Screening of anti-Acinetobacter baumannii monoclonal antibodies as a tool for immunotherapy and immunodiagnosis

Introduction: Health agencies have highlighted Acinetobacter baumannii as a critical priority for new therapies, a multi-resistant bacterium associated with nosocomial pneumonia.Monoclonal antibodies (mAbs) are known for higher affinity and specificity, and lower toxicity compared to conventional antibacterials.Anti-A.baumannii mAbs might be an important tool to combat and diagnose A. baumannii infections.Objectives: To evaluate the specificity and cross-reactivity of 8 mAbs that recognize an A. baumannii outer membrane protein (OMP) against clinically relevant pathogenic bacteria.Methodology: 8 previously developed anti-A.baumannii OMP mAbs supernatants were used in Western blot analysis to evaluate cross-reactivity against clinically relevant Gram-negative bacteria OMPs: A. baumannii ST162, A. nosocomialis CCBH36141, A. pittii CCBH35103, Klebsiella pneumoniae CCBH36630, K. oxytoca CCBH36653, Pseudomonas aeruginosa CCBH36704, and Stenotrophomonas maltophilia CCBH36624; and Escherichia coli ATCC25922 reference strain.E. coli Top10 was used as a negative control.Results: mAbs 1, 2, and 3 exhibited the same recognition pattern.Besides A. baumannii native target protein (96 kDa), they also recognized equivalent molecular weight (MW) and lower MW proteins in A. nosocomialis, A. pittii, and S. maltophilia (possible degradation product or other isoforms).mAbs 4 and 5 presented a similar recognition profile.Although mAb 4 recognizes only one protein with 96 kDa in S. maltophilia, surprisingly, mAb 5 also recognized a 96 kDa protein in E. coli Top10.mAb 6 and 7 showed greater specificity by recognizing only A. baumannii native protein and homologous proteins in S. maltophilia.However, mAb 7 also recognized an A. baumannii 60 kDa protein and demonstrated a less intense staining in the 96 kDa.mAb 8 was able to recognize A. baumannii, A. nosocomialis, and A. pittii native protein, and a similar MW one in S. maltophilia, also recognized 30 kDa proteins in K. pneumoniae, K. oxytoca, and S. maltophilia. Conclusion:These mAbs, except mAb 5, showed potential for immunotherapy.Despite presenting crossreactivity to other bacteria homologous proteins, that highlights their possible application against different bacterial infections.Due to its greater specificity, mAb 6 showed a higher potential for immunodiagnostics.