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Maternal asthma is associated with increased rates of neonatal lung disease, and fetuses from asthmatic ewes have fewer surfactant‐producing cells and lower surfactant‐protein B gene (SFTPB) expression than controls. Antenatal betamethasone increases lung surfactant production in preterm babies, and we therefore tested this therapy in experimental maternal asthma. Ewes were sensitised to house dust mite allergen, and an asthmatic phenotype induced by fortnightly allergen lung challenges; controls received saline. Pregnant asthmatic ewes were randomised to receive antenatal saline (asthma) or 12 mg intramuscular betamethasone (asthma+beta) at 138 and 139 days of gestation (term = 150 days). Lambs were delivered by Caesarean section at 140 days of gestation and ventilated for 45 min before tissue collection. Lung function and structure were similar in control lambs (n = 16, 11 ewes) and lambs from asthma ewes (n = 14, 9 ewes). Dynamic lung compliance was higher in lambs from asthma+beta ewes (n = 12, 8 ewes) compared to those from controls (P = 0.003) or asthma ewes (P = 0.008). Lung expression of surfactant protein genes SFTPA (P = 0.048) and SFTPB (P < 0.001), but not SFTPC (P = 0.177) or SFTPD (P = 0.285), was higher in lambs from asthma+beta than those from asthma ewes. Female lambs had higher tidal volume (P = 0.007), dynamic lung compliance (P < 0.001), and SFTPA (P = 0.037) and SFTPB gene expression (P = 0.030) than males. These data suggest that betamethasone stimulates lung maturation and function of near‐term neonates, even in the absence of impairment by maternal asthma. What is the central question of this study?Does antenatal betamethasone before near‐term delivery mitigate the increased risk of neonatal lung disease in a sheep model of maternal asthma?What is the main finding and its importance?Maternal asthma did not impair neonatal lung function or reduce surfactant gene expression, likely reflecting a mild maternal and fetal phenotype in this cohort. Nevertheless, antenatal maternal betamethasone treatment in asthmatic pregnancies increased dynamic lung compliance and surfactant protein A and B mRNA expression in newborn lambs. These data suggest potential benefits of betamethasone on lung maturation when mothers have asthma. [ABSTRACT FROM AUTHOR]

Abstract Background The airway epithelium is thought to play an important role in the pathogenesis of asthmatic disease. However, much of our understanding of airway epithelial cell function in asthma has been derived from in vitro studies that may not accurately reflect the interactive cellular and molecular pathways active between different tissue constituents in vivo. Methods Using a sheep model of allergic asthma, tracheal explants from normal sheep and allergic sheep exposed to house dust mite (HDM) allergen were established to investigate airway mucosal responses ex vivo. Explants were cultured for up to 48 h and tissues were stained to identify apoptotic cells, goblet cells, mast cells and eosinophils. The release of cytokines (IL-1α, IL-6 and TNF-α) by cultured tracheal explants, was assessed by ELISA. Results The general morphology and epithelial structure of the tracheal explants was well maintained in culture although evidence of advanced apoptosis within the mucosal layer was noted after culture for 48 h. The number of alcian blue/PAS positive mucus-secreting cells within the epithelial layer was reduced in all cultured explants compared with pre-cultured (0 h) explants, but the loss of staining was most evident in allergic tissues. Mast cell and eosinophil numbers were elevated in the allergic tracheal tissues compared to naïve controls, and in the allergic tissues there was a significant decline in mast cells after 24 h culture in the presence or absence of HDM allergen. IL-6 was released by allergic tracheal explants in culture but was undetected in cultured control explants. Conclusions Sheep tracheal explants maintain characteristics of the airway mucosa that may not be replicated when studying isolated cell populations in vitro. There were key differences identified in explants from allergic compared to control airways and in their responses in culture for 24 h. Importantly, this study establishes the potential for the application of tracheal explant cultures in relevant ex vivo investigations on the therapeutic and mechanistic modalities of asthmatic disease.

