Cystic fibrosis (CF) lung disease is characterised by early airways infection and
inflammation, chronic suppuration, frequent infective exacerbations and an
increased influx of acute, and chronic inflammatory cells. The inflammatory
process involves activation of many cell types including neutrophils,
macrophages and epithelial cells, and leads ultimately to the development of
progressive respiratory failure and death. Accurate assessment of the
inflammatory process is a crucial part of disease monitoring and should allow
appropriate evaluation of therapeutic interventions so as to maximize control of
the respiratory sequelae of the disorder.
Lung function markers such as FEV1 are insensitive and indirect. Direct but
invasive methods such as fibreoptic bronchoscopy and biopsy are limited in
application, repeatability and safety. Non-invasive methods of assessment are,
therefore, attractive. Exhaled Breath Gases, Exhaled Breath Condensate and
Induced Sputum provide potential for such measures. These techniques are
safe, simple, repeatable and could assess all airways and can be used in
children as young as 6 years. We hypothesised that biomarkers of inflammation
in Cystic Fibrosis Lung Disease are measurable in samples collected noninvasively,
and can be developed into clinically useful assays. These assays
would have the ability to reflect the level of inflammation in the CF lungs as well
as holding the potential to act as surrogate markers of CFTR function.
Methods
Non-invasive markers of inflammation in Cystic Fibrosis lung disease
Methods. Exhaled breath gases, exhaled breath condensate, bronchoalveolar lavage fluid
and induced sputum were investigated using a number of analysis techniques
to identify the markers which best discriminated CF from non CF subjects.
Analysis techniques used were electrochemical cells, chemiluminescene,
ELISA, EIA, ion selective probes and mass spectrometry.
Results
Markers found to discriminate CF from non CF subjects were EBC pH and
ammonium, and 38 proteomic markers were found in induced sputum. 21
proteomic markers were found in bronchoalveolar lavage fluid. One biomarker
has been identified with confidence, Calgranulin A.
Discussion
A large component of the work of this thesis was focussed on exhaled breath
condensate. Two markers, pH and Ammonium were different between the CF
and control groups. The measurement of EBC pH and ammonium as markers
of inflammation should be used in future gene therapy trials as they are cheap,
quick and simple to perform
Using clean techniques free from contamination, no proteins are repeatedly
detectable in EBC using highly sensitive SELDI techniques. This technique
reflects the highest sensitivity of any available proteomics instrument and
therefore until new technologies become available, it would be incorrect to
assay any proteins in EBC.
The induced sputum proteomics study identified 38 independent markers of CF
lung inflammation Therefore, sampling by collection of induced sputum should be used in gene therapy trials. The endpoints should be assessed by a
combination of SELDI as an endpoint and by ELISA where this is available.
The marker Calgranulin is likely to report on neutrophil recruitment to the lung.
It is anticipated that this will be a sensitive marker of inflammation in the lung
and it also has the potential to report on successful of gene transfer as it is
raised in heterozygote carriers as well as homozygotes with CF.
Therefore, the non-invasive technique induced sputum coupled to proteomic
analysis would have the ability to reflect the level of inflammation in CF subjects
and may also report on CFTR function