Abstract
Acinetobacter baumannii is a known hospital aquired pathogenic bacterium that increasingly resists antibiotics treatment. In order to characterize and produce a soluble OmpA protein that can be used to develop Acinetobacter vaccine, polymerase chain reaction (PCR) was used to produce the ompA gene, of A. baumannii strain LI311, which was cloned into the histidin taged pET19b expression plasmid. Immobilized metal affinity chromatography (IMAC) was utilized to purify the recombinant protein, and amino acid sequences for OmpA protein homologs were attained from the National Center for Biotechnology Information (NCBI) protein resource then analyzed using the blast tool and Jalview program. Protein topology prediction was done using NCBI tools and PRED-TMBB2. Analysis of amino acid sequence of OmpA of A. baumannii strain LI311 showed that it has homologies to other clinical Acinetobacter spices , including: A. pittii , A.nosocomialis , A.seifertii, A. calcoaceticus, and A. ursingii with identity percentages of 100%, 100%, 96%, 92%, and 91%. Protein topology prediction revealed two conserved domains belonging to OmpA family protein ,which are beta-barrel domain outer membrane protein (OMP_b-brl) and OmpA-C-like domain, and it is a 10-βeta -stranded transmembrane Outer Membrane Protein with a signal peptide at residues 1–22A. A recombinant Histidine tagged- OmpA (39.31kDa )was successfully expressed and purified in this study. In conclusion, OmpA protein of A.baumannii strain LI31 is highly conserved across clinical species of Acinetobacter, and the soluble recombinant OmpA created in this study can be used to develop a putative vaccine that may prevent infections caused by the clinical species of Acinetobacter.
Highlights
The Gram-negative genus, Acinetobacter, involves a naturally varied group of aerobic bacteria, non-fastidious, oxidase negative, unable to motile,catalasepositive bacilli (Peleg et al, 2008)
Acinetobacter members are generally depicted as ubiquitous nonpathogenic bacteria, strains of the Acinetobacter baumannii-Acinetobacter calcoaceticus become apparent as important opportunistic pathogenic bacteria to humans(Dijkshoorn et al, 2007; Perez et al, 2007)
Due to the high immunogenic properties of OmpA, it has been previously identified as a putative antigen to develope vaccines as well as passive immunotherapy for diseases caused by this bacterium (Fajardo Bonin et al, 2014; Moriel et al, 2013)
Summary
The Gram-negative genus, Acinetobacter, involves a naturally varied group of aerobic bacteria, non-fastidious , oxidase negative , unable to motile ,catalasepositive bacilli (Peleg et al, 2008). A. baumannii has the ability to survive and resist in hospitals conditions, so it has become one of the highly thriving hospital acquired pathogenic bacterium that can stimulate cruicial infections to humans((Howard et al, 2012; Montefour et al, 2008; Peleg et al, 2008). The outer membrane proteins (OMPs) in Gram negative bacteria are distinctive classes of essential membrane proteins These proteins have vital functions for the cell, such as adhesion , nutrients utilization, signaling, secretion of waste as well as serving as a virulence factor in pathogenic strains. A successful vaccine antigen to A. baumannii infections may be helpful to protect against Acinetobacter spices; , the current study aimed to:
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