A protective role for IL-6 in staphylococcal microbial keratitis

Rose Bengal Photodynamic Therapy (RB-PDT) Modulates the Inflammatory Response in LPS-Stimulated Human Corneal Fibroblasts By Influencing NF-κB and p38 MAPK Signaling Pathways

PURPOSE

To investigate the effect of rose bengal photodynamic therapy on lipopolysaccharide-induced inflammation in human corneal fibroblasts. Furthermore, to analyze potential involvement of the mitogen-activated protein kinase and nuclear factor kappa B signaling pathways in this process.

METHODS

Human corneal fibroblast cultures underwent 0-2.0 µg/mL lipopolysaccharide treatment, and 24 h later rose bengal photodynamic therapy (0.001% RB, 565 nm wavelength illumination, 0.17 J/cm2 fluence). Interleukin-6, interleukin-8, intercellular adhesion molecule-1, interferon regulatory factor-3, interferon α2, and interferon β1 gene expressions were determined by quantitative PCR. Interleukin-6, interleukin-8, and C-C motif chemokine ligand-4 concentrations in the cell culture supernatant were measured by enzyme-linked immunosorbent assays and intercellular adhesion molecule-1 protein level in human corneal fibroblasts by western blot. In addition, the nuclear factor kappa B and mitogen-activated protein kinase signaling pathways were investigated by quantitative PCR and phosphorylation of nuclear factor kappa B p65 and p38 mitogen-activated protein kinase by western blot.

RESULTS

Rose bengal photodynamic therapy in 2.0 µg/mL lipopolysaccharide-stimulated human corneal fibroblasts triggered interleukin-6 and interleukin-8 mRNA (p < .0001) and interleukin-6 protein increase (p < .0001), and downregulated intercellular adhesion molecule-1 expression (p < .001). C-C motif chemokine ligand-4, interferon regulatory factor-3, interferon α2, and interferon β1 expressions remained unchanged (p ≥ .2). Rose bengal photodynamic therapy increased IκB kinase subunit beta, nuclear factor kappa B p65, extracellular signal-regulated kinases-2, c-Jun amino terminal kinase, and p38 transcription (p ≤ .01), and triggered nuclear factor kappa B p65 and p38 mitogen-activated protein kinase phosphorylation (p ≤ .04) in lipopolysaccharide treated human corneal fibroblasts.

CONCLUSION

Rose bengal photodynamic therapy of lipopolysaccharide-stimulated human corneal fibroblasts can modify the inflammatory response by inducing interleukin-6 and interleukin-8 expression, and decreasing intercellular adhesion molecule-1 production. C-C motif chemokine ligand-4, interferon regulatory factor-3, and interferon α and β expressions are not affected by rose bengal photodynamic therapy in these cells. The underlying mechanisms may be associated with nuclear factor kappa B and p38 mitogen-activated protein kinase pathway activation.

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.

Human iPSC-derived macrophages for efficient Staphylococcus aureus clearance in a murine pulmonary infection model

Human iMφs show strong antimicrobial activity against S aureus in vitro and in vivo.

iMφs show accelerated and pronounced activation of a pro-inflammatory transcriptomic profile compared with monocyte-derived macrophages.

Primary or secondary immunodeficiencies are characterized by disruption of cellular and humoral immunity. Respiratory infections are a major cause of morbidity and mortality among immunodeficient or immunocompromised patients, with Staphylococcus aureus being a common offending organism. We propose here an adoptive macrophage transfer approach aiming to enhance impaired pulmonary immunity against S aureus. Our studies, using human-induced pluripotent stem cell-derived macrophages (iMφs), demonstrate efficient antimicrobial potential against methicillin-sensitive and methicillin-resistant clinical isolates of S aureus. Using an S aureus airway infection model in immunodeficient mice, we demonstrate that the adoptive transfer of iMφs is able to reduce the bacterial load more than 10-fold within 20 hours. This effect was associated with reduced granulocyte infiltration and less damage in lung tissue of transplanted animals. Whole transcriptome analysis of iMφs compared with monocyte-derived macrophages indicates a more profound upregulation of inflammatory genes early after infection and faster normalization 24 hours postinfection. Our data demonstrate high therapeutic efficacy of iMφ-based immunotherapy against S aureus infections and offer an alternative treatment strategy for immunodeficient or immunocompromised patients.

