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    Protectivity of combination of two outer membrane proteins against Acinetobacter baumannii infection in murine model

  • Mobina Mansouri,1 Iraj Rasooli,2,*
    1. Department of Biology, Shahed University, Tehran/Iran
    2. Department of Biology, Shahed University, Tehran/Iran


  • Introduction: The ability to absorb iron in its absence and to form biofilm has led to the development of multidrug-resistant isolates of Acinetobacter baumannii, making this pathogen a major global concern. Biofilm makes A. baumannii resistant to a wide range of antibiotics and disastrous environmental conditions. Biofilm-related protein (Bap) plays an indispensable role in biofilm formation by this pathogen. Bap is one of the most acidic and largest bacterial proteins with pI of ~3 and 8620 amino acids. Bap-related proteins are engaged in intercellular adhesion in the full-grown biofilms and are located in the outer membrane of Acinetobacter baumannii. On the other hand, the element iron is vital for the colonization and growth of the pathogen in its host. Acinetobactin (the siderophore of Acinetobacter baumannii) in iron deficit conditions gives A. baumannii the ability to absorb adequate iron over an extensive range of pH and Baumannii acinetobactin utilization (BauA), the most important member of the iron-regulated outer membrane proteins (IROMPs), absorbs the acinetobactin-ferric complex and inserts it into the periplasm of this bacterium. accordingly, disruption of BauA and Bap function can prevent the growth and formation of biofilms in the host and cause the elimination of this pathogen. BauA and Bap seem to be the most promising targets for developing a vaccine against Acinetobacter baumannii.
  • Methods: In this investigation, we expressed BauA and Bap at molecular weights of 78 and 41 kDa in competent cells of E. coli BL21 (DE3) and then purified them. Two purified surface proteins of Acinetobacter baumannii, Bap and BauA, were injected subcutaneously into three groups of BALB/c mice. Mice in the first group received Bap, the second group received BauA, and the third group received both proteins. This was done to induce antibody responses to protein antigens. The survival of mice was then appraised in challenge with heterologous strains of Acinetobacter baumannii.
  • Results: Bap and BauA were already reported to raise antibodies against these proteins. The same results were obtained. The combination of the two antigens led to significant protection against A.baumannii in comparison to the single antigens.
  • Conclusion: Administration of combined antigens triggers better protection than single antigens
  • Keywords: Acinetobacter baumannii., Antigen., Antibody, Vaccine., Bap., BauA