AB0058 ASSOCIATION BETWEEN HLA-DRB1*04:01, RHEUMATOID NODULES AND PARTICULAR EPITOPES OF CITRULLINATED FIBRIN IN PATIENTS WITH RHEUMATOID ARTHRITIS

Background:Rheumatoid arthritis (RA) is associated with HLA-DRB1 genes encoding the shared epitope (SE), a 5 amino acid motive. RA is usually preceded by the emergence of anti-citrullinated protein antibodies (ACPAs) detected by anti-CCP2 tests. Citrullin is a neutral amino acid resulting from post translational modification of arginin by Peptidyl Arginyl Deiminases (PADs). ACPAs recognize epitopes from citrullinated human fibrinogen (Fib-cit) and can be specifically detected by the AhFibA assay. Five peptides derived from Fib-cit together represent almost all of the epitopes recognized by patients with ACPA-positive RA: β60–74cit, α36–50cit, α621–635cit, α501–515cit and α171–185cit. As RA is a pleiomorphic disease, whose evolution is difficult to predict, the use of antibody fine specificity as a marker of clinical phenotypes has become a major challenge.Objectives:Our objective was to study whether clinical characteristics and HLA-DRB1 genetic background were associated with a specific reactivity against these epitopes.Methods:184 ACPA positive RA patients fulfilling the 2010 ACR/EULAR criteria were studied. Patients characteristics, including HLA-DRB1 genotype, were collected from their medical files. Anti-CCP2, AhFibA, Rheumatoid Factors (RF), and antibodies against the five major Fib-cit peptides were analyzed using ELISA assays.Results:Anti-CCP2 and AhFibA titres were strongly correlated (rs: 0.7037; p = 5.69x10-29, Pearson’s). Anti-α505-515cit antibodies were associated with HLA-DRB1*04:01 (OR = 5.52 [2.00 – 13.64]; p = 0.0003). High level anti-α505-515cit antibodies were significantly associated with rheumatoid nodules (OR = 2.71 [1.00 – 7.16], p= 0.044). Anti α501–515cit antibodies were associated with RF (OR=2.31 [1.10 – 4.78], p= 0.026).Conclusion:Immune complexes containing anti-α501–515cit antibodies and rheumatoid factors might be involved in the development of rheumatoid nodules on the HLA-DRB1*04:01 background. These findings highlight the role played by the HLA-DRB1*04:01 molecule and its rapid intracellular route into the lysosomes, enabling original antigen processing. Finally, purifying these epitope specific antibodies might be a new therapeutic opportunity for rheumatoid nodules.Disclosure of Interests:None declared

AB0240 PREDICTORS OF RESPONSE TO BIOLOGIC AGENTS IN RHEUMATOID ARTHRITIS

Background:In rheumatoid arthritis (RA), the ‘treat-to-target’ therapeutic approach imposes rigorous control of disease activity. Although biological agents have been shown to be effective, these therapies fail sometimes to achieve therapeutic goals.Objectives:In this study we tried to determine predictive factors of good therapeutic response to biologic disease-modifying antirheumatic drugs (bDMARD).Methods:This is a retrospective study including 374 Tunisian patients who received their first biotherapy between 2014 and 2016. Categorical variables were reported in numbers and percentages, while quantitative variables were expressed by mean with standard deviations. The univariate analysis was performed using the student t-test or the Chi2 test. Multivariate analysis was performed by binary logistic regression.Results:Average age of our cohort was 55 ± 12.5 years with a female predominance of 87.2%. The average duration of RA was 11.7 ± 6.7 years. Rheumatoid factors were positive in 79% and ACPA were positive in 72% of cases. After the introduction of biotherapy, low disease activity (LDA) or remission was achieved in 55% of cases (206 patients).No statistically significant difference between biotherapy responder and non-responder groups for age (55.7 vs. 54.7 years; p = 0.44), gender (Female: 86.5% vs. 88.7%; p = 0.08) and disease duration (12 years vs. 11.4 years; p = 0.41). A significant difference between the two groups was found for the positivity of rheumatoid factors (76.4% vs. 88.9%; p = 0.004), methotrexate’s association (65% vs. 53.4%; p = 0.02) and corticosteroids’ use (50% vs. 66.5%; p < 0.001).Positive predictive factors of remission or LDA by biotherapy were female sex (Odds Ratio = 2.2; p = 0.026), presence of rheumatoid factors (Odds Ratio = 2.64; p = 0.001), association with methotrexate (Odds Ratio = 1.69; p = 0.028). Whereas, corticosteroid use (OR = 0.41; p < 10-3) was a negative predictor of disease control by bDMARDs.Conclusion:Achieving LDA low level or even remission is currently achievable with biological treatments. Certain factors need to be studied in order to optimize RA treatment and adapt the right bDMARD for each patient.Disclosure of Interests:None declared

Rheumatoid Factor: A Novel Determiner in Cancer History

The possible interplay between autoimmunity and cancer is a topic that still needs to be deeply explored. Rheumatoid factors are autoantibodies that are able to bind the constant regions (Fc) of immunoglobulins class G (IgGs). In physiological conditions, their production is a transient event aimed at contributing to the elimination of pathogens as well as limiting a redundant immune response by facilitating the clearance of antibodies and immune complexes. Their production can become persistent in case of different chronic infections or diseases, being for instance a fundamental marker for the diagnosis and prognosis of rheumatoid arthritis. Their presence is also associated with aging. Some studies highlighted how elevated levels of rheumatoid factors (RFs) in the blood of patients are correlated with an increased cancer risk, tumor recurrence, and load and with a reduced response to anti-tumor immunotherapies. In line with their physiological roles, RFs showed in different works the ability to impair in vitro anti-cancer immune responses and effector functions, suggesting their potential immunosuppressive activity in the context of tumor immunity. Thus, the aim of this review is to investigate the emerging role of RFs as determiners of cancer faith.

