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SummaryViruses must adapt to the environment of their host cells to establish infection and persist. Diverse mammalian cells, including virus-infected cells, secrete extracellular vesicles such as exosomes containing proteins and miRNAs, and use these vesicles to mediate intercellular communications. However, the roles of exosomes in viral infection remain unclear. Here we screened viral proteins to identify those responsible for the exosome-mediated upregulation of Epstein-Barr virus (EBV) infection. We found BGLF2 protein encapsulated in exosomes, which were released from EBV-infected cells. BGLF2 protein is a tegument protein that exists the space between the envelope and the nucleocapsid, and it is released into the cytoplasm shortly after infection. BGLF2 protein-containing exosomes enhanced viral gene expression and repressed innate immunity, thereby assisting the EBV infection. In summary, the EBV tegument protein BGLF2 is encapsulated not only encapsulated in viral particles, but also in exosomes secreted from infected cells. Therefore, BGLF2 may play a crucial role in establishing EBV latent infection.