A potential role for chlamydial infection in rheumatoid arthritis development.

OBJECTIVES: To assess the relationship between self-reported and serologic evidence of prior chlamydial infection, rheumatoid arthritis (RA)-related autoantibodies and risk of RA-development. METHODS: This is a nested study within a prospective Swiss-based cohort including all first-degree relatives of RA patients (RA-FDR) who answered a question on past chlamydial infections. Primary outcome was systemic autoimmunity associated with RA (RA-autoimmunity) defined as positivity for anti-citrullinated peptide antibodies (ACPA) and/or rheumatoid factor (RF). Secondary outcomes were high levels of RA-autoimmunity, RA-associated symptoms and RA-autoimmunity, and subsequent seropositive RA diagnosis. We conducted a nested case-control analysis by measuring the serological status against Chlamydia trachomatis' major outer membrane protein. We replicated our analysis in an independent United States-based RA-FDR cohort. RESULTS: Among 1231 RA-FDRs, 168 (13.6%) developed RA-autoimmunity. Prevalence of self-reported chlamydial infection was significantly higher in individuals with RA-autoimmunity compared with controls (17.9% vs 9.8%, OR = 2.00, 95%CI: 1.27-3.09, p < 0.01). This association remained significant after adjustments (OR = 1.91, 95%CI: 1.20-2.95). Stronger effect sizes were observed in later stages of RA development. There was a similar trend between a positive C. trachomatis serology and high levels of RA-autoimmunity (OR = 3.05, 95% CI: 1.10-8.46, p= 0.032). In the replication cohort, there were significant associations between chlamydial infection and RF positivity and incident RA, but not anti-CCP positivity. CONCLUSIONS: Self-reported chlamydial infections are associated with elevated RA-autoimmunity in at risk individuals. The differing association of chlamydial infections and ACPA/RF between cohorts will need to be explored in future studies but is consistent with a role of mucosal origin of RA-related autoimmunity.

Detection of circulating highly expanded T-cell clones in at-risk individuals for rheumatoid arthritis before the clinical onset of the disease.

OBJECTIVES: To quantitatively profile the T-cell repertoire in the peripheral blood of individuals genetically at risk for RA, namely first-degree relatives of RA patients (RA-FDR) at different phases of disease development. METHODS: Next-generation sequencing of the TCR CDR3ß repertoire was performed on genomic DNA isolated from whole blood samples of RA-FDR selected at three different pre-clinical stages and of matched RA patients (n = 20/group). T-cell clones were identified by their unique sequence and their degree of expansion (frequency) within each sample was characterized. Clones with a frequency over 0.5% were considered highly expanded clones (HEC). RESULTS: The absolute number of HEC was significantly higher in established RA patients (mean 4.65) and tended to be higher in symptomatic RA-FDR (mean 3.4) compared with asymptomatic RA-FDR (mean 1.55, P =0.003 and P =0.07, respectively). Asymptomatic individuals with high levels of ACPA did not differ from asymptomatic RA-FDR in terms of absolute number and frequency of clones. The number of HEC tended to be slightly higher at the time of RA onset (P =0.055). Neither clones shared by several patients, nor clones previously associated with RA, were preferentially present within or between the different groups. Finally, a longitudinal analysis did not allow to uncover a kinetic expansion of RA-specific clones closely correlated with disease development. CONCLUSIONS: HEC were detected in the peripheral blood before the clinical onset of RA, in particular in the later pre-clinical phase of RA development, and their presence increased over time.

Predictive value of anti-CarP and anti-PAD3 antibodies alone or in combination with RF and ACPA for the severity of rheumatoid arthritis.

