Hartung, Thomas


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Human brain microphysiological systems in the study of neuroinfectious disorders

2023, Barreras, Paula, Pamies, David, Hartung, Thomas, Pardo, Carlos A.

Microphysiological systems (MPS) are 2D or 3D multicellular constructs able to mimic tissue microenvironments. The latest models encompass a range of techniques, including co-culturing of various cell types, utilization of scaffolds and extracellular matrix materials, perfusion systems, 3D culture methods, 3D bioprinting, organ-on-a-chip technology, and examination of tissue structures. Several human brain 3D cultures or brain MPS (BMPS) have emerged in the last decade. These organoids or spheroids are 3D culture systems derived from induced pluripotent cells or embryonic stem cells that contain neuronal and glial populations and recapitulate structural and physiological aspects of the human brain. BMPS have been introduced recently in the study and modeling of neuroinfectious diseases and have proven to be useful in establishing neurotropism of viral infections, cell-pathogen interactions needed for infection, assessing cytopathological effects, genomic and proteomic profiles, and screening therapeutic compounds. Here we review the different methodologies of organoids used in neuroinfectious diseases including spheroids, guided and unguided protocols as well as microglia and blood-brain barrier containing models, their specific applications, and limitations. The review provides an overview of the models existing for specific infections including Zika, Dengue, JC virus, Japanese encephalitis, measles, herpes, SARS-CoV2, and influenza viruses among others, and provide useful concepts in the modeling of disease and antiviral agent screening.

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"Der Weg ist das Ziel" : Thomas Hartung im Interview

2021-03-06, Hohenberger, Stefanie M., Hartung, Thomas

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Safer chemicals using less animals : kick-off of the European ONTOX project

2021, Vinken, Mathieu, Benfenati, Emilio, Busquet, François, Castell, José, Clevert, Djork-Arné, de Kok, Theo M., Dirven, Hubert, Fritsche, Ellen, Geris, Liesbet, Hartung, Thomas

The 3Rs concept, calling for replacement, reduction and refinement of animal experimentation, is receiving increasing attention around the world, and has found its way to legislation, in particular in the European Union. This is aligned by continuing high-level efforts of the European Commission to support development and implementation of 3Rs methods. In this respect, the European project called "ONTOX: ontology-driven and artificial intelligence-based repeated dose toxicity testing of chemicals for next generation risk assessment" was recently initiated with the goal to provide a functional and sustainable solution for advancing human risk assessment of chemicals without the use of animals in line with the principles of 21st century toxicity testing and next generation risk assessment. ONTOX will deliver a generic strategy to create new approach methodologies (NAMs) in order to predict systemic repeated dose toxicity effects that, upon combination with tailored exposure assessment, will enable human risk assessment. For proof-of-concept purposes, focus is put on NAMs addressing adversities in the liver, kidneys and developing brain induced by a variety of chemicals. The NAMs each consist of a computational system based on artificial intelligence and are fed by biological, toxicological, chemical and kinetic data. Data are consecutively integrated in physiological maps, quantitative adverse outcome pathway networks and ontology frameworks. Supported by artificial intelligence, data gaps are identified and are filled by targeted in vitro and in silico testing. ONTOX is anticipated to have a deep and long-lasting impact at many levels, in particular by consolidating Europe's world-leading position regarding the development, exploitation, regulation and application of animal-free methods for human risk assessment of chemicals.

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Toxicity testing in the 21st century : progress in the past decade and future perspectives

2020-01, Krewski, Daniel, Andersen, Melvin E., Tyshenko, Michael G., Krishnan, Kannan, Hartung, Thomas, Boekelheide, Kim, Wambaugh, John F., Jones, Dean, Whelan, Maurice, Thomas, Russell

Advances in the biological sciences have led to an ongoing paradigm shift in toxicity testing based on expanded application of high-throughput in vitro screening and in silico methods to assess potential health risks of environmental agents. This review examines progress on the vision for toxicity testing elaborated by the US National Research Council (NRC) during the decade that has passed since the 2007 NRC report on Toxicity Testing in the 21st Century (TT21C). Concomitant advances in exposure assessment, including computational approaches and high-throughput exposomics, are also documented. A vision for the next generation of risk science, incorporating risk assessment methodologies suitable for the analysis of new toxicological and exposure data, resulting in human exposure guidelines is described. Case study prototypes indicating how these new approaches to toxicity testing, exposure measurement, and risk assessment are beginning to be applied in practice are presented. Overall, progress on the 20-year transition plan laid out by the US NRC in 2007 has been substantial. Importantly, government agencies within the United States and internationally are beginning to incorporate the new approach methodologies envisaged in the original TT21C vision into regulatory practice. Future perspectives on the continued evolution of toxicity testing to strengthen regulatory risk assessment are provided.

