Active Immunization with Recombinant PilA protein Protects Against Pseudomonas aeruginosa Infection in a Mouse Burn Wound Model.

Pseudomonas aeruginosa as an opportunistic human pathogen that causes lethal infections in immunocompromised patients. Type IV pili are critical factors in virulence and colonization of P. aeruginosa in acute burn wound infection. The immunogenicity and efficacy of P. aeruginosa recombinant PilA (r-PilA) was evaluated in an experimental model of burn wound sepsis as a vaccine candidate. In this study, female C57BL/6 mice were divided into five groups. Mice in the experimental groups received either r-PilA vaccine alone or in combination with the alum adjuvant or complete Freund's adjuvant (CFA). Mice in the negative control group received phosphate-buffered saline (PBS). In order to characterize the response of Th1-Th2 to immunization, the cytokine profiles of spleen cells isolated from r-PilA immunized mice were investigated. Total IgG titers and isotopes were measured using ELISA method and finally, in order to study the systemic infection, bacterial titers in the liver, spleen and blood were also determined. Active immunization with r-PilA, which is followed by two booster shots, was sufficient to generate a robust immune response in mice. Cytokine analysis demonstrated the secretion of IL-4 and INF-ɣ from splenocytes in response to in vitro antigen stimulation. The IgG response to r-PilA was a Th2 type response consis¬¬ting predominantly of the isotype IgG1 accompanied by lower levels of IgG2a. In conclusion, in this burned mouse model, vaccination with r-PilA can increase the humoral immunity, thereby leading to an effective protection against P. aeruginosa infection.