Ex vivo C5b-9 Deposition Test to Monitor Complement Activity in Clinical and Subclinical Atypical Hemolytic Uremic Syndrome and in Transplantation-Associated Thrombotic Microangiopathy.

Introduction: Atypical hemolytic uremic syndrome (aHUS) is a complement system (CS)-mediated ultrarare disease that manifests as thrombotic microangiopathy (TMA) with preferential small kidney vessels involvement. Transient CS activation is also observed in secondary TMA or in patients at risk of developing aHUS. There is no gold standard test to monitor disease activity; however, the ex vivo C5b-9 deposition test seems to be a good approach. Methods: We assessed the C5b-9 deposition induced by serum samples of patients with aHUS (n = 8) and with TMA associated with kidney (n = 2), lung (n = 1) or hematopoietic stem cell (HSC) transplantation (HSCT, n = 2) during the acute phase of the disease or in remission. As control for transplant-associated TMA (TA-TMA), we analyzed samples of clinically stable kidney and HSC-transplanted patients without signs of TMA. In addition, we studied 1 child with genetic risk of aHUS during an acute infection. Results: In the acute disease phase or in patients with disease activity despite C5 blockade, a significant increase of C5b-9 deposition was detected. In all patients with clinical response to C5 blockade but one, levels of C5b-9 deposition were within the normal range. Finally, we detected increased C5b-9 deposition levels in an asymptomatic child with genetic risk of aHUS when a concomitant otitis episode was ongoing. Conclusion: The ex vivo C5b-9 deposition test is an auspicious tool to monitor CS activity in aHUS and TA-TMA. In addition, we demonstrate that the test may be useful to detect subclinical increase of CS activity, which expands the spectrum of patients that would benefit from a better CS activity assessment.

Identification of connective tissue disease autoantibodies and a novel autoantibody anti-annexin A11 in patients with "idiopathic" interstitial lung disease.

BACKGROUND: Autoantibodies are a hallmark feature of Connective Tissue Diseases (CTD). Their presence in patients with idiopathic interstitial lung disease (ILD) may suggest covert CTD. We aimed to determine the prevalence of CTD autoantibodies in patients diagnosed with idiopathic ILD. METHODS: 499 patient sera were analysed: 251 idiopathic pulmonary fibrosis (IPF), 206 idiopathic non-specific interstitial pneumonia (iNSIP) and 42 cryptogenic organising pneumonia (COP). Autoantibody status was determined by immunoprecipitation. RESULTS: 2.4% of IPF sera had a CTD-autoantibody compared to 10.2% of iNSIP and 7.3% of COP. 45% of autoantibodies were anti-synthetases. A novel autoantibody targeting an unknown 56 kDa protein was found in seven IPF patients (2.8%) and two NSIP (1%) patients. This was characterised as anti-annexin A11. CONCLUSION: Specific guidance on autoantibody testing and interpretation in patients with ILD could improve diagnostic accuracy. Further work is required to determine the clinical significance of anti-annexin A11.

Role of Skewed X-Chromosome Inactivation in Common Variable Immunodeficiency.

The term common variable immunodeficiency (CVID) encompasses a clinically diverse group of disorders, mainly characterized by hypogammaglobulinemia, insufficient specific antibody production, and recurrent infections. The genetics of CVID is complex, and monogenic defects account for only a portion of cases, typically <30%. Other proposed mechanisms include digenic, oligogenic, or polygenic inheritance and epigenetic dysregulation. In this study, we aimed to assess the role of skewed X-chromosome inactivation (XCI) in CVID. Within our cohort of 131 genetically analyzed CVID patients, we selected female patients with rare variants in CVID-associated genes located on the X-chromosome. Four patients harboring heterozygous variants in BTK (n = 2), CD40LG (n = 1), and IKBKG (n = 1) were included in the study. We assessed XCI status using the HUMARA assay and an NGS-based method to quantify the expression of the 2 alleles in mRNA. Three of the 4 patients (75%) exhibited skewed XCI, and the mutated allele was predominantly expressed in all cases. Patient 1 harbored a hypomorphic variant in BTK (p.Tyr418His), patient 3 had a pathogenic variant in CD40LG (c.288+1G>A), and patient 4 had a hypomorphic variant in IKBKG (p.Glu57Lys) and a heterozygous splice variant in TNFRSF13B (TACI) (c.61+2T>A). Overall, the analysis of our cohort suggests that CVID in a small proportion of females (1.6% in our cohort) is caused by skewed XCI and highly penetrant gene variants on the X-chromosome. Additionally, skewed XCI may contribute to polygenic effects (3.3% in our cohort). These results indicate that skewed XCI may represent another piece in the complex puzzle of CVID genetics.

Anti-nuclear valosin-containing protein-like autoantibody is associated with calcinosis and higher risk of cancer in systemic sclerosis.

