Search

Immunological homeostasis in the respiratory tract is thought to require balanced interactions between networks of dendritic cell (DC) subsets in lung microenvironments in order to regulate tolerance or immunity to inhaled antigens and pathogens. Influenza A virus (IAV) poses a serious threat of long-term disruption to this balance through its potent pro-inflammatory activities. In this study, we have used a BALB/c mouse model of A/PR8/34 H1N1 Influenza Type A Virus infection to examine the effects of IAV on respiratory tissue DC subsets during the recovery phase following clearance of the virus. In adult mice, we found differences in the kinetics and activation states of DC residing in the airway mucosa (AMDC) compared to those in the parenchymal lung (PLDC) compartments. A significant depletion in the percentage of AMDC was observed at day 4 post-infection that was associated with a change in steady-state CD11b+ and CD11b− AMDC subset frequencies and significantly elevated CD40 and CD80 expression and that returned to baseline by day 14 post-infection. In contrast, percentages and total numbers of PLDC were significantly elevated at day 14 and remained so until day 21 post-infection. Accompanying this was a change in CD11b+and CD11b− PLDC subset frequencies and significant increase in CD40 and CD80 expression at these time points. Furthermore, mice infected with IAV at 4 weeks of age showed a significant increase in total numbers of PLDC, and increased CD40 expression on both AMDC and PLDC, when analysed as adults 35 days later. These data suggest that the rate of recovery of DC populations following IAV infection differs in the mucosal and parenchymal compartments of the lung and that DC populations can remain disrupted and activated for a prolonged period following viral clearance, into adulthood if infection occurred early in life. [ABSTRACT FROM AUTHOR]

Background: IgE‐mediated sensitisation to egg is common in infants. In some cases, the processes leading to egg sensitisation are established in early life, even before introduction to solid foods. The underlying mechanisms remain poorly understood. Methods: We performed detailed immune cell phenotyping of peripheral blood mononuclear cells and determined in vitro cytokine responses following allergen specific and non‐specific immune stimulation. To determine if unique immune profiles were linked to early‐life egg sensitisation, we compared 92 infants at 4–6 months of age, with (EggCAP+, n = 41) and without (EggCAP−, n = 51) early egg sensitisation. Additionally, 47 cord blood samples were analysed. For a subset of participants (n = 39), matching cord blood mononuclear cells were assessed by flow cytometry to establish the impact of IgE sensitisation on immune developmental trajectories. Results: EggCAP+ infants were found to exhibit a unique immune phenotype characterised by increased levels of circulating CD4+ T regulatory cells (Treg), CD4+ effector memory (EM) Treg and increased expression of the IgE receptor, FcεR1, on basophils. The increased CD4+ EM Treg profiles were already present in cord blood samples from EggCAP+ infants. A general Th2‐skewing of the immune system was observed based on increased IL‐13 production following phytohemagglutinin stimulation and by comparing immune developmental trajectories, EggCAP+ infants displayed an expansion of basophils and reduced levels of CD4− T cells compared to EggCAP− infants. Conclusions: Immunological profiles associated with egg sensitisation are detectable in infant circulation at 4–6 months of age and at birth. Understanding the immune mechanisms underlying early‐life sensitisation could provide important insights for future food allergy prevention strategies. [ABSTRACT FROM AUTHOR]

Respiratory syncytial virus (RSV) causes annual epidemics of infections affecting the whole population. In vitro, it has been shown to infect and persist in human dendritic cells (DCs) for prolonged periods. Initially persistence is associated with low levels of replication before the virus becomes dormant. Reactivation of viral replication can be triggered many months later. Infection of DCs is likely to influence the host's ability to generate effective long-term memory responses. A well-established animal was utilized to confirm that RSV both infects and persists in pulmonary DCs in vivo. Mice were infected with a modified strain of RSV expressing red fluorescent protein (RSV-RFP) when replicating. Clinical symptoms of infection were monitored using weight change and inflammatory cell counts from bronchoalveolar lavage, which correlated with the RSV viral titer (quantitative polymerase chain reaction). Lung tissues were collected at 3, 5, 7, and 21 days postinfection (dpi) to assess leukocyte populations by flow cytometry. Clinical symptoms and RSV viral load peaked at 5 dpi. RSV-RFP was most prevalent in macrophages at 3 dpi and also observed in B cells and DCs. At 21 dpi, RSV-RFP remained evident in a subset of conventional DCs (CD103+CD11b+) even though both clinical symptoms and pulmonary inflammation had resolved. These results confirm that in this well-established mouse model, RSV persists in lung conventional DCs following resolution of the acute infection. Further work is required to explore whether the virus continues with low-level replication before becoming dormant in vivo, as has been described in vitro. [ABSTRACT FROM AUTHOR]

