Role of IL-27 in HSV-1-Induced Herpetic Stromal Keratitis.

Herpetic stromal keratitis (HSK) is a painful and vision-impairing disease caused by recurrent HSV-1 infection of the cornea. The virus replication in the corneal epithelium and associated inflammation play a dominant role in HSK progression. Current HSK treatments targeting inflammation or virus replication are partially effective and promote HSV-1 latency, and long-term use can cause side effects. Thus, understanding molecular and cellular events that control HSV-1 replication and inflammation is crucial for developing novel HSK therapies. In this study, we report that ocular HSV-1 infection induces the expression of IL-27, a pleiotropic immunoregulatory cytokine. Our data indicate that HSV-1 infection stimulates IL-27 production by macrophages. Using a primary corneal HSV-1 infection mouse model and IL-27 receptor knockout mice, we show that IL-27 plays a critical role in controlling HSV-1 shedding from the cornea, the optimum induction of effector CD4+ T cell responses, and limiting HSK progression. Using in vitro bone marrow-derived macrophages, we show that IL-27 plays an antiviral role by regulating macrophage-mediated HSV-1 killing, IFN-ß production, and IFN-stimulated gene expression after HSV-1 infection. Furthermore, we report that IL-27 is critical for macrophage survival, Ag uptake, and the expression of costimulatory molecules involved in the optimum induction of effector T cell responses. Our results indicate that IL-27 promotes endogenous antiviral and anti-inflammatory responses and represents a promising target for suppressing HSK progression.

Rapidly Dissolving Trans-scleral Microneedles for Intraocular Delivery of Cyclosporine A.

Cyclosporine A (CsA) is a cyclic peptide immunosuppressant drug that is beneficial in the treatment of various ocular diseases. However, its ocular bioavailability in the posterior eye is limited due to its poor aqueous solubility. Conventional CsA formulations such as a solution or emulsion permeate poorly across the eye due to various static and dynamic barriers of the eye. Dissolvable microneedle (MN)-based patches can be used to overcome barrier properties and, thus, enhance the ocular bioavailability of CsA in the posterior eye. CsA-loaded dissolvable MN patches were fabricated using polyvinylpyrrolidone (PVP) and characterized for MN uniformity and sharpness using SEM. Further characterization for its failure force, penetration force, and depth of penetration were analyzed using a texture analyzer. Finally, the dissolution time, ex vivo permeation, and ocular distribution of cyclosporine were determined in isolated porcine eyes. PVP MNs were sharp, uniform with good mechanical properties, and dissolved within 5 min. Ocular distribution of CsA in a whole porcine eye perfusion model showed a significant increase of CsA levels in various posterior segment ocular tissues as compared to a topically applied ophthalmic emulsion (Restasis®) (P < 0.001). Dissolving MNs of CsA were prepared, and the MN arrays can deliver CsA to the back of the eye offering potential for treating various inflammatory diseases.

IFN-λ Regulates Neutrophil Biology to Suppress Inflammation in Herpes Simplex Virus-1-Induced Corneal Immunopathology.

HSV-1 infection of the cornea causes a severe immunoinflammatory and vision-impairing condition called herpetic stromal keratitis (SK). The virus replication in corneal epithelium followed by neutrophil- and CD4+ T cell-mediated inflammation plays a dominant role in SK. Although previous studies demonstrate critical functions of type I IFNs (IFN-α/ß) in HSV-1 infection, the role of recently discovered IFN-λ (type III IFN), specifically at the corneal mucosa, is poorly defined. Our study using a mouse model of SK pathogenesis shows that HSV-1 infection induces a robust IFN-λ response compared with type I IFN production at the corneal mucosal surface. However, the normal progression of SK indicates that the endogenous IFN responses are insufficient to suppress HSV-1-induced corneal pathology. Therefore, we examined the therapeutic efficacy of exogenous rIFN-λ during SK progression. Our results show that rIFN-λ therapy suppressed inflammatory cell infiltration in the cornea and significantly reduced the SK pathologic condition. Early rIFN-λ treatment significantly reduced neutrophil and macrophage infiltration, and IL-6, IL-1ß, and CXCL-1 production in the cornea. Notably, the virucidal capacity of neutrophils and macrophages measured by reactive oxygen species generation was not affected. Similarly, ex vivo rIFN-λ treatment of HSV-1-stimulated bone marrow-derived neutrophils significantly promoted IFN-stimulated genes without affecting reactive oxygen species production. Collectively, our data demonstrate that exogenous topical rIFN-λ treatment during the development and progression of SK could represent a novel therapeutic approach to control HSV-1-induced inflammation and associated vision impairment.