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A human-derived 3D brain organoid model to study JC virus infection

2022-02, Barreras, Paula, Pamies, David, Monaco, Maria Chiara, Muñoz, Laura S., Zhong, Xiali, Major, Eugene O., Hogberg, Helena T., Hartung, Thomas, Pardo, Carlos A.

Progressive multifocal leukoencephalopathy (PML) is a frequent neurological complication in immunosuppressed patients. PML is caused by the JC virus (JCV), a neurotropic DNA polyomavirus that infects oligodendrocytes and astrocytes, causing inflammation and demyelination which lead to neurological dysfunction. The pathogenesis of PML is poorly understood due to the lack of in vitro or animal models to study mechanisms of disease as the virus most efficiently infects only human cells. We developed a human-derived brain organotypic system (also called brain organoid) to model JCV infection. The model was developed by using human-induced pluripotent stem cells (iPSC) and culturing them in 3D to generate an organotypic model containing neurons, astrocytes, and oligodendrocytes which recapitulates aspects of the environment of the human brain. We infected the brain organoids with the JCV MAD4 strain or cerebrospinal fluid of a patient with PML. The organoids were assessed for evidence of infection by qPCR, immunofluorescence, and electron microscopy at 1, 2, and 3 weeks post-exposure. JCV infection in both JCV MAD4 strain and PML CSF-exposed brain organoids was confirmed by immunocytochemical studies demonstrating viral antigens and electron microscopy showing virion particles in the nuclear compartment of oligodendrocytes and astrocytes. No evidence of neuronal infection was visualized. Infection was also demonstrated by JCV qPCR in the virus-exposed organoids and their media. In conclusion, the brain organoid model of JCV infection establishes a human model suitable for studying the mechanisms of JCV infection and pathogenesis of PML and may facilitate the exploration of therapeutic approaches.

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"Der Weg ist das Ziel" : Zwei Leben für die 3R-Forschung

2021-03-05, Hohenberger, Stefanie M., Leist, Marcel, Hartung, Thomas

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COVID-19 vaccines : ethical framework concerning human challenge studies

2020-12, Calina, Daniela, Hartung, Thomas, Docea, Anca Oana, Spandidos, Demetrios A., Egorov, Alex M., Shtilman, Michael I., Carvalho, Felix, Tsatsakis, Aristidis

The pandemic associated with the new SARS-CoV-2 coronavirus continues to spread worldwide. The most favorable epidemic control scenario, which provides long-term protection against COVID-19 outbreak, is the development and distribution of an effective and safe vaccine. The need to develop a new COVID-19 vaccine is pressing; however, it is likely to take a long time, possibly several years. This is due to the time required to demonstrate the safety and efficacy of the proposed vaccine. and the time required to manufacture and distribute millions of doses.

To accelerate this development and associated safety testing, the deliberate infection of healthy volunteers has been suggested. The purpose of this short communication is to describe the ethical aspects of this type of testing,

Deliberate infection of volunteers with a dangerous virus such as SARS-CoV-2 was initially considered unethical by researchers; but the current pandemic is so different from previous ones that these studies are considered ethical if certain criteria are met. Participants in human challenge studies must be relatively young, in good health and must receive the highest quality medical care, with frequent monitoring. Tests should also be performed with great caution and specialized medical supervision. Besides, the fact that obtaining vaccines faster through deliberate infection studies of healthy people has greater benefits than risks, has been demonstrated by obtaining other vaccines in other historical pandemics such as: smallpox, influenza, malaria, typhoid fever, Dengue fever and Zika.

One possibility to shorten the time required for the development of COVID-19 vaccines is to reduce clinical phases II and III by using human challenge studies through eliberate infection of healthy volunteers with SARS-CoV-2 after administration of the candidate vaccine. Accelerating the development of a COVID-19 vaccine even for a few weeks or months would have a great beneficial impact on public health by saving many lives.