Asthma exacerbations in children are associated with respiratory viral infection and atopy, resulting in systemic immune activation and infiltration of immune cells into the airways. The gene networks driving the immune activation and subsequent migration of immune cells into the airways remains incompletely understood. Cellular and molecular profiling of PBMC was employed on paired samples obtained from atopic asthmatic children (n = 19) during acute virus-associated exacerbations and later during convalescence. Systems level analyses were employed to identify coexpression networks and infer the drivers of these networks, and validation was subsequently obtained via independent samples from asthmatic children. During exacerbations, PBMC exhibited significant changes in immune cell abundance and upregulation of complex interlinked networks of coexpressed genes. These were associated with priming of innate immunity, inflammatory and remodelling functions. We identified activation signatures downstream of bacterial LPS, glucocorticoids and TGFB1. We also confirmed that LPS binding protein was upregulated at the protein-level in plasma. Multiple gene networks known to be involved positively or negatively in asthma pathogenesis, are upregulated in circulating PBMC during acute exacerbations, supporting the hypothesis that systemic pre-programming of potentially pathogenic as well as protective functions of circulating immune cells preceeds migration into the airways. Enhanced sensitivity to LPS is likely to modulate the severity of acute asthma exacerbations through exposure to environmental LPS. [ABSTRACT FROM AUTHOR]

Brown adipose tissue (BAT) may be an important metabolic regulator of whole‐body glucose. While important roles have been ascribed to macrophages in regulating metabolic functions in BAT, little is known of the roles of other immune cells subsets, particularly dendritic cells (DCs). Eating a high‐fat diet may compromise the development of hematopoietic stem and progenitor cells (HSPCs)—which give rise to DCs—in bone marrow, with less known of its effects in BAT. We have previously demonstrated that ongoing exposure to low‐dose ultraviolet radiation (UVR) significantly reduced the 'whitening' effect of eating a high‐fat diet upon interscapular (i) BAT of mice. Here, we examined whether this observation may be linked to changes in the phenotype of HSPCs and myeloid‐derived immune cells in iBAT and bone marrow of mice using 12‐colour flow cytometry. Many HSPC subsets declined in both iBAT and bone marrow with increasing metabolic dysfunction. Conversely, with rising adiposity and metabolic dysfunction, conventional DCs (cDCs) increased in both of these tissues. When compared with a low‐fat diet, consumption of a high‐fat diet significantly reduced proportions of myeloid, common myeloid and megakaryocyte–erythrocyte progenitors in iBAT, and short‐term hematopoietic stem cells in bone marrow. In mice fed the high‐fat diet, exposure to low‐dose UVR significantly reduced proportions of cDCs in iBAT, independently of nitric oxide release from irradiated skin [blocked using the scavenger 2‐(4‐carboxyphenyl)‐4,4,5,5‐tetramethylimidazoline‐1‐oxyl‐3‐oxide potassium salt (cPTIO)], but did not significantly modify HSPC subsets in either tissue. Further studies are needed to determine whether changes in these cell populations contribute towards metabolic dysfunction. [ABSTRACT FROM AUTHOR]

