Abstract Background Immune-mediated diseases (IMIDs), like Crohn’s disease (CD), ulcerative colitis (UC), psoriatic arthritis (PsA) and type I diabetes (T1D), have common features, including intestinal microbial dysbiosis. However, it is unclear whether dysbiosis contributes to IMID pathogenesis and whether the host immune system perceives dysbiotic commensals. In CD, high IgG and T-cell responses to Lachnospiraceae-derived flagellins associate with complex disease, while Lachnospiraceae fecal abundance is decreased in CD, suggesting that individual variation in the host-microbial mutualism is important. We studied IgG responses to dysbiotic microbial species across IMIDs, and questioned whether changes in these IgG responses are homogeneous within each IMID and shared among IMIDs. Methods Using shotgun metagenomic sequencing of feces from 6 IMID cohorts (n=5650), dysbiosis was extrapolated to species level. Plasma IgG reactivity to lysates of 71 dysbiotic species was measured in adult CD (aCD, n=50), adult UC (aUC, n=50), PsA (n=100), rheumatoid arthritis (RA, n=74), T1D (n=75), healthy controls (aHC, n=97), pediatric CD (pCD, n=103), pediatric UC (pUC, n=48), pediatric HC (pHC, n=58), pediatric celiac disease (CeD, n=103) and no-CeD HC (n=68). Multiple ordinal regression analysis was performed corrected for age, sex and multiple testing. Results Anti-microbial IgG responses compared to age-matched HC were increased in aCD (2/71); pCD (46/71); PsA (3/71); RA (1/71); decreased in T1D (10/71) and pUC (1/71), and not different in CeD and aUC. Shared increased responses occurred to: Klebsiella oxytoca and Roseburia inulinivorans in aCD and pCD, Streptococcus parasanguinis and Streptococcus vestibularis in PsA and pCD, and Acidaminococcus intestini in both arthritic diseases PsA and RA. As changes were heterogeneous within each IMID, hierarchical clustering of all anti-microbial responses across adult IMIDs was performed. Clusters had a mix of IMIDs, uncovering shared response patterns across IMIDs. Although aCD and aUC patients had disease-specific responses, their overall anti-microbial response pattern was not different from other IMIDs. In contrast, pCD patients were clearly distinct from pUC and pHC, with high number of significantly increased anti-microbial IgG responses and separate hierarchical clustering, demonstrating overall increased anti-microbial responses in pCD versus aCD. Interestingly, clustering grouped pCD patients with similar clinicopathological parameters, arguing that anti-microbial IgG response patterns may relate to disease pathogenesis. Conclusion We show that the immune system perceives dysbiotic commensals and uncover shared and non-shared anti-microbial IgG responses among adult and pediatric IBD and other IMID patients.

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a prototypic autoimmune disease, with a subset of AAV patients manifesting anti-myeloperoxidase (MPO) IgG. Patients with AAV respond positively to B cell-targeting and complement-targeting therapies, but disease flares are not uncommon. Here, by comparing samples from healthy individuals and MPO+ AVV patients, we show that B cell autoreactivity against MPO in the circulation of patients is dominated by CD27+IgM+ B cells whereas MPO-specific IgG+ cells are infrequent. Additionally, while naive anti-MPO-IgM B cells are present in both patients and controls and produce anti-MPO IgM upon stimulation, anti-MPO-IgM memory B cells and serum anti-MPO IgM are features of patients. Our results thus hint that defective elimination of B cell reactivity to MPO in the human repertoire, the presence of activated IgM+ anti-MPO B cells in disease, and a dominant role for anti-MPO IgM in complement activation, may all contribute to MPO+ AAV etiology and thereby serve as potential target for therapy.