OBJECTIVES: The objective of this study was to analyse the predictive value of anti-carbamylated protein (anti-CarP) and anti-peptidyl-arginine deiminase type-3 (anti-PAD3) antibodies, alone or in combination with RF and ACPA, to identify patients at high risk of developing severe RA outcomes. METHODS: Patients within the Swiss Clinical Quality Management registry with a biobank sample were tested for RF, ACPA, anti-CarP, and anti-PAD3 antibodies. We examined the association of each autoantibody with DAS28, HAQ and radiographic damage (Ratingen) at baseline and longitudinally. RESULTS: Analyses included 851 established RA patients and 516 disease controls [axial spondyloarthritis (axSpA = 320) and PsA (196)]. Anti-CarP and anti-PAD3 antibodies were, respectively, present in 22.4% and 10.7% of the whole RA population, and in 13.2% and 3.8% of the RF and ACPA double seronegative patients. At baseline, RA patients with anti-PAD3 had higher DAS28 (4.2 vs 3.7; P= 0.005) and significantly more radiographic damage (14.9 vs 8.8; P= 0.02) than anti-PAD3-negative patients. In the ACPA-negative subgroup, baseline Ratingen scores were significantly higher in anti-PAD3-positive patients (P= 0.01). The combination of anti-PAD3, RF IgM, and ACPA was associated with significantly higher baseline radiographic scores than the double seropositive group (P= 0.04). The presence of any two of the previous autoantibodies was associated with significantly greater radiographic progression over 10 years than if all were absent (P= 0.02). There were no differences in RA outcome measures with regards to anti-CarP. CONCLUSIONS: Anti-PAD3 antibodies are associated with higher disease activity and joint damage scores in RA patients.

Identification of biological pathways specific to phases preceding rheumatoid arthritis development through gene expression profiling.

The etiopathogenesis of rheumatoid arthritis is partially understood; however, it is believed to result from a multi-step process. The immune onset followed by pre-clinical phases will eventually lead to the development of symptomatic disease. We aim at identifying differentially expressed genes in order to highlight pathways involved in the pre-clinical stages of rheumatoid arthritis development. The study population consisted of first-degree relatives of patients with rheumatoid arthritis, known to have an increased risk of developing disease as compared to the general population. Whole transcriptome analysis was performed in four groups: asymptomatic without autoantibodies or symptoms associated with possible rheumatoid arthritis (controls); having either clinically suspect arthralgias, undifferentiated arthritis or autoimmunity associated with RA (pre-clinical stages of RA: Pcs-RA); having subsequently developed classifiable RA (pre-RA); and early untreated rheumatoid arthritis patients (RA). Differentially expressed genes were determined, and enrichment analysis was performed. Functional enrichment analysis revealed 31 pathways significantly enriched in differentially expressed genes for Pcs-RA, pre-RA and RA compared to the controls. Osteoclast pathway is among the seven pathways specific for RA. In Pcs-RA and in pre-RA, several enriched pathways include TP53 gene connections, such as P53 and Wnt signalling pathways. Analysis of whole transcriptome for phenotypes related to rheumatoid arthritis allows highlighting which pathways are requested in the pre-clinical stages of disease development. After validation in replication studies, molecules belonging to some of these pathways could be used to identify new specific biomarkers for individuals with impending rheumatoid arthritis.

Prevotella copri in individuals at risk for rheumatoid arthritis.

OBJECTIVES: Rheumatoid arthritis (RA) has been associated with a relative expansion of faecal Prevotellaceae. To determine the microbiome composition and prevalence of Prevotella spp. in a group of individuals at increased risk for RA, but prior to the development of the disease. METHODS: In an ongoing cohort study of first-degree relatives (FDRs) of patients with RA, we identified 'FDR controls', asymptomatic and without autoantibodies, and individuals in pre-clinical RA stages, who had either developed anticitrullinated peptide antibodies or rheumatoid factor positivity and/or symptoms and signs associated with possible RA. Stool sampling and culture-independent microbiota analyses were performed followed by descriptive statistics and statistical analyses of community structures. RESULTS: A total of 133 participants were included, of which 50 were categorised as 'FDR controls' and 83 in 'pre-clinical RA stages'. The microbiota of individuals in 'pre-clinical RA stages' was significantly altered compared with FDR controls. We found a significant enrichment of the bacterial family Prevotellaceae, particularly Prevotella spp., in the 'pre-clinical RA' group (p=0.04). CONCLUSIONS: Prevotella spp. enrichment in individuals in pre-clinical stages of RA, before the onset of RA, suggests a role of intestinal dysbiosis in the development of RA.

Female hormonal factors and the development of anti-citrullinated protein antibodies in women at risk of rheumatoid arthritis.

