Passive anti-PcrV treatment protects burned mice against Pseudomonas aeruginosa challenge.

The type III secretion system consists of secreted exoproducts and structural components, such as PcrV, and this system plays an important role in the virulence of Pseudomonas aeruginosa in burned hosts. The purpose of this study was to determine if passive anti-PcrV treatment would protect burned mice from fatal P. aeruginosa challenge, and to determine the type III exoproduct phenotype of the P. aeruginosa used as challenge strains. Antiserum was raised in rabbits. Mice were given a third degree burn, challenged with a lethal dose of P. aeruginosa, and treated with either anti-PcrV or control immunoglobulin intraperitoneally. Protection against three different pseudomonads was tested. Genotyping by PCR and phenotyping by immunoblots showed the P. aeruginosa strains to all be of the invasive type III phenotype: ExoS+ and/or ExoT+, ExoU-, ExoY+. Against all strains, the anti-PcrV treatment yielded significantly better survival (p<0.05) than the control immunoglobulin treatment. Duration of significant protection was improved by giving a second injection of PcrV antisera at 24h postburn. Hence, passive anti-PcrV immunization could protect burned mice against fatal challenge with P. aeruginosa of an invasive type III phenotype. This immunotherapy might be explored further as possible treatment for highly antibiotic resistant P. aeruginosa infections in burned hosts.