Interleukin 17 expression in peripheral blood neutrophils from fungal keratitis patients and healthy cohorts in southern India

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.

Cytokine Profile of Invasive Pulmonary Aspergillosis in Severe COVID-19 and Possible Therapeutic Targets

During the SARS-CoV-2 pandemic, a higher incidence of invasive pulmonary aspergillosis was observed in patients affected by Coronavirus disease 2019 (COVID-19), leading to the delineation of a new entity named COVID-19 associated pulmonary aspergillosis (CAPA). A predisposition to invasive infection caused by Aspergillus spp. in SARS-CoV-2 infected patients can be ascribed either to the direct viral-mediated damage of the respiratory epithelium, as already observed in influenza H1N1 virus infections, or to the dysregulated immunity associated with COVID-19. This narrative review focuses on the impact of immune impairment, particularly due to cytokine dysregulation caused by Aspergillus spp. superinfection in COVID-19 for a more in-depth understanding of the molecular pathways implicated in CAPA. As immune competence has proven to be essential in protecting against CAPA onset, a role already threatened by SARS-CoV-2 infection itself, preventive strategies should focus on reducing factors that could further target the host immune system. We also aimed to focus on well-known and less-known risk factors for IPA in COVID-19 patients, related to the main causes of immune suppression, both virus-mediated and iatrogenic, including treatments currently indicated for COVID-19. Lastly, possible preventive strategies aimed at reducing morbidity and mortality due to CAPA could be implemented.

Recombinant IL-22 promotes protection in a murine model of Aspergillus flavus keratitis and mediates host immune responses in human corneal epithelial cells

Aspergillus flavus is a leading cause of corneal infections in India and worldwide, resulting in severe visual impairment. We studied the host immune response towards A. flavus in immortalised human corneal epithelial cells (HCEC) and found increased expression of Toll-like receptors, antimicrobial peptides and proinflammatory cytokines like IL-6 and IL-8. Differential expressions of antimicrobial peptides were determined in corneal scrapings from A. flavus keratitis patients with significantly increased expression of LL-37, S100A12 and RNase 7. Increased levels of IL-22 expression were observed both in patients with A. flavus keratitis and in experimental mice model of corneal infections along with IL-17, IL-23 and IL-18. IL-22 is an important mediator of inflammation during microbial infections, and acts primarily on fibroblasts and epithelial cells. We observed constitutive expression of IL-22 receptors in HCEC, and IL-22 mediated activation of NF-κB, MAPK pathways and STAT3, along with increased expression of antimicrobial peptides in these cells. IL-22 also efficiently lessened cell deaths in corneal epithelial cells during A. flavus infection in vitro. Furthermore, recombinant IL-22 reduced fungal burden and corneal opacity in an experimental murine model of A. flavus keratitis.

Enhanced in vivo antifungal activity of novel cell penetrating peptide natamycin conjugate for efficient fungal keratitis management

Natamycin is the only FDA approved drug that is used as a first line of treatment for fungal keratitis caused by filamentous fungi, however natamycin is known for poor corneal penetration. Cell penetrating peptides (CPPs) are emerging nanocarriers for the enhanced delivery of various macromolecules owing to their distinct cellular translocation ability. In the present study, tissue penetration ability and antifungal efficacy of CPP (Tat₂) conjugated natamycin has been investigated and compared with natamycin alone in vivo. Results show that Tat₂natamycin exhibits five- fold higher ocular penetration than natamycin alone when given topically. Complete resolution of fungal keratitis in 44% of the animals in Tat₂natamycin treated group as compared to only 13% of the animals in natamycin treated group further highlights its increased antifungal efficacy. Hence, this conjugate is a promising antifungal molecule with enhanced ocular penetration as well as antifungal efficacy against selected fungal species.