Objectives: To analyse the association between female hormonal factors and the development of systemic autoimmunity associated with RA in women at increased risk for RA, namely first-degree relatives of patients with RA (RA-FDRs). Methods: In an ongoing cohort study of RA-FDRs, we analysed all women with available ACPA status. The primary outcome was ACPA positivity. The predictors of interest were female hormonal factors, such as oral contraceptives, breastfeeding, post-menopausal status, early post-menopausal period and total number of ovulatory years. Results: A total of 768 female RA-FDRs were analysed, of which 42 (5%) had developed ACPA positivity. ACPA-positive women were older (52 vs 44 years, P = 0.001). Hormonal factors significantly and independently associated with the presence of ACPA were the post-menopausal (P < 0.001) and the early post-menopausal periods (P = 0.040). Conclusions: In women at increased risk of RA, characteristic systemic autoimmunity was associated with menopause, suggesting that the acute decline in ovarian function might contribute to the development of autoimmunity associated with RA and potentially to the increased risk of RA in women.

IL-36 signaling amplifies Th1 responses by enhancing proliferation and Th1 polarization of naive CD4+ T cells.

The interleukin-1 (IL-1) superfamily of cytokines comprises a set of pivotal mediators of inflammation. Among them, the action of IL-36 cytokines in immune responses has remained elusive. In a recent study, we demonstrated a direct effect of IL-36 on immune cells. Here we show that, among T cells, the IL-36 receptor is predominantly expressed on naive CD4(+) T cells and that IL-36 cytokines act directly on naive T cells by enhancing both cell proliferation and IL-2 secretion. IL-36ß acts in synergy with IL-12 to promote Th1 polarization and IL-36 signaling is also involved in mediating Th1 immune responses to Bacillus Calmette-Guerin infection in vivo. Our findings point toward a critical function of IL-36 in the priming of Th1 cell responses in vitro, and in adaptive immunity in a model of mycobacterial infection in vivo.

Immune-mediated experimental arthritis in IL-33 deficient mice.

Previous work suggested implication of the interleukin (IL)-1 family cytokine IL-33, signaling through its receptor ST2, in the pathogenesis of human and mouse arthritis. In this study, we directly investigated the role of endogenous IL-33 in antigen-induced arthritis (AIA) and collagen-induced arthritis (CIA) using IL-33 KO mice. AIA was induced by injection of methylated bovine serum albumin (mBSA) into knee joints of previously immunized mice. CIA was induced by immunization with bovine type II collagen. Disease severity was evaluated by clinical and histological scoring and cellular immune responses were assessed in cultured draining lymph node cells. Our results indicate that the development of AIA or CIA, as assessed by clinical or histological evaluation, is not impaired in IL-33 deficient mice. We did not observe any consistent modifications in humoral or cellular immune responses in IL-33 KO mice, although IL-33 deficiency enhanced antigen-specific IFN-γ production, proliferation or IgG2a titers in some experiments, suggesting that endogenous IL-33 may contribute to shaping the adaptive immune response. In conclusion, our data suggest that IL-33 plays a modifying rather than a pivotal role in disease development in two models of immune-mediated arthritis.

Gut microbiome and intestinal inflammation in preclinical stages of rheumatoid arthritis.

BACKGROUND: Faecal Prevotellaceae, and other microbes, have been associated with rheumatoid arthritis (RA) and preclinical RA. We have performed a quantitative microbiome profiling study in preclinical stages of RA. METHODS: First-degree relatives of patients with RA (RA-FDRs) from the SCREEN-RA cohort were categorised into four groups: controls, healthy asymptomatic RA-FDRs; high genetic risk, asymptomatic RA-FDRs with two copies of the shared epitope; autoimmunity, asymptomatic RA-FDRs with RA-associated autoimmunity; and symptomatic, clinically suspect arthralgias or untreated new-onset RA.Faecal samples were collected and frozen. 16S sequencing was performed, processed with DADA2 pipeline and Silva database. Cell counts (cytometry) and faecal calprotectin (enzyme-linked immunosorbent assay, ELISA) were also obtained. Microbial community analyses were conducted using non-parametric tests, such as permutational multivariate analysis of variance (PERMANOVA), Wilcoxon and Kruskal-Wallis, or Aldex2. RESULTS: A total of 371 individuals were included and categorised according to their preclinical stage of the disease. Groups had similar age, gender and body mass index. We found no significant differences in the quantitative microbiome profiles by preclinical stages (PERMANOVA, R2=0.00798, p=0.56) and, in particular, no group differences in Prevotellaceae abundance. Results were similar when using relative microbiome profiling data (PERMANOVA, R2=0.0073, p=0.83) or Aldex2 on 16S sequence counts. Regarding faecal calprotectin, we found no differences between groups (p=0.3). CONCLUSIONS: We could not identify microbiome profiles associated with preclinical stages of RA. Only in a subgroup of individuals with the most pronounced phenotypes did we modestly retrieve the previously reported associations.