IL-6 Signaling Protects Zebrafish Larvae during Staphylococcus epidermidis Infection in a Bath Immersion Model

The host immune responses to Staphylococcus epidermidis, a frequent cause of nosocomial infections, are not well understood. We have established a bath immersion model of this infection in zebrafish (Danio rerio) larvae. Macrophages play a primary role in the host immune response and are involved in clearance of infection in the larvae. S. epidermidis infection results in upregulation of tlr-2 There is marked inflammation characterized by heightened NF-κB signaling and elevation of several proinflammatory cytokines. There is rapid upregulation of il-1b and tnf-a transcripts, whereas an increase in il-6 levels is relatively more delayed. The IL-6 signaling pathway is further amplified by elevation of IL-6 signal transducer (il-6st) levels, which negatively correlates with miRNA dre-miR-142a-5p. Enhanced IL-6 signaling is protective to the host in this model as inhibition of the signaling pathway resulted in increased mortality upon S. epidermidis infection. Our study describes the host immune responses to S. epidermidis infection, establishes the importance of IL-6 signaling, and identifies a potential role of miR-142-5p-il-6st interaction in this infection model.

Foundational concepts in the biology of bacterial keratitis

Bacterial infections of the cornea, or bacterial keratitis (BK), are notorious for causing rapidly fulminant disease and permanent vision loss, even among treated patients. In the last sixty years, dramatic upward trajectories in the frequency of BK have been observed internationally, driven in large part by the commercialization of hydrogel contact lenses in the late 1960s. Despite this worsening burden of disease, current evidence-based therapies for BK - including broad-spectrum topical antibiotics and, if indicated, topical corticosteroids - fail to salvage vision in a substantial proportion of affected patients. Amid growing concerns of rapidly diminishing antibiotic utility, there has been renewed interest in urgently needed novel treatments that may improve clinical outcomes on an individual and public health level. Bridging the translational gap in the care of BK requires the identification of new therapeutic targets and rational treatment design, but neither of these aims can be achieved without understanding the complex biological processes that determine how bacterial corneal infections arise, progress, and resolve. In this chapter, we synthesize the current wealth of human and animal experimental data that now inform our understanding of basic BK pathophysiology, in context with modern concepts in ocular immunology and microbiology. By identifying the key molecular determinants of clinical disease, we explore how novel treatments can be developed and translated into routine patient care.

Loss of Interleukin-6 Influences Transcriptional Immune Signatures and Alters Bacterial Colonization in the Skin

The skin functions as a protective barrier to inhibit the entry of foreign pathogens, all the while hosting a diverse milieu of microorganisms. Over time, skin cells, immune cells, cytokines, and microbes interact to integrate the processes of maintaining the skin's physical and immune barrier. In the present study, the basal expression of two immunologically divergent mouse strains C57BL/6 and BALB/c, as well as a strain on the C57 background lacking IL-6, was characterized. Additionally, cutaneous antimicrobial gene expression profiles and skin bacterial microbiome were assessed between strains. Total RNA sequencing was performed on untreated C57BL/6 (control), BALB/c, and IL-6-deficient skin samples and found over 3,400 genes differentially modulated between strains. It was found that each strain modulated its own transcriptional "profile" associated with skin homeostasis and also influenced the overall bacterial colonization as indicated by the differential phyla present on each strain. Together, these data not only provide a comprehensive view of the transcriptional changes in homeostatic skin of different mouse strains but also highlight the possible influence of the strain differences (e.g., Th1/Th2 balance) as well as a role for IL-6 in overall skin immunity and resident microbial populations.

Fusarium infection complicating rheumatic keratitis that acutely progressed to endophthalmitis during regular infusion of tocilizumab: a case report

Background

Filamentous fungi are ubiquitous in plants, water, and soil. The predominant fungi that infect the human cornea include Fusarium and Aspergillus species. The onset of fungal endophthalmitis is indolent, and typically takes weeks to months to develop after corneal infection. We report a case of Fusarium infection complicating rheumatic keratitis that acutely progressed to endophthalmitis during intravenous tocilizumab therapy.

Case presentation

A 65-year-old female patient was referred to our department due to pain and decreased vision in her left eye. Slit-lamp examination showed a white focus on the upper peripheral cornea, hypopyon, anterior chamber fibrin formation, marked ciliary hyperemia, and whole corneal epithelial defects. As the corneal scraping smear was positive for filamentous fungi and Fusarium species were detected by aqueous humor polymerase chain reaction, anti-fungal therapy was started. Although the initial response to anti-fungal therapy was good, we observed corneal infiltration, worsening hypopyon, and vitreous opacity after tocilizumab infusion. Given that the infection continued to progress despite conservative therapy, we performed penetrating keratoplasty combined with vitrectomy. After removal of the white focus beneath the intraocular lens, a temporary corneal prosthesis was mounted and the dense vitreous opacity was removed. Finally, a frozen donor graft was sutured in place. The corneal infiltration, hypopyon, and vitreous opacity all disappeared after the operation.

Conclusion

The rapid progression of Fusarium keratitis to endophthalmitis in a patient who was receiving a regular infusion of tocilizumab demonstrates that ocular condition should be closely monitored during systemic tocilizumab administration due to increased risk of infection.