Short palate, lung, and nasal epithelial clone 1 (SPLUNC1) level determines steroid-resistant airway inflammation in aging.

Asthma and its heterogeneity change with age. Increased airspace neutrophil numbers contribute to severe steroid-resistant asthma exacerbation in the elderly, which correlates with the changes seen in adults with asthma. However, whether that resembles the same disease mechanism and pathophysiology in aged and adults is poorly understood. Here, we sought to address the underlying molecular mechanism of steroid-resistant airway inflammation development and response to corticosteroid (Dex) therapy in aged mice. To study the changes in inflammatory mechanism, we used a clinically relevant treatment model of house-dust mite (HDM)-induced allergic asthma and investigated lung adaptive immune response in adult (20-22 wk old) and aged (80-82 wk old) mice. Our result indicates an age-dependent increase in airway hyperresponsiveness (AHR), mixed granulomatous airway inflammation comprising eosinophils and neutrophils, and Th1/Th17 immune response with progressive decrease in frequencies and numbers of HDM-bearing dendritic cells (DC) accumulation in the draining lymph node (DLn) of aged mice as compared with adult mice. RNA-Seq experiments of the aged lung revealed short palate, lung, and nasal epithelial clone 1 (SPLUNC1) as one of the steroid-responsive genes, which progressively declined with age and further by HDM-induced inflammation. Moreover, we found increased glycolytic reprogramming, maturation/activation of DCs, the proliferation of OT-II cells, and Th2 cytokine secretion with recombinant SPLUNC1 (rSPLUNC1) treatment. Our results indicate a novel immunomodulatory role of SPLUNC1 regulating metabolic adaptation/maturation of DC. An age-dependent decline in the SPLUNC1 level may be involved in developing steroid-resistant airway inflammation and asthma heterogeneity.

Quantitative proteomics of hamster lung tissues infected with SARS-CoV-2 reveal host factors having implication in the disease pathogenesis and severity.

Syrian golden hamsters (Mesocricetus auratus) infected by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) manifests lung pathology. In this study, efforts were made to check the infectivity of a local SARS-CoV-2 isolate in a self-limiting and non-lethal hamster model and evaluate the differential expression of lung proteins during acute infection and convalescence. The findings of this study confirm the infectivity of this isolate in vivo. Analysis of clinical parameters and tissue samples show the pathophysiological manifestation of SARS-CoV-2 infection similar to that reported earlier in COVID-19 patients and hamsters infected with other isolates. However, diffuse alveolar damage (DAD), a common histopathological feature of human COVID-19 was only occasionally noticed. The lung-associated pathological changes were very prominent on the 4th day post-infection (dpi), mostly resolved by 14 dpi. Here, we carried out the quantitative proteomic analysis of the lung tissues from SARS-CoV-2-infected hamsters on day 4 and day 14 post-infection. This resulted in the identification of 1585 proteins of which 68 proteins were significantly altered between both the infected groups. Pathway analysis revealed complement and coagulation cascade, platelet activation, ferroptosis, and focal adhesion as the top enriched pathways. In addition, we also identified altered expression of two pulmonary surfactant-associated proteins (Sftpd and Sftpb), known for their protective role in lung function. Together, these findings will aid in understanding the mechanism(s) involved in SARS-CoV-2 pathogenesis and progression of the disease.

Immunoproteomic analysis of fish ectoparasite, Argulus siamensis antigens.