Anti-apolipoprotein A-1 IgG, incident cardiovascular events, and lipid paradox in rheumatoid arthritis.

Objective: To validate the prognostic accuracy of anti-apolipoprotein A-1 (AAA1) IgG for incident major adverse cardiovascular (CV) events (MACE) in rheumatoid arthritis (RA) and study their associations with the lipid paradox at a multicentric scale. Method: Baseline AAA1 IgG, lipid profile, atherogenic indexes, and cardiac biomarkers were measured on the serum of 1,472 patients with RA included in the prospective Swiss Clinical Quality Management registry with a median follow-up duration of 4.4 years. MACE was the primary endpoint defined as CV death, incident fatal or non-fatal stroke, or myocardial infarction (MI), while elective coronary revascularization (ECR) was the secondary endpoint. Discriminant accuracy and incidence rate ratios (IRR) were respectively assessed using C-statistics and Poisson regression models. Results: During follow-up, 2.4% (35/1,472) of patients had a MACE, consisting of 6 CV deaths, 11 MIs, and 18 strokes; ECR occurred in 2.1% (31/1,472) of patients. C-statistics indicated that AAA1 had a significant discriminant accuracy for incident MACE [C-statistics: 0.60, 95% confidence interval (95% CI): 0.57-0.98, p = 0.03], mostly driven by CV deaths (C-statistics: 0.77; 95% CI: 0.57-0.98, p = 0.01). IRR indicated that each unit of AAA1 IgG increase was associated with a fivefold incident CV death rate, independent of models' adjustments. At the predefined and validated cut-off, AAA1 displayed negative predictive values above 97% for MACE. AAA1 inversely correlated with total and HDL cholesterol. Conclusions: AAA1 independently predicts CV deaths, and marginally MACE in RA. Further investigations are requested to ascertain whether AAA1 could enhance CV risk stratification by identifying patients with RA at low CV risk.

Mice deficient in hepatocyte-specific IL-1Ra show delayed resolution of concanavalin A-induced hepatitis.

Interleukin-1 receptor antagonist (IL-1Ra) is a specific IL-1 inhibitor that possesses anti-inflammatory activities. Several studies in human and mouse suggested a protective role for IL-1Ra in liver inflammation, and we previously demonstrated that hepatocytes produce high levels of IL-1Ra in response to inflammatory challenge in vitro and in vivo. In the present study, we investigated the production and the biological function of hepatocyte-derived IL-1Ra in concanavalin A (ConA)-induced hepatitis in mice. We show that the injured liver produces large amounts of IL-1Ra and that secreted and intracellular IL-1Ra isoforms are produced with different kinetics during the course of hepatitis. By using hepatocyte-specific IL-1Ra-deficient mice (IL-1Ra(ΔH)), we demonstrate that hepatocytes represent the major cellular source of local IL-1Ra. Most interestingly, hepatic necrosis and inflammation were increased in IL-1Ra(ΔH) as compared with wild-type mice during the late phase of the disease, leading to a delayed resolution of hepatitis in IL-1Ra(ΔH) mice. In conclusion, our results show that the local production of IL-1Ra by hepatocytes contributes to the resolution of hepatitis.

IL-36R ligands are potent regulators of dendritic and T cells.

