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Childhood asthma derives from complex host-environment interactions occurring in the perinatal and infant period, a critical time for lung development. Sphingolipids are bioactive molecules consistently implicated in the pathogenesis of childhood asthma. Genome wide association studies (GWAS) initially identified a link between alleles within the 17q21 asthma-susceptibility locus, childhood asthma, and overexpression of the ORMDL sphingolipid biosynthesis regulator 3 (ORMDL3), an inhibitor of de novo sphingolipid synthesis. Subsequent studies of pediatric asthma offer strong evidence that these asthma-risk alleles correlate with early-life aberrancies of sphingolipid homeostasis and asthma. Relationships between sphingolipid metabolism and asthma-related risk factors, including maternal obesity and respiratory viral infections, are currently under investigation. This review will summarize how these perinatal and early life exposures can synergize with 17q21 asthma risk alleles to exacerbate disruptions of sphingolipid homeostasis and drive asthma pathogenesis.

Omega-3 polyunsaturated fatty acids (n-3 PUFAs) are essential nutrients that can affect inflammatory responses. While n-3 PUFAs are generally considered beneficial for cardiovascular disease and obesity, the effects on asthma, the most common inflammatory lung disease are unclear. While prenatal dietary n-3 PUFAs decrease the risk for childhood wheezing, postnatal dietary n-3 PUFAs can worsen allergic airway inflammation. Sphingolipid metabolism is also affected by dietary n-3 PUFAs. Decreased sphingolipid synthesis leads to airway hyperreactivity, besides inflammation, a cardinal feature of asthma, and common genetic asthma risk alleles lead to lower sphingolipid synthesis. We investigated the effect of dietary n-3 PUFAs on sphingolipid metabolism and airway reactivity. Comparing a fish-oil diet with a high n-3 PUFA content (FO) to an isocaloric coconut oil-enriched diet (CO), we found an n-3 PUFA-dependent effect on increased airway reactivity, that was not accompanied by inflammation. Lung and whole blood content of dihydroceramides, ceramides, sphingomyelins, and glucosylceramides were lower in mice fed the n-3 PUFA enriched diet consistent with lower sphingolipid synthesis. In contrast, phosphorylated long chain bases such as sphingosine 1-phosphate were increased. These findings suggest that dietary n-3 PUFAs affect pulmonary sphingolipid composition to favor innate airway hyperreactivity, independent of inflammation, and point to an important role of n-3 PUFAs in sphingolipid metabolism.

Asthma phenotypes and endotypes have mainly been defined by clinical features, markers of atopy, airway immune cells and inflammatory markers.1 While clustering has helped the advancement of biologics specific targeting immune receptors or IgE, there has been less success in using clustering by other parameters such as genetics or environmental factors therapeutically.2 Despite a wealth of information on the detrimental effects of environmental factors such as air pollution and tobacco smoke exposure on asthma,3 their role in asthma pathogenesis is still unclear. Common 17q21 genetic variations are known to change the expression of the sphingolipid regulator ORMDL3, a key inhibitor of sphingolipid synthesis.6 This has led to several studies demonstrating that children with asthma-associated genotypes have lower blood levels of sphingolipids mainly produced by de novo synthesis7 and this also reflected nasal gene expression of sphingolipid synthesis-associated genes.8 These studies analysed a larger number of sphingolipids using mass spectrometry. For other chronic inflammatory conditions such as atherosclerosis, plasma sphingolipids were also increased with PM2.5 exposure and possibly mediating proatherogenic effects.9 Increased oxidative stress increases sphingolipid metabolism, generating bioactive lipid metabolites and key signalling mediators, mainly studied for chronic obstructive pulmonary disease (COPD) and less for asthma.10 Subjects with COPD and asthma were excluded from this study.

•A vaccine against established P. aeruginosa respiratory infections would be helpful.•Capsid-modified AdC7 vectors are potent inducers of respiratory mucosal immunity.•Immunization with AdC7OprF.RGD against established P. aeruginosa lung infections was evaluated.•AdC7OprF.RGD immunization induced robust humoral and cellular immunity against P. aeruginosa.•The induced immunity enhanced clearance of P. aeruginosa from rodent lungs. Respiratory infections with Pseudomonas aeruginosa are major health problems, particularly in patients with cystic fibrosis (CF). No vaccine against P. aeruginosa is yet available. A vaccine that controls colonization of the respiratory tract with P. aeruginosa could be useful to prevent chronic infection and exacerbations. Replication-deficient adenoviral (Ad) vectors based on non-human serotypes are attractive vaccine platforms as they can circumvent the problem of pre-existing anti-Ad immunity in humans. The primate-based AdC7 vector AdC7OprF.RGD that expresses the outer membrane protein F (OprF) of P. aeruginosa (AdC7OprF) and that displays an integrin-binding arginine–glycine–aspartic acid (RGD) sequence is a potent inducer of lung mucosal and protective immunity. Here, we investigated the efficacy of immunization with AdC7OprF.RGD to clear an already established P. aeruginosa respiratory infection in mice (wild-type and CF) and rats. Intratracheal administration of the clinical P. aeruginosa strain RP73 embedded in agar beads was used to establish persistent infection. Subsequent intranasal immunization with AdC7OprF.RGD induced robust P. aeruginosa-specific systemic and mucosal, humoral and cellular immune responses. Importantly, the AdC7OprF.RGD immunized mice effectively cleared P. aeruginosa from the lungs. Likewise, immunization with AdC7OprF.RGD of CF mice and Sprague Dawley rats with established P. aeruginosa respiratory infection showed enhanced anti-Pseudomonas immune responses and increased clearance of P. aeruginosa from the lungs. These data suggest that AdC7OprF.RGD can be effective as a post-exposure vaccine and may be useful in clinical settings in particular for patients with CF who frequently harbor the bacteria over prolonged periods.