AIM: An immunoproteomic approach was followed to identify immunoreactive antigens of fish ectoparasite, Argulus siamensis with rohu (Labeo rohita) immune sera for screening of potential vaccine candidates. MATERIALS AND RESULTS: The whole adult Argulus antigen was run in 2D electrophoresis with IEF in 7 cm IPG strips of pH 4-7 and SDS-PAGE with 12% acrylamide concentration. Two parallel gels were run; one was stained with silver stain, and the other was Western blotted to nitrocellulose paper (NCP) and reacted with rohu anti-A siamensis sera. Fourteen protein spots corresponding to the spots developed in NCP were picked from the silver-stained gel and subjected to mass spectrometry in MALDI-TOF/TOF. The MS/MS spectra were analysed in MASCOT software with taxonomy 'other metazoa' and the proteins identified based on similarity with the proteins from heterologous species. The gene ontology analysis revealed a majority of proteins being involved in binding activity in 'molecular function' and belonging to metabolic processes in 'biologic process' categories. The possibility of these proteins as vaccine candidates against A siamensis is discussed in the paper. CONCLUSION: Three of the identified proteins namely, bromodomain-containing protein, anaphase-promoting complex subunit 5 and elongation factor-2 could possibly serve as vaccine candidates against argulosis in carps.

Plasma membrane proteome of adhesion-competent endometrial epithelial cells and its modulation by Rab11a.

Human endometrial epithelium (EE) is composed of a multitude of proteins, amongst which those localized on the plasma membrane [plasma membrane proteins (PMPs)] are of critical relevance in the early stages of implantation. Evidence supports the key role of few PMPs in implantation. However, many remain unidentified, as efforts have not been made till date to generate the plasma membrane proteome of human EE cells, using a gel-free approach. This study presents a protein catalog of the PMP enriched fraction of Ishikawa cell line; often used as an in vitro model for embryo-adhesive EE. Liquid chromatography with tandem mass spectrometry identified 3,598 proteins. Of these, 1,963 proteins were annotated for their membrane localization. Of 1,963 proteins, 1,321 were found to have a transmembrane domain and 43 proteins had glycophosphatidylinositol (GPI) anchor. Extensive data mining revealed endometrial expression of 943 proteins reported in humans and/or rodents. Further, quantitative alterations were observed in the plasma membrane proteome on the perturbation of intracellular trafficking. Silencing of Rab11a (known for its role in plasma membrane organization) expression caused alteration in the abundance of 74 proteins. Caveolin-1 and EpCAM levels were reduced whereas Rab4a abundance increased in the PMP extracts of Rab11a deficient cells, compared with control cells. Briefly, the study reports the identity of several novel plasma membrane-localized proteins. A major spin-off of the study is the identification of novel proteins trafficked by Rab11a to the plasma membrane. Targeted analysis of novel PMPs may reveal their specific roles in endometrial receptivity and implantation.

GPR81, a Cell-Surface Receptor for Lactate, Regulates Intestinal Homeostasis and Protects Mice from Experimental Colitis.

At mucosal sites such as the intestine, the immune system launches robust immunity against invading pathogens while maintaining a state of tolerance to commensal flora and ingested food Ags. The molecular mechanisms underlying this phenomenon remain poorly understood. In this study, we report that signaling by GPR81, a receptor for lactate, in colonic dendritic cells and macrophages plays an important role in suppressing colonic inflammation and restoring colonic homeostasis. Genetic deletion of GPR81 in mice led to increased Th1/Th17 cell differentiation and reduced regulatory T cell differentiation, resulting in enhanced susceptibility to colonic inflammation. This was due to increased production of proinflammatory cytokines (IL-6, IL-1ß, and TNF-α) and decreased expression of immune regulatory factors (IL-10, retinoic acid, and IDO) by intestinal APCs lacking GPR81. Consistent with these findings, pharmacological activation of GPR81 decreased inflammatory cytokine expression and ameliorated colonic inflammation. Taken together, these findings identify a new and important role for the GPR81 signaling pathway in regulating immune tolerance and colonic inflammation. Thus, manipulation of the GPR81 pathway could provide novel opportunities for enhancing regulatory responses and treating colonic inflammation.

Histocompatibility locus antigens regions contribute to the ethnicity bias of Epstein-Barr virus-associated nasopharyngeal carcinoma in higher-incidence populations.