IL-36α (IL-1F6), IL-36ß (IL-1F8), and IL-36γ (IL-1F9) are members of the IL-1 family of cytokines. These cytokines bind to IL-36R (IL-1Rrp2) and IL-1RAcP, activating similar intracellular signals as IL-1, whereas IL-36Ra (IL-1F5) acts as an IL-36R antagonist (IL-36Ra). In this study, we show that both murine bone marrow-derived dendritic cells (BMDCs) and CD4(+) T lymphocytes constitutively express IL-36R and respond to IL-36α, IL-36ß, and IL-36γ. IL-36 induced the production of proinflammatory cytokines, including IL-12, IL-1ß, IL-6, TNF-α, and IL-23 by BMDCs with a more potent stimulatory effect than that of other IL-1 cytokines. In addition, IL-36ß enhanced the expression of CD80, CD86, and MHC class II by BMDCs. IL-36 also induced the production of IFN-γ, IL-4, and IL-17 by CD4(+) T cells and cultured splenocytes. These stimulatory effects were antagonized by IL-36Ra when used in 100- to 1000-fold molar excess. The immunization of mice with IL-36ß significantly and specifically promoted Th1 responses. Our data thus indicate a critical role of IL-36R ligands in the interface between innate and adaptive immunity, leading to the stimulation of T helper responses.

Endogenous IL-1α is a chromatin-associated protein in mouse macrophages.

The cytokine interleukin-1α (IL-1α) is synthesized as a 31kDa peptide that lacks a leader peptide and is not secreted by the conventional secretory pathway. A distinctive characteristic of pro-IL-1α is the presence of a nuclear localization sequence in its amino-terminal moiety that allows its translocation to the nucleus. However no nuclear function(s) of the endogenous pro-IL-1α has been reported to date. In the present study, we used murine macrophages that produce IL-1α in response to pro-inflammatory stimuli, to gain further insight into the biology of the endogenous IL-1α protein in innate immune cells. We show that endogenous IL-1α is essentially found as a chromatin-associated nuclear protein in LPS-stimulated macrophages. In contrast to IL-1ß, IL-1α was not released upon inflammasome activation unless significant cell damage occurred. IL-1ß mRNA and protein levels were specifically decreased in IL-1α deficient macrophages after LPS stimulation. However, overexpression of human pro-IL-1α did not rescue this defective IL-1ß production, suggesting that this finding might be related to the insertion of the targeting construct into the IL-1 locus, rather than to a specific nuclear function of pro-IL-1α. Finally, by using both genomic and proteomic approaches, we could not identify a nuclear function of IL-1α. Taken together, these observations suggest that in macrophages IL-1α primarily acts as an alarmin that is rapidly released upon cell damage to activate early mechanisms of host defense.

Long-term amelioration of established collagen-induced arthritis achieved with short-term therapy combining anti-CD3 and anti-tumor necrosis factor treatments.

OBJECTIVE: The goal of rheumatoid arthritis (RA) treatment is to achieve clinical remission in order to limit structural damage and physical disability. To this end, recent emphasis has been placed on aggressive treatment early in the course of disease with drugs such as anti-tumor necrosis factor (anti-TNF) agents. As T cells are also thought to play an important role in the initiation of RA, we hypothesized that targeting both TNF and T cells would result in better outcomes. The aim of this study was to examine the efficacy of combined therapy with anti-CD3 and anti-TNF in experimental RA. METHODS: Two anti-mouse antibodies were developed as surrogate reagents for anti-TNF and anti-CD3 therapies. Collagen-induced arthritis (CIA) was induced in DBA/1 mice, and antibodies were injected intraperitoneally, either alone on in combination, at predetermined subtherapeutic doses. The frequency and number of pathogenic and regulatory CD4+ T cell subsets in the draining lymph nodes were determined in order to investigate the mechanisms of action. RESULTS: Strikingly, the combination of the two antibodies demonstrated a potent synergy in established CIA, with long-term inhibition of disease progression and protection from joint destruction. The results did not demonstrate any enhancement of CD25+FoxP3+ regulatory T cells, but a profound depletion of pathogenic T cells from the draining lymph nodes was associated with reduced numbers of T cells in the joints. CONCLUSION: A short course of combination therapy with anti-CD3 and anti-TNF efficiently depletes pathogenic T cells from the draining lymph nodes, reducing the numbers of T cells in the joints and affording long-lasting inhibition of established CIA.

Predicting the onset of rheumatoid arthritis.

