Induction of interleukin-6 in human retinal epithelial cells by an attenuated Herpes simplex virus vector requires viral replication and NFκB activation

Gene delivery has potential for treating ocular disease and a number of delivery systems have been tested in animal models. However, several viral vectors have been shown to trigger undesirable transient inflammatory responses in the eye. Previously, it was shown that an attenuated Herpes simplex virus vector (hrR3) transduced numerous cell types in the anterior and posterior segments of monkey eyes, but this was accompanied by inflammation. In the retina, retinal pigment epithelial cells were the predominant cell type transduced by hrR3. IL-6 is an important pro-inflammatory cytokine and may play a role in the response to the hrR3 vector. Infection of human ARPE-19 cells with hrR3 resulted in increased IL-6 expression and secretion 3-4 h post-infection. In the presence of acyclovir (70 μM) or in cells infected with UV-inactivated hrR3, IL-6 was not up-regulated indicating viral replication was required. Expression of the HSV-1 α and β genes may be necessary but was not sufficient for NF-κB activation and IL-6 up-regulation. The translocation of NF-κB into the nucleus also occurred between 3 and 4 h post-infection, coincident with increased IL-6 expression. Inhibition of NF-κB translocation by an Adenovirus vector expressing a dominant negative IκB (AdIκBam) inhibited IL-6 up-regulation, indicating that NF-κB plays a role in increasing IL-6 expression in APRE-19 cells. The hrR3 virus lacks viral ribonucleotide reductase (RR) activity, thus RR is not required for NF-κB activation or IL-6 up-regulation in ARPE-19 cells.