American Academy of Optometry Microbial Keratitis Think Tank

SIGNIFICANCE

Think Tank 2019 affirmed that the rate of infection associated with contact lenses has not changed in several decades. Also, there is a trend toward more serious infections associated with Acanthamoeba and fungi. The growing use of contact lenses in children demands our attention with surveillance and case-control studies.

PURPOSE

The American Academy of Optometry (AAO) gathered researchers and key opinion leaders from around the world to discuss contact lens-associated microbial keratitis at the 2019 AAO Annual Meeting.

METHODS

Experts presented within four sessions. Session 1 covered the epidemiology of microbial keratitis, pathogenesis of Pseudomonas aeruginosa, and the role of lens care systems and storage cases in corneal disease. Session 2 covered nonbacterial forms of keratitis in contact lens wearers. Session 3 covered future needs, challenges, and research questions in relation to microbial keratitis in youth and myopia control, microbiome, antimicrobial surfaces, and genetic susceptibility. Session 4 covered compliance and communication imperatives.

RESULTS

The absolute rate of microbial keratitis has remained very consistent for three decades despite new technologies, and extended wear significantly increases the risk. Improved oxygen delivery afforded by silicone hydrogel lenses has not impacted the rates, and although the introduction of daily disposable lenses has minimized the risk of severe disease, there is no consistent evidence that they have altered the overall rate of microbial keratitis. Overnight orthokeratology lenses may increase the risk of microbial keratitis, especially secondary to Acanthamoeba, in children. Compliance remains a concern and a significant risk factor for disease. New insights into host microbiome and genetic susceptibility may uncover new theories. More studies such as case-control designs suited for rare diseases and registries are needed.

CONCLUSIONS

The first annual AAO Think Tank acknowledged that the risk of microbial keratitis has not decreased over decades, despite innovation. Important questions and research directions remain.

Morphological and cytokine profiles as key parameters to distinguish between Gram-negative and Gram-positive bacterial keratitis

Bacterial keratitis (BK) is an ocular disorder associated with poor visual prognosis. Quantification of the associated inflammatory response may provide insight into the pathogenesis of BK and guide treatment options. In this exploratory study, we evaluated 45 BK patients and 20 healthy controls by optical coherence tomography and pro-inflammatory tear cytokine analysis. The aim was to quantify the differential morphological and cytokine inflammatory response between Gram-negative and Gram-positive BK and to determine the diagnostic value of corneal thickness (CT) and infiltrate thickness (IT) in distinguishing Gram-ve BK in a clinical cohort. Greater CT and IT, at clinical presentation, were indicative of Gram-ve infection with values detected of ≥ 950 μm and ≥ 450 μm, respectively. Combination of these CT and IT values had a 100% sensitivity and 83.3% specificity as a diagnostic indicator of Gram-ve infection. Similarly, there were higher levels of IL-1β, IL-6 and IL-8 cytokines were quantified in keratitis caused by Gram-negative bacteria. Among the different tear cytokines analysed, a significant reduction after three days of treatment was detected for pro-inflammatory cytokines IL-1β, IL-2, IL-6, IL-8 and TNF-α, prior to starting with the administration of steroid drops. Overall, this study shows the potential value of serial OCT and tear cytokine measurements in the management of BK.

Targeting miR-223 in neutrophils enhances the clearance of Staphylococcus aureus in infected wounds

Argonaute 2 bound mature microRNA (Ago2-miRNA) complexes are key regulators of the wound inflammatory response and function in the translational processing of target mRNAs. In this study, we identified four wound inflammation-related Ago2-miRNAs (miR-139-5p, miR-142-3p, miR-142-5p, and miR-223) and show that miR-223 is critical for infection control. miR-223 ^Y/- mice exhibited delayed sterile healing with prolonged neutrophil activation and interleukin-6 expression, and markedly improved repair of Staphylococcus aureus-infected wounds. We also showed that the expression of miR-223 was regulated by CCAAT/enhancer binding protein alpha in human neutrophils after exposure to S. aureus peptides. Treatment with miR-223 ^Y/--derived neutrophils, or miR-223 antisense oligodeoxynucleotides in S. aureus-infected wild-type wounds markedly improved the healing of these otherwise chronic, slow healing wounds. This study reveals how miR-223 regulates the bactericidal capacity of neutrophils at wound sites and indicates that targeting miR-223 might be of therapeutic benefit for infected wounds in the clinic.

Potential Role of Ocular Microbiome, Host Genotype, Tear Cytokines, and Environmental Factors in Corneal Infiltrative Events in Contact Lens Wearers

Purpose

The purpose of this study was to explore differences in genotype, ocular surface microbiome, tear inflammatory markers, and environmental and behavioral exposures in soft contact lens (SCL) wearers with and without a history of corneal infiltrative events (CIEs).

