Spearhead Nanometric Field-Effect Transistor Sensors for Single-Cell Analysis.

Nanometric field-effect-transistor (FET) sensors are made on the tip of spear-shaped dual carbon nanoelectrodes derived from carbon deposition inside double-barrel nanopipettes. The easy fabrication route allows deposition of semiconductors or conducting polymers to comprise the transistor channel. A channel from electrodeposited poly pyrrole (PPy) exhibits high sensitivity toward pH changes. This property is exploited by immobilizing hexokinase on PPy nano-FETs to give rise to a selective ATP biosensor. Extracellular pH and ATP gradients are key biochemical constituents in the microenvironment of living cells; we monitor their real-time changes in relation to cancer cells and cardiomyocytes. The highly localized detection is possible because of the high aspect ratio and the spear-like design of the nano-FET probes. The accurately positioned nano-FET sensors can detect concentration gradients in three-dimensional space, identify biochemical properties of a single living cell, and after cell membrane penetration perform intracellular measurements

Exceptional Heterogeneity in Viral Evolutionary Dynamics Characterises Chronic Hepatitis C Virus Infection.

The treatment of HCV infection has seen significant progress, particularly since the approval of new direct-acting antiviral drugs. However these clinical achievements have been made despite an incomplete understanding of HCV replication and within-host evolution, especially compared with HIV-1. Here, we undertake a comprehensive analysis of HCV within-host evolution during chronic infection by investigating over 4000 viral sequences sampled longitudinally from 15 HCV-infected patients. We compare our HCV results to those from a well-studied HIV-1 cohort, revealing key differences in the evolutionary behaviour of these two chronic-infecting pathogens. Notably, we find an exceptional level of heterogeneity in the molecular evolution of HCV, both within and among infected individuals. Furthermore, these patterns are associated with the long-term maintenance of viral lineages within patients, which fluctuate in relative frequency in peripheral blood. Together, our findings demonstrate that HCV replication behavior is complex and likely comprises multiple viral subpopulations with distinct evolutionary dynamics. The presence of a structured viral population can explain apparent paradoxes in chronic HCV infection, such as rapid fluctuations in viral diversity and the reappearance of viral strains years after their initial detection.status: publishe

The upper and lower airway microbiome in severe asthma

Introduction: Severe asthma is complex and immunologically heterogenous; airways infection and innate immune dysregulation may confer inhaled corticosteroid resistance and remains clinically challenging. We hypothesise that marked airway microbiome compositional shifts in severe asthma represent a ‘treatable trait’, with dominance of pathogenic species, warranting targeted therapy. Additionally, these changes are thought to be distinct in the paucibacillary lower airway vs. heavily colonised nasopharynx. Methods: We performed Oxford Nanopore metagenomic sequencing, and RT-qPCR of induced sputum (n=67), bronchoalveolar lavage (BAL;n=71) and nasal lavage (NL;n=28 paired with sputum) samples from the Wessex Severe Asthma Cohort encompassing mild/moderate/severe asthma and health. Findings were integrated with clinical and cytokine data. Key Results: A dominant pathogenic organism (H.influenzae, S.pneumoniae, M.catarrhalis) was identified in sputua of 21% of patients with severe asthma and accompanied by sputum neutrophilia and elevated type-1 cytokines (including IL-1β, IL-6, IL-8, TNF;p<0.01, unpaired t-test, Benjamini-Hochberg correction). From BAL, airways infection was identified infrequently (Severe asthma, n=1/21 H.influenzae; Mild-Moderate asthma,n=2/25 T.whipplei). Metagenomic analysis of NL demonstrated a distinct microbiome; presence of pathogenic organisms in the upper airways did not predict concurrent presence in sputum of severe asthmatics. Conclusion: Airways infection is reliably identified in sputum using metagenomic sequencing and is associated with neutrophilic inflammation. The microbiome in the upper and lower airway are distinct and ongoing work is exploring its impact on mucosal immune responses at these sites

In vivo rate-determining steps of tau seed accumulation in Alzheimer's disease

Both the replication of protein aggregates and their spreading throughout the brain are implicated in the progression of Alzheimer’s disease (AD). However, the rates of these processes are unknown and the identity of the rate-determining process in humans has therefore remained elusive. By bringing together chemical kinetics with measurements of tau seeds and aggregates across brain regions, we can quantify their replication rate in human brains. Notably, we obtain comparable rates in several different datasets, with five different methods of tau quantification, from postmortem seed amplification assays to tau PET studies in living individuals. Our results suggest that from Braak stage III onward, local replication, rather than spreading between brain regions, is the main process controlling the overall rate of accumulation of tau in neocortical regions. The number of seeds doubles only every ∼5 years. Thus, limiting local replication likely constitutes the most promising strategy to control tau accumulation during AD

