are enriched in RA joints. These findings shed important new light on the mucosal connection in RA development.

Impact of autoimmune serology test results on RA classification and diagnosis

Rheumatoid arthritis (RA) is the most common systemic autoimmune disease and also the most severe arthritic disorder. The measurement of rheumatoid factor (RF) and anti-citrullinated protein antibodies (ACPA) in serum supports the diagnosis of RA, which gained increasing significance over the last 65 years. However, a high variability between RF and ACPA methods has been described, impacting the diagnostic performance of the current ACR/EULAR RA classification criteria.

The great number of commercially available assays, often lacking traceability to an international standard, is a major factor attributing to this in-between assay variability. The adoption of an international standard for ACPA, as is since long available for rheumatoid factor, is therefore highly desirable.

Further harmonization in clinical interpretation of RF/ACPA assays could be obtained by harmonization of the cut-offs, for both the low and high antibody levels, based on predefined specificity in disease controls. Reporting test result specific likelihood ratios (LR) adds value in the interpretation of autoantibody tests. However, a good understanding of the control population used to define antibody test result interval-associated LRs is crucial in defining the diagnostic performance characteristics of antibody serology.

Finally, specificity in RA classification can be improved by refining serological weight scoring taking into account the nature of the antibody, the antibody level and double RF + ACPA positivity.

The citrullinated/native index of autoantibodies against hnRNP-DL predicts an individual "window of treatment success" in RA patients

BACKGROUND

There is a need for biomarker to identify patients "at risk" for rheumatoid arthritis (risk-RA) and to better predict the therapeutic response and in this study we tested the hypothesis that novel native and citrullinated heterogeneous nuclear ribonucleoprotein (hnRNP)-DL autoantibodies could be possible biomarkers.

METHODS

Using protein macroarray and ELISA, epitope recognition against hnRNP-DL was analysed in sera from different developed RA disease and diagnosed SLE patients. Toll-like receptor (TLR) 7/9 and myeloid differentiation primary response gene 88 (MyD88)-dependency were studied in sera from murine disease models. HnRNP-DL expression in cultivated cells and synovial tissue was analysed by indirect immunofluorescence, immunoblot and immunohistochemistry.

RESULTS

HnRNP-DL was highly expressed in stress granules, citrullinated in the rheumatoid joint and targeted by autoantibodies either as native or citrullinated proteins in patient subsets with different developed RA disease. Structural citrullination dependent epitopes (SCEs) of hnRNP-DL were detected in 58% of the SLE patients although 98% of these sera were α-CCP-2-negative. To obtain a specific citrullinated signal value, we subtracted the native antibody value from the citrullinated signal. The citrullinated/native index of autoantibodies against hnRNP-DL (CNDL-Index) was identified as a new value for an "individual window of treatment success" in early RA and for the detection of RF IgM/α-CCP-2 seronegative RA patients (24-46%). Negative CNDL-index was found in SLE patients, risk-RA and early RA cohorts such as EIRA where the majority of these patients are DAS28-responders to methotrexate (MTX) treatment (87%). High positive CNDL-values were associated with more severe RA, shared epitope and parenchymal changes in the lung. Specifically, native α-hnRNP-DL is TLR7/9-dependent, associated with pain and ROC analysis revealed an association to initial MTX or etanercept treatment response, especially in seronegative RA patients.

CONCLUSION

CNDL-index defines people at risk to develop RA and the "window of treatment success" thereby closing the sensitivity gap in RA.

POS0009 THE RELATIONSHIP BETWEEN DIFFERENT IGG AND IGA ANTI-MODIFIED PROTEIN AUTOANTIBODIES IN RHEUMATOID ARTHRITIS

Background:

Seropositive rheumatoid arthritis (RA) is characterized by the presence of rheumatoid factor (RF) and anti-citrullinated protein autoantibodies (ACPA) with different fine-specificities. Yet, other serum anti-modified protein autoantibodies (AMPA), e.g. anti-carbamylated (Carb), anti-acetylated (KAc), and anti-malondialdehyde acetaldehyde (MAA) modified protein antibodies, have been described. By using RA patient single-cell derived monoclonal antibodies we have previously shown that individual ACPA clones recognize small distinct citrulline-containing epitopes giving them extensive multireactivity when these epitopes are found in many peptides and proteins. Moreover, certain CCP2+ multireactive ACPA clones bind also to cabamylated and acetylated autoantigens [1].

Objectives:

To provide a comprehensive evaluation of serum IgG and IgA autoreactivity to different post-translational modifications in RA.

Methods:

We analyzed 30 different IgG and IgA AMPA reactivities to modified antigens by ELISA and autoantigen arrays, in N=1985 newly diagnosed RA patients and population controls. The study utilized both previously established (i.e IgG and IgA CCP2; IgG ACPA fine-specificities; IgG anti-Carb fibrinogen and Carb FCS; IgG and IgA Cit/Carb/KAc/Orn(Ac)-vimentin), and novel assays (e.g. IgG anti-MAA and IgG anti-acetylated histones). Association with patient characteristics such as smoking and disease activity were explored. The newly developed assays were also evaluated in SLE disease controls and CCP2+ RA-risk individuals without arthritis.

Results:

Carb and KAc reactivities by different assays were primarily seen in patients also positive for citrulline-reactivity. Modified vimentin (mod-Vim) peptides were used for direct comparison of different AMPA reactivities, revealing that IgA AMPA recognizing mod-Vim was mainly detected in subsets of patients with high IgG anti-Cit-Vim levels and a history of smoking. IgG acetylation reactivity was mainly detected in a subset of patients with Cit and Carb reactivity. Anti-acetylated histone 2B reactivity was RA-specific and associated with high anti-CCP2 IgG levels, multiple ACPA fine-specificities, and smoking. This reactivity was also found to be present in CCP2+ RA-risk individuals without arthritis. Our data further demonstrate that IgG autoreactivity to MAA was increased in RA compared to controls with highest levels in CCP2+ RA, but was not RA-specific, and showed low correlation with other AMPA. Anti-MAA was instead associated with disease activity and was not significantly increased in CCP2+ individuals at risk of RA. Notably, RA patients could be subdivided into four different subsets based on their AMPA IgG and IgA reactivity profiles.

Conclusion:

We conclude that autoantibodies exhibiting different patterns of ACPA fine-specificities as well as Carb and KAc reactivity are present in RA and may be derived from multireactive B-cell clones. Anti-Carb and anti-KAc could be considered reactivities within the “Cit-umbrella” similar to ACPA fine-specificities, while MAA is distinctly different.