Methods

Nine SCL wearers with a recent CIE and nine age-, sex-, and SCL material- and modality-matched controls were enrolled. The Contact Lens Risk Survey, slit-lamp examination data, basal tears, conjunctival microbial cultures, and peripheral blood samples were collected. Tear inflammatory mediator concentrations, genomic DNA from swabs, and whole exome sequencing of blood samples were quantified.

Results

There were no marked differences in SCL wear behaviors or exposures between case and control subjects. Predominant organisms detected among case and control subjects were Staphylococcus, Propionibacterium, Streptococcus, and Corynebacterium. Marginally higher levels of Neisseria were found in three of nine cases but zero of nine control samples (P = 0.056). A potentially deleterious missense single nucleotide polymorphism (SNP) variant in IL-6 Signal Transducer (IL6ST) was found in seven of eight cases and zero of nine controls (rs2228046; P = 0.03). The concentration of tear IL-6 was significantly higher in cases (4.5 [range, 2.1 to 6.2] pg/mL) versus controls (3.5 [range, 2.5 to 6.6] Pg/mL; = 0.02).

Conclusions

Tear IL-6 concentration was higher, and SNP variants were detected in subjects with a history of CIEs compared with healthy controls. The synthesis, signaling, and ocular surface cytokine concentration of IL-6 may be related to susceptibility to CIE. A larger study population is required to further explore relationships between genetic variations, the ocular surface microbiome, inflammatory mediators, and environmental exposures.

Staphylococcus aureus alpha-hemolysin impairs corneal epithelial wound healing and promotes intracellular bacterial invasion

Colonization by Staphylococcus aureus (S. aureus) has been implicated in many infectious and wound healing disorders. This study was performed to characterize the pathogenic role of S. aureus alpha-hemolysin (alpha-toxin) in corneal epithelial wound healing and infectious keratitis in the setting of a corneal wound. The effect of wild-type and isogenic Hla mutant (α-hemolysin gene deleted) S. aureus bacteria and conditioned media on corneal epithelial wound healing was tested in vitro using a scratch assay and in vivo using a murine epithelial debridement model. The invasiveness of wild-type and Hla mutant S. aureus was evaluated in vitro in human corneal epithelial cells and in vivo in a murine model of infectious keratitis following total epithelial debridement. S. aureus and its conditioned media significantly delayed epithelial wound closure both in vitro (P < 0.05) and in vivo (P < 0.05). The effect of S. aureus on wound healing was significantly diminished with the Hla mutant strain (P < 0.05). Likewise, compared to the wild-type strain, the Hla mutant strain demonstrated significantly reduced ability to invade corneal epithelial cells in vitro (P < 0.05) and infect murine corneas following total epithelial debridement in vivo (P < 0.05). In conclusion, S. aureus alpha-hemolysin plays a major role in the pathologic modulation of corneal epithelial wound healing and the intracellular invasion of the bacteria. Limiting colonization by S. aureus and/or blocking alpha-hemolysin may provide a therapeutic approach for corneal wound healing and infectious disorders.

Association of a placental Interleukin-6 genetic variant (rs1800796) with DNA methylation, gene expression and risk of acute chorioamnionitis

BACKGROUND

Acute chorioamnionitis (aCA), inflammation of the placenta and fetal membranes, is a frequently reported lesion in preterm deliveries. Genetic variants in innate immune system genes such as Interleukin-6 (IL6) may contribute to the placenta's inflammatory response, thus predisposing some pregnancies to aCA. These genetic variants may modulate molecular processes such as DNA methylation and gene expression, and in turn might affect susceptibility to aCA. Currently, there is remarkably little research on the role of fetal (placental) genetic variation in aCA. We aimed to explore the associations between genetic variants in candidate immune-system genes and susceptibility towards inflammatory responses in the placenta, which is linked to a strong inflammatory response in the newborn.

METHODS

DNA samples from 269 placentas (72 aCA cases, 197 non-aCA cases) were collected for this study. Samples were genotyped at 55 ancestry informative markers (AIMs) and 16 additional single nucleotide polymorphisms (SNPs) in 12 candidate innate immune system genes using the Sequenom iPLEX Gold Assay. Publicly available datasets were used to obtain DNA methylation (GSE100197, GSE74738, GSE115508, GSE44667, GSE98224) and gene expression data (GSE44711, GSE98224).

RESULTS

Differences in IL6 placental allele frequencies were associated with aCA (rs1800796, p = 0.04) with the CC genotype specifically implicated (OR = 3.1; p = 0.02). In a subset of the placental samples (n = 67; chorionic villi), we showed that the IL6 SNP (rs1800796) was associated with differential DNA methylation in five IL6-related CpG sites (cg01770232, cg02335517, cg07998387, cg13104385, and cg0526589), where individuals with a CC genotype showed higher DNA methylation levels than individuals carrying the GG genotype. Using two publicly available datasets, we observed that the DNA methylation levels at cg01770232 negatively correlated with IL6 gene expression in the placenta (r = - 0.67, p < 0.004; r = - 0.56, p < 2.937e-05).