Nasopharyngeal carcinoma (NPC) is one the most confusing and rare malignancy in most part of the world with significantly high occurrence in some populations of Southeast Asia, North Africa and Alaska. Apart from the dietary and environmental factors, NPC is well-associated with Epstein-Barr virus (EBV) infection in these ethnic groups. However, the internal molecular mechanism(s) for such association in specific populations is not known till date. Polymorphisms in the genes of histocompatibility locus antigens (HLA) are reported in NPC, but association of any particular polymorphism with ethnicity is not established yet. Here, we report a set of HLA polymorphisms in EBV-infected NPC samples from Northeast Indian population. These polymorphisms might play an important role for the lack of proper immune function against EBV infection and thus, eventually, for NPC generation in endemic populations like those of Northeast India.

RIG-I Signaling Is Critical for Efficient Polyfunctional T Cell Responses during Influenza Virus Infection.

Retinoic acid inducible gene-I (RIG-I) is an innate RNA sensor that recognizes the influenza A virus (IAV) RNA genome and activates antiviral host responses. Here, we demonstrate that RIG-I signaling plays a crucial role in restricting IAV tropism and regulating host immune responses. Mice deficient in the RIG-I-MAVS pathway show defects in migratory dendritic cell (DC) activation, viral antigen presentation, and priming of CD8+ and CD4+ T cell responses during IAV infection. These defects result in decreased frequency of polyfunctional effector T cells and lowered protection against heterologous IAV challenge. In addition, our data show that RIG-I activation is essential for protecting epithelial cells and hematopoietic cells from IAV infection. These diverse effects of RIG-I signaling are likely imparted by the actions of type I interferon (IFN), as addition of exogenous type I IFN is sufficient to overcome the defects in antigen presentation by RIG-I deficient BMDC. Moreover, the in vivo T cell defects in RIG-I deficient mice can be overcome by the activation of MDA5 -MAVS via poly I:C treatment. Taken together, these findings demonstrate that RIG-I signaling through MAVS is critical for determining the quality of polyfunctional T cell responses against IAV and for providing protection against subsequent infection from heterologous or novel pandemic IAV strains.

Homeostatic PPARα Signaling Limits Inflammatory Responses to Commensal Microbiota in the Intestine.

Dietary lipids and their metabolites activate members of the peroxisome proliferative-activated receptor (PPAR) family of transcription factors and are critical for colonic health. The PPARα isoform plays a vital role in regulating inflammation in various disease settings, but its role in intestinal inflammation, commensal homeostasis, and mucosal immunity in the gut are unclear. In this study, we demonstrate that the PPARα pathway in innate immune cells orchestrates gut mucosal immunity and commensal homeostasis by regulating the expression of IL-22 and the antimicrobial peptides RegIIIß, RegIIIγ, and calprotectin. Additionally, the PPARα pathway is critical for imparting regulatory phenotype in intestinal macrophages. PPARα deficiency in mice led to commensal dysbiosis in the gut, resulting in a microbiota-dependent increase in the expression of inflammatory cytokines and enhanced susceptibility to intestinal inflammation. Pharmacological activation of this pathway decreased the expression of inflammatory cytokines and ameliorated colonic inflammation. Taken together, these findings identify a new important innate immune function for the PPARα signaling pathway in regulating intestinal inflammation, mucosal immunity, and commensal homeostasis. Thus, the manipulation of the PPARα pathway could provide novel opportunities for enhancing mucosal immunity and treating intestinal inflammation.

IL-17A-mediated protection against Acanthamoeba keratitis.

Acanthamoeba keratitis (AK) is a very painful and vision-impairing infection of the cornea that is difficult to treat. Although past studies have indicated a critical role of neutrophils and macrophages in AK, the relative contribution of the proinflammatory cytokine, IL-17A, that is essential for migration, activation, and function of these cells into the cornea is poorly defined. Moreover, the role of the adaptive immune response, particularly the contribution of CD4(+) T cell subsets, Th17 and regulatory T cells , in AK is yet to be understood. In this report, using a mouse corneal intrastromal injection-induced AK model, we show that Acanthamoeba infection induces a strong CD4(+) T effector and regulatory T cell response in the cornea and local draining lymph nodes. We also demonstrate that corneal Acanthamoeba infection induces IL-17A expression and that IL-17A is critical for host protection against severe AK pathology. Accordingly, IL-17A neutralization in Acanthamoeba-infected wild-type mice or Acanthamoeba infection of mice lacking IL-17A resulted in a significantly increased corneal AK pathology, increased migration of inflammatory cells at the site of inflammation, and a significant increase in the effector CD4(+) T cell response in draining lymph nodes. Thus, in sharp contrast with other corneal infections such as herpes and Pseudomonas aeruginosa keratitis where IL-17A exacerbates corneal pathology and inflammation, the findings presented in this article suggest that IL-17A production after Acanthamoeba infection plays an important role in host protection against invading parasites.

