Receptor Usage by HSV–1 Limited to Nectin–1 Does Not Significantly Change the Replication of HSV–1 in Ocular Tissues and Does Not Affect the Capacity of the Virus to Spread to the Trigeminal Ganglia

Abstract

Abstract: : Purpose: Primary infection of the cornea by herpes simplex virus (HSV) and recurrent HSV keratitis due to viral reactivation of latent HSV in the trigeminal ganglia are important causes of ocular disease. HSV uses three known classes of receptors for cell entry that are thought to be the key determinants of viral tissue tropism and cell–to–cell spread. These include herpesvirus entry mediator (HVEM), nectin–1 and nectin–2 (members of the immunoglobulin superfamily) and 3–O–sulfated heparan sulfate. Which of these receptors HSV uses to enter corneal cells and nerve endings in the eye is not known. The purpose of this research was to better understand receptor usage by HSV during ocular infection. Methods: Groups of BALB/c mice were inoculated on their corneas with 1 x 10⁵ PFU of either a wild type HSV–1 strain (KOS–tk12) or a genetically defined mutant HSV–1 strain (KOS–rid–1–tk12). The entry receptor usage by KOS–rid–1–tk12 is restricted to nectin–1 in mice, and therefore, it provides a unique opportunity to monitor the entry and spread of HSV in mouse tissues solely via nectin–1. Two days after inoculation mice were euthanized and the eyeballs and trigeminal ganglia were aseptically removed. Ocular tissues were processed for determination of the presence of infectious HSV–1 by plaque assay. Trigeminal ganglion tissues were processed for the detection of HSV–1 DNA by real–time PCR. Results: HSV–1 titers in the eyeballs were similar at 3.6 x 10⁴ PFU and 2.9 x 10⁴ PFU for KOS–tk12 and KOS–rid–1–tk12–inoculated mice, respectively. HSV–1 DNA was detected (at threshold cycles, C_T, of around 15) in trigeminal ganglion tissues derived from both KOS–tk12 and KOS(Rid1)–tk12 inoculated animals. Conclusions: These findings suggest that receptor usage limited to nectin–1 does not significantly change the capacity of HSV–1 to replicate in ocular tissues and to spread to the trigeminal ganglia. These observations suggest that nectin–1 plays a critical role in mediating HSV cell entry and cell–to–cell spread in the eye and HSV–1 spread to the nervous system. This research may help to develop novel preventive and therapeutic strategies against HSV–induced ocular disease.

Keywords: keratitis • herpes simplex virus • receptors