Neurotropism of enterovirus D68 isolates is independent of sialic acid and is not a recently acquired phenotype

Abstract

Acute flaccid myelitis /acute flaccid paralysis (AFM/AFP) is a rare but serious illness of the nervous system, specifically affecting the grey matter of the spinal cord, motor controlling regions of the brain and the cranial nerve. Most cases of AFM/AFP are pathogen associated, typically with poliovirus and enterovirus infections, and occur in children under the age of 6 years old. Enterovirus D68 (EV-D68) was first isolated from children with pneumonia in 1962, but an association with AFM/AFP was not observed until the 2014 outbreak. Organotypic mouse brain slice cultures generated from postnatal day 1 to 10 mice were used to determine if neurotropism of EV-D68 is shared among virus isolates. Six of the seven EV-D68 isolates examined, including two from 1962 and four from the 2014 outbreak, replicated in neurons, and all replicated in astrocytes. Furthermore, a putative viral receptor, sialic acid, is not required for neurotropism of EV-D68, as both sialic acid dependent and independent viruses replicated within neurons. These observations demonstrate that EV-D68 is neurotropic independent of its genetic lineage, can infect both neurons and astrocytes, and that neurotropism is not a recently acquired characteristic as has been suggested.\n\nSignificanceRecently there has been an increase in the number of children infected with enterovirus D68 (EV-D68). Most infections are associated with mild flu-like symptoms, but neurological dysfunction may develop in a small number of children. How the biochemical and genetic differences among EV-D68 isolates relates to development of neurological disease remains an unanswered question. Assessing infection of multiple viral isolates in organotypic brain slice cultures from postnatal day 1 to 10 mice revealed that multiple isolates are neurotropic. Both neuraminidase sensitive and resistant viruses infected neurons, indicating that sialic acid binding does not play a role in EV-D68 neuropathogenesis. Establishment of a genetically and pharmacologically amenable system using organotypic brain slice cultures will provide insight into how EV-D68 neuropathologies develop.