Objectives: Incomplete maturation of immune regulatory functions at birth is antecedent to the heightened risk for severe respiratory infections during infancy. Our forerunner animal model studies demonstrated that maternal treatment with the microbial‐derived immune training agent OM‐85 during pregnancy promotes accelerated postnatal maturation of mechanisms that regulate inflammatory processes in the offspring airways. Here, we aimed to provide proof of concept for a novel solution to reduce the burden and potential long‐term sequelae of severe early‐life respiratory viral infection through maternal oral treatment during pregnancy with OM‐85, already in widespread human clinical use. Methods: In this study, we performed flow cytometry and targeted gene expression (RT‐qPCR) analysis on lungs from neonatal offspring whose mothers received oral OM‐85 treatment during pregnancy. We next determined whether neonatal offspring from OM‐85 treated mothers demonstrate enhanced protection against lethal lower respiratory infection with mouse‐adapted rhinovirus (vMC0), and associated lung immune changes. Results: Offspring from mothers treated with OM‐85 during pregnancy display accelerated postnatal seeding of lung myeloid populations demonstrating upregulation of function‐associated markers. Offspring from OM‐85 mothers additionally exhibit enhanced expression of TLR4/7 and the IL‐1β/NLRP3 inflammasome complex within the lung. These treatment effects were associated with enhanced capacity to clear an otherwise lethal respiratory viral infection during the neonatal period, with concomitant regulation of viral‐induced IFN response intensity. Conclusion: These results demonstrate that maternal OM‐85 treatment protects offspring against lethal neonatal respiratory viral infection by accelerating development of innate immune mechanisms crucial for maintenance of local immune homeostasis in the face of pathogen challenge. [ABSTRACT FROM AUTHOR]

Background: Low vitamin D levels have been associated with allergic diseases. Vitamin D has potent immunomodulatory properties, but the mechanisms remain unclear. We have investigated the effect of oral vitamin D supplementation on circulating immune cell phenotypes in infants. Method: A double‐blinded randomised controlled trial was conducted to investigate the effect of oral vitamin D supplementation (400 IU/d) on eczema and immune development. A subset of 78 infants was included in this analysis. Phenotypic analysis of immune cell subsets was performed using flow cytometry. Results: Vitamin D supplementation resulted in median 25(OH)D levels of 80.5 vs 59.5 nmol/L in the placebo group at 3 months of age (P =.002) and 87.5 vs 77 nmol/L at 6 months of age (P =.08). We observed significant changes in immune cell composition from birth (cord blood) to 6 months of age. Vitamin D supplementation did not impact these changes, nor did immune cell composition correlate with plasma 25(OH)D levels. Through exploratory analysis, we identified possible associations with eczema development and increased abundance of naïve CD4‐ T cells at birth, as well as associations with basophils, iNKT and central memory CD4+ T cells, and altered expression patterns of IgE receptor (FcεR1) on monocytes and dendritic cells with eczema at 6 months. Conclusions: Vitamin D supplementation in infants who were vitamin D sufficient at birth did not affect developmental changes in immune cells during the first 6 months of life. However, immune cell profiles at birth and at 6 months of age were associated with early life eczema. [ABSTRACT FROM AUTHOR]

Background: The prevalence and severity of asthma, particularly the most common (atopic) form of the disease, increase amongst females but not males after puberty, and asthma activity also changes throughout the menstrual cycle and during pregnancy. The contribution of female sex hormones to asthma pathogenesis is incompletely understood. Objective: To obtain insight into the role of oestrogen (E2) in experimental atopic asthma, and guide future research on sex‐related variations in atopic asthma susceptibility/intensity in humans. Methods: We utilized an experimental model comprising rat strains expressing dichotomous Th2‐high vs Th2‐low immunophenotypes exemplified by eosinophilia, mirroring differences between human atopics/non‐atopics. We compared the efficiency of Th2‐associated immunoinflammatory mechanisms, which differed markedly between the two strains, and between sexes in the Th2‐high strain, and determined the effects of E2 administration on these differences. Results: Unique to the Th2‐high strain, eosinophil: neutrophil ratios in the airways at baseline and following sensitization/aeroallergen challenge were logfold higher in females relative to males, and this was reflected by higher baseline blood eosinophil numbers in females. Pretreatment of Th2‐high males with E2 abrogated this sex difference by selectively boosting Th2‐associated genes in the airways and eosinophilia, but was without corresponding effect in the Th2‐low strain. In contrast, parallel E2 effects on myeloid and lymphoid cell populations were relatively modest. Conclusions and Clinical Relevance: E2 acts to amplify the eosinophilic component of pre‐existing Th2‐high immunophenotype, possibly acting at the level of the common eosinophil/neutrophil precursor in bone marrow to preferentially drive eosinophil differentiation. Constitutive granulocyte profiles in which the balance between eosinophils and neutrophils is skewed towards eosinophils have been identified in independent cohort studies as markers of asthma risk, and these findings suggest that more detailed studies on the role of E2 in this context, and in relation to asthma pathogenesis in post‐pubertal females in particular, appear warranted. [ABSTRACT FROM AUTHOR]