CONCLUSIONS

We demonstrated that the minor C allele at the IL6 SNP (rs1800796), which is largely limited to East Asian populations, is associated with the presence of aCA. This SNP was associated with increased DNA methylation at a nearby MEPC2 binding site, which was also associated with decreased expression of IL6 in the placenta. Decreased expression of IL6 may increase vulnerability to microbial infection. Additional studies are required to confirm this association in Asian populations with larger sample sizes.

Acute tobacco smoke exposure exacerbates the inflammatory response to corneal wounds in mice via the sympathetic nervous system

Exposure to tobacco smoke is a major public health concern that can also affect ophthalmic health. Based on previous work demonstrating the important role of the sympathetic nervous system (SNS) in corneal wound repair, we postulated that acute tobacco smoke exposure (ATSE) may act through the SNS in the impairment of corneal wound repair. Here we find that ATSE rapidly increases the markers of inflammatory response in normal corneal limbi. After an abrasion injury, ATSE exaggerates inflammation, impairs wound repair, and enhances the expression of nuclear factor-κB (NF-κB) and inflammatory molecules such as interleukin-6 (IL-6) and IL-17. We find that chemical SNS sympathectomy, local adrenergic receptor antagonism, NF-κB1 inactivation, and IL-6/IL-17A neutralization can all independently attenuate ATSE-induced excessive inflammatory responses and alleviate their impairment of the healing process. These findings highlight that the SNS may represent a major molecular sensor and mediator of ATSE-induced inflammation.

The Pathogenesis of Staphylococcus aureus Eye Infections

Staphylococcus aureus is a major pathogen of the eye able to infect the tear duct, eyelid, conjunctiva, cornea, anterior and posterior chambers, and the vitreous chamber. Of these infections, those involving the cornea (keratitis) or the inner chambers of the eye (endophthalmitis) are the most threatening because of their potential to cause a loss in visual acuity or even blindness. Each of these ocular sites is protected by the constitutive expression of a variety of antimicrobial factors and these defenses are augmented by a protective host response to the organism. Such infections often involve a predisposing factor that weakens the defenses, such as the use of contact lenses prior to the development of bacterial keratitis or, for endophthalmitis, the trauma caused by cataract surgery or intravitreal injection. The structural carbohydrates of the bacterial surface induce an inflammatory response able to reduce the bacterial load, but contribute to the tissue damage. A variety of bacterial secreted proteins including alpha-toxin, beta-toxin, gamma-toxin, Panton-Valentine leukocidin and other two-component leukocidins mediate tissue damage and contribute to the induction of the inflammatory response. Quantitative animal models of keratitis and endophthalmitis have provided insights into the S. aureus virulence and host factors active in limiting such infections.

Interleukin-6 participation in pathology of ocular diseases

Interleukin-6 (IL-6) is a multifunctional cytokine that affects a variety of cells in the body such as osteoclasts, hepatocytes, endothelial cells, epithelial cells, white and red blood cells and etc. Elevated levels of IL-6 have been detected in many ocular diseases. Studies show that IL-6 has a major role in the pathology of glaucoma, CRVO, macular edema, ocular neovascularization, posterior capsule opacity formation, keratitis, dry eye disease, allergic eye disease, ocular autoimmune disease, corneal chemical burn, ocular inflammation and so on. IL-6 does its effects through the classic or trans-signal pathways in cells. Blocking of IL-6 signal pathways via Tocilizumab or other chemicals and therapeutics will help to overcome complications related to ocular diseases.

Cerebrospinal fluid Th1/Th2 cytokine profiles in children with enterovirus 71-associated meningoencephalitis

Enterovirus 71 (EV71) infection can cause severe neurological complications including meningoencephalitis (ME) in some patients with hand, foot and mouth disease (HFMD). However, to date no studies have reported changes in cytokine concentrations and their correlations with clinical variables in patients with ME following EV71 infection. In this study, responses of Th1/Th2 cytokine, including IL-2, IL-4, IL-6, IL-10, TNF-α and IFN-γ, in cerebrospinal fluid (CSF) from patients with EV71-related HFMD with ME and patients with febrile convulsions (FC) were analyzed using cytometric bead array technology. It was found that CSF IL-6 and IFN-γ concentrations were significantly higher in patients with EV71-related ME than in those with FC. Additionally, both CSF IL-6 and IFN-γ concentrations were correlated with CSF cytology, fever duration and duration of hospital stay. More interestingly, a positive correlation between CSF IL-6 and IFN-γ concentrations was observed. Finally, receiver operating characteristic analysis revealed that when a cutoff value of 9.40 pg/mL was set for IL-6, the sensitivity and specificity were 84.5% and 85.5%, respectively, for discriminating EV71-related ME from FC. In conclusion, IL-6 and IFN-γ may be associated with EV71-induced neuropathology.

