Sensitization to fungi, such as the mold Aspergillus fumigatus, is increasingly becoming linked with asthma severity. Over the last several years, our laboratory has identified protective roles for Dectin-1 mediated beta-glucan recognition and Dectin-1 dependent IL-17A and IL-22 production during acute challenge with A. fumigatus (invasive aspergillosis, IA). Unexpectedly, in a chronic A. fumigatus exposure model of fungal asthma (A. fumigatus associated asthma, AFAA), we recently reported that the absence of Dectin-1 or IL-22 resulted in markedly improved lung function in the presence of reductions in multiple pro-allergic and pro- inflammatory mediators (Lilly et al., J Immunol 189:3653; 2012). Our studies further suggested that reduced severity of AFAA observed in the absence of Dectin-1 or IL-22 correlated with lower levels of the pro-allergic and known asthma susceptibility cytokine IL-33 (IL-1F11). Indeed, preliminary data from mice deficient in IL- 33R show reduced AFAA severity. However, a link between IL-22 and IL-33 is not known. In preliminary data, we show that during AFAA, production of IL-1? (IL-1F1) is dependent on IL-22. We further show that the novel IL-1 family member IL-36? (IL-1F9) was upregulated in the lungs more than 100-fold during IA, yet significantly reduced in Il22-/- mice during both IA and AFAA. IL-36? can induce IL-1? in the lungs and IL-? has been recently reported to induce IL-33 production by epithelial cells, suggesting a possible IL-22? IL-36??IL-1??L-33 axis in immunopathogenesis during fungal asthma. In new preliminary studies, we show that the absence of IL-36R signaling or neutralization of IL-1? leads to lower CCL17 levels during AFAA. We further show that chronic exposure to an A. fumigatus trehalose-6-phosphate phosphatase mutant (orlA), which has elevated cell wall alpha-glucan levels, resulted in more severe AFAA (higher induction of IL-22, IL-33 and CCL17). These results suggest that recognition of moieties in the A. fumigatus cell wall affects severity of fungal asthma. Finally, in collaboration with the NHLBI-sponsored Severe Asthma Research Program (SARP), we have identified multiple SNPs in Il23, Il17a and Il22 in fungal skin-test (+) asthmatics that correlated with asthma severity. In new pilot studies, we show feasibility of measuring cytokines and chemokines in sputum or BAL fluid from skin test (+) vs. skin test (-) asthmatics and our ability to correlate them with asthma severity. Further studies are required to determine the magnitude by which IL-23, IL-17A and IL-22 levels are modulated in these individuals as well as whether the levels of IL-36?, IL-1? and IL-33 are also modulated. Collectively, our central hypothesis is that IL-22-induced IL-1 family members contribute to immunopathogenesis during fungal asthma. To address this hypothesis, we have proposed the following three independent, interrelated Aims: (1) elucidate IL-22-dependent mechanisms contributing to immunopathogenesis during fungal asthma, (2) examine the contribution of specific fungal cell wall moieties in IL-22 induction and fungal asthma severity and (3) define the IL-23/IL-17A/IL-22 axis in human asthmatics that are skin-test (+) for fungi.
Studies proposed in the current proposal seek to understand the mechanisms by which the cytokine IL-22 contributes to fungal asthma severity, which fungal cell wall moieties drive asthma severity and translate our results with human asthmatics that are skin-test (+) for fungi.
