Evaluationof the New Outer Membrane Protein A Epitope-based Vaccines for Mice Model of Acinetobacter baumannii Associated Pneumonia and Sepsis Infection

Nosocomial infections caused by Acinetobacter baumannii (A. baumannii) nosocomial infections caused by Acinetobacter baumannii (A. baumannii) are considered as a global serious problem in hospitalized patients because of emerging antibiotic resistance. Immunotherapy approaches are promising to prevent such infections. In our previous study, five antigenic epitopes of outer membrane protein A (OmpA), as the most dangerous virulence molecule in A. baumanii, were predicted in silico. In this study, the investigators evaluated some immunological aspects of the peptides. Five peptides were separately injected into C5BL/6 mice; then the cytokine production (interleukin-4 and interferongamma) of splenocytes and opsonophagocytic activity of immunized serum were assessed. To identify the protective function of the peptides, animal models of sepsis and pneumonia infections were actively and passively immunized with selected peptides and pooled sera of immunized mice, respectively. Then, survival rates of them were compared with the noninfected controls. Based on the results, activated spleen cells in P127 peptideimmunized mice exhibited an increase level of IFN-ɣ compared with the other experimental groups, but not about the IL-4 concentration. The results of opsonophagocytic assay revealed an appropriate killingthe activity of produced antibodies against A. baumannii in a dosedependent manner. Further, the survival rates of the mice under passive immunization with the immunized sera or active immunization with P127 peptide were significantly more than those in the control group. Moreover, the survival rate of the P127 peptide immunized group was considerably higher than that among the other peptideimmunized group. In conclusion, findings indicated that peptides derived from outer membrane proteinA can be used as a promising tool for designing the epitopebased vaccines against infections caused by A. baumannii.the the