A Pyrrhic Victory: The PMN Response to Ocular Bacterial Infections

Some tissues of the eye are susceptible to damage due to their exposure to the outside environment and inability to regenerate. Immune privilege, although beneficial to the eye in terms of homeostasis and protection, can be harmful when breached or when an aberrant response occurs in the face of challenge. In this review, we highlight the role of the PMN (polymorphonuclear leukocyte) in different bacterial ocular infections that invade the immune privileged eye at the anterior and posterior segments: keratitis, conjunctivitis, uveitis, and endophthalmitis. Interestingly, the PMN response from the host seems to be necessary for pathogen clearance in ocular disease, but the inflammatory response can also be detrimental to vision retention. This "Pyrrhic Victory" scenario is explored in each type of ocular infection, with details on PMN recruitment and response at the site of ocular infection. In addition, we emphasize the differences in PMN responses between each ocular disease and its most common corresponding bacterial pathogen. The in vitro and animal models used to identify PMN responses, such as recruitment, phagocytosis, degranulation, and NETosis, are also outlined in each ocular infection. This detailed study of the ocular acute immune response to infection could provide novel therapeutic strategies for blinding diseases, provide more general information on ocular PMN responses, and reveal areas of bacterial ocular infection research that lack PMN response studies.

Endogenous stimulation is responsible for the high frequency of IL-17A-producing neutrophils in patients with rheumatoid arthritis

Background

Neutrophils play an important role in the pathogenesis of rheumatoid arthritis (RA). It has recently been reported that in addition to T helper (Th) 17 cells, other cells, including neutrophils, produce IL-17A, an important inflammatory cytokine involved in the pathogenesis of RA. The purpose of this study was to examine the presence of interleukin 17A-producing neutrophils in patients with RA.

Methods

We performed a cross-sectional study including 106 patients with RA and 56 healthy individuals. Whole peripheral blood cells were analyzed by flow cytometry to identify CD66b+ CD177+ IL-17A+ neutrophils and CD3+ CD4+ IL-17A+ T cells. Serum levels of IL-17A and IL-6 were measured by means of cytometry bead array (CBA). In purified neutrophils, mRNA levels of IL-17 and RORγ were measured by RT-PCR. In addition, purified neutrophils from patients and healthy controls were stimulated with the cytokines IL-6 and IL-23 to evaluate differences in their capacity to produce IL-17A.

Results

Neutrophils from RA patients expressed IL-17 and RORγ mRNA. Consequently, these cells also expressed IL-17A. Serum IL-17A levels but not Th17 cell numbers were increased in RA patients. Neutrophils positive for cytoplasmic IL-17A were more abundant in patients with RA (mean 1.2 ± 3.18%) than in healthy individuals (mean 0.07 ± 0.1%) (p < 0.0001). Although increased IL-17A+ neutrophil numbers were present in RA patients regardless of disease activity (mean 6.5 ± 5.14%), they were more frequent in patients with a more recent diagnosis (mean time after disease onset 3.5 ± 4.24 years). IL-6 and IL-23 induced the expression of RORγ but failed to induce IL-17A expression by neutrophils from RA patients and healthy individuals after a 3 h stimulation.

Conclusion

IL-17A-producing neutrophils are increased in some RA patients, which are not related to disease activity but have an increased frequency in patients with recent-onset disease. This finding suggests that IL-17A-producing neutrophils play an early role in the development of RA.

Electronic supplementary material

The online version of this article (10.1186/s13223-019-0359-9) contains supplementary material, which is available to authorized users.

Quantitative profiling of tear proteome reveals down regulation of zinc alpha-2 glycoprotein in Aspergillus flavus keratitis patients

Corneal mycotic ulceration is predominantly due to Aspergillus and Fusarium solani infection in tropical countries. In this study, we examined the proteome profile of tear samples from A. flavus keratitis patients at various stages of infection. The proteome was profiled using 2D PAGE and the protein levels were quantified using 2D DIGE. Alpha-1-antitrypsin, apolipoprotein, haptoglobin, lactoferrin and albumin were up regulated while cystatin SA III precursor, lacrimal lipocalin precursor, lacritin precursor and Zinc alpha-2 glycoprotein (ZAG) were down regulated in tear fluid. In the case of ZAG all proteoforms were down regulated as the disease progressed from early to late stage of infection. Western blot analysis confirmed the results observed using DIGE. Further, there were no gender specific differences in the levels of ZAG expression in keratitis patient tear film. Published results show up regulation of ZAG in Fusarium keratitis patient tear indicating subtle changes in the early events of host response to these two fungal pathogens. We conclude that ZAG level could be used as an indicator of A. flavus or F. solani infection, even during the early stage of the disease.

