Exosomes Derived From HTLV-1 Infected Cells Contain Viral Proteins




Jaworski, Elizabeth

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Human T-lymphotropic virus type 1 (HTLV-1) is the causative agent of adult T-cell leukemia (ATL) and HTLV-1-associated myelopathy (HAM)/tropical spastic paraparesis (TSP). The HTLV-1 transactivator protein Tax controls many critical cellular pathways including host cell DNA damage response mechanisms, cell cycle progression, and apoptosis. Recently, exosomes have been shown to play critical roles during pathogenic viral infections as delivery vehicles for host and viral components including proteins, mRNA and miRNA. We hypothesized that exosomes derived from HTLV-1 infected cells contain unique host and viral proteins that may contribute to pathogenesis. Exosomes from virally infected cells have been shown to transfer functional proteins and miRNA to recipient cells, which influence target cell signaling and gene expression. Herein we have characterized exosomes released from uninfected (CEM) and HTLV-1 infected [C8166-45, MT-2, and ED40515(-)] cell lines that were isolated from cell culture supernatants via filtration and ultracentrifugation. Exosome protein profiling was conducted via LC-MS/MS and western blot analysis. We next determined whether viral proteins were incorporated into these exosomes. We utilized Jurkat T-cells that were infected with HTLV-1 clone (pACH) and analyzed exosomes from these cells by western blot. Furthermore, the functional impact of exosomes derived from HTLV-1 infected cells on naïve recipient cells was evaluated by utilizing transcription and reactive oxygen species (ROS) assays. We were able to isolate exosomes from HTLV-1 infected T-cell lines, which displayed phenotypic characteristics including standard established exosome marker proteins. Exosomes from HTLV-1 infected cells displayed unique proteomic profiles distinct from exosomes derived from uninfected cells. Here, we show that proinflammatory mediators are contained within the exosomes, as well as viral mRNA transcripts including Tax, HBZ, and Env. Furthermore, we found that exosomes from infected cells deliver functional Tax to naïve recipient cells and induce reactive oxygen species (ROS) production. Collectively, our results suggest that exosomes may play an important role in extracellular delivery of functional HTLV-1 proteins and mRNA to recipient cells. We also found a mechanism for release of intra-exosomal cytokines via MDR-1, an ATP-binding cassette transporter onto target cells. Furthermore, exosomes derived from infected cells are capable of inducing an ROS response in naïve cells.



Exosomes, Retrovirus, HTLV-1, Signal messenger, Vesicles