During the COVID-19 pandemic, the daily life of many patients with dermatological immune-mediated inflammatory diseases (DIMIDs), such as atopic dermatitis (AD), psoriasis, and vitiligo, was impacted by social restrictions caused by (fear of) morbidity, mortality associated with COVID-19, and vaccine hesitancy. This prospective observational, multicenter, multidisciplinary cohort study explored the impact of COVID-19 disease and vaccination on DIMIDs, specifically AD, psoriasis, and vitiligo. Data from patients with DIMIDs were collected as part of the Target2B! study (between February 2021 and October 2022). We analyzed the differences in baseline characteristics, risk of developing COVID-19, proportion of DIMIDs in patients reaching seroconversion upon vaccination per DIMID, and self-reported increase in DIMID activity by multivariable logistic regression and sensitivity analyses. A total of 424 patients with DIMID were included. COVID-19 disease commonly occurred in patients with vitiligo (51.1%), AD (42.0%), and psoriasis (34.3%) (p = 0.038). COVID-19 was not associated with the use of immunosuppressive therapy. Three patients (two with AD and one with vitiligo) were hospitalized due to COVID-19. Nearly all patients with DIMIDs exhibited effective seroconversion after regular vaccination regimens (vitiligo 100%, psoriasis 97.9%, AD 96.5%). Increased DIMID activity after COVID-19 (6.6%) or severe acute respiratory syndrome-related coronavirus (SARS-CoV-2) vaccination (12.26%) was reported in a minority of patients, with baseline progressive disease (disease activity 3 months preceding baseline survey) being the only associated risk factor (COVID-19: odds ratio [OR], 4.27 [p = 0.02]; vaccination OR, 3.45 [p = 0.002]). In conclusion, no alarming signs were shown in this study regarding (severe) COVID-19 in patients with AD, psoriasis, or vitiligo. Vaccination against COVID-19 is advised in patients with DIMIDs. Moreover, patients with DIMIDs can safely continue their immunosuppressant therapy, since this does not increase the risk of COVID-19, while vaccination-induced humoral responses are adequate. In only a minority of patients, increased DIMID activity after COVID-19 or SARS-CoV-2 vaccination occurred.

Background: PD-1 immune checkpoint inhibitors are able to re-activate restrained anti-tumor T-cell responses in melanoma patients. However, PD-1 inhibition may also activate auto-reactive T-cells leading to immune-related adverse events (irAEs). Autoantibodies might also play a role in anti-PD-1 induced irAEs and could potentially be used to identify patients at risk of developing these irAEs. Objectives: To investigate the association between autoantibody-positivity and treatment toxicity and response in melanoma patients treated with anti-PD-1. Methods: This multicenter, retrospective study included 143 advanced melanoma patients treated with anti-PD-1. Until six months after treatment initiation, toxicities grade ≥2 and recurrences/responses were captured. Autoantibody measurements, comprising IgM rheumatoid factor (RF), antinuclear antibodies (ANA), anti-cyclic citrullinated peptide antibodies (anti-CCP2), anti-thyroid peroxidase (anti-TPO) and anti-thyroglobulin (anti-Tg) were performed in an ISO15189 accredited laboratory at baseline and after three months of treatment. Results: A total of 169 irAEs were experienced by 86 patients, the most common being thyroiditis (n=25), dermatitis (n=24), and sicca complaints (n=19). More irAE (30/37 [81%]) were observed in patients with pre-existing detectable autoantibodies than in patients without these autoantibodies (55/106 [52%], p = 0.003) (table 1). This was mainly due to the strong association of anti-thyroid antibodies and thyroid dysfunction (69% in anti-TPO and/or anti-Tg positive patients versus 12% in anti-TPO and/or anti-Tg negative patients, p <0.001). No association between anti-CCP2, RF or ANA and arthritis, dermatitis, sicca or colitis was observed. The association with thyroid antibodies was strongest in female patients: of seropositive female patients 7/7 (100%) developed thyroiditis, compared to only 10/48 (21%) of anti-TPO and anti-Tg negative patients. Seroconversion during anti-PD-1-treatment was only seen for thyroid antibodies. Here the combined positivity for anti-TPO and/or anti-Tg increased from 13/143 (9.1%) at baseline to 24/143 (17%) on treatment (p = 0.003). For the other autoantibodies the total number of seropositive patients stayed stable or decreased on treatment (table 2). Seroconversion of anti-Tg and/or anti-TPO