Innovative in cellulo method as an alternative to in vivo neurovirulence test for the characterization and quality control of human live Yellow Fever virus vaccines: a pilot study

International audienceLive attenuated vaccines have proved to be mostly valuable in the prevention of infectious diseases in humans, especially in developing countries. The safety and potency of vaccine, and the consistency of vaccine batch-to-batch manufacturing, must be proven before being administrated to humans. For now, the tests used to control vaccine safety largely involve animal testing. For live viral vaccines, regulations require suppliers to demonstrate the absence of neurovirulence in animals, principally in non-human primates and mice. In a search to reduce the use of animals and embracing the 3Rs principles (Replacement, Reduction, Refinement in the use of laboratory animals), we developed a new Blood-Brain Barrier Minibrain (BBB-Minibrain) in cellulo device to evaluate the neuroinvasiveness/neurovirulence of live Yellow Fever virus (YFV) vaccines. A pilot study was performed using the features of two distinct YFV strains, with the ultimate goal of proposing a companion test to characterize YFV neurovirulence. Here, we demonstrate that the BBB-Minibrain model is a promising alternative to consider for future replacement of YFV vaccine in vivo neurovirulence testing (see graphical abstract)

A Human Blood-Brain Interface Model to Study Barrier Crossings by Pathogens or Medicines and Their Interactions with the Brain

International audienceThe early screening of nervous system medicines on a pertinent and reliable in cellulo BBB model for their penetration and their interaction with the barrier and the brain parenchyma is still an unmet need. To fill this gap, we designed a 2D in cellulo model, the BBB-Minibrain, by combining a polyester porous membrane culture insert human BBB model with a Minibrain formed by a tri-culture of human brain cells (neurons, astrocytes and microglial cells). The BBB-Minibrain allowed us to test the transport of a neuroprotective drug candidate (e.g., Neurovita), through the BBB, to determine the specific targeting of this molecule to neurons and to show that the neuroprotective property of the drug was preserved after the drug had crossed the BBB. We have also demonstrated that BBB-Minibrain constitutes an interesting model to detect the passage of virus particles across the endothelial cells barrier and to monitor the infection of the Minibrain by neuroinvasive virus particles. The BBB-Minibrain is a reliable system, easy to handle for researcher trained in cell culture technology and predictive of the brain cells phenotypes after treatment or insult. The interest of such in cellulo testing would be twofold: introducing derisking steps early in the drug development on the one hand and reducing the use of animal testing on the other hand

Comparative analysis of neuroinvasion by Japanese encephalitis virulent and vaccine strains in an in cellulo model of human blood-brain barrier

Japanese encephalitis virus (JEV) is the major cause of viral encephalitis in South East Asia. It has been suggested that JEV getsaccess to the central nervous system (CNS) as a consequence of a precedinginflammatory process which leads to the blood-brain barrier (BBB) disruption and viral neuroinvasion. However, what happens at early times ofJEV contact with the BBB is poorly understood. In the present work, we evaluated the ability of both a virulent and a vaccine strain of JEV (JEV RP9 and SA14-14-2, respectively) to cross an in cellulo humanBBB model consisting of hCMEC/D3 human endothelial cells cultivated on permeable insertsabove SK-N-SH human neuroblastoma cells. Usingthis system, we demonstrated that both JEV RP9 and SA14-14-2 are able to cross the BBB without disruptingit at early times post-addition. Furthermore, this BBB model was able to discriminate between the virulent RP9 and the vaccine SA14-14-2 strains, as demonstrated by the presence of almost 10 times more RP9 infectious particles that crossed the BBB than SA14-14 particlesat a high MOI. Besidescontributingtothe understanding of early events in JEV neuroinvasion,thisin celluloBBB model represents asuitable anduseful systemto studythe viral determinants of JEV neuroinvasiveness and the molecular mechanisms by which this flavivirus crossesthe BBBat early times of neuroinvasio

Quantitative Automated Assays in Living Cells to Screen for Inhibitors of Hemichannel Function

