Production of key molecules by ocular neutrophils early after herpetic infection of the cornea

The immunobiology of corneal HSV-1 infection and herpetic stromal keratitis

SUMMARYHuman alphaherpesvirus 1 (HSV-1) is a highly successful neurotropic pathogen that primarily infects the epithelial cells lining the orofacial mucosa. After primary lytic replication in the oral, ocular, and nasal mucosal epithelial cells, HSV-1 establishes life-long latency in neurons within the trigeminal ganglion. Patients with compromised immune systems experience frequent reactivation of HSV-1 from latency, leading to virus entry in the sensory neurons, followed by anterograde transport and lytic replication at the innervated mucosal epithelial surface. Although recurrent infection of the corneal mucosal surface is rare, it can result in a chronic immuno-inflammatory condition called herpetic stromal keratitis (HSK). HSK leads to gradual vision loss and can cause permanent blindness in severe untreated cases. Currently, there is no cure or successful vaccine to prevent latent or recurrent HSV-1 infections, posing a significant clinical challenge to managing HSK and preventing vision loss. The conventional clinical management of HSK primarily relies on anti-virals to suppress HSV-1 replication, anti-inflammatory drugs (such as corticosteroids) to provide symptomatic relief from pain and inflammation, and surgical interventions in more severe cases to replace damaged cornea. However, each clinical treatment strategy has limitations, such as local and systemic drug toxicities and the emergence of anti-viral-resistant HSV-1 strains. In this review, we summarize the factors and immune cells involved in HSK pathogenesis and highlight alternate therapeutic strategies for successful clinical management of HSK. We also discuss the therapeutic potential of immunoregulatory cytokines and immunometabolism modulators as promising HSK therapies against emerging anti-viral-resistant HSV-1 strains.

Inflammatory Cytokines and Chemokines Are Synergistically Induced in a ROS-Dependent Manner by a Co-Culture of Corneal Epithelial Cells and Neutrophil-like Cells in the Presence of Particulate Matter

Ocular exposure to particulate matter (PM) causes local inflammation; however, the influence of neutrophils on PM-induced ocular inflammation is still not fully understood. In this study, we constructed a system to investigate the role of PM in ocular inflammation using a co-culture of human corneal epithelial cells (HCE-T) and differentiation-induced neutrophils (dHL-60). To investigate whether HCE-T directly endocytosed PM, we performed a holographic analysis, which showed the endocytosis of PM in HCE-T. The cytokines and chemokines produced by HCE-T were measured using an ELISA. HCE-T treated with PM produced IL-6 and IL-8, which were inhibited by N-Acetyl-L-cysteine (NAC), suggesting the involvement of ROS. Their co-culture with dHL-60 enhanced their production of IL-6, IL-8, and MCP-1. This suggests an inflammatory loop involving intraocular corneal epithelial cells and neutrophils. These cytokines and chemokines are mainly regulated by NF-κB. Therefore, this co-culture system was examined in the presence of an IKK inhibitor known to downregulate NF-κB activity. The IKK inhibitor dramatically suppressed the production of these factors in co-culture supernatants. The results suggest that the inflammatory loop observed in the co-culture is mediated through ROS and the transcription factor NF-κB. Thus, the co-culture system is considered a valuable tool for analyzing complex inflammations.

Phylogenetic and Genomic Characterization of Whole Genome Sequences of Ocular Herpes Simplex Virus Type 1 Isolates Identifies Possible Virulence Determinants in Humans

Purpose

There are limited data on the prevalence and genetic diversity of herpes simplex virus type 1 (HSV-1) virulence genes in ocular isolates. Here, we sequenced 36 HSV-1 ocular isolates, collected by the Bascom Palmer Eye Institute, a university-based eye hospital, from three different ocular anatomical sites (conjunctiva, cornea, and eyelid) and carried out a genomic and phylogenetic analyses.

Methods

The PacBio Sequel II long read platform was used for genome sequencing. Phylogenetic analysis and genomic analysis were performed to help better understand genetic variability among common virulence genes in ocular herpetic disease.

Results

A phylogenetic network generated using the genome sequences of the 36 Bascom Palmer ocular isolates, plus 174 additional strains showed that ocular isolates do not group together phylogenetically. Analysis of the thymidine kinase and DNA polymerase protein sequences from the Bascom Palmer isolates showed multiple novel single nucleotide polymorphisms, but only one, BP-K14 encoded a known thymidine kinase acyclovir resistance mutation. An analysis of the multiple sequence alignment comprising the 51 total ocular isolates versus 159 nonocular strains detected several possible single nucleotide polymorphisms in HSV-1 genes that were found significantly more often in the ocular isolates. These genes included UL6, gM, VP19c, VHS, gC, VP11/12, and gG.

Conclusions

There does not seem to be a specific genetic feature of viruses causing ocular infection. The identification of novel and common recurrent polymorphisms may help to understand the drivers of herpetic pathogenicity and specific factors that may influence the virulence of ocular disease.

E3 ligase RNF5 inhibits type I interferon response in herpes simplex virus keratitis through the STING/IRF3 signaling pathway

Herpes simplex keratitis (HSK), caused by the herpes simplex virus 1 (HSV-1), is a major blinding disease in developed countries. HSV-1 can remain latent in the host for life and cannot be eradicated. The infection causes the secretion of various cytokines and aggregation of inflammatory cells. In the early stage of inflammation, mainly neutrophils infiltrate the cornea, and CD4⁺ T cells mediate the immunopathological changes in herpetic stromal keratitis in the subsequent progression. The STING/IRF3-mediated type I interferon (IFN) response can effectively inhibit viral replication and control infection, but the activity of STING is affected by various ubiquitination modifications. In this study, we found that the expression of RNF5 was elevated in corneal tissues and corneal epithelial cells after infection with HSV-1. Immunofluorescence staining confirmed that RNF5 was mainly expressed in the corneal epithelial layer. We silenced and overexpressed RNF5 expression in corneal epithelial cells and then inoculated them with HSV-1. We found that the expressions of STING, p-IRF3, p-TBK1, and IFN-β mRNA increased after RNF5 silencing. The opposite results were obtained after RNF5 overexpression. We also used siRNA to silence RNF5 in the mouse cornea and then established the HSK model. Compared with the siRNA-control group, the siRNA-RNF5 group showed significantly improved corneal inflammation, reduced clinical scores and tear virus titers, and significantly increased corneal IFN-β expression. In addition, the expressions of the proinflammatory cytokines IL-6 and TNF-α in the corneal tissue were significantly decreased, indicating that RNF5 silencing could effectively promote IFN-I expression, inhibit virus replication, alleviate inflammation, and reduce corneal inflammatory damage. In summary, our results suggest that RNF5 limits the type I IFN antiviral response in HSV corneal epithelitis by inhibiting STING/IRF3 signaling.

Intramuscular Vaccination With the HSV-1(VC2) Live-Attenuated Vaccine Strain Confers Protection Against Viral Ocular Immunopathogenesis Associated With γδT Cell Intracorneal Infiltration

Herpes simplex virus type-1 (HSV-1) ocular infection is one of the leading causes of infectious blindness in developed countries. The resultant herpetic keratitis (HK) is caused by an exacerbated reaction of the adaptive immune response that persists beyond virus clearance causing substantial damage to the cornea. Intramuscular immunization of mice with the HSV-1(VC2) live-attenuated vaccine strain has been shown to protect mice against lethal ocular challenge. Herein, we show that following ocular challenge, VC2 vaccinated animals control ocular immunopathogenesis in the absence of neutralizing antibodies on ocular surfaces. Ocular protection is associated with enhanced intracorneal infiltration of γδ T cells compared to mock-vaccinated animals. The observed γδ T cellular infiltration was inversely proportional to the infiltration of neutrophils, the latter associated with exacerbated tissue damage. Inhibition of T cell migration into ocular tissues by the S1P receptors agonist FTY720 produced significant ocular disease in vaccinated mice and marked increase in neutrophil infiltration. These results indicate that ocular challenge of mice immunized with the VC2 vaccine induce a unique ocular mucosal response that leads into the infiltration of γδ T cells resulting in the amelioration of infection-associated immunopathogenesis.