Background: Antigen‐specific IgE binds the Fcε receptor I (FcεRI) expressed on several types of immune cells, including dendritic cells (DCs). Activation of FcεRI on DCs in atopics has been shown to modulate immune responses that potentially contribute to asthma development. However, the extent to which DC subsets differ in FcεRI expression between atopic children with or without asthma is currently not clear. This study aimed to analyse the expression of FcεRI on peripheral blood mononuclear cells (PBMCs) from atopic children with and without asthma, and non‐atopic/non‐asthmatic age‐matched healthy controls. Methods: We performed multiparameter flow cytometry on PBMC from 391 children across three community cohorts and one clinical cohort based in Western Australia. Results: We confirmed expression of FcεRI on basophils, monocytes, plasmacytoid and conventional DCs, with higher proportions of all cell populations expressing FcεRI in atopic compared to non‐atopic children. Further, we observed that levels of FcεRI expression were elevated across plasmacytoid and conventional DC as well as basophils in atopic asthmatic compared to atopic non‐asthmatic children also after adjusting for serum IgE levels. Conclusion: Our data suggest that the expression pattern of FcεRI on DC and basophils differentiates asthmatic from non‐asthmatic atopic children. Given the significant immune modulatory effects observed as a consequence of FcεRI expression, this altered expression pattern is likely to contribute to asthma pathology in children. [ABSTRACT FROM AUTHOR]

Background: Influenza virus infection during pregnancy is associated with enhanced disease severity. However, the underlying mechanisms are still not fully understood. We hypothesized that normal alveolar macrophage (AM) functions, which are central to maintaining lung immune homeostasis, are altered during pregnancy and that this dysregulation contributes to the increased inflammatory response to influenza virus infection.Methods: Time-mated BALB/c mice were infected with a low dose of H1N1 influenza A virus at gestation day 9.5. Inflammatory cells in bronchoalveolar lavage (BAL) fluid were assessed by flow cytometry.Results: Our findings confirm previous reports of increased severity of influenza virus infection in pregnant mice. The heightened inflammatory response detected in BAL fluid from infected pregnant mice was characterized by neutrophil-rich inflammation with concomitantly reduced numbers of AM, which were slower to return to baseline counts, compared with nonpregnant infected mice. The increased infection severity and inflammatory responses to influenza during pregnancy were associated with a pregnancy-induced shift in AM phenotype at homeostatic baseline, from the M1 (ie, classical activation) state toward the M2 (ie, alternative activation) state, as evidence by increased expression of CD301 and reduced levels of CCR7.Conclusion: These results show that pregnancy is associated with an alternatively activated phenotype of AM before infection, which may contribute to heightened disease severity. [ABSTRACT FROM AUTHOR]

