New monoclonal antibodies to non-glycosylated domains of the secreted mucins MUC5B and MUC7

The separation and characterization of salivary mucins is not straightforward because of their large size, heterogeneity, and molecular interactions. The MUC5B and MUC7 mucins are major glycoprotein components of saliva that are thought to play a vital role in maintaining oral health. MUC5B is also a major component of respiratory mucus and is produced by the tracheal and bronchial glands, while MUC7 has a more limited pattern of expression in the bronchial tree. MUC5B is a gel-forming mucin and thus confers viscosity, whereas MUC7 is much smaller. MUC7 has anti-fungal activity, and both mucins interact with bacteria. The aim of this work was to produce new monoclonal antibodies that can be used to quantify and characterize these mucins by standard laboratory procedures. Peptide sequences in non-conserved and non-glycosylated regions were selected and monoclonal antibodies produced by an efficient immunization and cloning strategy, and screening against purified mucins. Three new antibodies-EU-MUC5Ba and EU-MUC5Bb (against MUC5B) and EU-MUC7a (against MUC7)-were isolated that do not show cross-reactivity with other gel-forming mucins. All work on immunohistochemistry can be used for semi-quantitative immunoblotting after agarose gel electrophoresis. These reagents are valuable tools to study changes in these mucins in oral and respiratory disease, and unlike other monoclonal antibodies to these mucins they recognize epitopes that are not affected by glycosylation.