Pathogenesis and virulence of herpes simplex virus

Two of the most prevalent human viruses worldwide, herpes simplex virus type 1 and type 2 (HSV-1 and HSV-2, respectively), cause a variety of diseases, including cold sores, genital herpes, herpes stromal keratitis, meningitis and encephalitis. The intrinsic, innate and adaptive immune responses are key to control HSV, and the virus has developed mechanisms to evade them. The immune response can also contribute to pathogenesis, as observed in stromal keratitis and encephalitis. The fact that certain individuals are more prone than others to suffer severe disease upon HSV infection can be partially explained by the existence of genetic polymorphisms in humans. Like all herpesviruses, HSV has two replication cycles: lytic and latent. During lytic replication HSV produces infectious viral particles to infect other cells and organisms, while during latency there is limited gene expression and lack of infectious virus particles. HSV establishes latency in neurons and can cause disease both during primary infection and upon reactivation. The mechanisms leading to latency and reactivation and which are the viral and host factors controlling these processes are not completely understood. Here we review the HSV life cycle, the interaction of HSV with the immune system and three of the best-studied pathologies: Herpes stromal keratitis, herpes simplex encephalitis and genital herpes. We also discuss the potential association between HSV-1 infection and Alzheimer's disease.

Adjunctive Thymosin Beta-4 Treatment Influences MΦ Effector Cell Function to Improve Disease Outcome in Pseudomonas aeruginosa-Induced Keratitis

Our previous work has shown that topical thymosin beta 4 (Tβ4) as an adjunct to ciprofloxacin treatment reduces inflammatory mediators and inflammatory cell infiltrates (neutrophils/PMN and macrophages/MΦ) while enhancing bacterial killing and wound healing pathway activation in an experimental model of P. aeruginosa-induced keratitis. This study aimed to mechanistically examine how Tβ4 influences MΦ function in particular, leading to reduced inflammation and enhanced host defense following P. aeruginosa-induced infection of the cornea. Flow cytometry was conducted to profile the phenotype of infiltrating MΦ after infection, while generation of reactive nitrogen species and markers of efferocytosis were detected to assess functional activity. In vitro studies were performed utilizing RAW 264.7 cells to verify and extend the in vivo findings. Tβ4 treatment decreases MΦ infiltration and regulates the activation state in response to infected corneas. MΦ functional data demonstrated that the adjunctive Tβ4 treatment group significantly downregulated reactive nitrogen species (RNS) production and efferocytotic activity. In addition, the in vitro studies showed that both Tβ4 alone and adjunctive Tβ4 treatment influenced MΦ cellular function following LPS stimulation. Collectively, these data provide further evidence that adjunctive Tβ4 + ciprofloxacin treatment offers a more efficacious option for treating bacterial keratitis. Not only does the adjunctive therapy address both the infectious pathogen and corneal wound healing response, but it also influences MΦ infiltration, activation, and function, as revealed by the current study.

Local Immune Control of Latent Herpes Simplex Virus Type 1 in Ganglia of Mice and Man

Herpes simplex virus type 1 (HSV-1) is a prevalent human pathogen. HSV-1 genomes persist in trigeminal ganglia neuronal nuclei as chromatinized episomes, while epithelial cells are typically killed by lytic infection. Fluctuations in anti-viral responses, broadly defined, may underlay periodic reactivations. The ganglionic immune response to HSV-1 infection includes cell-intrinsic responses in neurons, innate sensing by several cell types, and the infiltration and persistence of antigen-specific T-cells. The mechanisms specifying the contrasting fates of HSV-1 in neurons and epithelial cells may include differential genome silencing and chromatinization, dictated by variation in access of immune modulating viral tegument proteins to the cell body, and protection of neurons by autophagy. Innate responses have the capacity of recruiting additional immune cells and paracrine activity on parenchymal cells, for example via chemokines and type I interferons. In both mice and humans, HSV-1-specific CD8 and CD4 T-cells are recruited to ganglia, with mechanistic studies suggesting active roles in immune surveillance and control of reactivation. In this review we focus mainly on HSV-1 and the TG, comparing and contrasting where possible observational, interventional, and in vitro studies between humans and animal hosts.

Nitric Oxide Interaction with the Eye

Nitric oxide (NO) is acknowledged as a vital intercellular messenger in multiple systems in the body. Medicine has focused on its functions and therapeutic applications for decades, especially in cardiovascular and nervous systems, and its role in immunological responses. This review was composed to demonstrate the prevalence of NO in components of the ocular system, including corneal cells and multiple cells in the retina. It discussed NO's assistance during the immune, inflammation and wound-healing processes. NO is identified as a vascular endothelial relaxant that can alter the choroidal blood flow and prompt or suppress vascular changes in age-related macular degeneration and diabetes, as well as the blood supply to the optic nerve, possibly influencing the progression of glaucoma. It will provide a deeper understanding of the role of NO in ocular homeostasis, the delicate balance between overproduction or underproduction and the effect on the processes from aqueous outflow and subsequent intraocular pressure to axial elongation and the development of myopia. This review also recognized the research and investigation of therapies being developed to target the NO complex and treat various ocular diseases.

The role of nitric oxide in ocular surface physiology and pathophysiology

Nitric oxide (NO) has a wide array of biological functions including the regulation of vascular tone, neurotransmission, immunomodulation, stimulation of proinflammatory cytokine expression and antimicrobial action. These functions may depend on the type of isoform that is responsible for the synthesis of NO. NO is found in various ocular tissues playing a pivotal role in physiological mechanisms, namely regulating vascular tone in the uvea, retinal blood circulation, aqueous humor dynamics, neurotransmission and phototransduction in retinal layers. Unregulated production of NO in ocular tissues may result in production of toxic superoxide free radicals that participate in ocular diseases such as endotoxin-induced uveitis, ischemic proliferative retinopathy and neurotoxicity of optic nerve head in glaucoma. However, the role of NO on the ocular surface in mediating physiology and pathophysiological processes is not fully understood. Moreover, methods used to measure levels of NO in the biological samples of the ocular surface are not well established due to its rapid oxidation. The purpose of this review is to highlight the role of NO in the physiology and pathophysiology of ocular surface and propose suitable techniques to measure NO levels in ocular surface tissues and tears. This will improve the understanding of NO's role in ocular surface biology and the development of new NO-based therapies to treat various ocular surface diseases. Further, this review summarizes the biochemistry underpinning NO's antimicrobial action.

The Role of Tissue Resident Memory CD4 T Cells in Herpes Simplex Viral and HIV Infection

Tissue-resident memory T cells (TRM) were first described in 2009. While initially the major focus was on CD8+ TRM, there has recently been increased interest in defining the phenotype and the role of CD4+ TRM in diseases. Circulating CD4+ T cells seed CD4+ TRM, but there also appears to be an equilibrium between CD4+ TRM and blood CD4+ T cells. CD4+ TRM are more mobile than CD8+ TRM, usually localized deeper within the dermis/lamina propria and yet may exhibit synergy with CD8+ TRM in disease control. This has been demonstrated in herpes simplex infections in mice. In human recurrent herpes infections, both CD4+ and CD8+ TRM persisting between lesions may control asymptomatic shedding through interferon-gamma secretion, although this has been more clearly shown for CD8+ T cells. The exact role of the CD4+/CD8+ TRM axis in the trigeminal ganglia and/or cornea in controlling recurrent herpetic keratitis is unknown. In HIV, CD4+ TRM have now been shown to be a major target for productive and latent infection in the cervix. In HSV and HIV co-infections, CD4+ TRM persisting in the dermis support HIV replication. Further understanding of the role of CD4+ TRM and their induction by vaccines may help control sexual transmission by both viruses.

