Human brain microphysiological systems in the study of neuroinfectious disorders.

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.

COVID-19 - prime time for microphysiological systems, as illustrated for the brain.

The development of therapies for and preventions against infectious diseases depends on the availability of disease models. Bioengineering of human organoids and organs-on-chips is one extremely promising avenue of research. These miniature, laboratory-grown organ systems have been broadly used during the ongoing, unprecedented coronavirus 2019 (COVID-19) pandemic to show the many effects of the etiologic agent, severe acute respiratory coronavirus 2 (SARS-CoV-2) on human organs. In contrast, exposure of most animals either did not result in infection or caused mild clinical signs - not the severe course of the infection suffered by many humans. This article illuminates the opportunities of microphysiological systems (MPS) to study COVID-19 in vitro, with a focus on brain cell infection and its translational rel-evance to COVID-19 effects on the human brain. Neurovirulence of SARS-CoV-2 has been reproduced in different types of human brain organoids by 10 groups, consistently showing infection of a small portion of brain cells accompanied by limited viral replication. This mirrors increasingly recognized neurological manifestations in COVID-19 patients (evidence of virus infection and brain-specific antibody formation in brain tissue and cerebrospinal fluid). The pathogenesis of neuro-logical signs, their long-term consequences, and possible interventions remain unclear, but future MPS technologies offer prospects to address these open questions.

Challenges and Scientific Prospects of the Newest Generation of mRNA-Based Vaccines against SARS-CoV-2.

In the context of the current COVID-19 pandemic, traditional, complex and lengthy methods of vaccine development and production would not have been able to ensure proper management of this global public health crisis. Hence, a number of technologies have been developed for obtaining a vaccine quickly and ensuring a large scale production, such as mRNA-based vaccine platforms. The use of mRNA is not a new concept in vaccine development but has leveraged on previous knowledge and technology. The great number of human resources and capital investements for mRNA vaccine development, along with the experience gained from previous studies on infectious diseases, allowed COVID-19 mRNA vaccines to be developed, conditionally approved and commercialy available in less than one year, thanks to decades of basic research. This review critically presents and discusses the COVID-19 mRNA vaccine-induced immunity, and it summarizes the most common anaphylactic and autoimmune adverse effects that have been identified until now after massive vaccination campaigns.

Erratum to "COVID-19 pandemic and alcohol consumption: Impacts and interconnections" [Toxicol. Rep. 8C (2021) 529 - 535/1078].

[This corrects the article DOI: 10.1016/j.toxrep.2021.03.005.].

COVID-19 pandemic and alcohol consumption: Impacts and interconnections.

Alcohol consumption is associated with multiple diseases and might contribute to vulnerability to SARS-CoV-2 infection. It can also catalyze exacerbations of mental and organic illnesses and predispose to behaviors with an increased risk of infection, severity of disease but also independently of sociopathic behavior and violence. Globally, millions of premature deaths from excessive alcohol consumption occur each year. This paper discusses the effects of increased alcohol consumption and the most important consequences on the health of the population during the social isolation and lockdown during current COVID-19 pandemic.

Improved strategies to counter the COVID-19 pandemic: Lockdowns vs. primary and community healthcare.

