Human cytomegalovirus circumvents NF-κB dependence in retinal pigment epithelial cells

The human CMV (HCMV) is a persistent virus that may cause severe inflammatory responses especially in immunocompromised hosts. In different cell types, HCMV infection leads to the activation of the pleiotropic transcription factor, NF-kappaB, which triggers virus replication but also propagates cell-mediated inflammatory mechanisms that largely depend on PG synthesis. We investigated the interactions of HCMV and the NF-kappaB-dependent PG synthesis pathway in cultures of retinal pigment epithelial (RPE) cells that are known to be infected in HCMV retinitis patients. Unlike in other cell types, HCMV increased neither NF-kappaB activity nor p65 and p105/50 mRNA levels in RPE cells. Both TNF-ce and phorbol ester 12,0-tetradecanoylphorbol 13-acetate (TPA) enhanced NF-kappaB activity but only TPA increased HCMV replication. Cyclooxygenase-2 expression and PGE(2) release was increased by TPA and TNF-a but not by HCMV infection. Stimulatory activity of TPA on HCMV replication was suppressed by protein kinase C inhibitors and inhibitors of p42/44 and p38 mitogen-activated protein kinases but not by NF-kappaB inhibitors. In conclusion, HCMV circumvents the NF-kappaB route in favor of the protein kinase C-dependent mitogen-activated protein kinase pathway in RPE cells. This virus/host cell interaction might be a mechanism that promotes HCMV persistence in immune-privileged organs such as the eye.