Various scores have attempted to predict the onset of rheumatoid arthritis (RA). In particular, EULAR proposed a simple rule to identify new-onset arthralgia suspicious for progression to RA. However, its specificity would likely be higher if serological tests were included. In patients with clinical arthritis, reliable predictive criteria for progression to RA have also been identified. Overall, the validity of the available scores is still being debated. Such scores do not fully account for the interactions between risk factors in specific subpopulations. New technologies could help to overcome these limitations, but we need databases containing a sufficient number of RA and pre-RA patients, including pre-diagnostic monitoring. Today, the existing predictive rules cannot compete with expert opinions.

Brief report: can COVID-19 infection trigger rheumatoid arthritis-associated autoimmunity in individuals at risk for the disease? A nested cohort study.

Objectives: To investigate the association between severe acute respiratory syndrome-associated coronavirus-2 (SARS-CoV-2) infection and subsequent development of autoimmunity or pre-clinical manifestations associated with rheumatoid arthritis (RA) in at risk population. Methods: This is a nested study within a prospective cohort of first-degree relatives of RA patients (RA-FDR). Participants are tested for RA-associated autoantibodies (anti-citrullinated peptide antibodies (ACPA)/rheumatoid factor (RF)) and clinical signs and symptoms suggestive of early disease. SARS-CoV-2 infections were self-reported between March 2020 and January 2023. All individuals with a pre-pandemic (sample 1) and a post-pandemic sample (sample 2) were included in the analysis. The exposure of interest was self-reported SARS-CoV-2 infection. The primary outcome was a clinically significant change in RA-associated autoantibody serum titers. Secondary outcomes included: becoming seropositive, becoming symptomatic, developing classifiable RA. Results: Among 168 RA-FDRs, 109 reported a SARS-CoV-2 infection between sample 1 and sample 2. During this period, 2 RA-FDRs (1.2%) became anti-CCP2 seropositive, none became anti-CCP3 IgG positive, 6 (3.6%) became RF IgM seropositive, 1 became (0.6%) RF IgA seropositive, 19 (11.3%) became symptomatic and none developed classifiable RA. SARS-CoV-2 infection was not significantly associated with increases in RA autoantibody titers or with secondary outcomes. Conclusion: We could not detect an association between SARS-CoV-2 infection and subsequent development of RA-associated autoimmunity, nor signs or symptoms of RA in an at risk population. These findings do not support the hypothesis that SARS-CoV-2 infections triggers the immune onset of RA.

Brief report: Assessment of mucosal barrier integrity using serological biomarkers in preclinical stages of rheumatoid arthritis.

Background: The pathogenesis of rheumatoid arthritis (RA) is believed to initiate at mucosal sites. The so-called 'mucosal origin hypothesis of RA' postulates an increased intestinal permeability before disease onset. Several biomarkers, including lipopolysaccharide binding protein (LBP) and intestinal fatty acid binding protein (I-FABP), have been proposed to reflect gut mucosa permeability and integrity, while serum calprotectin is a new inflammation marker proposed in RA. Methods: We analyzed serum samples of individuals genetically at increased risk of RA in a nested-case-control study. Participants from a longitudinal cohort of first-degree relatives of RA patients (SCREEN-RA cohort) were divided into three pre-clinical stages of RA, based on the presence of risk factors for subsequent RA onset: 1) low-risk healthy asymptomatic controls; 2) intermediate-risk individuals without symptoms, but with RA-associated auto-immunity; 3) high-risk individuals with clinically suspect arthralgias. Five patients with newly diagnosed RA were also sampled. Serum LBP, I-FABP and calprotectin were measured using commercially available ELISA kits. Results: We included 180 individuals genetically at increased risk for RA: 84 asymptomatic controls, 53 individuals with RA-associated autoimmunity and 38 high risk individuals. Serum LBP, I-FAPB or calprotectin concentrations did not differ between individuals in different pre-clinical stages of RA. Conclusion: Based on the serum biomarkers LBP, I-FABP and calprotectin, we could not detect any evidence for intestinal injury in pre-clinical stages of RA.

Impact of SARS-CoV2 infection on anti-apolipoprotein A-1 IgG response in inflammatory rheumatic diseases.