Canonical wnt signaling in dendritic cells regulates Th1/Th17 responses and suppresses autoimmune neuroinflammation.

Breakdown in immunological tolerance to self-Ags or uncontrolled inflammation results in autoimmune disorders. Dendritic cells (DCs) play an important role in regulating the balance between inflammatory and regulatory responses in the periphery. However, factors in the tissue microenvironment and the signaling networks critical for programming DCs to control chronic inflammation and promote tolerance are unknown. In this study, we show that wnt ligand-mediated activation of ß-catenin signaling in DCs is critical for promoting tolerance and limiting neuroinflammation. DC-specific deletion of key upstream (lipoprotein receptor-related protein [LRP]5/6) or downstream (ß-catenin) mediators of canonical wnt signaling in mice exacerbated experimental autoimmune encephalomyelitis pathology. Mechanistically, loss of LRP5/6-ß-catenin-mediated signaling in DCs led to an increased Th1/Th17 cell differentiation but reduced regulatory T cell response. This was due to increased production of proinflammatory cytokines and decreased production of anti-inflammatory cytokines such as IL-10 and IL-27 by DCs lacking LRP5/6-ß-catenin signaling. Consistent with these findings, pharmacological activation of canonical wnt/ß-catenin signaling delayed experimental autoimmune encephalomyelitis onset and diminished CNS pathology. Thus, the activation of canonical wnt signaling in DCs limits effector T cell responses and represents a potential therapeutic approach to control autoimmune neuroinflammation.

Galectin-8 promotes regulatory T-cell differentiation by modulating IL-2 and TGFß signaling.

Galectins (Gals) have emerged as potent immunoregulatory molecules that control chronic inflammation through distinct mechanisms. Gal-8, a tandem-repeat type Gal with unique preference for α2,3-sialylated glycans, is ubiquitously expressed, but little is known about its role in T-cell differentiation. Here we report that Gal-8 promotes the polyclonal differentiation of primary mouse regulatory T (Treg) cells in vitro. We further show that Gal-8 also facilitates antigen-specific differentiation of Treg cells, and that Treg cells polarized in the presence of Gal-8 express cytotoxic T-lymphocyte antigen-4 and interleukin (IL)-10 at a higher frequency than control Treg cells, and efficiently inhibit proliferation of activated T-cells in vitro. Investigation of the mechanism by which Gal-8 promotes Treg conversion revealed that Gal-8 activates transforming growth factor-ß signaling and promotes sustained IL-2R signaling. Taken together, these data suggest that Gal-8 promotes the differentiation of highly suppressive Treg cells, which has implications for the treatment of inflammatory and autoimmune diseases.

HSP60 plays a regulatory role in IL-1ß-induced microglial inflammation via TLR4-p38 MAPK axis.

