Immunological evaluation of OMP-F of native Iranian Pseudomonas aeruginosa as a protective vaccine

INTRODUCTION: This study involved 300 Pseudomonas aeruginosa strains isolated from patients admitted in four Tehran hospitals. Using standard O-specific typing sera, they were all grouped into 16 strains out of 17 known P. aeruginosa. The strains were lyophilized and each was given a code according to the Collection of Standard Bacteria, Pasteur Institute of Iran (CSBPI) for further investigations. METHODOLOGY: Among all clinical samples, CSBPI: 16-190 was the most prevalent P. aeruginosa serotype which showed a high agglutination titer (4+, 320) against homologous O-specific typing sera. This serotype was selected for extraction of P. aeruginosa major outer membrane vesicles (OMP-F). OMP-F vesicles were extracted and purified according to the Deoxycholate Ultracentrifuge Differentiation Technique. Purity and molecular weight of OMP-F were determined by SDS-PAGE and the ability of OMP-F vesicles to induce high titers of antibody in rabbit, which was shown as a sharp antibody-antigen precipitation line in the agarose gel immune-diffusion technique. RESULTS: Passive immunization of mice with anti-rabbit OMP-F antisera induced a high level of protection when the mice were post-challenged with 2×LD50 of live P. aeruginosa CSBPI: 16-190. Furthermore, active immunization of mice with 50 µg of OMP-F could protect mice against 2xLD50 of live homologous (100% protection) and 15 heterologous native Iranian P. aeruginosa serotypes with 50-100% level of protection. CONCLUSIONS: These investigations indicate that purified OMP-F of CSBPI: 16-190 can be regarded as a safe protective immunogen in vaccinothrapy against all P. aeruginosa immunotype isolated in Iran.