Toll–like Receptor 7 Up–regulation and NF–kB Activation in Response to HSV–1 Infection in Corneal Epithelial Cells

Abstract

Abstract: : Purpose:Herpetic epithelial and stromal keratitis is a sight threatening ocular infection. . Our aim is to study the role of epithelial cells in innate response to HSV–1 infection of the cornea. Methods:A telomerase–immortalized HCE cell line, HUCL was infected with HSV–1 (KOS strain, 5 moi ). Inhibitory IkB–α phosphorylation and degradation and TLR7 expression were detected by Western Blot. Cytokines expression at mRNA levels was assessed by RT–PCR. Enzyme–linked immunosorbent assay was used to quantify IL–6 and IL–8 secretion. Inhibitors and function–blocking antibodies were used for functional blocking of NF–kB activation after HSV–1 challenge. Results:HSV–1 infection of HUCL cells resulted in a two phases activation of nuclear factor–kappaB (NF–kB), JNK and p38, one at 1 to 4 h and second peak after 8 h. Concomitant with the first peak of activation, transcriptional expression of TNF–α and/or subsequent secretion of IL–6 and IL–8 in these cells were rapid induced in HSV–1 infected cells. On the other hand, the up–regulation of IFN–α and –ß was induced at a later stage, 8 hour post infection. The expression of these antiviral cytokines is correlated to expression of Toll–like receptor–7 (TLR7) in HUCL cells after HSV–1 exposure. Conclusions:In response to HSV–1 infection corneal epithelial cells, through activation of NF–kB, produce early response proinflammatory cytokines leading to infiltration and express IFNs at a later stage to enhance the antiviral activity in the cornea. The epithelium is an important part of innate immunity of the cornea in response to viral infection.

Keywords: herpes simplex virus • signal transduction • cornea: epithelium