Systemic IL-1β production as a consequence of corneal HSV-1 infection-contribution to the development of herpes simplex keratitis

This study sought to identify potential therapeutic targets in herpes simplex keratitis (HSK) patients with active and inactive infection by investigating peripheral cytokine production. Peripheral blood mononuclear cells (PBMCs) and serum were prepared from healthy controls and HSK patients during active infection or following treatment (inactive infection). Serum antibody titres were determined by ELISA. Protein expression levels were analysed by Western blot. Cytokine levels were determined by multiplex ELISA. Active corneal herpes simplex virus type 1 (HSV-1) infection resulted in significantly elevated peripheral levels of IL-1β in HSK patients compared to healthy controls, and remained significantly increased following treatment. Elevated production of IL-1β in inactive patients was associated with significantly increased levels of IRF3 and STAT1, key proteins involved in promoting anti-viral immune responses. Our data suggest that inflammation persists beyond the period that it is clinically evident and that enhanced peripheral production of IL-1β may have implications for HSV-1 viral clearance in active and inactive HSK patients.

Pancreas of coxsackievirus-infected dams and their challenged pups: A complex issue

Enteroviral infections are frequent, often asymptomatic in humans and during gravidity.

The present study is an extension of our previous investigations where we had shown pancreatitis in challenged pups of CVB4-E2-infected dams. Present investigation describes the effect of gestational infection with this virus on the pancreas of both dams and their challenged pups. Gravid CD1 outbred mice were orally infected with CVB4-E2 virus at different gestation times. Pups were challenged orally with the same virus after 25 days of birth. Organs were collected at selected intervals postinfection (p.i.), and replicating virus and viral-RNA copies were analyzed. Additional readouts included histopathology and immunohistochemical (IHC) analysis for localization and identification of Ly6G+ cells (neutrophils), CD11b+ cells (macrophages), and viral protein in pancreatic tissue sections of the infected dams and their challenged pups. Our results show the presence of replicating virus in the pancreas of infected dams and their challenged pups, with inflammation leading to chronic necrotizing pancreatitis and atrophy of pancreatic acini of the dams and their offspring. IHC analysis of the infiltrating cells showed pronounced Ly6G+ neutrophils in dams only, whereas CD11b+ macrophages were present in tissues of both, the pups and the dams. Time of infection during gravidity as well as the p.i. intervals when mice were sacrificed influenced the pancreatic pathophysiology in both groups. We conclude that coxsackievirus infection during pregnancy is a risk factor for chronic affliction of the exocrine tissue and could affect endocrine pancreas in the mother and child.

The Role of T Cells in Herpes Stromal Keratitis

The blinding inflammatory lesion stromal keratitis (SK), which occurs in some patients in response to ocular herpes simplex virus (HSV) infection, represents mainly an immune cell mediated inflammatory response to the virus infection. The principal orchestrators of the immunopathological lesions are T cells although additional events participate that include the extent of recruitment of non-lymphoid cells, the extent of neoangiogenesis, and the extent of damage to nerve function. This review focuses on evidence that the balance of the functional subsets of T cells has a major impact on lesion severity and duration. Accordingly, if proinflammatory Th1 and Th17 CD4 T cells, and perhaps in some cases CD8 T cells, predominate lesions occur earlier and are more severe. Lesions are diminished when cells with regulatory function predominate. Moreover, when regulatory cells acquire the property to produce Amphiregulin this may facilitate lesion resolution. An objective to controlling lesions is to learn how to manipulate the balance of T cells to favor the representation and function of regulatory T cells and their products over proinflammatory cells. In this review we emphasize how exploiting the differential metabolic requirements of immune cells could be a valuable approach to control SK.

Pathogenesis of herpes simplex keratitis: The host cell response and ocular surface sequelae to infection and inflammation

Herpes simplex virus type 1 (HSV) keratitis is a leading cause of infectious blindness. Clinical disease occurs variably throughout the cornea from epithelium to endothelium and recurrent HSV stromal keratitis is associated with corneal scarring and neovascularization. HSV keratitis can be associated with ocular pain and subsequent neutrophic keratopathy. Host cell interactions with HSV trigger an inflammatory cascade responsible not only for clearance of virus but also for progressive corneal opacification due to inflammatory cell infiltrate, angiogenesis, and corneal nerve loss. Current antiviral therapies target viral replication to decrease disease duration, severity and recurrence, but there are limitations to these agents. Therapies directed towards viral entry into cells, protein synthesis, inflammatory cytokines and vascular endothelial growth factor pathways in animal models represent promising new approaches to the treatment of recurrent HSV keratitis.

Role of Herpes Simplex Virus Type 1 (HSV-1) Glycoprotein K (gK) Pathogenic CD8+ T Cells in Exacerbation of Eye Disease

HSV-1-induced corneal scarring (CS), also broadly referred to as Herpes Stromal Keratitis (HSK), is the leading cause of infectious blindness in developed countries. It is well-established that HSK is in fact an immunopathological disease. The contribution of the potentially harmful T cell effectors that lead to CS remains an area of intense study. Although the HSV-1 gene(s) involved in eye disease is not yet known, we have demonstrated that gK, which is one of the 12 known HSV-1 glycoproteins, has a crucial role in CS. Immunization of HSV-1 infected mice with gK, but not with any other known HSV-1 glycoprotein, significantly exacerbates CS, and dermatitis. The gK-induced eye disease occurs independently of the strain of the virus or mouse. HSV-1 mutants that lack gK are unable to efficiently infect and establish latency in neurons. HSV-1 recombinant viruses expressing two additional copies of the gK (total of three gK genes) exacerbated CS as compared with wild type HSV-1 strain McKrae that contains one copy of gK. Furthermore, we have shown that an 8mer (ITAYGLVL) within the signal sequence of gK enhanced CS in ocularly infected BALB/c mice, C57BL/6 mice, and NZW rabbits. In HSV-infected “humanized” HLA-A^*0201 transgenic mice, this gK 8mer induced strong IFN-γ-producing cytotoxic CD8⁺ T cell responses. gK induced CS is dependent on gK binding to signal peptide peptidase (SPP). gK also binds to HSV-1 UL20, while UL20 binds GODZ (DHHC3) and these quadruple interactions are required for gK induced pathology. Thus, potential therapies might include blocking of gK-SPP, gK-UL20, UL20-GODZ interactions, or a combination of these strategies.

Application of our understanding of pathogenesis of herpetic stromal keratitis for novel therapy

HSV-1 ocular infection can cause herpes stromal keratitis (SK), an immunopathological lesion. Frequent recurrences can lead to progressive corneal scaring which can result in vision impairment if left untreated. Currently, the acute and epithelial forms of SK are usually controlled using anti-viral drugs. However, chronic forms of SK which are inflammatory in nature, require the addition of a topical corticosteroid to the anti-viral treatment regimen. In this review, we highlight the essential events involved in SK pathogenesis which can be targeted for improved therapy. We also examine some approaches which can be combined with the current treatments to effectively control SK.

Murine Corneal Inflammation and Nerve Damage After Infection With HSV-1 Are Promoted by HVEM and Ameliorated by Immune-Modifying Nanoparticle Therapy

Purpose

To determine cellular and temporal expression patterns of herpes virus entry mediator (HVEM, Tnfrsf14) in the murine cornea during the course of herpes simplex virus 1 (HSV-1) infection, the impact of this expression on pathogenesis, and whether alterations in HVEM or downstream HVEM-mediated effects ameliorate corneal disease.

Methods

Corneal HVEM levels were assessed in C57BL/6 mice after infection with HSV-1(17). Leukocytic infiltrates and corneal sensitivity loss were measured in the presence, global absence (HVEM knockout [KO] mice; Tnfrsf14-/-), or partial absence of HVEM (HVEM conditional KO). Effects of immune-modifying nanoparticles (IMPs) on viral replication, corneal sensitivity, and corneal infiltrates were measured.

Results

Corneal HVEM+ populations, particularly monocytes/macrophages during acute infection (3 days post infection [dpi]) and polymorphonuclear neutrophils (PMN) during the chronic inflammatory phase (14 dpi), increased after HSV-1 infection. Herpes virus entry mediator increased leukocytes in the cornea and corneal sensitivity loss. Ablation of HVEM from CD45+ cells, or intravenous IMP therapy, reduced infiltrates in the chronic phase and maintained corneal sensitivity.