was associated with thyroid dysfunction in female patients: 6/10 [60%] of seroconverted patients developed thyroid dysfunction compared to 3/38 [8%] patients that remained seronegative (p = 0.001). Autoantibody-positivity was not associated with disease recurrence (p = 0.45) or response (p = 0.69). Conclusion: Autoantibody-positivity prior to anti-PD-1 therapy is associated with the development of irAEs in melanoma patients, indicating that anti-PD-1 therapy not only leads to loss of tolerance to tumor antigens but also to nontumor autoantigens. Baseline positivity and seroconversion of anti-thyroid antibodies were associated with the development of thyroiditis. Autoantibody-positivity prior to anti-PD-1 therapy is associated with the development of irAEs in melanoma patients, indicating that anti-PD-1 therapy not only leads to loss of tolerance to tumor antigens but also to nontumor autoantigens. Baseline positivity and seroconversion of anti-thyroid antibodies were associated with the development of thyroiditis.REFERENCES: NIL. Acknowledgements: NIL. Disclosure of Interests: Tineke J. van Wesemael: None declared, Jessica S.W Borgers: None declared, K.A. Gelderman: None declared, E. M. E. Verdegaal: None declared, C.M. Korse: None declared, M. J. P. Welters: None declared, H. W. Kapiteijn: None declared, W. J van Houdt: None declared, S. H. van der Burg: None declared, Rene E.M. Toes: None declared, J.V. Thienen: None declared, John Haanen received compensation for advisory roles for Achilles Therapeutics, BioNTech, BMS, CureVac, Gadeta, Imcyse, Immunocore, Instil Bio, Iovance Biotherapeutics, Ipsen, MSD, Merck Serono, Molecular Partners, Neogene Therapeutics, Novartis, Pfizer, Roche/Genentech, Sanofi, Scenic, Third Rock Ventures, and T-knife, has received grants (all paid to the institute) from Amgen, Asher Bio, BioNTech, BMS, MSD, Novartis, Neogene Therapeutics and Sastra Cell Therapy. DW: declares no competing interests, Diane van der Woude: None declared.

Background: Rheumatoid arthritis (RA) is a prevalent autoimmune disease characterized by B-cells that produce autoantibodies against post translationally modified proteins, such as anti-citrullinated protein antibodies (ACPA), anti-acetylated protein antibodies (AAPA) and anti-carbamylated protein antibodies (a-CarP), together called anti-modified protein antibodies (AMPA). What initially leads to the breach in tolerance and eventually causes rheumatoid arthritis is still unknown, but there are indications, such as changes in the fecal microbiome composition of RA patients, that this tolerance breach takes place in the intestines. Objectives: Since antibody responses in the intestines are dominated by IgA, particularly in dimeric form, we set out to characterize the AMPA IgA response in detail. Methods: Sera from ACPA-positive RA, ACPA-negative RA and healthy donors were fractionated using size exclusion chromatography, separating proteins on size. Next, all fractions were tested by ELISA for ACPA IgA, AAPA IgA and anti-CarP IgA, as well as total IgM, IgA and IgG. Additionally, AMPA were purified from serum to determine their size by IgA western blot and to investigate the IgA tailpiece by tandem mass spectrometry (MS/MS). Lastly, monoclonal IgA was produced with both tailpiece variants, after which its ability to polymerize was analyzed. Results: Intriguingly, of all AMPA IgA, ~70% was found to be polymeric, while total IgA contained only ~20% polymeric IgA. MS/MS analysis furthermore showed a difference in the AMPA IgA tailpiece: in the dimeric fraction ~60% had the complete tailpiece, while in the monomeric fraction this was ~20%. Recombinant IgA with such a complete tailpiece formed up to ~90% polymers, while this was ~40% in IgA with a truncated tailpiece. Conclusion: These data indicate that AMPA IgA responses are differently regulated compared to the total IgA antibody response and that the tailpiece might be related to a difference in polymer formation. Moreover, the high abundance of polymeric AMPA IgA suggests a mucosal origin. REFERENCES: NIL. Acknowledgements: NIL. Disclosure of Interests: Anouk G. van Mourik: None declared, Sanne Reijm: None declared, Alice Bacon: None declared, Myrthe A.M van Delft: None declared, Nivine Levarht: None declared, Rayman Tjokrodirijo: None declared, Peter van Veelen: None declared, Leendert A Trouw Research funding from INOVA diagnostics, part of Werfen, Rene E.M. Toes Research funding from INOVA diagnostics, part of Werfen, Karin A. van Schie: None declared, Diane van der Woude Galapagos, Galapagos.

