Mouse anti-Human FAIM3 polyclonal antibody

BACKGROUND: The cellular surface molecule HsTOSO/FAIM3/HsFc mu R has been identified as an IgM-specific Fc receptor expressed on lymphocytes. Here, we show that its extracellular immunoglobulin-like domain (HsFc mu R-Igl) specifically binds to IgM/antigen immune complexes (ICs) and exploit this property for the development of novel detection systems for IgM antibodies directed against Crimean-Congo hemorrhagic fever virus (CCHFV) and Zika virus (ZIKV). METHODS: His-tagged HsFc mu R-Igl was expressed in Escherichia coli and purified by affinity chromatography, oxidative refolding, and size-exclusion chromatography. Specific binding of HsFc mu R-Igl to IgM/antigen ICs was confirmed, and 2 prototypic ELISAs for the detection of anti-CCHFV and anti-ZIKV IgM antibodies were developed. Thereby, patient sera and virus-specific recombinant antigens directly labeled with horseradish peroxidase (HRP) were coincubated on HsFc mu R-Igl-coated ELISA plates. Bound ICs were quantified by measuring turnover of a chromogenic HRP substrate. RESULTS: Assay validation was performed using paired serum samples from 15 Kosovar patients with a PCR-confirmed CCHFV infection and 28 Brazilian patients with a PCR-confirmed ZIKV infection, along with a panel of a priori CCHFV/ZIKV-IgM-negative serum samples. Both ELISAs were highly reproducible. Sensitivity and specificity were comparable with or even exceeded in-house gold standard testing and commercial kits. Furthermore, latex beads coated with HsFc mu R-Igl aggregated upon coincubation with an IgM-positive serum and HRP-labeled antigen but not with either component alone, revealing a potential for use of HsFc mu R-Igl as a capture molecule in aggregation-based rapid tests. CONCLUSIONS: Recombinant HsFc mu R-Igl is a versatile capture molecule for IgM/antigen ICs of human and animal origin and can be applied for the development of both plate-and bead-based serological tests. (c) 2018 American Association for Clinical Chemistry

Rationale: Community-acquired pneumonia (CAP) accounts for a major proportion of intensive care unit (ICU) admissions for respiratory failure and sepsis. Diagnostic uncertainty complicates case management, which may delay appropriate cause-specific treatment. Objectives: To characterize the blood genomic response in patients with suspected CAP and identify a candidate biomarker for the rapid diagnosis of CAP on ICU admission. Methods: The study comprised two cohorts of consecutively enrolled patients treated for suspected CAP on ICU admission. Patients were designated CAP (cases) and no-CAP patients (control subjects) by post hoc assessment. The first (discovery) cohort (101 CAP and 33 no-CAP patients) was enrolled between January 2011 and July 2012; the second (validation) cohort (70 CAP and 30 no-CAP patients) between July 2012 and June 2013. Blood was collected within 24 hours of ICU admission. Measurements and Main Results: Blood microarray analysis of CAP and no-CAP patients revealed shared and distinct gene expression patterns. A 78-gene signature was defined for CAP, from which a FAIM3:PLAC8 gene expression ratio was derived with area under curve of 0.845 (95% confidence interval, 0.764-0.917) and positive and negative predictive values of 83% and 81%, respectively. Robustness of the FAIM3:PLAC8 ratio was ascertained by quantitative polymerase chain reaction in the validation cohort. The FAIM3:PLAC8 ratio outperformed plasma procalcitonin and IL-8 and IL-6 in discriminating between CAP and no-CAP patients. Conclusions: CAP and no-CAP patients presented shared and distinct blood genomic responses. We propose the FAIM3:PLAC8 ratio as a candidate biomarker to assist in the rapid diagnosis of CAP on ICU admission.