Production and characterization of novel monoclonal antibodies against outer membrane protein A (OmpA) of Acinetobacter baumannii

Background: Infection caused by Acinetobacter baumannii has emerged as a significant clinical problem with unacceptably high mortality rate due to the increase in antibiotic-resistant strains. Producing novel monoclonal antibody (MAb) against outer membrane protein A (OmpA) could be considered as a potential tool to improve treatment of A. baumannii infections. Objectives: In this study, we aimed to produce murine MAbs against OmpA peptide of A. baumannii. Materials and methods: BALB/c mice were immunized with 18-mer amino acid peptide as a part of the OmpA protein. Four antibody-secreting hybridomas were obtained using hybridoma technology and then characterized according to isotypes, affinity constant, reactivity in ELISA, flow cytometry, indirect immunofluorescence (IFA) and opsonophagocytic killing assays. Results: All four produced MAbs (1A1-D10, 1G1-E7, 2C11-F10, and 4H2-H9) had IgG1 isotype with Kappa light chain. One of these MAbs, 1G1-E7 was purified and selected for further characterizations. 1G1-E7 showed a high reactivity with both immunogenic peptide and A. baumannii in ELISA. Our results indicated that 1G1-E7 MAb reacted with 95.3% of A. baumannii in flow cytometry as well as IFA. Moreover, the affinity of the 1G1-E7 MAb was measured 1.37 pound 108 M inverted exclamation 1. The 1G1-E7 significantly improved opsonophagocytic killing of a clinical isolate of A. baumannii. Conclusion: Our findings showed that the OmpA can be identified by produced MAbs. The efficacy of novel antiOmpA antibodies in A. baumannii targeting needs to be further investigated in challenging models, and then could be subjected for genetic engineering to produce therapeutic antibody against A. baumannii.