IL-17 produced by Th17 cells alleviates the severity of fungal keratitis by suppressing CX43 expression in corneal peripheral vascular endothelial cells

Fungal keratitis is a relatively common ocular disease requiring positive medical management combined with surgical intervention. Interleukin-17 (IL-17) was reported to promote the activation and mobilization of neutrophile granulocyte to foci of inflammation. This study investigated the effect of IL-17 production from Th17 cells on the progression of fungal keratitis. A mouse model of fungal keratitis induced by Candida albicans was successfully constructed to detect infiltration of inflammatory cells in corneal tissues by hematoxylin-eosin (HE) staining and immunohistochemistry. Fungal load capacity of mouse cornea was also detected. The regulatory role of IL-17 in fungal keratitis with the involvement of CX43 was investigated with the relevant expression of inflammatory factors detected and activation of vascular endothelial cells assessed. Furthermore, in vivo experiment was also performed to confirm the role of CX43 in keratitis. Mice with fungal keratitis showed increased level of inflammatory cytokines and infiltration of inflammatory cells. Silencing IL-17 in Th17 cells and overexpressing CX43 could inhibit the activation of vascular endothelial cells. Besides, CX43 knockdown in vivo alleviated fungal keratitis in mice. The possible mechanism of the above findings could be IL-17 inhibiting the level of CX43 through the AKT signaling pathway. Taken together, IL-17 could inhibit the occurrence and development of fungal keratitis by suppressing CX43 expression through the AKT signaling pathway. Therefore, this study provides a potential target for the treatment of fungal keratitis.

Cytokine production by human neutrophils: Revisiting the "dark side of the moon"

Polymorphonuclear neutrophils are the most numerous leucocytes present in human blood, and function as crucial players in innate immune responses. Neutrophils are indispensable for the defence towards microbes, as they effectively counter them by releasing toxic enzymes, by synthetizing reactive oxygen species and by producing inflammatory mediators. Interestingly, recent findings have highlighted an important role of neutrophils also as promoters of the resolution of inflammation process, indicating that their biological functions go well beyond simple pathogen killing. Consistently, data from the last decades have highlighted that neutrophils may even contribute to the development of adaptive immunity by performing previously unanticipated functions, including the capacity to extend their survival, directly interact with other leucocytes or cell types, and produce and release a variety of cytokines. In this article, we will summarize the main features of, as well as emphasize some important concepts on, the production of cytokines by human neutrophils.

A Review of the Cytokine IL-17 in Ocular Surface and Corneal Disease

Aim: To investigate the role of interleukin-17 in ocular surface and corneal disease. Ocular surface and corneal disease is a leading cause of blindness and is an ongoing challenge for the public health sector to implement effective therapies. The majority of cells in corneal lesions are derived primarily from neutrophils that induce inflammatory events that lead to tissue damage. One of the key pro-inflammatory cytokines is IL-17, and it has been investigated in order to facilitate the understanding of the pathogenesis of ocular surface lesion development. Method: A review of the literature was performed through a systematic approach. Results: IL-17 has been shown to exacerbate dry eye disease, viral and bacterial keratitis lesion severity, although it was found to be protective for Acanthamoeba. Antibodies developed to neutralize IL-17 have shown some promise in reducing the severity of some diseases. Conclusion: IL-17 plays a role in the pathogenesis of ocular surface and corneal disease and targeting this cytokine may provide a useful treatment option in the future.

A Reappraisal on the Potential Ability of Human Neutrophils to Express and Produce IL-17 Family Members In Vitro: Failure to Reproducibly Detect It