Quantification of DNA-associated proteins inside eukaryotic cells using single-molecule localization microscopy

Development of single-molecule localization microscopy techniques has allowed nanometre scale localization accuracy inside cells, permitting the resolution of ultra-fine cell structure and the elucidation of crucial molecular mechanisms. Application of these methodologies to understanding processes underlying DNA replication and repair has been limited to defined in vitro biochemical analysis and prokaryotic cells. In order to expand these techniques to eukaryotic systems, we have further developed a photo-activated localization microscopy-based method to directly visualize DNA-associated proteins in unfixed eukaryotic cells. We demonstrate that motion blurring of fluorescence due to protein diffusivity can be used to selectively image the DNA-bound population of proteins. We designed and tested a simple methodology and show that it can be used to detect changes in DNA binding of a replicative helicase subunit, Mcm4, and the replication sliding clamp, PCNA, between different stages of the cell cycle and between distinct genetic backgrounds

Virtual-'light-sheet' single-molecule localisation microscopy enables quantitative optical sectioning for super-resolution imaging.

Single-molecule super-resolution microscopy allows imaging of fluorescently-tagged proteins in live cells with a precision well below that of the diffraction limit. Here, we demonstrate 3D sectioning with single-molecule super-resolution microscopy by making use of the fitting information that is usually discarded to reject fluorophores that emit from above or below a virtual-'light-sheet', a thin volume centred on the focal plane of the microscope. We describe an easy-to-use routine (implemented as an open-source ImageJ plug-in) to quickly analyse a calibration sample to define and use such a virtual light-sheet. In addition, the plug-in is easily usable on almost any existing 2D super-resolution instrumentation. This optical sectioning of super-resolution images is achieved by applying well-characterised width and amplitude thresholds to diffraction-limited spots that can be used to tune the thickness of the virtual light-sheet. This allows qualitative and quantitative imaging improvements: by rejecting out-of-focus fluorophores, the super-resolution image gains contrast and local features may be revealed; by retaining only fluorophores close to the focal plane, virtual-'light-sheet' single-molecule localisation microscopy improves the probability that all emitting fluorophores will be detected, fitted and quantitatively evaluated.We thank the Wellcome Trust for the PhD studentship of MP (093756/B/10/Z), and the Royal Society for the University Research Fellowship of SFL (UF120277). The work by SB and DL was also funded by the Wellcome Trust (082010/Z/07/Z). UE and MH acknowledge funding by the German Science Foundation (grants EXC 115 and SFB 902). SB is funded by a BBSRC grant (BB/K013726/1). AMC acknowledges ERC Award 268788-SMI-DDR. We also thank the European Commision for support through the 4DCellFate project (EC FP7 CP 277899).This is the final version of the article. It first appeared from PLOS via http://dx.doi.org/10.1371/journal.pone.012543

In vivo rate-determining steps of tau seed accumulation in Alzheimer's disease.

[Figure: see text].We acknowledge funding from Sidney Sussex College Cambridge (GM) and the European Research Council Grant Number 669237 (to D.K.) and the Royal Society (to D.K.). The Cambridge Brain Bank is supported by the NIHR Cambridge Biomedical Research Centre

Analysis of Successful Immune Responses in Persons Infected with Hepatitis C Virus

Although hepatitis C virus (HCV) infection is very common, identification of patients during acute infection is rare. Consequently, little is known about the immune response during this critical stage of the disease. We analyzed the T lymphocyte response during and after acute resolving HCV infection in three persons, using interferon (IFN)-γ enzyme-linked immunospot (ELISPOT) and human histocompatibility leukocyte antigen (HLA) peptide tetramer assays. Acute infection was associated with a broadly directed T helper and cytotoxic T lymphocyte (CTL) response, which persisted after resolution of clinical hepatitis and clearance of viremia. At the earliest time point studied, highly activated CTL populations were observed that temporarily failed to secrete IFN-γ, a “stunned” phenotype, from which they recovered as viremia declined. In long-term HCV-seropositive persons, CTL responses were more common in persons who had cleared viremia compared with those with persistent viremia, although the frequencies of HCV-specific CTLs were lower than those found in persons during and after resolution of acute HCV infection. These studies demonstrate a strong and persistent CTL response in resolving acute HCV infection, and provide rationale to explore immune augmentation as a therapeutic intervention in chronic HCV infection