Development and multi-center validation of a fully automated digital immunoassay for neurofilament light chain: toward a clinical blood test for neuronal injury.

OBJECTIVES: Neurofilament light chain (NfL) has emerged as a promising biomarker for detecting and monitoring axonal injury. Until recently, NfL could only be reliably measured in cerebrospinal fluid, but digital single molecule array (Simoa) technology has enabled its precise measurement in blood samples where it is typically 50-100 times less abundant. We report development and multi-center validation of a novel fully automated digital immunoassay for NfL in serum for informing axonal injury status. METHODS: A 45-min immunoassay for serum NfL was developed for use on an automated digital analyzer based on Simoa technology. The analytical performance (sensitivity, precision, reproducibility, linearity, sample type) was characterized and then cross validated across 17 laboratories in 10 countries. Analytical performance for clinical NfL measurement was examined in individual patients with relapsing remitting multiple sclerosis (RRMS) after 3 months of disease modifying treatment (DMT) with fingolimod. RESULTS: The assay exhibited a lower limit of detection (LLoD) of 0.05 ng/L, a lower limit of quantification (LLoQ) of 0.8 ng/L, and between-laboratory imprecision <10 % across 17 validation sites. All tested samples had measurable NfL concentrations well above the LLoQ. In matched pre-post treatment samples, decreases in NfL were observed in 26/29 RRMS patients three months after DMT start, with significant decreases detected in a majority of patients. CONCLUSIONS: The sensitivity characteristics and reproducible performance across laboratories combined with full automation make this assay suitable for clinical use for NfL assessment, monitoring in individual patients, and cross-comparisons of results across multiple sites.

Hydrogen production driven by formate oxidation in Shewanella oneidensis MR-1.

Shewanella oneidensis MR-1 is a potent hydrogen producer in the deficiency of exogenous electron acceptors. The electron transfer pathway for hydrogen production remains unclear, although enzymes for hydrogen production have been identified in S. oneidensis MR-1. In this study, we investigated the electron transfer pathway from formate to hydrogen, given that formate is commonly a key chemical for bacterial hydrogen production. We revealed that two formate dehydrogenases FdhA1B1C1 and FdhA2B2C2, rather than FdnGHI, played a dominant role in formate-driven hydrogen production. Menaquinone was indispensable for the electron transfer from formate to hydrogen, which excluded the presence of formate hydrogen-lyase in S. oneidensis MR-1. A previously proposed formate dehydrogenase subunit HydC was identified as a menaquinone-binding subunit of [FeFe] hydrogenase HydAB, and the hydABC operon is conserved in bacteria living in diverse environments. A formate exporter FocA and transcriptional regulator FhlA were identified for their effect on formate metabolism and hydrogen production. FhlA positively affected the metabolism of formate and hydrogen by regulating the expression of fdhA2B2C2, fdnGHI, focA, and dld-II. Overall, the electron transfer pathway deciphered in this work will facilitate the improvement of biohydrogen production by S. oneidensis MR-1.Key Points• The electron transfer pathway from formate to hydrogen in MR-1 is deciphered.• Menaquinone is indispensable for hydrogen production.• A cytochrome b subunit transfers electrons from menaquinone to [FeFe] hydrogenase.