A suitable model to investigate acute neurological consequences of coronavirus infection (preprint)

Objective and design:  The present study aimed to investigate the neurochemical and behavioral effects of the acute consequences after coronavirus infection through a murine model.  Material:  Wild type C57 BL/6 mice were infected intranasally (i.n) with the murine coronavirus 3 (MHV-3).  Methods:  Mice were submitted to behavioral tests. Euthanasia was performed on the fifth day after infection (5 dpi), and the brain tissue was subjected to plaque assays for viral titration, synaptosome, ELISA, histopathological and immunohistochemical analysis.  Results: Increased viral titers associated with mild histological changes, including signs of neuronal degeneration, were observed in the cerebral cortex of infected mice. Importantly, MHV-3 infection induced an increase in cortical levels of glutamate and calcium, as well as increased levels of pro-inflammatory cytokines (IL-6, IFN-γ) and reduced levels of neuroprotective mediators (BDNF and CX3CL1) in the mice brain, which is suggestive of excitotoxicity. Finally, behavioral analysis showed impaired motor, anhedonic and anxiety-like behaviors in animals infected with MHV-3. Conclusions: Overall, the data presented emulate many aspects of the acute neurological outcomes seen in patients with COVID-19. Therefore, this model may provide a preclinical platform to study acute neurological sequelae induced by coronavirus infection and test possible therapies.

A suitable murine model for studying respiratory coronavirus infection and therapeutic countermeasures in BSL-2 laboratories (preprint)

Several animal models are being used to explore important features of COVID-19, nevertheless none of them recapitulates all aspects of the disease in humans. The continuous refinement and development of other options of in vivo models are opportune, especially ones that are carried out at BSL-2 (Biosafety Level 2) laboratories. In this study, we investigated the suitability of the intranasal infection with the murine betacoronavirus MHV-3 to recapitulate multiple aspects of the pathogenesis of COVID-19 in C57BL/6J mice. We demonstrate that MHV-3 replicated in lungs 1 day after inoculation and triggered respiratory inflammation and dysfunction. This MHV-model of infection was further applied to highlight the critical role of TNF in cytokine-mediated coronavirus pathogenesis. Blocking TNF signaling by pharmacological and genetic strategies greatly increased the survival time and reduces lung injury of MHV-3-infected mice. In vitro studies showed that TNF blockage decreased SARS-CoV-2 replication in human epithelial lung cells and resulted in the lower release of IL-6 and IL-8 cytokines beyond TNF itself. Taken together, our results demonstrate that this model of MHV infection in mice is a useful BSL-2 screening platform for evaluating pathogenesis for human coronaviruses infections, such as COVID-19.