Safety and immunogenicity of a Pseudomonas aeruginosa outer membrane protein I vaccine in human volunteers.

The outer membrane protein I (OprI) of Pseudomonas aeruginosa was expressed in Escherichia coli and purified by Ni2+ chelate-affinity chromatography. After safety and pyrogenicity evaluation in animals, four groups of seven adult human volunteers were vaccinated three times at four week intervals with either 500 micrograms, 200 micrograms, 50 micrograms or 20 micrograms of OprI adsorbed onto Al(OH)3. All vaccinations were well tolerated and no systemic side effects were detected. A significant rise of antibody titers against OprI could be measured in the serum of all volunteers who had received the 500 micrograms, 200 micrograms or 50 micrograms doses. Elevated antibody titers against OprI could still be measured 30 weeks after the final vaccination. Binding of the complement component C1q to the elicited antibodies could be demonstrated, showing the ability of the latter to promote antibody-mediated complement-dependent opsonization.