Virus-like vesicles of Kaposi’s Sarcoma-Associated Herpesvirus activate lytic replication through triggering differentiation signaling (mRNA)

Virus-like vesicles (VLVs) are membrane derived cellular vesicles that resemble native envelope viruses in organization and conformation, but lack viral capsid and/or genome. During productive virus infection, both infectious virions and non-infectious VLVs are produced and released into the extracellular space. VLVs have been shown to play a role in intercellular communication and in facilitating virus infection. The study of VLVs in the context of gammaherpesvirus infection has been largely restricted due to the technical difficulty of separating VLVs and virions. Here we report a strategy for using a KSHV mutant deficient in capsid assembly to isolate VLVs during infection. Using Mass Spectrometry analysis, we identified that VLVs contain viral glycoproteins required for cellular entry, and tegument proteins involved in regulating lytic replication. Functional analysis showed that VLVs could activate the RTA promoter, the lytic switch for KSHV, and further induce KSHV lytic gene expression from latency. We used RNA sequencing to do a genome-wide analysis of cellular responses triggered by VLVs, and revealed that PRDM1, a master regulator in cell differentiation, was up-regulated. Our data shows that VLVs play an important role in promoting KSHV lytic replication by inducing PRDM1 expression which activates the RTA promoter. Our study significantly extends our current understanding of VLVs. Overall design: 1. Analyze KSHV lytic gene expression profile induced by VLV. 2. Globally analyze cellular response induced by VLV.