Search

Summary During mammalian development, liver differentiation is driven by signals that converge on multiple transcription factor networks. The hepatocyte nuclear factor signaling network is known to be essential for hepatocyte specification and maintenance. In this study, we have generated deletion and point mutants of hepatocyte nuclear factor-4alpha (HNF4α) to precisely evaluate the function of protein domains during hepatocyte specification from human pluripotent stem cells. We demonstrate that nuclear HNF4α is essential for hepatic progenitor specification, and the introduction of point mutations in HNF4α′s Small Ubiquitin-like Modifier (SUMO) consensus motif leads to disrupted hepatocyte differentiation. Taking a multiomics approach, we identified key deficiencies in cell biology, which included dysfunctional metabolism, substrate adhesion, tricarboxylic acid cycle flux, microRNA transport, and mRNA processing. In summary, the combination of genome editing and multiomics analyses has provided valuable insight into the diverse functions of HNF4α during pluripotent stem cell entry into the hepatic lineage and during hepatocellular differentiation., Graphical Abstract, Highlights • Deletion of HNF4α's DNA-binding domain blocks hepatic progenitor formation • HNF4α′s C-terminal SUMO consensus motif plays roles in hepatocyte specification • Multiomics analyses reveal various processes regulated by HNF4α during differentiation, Biological Sciences; Cell Biology; Developmental Biology; Stem Cells Research

Polysaccharide (PS) based meningococcal vaccines are primarily evaluated by physicochemical methods to ensure batches are consistently manufactured. As PS content is determined by different methods across numerous laboratories, there is a need for International Standards (IS) to calibrate the assays. Following the successful introduction of the WHO Meningococcal group C (MenC) IS in 2011, NIBSC initiated projects to prepare similar standards for groups A, W, Y and X (MenA/W/Y/X) to standardise all meningococcal- PS based vaccines. On the basis of results from a collaborative study to evaluate preparations of MenA and MenX PS, both were established by the WHO Expert Committee on Biological Standardization in Oct 2015 as; the First WHO International Standard for the Meningococcal Group A polysaccharide with a content of 0.845 ± 0.043 mg MenA PS per ampoule (expanded uncertainty with coverage factor of k=2.45 corresponding to a 95% level of confidence); the First WHO International Standard for the Meningococcal Group X polysaccharide with a content of 0.776 ± 0.089 mg MenX PS per ampoule (expanded uncertainty with coverage factor of k=2.45), as determined by quantitative NMR. The standards are available from NIBSC, who act as guardians and distributors of the material under the auspices of WHO.

USP’s peptide reference standards content is typically determined using an HPLC assay against an external standard for which the purity was determined by a mass balance approach. To explore the use of other analytical methods, the USP Biologics Department conducted a multi-laboratory collaborative study. The study determined the inter-laboratory variability for peptide quantitation using the following methods: HPLC assay, quantitative nuclear magnetic resonance (qNMR) spectroscopy, or amino acid analysis (AAA). The three methods were compared with regard to their suitability for quantitation of the nonapeptide oxytocin. In this study, the HPLC assay method using the same peptide bulk material as the standard showed the lowest inter-lab variability. The coefficient of variation (%CV) was calculated without counting the uncertainty associated with the purity assignment of the standard with mass balance. The proton qNMR method is a direct measurement of the peptide against an internal standard, which is not difficult to perform under common laboratory conditions. Because of the simpler operation and shorter analytical time, qNMR as a primary method for peptide reference standard value assignment deserves further exploration.

Numerous Vi capsular polysaccharide (Vi PS) conjugate vaccines to protect young children and infants from Typhoid are either licensed or under development. These vaccines are evaluated by laboratory methods to ensure their potency and that quality requirement are met. International Standard (IS) preparations of Vi PS are needed to calibrate and harmonise these assays. Twenty laboratories from 12 countries participated in a collaborative study to evaluate two candidate ISs: Citrobacter freundii Vi PS (NIBSC code 12/244) and Salmonella enterica serovar Typhi Vi PS (16/126). On the basis of returned results and stability profiles, these standards were established by the WHO Expert Committee on Biological Standardization in Oct 2017 as the First WHO IS for C. freundii Vi PS with a content of 1.94 ± 0.12 mg Vi PS per ampoule (expanded uncertainty with coverage factor of k = 2.11 corresponding to a 95% level of confidence) and the First WHO IS for S. Typhi Vi PS with a content of 2.03 ± 0.10 mg Vi PS per ampoule (expanded uncertainty with coverage factor of k = 2.11), as determined by quantitative NMR. The study also showed the ISs are suitable for physicochemical and immuno assays used for the quantitation of the Vi PS component in Vi PS and conjugate vaccines.

Serogroup X Neisseria meningitidis (MenX) has recently emerged as a cause of localized disease outbreaks in sub-Saharan Africa. In order to prepare for vaccine development, MenX polysaccharide (MenX PS) was purified by standard methods and analyzed for identity and structure by NMR spectroscopy. This study presents the first full assignment of the structure of the MenX PS using (13)C, (1)H and (31)P NMR spectroscopy and total correlation spectroscopy (TOCSY) and (1)H-(13)C heteronuclear single quantum coherence (HSQC). Molecular size distribution analysis using HPLC-SEC with multi-angle laser light scattering (MALLS) found the single peak of MenX PS to have a weight-average molar mass of 247,000g/mol, slightly higher than a reference preparation of purified serogroup C meningococcal polysaccharide. MenX PS tended to be more thermostable than serogroup A PS. A method for the quantification of MenX PS was developed by use of high performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD). A novel and specific ELISA assay for quantification of human anti-MenX PS IgG based on covalent linkage of the MenX PS to functionally modified microtitre plates was developed and found valid for the assessment of the specific antibody concentrations produced in response to MenX vaccination or natural infection. The current work thus provides the necessary background for the development of a MenX PS-based vaccine to prevent meningococcal infection caused by bacteria bearing this capsule.

Lyophilized Influenza antigen reference reagents are a critical resource in the quality control of influenza vaccines. A standard formulation has been used successfully at NIBSC for many years however, following the unexpected occurrence of a collapsed appearance in a particular batch a study was carried out to establish the impact of the sugar concentration in the formulation using modulated differential scanning calorimetry (mDSC) and nuclear magnetic resonance spectroscopy (NMR).There was a correlation between the presence and size of the mDSC eutectic temperature events and the freeze dried appearance of the cakes, which became progressively worse with increasing amounts of sugar. NMR spectroscopy could be used to positively identify and quantify the sugars in the formulations. MDSC can rapidly predict if the freeze dried appearance will be acceptable so as to assure the successful lyophilization of influenza reference preparations.