scholarly journals In Silico Design and Evaluation of Acinetobacter baumannii Outer Membrane Protein A (OmpA) Antigenic Peptides as Vaccine Candidate in Immunized Mice

2020 ◽  
Author(s):  
Kobra Mehdinejadiani ◽  
Mojgan Bandehpour ◽  
Ali Hashemi ◽  
Mohammad Mehdi Ranjbar ◽  
Sodabeh Taheri ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Acinetobacter Baumannii ◽  
Outer Membrane ◽  
Outer Membrane Protein ◽  
Protein A ◽  
Epitope Prediction ◽  
Effective Vaccine ◽  
Enzyme Linked Immunosorbent Assay ◽  
Antigenic Peptides ◽  
Outer Membrane Protein A

Acinetobacter baumannii is a Gram-negative bacterium that has recently been identified as a leading nosocomial pathogen. Infections by this pathogen result in significant mortality due to antibiotic resistance. An effective vaccine would help alleviate the burden of disease incurred by this pathogen; however, there are currently no licensed vaccines offering protection against Acinetobacter baumannii infection. In this study, considering the fact that outer membrane protein A is one of the most promising vaccine candidates, we predicted T cell and B cell epitopes on this protein using sequence-based epitope prediction tools and determined whether or not mice immunized with these peptides induce an immune response. We selected consensus epitopes including five peptides in different tools with the highest score. 48 female C5BL/6 SPF injected subcutaneously with the peptides (peptide1 to peptide 5 separately) in 100 μL of the solution and sham groups received adjuvant and PBS alone on the same schedule: on day 0 (primary dose) and two booster doses were administered on days 14 and 28. At the end of time, animals euthanized by Isoflurane, and collected sera for assessment of specific antibodies against each peptide by ELISA (Enzyme-linked immunosorbent assay). Immunization of mice showed one of the novel synthetic peptides (peptide 1 (24-50 amino acids)) elicited immune responses. We conclude to combine theoretical methods of epitope prediction and evaluating the potential of immunogenicity for developing vaccines is important.

scholarly journals Immunoprotective evaluation of Escherichia coli outer membrane protein A against the main pathogens of animal mastitis

2020 ◽  
Vol 19 (1) ◽  
pp. 155-162
Author(s):  
Chen Chen ◽  
Nana Wu ◽  
Na Rong ◽  
Chao Kang ◽  
Chunlin Chen ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Membrane Protein ◽  
Outer Membrane ◽  
Outer Membrane Protein ◽  
Protein A ◽  
Enzyme Linked Immunosorbent Assay ◽  
Protective Function ◽  
E Coli ◽  
Ompa Protein ◽  
Outer Membrane Protein A

Purpose: To evaluate prokaryotic expression of the Escherichia coli (E. coli) outer membrane protein A (OmpA) and its immunoprotective function against the main pathogens of animal mastitis.Methods: A molecular cloning method was used to develop a prokaryotic strain expressing OmpA protein, which was purified by Ni-affinity  chromatography. Polyclonal antiserum was generated in mice immunized with OmpA protein. Enzyme-linked immunosorbent assay (ELISA) and western blotting were used to determine the titer and verify anti-OmpA serum specificity, respectively. Interaction between OmpA antiserum and main pathogens of animal mastitis was verified by ELISA and a pull-down method. The immune protective function of OmpA protein was evaluated in mice challenged with pathogens of animal mastitis. Optimal fermentation conditions to produce OmpA protein were determined by the L9(34) orthogonal test.Results: A prokaryotic strain expressing OmpA protein was developed, and purified OmpA was used to develop a mouse polyclonal antibody. The anti-OmpA serum exhibited high specificity and a titer of 1:1600. Anti-OmpA serum directly interacted with E. coli and Staphylococcus aureus (S. aureus). OmpA demonstrated a significant immune protective function of 58.33 % against E. coli and 46.15 % against S. aureus. The optimal conditions for expressing fermentation OmpA were a strain absorbance of 0.5 at a wavelength of 600 nm, IPTG final concentration of 0.3 mmol/L, induction time of 12 h, and induction temperature of 28 °C.Conclusion: OmpA possesses selective immunogenicity and a significant immune protective effect against the main pathogens of animal mastitis. The results suggest that OmpA may potentially be used as a vaccine for animal mastitis. Keywords: E. coli, OmpA protein, Immunoprotection, Animal mastitis, Protein fermentation

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

2021 ◽  
Author(s):  
Kobra Mehdinejadiani ◽  
Ali Hashemi ◽  
Mojgan Bandehpour ◽  
Hoda Rahmani ◽  
Mohammad Mehdi Ranjbar ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Acinetobacter Baumannii ◽  
Outer Membrane ◽  
Outer Membrane Protein ◽  
Protein A ◽  
Survival Rates ◽  
The Other ◽  
Dependent Manner ◽  
Protective Function ◽  
Outer Membrane Protein A

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, their survival rates were compared with the non-infected controls.Based on the results, activated spleen cells in P127 peptide-immunized mice exhibited an increased level of IFN-γ compared with the other experimental groups, but not about the IL-4 concentration. The results of the opsonophagocytic assay revealed an appropriate killing the 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 of the other peptide-immunized group.In conclusion, findings indicated that peptides derived from OmpA can be used as a promising tool for designing the epitope-based vaccines against infections caused by A. baumannii.   

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