References:

[1]Sahlström P, Hansson M, Steen J, Amara K, Titcombe PJ, Forsström B, Stålesen R, Israelsson L, Piccoli L, Lundberg K, Klareskog L, Mueller DL, Catrina AI, Skriner K, Malmström V, Grönwall C. Different Hierarchies of Anti-Modified Protein Autoantibody Reactivities in Rheumatoid Arthritis. Arthritis Rheumatol. 2020 Oct;72(10):1643-1657. PMID: 32501655

Caroline Grönwall: None declared, Lisa Liljefors: None declared, Holger Bang Employee of: Employee at ORGENTEC Diagnostika GmbH, Aase Hensvold: None declared, Monika Hansson: None declared, Linda Mathsson-Alm Employee of: Employee at Thermo Fisher Scientific, Lena Israelsson: None declared, Anna Svärd: None declared, Cyril CLAVEL: None declared, Elisabet Svenungsson: None declared, Iva Gunnarsson: None declared, Guy Serre: None declared, Saedis Saevarsdottir: None declared, Alf Kastbom: None declared, Lars Alfredsson: None declared, Vivianne Malmström: None declared, Johan Rönnelid: None declared, Anca Catrina: None declared, Karin Lundberg: None declared, Lars Klareskog: None declared

AB0122 THE NORA PROJECT - PREDICTION OF THERAPY RESPONSE IN RHEUMATOID ARTHRITIS

Background:

Personalized medicine in Rheumatoid arthritis (RA) especially regarding therapy response is still in early stages. The Nordic RA (NORA) project is aiming to improve the prediction of therapy outcome by combining established serologic marker with new markers, genetic information and patient-derived data.

Objectives:

As an initial step in the project the aim was to select clinically characterized patient cohorts and evaluate if changes or patterns in serological markers could predict therapy response and/or disease progress.

Methods:

The ARCTIC (Aiming for Remission in rheumatoid arthritis: a randomised trial examining the benefit of ultrasound in a Clinical TIght Control regimen) study [1] was designed to compare two tight control treatment strategies for early Rheumatoid arthritis and was used as a first cohort. Plasma samples (n=1622) from 224 RA patients from the ARCTIC study were included and taken at baseline and 3, 4, 6, 8, 10, 12, 14, 16, 20, and 24 months from trial start, and analyzed for the presence of EliATM RF (IgM, IgA, IgG), anti-CCP (IgG, IgA) and anti-RA33 (IgM, IgA, IgG) autoantibodies, as well as Calprotectin using the EliA instrument platform (Phadia AB, Uppsala, Sweden). In addition, a custom-made multiplex chip (Thermo Fisher Scientific, Sweden) [2] was used for measurement of anti-IgG antibodies against RA-specific antigens (citrullinated, acetylated and carbamylated), and established CTD-markers (Connective Tissue Disease), e.g. Ro52/60 and dsDNA. The citrullinated peptides on the multiplex chip were both multiple as well as single citrullinated at different positions within the peptide sequence. Additionally, we included an ELISA to measure antibodies against native human collagen II [3].

Results:

The different single assays in the baseline samples varied between 7 – 80% positive test results, e.g. anti-CCP IgG 80%. For some patients we could see changes in levels for anti-CCP, RF and anti-RA33 in the follow up samples, which varied from negative to more than 3-10xULN (Upper Limit of Normal). For anti-CCP IgG we found 9 patients (4%), who changed from negative to positive (patient 1-5) or from positive to negative (patient 6-8), while patient 9 had a peak at visit 6 (=12 months) and declined afterwards (figure 1). In addition, the above mentioned 9 patients showed clear changes in signal strength for the markers included on the multiplex chip and followed a similar pattern as the anti-CCP IgG signal. Different antibody patterns against single citrullinated peptides were observed and number of ACPA-positive peptides correlated with IgG anti-CCP levels.

Figure 1.

Anti-CCP IgG value normalised to cutoff (blue line) for patient 1 to 9. The heatmap visualizes the change over time in anti-CCP IgG signal with dark blue showing negative results and orange/red showing results >5xULN.

Anti-Collagen II antibodies (anti-CII) were detected in 15% of the baseline samples and in most cases declined over time. Two patients showed low baseline anti-CII levels that increased in the follow up samples. The changes in serological markers and the different reactivity patterns could possibly correlate with clinical outcome and define subgroups of patients with different response to therapy.

Results could be repeated in RA patients from the NOR-VEAC [4] cohort. At baseline 73% of the 106 RA patients had a positive anti-CCP IgG result and 11 patients (10%) showed a significant change of anti-CCP IgG level over time.

Conclusion:

Different response patterns and changes in serological antibody levels over the first 24 months after RA diagnosis could possibly reveal subgroups of patients with different prognosis and response to treatment. Further evaluations in additional treatment cohorts and correlation with clinical data are ongoing.

References:

[1]Haavardsholm et al., BMJ 2016;354:i4205.

[2]Hansson et al. Arthritis Research & Therapy 2012, 14:R201.

[3]Manivel et al Ann Rheum Dis. 2017 Sep;76(9):1529-1536.

[4]Mjaavatten et al., Arthritis Research & Therapy 2009, 11:R146.

Acknowledgements:

The NORA project is a NordForsk funded project.

Disclosure of Interests:

Linda Mathsson-Alm Employee of: Employee of Thermo Fisher Scientific, Isabel Gehring Employee of: Employee of Thermo Fisher Scientific, Maryam Poorafshar Employee of: Employee of Thermo Fisher Scientific, Johan Rönnelid: None declared, Johan Askling Grant/research support from: Research grants from Abbvie, Astra-Zeneca, BMS, Eli Lilly, MSD, Pfizer, Roche, Samsung Bioepis, Sanofi, and UCB, mainly in the context of safety monitoring (ARTIS), Espen Haavardsholm: None declared, Hilde Berner Hammer: None declared

POS0355 ASSOCIATIONS BETWEEN HLA-DRB1 SHARED EPITOPES ALLELES AND ANTI-RA33 ANTIBODIES IN DIFFERENT SUBSETS OF RHEUMATOID ARTHRITIS IN MALAYSIAN POPULATION

Background:

The mechanisms affecting anti-RA33 antibody’s involvement in RA pathogenesis is still unclear. Refining our understanding of anti-RA33’s role in RA in relation to known RA-associated genes and serological elements is needed.

Objectives:

We investigated the relationship between RA-associated HLA-DRB1 epitope (SE) allele and presence of anti-RA33 antibodies in different serological subsets of rheumatoid arthritis in a Malaysian population.

Methods:

Serum samples from 550 RA cases comprising seronegative (negative for anti-CCP2, IgG and IgM, n=250), seropositive (triple-autoantibody positive, n=150), singular anti-CCP2 positive (n=100), and double RF positive RA (n=50) were chosen from the Malaysian Epidemiological Investigations of RA (MyEIRA) case-control study. Three hundred MyEIRA population controls were used for comparison. All serum samples were assayed using a commercial anti-RA33 ELISA kit. All genetic samples were genotyped for four-digit HLA-DRB1 alleles using the PCR-SSO method on Luminex platform.

Results:

The proportions of anti-RA33 positive was 20.9% in all RA cases (i.e. 34% in RF only positive RA; 25% in seropositive RA; 18% in seronegative RA and 18% in anti-CCP2 only positive RA). The HLA-DRB1 shared epitope alleles were significantly associated with anti-RA33 positive in the seropositive RA subgroup (OR=6.9, 95% CI 1.4-34.8; p=0.02). We observed significant association between anti-RA33 negative and HLA-DRB1 SE alleles among the seropositive RA patients (OR=4.5, 95% CI 2.8-7.2; p<0.001) and among CCP only positive RA (OR=4.4; 95% CI 2.6-7.4; p<0.01). No association was observed between anti-RA33 status and HLA-DRB1 SE alleles in seronegative RA and RF only positive RA.