The inflammatory milieu in the respiratory tract in cystic fibrosis (CF) has been linked to the defective expression of the cystic transmembrane regulator (CFTR) in epithelial cells. Alveolar macrophages (AM), important contibutors to inflammatory responses in the lung, also express CFTR. The present study analyzes the phenotype of human AM with silenced CFTR. Expression of CFTR mRNA and the immature form of the CFTR protein decreased 100-fold and 5.2-fold, respectively, in AM transfected with a CFTR specific siRNA (CFTR-siRNA) compared to controls. Reduction of CFTR expression in AM resulted in increased secretion of IL-8, increased phosphorylation of NF-kappaB, a positive regulator of IL-8 expression, and decreased expression of IkappaB-alpha, the inhibitory protein of NF-kappaB activation. AM with silenced CFTR expression also showed increased apoptosis. We hypothesized that caveolin-1 (Cav1), a membrane protein that is co-localized with CFTR in lipid rafts and that is related to inflammation and apoptosis in macrophages, may be affected by decreased CFTR expression. Messenger RNA and protein levels of Cav1 were increased in AM with silenced CFTR. Expression and transcriptional activity of sterol regulatory element binding protein (SREBP), a negative transcriptional regulator of Cav1, was decreased in AM with silenced CFTR, but total and free cholesterol mass did not change. These findings indicate that silencing of CFTR in human AM results in an inflammatory phenotype and apoptosis, which is associated to SREBP-mediated regulation of Cav1.

OBJECTIVES/GOALS: MgSO4 is a frequently used to treat asthma exacerbations. Its role in the management of pediatric asthma remains controversial. Our objective is to demonstrate that the response of the small (peripheral) airways depends on airway de novo sphingolipid synthesis, clinically and experimentally. The small airways are the main site of asthma pathology. METHODS/STUDY POPULATION: We investigated airway reactivity in response to MgSO4 in murine small airways and children 1. Precision-cut lung slices (PCLS): Using heterozygous knockouts mice of one of the Sptlc2 subunit of the serine palmitoyl-CoA transferase (SPT) which results in reduced tissue sphingolipid levels compared to wild-type control littermates (Sptlc2+/+). We compared small airway dilation to MgSO4 in Sptlc2+/- and Sptlc2+/+ mice. This was assessed by directly visualization of small airway contractility in PCLS from Sptlc2+/- mice using video phase-contrast microscopy 2. Clinical response to MgSO4 in children by using a respiratory score before and after the treatment. The response to MgSO4 was the correlated to asthma-associated 17q21 specific single nucleotide polymorphisms (SNPs) from DNA isolated from buccal swabs RESULTS/ANTICIPATED RESULTS: Sphingolipid-mediated activity alters magnesium response in small airways. We assessed whether downregulation of SPT could lead to alterations in MgSO4-induced small airway dilation and in MgSO4 responsiveness in mouse tracheal rings and found that the magnesium-induced relaxation of airways pre-contracted with methacholine was impaired in Sptlc+/- mice compared to the control group (p=<0.05) Clinical response to MgSO4 in children with status asthmaticus. A respiratory score was assessed in a cohort of 5 to 21-year-old who received IV MgSO4. An increase of 3 or more points was considered positive. Only 32% of the patients showed a favorable improvement to the medication, showing variability of response between individuals. The correlation of sphingolipid-deficient SNPs and MgSO4 responsiveness is ongoing DISCUSSION/SIGNIFICANCE: This suggest that decreased SPT activity in the respiratory track alters the response of the airways to magnesium. Connecting decreased de novo SL synthesis to alterations in cellular magnesium homeostasis provides a mechanistic link to differential airway reactivity to MgSO4 in pediatric asthma management.

Elevated levels of IL-8 have been found not only in BAL of suppurative airway diseases such as cystic fibrosis (CF), chronic obstructive pulmonary disease (COPD), and non-CF bronchiectasis but also in lung tissue and BAL from patients with idiopathic pulmonary fibrosis, acute respiratory distress syndrome, and asthma. [...]bacterial infection of the IL-8 transgenic mice did not result in enhanced IFN-g recall responses in cells from draining lymph nodes. [...]they do not mimic important human disease-specific conditions, such as an altered cellular composition of the airway epithelium with an increase in goblet cells or the alterations in luminal junctional complexes as seen in CF and COPD (6).

