PDGFRA and cytomegalovirus infection: The soluble receptor mutants were expressed in 293F cells and affinity purified using Protein A. To identify sites which are dispensable for binding to HCMV, the capacity of the PDGFRα-Fc deletion mutants to inhibit HCMV infection was assessed with a standard neutralization assay utilizing a Gaussia luciferase reporter virus (TB40-BAC4-IE-GLuc, [48]).