Glutamate Excitotoxicity Is Involved in the Induction of Paralysis in Mice after Infection by a Human Coronavirus with a Single Point Mutation in Its Spike Protein

Abstract

Human coronaviruses (HCoV) are recognized respiratory pathogens, and some strains, including HCoV-OC43, can infect human neuronal and glial cells of the central nervous system (CNS) and activate neuroinflammatory mechanisms. Moreover, HCoV-OC43 is neuroinvasive, neurotropic, and neurovirulent in susceptible mice, where it induces chronic encephalitis. Herein, we show that a single point mutation in the viral spike (S) glycoprotein (Y241H), acquired during viral persistence in human neural cells, led to a hind-limb paralytic disease in infected mice. Inhibition of glutamate excitotoxicity using a 2-amino-3-(5-methyl-3-oxo-1,2-oxazol-4-yl)propranoic acid (AMPA) receptor antagonist (GYKI-52466) improved clinical scores related to the paralysis and motor disabilities in S mutant virus-infected mice, as well as protected the CNS from neuronal dysfunctions, as illustrated by restoration of the phosphorylation state of neurofilaments. Expression of the glial glutamate transporter GLT-1, responsible for glutamate homeostasis, was downregulated following infection, and GYKI-52466 also significantly restored its steady-state expression level. Finally, GYKI-52466 treatment of S mutant virus-infected mice led to reduced microglial activation, which may lead to improvement in the regulation of CNS glutamate homeostasis. Taken together, our results strongly suggest an involvement of excitotoxicity in the paralysis-associated neuropathology induced by an HCoV-OC43 mutant which harbors a single point mutation in its spike protein that is acquired upon persistent virus infection.

The OC43 human coronavirus envelope protein is critical for infectious virus production and propagation in neuronal cells and is a determinant of neurovirulence and CNS pathology

“…Disappearance of respiratory tract disease was observed for SARS-CoV in which E PBM was abrogated, preventing interaction of the viral protein with the PDZcontaining protein syntenin Regla-Nava et al, 2015). The absence of neurological symptoms following infection by either rOC/E stop or rOC/E-PBM D82A-V84A could potentially be linked to glutamate excitotoxicity that we have previously observed in mice (Brison et al, 2011), possibly by interfering with PDZ-domain containing proteins found in neuronal cells (Feng and Zhang, 2009). We also demonstrate that HCoV-OC43 putative TMD plays a role in the neuropathogenesis following the CNS infection, albeit to a lesser extent than its PBM.…”

“…As HCoV-OC43 is naturally neuroinvasive and neurovirulent in mice (Brison et al, 2011;Desforges et al, 2014;Le Coupanec et al, 2015) and that the E protein is important for efficient propagation in neuronal cells (Figs. 3 and 4), we wished to investigate the importance of the two functional domains of E in the process of neuroinvasion.…”

Human coronaviruses: Viral and cellular factors involved in neuroinvasiveness and neuropathogenesis

“…The increased cytokine production following infection by the S-mutant viruses may induce direct damage to neurons (Amor et al, 2010) and/or disturb glutamate homeostasis by down-regulating the glutamate transporter GLT-1 on astrocytes that should recapture the excess of glutamate, which may generate glutamate excitotoxicity (Carmen et al, 2009) and thereby contribute to neuronal degeneration (Fig. 4;Brison et al, 2011), which can be associated with hind-limb paralysis and possible demyelination Jacomy et al, 2010). The outcome of the observed degeneration of neurons may eventually be death of these essential cells.…”

Glutamine antagonist-mediated immune suppression decreases pathology but delays virus clearance in mice during nonfatal alphavirus encephalomyelitis

“…To evaluate the potential role of DON treatment in mitigating glutamate excitotoxicity during SINV infection, glial cell markers associated with glutamate excitotoxicity during virus infection were examined (Brison et al, 2011; Darman et al, 2004). Expression of GFAP and GLT1 by astrocytes and IBA1 by microglial cells was assessed by immunohistochemistry (IHC) and immunoblot.…”