International audienceIn vertebrates, intercellular communication is largely mediated by connexins (Cx), a family of structurally related transmembrane proteins that assemble to form hemichannels (HCs) at the plasma membrane. HCs are upregulated in different brain disorders and represent innovative therapeutic targets. Identifying modulators of Cx-based HCs is of great interest to better understand their function and define new treatments. In this study, we developed automated versions of two different cell-based assays to identify new pharmacological modulators of Cx43-HCs. As HCs remain mostly closed under physiological conditions in cell culture, depletion of extracellular Ca 2+ was used to increase the probability of opening of HCs. The first assay follows the incorporation of a fluorescent dye, Yo-Pro, by real-time imaging, while the second is based on the quenching of a fluorescent protein, YFP QL , by iodide after iodide uptake. These assays were then used to screen a collection of 2242 approved drugs and compounds under development. This study led to the identification of 11 candidate hits blocking Cx43-HC, active in the two assays, with 5 drugs active on HC but not on gap junction (GJ) activities. To our knowledge, this is the first screening on HC activity and our results suggest the potential of a new use of already approved drugs in central nervous system disorders with HC impairments

Emergence and Dissemination of Extended‐Spectrum β‐Lactamase–Producing Escherichia coli in the Community: Lessons from the Study of a Remote and Controlled Population

International audienceIntestinal carriage is a key factor in extended-spectrum beta-lactamase (ESBL) infection epidemiology but is difficult to study in open communities. To overcome this problem, we studied a highly stable group of Amerindians for whom we reported an ESBL carriage prevalence of 3.2% in 2001

Evaluation of drug-induced neurotoxicity based on metabolomics, proteomics and electrical activity measurements in the complementary CNS in vitro models

The present study was performed in an attempt to develop an in vitro integrated testing strategy to evaluate neurotoxicity of drugs during development phase. A number of endpoints was analyzed using two complementary brain cell culture models, and an in vitro blood-brain barrier model after acute, sub-chronic, and repeated-dose treatments with a series of selected drugs. The developed in vitro BBB model allowed to detect toxic effects on the BBB and to evaluate drug transport through the BBB for prediction free brain concentrations of studied drugs. The electrical activity of cortical neuronal networks recorded with a micro-electrode array was found to be a good tool to predict the neuroactivity and neurotoxicity of drugs and it is suggested as a first-step high content screening test. The histotypic 3D re-aggregating brain cell cultures, containing all brain cell types, were found well suitable for OMICs analyzes. The obtained data suggest that an in vitro integrated testing strategy (ITS), including toxicity to and transport through BBB, as well as metabolomics, proteomics and neuronal electrical activity, measured in stable rodent brain cell culture systems (in the future human stem cell-derived neuronal models), may considerably improve current drug-induced neurotoxicity evaluation. Robustness of this ITS has to be further evaluated with a larger number of studied drugs.JRC.I.5-Systems Toxicolog

Connexin channels provide a target to manipulate brain endothelial calcium dynamics and blood-brain barrier permeability.

The cytoplasmic Ca(2+) concentration ([Ca(2+)](i)) is an important factor determining the functional state of blood-brain barrier (BBB) endothelial cells but little is known on the effect of dynamic [Ca(2+)](i) changes on BBB function. We applied different agonists that trigger [Ca(2+)](i) oscillations and determined the involvement of connexin channels and subsequent effects on endothelial permeability in immortalized and primary brain endothelial cells. The inflammatory peptide bradykinin (BK) triggered [Ca(2+)](i) oscillations and increased endothelial permeability. The latter was prevented by buffering [Ca(2+)](i) with BAPTA, indicating that [Ca(2+)](i) oscillations are crucial in the permeability changes. Bradykinin-triggered [Ca(2+)](i) oscillations were inhibited by interfering with connexin channels, making use of carbenoxolone, Gap27, a peptide blocker of connexin channels, and Cx37/43 knockdown. Gap27 inhibition of the oscillations was rapid (within minutes) and work with connexin hemichannel-permeable dyes indicated hemichannel opening and purinergic signaling in response to stimulation with BK. Moreover, Gap27 inhibited the BK-triggered endothelial permeability increase in in vitro and in vivo experiments. By contrast, [Ca(2+)](i) oscillations provoked by exposure to adenosine 5' triphosphate (ATP) were not affected by carbenoxolone or Gap27 and ATP did not disturb endothelial permeability. We conclude that interfering with endothelial connexin hemichannels is a novel approach to limiting BBB-permeability alterations.Journal ArticleResearch Support, N.I.H. ExtramuralResearch Support, Non-U.S. Gov'tSCOPUS: ar.jinfo:eu-repo/semantics/publishe