Laura C. Hooper

IFN-β Provides Immuno-Protection in the Retina by Inhibiting ICAM-1 and CXCL9 in Retinal Pigment Epithelial Cells

The retinal pigment epithelial (RPE) cell is a potent regulatory cell that facilitates normal physiologic processes and plays a critical role in a variety of retinal diseases. We evaluated IFN-β production in human RPE cells through TLR signaling and investigated the effects of IFN-β on RPE cells. RPE cells treated with poly(I:C) or infected with an RNA virus produce IFN-β. Kinetic studies revealed that IFN-β levels continue to increase over a 48-h period and this was associated with the up-regulation of IRF-7 gene expression, a known positive feedback molecule for IFN-β production. Microarray analysis revealed that in IFN-β treated cells, 480 genes of 22,283 genes were up or down-regulated by >2-fold. We hypothesize that IFN-β induction during TLR signaling in the retina is an immunosuppressive factor produced to limit immunopathologic damage. Cytokine activation of RPE cells results in the production of the chemokines, CXCL9 and CXCL10, and the adhesion molecule, ICAM-1. Pretreatment of RPE cells with IFN-β resulted in inhibition of ICAM-1 production and elimination of CXCL9 production. This treatment did not alter CXCL10 production. Anti-IFN-β Ab blocked the inhibitory action of IFN-β. Real time PCR analysis revealed that IFN-β treatment inhibited gene expression of sICAM-1 and CXCL9. The results indicate a critical role for RPE cell derived IFN-β in the down-regulation of CXCL9 and ICAM-1 expression in the retina and suggest that the inhibition of CXCL9 is an immuno-suppressive mechanism that protects the retina from excessive inflammation.

Interferon-β and adhesion molecules (E-selectin and s-intracellular adhesion molecule-1) are detected in sera from patients with retinal vasculitis and are induced in retinal vascular endothelial cells by Toll-like receptor 3 signalling

Retinal vasculitis is a major component of ocular inflammation that plays a role in retinal tissue damage in patients with idiopathic uveitis and Behçets disease. Here we show that type 1 interferons (IFN α/β) were not detected in sera from normal individuals but were identified in up to 46% of the sera from retinal vasculitis patients. The predominant form of IFN observed was IFN‐β, which was detected in 39% of Behçets disease patients and 47% of idiopathic uveitis patients. Seven patients whose sera contained IFN‐β were monitored prospectively. IFN‐β was shown to be present for 6–12 months in all seven of the sera samples tested. Furthermore, the adhesion molecule profile identified in this study was strikingly different when Behçets and uveitis patient sera were compared to sera from normal controls. Sera from Behçets disease patients contained significantly elevated levels of the soluble adhesion molecules, sE‐selectin and s‐intracellular adhesion molecule‐1 (sICAM‐1), whereas sera from patients with idiopathic uveitis contained significantly increased sE‐selectin. In vitro studies evaluating the cell source of these cytokines revealed that polyriboinosinic polyribocytidylic acid (poly I:C) activated retinal vascular endothelial cells produce sE‐selectin, sICAM‐1 and IFN‐β. Production of these molecules was inhibited by pretreatment with anti‐Toll‐like receptor 3 (TLR‐3) antibody. In conclusion, IFN‐β, sE‐selectin and sICAM‐1 are elevated in patients with retinal vasculitis and are induced in retinal vascular endothelial cells in vitro by activating the innate immune system through TLR‐3. Further analysis of innate immune signalling may prove to be a novel target for future studies on pathogenic mechanisms and therapeutic approaches in retinal vasculitis.

Corneal buttons obtained from patients with HSK harbor high copy numbers of the HSV genome.