Chronic allergic inflammatory diseases are a major cause of morbidity, with allergic asthma alone affecting over 300 million people worldwide. Epidemiological studies demonstrate that environmental stimuli are associated with either the promotion or prevention of disease. Major reductions in asthma prevalence are documented in European and US farming communities. Protection is associated with exposure of mothers during pregnancy to microbial breakdown products present in farm dusts and unprocessed foods and enhancement of innate immune competence in the children. We sought to develop a scientific rationale for progressing these findings toward clinical application for primary disease prevention. Treatment of pregnant mice with a defined, clinically approved immune modulator was shown to markedly reduce susceptibility of their offspring to development of the hallmark clinical features of allergic airway inflammatory disease. Mechanistically, offspring displayed enhanced dendritic cell-dependent airway mucosal immune surveillance function, which resulted in more efficient generation of mucosal-homing regulatory T cells in response to local inflammatory challenge. We provide evidence that the principal target for maternal treatment effects was the fetal dendritic cell progenitor compartment, equipping the offspring for accelerated functional maturation of the airway mucosal dendritic cell network following birth. These data provide proof of concept supporting the rationale for developing transplacental immune reprogramming approaches for primary disease prevention. [ABSTRACT FROM AUTHOR]

IgE sensitisation has increased significantly over the last decades and is a crucial factor in the development of allergic diseases. IgE antibodies are produced by B cells through the process of antigen presentation by dendritic cells, subsequent differentiation of CD4+ Th2 cells, and class switching in B cells. However, many of the factors regulating these processes remain unclear. These processes affect males and females differently, resulting in a significantly higher prevalence of IgE sensitisation in males compared to females from an early age. Before the onset of puberty, this increased prevalence of IgE sensitisation is also associated with a higher prevalence of clinical symptoms in males; however, after puberty, females experience a surge in the incidence of allergic symptoms. This is particularly apparent in allergic asthma, but also in other allergic diseases such as food and contact allergies. This has been partly attributed to the pro- versus anti-allergic effects of female versus male sex hormones; however, it remains unclear how the expression of sex hormones translates IgE sensitisation into clinical symptoms. In this review, we describe the recent epidemiological findings on IgE sensitisation in male and females and discuss recent mechanistic studies casting further light on how the expression of sex hormones may influence the innate and adaptive immune system at mucosal surfaces and how sex hormones may be involved in translating IgE sensitisation into clinical manifestations. [ABSTRACT FROM AUTHOR]

Abstract: Respiratory IgE‐sensitization to innocuous antigens increases the risk for developing diseases such as allergic asthma. Dendritic cells (DC) residing in the airways orchestrate the immune response following antigen exposure and their ability to sample and present antigens to naïve T cells in airway draining lymph nodes contributes to allergen‐specific IgE‐sensitization. In order to characterize inhaled antigen capture and presentation by DC subtypes in vivo, we used an adjuvant‐free respiratory sensitization model using two genetically distinct rat strains, one of which is naturally resistant and the other naturally susceptible to allergic sensitization. Upon multiple exposures to ovalbumin (OVA), the susceptible strain developed OVA‐specific IgE and airway inflammation, whereas the resistant strain did not. Using fluorescently tagged OVA and flow cytometry, we demonstrated significant differences in antigen uptake efficiency and presentation associated with either IgE‐sensitization or resistance to allergen exposures in respective strains. We further identified CD4+ conventional DC (cDC) as the subset involved in airway antigen sampling in both strains, however, CD4+ cDC in the susceptible strain were less efficient in OVA sampling and displayed increased MHC‐II expression compared with the resistant strain. This was associated with generation of an exaggerated Th2 response and a deficiency of airway regulatory T cells in the susceptible strain. These data suggest that subsets of cDC are able to induce either sensitization or resistance to inhaled antigens as determined by genetic background, which may provide an underlying basis for genetically determined susceptibility to respiratory allergic sensitization and IgE production in susceptible individuals. [ABSTRACT FROM AUTHOR]

Folate intake during pregnancy may affect the regulation of DNA methylation during fetal development. The genomic regions in the offspring that may be sensitive to folate exposure during in utero development have not been characterized. Using genome-scale profiling, we investigated DNA methylation in 2 immune cell types (CD4+ and antigen-presenting cells) isolated from neonatal cord blood, selected on the basis of in utero folate exposure. High-folate (HF; n=11) and low-folate (LF; n=12) groups were selected from opposite extremes of maternal serum folate levels measured in the last trimester of pregnancy. A comparison of these groups revealed differential methylation at 7 regions across the genome. By far, the biggest effect observed was hypomethylation of a 923 bp region 3 kb upstream of the ZFP57 transcript, a regulator of DNA methylation during development, observed in both cell types. Levels of H3/H4 acetylation at ZFP57 promoter and ZFP57 mRNA expression were higher in CD4+ cells in the HF group relative to the LF group. Hypomethylation at this region was replicated in an independent sample set. These data suggest that exposure to folate has effects on the regulation of DNA methylation during fetal development, and this may be important for health and disease. [ABSTRACT FROM AUTHOR]