Conclusion:

The HLA-DRB1 SE alleles increased the risk of seropositive and CCP only positive RA independent of anti-RA33 positivity.

References:

[1]Boeters, Debbie M et al. “The 2010 ACR/EULAR criteria are not sufficiently accurate in the early identification of autoantibody-negative rheumatoid arthritis: Results from the Leiden-EAC and ESPOIR cohorts.” Seminars in arthritis and rheumatism vol. 47,2 (2017): 170-174.

[2]de Brito Rocha, Sara et al. “Clinical and pathophysiologic relevance of autoantibodies in rheumatoid arthritis.” Advances in rheumatology (London, England) vol. 59,1 2. 17 Jan. 2019.

Acknowledgements:

The authors would like to thank the Director General of Health, Ministry of Health Malaysia for supporting this study. The authors are also indebted to participants for their kind participation. This study was financially supported by the Ministry of Health, Malaysia (JPP-IMR 08-012).

Disclosure of Interests:

None declared

POS0457 CHANGES OF RF ISOTYPE PROFILE IN PATIENTS WITH RHEUsMATOID ARTHRITIS: DATA FROM 10 YEARS FOLLOW-UP STUDY

Background:

Presence of autoantibodies such as anti-cyclic citrullinated peptide (anti-CCP2) and rheumatoid factor (RF) is of considerable diagnostic and prognostic value in patients with rheumatoid arthritis (RA). Limited data are available for autoantibody profile changes over time in patients with RA.

Objectives:

Thus, we compared the presence of anti-CCP2 and different RF isotypes in individual RA patients at baseline and during 10 years follow-up.

Methods:

A total of 320 RA patients from the Malaysian Epidemiological Investigation of Rheumatoid Arthritis (MyEIRA) case-control study was included in this study. The presence of anti-CCP2, IgM RF, IgG RF, and IgA RF at baseline and at later time point (±10 years) were determined using enzyme-linked immunosorbent assays, with identical techniques in paired samples. Seropositive RA is defined by the presence of at least one autoantibody, whilst seronegative RA is defined by the absence of all investigated autoantibodies.

Results:

The proportion of seropositive RA were higher for the follow-up samples (n=263, 82.2%) as compared to the baseline samples (n=251, 78.4%). Among the baseline samples, 105 (41.8%) were positive for anti-CCP2 and all RF isotypes. Of these individuals, 85 (81.0%) remained positive for all antibodies at the follow-up, while 20 (19.0%) lost one or more RF isotypes (4 IgM RF, 19 IgG RF and 13 IgA RF). Interestingly, 14 (5.6%) RA patients who were seropositive at baseline became totally seronegative after follow-up. Among the 69 patients seronegative at baseline, 26 (37.7%) acquired one or more autoantibodies at follow-up (14 IgM RF, 2 IgG RF, 9 IgA RF and 8 anti-CCP2) (Figure 1).

Conclusion:

Anti-CCP2 present at baseline usually remained at follow-up. Among Malaysian RA patients, changes in status were mainly found for RF of all isotypes.

References:

[1]Barra, Lillian et al. “Lack of seroconversion of rheumatoid factor and anti-cyclic citrullinated peptide in patients with early inflammatory arthritis: a systematic literature review.” Rheumatology (Oxford, England) vol. 50,2 (2011): 311-6.

[2]van Delft, Myrthe A M, and Tom W J Huizinga. “An overview of autoantibodies in rheumatoid arthritis.” Journal of autoimmunity vol. 110 (2020): 102392.

Figure 1.

Comparison of serum autoantibody profile in rheumatoid arthritis patients during baseline enrolment and 10 years follow-up.

Acknowledgements:

The authors would like to thank the Director General of Health, Ministry of Health Malaysia for supporting this study. The authors are also indebted to participants for their kind participation. This study was financially supported by the Ministry of Health, Malaysia (JPP-IMR 08-012; 18-051).

Disclosure of Interests:

None declared

A Comprehensive Evaluation of the Relationship Between Different IgG and IgA Anti-Modified Protein Autoantibodies in Rheumatoid Arthritis

Seropositive rheumatoid arthritis (RA) is characterized by the presence of rheumatoid factor (RF) and anti-citrullinated protein autoantibodies (ACPA) with different fine-specificities. Yet, other serum anti-modified protein autoantibodies (AMPA), e.g. anti-carbamylated (Carb), -acetylated (KAc), and malondialdehyde acetaldehyde (MAA) modified protein antibodies, have been described. In this comprehensive study, we analyze 30 different IgG and IgA AMPA reactivities to Cit, Carb, KAc, and MAA antigens detected by ELISA and autoantigen arrays in N=1985 newly diagnosed RA patients. Association with patient characteristics such as smoking and disease activity were explored. Carb and KAc reactivities by different assays were primarily seen in patients also positive for anti-citrulline reactivity. Modified vimentin (mod-Vim) peptides were used for direct comparison of different AMPA reactivities, revealing that IgA AMPA recognizing mod-Vim was mainly detected in subsets of patients with high IgG anti-Cit-Vim levels and a history of smoking. IgG reactivity to acetylation was mainly detected in a subset of patients with Cit and Carb reactivity. Anti-acetylated histone reactivity was RA-specific and associated with high anti-CCP2 IgG levels, multiple ACPA fine-specificities, and smoking status. This reactivity was also found to be present in CCP2+ RA-risk individuals without arthritis. Our data further demonstrate that IgG autoreactivity to MAA was increased in RA compared to controls with highest levels in CCP2+ RA, but was not RA-specific, and showed low correlation with other AMPA. Anti-MAA was instead associated with disease activity and was not significantly increased in CCP2+ individuals at risk of RA. Notably, RA patients could be subdivided into four different subsets based on their AMPA IgG and IgA reactivity profiles. Our serology results were complemented by screening of monoclonal antibodies derived from single B cells from RA patients for the same antigens as the RA cohort. Certain CCP2+ clones had Carb or Carb+KAc+ multireactivity, while such reactivities were not found in CCP2- clones. We conclude that autoantibodies exhibiting different patterns of ACPA fine-specificities as well as Carb and KAc reactivity are present in RA and may be derived from multireactive B-cell clones. Carb and KAc could be considered reactivities within the “Cit-umbrella” similar to ACPA fine-specificities, while MAA reactivity is distinctly different.