Human TYK2 deficiency: Mycobacterial and viral infections without hyper-IgE syndrome

Kreins et al. report the identification and immunological characterization of a group of TYK2-deficient patients.

Autosomal recessive, complete TYK2 deficiency was previously described in a patient (P1) with intracellular bacterial and viral infections and features of hyper-IgE syndrome (HIES), including atopic dermatitis, high serum IgE levels, and staphylococcal abscesses. We identified seven other TYK2-deficient patients from five families and four different ethnic groups. These patients were homozygous for one of five null mutations, different from that seen in P1. They displayed mycobacterial and/or viral infections, but no HIES. All eight TYK2-deficient patients displayed impaired but not abolished cellular responses to (a) IL-12 and IFN-α/β, accounting for mycobacterial and viral infections, respectively; (b) IL-23, with normal proportions of circulating IL-17⁺ T cells, accounting for their apparent lack of mucocutaneous candidiasis; and (c) IL-10, with no overt clinical consequences, including a lack of inflammatory bowel disease. Cellular responses to IL-21, IL-27, IFN-γ, IL-28/29 (IFN-λ), and leukemia inhibitory factor (LIF) were normal. The leukocytes and fibroblasts of all seven newly identified TYK2-deficient patients, unlike those of P1, responded normally to IL-6, possibly accounting for the lack of HIES in these patients. The expression of exogenous wild-type TYK2 or the silencing of endogenous TYK2 did not rescue IL-6 hyporesponsiveness, suggesting that this phenotype was not a consequence of the TYK2 genotype. The core clinical phenotype of TYK2 deficiency is mycobacterial and/or viral infections, caused by impaired responses to IL-12 and IFN-α/β. Moreover, impaired IL-6 responses and HIES do not appear to be intrinsic features of TYK2 deficiency in humans.

The Sbi Protein Contributes to Staphylococcus aureus Inflammatory Response during Systemic Infection

Staphylococcus aureus is an important human pathogen that causes infections that may present high morbidity and mortality. Among its many virulence factors protein A (SpA) and Staphylococcal binding immunoglobulin protein (Sbi) bind the Fc portion of IgG interfering with opsonophagocytosis. We have previously demonstrated that SpA interacts with the TNF-α receptor (TNFR) 1 through each of the five IgG binding domains and induces the production of pro-inflammatory cytokines and chemokines. The IgG binding domains of Sbi are homologous to those of SpA, which allow us to hypothesize that Sbi might also have a role in the inflammatory response induced by S. aureus. We demonstrate that Sbi is a novel factor that participates in the induction of the inflammatory response during staphylococcal infections via TNFR1 and EGFR mediated signaling as well as downstream MAPKs. The expression of Sbi significantly contributed to IL-6 production and modulated CXCL-1 expression as well as neutrophil recruitment to the site of infection, thus demonstrating for the first time its relevance as a pro-inflammatory staphylococcal antigen in an in vivo model.

Host defense at the ocular surface

Microbial infections of the cornea frequently cause painful, blinding and debilitating disease that is often difficult to treat and may require corneal transplantation. In addition, sterile corneal infiltrates that are associated with contact lens wear cause pain, visual impairment and photophobia. In this article, we review the role of Toll-Like Receptors (TLR) in bacterial keratitis and sterile corneal infiltrates, and describe the role of MD-2 regulation in LPS responsiveness by corneal epithelial cells. We conclude that both live bacteria and bacterial products activate Toll-Like Receptors in the cornea, which leads to chemokine production and neutrophil recruitment to the corneal stroma. While neutrophils are essential for bacterial killing, they also cause tissue damage that results in loss of corneal clarity. These disparate outcomes, therefore, represent a spectrum of disease severity based on this pathway, and further indicate that targeting the TLR pathway is a feasible approach to treating inflammation caused by live bacteria and microbial products. Further, as the P. aeruginosa type III secretion system (T3SS) also plays a critical role in disease pathogenesis by inducing neutrophil apoptosis and facilitating bacterial growth in the cornea, T3SS exotoxins are additional targets for therapy for P. aeruginosa keratitis.

Effects of small intestinal submucosa (SIS) on the murine innate immune microenvironment induced by heat-killed Staphylococcus aureus

