Purpose:
Herpes simplex keratitis (HSK) is the leading cause of infection-associated blindness in the developed nations, with the United States alone having a prevalence of over 400,000. Despite the availability of several antivirals, such as acyclovir and famciclovir, a significant portion of patients do not respond to the chemotherapy effectively enough to prevent permanent corneal damage that necessitates surgical intervention. In addition, acyclovir resistant strains of the herpes simplex virus (HSV) are beginning to emerge, further emphasizing the need for new antiviral lines of defense in combatting HSK. The purpose of this study was to identify novel therapeutic targets against HSV by characterizing the molecular interactions between HSV and the DNA damage response pathways of corneal epithelial cells. We specifically focused on the role of ataxia telangiectasia mutated (ATM) kinase and its downstream target Chk2 in facilitating productive HSV infection in the cornea.
Methods:
We used two different human corneal epithelial cell lines (hTCEpi and HCE) as in vitro models of HSK. In addition, we developed an ex vivo HSK model, in which intact corneoscleral buttons from rabbits were infected in organ culture. Small molecule inhibitors of ATM (KU-55933, wortmannin, caffeine) and Chk2 (Chk2 inhibitor II), as well as RNAi against ATM and Chk2, were used to inhibit the host DNA damage response. Plaque assays and quantitative PCR assays were used to assess the transcriptional activity, genome replication, and infectious particle production of HSV in corneal epithelial cells.
Results:
Inhibition of ATM and Chk2 with small molecule inhibitors or RNAi effectively suppressed infectious particle production (Fig. 1), genome replication, and transcriptional activity of HSV in two different human corneal epithelial cell lines, as well as in the intact explanted rabbit corneas.
Conclusions:
Our study identifies ATM and Chk2 proteins of the DNA damage response pathway as novel targets for limiting HSV infection in corneal epithelium.
Keywords: herpes simplex virus • keratitis • cornea: epithelium