Validation of an indirect ELISA assay for assessment of autoantibodies against full-length TRIM21 and its individual domains.

Anti-SSA-autoantibodies are common in patients with rheumatologic disease, especially Sjögren's syndrome, systemic lupus erythematosus and rheumatoid arthritis. They consist of both autoantibodies towards Ro60 and Ro52, the latter also known as TRIM21. TRIM21 is an intracellular protein consisting of four domains; PRY/SPRY, Coiled-Coil, B-box and RING. The aim of this study was to establish an indirect ELISA detecting autoantibodies towards both the full-length TRIM21 protein and its four domains. We expressed the five constructs, created, and validated indirect ELISA protocols for each target using plasma from anti-SSA positive patients and healthy controls. Our findings were validated to the clinically used standards. We measured significantly higher levels of autoantibodies towards our full-length TRIM21, and the PRY/SPRY, Coiled-Coil and RING domains in patients compared to healthy controls. No significant difference in the level of autoantibodies were detected against the B-box domain. Our setups had a signal to noise ratio in the range of 30 to 184, and an OD between 2 and 3. Readings did not decline using NaCl of 500 mM as wash, affirming the high binding affinity of the autoantibodies measured. Our protocols allow us to further study the different autoantibodies of anti-SSA positive patients. This creates the possibility to stratify our patients into subgroups regarding autoantibody profile and specific pheno- or endotype.

[VEXAS gene variants explain previously unrecognized clinical syndrome].

This review aims to make clinicians aware of the newly described syndrome, VEXAS. VEXAS should become an obvious differential diagnosis in cases of unexplained inflammation, anemia, and rheumatological and/or hematological manifestations. Patients with VEXAS are typically male aged > 60, with inflammation, and macrocytic anaemia. On suspicion of cancer or infections patients have frequently been exposed to extensive diagnostic procedures and hospital admissions. In this review, we summarise the current knowledge of VEXAS regarding pathogenesis, symptoms, diagnosis, and treatment.

Patients with VEXAS diagnosed in a Danish tertiary rheumatology setting have highly elevated inflammatory markers, macrocytic anaemia and negative autoimmune biomarkers.

BACKGROUND: Vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic (VEXAS) is an autoinflammatory condition with overlapping features of rheumatology and haematology caused by somatic mutations in the UBA1 gene. Patients present with highly variable symptoms and their path towards diagnosis are often complicated and characterised by extensive examinations. It is, therefore, pivotal that clinicians become familiar with the clinical presentation of VEXAS to advance identification of patients with the disease. OBJECTIVES: We aimed to (1) characterise patients diagnosed with VEXAS in a tertiary rheumatology referral centre, (2) identify common rheumatological biomarkers that may distinguish VEXAS from other rheumatic diseases and (3) suggest which clinical findings should motivate genetic testing for VEXAS. METHODS: Patients were identified and diagnosed at the department of Rheumatology, Aarhus University Hospital (AUH), Denmark. Blood samples were examined for VEXAS-associated UBA1 variants by Sanger sequencing at the department of Clinical Immunology, AUH. Clinical and biochemical data were retrieved from the hospital electronic patient chart. RESULTS: Eleven male patients with clinical suspicion of VEXAS underwent sequencing. Five of these carried known VEXAS-associated variants. Median age at diagnosis was 84 (75-87) years. All patients had significantly elevated inflammatory markers with a median C-reactive protein (CRP) of 297 (196-386) mg/L and macrocytic anaemia. None of the patients presented common biomarkers for autoimmunity. CONCLUSION: Danish patients with VEXAS syndrome are men with persistent inflammation, constitutional symptoms and heterogeneous clinical presentations. Shared features for all patients in this study were highly elevated inflammatory markers, macrocytic anaemia and negative autoimmune biomarkers.

Hepatitis B virus upregulates host microRNAs that target apoptosis-regulatory genes in an in vitro cell model.