• A model of rhinovirus induced exacerbation of cigarette smoke induced lung disease. • HRV-1A infection post cigarette-smoke exposure altered mouse lung structure. • Long-term cigarette smoke exposure and HRV have independent and combined effects. A significant proportion of chronic obstructive pulmonary disease exacerbations are strongly associated with rhinovirus infection (HRV). In this study, we combined long-term cigarette smoke exposure with HRV infection in a mouse model. Our aim was to better understand the effects of HRV infection on such exacerbations, using a realistic method for generating a COPD-like phenotype. After 12-weeks of cigarette smoke exposure, adult female BALB/c mice were infected with HRV-1A and three days later we assessed a range of outcomes including lung volume and function, collected lung tissue for measurement of viral titre, bronchoalveolar lavage for assessment of pulmonary inflammation and levels of key mediators, and fixed lungs for stereological structural analyses. Cigarette smoke exposure alone significantly increased total cells and macrophages, and reduced MIP-2 in bronchoalveolar lavage. HRV-1A infection alone increased neutrophilic inflammation, IP-10 and total protein in lavage and also increased specific airway resistance measured at functional residual capacity. Cigarette smoke and HRV-1A together impacted various lung structural parameters including increasing stereological lung volume. Our results show that long-term cigarette smoke exposure and HRV-1A infection both individually impact respiratory outcomes and combine to alter aspects of lung structure in a mouse model, thus providing insight into the development of future mechanistic studies and appropriate interventions in human disease. [ABSTRACT FROM AUTHOR]

Dendritic cells (DCs) play a central role in regulating innate and adaptive immune responses. It is well accepted that their regulatory functions change over the life course. In order to study DCs function during early life it is important to characterize the function of neonatal DCs. However, the availability of neonatal DCs is limited due to ethical reasons or relative small samples of cord blood making it difficult to perform large-scale experiments. Our aim was to establish a robust protocol for the generation of neonatal DCs from cord blood derived CD34+ hematopoietic stem cells. For the expansion of DC precursor cells we used a cytokine cocktail containing Flt-3 L, SCF, TPO, IL-3 and IL-6. The presence of IL-3 and IL-6 in the first 2 weeks of expansion culture was essential for the proliferation of DC precursor cells expressing CD14. After 4 weeks in culture, CD14+ precursor cells were selected and functional DCs were generated in the presence of GM-CSF and IL-4. Neonatal DCs were then stimulated with Poly(I:C) and LPS to mimic viral or bacterial infections, respectively. Poly(I:C) induced a higher expression of the maturation markers CD80, CD86 and CD40 compared to LPS. In line with literature data using cord blood DCs, our Poly(I:C) matured neonatal DCs cells showed a higher release of IL-12p70 compared to LPS matured neonatal DCs. Additionally, we demonstrated a higher release of IFN-γ, TNF-α, IL-1β and IL-6, but lower release of IL-10 in Poly(I:C) matured compared to LPS matured neonatal DCs derived from cord blood CD34+ hematopoietic stem cells. In summary, we established a robust protocol for the generation of large numbers of functional neonatal DCs. In line with previous studies, we showed that neonatal DCs generated form CD34+ cord blood progenitors have a higher inflammatory potential when exposed to viral than bacterial related stimuli. • A robust protocol for the generation of high numbers of neonatal dendritic cells. • IL-3 and IL-6 are crucial for the proliferation of cord blood CD34+ progenitors. • Neonatal DCs have a higher inflammatory potential when exposed to viral stimuli. • LPS induces higher release of IL-10 in neonatal DCs compared to Poly(I:C). [ABSTRACT FROM AUTHOR]