Epithelial Barrier: Protector and Trigger of Allergic Disorders

The epithelial barrier has been classically considered as only the first line of defense against irritants, pathogens, and allergens, but it is now known that it also plays an essential role in the immunological response against exogenous agents. In fact, recent reports postulate the epithelial barrier hypothesis as a possible explanation for the increasing incidence and severity of allergic diseases. The epithelial barrier preserves the isolation of the inner tissues from potential external threats. Moreover, a coordinated interaction between epithelial and immune cells ensures the unique immune response taking place in mucosal tissues and that is has been reported to be dysregulated in allergic diseases. Herein, we and others have demonstrated that in severe allergic phenotypes, the epithelial barrier experiments several histological modifications and increased in immune cells infiltration, leading to its dysfunction. This is common in atopic dermatitis, asthma, and/or food allergy. However, the precise role of the epithelial barrier in the mucosal biology during allergic diseases progression is not well understood yet. In this review, we aim to compile recent knowledge regarding the histological structure and immunological function of the epithelial barrier and to shed light on the role of this compartment in the onset, and progression of allergic diseases.

Lactoferrin-Functionalized Noble Metal Nanoparticles as New Antivirals for HSV-2 Infection

(1) Background: Lactoferrin has been recognized as a potent inhibitor of human herpetic viruses, such as herpes simplex type 1 (HSV-1) and 2 (HSV-2). In this work, we tested if silver and gold nanoparticles modified with lactoferrin (LF-Ag/AuNPs) can become novel microbicides with additional adjuvant properties to treat genital herpes infection. (2) Methods: The antiviral and cytotoxic activities of LF-Ag/AuNPs were tested in human skin HaCaT and vaginal VK-2-E6/E7 keratinocytes. Viral titers and immune responses after treatment with LF-Ag/AuNPs were tested in murine vaginal HSV-2 infection. (3) Results: LF-Ag/AuNPs inhibited attachment and entry of HSV-2 in human keratinocytes much better than lactoferrin. Furthermore, pretreatment with LF-AgNPs led to protection from infection. Infected mice treated intravaginally with LF-Ag/AuNPs showed lower virus titers in the vaginal tissues and spinal cords in comparison to treatment with lactoferrin. Following treatment, vaginal tissues showed a significant increase in CD8+/granzyme B + T cells, NK cells and dendritic cells in comparison to NaCl-treated group. LF-Ag/AuNPs-treated animals also showed significantly better expression of IFN-γ, CXCL9, CXCL10, and IL-1β in the vaginal tissues. (4) Conclusions: Our findings show that LF-Ag/AuNPs could become effective novel antiviral microbicides with immune-stimulant properties to be applied upon the mucosal tissues.

Epithelial MHC class II directs microbiota-specific intestinal immune homeostasis

Dysregulated immune responses to resident microbes promote pathologic inflammation, however, the mechanisms instructing commensal-specific T cells remain poorly understood. Here, we find that non-hematopoietic intestinal epithelial cells (IECs) represent the primary cells expressing major histocompatibility complex (MHC) II at the intestinal host-microbiota interface. Interestingly, epithelial MHCII and commensal-specific CD4+ T cells were concurrently induced by post-natal microbiota colonization, provoking the hypothesis that epithelial MHCII regulates local commensal-specific CD4+ T cells. While MHCII on classical antigen presenting cells directs expansion of antigen-specific CD4+ T cells, loss of IEC-intrinsic MHCII surprisingly led to elevated commensal-specific CD4+ T cells in the intestine. Further, epithelial MHCII expression actively limited accumulation of antigen-specific CD4+ T cells in adult mice. Expansion of commensal-specific Th17 cells was restricted by epithelial MHCII, and remarkably mice lacking epithelial MHCII were highly susceptible to microbiota-triggered inflammation. Collectively, these data indicate that impaired epithelial MHCII-T cell regulation within mucosal tissues alters microbiota-specific immunity and predisposes to chronic inflammation.

MIR-181A-5P Attenuates Ovalbumin-Induced Allergic Inflammation in Nasal Epithelial Cells by Targeting IL-33/P38 MAPK Pathway

