IL-6 Contributes to Corneal Nerve Degeneration after Herpes Simplex Virus Type I Infection

Commercial human 3D corneal epithelial equivalents for modeling epithelial infection in herpes keratitis

Herpes stromal keratitis is the leading cause of infectious blindness in the western world. Infection by HSV1 is most common, but VZV and hCMV also infect the cornea. Multiple models of HSV1 corneal infection exist, but none for VZV and hCMV because of their host specificity. Here, we used commercially available 3D human corneal epithelial equivalents (HCEE) to study infection by these herpesviruses. HCEE was infected by HSV-1 and hCMV without requiring scarification and resulted in spreading infections. Spread of HSV-1 infection was rapid, while that of hCMV was slow. In contrast, infections with VZV required damage to the HCEE and did not spread. Acyclovir dramatically reduced replication of HSV-1 in this model. We conclude that highly quality-controlled, readily available HCEE is a useful model to study human-restricted herpesvirus infection of the human corneal epithelium and for screening of antiviral drugs for treating HSK in an 3D model system.

Association of Psoas: Lumbar Vertebral Index (PLVI) with Postherpetic Neuralgia in Patients Aged 60 and Older with Herpes Zoster

Background/Objectives: The psoas: lumbar vertebral index (PLVI) is a simple and convenient measure to assess central sarcopenia. Recent studies have utilized the psoas area to indirectly assess sarcopenia and frailty, exploring their associations with various health outcomes. This study aims to investigate the relationship between the PLVI and postherpetic neuralgia (PHN) in patients aged 60 years and above following a herpes zoster (HZ) infection. Methods: We conducted a retrospective analysis of data from 351 patients (≥60 years) who developed HZ between January 2019 and December 2023; the patients were divided into two groups based on the presence or absence of PHN after HZ onset. Results: The analyses using receiver operating characteristic curves revealed a value for the area under the curve of 0.813 for PLVI and 0.769 for the modified frailty index (mFI). In a multivariate logistic regression analysis, numerical rating scale scoring, a low PLVI, and a greater number of categorical mFI variables (adjusted odds ratio: 1.30, 3.27, and 2.46, respectively) were found to be significant independent predictors of PHN. Conclusions: Our findings highlight the association between a low PLVI and PHN in an older population. The PLVI may have potential as a predictive tool for PHN in older patients with HZ, but further research is needed to confirm these results.

Meeting the Challenge of Controlling Viral Immunopathology

The mission of this review is to identify immune-damaging participants involved in antiviral immunoinflammatory lesions. We argue these could be targeted and their activity changed selectively by maneuvers that, at the same time, may not diminish the impact of components that help resolve lesions. Ideally, we need to identify therapeutic approaches that can reverse ongoing lesions that lack unwanted side effects and are affordable to use. By understanding the delicate balance between immune responses that cause tissue damage and those that aid in resolution, novel strategies can be developed to target detrimental immune components while preserving the beneficial ones. Some strategies involve rebalancing the participation of immune components using various approaches, such as removing or blocking proinflammatory T cell products, expanding regulatory cells, restoring lost protective cell function, using monoclonal antibodies (moAb) to counteract inhibitory molecules, and exploiting metabolic differences between inflammatory and immuno-protective responses. These strategies can help reverse ongoing viral infections. We explain various approaches, from model studies and some clinical evidence, that achieve innate and adaptive immune rebalancing, offering insights into potential applications for controlling chronic viral-induced lesions.

Complement Suppresses the Initial Type 1 Interferon Response to Ocular Herpes Simplex Virus Type 1 Infection in Mice

The complement system (CS) contributes to the initial containment of viral and bacterial pathogens and clearance of dying cells in circulation. We previously reported mice deficient in complement component 3 (C3KO mice) were more sensitive than wild-type (WT) mice to ocular HSV-1 infection, as measured by a reduction in cumulative survival and elevated viral titers in the nervous system but not the cornea between days three and seven post infection (pi). The present study was undertaken to determine if complement deficiency impacted virus replication and associated changes in inflammation at earlier time points in the cornea. C3KO mice were found to possess significantly (p < 0.05) less infectious virus in the cornea at 24 h pi that corresponded with a decrease in HSV-1 lytic gene expression at 12 and 24 h pi compared to WT animals. Flow cytometry acquisition found no differences in the myeloid cell populations residing in the cornea including total macrophage and neutrophil populations at 24 h pi with minimal infiltrating cell populations detected at the 12 h pi time point. Analysis of cytokine and chemokine content in the cornea measured at 12 and 24 h pi revealed that only CCL3 (MIP-1α) was found to be different between WT and C3KO mice with >2-fold increased levels (p < 0.05, ANOVA and Tukey's post hoc t-test) in the cornea of WT mice at 12 h pi. C3KO mouse resistance to HSV-1 infection at the early time points correlated with a significant increase in type I interferon (IFN) gene expression including IFN-α1 and IFN-β and downstream effector genes including tetherin and RNase L (p < 0.05, Mann-Whitney rank order test). These results suggest early activation of the CS interferes with the induction of the type I IFN response and leads to a transient increase in virus replication following corneal HSV-1 infection.