BACKGROUND: IL-1ß, also known as "the master regulator of inflammation", is a potent pro-inflammatory cytokine secreted by activated microglia in response to pathogenic invasions or neurodegeneration. It initiates a vicious cycle of inflammation and orchestrates various molecular mechanisms involved in neuroinflammation. The role of IL-1ß has been extensively studied in neurodegenerative disorders; however, molecular mechanisms underlying inflammation induced by IL-1ß are still poorly understood. The objective of our study is the comprehensive identification of molecular circuitry involved in IL-1ß-induced inflammation in microglia through protein profiling. METHODS: To achieve our aim, we performed the proteomic analysis of N9 microglial cells with and without IL-1ß treatment at different time points. Expression of HSP60 in response to IL-1ß administration was checked by quantitative real-time PCR, immunoblotting, and immunofluorescence. Interaction of HSP60 with TLR4 was determined by co-immunoprecipitation. Inhibition of TLR4 was done using TLR4 inhibitor to reveal its effect on IL-1ß-induced inflammation. Further, effect of HSP60 knockdown and overexpression were assessed on the inflammation in microglia. Specific MAPK inhibitors were used to reveal the downstream MAPK exclusively involved in HSP60-induced inflammation in microglia. RESULTS: Total 21 proteins were found to be differentially expressed in response to IL-1ß treatment in N9 microglial cells. In silico analysis of these proteins revealed unfolded protein response as one of the most significant molecular functions, and HSP60 turned out to be a key hub molecule. IL-1ß induced the expression as well as secretion of HSP60 in extracellular milieu during inflammation of N9 cells. Secreted HSP60 binds to TLR4 and inhibition of TLR4 suppressed IL-1ß-induced inflammation to a significant extent. Our knockdown and overexpression studies demonstrated that HSP60 increases the phosphorylation of ERK, JNK, and p38 MAPKs in N9 cells during inflammation. Specific inhibition of p38 by inhibitors suppressed HSP60-induced inflammation, thus pointed towards the major role of p38 MAPK rather than ERK1/2 and JNK in HSP60-induced inflammation. Furthermore, silencing of upstream modulator of p38, i.e., MEK3/6 also reduced HSP60-induced inflammation. CONCLUSIONS: IL-1ß induces expression of HSP60 in N9 microglial cells that further augments inflammation via TLR4-p38 MAPK axis.

TLR2-dependent activation of ß-catenin pathway in dendritic cells induces regulatory responses and attenuates autoimmune inflammation.

Dendritic cells (DCs) sense microbes via multiple innate receptors. Signals from different innate receptors are coordinated and integrated by DCs to generate specific innate and adaptive immune responses against pathogens. Previously, we have shown that two pathogen recognition receptors, TLR2 and dectin-1, which recognize the same microbial stimulus (zymosan) on DCs, induce mutually antagonistic regulatory or inflammatory responses, respectively. How diametric signals from these two receptors are coordinated in DCs to regulate or incite immunity is not known. In this study, we show that TLR2 signaling via AKT activates the ß-catenin/T cell factor 4 pathway in DCs and programs them to drive T regulatory cell differentiation. Activation of ß-catenin/T cell factor 4 was critical to induce regulatory molecules IL-10 (Il-10) and vitamin A metabolizing enzyme retinaldehyde dehydrogenase 2 (Aldh1a2) and to suppress proinflammatory cytokines. Deletion of ß-catenin in DCs programmed them to drive Th17/Th1 cell differentiation in response to zymosan. Consistent with these findings, activation of the ß-catenin pathway in DCs suppressed chronic inflammation and protected mice from Th17/Th1-mediated autoimmune neuroinflammation. Thus, activation of ß-catenin in DCs via the TLR2 receptor is a novel mechanism in DCs that regulates autoimmune inflammation.

Development of novel antibodies against non-structural proteins nsP1, nsP3 and nsP4 of chikungunya virus: potential use in basic research.

Chikungunya virus (CHIKV) has reemerged recently as an important pathogen, causing several large epidemics worldwide. This necessitates the development of better reagents to understand its biology and to establish effective and safe control measures. The present study describes the development and characterization of polyclonal antibodies (pAbs) against synthetic peptides of CHIKV non-structural proteins (nsPs; nsP1, nsP3 and nsP4). The reactivity of these pAbs was demonstrated by ELISA and Western blot. Additionally, in vitro infection studies in a mammalian system confirmed that these pAbs are highly sensitive and specific for CHIKV nsPs, as these proteins were detected very early during viral replication. Homology analysis of the selected epitope sequences revealed that they are conserved among all of the CHIKV strains of different genotypes, while comparison with other alphavirus sequences showed that none of them are 100% identical to the epitope sequences (except Onyong-nyong and Igbo Ora viruses, which show 100% identity to the nsP4 epitope). Interestingly, two different forms of CHIKV nsP1 and three different forms of nsP3 were detected in Western blot analysis during infection; however, further experimental investigations are required to confirm their identity. Also, the use of these antibodies demonstrated faster and enhanced expression profiles of all CHIKV nsPs in 2006 Indian outbreak strains when compared to the CHIKV prototype strain, suggesting the epidemic potential of the 2006 isolate. Accordingly, it can be suggested that the pAbs reported in this study can be used as sensitive and specific tools for experimental investigations of CHIKV replication and infection.

