Enterovirus 71-induced autophagosome fusion with multivesicular bodies facilitates viral RNA packaging into exosomes.

Exosomes have been shown to release from cells infected by viruses and deliver viral particles, genomes, and other viral genetic elements to neighboring cells resulting in modulating host immune response. Our previous study demonstrated that exosomes released from Enterovirus 71 (EV71)-infected cells contained replication-competent EV71 RNA in complex with miR-146a, Ago2, and GW182, which can be successfully transferred to recipient/target cells to establish productive infection. However, the molecular mechanisms that control viral genome package into exosomes are still unclear. In this study, we showed that the EV71-induced autophagy response contributed to viral genome package into exosomes rather than process of exosomes biogenesis. Further study showed that the autophagosomes accumulation facilitated their fusion with MVBs, which resulted in EV71 RNA package into exosome vesicles. Moreover, prevention of autophagosomes-MVBs fusion could abolish this sorting of viral RNA into exosomes. Knockdown of GW182 or Ago2 could weaken the replication ability of exosomal EV71 RNA in recipient cells through decreasing the amount of miR-146a in exosomes, but did not affect the package of viral RNA into exosomes. Our findings strongly suggested that the accumulation of autophagosomes that were induced by EV71 infection play a key role on viral spreading through exosome vesicles.