The role of the JAK/STAT3 signaling pathway in acquired corneal diseases

Acquired corneal diseases such as dry eye disease (DED), keratitis and corneal alkali burns are significant contributors to vision impairment worldwide, and more effective and innovative therapies are urgently needed. The Janus kinase/signal transducer and activator of transcription 3 (JAK/STAT3) signaling pathway plays an indispensable role in cell metabolism, inflammation and the immune response. Studies have shown that regulators of this pathway are extensively expressed in the cornea, inducing significant activation of JAK/STAT3 signaling in specific acquired corneal diseases. The activation of JAK/STAT3 signaling contributes to various pathophysiological processes in the cornea, including inflammation, neovascularization, fibrosis, and wound healing. In the context of DED, the hypertonic environment activates JAK/STAT3 signaling to stimulate corneal inflammation. Inflammation and injury progression in infectious keratitis can also be modulated by JAK/STAT3 signaling. Furthermore, JAK/STAT3 signaling is involved in every stage of corneal repair after alkali burns, including acute inflammation, angiogenesis and fibrosis. Treatments modulating JAK/STAT3 signaling have shown promising results in attenuating corneal damage, indicating its potential as a novel therapeutic target. Thus, this review emphasizes the multiple roles of the JAK/STAT3 signaling pathway in common acquired corneal disorders and summarizes the current achievements of JAK/STAT3-targeting therapy to provide new insights into future applications.

An ocular Th1 immune response promotes corneal nerve damage independently of the development of corneal epitheliopathy

Proper sight is not possible without a smooth, transparent cornea, which is highly exposed to environmental threats. The abundant corneal nerves are interspersed with epithelial cells in the anterior corneal surface and are instrumental to corneal integrity and immunoregulation. Conversely, corneal neuropathy is commonly observed in some immune-mediated corneal disorders but not in others, and its pathogenesis is poorly understood. Here we hypothesized that the type of adaptive immune response may influence the development of corneal neuropathy. To test this, we first immunized OT-II mice with different adjuvants that favor T helper (Th)1 or Th2 responses. Both Th1-skewed mice (measured by interferon-γ production) and Th2-skewed (measured by interleukin-4 production) developed comparable ocular surface inflammation and conjunctival CD4+ T cell recruitment but no appreciable corneal epithelial changes upon repeated local antigenic challenge. Th1-skewed mice showed decreased corneal mechanical sensitivity and altered corneal nerve morphology (signs of corneal neuropathy) upon antigenic challenge. However, Th2-skewed mice also developed milder corneal neuropathy immediately after immunization and independently of ocular challenge, suggestive of adjuvant-induced neurotoxicity. All these findings were confirmed in wild-type mice. To circumvent unwanted neurotoxicity, CD4+ T cells from immunized mice were adoptively transferred to T cell-deficient mice. In this setup, only Th1-transferred mice developed corneal neuropathy upon antigenic challenge. To further delineate the contribution of each profile, CD4+ T cells were polarized in vitro to either Th1, Th2, or Th17 cells and transferred to T cell-deficient mice. Upon local antigenic challenge, all groups had commensurate conjunctival CD4+ T cell recruitment and macroscopic ocular inflammation. However, none of the groups developed corneal epithelial changes and only Th1-transferred mice showed signs of corneal neuropathy. Altogether, the data show that corneal nerves, as opposed to corneal epithelial cells, are sensitive to immune-driven damage mediated by Th1 CD4+ T cells in the absence of other pathogenic factors. These findings have potential therapeutic implications for ocular surface disorders.

Role of Innate Interferon Responses at the Ocular Surface in Herpes Simplex Virus-1-Induced Herpetic Stromal Keratitis

Herpes simplex virus type 1 (HSV-1) is a highly successful pathogen that primarily infects epithelial cells of the orofacial mucosa. After initial lytic replication, HSV-1 enters sensory neurons and undergoes lifelong latency in the trigeminal ganglion (TG). Reactivation from latency occurs throughout the host’s life and is more common in people with a compromised immune system. HSV-1 causes various diseases depending on the site of lytic HSV-1 replication. These include herpes labialis, herpetic stromal keratitis (HSK), meningitis, and herpes simplex encephalitis (HSE). HSK is an immunopathological condition and is usually the consequence of HSV-1 reactivation, anterograde transport to the corneal surface, lytic replication in the epithelial cells, and activation of the host’s innate and adaptive immune responses in the cornea. HSV-1 is recognized by cell surface, endosomal, and cytoplasmic pattern recognition receptors (PRRs) and activates innate immune responses that include interferons (IFNs), chemokine and cytokine production, as well as the recruitment of inflammatory cells to the site of replication. In the cornea, HSV-1 replication promotes type I (IFN-α/β) and type III (IFN-λ) IFN production. This review summarizes our current understanding of HSV-1 recognition by PRRs and innate IFN-mediated antiviral immunity during HSV-1 infection of the cornea. We also discuss the immunopathogenesis of HSK, current HSK therapeutics and challenges, proposed experimental approaches, and benefits of promoting local IFN-λ responses.

Myeloid cells protect corneal nerves against sterile injury through negative-feedback regulation of TLR2-IL-6 axis

BACKGROUND

Mounting evidence suggests that the immune system plays detrimental or protective roles in nerve injury and repair.

MAIN BODY

Herein we report that both CD11b^hiLy6G^hi and CD11b^hiLy6C^hiLy6G^lo myeloid cells are required to protect corneal nerves against sterile corneal injury. Selective depletion of CD11b^hiLy6G^hi or CD11b^hiLy6C^hiLy6G^lo cells resulted in aggravation of corneal nerve loss, which correlated with IL-6 upregulation. IL-6 neutralization preserved corneal nerves while reducing myeloid cell recruitment. IL-6 replenishment exacerbated corneal nerve damage while recruiting more myeloid cells. In mice lacking Toll-like receptor 2 (TLR2), the levels of IL-6 and myeloid cells were decreased and corneal nerve loss attenuated, as compared to wild-type and TLR4 knockout mice. Corneal stromal fibroblasts expressed TLR2 and produced IL-6 in response to TLR2 stimulation.