Galectin-1-mediated suppression of Pseudomonas aeruginosa-induced corneal immunopathology.

Corneal infection with Pseudomonas aeruginosa leads to a severe immunoinflammatory lesion, often causing vision impairment and blindness. Although past studies have indicated a critical role for CD4(+) T cells, particularly Th1 cells, in corneal immunopathology, the relative contribution of recently discovered Th17 and regulatory T cells is undefined. In this study, we demonstrate that after corneal P. aeruginosa infection, both Th1 and Th17 cells infiltrate the cornea with increased representation of Th17 cells. In addition to Th1 and Th17 cells, regulatory T cells also migrate into the cornea during early as well as late stages of corneal pathology. Moreover, using galectin-1 (Gal-1), an immunomodulatory carbohydrate-binding molecule, we investigated whether shifting the balance among various CD4(+) T cell subsets can modulate P. aeruginosa-induced corneal immunopathology. We demonstrate in this study that local recombinant Gal-1 (rGal-1) treatment by subconjunctival injections significantly diminishes P. aeruginosa-mediated corneal inflammation through multiple mechanisms. Specifically, in our study, rGal-1 treatment significantly diminished corneal infiltration of total CD45(+) T cells, neutrophils, and CD4(+) T cells. Furthermore, rGal-1 treatment significantly reduced proinflammatory Th17 cell response in the cornea as well as local draining lymph nodes. Also, rGal-1 therapy promoted anti-inflammatory Th2 and IL-10 response in secondary lymphoid organs. Collectively, our results indicate that corneal P. aeruginosa infection induces a strong Th17-mediated corneal pathology, and treatment with endogenously derived protein such as Gal-1 may be of therapeutic value for the management of bacterial keratitis, a prevalent cause of vision loss and blindness in humans worldwide.

IL-17A differentially regulates corneal vascular endothelial growth factor (VEGF)-A and soluble VEGF receptor 1 expression and promotes corneal angiogenesis after herpes simplex virus infection.

Ocular infection with HSV causes corneal neovascularization (CV), an essential step in the pathogenesis of the blinding immunoinflammatory lesion stromal keratitis. The infection results in IL-17A production, which contributes to CV in ways that together serve to shift the balance between corneal concentrations of vascular endothelial growth factor A (VEGF-A) and the soluble vascular endothelial growth factor receptor 1 molecule, which binds to VEGF-A and blocks its function (a so-called VEGF trap). Accordingly, animals lacking responses to IL-17A signaling, either because of IL-17 receptor A knockout or wild-type animals that received neutralizing mAb to IL-17A, had diminished CV, compared with controls. The procedures reduced VEGF-A protein levels but had no effect on the levels of soluble vascular endothelial growth factor receptor 1. Hence the VEGF trap was strengthened. IL-17A also caused increased CXCL1/KC synthesis, which attracts neutrophils to the inflammatory site. Neutrophils further influenced the extent of CV by acting as an additional source of VEGF-A, as did metalloproteinase enzymes that degrade the soluble receptor, inhibiting its VEGF-blocking activity. Our results indicate that suppressing the expression of IL-17A, or increasing the activity of the VEGF trap, represents a useful approach to inhibiting CV and the control of an ocular lesion that is an important cause of human blindness.

On the role of regulatory T cells during viral-induced inflammatory lesions.

Ocular HSV-1 infection can result in stromal keratitis, a blinding immunoinflammatory lesion that represents an immunopathological response to the infection. CD4(+) T cells are the main orchestrators, and lesions are more severe if the regulatory T cell (Treg) response is compromised from the onset of infection. Little is known about the role of Foxp3(+)CD4(+) Tregs during ongoing inflammatory reactions, which is the topic of this article. We used DEREG mice and depleted Tregs at different times postinfection. We show that lesions became more severe even when depletion was begun in the clinical phase of the disease. This outcome was explained both by Tregs' influence on the activity of inflammatory effector T cells at the lesion site and by an effect in lymphoid tissues that led to reduced numbers of effectors and less trafficking of T cells and neutrophils to the eye. Our results demonstrate that Tregs can beneficially influence the impact of ongoing tissue-damaging responses to a viral infection and imply that therapies boosting Treg function in the clinical phase hold promise for controlling a lesion that is an important cause of human blindness.