Purpose: To detect herpes simplex virus (HSV) genome in the cornea, we sampled the limbal corneas and scleras of the imported eye bank eyes and recipients corneal buttons and quantitated HSV genome in them by real-time polymerase chain reaction (PCR). Methods: Forty-four recipient corneas including 7 corneas with and 37 corneas without a history of herpetic keratitis, 70 eye bank donor limbal corneas, and 35 eye bank donor scleras were obtained. Primers for real-time PCR were synthesized using the HSV-1 and -2 common regions of the viral DNA polymerase. Primers for conventional PCR were designed to detect HSV-1 and -2 and varicella zoster virus (VZV). Results: Significantly higher copy number of HSV DNA was detected in corneas with a history of herpetic keratitis 85.7% (6/7), with an average of 1.6 × 104 copies/mg tissue weight than in corneas without a history of herpetic keratitis 10.8% (4/37), with an average of 8.7 copies/mg tissue weight (P < 0.05, Mann-Whitney U test). HSV DNA was detected in 5.7% (4/70) of the eye bank donor corneas, with an average of 4.9 × 102 copies/mg tissue weight, and in 8.6% (3/35) of the donor scleras, with an average of 10.6 copies/mg tissue weight. HSV-2 and VZV-DNA were not detected in these samples. Conclusions: Real-time PCR quantitated HSV genome in the cornea even at a quiescent phase of infection. HSV genome was detected in the corneas and scleras without a past history of herpetic keratitis by this method.

HSV immune complex (HSV-IgG: IC) and HSV-DNA elicit the production of angiogenic factor VEGF and MMP-9

Angiogenesis and inflammatory mediators are critical pathogenic factors in herpetic stromal keratitis (HSK). Since disease progresses without infectious virus, HSV-DNA and HSV-IgG complexes (HSV-IC) may contribute to HSK by triggering these factors. Production of VEGF and MMP-9 was studied in vitro using corneal epithelial cells (HCE), fibroblasts (HCRF) and macrophages (THP-1). VEGF was elevated in HCRF and THP-1 following treatment with HSV-DNA and HSV-IC. MMP-9 was elevated in THP-1 but not in corneal cells. When anti-HSV-IgG(Fab′)2 complexes stimulated THP-1, MMP-9 was reduced to control levels. Pretreatment of THP-1 with anti-TLR-2 and -3 inhibited MMP-9 production. Thus, HSV-IC may stimulate THP-1 through the Fc receptor and TLRs. Proinflammatory cytokines (IL-1b, IL-6, and TNF-α) increased VEGF and MMP-9 in corneal cells and macrophages. These studies indicate that the continued presence of HSV-DNA and HSV-IC contribute to angiogenesis and inflammation in HSK. Thus, cytokines and TLRs may be potential targets for intervention.

Inhibition of HSV-1 by chemoattracted neutrophils: supernatants of corneal epithelial cells (HCE) and macrophages (THP-1) treated with virus components chemoattract neutrophils (PMN), and supernatants of PMN treated with these conditioned media inhibit viral growth

The role of PMNs (neutrophils) in corneal herpes was studied using an in vitro system. Human corneal cells (HCE) and macrophages (THP-1) infected with HSV-1 or treated with virus components (DNA or virus immune complexes) released chemokines, which attracted PMNs. Highly reactive oxygen species were detected in PMNs. PMNs inhibited HSV when overlaid onto infected HCE cells (50:1). PMNs incubated with the supernatants of HCE cells treated with virus components released H2O2 and myeloperoxidase. These inhibited virus growth. PMNs released NO and MIG, which may differentiate CD4 T cells to Th1. PMNs participate in innate immune responses, limit virus growth, and initiate immunopathology.

Experimental coronavirus retinopathy (ECOR): Retinal degeneration susceptible mice have an augmented interferon and chemokine (CXCL9, CXCL10) response early after virus infection

Abstract Mouse hepatitis virus induces a biphasic disease in BALB/c mice that consists of an acute retinitis followed by progression to a chronic retinal degeneration with autoimmune reactivity. Retinal degeneration resistant CD-1 mice do not develop the late phase. What host factors contribute to the distinct responses to the virus are unknown. Herein, we show that IFN-α, IFN-β and IFN-γ act in concert as part of the innate immune response to the retinal infection. At day 2, high serum levels of IFN-γ, CXCL9 and CXCL10, were detected in BALB/c mice. Moreover, elevated levels of CXCL9 and CXCL10 gene expression were detected in retinal tissue. Although IFN-γ and the chemokines were detected in CD-1 mice, they were at significantly lower levels compared to BALB/c mice. These augmented innate responses observed correlated with the development of autoimmune reactivity and retinal degeneration and thus may contribute to the pathogenic processes.