In addition to the traditional activation of resident receptors by release of local mediators, new evidence favors the existence of exosomes in cell-to-cell communication that mediates delivery of specific cargo to modulate recipient cell function. We report that mast cell exosomes are an additional source of pro-fibrotic substances and constitute a unique pathway for the generation of excess collagen. We use primary human lung fibroblasts (HLFs) to demonstrate the uptake of labeled exosomes isolated from the human mast cell line HMC-1 (MC-EXOs), previously shown to contain protein cargo in common with human mast cell exosomes. The MC-EXO uptake by HLF is to the cytosol and increases both proline hydroxylation in HLF lysate and secreted collagen, within 24 h, which is sustained over 72 h, the same time required for transforming growth factor-β (TGF-β) to activate collagen synthesis in the HLFs. Unlike TGF-β, MC-EXO uptake does not induce fibrillar gene activation or invoke the Smad-nuclear transcription pathway. We show that MC-EXO uptake and TGF-β have an additive effect on collagen synthesis in HLF and postulate that MC-EXO uptake by HLFs is a contributing factor to excess collagen synthesis and represents a unique paradigm for understanding fibrosis. It is known that, in the lungs, mast cells are more activated and increase in number with inflammation, injury and viral infection associated with fibrosis. With the reported increased incidence of post-COVID-pulmonary fibrosis (PCPF), data from patients with severe COVID-19 are presented that show an increase in the mast cell number in lung parenchyma, the site of PCPF. Our findings provide a rationale for targeting multiple fibrogenic pathways in the management of lung fibrosis and the use of mast cell exosomes as a biomarker for the prognostic and diagnostic management of evolving fibrotic lung disease.

Adenovirus (Ad) vector-based vaccines displaying pathogen-derived epitopes on Ad capsid proteins can elicit anti-pathogen immunity. This approach seems to be particularly efficient with epitopes incorporated into the Ad fiber protein. Here, we explore epitope insertion into various sites of the Ad fiber to elicit epitope-specific immunity. Ad vectors expressing the 14-mer Pseudomonas aeruginosa immune-dominant outer membrane protein F (OprF) epitope 8 (Epi8) in five distinct sites of the Ad5 fiber, loops CD (AdZ.F(CD)Epi8), DE (AdZ.F(DE)Epi8), FG (AdZ.F(FG)Epi8), HI (AdZ.F(HI)Epi8) and C terminus (AdZ.F(CT)Epi8), or the hexon HVR5 loop (AdZ.HxEpi8) were compared in their capacity to elicit anti-P. aeruginosa immunity to AdOprF, an Ad expressing the entire OprF protein. Intramuscular immunization of BALB/c mice with AdZ.F(FG)Epi8 or AdZ.F(HI)Epi8 elicited higher anti-OprF humoral and cellular CD4 and CD8 responses as well as enhanced protection against respiratory infection with P. aeruginosa compared to immunization with AdZ.F(CD)Epi8, AdZ.F(DE)Epi8, AdZ.F(CT)Epi8 or AdZ.HxEpi8. Importantly, repeat administration of the fiber- and hexon-modified Ad vectors boosted the OprF-specific humoral immune response in contrast to immunization with AdOprF. Strikingly, following three doses of AdZ.F(FG)Epi8 or AdZ.F(HI)Epi8 anti-OprF immunity surpassed that induced by AdOprF. Furthermore, in the presence of anti-Ad5 immunity, immunization with AdZ.F(FG)Epi8 or AdZ.F(HI)Epi8, but not with AdOprF, induced protective immunity against P. aeruginosa. This suggests that incorporation of epitopes into distinct sites of the Ad fiber is a promising vaccine strategy.

Respiratory syncytial virus (RSV) is one of the leading causes of lower respiratory tract infection in infants. Immunoprophylaxis with the anti-RSV monoclonal antibody, palivizumab, reduces the risk for RSV-related hospitalizations, but its use is restricted to high-risk infants due to the high costs. In this study, we investigated if genetic delivery of anti-RSV antibody to neonatal mice by chimpanzee adenovirus type 7 expressing the murine form of palivizumab (AdC7αRSV) can provide protection against RSV. Intranasal and intramuscular administration of AdC7αRSV to adult mice resulted in similar levels of anti-RSV IgG in the serum. However, only intranasal administration resulted in detectable levels of anti-RSV IgG in the bronchoalveolar lavage fluid. Intranasal administration of AdC7αRSV provided protection against subsequent RSV challenge. Expression of the anti-RSV antibody was prolonged following intranasal administration of AdC7αRSV to neonatal mice. Protection against RSV was confirmed at 6 weeks of age. These data suggest that neonatal genetic delivery of anti-RSV antibody by AdC7αRSV can provide protection against RSV.