Outer membrane protein F preparation of Pseudomonas aeruginosa as a vaccine against chronic pulmonary infection with heterologous immunotype strains in a rat model.

Outer membrane protein F (porin) was purified by extraction from polyacrylamide gels of cell envelope proteins of the Pseudomonas aeruginosa PAO1 strain. Rats were immunized intramuscularly with 25 micrograms of protein F on days 1 and 14 and then challenged on day 28 via intratracheal inoculation of bacterium-containing agar beads. On day 35 the lungs were either fixed for histological examination or submitted for quantitation of the bacteria present. protein F immunization afforded significant protection against challenge with six of six heterologous lipopolysaccharide immunotype strains of P. aeruginosa. By an enzyme-linked immunosorbent assay, the protein F-immunized rats had both immunoglobulin G and M antibody responses to cell envelopes of all six of the heterologous immunotype strains. Protein F immunization greatly enhanced the ability of the rats to clear the inoculated P. aeruginosa from the lungs and significantly reduced the incidence and severity of pulmonary lesions as compared with those in bovine serum albumin-immunized control rats. These data show the efficacy of outer membrane protein F as a protective vaccine in a rat model of chronic pulmonary infection.