Objectives: To investigate the impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) infection on anti-apolipoprotein A-1 IgG (AAA1) humoral response in immunosuppressed inflammatory rheumatic diseases (IRD) patients. Methods: This is a nested cohort study from the prospective Swiss Clinical Quality Management registry. A total of 368 IRD patients for which serum samples were available before and after the SARS-CoV2 pandemic were included. Autoantibodies against ApoA-1 (AAA1) and its c-terminal region (AF3L1) were measured in both samples. The exposure of interest was anti-SARS-CoV2 spike subunit 1 (S1) seropositivity measured in the second sample. The effect of SARS-CoV2 infection (anti-S1 seropositivity) on becoming AAA1 or AF3L1 positive and on the change of AAA1 or AF3L1 optical density (OD) between the two samples was tested with multivariable regressions. Results: There were 12 out of 368 IRD patients who were seroconverted against S1. The proportion of patients becoming AF3L1 seropositive was significantly higher in anti-S1-positive patients, compared with anti-S1-negative patients (66.7% versus 21.6%, p = 0.001). Adjusted logistic regression analyses indicated that anti-S1 seroconversion was associated with a sevenfold increased risk of AFL1 seropositivity (odds ratio: 7.4, 95% confidence interval (95% CI): 2.1-25.9) and predicted median increase in AF3L1 OD values (+0.17, 95% CI: 0.08-0.26). Conclusions: SARS-CoV2 infection is associated with a marked humoral response against the immunodominant c-terminal region of ApoA-1 in IRD patients. The possible clinical impact of AAA1 and AF3L1 antibodies on disease progression, cardiovascular complications, or long COVID syndrome deserves future investigations.

GWAS meta-analysis of psoriasis identifies new susceptibility alleles impacting disease mechanisms and therapeutic targets.

Psoriasis is a common, debilitating immune-mediated skin disease. Genetic studies have identified biological mechanisms of psoriasis risk, including those targeted by effective therapies. However, the genetic liability to psoriasis is not fully explained by variation at robustly identified risk loci. To move towards a saturation map of psoriasis susceptibility we meta-analysed 18 GWAS comprising 36,466 cases and 458,078 controls and identified 109 distinct psoriasis susceptibility loci, including 45 that have not been previously reported. These include susceptibility variants at loci in which the therapeutic targets IL17RA and AHR are encoded, and deleterious coding variants supporting potential new drug targets (including in STAP2, CPVL and POU2F3). We conducted a transcriptome-wide association study to identify regulatory effects of psoriasis susceptibility variants and cross-referenced these against single cell expression profiles in psoriasis-affected skin, highlighting roles for the transcriptional regulation of haematopoietic cell development and epigenetic modulation of interferon signalling in psoriasis pathobiology.

Articular inflammation is controlled by myeloid cell-derived interleukin 1 receptor antagonist during the acute phase of arthritis in mice.

OBJECTIVES: To define the cell type (myeloid vs other cells) specific effect of interleukin 1 (IL-1) receptor antagonist (IL-1Ra) deficiency on the acute inflammatory phase of arthritis. METHODS: Arthritis was induced by K/BxN serum transfer in wild-type (WT), IL-1Ra-deficient (IL-1Ra(-/-)) and conditional knockout mice. In the latter, IL-1Ra production was specifically targeted in myeloid cells (IL-1Ra(ΔM)) or in both hepatocytes and myeloid cells (IL-1Ra(ΔH+M)). Arthritis severity was clinically evaluated and ankle sections were scored for synovial inflammation and cartilage erosion. Quantitative RT-PCR, western blot and immunohistochemical analyses measured expression, localisation and cellular sources of the different IL-1Ra isoforms in arthritic joints. RESULTS: Total and myeloid cell-specific IL-1Ra deficiency was associated with increased arthritis severity, although disease incidence was similar to that of WT mice. Increased clinical scores were associated with exacerbated synovial inflammation. All IL-1Ra isoforms, except for intracellular (ic)IL-1Ra2, were expressed in arthritic joints of WT mice. In contrast, production of secreted (s)IL-1Ra and icIL-1Ra3 isoforms was markedly decreased in arthritic joints of both IL-1Ra(ΔM) and IL-1Ra(ΔH+M) mice. Immunohistochemical and western blot analyses suggested that the icIL-1Ra1 isoform is produced primarily by synovial fibroblasts. CONCLUSION: Myeloid cell-derived IL-1Ra, including both sIL-1Ra and icIL-1Ra3 isoforms, controls articular inflammation during the acute phase of K/BxN serum transfer-induced arthritis.