CONCLUSION

Collectively, our data suggest that CD11b^hiLy6G^hi and CD11b^hiLy6C^hiLy6G^lo myeloid cells confer corneal nerve protection under sterile injury by creating a negative-feedback loop to suppress the upstream TLR2-IL-6 axis that drives corneal nerve loss.

Osteopontin contributes to virus resistance associated with type I IFN expression, activation of downstream ifn-inducible effector genes, and CCR2+CD115+CD206+ macrophage infiltration following ocular HSV-1 infection of mice

Ocular pathology is often associated with acute herpes simplex virus (HSV)-1 infection of the cornea in mice. The present study was undertaken to determine the role of early T lymphocyte activation 1 protein or osteopontin (OPN) in corneal inflammation and host resistance to ocular HSV-1 infection. C57BL/6 wild type (WT) and osteopontin deficient (OPN KO) mice infected in the cornea with HSV-1 were evaluated for susceptibility to infection and cornea pathology. OPN KO mice were found to possess significantly more infectious virus in the cornea at day 3 and day 7 post infection compared to infected WT mice. Coupled with these findings, HSV-1-infected OPN KO mouse corneas were found to express less interferon (IFN)-α1, double-stranded RNA-dependent protein kinase, and RNase L compared to infected WT animals early post infection that likely contributed to decreased resistance. Notably, OPN KO mice displayed significantly less corneal opacity and neovascularization compared to WT mice that paralleled a decrease in expression of vascular endothelial growth factor (VEGF) A within 12 hr post infection. The change in corneal pathology of the OPN KO mice aligned with a decrease in total leukocyte infiltration into the cornea and specifically, in neutrophils at day 3 post infection and in macrophage subpopulations including CCR2+CD115+CD206+ and CD115+CD183+CD206+ -expressing cells. The infiltration of CD4+ and CD8+ T cells into the cornea was unaltered comparing infected WT to OPN KO mice. Likewise, there was no difference in the total number of HSV-1-specific CD4+ or CD8+ T cells found in the draining lymph node with both sets functionally competent in response to virus antigen comparing WT to OPN KO mice. Collectively, these results demonstrate OPN deficiency directly influences the host innate immune response to ocular HSV-1 infection reducing some aspects of inflammation but at a cost with an increase in local HSV-1 replication.

Serum interleukin-6 levels are increased in post-herpetic neuralgia: a single-center retrospective study

BACKGROUND

Studies have shown that the overall incidence rate of herpeszoster (HZ) in China is 6.64 cases per 1000 people, despite such harms brought by postherpetic neuralgia (PHN), the mechanism of the disease remains unclear in China. Currently, effective biomarkers to predict PHN remain unavailable, which makes it difficult to prevent and successfully treat PHN.

OBJECTIVE

The aim of the study was to determine the serum interleukin-6 level in PHN.

METHODS

The serum levels of interleukin 6 (IL-6) were measured by multi-antibody sandwich ELISA. The likert scale was used to represent the degree of neuralgia in the patients. Patients with PHN were divided into a mild PHN group and a severe PHN group according to the Likert scale. ROC curve was performed for evaluating the diagnostic efficiency of IL6 for PHN. The correlation between the IL6 level and the Likert scale before and after treatment with gabapentin and mecobalamin was analyzed.

RESULTS

IL6 levels in PHN patients resulted higher compared to volunteers. Patients in the severe PHN group had a higher serum IL6 level than in the mild PHN group. The Likert scale score was related to the serum IL6 levels and the frequency of IL6 levels above the cutoff value (4.95 pg/mL) in PNH groups before and after treatment (p < 0.05).

STUDY LIMITATIONS

Pain is subjective. Some mental states, such as anxiety and depression, greatly influence an individual's perception of pain, and pain tolerance can vary between people. Therefore, pain scores can be affected by different individual factors.

CONCLUSIONS

The serum IL6 levels may be used as a biochemical indicator of the severity of PNH.

Association of Single-Nucleotide Polymorphisms in Interleukin Genes with Microbial Keratitis in a South Indian Population

BACKGROUND

To examine the relationship between single-nucleotide polymorphisms (SNPs) in interleukin (IL) genes and keratitis and its clinical manifestations.

METHODS

SNPs in IL1B, IL6, CXCL8, IL10, and IL12B were analysed. Differences in frequencies of alleles, genotypes and haplotypes between cases and controls as well as associations between SNPs and clinical variables were calculated by χ2 tests with odds ratios.

RESULTS

The minor homologous genotype in IL1B rs16944 (p = 0.036; odds ratio (OR) = 2.063, 95% confidence interval (CI): 1.048-4.061) and CXCL8 rs4073 (p = 0.041; OR = 0.463, 95% CI: 0.224-0.956) and the heterologous genotypes in IL6 rs1800795 (p = 0.046; OR = 0.563, 95% CI: 0.326-0.972) and IL12B rs2569254 (p = 0.0446; OR = 0.557, 95% CI: 0.314-0.989) or rs730691 (p = 0.0051; OR = 0.451, 95% CI: 0.260-0.784) were associated with keratitis. The minor genotype of rs16944 was associated with severe infection (p = 0.046). The heterologous genotype in rs2569254 was associated with hospital admission, photophobia, and mode of contact lens wear (p ≤ 0.041). The heterologous genotype in rs730691 was associated with blurred vision, discharge, anterior chamber reaction, and mode of wear (p ≤ 0.047).