Background Many autoimmune diseases (AIDs) are characterized by aberrant, autoreactive B cell responses and autoantibody production. Rheumatoid arthritis (RA) is a common AID in which autoantibodies recognizing post-translational modifications (PTMs), collectively called anti-modified protein antibodies (AMPA), are intimately associated with disease pathogenesis. Previously, we observed that memory B cells (mBC) against one of these PTM-antigens, citrulline, are highly activated. This phenotype persists for years in patients with established disease [1]. The evolution, dynamics and more detailed phenotypic characteristics of the PTM-directed B cell compartment are still ill defined, however, partly owing to challenges linked to the visualization of such cells in human samples and the limitations of conventional flow cytometry. Here, we visualized the autoreactive B cell response against three different PTM antigens (citrulline, homocitrulline, acetyllysine) by spectral flow cytometry, allowing us to address cross-reactivity on the B cell level and to perform deep phenotypic profiling of individual B cell compartments. Objectives To develop a detailed understanding of the autoreactive B cell response against PTM-antigens in RA with the aim to elucidate features associated with its cross-reactivity, state of activation in the disease context, and its remarkable persistence for years without signs of exhaustion or decay. Methods We developed a spectral flow cytometry staining approach using differentially labelled streptavidin molecules coupled to individual PTM-antigens. B cells reactive to each antigen were identified together in individual samples by double staining for each antigen, while at the same time excluding cells reactive to either arginine or lysine control peptides. This combinatorial staining was further extended by the concomitant visualization of tetanus-toxoid specific B cells and expression levels of various activation and homing markers, and applied to peripheral blood samples of patients with established RA. Importantly, we performed intracellular stainings, allowing us to additionally enumerate and characterize circulating plasmablasts and plasmacells. Results We successfully visualized autoreactive B cells directed against different PTM-antigens and their subset distribution in individual patient samples. We observed extensive cross-reactivity against all three PTM antigens with citrulline as dominant antigen. Unsupervised clustering revealed several memory B cell populations, with most autoreactive B cells populating the most recently activated, mostly class-switched, CD80highCD24lowCD21low mBC compartment. We also noted large expansions of CXCR3+ IgG or IgA-expressing antibody secreting cells (ASC), comprising up to 50% of the autoreactive B cell compartment. Anti-tetanus toxoid B cells clustered with a different, more resting mBC subset. Conclusion Our results identify citrulline as the most prominent antigen recognized by AMPA-expressing B cells. The study highlights the recent and persistent activation state of PTM-reactive mBC and their continuous differentiation towards ASC. Such ASC may home towards CXCR3 ligands known to be abundant in the synovial compartment. This degree of mBC activation was also found in patients with low clinical disease activity scores, indicating that conventional therapeutic interventions may suppress inflammation but fail to silence the most disease-specific autoreactive B cell response in RA. Targeting this compartment may therefore be relevant for future therapeutic interventions aiming at the induction of tolerance and/or permanent cure. Finally, the combinatorial staining approach presented will be a valuable tool to delineate the development of PTM-directed autoimmunity in the pre-disease phase as well as its state of activation in phases of sustained drug-free remission and/or during tolerogenic interventions. Reference [1]Kristyanto et al., Sci Transl Med. 2020 Nov 18;12(570):eaaz5327 Acknowledgements: NIL. Disclosure of Interests Sanne Reijm: None declared, Joanneke Kwekkeboom: None declared, Nienke Blomberg: None declared, Jolien Suurmond Grant/research support from: Janssen, Diane van der Woude: None declared, Rene Toes: None declared, Hans Ulrich Scherer Speakers bureau: BMS, Lilly, Pfizer, Consultant of: Galapagos, Grant/research support from: BMS, Lilly, Pfizer, Janssen.