Neutrophils are known to perform a series of effector functions that are crucial for the innate and adaptive responses, including the synthesis and secretion of a variety of cytokines. In light of the controversial data in the literature, the main objective of this study was to more in-depth reevaluate the capacity of human neutrophils to express and produce cytokines of the IL-17 family in vitro. By reverse transcription quantitative real-time PCR, protein measurement via commercial ELISA, immunohistochemistry (IHC) and immunofluorescence (IF), flow cytometry, immunoblotting, chromatin immunoprecipitation (ChIP), and ChIP-seq experiments, we found that highly pure (>99.7%) populations of human neutrophils do not express/produce IL-17A, IL-17F, IL-17AF, or IL-17B mRNA/protein upon incubation with a variety of agonists. Similar findings were observed by analyzing neutrophils isolated from active psoriatic patients. In contrast with published studies, IL-17A and IL-17F mRNA expression/production was not even found when neutrophils were incubated with extremely high concentrations of IL-6 plus IL-23, regardless of their combination with inactivated hyphae or conidia from Aspergillus fumigatus. Consistently, no deposition of histone marks for active (H3K27Ac) and poised (H3K4me1) genomic regulatory elements was detected at the IL-17A and IL-17F locus of resting and IL-6 plus IL-23-stimulated neutrophils, indicating a closed chromatin conformation. Concurrent experiments revealed that some commercial anti-IL-17A and anti-IL-17B antibodies (Abs), although staining neutrophils either spotted on cytospin slides or present in inflamed tissue samples by IHC/IF, do not recognize intracellular protein having the molecular weight corresponding to IL-17A or IL-17B, respectively, in immunoblotting experiments of whole neutrophil lysates. By contrast, the same Abs were found to more specifically recognize other intracellular proteins of neutrophils, suggesting that their ability to positively stain neutrophils in cytospin preparations and, eventually, tissue samples derives from IL-17A- or IL-17B-independent detections. In sum, our data confirm and extend, also at epigenetic level, previous findings on the inability of highly purified populations of human neutrophils to express/produce IL-17A, IL-17B, and IL-17F mRNAs/proteins in vitro, at least under the experimental conditions herein tested. Data also provide a number of justifications explaining, in part, why it is possible to false positively detect IL-17A⁺-neutrophils.

Characterization and biological significance of IL-23-induced neutrophil polarization

Neutrophils are heterogeneous with distinct subsets, and can switch phenotypes to exert regulatory functions on immunity. We herein demonstrate that IL-23-treated neutrophils selectively produce IL-17A, IL-17F and IL-22, and display a distinct gene expression profile in contrast to resting and lipopolysaccharide-treated neutrophils. IL-17⁺ neutrophils are present in the colons of mice with dextran sulfate sodium-induced colitis. Adoptive transfer of IL-23-treated neutrophils significantly promotes pathogenesis in this model. IL-23 induces neutrophil polarization through STAT3-dependent RORγt and BATF pathways. Thus, IL-23-induced neutrophil polarization expresses a unique cytokine-producing profile, which may contribute to IL-23-mediated inflammatory diseases.

Review of clinical and basic approaches of fungal keratitis

Fungal keratitis (FK) is a serious disease which can cause blindness. This review has current information about the pathogenesis, limitations of traditional diagnosis and therapeutic strategies, immune recognition and the diagnosis and therapy of FK. The information of this summary was reviewed regularly and updated as what we need in the diagnosis and therapy of FK nowadays.

IL-17A promotes neutrophilic inflammation and disturbs acute wound healing in skin

In the wound healing process, neutrophils are the first inflammatory cells to move to the wound tissues. They sterilize wounds by killing microbes, and they stimulate other immune cells to protect the host from infection. In contrast, neutrophil-derived proteases cause damage to host tissues, so neutrophils play dual opposite roles in wound healing. Interleukin-17A (IL-17A) is a proinflammatory cytokine that promotes the recruitment of these cells. The role of this cytokine in the wound healing process is not fully clarified. In the present study, therefore, we examined how defect in IL-17A production affected the wound healing in skin. IL-17A-knockout (KO) mice showed promoted wound closure, myofibroblast differentiation and collagen deposition and decreased the neutrophil accumulation compared with wild-type (WT) mice. In contrast, the administration of recombinant IL-17A led to delayed wound closure, low collagen deposition and accelerated neutrophilic accumulation. In addition, the treatment of IL-17A-administered mice with a neutrophil elastase inhibitor improved the wound repair to the same level as that of WT mice. These results indicated that IL-17A hampered the wound healing process and suggested that neutrophilic inflammation caused by IL-17A may be associated with impaired wound healing in skin.

Interleukin-17-Producing Neutrophils Link Inflammatory Stimuli to Disease Progression by Promoting Angiogenesis in Gastric Cancer