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Assessment of the combined effects of chromium and benzene on the rat neuroendocrine and immune systems

2022, Karaulov, Alexander Viktorovich, Smolyagin, Alexander Ivanovich, Mikhailova, Irina Valeryevna, Stadnikov, Alexander Abramovich, Ermolina, Evgenia Vyacheslavovna, Filippova, Yulia Vladimirovna, Kuzmicheva, Natalia Aleksandrovna, Vlata, Zacharenia, Djordjevic, Aleksandra Buha, Hartung, Thomas

This study assessed the hypothalamic-pituitary-adrenocortical (HPA) axis and lymphoid organs (thymus, spleen, and bone marrow) of Wistar rats treated with a mixture of chromium and benzene. Animals were assessed at three time-points (45, 90 and 135 days) following oral mixture exposure. The hypothalamus-pituitary system was examined in light and electron microscopy. Lymphoid organs underwent a morphological assessment and the immunophenotype of splenocytes was characterized immunohistochemically using monoclonal antibodies. Splenocytes cytokine production of was determined by ELISA after Con-A stimulation. Combined exposure to chromium and benzene in average doses of 20 mg Cr (VI)/kg body weight/day and 0.6 ml benzene/kg body weight/day impaired the responsiveness of the central compartment of the HPA axis, as evidenced by functional activation of the secretory activity of the hypothalamus and pituitary gland, which was not followed by a sufficient extrusion of nonapeptides at the neurohypophysis and hypothalamic median eminence. Chromium and benzene exposure reduced the thymus mass, thymocytes count, and caused a number of structural and functional changes indicative of transient thymus involution. In the spleen, exposure to both chemicals resulted in lymphoreticular hyperplasia and plasma cell-macrophage transformation (also observed in lymph nodes). Apoptosis of thymocytes and lymphocytes was also observed in T-zones of the spleen. Notably, the effects were similar to those observed earlier for the single agents, under the same experimental conditions, without evidence of additivity.

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Mapping Chemical Respiratory Sensitization : How Useful Are Our Current Computational Tools?

2021-02-15, Golden, Emily, Maertens, Mikhail, Hartung, Thomas, Maertens, Alexandra

Chemical respiratory sensitization is an immunological process that manifests clinically mostly as occupational asthma and is responsible for 1 in 6 cases of adult asthma, although this may be an underestimate of the prevalence, as it is under-diagnosed. Occupational asthma results in unemployment for roughly one-third of those affected due to severe health issues. Despite its high prevalence, chemical respiratory sensitization is difficult to predict, as there are currently no validated models and the mechanisms are not entirely understood, creating a significant challenge for regulatory bodies and industry alike. The Adverse Outcome Pathway (AOP) for respiratory sensitization is currently incomplete. However, some key events have been identified, and there is overlap with the comparatively well-characterized AOP for dermal sensitization. Because of this, and the fact that dermal sensitization is often assessed by in vivo, in chemico, or in silico methods, regulatory bodies are defaulting to the dermal sensitization status of chemicals as a proxy for respiratory sensitization status when evaluating chemical safety. We identified a data set of known human respiratory sensitizers, which we used to investigate the accuracy of a structural alert model, Toxtree, designed for skin sensitization and the Centre for Occupational and Environmental Health (COEH)'s model, a model developed specifically for occupational asthma. While both models had a reasonable level of accuracy, the COEH model achieved the highest balanced accuracy at 76%; when the models agreed, the overall accuracy was 87%. There were important differences between the models: Toxtree had superior performance for some structural alerts and some categories of well-characterized skin sensitizers, while the COEH model had high accuracy in identifying sensitizers that lacked identified skin sensitization reactivity domains. Overall, both models achieved respectable accuracy. However, neither model addresses potency, which, along with data quality, remains a hurdle, and the field must prioritize these issues to move forward.

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Key read across framework components and biology based improvements

2020-05, Ball, Nicholas, Madden, Judith, Paini, Alicia, Mathea, Miriam, Palmer, Andrew David, Sperber, Saskia, Hartung, Thomas, van Ravenzwaay, Bennard

At the 2019 annual meeting of the European Environmental Mutagen and Genomics Society a workshop session related to the use of read across concepts in toxicology was held. The goal of this session was to provide the audience an overview of general read-across concepts. From ECHA’s read across assessment framework, the starting point is chemical similarity. There are several approaches and algorithms available for calculating chemical similarity based on molecular descriptors, distance/similarity measures and weighting schemata for specific endpoints. Therefore, algorithms that adapt themselves to the data (endpoint/s) and provide a good ability to distinguish between structural similar and not similar molecules regarding specific endpoints are needed and their use discussed. Toxico-dynamic end points are usually in the focus of read across cases. However, without appropriate attention to kinetics and metabolism such cases are unlikely to be successful. To further enhance the quality of read across cases new approach methods can be very useful. Examples based on a biological approach using plasma metabolomics in rats are given. Finally, with the availability of large data sets of structure activity relationships, in silico tools have been developed which provide hitherto undiscovered information. Automated process is now able to assess the chemical – activity space around the molecule target substance and examples are given demonstrating a high predictivity for certain endpoints of toxicity. Thus, this session provides not only current state of the art criteria for good read across, but also indicates how read-across can be further developed in the near future.