Conclusions

Herpes virus entry mediator was expressed on two key populations: corneal monocytes/macrophages and PMNs. Herpes virus entry mediator promoted the recruitment of myeloid cells to the cornea in the chronic phase. Herpes virus entry mediator-associated corneal sensitivity loss preceded leukocytic infiltration, suggesting it may play an active role in recruitment. We propose that HVEM on resident corneal macrophages increases nerve damage and immune cell invasion, and we showed that prevention of late-phase infiltration of PMN and CD4+ T cells by IMP therapy improved clinical symptoms and mortality and reduced corneal sensitivity loss caused by HSV-1.

Nitric oxide secretion in human conjunctival fibroblasts is inhibited by alpha linolenic acid

Purpose

It is known that both human conjunctival fibroblasts (HCF) and corneal epithelial (HCE) cells contribute to the inflammatory process in the ocular surface by releasing inflammatory cytokines. In addition, nitric oxide (NO) has an important role in inflammatory responses in the ocular surface. In the present study, we aimed to characterize the capacity of these cells to release nitric oxide in response to cytokines and Lipopolysaccharide (LPS), and show that Alpha-linoleic acid (ALA) inhibits these responses.

Methods

HCF, HCE cells, peripheral blood mononuclear cells (PBMCs) and co-culture of HCF and PBMC were treated with different combinations of inflammatory inducers, including interleukin)IL- (6, tumor necrosis factors (TNF)-α, interferon (IFN)- γ and IL-1β and LPS. Nitrite levels were measured in cell supernatants with and without ALA by the Griess reaction test at 24, 48 and 72 h respectively. Expression of nitric oxide synthase 2 (NOS-2) was evaluated by real-time PCR.

Results

All cytokine combinations had an inducible effect on nitrite secretion in HCF, PBMC and co-cultured PBMC and HCF, but not in HCE cells. Treatment with a combination of IL-6, LPS, TNF-α, IFN- γ and IL-1β induced the highest nitrite secretion (2.91 fold, P < 0.01) as compared to cells incubated in medium alone. nitrite secretion was reduced by 38.9 % (P < 0.05) after treatment with ALA alone. Co-culturing PBMC with HCF with and without ALA treatment demonstrated similar results in nitrite level as,compared to PBMC alone. In addition, ALA significantly decreased NOS-2 expression in HCF by 48.9 % (P < 0. 001) after 72 h.

Conclusions

The decrease in nitrite release and inhibition of NOS-2 expression indicate that ALA may have an anti-inflammatory effect both on HCF and on peripheral immune cells. This indicates that ALA may serve as a potent anti-inflammatory agent in ocular surface inflammation.

Herpesvirus entry mediator on radiation-resistant cell lineages promotes ocular herpes simplex virus 1 pathogenesis in an entry-independent manner

Ocular herpes simplex virus 1 (HSV-1) infection leads to a potentially blinding immunoinflammatory syndrome, herpes stromal keratitis (HSK). Herpesvirus entry mediator (HVEM), a widely expressed tumor necrosis factor (TNF) receptor superfamily member with diverse roles in immune signaling, facilitates viral entry through interactions with viral glycoprotein D (gD) and is important for HSV-1 pathogenesis. We subjected mice to corneal infection with an HSV-1 mutant in which HVEM-mediated entry was specifically abolished and found that the HVEM-entry mutant produced clinical disease comparable to that produced by the control virus. HVEM-mediated induction of corneal cytokines, which correlated with an HVEM-dependent increase in levels of corneal immune cell infiltrates, was also gD independent. Given the complexity of HVEM immune signaling, we used hematopoietic chimeric mice to determine which HVEM-expressing cells mediate HSV-1 pathogenesis in the eye. Regardless of whether the donor was a wild-type (WT) or HVEM knockout (KO) strain, HVEM KO recipients were protected from ocular HSV-1, suggesting that HVEM on radiation-resistant cell types, likely resident cells of the cornea, confers wild-type-like susceptibility to disease. Together, these data indicate that HVEM contributes to ocular pathogenesis independently of entry and point to an immunomodulatory role for this protein specifically on radiation-resistant cells.

Immune privilege is maintained in the eye in order to protect specialized ocular tissues, such as the translucent cornea, from vision-reducing damage. Ocular herpes simplex virus 1 (HSV-1) infection can disrupt this immune privilege, provoking a host response that ultimately brings about the majority of the damage seen with the immunoinflammatory syndrome herpes stromal keratitis (HSK). Our previous work has shown that HVEM, a host TNF receptor superfamily member that also serves as a viral entry receptor, is a critical component contributing to ocular HSV-1 pathogenesis, although its precise role in this process remains unclear. We hypothesized that HVEM promotes an inflammatory microenvironment in the eye through immunomodulatory actions, enhancing disease after ocular inoculation of HSV-1. Investigating the mechanisms responsible for orchestrating this aberrant immune response shed light on the initiation and maintenance of HSK, one of the leading causes of infectious blindness in the developed world.

Enhanced neutrophil activity is associated with shorter time to tumor progression in glioblastoma patients

Glioblastoma multiforme (GBM) is a highly malignant tumor with a poor outcome that is often positive for human cytomegalovirus (HCMV). GBM patients often have excessive numbers of neutrophils and macrophages near and within the tumor. Here, we characterized the cytokine patterns in the blood of GBM patients with and without Valganciclovir treatment. Furthermore, we determined whether neutrophil activation is related to HCMV status and patient outcome. Blood samples for analyses of cytokines and growth factors were collected from 42 GBM patients at the time of diagnosis (n = 42) and at weeks 12 and 24 after surgery. Blood neutrophils of 28 GBM patients were examined for CD11b expression. The levels of pro- and anti-inflammatory cytokines and chemokines-including interleukin (IL)-1β, IL-2, IL-6, IL-8, IL-10, IL-12p70, IL-17A, transforming growth factor (TGF)-β1, interferon-γ, interferon-α, tumor necrosis factor α, and monocyte chemoattractant protein (MCP)-1were analyzed with a bead-based flow cytometry assay. During the first six months after surgery, neutrophil activity was increased in 12 patients and was unchanged or decreased in 16. Patients with increased neutrophil activity had enhanced IL-12p70, high grade HCMV and a shorter time to tumor progression (TTP) than patients without or decreased neutrophil activity (median TTP; 5.4 vs. 12 months, 95% confidence interval; 1.6-10 vs. 0.1-0.6, hazard ratio = 3 vs. 0.4, p = 0.004). The levels of IL-12p70 were significantly decreased in Valganciclovir treated patients (n = 22, T 12W vs. T 24W, p = 0.03). In conclusion, our findings suggest that neutrophil activation is an early sign of tumor progression in GBM patients.

Role of miR-155 in the pathogenesis of herpetic stromal keratitis

Ocular infection with herpes simplex virus 1 can result in a chronic immunoinflammatory stromal keratitis (SK) lesion that is a significant cause of human blindness. A key to controlling SK lesion severity is to identify cellular and molecular events responsible for tissue damage and to manipulate them therapeutically. Potential targets for therapy are miRNAs, but these are minimally explored especially in responses to infection. Here, we demonstrated that Mir155 expression was up-regulated after ocular herpes simplex virus 1 infection, with the increased Mir155 expression occurring mainly in macrophages and CD4(+) T cells and to a lesser extent in neutrophils. In vivo studies indicated that Mir155 knockout mice were more resistant to herpes SK with marked suppression of T helper cells type 1 and 17 responses both in the ocular lesions and the lymphoid organs. The reduced SK lesion severity was reflected by increased phosphatidylinositol-3,4,5-trisphosphate 5-phosphatase 1 and interferon-γ receptor α-chain levels in activated CD4(+) T cells in the lymph nodes. Finally, in vivo silencing of miR-155 by the provision of antagomir-155 nanoparticles to herpes simplex virus 1-infected mice led to diminished SK lesions and corneal vascularization. In conclusion, our results indicate that miR-155 contributes to the pathogenesis of SK and represents a promising target to control SK severity.

