الفهرس 
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Abstract
The present study aimed at investigating the efficacy of using either Acinetobacter baumannii isolated outer membrane proteins, capsular polysaccharides, or their combinations as possible immunogens in protection against A. baumannii. To fulfill this aim, firstly, two OMPs (wza and yiaD) were chosen to be evaluated as vaccine candidates. Both proteins were cloned, expressed and purified. In addition, Capsular polysaccharides of standard ATCC 19606 strain as well as 5 clinical A. baumannii isolates (isolates No. 51, 63, 76, 79, and 100) were extracted and quantified to be evaluated as vaccine candidates. All prepared immunogens were then used in vivo to protect mice against A. baumannii. Immunization of mice groups with either wza or yiaD significantly protected mice against the standard strain, clinical isolate No. 62, and No. 100 with significantly increased survival rates ranging from 60% to 70%, while failed to protect against isolate No. 63. On the other hand, immunization with the recombinant proteins pool protected the challenged mice with 90% to even 100% survival rate in case of all tested bacterial challenges. Immunization with the extracted capsular polysaccharides of the standard strain completely protected mice with 100% survival rate following standard strain challenge. Upon challenging immunized mice with the capsular polysaccharides pool, survival rates ranged from 70% to 90% for all tested challenges. Immunization with the pentavalent pool completely protected the challenged mice with 100% survival in case of all bacterial challenges using the standard strain and clinical isolates No. 62, No. 63 and No. 100. To sum up, we have introduced for the first time, as far as we know, several new promising vaccine candidates against A. baumannii infections, including two recombinant proteins wza and yiaD, a pool of both wza and yiaD, a pool of three capsular polysaccharides, and a pentavalent pool of wza, yiaD and three capsular polysaccharides. Among them, the pentavalent pool managed not only to completely protect immunized mice against challenge with all tested A. baumannii, but also to significantly reduce bioburden and inflammation levels in tissues of immunized mice compared to non-immunized control mice, which have enhanced the overall vaccine efficacy.