Enhancement of Pseudomonas aeruginosa lung clearance after local immunization with a temperature-sensitive mutant

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Abstract
We investigated the capacity of the temperature-sensitive mutant strain A/10/25 of Pseudomonas aeruginosa (ts-Psa) to induce enhancement of lung defenses against wild type P. aeruginosa (wt-Psa). Mice of the DBA/2J inbred strain were immunized by aerosolization with a single dose of 2 x 10(5) to 4 x 10(5) CFU of ts-Psa and were challenged 7, 14, and 21 days later with wt-Psa. The uncleared bacteria ratio was determined 4 h after aerosol exposure; significant enhancement in lung clearance of wt-Psa (P less than 0.01) was evident as early as 7 days after immunization and detectable for at least 21 days. Aerosol immunization with Staphylococcus aureus did not enhance lung clearance of wt-Psa; however, slight but significant enhancement in S. aureus clearance was observed in mice immunized 7 days before with ts-Psa. No enhancement of S. aureus clearance was seen in ts-Psa immunized animals after 14 and 21 days. Analysis of the cell composition of lung lavage fluids revealed a transient cell response characterized by rapid increase in the absolute number of polymorphonuclear leukocytes, followed later by an increase in alveolar macrophages. The characteristics of lung lavages returned to base-line values 6 days after aerosol immunization, and a second exposure to a ts-Psa aerosol produced a response of similar magnitude and quality. We conclude that aerosol immunization with a temperature-sensitive mutant of P. aeruginosa enhances specific pulmonary defense mechanisms against the parental pathogen in mice.