Animal models of herpes simplex virus immunity and pathogenesis

Herpes simplex viruses are ubiquitous human pathogens represented by two distinct serotypes: herpes simplex virus (HSV) type 1 (HSV-1); and HSV type 2 (HSV-2). In the general population, adult seropositivity rates approach 90% for HSV-1 and 20-25% for HSV-2. These viruses cause significant morbidity, primarily as mucosal membrane lesions in the form of facial cold sores and genital ulcers, with much less common but more severe manifestations causing death from encephalitis. HSV infections in humans are difficult to study in many cases because many primary infections are asymptomatic. Moreover, the neurotropic properties of HSV make it much more difficult to study the immune mechanisms controlling reactivation of latent infection within the corresponding sensory ganglia and crossover into the central nervous system of infected humans. This is because samples from the nervous system can only be routinely obtained at the time of autopsy. Thus, animal models have been developed whose use has led to a better understanding of multiple aspects of HSV biology, molecular biology, pathogenesis, disease, and immunity. The course of HSV infection in a spectrum of animal models depends on important experimental parameters including animal species, age, and genotype; route of infection; and viral serotype, strain, and dose. This review summarizes the animal models most commonly used to study HSV pathogenesis and its establishment, maintenance, and reactivation from latency. It focuses particularly on the immune response to HSV during acute primary infection and the initial invasion of the ganglion with comparisons to the events governing maintenance of viral latency.

Corneal lymphangiogenesis in herpetic stromal keratitis

Corneal lymphangiogenesis is the extension of lymphatic vessels into the normally alymphatic cornea, a process that compromises the cornea's immune-privileged state and facilitates herpetic stromal keratitis (HSK). HSK results most commonly from infection by herpes simplex virus-1 (HSV-1) and is characterized by immune- and inflammation-mediated damage to the deep layers of the cornea. Current research demonstrates the potential of anti-lymphangiogenic therapy to decrease and prevent herpes-induced lymphangiogenesis.

Who pays the toll for solving the enigma of corneal herpes?

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-γ (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.

Potential function of miRNAs in herpetic stromal keratitis

MicroRNAs (miRNAs), the newly discovered regulators of gene expression, act by promoting degradation of mRNA and/or by inhibiting protein expression. Dysregulation of miRNA expression has been noted in an expanding number of diseases; and in some instances, manipulating miRNA expression holds promise as a new form of therapy. Herpetic stromal keratitis (HSK) is an important vision-impairing lesion and currently any role that miRNA dysregulation plays during its pathogenesis is only just beginning to be investigated. In this review, we discuss the likely participation of specific miRNAs during HSK and discuss the prospect of modulating their expression as a means of therapy.

Interleukin-17 enhanced immunoinflammatory lesions in a mouse model of recurrent herpetic keratitis

Interleukin-17 (IL-17), mainly produced by activated (memory) T cells, has been found in the corneas from herpetic stromal keratitis (HSK) patients. To better understand the role of IL-17 and to optimize fidelity to human recurrent HSK, in this study, we utilized a mouse model of recurrent HSK, examined the expression of IL-17 and Th17 cells, and determine the alterability of virus-induced corneal inflammation after anti-IL-17 antibody treatment during murine recurrent HSK. We found that Th17 cells were obviously up-regulated in both cornea and DLNs of recurrent mice. Peak IL-17 protein present in recurrent cornea in conjunction with peak opacity mediated by CD4(+) T cells. Systemic administration of anti-IL-17 antibody resulted in a diminished severity of corneal opacity, neovascularization, and CD4(+) T cells infiltration compared to control. Anti-IL-17 treatment down-regulated the mRNA and protein levels of TNF-α expression in recurrent corneas, and decreased HSV-specific DTH responses. Our results indicate that elevated IL-17 expression may be involved in the development of recurrent HSK. The likely mechanisms of action for IL-17 are through up-regulating TNF-α expression and promoting HSV-specific DTH responses. Thus, IL-17 might constitute a useful target for therapeutic intervention in recurrent HSK.

Substance P in the corneal stroma regulates the severity of herpetic stromal keratitis lesions

PURPOSE

To determine whether substance P (SP) in herpes simplex virus-1 (HSV-1) infected cornea regulates the severity of herpetic stromal keratitis (HSK) lesions in a mouse model.

METHODS

C57BL/6 mice were infected ocularly with HSV-1 (RE). The corneas with HSK lesions, on Day 15 postinfection, were grouped on the basis of the corneal opacity as mild (≤2) or severe (>2). The amount of SP was determined in the corneas with mild or severe HSK lesions by enzyme immunosorbent assay (EIA) and confocal microscopy. Subconjunctival inoculation of spantide I, SP receptor antagonist, was carried out during the clinical phase of HSK. ELISA and flow cytometry were used to determine the level of cytokines, chemokines, and influx of immune cell types in the corneal lesions.

RESULTS

The authors determined a significantly higher level of SP in the corneas with severe HSK lesions in comparison with mild lesions. The corneas with a higher level of SP also exhibited higher amounts of proinflammatory cytokines (IL-6, IFN-γ) and chemokines (CCL3, CXCL2) when compared with the corneas with a lower level of SP. SP receptor NK1R expression was determined in CD45- and CD45+ cells in infected cornea. SP present in the corneal stroma of the eyes with severe HSK lesions colocalized with β-III tubulin(+) and IA(b+) cell types. Subconjunctival inoculation of spantide I during the clinical phase of HSK resulted in significant reduction in the corneal opacity and angiogenesis.

CONCLUSIONS

Collectively, these results demonstrate the relative contribution of substance P in regulating the clinical severity of HSK lesions in a mouse model.

Significance of lipid mediators in corneal injury and repair

Corneal injury induces an inflammatory reaction and damages the sensory nerves that exert trophic influences in the corneal epithelium. Alterations in normal healing disrupt the integrity and function of the tissue with undesirable consequences, ranging from dry eye and loss of transparency to ulceration and perforation. Lipids play important roles in this complex process. Whereas lipid mediators such as platelet activating factor (PAF) and cyclooxygenease-2 metabolites contribute to tissue damage and neovascularization, other mediators, such as the lipoxygenase (LOX) derivatives from arachidonic acid, 12- and 15-hydroxy/hydroperoxyeicosatetraenoic acids, and lipoxin A4, act as second messengers for epidermal growth factor to promote proliferation and repair. Stimulation of the cornea with pigment epithelial derived factor in the presence of docosahexaenoic acid gives rise to the synthesis of neuroprotectin D1, a derivative of LOX activity, and increases regeneration of corneal nerves. More knowledge about the role that lipids play in corneal wound healing can provide insight into the development of new therapeutic approaches for treating corneal injuries. PAF antagonists, lipoxins, and neuroprotectins can be effective therapeutic tools for maintaining the integrity of the cornea.

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.

Neutrophils protect the retina of the injected eye from infection after anterior chamber inoculation of HSV-1 in BALB/c mice

PURPOSE

To determine whether infiltrating polymorphonuclear leukocytes PMNs play a role in preventing early direct anterior-to-posterior spread of herpes simplex virus (HSV)-1 and/or in preventing the spread of HSV-1 from the brain back to the retina of the injected eye after anterior chamber (AC) inoculation.

METHODS

BALB/c mice were treated with monoclonal antibody RB6-8C5 (Gr-1) against PMNs or control IgG and inoculated with HSV-1.

RESULTS

In Gr-1-treated mice, PMNs were depleted in the peripheral blood and in the HSV-1-infected eye. More virus (2-3 logs) was recovered from the inoculated eye of Gr-1 antibody-treated mice than from control mice. Immunohistochemistry revealed disseminated virus-infected cells in the junction between the anterior and the posterior segment and also in the posterior segment of the HSV-1-inoculated eye in Gr-1-treated mice. In control IgG-treated mice, virus-infected cells were observed only within the AC. More virus (3 logs) was recovered from the contralateral suprachiasmatic nucleus (SCN), and increased virus staining was observed in the ipsilateral optic nerve of Gr-1-treated mice compared with control mice. In Gr-1-treated mice, the central retina was virus-infected in a patchy fashion beginning on day 7 post infection (pi), and the infection progressed to involve the entire retina.

