A. M. Nanzer

Distinct endotypes of steroid-resistant asthma characterized by IL-17Ahigh and IFN-γhigh immunophenotypes: Potential benefits of calcitriol

Background A small population of patients with severe asthma does not respond to glucocorticoids (steroid resistant [SR]). They have high morbidity, highlighting an urgent need for strategies to enhance glucocorticoid responsiveness. Objective We investigated the immunologic differences between steroid-sensitive (SS) and SR asthmatic patients and the effect on immunophenotype of oral calcitriol treatment because it has been previously shown to beneficially modulate the clinical response to glucocorticoids in patients with SR asthma. Methods CD8-depleted PBMCs were isolated from 12 patients with SS and 23 patients with SR asthma and cultured for 7 days with anti-CD3 and IL-2 with or without dexamethasone. Cytokine production was assessed in supernatants by using the Cytometric Bead Array. Patients with SR asthma were subsequently randomized to oral calcitriol or placebo therapy, and identical studies were repeated. Results Patients with SR asthma produced significantly increased IL-17A and IFN-γ levels compared with those in patients with SS asthma, although it was evident that cells from individual patients might overproduce one or the other of these cytokines. Production of IL-17A was inversely and production of IL-13 was positively associated with the clinical response to prednisolone. Oral calcitriol, compared with placebo, therapy of the patients with SR asthma significantly improved dexamethasone-induced IL-10 production in vitro while suppressing dexamethasone-induced IL-17A production. This effect mirrored the previously demonstrated improvement in clinical response to oral glucocorticoids in calcitriol-treated patients with SR asthma. Conclusions IL-17Ahigh and IFN-γhigh immunophenotypes exist in patients with SR asthma. These data identify immunologic pathways that likely underpin the beneficial clinical effects of calcitriol in patients with SR asthma by directing the SR cytokine profile toward a more SS immune phenotype, suggesting strategies for identifying vitamin D responder immunophenotypes.

Serum 25-dihydroxyvitamin D levels correlate with CD4+Foxp3+ T-cell numbers in moderate/severe asthma

impact of B-cell immunodeficiency in cases of PNP deficiency and is probably explained by the complete lack of PNP enzyme activity due to the reported nonsense mutation. Numerous symptomatic mutations, mostly missense, of the PNP gene have been identified. These mutations produce proteins with variable degrees of enzymatic activity, which correlate with the accumulation of nucleoside substrates and, to some degree, with the clinical course. It is the progressive accumulation of deoxyguanosine triphosphate in PNP deficiency that leads to progressive disease. Interestingly, similar to the progressive T-cells toxicity caused by PNP deficiency during the first years of life, the more severe B-cell defect observed in our older patient also suggests accumulating effects of PNP deficiency on B cells. Our results concur with several recent in vitro and in vivo studies describing B-cell death following PNP inhibition with excess deoxyguanosine/deoxyguanosine triphosphate concentrations, albeit at a reduced frequency compared with T-cell apoptosis. Additional studies, including longitudinal studies, are still required to determine whether B-cell function, like T-cell function, deteriorates over time in PNP-deficient patients. In normal peripheral blood B cells, the addition of deoxyguanosine leads to an inhibition of proliferation and differentiation. This effect was found to be independent of deoxyguanosine accumulation. Complete lack of PNP (as observed in our patients) triggers accumulation of deoxyguanosine, thereby disrupting B-cell development, the consequence of which is more profound with time, as indeed was found in the older sister. Another line supporting the hypothesis that the accumulation of deoxyguanosine results in global cell toxicity and that it is not restricted to T cells alone came from the use of purine and pyrimidine nucleoside analogs to treat certain malignancies, including B-cell malignancies. For example, forodesine, a PNP inhibitor, converts deoxyguanine to deoxyguanosine triphosphate and causes general apoptotic cell effect, similar to what is seen in PNP deficiency. We conclude that the variable effect on B-cell function that is observed in PNP deficiencymay be an independent event of T-cell dysfunction and that it is subject to the severity of the deficiency and the duration of the disease. Raz Somech, MD, PhD Atar Lev, MSc Amos J. Simon, PhD Suhair Hanna, MD Amos Etzioni, MD

Dendritic cell phenotype in severe asthma reflects clinical responsiveness to glucocorticoids.

Subsets of patients with severe asthma remain symptomatic despite prolonged, high‐dose glucocorticoid therapy. We hypothesized that the clinical glucocorticoid sensitivity of these asthmatics is reflected in differences in peripheral blood dendritic cell subsets.

P193 A role for active Vitamin D in steroid resistant asthma patients who have enhanced production of IL-17A and reduced IL-10

Background Steroid refractory (SR) asthma, a distinct disease phenotype, has a high morbidity and mortality and takes up a disproportional burden of healthcare cost. IL-17A is a pro-inflammatory cytokine that is essential for host defence against pathogens but can also lead to damage of the surrounding tissues associated with immune diseases and is linked with severe asthma. IL-10 has crucial immunregulatory properties, and we have previously shown in vitro, that T cells from steroid refractory asthma patients fail to respond to glucocorticosteroids for the induction of IL-10 synthesis. Methods We assessed IL-17A and IL-10 synthesis in steroid sensitive, SS, (mean% change in FEV1 following 2 weeks of oral prednisolone 16%) versus SR (mean% change FEV1 0%) asthma patients and investigated their response to dexamethasone. Results PBMC from SR individuals synthesised 7-fold higher levels of IL-17A than disease-severity matched SS patients (by flow cytometry and CBA). Interestingly IL-17A levels inversely correlated with changes in lung function following oral steroids whereas higher IL-10 levels were associated with an increase in lung function. Dexamethasone failed to inhibit IL-17A, but, surprisingly, increased protein synthesis, an effect that was also seen in vivo: inhaled glucocorticosteroid dosages correlated with IL-17A protein levels. This suggests the potentially detrimental effects corticosteroids might have in certain asthma phenotypes. The production of IL-10 by T cells was impaired in cultures from SR asthmatics, but not in healthy controls or SS asthma patients implying an associated impaired IL-10 response with poor asthma control. 1alpha,25-dihydroxyvitamin D3 (1,25(OH)D) not only restored the capacity of T cells to produce IL-10 upon stimulation with dexamethasone in SR asthma patients, but also inhibited IL-17A synthesis in culture independently of steroid. Conclusion High IL-17A levels are associated with poor response to steroids and more severe asthma. Our data supports a steroid-enhancing property of 1,25(OH)D in severe asthma through inhibition of IL-17A and via enhancement of IL-10 synthesis.