OBJECTIVES: Systemic sclerosis (SSc)-specific autoantibodies allow the diagnosis and predict the prognosis of SSc patients with different clinical characteristics. The aim of this study was to describe new SSc-related autoantibodies by a novel protein immunoprecipitation (IP) assay. METHODS: Serum samples and clinical data were collected from 307 SSc patients. Antinuclear autoantibodies were tested in all patients by indirect immunofluorescence (IIF) on HEp-2 cells. SSc-specific autoantibodies were evaluated with a commercial immunoblot and chemiluminescence immunoassay, and traditional RNA-IP. Patients negative for all these autoantibodies (n = 51) were further tested with a non-radioactive protein IP assay. Protein bands detected on SDS-PAGE were then analysed by mass spectrometry (MS) and confirmed by western blot (WB). Additional 56 patients with nucleolar pattern by IIF were tested by protein IP-WB. RESULTS: Five patients who underwent protein IP testing showed a 110-115kDa molecular weight band on SDS-PAGE and a homogeneous nucleolar pattern by IIF. MS identified the bands as nuclear valosin-containing protein-like (NVL). An additional positive patient was detected by IP-WB. As compared with the remaining 101 negative patients, anti-NVL positive patients showed a greater prevalence of calcinosis (100% vs 18.9%, p< 0.001), and cancer (66.7% vs 8.9%, p= 0.002), with a particular association with synchronous cancer (OR = 16.3; p= 0.024). CONCLUSION: We identified NVL as a new autoantibody target by a novel protein IP assay in SSc patients with a homogeneous nucleolar IIF pattern, testing negative for all known SSc-specific autoantibodies by commercial assays and RNA IP. Anti-NVL identifies a new clinical phenotype, characterized by calcinosis and cancer.

Anti-U11/U12 Antibodies as a Rare but Important Biomarker in Patients with Systemic Sclerosis: A Narrative Review.

Anti-nuclear (ANA) are present in approximately 90% of systemic sclerosis (SSc) patients and are key biomarkers in supporting the diagnosis and determining the prognosis of this disease. In addition to the classification criteria autoantibodies for SSc [i.e., anti-centromere, anti-topoisomerase I (Scl-70), anti-RNA polymerase III], other autoantibodies have been associated with important SSc phenotypes. Among them, anti-U11/U12 ribonucleoprotein (RNP) antibodies, also known as anti-RNPC-3, were first reported in a patient with SSc, but very little is known about their association and clinical utility. The U11/U12 RNP macromolecular complex consists of several proteins involved in alternative mRNA splicing. More recent studies demonstrated associations of anti-anti-U11/U12 antibodies with SSc and severe pulmonary fibrosis as well as with moderate to severe gastrointestinal dysmotility. Lastly, anti-U11/U12 autoantibodies have been strongly associated with malignancy in SSc patients. Here, we aimed to summarize the knowledge of anti-U11/U12/RNPC-3 antibodies in SSc, including their seroclinical associations in a narrative literature review.

Serum CXCL13, BAFF, IL-21 and IL-22 levels are related to disease activity and lymphocyte profile in primary Sjögren's syndrome.

OBJECTIVES: To investigate the utility of serum BAFF, IL-17, IL-18, IL-21, IL-22, CXCL13, TNF-R2 and PD-L2 as biomarkers of disease activity in primary Sjögren's syndrome (pSS), their relationship with lymphocyte subpopulations and their accuracy to discriminate pSS from Sicca syndrome. METHODS: We conducted an observational study on 66 pSS patients and 48 controls (25 with Sicca syndrome and 23 healthy volunteers). Serum levels of BAFF, IL-17 A/F, IL-18, IL-21, IL-22, CXCL13, TNF-R2 and PD-L2 were measured using a multiplex immunoassay. Lymphocyte subpopulations were analysed by flow cytometry. Disease activity of pSS was assessed with ESSDAI at study inclusion. RESULTS: Patients with pSS presented higher serum CXCL13 (364.7 vs. 205.2 pg/mL), IL-21 (43.2 vs. 0 pg/mL) and BAFF (1646 vs. 1369 pg/mL), and lower PD-L2 levels (1950.8 vs. 2792.3 pg/mL) than controls. ESSDAI was associated with BAFF, IL-18 and IL-22. Patients with ESSDAI >0 exhibited higher CXCL13, IL-21, IL-22 and TNFR2 concentrations. IL-21 levels correlated with lower memory B-cell and higher naïve B-cell percentages and IL-22 levels correlated with increased circulating activated CD4+ T-cells. The combination of serum CXCL13, BAFF and PDL2 levels using the formula [ln(CXCL13)+ln(BAFF)]/ln(PDL2) exhibit an AUC of 0.854 (95% CI: 0.750-0.919) to discriminate between pSS and Sicca syndrome (sensitivity 77.2% and specificity 86.4% using a cut-off of 1.7). CONCLUSIONS: CXCL13, BAFF, IL-21, and IL-22 are potential biomarkers of pSS activity and IL-21 and IL-22 are associated with disturbances of lymphocyte subpopulations in pSS. The combination of serum CXCL13, BAFF, and PD-L2 levels allows discrimination between pSS and Sicca syndrome.