CONCLUSIONS

Since both direct anterior-to-posterior spread of virus and spread via the optic nerve occurred in PMN-depleted mice, these results suggest that PMNs play an important role both in limiting intraocular spread of virus in the injected eye and in controlling spread of the virus from the brain into the optic nerve and retina of the injected eye.

CXCR2 is required for neutrophil recruitment to the lung during influenza virus infection, but is not essential for viral clearance

Neutrophils traffic to the lungs in large numbers during influenza virus infection. Although the ability of these cells to respond to numerous chemotactic stimuli has been described in other systems, the chemokine receptors mediating recruitment of neutrophils to the lungs during influenza virus infection and the role of this cell type in viral clearance are currently undefined. In the present study, we used CXCR2(/) mice to investigate the role of the chemokine receptor CXCR2 in neutrophil recruitment to the lungs during influenza virus infection and to determine the role of neutrophils in viral clearance. We infected CXCR2(/) or wild-type mice with influenza and assessed the level of inflammation, the cellular composition of the inflammatory infiltrate, and viral titers in the lungs. Absence of CXCR2 ablated neutrophil recruitment to the lungs, but had no effect on peak viral titers or on the kinetics of viral clearance. Thus, it appears that CXCR2 is the major receptor mediating neutrophil trafficking to the lung during influenza virus infection, but that neutrophils do not play an essential role in viral clearance.

Topical antisense-oligonucleotides targeting IFN-gamma mRNA improve incidence and severity of herpetic stromal keratitis by cytokine specific and sequence unspecific effects

BACKGROUND

Corneal infection with herpes simplex virus-1 (HSV) can cause an inflammatory eye disease termed herpetic stromal keratitis (HSK). Interferon-gamma (IFN-gamma) is known to be involved in the development of this disease. In this study, antisense oligonucleotides targeting IFN-gamma mRNA (IFN-gamma-ASON) were investigated for their effects in experimental HSK.

METHODS

Splenic cells were used to examine the efficacy of IFN-gamma-ASON to decrease IFN-gamma- release into the cell culture supernatants as measured by ELISA. Mice were corneally infected with 10(5) PFU HSV, and IFN-gamma-ASON were given subepithelially. Alternatively, mice were infected without any further treatment, received only buffer, or received control oligonucleotides (CON) to observe substance specific effects. The animals were followed up clinically for the signs of herpetic keratitis. On days 14 and 28 post infection (p.i.), animals were sacrificed, and eyes were collected for histological analysis. On day 7 p.i., infectious virus particles in the eyes were determined by a plaque assay.

RESULTS

While IFN-gamma-ASON diminished the content of IFN-gamma in a concentration-dependent manner in vitro, CON showed no significant effects. Whereas buffer-treated and only infected mice showed severe necrotizing keratitis on day 14 p.i., this was abolished after treatment with IFN-gamma-ASON, even after 28 and 52 days. CON-treated mice also showed an improved HSK on day 14, but not on day 28. The incidence of the disease was also clearly diminished after treatment with IFN-gamma-ASON at all time points examined. The number of inflammatory cells in both the central and the peripheral cornea were strongly reduced after the application of IFN-gamma-ASON as compared to the controls. In contrast, the infectious viral particles in eyes at day 7 p.i. did not differ between the four groups.

CONCLUSIONS

Topical treatment with IFN-gamma-ASON induced a long-term improvement of the course and the incidence of HSK in the murine model. IFN-gamma seems to be involved in a proinflammatory manner during the pathogenesis of HSK, while the antiviral defense against HSV was not affected by this topical cytokine inhibition. Unspecific CON induced a transient and cytokine independent improvement of HSK.

Cathelicidin-deficient (Cnlp -/- ) mice show increased susceptibility to Pseudomonas aeruginosa keratitis

PURPOSE

To examine the clinical progression and innate immune responses during Pseudomonas aeruginosa (PA) keratitis in cathelicidin-deficient (KO) mice.

METHODS

PA (ATCC 19660) keratitis was induced in KO mice and wild-type (WT) littermates generated on a 129/SVJ background. Clinical score and histopathology were used to monitor the progression of infection at postinfection (PI) days 1, 3, 7, 14, and 21. Mouse corneas were harvested for viable bacteria quantitation, and myeloperoxidase (MPO) assays were performed to determine the number of infiltrating neutrophils. ELISA was used to quantitate interleukin (IL)-1beta, IL-6, macrophage inflammatory peptide (MIP)-2, keratinocyte-derived chemokine (KC), tumor necrosis factor (TNF)-alpha, and vascular endothelial growth factor (VEGF) levels in the corneas.

RESULTS

WT mice were resistant (cornea healed), whereas KO mice showed increased susceptibility (corneas failed to recover by 21 days or perforated) to PA infection. Clinical scores were significantly elevated in the infected corneas of KO mice versus WT mice at 7, 14, and 21 days PI. Absence of cathelicidin resulted in significantly delayed clearance of PA in the cornea and an increased number of infiltrating neutrophils at 1, 3, 7, and 14 days PI. KO mice also exhibited differential expression of protein levels for IL-1beta, IL-6, MIP-2, KC, TNF-alpha, and VEGF up to day 21 PI compared with the WT mice.

CONCLUSIONS

Cathelicidin-deficient mice showed considerable susceptibility to PA keratitis. The present study demonstrates direct in vivo evidence that endogenous expression of cathelicidin provides defense against corneal PA infection indicating its importance in host innate immunity at the ocular surface.

On the influence of neutrophils in corneas with necrotizing HSV-1 keratitis following amniotic membrane transplantation

Necrotizing herpetic stromal keratitis (HSK) in mice rapidly improved after amniotic membrane transplantation (AMT). In this study we determined the fate of polymorphonuclear neutrophils (PMN) after AMT. AMT or tarsorrhaphy (T) was performed in BALB/c mice with ulcerative HSK. After 2 days, corneas were studied histologically and by transmission electron microscopy (TEM). CD11b, Gr-1, and TUNEL-positive cells were identified. Macrophages were depleted by subconjunctival injection of dichloromethylene-diphosphonate-liposomes (Cl(2)MDP-LIP) before AMT. Corneas were studied for interleukin (IL)-1alpha, IL-2, interferon (IFN)-gamma, CXCL1, CXCL2, and tumor necrosis factor (TNF)-alpha production by ELISA. PMN-enriched cell preparations co-cultured with amniotic membrane (AM) or with AM and such recombinant (r) cytokines as rIL-1alpha, rIL-2, and rTNF-alpha or supernatants from activated lymphocytes were investigated by flow cytometry (Annexin-V/7-AAD and TUNEL), and a dimethylthiazolyl-diphenyltetrazolium-bromide (MTT)-viability assay. Corneas in the AMT mice had less inflammation, fewer PMN-like cells and fewer CD11b+, and Gr-1+ cells (P<0.01), but a higher ratio of apoptotic to viable PMN-resembling cells (P<0.01) than the T mice. Phagocytic removal of apoptotic PMN-like cells by macrophages was evident in the AMT group. After Cl(2)MDP-LIP treatment, the corneas had more cell debris and apoptotic cells with PMN-like morphology. The concentrations of IL-1alpha, IL-2, CXCL1, and TNF-alpha were reduced in corneas of the AMT group as compared to that of the T group, while the concentration of CXCL2 was increased. Apoptosis of PMN-resembling cells was detected following cocultivation with AM, even when proinflammatory cytokines were present. Resolution of corneal inflammation in mice with necrotizing HSK after AMT is associated with increased apoptosis of PMN-like cells, reduction of pro-inflammatory cytokines, an increase of CXCL2, and increased removal of apoptotic PMN-like cells by macrophages.

