RESUMEN
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 interferon-gamma) 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 non-infected controls. Based on the results, activated spleen cells in P127 peptide-immunized mice exhibited an increase level of IFN-γ compared with the other experimental groups, but not about the IL-4 concentration. The results of opsonophagocytic assay revealed an appropriate killing activity of produced antibodies against A. baumannii in a dose-dependent 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 peptide-immunized group. In conclusion, findings indicated that peptides derived from outer membrane protein-A can be used as a promising tool for designing the epitope-based vaccines against infections caused by A. baumannii.
Asunto(s)
Infecciones por Acinetobacter/prevención & control , Acinetobacter baumannii/inmunología , Proteínas de la Membrana Bacteriana Externa/inmunología , Vacunas Bacterianas/inmunología , Epítopos/inmunología , Neumonía Bacteriana/prevención & control , Sepsis/prevención & control , Infecciones por Acinetobacter/inmunología , Infecciones por Acinetobacter/mortalidad , Animales , Antígenos Bacterianos/inmunología , Vacunas Bacterianas/administración & dosificación , Citocinas/metabolismo , Modelos Animales de Enfermedad , Interacciones Huésped-Patógeno/inmunología , Inmunización , Ratones , Neumonía Bacteriana/inmunología , Neumonía Bacteriana/mortalidad , Pronóstico , Sepsis/inmunología , Sepsis/mortalidad , Resultado del TratamientoRESUMEN
Nosocomial infections with a bacterial origin are considered one of the most dangerous threats to global health. Among the causes of these infections, Acinetobacter baumannii is playing a significant role, and the present study aimed to determine the immunogenic proteins of this bacteria. Clinical isolates of A. baumannii were obtained from positive sputum cultures of intensive care unit (ICU) patients confirmed by Polymerase chain reaction (PCR) of the OXA-51 gene, and sera was obtained from 20 colonized patients. In addition, 20 and 30 serum samples were collected from ICU nurses and healthy controls, respectively. All the samples were screened in the presence of antibodies against A. baumannii by enzyme-linked immunosorbent assay (ELISA). IgG purified from the serum samples by affinity chromatography was used to isolate the bacteria by the Magnetic-activated cell sorting (MACS) procedure. After the bacteria were cultured, the identified antigen proteins were studied by western blotting and Mass spectrometry (MS). The MS results were analyzed with MASCOT software and revealed a 35 KD protein, which corresponds to outer membrane protein A (OmpA) of A. baumannii, a 25 KD band, which is a carbapenem-associated resistance protein precursor, and a 60 KD protein band, identified as a stress-induced bacterial acidophilic repeat motif protein. According to the properties of immunogen antigens and bio informatics tools, the outer membrane proteins (OMPs) can be used as a vaccine candidate in animal models.