مشخصات پژوهش

Introduction Acinetobacter baumannii is an opportunistic pathogen which can cause human life-threatening infections due to increasing rate of antibiotic resistance A. baumannii strains. phospholipase D (PLD) is as an important virulence factor associated with A. baumannii development in the host. It was proven that immune responses elicited by antigens expressed on L. lactis surface are stronger than those expressed intracellularly. The present study was designed to evaluate immunogenicity of phospholipase D displayed on Lactococcus lactis as a vaccine candidate against A. baumannii. Material and Methods In order to produce PLD on L. lactis surface, a chimeric gene was designed. The synthetic gene was then subcloned into a lactococcal vector for the expression of gene under the control of nisin A inducible promoter. Mice vaccine group received four cycles of orogastric immunizations at 2-week intervals. Each cycle consisted of gavaging 2 × 109 CFU for 3 consecutive days of induced recombinant L. lactis suspended in 100 μL sterile PBS. Control group received L. lactis:vector in the same manner. The resulted serum IgG immune responses were analyzed and the mice were challenged with lethal doses of A. baumannii Results Immunized mice group exhibited IgG rise and 100% survival rate at 108 and 109 lethal doses of A. baumannii. Those receiving 1010 and 1011 bacteria were protected 80% and 40% respectively. All the control groups died within 24 hours of challenge. Conclusion Recombinant L. lactis displaying PLD was potentially effective in triggering a high antibody response and protecting mice against A. baumannii.