Herpes simplex virus and the chemokines that mediate the inflammation

Herpes simplex viruses (HSV) are highly pervasive pathogens in the human host with a seroconversion rate upwards of 60% worldwide. HSV type 1 (HSV-1) is associated with the disease herpetic stromal keratitis, the leading cause of infectious corneal blindness in the industrialized world. Individuals suffering from genital herpes associated with HSV type 2 (HSV-2) are found to be two- to threefold more susceptible in acquiring human immunodeficiency virus (HIV). The morbidity associated with these infections is principally due to the inflammatory response, the development of lesions, and scarring. Chemokines have become an important aspect in understanding the host immune response to microbial pathogens due in part to the timing of expression. In this paper, we will explore the current understanding of chemokine production as it relates to the orchestration of the immune response to HSV infection.

Tumor necrosis factor (TNF) protects resistant C57BL/6 mice against herpes simplex virus-induced encephalitis independently of signaling via TNF receptor 1 or 2

Tumor necrosis factor (TNF) is a multifunctional cytokine that has a role in induction and regulation of host innate and adaptive immune responses. The importance of TNF antiviral mechanisms is reflected by the diverse strategies adopted by different viruses, particularly members of the herpesvirus family, to block TNF responses. TNF binds and signals through two receptors, Tnfrsf1a (TNF receptor 1 [TNFR1], or p55) and Tnfrsf1b (TNFR2, or p75). We report here that herpes simplex virus 1 (HSV-1) infection of TNF-/- mice on the resistant C57BL/6 genetic background results in significantly increased susceptibility (P < 0.0001, log rank test) to fatal HSV encephalitis (HSE) and prolonged persistence of elevated levels of virus in neural tissues. In contrast, although virus titers in neural tissues of p55-/- N13 mice were elevated to levels comparable to what was found for the TNF-/- mice, the p55-/- N13 mice were as resistant as control C57BL/6 mice (P > 0.05). The incidence of fatal HSE was significantly increased by in vivo neutralization of TNF using soluble TNFR1 (sTNFR1) or depletion of macrophages in C57BL/6 mice (P = 0.0038 and P = 0.0071, respectively). Strikingly, in vivo neutralization of TNF in HSV-1-infected p55-/- p75-/- mice by use of three independent approaches (treatment with soluble p55 receptor, anti-TNF monoclonal antibody, or in vivo small interfering RNA against TNF) resulted in significantly increased mortality rates (P = 0.005), comparable in magnitude to those for C57BL/6 mice treated with sTNFR1 (P = 0.0018). Overall, these results indicate that while TNF is required for resistance to fatal HSE, both p55 and p75 receptors are dispensable. Precisely how TNF mediates protection against HSV-1 mortality in p55-/- p75-/- mice remains to be determined.

Improvement of herpetic stromal keratitis with fumaric acid derivate is associated with systemic induction of T helper 2 cytokines

Fumaric acid derivates have been shown to stimulate T helper-2-cytokines (interleukin (IL)-4, -5) without affecting the T-helper-1-cytokine (IL-2, interferon (IFN)-gamma)-response. Herein, the influence of systemic treatment with the fumaric acid derivate dimethylfumarate (DMF) on the secretion of T helper-cytokines and the development of HSV-1 stromal keratitis (HSK) was studied in mice. The corneas from BALB/c mice were infected with 10(5) PFU of HSV-1 (KOS strain). While one group of mice was treated intraperitoneally with PBS, another group of mice received DMF at 15 mg/kg of body weight. Expression of IL-2, -4, -10 and IFN-gamma was analysed in HSV-1 activated lymphocytes by ELISA. The severity of epithelial and stromal herpetic keratitis was investigated clinically. Corneas were studied for the inflammatory cell infiltration, and the CD3-, CD4- and CD8-positive cells were analysed by immunohistochemistry. The IL-2, -4, 10 and IFN-gamma content was measured in the corneas. Virus replication in the eyes was analysed by a plaque-assay. The DTH-response, the HSV-specific T cell proliferation and the serum neutralizing antibody-titres were investigated. DMF increased IL-4 and IL-10, but not IL-2 and IFN-gamma, secretion in activated lymphocytes from the spleen. Incidence and severity of stromal HSV-1 keratitis was reduced in the DMF group (P < 0.01). In the corneas from DMF-treated mice, the numbers of CD3+ and CD4+ cells were decreased and IL-4 was increased. Severity of epithelial disease and the virus-clearance from the eyes did not differ between the PBS and DMF group of mice. DTH, HSV-specific T cell proliferation and the neutralizing antibody-titres were not impaired. DMF increased the T helper-2-cytokine secretion in activated lymphocytes. After corneal HSV-1 infection, corneas from DMF treated mice had increased IL-4 content. This is associated with an improvement of herpetic stromal keratitis and reduced corneal T cell infiltration. DMF did not impair the systemic antiviral response.

Role of inflammatory cytokine-induced cyclooxygenase 2 in the ocular immunopathologic disease herpetic stromal keratitis

Ocular infection with herpes simplex virus (HSV) results in a blinding immunoinflammatory stromal keratitis (SK) lesion. Early preclinical events include polymorphonuclear neutrophil (PMN) infiltration and neovascularization in the corneal stroma. We demonstrate here that HSV infection of the cornea results in the upregulation of the cyclooxygenase 2 (COX-2) enzyme. Early after infection, COX-2 was produced from uninfected stromal fibroblasts as an indirect effect of virus infection. Subsequently, COX-2 may also be produced from other inflammatory cells that infiltrate the cornea. The induction of COX-2 is a critical event, since inhibition of COX-2 with a selective inhibitor was shown to reduce corneal angiogenesis and SK severity. The administration of a COX-2 inhibitor resulted in compromised PMN infiltration into the cornea, as well as diminished corneal vascular endothelial growth factor levels, likely accounting for the reduced angiogenic response. COX-2 stimulation by HSV infection represents a critical early event accessible for therapy and the control of SK severity.

The role of viral and host genes in corneal infection with herpes simplex virus type 1

Herpes simplex virus infection of the eye is the leading cause of blindness due to infection in the US despite the availability of several antiviral drugs. Studies with animal models have shown that three factors, innate host resistance, the host adaptive immune response, and the strain of virus interact to determine whether an infection is asymptomatic or proceeds to the development of blinding keratitis (HSK). Of these, the role of adaptive immunity has received the most attention. This work has clearly shown that stromal keratitis is an immunopathological disease, most likely due to the induction of a delayed type hypersensitivity response. Substantially less is known about the role of specific host genes in resistance to HSK. The fact that different strains of virus display different disease phenotypes indicates that viral 'virulence' genes are critical. Of the 80 plus HSV genes, few have been formally tested for their role in HSV keratitis. Most studies of virulence genes to date have focused on a single gene or protein and large changes in disease phenotypes are usually measured. Large changes in the ability to cause disease are likely to reduce the fitness of the virus, thus such studies, although useful, do not mimic the natural situation. Viral gene products are known to interact with each other, and with host proteins and these interactions are critical in determining the outcome of infection. In reality, the 'constellation' of genes encoded by each particular strain is critical, and how this constellation of genes works together and with host proteins determines the outcome of an infection. The goal of this review is to discuss the current state of knowledge regarding the role of host and viral genes in HSV keratitis. The roles of specific genes that have been shown to influence keratitis are discussed. Recent data showing that different viral genes cooperate to influence disease severity and confirming that the constellation of genes within a particular strain determines the disease phenotype are also discussed, as are the methods used to test the role of viral genes in virulence. It will become apparent that there is a paucity of information regarding the function of many viral genes in keratitis. Improving our knowledge of the role of viral genes is critical for devising more effective treatments for this disease.

