Flagellin and pilin immunization against multi-drug resistant Pseudomonas aeruginosa protects mice in the burn wound sepsis model

Pseudomonas aeruginosa is a formidable pathogen and a major threat to burn patients. Antimicrobial therapy is often unsuccessful because P. aeruginosa can develop multi-drug resistance; thus, immunotherapy and vaccine can be a rational alternative. Flagella and type IV pili have been identified as important virulence factors in the colonization and pathogenesis of P. aeruginosa in burn wound infections. Immuno-genicity and efficacy of mixed recombinant full-length type b flagellin (r-b-flagellin) and recombinant PiIA (r-PilA) as candidate vaccines were assessed by measuring humoral and cellular responses, using an experimental burned mouse model. Primary immunization with r-b-flagellin + r-PilA followed by two booster shots was sufficient to generate a robust humoral response, which was predominantly a Th2 response consisting mainly of subtype IgG1 and low levels of IgG2a. Analysis of the cytokine response among immunized mice showed an increased production of IL-4, INF-gamma and IL-17 by splenocytes upon stimulation by r-b-flagellin + r-PilA. Opsonophagocytosis assays confirmed the enhanced killing of bacteria by anti r-b-flagellin + r-PilA immune sera. These antibodies were also able to reduce bacterial load in the site of original infection into the liver and spleen of challenged mice. The reduction of systemic bacterial spread resulted in an increased survival rate of challenged immunized mice. In conclusion, immunization with r-b-flagellin + r-PilA proteins provides a better protective response against P. aeruginosa infection in the burn mouse model. (C) 2016 European Federation of Immunological Societies. Published by Elsevier B.V. All rights reserved.