Contemporary Enterovirus D68 strains show enhanced replication and translation at 37° C

Enterovirus D68 (EV-D68) emerged in 2014 as an important pathogen linked to severe lower respiratory disease and acute flaccid myelitis outbreaks. Historically associated with mild common-cold-like symptoms, clusters of severe disease attributed to EV-D68 appeared during a series of outbreaks in 2014, 2016, and 2018. Previous studies of historic EV-D68 strains demonstrated attenuated replication at temperatures of the lower respiratory tract (37°C), when compared to the upper respiratory tract (32°C). By testing a panel of historic and contemporary EV-D68 strains at 32°C and 37°C, we demonstrate that contemporary strains of EV-D68 undergo little to no attenuation at increased temperatures. Contemporary strains produced higher levels of viral proteins at 32°C and 37°C than historic strains, although both strains infected similar numbers of cells and had comparable amounts of replication complexes. IRES activity assays with dual-luciferase reporter plasmids demonstrated enhanced translation in recent EV-D68 strains mapped to regions of variability in the 5’ UTR found only in contemporary strains. Using an infectious clone system, we demonstrate that the translation advantage dictated by the 5’ UTR does not solely mediate temperature sensitivity. The strain-dependent effects of temperature on the EV-D68 life cycle gives insight into the susceptibility of the lower respiratory system to contemporary strains.