DEFA1B inhibits ZIKV replication and retards cell cycle progression through interaction with ORC1

Zika virus (ZIKV) infection causes a public health concern because of its potential association with the development of microcephaly. During viral infections, the host innate immune response is mounted quickly to produce some endogenous functional molecules to limit virus replication and spread. Exosomes contain molecules from their cell of origin following virus infection and can enter recipient cells for intercellular communication. Here, we aim to clarify whether ZIKV-induced exosomes can regulate viral pathogenicity by transferring specific RNAs.

In this study, exosomes were isolated from the supernatants of A549 cells with or without ZIKV infection. Human transcriptome array (HTA) was performed to analyze the profiling of RNAs wrapped in exosomes. Then qPCR, western blotting and ELISA were used to determine ZIKV replication. CCK-8 and flow cytometry were used to test the cell proliferation and cell cycles. Co-culture assay was used to analyze the effect of exosomes on the cell cycles of recipient cells.

Through human transcriptome array (HTA) we found the defensin alpha 1B (DEFA1B) expression was significantly increased within exosomes isolated from ZIKV infected A549 cells. Additionally, we found that the extracellular DEFA1B exerts significant anti-ZIKV activity, mainly before ZIKV entering host cells. Interestingly, up-regulated DEFA1B retards the cell cycle of host cells. Further studies demonstrated that DEFA1B interacted with the origin recognition complex 1 (ORC1) which is required to initiate DNA replication during the cell cycle and increased DEFA1B expression decreased the ORC1 level in the cell nuclei. Accordingly, DEFA1B-containing exosomes can be internalized by the recipient cells to retard their cell cycles.

Together, our results demonstrated that the anti-ZIKV activity of DEFA1B can be mediated by exosomes, and DEFA1B interacts with ORC1 to retard cell cycles. Our study provides a novel concept that DEFA1B not only acts as an antiviral molecule during ZIKV infection but also may correlate with cell proliferation by retarding the progression of cell cycles.