Use of immunogenic moiety of Pseudomonas aeruginosa exotoxin A as a DNA vaccine in experimentally contaminated mice

Background: DNA immunization is an appropriate method to produce an immunological response. Pseudomonas aeruginosa produces exotoxin A which is highly cytotoxic for eukaryotic cells. Since domains II (translocation domain) and 1b of the toxin have antigenic qualities, so they could be useful candidates to protect against pseudomonas infections. Objectives: To evaluate if recombinant plasmid containing immunogenic domain of exotoxin A might be protective against Pseudomonas aeruginosa infections. Methods: To study the biologic and immunological effects of antigenic domains of exotoxin A, plasmid expression vector (pET28a) containing domain II and 1b of exotoxin was constructed. To evaluate the effects of intracellular recombinant gene expression, BALB/C mice were immunized with the recombinant plasmid and then subjected to third degree thermal injury and the humoral immunity responses were assayed. Results: Immunization with the recombinant plasmid containing translocation and 1b domains of exotoxin A resulted in increasing antibodies production (IgA and IgG) against Pseudomonas aeruginosa. DNA immunization significantly decreased the bacterial count liver, spleen, blood and inoculated burns after challenging with P. aeruginosa and dramatically improved the survival rate of burn-injured mice. Conclusions: Finally, immunization by gene encoding antigenic products may be a good technique for protection against P. aeruginosa infections.