Autoantibodies in Rheumatoid Arthritis - Laboratory and Clinical Perspectives

Measurement of two groups of autoantibodies, rheumatoid factor (RF) and anti-citrullinated protein/peptide antibodies (ACPA) have gained increasing significance in the diagnosis and classification of rheumatoid arthritis (RA) over the last 65 years. Despite this rising importance of autoimmune serology in RA, there is a palpable lack of harmonization between different commercial RF and ACPA tests. While a minimal diagnostic specificity has been defined for RF tests, which almost always are related to an international reference preparation, neither of this applies to ACPA. Especially assays with low diagnostic specificity are associated with very low positive predictive values or post-test probabilities in real world settings. In this review we focus on issues of practical bearing for the clinical physician diagnosing patients who potentially have RA, or treating patients diagnosed with RA. We advocate that all clinically used assays for RF and ACPA should be aligned to a common diagnostic specificity of 98-99% compared to healthy controls. This high and rather narrow interval corresponds to the diagnostic specificity seen for many commercial ACPA tests, and represents a specificity that is higher than what is customary for most RF assays. Data on antibody occurrence harmonized in this way should be accompanied by test result-specific likelihood ratios for the target diagnosis RA on an ordinal or interval scale, which will provide the clinical physician with more granular and richer information than merely relating numerical values to a single cut-off point. As many physicians today are used to evaluate autoantibodies as positive or negative on a nominal scale, the introduction of test result-specific likelihood ratios will require a change in clinical mindset. We also discuss the use of autoantibodies to prognosticate future arthritis development in at-risk patients as well as predict severe disease course and outcome of pharmacological treatment.

Associations with thrombosis are stronger for antiphosphatidylserine/prothrombin antibodies than for the Sydney criteria antiphospholipid antibody tests in SLE

Objectives

Antiphosphatidylserine/prothrombin complex antibodies (aPS/PT) are risk factors for thrombosis, yet further validation of their clinical relevance in different ethnic groups is required. We investigated the performance of aPS/PT of IgA/G/M isotypes among Sudanese and Swedish systemic lupus erythematosus (SLE) patients.

Methods

Consecutive SLE patients/matched controls from Sudan (n = 91/102) and Sweden (n = 332/163) were included. All patients fulfilled the 1982 ACR SLE classification criteria. IgA/G/M of aPS/PT, anti-cardiolipin and anti-β₂glycoprotein I (anti-β₂GPI) were tested in both cohorts, and lupus anticoagulant (LA) also in the Swedish cohort. Clinical antiphospholipid syndrome-related events and atherosclerosis, measured as carotid plaques were assessed for associations. Univariate and multivariate analyses adjusting for cardiovascular risk factors were performed.

Results

Sudanese SLE patients had higher levels of IgM aPS/PT, but using national cut-offs, the frequency of positivity was similar to Swedish patients for all isotypes. Among Swedish patients, all isotypes of aPS/PT associated with venous thromboembolism (VTE), while only IgA aPS/PT associated with arterial thrombosis (AT). aPS/PT antibodies associated strongly with LA and they were, independently, the best predictor for VTE. Double positivity for aPS/PT and anti-β₂GPI associated with higher VTE risk than the conventional triple positivity. Carotid plaques did not associate with any antiphospholipid antibody.

Conclusions

IgA aPS/PT associated with AT, and the association of IgG/M aPS/PT with VTE outperforms LA and criteria antiphospholipid antibodies in Swedish SLE patients. Furthermore, double positivity for aPS/PT and anti-β₂GPI performed better than conventional triple positivity. Future studies need to address if aPS/PT can replace LA, as this would simplify clinical procedures.

False Positive Results in SARS-CoV-2 Serological Tests for Samples From Patients With Chronic Inflammatory Diseases

Patients with chronic inflammatory diseases are often treated with immunosuppressants and therefore are of particular concern during the SARS-CoV-2 pandemic. Serological tests will improve our understanding of the infection and immunity in this population, unless they tests give false positive results. The aim of this study was to evaluate the specificity of SARS-Cov-2 serological assays using samples from patients with chronic inflammatory diseases collected prior to April 2019, thus defined as negative. Samples from patients with multiple sclerosis (MS, n=10), rheumatoid arthritis (RA, n=47) with or without rheumatoid factor (RF) and/or anti-cyclic citrullinated peptide antibodies (anti-CCP2) and systemic lupus erythematosus (SLE, n=10) with or without RF, were analyzed for SARS-CoV-2 antibodies using 17 commercially available lateral flow assays (LFA), two ELISA kits and one in-house developed IgG multiplex bead-based assay. Six LFA and the in-house validated IgG assay correctly produced negative results for all samples. However, the majority of assays (n=13), gave false positive signal for samples from patients with RA and SLE. This was most notable in samples from RF positive RA patients. No false positive samples were detected in any assay using samples from patients with MS. Poor specificity of commercial serological assays could possibly be, at least partly, due to interfering antibodies in samples from patients with chronic inflammatory diseases. For these patients, the risk of false positivity should be considered when interpreting results of the SARS-CoV-2 serological assays.

Clinical characteristics of Vietnamese patients with idiopathic inflammatory myopathies and autoantibodies to aminoacyl-transfer RNA synthetases

OBJECTIVE

To assess clinical phenotypes of anti-aminoacyl-transfer RNA synthetases (aaRS) autoantibodies in Vietnamese patients of Kinh ethnicity with idiopathic inflammatory myopathies (IIM).

METHODS

In a cross-sectional study 23 patients with anti-aaRS autoantibodies were compared to 36 patients with other myositis-specific antibodies and to 69 seronegative patients with IIM. Assessments included muscle performance, extra-muscular involvement, and disease activity according to the International Myositis Assessment and Clinical Studies (IMACS). Sera were tested by a line immunoassay (Euroline Myositis Profile 4).

RESULTS

The frequency of anti-Jo-1 antibodies was 56.5%, anti-EJ antibodies 26.1%, and anti-PL-7 antibodies 17.4%, while anti-PL-12 and anti-OJ antibodies were not present in any case. All patients with anti-aaRS autoantibodies had signs of myositis. At time of investigation 22/23 patients had muscle weakness, 52.2% arthritis, 34.8% Raynaud's phenomenon, 73.9% fever, 14.3% mechanic's hands and 56.5% dysphagia. Interstitial lung disease was present in 52.2%, and pulmonary hypertension in 56.5%. The anti-aaRS autoantibody positive group had higher disease activity in the domains of skin and pulmonary disease compared to the seronegative group and had lower disease activity in skeletal disease compared to the anti-melanoma differentiation-associated protein 5-positive patients. The clinical presentation of antisynthetase syndrome was similar between the aaRS autoantibody specificities with the exception of more frequent pulmonary hypertension in anti-Jo-1 positive patients.

CONCLUSIONS

Different aaRS autoantibody specificities may vary between different ethnic populations for reasons that still need to be clarified. Furthermore, the high frequency of pulmonary hypertension is noteworthy but otherwise clinical manifestations associated with aaRS autoantibodies did not differ from other ethnic populations.

