Figure 4.

Knockdown of viral glycoprotein O (gO) and its cellular receptor PDGFRα both reduce the growth of cell-associated clinical HCMV isolates. Human fibroblasts infected with recent HCMV isolates were transfected with siRNAs targeting transcripts of the viral gene UL74 (encoding gO) or the cellular gene encoding the receptor PDGFRα. Nontargeting siRNAs (NT) were included as a control. (A) Four days after transfection, cultures were lysed and analyzed by immunoblotting for expression of gO or PDGFRα, including detection of actin as a loading control. Chemiluminescence signals were analyzed by densitometry, and UL128/actin ratios were calculated and normalized to the NT controls. (B),C) Replicates of the transfected cultures were fixed and immunostained for viral immediate early (IE) antigen as an indicator of viral growth. Both knockdown of gO and knockdown of PDGFRα inhibited viral growth to a degree that corresponded to the expression levels of the proteins after siRNA treatment. Bars indicate mean values of three biological replicates (different isolates). Error bars represent the standard error of the mean (SEM). Asterisks indicate significant differences as compared with NT (**, p < 0.01; *, p < 0.05).