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Abstract
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Acinetobacter baumannii, a major threat for hospitalized patients, intensive care units (ICUs) residents, military forces, is a public health problem due to increasing rate of antibiotic resistance. A specific cell surface protein named biofilm associated protein (Bap) was defined in a bloodstream isolate of A. baumannii. This protein play an important role in bacterial infectious processes. It was proven that immune responses elicited by antigens expressed on L. lactis surface are stronger than those expressed intracellularly. In the present study Biofilm associated protein (Bap) were displayed on Lactococcus lactis and the efficacies of these recombiant bacteria as oral vaccines were evaluated in murine model
A chimeric gene was designed and subcloned into a lactococcal vector in order to expression of Bap 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
Mice Immunized with recombinant L. lactis, showed 100% protection against 108, 109 and 1010 bacterial challenge. 80% protection was achieved at 1011 bacterial challenge level. All the control groups died within 24 hours of challenge.
the results support the possibility of developing this recombinant strain as a vaccine for controlling A. baumannii infection
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