Cystic fibrosis (CF), the most common fatal monogenic disease in the United States, results from mutations in CF transmembrane conductance regulator (CFTR), a chloride channel. The mechanisms by which CFTR mutations cause lung disease in CF are not fully defined but may include altered ion and water transport across the airway epithelium and aberrant inflammatory and immune responses to pathogens within the airways. We have shown that Cftr(-/-) mice mount an exaggerated IgE response toward Aspergillus fumigatus, with higher levels of IL-13 and IL-4, mimicking both the T helper cell type 2-biased immune responses seen in patients with CF. Herein, we demonstrate that these aberrations are primarily due to Cftr deficiency in lymphocytes rather than in the epithelium. Adoptive transfer experiments with CF splenocytes confer a higher IgE response to Aspergillus fumigatus compared with hosts receiving wild-type splenocytes. The predilection of Cftr-deficient lymphocytes to mount T helper cell type 2 responses with high IL-13 and IL-4 was confirmed by in vitro antigen recall experiments. Conclusive data on this phenomenon were obtained with conditional Cftr knockout mice, where mice lacking Cftr in T cell lineages developed higher IgE than their wild-type control littermates. Further analysis of Cftr-deficient lymphocytes revealed an enhanced intracellular Ca(2+) flux in response to T cell receptor activation. This was accompanied by an increase in nuclear localization of the calcium-sensitive transcription factor, nuclear factor of activated T cell, which could drive the IL-13 response. In summary, our data identified that CFTR dysfunction in T cells can lead directly to aberrant immune responses. These findings implicate the lymphocyte population as a potentially important target for CF therapeutics.

In cystic fibrosis (CF), respiratory failure caused by progressive airway obstruction and tissue damage is primarily a result of the aberrant inflammatory responses to lung infections with Pseudomonas aeruginosa. Despite considerable improvement in patient survival, conventional therapies are mainly supportive. Recent progress toward gene therapy for CF has been encouraging; however, several factors such as immune response and transduced cell turnover remain as potential limitations to CF gene therapy. As alternative gene therapy vectors for CF, we examined the feasibility of using recombinant SV40-derived vectors (rSV40s), which may circumvent some of these obstacles. To accommodate the large cystic fibrosis transmembrane conductance regulator (CFTR) cDNA, we removed not only SV40 Tag genes, but also all capsid genes. We, therefore, tested whether 'gutless' rSV40s could be packaged and were able to express a functional human CFTR cDNA. The results from our in vitro analysis determined that rSV40-CFTR was able to successfully result in the expression of CFTR protein, which localized to the plasma membrane and restored channel function to CFTR-deficient cells. Similarly, in vivo experiments delivering rSV40-CFTR to the lungs of Cftr-/- mice resulted in a reduction of the pathology associated with intra-tracheal P. aeruginosa challenge. rSV40-CFTR-treated mice had less weight loss when compared with control-treated mice as well as demonstrably reduced lung inflammation as evidence by histology and reduced inflammatory cytokines in the broncho-alveolar lavage. The reduction in inflammatory cytokine levels led to an evident decrease in neutrophil influx to the airways. These results indicate that further study of the application of rSV40-CFTR to CF gene therapy is warranted.

Cystic fibrosis (CF) patients have decreased levels of lung epithelial interleukin (IL)-10 and increased levels of proinflammatory cytokines (tumor necrosis factor-alpha, IL-4, IL-8 and IL-6). This has also been documented in Cftr (cystic fibrosis transmembrane conductance regulator)-deficient mice (Cftr 489X(-/-), FABP-hCFTR(+/+)). Our laboratory has recently characterized a peculiar hyper-IgE phenotype in these mice, in response to Aspergillus fumigatus crude protein extract (Af-cpe). Thus, we hypothesized that sustained systemic circulating IL-10 levels achieved through skeletal muscle transduction with recombinant adeno-associated vectors expressing IL-10 (rAAV1-IL-10) would serve to downregulate Th1 and Th2 cytokine production. This in turn would dampen the allergic response in the Cftr(-/-)-dependent mouse model of allergic bronchopulmonary aspergillosis. After Af-cpe sensitization and airway challenge, mice treated with rAAV1-IL-10 had markedly lower IgE levels when compared to the control-treated rAAV1-GFP group. This was accompanied by a significant reduction in the levels of IL-5, IL-4 and IL-13 in the lung compartment. The lower lung cytokine profiles resulted in a near absence of eosinophil recruitment in the lung and a lower inflammatory response in the lung tissue of mice receiving rAAV1-IL-10. Unfortunately, sustained secretion of IL-10 from transduced muscle did lead to thrombocytopenia and splenomegaly in mice injected with rAAV1-IL-10. These results highlight that while IL-10 gene therapy is very effective for treating allergic responses caution must be taken with the prolonged secretion of IL-10.

To gain insight into aberrant cytokine regulation in cystic fibrosis (CF), we compared the phenotypic manifestations of allergen challenge in gut-corrected CFTR-deficient mice with background-matched C57Bl6 (B6) mice. Aspergillus fumigatus (Af) antigen was used to mimic allergic bronchopulmonary aspergillosis, a peculiar hyper-IgE syndrome with a high prevalence in CF patients. CFTR-/-, C57BL/6 and FVB/NJ mice were sensitized with Af antigen by serial intraperitoneal injections. Control mice were mock sensitized with PBS. Challenges were performed by inhalation of Af antigen aerosol. After Af antigen challenge, histologic analysis showed goblet cell hyperplasia and lymphocytic infiltration in both strains. However, total serum IgE levels were markedly elevated in CF mice. Sensitized CF mice showed a five-fold greater IgE response to sensitization as compared with B6- and FVB-sensitized controls. Additional littermate controls to fully normalize for B6-FVB admixture in the strain background confirmed the role of CFTR mutation in the hyper-IgE syndrome. Cytokine mRNA levels of IL-5 and GM-CSF in the bronchoalveolar lavage (BAL) fluid, and BAL cell differentials indicated that CFTR mutation caused a shift from an IL-5-predominant to an IL-4-predominant cytokine profile. This system models a very specific type of airway inflammation in CF and could provide insights into pathogenesis and treatment of the disease.

Despite extensive experience with recombinant adeno-associated virus (rAAV) 2 vectors in the lung, gene expression has been low in the context of cystic fibrosis (CF) gene therapy, where the large size of the cystic fibrosis transmembrane conductance regulator (CFTR) coding sequence has prompted the use of compact endogenous promoter elements. We evaluated the possibility that gene expression from recombinant adeno-associated virus (rAAV) could be improved by using alternate AAV capsid serotypes that target different cell-surface receptors (i.e., rAAV5) and/or using stronger promoters. The relative activities of the cytomegalovirus (CMV) Rous sarcoma virus (RSV) promoter, the CMV enhancer/beta-actin (CB) promoter combination, and the CMV enhancer/RSV promoter hybrid were assessed in vitro in a CF bronchial cell line. The CB promoter was the most efficient. AAV capsid serotypes, rAAV2 and rAAV5, were also compared, and rAAV5 was found to be significantly more efficient. Based on these studies a rAAV5-CB-promoter-driven CFTR minigene vector was then used to correct the CF chloride transport defect in vitro, as well as the hyperinflammatory lung phenotype in Pseudomonas-agarose bead challenged CF mouse lungs in vivo. These studies provide functional characterization of a new version of rAAV-CFTR vectors.