Cystic Fibrosis (CF) is an autosomal recessive disorder, which leads to the abnormal composition and physical properties of airway secretions in CF patients. Additionally, the lungs of CF patients are particularly susceptible to chronic bacterial infections with >80% of CF patients becoming chronically infected by 18 years of life with mucoid forms of Pseudomonas aeruginosa that over-produce the surface polysaccharide alginate. The long term goal of this project (which is outside the scope of this application) is to investigate the use of alginate specific monoclonal antibodies (mAb) as an immunotherapeutic to treat chronic P. aeruginosa lung infections in CF patients. The major hypothesis to be tested is whether alginate specific mAbs can be used to reduce P. aeruginosa lung infections and result in improvement in lung function. One key observation of P. aeruginosa infections in CF is that the infection fails to elicit opsonic/protective antibodies in patients. This ineffective immune response allows the organism to escape elimination by acquired host immune defenses and underlies the progressive decline in lung function. The alginate-specific human mAbs are both opsonic and protective against both mucoid strains of P. aeruginosa as well as classical non- mucoid strains isolated from patients with nosocomial infections. Preliminary data indicate that these human mAbs recognize an epitope on alginate that is defined by the highly charged carboxylic acid component of the uronic acid monomers that make up alginate, and represent a broadly reactive epitope that may be an effective target for immunotherapeutic intervention. In this application, we propose further preclinical development of alginate-based immunotherapeutics by preparing and testing the protective activities of a human mAb against acute P. aeruginosa pulmonary infection in wild-type (WT) mice and chronic P. aeruginosa oropharyngeal colonization and lung disease in transgenic CF mice. We will first develop cell culture processes to provide sufficient quantities of a mAb to perform preclinical testing in animal models and to determine whether the existing cell lines expressing mAb will be adequate to provide sufficient quantities for clinical testing. We will also investigate whether a mAb can be formulated and delivered optimally as a liquid in a mouse inhalation model. ? ? The studies proposed in this application are designed to further development of a human monoclonal antibody to treat chronic Pseudomonas aeruginosa lung infections of CF patients. At present, 80-95% of CF patients ultimately succumb to respiratory failure due to chronic P. aeruginosa infection and airway inflammation. ? ? ?