CONCLUSIONS

This study demonstrates that SNPs in IL1B and CXCL8 are associated with risk of developing keratitis. The study also found relationships between SNPs and clinical measures of keratitis. The potential for ethnic differences in frequency of SNPs and their association with keratitis should be followed up using different populations.

Neuroimmune crosstalk in the cornea: The role of immune cells in corneal nerve maintenance during homeostasis and inflammation

In the cornea, resident immune cells are in close proximity to sensory nerves, consistent with their important roles in the maintenance of nerves in both homeostasis and inflammation. Using in vivo confocal microscopy in humans, and ex vivo immunostaining and fluorescent reporter mice to visualize corneal sensory nerves and immune cells, remarkable progress has been made to advance our understanding of the physical and functional interactions between corneal nerves and immune cells. In this review, we summarize and discuss recent studies relating to corneal immune cells and sensory nerves, and their interactions in health and disease. In particular, we consider how disrupted corneal nerve axons can induce immune cell activity, including in dendritic cells, macrophages and other infiltrating cells, directly and/or indirectly by releasing neuropeptides such as substance P and calcitonin gene-related peptide. We summarize growing evidence that the role of corneal intraepithelial immune cells is likely different in corneal wound healing versus other inflammatory-dominated conditions. The role of different types of macrophages is also discussed, including how stromal macrophages with anti-inflammatory phenotypes communicate with corneal nerves to provide neuroprotection, while macrophages with pro-inflammatory phenotypes, along with other infiltrating cells including neutrophils and CD4⁺ T cells, can be inhibitory to corneal re-innervation. Finally, this review considers the bidirectional interactions between corneal immune cells and corneal nerves, and how leveraging this interaction could represent a potential therapeutic approach for corneal neuropathy.

The effect of topical decorin on temporal changes to corneal immune cells after epithelial abrasion

BACKGROUND

Corneal immune cells interact with corneal sensory nerves during both homeostasis and inflammation. This study sought to evaluate temporal changes to corneal immune cell density in a mouse model of epithelial abrasion and nerve injury, and to investigate the immunomodulatory effects of topical decorin, which we have shown previously to promote corneal nerve regeneration.

METHODS

Bilateral corneal epithelial abrasions (2 mm) were performed on C57BL/6J mice. Topical decorin or saline eye drops were applied three times daily for 12 h, 24 h, 3 days or 5 days. Optical coherence tomography imaging was performed to measure the abrasion area. The densities of corneal sensory nerves (β-tubulin III) and immune cells, including dendritic cells (DCs; CD11c⁺), macrophages (Iba-1⁺) and neutrophils (NIMP-R14⁺) were measured. Cx3cr1^gfp/gfp mice that spontaneously lack resident corneal intraepithelial DCs were used to investigate the specific contribution of epithelial DCs. Neuropeptide and cytokine gene expression was evaluated using qRT-PCR at 12 h post-injury.

RESULTS

In decorin-treated corneas, higher intraepithelial DC densities and lower neutrophil densities were observed at 24 h after injury, compared to saline controls. At 12 h post-injury, topical decorin application was associated with greater re-epithelialisation. At 5 days post-injury, corneal stromal macrophage density in the decorin-treated and contralateral eyes was lower, and nerve density was higher, compared to eyes treated with saline only. Lower expression of transforming growth factor beta (TGF-β) and higher expression of CSPG4 mRNA was detected in corneas treated with topical decorin. There was no difference in corneal neutrophil density in Cx3cr1^gfp/gfp mice treated with or without decorin at 12 h.

CONCLUSIONS

Topical decorin regulates immune cell dynamics after corneal injury, by inhibiting neutrophils and recruiting intraepithelial DCs during the acute phase (< 24 h), and inhibiting macrophage density at the study endpoint (5 days). These immunomodulatory effects were associated with faster re-epithelialisation and likely contribute to promoting sensory nerve regeneration. The findings suggest a potential interaction between DCs and neutrophils with topical decorin treatment, as the decorin-induced neutrophil inhibition was absent in Cx3cr1^gfp/gfp mice that lack corneal epithelial DCs. TGF-β and CSPG4 proteoglycan likely regulate decorin-mediated innate immune cell responses and nerve regeneration after injury.

Tripartite-Motif 21 (TRIM21) Deficiency Results in a Modest Loss of Herpes Simplex Virus (HSV)-1 Surveillance in the Trigeminal Ganglia Following Cornea Infection

Tripartite-motif 21 (TRIM21) is thought to regulate the type I interferon (IFN) response to virus pathogens and serve as a cytosolic Fc receptor for immunoglobulin. Since herpes simplex virus (HSV)-1 is sensitive to type I IFN and neutralizing antibody, we investigated the role of TRIM21 in response to ocular HSV-1 infection in mice. In comparison to wild type (WT) mice, TRIM21 deficient (TRIM21 KO) mice were found to be no more susceptible to ocular HSV-1 infection than WT animals, in terms of infectious virus recovered in the cornea. Similar pathology, in terms of neovascularization, opacity, and loss of peripheral vision function, was observed in both WT and TRIM21 KO mice. However, TRIM21 KO mice did possess a significant increase in infectious virus recovered in the trigeminal ganglia, in comparison to the WT animals. The increased susceptibility was not due to changes in HSV-1-specific CD4+ or CD8+ T cell numbers or functional capabilities, or in changes in type I IFN or IFN-inducible gene expression. In summary, the absence of TRIM21 results in a modest, but significant, increase in HSV-1 titers recovered from the TG of TRIM21 KO mice during acute infection, by a mechanism yet to be determined.

