The sialylation of bronchial mucins secreted by patients suffering from cystic fibrosis or from chronic bronchitis is related to the severity of airway infection

Bronchial mucins were purified from the sputum of 14 patients suffering fro m cystic fibrosis and 24 patients suffering from chronic bronchitis, using two CsBr density-gradient centrifugations, The presence of DNA in each secr etion was used as an index to estimate the severity of infection and allowe d to subdivide the mucins into four groups corresponding to infected or non infected patients with cystic fibrosis, and to infected or noninfected pati ents with chronic bronchitis. All infected patients suffering from cystic f ibrosis were colonized by Pseudomonas aeruginosa. As already observed, the mucins from the patients with cystic fibrosis had a higher sulfate content than the mucins from the patients with chronic bronchitis. However, there w as a striking increase in the sialic acid content of the mucins secreted by severely infected patients as compared to noninfected patients. Thirty-six bronchial mucins out of 38 contained the sialyl-Lewis x epitope which was even expressed by subjects phenotyped as Lewis negative, indicating that at least one alpha 1,3 fucosyltransferase different from the Lewis enzyme was involved in the biosynthesis of this epitope, Finally, the sialyl-Lewis x determinant was also overexpressed in the mucins from severely infected pat ients. Altogether these differences in the glycosylation process of mucins from infected and noninfected patients suggest that bacterial infection inf luences the expression of sialyltransferases and alpha 1,3 fucosyltransfera ses ire the human bronchial mucosa.