Purpose: Chronic inflammation of the nasal mucosal tissues plays an important role in the pathogenesis of allergic rhinitis (AR). Aberrantly-expressed micro ribonucleic acid (miRNA) has been found to have strong associations with the inflammatory reactions in allergic diseases; however, its functional significance and molecular mechanism in AR remains unclear. The purpose of this study is to determine the functional role and mechanism of miR-181a-5p in AR. Methods: Allergic inflammatory reaction was induced by ovalbumin in human nasal epithelial cell line RPMI2650. The anti-inflammatory effects of miR-181a-5p were evaluated by examining pro-inflammatory cytokines (interleukin (IL)-1β, IL-6, tumor necrosis factor-α (TNF-α)) in the culture of RPMI-2650 cells stimulated by ovalbumin, using quantitative real-time reverse transcription polymerase chain reaction and enzyme-linked immunosorbent assay. Luciferase assay and gain-of-function assay were used to investigate the association of miR-181a-5p and IL-33/p38 MAPK axis. Results: MiR-181a-5p was significantly downregulated in mucosal tissues of AR patients and in RPMI-2650 cells treated with ovalbumin. The overexpression of miR-181a-5p showed prominent suppression of inflammatory cytokine production in RPMI-2650 cells with the stimulation of ovalbumin. MiR-181a-5p directly targeted, and negatively regulated IL-33 to suppress the activation of p38 MAPK signalling. Conclusion: The results suggest that miR-181a-5p restricted allergic inflammation through inhibition of IL-33/p38 MAPK pathway, indicating miR-181a-5p may play an anti-inflammatory role in AR.

Single cell RNA sequencing and lineage tracing confirm mesenchyme to epithelial transformation (MET) contributes to repair of the endometrium at menstruation

The human endometrium experiences repetitive cycles of tissue wounding characterised by piecemeal shedding of the surface epithelium and rapid restoration of tissue homeostasis. In this study we used a validated mouse model of endometrial repair in combination with three transgenic lines of mice to investigate whether epithelial cells that become incorporated into the newly formed luminal epithelium have their origins in one or more of the mesenchymal cell types present in the stromal compartment of the cycling endometrium. Using scRNAseq we identified a novel population of PDGFRb+ cells that arose in the endometrium in response to endometrial breakdown/repair. These cells expressed genes usually considered specific to epithelial cells and in silico trajectory analysis suggested they arose from stromal fibroblasts and were in transition to becoming epithelial cells. To confirm our hypothesis we used a lineage tracing strategy to compare the fate of stromal fibroblasts (PDGFRa+) and stromal perivascular cells (NG2+). We demonstrate for the first time that stromal fibroblasts can undergo a mesenchyme to epithelial transformation and become incorporated into the re-epithelialised luminal surface of the repaired tissue. This study is the first to discover a novel population of wound-responsive, plastic endometrial stromal fibroblasts that contribute to restoration of tissue integrity during endometrial repair. These findings form a platform for comparisons both to endometrial pathologies which involve a fibrotic response (Ashermans syndrome, endometriosis) as well as other mucosal tissues which have a variable response to wounding.

Harnessing the Potential of MAIT Cells as Cellular Adjuvants in Mucosal Vaccines

<p>The development of vaccines is considered one of the most successful medical interventions to date, preventing millions of deaths every year. However, the majority of vaccines are administered peritoneally, despite the vast majority of pathogens invade the human host at mucosal sites. By vaccinating at distal sites, little to no protection is developed at the mucosa where the initial invasion occurs. There are however, a handful of licenced mucosally administered vaccines against infections such as poliovirus, influenza and Salmonella Typhi that are able to induce both a systemic and mucosal protective immune response. All but one of the current licenced mucosal vaccines are live attenuated due in part to the difficulty of developing new mucosal adjuvants. Recombinant cholera toxin subunit B is the only adjuvant used in the current licenced mucosal vaccines. While inactivated and subunit vaccines are considered safer as they are unable to revert back to virulent pathogens, adjuvants are required to boost their immunogenicity. This thesis therefore explores whether mucosal-associated invariant T (MAIT) cells which are found in mucosal tissues, are invariant in nature and have rapid activation, could be exploited as cellular adjuvants in mucosal vaccines. This thesis was able to show that intranasally administered MAIT cell agonist components, 5-A-RU and methylglyoxal (MG), are able to induce both MAIT cell and conventional dendritic cell (cDC) activation in the lung tissue and mediastinal lymph node (mLN). In this model CD40L and RANKL co-stimulatory interactions are involved in ICOSL expression on cDCs in the lung and associated with cDC activation. The MAIT cells within this model also maintained a RORyT and GATA3 phenotype after both one and three doses of the 5-A-RU + MG vaccine. Furthermore, a prime-boost intranasal vaccine scheme of 5-A-RU + MG and the model antigen OVA, was able to induce MR1-dependent accumulation of TFH cells and antigen-specific germinal center B cells in the mLN along with systemic antigen-specific IgG antibody production. This humoral response was also dependent on the presence of both cDC1 and cDC2 populations. Together, this thesis suggests MAIT cells have the potential to be utilised as cellular adjuvants in mucosal vaccines.</p>