The use of biological scaffold materials for wound healing and tissue remodeling has profoundly impacted regenerative medicine and tissue engineering. The porcine-derived small intestinal submucosa (SIS) is a licensed bioscaffold material regularly used in wound and tissue repair, often in contaminated surgical fields. Complications and failures due to infection of this biomaterial have therefore been a major concern and challenge. SIS can be colonized and infected by wound-associated bacteria, particularly Staphylococcus aureus. In order to address this concern and develop novel intervention strategies, the immune microenvironment orchestrated by the combined action of S. aureus and SIS should be critically evaluated. Since the outcome of tissue remodeling is largely controlled by the local immune microenvironment, we assessed the innate immune profile in terms of cytokine/chemokine microenvironment and inflammasome-responsive genes. BALB/c mice were injected intra-peritoneally with heat-killed S. aureus in the presence or absence of SIS. Analyses of cytokines, chemokines and microarray profiling of inflammasome-related genes were done using peritoneal lavages collected 24 hours after injection. Results showed that unlike SIS, the S. aureus-SIS interactome was characterized by a Th1-biased immune profile with increased expressions of IFN-γ, IL-12 and decreased expressions of IL-4, IL-13, IL-33 and IL-6. Such modulation of the Th1/Th2 axis can greatly facilitate graft rejections. The S. aureus-SIS exposure also augmented the expressions of pro-inflammatory cytokines like IL-1β, Tnf-α, CD30L, Eotaxin and Fractalkine. This heightened inflammatory response caused by S. aureus contamination could enormously affect the biocompatibility of SIS. However, the mRNA expressions of many inflammasome-related genes like Nlrp3, Aim2, Card6 and Pycard were down-regulated by heat-killed S. aureus with or without SIS. In summary, our study explored the innate immune microenvironment induced by the combined exposure of SIS and S. aureus. These results have practical implications in developing strategies to contain infection and promote successful tissue repair.

Association of single nucleotide polymorphisms of interleukins-1β, -6, and -12B with contact lens keratitis susceptibility and severity

PURPOSE

To investigate whether single nucleotide polymorphisms (SNPs) in interleukin (IL)-1β, IL-6, and IL-12β are associated with the susceptibility and severity of contact lens-related keratitis.

DESIGN

Retrospective, case control study.

PARTICIPANTS

One hundred twelve cases of keratitis and 225 controls were recruited from studies conducted at Moorfields Eye Hospital and in Australia during 2003 through 2005.

METHODS

Buccal swab samples were collected on Whatman FTA cards and were mailed by post for analysis. IL-1β (-31), IL-6 (-174, -572, -597), and IL-12B (3'+1158) genotypes were analyzed with pyrosequencing and analyzed using a regression model for susceptibility (sterile, microbial keratitis, controls) and severity. Statistical significance was set at 0.05.

MAIN OUTCOME MEASURES

The relative risk of developing contact lens-related keratitis and more severe forms of the disease based on allele, genotype, and haplotype associations.

RESULTS

Carriers of IL-6 SNPs were more likely to experience moderate and severe events compared with those with nonmutated genotypes (-174 heterozygous: odds ratio [OR], 3.1; 95% confidence interval [CI], 1.1-8.3; homozygous: OR, 6.4; 95% CI, 1.4-28.4; -174/-597: OR, 4.1; 95% CI, 1.6-11.0). More severe keratitis and microbial keratitis were less likely to occur in wearers with the nonmutated IL-6 haplotype (severity OR, 0.4 [95% CI, 0.2-0.7]; microbial OR, 0.6 [95% CI, 0.4-0.9]). Wearers carrying an IL-12B SNP had an increased risk of sterile keratitis (OR, 9.7; 95% CI, 1.2-76.9) compared with controls.

CONCLUSIONS

The IL-6 SNPs are known to reduce protein expression of this cytokine and thus ocular immune defense, and carriers of these SNPs were more likely to experience more severe and microbial keratitis, suggesting that IL-6 decreases the severity and susceptibility of contact lens-related keratitis. Carriers of a functional SNP of IL-12B that is known to increase IL-12 expression and stability are more likely to experience sterile keratitis, suggesting that this is associated with the intense inflammatory reaction that occurs in this condition.

The protective and immunomodulatory effects of hypothalamic proline-rich polypeptide galarmin against methicillin-resistant Staphylococcus aureus infection in mice

The present research summarizes the protective and immunomodulatory activity of hypothalamic proline-rich polypeptide galarmin against methicillin-resistant Staphylococcus aureus (MRSA). The protective effect of galarmin was shown on MRSA-infected animals' survival and weight loss recovery. The immunological impact of galarmin was evaluated in terms of immunocompetent cell recruitment, serum immunoglobulins, complement components C3 and C4, and pro- and anti-inflammatory cytokines (IL-6, IL-8, IL-10, IL-1b, TNFa, and KC) secretion. Galarmin efficiently protects mice against lethal MRSA infection (100% of survival vs. 0% in the untreated group) when intramuscularly injected 24 h before infection and during the 1-h post-infection period at a concentration of 1 μg per mouse, while its higher concentrations (5 and 10 μg) were protective when injected in parallel to the infection process. The protective effect of galarmin was not due to a direct effect on MRSA, but should be attributed to an action on the host response to infection. Galarmin significantly increased and modulated the levels of IL-6, IL-8, IL-1b, IL-10, and KC in both peritoneal lavages and blood, leukocyte and platelet counts, lymphocytes percentage, serum IgM and IgG, and complement C3 and C4 components secretion. The experimental results allow concluding that galarmin is a powerful immunomodulatory and protective agent for the in vivo prophylaxis and treatment of MRSA-induced infection.

