TLR2 ACTIVATION IN CORNEAL EPITHELIAL CELLS BY SECRETED GLYCOPROTEIN B OF HERPES SIMPLEX VIRUS TYPE 1 IN AN EX VIVO KERATITIS MODEL

Introduction: Herpes simplex virus (HSV) is a prevalent viral pathogen infecting the majority of world’s population. While oral and genital pathogen are the most common manifestations of infection, HSV type 1 (HSV-1) can cause disease in all of the major ocular tissues, including the lids, conjunctiva, cornea, uveal tract and retina and it is one of the leading cause of blindness. HSV-1 corneal infections have been studied in a variety of animal models, where rabbits display many of the features of HSV1 ocular disease in humans. Accordingly to several studies HSV-1 clearance from the cornea during primary infection is largely through an innate immune response. Corneal epithelial cells can initiate immune response to HSV-1 through expression of toll like receptors (TLR). It has been reported that TLR2, 4, 7 and 9 may be implicated in the pathogenesis of active HSV infection in the cornea. However, the possible mechanisms by which TLRs recognition of HSV constituent leads to increase inflammation and promotes the subsequent development of inflammation-associated lesions are not well defined. Recent studies have shown that HSV glycoproteins gH/gL and gB are able to interact with TLR2 and activate NF-kB inducing the production of pro-inflammatory cytokines. The aim of this study was to investigate the expression and function of TLR2 of corneal epithelial cells in an ex vivo keratitis model induced by secreted protein gB1 (gB1s) of HSV-1. Methods: gB1s was obtained from human 293 cells constitutively expressing the secreted form of the glycoprotein and subsequently purified by affinity chromatography. Rabbit corneas with sclera rims, maintained in culture at an air-liquid interface, were assigned to two groups: (a) abraded corneas and (b) abraded corneas exposed to gB1s. The epithelial cells acquired by impression cytology were examined by quantitative real-time RT-PCR to determine TLR2 mRNA e IL-8 mRNA. Results: The results demonstrated that TLR2 and IL-8 mRNA were significantly expressed in the epithelial cells of the group exposed to gB1s. Moreover, each of the corneas exposed to gB1s developed pupillary dilation, a clinical sign of HSV keratouveitis. Conclusions: Our results demonstrate that TLR2 ligand activity of HSV is a property of gB and play a role in the induction of an immunopathological response in the cornea.