Novel reagents for the diagnosis of mucin composition in chronic inflammatory airway diseases

Introduction:

In chronic inflammatory airway diseases the composition and glycosylation pattern of airway mucins appear to vary depending on certain disease features. In COPD, the ratio of the two major airway mucins MUC5AC and MUC5B is altered compared to healthy individuals. Furthermore, changes in the carbohydrate pattern of mucus were reported during exacerbation and airway infections of cystic fibrosis patients and after induction of experimental asthma in animal models. These findings suggest that the analysis of mucin composition and glycosylation in patient samples may provide a valuable tool for the diagnosis and monitoring of inflammatory airway disorders but would require the direct and quantitative capturing of mucins from patient samples, independently of their glycosylation or disease status.

Methods:

To identify appropriate reagents suited for this task, we tested a battery of anti-mucin antibodies on human bronchoalveolar lavage samples in immunoblot assays. We first examined all commercially obtainable antibodies against the major secretory airway mucin MUC5AC, excluding those antibodies with known specificity for glycostructures.

Results:

Our results reveal substantial inter-patient and inter-antibody variabilities in mucin recognition for all antibodies and samples tested which renders the currently available antibodies unsuited to our purpose.

Discussion:

We assume that many of the anti-mucin antibodies recognize at least in part the highly variable carbohydrate modifications of secreted mucin or epitopes blocked by glycostructures in some individuals. In order to obtain antibodies that bind mucins in a patient- and disease-independent manner we are now in the process of identifying conserved, antibody-accessible, linear epitopes on the protein backbone of human airway mucins. For this purpose, polyclonal antibodies are currently generated against different preparations of native mucins purified from bronchoalveolar lavages of chronic airway diseased patients and of healthy individuals. The recognition profile of these antibodies is analyzed using peptide libraries of human airway mucin protein backbones.

*Presenting author