Regenerative therapy for the Cornea

The cornea is the outmost layer of the eye, unique in its transparency and strength. The cornea not only transmits the light essential for vision, also refracts light, giving focus to images. Each of the three layers of the cornea has properties essential for the function of vision. Although the epithelium can often recover from injury quickly by cell division, loss of limbal stem cells can cause severe corneal surface abnormalities leading to corneal blindness. Disruption of the stromal extracellular matrix and loss of cells determining this structure, the keratocytes, leads to corneal opacity. Corneal endothelium is the inner part of the cornea without self-renewal capacity. It is very important to maintain corneal dehydration and transparency. Permanent damage to the corneal stroma or endothelium can be effectively treated by corneal transplantation; however, there are drawbacks to this procedure, including a shortage of donors, the need for continuing treatment to prevent rejection, and limits to the survival of the graft, averaging 10-20 years. There exists a need for new strategies to promote regeneration of the stromal structure and restore vision. This review highlights critical contributions in regenerative medicine with the aim of corneal reconstruction after injury or disease. These approaches include corneal stromal stem cells, corneal limbal stem cells, embryonic stem cells, and other adult stem cells, as well as induced pluripotent stem cells. Stem cell-derived trophic factors in the forms of secretomes or exosomes for corneal regeneration are also discussed. Corneal sensory nerve regeneration promoting corneal transparency is discussed. This article provides description of the up-to-date options for corneal regeneration and presents exciting possible avenues for future studies toward clinical applications for corneal regeneration.

Mucosal immunology of the ocular surface

The eye is a sensory organ exposed to the environment and protected by a mucosal tissue barrier. While it shares a number of features with other mucosal tissues, the ocular mucosal system, composed of the conjunctiva, Meibomian glands, and lacrimal glands, is specialized to address the unique needs of (a) lubrication and (b) host defense of the ocular surface. Not surprisingly, most challenges, physical and immunological, to the homeostasis of the eye fall into those two categories. Dry eye, a dysfunction of the lacrimal glands and/or Meibomian glands, which can both cause, or arise from, sensory defects, including those caused by corneal herpes virus infection, serve as examples of these perturbations and will be discussed ahead. To preserve vision, dense neuronal and immune networks sense various stimuli and orchestrate responses, which must be tightly controlled to provide protection, while simultaneously minimizing collateral damage. All this happens against the backdrop of, and can be modified by, the microorganisms that colonize the ocular mucosa long term, or that are simply transient passengers introduced from the environment. This review will attempt to synthesize the existing knowledge and develop trends in the study of the unique mucosal and immune elements of the ocular surface.

An intact complement system dampens cornea inflammation during acute primary HSV-1 infection

Corneal transparency is an essential characteristic necessary for normal vision. In response to microbial infection, the integrity of the cornea can become compromised as a result of the inflammatory response and the ensuing tissue pathology including neovascularization (NV) and collagen lamellae destruction. We have previously found complement activation contributes to cornea pathology-specifically, denervation in response to HSV-1 infection. Therefore, we investigated whether the complement system also played a role in HSV-1-mediated neovascularization. Using wild type (WT) and complement component 3 deficient (C3 KO) mice infected with HSV-1, we found corneal NV was accelerated associated with an increase in inflammatory monocytes (CD11b⁺CCR2⁺CD115^+/-Ly6G^-Ly6C^high), macrophages (CD11b⁺CCR2⁺CD115⁺Ly6G^-Ly6C^high) and a subpopulation of granulocytes/neutrophils (CD11b⁺CCR2^-CD115⁺Ly6G⁺Ly6C^low). There were also increases in select pro-inflammatory and pro-angiogenic factors including IL-1α, matrix metalloproteinases (MMP)-2, MMP-3, MMP-8, CXCL1, CCL2, and VEGF-A that coincided with increased inflammation, neovascularization, and corneal opacity in the C3 KO mice. The difference in inflammation between WT and C3 KO mice was not driven by changes in virus titer. However, viral antigen clearance was hindered in C3 KO mouse corneas suggesting the complement system has a dynamic regulatory role within the cornea once an inflammatory cascade is initiated by HSV-1.

Lack of neonatal Fc receptor does not diminish the efficacy of the HSV-1 0ΔNLS vaccine against ocular HSV-1 challenge

The neonatal Fc receptor (FcRn) is constitutively expressed in the cornea and is up-regulated in response to herpes simplex virus type 1 (HSV-1). Previously, we found targeting cornea FcRn expression by small interfering RNA-mediated knockdown reduced the local efficacy of HSV-1 0ΔNLS vaccinated C57BL/6 mice against ocular challenge with HSV-1. The current study was undertaken to evaluate the HSV-1 0ΔNLS vaccine efficacy in FcRn deficient (FcRn KO) mice challenged with HSV-1. Whereas there was little neutralizing antibody detected in the serum of HSV-1 0ΔNLS vaccinated FcRn KO mice, these mice exhibited the same degree of protection against ocular challenge with HSV-1 as wild type (WT) C57BL/6 mice as measured by cumulative survival, infectious virus shed or retained in tissue, and corneal pathology including opacity and neovascularization. Mock-vaccinated FcRn KO mice were found to be more sensitive to ocular HSV-1 infection compared to mock-vaccinated (WT) mice in terms of cumulative survival and virus shedding. In addition, the FcRn KO mice generated significantly fewer effector (CD3⁺CD44⁺CD62L^-) and central (CD3⁺CD44⁺CD62L⁺) memory CD8⁺ T cells compared to the WT mice 7 days post infection. Collectively, mock-vaccinated FcRn KO mice are susceptible to ocular HSV-1 infection but HSV-1 0ΔNLS vaccinated FcRn KO mice are resistant suggesting that in addition to the FcRn, other pathways are involved in mediating the protective effect of the HSV-1 0ΔNLS vaccine against subsequent HSV-1 challenge.