Contact lens-related microbial keratitis: how have epidemiology and genetics helped us with pathogenesis and prophylaxis

Contact lens wear is a common predisposing factor in microbial keratitis and is one of the two preventable risk factors for corneal infection in a working age population. Our understanding of the prevention and prophylaxis of contact lens-related corneal infection is informed by recent epidemiological studies describing the incidence of and risk factors for the disease, the effect of causative organism on disease severity, and an appreciation of individual immune profiles in susceptibility to and severity of the disease. Although contemporary contact lenses have not reduced the overall incidence of keratitis, a reduction in morbidity may be achievable through recognition of appropriate risk factors in severe disease, including avoiding delays in presenting for appropriate treatment, and attention to storage case hygiene practise. Severe keratitis is most commonly associated with an environmental causative organism, and daily disposable lenses are associated with less severe disease. Pseudomonas aeruginosa remains the commonest cause of contact lens-related corneal infection probably because of its unique virulence characteristics and ability to survive in the contact lens/storage case/ocular environment. In two recent outbreaks of contact lens-related infections, there has been a strong association demonstrated with particular contact lens solutions. Since the recall of these specific contact lens solutions, the rate of Acanthamoeba keratitis has remained above the expected baseline, indicating unidentified risk factors that may include environmental exposures. Individual differences in susceptibility to microbial keratitis may be partly explained by differences in single-nucleotide polymorphisms in certain cytokine genes, particularly those with a proven protective role in corneal infection.

Animal models of bacterial keratitis

Bacterial keratitis is a disease of the cornea characterized by pain, redness, inflammation, and opacity. Common causes of this disease are Pseudomonas aeruginosa and Staphylococcus aureus. Animal models of keratitis have been used to elucidate both the bacterial factors and the host inflammatory response involved in the disease. Reviewed herein are animal models of bacterial keratitis and some of the key findings in the last several decades.

Development of a Streptococcus pneumoniae keratitis model in mice

BACKGROUND

Streptococcus pneumoniae is a common cause of bacterial keratitis, and models to examine the ocular pathogenesis of this bacterium would aid in efforts to treat pneumococcal keratitis. The aim of this study was to establish a murine model of pneumococcal keratitis.

METHODS

The corneas of A/J, BALB/c or C57BL/6 mice were scratched and topically infected with a clinical strain of S. pneumoniae. Slitlamp examination (SLE), enumeration of bacteria in the corneas and histology were performed.

RESULTS

Bacteria were recovered from the eyes of A/J mice on postinfection (PI) days 1 [1.96 +/- 0.61 log(10) colony-forming units (CFU)] and 3 (1.41 +/- 0.71 log(10) CFU). SLE scores were significantly higher in the infected A/J mice as compared to the BALB/c or C57BL/6 mice on PI day 3 (p < 0.0001) and steadily increased over time, reaching a maximal value of 3.00 +/- 0.35 on PI day 10. Histopathology revealed stromal edema and the influx of polymorphonuclear leukocytes on PI days 7 and 10, and corneal disruption on PI day 7.

CONCLUSIONS

S. pneumoniae keratitis was established in A/J mice, but not BALB/c or C57BL/6 mice.

Effect of IL-6 deficiency on susceptibility to HSV-1 respiratory infection and intrinsic macrophage antiviral resistance

Cytokines play important roles in the mechanisms of disease development. Interleukin-6 (IL-6) is associated with clearance of herpes simplex virus (HSV) infections and in virus-induced immunopathology. However, the importance of IL-6 in host defense against HSV-1 respiratory infection is unknown. This study tested the effect of knockout mice deficient for IL-6 on susceptibility to HSV-1 respiratory infection and on intrinsic macrophage antiviral resistance to HSV-1. Control C57BL/6 IL-6+/+ mice and IL-6 knockout mice (IL-6-/-) were intranasally inoculated with 50 microL of a standardized dose (3.2 x 10(5)) of HSV-1. Morbidity, mortality, and symptom severity were monitored for 21 days. A subset of mice was sacrificed at 48-h postinfection and lungs were analyzed for viral titers. Peritoneal macrophages were obtained from a third set of mice and assayed for antiviral resistance to HSV-1. IL-6-/- increased morbidity by 84%, mortality by 84%, and symptom severity score on days 7.5 through 11 (p < 0.05). IL-6-/- increased virus titers in the lung 4-fold (p < 0.01) and resulted in a decrease in macrophage antiviral resistance (p < 0.001). Results indicate that IL-6 plays an important role in susceptibility to respiratory infection in mice, which may be mediated at least in part by its effect on macrophage antiviral resistance.