Investigation of EVD68 Pathogenesis in the Human Spinal Cord
EV-D68 has been implicated in severe respiratory illness and acute flaccid myelitis (AFM), a polio-like illness causing paralysis in children. AFM peaked biennially from 2012-2018 during the same months as EV-D68 circulation. There are no specific treatments for AFM and most children are left with residual deficits. We previously showed that historic (prior to AFM) and contemporary (from AFM peak years) EV-D68 isolates differ in temperature and acid sensitivity and cellular tropism between the respiratory and gastric epithelia, suggesting one mechanism of this apparent change in disease phenotype. However, reasons why contemporary EV-D68 targets the nervous system are unknown.
While EV have only rarely been detected in cerebral spinal fluid (CSF) of individuals with AFM, antibodies against EV-D68 have been detected in CSF. Moreover, EV-D68 isolates infect human neuronal cell lines, murine spinal cords, and cause paralysis in neonatal mice with intracerebral or intramuscular injection. Because most children with this illness survive and the spinal cord is not a safe site for biopsy, human spinal cord tissue is rarely available for study. The inability to isolate spinal cord tissue contributes to the lack of understanding of the mechanism of neural pathogenesis of EV-D68 and paralysis.
Cell culture models traditionally exist only in two dimensions (2D) and are a singular cell type, which do not replicate the complex, multicellular interactions of human tissues, such as the spinal cord. Viruses can cause immunologic damage to normally immune privileged sites such as spinal cord, but also cause cellular injury via direct infection and bystander injury to neighboring cells. The mechanisms by which EV-D68 causes paralysis are unknown and studies have been limited due to inadequate human model systems. We will use human spinal motor neurons and multicellular spinal cord organoids to define EV-D68 pathogenesis in the CNS. We hypothesize that EV-D68 causes AFM via infection of human spinal cord motor neuron cells, resulting in neuronal damage and paralysis.
- Define spinal cord replication of EVD68 in a new model for the pathogenesis of paralysis.
- Define factors associated with AFM development through creation of a clinical sample library of spinal cord organoids (SCO)