RESEARCH ARTICLE The host exosome pathway underpins biogenesis of the human cytomegalovirus virion Declan L Turner1, Denis V Korneev2, John G Purdy3, Alex de Marco4,5,6, Rommel A Mathias1,4* 1Infection and Immunity Program, Monash Biomedicine Discovery Institute, Department of Microbiology, Monash University, Victoria, Australia; 2School of Biological Sciences, Monash University, Victoria, Australia; 3Department of Immunobiology and BIO5 Institute, University of Arizona, Tucson, United States; 4Infection and Immunity Program, Monash Biomedicine Discovery Institute, Department of Biochemistry and Molecular Biology, Monash University, Victoria, Australia; 5ARC Centre of Excellence in Advanced Molecular Imaging, Monash University, Victoria, Australia; 6University of Warwick, Coventry, United Kingdom Abstract Human Cytomegalovirus (HCMV) infects over half the world’s population, is a leading cause of congenital birth defects, and poses serious risks for immuno-compromised individuals. To expand the molecular knowledge governing virion maturation, we analysed HCMV virions using proteomics, and identified a significant proportion of host exosome constituents. To validate this acquisition, we characterized exosomes released from uninfected cells, and demonstrated that over 99% of the protein cargo was subsequently incorporated into HCMV virions during infection. This suggested a common membrane origin, and utilization of host exosome machinery for virion assembly and egress. Thus, we selected a panel of exosome proteins for knock down, and confirmed that loss of 7/9 caused significantly less HCMV production. Saliently, we report that *For correspondence: VAMP3 is essential for viral trafficking and release of infectious progeny, in various HCMV strains
[email protected] and cell types. Therefore, we establish that the host exosome pathway is intrinsic for HCMV Competing interests: The maturation, and reveal new host regulators involved in viral trafficking, virion envelopment, and authors declare that no release.