Distinguishing Features of High- and Low-Dose Vaccine against Ocular HSV-1 Infection Correlates with Recognition of Specific HSV-1-Encoded Proteins

The protective efficacy of a live-attenuated HSV type 1 (HSV-1) vaccine, HSV-1 0∆ nuclear location signal (NLS), was evaluated in mice prophylactically in response to ocular HSV-1 challenge. Mice vaccinated with the HSV-1 0∆NLS were found to be more resistant to subsequent ocular virus challenge in terms of viral shedding, spread, the inflammatory response, and ocular pathology in a dose-dependent fashion. Specifically, a strong neutralizing Ab profile associated with low virus titers recovered from the cornea and trigeminal ganglia was observed in vaccinated mice in a dose-dependent fashion with doses ranging from 1 × 10³ to 1 × 10⁵ PFU HSV-1 0∆NLS. This correlation also existed in terms of viral latency in the trigeminal ganglia, corneal neovascularization, and leukocyte infiltration and expression of inflammatory cytokines and chemokines in infected tissue with the higher doses (1 × 10⁴-1 × 10⁵ PFU) of the HSV-1 0∆NLS-vaccinated mice, displaying reduced viral latency, ocular pathology, or inflammation in comparison with the lowest dose (1 × 10³ PFU) or vehicle vaccine employed. Fifteen HSV-1-encoded proteins were uniquely recognized by antisera from high-dose (1 × 10⁵ PFU)-vaccinated mice in comparison with low-dose (1 × 10³ PFU)- or vehicle-vaccinated animals. Passive immunization using high-dose-vaccinated, but not low-dose-vaccinated, mouse sera showed significant efficacy against ocular pathology in HSV-1-challenged animals. In summary, we have identified the minimal protective dose of HSV-1 0∆NLS vaccine in mice to prevent HSV-mediated disease and identified candidate proteins that may be useful in the development of a noninfectious prophylactic vaccine against the insidious HSV-1 pathogen.

Role of the XIST-miR-181a-COL4A1 axis in the development and progression of keratoconus

Background

As a disorder occurs in the eyes, keratoconus (KC) is induced by the thinning of the corneal stroma. This study was designed to reveal the key long non-coding RNAs (lncRNAs), microRNAs (miRNAs), and mRNAs involved in the mechanisms of KC.

Methods

Transcriptome RNA-seq data set GSE112155 was acquired from the Gene Expression Omnibus database, which contained 10 KC samples and 10 myopic control samples. Using the edgeR package, the differentially expressed (DE)-mRNAs between KC and control samples were screened. The DE-lncRNAs and DE-miRNAs in this data set were identified using the HUGO Gene Nomenclature Committee (HGNC). Using the pheatmap package, bidirectional hierarchical clustering of the DE-RNAs was conducted. Then, an enrichment analysis of the DE-mRNAs was performed using the DAVID tool. Moreover, a competitive endogenous RNA (ceRNA) regulatory network was built using the Cytoscape software. After KC-associated pathways were searched within the Comparative Toxicogenomics Database, a KC-associated ceRNA regulatory network was constructed.

Results

There were 282 DE-lncRNAs (192 upregulated and 90 downregulated), 40 DE-miRNAs (29 upregulated and 11 downregulated), and 910 DE-mRNAs (554 upregulated and 356 downregulated) between the KC and control samples. A total of 34 functional terms and 9 pathways were enriched for the DE-mRNAs. In addition, 6 mRNAs (including PPARG, HLA-B, COL4A1, and COL4A2), 5 miRNAs (including miR-181a), 9 lncRNAs (including XIST), and the XIST-miR-181a-COL4A1 axis were involved in the KC-associated ceRNA regulatory network.

Conclusions

PPARG, HLA-B, COL4A1, COL4A2, miR-181a, and XIST might be correlated with the development of KC. Further, the XIST-miR-181a-COL4A1 axis might be implicated in the pathogenesis of KC.

Varicella Zoster Virus Alters Expression of Cell Adhesion Proteins in Human Perineurial Cells via Interleukin 6

BACKGROUND

In temporal arteries (TAs) from patients with giant cell arteritis, varicella zoster virus (VZV) is seen in perineurial cells that surround adventitial nerve bundles and form the peripheral nerve-extrafascicular tissue barrier (perineurium). We hypothesized that during VZV reactivation from ganglia, virus travels transaxonally and disrupts the perineurium to infect surrounding cells.

METHODS

Mock- and VZV-infected primary human perineurial cells (HPNCs) were examined for alterations in claudin-1, E-cadherin, and N-cadherin. Conditioned supernatant was analyzed for a soluble factor(s) mediating these alterations and for the ability to increase cell migration. To corroborate in vitro findings, a VZV-infected TA was examined.

