Project description:In 2014, enterovirus D68 (EV-D68), previously associated primarily with mild respiratory illness, caused a large outbreak of severe respiratory illness and, in rare instances, paralysis. We compared viral binding and replication of eight recent EV-D68 clinical isolates and the prototype Fermon strain from 1962 in cultured HeLa cells and differentiated human primary bronchial epithelial cells (BEC) to understand the possible reasons for the change in virus pathogenicity. We found no significant differences in binding or replication in HeLa cell cultures between the recent clinical isolates. However, in HeLa cells, Fermon had significantly greater (1.5-2 log) binding and virus progeny yields but a similar level of replication (~2-log increase in viral RNA from 2h to 24h post infection) compared to recent isolates. In differentiated BECs, Fermon and the recent EV-D68 isolates had similar levels of binding; however, the recent isolates produced 1-2-log higher virus progeny yields than Fermon due to increased replication. We then utilized RNA-seq to define the transcriptional responses in BECs infected with four recent EV-D68 isolates, representing major phylogenetic clades, and Fermon strain. All the tested clinical isolates induced similar responses in BECs; however, numerous upregulated genes in antiviral and pro-inflammatory response pathways were identified when comparing the response to clinical isolates versus Fermon. These results indicate that the recent emergence in severe EV-D68 cases could be explained by increased replication efficiency and enhanced inflammatory response induced by newly emerged clinical isolates.
Project description:The mechanisms by which enteroviruses, particularly enterovirus D-68 (EV-D68) and enterovirus A-71 (EV-A71), contribute to acute flaccid myelitis (AFM), a severe neurological condition characterized by sudden muscle weakness and paralysis, remain poorly understood. To investigate the cellular tropism and infection dynamics of these enteroviruses, we utilized human spinal cord organoids (hSCOs) derived from induced pluripotent stem cells (iPSCs). We performed single-cell RNA sequencing (scRNA-seq) to profile the cellular composition of hSCOs and identify infected cell types post-infection. We found that hSCOs exhibit a diverse cellular landscape, including neurons, astrocytes, oligodendrocyte progenitor cells (OPCs), and multipotent glial progenitor cells (mGPCs), with astrocytes predominant in earlier developmental stages and neurons more abundant in later stages. Upon infection with two EV-D68 strains (US/IL/14-18952 and US/CO/18-23089) and one EVA71 strain (Tainan/4643/1998), we observed distinct viral tropism. EV-D68-18952 showed a significant increase in infected neurons, while EV-D68-23089 exhibited higher infection rates in cycling astrocytes and OPCs. In contrast, EVA71 demonstrated a broader tropism, with a statistically significant increase in infected mGPCs, suggesting enhanced infection efficiency across multiple cell types. These findings provide novel insights into the cell-type specificity of EV-D68 and EVA71 in the spinal cord, offering a deeper understanding of potential mechanisms underlying AFM pathogenesis. Understanding the dynamics of infection at single-cell resolution will inform future therapeutic strategies aimed at mitigating the neurological impact of enteroviral infections.