Arthritis in systemic lupus erythematosus is characterized by local IL-17A and IL-6 expression in synovial fluid

Arthritis is a common clinical feature of systemic lupus erythematosus (SLE) and is usually non‐erosive, as opposed to rheumatoid arthritis (RA). While RA synovial pathology has been extensively studied, little is known about the pathophysiology of lupus arthritis. Here, we aimed to explore the cytokine and cellular compartments in synovial fluids of SLE patients with arthritic manifestations. Acellular synovial fluid and paired serum samples from SLE patients (n = 17) were analyzed with cytokine bead array for T helper‐associated cytokines. From two SLE patients, synovial fluid mononuclear cells (SFMC) could also be captured and were analyzed by multiparameter flow cytometry to dissect T cell, B cell, monocyte and dendritic cell phenotypes. SLE‐derived SFMC were further stimulated in vitro to measure their capacity for producing interferon (IFN)‐γ and interleukin (IL)‐17A. All patients fulfilled the ACR 1982 classification criteria for SLE. Clinical records were reviewed to exclude the presence of co‐morbidities such as osteoarthritis or overlap with RA. IL‐17A and IL‐6 levels were high in SLE synovial fluid. A clear subset of the synovial CD4⁺ T cells expressed CCR6⁺, a marker associated with T helper type 17 (Th17) cells. IL‐17A‐production was validated among CD4⁺CCR6⁺ T cells following in‐vitro stimulation. Furthermore, a strong IFN‐γ production was observed in both CD4⁺ and CD8⁺ cells. Our study shows high IL‐17A and IL‐6 levels in synovial fluids of patients with lupus arthritis. The Th17 pathway has been implicated in several aspects of SLE disease pathogenesis and our data also point to Th17 involvement for lupus arthritis.

Accumulation of antinuclear associated antibodies in circulating immune complexes is more prominent in SLE patients from Sudan than Sweden

The role of anti-nuclear autoantibody (ANA) specificities in immune complexes (IC) formation has been studied to a limited extent in SLE, and not at all in African SLE patients. We compared ANA in IC from Sudanese and Swedish SLE patients. We included 93 Sudanese and 332 Swedish SLE patients fulfilling the 1982 ACR criteria. IC were captured using C1q-coated beads. ANA specificities were quantified in sera and IC. Results were related to modified SLEDAI. Whereas serum levels of anti-Sm, anti-dsDNA and anti-ribosomal P were higher in Swedish patients, IC levels of most ANA specificities were higher among Sudanese patients. This difference was especially prominent for anti-chromatin antibodies, which remained after adjustment for age, disease duration and treatment. Total levels of C1q-binding IC correlated with levels of specific ANA in IC, with highest correlations for anti-chromatin antibodies among Sudanese patients. Whereas occurrence of anti- SSA/Ro60, anti-histone and anti-U1RNP in both serum and IC associated with high SLEDAI score, anti-dsDNA in IC but not in serum associated with high SLEDAI. ANA, especially antibodies targeting chromatin, accumulate more in IC from Sudanese SLE patients. If the autoantibody fraction forming IC is pathogenically important, this might explain the generally described severe SLE in black populations.

Anti-Citrullinated Protein Antibody Specificities, Rheumatoid Factor Isotypes, and Incident Cardiovascular Events in Patients With Rheumatoid Arthritis

OBJECTIVE

To investigate the relationship between anti-citrullinated protein antibodies (ACPAs), specific ACPA subspecificities, rheumatoid factor (RF) isotypes, and incident cardiovascular (CV) events in patients with rheumatoid arthritis (RA).

METHODS

Serum samples from Swedish patients with new-onset RA (diagnosed within 1 year of symptom onset between 1996 and 2009) were centrally typed for anti-cyclic citrullinated peptide 2 (anti-CCP2) antibodies, 20 ACPA subspecificities, and RF isotypes. Patients were followed up longitudinally in nationwide registers to monitor the occurrence of acute coronary syndrome (ACS), stroke, CV-related death, and major adverse CV events (MACE). The association between each serologic marker and CV outcome, and the impact of adjustment for the Disease Activity Score in 28 joints (DAS28), smoking status, and income at baseline, were assessed using Cox proportional hazards models. In addition, associations of serologic markers with all-cause mortality were explored.

RESULTS

In total, 2,814 patients with RA were included in the study. The median follow-up was 13 years, during which the CV end points of ACS, stroke, or CV-related death were reported to occur in 375 patients. Occurrence and/or levels of anti-CCP2 were associated with risk of incident ACS (hazard ratio [HR] 1.46, 95% confidence interval [95% CI] 1.03-2.06), stroke (HR 1.47, 95% CI 1.03-2.10), CV-related death (P = 0.024 for association with anti-CCP2 levels), and MACE (HR 1.34, 95% CI 1.06-1.70). Similarly, an association with the number of ACPA subspecificities was observed; however, this could not be attributed to any individual or group of ACPA subspecificities. Presence of IgM-RF was associated with all CV end points except ACS, and IgA-RF was exclusively associated with CV-related death. Adjustment for smoking status, income, and DAS28 scores decreased most of the HRs, whereas IgA-RF remained associated with CV-related death (HR 1.61, 95% CI 1.05-2.48). All of the assessed serologic makers were associated with all-cause mortality.

CONCLUSION

RF isotypes and ACPAs are associated with future CV events in patients with RA. ACPA levels and number of subspecificities seem more important than the occurrence of particular subspecificities, and these associations were not explained by a history of ever smoking.

Quality and best practice in medical laboratories: specific requests for autoimmunity testing

Special conditions associated with laboratory autoimmune testing are not well compatible with recent developments in regulatory frameworks such as EN/ISO 15189 accreditation or in vitro diagnostic medical device regulation (IVD-R). In addition, international recommendations, guidelines and disease criteria are poorly defined with respect to requirements on autoantibody testing. Laboratory specialists from Austria, Belgium, Croatia, Estonia, Finland, France, Germany, Greece, Hungary, Italy, Norway, Poland, Portugal, South Africa, Spain, Sweden, Switzerland, and The Netherlands collected information, reported national experience, and identified quality issues in relation to autoantibody testing that require consensus on interpretation of the regulatory frameworks and guidelines. This process has been organized by the European Autoimmunity Standardisation Initiative (EASI). By identifying the critical items and looking for a consensus, our objective was to define a framework for, in particular, EN/ISO accreditation purposes. Here, we present a review of current publications and guidelines in this field to unify national guidelines and deliver in this way a European handout on quality control and accreditation for laboratories involved in autoantibody testing. We focus on quality items that can be checked during accreditation visits. Despite various local varieties, we encountered an overwhelming dedication to quality assurance in all contributing countries.

Sudanese and Swedish patients with systemic lupus erythematosus: immunological and clinical comparisons

Objective

SLE is known to have an aggressive phenotype in black populations, but data from African cohorts are largely lacking. We therefore compared immunological and clinical profiles between Sudanese and Swedish patients using similar tools.

Methods

Consecutive SLE patients from Sudan (n = 115) and Sweden (n = 340) and from 106 Sudanese and 318 Swedish age- and sex-matched controls were included. All patients fulfilled the 1982 ACR classification criteria for SLE. Ten ANA-associated specificities and C1q-binding immune complexes (CICs) were measured. Cut-offs were established based on Sudanese and Swedish controls, respectively. Disease activity was measured with a modified SLEDAI and organ damage with the SLICC Damage Index. In a nested case–control design, Swedish and Sudanese patients were matched for age and disease duration.