Macrophages and cytokines in the early defence against herpes simplex virus

Herpes simplex virus (HSV) type 1 and 2 are old viruses, with a history of evolution shared with humans. Thus, it is generally well-adapted viruses, infecting many of us without doing much harm, and with the capacity to hide in our neurons for life. In rare situations, however, the primary infection becomes generalized or involves the brain. Normally, the primary HSV infection is asymptomatic, and a crucial element in the early restriction of virus replication and thus avoidance of symptoms from the infection is the concerted action of different arms of the innate immune response. An early and light struggle inhibiting some HSV replication will spare the host from the real war against huge amounts of virus later in infection. As far as such a war will jeopardize the life of the host, it will be in both interests, including the virus, to settle the conflict amicably. Some important weapons of the unspecific defence and the early strikes and beginning battle during the first days of a HSV infection are discussed in this review. Generally, macrophages are orchestrating a multitude of anti-herpetic actions during the first hours of the attack. In a first wave of responses, cytokines, primarily type I interferons (IFN) and tumour necrosis factor are produced and exert a direct antiviral effect and activate the macrophages themselves. In the next wave, interleukin (IL)-12 together with the above and other cytokines induce production of IFN-gamma in mainly NK cells. Many positive feed-back mechanisms and synergistic interactions intensify these systems and give rise to heavy antiviral weapons such as reactive oxygen species and nitric oxide. This results in the generation of an alliance against the viral enemy. However, these heavy weapons have to be controlled to avoid too much harm to the host. By IL-4 and others, these reactions are hampered, but they are still allowed in foci of HSV replication, thus focusing the activity to only relevant sites. So, no hero does it alone. Rather, an alliance of cytokines, macrophages and other cells seems to play a central role. Implications of this for future treatment modalities are shortly considered.

[Do antisense oligonucleotides improve viral immunopathology?]

BACKGROUND

Tumor necrosis factor (TNF)-alpha as a proinflammatory cytokine is of great importance during the development of herpes simplex virus-1 keratitis (HSK). In this study the local administration of antisense oligonucleotides (ASON) targeting TNF-alpha was examined for its usefulness in ameliorating this disease.

METHODS

Uptake and efficacy of the oligonucleotides were studied in vitro by fluorescence microscopy and flow cytometry. Substance- and sequence-specific influences on the development of HSK were scrutinized in an animal model.

RESULTS

Quick and stable uptake of FITC-labeled ASON by isolated spleen and lymph node cells was proved. The production of TNF-alpha by these cells after stimulation with HSV antigen or concanavalin A (ConA) was clearly downregulated after addition of ASON. In vivo, incidence and development of HSK were ameliorated after subepithelial corneal injection of ASON targeting TNF-alpha. When buffer and control oligonucleotides were given, no significant influence on the disease was found.

CONCLUSION

The ASON effectively reduced TNF-alpha secretion in vitro and suppressed the development of experimental HSK in vivo.

Immunohistochemical detection and Western blot analysis of nitrated protein in stored human corneal epithelium

While the production of nitric oxide by human corneas in storage has recently been demonstrated, protein nitration as a result of this production has not been demonstrated. In this study, nitrated protein accumulation in the epithelium of stored human corneas was assessed. One half of five donor corneas maintained in storage media for 3 days were prepared for immunohistochemical studies. The other halves remained in storage media for 7 additional days and were also processed for immunohistochemistry. Mouse monoclonal antibody to nitrotyrosine adducts was used to define the localisation of these epitopes. The density of antibody staining was observed and quantified on a digital camera system and statistically analysed. Immunostaining in the epithelium was greater in tissues recovered after 10 days in storage compared to the intensity of staining after 3 days of storage (p<0.0001). No staining was evident in the epithelium in sections exposed to non-immune mouse IgG. Western blot analysis was performed on epithelial cells scraped from corneal surfaces of one-half of four donor corneas in storage for 3 days and from the other half at 10 days of storage. Nitrated BSA was used as a positive control. After extraction and homogenisation, identical protein concentrations of each sample were loaded per lane on 10% gels and subjected to SDS-PAGE. Proteins were blotted and probed with the anti-nitrotyrosine antibody. Western blot immunoreactivity was detected in epithelial samples at the 3 and 10 day recovery times with the latter samples showing greater staining intensity. Nitrated protein, thought to indicate toxic peroxynitrite formation, accumulates in the human corneal epithelium with time of storage. Our study shows that there is an association between increased nitrated protein and storage time.

Early events in HSV keratitis--setting the stage for a blinding disease

The last decade has seen herpes simplex virus (HSV)-induced stromal keratitis (SK) research shift from being a topic only of interest to vision researchers to one that fascinates the general field of inflammatory disease. Studies on experimental mouse lesions have uncovered several fundamental processes that explain lesion development. In this model, the chronic immuno-inflammatory lesions are mainly orchestrated by CD4+ T cells, but multiple early events occur that set the stage for the subsequent pathology. These include virus replication, the production of key cytokines and chemokines, neovascularization of the avascular cornea and the influx of certain inflammatory cell types. Many of these early events are subject to modulation, providing an approach to controlling this important cause of human blindness. We also comment on events ongoing during chronic SK, debating whether or not these represent virus-induced or autoimmune lesions.

IL-12 Protects against Coxsackievirus B3-Induced Myocarditis by Increasing IFN-γ and Macrophage and Neutrophil Populations in the Heart

Th1-type immune responses, mediated by IL-12-induced IFN-gamma, are believed to exacerbate certain autoimmune diseases. We recently found that signaling via IL-12Rbeta1 increases coxsackievirus B3 (CVB3)-induced myocarditis. In this study, we examined the role of IL-12 on the development of CVB3-induced myocarditis using mice deficient in IL-12p35 that lack IL-12p70. We found that IL-12 deficiency did not prevent myocarditis, but viral replication was significantly increased. Although there were no changes in the total percentage of inflammatory cells in IL-12-deficient hearts compared with wild-type BALB/c controls by FACS analysis, macrophage and neutrophil populations were decreased. This decrease corresponded to reduced TNF-alpha and IFN-gamma levels in the heart, suggesting that macrophage and/or neutrophil populations may be a primary source of TNF-alpha and IFN-gamma during acute CVB3 myocarditis. Increased viral replication in IL-12-deficient mice was not mediated by reduced TNFRp55 signaling, because viral replication was unaltered in TNFRp55-deficient mice. However, STAT4 or IFN-gamma deficiency resulted in significantly increased viral replication and significantly reduced TNF-alpha and IFN-gamma levels in the heart, similar to IL-12 deficiency, indicating that the IL-12/STAT4 pathway of IFN-gamma production is important in limiting CVB3 replication. Furthermore, STAT4 or IFN-gamma deficiency also increased chronic CVB3 myocarditis, indicating that therapeutic strategies aimed at reducing Th1-mediated autoimmune diseases may exacerbate common viral infections such as CVB3 and increase chronic inflammatory heart disease.

Wolbachia-induced neutrophil activation in a mouse model of ocular onchocerciasis (river blindness)

Endosymbiotic Wolbachia bacteria are abundant in the filarial nematodes that cause onchocerciasis (river blindness), including the larvae (microfilariae) that migrate into the cornea. Using a mouse model of ocular onchocerciasis, we recently demonstrated that it is these endosymbiotic bacteria rather than the nematodes per se that induce neutrophil infiltration to the corneal stroma and loss of corneal clarity (Saint Andre et al., Science 295:1892-1895, 2002). To better understand the role of Wolbachia organisms in the pathogenesis of this disease, we examined the fate of these bacteria in the cornea by immunoelectron microscopy. Microfilariae harboring Wolbachia organisms were injected into mouse corneas, and bacteria were detected with antibody to Wolbachia surface protein. Within 18 h of injection, neutrophils completely surrounded the nematodes and were in close proximity to Wolbachia organisms. Wolbachia surface protein labeling was also prominent in neutrophil phagosomes, indicating neutrophil ingestion of Wolbachia organisms. Furthermore, the presence of numerous electron-dense granules around the phagosomes indicated that neutrophils were activated. To determine if Wolbachia organisms directly activate neutrophils, peritoneal neutrophils were incubated with either parasite extracts containing Wolbachia organisms, parasite extracts depleted of Wolbachia organisms (by antibiotic treatment of worms), or Wolbachia organisms isolated from filarial nematodes. After 18 h of incubation, we found that isolated Wolbachia organisms stimulated production of tumor necrosis factor alpha and CXC chemokines macrophage inflammatory protein 2 and KC by neutrophils in a dose-dependent manner. Similarly, these cytokines were induced by filarial extracts containing Wolbachia organisms but not by Wolbachia-depleted extracts. Taken together, these findings indicate that neutrophil activation is an important mechanism by which Wolbachia organisms contribute to the pathogenesis of ocular onchocerciasis.