Purpose: Elevated levels of neutrophils have been associated with poor survival in various cancers, but direct evidence supporting a role for neutrophils in the immunopathogenesis of human cancers is lacking.Experimental Design: A total of 573 patients with gastric cancer were enrolled in this study. Immunohistochemistry and real-time PCR were performed to analyze the distribution and clinical relevance of neutrophils in different microanatomic regions. The regulation and function of neutrophils were assessed both in vitro and in vivoResults: Increased neutrophil counts in the peripheral blood were associated with poor prognosis in gastric cancer patients. In gastric cancer tissues, neutrophils were enriched predominantly in the invasive margin, and neutrophil levels were a powerful predictor of poor survival in patients with gastric cancer. IL17⁺ neutrophils constitute a large portion of IL17-producing cells in human gastric cancer. Proinflammatory IL17 is a critical mediator of the recruitment of neutrophils into the invasive margin by CXC chemokines. Moreover, neutrophils at the invasive margin were a major source of matrix metalloproteinase-9, a secreted protein that stimulates proangiogenic activity in gastric cancer cells. Accordingly, high levels of infiltrated neutrophils at the invasive margin were positively correlated with angiogenesis progression in patients with gastric cancer.Conclusions: These data provide direct evidence supporting the pivotal role of neutrophils in gastric cancer progression and reveal a novel immune escape mechanism involving fine-tuned collaborative action between cancer cells and immune cells in the distinct tumor microenvironment. Clin Cancer Res; 23(6); 1575-85. ©2016 AACR.

Challenges of corneal infections

INTRODUCTION

Ocular infections remain an important cause of blindness worldwide and represent a challenging public health concern. In this regard, microbial keratitis due to fungal, bacterial, or viral infection can result in significant vision loss secondary to corneal scarring or surface irregularity. Left untreated corneal perforation and endophthalmitis can result, leading to loss of the eye. Rigorously studied animal models of disease pathogenesis have provided novel information that suggests new modes of treatment that may be efficacious clinically and emerging clinical data is supportive of some of these discoveries.

AREAS COVERED

This review focuses on advances in our understanding of disease pathogenesis in animal models and clinical studies and how these relate to improved clinical treatment. We also discuss a novel approach to treatment of microbial keratitis due to infection with these bacterial pathogens using PACK-CXL and recommend increased basic and clinical studies to address and refine the efficacy of this procedure.

EXPERT COMMENTARY

Because resistance to antibiotics has developed over time to these bacterial pathogens, caution must be exercised in treatment. Attractive novel modes of treatment that hold new promise for further investigation include lipid based therapy, as well as use of small molecules that bind deleterious specific host responsive molecules and use of microRNA based therapies.

Neutrophils from F508del cystic fibrosis patients produce IL-17A and express IL-23 - dependent IL-17RC

Cystic fibrosis (CF) is a chronic pulmonary disease that is associated with persistent microbial infection and chronic neutrophil infiltration, and also with elevated production of the pro-inflammatory cytokine IL-17A (IL-17). In the current study, we examined IL-17 and the inducible IL-17RC receptor subunit in neutrophils from Pseudomonas aeruginosa infected F508del CF patients at the time of pulmonary exacerbation, and again following intravenous antibiotic treatment. Neutrophils expressed Il17a and Il17rc transcripts and protein at the time of pulmonary exacerbation, which were absent following antibiotic treatment. Further, CF sputum induced IL-23 - dependent Il17rc expression in neutrophils from healthy individuals. Similarly, IL-17 producing neutrophils were detected in F508del and Cftr(-/-) mice infected intranasally with P. aeruginosa. In the sputum of CF subjects, the percentage IL-17 producing neutrophils correlated with elastase and MMP9 activity; therefore, this population of neutrophils may be an important contributor to the severity of pulmonary disease in CF patients.

JAK/STAT regulation of Aspergillus fumigatus corneal infections and IL-6/23-stimulated neutrophil, IL-17, elastase, and MMP9 activity

IL-6 and IL-23 (IL-6/23) induce IL-17A (IL-17) production by a subpopulation of murine and human neutrophils, resulting in autocrine IL-17 activation, enhanced production of reactive oxygen species, and increased fungal killing. As IL-6 and IL-23 receptors trigger JAK1, -3/STAT3 and JAK2/STAT3 phosphorylation, respectively, we examined the role of this pathway in a murine model of fungal keratitis and also examined neutrophil elastase and gelatinase (matrix metalloproteinase 9) activity by IL-6/23-stimulated human neutrophils in vitro. We found that STAT3 phosphorylation of neutrophils in Aspergillus fumigatus-infected corne as was inhibited by the JAK/STAT inhibitor Ruxolitinib, resulting in impaired fungal killing and decreased matrix metalloproteinase 9 activity. In vitro, we showed that fungal killing by IL-6/23-stimulated human peripheral blood neutrophils was impaired by JAK/STAT inhibitors Ruxolitinib and Stattic, and by the retinoic acid receptor-related orphan receptor γt inhibitor SR1001. This was also associated with decreased reactive oxygen species, IL-17A production, and retinoic acid receptor-related orphan receptor γt translocation to the nucleus. We also demonstrate that IL-6/23-activated neutrophils exhibit increased elastase and gelatinase (matrix metalloproteinase 9) activity, which is inhibited by Ruxolitinib and Stattic but not by SR1001. Taken together, these observations indicate that the regulation of activity of IL-17-producing neutrophils by JAK/STAT inhibitors impairs reactive oxygen species production and fungal killing activity but also blocks elastase and gelatinase activity that can cause tissue damage.