Results

Females constituted 95.6% and 88.1% of Sudanese and Swedish patients, respectively (P = 0.02), with younger age at inclusion (33 vs 47.7 years; P < 0.0001) and shorter disease duration (5 vs 14 years; P < 0.0001) among Sudanese patients. Anti-Sm antibodies were more frequent in Sudanese patients, whereas anti-dsDNA, anti-histone and CICs were higher in Swedish patients. In the matched analyses, there was a trend for higher SLEDAI among Swedes. However, Sudanese patients had more damage, solely attributed to high frequencies of cranial/peripheral neuropathy and diabetes.

Conclusion

While anti-Sm is more common in Sudan than in Sweden, the opposite is found for anti-dsDNA. Sudanese patients had higher damage scores, mainly because of neuropathy and diabetes. Sudanese patients were younger, with a shorter SLE duration, possibly indicating a more severe disease course with impact on survival rates.

High IgA antiphospholipid autoantibodies in healthy Sudanese explain the increased prevalence among Sudanese compared to Swedish systemic lupus erythematosus patients

Objectives

IgA antiphospholipid antibodies (aPL) are prevalent in systemic lupus erythematosus (SLE) patients of African American, Afro-Caribbean and South African origin. Nevertheless, data from North Africa are lacking, and most studies use manufacturer-suggested cut-offs based on Caucasian controls. Therefore, we compared aPL isotypes in Sudanese and Swedish SLE patients using nation-based cut-offs.

Methods

Consecutive SLE patients and age- and sex-matched controls from Sudan (N = 115/106) and Sweden (N = 340/318) were included. All patients fulfilled the 1982 American College of Rheumatology SLE classification criteria. Antiphospholipid syndrome–related events were obtained from patients’ records. IgA/G/M anticardiolipin and anti-β₂ glycoprotein I (β₂GPI) were analysed with two independent assays. IgA anti-β₂GPI domain 1 (D1) was also investigated. Manufacturers’ cut-offs and the 95th and 99th percentile cut-offs based on national controls were used.

Results

Sudanese patients and controls had higher levels and were more often positive for IgA aPL than Swedes when using manufacturers’ cut-offs. In contrast, using national cut-offs, the increase in IgA aPL among Sudanese patients was lost. Occurrence of IgA anti-D1 did not differ between the countries. Venous thromboses were less common among Sudanese patients and did not associate with aPL. No clinical associations were observed with IgA anti-β₂GPI in Sudanese patients. Thromboses in Swedes were associated with IgG/M aPL. Fetal loss was associated with aPL in both cohorts.

Conclusions

IgA anti-β₂GPI prevalence was higher among Sudanese compared to Swedish patients when manufacturers’ cut-offs were used. This situation was reversed when applying national cut-offs. Anti-D1 was not increased in Sudanese patients. Previous studies on populations of African origin, which demonstrate a high prevalence of IgA aPL positivity, should be re-evaluated using a similar cut-off approach.

Presence of autoantibodies in "seronegative" rheumatoid arthritis associates with classical risk factors and high disease activity

Background

Rheumatoid arthritis (RA) is classified as seropositive or seronegative, depending on the presence/absence of rheumatoid factor (RF), primarily IgM RF, and/or anti-citrullinated protein antibodies (ACPA), commonly detected using anti-cyclic citrullinated peptide (CCP) assays. Known risk factors associate with the more severe seropositive form of RA; less is known about seronegative RA. Here, we examine risk factors and clinical phenotypes in relation to presence of autoantibodies in the RA subset that is traditionally defined as seronegative.

Methods

Anti-CCP2 IgG, 19 ACPA fine-specificities, IgM/IgG/IgA RF, anti-carbamylated-protein (CarP) antibodies, and 17 other autoantibodies, were analysed in 2755 RA patients and 370 controls. Antibody prevalence, levels, and co-occurrence were examined, and associations with risk factors and disease activity during 5 years were investigated for different antibody-defined RA subsets.

Results

Autoantibodies were detected in a substantial proportion of the traditionally defined seronegative RA subset, with ACPA fine-specificities found in 30%, IgA/IgG RF in 9.4%, and anti-CarP antibodies in 16%, with a 9.6% co-occurrence of at least two types of RA-associated autoantibodies. HLA-DRB1 shared epitope (SE) associated with the presence of ACPA in anti-CCP2-negative RA; in anti-CCP2-positive RA, the SE association was defined by six ACPA fine-specificities with high co-occurrence. Smoking associated with RF, but not with ACPA, in anti-CCP2-negative RA. Presence of ACPA and RF, but not anti-CarP antibodies, in conventionally defined “seronegative” RA, associated with worse clinical outcome.

Conclusions

“Seronegative” RA is not truly a seronegative disease subset. Additional screening for ACPA fine-specificities and IgA/IgG RF defines a group of patients that resembles seropositive patients with respect to risk factors and clinical picture and may contribute to earlier diagnosis for a subset of anti-CCP2−/IgM RF− patients with a high need for active treatment.

AB0127 ACCUMULATION OF ANTI-NUCLEAR ASSOCIATED AUTOANTIBODIES IN CIRCULATING IMMUNE COMPLEXES IS MORE PROMINENT IN SLE PATIENTS FROM SUDAN COMPARED TO SWEDEN

Background:

Systemic Lupus Erythematosus (SLE) is a systemic immune complex (IC)-mediated disease associated with autoantibodies targeting multiple nuclear specificities (ANA). SLE has an aggressive nature among African populations. The role of SLE-related autoantibodies in the formation of IC has only been studied to a limited extent, and not at all in African SLE patients.

Objectives:

To quantify ANA specificities present in circulating IC in Sudanese and Swedish SLE sera and to compare to corresponding serum levels

Methods:

93 Sudanese and 337 Swedish SLE patients who fulfilled the 1982 ACR classification criteria were included. IC were captured using magnetic microparticles coated with purified human C1q, then separated by a two-step elusion procedure (Figure 1). ANA-associated autoantibodies against dsDNA, Sm, the Sm/U1RNP complex, U1RNP, SSA/Ro52, SSA/Ro60, SSB/La, ribosomal P antigen, proliferating cell nuclear antigen (PCNA) and histones were quantified in sera and corresponding IC using a bead-based multiplex immunoassay. The IC purification technique has been developed and validated in our laboratory (Sohrabian ARD 2018), and previously used to study treatment responses to belimumab in Swedish SLE patients (Sohrabian ART 2019). Occurrence of ANA specificities in serum was determined using manufacturer’s suggested cutoffs. These cutoffs were used in regression formulas to determine cutoffs for ANA levels detected in the corresponding IC.

Results:

Swedish patients had higher serum levels of anti-Sm, anti-dsDNA and anti-ribosomal P antibodies compared to Sudanese patients. On the contrary, IC levels of all ANA specificities except anti-SSA/Ro52 and anti-SSA/Ro60 were higher in Sudanese patients (Table 1 and Figure 2). Sudanese patients were more often positive for anti-Sm, anti- Sm/U1RNP, anti-dsDNA and anti-histone antibodies in IC, whereas a borderline statistical significance was found for only anti-Sm in corresponding serum samples (Table 1).

