Research funded by the Irish Thoracic Society through the MRCG HRB Joint Funding Scheme, completed in 2016/2017
The Role of Aspirated Bile Acids Driving Chronic Lung Infections; (Prof F. O’Gara and Dr J Reen, Biomerit Research Centre UCC. Cork.
This study was the first to investigate the unexplained link between gastro-oesophageal reflux (GOR) and severe microbial respiratory disease. Very little is known about the triggers that cause disease causing microbes to adopt a persistent antibiotic tolerant lifestyle. While to date, GOR-associated bile aspiration has been linked with reduced lung function, inflammation, and other complications in patients with respiratory disease, its impact on the microbiology status of the lung has not been investigated.
We have established (paediatric cohort ages 2-16) the positive correlation between the aspiration of bile acids into the lungs and the presence of pathogen-dominated, low-biodiversity microbiomes that are characteristic of chronically infected patients. This new knowledge offers the potential for new innovations in the clinical management of infection in patients with respiratory disease.
To further delineate how aspirated bile causes infecting bacteria to establish persistent communities, expression profiles of chronic associated genes was performed on bile treated cells grown in Artificial Sputum Medium. Expression of persistence genes in Pseudomonas aeruginosa and Staphylococcus aureus was found to be increased in the presence of bile. In tandem, we developed and optimised an early detection system for infection biomarkers in P. aeruginosa, with potential for follow on as a point of care device.
Expression profiling of the CF BALF samples, for which clinical data and microbiome/bile profiles have been generated, has provided a unique clinical data set with which to understand the progression of respiratory infections to the chronic untreatable state. The strong correlations between bile acid levels, pathogen dominance, and inflammation status supports a role for bile aspiration as a causative agent in the promotion of persistent antibiotic tolerant infections and chronic inflammation in patients with respiratory disease. We are currently engaged in a longitudinal study to follow the onset and progression of chronic infection and inflammatory disease in this patient cohort.
Clinical Implications and Utility of an Endotoxin tolerant (ET) state in Cystic Fibrosis
Prof Barry Plant, UCC, Cork
The immune system is very important for responses to infection. Recent studies in non-CF adults with severe bacterial infection show that the immune system generates a large initial response to the bacteria followed by a temporarily reduced one. This concept is known as endotoxin tolerance (ET). It is thought that this pattern exists as a protective mechanism to prevent death due to an overwhelming immune response to infection but there is a risk of secondary infection associated with it. Recent small studies have shown a similar reduction in inflammatory immune system responses in stable patients with Cystic Fibrosis (PWCF). Our group has already demonstrated that this effect is present and more marked with poorer lung function. We demonstrated that children with CF do not have this decreased immune response. Thus it appears that the blunted immune response seen in adults with CF , develop it as a consequence of recurrent exposure to bacteria with the development of lung bacteria colonisation.
Ignoring the Nonsense – Personalised Medicine for Genetic Lung Disorders
Professor NG McElvaney, RCSI Beaumont Hospital, Dublin
The blood protein alpha-1 antitrypsin (AAT) protects the lungs from the destructive effects of cigarette smoke and other inhaled irritants. AAT also has the ability to dampen or calm the immune system by binding to substances that drive inflammation in the body. AAT deficiency (AATD) is one of the most common genetic conditions in Ireland with an estimated 3,000 people on the island severely affected. AATD is usually associated with lung disease, most commonly emphysema and COPD. A very rare form of severe AATD is caused by Null (also called nonsense) mutations in the gene that codes for AAT. These Null mutations are similar to a full stop in the middle of a sentence. When they appear in the middle of a gene they block production of the working protein from the gene blueprint. The goal of this project was to study people born with 2 Null mutations leading to a complete absence of this protective protein in their blood. Blood was collected from a patient diagnosed with 2 copies of the rare null Bolton mutation (called Nullbolton/Nullbolton). A slightly shorter AAT protein was successfully purified, albeit in very small quantities. The shortened protein was then studied very closely. It showed an ability to do many of the jobs the normal AAT protein can do. Working with international collaborators and using several different experimental models and techniques, several drugs were tested to see if they could remove the premature full stop and produce full length corrected protein. We were able to increase the amount of the shortened AAT, but not the size of the protein. This is the first ever report of the presence of a functional AAT protein in the blood of a patient who is not supposed to be able to produce this important protein.