Harnessing the Potential of MAIT Cells as Cellular Adjuvants in Mucosal Vaccines

<p>The development of vaccines is considered one of the most successful medical interventions to date, preventing millions of deaths every year. However, the majority of vaccines are administered peritoneally, despite the vast majority of pathogens invade the human host at mucosal sites. By vaccinating at distal sites, little to no protection is developed at the mucosa where the initial invasion occurs. There are however, a handful of licenced mucosally administered vaccines against infections such as poliovirus, influenza and Salmonella Typhi that are able to induce both a systemic and mucosal protective immune response. All but one of the current licenced mucosal vaccines are live attenuated due in part to the difficulty of developing new mucosal adjuvants. Recombinant cholera toxin subunit B is the only adjuvant used in the current licenced mucosal vaccines. While inactivated and subunit vaccines are considered safer as they are unable to revert back to virulent pathogens, adjuvants are required to boost their immunogenicity. This thesis therefore explores whether mucosal-associated invariant T (MAIT) cells which are found in mucosal tissues, are invariant in nature and have rapid activation, could be exploited as cellular adjuvants in mucosal vaccines. This thesis was able to show that intranasally administered MAIT cell agonist components, 5-A-RU and methylglyoxal (MG), are able to induce both MAIT cell and conventional dendritic cell (cDC) activation in the lung tissue and mediastinal lymph node (mLN). In this model CD40L and RANKL co-stimulatory interactions are involved in ICOSL expression on cDCs in the lung and associated with cDC activation. The MAIT cells within this model also maintained a RORyT and GATA3 phenotype after both one and three doses of the 5-A-RU + MG vaccine. Furthermore, a prime-boost intranasal vaccine scheme of 5-A-RU + MG and the model antigen OVA, was able to induce MR1-dependent accumulation of TFH cells and antigen-specific germinal center B cells in the mLN along with systemic antigen-specific IgG antibody production. This humoral response was also dependent on the presence of both cDC1 and cDC2 populations. Together, this thesis suggests MAIT cells have the potential to be utilised as cellular adjuvants in mucosal vaccines.</p>

Characterization of M Cells in Tear Duct-Associated Lymphoid Tissue of Mice: A Potential Role in Immunosurveillance on the Ocular Surface

The ocular mucosal tissues are exposed to potentially harmful foreign antigens in the air and tear fluid. The tear duct-associated lymphoid tissue (TALT) may contribute to immune surveillance in the eye region. Follicle-associated epithelium (FAE) of TALTs is classified as stratified squamous epithelium and consists of squamous epithelial cells arranged in layers on the basement membrane. In contrast, most mucosa-associated lymphoid tissue is covered by a monolayer of epithelium containing microfold (M) cells. Therefore, antigen uptake and the presence of M cells in TALT are not fully understood. The present study found that a small population of FAE cells in the TALT expressed intestinal M-cell markers, namely Sox8, Tnfaip2, GP2, and OPG. This cell population was identified as functional M cells because of their uptake capacity of luminal nanoparticles. In addition, RANKL, which is essential for M-cell differentiation, was expressed by stroma-like cells at the subepithelial region and its receptor RANK by the FAE in the TALT. The administration of RANKL markedly increased the number of Sox8+ M cells. In contrast, deficiency in OPG, an endogenous inhibitor of RANKL, increased the number of M cells in the TALT. These data demonstrate that the RANKL-RANK axis is essential for M-cell differentiation in the TALT. Furthermore, immunization via eye drops elicited the production of antigen-specific antibodies in tears, which was enhanced by RANKL administration. Thus, TALT M cells play an important role in the immunosurveillance of the eye region.

Comparison of Effects of Aminosalicylic Acid, Glucocorticoids and Immunosuppressive Agents On The Expression of Multidrug-Resistant Genes in Ucerative Colitis

Objective: To compare the effects of aminosalicylic acid, glucocorticoids and immunosuppressive agents on the expression levels of multidrug-resistant genes in ucerative colitis (UC) patients, aiming to provide theoretical and therapeutic basis for the diagnosis, treatment and prevention of UC.Methods: Fresh specimen of colon mucosal tissues pathological mucosal tissues under endoscopy or postoperative pathological biopsy tissues were collected from 148 UC patients and then prepared for subsequent experiment.Immunohistochemical staining was conducted to detect the distribution site and pattern of P-glycoprotein （P-gp）. The effects of ASA glucocorticoids and immunosupresive agents on P-gp were statistically compared.The expression levels of Multidrug resistance gene （MDR1）mRNA before and after corresponding treatment were quantitatively measured by using RT-PCR. In addition, the effects of three agents upon MDR1 mRNA were also comparatively analyzed.Results: Administration of 5-aminosalicylic acid (5-ASA) drugs were not correlated with the expression of multidrug resistance genes in UC, whereas delivery of glucocorticoids and immunosuppressant drugs was positively correlated with the expression profile. The expression levels of MDR1 gene and its product P-gp were significantly up-regulated in patients who were nonresponsive to glucocorticoids and immunosuppressant agents.Conclusions: Overall, the findings in the present study demonstrate that 5-ASA exerts no effect upon the expression levels of MDR1 and its product P-gp in patients diagnosed with UC. Nevertheless, administration of glucocorticoids and immunosuppressant drugs can up-regulate the expression levels of MDR1.