RESULTS

In VZV-infected HPNCs, claudin-1 redistributed to the nucleus; E-cadherin was lost and N-cadherin gained, with similar changes seen in VZV-infected perineurial cells in a TA. VZV-conditioned supernatant contained increased interleukin 6 (IL-6) that induced E-cadherin loss and N-cadherin gain and increased cell migration when added to uninfected HPNCs; anti-IL-6 receptor antibody prevented these changes.

CONCLUSIONS

IL-6 secreted from VZV-infected HPNCs facilitated changes in E- and N-cadherin expression and cell migration, reminiscent of an epithelial-to-mesenchymal cell transition, potentially contributing to loss of perineurial cell barrier integrity and viral spread. Importantly, an anti-IL-6 receptor antibody prevented virus-induced perineurial cell disruption.

An off-target effect of BX795 blocks herpes simplex virus type 1 infection of the eye

Herpes simplex virus type 1 (HSV-1) causes recurrent mucocutaneous lesions in the eye that may advance to corneal blindness. Nucleoside analogs exemplified by acyclovir (ACV) form the primary class of antiherpetic drugs, but this class suffers limitations due to the emergence of viral resistance and other side effects. While studying the molecular basis of ocular HSV-1 infection, we observed that BX795, a commonly used inhibitor of TANK-binding kinase 1 (TBK1), strongly suppressed infection by multiple strains of HSV-1 in transformed and primary human cells, cultured human and animal corneas, and a murine model of ocular infection. Our investigations revealed that the antiviral activity of BX795 relies on targeting Akt phosphorylation in infected cells, leading to the blockage of viral protein synthesis. This small-molecule inhibitor, which was also effective against an ACV-resistant HSV-1 strain, shows promise as an alternative to existing drugs and as an effective topical therapy for ocular herpes infection. Collectively, our results obtained using multiple infection models and virus strains establish BX795 as a promising lead compound for broad-spectrum antiviral applications in humans.

Complement and CD4+ T cells drive context-specific corneal sensory neuropathy

Whether complement dysregulation directly contributes to the pathogenesis of peripheral nervous system diseases, including sensory neuropathies, is unclear. We addressed this important question in a mouse model of ocular HSV-1 infection, where sensory nerve damage is a common clinical problem. Through genetic and pharmacologic targeting, we uncovered a central role for C3 in sensory nerve damage at the morphological and functional levels. Interestingly, CD4 T cells were central in facilitating this complement-mediated damage. This same C3/CD4 T cell axis triggered corneal sensory nerve damage in a mouse model of ocular graft-versus-host disease (GVHD). However, this was not the case in a T-dependent allergic eye disease (AED) model, suggesting that this inflammatory neuroimmune pathology is specific to certain disease etiologies. Collectively, these findings uncover a central role for complement in CD4 T cell-dependent corneal nerve damage in multiple disease settings and indicate the possibility for complement-targeted therapeutics to mitigate sensory neuropathies.

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.

PEDF Reduces the Severity of Herpetic Simplex Keratitis in Mice

Purpose

The purpose of this study was to explore the effects of pigment epithelium derived factor (PEDF) and PEDF-derived peptides Mer44 and Mer34 on the severity of herpetic simplex keratitis (HSK) in mice.

Methods

Adult C57BL/6 mice were infected ocularly with the herpes simplex virus type 1 (HSV-1, McKrae strain) and injected subconjunctivally with PEDF, Mer44, or Mer34. Corneal nerve degeneration, neovascularization, sensitivity, neutrophils, macrophages and CD4+ T-cell infiltration, virus contents, and expressions of VEGF, PEDF, and proinflammatory factors were evaluated during acute period. The direct inhibitory effect of PEDF on HSV-1 replication was further evaluated in cultured monkey Vero cells.

Results

Following HSV-1 infection, corneal PEDF expression decreased at 3 and 7 days postinfection (dpi) but increased at 15 dpi, and returned to the similar level of normal mice at 45 dpi, which was accompanied with the progress of corneal nerve degeneration and neovascularization. Exogenous PEDF application attenuated corneal nerve degeneration and neovascularization and improved the impaired corneal sensitivity. Moreover, PEDF attenuated the neutrophils, but not macrophage or CD4+ T-cell infiltration, with the reduced expressions of IL-1β, IL-6, TNF-α, and VEGF. In addition, PEDF inhibited the replication of HSV-1 both in vitro and in mice. Mer44 attenuated corneal nerve degeneration more significantly than Mer34, whereas Mer34 inhibited corneal neovascularization.

Conclusions

PEDF and its derived peptides reduce the severity of herpetic simplex keratitis in mice, representing the potential therapeutic approach to control HSK lesions.

Autophagy Quantification and STAT3 Expression in a Human Skin Organ Culture Model for Innate Immunity to Herpes Zoster

The goal of this project was to document the autophagy response in human neonatal skin organ culture (SOC) after infection with varicella-zoster virus (VZV). The VZV-infected SOC model has attributes of herpes zoster, in that an injection of virus into the skin is analogous to exit of virus from the sensory nerve termini into skin during herpes zoster. Cultures were maintained for 28 days and periodically examined for an autophagy response by quantitation of autophagosomes with Imaris software. Expression of the STAT3 protein was plentiful in the VZV-infected SOC. Abundant autophagy was observed in VZV-infected SOC between 14 and 28 days after infection, while autophagy in mock-infected SOC was minimal (p = 0.0003). The autophagic response after infection of SOC with a recombinant VZV genome containing the herpes simplex virus ICP34.5 neurovirulence gene was similar to wild-type VZV (p = 0.3). These results suggested that the VZV-infected SOC system resembled biopsy data from herpes zoster infection of skin. An enhanced autophagy response has now been reported after infection with two additional alpha herpesviruses besides VZV, namely, pseudorabies virus and duck enteritis herpes virus; both lack the ICP34.5 protein.

