Investigating the effect of corneal Herpes Simplex Virus-1 infection on Toll-Like Receptor expression in human peripheral blood mononuclear cells

Introduction Herpes Simplex keratitis (HSK), caused by Herpes Simplex Virus type 1 (HSV-1), is the leading cause of infectious corneal blindness in the western world [1]. Initial infection develops through ocular surface entry from droplet spread [2]. Once HSV-1 has breached the epithelial barrier of the ocular surface, it is recognized by Toll-Like Receptors (TLRs), which then activate the appropriate innate immune response. Despite the high prevalence of HSV-1, only a small minority of patients develop ocular manifestations. Therefore, we hypothesized that TLR expression and activity may be deregulated in patients with HSK, which would reflect in peripheral blood mononuclear cell (PBMC) responses observed in these patients. We investigated the effects of the TLR ligands 3, 4, 7 and 9 (as they are involved in anti-viral immune defence [3]) on cytokine induction from a patient with active HSK and compared responses of this patient to TLR ligands on a subsequent follow up visit where disease was diagnosed to be inactive.