Who (What) Pays Toll for the Development of Herpetic Stromal Keratitis (HSK)

In the herpetic stromal keratitis (HSK), HSV DNA fragments and HSV-IgG immune complexes (HSV-IC) are present in most of the corneas long after infective virus has disappeared. These viral components are highly immunogenic and potentiate production of proinflammatory cytokines and chemokines via Toll-like receptors (TLRs) expressed on the corneal cells and macrophages. In addition angiogenic factors, such as vascular endothelium growth factor (VEGF) and the tissue damaging enzyme matrix metalloproteinase 9 (MMP-9) deeply involved in the pathogenesis of HSK, are also induced by corneal cells and macrophages through the recognition of these viral components. These processes elicited by residual viral DNA and HSV-IC are likely one of the sustained driving force in the development of HSK. Hence, strategies developed to alter these pathways should lead to new preventative and therapeutic measures.

Retinal degeneration in experimental coronavirus retinopathy (ECOR) is associated with increased TNF-α, soluble TNFR2 and altered TNF-α signaling

Abstract Experimental coronavirus retinopathy (ECOR) is a virally triggered model of retinal degeneration composed of both genetic and autoimmune components. Since TNF-α plays a role in immune-mediated processes we evaluated the levels of TNF-α/TNF-α receptors and the downstream signaling molecule nitric oxide (NO) during disease in both retinal degeneration susceptible BALB/c and degeneration resistant CD-1 mice. Following coronavirus injection, TNF-α mRNA was detected at higher levels within the retinas, and concentrations of TNF-α (p <0.005) and sTNFR1 (p <0.0005) proteins were increased within the sera of BALB/c but not CD-1 mice. While concentrations of sTNFR2 proteins were elevated in both BALB/c (p <0.00005) and CD-1 (p <0.005) mice compared to controls, concentrations were higher in BALB/c mice (p <0.0005). Gene expression of iNOS while initially high in BALB/c mice decreased during the acute phase of infection, while it increased in CD-1 mice. These trends are attributable to differences in monocyte TNFR2 release (p <0.0005) between the strains since sTNFR2 decreased (p <0.01) levels of NO production. These studies demonstrate that retinal degeneration following viral infection is associated with increased release of TNF-α/TNF receptors combined with a down-regulation of NO. Furthermore they suggest that these molecules are involved in alterations in immune response leading to autoimmune reactivity.

Who pays the toll for solving the enigma of corneal herpes

Abstract: In herpetic stromal keratitis (HSK), herpes simplex virus type-1 DNA fragments and herpes simplex virus-immunoglobulin G immune complexes are present in corneas long after the infective virus has disappeared. These viral components are highly immunogenic and potentiate the production of proinflammatory cytokines and chemokines via Toll-like receptors expressed on corneal cells and macrophages. In addition, angiogenic factors, such as the vascular endothelium growth factor and the tissue-damaging enzyme, matrix metalloproteinase 9, are induced by corneal cells and macrophages through the recognition of these viral components in the pathogenesis of HSK. Upon neovascularization, robust infiltration of leukocytes via leaky new vessels is elicited. Activated polymorphonuclear leukocytes (PMNs) secrete hydrogen peroxide and myeloperoxidase, which inhibit viral growth. PMNs also produce tumor necrosis factor, monokine-induced by interferon-&ggr; (CXCL9), and nitric oxide. These factors provide a local environment that can induce the differentiation of peripheral CD4+ T cells to induce Th1-predominant immunopathology. Thus, strategies developed to alter these pathways should lead to new preventative and therapeutic measures for the treatment of HSK.

Identification of α-fodrin as an autoantigen in experimental coronavirus retinopathy (ECOR)

Abstract The coronavirus, mouse hepatitis virus (MHV), JHM strain induces a biphasic disease in BALB/c mice that consists of an acute retinitis followed by progression to a chronic retinal degeneration with autoimmune reactivity. Retinal degeneration resistant CD-1 mice do not develop either the late phase or autoimmune reactivity. A mouse RPE/choroid DNA expression library was screened using sera from virus infected BALB/c mice. Two clones were identified, villin-2 protein and α-fodrin protein. α-Fodrin protein was used for further analysis and western blot reactivity was seen only in sera from virus infected BALB/c mice. CD4 T cells were shown to specifically react with MHV antigens and with α-fodrin protein. These studies clearly identified both antibody and CD4 T cell reactivities to α-fodrin in sera from virus infected, retinal degenerative susceptible BALB/c mice.