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.

Colony Stimulating Factor-1 Receptor Expressing Cells Infiltrating the Cornea Control Corneal Nerve Degeneration in Response to HSV-1 Infection

Purpose

Herpes simplex virus type-1 (HSV-1) is a leading cause of neurotrophic keratitis, characterized by decreased or absent corneal sensation due to damage to the sensory corneal innervation. We previously reported the elicited immune response to infection contributes to the mechanism of corneal nerve regression/damage during acute HSV-1 infection. Our aim is to further establish the involvement of infiltrated macrophages in the mechanism of nerve loss upon infection.

Methods

Macrophage Fas-Induced Apoptosis (MAFIA) transgenic C57BL/6 mice were systemically treated with AP20187 dimerizer or vehicle (VEH), and their corneas, lymph nodes, and blood were assessed for CD45+CD11b+GFP+ cell depletion by flow cytometry (FC). Mice were ocularly infected with HSV-1 or left uninfected. At 2, 4, and/or 6 days post infection (PI), corneas were assessed for sensitivity and harvested for FC, nerve structure by immunohistochemistry, viral content by plaque assay, soluble factor content by suspension array, and activation of signaling pathways by Western blot analysis. C57BL6 mice were used to compare to the MAFIA mouse model.

Results

MAFIA mice treated with AP20187 had efficient depletion of CD45+CD11b+GFP+ cells in the tissues analyzed. The reduction of CD45+CD11b+GFP+ cells recruited to the infected corneas of AP20187-treated mice correlated with preservation of corneal nerve structure and function, decreased protein concentration of inflammatory cytokines, and decreased STAT3 activation despite no changes in viral content in the cornea compared to VEH-treated animals.

Conclusions

Our results suggest infiltrated macrophages are early effectors in the nerve regression following HSV-1 infection. We propose the neurodegeneration mechanism involves macrophages, local up-regulation of IL-6, and activation of STAT3.

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.

Long-term consequences of topical dexamethasone treatment during acute corneal HSV-1 infection on the immune system

Herpes simplex virus type 1 (HSV-1) is a leading cause of neurotrophic keratitis (NTK). NTK is characterized by decreased corneal sensation from damage to the corneal sensory fibers. We have reported on the regression of corneal nerves and their function during acute HSV-1 infection. That nerve loss is followed by an aberrant process of nerve regeneration during the latent phase of infection that lacks functional recovery. We recently showed the elicited immune response in the infected cornea, and not viral replication itself, is part of the mechanism responsible for the nerve degeneration process after infection. Specifically, we showed infected corneas topically treated with dexamethasone (DEX) significantly retained both structure and sensitivity of the corneal nerve network in comparison to mice treated with control eye drops, consistent with decreased levels of proinflammatory cytokines and reduced influx of macrophages and CD8+ T cells into the cornea. This study was undertaken to analyze the long-term effect of such a localized, immunosuppressive paradigm (DEX drops on the cornea surface during the first 8 d of HSV-1 infection) on the immune system and on corneal pathology. We found the profound immunosuppressive effect of DEX on lymphoid tissue was sustained in surviving mice for up to 30 d postinfection (p.i.). DEX treatment had prolonged effects, preserving corneal innervation and its function and blunting neovascularization, as analyzed at 30 d p.i. Our data support previously reported observations of an association between the persistent presence of inflammatory components in the latently infected cornea and structural and functional nerve defects in NTK.

Impact of Type I Interferon on the Safety and Immunogenicity of an Experimental Live-Attenuated Herpes Simplex Virus 1 Vaccine in Mice

Viral fitness dictates virulence and capacity to evade host immune defenses. Understanding the biological underpinnings of such features is essential for rational vaccine development. We have previously shown that the live-attenuated herpes simplex virus 1 (HSV-1) mutant lacking the nuclear localization signal (NLS) on the ICP0 gene (0ΔNLS) is sensitive to inhibition by interferon beta (IFN-β) in vitro and functions as a highly efficacious experimental vaccine. Here, we characterize the host immune response and in vivo pathogenesis of HSV-1 0ΔNLS relative to its fully virulent parental strain in C57BL/6 mice. Additionally, we explore the role of type 1 interferon (IFN-α/β) signaling on virulence and immunogenicity of HSV-1 0ΔNLS and uncover a probable sex bias in the induction of IFN-α/β in the cornea during HSV-1 infection. Our data show that HSV-1 0ΔNLS lacks neurovirulence even in highly immunocompromised mice lacking the IFN-α/β receptor. These studies support the translational viability of the HSV-1 0ΔNLS vaccine strain by demonstrating that, while it is comparable to a virulent parental strain in terms of immunogenicity, HSV-1 0ΔNLS does not induce significant tissue pathology.IMPORTANCE HSV-1 is a common human pathogen associated with a variety of clinical presentations ranging in severity from periodic "cold sores" to lethal encephalitis. Despite the consistent failures of HSV subunit vaccines in clinical trials spanning the past 28 years, opposition to live-attenuated HSV vaccines predicated on unfounded safety concerns currently limits their widespread acceptance. Here, we demonstrate that a live-attenuated HSV-1 vaccine has great translational potential.