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. 2022 Sep;25(9):1141-1149.
doi: 10.22038/IJBMS.2022.64062.14106.

Anti- Acinetobacter baumannii single-chain variable fragments show direct bactericidal activity

Eilnaz Basardeh  1   2 , Somayeh Piri-Gavgani  1   2 , Behnoush Soltanmohammadi  1   2 , Mostafa Ghanei  3 , Mir Davood Omrani  4 , Mahdieh Soezi  1   2 , Mohammad Ali Shokrgozar  5 , Masoumeh Azizi  6 , Abolfazl Fateh  1   2 , Farzam Vaziri  1   2 , Seyed Davar Siadat  1   2 , Zahra Sharifzadeh  7 , Fatemeh Rahimi-Jamnani  1   2
Affiliations

Anti- Acinetobacter baumannii single-chain variable fragments show direct bactericidal activity

Eilnaz Basardeh et al. Iran J Basic Med Sci. 2022 Sep.

Abstract

Objectives: The high resistance rate of Acinetobacter baumannii and the limited number of available antibiotics have prompted a worldwide effort to develop effective antimicrobial agents. Accordingly, identifying single-chain variable fragment antibodies (scFvs), capable of exerting direct antibacterial activity in an immune system-independent manner, may be making immunocompromised patients more susceptible to A. baumannii infections.

Materials and methods: To isolate bactericidal scFvs targeting A. baumannii, we panned a large human scFv phage display library against whole-cell extensively drug-resistant (XDR) A. baumannii strains grown as biofilm or cultured with human blood or human peripheral blood mononuclear cells plus plasma. The binding of scFv-phages to A. baumannii was assessed by the dot-blot assay. Soluble scFvs, derived from the selected phages, were assessed based on their ability to bind and inhibit the growth of A. baumannii.

Results: Five phage clones showed the highest reactivity toward A. baumannii. Among five soluble scFvs, derived from positive phage clones, two scFvs, EB211 and EB279, had high expression yields and displayed strong binding to A. baumannii compared with the controls. Moreover, XDR A. baumannii strains treated with positively-charged scFvs, including EB211, EB279, or a cocktail of EB211 and EB279 (200 µg/ml), displayed lower viability (approximately 50%, 78%, and 40% viability, respectively) compared with PBS-treated bacteria.

Conclusion: These results suggest that combining last-resort antibiotics with bactericidal scFvs could provide promising outcomes in immunocompromised individuals with A. baumannii infections.

Keywords: Acinetobacter baumannii; Antibacterial agents; Colistin; Monoclonal antibody; Phage display library; Single-chain variable-fragment.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
The selected scFv-phages exhibited significant binding to Acinetobacter baumannii
Figure 2
Figure 2
Expression of five soluble scFvs was analyzed by SDS-PAGE and immunoblot assay. (A) SDS-PAGE. Five scFvs (EB204, EB209, EB211, EB279, and EB281) were expressed in Escherichia coli HB2151 and assessed by SDS-PAGE. Lane M: molecular weight marker. (B) Immunoblotting. The proteins were electrophoretically transferred from a 12% SDS-PAGE gel to the polyvinylidene fluoride (PVDF) membrane, followed by incubation with a mouse anti-human scFv fragment polyclonal antibody. After incubation with a goat anti-mouse immunoglobulin G (IgG) antibody conjugated with horse radish peroxidase, the membrane was developed by DAB/H2O2. A single protein band corresponding to the scFv was observed at about 27 kDa
Figure 3
Figure 3
EB211 and EB279 had unique amino acid sequences
Figure 4
Figure 4
EB211 and EB279 scFvs showed binding to Acinetobacter baumannii, Klebsiella pneumoniae, and Pseudomonas aeruginosa
Figure 5
Figure 5
EB211 and EB279 scFvs inhibited the growth of Acinetobacter baumannii
Figure 6
Figure 6
EB211 and EB279 scFvs elicited significant antibacterial activity against Acinetobacter baumannii
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References

    1. Wang J, Xiong K, Pan Q, He W, Cong Y. Application of TonB-dependent transporters in vaccine development of gram-negative bacteria. Front Cell Infect Microbiol. 2020;10:589115. - PMC - PubMed
    1. Isler B, Doi Y, Bonomo RA, Paterson DL. New treatment options against carbapenem-resistant Acinetobacter baumannii infections. Antimicrob Agents Chemother. 2019;63:1110–1118. - PMC - PubMed
    1. Harding CM, Hennon SW, Feldman MF. Uncovering the mechanisms of Acinetobacter baumannii virulence. Nat Rev Microbiol. 2018;16:91–102. - PMC - PubMed
    1. Zeighami H, Valadkhani F, Shapouri R, Samadi E, Haghi F. Virulence characteristics of multidrug resistant biofilm forming Acinetobacter baumannii isolated from intensive care unit patients. BMC Infect Dis. 2019;19:629. - PMC - PubMed
    1. Irani N, Basardeh E, Samiee F, Fateh A, Shooraj F, Rahimi A, et al. The inhibitory effect of the combination of two new peptides on biofilm formation by Acinetobacter baumannii. Microb Pathog. 2018;121:310–317. - PubMed

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