High Frequency of Gamma Interferon-Producing PLZF^loRORγt^loInvariant Natural Killer 1 Cells Infiltrating Herpes Simplex Virus 1-Infected Corneas Is Associated with Asymptomatic Ocular Herpesvirus Infection

Abstract

Invariant natural killer (iNKT) cells are among the first innate immune cells to elicit early protective immunity that controls invading viral pathogens. The role of the iNKT cell subsets iNKT1, iNKT2, and iNKT17 in herpesvirus immunity remains to be fully elucidated. In this study, we examined the protective role of cornea-resident iNKT cell subsets using the mouse model of ocular herpesvirus infection and disease. Wild-type (WT) C57BL/6 (B6) mice and CD1d knockout (KO) mice were infected ocularly with herpes simplex virus 1 (HSV-1) (strain McKrae). Cornea, spleen, and liver were harvested at 0, 2, 5, 8, and 14 days postinfection (p.i.), and the frequency and function of the three major iNKT cell subsets were analyzed and correlated with symptomatic and asymptomatic corneal herpesvirus infections. The profiles of 16 major pro- and anti-inflammatory cytokines were analyzed in corneal lysates using Western blot and Luminex assays. Early during ocular herpesvirus infection (i.e., day 2), the gamma interferon (IFN-γ)-producing PLZFloRORγtlo (promyelocytic leukemia zinc finger, retinoic acid-related orphan receptor gT) iNKT1 cell subset was the predominant iNKT cell subset in infected asymptomatic corneas. Moreover, compared to the asymptomatic corneas of HSV-1-infected WT mice, the symptomatic corneas CD1d KO mice, with iNKT cell deficiency, had increased levels of the inflammatory cytokine interleukin-6 (IL-6) and decreased levels of IL-12, IFN-γ, and the JAK1, STAT1, NF-κB, and extracellular signal-regulated kinase 1/2 (ERK1/2) pathways. Our findings suggest that IFN-γ-producing PLZFloRORγtlo iNKT1 cells play a role in the protective innate immune response against symptomatic ocular herpes. IMPORTANCE We investigated the protective role of iNKT cell subsets in asymptomatic ocular herpesvirus infection. We found that early during ocular herpesvirus infection (i.e., on day 2 postinfection), IFN-γ-producing PLZFloRORγtlo iNKT1 cells were the predominant iNKT cell subset in infected corneas of asymptomatic B6 mice (with little to no corneal herpetic disease), compared to corneas of symptomatic mice (with severe corneal herpetic disease). Moreover, compared to asymptomatic corneas of wild-type (WT) B6 mice, the symptomatic corneas of CD1d KO mice, which lack iNKT cells, showed (i) decreases in the levels of IFN-γ and IL-12, (ii) an increase in the level of the inflammatory cytokine IL-6; and (iii) downregulation of the JAK1, STAT1, NF-κB, and ERK1/2 pathways. The findings suggest that early during ocular herpesvirus infection, cornea-resident IFN-γ-producing PLZFloRORγtlo iNKT1 cells provide protection from symptomatic ocular herpes.

Berberine Inhibits Herpes Simplex Virus 1 Replication in HEK293T Cells

“…HSV-1 Infection. HSV-1 triggers inflammatory responses, such as gingival stomatitis, cold sores, keratitis, and meningitis [26,27]. To investigate the effect of berberine on inflammatory responses caused by HSV-1, RT-qPCR and ELISA were conducted.…”

Herpes Simplex Virus Type 1 Interactions with the Interferon System

“…It has recently been shown that in vitro, IFNκ is also secreted by human keratinocytes and blocking IFNκ expression enhances HSV-1 replication, indicating it may also play a role in controlling HSV-1 in herpes lesions [ 140 ]. Secreted type I IFN, among other cytokines, including IL12, IL15, and IL18, activate NK cells, which produce IFNγ, which plays an important protective role against both HSV-1 and HSV-2 infections [ 35 , 141 , 142 ]. CD4+ and CD8+ T cells also infiltrate the dermis contributing to the production of IFNγ [ 143 , 144 , 145 ] ( Figure 2 ).…”

Cytokines and chemokines: The vital role they play in herpes simplex virus mucosal immunology

“…This has important implications for which NK cell subsets home to particular sites during infection and the kinetics of doing so depending on the cascade of cytokines and chemokines produced over time. In addition to NK cells, decreased IFN-g, IL-6 and IL-12 were observed in symptomatic mice where invariant natural killer T (iNKT) cells were lacking (104). The relative importance of iNKT cells in HSV infection is still poorly understood, although a role for them has been shown in mouse models (104).…”

“…In addition to NK cells, decreased IFN-g, IL-6 and IL-12 were observed in symptomatic mice where invariant natural killer T (iNKT) cells were lacking (104). The relative importance of iNKT cells in HSV infection is still poorly understood, although a role for them has been shown in mouse models (104). Therefore the relative roles of NK and iNKT cells in HSV infection should be further explored, partly in human ex vivo model systems.…”