Chronic hepatitis B (CHB) infection increases the risk of developing severe liver disease including cirrhosis and hepatocellular carcinoma (HCC). As microRNAs may modulate host - virus interactions, we here investigated if hepatitis B virus (HBV) infection modulate microRNA expression using an in vitro HepG2 cell model system with inducible HBV replication. We found that HBV replication was associated with upregulation of miR-192-5p, miR-194-5p and miR-215-5p, of which miR-192-5p and miR-215-5p have identical seed sequences. Bioinformatics analyses revealed a significant enrichment of potential target genes involved in apoptosis signaling of all three microRNAs. In line with this, transfection with a mimic of miR-192-5p suppressed the protein level of pro-apoptotic BIM and reduced endoplasmic reticulum (ER) stress-induced apoptosis in HepG2 cells. In contrast, transfection with a mimic of miR-194-5p downregulated the anti-apoptotic proteins SODD and cFLIP, and sensitized HepG2 cells to both ER stress- and cytokine-induced apoptosis. In conclusion, our study suggests that HBV upregulates the expression of miR-192-5p and miR-194-5p in the host cell. These microRNAs target important apoptosis-regulatory proteins, and may thus contribute to the development of HBV-related liver disease.

Hepatitis B virus suppresses the secretion of insulin-like growth factor binding protein 1 to facilitate anti-apoptotic IGF-1 effects in HepG2 cells.

Hepatitis B virus (HBV) infection is a major global health burden as chronic hepatitis B (CHB) is associated with the development of liver diseases including hepatocellular carcinoma (HCC). To gain insight into the mechanisms causing HBV-related HCC, we investigated the effects of HBV replication on global host cell gene expression using human HepG2 liver cells. By microarray analysis, we identified 54 differentially expressed genes in HBV-replicating HepG2 cells. One of the differentially-expressed genes was insulin-like growth factor binding protein 1 (IGFBP1) which was downregulated in HBV-replicating cells. Consistent with the gene expression data, IGFBP1 was suppressed at both the cellular and secreted protein levels in the presence of HBV replication. Transient transfection experiments with an inducible plasmid encoding the HBV X protein (HBx) revealed that HBx alone was sufficient to modulate IGFBP1 expression. Small interference RNA (siRNA)-mediated loss of function studies revealed that knockdown of IGFBP1 reduced apoptosis induced by either thapsigargin (TG) or staurosporine (STS). Treatment of cells with recombinant insulin-like growth factor 1 (IGF-1) decreased both TG- or STS-induced apoptosis. Interestingly, addition of recombinant IGFBP1 reversed the anti-apoptotic effect of IGF-1 on TG-induced, but not STS-induced, apoptosis. In conclusion, our results suggest an anti-apoptotic autocrine function of HBV-mediated downregulation of IGFBP1 in HepG2 cells. Such an effect may contribute to the development of HBV-mediated HCC by increasing pro-survival and anti-apoptotic IGF-1 effects.

Identification of valid reference genes for microRNA expression studies in a hepatitis B virus replicating liver cell line.

BACKGROUND: MicroRNAs are regulatory molecules and suggested as non-invasive biomarkers for molecular diagnostics and prognostics. Altered expression levels of specific microRNAs are associated with hepatitis B virus infection and hepatocellular carcinoma. We previously identified differentially expressed microRNAs with liver-specific target genes in plasma from children with chronic hepatitis B. To further understand the biological role of these microRNAs in the pathogenesis of chronic hepatitis B, we have used the human liver cell line HepG2, with and without HBV replication, after transfection of hepatitis B virus expression vectors. RT-qPCR is the preferred method for microRNA studies, and a careful normalisation strategy, verifying the optimal set of reference genes, is decisive for correctly evaluating microRNA expression levels. The aim of this study was to provide valid reference genes for the human HCC-derived cell line HepG2. RESULTS: A panel of 739 microRNAs was screened to identify the most stably expressed microRNAs, followed by a PubMed search identifying microRNAs previously used as reference genes. Sixteen candidate reference genes were validated by RT-qPCR. Reference gene stabilities were calculated first by standard deviations of ΔCt values and then by geNorm and NormFinder analyses, taking into account the amplification efficiency of each microRNA primer set. The optimal set of reference genes was verified by a target analysis using RT-qPCR on miR-215-5p. CONCLUSION: We identified miR-24-3p, miR-151a-5p, and miR-425-5p as the most valid combination of reference genes for microRNA RT-qPCR studies in our hepatitis B virus replicating HepG2 cell model.