No abstract

PURPOSE. We previously have reported that ICP22, an immediate early gene of herpes simplex virus type 1 (HSV-1), binds to the CD80 promoter to suppress CD80 expression in antigenpresenting cells, leading to reduced T-cell function and protection. In contrast, overexpression of CD80 exacerbates corneal scarring (CS) in ocularly infected mice. In this study we tested the hypothesis that the absence of ICP22 could increase disease severity. METHODS. To test our hypothesis, BALB/c mice were ocularly infected after corneal scarification with a recombinant HSV-1 lacking the ICP22 gene with its parental wild-type (WT) virus (KOS) as a control. Virus replication in the eye, CS, angiogenesis, latency, and reactivation between ICP22 null virus and WT KOS were determined. In addition, expression of IL-2, IL-4, IFN-c, IFNa, granzyme A, granzyme B, and perforin by CD4 and CD8 T cells in corneas of infected mice on days 3, 5, 7, 10, 14, 21, and 28 postinfection were determined by flow cytometry. RESULTS. We found similar levels of eye disease and angiogenesis in mice following corneal scarification and ocular infection with the ICP22 null virus or parental WT virus despite reduced virus replication in the eye and reduced latency and reactivation in mice ocularly infected with ICP22 null virus. The similar level of eye disease in ICP22 null virus-and WT virus-infected mice correlated with expression of various proinflammatory cytokines that infiltrated the eye after HSV-1 infection. CONCLUSIONS. Our study identified a critical role for ICP22 in HSV-1 pathogenicity and suggests that HSV-1-associated CS is more dependent on host immune responses to infection than to virus replication in the eye. Thus, HSV-1 as means of survival uses ICP22 as a mechanism of immune escape that protects the host from increased pathology.

This report deals with physiological changes and their implication following ocular infection with herpes simplex virus (HSV). This infection usually results in a blinding inflammatory reaction in the cornea orchestrated mainly by pro-inflammatory CD4 T cells and constrained in severity by regulatory T cells (Treg). In the present report, we make the unexpected finding that blood glucose levels change significantly during the course of infection. Whereas levels remained normal during the early phase of infection when the virus was actively replicating in the cornea, they increased around two fold during the time when inflammatory responses to the virus was occurring. We could show that glucose levels influenced the extent of induction of the inflammatory T cell subset in vitro that mainly drives lesions, but not regulatory T cells. Additionally, if glucose utilization was limited in vivo as a consequence of therapy in the inflammatory phase with the drug 2DG, lesions were diminished compared to untreated infected controls. In addition, lesions in 2DG treated animals contained less pro-inflammatory effectors. Glucose metabolism also influenced the acute phase of infection when replicating virus was present in the eye. Thus, therapy with 2DG to limit glucose utilization caused mice to become susceptible to the lethal effects of HSV infection, with virus spreading to the brain causing encephalitis. Taken together, our results indicate that glucose metabolism changed during the course of HSV infection and that modulating glucose levels can influence the outcome of infection, being detrimental or beneficial according to the stage of viral pathogenesis.

Ocular infection with Herpes Simplex Virus causes a chronic T-cell mediated inflammatory lesion in the cornea. Lesion severity is affected by the balance of different CD4 T-cell subsets with greater severity occurring when the activity of regulatory T-cells is compromised. In the present report, fate-mapping mice were used to assess the stability of Treg function in ocular lesions. We show that cells that were once FoxP3+ functional Treg may lose FoxP3 and become Th1 cells which themselves could contribute to lesion expression. The instability mostly occurred with IL-2 receptor low Treg and was shown to be in part the consequence of exposure to IL-12. Lastly, in-vitro generated iTreg were shown to be highly plastic and capable of inducing SK when adoptively transferred into Rag1−/− mice, with 95% of iTreg converting into ex-Treg in the cornea. This plasticity of iTreg could be prevented when they were generated in the presence of Vitamin-C and Retinoic acid. Importantly, adoptive transfer of these stabilized iTreg to HSV-1 infected mice more effectively prevented the development of SK lesions than did the control iTreg. Our results demonstrate that CD25lo Treg and iTreg instability occurs during a viral immuno-inflammatory lesion and that its control may help avoid lesion chronicity.