Many autoimmune diseases (AIDs) are characterized by persistence of autoreactive B cell responses which is often directly implicated in disease pathogenesis. How and why these cells are generated or how they are maintained for years is largely unknown. Rheumatoid arthritis is among the most common AIDs and characterized by autoantibodies recognizing proteins with post-translational modifications (PTMs). This PTM-directed, autoreactive B cell compartment is ill defined. Here, we visualized the B cell response against the three main types of PTM antigens implicated in RA by spectral flow cytometry. Our results show extensive cross-reactivity of autoreactive B cells against all three PTM antigens (citrulline, homocitrulline and acetyllysine). Unsupervised clustering revealed several distinct memory B cell (mBC) populations. Autoreactive cells clustered with the most recently activated, class-switched mBC phenotype, expressing high CD80, low CD24 and low CD21. Notably, patients also harbored large fractions of autoreactive plasmablasts (PB). Both PTM-directed mBC and PB showed high expression of CXCR3, a receptor for chemokines abundantly present in arthritic joints. Together, our data provide novel, detailed insight into the biology of B cell autoreactivity and its remarkable, seemingly exhaustless persistence in a prominent human AID.

BackgroundAnti-modified protein antibodies (AMPA) are an important hallmark of rheumatoid arthritis (RA) and the fact that they have consistently been found to develop years before disease onset, has provided important insights into the immunopathology underlying RA. In (auto)antibody development, IgM is the first isotype to be produced. However, it is unclear whether IgM-autoimmunity differs between AMPA targeting different post-translational modifications (citrulline, homocitrulline and acetylated residues), which could provide clues about the starting point of the AMPA response.ObjectivesWe therefore investigated IgM-levels of anti-citrullinated protein antibodies (ACPA), anti-carbamylated protein antibodies (anti-CarP) and anti-acetylated protein antibodies (AAPA) in healthy individuals, non-RA and RA patients.MethodsAutoantibodies were investigated in 2 cohorts:1) a Japanese cohort of healthy individuals (community based Nagasaki Island study) known to be ACPA-positive (n=65) or ACPA-negative (n=197) were compared to Dutch healthy donors (n=30) and ACPA-positive RA patients (n=29). ACPA, anti-CarP and AAPA IgG were measured by ELISAs using CCP4, CHcitP4 and CAcetylP4 peptides with sequences similar to the commercial CCP2 antigen and native control peptides.2) early arthritis patients from the Leiden Early Arthritis Clinic who had RA (n=648) or another form of arthritis (non-RA, n=555) and healthy controls (n=80). ACPA and AAPA were determined by ELISAs using CCP2 and cACP2 peptides and their native control peptides, while anti-CarP was measured on homocitrullinated versus native fetal calf serum. Mann-Whitney U-tests were performed for statistical comparisons.ResultsACPA IgM reactivity was mainly present in established ACPA-positive RA patients (Figure 1A) and to a lesser extent in ACPA-positive healthy Japanese individuals, and non-RA arthritis patients (Figure 1D). A similar picture was observed for anti-CarP IgM reactivity, for which again highest levels were found in established RA patients (1B and 1E) and ACPA-positive compared to ACPA-negative healthy Japanese individuals (1B). Intriguingly, AAPA IgM reactivity-levels displayed a different pattern as these were comparable between healthy individuals and ACPA-positive RA patients (1C and 1F). Likewise, AAPA