Immunization against experimental Pseudomonas aeruginosa and Serratia marcescens keratitis. Vaccination with lipopolysaccharide endotoxins and proteases.

Rabbits vaccinated with lipopolysaccharide endotoxins or with purified protease preparations from Pseudomonas aeruginosa and Serratia marcescens before corneal challenge with the viable bacteria exhibited significantly less corneal damage than rabbits not vaccinated with the bacterial products. However, the rabbits vaccinated with the lipopolysaccharide endotoxin preparations were significantly better protected than rabbits vaccinated with the bacterial proteases. Rabbits vaccinated with antisera raised against the proteases showed significantly less corneal damage than rabbits vaccinated with normal rabbit serum, and the passive protection was not significantly different than that elicited by active immunization against the bacterial proteases. The ability of the antiserum raised against the pseudomonas elastolytic protease to passively protect against severe corneal damage produced by experimentally induced pseudomonas keratitis was confirmed in mice. These findings support the idea that the bacterial endotoxins and proteases are virulence factors during the development of pseudomonas and serratia keratitis.