Progranulin signaling in sepsis, community-acquired bacterial pneumonia and COVID-19: a comparative, observational study

BACKGROUND Progranulin is a widely expressed pleiotropic growth factor with a central regulatory effect during the early immune response in sepsis. Progranulin signaling has not been systematically studied and compared between sepsis, community-acquired pneumonia (CAP), COVID-19 pneumonia and a sterile systemic inflammatory response (SIRS). We delineated molecular networks of progranulin signaling by next-generation sequencing (NGS), determined progranulin plasma concentrations and quantified the diagnostic performance of progranulin to differentiate between the above-mentioned disorders using the established biomarkers procalcitonin (PCT), interleukin-6 (IL-6) and C-reactive protein (CRP) for comparison. METHODS The diagnostic performance of progranulin was operationalized by calculating AUC and ROC statistics for progranulin and established biomarkers in 241 patients with sepsis, 182 patients with SIRS, 53 patients with CAP, 22 patients with COVID-19 pneumonia and 53 healthy volunteers. miRNAs and mRNAs in blood cells from sepsis patients (n = 7) were characterized by NGS and validated by RT-qPCR in an independent cohort (n = 39) to identify canonical gene networks associated with upregulated progranulin at sepsis onset. RESULTS Plasma concentrations of progranulin (ELISA) in patients with sepsis were 57.5 (42.8-84.9, Q25-Q75) ng/ml and significantly higher than in CAP (38.0, 33.5-41.0~ng/ml, p < 0.001), SIRS (29.0, 25.0-35.0~ng/ml, p < 0.001) and the healthy state (28.7, 25.5-31.7~ng/ml, p < 0.001). Patients with COVID-19 had significantly higher progranulin concentrations than patients with CAP (67.6, 56.6-96.0 vs. 38.0, 33.5-41.0~ng/ml, p < 0.001). The diagnostic performance of progranulin for the differentiation between sepsis vs. SIRS (n = 423) was comparable to that of procalcitonin. AUC was 0.90 (95% CI = 0.87-0.93) for progranulin and 0.92 (CI = 0.88-0.96, p = 0.323) for procalcitonin. Progranulin showed high discriminative power to differentiate bacterial CAP from COVID-19 (sensitivity 0.91, specificity 0.94, AUC 0.91 (CI = 0.8-1.0) and performed significantly better than PCT, IL-6 and CRP. NGS and partial RT-qPCR confirmation revealed a transcriptomic network of immune cells with upregulated progranulin and sortilin transcripts as well as toll-like-receptor 4 and tumor-protein 53, regulated by miR-16 and others. CONCLUSIONS Progranulin signaling is elevated during the early antimicrobial response in sepsis and differs significantly between sepsis, CAP, COVID-19 and SIRS. This suggests that progranulin may serve as a novel indicator for the differentiation between these disorders. TRIAL REGISTRATION Clinicaltrials.gov registration number NCT03280576 Registered November 19, 2015

Detection of myelin autoantibodies: evaluation of an assay system for diagnosis of multiple sclerosis in differentiation from other central nervous system diseases

Background: Multiple sclerosis (MS) is a frequent and often severe autoimmune disease of the central nervous system. We describe a newly developed enzyme-linked immunosorbent assay (ELISA)-based test system for the assessment of neuronal autoantibodies in serum and cerebrospinal fluid (CSF). This tool could help define autoimmune status and thus be a potential means of therapeutic surveillance. Methods: We used an assay system (ELISA, E100, Mediagnost) based on purified bovine antigens [myelin-oligodendrocyte glycoprotein (MOG), myelin basic protein (MBP), myelin-associated glycoprotein (MAG), proteolipid protein (PLP) and alpha-B-crystalline (CRY)] antibodies for the measurement of specific immunoglobulin G (IgG) and immunoglobulin M (IgM) antibodies. Assay characteristics and preliminary validation were conducted by measurement of serum and CSF samples from 41 MS patients and 128 patients with other neurological diseases (OND). Results: We measured the inter- (17.8/10.1%) and intra-assay variability (5.5/6.7%); linearity (1:250– 1:16,000), and specificity of IgG and IgM. We demonstrate that by the results of this test system MS patients can be differentiated from patients with OND. Conclusions: The ELISA kit we evaluated is suitable for the measurement of neuronal autoantibodies. The initial validation demonstrates its potential use in the differential diagnosis of central neuronal system diseases. Clin Chem Lab Med 2009;47:1395–400.Peer Reviewe

Long-Term Humoral Immune Response against SARS-CoV-2 after Natural Infection and Subsequent Vaccination According to WHO International Binding Antibody Units (BAU/mL)

The new WHO reference standard allows for the definition of serum antibodies against various SARS-CoV-2 antigens in terms of binding antibody units (BAU/mL) and thus to compare the results of different ELISA systems. In this study, the concentration of antibodies (ABs) against both the S- and the N-protein of SARS-CoV-2 as well as serum neutralization activity were evaluated in three patients after a mild course of COVID-19. Serum samples were collected frequently during a period of over one year. Furthermore, in two individuals, the effects of an additional vaccination with a mRNA vaccine containing the S1-RBD sequence on these antibodies were examined. After natural infection, the antibodies (IgA, IgG) against the S1-protein remained elevated above the established cut-off to positivity (S-IgA 60 BAU/mL and S-IgG 50 BAU/mL, respectively) for over a year in all patients, while this was not the case for ABs against the N-protein (cut-off N-IgG 40 BAU/mL, N-IgA 256 BAU/mL). Sera from all patients retained the ability to neutralize SARS-CoV-2 for more than a year. Vaccination resulted in a rapid boost of antibodies to S1-protein but, as expected, not to the N-protein. Most likely, the wide use of the WHO reference preparation will be very useful in determining the individual immune status of patients after an infection with SARS-CoV-2 or after vaccination