Immune-epithelial cell defects in CF

Biofilm_CF Patient
(Biofilm from CF chronic rhinosinusitis patient (green, P. aeruginosa; red, S. aureus)

Th17 mediated inflammation in CF (Kolls, Chen, Alcorn): The Kolls/Chen group has further shown that antigen specific memory Th17 cells can provide clade-specific immunity in the lung by recognizing conserved outer membrane proteins. Preliminary evidence supports the concept that the protective nature of these responses requires IL-17R signaling in airway epithelia which includes the induction of antimicrobial peptides and also HCO3 transport. The Kolls/Chen group hypothesizes that these responses can also be pathologic in CF, leading to airway injury and bronchiectasis as the disease progresses. Thus, blocking Th17 responses may be therapeutic for CF. The Kolls/Chen group has initiated collaboration with Constellation Pharma to investigate the pre-clinical safety and efficacy of bromodomain (BRD) inhibition in CF Th17 cells. Importantly, these compounds inhibit IL-17 but do not inhibit TNF (which is controlled by DNA methylation); this is important in the host immune response to Mycobacteria spp. In the collaborative study with Constellation Pharma, these CF Investigators are assessing the efficacy of CP-203 to inhibit P. aeruginosa and A. fumigatus specific Th17 responses in lung and lymph node T-cells processed by Core A at the time of lung transplant.  Moreover, since bromodomain inhibition should selectively inhibit regions where BRD2-4 binds, the group is using RNA-seq to define the BRD sensitive areas of the transcriptome in CF and non-CF T-cells (Core C). Targeting Th17 cells in CF might provide a novel therapeutic angle to address the excessive and damaging inflammation in the CF airway.

P. aeruginosa targets pro-resolving lipid mediators in the lung (Bomberger, Kolls, Kagan):  Lipoxins are bioactive eicosanoids that mediate resolution of inflammation and are dramatically reduced in the CF airway. Dr. Bomberger’s laboratory has demonstrated that a secreted P. aeruginosa protein, Cif, reduces lipoxins in the airway and thus, prevents the resolution of inflammation in CF. These studies required support from both Cores A and D. They showed the first evidence of bacterial inhibition of pro-resolving mediators, as well as described a new bacterial virulence mechanism. Dr. Bomberger is now examining antimicrobial functions for lipoxin in the airways (with Bruce Levy, Brigham and Women’s Hospital), with the long-term goal of adapting stable lipoxin orthologs or small molecule inhibitors of Cif (with Dean Madden, Dartmouth) for therapeutic applications in CF. P. aeruginosa also makes other host lipid metabolism genes, including the 15-lipoxygenase LoxA, that are required for biofilm growth in association with CF airway epithelial cells. The Bomberger lab is collaborating with Dr. Valerian Kagan (EOH, Pitt) to investigate the mechanism of biofilm stimulation by LoxA, as a potential new therapeutic target to prevent chronic P. aeruginosa infections.

IL-22 signaling in the respiratory tract (Alcorn, Kolls, Chen, S. Lee, Bomberger): IL-22 has been reported to exert a protective effect in respiratory infections, but the mechanisms are unclear. Dr. Alcorn is examining a role for IL-22 in host defense during influenza superinfection with S. aureus using in vitro HBE studies and mouse models (Core A, C). Dr. Kolls is also examining the host defense properties of IL-22, focusing his efforts on IL-22BP, a decoy receptor for IL-22. Interestingly, sinonasal aspirates from CF chronic rhinosinusitis patients (Cores C, D) show incredibly high levels of IL-22BP, a feature the Kolls lab hypothesizes disrupts effective host defense and prevents clearance of infections. These preliminary results are under continued investigation, as are mechanisms by which IL-22 regulates host defense in the CF respiratory tract by the Kolls and Alcorn labs.

TSP-1 and P. aeruginosa infections (J. Lee, Bomberger, Thibodeau):  P. aeruginosa is a major cause of chronic lung infections in CF and secretes proteases to promote tissue injury. Dr. Lee’s laboratory, with Cores B, C and D, has identified thrombospondin-1 (TSP-1), a host-derived matricellular glycoprotein released during lung inflammation, dose-dependently inhibits the P. aeruginosa elastase, LasB.  TSP-1 deficient mice (Thbs1-/-) show impaired host defense, and exaggerated neutrophil activation following intrapulmonary Pa infection. TSP-1 provides an additional line of defense by directly subduing host-derived proteolysis, with dose-dependent inhibition of neutrophil elastase activity from airway neutrophils of mechanically ventilated patients. Thus, TSP-1 provides a dual level of protection against pathogen-initiated and host-sustained proteolytic injury following a microbial trigger and may provide a potential therapeutic target to counter infection-triggered lung damage. 

Microbiota-driven immune changes in CF (Hand, Methé, Morris): The Hand group is investigating the role of the CF microbiota-driven immune response in the development of Distal Intestinal Obstruction Syndrome and cirrhosis; two health issues of growing concern in the CF patient community. Using a mouse model to specifically drive GI complications associated with CF, they have shown that bacteria-driven neutrophils accumulate in the liver and intestine of these mice prior to the development of overt symptoms. The Hand lab is currently determining whether intervening into the microbiota or neutrophil response can prevent GI disease. Examining the impact of pulmonary exacerbations on the microbiome and the host response at the respiratory mucosa is also a topic of the pilot proposal by Drs. Methé and Morris. Immune-microbiome interactions is a major interest in the CF Center and is also the focus of a long-term initiative from the Center for Medicine and the Microbiome, showing the collaboration and cross-fertilization of fields at Pitt.