Abstract Background House dust mite (HDM) allergens are a major cause of allergic asthma. Most studies using animal models of allergic asthma have used rodents sensitized with the 'un-natural' allergen ovalbumin. It has only recently been recognized that the use of animal models based on HDM provide a more relevant insight into the allergen-induced mechanisms that underpin human allergic disease. We have previously described a sheep model of human allergic asthma that uses Dermatophagoides pteronyssinus HDM. The present study extends our understanding of the immune effects of HDM and the allergens Der p 1 and Der p 2 in the sheep model of asthma. Methods Peripheral blood sera from non-sensitized (control) sheep and sheep sensitized to HDM was collected to determine immunoglobulin (Ig) reactivities to HDM, Der p 1 and Der p 2 by ELISA. Bronchoalveolar lavage (BAL) fluid collected following allergen challenge was also assessed for the presence of HDM-specific antibodies. To examine the cellular immune response to HDM allergens, T cell proliferation and cutaneous responses were assessed in sensitized and control sheep. Results Strong HDM- and Der p 1-specific IgE, IgG1, IgG2 and IgA serum responses were observed in sensitized sheep, while detectable levels of HDM-specific IgG1 and IgA were seen in BAL fluid of allergen-challenged lungs. In contrast, minimal antibody reactivity was observed to Der p 2. Marked T cell proliferation and late phase cutaneous responses, accompanied by the recruitment of eosinophils, indicates the induction of a cellular and delayed-type hypersensitivity (DTH) type II response by HDM and Der p 1 allergen, but not Der p 2. Conclusion This work characterizes the humoral and cellular immune effects of HDM extract and its major constituent allergens in sheep sensitized to HDM. The effects of allergen in HDM-sensitized sheep were detectable both locally and systemically, and probably mediated via enzymatic and immune actions of the major HDM allergen Der p 1. This study extends our understanding of the actions of this important allergen relevant to human allergic asthma and its effects in sheep experimentally sensitized to HDM allergens.

Abstract Background There is strong evidence implicating eosinophils in host defence against parasites as well as allergic disease pathologies. However, a lack of reagents such as monoclonal antibodies (mAbs) specific for eosinophils has made it difficult to confirm the functional role of eosinophils in such disease conditions. Using an established mammary model of allergic inflammation in sheep, large numbers of inflammatory cells enriched for eosinophils were collected from parasite-stimulated mammary glands and used for the generation of mAbs against ovine eosinophils. Results A panel of mAbs was raised against ovine eosinophils of which two were shown to be highly specific for eosinophils. The reactivity of mAbs 3.252 and 1.2 identified eosinophils from various cell and tissue preparations with no detectable reactivity on cells of myeloid or lymphoid lineage, tissue mast cells, dendritic cells, epithelial cells or other connective tissues. Two other mAbs generated in this study (mAbs 4.4 and 4.10) were found to have reactivity for both eosinophils and neutrophils. Conclusion This study describes the production of new reagents to identify eosinophils (as well as granulocytes) in sheep that will be useful in studying the role of eosinophils in disease pathologies in parasite and allergy models.

Purpose: Inhaled delivery of pirfenidone to the lungs of patients with idiopathic pulmonary fibrosis holds promise to eliminate oral-observed side effects while enhancing efficacy. This study aimed to comprehensively describe the pulmonary pharmacokinetics of inhaled aerosol pirfenidone in healthy adult sheep. Methods: Pirfenidone concentrations were evaluated in plasma, lung-derived lymph and epithelial lining fluid (ELF) with data subjected to non-compartmental pharmacokinetic analysis. Results: Compartmental pharmacokinetic evaluation indicated that a 49 mg lung-deposited dose delivered an ELF Cmax of 62 ± 23 mg/L, and plasma Cmax of 3.1 ± 1.7 mg/L. Further analysis revealed that plasma pirfenidone reached Tmax faster and at higher concentrations than in lymph. These results suggested inhaled pirfenidone was cleared from the alveolar interstitium via blood faster than the drug could equilibrate between the lung interstitial fluid and lung lymphatics. However, the data also suggested that a 'reservoir' of pirfenidone feeds into lung lymph at later time points (after it has largely been cleared from plasma), prolonging lung lymphatic exposure. Conclusions: This study indicates inhaled pirfenidone efficiently deposits in ELF and is cleared from the lungs by initial absorption into plasma, followed by later equilibrium with lung interstitial and lymph fluid. [ABSTRACT FROM AUTHOR]