Exosomal release of the virus-encoded chemokine receptor US28 contributes to chemokine scavenging

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Bebelman, Maarten, P | Setiawan, Irfan, M | Bergkamp, Nick, D | van Senten, Jeffrey, R | Crudden, Caitrin | Bebelman, Jan Paul M. | Verweij, Frederik, J | van Niel, Guillaume | Siderius, Marco | Pegtel, D. Michiel | Smit, Martine, J

Edité par CCSD ; Elsevier -

International audience. The human cytomegalovirus (HCMV)-encoded chemokine receptor US28 contributes to various aspects of the viral life cycle and promotes immune evasion by scavenging chemokines from the microenvironment of HCMV-infected cells. In contrast to the plasma membrane localization of most human chemokine receptors, US28 has a predominant intracellular localization. In this study, we used immunofluorescence and electron microscopy to determine the localization of US28 upon exogenous expression, as well as in HCMV-infected cells. We observed that US28 localizes to late endosomal compartments called multivesicular bodies (MVBs), where it is sorted in intraluminal vesicles. Live-cell total internal reflection fluorescence (TIRF) microscopy revealed that US28-containing MVBs can fuse with the plasma membrane, resulting in the secretion of US28 on exosomes. Exosomal US28 binds the chemokines CX3CL1 and CCL5, and US28-containing exosomes inhibited the CX3CL1-CX3CR1 signaling axis. These findings suggest that exosomal release of US28 contributes to chemokine scavenging and immune evasion by HCMV.

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