Immune Interactions with Pathogenic and Commensal Fungi: A Two-Way Street

We are exposed to a wide spectrum of fungi including innocuous environmental organisms, opportunistic pathogens, commensal organisms, and fungi that can actively and explicitly cause disease. Much less is understood about effective host immunity to fungi than is generally known about immunity to bacterial and viral pathogens. Innate and adaptive arms of the immune system are required for effective host defense against Candida, Aspergillus, Cryptococcus, and others, with specific elements of the host response regulating specific types of fungal infections (e.g., mucocutaneous versus systemic). Here we will review themes and controversies that are currently shaping investigation of antifungal immunity (primarily to Candida and Aspergillus) and will also examine the emerging field of the role of fungi in the gut microbiome.

Temporal retinal transcriptome and systems biology analysis identifies key pathways and hub genes in Staphylococcus aureus endophthalmitis

Bacterial endophthalmitis remains a devastating inflammatory condition associated with permanent vision loss. Hence, assessing the host response in this disease may provide new targets for intervention. Using a mouse model of Staphylococcus aureus (SA) endophthalmitis and performing retinal transcriptome analysis, we discovered progressive changes in the expression of 1,234 genes. Gene ontology (GO) and pathway analyses revealed the major pathways impacted in endophthalmitis includes: metabolism, inflammatory/immune, antimicrobial, cell trafficking, and lipid biosynthesis. Among the immune/inflammation pathways, JAK/Stat and IL-17A signaling were the most significantly affected. Interactive network-based analyses identified 13 focus hub genes (IL-6, IL-1β, CXCL2, STAT3, NUPR1, Jun, CSF1, CYR61, CEBPB, IGF-1, EGFR1, SPP1, and TGM2) within these important pathways. The expression of hub genes confirmed by qRT-PCR, ELISA (IL-6, IL-1β, and CXCL2), and Western blot or immunostaining (CEBP, STAT3, NUPR1, and IGF1) showed strong correlation with transcriptome data. Since TLR2 plays an important role in SA endophthalmitis, counter regulation analysis of TLR2 ligand pretreated retina or the use of retinas from TLR2 knockout mice showed the down-regulation of inflammatory regulatory genes. Collectively, our study provides, for the first time, a comprehensive analysis of the transcriptomic response and identifies key pathways regulating retinal innate responses in staphylococcal endophthalmitis.

Neutrophils Do Not Express IL-17A in the Context of Acute Oropharyngeal Candidiasis

IL-17 protects against pathogens by acting on nonhematopoietic cells to induce neutrophil recruitment through upregulation of chemokines and G-CSF. IL-17- and Th17-deficient humans and mice are susceptible to mucosal Candida albicans infections, linked to impaired neutrophil responses. IL-17 production is traditionally associated with CD4⁺ Th17 cells. However, IL-17 is also expressed during innate responses to facilitate rapid pathogen clearance. Innate IL-17-expressing cells include various lymphocyte-type subsets, including ILC3, NKT, γδ-T and “natural” Th17 (nTh17) cells. Some reports suggest that neutrophils can express IL-17 during fungal infections. Here, we asked whether neutrophils serve as a source of IL-17 during acute oropharyngeal candidiasis (OPC) using an IL-17A fate-tracking reporter mouse. Mice were subjected to OPC for two days, and oral tissue was analyzed by flow cytometry. IL-17A was expressed by γδ-T cells and TCRβ⁺ natural Th17 (nTh17) cells, as recently reported. Although infiltrating neutrophils were recruited to the tongue following infection, they did not express the IL-17A reporter. Moreover, neutrophil-depleted mice exhibited normal transcription of both Il17a and downstream IL-17-dependent gene targets after Candida challenge. Thus, in acute OPC, neutrophils are not a measurable source of IL-17 production, nor are they necessary to trigger IL-17-dependent gene expression, although they are essential for ultimate pathogen control.