Protective immunization against chronic Pseudomonas aeruginosa pulmonary infection in rats

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Abstract
Rats were immunized systemically with various doses of the polyvalent P. aeruginosa vaccine PEV-01. After a series of 2 or 3 doses (25-50 .mu.g each) at 8-11 day intervals, animals were challenged intratracheally by the agarose bead technique with a serotype 5 P. aeruginosa strain at periods of 9-42 days. Immunized animals developed circulating antibodies (primarily IgM) against vaccine components at levels significantly higher than challenged, nonimmunized controls (P < 0.005). At 8-10 days postinfection, histological sections of lungs from immunized animals showed only minimal inflammation associated with infectious foci (agarose beads) as compared with the extensive pathological changes of airways and parenchyma seen in infected nonimmunized control animals. No significant reduction in bacterial numbers was observed. Such protection lasted at least 6 wk after the final immunization. Apparently, the vaccine may contain components of cell surface proteins and virulence exoproducts.