COVID-19 pandemic mitigation strategies are mainly based on social distancing measures and healthcare system reinforcement. However, many countries in Europe and elsewhere implemented strict, horizontal lockdowns because of extensive viral spread in the community which challenges the capacity of the healthcare systems. However, strict lockdowns have various untintended adverse social, economic and health effects, which have yet to be fully elucidated, and have not been considered in models examining the effects of various mitigation measures. Unlike commonly suggested, the dilemma is not about health vs wealth because the economic devastation of long-lasting lockdowns will definitely have adverse health effects in the population. Furthermore, they cannot provide a lasting solution in pandemic containment, potentially resulting in a vicious cycle of consecutive lockdowns with in-between breaks. Hospital preparedness has been the main strategy used by governments. However, a major characteristic of the COVID-19 pandemic is the rapid viral transmission in populations with no immunity. Thus, even the best hospital system could not cope with the demand. Primary, community and home care are the only viable strategies that could achieve the goal of pandemic mitigation. We present the case example of Greece, a country which followed a strategy focused on hospital preparedness but failed to reinforce primary and community care. This, along with strategic mistakes in epidemiological surveillance, resulted in Greece implementing a second strict, horizontal lockdown and having one of the highest COVID-19 death rates in Europe during the second wave. We provide recommendations for measures that will reinstate primary and community care at the forefront in managing the current public health crisis by protecting hospitals from unnecessary admissions, providing primary and secondary prevention services in relation to COVID-19 and maintaining population health through treatment of non-COVID-19 conditions. This, together with more selective social distancing measures (instead of horizontal lockdowns), represents the only viable and realistic long-term strategy for COVID-19 pandemic mitigation.

COVID-19 vaccines: ethical framework concerning human challenge studies.

BACKGROUND: 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. OBJECTIVES: 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, RESULTS: 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. CONCLUSIONS: 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.

Infectability of human BrainSphere neurons suggests neurotropism of SARS-CoV-2

Reports from Wuhan suggest that 36% of COVID-19 patients show neurological symptoms, and cases of viral encephalitis have been reported, suggesting that the virus is neurotropic under unknown circumstances. This is well established for other coronaviruses. In order to understand why some patients develop such symptoms and others do not, we address herein the infectability of the central nervous system (CNS). Reports that the ACE2 receptor ­ critical for virus entry into lung cells ­ is found in different neurons support this expectation. We employed a human induced pluripotent stem cell (iPSC)- derived BrainSphere model, which we used earlier for Zika, Dengue, HIV and John Cunningham virus infection studies. We detected the expression of the ACE2 receptor, but not TMPRSS2, in the model. Incubating the BrainSpheres for 6 hours with SARS-CoV-2 at a multiplicity of infection (MOI) of 0.1 led to infection of a fraction of neural cells with replication of the virus evident at 72 hpi. Virus particles were found in the neuronal cell body extending into apparent neurite structures. PCR measurements corroborated the replication of the virus, suggesting at least a tenfold increase in virus copies per total RNA. Leveraging state-of-the-art 3D organotypic cell culture, which has been shown to allow both virus infection and modeling of (developmental) neurotoxicity but is at the same time simple enough to be transferred and used in a BSL-3 environment, we demonstrate, for the first time, the potential critically important neurotropism of SARS-CoV-2.

Harnessing the power of novel animal-free test methods for the development of COVID-19 drugs and vaccines.

The COVID-19-inducing virus, SARS-CoV2, is likely to remain a threat to human health unless efficient drugs or vaccines become available. Given the extent of the current pandemic (people in over one hundred countries infected) and its disastrous effect on world economy (associated with limitations of human rights), speedy drug discovery is critical. In this situation, past investments into the development of new (animal-free) approach methods (NAM) for drug safety, efficacy, and quality evaluation can be leveraged. For this, we provide an overview of repurposing ideas to shortcut drug development times. Animal-based testing would be too lengthy, and it largely fails, when a pathogen is species-specific or if the desired drug is based on specific features of human biology. Fortunately, industry has already largely shifted to NAM, and some public funding programs have advanced the development of animal-free technologies. For instance, NAM can predict genotoxicity (a major aspect of carcinogenicity) within days, human antibodies targeting virus epitopes can be generated in molecular biology laboratories within weeks, and various human cell-based organoids are available to test virus infectivity and the biological processes controlling them. The European Medicines Agency (EMA) has formed an expert group to pave the way for the use of such approaches for accelerated drug development. This situation illustrates the importance of diversification in drug discovery strategies and clearly shows the shortcomings of an approach that invests 95% of resources into a single technology (animal experimentation) in the face of challenges that require alternative approaches.