The present invention provides polypeptides having protease activity for use in the treatment or prevention of microbial infections in a subject with or susceptible to immunodeficiency. For example, the polypeptide may be administered as a mouth spray, nasal spray, lozenge, pastille, chewing gum or liquid to treat or prevent microbial infections in a patient with primary immunodeficiency. In particular, the polypeptides are useful in the treatment or prevention of rhinorrhea and/or fungal infection of the oral cavity and/or gum sores. In one embodiment, the polypeptide is a trypsin enzyme from Atlantic cod, or a fragment or variant thereof.
