Genomic and molecular determinants of EV-D68 neuroinvasive disease

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Virus infections of the central nervous system (CNS) are a significant cause of morbidity and mortality worldwide. Proven treatments are limited to only a few viruses and even when treatments exist (e.g. acyclovir for herpes simplex encephalitis) disability and death remain significant. Our knowledge of viral CNS infections, particularly those involving the spinal cord, is limited and serves as a barrier against the development of novel treatments for these devastating diseases. Enteroviruses are an important cause of virus-induced CNS infections. Poliovirus is the most infamous member of the neurotrophic enteroviruses. However, several non- polio human enteroviruses (NPEVs), including EV-D68, also target the CNS. NPEVs are common, causing an estimated 10–15 million symptomatic annual infections in the US alone. Although most of these infections do not result in CNS disease, these viruses can acquire the ability to be neuro-virulent. Recently, large outbreaks of NPEVs have occurred worldwide that have been associated with neurologic disease and these viruses are designated “re-emerging pathogens”. For example, in 2014, the United States experienced an epidemic of acute flaccid myelitis (AFM) cases in children during a nationwide outbreak of previously rare enterovirus D68 (EV- D68) respiratory disease. Approximately 50% of AFM patients had EV-D68 in respiratory secretions. However, EV-D68 was not detected in the cerebrospinal fluid of any patient, preventing the establishment of a causative link between EV-D68 and AFM. We have recently shown that many (including IL/52 and MO/47), but not all (such as CA4231), clinical isolates of EV-D68 from the 2014 outbreak cause neurologic disease in neonatal mice and propose to use this novel model of virus-induced CNS disease to define patterns and mechanisms of EV- D68-induced paralysis. Using chimeric viruses we have demonstrated that the 5’ untranslated region (UTR) and the viral structural proteins VP3 and VP1 are determinants of paralysis. In the proposed studies we will use similar methods to determine which viral sequences are involved in specific mechanisms of paralysis, including neuronal infectivity and apoptosis. An increased knowledge of pathogenic mechanisms that are involved in EV- D68-induced CNS disease will inform the development of antivirals for EV-D68-induced AFM. In addition, by focusing our efforts on host responses to EV-D68 infections our experiments may identify therapeutic strategies that have broad spectrum applicability to additional EVs. Our studies may also have relevance for other viral and non-viral causes of CNS disease.