Platelet-derived growth factor-α receptor activation is required for human cytomegalovirus infection

Abstract

Human cytomegalovirus (HCMV) is a ubiquitous human herpesvirus that can cause life-threatening disease in the fetus and the immunocompromised host¹. Upon attachment to the cell, the virus induces robust inflammatory, interferon- and growth-factor-like signalling^{2,3,4,5,6,7,8,9}. The mechanisms facilitating viral entry and gene expression are not clearly understood⁴. Here we show that platelet-derived growth factor-α receptor (PDGFR-α) is specifically phosphorylated by both laboratory and clinical isolates of HCMV in various human cell types, resulting in activation of the phosphoinositide-3-kinase (PI(3)K) signalling pathway. Upon stimulation by HCMV, tyrosine-phosphorylated PDGFR-α associated with the p85 regulatory subunit of PI(3)K and induced protein kinase B (also known as Akt) phosphorylation, similar to the genuine ligand, PDGF-AA. Cells in which PDGFR-α was genetically deleted¹⁰ or functionally blocked were non-permissive to HCMV entry, viral gene expression or infectious virus production. Re-introducing human PDGFRA gene into knockout cells restored susceptibility to viral entry and essential viral gene expression. Blockade of receptor function with a humanized PDGFR-α blocking antibody (IMC-3G3)¹¹ or targeted inhibition of its kinase activity with a small molecule (Gleevec)¹² completely inhibited HCMV viral internalization and gene expression in human epithelial, endothelial and fibroblast cells. Viral entry in cells harbouring endogenous PDGFR-α was competitively inhibited by pretreatment with PDGF-AA. We further demonstrate that HCMV glycoprotein B directly interacts with PDGFR-α, resulting in receptor tyrosine phosphorylation, and that glycoprotein B neutralizing antibodies¹³ inhibit HCMV-induced PDGFR-α phosphorylation. Taken together, these data indicate that PDGFR-α is a critical receptor required for HCMV infection, and thus a target for novel anti-viral therapies.