Immunoprotectivity of Loop ۳ from Omp۳۴ against A.baumannii in murine model

Background and Aim : Acinetobacter baumannii is one of the most important species of nosocomial infections and its clinical importance is due to its special ability to acquire and regulate virulence factors, making it one of the most successful multidrug resistant organisms (MDRs). Several different resistance mechanisms are involved in the development of multidrug-resistant phenotypes in A.baumannii, one of which is to reduce the permeability of the outer membrane protein (OMP). The aim of this study was to investigate the partial protection of loop ۳ of Omp۳۴ protein against A.baumannii in a mouse model.In this study, we targeted Omp۳۴ protein by selecting immunologically active loops from A.baumannii. The surface epitopes were displayed and a hybrid antigen from the loopless C lobe of the Omp۳۴ protein of Neisseria meningitides referred to as LCL was constructed. The nucleotide sequences of the immunogenic loops of Omp۳۴ were amplified and implanted in the LCL.Methods : The recombinant genes were expressed and purified. The purified proteins were administered to BALB/c mice. Both active and passive immunizations were carried out. The mice were then challenged with a clinical isolate of A.baumannii. Indirect ELISA confirmed significant antibody rise to the antigens. Results : In the active immunization, the survival rates of ۶۶.۸%, ۸۳%, and ۵۰% were achieved with the loops derived from Omp۳۴, and combination of both loops respectively. Significant decrease in the bacterial loads were noted in the spleen, liver and lungs of the immunized mice groups Conclusion : In conclusion, Loop ۳ of Omp۳۴ plays an effective role in immunoprotectivity against A.baumannii infections