IgM reactivity-levels were also not increased in ACPA-positive healthy Japanese individuals, who instead had lower levels compared to their ACPA-negative counterparts. Furthermore, the AAPA IgM-reactivity levels did not differ between non-RA arthritis patients, healthy controls and RA patients (1F). AAPA IgG-levels on the other hand were clearly elevated in RA patients compared to healthy controls and non-RA arthritis patients (1G).ConclusionAAPA are exceptional compared to other AMPA because IgM AAPA-levels are similar among healthy individuals, non-RA arthritis and RA patients. This suggests that AAPA IgM is part of the “normal” immune repertoire and could constitute the starting point for RA-associated AMPA responses, with isotype switching and epitope spreading to other post-translational modifications leading to the typical RA-associated mature AMPA response.Disclosure of InterestsNone declared

Abstract Background The aim of this study was to investigate the effect of various immunosuppressants on the humoral immune responses after vaccination against SARS-CoV-2 in patients with immune-mediated inflammatory diseases (IMIDs). Methods The Target to B! SARS-CoV-2 study is a multicentre study, taking place in 7 Dutch academic hospitals. Patients with the following IMIDs were recruited: Crohn’s disease (CD), ulcerative colitis (UC), auto-immune hepatitis, rheumatic (e.g. rheumatoid arthritis), neurological (e.g. multiple sclerosis) and dermatological IMIDs (e.g. atopic dermatitis). Patients were recruited based on immunosuppressants (table 1) and previous SARS-CoV-2 infection. The control group consisted of healthy subjects and IMID patients without immunosuppressants. SARS-CoV-2 receptor binding domain (RBD) antibodies were measured 28 days after completed SARS-CoV-2 vaccination. Seroconversion was defined as anti-RBD IgG >4 AU/mL. In this abstract, we focus on therapies relevant for inflammatory bowel diseases (IBD) and present results for these treatments from patients with IBD, but also other IMIDs. Results Numbers of recruited patients with each immunosuppressant are shown in table 1. Amongst these patients, 312 patients had CD and 176 UC, the rest was diagnosed with another IMID. Seroconversion was reduced in patients receiving sphingosine 1-phosphate (S1P) modulators (all multiple sclerosis patients) while seroconversion was similar to controls in the other treatment groups. However, use of Anti-tumour necrosis factor (TNF), methotrexate, janus kinase (JAK) inhibitor monotherapy and all combination therapies (except for corticosteroids combined with other immunosuppressants) were associated with reduced Sars-CoV-2 antibody titres. Patients with a previous SARS-CoV-2 infection had higher median antibody titres after second vaccination than those without a previous SARS-CoV-2 infection. The type of IMID did not affect seroconversion rates. Conclusion No immunosuppressant, registered for IBD, reduced the rates of seroconversion after vaccination against SARS-CoV-2. Some immunosuppressants were associated with lower antibody titres. However, the clinical relevance of lower antibody titres remains unknown. S1P modulators, had a clear negative impact on the humoral response against SARS-CoV-2 after vaccination. This might be relevant in the future as this therapy is currently being approved for UC. Disease aetiology did not impair immunity against SARS-CoV-2 immunity after vaccination. Disclaimer: Absolute numbers of antibody titres and rates of seroconversion will be reported at the conference and are not reported in this abstract as this might negatively impact the current submission process.

