The potential role of human immune cells in the systemic dissemination of enterovirus-D68

Enterovirus-D68 (EV-D68) often causes mild respiratory infections, but can also cause severe respiratory infections and extra-respiratory complications, including acute flaccid myelitis (AFM). Systemic dissemination of EV-D68 is crucial for the development of extra-respiratory diseases, but it is currently unclear how EV-D68 viremia occurs. We hypothesize that immune cells contribute to the systemic dissemination of EV-D68, as this is a mechanism commonly used by other enteroviruses. Therefore, we investigated the susceptibility and permissiveness of human primary immune cells for different EV-D68 isolates. In human peripheral blood mononuclear cells (PBMC) inoculated with EV-D68, only B cells were susceptible but virus replication was limited. However, B cell-rich cultures, such as Epstein-Barr virus-transformed B-lymphoblastoid cell line (BLCL) and primary lentivirus-transduced B cells, were productively infected. In BLCL, neuraminidase treatment to remove α2,6- and α2,3-linked sialic acids resulted in a significant decrease of EV-D68 infected cells, suggesting that sialic acids are the functional receptor on B cells. Subsequently, we showed that dendritic cells (DCs), particularly immature DCs, are susceptible and permissive for EV-D68 infection and that they can spread EV-D68 to autologous BLCL. Altogether, our findings suggest that immune cells, especially B cells and DCs, play an important role in the development the systemic dissemination of EV-D68 during an infection, which is an essential step towards the development of extra-respiratory complications. Author summary Enterovirus D68 (EV-D68) is an emerging respiratory virus that has caused outbreaks worldwide since 2014. EV-D68 infects primarily respiratory epithelial cells and the infection commonly results in mild respiratory diseases. However, EV-D68 infection is also associated with complications outside the respiratory tract, including a polio-like paralysis. Despite the severity of these extra-respiratory complications, it is unclear how EV-D68 is able to spread outside the respiratory tract and infect other organs, like the central nervous system (CNS). To understand this, we investigated if immune cells play a role in the extra-respiratory spread of EV-D68. We showed that EV-D68 can infect and replicate in specific immune cells, i.e. B cells and dendritic cells (DCs), and that the virus can be transferred from DCs to B cells. Our findings suggest that lymphoid tissues, which harbor many immune cells, can be a secondary replication site for EV-D68, from where virus is released in the circulation. Our data reveal the importance of immune cells in the systemic spread of EV-D68, which is essential for infection of extra-respiratory tissues. Intervention strategies that prevent EV-D68 infection of immune cells will therefore potentially prevent virus spread from the respiratory tract to other organs.