Passive immunisation against Pseudomonas aeruginosa recombinant flagellin in an experimental model of burn wound sepsis.

Background: This study was aimed to investigate whether anti-recombinant flagellin type A (anti r-fla-A) immunoglobulin G (IgG) provides protection in a mouse burn model of infection, and to determine the role of anti r-fla-A IgG as an opsonin and motility inhibitor in local and systemic infections.

Methods: Following the preparation of r-flagellin type A, rabbit polyclonal IgG was prepared. Specificity of anti r-flagellin for r-flagellin was evaluated by immunoblot analysis. After burn and challenge, mortality rate was screened in the mice treated with anti r-fla-A IgG. The ability of antiserum to promote phagocytosis of bacteria was assessed by the opsonophagocytosis testing. Functional activity of anti r-fla-A IgG was assessed in vitro by motility inhibition assay. Bacterial quantity in skin and internal organs was evaluated to study systemic infection.

Results: In vivo administration of anti r-fla-A IgG resulted in a significant improvement in survival in mice infected by a homologous strain of Pseudomonas aeruginosa from 16.6% to 75% compared with the control IgG. By contrast, this rate was 33.3% in the mice infected by the heterologous strain, PAO1 (type B flagellated strain). Protection was improved by giving a second treatment of r-flagellin antisera at 24-h post-burn and infection. Furthermore, anti r-fla-A IgG enhanced considerably the phagocytosis of the homologous strain but it was slight in the heterologous strain. The antiserum against r-flagellin type A was able to inhibit the motility of the PAK strain (type A flagellated strain), but slight inhibition was observed against PAO1. Meanwhile, anti r-fla-A IgG inhibited the systemic spread of PAK strain from the site of infection to internal organs.

Conclusion: In this study, passive immunisation with anti r-fla-A IgG was active against a homologous strain of infecting P. aeruginosa, but lost most of its efficiency against a heterologous strain. Therefore, passive treatment with anti r-fla-A IgG might protect burned mice against local and systemic infection of P. aeruginosa.