Background In rheumatoid arthritis (RA) around two-thirds of patients are autoantibody-positive for rheumatoid factor, anti-citrullinated protein antibodies (ACPA) and/or anti-carbamylated protein antibodies (anti-CarP). The remaining seronegative subgroup of RA is clinically heterogeneous and thus far, biomarkers predicting the disease course in these patients are lacking. Therefore, we set out to investigate the value of a new/different autoantibody in rheumatoid arthritis directed against advanced glycation end-product (AGE) modified proteins (anti-AGE). AGEs are a marker of oxidative stress, and anti-AGE have been described in multiple diseases including diabetes, and hypertension. Objectives To investigate the prevalence of anti-AGE in RA and non-RA arthritis patients, as well as their association with clinical parameters and disease outcome in RA. Methods In 648 RA patients and 538 non-RA arthritis patients from the Leiden Early Arthritis Clinic anti-AGE IgG antibody levels were measured using an in-house fetal calf serum (FCS) ELISA based assay using native FCS as control. The cutoff for positivity was set as the mean optical density plus two times the standard deviation of 80 healthy controls. Radiological progression was measured with the with Sharp van der Heijde score (SHS) on yearly basis and the association with anti-AGE was assessed with a multivariate normal regression model. Results Anti-AGE was found in 299 (46%) of RA patients versus 163 (30%) of non-RA arthritis patients. Interestingly, 67 (34%) of completely seronegative (RF-, ACPA- and anti-CarP-negative) RA patients were positive for anti-AGE. Within RA, anti-AGE-positive patients had significantly higher ESR (median anti-AGE-positive: 38, anti-AGE-negative: 32, p<0.001) and CRP (median anti-AGE-positive: 19, anti-AGE-negative: 17, p<0.001), indicating an more inflammatory profile in these patients. Radiographic progression, was significantly higher in anti-AGE+ patients (Figure 1A, B=1.05, p<0.001). Since ACPA and anti-CarP (in ACPA-patients) are associated with radiological progression, the analysis was first stratified for ACPA-status. In the anti-AGE+ACPA- patients a significant association with SHS was found (Figure 1B: B=1.04, P<0.001), indicating that anti-AGE is associated with radiological progression in ACPA-negative patients. Next, the ACPA-negative stratum was also stratified for anti-CarP. Interestingly, SHS was significantly higher in all anti-AGE+ groups compared to the autoantibody-negative group. Conclusion Almost half of the RA patients are anti-AGE positive including a substantial part of otherwise completely seronegative RA patients. Anti-AGE antibodies are associated with inflammatory parameters and radiologic progression in seronegative RA patients. Therefore, although these autoantibodies are not specific for RA, anti-AGE could potentially identify patients with a more inflammatory phenotype and more severe disease outcome in “classic” autoantibody-negative RA patients. Disclosure of Interests None declared.

Objective To evaluate the relationship between reported coronavirus disease 2019 (COVID-19)-like symptoms and the presence of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) antibodies in patients with an immune-mediated inflammatory disorder or post-solid organ transplantation (IMIDT) with and without immunosuppressive medication (imed) and controls. Method The IENIMINI cohort was a prospective cohort study set up in the Netherlands in March 2020, with 2 monthly (paper) or weekly (online) questionnaires about COVID-19-like symptoms. Participants from this cohort who reported these symptoms between March 2020 and November 2020 were approached for this substudy. SARS-CoV-2 antibodies were tested using a total antibody assay. Results Of the 1203 participants approached, 629 agreed to participate and were sent a fingerprick test; 565 participants collected a capillary blood sample, of which 562 were usable. Analysis showed that 57/202 (28.2%) of the tested IMIDT group with imed, 48/16 3(29.4%) of the IMIDT group without imed, and 69/197 (35.0%) of the control group tested positive for SARS-CoV-2 antibodies. Seroprevalences of SARS-CoV-2 antibodies between males and females, biological disease-modifying anti-rheumatic drug users and non-users, and those who had had a serious disease period (defined as an episode with dyspnoea and fever) and those who had not, were not statistically different between the three groups. Conclusions Approximately 30% of patients who had reported COVID-19-like symptoms had SARS-CoV-2 antibodies. The seroprevalence of SARS-CoV-2 antibodies after reported COVID-19-like symptoms was similar in IMIDT patients with and without imed compared to controls.