Role of CD8⁺T Cells and Lymphoid Dendritic Cells in Protection from Ocular Herpes Simplex Virus 1 Challenge in Immunized Mice

Abstract

The development of immunization strategies to protect against ocular infection with herpes simplex virus 1 (HSV-1) must address the issue of the effects of the strategy on the establishment of latency in the trigeminal ganglia (TG). It is the reactivation of this latent virus that can cause recurrent disease and corneal scarring. IMPORTANCEIn the past 2 decades, two large clinical HSV vaccine trials were performed, but both vaccine studies failed to reach their goals. Thus, as an alternative to conventional vaccine studies, we have used a different strategy to manipulate the host immune responses in an effort to induce greater protection against HSV infection. In lieu of the pleiotropic effect of CD8␣ ؉ DCs in HSV-1 latency, in this report, we show that the absence of CD8␣ ؉ T cells and CD8␣ ؉ DCs has no adverse effect on vaccine efficacy. In line with our hypothesis, we found that pushing DC subpopulations from CD8␣ ؉ DCs toward CD8␣ ؊ DCs by injection of GM-CSF reduced the amount of latent virus and T-cell exhaustion in TG. While these studies point to the lack of a role for CD8␣ ؉ T cells in vaccine efficacy, they in turn point to a role for GM-CSF in reducing HSV-1 latency.

CD8 + T Cells Play a Bystander Role in Mice Latently Infected with Herpes Simplex Virus 1

“…In addition, T cell exhaustion was blocked by a recombinant HSV-1 strain expressing CD80 that binds to PD-L1 on the surfaces of DCs (32). Overall, our previous and current findings suggest that CD8␣ ϩ DCs contribute to increased HSV-1 latency and T cell exhaustion (17,22,25,26,28,32). Our previously published studies with regard to the role of LAT in T cell exhaustion were done with mice.…”

“…Previously, we showed that LAT expression and increased latency correlate with T cell exhaustion (17,22,26,32). We also demonstrated that latency in PD-1 Ϫ/Ϫ mice was lower than that in their wt counterparts (17).…”

“…However, we have also found that CD8␣ ϩ lymphoid dendritic cells (DCs) enhance latency in the TG of infected mice. Injection of mice with FMS-like tyrosine kinase 3 ligand (Flt3L) increases the population of CD8␣ ϩ lymphoid-related DCs and enhances the level of latent virus in the TG (24,25), while injection with granulocyte-macrophage colony-stimulating factor (GM-CSF) reduces the number of functional lymphoid-related DCs and also inhibits latency (26). DCs are classified into several subsets, based on their cell surface phenotypes, locations of residence, and functional differences (27).…”

“…Relative copy numbers of gB DNA and LAT RNA were calculated using standard curves generated from the plasmids pAc-gB1 and pGem5317, respectively, as we described previously (22,26,28,32). In all experiments, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was used for normalization of transcripts.…”

Mutations within the Pathogenic Region of Herpes Simplex Virus 1 gK Signal Sequences Alter Cell Surface Expression and Neurovirulence

“…Isolated tissues were immersed in RNAlater RNA stabilization reagent and stored at Ϫ20°C until processing. The corneas, TG, or brain from each animal were processed for RNA extraction using TRIzol reagent as we described previously (44). Isolated total RNA was reverse-transcribed with random hexamer primers and murine leukemia virus reverse transcriptase provided in a high-capacity cDNA reverse transcription kit (Applied Biosystems) according to the manufacturer's recommendations.…”