Table 1.Levels median/meanSudanserumSweden serumPSudanICSwedenICPSSA/Ro5216/52.117/52.30.82.9/14.42.4/10.70.07SSA/Ro602.0/47.23.0/48.70.21.5/14.61.3/12.50.7SSB/La2.0/222.0/220.61.1/4.20.8/5.50.02Sm1.0/21.71.0/11.40.00080.5/4.20.3/1.3<0.0001SmRNP1.0/20.51.0/160.23.7/8.62.0/4.6<0.0001U1RNP6.0/43.87.0/40.20.91.0/3.50.6/2.20.0005dsDNA14.0/124.528.0/198.30.00132.1/50.812.4/25.4<0.0001Ribosomal P1.0/9.32.0/11.70.00061.7/3.31.4/2.90.005Histone5.0/20.56.0/19.30.24.0/5.91.9/3.4<0.0001PCNA5.0/8.45.0/8.90.611.1/14.27.0/11<0.0001Occurrence n(%)serumserumPICICPSSA/Ro5230(32.2)105(31.7)0.918(19.3)55(16.6)0.5SSA/Ro6034(36.6)122(36.9)0.927(29)89(26.8)0.7SSB/La15(16.1)64(19.3)0.59(9.7)38(11.4)0.3Sm12(12.9)21(6.3)0.046(6.4)5(1.5)0.008SmRNP15(16.1)42(12.7)0.417(18.3)33(9.9)0.03U1RNP20(21.5)69(20.8)0.922(23.7)55(16.6)0.1dsDNA31(33.3)147(44.4)0.05564(68.8)105(31.6)<0.0001Ribosomal P4(4.3)20(6)0.52(2.1)9(2.7)0.8Histone10(10.7)34(10.3)0.934(36.6)58(17.5)<0.0001PCNA1(1.1)10(3)0.320(21.5)45(13.5)0.06

Conclusion:

ANA-associated autoantibodies are more accumulated in circulating IC from Sudanese than Swedish SLE patients. The clinical significance of these findings is yet to be investigated in our upcoming analyses

Disclosure of Interests:

None declared

SAT0204 COMPARING OCCURRENCE AND CLINICAL SIGNIFICANCE OF ANTI-PHOSPHOLIPID AUTOANTIBODIES AMONG SUDANESE AND SWEDISH SLE PATIENTS USING CONVENTIONAL AND NATION-BASED CUTOFFS

Background:

Antiphospholipid antibodies (aPL) of IgA isotype are prevalent in SLE patients of African-American, Afro-Caribbean and South-African origin, but data from North Africa are lacking

Objectives:

To compare and determine clinical significance of aPL isotypes in Sudanese and Swedish SLE patients using nation-based cutoffs

Methods:

Consecutive Sudanese (n=115) and Swedish (n=340) SLE patients and 106 and 318 age- and sex-matched national controls were included. All patients fulfilled the 1982 ACR SLE classification criteria. IgA/G/M anti-cardiolipin and anti-β2GPI were analyzed with two independent assays (Fluorescence Enzyme Immuno Assay (FEIA) from Thermo Fisher Scientific and Particle-based Multi-Analyte Technology (PMAT) from Inova Diagnostics). IgA anti-β2GPI domain1 (D1) was investigated with chemiluminescence (CIA), Inova Diagnostics. APS-related events were obtained from patients’ records. Manufacturers’, 95thand 99thpercentile cutoffs, based on national controls calculated by non-parametric methods, were used

Results:

Sudanese patients had higher levels and prevalence of IgA aPL using manufacturers’ cutoffs (Table 1 and Figure 1). IgA/IgG aPL were also higher among Sudanese controls, But, Swedish patients were more often positive for IgA anti-β2GPI with both assays when national cutoffs were applied (Table 1). Occurrence of IgA anti-D1 did not differ between the countries. Venous thromboses were less common among Sudanese patients and no aPL, including IgA anti-β2GPI associated with thrombosis in Sudanese patients. Thrombosis in Swedes associated with IgG/IgM aPL. Fetal loss associated with aPL in both cohorts most evident after national adjustments

Table 1.FEIASudann=92FEIASweden n=291PPMAT/CIASudann=93PMAT/CIASweden n=333PIgA CL median/IQR6.5/5.24.0/4.1<0.0001194/185148/112<0.0001IgG CL4.1/5.13.0/4.50.0002205/137190/215.10.09IgM CL2.7/6.83.7/5.40.02214/251.5193/35020.2IgA β2GPI6.3/14.22.7/3.8<0.0001212/347118/152<0.0001IgG β2GPI4.2/2.91.8/2.3<0.0001158/110.7145.2/147.50.04IgM β2GPI2.0/3.01.4/2.20.006146.2/189.7132.5/235.40.09IgA B2GP1 D11542/1253.51683/1518.10.045IgA CL common cutoff n(%)9(9.8)17(5.8)0.232(35.2)75(22.7)0.02IgG CL4(4.3)21(6.7)0.414(15)72(22.1)0.1IgM CL3(3.2)14(4.5)0.610(11.4)43(13.1)0.6IgA β2GPI32(34.8)43(14.9)<0.000138(41.8)76(23)0.0004IgG β2GPI10(10.9)44(14.1)0.45(5.4)50(15.3)0.01IgM β2GPI10(10.9)27(8.7)0.512(13.6)42(12.9)0.8IgA B2GP1 D16(6.4)38(11.4)0.2IgA CL 95thcutoffn(%)9(9.8)54(18.6)0.04736(39.6)121(26.6)0.6IgG CL8(8.7)42(13.5)0.224(25.8)103(31.6)0.3IgM CL8(8.7)39(12.5)0.316(18.2)47(14.4)0.4IgA β2GPI18(19.6)100(34.7)0.00620(22)125(37.8)0.005IgG β2GPI2(2.1)67(21.5)<0.000119(20.4)83(25.5)0.3IgM β2GPI14(15.22)57(18.3)0.520(22.7)57(17.5)0.3IgA B2GP1 D125(26.9)69(20.7)0.2Figure 1.

