Downregulation of the epidermal growth factor receptor by human cytomegalovirus infection in human fetal lung fibroblasts

Epidermal growth factor plays a key role in late fetal lung development and differentiation as well as in regulating surfactant protein A synthesis, which is involved in innate immunity of the lung. Here we show that human cytomegalovirus (HCMV), a known lung pathogen in connatal and postnatal infection of neonates as well as transplant recipients, completely downregulates EGF receptor (EGF-R) on the surface of human fetal lung fibroblasts. Inhibition of EGF-R synthesis occurs on the transcriptional rather than on the posttranscriptional level. The effect essentially depends on expression of viral immediate early and/or early genes, as binding of ultraviolet light-inactivated virus to the cells had no effect on EGF-R expression. Furthermore, the anti-HCMV drug ganciclovir, which blocks HCMV DNA replication and late gene expression, cannot overcome HCMV-mediated inhibition of EGF-R, suggesting that immediate early or early gene products may be responsible for down-regulation of EGF-R. Interestingly, the glucocorticoid dexamethasone, which is used for its anti inflammatory action to prevent chronic lung disease in preterm infants, promotes HCMV-associated downregulation of the EGF-R by stimulation of viral gene expression. From these data it can be hypothesized that the pathogenesis of HCMV lung infection involves downregulation of EGF-R and that congenital HCMV infection may cause retardation in lung maturation and surfactant protein synthesis.