Evaluating Ten Commercially-Available SARS-CoV-2 Rapid Serological Tests Using the STARD (Standards for Reporting of Diagnostic Accuracy Studies) Method.

Numerous SARS-CoV-2 rapid serological tests have been developed, but their accuracy has usually been assessed using very few samples, and rigorous comparisons between these tests are scarce. In this study, we evaluated and compared 10 commercially-available SARS-CoV-2 rapid serological tests using the STARD methodology (Standards for Reporting of Diagnostic Accuracy Studies). 250 sera from 159 PCR-confirmed SARS-CoV-2 patients (collected from 0 to 32 days after onset of symptoms) were tested with rapid serological tests. Control sera (N = 254) were retrieved from pre-COVID periods from patients with other coronavirus infections (N = 11), positive rheumatoid factors (N = 3), IgG/IgM hyperglobulinemia (N = 9), malaria (n = 5), or no documented viral infection (N = 226). All samples were tested using rapid lateral flow immunoassays (LFIA) from 10 manufacturers. Only four tests achieved ≥98% specificity, with other tests ranging from 75.7%-99.2%. Sensitivities varied by the day of sample collection, from 31.7%-55.4% (Days 0-9), 65.9%-92.9% (Days 10-14), and 81.0%-95.2% (>14 days) after the onset of symptoms, respectively. Only three tests evaluated met French Health Authorities’ thresholds for SARS-CoV-2 serological tests (≥90% sensitivity + ≥98% specificity). Overall, the performances between tests varied greatly, with only a third meeting acceptable specificity and sensitivity thresholds. Knowing the analytical performance of these tests will allow clinicians and most importantly laboratorians to use them with more confidence, could help determine the general population’s immunological status, and may help to diagnose some patients with false-negative RT-PCR results.

Detection of anti-SARS-CoV-2 antibodies in patients with rheumatoid arthritis.

Objectives: The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes coronavirus disease 2019 (COVID-19) and the outbreak of COVID-19 was reported in December 2019 in Wuhan, China. Serological test is conducted to discriminate prior infection of SARS-CoV-2. The influence of auto-antibodies on the results of anti-SARS-CoV-2 antibodies was investigated in a few studies. Here, we investigated whether the results of anti-SARS-CoV-2 antibodies would be modified in patients with rheumatoid arthritis (RA). Methods: Patients with RA were recruited at Sagamihara National Hospital from July 2014 to October 2015 (n=38, 2014 cohort) and at Tokyo National Hospital from June to October 2020 (n=93, 2020 cohort). Anti-SARS-CoV-2 antibodies were measured in collected sera from these RA patients by electrochemiluminescence immunoassay (ECLIA) or immunochromatographic assay (ICA). Results: Anti-SARS-CoV-2 antibodies were not detected in all the samples form RA patients in both cohorts by the ECLIA. However, anti-SARS-CoV-2 antibodies were detected in the serum samples from three (7.9%) in 2014 cohort by the ICA and fifteen (16.1%) in 2020 cohort. The IgM rheumatoid factor levels were increased in RA patients with IgM anti-SARS-CoV-2 antibodies by ICA compared with RA without any anti-SARS-CoV-2 antibodies (mean ± standard deviation [IU/ml], 1223.0 ± 1308.7 vs. 503.6 ± 1947.2, P=0.0101). The levels of IgG rheumatoid factor were also upregulated in RA patients with IgM anti-SARS-CoV-2 antibodies by ICA (4.0 ± 0.7 vs. 2.4 ± 0.9, P=0.0013). Conclusion: The results of IgM anti-SARS-CoV-2 antibody by the ICA would be modified by IgM or IgG rheumatoid factors in RA patients.

Hypeprolactinemia: still an insidious diagnosis

Hyperprolactinemia can have different causes: physiological, pharmacological, and pathological. When investigating the etiology of hyperprolactinemia, clinicians need to be aware of several conditions leading to misdiagnosis. The most popular pitfalls are: acute physical and psychological stress, macroprolactin, hook effect, even though antibodies interferences and biotine use have to be considered. A 52-year-old woman was referred to Endocrinology clinic for oligomenorrhoea and headache. She worked as a butcher. Hormonal evaluation showed very high PRL (305 ng/ml, reference interval: <24 ng/ml) measured with the ECLIA immunoassay analyzer Elecsys 170. The patient’s pituitary MRI was normal and macroprolactin was normal. Hormonal workup showed LH: 71.5 mU/ml (2–10.9 mU/ml), FSH: 111.4 mU/ml (3.9–8.8 mU/ml), Estradiol: 110.7 pg/mL (27–122 pg/ml). Since an interference was suspected, the sample was sent to another laboratory using a different assay. After antibody blocking tubes treatment (Heterophilic Blocking Tube, Scantibodies) PRL was 28.8 ng/ml (reference interval < 29.2 ng/ml). Analytical interference should be suspected when assay results are not consistent with the clinical picture. Endogenous antibodies (EA) include heterophile, human anti-animal, autoimmune and other nonspecific antibodies, and rheumatoid factors, that have structural similarities and can cross-react with the antibodies employed by the immunoassay, causing hyperprolactinemia misdiagnosis. The patient’s job (butcher), led us to suspect the presence of anti-animal antibodies. Clinicians should also carefully investigate the use of supplements. Biotin can falsely increase hormone concentration in competitive assays. Many clinicians are still not informed about these pitfalls that are not mentioned in some recent reviews on PRL measurement.