Conclusion:

IgA anti-β2GPI levels were generally higher among Sudanese compared to Swedish SLE patients and controls, but after national adjustments more Swedish than Sudanese patients were positive. IgA anti-D1 was not increased in Sudanese patients. Previous studies on populations of African-origin, which demonstrate high prevalence of IgA aPL positivity, should be re-evaluated using similar cutoff approach

Acknowledgments: :

We thank Maryam Poorafshar at Thermo Fischer Scientific and Silvia Casas and Michael Mahler at Inova Diagnostics for help with analyses

Disclosure of Interests:

None declared

Autoantibody and Cytokine Profiles during Treatment with Belimumab in Patients with Systemic Lupus Erythematosus

We investigated whether belimumab treatment impacts on levels of autoantibodies and cytokines of interest in systemic lupus erythematosus (SLE). Longitudinally collected serum samples from 78 belimumab-treated Swedish SLE patients were analysed. Serum cytokine levels were determined using Luminex xMAP technology, and nuclear antigen autoantibody specificities using addressable laser bead immunoassay. In patients with detectable levels at baseline, interferon (IFN)-α2 levels were lower at month 6 (median; interquartile range (IQR): 8.9; 1.5-54.9 pg/mL) versus baseline (28.4; 20.9-100.3 pg/mL; p = 0.043). Interleukin (IL)-6 (baseline: 7.1; 2.9-16.1 pg/mL) decreased from month 6 (0.5; 0.5-6.3 pg/mL; p = 0.018) and throughout a 24 month follow-up. IL-10 (baseline: 12.6; 2.8-29.7 pg/mL) showed more rapid decreases from month 3 (1.8; 0.6-9.1 pg/mL; p = 0.003). Levels of anti-dsDNA (p < 0.001), anti-Smith antigen (Sm) (p = 0.002), anti-U1 small nuclear ribonucleoprotein (U1RNP) (p < 0.001), anti-Sm-U1RNP complex (p = 0.028), and anti-ribosomal P (p = 0.012) antibodies decreased from month 3 and remained decreased. Anti-Sm positivity at baseline was associated with higher probability and/or shorter time to achieve sustained SLE responder index-4 response (hazard ratio (HR): 2.52; 95% CI: 1.20-5.29; p = 0.015), independently of other factors. Decline of IL-6 levels through month 3 was greater in responders. In summary, belimumab treatment lowered IFN-α2, IL-6, and IL-10 levels, as well as levels of multiple autoantibodies, however after different time spans. Notably, anti-Sm positivity and early decline in IL-6 levels were associated with favorable treatment outcome.

The importance of differences; On environment and its interactions with genes and immunity in the causation of rheumatoid arthritis

The current review uses rheumatoid arthritis (RA) as a prominent example for how studies on the interplay between environmental and genetic factors in defined subsets of a disease can be used to formulate aetiological hypotheses that subsequently can be tested for causality using molecular and functional studies. Major discussed findings are that exposures to airways from many different noxious agents including cigarette smoke, silica dust and more interact with major susceptibility genes, mainly HLA-DR genetic variants in triggering antigen-specific immune reactions specific for RA. We also discuss how several other environmental and lifestyle factors, including microbial, neural and metabolic factors, can influence risk for RA in ways that are different in different subsets of RA.The description of these processes in RA provides the best example so far in any immune-mediated disease of how triggering of immunity at one anatomical site in the context of known environmental and genetic factors subsequently can lead to symptoms that precede the classical inflammatory disease symptoms and later contribute also to the classical RA joint inflammation. The findings referred to in the review have led to a change of paradigms for very early therapy and prevention of RA and to efforts towards what we have named 'personalized prevention'. We believe that the progress described here for RA will be of relevance for research and practice also in other immune-mediated diseases.

Elevated IgA antiphospholipid antibodies in healthy pregnant women in Sudan but not Sweden, without corresponding increase in IgA anti-β2 glycoprotein I domain 1 antibodies

Objective

The role of antiphospholipid antibodies (aPL) during apparently normal pregnancy is still unclear. IgA aPL are prevalent in populations of African origin. Our aim was to measure all isotypes of anticardiolipin (anti-CL) and anti–β₂ glycoprotein I (anti-β₂GPI) in healthy pregnant and non-pregnant women of different ethnicities.

Methods

Healthy Sudanese pregnant women (n = 165; 53 sampled shortly after delivery), 96 age-matched Sudanese female controls and 42 healthy pregnant and 249 non-pregnant Swedish women were included. IgA/G/M anti-CL and anti-β₂GPI were tested at one time point only with two independent assays in Sudanese and serially in pregnant Swedes. IgA anti-β₂GPI domain 1 and as controls IgA/G/M rheumatoid factor (RF), IgG anti–cyclic citrullinated peptide 2 (anti-CCP2) and anti–thyroid peroxidase (anti-TPO) were investigated in Sudanese females.

Results

Pregnant Sudanese women had significantly higher median levels of IgA anti-CL, IgA anti-β₂GPI (p < 0.0001 for both antibodies using two assays) and IgM anti-β₂GPI (both assays; p < 0.0001 and 0.008) compared with non-pregnant Sudanese. IgA anti-CL and anti-β₂GPI occurrence was increased among Sudanese pregnant women compared with national controls. No corresponding increase during pregnancy was found for IgA anti-β₂GPI domain 1 antibodies. Both IgG anti-CL and IgG control autoantibodies decreased during and directly after pregnancy among Sudanese. Serially followed Swedish women showed no changes in IgA aPL, whereas IgG/M anti-CL decreased.

Conclusions

IgA aPL are increased in Sudanese but not in Swedish women, without corresponding increase in IgA domain 1. Whether due to ethnicity and/or environmental influences the occurrence of IgA aPL during Sudanese pregnancies, and its clinical significance, is yet to be determined.

Longitudinal anti-nuclear antibody (ANA) seroconversion in systemic lupus erythematosus: a prospective study of Swedish cases with recent-onset disease

Serum immunoglobulin (Ig)G anti-nuclear antibodies (ANA) detected by indirect immunofluorescence (IF) microscopy remains a hallmark of systemic lupus erythematosus (SLE). Whether or not IF-ANA status varies over time is controversial. We therefore designed a prospective study with longitudinal follow-up of patients with recent-onset SLE. The study population consisted of 54 recently diagnosed SLE cases, all meeting the 1982 American College of Rheumatology (ACR) and/or the 2012 Systemic Lupus International Collaborating Clinics (SLICC) criteria. Clinical follow-up data, including disease activity, organ damage and sera, were collected from clinical onset of SLE and onwards, in most cases yearly (0-96 months). IF-ANA was analysed on human epithelial cells-2 (HEp-2) cells and categorized regarding staining patterns. Using an addressable laser bead assay (FIDIS™ Connective profile), we measured IgG-ANA fine specificities against Ro52/SSA, Ro60/SSA, Sjögren's syndrome type B antigen (La/SSB), Smith antigen (Sm), Smith antigen/ribonucleoprotein (Sm/RNP), U1 RNP (U1RNP), dsDNA, ribosomal-P protein and histone. At baseline, all patients were judged ANA-positive at an abnormal titre corresponding to the 95th percentile of healthy blood donors, but seven of 54 patients (13%) lost ANA-positivity over time. Homogeneous (AC-1; 46%) and speckled (AC-4 or 5; 31%) were the most frequently observed patterns at inclusion, whereas 7% switched pattern at least once during follow-up. Established associations between ANA fine specificities and clinical data were confirmed. Levels of anti-Sm/RNP, but not of anti-dsDNA, correlated with clinical disease activity [modified SLE disease activity 2000 (mSLEDAI-2K)]. Our data indicate that a considerable proportion of Swedish patients with SLE lose ANA-positivity over time, whereas consistent staining patterns were frequent. The clinical and mechanistic relevance of ANA seroconversion remains uncertain. Further prospective evaluations in larger SLE populations with more diverse ethnicities are warranted.