Catalase immunization from Pseudomonas aeruginosa enhances bacterial clearance in the rat lung

Pseudomonas aeruginosa is a common cause of infection in immunocompromised patients and is the major contributor to morbidity in individuals with cyst ic fibrosis (CF). The antibiotic resistance shown by this pathogen and morb idity in patients with chronic infection has encouraged investigations into the development of a vaccine. This study reports the purification of a 60 kDa protein, isolated from a mucoid strain of P. aeruginosa, identified by amino acid sequence analysis as the catalase protein (KatA). A rat model of acute P. aeruginosa respiratory infection was used to investigate the immu nogenicity of KatA and determine the potential of mucosal immunization with KatA to protect against infection. Immunization regimens compared a single intra-Peyer's patch (IPP) immunization with an IPP primary inoculation fol lowed by an intratracheal boost to the lungs. Mucosal immunization with Kat A resulted in significant pulmonary clearance of both homologous (p < 0.001 ) and heterologous (p < 0.05) strains of P. aeruginosa. Both immunization r egimens enhanced bacterial clearance, increased the rate of recruitment of phagocytes to the bronchoalveoli and induced KatA-specific antibody. Howeve r, the regimen that included a boost induced a more effective immune respon se that also resulted in better clearance of P. aeruginosa from the lungs. Mucosal immunization induced KatA- specific antibodies in the serum and the bronchoalveolar lavage, and KatA-specific lymphocyte proliferation in vitr o in cells isolated from the mesenteric lymph nodes of immunized rats. The data presented suggests that KatA has the potential to afford a protective immune response against pulmonary infection by P. aeruginosa (C) 2000 Elsev ier Science Ltd. All rights reserved.